A novel surface engineering technique for improving tribological performance of low-cost beta titanium alloy

A novel surface engineering technique has been developed to integrate bulk solution treatment with Catalytic Ceramic Conversion Treatment (C3T) to enhance the tribological performance of low-cost beta (LCB) titanium alloy (Ti-6.8Mo-4.5Fe-1.5Al). This new integrated technique can effectively address the technical limitation of low bonding strength at the oxide layer-matrix interface formed by the previous combination of solution treatment with conventional Ceramic Conversion Treatment (C2T). Reciprocating pin-on-disc sliding wear tests were performed against WC balls under dry conditions. Computational analyses of electronic structure changes and post-examination of the surface structure were conducted to investigate the catalytic mechanism of gold. Profilometry-based Indentation Plastometry (PIP) was carried out to assess the impact of surface treatment on the bulk material properties.

Experimental results demonstrate that the wear resistance of the LCB titanium alloy can be improved by approximately 200 times by the new C3T; the oxide layer is 20 times thicker than that of the C2T-treated samples; the coefficient of friction decreased from 0.4 to 0.8 for untreated samples to 0.1–0.2 for the C3T treated samples. The typical wear mechanism of titanium, characterised by severe adhesive wear, is replaced by mild abrasive wear for C3T treated LCB titanium alloy when sliding against WC balls in air; and delamination wear caused by weak interface bonding in conventional C2T-treated surface is eliminated. Interestingly, the pre-addition of a gold film decreased the surface hardness while improving the wear resistance, and acting as a lubricant in the tribological process, particularly under low loads due to the soft and chemically stable nature of gold.