tribological properties of titanium alloys

7/30/2019 Tribological Properties of Titanium Alloys

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Wear, 151 (1991) 203-217 203

Tribological properties of titanium alloys*Kenneth G. BudinskiEastman Kodak Company, Bui lding 23, 5th F loor, Kodak Par k, Rochester, NY I 4650 (U.S.A.)

(Received April 30, 1991)

AbstractTitanium is often the most cost-effective corrosion-resistant material for applications inthe chemical process industry that involve resistance to halides. Unfortunately, there areusually some components in these systems that involve relative sliding-titanium tribosystems- e.g. bolts and nuts, valves, piping connections, etc.Titanium and its alloys have had a reputation for poor tribocharacteristics, but detailedinformation on suitable counterfaces and wear specifics is scarce. This paper summarizesa study conducted on the two most widely used titanium alloys, Grade 2 commerciallypure titanium and the age-hardenable Ti6Al4V. Dry sand-rubber wheel tests were conductedto assess abrasion resistance; fretting, galling and reciprocating pin-on-plane tests wereconducted to determine if there is a best counterface for these two titanium alloys.

The test results are distilled into recommendations for use of titanium alloys intribosystems in the chemical process industry. Both alloys have poor abrasion resistance.Grade 2 pure titanium should be avoided in all titanium tribosystems and there arepreferred counterfaces for the Ti6Al4V alloy, but the best metal-to-metal wear resistanceis obtained when the alloy is anodized and coated with a dry film lubricant.

1. IntroductionIn the past decade, titanium alloys have been adopted as standard materials of

construction for pipes, fittings, valves and similar equipment in the chemical processindustry. Titanium alloys are often the best choices for handling halides and bleaches.They have far better resistance to these environments than the best 300 series stainlesssteels. The most popular alloys for this type of service are pure titanium (ASTM B348Grade 2) and the Ti6Al4V alloy (ASTM B348 Grade 5) [l]. The Grade 2 pure titaniumis one of four grades of pure titanium which differ in impurity level and strength;the 6A14V alloy can be solution treated and age hardened. The Rockwell C hardnessis normally 30-36 HRC in the annealed condition and may increase to 39 HRC onage hardening. The hardness is about 36 HRC in the solution-treated and over-agedcondition.

Pieces of equipment made from these alloys do their job from the corrosionstandpoint but occasionally the alloys must be used in parts of equipment that involvesliding of titanium on other counterfaces - titanium tribosystems. Titanium is anextremely reactive metal and has a reputation for poor tribological properties [2-51.For this reason, machine designers have tried to avoid its use in sliding systems, but

*Paper presented at the International Conference on Wear of Materials, Orlando, FL,U.S.A., April 7-11, 1991.

0043-1648/91/$3.50 0 1991 - Elsevier Sequoia, Lausanne


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204there are times when this is not possible. For example, it is often necessary to usetitanium fasteners to assemble titanium components. Periodic disassembly and reassemblyof fasteners causes tapped holes in extremely expensive equipment to wear out. Thiseventually causes components to become useless. There are other unavoidable titaniumtribosystems where similar wear problems can cause loss of extremely expensive (andcritical) equipment.

It is the purpose of this paper to present the results of a comprehensive laboratorystudy on the tribological properties of two titanium alloys (Grade 2 and Grade 5).The objective of this study was fourfold: (I) to determine the severity of the problem,(2) to determine if there are any counterfaces that mitigate wear of the titaniummember, (3) to determine if surface treatments alter wear effects and (4) to determinethe abrasion resistance of titanium. Using this information, we make recommendationsto machine designers on how to prevent potential wear problems when titaniumtribosystems are unavoidably present in chemical-handling machines. The overallobjective of this study is to prevent loss of equipment or degradation of product qualitydue to wear failures.

Titanium may be subject to different forms of wear in chemical process systems;the plan of this study was to assess the tribocharacteristics of titanium in the threewear modes that are likely to occur in these systems: abrasion, metal-to-metal wearand fretting wear. We will present the results that we obtained in this study in galling,abrasion, metal-to-metal and fretting tests. We will conclude with design recommen-dations for the use of titanium in tribosystems.

