Constructing heterostructure Ti6Al4V alloy by electropulsing assisted ultrasonic surface strengthening to improve its fretting wear performance

Abstract

Simultaneously improving the fatigue performance and wear resistance of titanium alloys is a trade-off process, and the surface mechanical strengthening method is a feasible way to balance the two. The ultrasonic surface strengthening (USS) technology can achieve most of the beneficial effects of other surface mechanical strengthening methods while reducing roughness, but it has the potential to be further enhanced. Besides, the load-dependent fretting wear mechanisms of heterostructure Ti6Al4V alloy prepared by the USS technology have not been systematically analyzed. This study utilized electropulsing assisted ultrasonic surface strengthening (EUSS) technology to enhance the surface properties of heterostructure Ti6Al4V alloy. Through microstructural characterization and theoretical analysis, the surface hardening mechanism of heterostructure Ti6Al4V alloy is elucidated. The results show that the gain effect of the EUSS treatment originates from the electroplasticity, while the opening of the {10−11}< -1–123 > pyramidal slip is considered to be the main cause. Subsequently, fretting wear tests under different loads were designed, combined with Hertzian contact analysis, to elucidate the load-dependent fretting damage mechanisms of heterostructure Ti6Al4V alloy. Heterostructure Ti6Al4V alloy has good fretting wear resistance due to high hardness at low loads, but fretting wear resistance disappears at high loads due to loss of plasticity.