Electrochemical Corrosion Behavior of Ni-based Single-Crystal Superalloy Treated by Laser Shock Peening

Abstract:

Ni-based single-crystal (SC) superalloys were treated by laser shock peening (LSP) and then exposed at 750 and 850 °C for 2 h. The electrochemical corrosion behavior of the as-obtained specimens was investigated in 3.5wt% NaCl solution. The results show an increase in the corrosion resistance of SC alloy treated by LSP; it is related to the compressive residual stresses (CRS) and significantly different dislocation structures in γ/γ′ phases. The non-uniformly distributed dislocations in γ/γ′ phases raise the two-phase misfit. The electrochemical corrosion tests of LSP-treated specimens after heat exposure indicate that CRS and two-phase misfit are the two major factors influencing the corrosion resistance of SC alloys. CRS can enhance the corrosion resistance while the two-phase misfit deteriorates the corrosion resistance of SC alloys. In addition, the improved corrosion resistance of SC superalloys is linked to the formation of Ta₂O₅ and WO₃ oxides.

Key words:Ni-based SC superalloy;laser shock peening;electrochemical corrosion;lattice misfit;CRS