2. Galling studiesIn a 1989 unpublished study we conducted tests to find an appropriate material

to use for nuts on titanium bolts. There was a concern that galling would occur,making disassembly difficult or impossible. In test on actual bolts and nuts it wasdetermined that titanium bolts did not gall with a titanium nut or with nuts madefrom hard and soft stainless steels (type 316, 90 HRE3; 17-4, 43 HRC, 440 C, 58 HRC).However, after about 20 tightenings of a nut on a bolt 12.5 mm in diameter thethreads on the titanium bolts were almost completely removed. It appeared thattitanium does not gall like soft stainless steels. When soft stainless steel slides onitself under high normal forces, it forms macroscopic excrescences that in turn canlead to seizure. The titanium alloy that we tested, 6Al4V alloy, wore by adhesivetransfer of Aat platelets to the mating material (Fig. l(a)). This type of transfer hasbeen noted by other investigators [63 and is probably due to the reactivity of titaniumwhen surface fihns have been removed by mechanical action. The material removalrate was higher than can be tolerated on bolts that are reused. As a result of thisstudy we recommend a PH stainless steel counterface (43 HRC) coupled with surfacelubrication (polytetrafluoroethylene (PTFE) or MO& coatings) to mitigate thread wear.In this study we also investigated the effect of heat treatment on the gallingcharacteristics of the Ti6Al4V alloy. This alloy is received in the annealed condition(30-36 HRC). Most parts are made from this alloy in this condition; some parts receivea stress relief at 760 C (as part of the fabrication process) and occasionally, wheremaximum strength is required, the Ti6A14V alloy is solution treated and aged at 538C (35-39 HRC). One technique that has been used to mitigate wear problems onheat-treated alloys is to perform the heat treatment in air and to leave the oxide thatis formed on the titanium in place to act as a wear adjuvant. Galling tests were


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Fig. 1. (a) Typical adhesive transfer of titanium: Ti6Al4V vs. itself (original magnification, X40).(b) Large excrescence formed in tantalum rider after rotation on Ti6Al4V at 14 MPa apparentpressure.

performed on the following couples: (1) annealed Ti6A14V stress relieved at 760 Cvs. itself (oxide removed); (2) annealed pure titanium stress relieved at 538 C (oxideon contact surfaces) vs. itself; (3) annealed Ti6A14V stress relieved at 538 C (oxideon contact surfaces) vs. itself; (4) solution-treated and aged Ti6A14V vs. itself (oxideremoved); (5) annealed pure titanium vs. Ti6A14V stress relieved at 760 C (oxideremoved).

The ASTM G98-89 galling test [7] was used with modified sample geometry. Inthis test the end of a 12.5 mm pin is rotated through 360 on a flat counterface underincreasing normal forces and both surfaces are visually examined for galling. In ourstudies the upper sample was an annular ring with a contact area of 0.29 cm. Testsurfaces were freshly abraded to produce a random scratch pattern and a roughnessR, of 0.1-0.5 pm. The criterion for galling was the formation of macroscopic excrescences.Samples were tested with increasing normal forces until they galled or until we reachedthe capacity of the machine, 3.5 X lo4 N (276 MPa). Typical load increments were 4kN. The criterion for galling was the ASTM G98 definition of galling: in Tribology,a severe form of wear characterized by localized, macroscopic material transfer, removalor formation of surface protrusions when two solid surfaces experience relative slidingunder load. Surfaces were examined after rotation of the annular ring; if galling didnot occur, the samples were refinished and retested. The surfaces were used as abradedand pure dry air was used to remove fine grinding detritus. Three replicates of eachcouple were tested. The results were essentially the same for all these couples; thethreshold galling stress was over 276 MPa and there was no diminution of the tendencyfor wear and transfer. The coefficient of friction was higher on the pure titaniumcouples (Fig. 2) and definitely shows significant deformation during testing.

