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ISSN 2347 3037

Volume 7 Number 1 July 2015

Editorial Board

Editor

Satish V. KailasIndian Institute of Science

Associate-Editor

Ramesh C. S., P.E.S. University, Bangalore

Editorial Board

Ajay KumarIndian Oil Corporation R&D, Faridabad

Barun ChakrabartiR&D - L&T Hydrocarbon Engineering, Mumbai

Bobji M. S.IISc, Bangalore

Kamal MukherjeeCoal India Limited, Gevra

Sharma S. C.IIT Roorkee

Sujeet K. SinhaIIT Delhi, Delhi

Printed on Behalf of the Tribology Society of India

(Affiliated the the International Tribology Council (UK))C/o. Indian Oil Corporation Ltd.

R&D Centre, Sector-13., Faridabad. HARYANAPhone no: +91-129-2294264

E-mail : [email protected]

Indian Journal of TribologyISSN 2347 3037

Vol. 1, No. 1, September 2015

Contents

Studies on Cup Profile Thickness Variation of Deep Drawn AA 6061 Sheet using Green Lubricants / 1-4Y.M. SHASHIDHARA and S.R. JAYARAM

Fatigue Life Analysis of a Connecting Rod Big-end Journal Bearing / 5-10K. S. ABHINANDHAN, T. NAGARAJU and R. K. ANANDA

Abrasive Wear Behaviour of Inconel 718 Microwave Clad / 11-15SUNNY ZAFAR and APURBBA KUMAR SHARMA

Study of Tribo-chemistry in Establishing Synergy of Friction Modifiers and Viscosity Modifiers in Engine Oils / 16-20SHIV KUMAR VABBINA, ANIL BHARDWAJ, SANJIV KUMAR MAZUMDAR and MUKESH SAXENA

Slurry Erosive Wear Behavior of Carbon Fibre Rod Reinforced Al6061 Heat Treated Composites / 21-25ADARSHA H and PADMAPRIYA N

Theoretical and Experimental Studies on the Tribological Behavior of Saps-free Salicylaldehyde Propanoylhydrazone Schiff Base and its Cu (Ll) Complex in Paraffin Oil for Steel-steel Contact / 26-32VINAY JAISWAL, KALYANI, RASHMI B. RASTOGI AND RAJESH KUMAR

Study of Soot Contaminant on Tribological Properties using Steel and Silicon Nitride Sliding Contacts / 33-38YADVENDRA KAUSHIK and P. RAMKUMAR

Powder and Granular Lubrication of Journal and Thrust Bearings: A Review / 39-43 F. RAHMANI, R. K. PANDEY and J. K. DUTT

Performance Analysis of A Capillary Compensated Partial Non-recess Hole Entry Hybrid Journal Bearing System / 44-47CHANDRA B. KHATRI and SATISH C SHARMA

Tribological Characteristics of Journal Bearing Materials Under Modified Soyabean Oil / 48-51BASKAR S, MANU M and ROHIT SINGH

Possibility of Using Fluidics Principle in the Design of Water-lubricated Bearing / 52-54Dr. SUBRAMANYA KRISHNA BHAT

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Editorial

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Journal of Tribology. This issue is coming after a hiatus and we do hope to bring this out regularly. The

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Indian Journal of Tribology 1

STUDIES ON CUP PROFILE THICKNESS VARIATION OF DEEPDRAWN AA 6061 SHEET USING GREEN LUBRICANTS

Y.M. Shashidhara1 and S.R. Jayaram2

1Professor, Department of Automobile Engineering,2Professor, Department of Mechanical EngineeringMalnad College of Engineering, HASSAN- 573 202, Karnataka State.Corresponding author: [email protected]

KEYWORDS: Forming, Pongammia pinnata, Jatropha Curcass, Lubricant, Thickness profile

ABSTRACT

The present work deals with the evaluation of deepdrawing process using two non edible oils, Pongam(Pongammia pinnata) and Jatropha (Jatropha carcass) asMetal forming lubricants. Experiments are conducted on AA6061 Aluminium sheets under the raw and modified oils withsuitable punch and die on a hydraulic press of 250 toncapacity. The wall thickness distribution, draw-in-length,punch load for deep drawn cups are observed. The drawncups are scanned using Laser scanning technique and 3Dmodels are generated using modeling package. The wallthickness profiles of cups at different sections (or height)are measured using CAD package. Among all the oils, thedrawn cups under raw Pongam oil and its modified version,have uniform wall thickness profile. Uneven flow of materialis observed under methyl esters of Pongam and Jatrophaoil and mineral oil lubricated conditions. However, the resultsare observed under Pongam and epoxidised Pongam oil withuniform metal flow and wall thicknesses compared topetroleum based and other versions of vegetable oils

INTRODUCTION

Sheet metal forming operations constitute a majorsegment of manufacturing worldwide. Deep drawing/stamping, is one such operation, which has many applicationin Automotive, Marine and Aerospace industries. The mostimportant factor deciding the success of deep drawing isinitiating the flow. The role of lubricant is vital in initiatingthe metal flow, which decides the quality of the component(1). Currently, in industry, lubricating oils being used arepetroleum based. With the introduction of environmentallegislation series, consumption of mineral based metalworking fluids is reducing. There is a huge potential forut ilizing vegetable oi ls as metal working flu ids inmanufacturing sector (2).

Vegetable oils consist of primarily of triglycerides,which are glycerol molecules with three long chain fattyacids attached at the hydroxyl groups via ester linkages (3).

It is reported that triglyceride structure provides desirablequalities for boundary lubrication due to their long and polarfatty acid chains. It provides high strength lubricant filmsthat interact strongly with metallic surfaces, reducing bothfriction and wear (4). Due to their higher monosaturates(Oleic acid) in their fatty acid composition (Table 1) andhigher thermal & oxidative stability, they are projected aspotential lubricants for wide range of operations.

Table 1 : Fat ty acid composition of Pongam andJatropha oil.

Compound Name Pongama raw Jotraphaoil (%) raw oil (%)

Lauric acid (C 20:0) 00.30 00.40

Myristic acid (C14:0) 00.00 00.00

Palmitic acid (C16:0) 12.00 14.60

Stearic acid (C 18:0) 06.70 06.60

Arachidic acid(C20:4) 01.60 00.22

Palmitoleic acid(C16:1) 00.00 01.20

Oleic acid ( C 18:1) 53.20 40.60

Linoleic acid (C18:2) 20.80 36.20

Linolenic acid (C18:3) 04.00 00.30

The performance of Sunflower, Corn, Soybean andOlive oils are evaluated as forming lubricants on steel sheetsunder stamping operation (5). Lower dynamic friction valuesare reported during the experiments under these oilscompared to mineral oil. A study (6) revealed that theinterfacial friction characteristics under Canola oil and boricacid powder (5 wt.%) lubrication, was dropped by 44 percentcompared to a transmission fluid during deep drawingoperation. Further, the combination (Ra = 0.58) providedsubstantially better separation between the su rfaces.Linseed oil is used to lubricate Aluminum sheets forstamping operation (7). High friction and adhesive wear isreported under this oil. However, the authors claim that, hisproblem might be solved by increasing the oil thickness.

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Indian Journal of Tribology2

Qual itative and quanti tative analyses criteria isproposed (8) to determine the effectiveness of lubricants indeep drawing process based on side-wall thinning of thedeep-drawn cup and draw-in length in the ûange. In thepresent work, formulated non edible vegetable oils, Pongamand Jatropha are used for deep drawing of Aluminium sheetsand the side wall thinning and draw-in-lengths are studied.

EXPERIMENTAL DETAILS

The two vegetable raw oils, Pongam (PRO) and Jatropha(JRO) are chemically modified. Transesterification processis followed to produce Pongam oil methyl ester (EPME) andJatropha oil methyl esters (EJME) under carboxyl groupmodification method. Epoxidation process is followed toproduce Epoxidised Pongam raw oil (EPRO) EpoxidisedJatropha raw oil (EJRO) under fatty acid chain modificationmethod.

Experiments are conducted on AA 6061 sheets underthe raw and modified oils with suitable punch and die on ahydraulic press of 250 ton capacity, double acting withmaximum stroke of 500 mm (Fig.1). The process parameterslike punch load, punch travel and blank holding force aremeasured. The wall thickness profile, an indication of uniformfriction between drawing surfaces and draw-in-length, thediameter of blank before and after the draw are studied toasses the behaviour of lubricant.

The thickness profiles of deep drawn cups are observedwith raw and modified oils as lubricants. The drawn cupsare scanned using laser scanning and 3D models aregenerated using modeling package. The thickness profilesof cups at different sections (or heights) are measured usinga CAD package.

RESULTS AND DISCUSSION

Punch load

Fig.2 shows variation of Punch load with punch travel.In the initial stages of drawing, about 17 % of higher forcesare recorded under JRO and EPME modes compared tounder mineral oil (MRO) and the epoxidised versions ofPongam and Jatropha raw oils showed 30 % higher forces.This may be due to initial bending and unbending of blankover the die corner and material flow, which generates higherfriction between blank and die. However, the loadrequirement under PRO is almost similar to that of forcesunder mineral oil. As the punch reaches mid of the stroke,equal magnitudes of forces are obesrved under all oilsexcept JRO and EJME. JRO shows about 14 % drop inpunch force while the latter exhibits about 14 % increase inforce compared under petroleum oil.

At the end of stroke, PRO and JRO exhibit lower forces(about 20 % and 25 % respectively) compared to mineraloil. However, under MRO, EPRO and EPME, the magnitudesof punch forces are closer.

Fig. 1: Experimental setup (Courtsey: Peenya FineComponent Ltd, Bangalore, India)

Fig. 2: Variation of Punch load with punch travel

The draw-in-lengths indicate the effect of frictionbetween blank and die. The increase in length indicates lowerfriction during the operation. Fig. 3 shows the draw-in-lengths under different lubricants. Higher values of draw-in-length are observed under raw and epoxidised versionsof Pongam & Jatropha oils. However, epoxidised methylesters of both the oils and mineral oil show lower draw-in lengths. For instance, about 20 % and 16% more draw-in-length is achieved under PRO and EPRO mode of lubricationrespectively compared to mineral oil. Further, under JRO andEJRO, only 13% more draw-in-length is seen.

