Influence of laser shock peening on the fretting wear behaviour of CuNiIn coating

Abstract

TC4 titanium alloy (Ti-6Al-4 V) has excellent mechanical properties, corrosion resistance, and high temperature stability. The CuNiIn coating acts as a solid lubricant to improve fretting wear resistance. However, the life of the coating is limited by porosity and inhomogeneous stress distribution. Laser shock peening (LSP) produces a hardened layer on metallic surfaces, thereby improving fretting wear resistance. In this study, LSP was applied to improve CuNiIn coatings. The effects of LSP on wear resistance and the underlying mechanisms were investigated. SEM, EDS, XRD, Vickers microhardness testing, and X-ray residual stress analysis were used to characterize the microstructural evolution induced by laser shock waves. The results showed a significant improvement in wear resistance after LSP. The wear volume decreased from 8.55 × 10⁵ μm³ to 6.93 × 10⁵ μm³, with the porosity reduction achieved by laser-induced plastic deformation. With increasing laser energy, the average grain size decreased to 0.82 μm, while the KAM angle increased to 0.38°. After LSP treatment, the microhardness increased from 162.6 HV_0.2 to 204.3 HV_0.2, and the residual stress state changed from tensile (+234.5 MPa) to compressive (−41.5 MPa). This study provides theoretical guidance for optimizing LSP applications in CuNiIn coatings.