Improved corrosion resistance of Ni-base Alloy 600 welded joint by laser shock peening

Abstract

Stress corrosion cracking (SCC) of welded joint is one of the salient problems influencing the safety of nuclear power structure. In this work, laser shock peening (LSP) was introduced to enhance the corrosion resistance of Ni-base Alloy 600 welded joint. The corrosion behavior was evaluated by electrochemical corrosion and SCC tests, and its anti-corrosion mechanism was analyzed in terms of the residual stress and microstructure evolution. The results indicate that LSP treatment could significantly reduce the electrochemical corrosion rate and SCC sensibility of the weldments by 81 % and 14 %, respectively. The enhanced corrosion resistance of the welded joint was attributed to the compressive residual stress and high-density dislocation tangles induced by LSP. The maximum compressive residual stress of ~460 MPa in weld zone could be obtained with the laser power of 25 J. The microstructure evolution of LSP for weld zone and base metal is dominated by the dislocation activities.