It is seen from Fig.3 that, the raw and epoxidisedversions of both oils offer better capabilities than theirepoxidised methyl esters. Pongam raw oil found to be thesuitable lubricant among all oils.


Fig. 3: Variation of Draw-in-length for differentlubricants.

Thickness profile

The 3D image of the deep drawn cup is shown in Fig.4. The wall thickness profiles from flange to bottom of cupunder different oils considered are shown in Fig. 5 throughFig. 10. Almost, uniform wall thickness profiles are noticedunder Pongam raw and its epoxidised version (Fig. 6 andFig. 7), indicating better lubrication between the surfaces ofdrawing. This could be due to its higher monounsaturatedfatty acid structure of the oil. However, variations in the wallthicknesses across left and right sections are observedunder Pongam raw oil. This can be avoided by better controlof operational parameters.

Fig.7: Wall thickness under Epoxidised Pongam raw oil

Fig. 4: 3D image of drawn cup

Fig. 5: Wall thickness under Mineral oil

Fig. 6: Wall thickness under Pongam Raw oil

Fig.8: Wall thickness under EpoxidisedPongam methyl ester

Fig. 9: Wall thickness under Jatropha raw oil

Fig. 10:Wall thickness under Epoxidised Jatropha raw oil

But, thinning is observed under Jatropha and itsmodified versions of oils (Fig. 9 & Fig. 10). It can beattributed to higher unsaturated fatty structure.

CONCLUSIONS

Lower punch loads are encountered under both Pongamand Jatropha raw oils compared to mineral and othervegetable oil modes. Better material flow/draw-in-length isnoticed under vegetable oil mode of lubrication, particularlyunder Pongam raw oil. Uniform thickness profiles areobserved with Pongam and its epoxidised version oflubrication.

Deep drawing of AA 6061 cups is more appropriateunder Pongam raw oil lubrication as it exhibits lower punchforce, better draw-in-length and uniform cup wall thickness.

ACKNOWLEDGEMENTS

Authors express thei r grati tude to VisvesvarayaTechnological University-Belgaum and M/s Peenya FineComps. Pvt. Ltd., Bangalore.


REFERENCES

1. Yang, T. S. Investigation of the strain distribution withlubrication during the deep drawing process, TribologyInternational, 2010, Vol. 43, 1041112.

2. Norrby T. Environmentally adopted lubricants whereare the opportunities? Stat. oil Lubricants R&D, 2003.

3. Fox NJ. Stachowiak G.W. Vegetable oil basedlubricants A review o f oxidat ion, TribologyInternational, 2007, Vol. 40, 1035-1046.

4. Matthew T. Siniawski. Nader Saniei. Bigyan Adhikariand Lambert A. Doezema. Influence of fatty acidcomposition on the tribological performance of twovegetable-based lubricants. Journal of SyntheticLubrication, 2007, Vol. 24, 101110.

5. Carcel AX. Evaluation of vegetable oils as pre-lube oilsfor stamping. Materials & Design, 2005, Vol. 26,587-593.

6. Lovell M. Increasing formability in sheet metalstamping operations using environmentally friendlylubricants, Journal of Materials ProcessingTechnology, 2006, Vol. 177, 8790.

7. Ulf Bexell. A tribological study of a novel pre-treatmentwith linseed oil bonded to mercaptosilane treatedaluminium. Surface coating & Technology, 2003,Vol. 166, 141-152.

8. Kim, H., Sung, J. Sivakumar, R., Altan, T. Evaluationof stamping lubricants using the deep drawing test.International Journal o f Machine Tools andManufacturer, 2007, Vol. 47, 21202132.


RESEARCH ARTICLE

FATIGUE LIFE ANALYSIS OF A CONNECTING RODBIG-END JOURNAL BEARING

K. S. Abhinandhan1, T. Nagaraju1* and R. K. Ananda1

1 Department of Mechanical Engineering P E S College of Engineering, Mandya-571401, Karnataka, India *Corresponding author (E-mail: [email protected]; [email protected])

KEY WORDS: Big-end bearing; fatigue life

ABSTRACT

The present work predicts the fatigue l ife andprobability of survival of a connecting rod big-end journalbearing under its realistic dynamic load. The cylinder gaspressure of a typical spark ignition (SI) engine has beensimulated and the bearing dynamic load has been computed.The cyclic variation of fluid-film pressure in the clearancespace of bearing and the resulting deformation fields ofbearing liner are obtained by simultaneously solvingReynolds and 3D elasticity equations using finite elementmethod. Bearing bush is considered as 3D elastic body andsix components of stresses and Von Mises stress have beencomputed during a load cycle. The effects of coefficient ofdeformation of the bearing bush, engine speed, journal massof the bearing and intake manifold pressure on Von Misesstress, fatigue life and probability of survival of theconnecting rod big-end bearing bush are presented anddiscussed on a comparative basis. The fatigue life andprobability of survival of the bearing were found to besignificantly affected by the above mentioned parameters.

INTRODUCTION

The connecting rod big-end bearing which is subjectedto a complex dynamic load is an important component of anIC engine. The modulus of elasticity of lining material of thisbearing is as low as possible to allow conformity betweenjournal and bearing. This leads the bearing liner to undergosevere deformation under steep gradients of fluid-filmpressure. Also the load on this bearing varies in directionand magnitude during each cycle. This results into the cyclicdeformation of bearing liner and causes its surface fatiguefailure in the form of cracks. Hence it is necessary to evaluatethe fatigue failure in the analysis of connecting rod big-endjournal bearing.

Over the last few decades numerous studies ondynamically loaded journal bearing systems have beencarried out and reported in the literature. Most of thesestudies were mainly devoted to the prediction of minimumfluid-film thickness and maximum fluid-film pressure in

dynamically loaded journal bearings. Booker [1] proposed amobility method to predict journal eccentricities underdynamic loading. Later, Martin and Booker [2] demonstratedthat the minimum fluid-film thickness in connecting rodbearing is more dependent on inertia forces than the peakfiring gas force. Goenka [3] has developed the mobility curvefits, by which the mobility vector and the maximum filmpressure are given in the algebraic expressions. Paranjpe andGoenka [4] implemented a mass conserving ElrodAdamsalgorithm which uses the Jackobsson, Floberg and Olsson(JFO) cavitation boundary conditions to analyze enginebearings. Hirani et al. [5, 6] proposed an analytical solutionmethod [5] as well as a hybrid solution scheme [6] for theanalysis of dynamically loaded journal bearings. Goenka [7]described the versatility of finite element method throughthe analysis of 17 different cases of connecting-rod bearinggeometries. Pal et al. [8] also used the finite element methodto analyze big-end bearing. They presented a time-marchingnumerical integration scheme to obtain the journal centrelocus of the bearing.

Generally, journal bearings are expected to have aninfinite life as compared to the antifriction bearings. However,the experimental work by Blundell [9] predicts the fatiguefailure of dynamically loaded journal bearing. The positionof failure was found to be generally occurring between theposition of maximum peak pressure and the maximumeccentricity. Sikora et al. [10, 11] also experimentallydemonstrated the failure of slide bearings under dynamicload. The failure, in their study, was shown to be dependenton the effects of lubricating oils, their temperature, loadingstress ratio, shape and dimensions of the bearing housing,etc.

A scan of available literature revealed that the studieswhich predict the fatigue failure of dynamically loadedbearings are very limited and hence more studies need tobe carried out. Thus, the present work theoretically predictsthe influence of coefficient of deformation of bearing bush,engine speed and journal mass of the bearing on fatigue lifeand probability of survival of the connecting rod big-endjournal bearing bush.

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MATHEMATICAL MODELS

Referring to Fig. 1, the equations of motion for a journal(i.e. crank pin) are

where , ,IVC SOC EOC and EVO are the crankposition corresponding to intake valve close, start ofcombustion, end of combustion and exhaust valve openrespectively. kc and ke are polytropic coefficients duringcompression and expansion strokes respectively.

The unsteady state reaction components in Eq. (1) areobtained by

where ,x zF F are the unsteady state reactioncomponents due to hydrodynamic pressure and aperitycontact pressure and ,ex ezF F are the external loads in x andz directions respectively.

The external load components exF and ezF areexpressed as

Fig. 1: Bearing coordinates

(1)

(2)

where 21 2 c jF M R is the centrifugal force of rotatingparts at big-end and 2F is the piston effort transmitted tothe bearing through the connecting rod. It is given by

where 1 2,M M are masses of reciprocating androtating parts and , ,c p pR A a are crank radius, piston area,piston acceleration respectively.

The cylinder gas pressure ( )gp of a typical SIengine is simulated using the expressions of Eriksson andAndersson [12].

(3)

(4)

(5)

The hydrodynamic fluid-film pressure p is obtainedby the Reynolds equation

(6)

Nodal deformation is obtained from the following finiteelement expression of 3D elasticity equation

(7)

For an ith element of a discretized bearing bush domain,six components of stresses are computed by the followingstress strain relation

(8)

where, , D and B are

the elasticity and strain displacement matrices and Q is theglobal displacement (deformation) vector corresponds to theith element.

Fatigue life of bearing bush is established using thestochastic model proposed by Zaretsky [13].

(9)

where , , ,N S v e and c are fatigue life, probability ofsurvival, stress affected material volume, Weibull slope andstress exponent respectively. eq is the equivalent stressrange experienced by the elementary material volume dv .In the present study, the distortion-energy (Von Mises-Hencky) failure theory is used as a criterion for the fatiguelife prediction. Hence, Von Mises stress is taken as theequivalent stress

(10)


where i and ij are the normal and tangential stresscomponents in cylindrical structure of bearing bush.

