Effect of cryogenic treatment on wear resistance of Ti-6Al-4V alloy for biomedical applications

The effect of cryogenic treatment on wear resistance of Ti-6Al-4V alloy for biomedical applications was experimentally investigated in this paper. Cryogenic treatments with the same soaking time of 24 h at different temperatures of -80 degrees C, -140 degrees C and -196 degrees C were conducted and the treatments at the same temperature of -196 degrees C were then further given different soaking time of 3 h, 48 h and 72 h to be investigated. After cryogenic treatment, the Vickers hardness of specimens was measured. Wear resistance of Ti-6Al-4V alloy was measured by pin-on-disk wear test under dry sliding condition. The results demonstrated that the Vickers hardness increased slightly with the reduction of temperature while it increased obviously with the elongation of soaking time at -196 degrees C. The friction coefficients of specimens cryo-treated at -196 degrees C were lower than those of untreated and of cryo-treated at -80 degrees C and -140 degrees C. And the longer the soaking time is during the cryogenic treatment, the higher the friction coefficient reduction can be achieved. The obvious reduction of mass loss can be obtained at -196 degrees C with 72 h soaking. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to detect the microstructure and worn surface of specimens. By cryogenic treatment, the plowing in the worn surface was smoothed and shallowed, and the degree of plastic deformation in the subsurface was decreased. There was no obvious phase transformation which can be detected in the microstructure after cryogenic treatment. However, the tendency of refinement in grain size can be detected by XRD which improved the wear resistance of Ti-6Al-4V alloy. (C) 2013 Elsevier Ltd. All rights reserved.