In an effort to determine if there is some material that will run against titaniumwithout the wear and transfer problem, we tested a variety of materials against solution-treated and aged 6A14V in the same ASTM G98 galling test. The results shown inTable 1 indicate that titanium only galled against one material, tantalum, out of the


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207treating oxides by themselves was not effective but several proprietary anodizing-lubricanttreatments did prevent transfer in the galling tests.

In summary, Grade 2 pure titanium and the 6Al4V alloy do not gall (formationof macroscopic excrescences) when mated against each other in any condition of heattreatment, but severe wear and transfer do occur. In the case of the pure alloy theplastic deformation that occurs makes this alloy totally inappropriate for use intribosystems. The Ti6Al4V alloy does not gall against a wide variety of other corrosion-resistant materials, but the titanium wear and transfer are such that these systemsshould not be used without a wear adjuvant. Suitable palliative treatments are: anodizingplus resin-bonded MoS, or PTPE; fluorocarbon enamels; MO&--Pb-Cu or similarantiseize compounds. Grade 2 pure titanium is totally unsatisfactory even for unlubricatedmetal-to-metal sliding and its use should be avoided.3. Abrasion Tests

A widely used test for assessing abrasion resistance of metals is the ASTM G65dry sand-rubber wheel abrasion test [8]. This test produces abrasion on the large faceof a 12 X 25 X75 mm3 sample cut from the test material. The sample is pressed againsta rubber-tired wheel and 50-70-mesh silica sand is metered between the specimenand the rotating wheel. After a prescribed number of wheel revolutions the wear onthe sample is assessed by gravimetric techniques and a volume loss is calculated. Inthis study we performed three replicate tests on Grade 2 pure titanium and on the6Al4V alloy in the age-hardened condition. The test results are compared with avariety of other materials in Fig. 3. These results indicate that the Grade 2 puretitanium has better abrasion resistance than the harder Ti6Al4V alloy. However, neithergrade had abrasion resistance comparable to soft stainless steel. The results obtainedon pure titanium appear to be incongruous with the Archard equation [9], whichpredicts abrasion resistance to be inversely proportional to material hardness:

MATERIAL IDENTIFICATIONCEMENTED CARBIDE l I, ,d HRC,

STELLITE 1016 (66 HRC,D2 TOOL STEEL

1060 STEEL*17-4 STAINLESS STEEL316 STAINLESS STEEL

TI GRADE 2TIBAUV

ALUMINUM 6061 T6 _I0 200 400 600 600 100012001400

VOLUME LOSS (mm)* FROM ASTM 066REFERENCEFig. 3. Abrasion rates of various materials compared with Grade 2 pure titanium and Ti6Al4V(ASTM G65 test, procedure A).


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where W is the wear rate, K is the wear coefficient, D is the sliding distance, P isthe load (normal force), h is the penetration hardness and LY s the included angleof abrasive particles.

We did not perform additional experiments to explain these results, but metal-lographic studies on the wear scars suggest that material removal occurs by differentmechanisms in the two materials. As shown in Fig. 4, the Grade 2 pure titanium wearscars had a lapped appearance and the Ti6Al4V scars showed a pattern suggestinghard and soft regions in the material. Neither material showed normal abrasion patterns.This type of wear scar was also obtained in abrasion tests vs. SC and A1203 byHutchings and Mercer [lo]. Ferrous materials usually have a scar consisting of finescratches - similar to a ground surface. It is possible to hypothesize that the mottledpattern in the Ti6Al4V alloy is from microstructural heterogeneities. It is a two-phasealloy, a mixture of stable a: phase and metastable p phase. The pure alloy is single-phase a. The fact that the pure titanium had better abrasion resistance than theharder (36 HRC) 6A14V alloy could be attributed to differences in the behavior ofthe sand in going through the rubber tire-sample interface. We have seen similarresults in copper alloys - pure copper (60 HRB) had better abrasion resistance inthis test than 1% Be-Cu at 42 HRC. There was strong evidence that the round andsubangular sand used in this test rolls through the sample-tire nip rather than becomingfixed in the rubber. The way that this test produces abrasion is that grains of sandbecome embedded in the rubber and are momentarily fixed to the rubber wheel sothat they are capable of plowing a furrow or scratch in the specimen. Rolling grainsof sand do not produce abrasion. This is probably the explanation of the lack ofcorrelation with the Archard equation. The adhesion of the sand to the pure titaniumis greater than to the alloy and this produces rolling grits rather than fixed grits, hencereduced abrasion.

