Dry Sliding Wear Behavior of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Alloy
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TITANIUM alloys have aroused great interest in recent years because of their very attractive combination of high strength, low density, and good corrosion resistance.[1] Furthermore, their high strength-to-density ratio results in considerable energy savings in transportation and aerospace sectors. Thus, titanium alloys are widely used in aerospace and automobile industries.[2] For the application in areas where wear resistance is mainly concerned, high wear resistance is required for titanium alloys. However, titanium alloys are well known to possess notoriously poor tribological property.[3,4] Undoubtedly, this precludes their applications. Currently, many surface treatment methods were usually applied to improve the tribological performance of titanium alloys, such as thermal oxidation, plasma nitridation, laser surface alloying, microarc oxidation, and physical vapor deposition.[4–9] The poor tribological resistance of titanium alloys was reported to be attributed to their low resistance to plastic shearing, low work hardening, and especially the low protection exerted by the surface oxides.[3,4,10–12] Molinari et al.[10] studied the dry sliding wear behavior of Ti-6Al-4V alloy sliding against itself and AISI M2 steel at room temperature. They considered that tribooxide layer of Ti-6Al-4V alloy did not adhere to the substrate, was brittle, and tended to be continuously fragmented, thus presenting no protective role. Ohidul Alam and Haseeb[11] studied the wear properties of Ti6Al-4V and Ti-24Ni-11Nb alloys against hardened steel under loads ranging from 15 to 45 N in air at room temperature. They found that the wear rate of Ti-24Ni11Nb alloy was much lower than that of Ti-6Al-4V L. WANG, Q.Y. ZHANG, and X.X. LI, Masters, and X.H. CUI and S.Q. WANG, Professors, are with the School of Materials Science and Engineering, Jiangsu University, 212013 Zhenjiang, P.R. China. Contact e-mail: [email protected], [email protected]. edu.cn Manuscript submitted June 11, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS A
alloy. This was attributed to the formation of a protective Ti-Nb oxide layer on the surface of Ti-24Ni-11Nb alloy and no formation of a protective tribo-oxide layer on the surface of Ti-6Al-4V alloy. Qiu et al.[12,13] studied tribological characteristics of Ti-6Al4V alloy against GCr15 steel under high-speed and dry sliding. They emphasized the important function of tribo-oxide layer, and considered that the oxides of TiO, TiO2, and V3O4 formed during the wear process, but did not improve the wear performance of Ti-6Al-4V alloy because these oxides were very loose and easy to spall off. However, in our previous studies,[14,15] the wear behavior and mechanism of Ti-6Al-4V alloy at 298 K to 773 K (25 °C to 500 °C) were investigated. Ti8O15 and TiO2 were found to form on worn surfaces of Ti6Al-4V alloy. Especially, as soon as a large amount of oxides at 673 K to 773 K (400 °C to 500 °C) appeared, the wear rate was substantially reduced. This phenomenon demonstrated that Ti-6Al-4V alloy possessed high wea
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