Tribological performance of laser peened Ti-6Al-4V

Ti-6Al-4V is a well-known metallic biomaterial used for implants, but its use is limited by its inferior hardness and tribological resistance in vivo. Laser peening (LP) is one potential means to enhance its tribological properties. LP induces surface residual compressive stresses due to plastic deformation caused by the propagation of a shock wave. Further, performing laser peening under water can enhance a material's hardness and wear resistance because it confines shock waves to the surface of the material. In the current research, the influence of an excimer laser (Kr-F, 248 nm) with varying fluence on the fretting behavior of Ti-6Al-4V was carried out. An optimized laser fluence of 100 J/cm(2) resulted in an increase in hardness by 28% in air and 35% in water confining media, respectively, when compared to that of an untreated Ti-6Al-4V substrate. It was observed that the residual compressive stresses from LP increased from 540 MPa in air to 604 MPa in water. Fretting wear against bearing steel type AISI E52100 shows a major wear reduction on LP Ti-6Al-4V samples as wear volume decreased from 1.211 x 10(-3) mm(3) to either 0.139 x 10(-3) mm(3) or to 0.106 x 10(-3) mm(3) in samples peened in air and water, respectively. Frictional hysteresis data show that the dissipation energy loss for Ti-6Al-4V substrate from 11.412 x 10(-4) J is decreased to 3.284 x 10(-4) J for LP sample at 20 N load. Moreover, a considerable fall in contact diameter is observed from the non-processed surface (0.29 x 10(-3) mu m) to the LP sample (0.176 x 10(-3) mu m). Friction log plots indicate that wear mechanisms are mostly adhesion, abrasion and delamination. Enhanced tribological performance of LP Ti-6Al-4V was observed using LP in a water medium, and indicates potential improvements when the alloy is used in joint replacements. (C) 2014 Elsevier B.V. All rights reserved.