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 (UTS) with those of textured surfaces (TS) under both dry sliding conditions (DSC) and lubricated sliding conditions (LSC). The results demonstrated a significant reduction in the COF and wear coefficients on the TS. 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 UTS tested under DSC and LSC (using PAO-4 and PAO-4 + 1% wt MoS2). Severe abrasion, adhesion, and delamination as the primary wear mechanisms were observed on the UTS and TS under DSC, while the LSC was characterized by mild adhesive and delamination wear on the UTS and TS. The carbon layer formation and concentration of Mo and S particles resulted in lower friction and wear coefficients for the UTS, and TS under LSC (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.