Regulation mechanism of in-situ synthesized (Nb,Ta)C/Ni composite cladding coatings by laser shock peening: Microstructure evolution and electrochemical corrosion behavior

Abstract

The surface microstructure of (Nb,Ta)C/Ni composite cladding coatings containing in-situ synthesized composite carbides (ISSCC-LCed coatings) was regulated by laser shock peening (LSP). The regulation mechanism of laser shock waves (LSW) on the microstructure evolution and electrochemical corrosion behavior of the ISSCC-LCed coatings was emphatically revealed. Correspondence between corrosion morphology and microstructure was established. Meanwhile, the phase evolution and residual stress variation laws were also tested and analyzed. The obtained results indicated that the LSW-induced surface structure exhibited interphase distribution characteristics of large and small grains through plastic deformation mechanisms such as extrusion, slip, folding, fracture, and cracking. Plastic deformation caused the relative movement of (Nb,Ta)C at the subsurface out of the surface, and the large (Nb,Ta)C fractured and extended over the entire carbide. Furthermore, element interdiffusion phenomenon existed between (Nb,Ta)C and Fe–Ni alloy. The coupling effect of LSW-induced surface fine grains and residual compressive stress inhibited corrosion propagation and improved electrochemical corrosion resistance.