Tribological performance and lubrication mechanism of polyacrylamide as a high-efficiency water-based lubricant additive for titanium alloys

Titanium alloys present challenges in terms of lubrication due to their difficult-to-machine nature, which necessitates the development of sustainable and environmentally friendly lubricants. Water-based lubricants are commonly used for titanium alloys because of their effective cooling properties, despite encountering challenges such as poor lubrication performance and complex mechanisms. This study first demonstrates that polyacrylamide (PAM) is an excellent water-based lubricant additive for the Ti6Al4V (TC4)/GCr15 interface. It results in a reduction of friction and wear in TC4 contacts by 40% and 90%, respectively, when utilizing a low concentration of 2.5 wt%. It is also found that oxidative wear is present on the rubbing surfaces of TC4 when exposed to water at ambient temperature. The exceptional lubricating properties of PAM can be attributed to the formation of a boundary lubrication film, which occurs through the adsorption of PAM onto tribo-oxide layer. Increased concentrations of PAM promote chemisorption and hydrogen-bond interactions, thereby increasing the stability of the boundary lubrication film.