Synergetic effect of oleophilic textured surfaces and MoS2 on the tribological properties of Ti-6Al-4V alloy under dry and lubricated sliding conditions

Abstract

In the present work, surface modification of Ti-6Al-4V alloy was carried out using Laser surface texturing (LST). The investigation aims to explore the synergetic impact of LST and molybdenum disulfide (MoS₂), as a solid lubricant, on the tribological properties of Ti-6Al-4V alloy. Three types of LST textures (Circular, triangular, and square textures) were created on the Ti6Al4V alloy. Subsequently, tribological tests were conducted on a universal tribometer (ball-on-disc), at a load of 20 N with a frequency of 15 Hz. The worn surface was analyzed using various methods, including optical microscopy, 3D-profilometer, FESEM, EDAX analysis, and Raman spectroscopy. The study compared the coefficient of friction (COF) and wear behavior of un-textured surfaces (U_TS) with those of textured surfaces (T_S) under both dry sliding conditions (D_SC) and lubricated sliding conditions (L_SC). The results demonstrated a significant reduction in the COF and wear coefficients on the T_S. Specifically, the circular texture exhibited significant results with a 10.30%, 10.42%, and 28.80% decrease in COF and a remarkable reduction of 39.22%, 47.51%, and 77.90% in wear coefficients compared to the U_TS tested under D_SC and L_SC (using PAO-4 and PAO-4 + 1% wt MoS₂). Severe abrasion, adhesion, and delamination as the primary wear mechanisms were observed on the U_TS and T_S under D_SC, while the L_SC was characterized by mild adhesive and delamination wear on the U_TS and T_S. The carbon layer formation and concentration of Mo and S particles resulted in lower friction and wear coefficients for the U_TS, and T_S under L_SC (PAO-4 + 1% wt MoS₂). The analysis indicated that the use of LST and solid lubricant nanoparticles on a Ti-6Al-4V alloy would result in improved service life and better endurance in cutting tools and tribo-mating parts.