Tribological and mechanical properties improvement of G20CrNiMo alloy via fabricating gradient composite layer through ultrasonic strengthening grinding process

Abstract

Fretting wear is one of the main causes of damage failure at the contact interface, which significantly limits the reliable application of mechanical parts. To address this issue, a composite microstructure comprising a gradient structure, α-Al2O3 particles, and micro-dimples was fabricated on the G20CrNiMo alloy by an improved method of ultrasonic strengthening grinding process (USGP). Subsequently, the fretting resistance and mechanical properties of the treated G20CrNiMo alloy were investigated. The results indicated that USGP could significantly enhance mechanical strength and wear resistance properties. The USGP-treated sample demonstrated an increment of approximately 25.32 % in tensile strength compared to the untreated sample. It also exhibited reductions of about 19.61 % and 49.56 % in friction coefficient and wear volume, respectively. After USGP treatment, the gradient structure incorporating dense dislocation and high-angle grain boundaries (HAGBs) limited the shear motion of the G20CrNiMo alloy, thereby enhancing its mechanical properties. Furthermore, the synergistic effect of gradient structure, Al2O3 particles, and micro-dimples effectively restricted shear deformation and formed a supplementary glaze to further improve its fretting wear resistance.