Irrespective of the differences between the pure and 6Al4V titanium alloy, theimportant finding of this test is that both grades of titanium have poor abrasionresistance. The abrasion rates of both grades were at least 15 times the abrasion ratesthat would be obtained on a hardened tool steel such as Type D2. These data suggestthat titanium should be avoided for applications involving low stress abrasion from

(4 0)Fig. 4. Wear scars on Ti6A14V and Grade 2 pure titanium after ASTM G65 sand abrasion test,procedure A (original magnification, x 100): (a) Grade 2 - note lapped appearance; (b) Ti6Al4V- note discontinuous removal of material.


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hard particles. Ayers [ll] verified the poor abrasion characteristics of titanium andproposed surface modification by injection of carbide particles by laser cladding. Thistechnique is not in wide use and is not ready for use in everyday machine design.

4. Fretting damageTitanium components used in chemical process systems are often intended to be

non-sliding systems, but many non-sliding parts can experience fretting motion in boltedassemblies. Temperature fluctuations or machine vibrations produce oscillatory relativemotion in the amplitude range 10-300 pm where fretting damage occurs.

In this study we tested titanium (Ti6Al4V) under fretting conditions against avariety of couples. We used the test rig shown schematically in Fig. 5 and the followingtest conditions: oscillatory motion, amplitude 50 pm, frequency 3.3 Hz, normal force30 N, test duration 3 x 10 cycles.

Hemispherical riders with an end radius of 6.25 mm were made from Ti6Al4Vand oscillated against flat samples of the following materials: (1) itself (36 HRC); (2)cemented carbide (WC-Co); (3) 17-4 stainless steel (43 HRC); (4) 440C stainlesssteel (57 HRC); (5) Stellite 6B @* (43 HRC); (6) chromium plate (on 1020 steel); (7)316 stainless steel (90 HRB); (8) itself plus anodize plus MO&

The test is described in detail in a previous publication [12], but essentially damageto the ball and counterface was assessed by profilometry. The scar depths were measuredin both members and a volume loss was calculated from these data.

IIILOCKJ

Fig. 5. Schematic diagram of fretting test rig. Test conditions: amplitude 50 pm, frequencyHz, normal force 30 N, test duration 25 h. 3.3

*Registered trademark of Stoody Deloro Stellite Co.


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210The test results presented in Fig. 6 suggest that this alloy is quite susceptible to

damage self-mated and mated against stainless steels. Photomicrographs of the coupleswith the most damage (Ti6Al4V vs. itself) and the least damage (Ti6A14V vs. Stellite6B) are presented in Figs. 7 and 8 respectively.The damage is substantial even against a hard stainless steel counterface (440Cstainless steel). Of the eight couples tested, the lowest system damage was obtainedwith a couple of Ti6Al4V vs. SteIlite 6B. The anodized and lubricated couple did notwear as well as the bare Steliite-titanium couple. However, most of the system wearwas in the anodize coating; the coating was 5 pm thick and did not penetrate. Thusthe wear on the titanium was low. Essentially, titanium vs. anodized and lubricated

36 30 26 20 IS IO 6 0 6 10 16 20 26 30 316VOLUME LO88 * 10 EXP-a hn?) VOLUME LOW . 10 EXP-8 htl

m RIDER m COUNTERFACEFig. 6. Results of fretting corrosion tests on Ti6A14V vs. various counterfaces. Titanium hemisphererider is oscillated on a flat counterface. Data are averages for three tests.

Fig. 7. Wear scars on (a} Ti6Ai4V rider and (b) counterface after 25 h fretting test (originalmagnification, X 50).


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(4 (b)Fig. 8. Wear scars on (a) titanium rider and (b) Stellite 6B counterface after 25 h fretting test(original magnification, X 50).

