performance evaluation of cvd coated tool by … · 2015-04-10 · performance evaluation of cvd...

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Int. J. Mech. Eng. & Rob. Res. 2014 Sushil D Ghodam, 2014

ISSN 2278 – 0149 www.ijmerr.com

Vol. 3, No. 3, July, 2014

© 2014 IJMERR. All Rights Reserved

Research Paper

PERFORMANCE EVALUATION OF CVD COATED

TOOL BY MEASURING TEMPERATURE USING

TOOL-WORK THERMOCOUPLE

Sushil D Ghodam1*

*Corresponding Author: Sushil D Ghodam � [email protected]

A continuous advancement and development in manufacturing industry demands the high speedmachining at less time which improves the efficiency of the machining. The hard to machinematerial put the limitation to the cutting speed and generates a lot of hear during machining.Due to machining of these hard materials,tool experiences a high temperature at the cuttingpoint which causes the tool to fail due to plastic deformation, change in mechanical propertiesor fracture failure of the tool. To avoid this generation of temperature, coating of TiN/TiC/Al2O3

has been used. In this paper, CVD coated tool is used for experimentation and the interfacetemperature is measured using tool work thermocouple. The nature of temperature with respectto different cutting speed and feed rate is explained.

Keywords: Tool-work thermocouple, CVD coating, Temperature measurement

INTRODUCTION

The mechanical work required for machiningis highly converted into the heat which causesnumber of technical and mechanicalproblems of machining. The importance ofknowledge on the temperature gradientandits distribution within the cutting zone resultingfrom changes in the cutting conditions is wellrecognized due to severe effects on the tooland work piece materials properties and aconsiderable influence on the tool wear (X LLiu et al., 2002); (W Grzesik and P Nieslony,2000). In general, three regions of intensive

1 M.Tech. Student, Production Engineering, Government College of Engineering, Amravati, (M.S.) India.

heat generation are distinguished, namely theprimary shear zone, the tool-chipinterface orthe secondary deformation zone and the tool-work piece interface.

Heat is removed from the primary,secondary and tertiaryzones by the chip, thetool and the work piece. Figure 1 schemati-cally shows this dissipation of heat. Thetemperature rise in the cutting tool is mainlydue to the secondary heat source, but theprimary heat source also contributes towardsthe temperature rise of the cutting tool andindirectly affects the temperature distribution

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on the tool rake face (N A Abukhshim et al.,2005; L B Abhang and M Hameedullah,2012).

Figure 1: Zones of Heat GenerationDuring the Metal Cutting Process

During the process, part of the heatgenerated at the shear plane flows byconvection into the chip and then through theinterface zone into the cutting tool. Therefore,the heat generated at the shear zone affectsthe temperature distributions of both the tooland the chip sides of the tool- chip interface,and the temperature rise on the tool rake faceis due to the combined effect of the heatgenerated in the primary and secondaryzones (L B Abhang and M Hameedullah,2012).

Heat flow in a tool is known inthermodynamics as heat conduction. Itsbehavior is obviously expressed by usingFourier’s law of conduction which is given by:

q = K (dT/dx)

Where q is heat flux (W/m2), K is thermalconductivity (W/mK), dT is difference intemperature and dx is the linear distanceperpendicular to which the flow oftemperature takes place (W Grzesik et al.,2004).

EXPERIMENTAL PROCEDURE

The cutting experiments were conductedonHMT heavy duty lathe LTM-20. Acommercially available CVD coated turninginsert CNMG 120408 PR 4225 and uncoatedtungsten carbide insert CNMG 120404 gradeK313 were used to compare the temperatureobtained during machining. The machiningwas performed using work piece EN8 alloysteel (250 mm long and 45 mm diameter).

Among the various temperature mea-suring techniques, tool-work thermocouplewas used to measure the interfacetemperature. Figure 2 schematically showsthe principle of tool-work thermocoupletechnique. The tool-work thermocouple workson the principle of see beck effect whichstates that if there is temperature differencebetween two junctions of dissimilar metalsthen an emf is produce between thosemetals. In this case tool and workcompromise two dissimilar metal and coldend of tool and work piece acts as onejunction whereas hot junction is cutting zone.The emf is produced only when the circuit iscomplete i.e. tool and work piece are incontact. The tool and work piece wereinsulated from the lathe machine using micaas an insulating material.

