Effect of microstructure evolution and phase precipitations on hot corrosion behavior of IN718 alloy subjected to multiple laser shock peening

High-temperature hot corrosion experiments of IN718 alloy subjected to multiple laser shock peening (LSP) were conducted by coating a salt mixture (75 wt% Na2SO4 + 25 wt% NaCl) on its surfaces at 700, 800 and 900 degrees C for 10 cycles. The effect of microstructure evolution and phase precipitations on high-temperature hot corrosion behavior of the specimens was investigated. Results showed that high-temperature hot corrosion behavior is associated with delta phase precipitations. Excessive delta phase precipitations significantly accelerate hot corrosion at 900 degrees C due to Na-containing oxides formation. According to corrosion kinetics, multiple LSP treated specimens exhibit lower mass loss compared with untreated specimens, indicating multiple LSP can relieve high-temperature hot corrosion. This is mainly attributed to crystal defects, which promote outward diffusion of Cr generating protective Cr-rich oxides.