By establishing a reference life refL , a unit volumerefV and a reference stress ref related to the reference life,

Eq. (9) can be rewritten as [13 ]

where iL is the fatigue life of individual element and AAis material factor given by

(11)

(12)

The fatigue life of the entire bearing bush ( sL ) isobtained from

(13)

where, ne is the total number of elements. Theprobability of survival ( iS ) and the fatigue life ( iL ) of theindividual stressed elements can be related to the referencevalue of survivability ( refS ) and fatigue life ( refL ) as [13]

Then the probability of survivability of entire bearingbush is obtained by

(15)

The journal centre positions at different crank anglesare obtained by integrating Eq. (1) using 4th order Runge-Kutta method. At each journal centre positions, the fluid-film pressure, bearing bush deformation and stresses arecomputed from Eqs. (6) (8). Then fatigue life and probabilityof survival of individual elements and entire bearing bushare computed from Eqs. (10) (15).


The dynamic load on big-end bearing is computedusing the simulated cylinder gas pressure of typical SIengine listed in Table 1.

Figure 2 shows the polar diagram of dynamic loadacting on connecting rod big-end bearing at different enginespeeds 1500 rpm, 3000 rpm and 4500 rpm (i .e. at

8.702,17.404, 26.12j ). The fatigue life of a big-endjournal bearing bush and its probability of survival underthese bearing dynamic loads are computed for 2e and

5c . Endurance limit of the bearing material (i.e. 33MPa),

(14)

Table 1: Typical SI engine specifications

Parameters Values

Cylinder bore 139.7 mm

Stroke 152.4 mm

Connrod length to crank radius, q 4.65

Total rotating mass, M2

4 kg

Total reciprocating masses, (M1 +

M

p ) 2.6 kg

Intake valve open position, ivo

5O BTDC

Intake valve closing position, ivc

43O ABDC

Exhaust valve open position, evo

53O BBDC

Exhaust valve closing position, evc

1O ATDC

Start of combustion, soc

23O BTDC

Combustion duration, 78O

Intake manifold pressure, Pgim

106.2 kPa

Gas manifold intake temperature, Tgim

300 K

Residual gas fraction, xr

0.07

Residual gas temperature, Tr

1000 K

Fuel conversion efficiency, (l) 95%

Stoichiometric air fuel ratio, (A / F)s

14.6

Relative air fuel ratio, l 0.8

Fig. 2: Polar load diagram

the number of cycle for the fatigue failure (i.e. 2E+7 cycles),the volume of one element and 90% probability of survivalare taken as the reference value for ref , refL , refV and

refS respectively..

In the following, the results computed for the following

nondimensional parameters of the bearing are presented and

discussed.

Aspect ratio, L/d = 1

Journal speed parameter, 8.7,17.4, 26.11j

Deformation coefficient, 0.001 0.015dC

Journal mass, 1.5791,3.1583jM


It may be noted that the stressed elements with fatiguelife i refL L (2.0E+7) and probability of survival i refS S(90%) are susceptible to failure.

Figure 3 shows the influence of coefficient ofdeformation ( dC ) on maximum Von Mises stress developedin connecting rod big-end bearing bush when the bearingis subjected to a dynamic load shown in Fig. 2 at an enginespeed of 1500 rpm (i.e at 8.702j ). The maximum VonMises stress was observed to occur at the bearing bushlocation 170o and 0 . For the fixed values of journalmass and engine speed, this maximum Von Mises stressincreases as the coefficient of deformation increases. Since

the bearing is subjected to maximum load during firing strokeas shown in Fig. 2, the maximum value of Von Mises stressis observed to occur for this firing stroke.

From the results of Table 2, it can be seen that for afixed value of coefficient of deformation dC , the fatigue lifeand probability of survival of individual stressed element andentire bearing bush decreases as speed of the engineincreases. At fixed value of journal speed, the fatigue lifeand probability of survival further decrease as the coefficientof deformation increases. For the value of nondimensionaldeformation coefficient, 0.001dC , the life of entire bearingbush and its probability of survival reduces to 8.97E+3 andzero respectively when the bearing operates at engine speedof 4500 rpm. As the values of dC increases, the life of thebearing bush reduces from their reference life of 2.0E+7cycles even for the lower engine speeds also.

As seen from Table 3 the fatigue life and probability ofsurvival of individual stressed element and entire bearingbush are significantly affected by the journal mass. The smalljournal mass leads to the failure of bearing bush irrespectiveof its material deformation coefficient, dC .

CONCLUSIONS

Based on the results presented in the previous section,the following conclusions are drawn.

Fatigue life and probability of survival of bearingbush was found to significantly affected by theengine speed and journal mass.

Fatigue life and probability of survival of bearingbush were found to reduce as the engine speedincreases and increases as journal mass increases.

Hence, bearing failure was found to be avoided bythe proper journal mass.

Fig. 3: Variation of maximum Von Mises stress withcoefficient of deformation

Table 2 : Effects of engine speed and coefficient of deformation on Von-Mises stress, Fatigue Life andsurvivability of bearing bush

W j Cd (sVM) Max (L1) Min (Si) Min Ls SsMPa cycles cycles

0.001 3.83 3.16×1012 100% 1.83×1012 100%8.702 0.005 16.93 1.44×109 99.99% 8.25×108 99.99%

(1500 rpm) 0.01 29.98 6.93×107 99.12% 3.92×107 97.28%

0.015 37.36 1.35×107 79.43% 7.55×106 47.87%

17.404 0.001 31.62 4.91×107 98.26% 2.59×107 93.91%(3000 rpm) 0.005 71.68 7.23×105 0 3.73×105 0

0.01 86.78 3.72×105 0 1.34×105 00.015 94.37 1.65×105 0 8.64×104 0

26.106 0.001 151.81 1.78×104 0 8.97×103 0(4500 rpm) 0.005 219.98 2.55×103 0 1.2×103 0

0.015 227.66 1.81×103 0 8.66×102 0


REFERENCES

1. Booker, J. F., Dynamically Loaded Journal Bearings:Mobility Method of Solution, Trans. ASME, J. BasicEngg., Vol. 87, Series D, Sept. 1965, pp. 537-546.

2. Martin, F. A., and Booker, J. F., Influence of EngineInertia Forces on Minimum Film Thickness inConnecting-Rod Big-End Bearings, Proc. IMechE.,Part 1, Vol. 181, 1966-67, p 749-764.

3. Goenka, P. K., Analytical Curve Fits for SolutionParameters of Dynamically Loaded Journal Bearings,Trans. ASME, J. Tribol., Vol . 106, Oct. 1984,pp. 421-428.

4. Paranjpe, R. S., and Goenka, P. K., Analysis ofCrankshaft Bearings Using a Mass ConservingAlgorithm, STLE Tribol. Trans., Vol. 33(3), 1990, pp.333-344

5. Hirani, H., Athre, K., and Biswas, S., DynamicallyLoaded Finite Length Journal Bearings: AnalyticalMethod of Solution, Trans. ASME, J. Tribol., Vol. 121,Oct. 1999, pp. 844-852.

6. Hirani, H., Athre, K., and Biswas, S., A Hybrid SolutionScheme for Performance Evaluation of CrankshaftBearings, Trans. ASME, J. Tribol., Vol. 122, Oct. 2000,pp. 733-740.

Table 3 : Variation of Von-Mises stress, Fatigue Life and survivability of bearing bush with journal mass at differentcoefficient of deformation (N = 3000 rpm).

M j Cd (sVM) Max (L1) Min (Si) Min Ls SsMPa cycles cycles

0.001 3.83 3.16×1012 100% 1.83×1012 100%

1.5791 0.001 31.62 4.91×107 98.26% 2.59×107 93.91%0.005 71.68 7.23×105 0 3.73×105 00.01 86.78 3.72×105 0 1.34×105 00.015 94.37 1.65×105 0 8.64×104 0

3.1583 0.001 2.25 4.06×1013 100% 2.16×1013 100%0.005 3.40 6.74×1012 100% 3.22×1012 100%0.01 6.80 2.10×1011 100% 1.01×1011 100%0.015 10.23 2.76×1010 99.99% 1.33×1010 99.99%

NOMENCLATURE

c : Radial clearance, mmD : Journal diameter, mmL : Bearing length, mmh : Nominal fluid-film thickness, mmR

J : Radius of journal and bearing respectively, mm

p : Pressure, N.m-2

PS : Supply pressure, N.m-2

z : Coordinate across fluid-film thickness, mmm : Dynamic viscosity of lubricant, N.sec.m-2

sa : Stress in circumferential direction, MPa

sy : stress in axial direction, MPa

sr : stress in radial direction, MPa

V : stressed volume, m3

Pg(q): Cylinder gas pressure, N/m2

Tr : Residual gas temperature, K

q : Connecting rod length to crank radius

Ap : Piston cross sectional area, m2

Rc : Crank radius, mm

q : Crank angle, degF

g : Cylinder gas force acting on the piston, N

ap : Acceleration of piston, m/s2

wb : Angular speed of bearing

wj : Angular speed of journal


7. Goenka, P. K., Dynamically loaded journal bearings:finite element method analysis, Trans. ASME, J. Tribol.,Vol. 106, Oct. 1984, pp. 429-439.

8. Pal, R., Sinhasan, R., and Singh, D. V., Analysis of abig-end bearing A finite element approach, Wear, Vol.114, 1987, pp. 275-293.

9. Blundell J. K., Fatigue Initiation in Thin-Wall JournalBearings, ASLE Trans., Vol. 33(2), 1978, pp. 131-140.

10. Sikora J., Klopocki J., Majewski W., and Kurzych K.,Some Problems of Slide Bearing Material FatigueEvaluation, J. of KONES Powertrain and Transport,Vol. 14(4), 2007, pp. 427-432.

11. Sikora J., Klopocki J., and Majewski W., SelectedProblems of Experimental Investigation of DynamicallyLoaded Journal Bearings, J. of KONES Powertrain andTransport, Vol. 14(4), 2007, pp. 433-440.