Figure 2: Tool-work Thermocouple Setup

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In this work, calibration of the tool workthermocouple was carried out by using aheating coil. This set-up is similar to one usedby (Abhijeet Amritkaret et al., 2012), in whichworkpiece was directly calibrated with thetool.

Figure 3 shows the calibration set-up fortool-work thermocouple. In this set-up,Junction of tool and work piece was connec-ted to the milli Voltmeter and also K-typeAlumel-Chromel thermocouple was connec-ted to the heating rod. The temperature indi-cator was used to display the temperature ofheating rod sensed by the Al-Cr thermo-couple.

Figure 3: Calibration Set-up ofa Tool-work Thermocouple

EXPERIMENTAL RESULTS

The primary objective of this test was toevaluate and compare the performance of aCVD coated Tungsten carbide insert withuncoated Tungsten Carbide turning insert.For this purpose cutting tests were conductedat cutting speeds (m/min) 35.32, 59.34,100.32 and 169.56 m/min and the depth ofcut was kept constant (1 mm) whereas thefeed rate (mm/rev) was varied as 0.83, 1.04,1.25 and 1.65 mm/rev. Using this cutting con-ditions the value of mV is measured on HMTheavy duty lathe which was further used tocalibrate the temperature obtained duringmachining of EN8 alloy steel.

The calibration curve obtained for un-coated and CVD coated Tungsten carbideinsert is shown in Figure 4 and Figure 5 re-spectively.

Figure 4: Calibration Curve forUncoated WC Tool

The nature of temperature obtained at cut-ting point of insert is represented with respectto different cutting speeds at various feedrate. Figure 6 represents the temperature vs.cutting speed curve at feed rate 0.83 (mm/rev). For Vc= 35.32 m/min, the temperaturedifference between uncoated and coated toolwas less but when cutting speed increasesfrom 35.32 m/min to 169.56 m/min, the un-coated tool experiences a higher amount oftemperature as compared to coated tool. ForVc = 35.32 m/min, coated tool experience8°C less temperature than the uncoated toolwhereas at Vc = 169.56 m/min this differencein temperature increases upto 80°C.

Figure 5: Calibration Curve forCVD Coated WC Tool

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Figure 6: Influence of Cutting Speed onTool Temperature at f=0.83 mm/rev

The similar results were obtained for feed rate1.04, 1.25 and 1.65 mm/rev. which are shownby Figures 7, 8 and 9 respectively.




It was observed at f=1.65 mm/rev, Vc=35.32 m/min, the temperature differencebetween coated and uncoated tool washigher i.e. 32°C as compared to the readingsobtained at f=0.83 mm/rev, Vc= 35.32 m/mini.e. 8 °C. At f=1.65 mm/rev,Vc=169.56 m/minthe temperature difference for betweencoated and uncoated tool was higher i.e.82°C as compared to the readings obtainedat f=0.83 mm/rev, Vc= 169.56 m/min i.e. 80°Cbut this difference is very less. Hence athigher cutting speed the coated tool found tobe efficient due to its heat resistive ability.

The heat generation per unit area withrespect to cutting speed by varying feed ratefrom 0.83 mm/rev to 169.56 mm/rev is shownin Figure 10 and 11 respectively.

Figure 10: Heat Flux vs. Cutting Speedat f= 0.83 mm/rev

Figure 11: Heat Flux vs. Cutting Speedat f= 1.65 mm/rev

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The heat generated for uncoated tool perunit area is much higher than that of coatedtool for different cutting speeds. The increasein heat flux for uncoated tool is rapid as com-pared to the coated tool.

CONCLUSION

This study evaluates the machining perfor-mance of commercially available Coated anduncoated cutting tool inserts in turning EN8alloy steel. Uncoated and coated tools wereexamined by measuring the temperature atthe cutting point of tool inserts. Tool-work ther-mocouple method was found to be efficientmethod to measure the temperature of thetool inserts. The coating material of a cuttingtool is having a less thermal conductivity dueto which coated tool resist the penetration oftemperature into the cutting tool whereas itwas found that uncoated tool experiences alarge heat as compared to coated tool. Hencethe coated tool can be used for high cuttingspeed machining for the same tool life. Dueto the resistive ability of coated tool, the lifeof a tool can be improved.

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performance evaluation of cvd coated tool by … · 2015-04-10 · performance evaluation of cvd...

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