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

• Published in: Wear 2015-01, Vol.322-323, p.203-217
• Main Authors: Kumar, Dharmesh, Nadeem Akhtar, Syed, Kumar Patel, Anup, Ramkumar, J., Balani, Kantesh
• Format: Article
• Language: English
• Subjects: Abrasion; Abrasion resistance; Bearing steels; Chromium steels; Compressive properties; Fretting; Laser processing; Lasers; Other materials (Ti–6Al–4V); Profilometry; Residual stress; Shock waves; Stick-slip; Surgical implants; Titanium base alloys; Tribology; Wear
• ISSN: 0043-1648; 1873-2577
• DOI: 10.1016/j.wear.2014.11.016

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, 248nm) with varying fluence on the fretting behavior of Ti–6Al–4V was carried out. An optimized laser fluence of 100J/cm2 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 540MPa in air to 604MPa 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 1.211×10−3mm3 to either 0.139 ×10−3mm3 or to 0.106×10−3mm3 in samples peened in air and water, respectively. Frictional hysteresis data show that the dissipation energy loss for Ti–6Al–4V substrate from 11.412×10−4J is decreased to 3.284×10−4J for LP sample at 20N load. Moreover, a considerable fall in contact diameter is observed from the non-processed surface (0.29×10−3μm) to the LP sample (0.176×10−3μm). 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. •Fretting behavior of Laser Peened (LP) Ti–6Al–4V.•Variation of laser fluence (20–100J/cm2) elicited change in surface hardening.•Water as confining medium enhanced the surface hardness (compared to air).•Lower wear-volume and wear-rate in water confined LP Ti–6Al–4V.•Friction hysteresis depicted the wear mechanism to be gross slip dominated.