12. Eriksson, L., and Andersson, I., An Analytical Modelfor Cylinder Pressure in a Four Stroke SI Engine, SAEpaper, 2002-01-0371.

13. Zaretsky, E. V., and Sherry, M. S., Effect of individualcomponent life distribution on engine life prediction,Nasa/TM-2003-212532.


RESEARCH ARTICLE

ABRASIVE WEAR BEHAVIOUR OF INCONEL 718 MICROWAVE CLAD

Sunny Zafar1* and Apurbba Kumar Sharma1

1Mechanical and Industrial Engineering Department, Indian Institute of Technology Roorkee, Roorkee*Corresponding author (E-mail: [email protected];[email protected])

KEY WORDS: Inconel 718; Microwave cladding; Microstructure; Microhardness; Abrasive wear.

ABSTRACT

This paper reports on a specific tribological behaviourof an engineered surface through a novel process. In thepresent work, Inconel 718 clads were developed on SS-304stainless steel substrate in a domestic microwave applicatorat 2.45 GHz and 900 W. Clads were developed due to partialmelting and dilution of the substrate with complete meltingof powder particles. The microstructural characterisation ofthe Inconel 718 clads was carried out using field emissionscanning electron microscopy. Microhardness of the Inconel718 microwave clads was assessed using a Vickersmicrohardness tester at the load of 25 g and dwell time of 10s.The average microhardness in the developed clads was564±22 HV. The abrasive wear characteristics of the Inconel718 clads were analysed using a pin-on-disc arrangementagainst a standard abrasive paper of 320 grit size and werecompared to that of the SS-304 substrate. Normal loadsensitivity was analysed for 10-20 N in steps of 5 N. TheInconel 718 clads exhibited significant abrasive wearresistance, in the form of reduced material loss, attributedto the presence of various hard phases like chromium andmolybdenum carbides formed during cladding. Further, themechanism of material removal during abrasive wear of theInconel 718 clads was found to be dominantly micro-grooving.

INTRODUCTION

Engineering components with longer product life aredesirable for uninterrupted and economic service life of asystem. Surface degradation, wear in part icular, ofengineering components is very common, which leads toreduction in-service perfo rmance and the li fe of thecomponents. Abrasion or abrasive wear is caused due todisplacement of materials caused due to hard particles orembedding of hard particles between to surfaces movingwith a relative velocity or hard pro-turbulences on one orboth relatively moving surfaces. Hard particle may be productof processing, example silica, alumina or work hardened wearfragment from entry of dirt from outside. Chutes, hydraulicpresses with dirt, extruders, rock crushers etc. have surfacesembedded with hard particles may suffer wear due toabrasion. Fig. 1 illustrates various systems endangered withabrasion. Different physical parameters may be involved

depending on the wearing materials, operating conditionssuch as type of abrasive particles and angle of attack.Hardness rather than toughness is the deciding factor forabrasive wear resistance.

Fig.1: Tribological systems endangered withabrasive wear [1].

Stainless steel (SS-304) is one of the importantengineering materials used. But it suffers severe metallicwear, due to the formation of strong adhesive junctionsbetween the contact surfaces and severe surface/subsurfaceplastic deformation [2]. Hence efforts were made to developwear resistant surface on the commercial grade stainlesssteel (SS-304) using one of the commonly used super alloys,Inconel 718. While looking for novel processing techniques,energy efficiency and environment friendliness are twoimportant criteria. Microwave cladding is one such potentialtechnique which has been developed [3]. Inconel 718 is amost commonly used Fe-Ni based superalloy, which exhibitssuperior wear and corrosion resistance at high temperaturescoupled with high impact strength at cryogenic temperatureswhich make it a perfect material to be used in aggressiveconditions like turbine blades, jet engines etc. [4]. In thepresent work, microwave hybrid heating (MHH) was exploredto develop clads of Inconel 718 super alloy on stainless steelsubstrate (SS-304) to enhance its surface properties. Thedeveloped Inconel 718 clads were subjected tomicrohardness study using a Vickers microhardness tester.Further, in this study, abrasive wear behaviour of microwavedeveloped Inconel 718 clads has been compared to that of


the SS-304 substrate. The wear mechanisms of the developedmicrowave clads and SS-304 substrate were studied usingscanning electron microscopy (SEM).

EXPERIMENTAL PROCEDURE

Materials details

The present study was carried out using a domesticmicrowave applicator (Make: LG, Model: Solar Dom) at 900W and 2.45 GHz. Inconel powder with an average powderparticle size of 30 µm was used to develop clads onaustenitic stainless steel (SS-304) substrate using MHHtechnique. A typical SEM of the Inconel 718 powder isillustrated in Fig. 2. The SS-304 substrates were machinedto a size of 10 × 20 × 6 mm3 and were thoroughlyultrasonicated in an acetone bath. Inconel 718 powder waspreplaced manually on the substrate (SS-304) with anapproximate thickness of 1 mm. The elemental compositionsof the Inconel 718 powder and stainless steel (SS-304)substrate were determined using an electron probe microanalyser (EPMA, Make: Cameca, Model: SX-100). The

chemical compositions of Inconel 718 powder and SS-304substrate are presented in Table 1. The details of the MHHand cladding process are presented in detail elsewhere [5].Various processing parameters used in the currentinvestigation are presented in Table 2.

Table 2: Microwave cladding parameters.

Parameter Description

Powder particle size 30 mApplicator MultimodePowder preheat temperature 120OCOptimised power 900 WFrequency 2.45 GHzOptimised time of exposure 12 minutes

Characterisations of the clads

The developed clads were ultrasonicated in an acetonebath and were sectioned using a low speed diamond saw(Make- Chennai Metco, Model- Baincut LSS). The sectionedInconel 718 clads were cold mounted in an epoxy resin andwere polished using standard metallographic techniques toattain mirror finish. The microstructure of the microwaveInconel 718 clad was analysed using a SEM at an acceleratedvoltage of 20 kV (Make: FEI, Model: Quanta 200 FEG).Microhardness of the microwave clad was assessed on theclad substrate interface using a Vickers microhardness tester(Make: Chennai Metco, Model: Economet VH 1MD) at a testload of 25 g with dwell time of 10 s. The distance betweentwo successive indentations was kept about 100 m fromthe top of the clad towards clad substrate interface.

Abrasive wear testing

Wear significantly influences the performance of thetribological components in the system. The Inconel 718 cladsdeveloped on SS-304 were subjected to abrasive wear testat room temperature. The abrasive wear behaviour of theclads was investigated on a pin-on-disc tribometer (Make:Ducom India, Model TR20LE). The schematic of pin-in-disctribometer is shown in Fig. 3. Prior to sliding wear test thesurface was polished with abrasive papers of 1500 and 2000grits to maintain an initial surface roughness of Ra = 0.2 m.The clad of size 10 × 10 × 6 mm3 was used as the wear pinwhich was held against the rotating counter disc. Thecounter discs were firmly attached with the standard SiCabrasive paper of 320 grit (Make: 3M) to act as a countersurface for sliding wear evaluation. Wear tracks werechanged every 2 minutes to expose the clad surface to freshabrasion. Table 3 presents the details of the abrasive weartest. The worn samples were cleaned with acetone and hotdried prior to weight loss measurement. The weight loss wasmeasured using an electronic weighing balance (Make:Shimadzu Japan, Model: AUW. 220D) before and after thetest. The material removal mechanism was from the wornsurfaces was analysed using SEM.

Fig. 2: Typical SEM image of Inconel 718 powder.

Table 1: Chemical composition of Inconel 718 powderand SS-304 substrate in weight (%).

Element Inconel 718 powder SS-304 substrate

Fe 18.8 Bal.Cr 17.78 9.8

Ni 53.5 19.0

Nb 5.21 -Mo 2.92 -

Ti 0.55 -

Mn - 2.1Si - 0.74

C - 0.08

Others 1.033 0.16


Fig. 3: Schematic of abrasive wear test setup.

Table 3: Details of abrasive wear tests.

Parameters Description

Testing set up Pin-on-disc tribometer

Wear pin Inconel 718 clad.Thickness: 1 mmInitial roughness: 0.2 mSS-304.Initial roughness: 0.2 m

Counter disc 320 grit SiC abrasive paper

Sliding distance (m) 2000

Sliding velocity (m/s) 1

Normal load (N) 10, 15, 20

Lubrication condition Dry

Temperature (OC) Ambient temperature


Microstructural observations

A typical microstructure of clad obtained throughelectron microscopy is illustrated in Fig. 4. The developedclad exhibits perfect metallurgical bonding between themolten Inconel 718 clad powder and the SS-304 substrate.The developed clad were free from interfacial crackingattributed to vo lumetric heating associated wi th themicrowave heating process. Metallic carbides (chromiumcarbide, molybdenum carbide) were segregated at the grainboundaries in the clad layer as shown in the inset (Fig. 4).The columnar structure is also uniform throughout the cladlayer without any trace of semi-molten particles. A smoothtransition from substrate to clad zone is clearly observed.The inset BSE image in Fig. 4, the shows a further magnifiedview of the typical dendritic structure formed in thedeveloped clad. During MHH, the powder particles absorbmicrowaves at higher temperature due to increase skin depth[6]. On melting, a pool of molten layer will form on the

metallic substrate. Melting of substrate is however limitedto a very small depth only [6]. Thus, substrate interfacereaches the molten stage that facilitates the mutual diffusionof elements from the substrate to the molten powder layerand from the molten powder layer to the substrate in anarrow zone may be termed as dilution zone. Thus heatflow will take place from the molten clad layer to the metallicsubstrate. The steep thermal gradient prevailing at theinterface favours columnar dendritic growth in a directionopposite to the heat extraction. The intermetallic carbidespresent in the Inconel 718 clads to enhance its hightemperature strength attributed to their poor solubility in thematrix at elevated temperatures.

