Synthesis of bioinspired gradient MoS2/TiO2 coatings for enhancing tribological performance of titanium alloys

To enhance the tribological performance of titanium alloys under high frictional load, a MoS2/TiO2 composite coating with grain size gradient (GSG) distribution was presented. Inspired by the design principles of dental structures, the coating was fabricated through precise control of step-up voltage during plasma electrolytic oxidation (PEO). The variation in the frequency distribution of MoS2 grain sizes along the coating growth direction, ranging from approximately 43.23 similar to 48.46 nm and 5.32 similar to 8.16 nm, is attributed to increased energy supply and a higher degree of subcooling as the PEO voltage was elevated. The GSG coating significantly reduces the average coefficient of friction and abrasion loss by 65.44 % and 30.62 % with loads increasing to 10 N, compared with the MoS2/TiO2 coating. This improvement is attributed to the cooperative deformation of grains with varying sizes within the GSG structure under high frictional loads, which promotes strain delocalization and facilitates the formation of strain transition zones. These mechanisms effectively mitigate strain localization and ultimately achieve superior anti-friction performance. This study is essential for enhancing the broad application of titanium alloys in high-frictional environments.