Surface characteristics and tribological performance of Ti6Al4V peened by sinking bead abrasive waterjet

Improving the wear resistance of Ti6Al4V to extend the service life has been a hot research topic for decades. A cost-effective and environmentally friendly method of using industrial waste sinking beads as shot media for abrasive waterjet peening is presented in this study. The peening characteristics and the intrinsic process mechanisms of the method are investigated. The friction and wear tests were conducted to evaluate the effectiveness of this method. It was found the technique can induce strong plastic deformation layers without changing the phase composition of Ti6Al4V. The shock wave induced by the impact of the sinking bead creates a plastic strain, resulting in a decrease in the grain diameter and an increase in the kernel average misorientation of the peened specimen. Although the surface quality of the peened specimens is reduced, the residual compressive stress on the surface is >800 MPa. The surface microhardness can be significantly increased by 21.9 %, 28.2 %, 36.2 %, and 40.1 % respectively, owing to the grain refinement and dislocation multiplication. The friction coefficients of the peened specimens showed slight reductions compared to the original ones, and the wear rates were reduced by 4.75 %, 13.6 %, 14.9 %, and 16.8 %, respectively. The main wear mechanisms for both the original and peened specimens are abrasive wear, oxidative wear, and adhesive wear. Reduced fatigue cracks on the peened specimens can be observed, owing to the increased fatigue strength and wear resistance.