Fig.4: A typical SEM image of Inconel 718microwave clad.

Microhardness study

Microhardness assessment of the Inconel 718 clad wascarried out on the clad substrate interface. Fig. 5 illustratesthe microhardness distribution across a typical the cladcross-section. The average microhardness in the clad zonewas observed to be 564±22 HV [7]. The observedmicrohardness values were nearly uniform throughout theclad layer. This is attributed to uniform distribution ofintermetallic carbides in the clad layer as observed in themicrostructure of the clad (Fig. 4). Phases of chromiumcarbides are responsible for the increase in hardness of theclad. Observed microhardness in the interface wasapproximately 425 HV (Fig. 5). The microhardness of theinterface was in between the SS-304 substrate (316±14 HV)and the Inconel 718 clad. This interface acts as the dilutionzone to compensate for the two materials with high propertygradient. This helps in enhancing the service life of the clad.The morphology of typical indentations on the clad andsubstrate is illustrated in Fig. 5 (inset). The non symmetricaland small indentions in the clad zone indicate presence ofhard phases like chromium carbides which inhibit plastic flowof the material. On the other hand, classical metallicindentation was observed on the substrate (inset, Fig. 5).


Fig. 5: Vickers microhardness distribution across atypical section of Inconel 718 clad, Inset: Indentation

geometries in clad and substrate.

ABRASIVE WEAR STUDY

Inconel 718 clads were evaluated for abrasive wearbehaviour on pin-on- disc tribometer against a 320 gritabrasive paper as counter surface. The different parametersused in testing are listed in Table 3.The Inconel 718 cladsexhibited lower cumulative weight loss than the SS-304substrate. The clad surface resists wear more effectively thanSS-304 substrate which was attributed to the presence ofcoherent precipitate such as Ni3Ti, Ni3Al and chromiumcarbides as indicated in the XRD spectrum of the developedclad [5]. The cumulative weight loss characteristics underdifferent loading conditions indicate lower weight loss fromthe Inconel 718 clads than the SS-304 substrate undervarious loading conditions as shown in Fig. 6. Withincreasing load the wear rate decreases due to the formationof a steady oxide film while rubbing with the mating surfaces.Archards equation assumes that the wear volume increaseslinearly as the contact stress and the sliding distanceincrease. The experimental results show that the wear volumeincreased linearly as the contact stress increased, as

expected from Archards equation. The wear behaviouranalyses indicate that clads show better wear resistanceowing to dense microstructure formed due to volumetricheating nature of microwave heating.

Inconel 718 clads were evaluated for abrasive wearbehaviour on pin-on- disc tribometer against a 320 gritabrasive paper as counter surface. The different parametersused in testing are listed in Table 3.The Inconel 718 cladsexhibited lower cumulative weight loss than the SS-304substrate. The clad surface resists wear more effectively thanSS-304 substrate which was attributed to the presence ofcoherent precipitate such as Ni3Ti, Ni3Al and chromiumcarbides as indicated in the XRD spectrum of the developedclad [5]. The cumulative weight loss characteristics underdifferent loading conditions indicate lower weight loss fromthe Inconel 718 clads than the SS-304 substrate undervarious loading conditions as shown in Fig. 6. Withincreasing load the wear rate decreases due to the formationof a steady oxide film while rubbing with the mating surfaces.Archards equation assumes that the wear volume increaseslinearly as the contact stress and the sliding distanceincrease. The experimental results show that the wear volumeincreased linearly as the contact stress increased, asexpected from Archards equation. The wear behaviouranalyses indicate that clads show better wear resistanceowing to dense microstructure formed due to volumetricheating nature of microwave heating.

Fig.6: Cumulative weight loss characteristics as afunction of normal load.

Fig. 7: Wear characteristics as cumulative weightloss at 20 N.

Cumulative weight loss characteristics after every 500m of sliding under 20 N load is shown in Fig. 7. It can beobserved that the material loss from clad surface even duringrun-in phase (may be up to 500 m of sliding distance) is lowas compared to the SS-304 substrate. After the run-in-wearphase, the mating surface attains stability and the wearsurfaces of Inconel 718 clad and SS-304 substrate showexcellent stability up to the sliding distance of 1000 m and1500 m respectively. Fig. 7 shows that for Inconel 718 clad,relatively higher weight loss was observed during sliding


distance of 1000 m to 1500 m (as characterised by the 1>>2), while corresponding to that of SS-304. While beyond1500 m of sliding distance, weight loss from the clad surfacegets reduced significantly as indicated by 1


ABSTRACT

This paper presents the performance featuressegregated on the basis of identified antioxidant propertythrough a unique approach of optimal combination ofFriction Modifier [FM] and Viscosity Modifier [VM]. Thestudy includes determination of coefficient of friction, filmthickness, and oxidative stability of various FM-VMcombinations. Engine oils are required to reduce friction andmaintain adequate film strength between moving parts whilepossessing higher thermo-oxidative stability. Synergism forthe three aspects of reduced friction, higher film strength andincreased oxidation inhibition has been characterized for anidentified set of optimal combination for the development ofEnergy Efficient Engine Oils.

INTRODUCTION

Transport sector scenario is considered to be one ofthe frequently changing, primarily because of the continuousefforts for reducing hazardous emissions. Presently there arearound 700 million vehicles running throughout the worldwhich is expected to touch 2 billion by 2050 [1] out of whichby 2040, the projected number of highway vehicles in Indiawould be 206-309 million [2]. Global CO

2 regulations are

becoming more stringent than ever before and converging.About 19.64 pounds of CO

2 are produced from burning a

gallon of gasoline and about 22.38 pounds of CO2

are

produced by burning a gallon of diesel fuel [3]. Consideringthe energy consumption within the engine as shown in Fig.1, friction losses accounts for the major part (~48%) of theenergy loss generated in an engine [4].

Energy-efficient engine oils with significant fuel-economy have become increasingly important on accountof both the saving of natural resources and the environment[5-8]. The above fact and the trends in engine designs addonto higher stress on the engine oil. Engine oils, therefore,are required to reduce friction in the moving parts whilemaintaining adequate film strength. This has become moreimportant in view of the increasing trends towards lowviscosity engine oils for both gasoline and diesel enginesegments. Additionally the crankcase lubricant is alsorequired to possess high oxidative stability to counter theviscous drag arising out of the oxidative oil thickeningduring service.

An engine is a very complex system that at any onetime can have multiple frictional regimes occurringsimultaneously [9]. Reducing engine oil viscosity to decreasefriction in the hydrodynamic region will have a negativeimpact at the boundary/mixed region which can lead tofrictional losses and wear. Hence addressing one frictionalregime leaving the other cannot maximize all the potentialgains that may be possible. Viscosity modifiers should haveoptimum balance on viscosity, which is of prime importancefor low wear while having decreased viscosity contributionsat lower temperatures that is so very important for fueleconomy. Viscosity modifiers should also help to reducewear by forming a protective film on metal surfaces [10]. Thispaper attempts to built-up an optimal FM-VM combinationto result in synergism towards oxidative stability andtribological behavior.

TEST LUBRICANTS

The test lubricants comprise of matrix of 1 DI (DetergentInhibitor) x 2 FMs x 3 VMs additive system in Group III BaseOil. 2 FMs of the type Organo-molybdenum compound Fig. 1: Energy consumption developed in an engine

STUDY OF TRIBO-CHEMISTRY IN ESTABLISHING SYNERGY OFFRICTION MODIFIERS AND VISCOSITY MODIFIERS IN ENGINE OILS

Shiv Kumar Vabbina1, Anil Bhardwaj2, Sanjiv Kumar Mazumdar3* and Mukesh Saxena4

123 Indian Oil Corporation Limited, Research & Development Centre, Sector 13, Faridabad, Haryana, India 1210074 University of Petroleum & Energy Studies, Dept. of Mechanical Engineering, Dehradun Currently at University of Technology & Management, Shillong* Corresponding author (E-mail: [email protected])# Paper was presented in National Tribology Conference, 15-17 December 2014.

KEY WORDS: Friction Modifier; Viscosity Modifier; Oxidative Stability; Film Strength; Friction; Tribo-Chemistry; Engine Oils



one with S and the second without S, 3 VMs of type OCP(olefin copolymer) with 1 of the type DOCP (dispersant OCP)and 2 of the type nDOCP (non-dispersant OCP) the 2nDOCP differing in SSI (shear stability index). The engineoil samples optimized with the DI-FM-VM combinations arepresented in table 1. Viscometrics of all the optimized blends(table 2) have been maintained at similar level for bettercomparison.

EXPERIMENTAL DESIGN AND METHODS

The test lubricants formulated are tested for variousproperties as discussed below in the following tests.

EHD Film Thickness

An initial film of oil is placed on a glass disk and isrotated against a steel ball. The parameters of the test profileare temperature, load and rotation speed which are controlledby computer. The instrument measures the lubricant filmthickness properties in the contact formed between a ¾(19.05mm) diameter steel ball and a rotating glass disk byoptical interferometer.

SRV Coefficient of Friction

DIN 51834 is the standard test method for measuringCoefficient of Friction. The SRV Linear Oscillating tribometer[11] measures the friction phenomena between a steel balland plate after placing a sample of oil on plate. The steelball is made to vibrate/oscillate at a given frequency and aforce is applied according to the test method. The test profileincludes load, frequency and temperature which arecontrolled by computer. The SRV test can determine frictionbetween materials actually used in an engine (for example,by taking a slice of the cylinder liner and the piston rings).

Oxidation Induction time (OIT):

OIT is determined by PDSC instrument according toASTM D6186 [12] method, in which about 3-5 mg of samplein pan is subjected in pressurized DSC cell of 500 psi Oxygenpressure at a constant temperature of 210 °C. OIT is anaccelerated aging test which is often used to predict the longterm stability of hydrocarbon materials quickly. PDSC is anexcellent test to determine the thermo-oxidative behavior ofthe samples in a very less time. PDSC determines thestrength of the sample to inhibit oxidation under pressurizedoxygen at high temperatures.