VOLUME LOSS * EXP-2 mm34 II

00 160 HO 660 660

COUNTERFACE HARDNESS (kg/mm)- COUNTERFACE - RIDER

Fig. 9. Effect of hardness on fretting damage: Ti6Al4V rider vs. various stainless steels.titanium is a reasonable couple if the lubricant can be tolerated. In a similar studyBall [12] concluded that a polyimide dry film lubricant was somewhat better thanMO& types of lubricants.

These results suggest that wherever titanium may be subject to fretting damage,a suitable counter-face would be Stellite 6B. We tested wrought Stellite but we anticipatethat the same or similar Stellite alloys applied as a hardfacing deposit would besatisfactory. The test data also suggest that the use of a hardened counter-face helps(Fig. 9). If the use of Stellite is not possible, the anodized and lubricated titaniumwould be the second choice. Additional counterface options are cemented carbide,chromium plating or hardened 440C stainless steel (58 HRC). Komanduri and Read[13] determined that the low binder WC-Co is a more suitable counterface for titaniumthan the high cobalt grades. The grade that we tested had 7% cobalt. A lower cobalt


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212grade may have produced better results. An easy-to-use palliative would be to chromiumplate the titanium counterface (titanium cannot be chromium plated by conventionalmeans). This is probably the minimum protection that should be taken to preventfretting damage. In summary, unlubricated self-mated titanium couples should beavoided in systems where fretting damage could affect serviceability. If they must beused, a suitable counterface would be Stellite 6. If both members must be titanium,they must be separated by a lubricious film.

5. Metal-to-metal wearTo assess the wear of self-mated titanium in simple sliding applications, we decided

to test the metal-to-metal wear characteristics of the pure titanium and the 6Al4Valloy against a variety of counterfaces in a reciprocating ball-on-plane test. This testuses a ball rider (12.5 mm diameter) oscillating on a flat counterface under a givennormal force for a given sliding distance at a controlled velocity (1 kgf normal force,2.5 cm amplitude, 0.08 m s-r sliding velocity, 516 m of sliding). Wear of both membersis assessed by profilometry of the ball scar and counterface scar (three traces each)and wear volumes are calculated from geometry changes. In this study we tested thecouples shown in Table 2.

There are not a significant number of options available when looking for a suitablecounterface for titanium. Acceptable counterfaces should have corrosion resistancecomparable to titanium since in the chemical process industry it is common to onlyuse titanium where conventional stainless steels have inadequate corrosion resistance(titanium costs five to ten times as much as stainless steel). The uncoated metals thatwe selected as candidates all have significant corrosion resistance: Nitronic 60 -similar to 304 stainless steel; Ferralium 255@* - exceptional pitting resistance inTABLE 2Test couples for ball-on-plane reciprocating wear test. Three tests of each ball were conductedon each counterface, with fresh surfaces each timeBall riders Flat counterfaces(1) Pure Ti Grade 2(2) Ti6Al4V(3) Chromium-plated 440C stainlesssteel(4) Grade 2 Ti + anodize + MoSr dry

film lube

(1) Grade 2 Ti + anodize + MoSr dry film lube(2) Nitronic 60 stainless steel (Ammo steel)(3) Gall Tough stainless steel (crucible steel)(4) Tantalum(5) Zirconium(6) Grade 2 Ti + anodize +PTFE dry film lube(7) Ti6Al4V + anodize + PTFE dry film lube(8) Ti6Al4V plated with Ni-P+PTFE(9) Ti6Al4V chromium plated(10) 316 stainless steel plated with Ni-P+PTFE(11) Grade 2 Ti plated with Ni-P+PTFE(12) Ferralium 255(13) Ti6Al4V PVD coated with TiN 2 pm thick

*Registered trademark of Cabot Corp.


