Effect of Laser Shock Peening on the Fatigue Life of Inconel 792 Superalloy After High-Temperature Hot-Corrosion Exposure in a Molten-Salt Environment

Abstract

This study investigated the effect of laser shock peening (LSP) on the fatigue behavior of Inconel 792 nickel-based superalloy after exposure to hot corrosion. Specimens were first subjected to corrosion in a molten salt bath containing 75 wt% Na2SO4 + 15 wt% NaCl + 10 wt% V2O5 at 700°C and were subsequently fatigue-tested at room temperature. LSP-treated specimens processed at different repetition rates were comprehensively evaluated to assess surface integrity, residual stress, and microstructural evolution. The results demonstrated that LSP generated a substantial compressive residual stress field and promoted grain refinement near the treated surface. Maximum surface hardness increased by approximately 27%, and fatigue life improved by about 2.5 times in air and 2.46 times after hot-corrosion exposure compared with untreated specimens. The improved performance was mainly attributed to delayed surface crack initiation and a shift in the crack origin from the surface to the subsurface. Despite the aggressive high-temperature corrosion environment, LSP-treated specimens exhibited greater resistance to oxidation-related damage and maintained improved protection against hot corrosion, owing to the stability of the compressive residual stress field and the hardened surface layer.