Oxidation Onset time (OOT):

OOT is determined by DSC instrument according toASTM E2009 [13] method, in which about 3-5 mg of samplein pan is subjected in DSC cell with continuous flow ofOxygen at 50 ml/min with a temperature ramp of 10 oC/minutefrom 40-300 oC. OOT test is an excellent test to determinethe temperature exactly where the oxidation of the sample

starts. DSC test determines the thermo-oxidative behaviorof the samples.

Results and Discussion

New generation engine oils need to be more energyefficient while protecting the engine parts adequately. Theoptimized engine oil should, therefore, have adequate filmstrength with an ability to reduce friction between the parts.Blends optimized (illustrated in tables 1 and 2) have beenevaluated for their tribological behavior vis-à-vis coefficientof friction and mechanical film thickness.

EHD Film Thickness

EHD fi lm strength has been evaluated at twotemperatures viz., 60 oC and 100 oC. EHD film strength data,evaluated for combinations represented in table 1 anddetermined at 60 oC and 100 oC, is illustrated in Fig. 2. Typicalgraph of the EHD film thickness is given in Fig. 3.

Fig. 2 : EHD film thickness data on blends

Fig. 3: Typical graph of EHD film thickness


Examination of the graphical representation in referenceto the data presented in table 1 clearly indicates that filmthickness is directly influenced by the VM and the FMcombination. All the three VMs used have shown significantimprovement in the film thickness strength with FM 2 ascompared to FM 1 and blends without FM. Synergism ofindividual VM with FM in the film thickness is in the orderof VM 3 > VM 2 > VM 1. The Dispersant-VM has givenbetter performance in film thickness than Non-DispersantVMs. It has also been observed that VM with high SSI hasability to form good film strength than the VM having lowerSSI among the Non-Dispersant VMs.

Coefficient of Friction

Coefficient of Friction has also been determined at twotemperatures viz., 60 oC and 100 oC. The load of the test wasmaintained at 300N with 1mm amplitude and was run for 1hour at the test temperature.

as compared to FM 1. The possible reason for thisadvantage may be due to the presence of sulphur in FM 2.Synergism for FM and VM combination was seen inBlend I (FM 2, VM 3) combination. The typical graphicalmanifestation is illustrated in Fig. 5.

PDSC Oxidation Induction Time (OIT)

The above blends have, further, been evaluated forOxidation Induction Time by PDSC. The typical graphobtained by PDSC instruments for these blends is given inFig. 6.

Fig. 6: PDSC graph of blends showing OIT

Oxidation Induction time is the time in minutes reportedup to which the blend can withstand oxidation underpressure at high temperatures. Hence, higher the OIT betteris the thermo-oxidative stability of the test sample. It is,therefore, evident that the oxidation stability of blends isgreatly enhanced by the addition of FM 2 when comparedto FM 1, while FM1 did not exhibit very significantimprovement over the blends without FM. These results arein line with the results obtained previously in EHD filmthickness and SRV coefficient of friction. Hence, it is justifiedto conclude that in this study positive effect of frictionmodifier in enhancing the oxidation stability of the engineoil is established. PDSC can be used as a guiding tool foridentifying such blends with optimal thermo-oxidativestability that can not only reduce friction but also form agood stable film thickness between the engines movingparts.

DSC Onset Oxidation Temperature (OOT)

To understand the possible reason for difference inperformance of the selected FM blend against all the otherblends, both the FMs have been added in differentconcentrations in the base oil combinations used in theblends for DSC studies. FM 1 when mixed with base oil wasnot miscible above 0.6 % and resulted in separation beyondthe threshold concentration.

Fig. 4 : Coefficient of Friction for the blends

Fig. 5 : Coefficient of friction graph from the instrument

Traces presented in Fig. 4 indicate the coefficient offriction to be decreasing with the addition of FM to theblends A, D & G. The blends B, E & H are optimized withFM 1 and the blends C, F & I are optimized with FM 2. FM2 has been found to be more effective in reducing friction


Fig. 7: Onset Oxidation Temperatures of Base oil dopedwith FM 1

The base oil blends with concentrations starting from0.1 to 0.6%wt in the incremental step of 0.1 %wt of two FMshave been subjected to evaluation for oxidative stability. TheOOT as calculated from DSC studies are shown in Fig. 7 &8 for FM 1 & FM 2 respectively.

Synergism in film strength and friction reductionshown by FM/VM combination is due to the oxidativeinhibition characteristic of FM.

Presence of sulphur in FM may be the possible reasonfor oxidation inhibition characteristic.

PDSC & DSC along with Tribo-testing routines havebeen found to be helpful in judging the optimalcombinations of VM & FM for developing EnergyEfficient Engine Oils.

ACKNOWLEDGEMENTS

Authors are thankful to the management of Indian OilR&D, Faridabad, India for granting permission to Mr. ShivKumar Vabbina for carrying out his doctoral program withUPES and for permitting to submit this paper for publicationin the Indian Journal of Tribology.

Table 1: Blend compositions with different FM & VM

Blend Compositions

A Base Oil + Additive Package + VM 1

B Base Oil + Additive Package + VM 1 + FM 1

C Base Oil + Additive Package + VM 1 + FM 2

D Base Oil + Additive Package + VM 2

E Base Oil + Additive Package + VM 2 + FM 1

F Base Oil + Additive Package + VM 2 + FM 2

G Base Oil + Additive Package + VM 3

H Base Oil + Additive Package + VM 3 + FM 1

I Base Oil + Additive Package + VM 3 + FM 2

VM 1&2 Non Dispersant Copolymer with differentSSI (25 & 35)

VM 3 Dispersant Copolymer with 24 SSI

FM 1 Organo Molybdenum compound withoutsulphur

FM 2 Organo Molybdenum compound with sulphur

Table 2: Viscometric data of Blends

Blend KV @ 40oC KV @ 60 oC KV @ 100 oC VI

A 61.62 30.18 10.76 167

B 61.62 30.18 10.76 167

C 61.62 30.18 10.76 167

D 69.71 32.26 10.76 144

E 69.71 32.26 10.76 144

F 69.71 32.26 10.76 144

G 66.47 31.71 10.95 156

H 66.47 31.71 10.95 156

I 66.47 31.71 10.95 156

Fig. 8: Onset Oxidation Temperatures of Base oildoped with FM 2

Comparison of the values for OOT tabulated in therespective illustrations in Fig. 7 & 8 indicate the oxidationstability of the base blend with FM 2 to be superior to thosewith FM 1. Further additions of FM1 in base oils have beenfound to have negative effect on oxidation stability. Whilethe oxidation stability has been found to be enhanced withincreasing concentration of FM 2, the trend start reversingbeyond a concentrat ion in excess of 0.7 % wt. Thisexperiment protocol has, therefore, been helpful in findingthe optimum concentration of the FM 2 in the formulatedengine oil

CONCLUSIONS

Blends with higher SSI VMs form thicker films thanlower SSI VMs.

Dispersant-VMs blends have better film formingcapability than non-Dispersant VMs.


REFERENCES

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RESEARCH ARTICLE

SLURRY EROSIVE WEAR BEHAVIOR OF CARBON FIBRE RODREINFORCED Al6061 HEAT TREATED COMPOSITES

Adarsha H1 and Padmapriya N2*

1Dept. of Mechanical Engineering, R V College of Engineering, Bangalore- 5600592 Dept. of Mechanical Engineering, PES Institute of Technology, Bangalore-560085*Corresponding author (E-mail: [email protected])

KEY WORDS: Metal Matrix Composites; Erosion; Corrosion; Carbon Fibre Rods.

ABSTRACT

Metall ic coated carbon fibre rod reinforcedAl6061composites were fabricated by liquid metallurgy routefollowed by T6 heat treatment technique. Carbon fibre rodsof 4mm and 6mm diameter were used as reinforcement. Thedeveloped composites were subjected to microstructure andsand slurry erosive wear studies. The influence ofexperimental parameters such as, slurry concentration, slurryspeed rotation, size of impinging particles and the testduration on slurry erosive wear behavior of developedcomposites have been studied. Results of the test reveal thatthe developed composites exhibited an improvement in wearresistance when compared with matrix alloy under identicaltest conditions. Scanning electron microscopy examinationswere carried out to validate the possible type of wearmechanisms.

INTRODUCTION

Aluminium matrix lightweight materials are in greatdemand in aerospace, automotive, defense and marineapplications. This demand is because of high thrust andpower operating conditions being imposed on many ofthe components necessitating the urgent need indeveloping materials which possess high strength andelastic modulus to weight ratio .The class of materials whichpossess these material characteristics are the fibre reinforcedcomposite materials. Among these, aluminium matrix carbonfibre reinforced composites are one of the serious contendersas potential materials in most of the engineering applicationsmentioned earlier. Most of the researchers have reportedon the development and characterization of short carbonfibre reinforced aluminium metal matrix composites [1-3]. Themanufacturing routes and the process parameters are mostsignificant in dictating the final mechanical properties of thecomposite product [4-5]. The reaction between carbon fibresand aluminium is one of the serious challenges that need

urgent attention as brittleness due to formation of aluminiumcarbide is inherent leading to severe deterioration inmechanical strength and ductility [6]. In recent years, thisproblem has been overcome by use of metallic coatings oncarbon fibres, either with copper or nickel [7-8]. Currently,short carbon fibres are being replaced by carbon fibre rodswhich possess excellent stiffness which are much higherthan individual carbon fibres and are being used as loadbearing members in many high-tech applications. Although,carbon fibre rods are good candidates as reinforcementmaterial in metal matrices, there are no reports as regardsdevelopment and characterization of carbon fibre reinforcedcomposites. In the light of the above work, this paperfocuses on development and assessment of slurry erosivewear of carbon fibre rod reinforces composites and exploringthe possibilities of use of these exotic composite materialsfor torbido blades, which are subjected to severe slurryerosive wear.