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chlorides; Gall Tougha - similar to 304 stainless steel; tantalum - the most corrosion-resistant non-noble metal; zirconium - resistant to a wide variety of corrodents.Thus, if one of these metals worked as a suitable counterface for titanium, it wouldprobably have adequate corrosion resistance to be used in hostile environments.A similar approach was taken in selecting coatings. We chose candidate corrosion-resistant coatings that can be applied to titanium. Coatability is a concern becausetitanium has a very passive oxide on its surface; it cannot be plated by conventionaltechniques. It can be anodized but this is not a standard coating and only proprietarytreatments are available to the average machine designer. The proprietary processesare combined with fluorocarbon (PTFE) treatments or other resin-bonded dry filmlubricants to provide lubricity. Some electroless nickel platings have shown promisefor adhering titanium and we tested three proprietary Ni-P-PTFE platings. They allcontained from 10% to 20% PTFE which was codeposited with the nickel. Finallywe tested a TiN coating since this is much harder than titanium and there are noadhesion problems. In summary, the types of coatings that we evaluated were essentially:(1) anodizing impregnated with PTFE or MoSz (4 pm thick); (2) Ni-P electrolessplating with PTFE (25 pm thick); (3) TiN physical vapour deposition (PVD) coating(2 pm thick); (4) chromium plating (1 pm thick).

The other part of the test matrix was a counterface of chromium-plated 440Cstainless steel. The rationale for selecting this as a candidate is that it is the hardestcorrosion-resistant counterface that is readily available. It can be chromium plated tomake a composite surface which will have respectable corrosion resistance (but notas good as titanium or the other metals tested). It is essentially the easiest-to-implementcounterface.

The reciprocating wear test results are presented in Fig. 10. Two counterfacesproduced low system wear against Ti6A14V, Grade 2 pure titanium and chromium-plated pure titanium: (1) pure titanium plus anodize plus MO& dry film lube plus460 lube; (2) Ni-P-PTFE plating on 316 stainless steel. Previous investigations [14]found that dilIi.rsed Ni-P platings improved the wear properties of Ti6Al4V. We believethe PTFE addition produced a lubrication effect that allows the use of these coatingsas deposited.

The most suitable counterface for chromium-plated 440C stainless steel was theanodized titanium alloys with MO& dry film lubricant. The couples that produced lowsystem wear are: (1) Ti6Al4V vs. anodized Grade 2 titanium plus anodize plus MO&;(2) Ti6A14V vs. Ni-P-PTFE plating; (3) Grade 2 titanium vs. anodized Grade 2titanium plus anodize plus MO&; (4) Grade 2 titanium vs. Ni-P-PTFE plating; (5)chromium-plated Grade 2 titanium r~. Grade 2 titanium; (6) chromium-plated puretitanium vs. Ni-P-PTFE plating; (7) chromium-plated 440C stainless steel vs. Grade2 titanium plus anodize plus MO&.

These results suggest that whenever titanium (pure or alloy) is used in a slidingsystem, the counterface should have a lubricious coating. None of the pure metal orspecialty alloy counterfaces compared with the PTFE or MO&-lubricated systems. Theresults are in agreement with previous investigations [15]. The friction results (Fig.11) show that the anodized plus MO&-treated counterfaces had the lowest kineticcoefficient of friction against pure and alloy titanium. This result is in line with whatone would expect. However, these data also show that the wear characteristics of thevarious lubricous coatings differed significantly. Some were more effective than othersin reducing system wear. These friction data suggest that designers could effectivelyprevent metal-to-metal wear in titanium tribosystems by having one of the titaniummembers treated with an anodize that is subsequently coated with a PTFE or MO!&


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0OLUME LOSS (mm !

COUNTERFACE

Fig. 10. Results of metal-to-metal wear tests on titanium and other corrosion-resistant materialsin a reciprocating ball-on-plane rig. Data are average values for three tests. Test conditions:1.6 Hz, 1.1 kgf normal force, 2 h test duration, 2.5 cm stroke amplitude. All metal sampleswere at their maximum working hardness.


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c 0.2 0.4 0.6 0.8 1. FTFE ,1-S REFFER TC DIFFERENT GOUtNO VENDORS COEFFICIENT OF FRICTIONFig. 11. Kinetic coefficient of friction of couples in bail-on-plane wear test. Coefkients werederived from average force readings during the test.


