Enhancement of wear resistance in TC6 titanium alloy through a combined treatment of laser shock peening and nitrogen ion implantation at 300 °C

Abstract

The TC6 titanium alloy was subjected to a combined treatment of laser shock peening (LSP) followed by nitrogen ion implantation at 300 °C. The effects of this combined treatment on the microstructure, surface mechanical properties, and tribological behaviors of TC6 were evaluated. The TC6 alloy demonstrated a gradient distribution in grain size and elemental composition in its surface after the combined treatment. Compared to untreated TC6, the surface nano-hardness increased from 4.95 GPa to 7.08 GPa after nitrogen ion implantation at 300 °C, 5.91 GPa after LSP treatment, and 7.70 GPa after combined treatment. The surface residual stress changed from an initial tensile stress of 50.60 MPa to a compressive stress of 42.41 MPa after nitrogen ion implantation at 300 °C, 875.10 MPa after LSP, and 735.99 MPa after combined treatment. These changes in microstructure and surface mechanical properties were attributed to the synergistic effects of the combined treatment. For the tribological behavior, the wear rate of TC6 after combined treatment was the lowest among all states. The wear mechanism changed to milder adhesive wear from severe abrasive wear and adhesive wear in untreated state, which was attributed to the formation of nanocrystals and nitrides in the surface as well as the increase in surface dislocation density.