EXPERIMENTAL/COMPUTATIONAL DETAILS

Al 6061 with standard chemical composition as reportedin Table 1 was used as matrix alloy. Carbon fibre rods of 4mmand 6mm diameter were used as reinforcement. The carbonfibre rods were subjected to electroless Ni-P coating followedby electroplating of copper. This treatment was performedto avoid the interfacial reaction between carbon fibre rodsand matrix alloy. Copper coated carbon fibre rods werearranged in circular array and molten metal of Al 6061 waspoured into the preheated die containing carbon fibre rods.The pouring temperature of 710oC was adopted. Thedeveloped composites were subjected to metallographicstudies, micro hardness tests and slurry erosive wear tests.Sand slurry containing Si sand particles of size ranging from312- 612 micron was used. Further 3.5% sodium chloride wasmaintained in the slurry to simulate the marine environment.The rotational speeds were varied 500rpm to 1500rpm. Thesand concentration in slurry was varied from 100-500g/L. The

Table.1

Elements Si Fe Cu Mn Ni Pb Zn Ti Sn Mg Cr Al

Percentage % 0.43 0.43 0.24 0.139


Microhardness Analysis

Fig.2 shows the variation of microhardness of cast Al6061 matrix alloy and the developed composites before andafter T6 heat treatment. The microhardness of the developedcomposites increases with the increase in volume percentageof carbon fibres. This trend is in agreement with several otherresearchers [10].

The enhancement in microhardness is 20% and 26%before heat treatment and 23% and 30% after T6 heattreatment for 4mm C

f and 6mm C

f rod composites respectively

when compared with the matrix alloy. This can be attributedto the reduction in grain size of the developed composites.Smaller the grain structure greater will be the hardness ofthe composites due to reduction in dislocation mobility [11].

worn surfaces of the matrix alloy and the developedcomposites were subjected to SEM studies.

RESULTS & DISCUSSIONS

Microstructural analysis

The influence of copper coated carbon fibre rods asreinforcement in the improvement of microstructure has beendiscussed in our earlier works [9]. Optical microscope imagesof the developed composites and matrix alloy after heattreatment are shown in Fig.1. The size of the grains in thedeveloped composites are smaller than the grains observedin the matrix alloy, eventually leading to an increase inhardness of the material and also providing superiormechanical properties in comparison with the matrix alloy.This can be attributed to the decrease in porosity andimproved cohesiveness of the aluminum grains in thecomposites.

(a) Heat Treated Al6061alloy

(b) Heat Treated Al6061-4mm Cf rod composite

(c) Heat Treated Al6061-6mm Cf rod composite

Fig.1: Variation of grain size of as castAl6061 alloy andits composites after T6 heat treatment

Fig. 2: Variation of Microhardness of Al6061 matrix alloyand its composites

3.3. Slurry Wear Loss

3.3.1. Effect of Reinforcement

Fig.3. shows variation of slurry erosive wear loss of Al6061 matrix alloy and the developed composites before andafter T6 heat treatment. It is observed that there is significantreduction in the wear rate of the developed compositeswhen compared with the matrix alloy. For the specified testconditions, there is a reduction in weight loss by 34% and52% before heat treatment and 42% and 61% after T6 heattreatment for 4mm C

f and 6mm C

f rod composites respectively

when compared with the matrix alloy. The improved slurryerosive wear resistance when compared with the matrix alloycan be attributed to the following two reasons.

The presence of carbon fibres in the compositesreduces the effective area of aluminium alloy in thecomposite exposed to slurry bath and reduces theformation of corrosion pits on the surface of thedeveloped composites leading to cracking of grainsin the matrix alloy [12].

Aluminium alloy forms the highly stable passiveoxide layer after reacting with water when exposed


to NaCl solution [13]. This oxide layer providesinsulation to the test surface from erosion corrosiontype of wear behavior.

Fig. 5: Variation of slurry erosive weight loss with slurryconcentration

For the developed composites and the matrix alloy it isobserved that there is an increase in weight loss with theincrease in slurry concentration. However the developedcomposites exhibit a reduction in weight loss when comparedwith the matrix alloy.

The increase in wear loss of the test sample with theincrease in concentration is due to higher chances of sandparticles coming in contact with the test sample.

Effect of Rotational Speed

The slurry erosive wear loss increases with increase inrotational speed for both heat treated and as cast matrix alloyand developed composites as shown in Fig 6. The increasedweight loss with increased rotational speed can be attributedto increased kinetic energy of the sand particles present inthe slurry. This increased kinetic energy of the sand particlesin the slurry will result in increased extent of plasticdeformation at the surfaces of the matrix alloy and developed

Fig. 3: Effect of Reinforcement on Weight Loss

The surface damage of the slurry eroded surfaces ofthe composites with different volume fractions are shownin Fig.4. It is observed that the composites with highervolume fractions of carbon fibres exhibit less surface damagewhen compared with the matrix alloy.

(a) Heat Treated Al6061alloy

(b) Heat Treated Al6061 - 4mm Cf rod composite

Fig. 4 : SEM of Al6061 alloy and its composites(Test Duration: 5Hrs, Slurry Concentration: 100g/Ltr,

Sand Size 312µm)

3.3.2. Effect of Slurry Concentration

The variation of weight loss of Al 6061 matrix alloy andthe developed composites before and after heat treatment

with the variation of concentration of slurry solution is asshown in Fig.5.

Fig.6: Variation of slurry erosive weight loss withrotational speed


composites. Greater the extent of plastic deformation at thesurface, larger is the material removal leading to higher slurryerosive wear loss. Further, at all the studied rotational speed,heat treatment has beneficial effects on both matrix alloy andthe composites. However heat treated compositescontaining carbon fibre rods of 6mm diameter possess theleast slurry erosive wear loss. This can be attributed to thefact that carbon fibres acting as reinforcement in matrix alloyretards the plastic deformation.

Effect of Particle SizeThe variation of slurry erosion weight loss with

increase in erodent particle size is shown in Fig.7. It isobserved that the slurry erosive wear loss increases withincrease in particle size of both matrix and developedcomposites under both heat treated and un-heat treatedconditions. This can be attributed to the fact that increaseerodent particle size results in increased contact surface areawith the surface of the samples. Larger the contact areahigher will be stress intensity at the surfaces resulting incracking eventually leading to higher material removal.

However heat treated composites containing 6mmcarbon fibre rod possesses least slurry erosive wear loss forall erodent particle sizes studied.

Institutions, Dr. K.N.B. Murthy, Director, PESIT, Bangalorein carrying out this work.

REFERENCES

1. H. Naji, S.M. Zebarjad and S.A. Sajjadi, The effectsof volume percent and aspect ratio of carbon fiber onfracture toughness of reinforced aluminum matrixcomposites, Materials Science and Engineering: A,Vol. 486 (2008), P. 413420.

2. Liu Lei, Li Weiwei, Tang Yiping, Shen Bin and HuWenbin, Friction and wear properties of short carbonfiber reinforced aluminum matrix composites, Wear,Vol. 266 (2009), P.733738.

3. Zeng Jun , Xu Jinchenga, Hua Wei , Xia Long, DengXiaoyan, Wang Sen, Tao Peng, Ma Xiaoming, YaoJing, Jiang Chao and Lin Lei, Wear performance ofthe lead free tin bronze matrix composite reinforced byshort carbon fibers, Applied Surface Science, Vol. 255(2009), P. 66476651.

4. B.K. Prasad, K.Venkateshwaralu, O.P. Modi, S. Das,A.K. Jha, R.Das Gupta and A.H. Yegneshwaran,Effects if SiC dispersion on sliding wear

characteristics of an Al-Cu alloy, in: InternationalConference on Aluminium, INCAL98, New Delhi,(1998), P. 9-16.

5. C.S.Ramesh, Mir Safiulla, and A.Ramachandra,Mechanical properties of extruded Al6061-CeO

2

composites, Proceedings of International Conferenceon Manufacturing Science and Technology, Melaka,Malaysia, 2006, P. 315-318.

6. Naji.H, Zebarjad.S.M, Sajjadi.S.A, The effects ofvolume percent and aspect ratio of carbon fiber onfracture toughness of reinforced aluminum matrixcomposites, Material Science Engineering A, Vol. 486(2008), P. 41320.

7. Rams.J, Urena.A, Escalera.M.D and Sanchez.M,Electroless nickel coated short carbon fibres in

aluminium matrix composites, Composites: Part A,Vol. 38 (2007), P.56675.

8. Gupta Nikhi l, Nguyen Nguyen.Q and RohatgiPradeep.K, Analysis of active cooling through nickelcoated carbon fibers in the solidification processingof aluminum matrix composites, Composites: Part B,Vol. 42 (2011), P.91625.

9. C.S.Ramesh, H.Adarsha, Ashutosh Gupta and LokeshSwami, Surface modification of carbon fibre rods,STLE Annual Meeting & Exhibition, Detroit, Michigan,USA, 2013.

10. Ramesh.C.S and Keshavamurthy.R, Influence offorging on mechanical properties of NiP coated Si

3N

4

reinforced Al6061 composites, Material ScienceEngineering: A, Vol. 551 (2012), P. 5966.

Fig.7. Variation of slurry erosive weight loss with erodentsand particle size

CONCLUSIONS

Al 6061 carbon fibre rod reinforced composites possesssuperior slurry erosive wear resistance when compared withmatrix alloy. The slurry erosive wear resistance of thedeveloped composites increases with increase in diameterof carbon fibre rods. Further, T6 heat treatment results inincreased slurry erosive wear resistance of both the matrixalloy and developed composites.

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the cooperationand support extended by Prof.D.Jawahar, CEO, PES


11. Urena. A, J. Rams, M.Campo and M. Sanchez, Effectof reinforcement coatings on the dry sliding wearbehaviour of aluminium/SiC particles/carbonfibres hybrid composites, Wear, Vol. 266 (2009),P. 1128-1136.