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dry film lube. All the dry film coatings tested were applied by spray and bake techniques.The MO& coating had an epoxy binder.

6. Summary and conclusionsThe various wear tests conducted in this study have shed considerable light on

the idiosyncracies of titanium alloys when they are used in sliding systems. The followingare the conclusions from these tests and recommendations for use of titanium indesign situations.

(1) Titanium does not gall against most metal counterfaces, but it does adhesivelytransfer and wears at a high rate (it can be used for threaded fasteners withoutconcern about seizure, but the threads wear). It can be used mated with 300 seriesstainless steels to form a galling-resistant (but not wear resistant) tribosystem.

(2) The wear of titanium alloys in sliding systems can be significantly reduced bythe use of an anodizing and subsequent treatment with dry film lubricant coating onone member of the couple (anodizing plus MO& or PTFE).

(3) Both the pure and alloy grade of titanium have poor abrasion resistance(poorer than soft 300 series stainless) and their use should be avoided in systemsinvolving low stress abrasion.

(4) Titanium is quite prone to fretting damage (coupled to itself and to soft andhard stainless steels). A counterface that reduces damage to both members is Stellite6B. This counterface should be used whenever possible. Other counterfaces can beused if they have a lubricous coating (anodize plus PTFE or MO& dry film lubricant).

(5) Pure titanium transfers and deforms badly in unlubricated tribosystems; itsuse in any tribosystem should be avoided.We have not learned everything that there is to know about the wear characteristics

of titanium, but adoption of the above guidelines by design engineers will producemajor reduction in wear problems with titanium alloys.

References1 Standard specification for titanium and titanium alloy bars and billets, ASTM 8348-83.2 S. Fayeulle, Tribological behavior of nitrogen implanted materials, Wear, 107 (1986) 61-70.3 T. S. Eyre and H. Asalin, Effect of boronizing on adhesive wear of titanium alloys, Tribologv,10 (1977) 281-285.4 I. S. Vaptying and V. I. Syshchikov, Effect of alloy content on frictional properties of titanium,Wear, 3 (1960) 332.5 I. J. Polmear, Light Al loys, Arnold, London, 1981, p. 198.6 S. L. Rice, Materials transport phenomenon in the impact wear of titanium alloys, Wear,65 (1980) 215-226.7 Standard test method for galling resistance of materials, ASTM G98-89, 1989.

8 Practice for conducting dry sand/rubber wheel abrasion test, ASZM G65-87, 1987.9 E. Rabinowicz, Friction and Wear of Materials, Wiley, New York, 1965, p. 168.10 I. M. Hutchings and A. P. Mercer, The influence of atmosphere composition on the abrasivewear of titanium and Ti6Al4V, Wear, I24 (1988) 165-176.11 J. D. Ayers, Wear behaviour of carbide-injected titanium and aluminum alloys, Wear, 97(1984) 249-266.12 R. C. Bill, Selected fretting-wear-resistant coatings for Ti-d%AU%V alloy, Wear, 102 (1985)283-301.


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13 R. Komanduri and W. R. Reed Jr., Evaluation of carbide grades and a new cutting geometryfor machining titanium alloys, Wear, 92 (1983) 113-123.

14 Guang-Xi Lu and Jung-Roug Liu, Unlubricated sliding wear behavior of nickel diffusioncoated Ti6Al4V, Wear, 121 (1988) 259-269.15 F. deLaat and T. Adams, Inhibiting the wear and galling characteristics of titanium, Met.Eng. Q., (August 1968) 39-47.16 K. G. Budinski, Wear characteristics of industrial platings, in R. Bayer (ed.), Selection andUse of Wear Tests for Coatings, ASTM Spec. Tech. Publ . 769, ASTM, Philadelphia, PA, 1982,pp. 118-133.17 K. G. Budinski, Evaluation of fretting corrosion by means of a new device for control ofoscillation amplitude, in S. D. Brown (ed.), Mareriulr Evaluation Under Fretting Conditions,ASTM Spec. Tech. PubI . 780, ASTM, Philadelphia, PA, 1982, pp. 49-67.

tribological properties of titanium alloys

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