12. H.Chen and A.T.Alpas, Wear of aluminium matrixcomposites reinforced with Nickel coated carbonfibers, Wear, Vol. 1-2 (1996), P. 186-198.

13. Davis. J.R, Aluminium and Aluminium Alloys, A.MSpeciality Handbook, A.S.M International, 1993, P.579.


RESEARCH ARTICLE

THEORETICAL AND EXPERIMENTAL STUDIES ON THETRIBOLOGICAL BEHAVIOR OF SAPS-FREE SALICYLALDEHYDE

PROPANOYLHYDRAZONE SCHIFF BASE AND ITSCU (ll) COMPLEX IN PARAFFIN OIL FOR STEEL-STEEL CONTACT

Vinay Jaiswal1, Kalyani1, Rashmi B. Rastogi*1 and Rajesh Kumar2

1Department of Chemistry, Indian Institute of Technology (Banaras Hindu University), Varanasi-221005, India2Department of Mechanical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi-221005, India*Corresponding author (E-mail: [email protected])

KEY WORDS: Low SAPS antiwear additives; Copper complex; Surface characterization: AFM; XPS; Tribochemistry andQuantum chemical calculations

ABSTRACT

1) Background: With a view to develop environmentfriendly antiwear addit ives, Su lfated Ash,Phosphorous and Sulfur (SAPS) free ligandsalicylaldehydepro-panoylhydrazone (H-Sph) and itscopper (II) complex [Cu(Sph)

2] has been synthesized.

2) Experimental: Tribological behavior of theseadditives has been evaluated in paraffin oil using four-ball tester. All the tribological tests have beenperformed at their optimized concentration (1%w/v)and by varying load for 30 min duration and varyingtest durations at 392N load. The performanceevaluation of these additives has been correlated withthe theoretical calculations using quantum chemicalcalculations.

3) Results: On the basis o f different tribologicalparameters like mean wear scar diameter (MWD), meanwear volume (MWV), friction coefficient and wearrates, copper (II) complex exhibits excellent tribologicalbehavior than H-Sph and ZDDP in paraffin oil alone.Copper complex effectively enhances antiwearproperties of base oil and possesses high loadcarrying capacity in comparison to the conventionalzinc dibutyldithiophosphate (ZDDP)/H-Sph alone.

4) Discussion: The Atomic Force Microscopy images ofworn surface lubricated with copper complex showdrastic decrease in surface roughness in comparisonto H-Sph/ZDDP alone. The tribochemistry of coppercomplex with metal surface has been investigatedusing X-ray Photoelectron Spectroscopy (XPS) whichshows protective tribofilms is made up of CuO, Cu

2O,

Fe2O

3, Fe

3O

4 and decomposition product of nitrogen.

Quantum chemical calculations for the interactions ofstudied additives with iron surface support a verygood correlation with experimental results.

5) Conclusions: As lubricant additives, both H-Sph and[Cu(Sph)

2] markedly improve the friction and wear

propert ies of base oil. These addit ives offerenvironment friendly alternative to high-SAPScontaining conventional ZDDP and have potential todevelop for lubricant applications.

INTRODUCTION

The efficiency of mechanical devices is stronglyreduced due to friction and wear between moving surfaces.Lubricants play an important role towards reduction infriction and wear between sliding surfaces by interposing athin film. The chemical composition and strength ofinterfacial film depends on the molecular structure of theantiwear additives. In order to increase the mechanicalefficiency of a machine, an appropriate additive should beadded to a lubricant to minimize the material loss. Theefficiency of an additive depends on its ability to form asufficiently hard and adherent protective film on the slidingsurfaces. This ability is related to their action mechanismthrough physical adsorption and/or chemisorption. Asreported earlier,1-3 the performance of an additive dependsupon: (i) the polarity of its functional groups, (ii) acomposition of chemically active elements, (iii) the reactivityof the decomposition products and (iv) the chemical activityof the metal surfaces. In boundary or mixed lubrication,under extreme conditions of high load and temperature, theseadditives undergo decomposition to form protective tribofilmthrough chemical reactions thereby prevent direct metal-to-metal contact.2,3 This minimizes friction and wear of theinteracting surfaces.

A critical examination of literature reveals that severalcategories of organic compounds such asdi thiodihydrazodicarbonamides, dithiocarbamates,triphenylphosphothionates and dialkyldithiophosphates andtheir metal complexes with molybdenum, tungsten,lanthanum, zinc etc. have been used as antiwear additives.4-



7 Among these types o f additives, zincdialkyldithiophosphates (ZDDP) have been widely used asmultifunctional lubricant additives and especially found tobe very effective for antiwear and antioxidation properties.In spite of their tremendous potentiality towards antifrictionand antiwear properties, it has some negative impact on theengine, human health as well as to the environment. Thus,high level of the sulphated ash, phosphorous and sulfurcontent (SAPS) of ZDDP limits its exhaustive application inautomotive industries. Over the last decade, concertedefforts have been made by both researchers and industriestowards developing new additives to replace the ZDDPwithout compromising friction and wear performances. Inorder to partially replace ZDDP, several classes ofcompounds such as Schiff bases,8 heterocyclic compounds,9

organoborates10 and metal complexes11 have beenextensively studied. Being the biologically active material,Schiff bases and their copper complexes are frequently usedas antitumor, antibacterial, antifungal and anticancer drugs.12

Schiff base copper complexes have good thermal stabilitywith decomposition temperature above 200°C. Therefore, itseems worthwhile to design and develop zero/low SAPScopper complexes which are environment friendly butpossess comparable tribological behavior to that ofconventional high SAPS containing ZDDP.

In the present communication, we report synthesis andtribological invest igat ions of salicylaldehydepro-panoylhydrazone Schiff base and its copper (II) complex inparaffin oil using four-ball lubricant tester. It is anticipatedthat the lubricant formulation of Schiff base copper complexin paraffin oil may provide good antiwear properties by virtueof forming protective in-situ tribochemical film at steel-steelinterface. In addition to this, structure-activity relationshipof the Schiff base and its copper complex with the ironsurface using quantum chemical calculations has to be donein order to correlate their experimentally obtained tribologicalbehavior with the theoretical one.

EXPERIMENTAL DETAILS

2.1 Chemicals

The starting materials salicylaldehyde (98%, SigmaAldrich), hydrazine hydrate (80%, Merck) and copper acetate(98%, Merck) were used to synthesize the Schiff base ligandand its copper complex. All other chemicals and solventsused in this work were of AR grade and used without furtherpurification.

The lubricating base oil, neutral liquid paraffin oil(Qualigens Fine Chemicals, Mumbai, India) having specificgravity 0.82 at 25OC, kinematic viscosity at 40OC and 100OC,30 and 5.5 cSt respectively, viscosity index 122, cloud point-2OC, pour point -8OC, flash point 180OC and fire point 200OC,was used without further purification.

2.2. Synthesis and characterization of lubricant additives

2.2.1. Salicylaldehydepropanoylhydrazine Schiff baseligand (H-Sph)

The Schiff base ligand, salicylaldehydepro-panoylhydrazone (H-Sph) was synthesized by reactinganhydrous ethanolic solution (50 ml) of salicylaldehyde(0.02mol) was added drop wise to a round bottom flask containingethanolic solution (50 ml) of propanoic acid hydrazide (0.02mol). The reaction mixture was refluxed for 5h (Scheme 1).The progress of the reaction was monitored by TLC. Aftercooling at room temperature, the obtained light pink colouredprecipitate was filtered on Büchner funnel, washed severaltimes with ethanol, recrystallized with methanol and thendried in vacuo. Yield (89%). M.p.170 oC. Anal. Calc. forC

10H

12O

2N

2 (192.089): C, 62.470; H, 6.295; N, 14.579. Found:

C, 62.87; H, 6.46; N, 14.41%. IR ( cm-1, KBr): (OH) 3428b;(NH) 3201s; (C=O) 1677s; (C=N) 1654s; (NN) 1022w.1H NMR (DMSO-d

6; ppm): 11.574 (1H, OH); 11.205 (1H,

NH); 10.142 (1H, HC=N); 8.334-6.827 (4H, aromatic protons);2.270-2.194 (2H, -CH

2); 1.106-1.036 (3H, -CH

3) . 13C NMR

(DMSO-d6; ppm): 178.723 (C=O); 174.553 (C1); 169.204(-

C=N); 157.262-116.088 (aromatic protons); 127.121(CH2);

9.460 (CH3).

Scheme 1: Synthesis of Schiff base ligand derived frompropanoylhydrazide with salicylaldehyde

2.2.2. Synthesis of copper (II) complex [Cu(Sph)2]

Copper (II) complex of H-Sph ligand was synthesizedby reacting 50 ml methanol ic solut ion of theCu(CH

3COO)

2.H

2O (10mmol) with salicylaldehydepro-

panoylhydrazone (H-Sph) (20 mmol) solution in hotmethanol (25 ml) in 1:2 (M:L) molar ratio in a round bottomflask (Scheme 2). On stirring the reaction mixture at roomtemperature, Cu (II) complex was precipitated immediately.The complex was filtered in a G-4 glass crucible, washedseveral times with methanol followed by diethyl ether anddried in vacuo. Green, yield (76%). M.p. >250oC. Anal. Calc.for C

20H

22N

4O

4Cu (445.093): Cu, 14.138; C, 53.921; H, 4.981;

N, 12.584. Found: Cu, 14.561; C, 54.455; H, 4.198; N, 12.238%.IR ( cm-1, KBr): (C=N) 1621s; (C-O-) 1342s; (NN) 1039w.UV-Vis (DMSO, nm): 642.

Scheme 2: Synthesis of Schiff base copper (II) complex


2.3. Tribological Characterization

2.3.1. Sample Preparation

Paraffin oi l blends of Schiff bases havingconcentrations 0.00, 0.25, 0.5, 0.75 and 1.0 % (w/v) were madeby

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