Significant improvement in hot corrosion resistance of Inconel 690 by laser shock peening

The effects of laser shock peening (LSP) with different peening times on the hot corrosion behavior (molten salt of 75 wt% Na2SO4 + 25 wt% NaCl) of Inconel 690 at three different temperatures (700 degrees C, 800 degree celsius, 900 degrees C) were investigated. The corrosion conditions of the three specimens were also compared in the extreme case, i.e. after 900 degree celsius, 300 h of hot corrosion. The results showed that LSP effectively prevented the surface oxides from shedding. As times of LSP increased, the strengthening effect improved and the rate of weight loss gradually slowed down. The dense oxide film generated by the high Cr content of the material itself, LSP-induced high-density dislocation structure, mechanical twinning and grain refinement is one of the key factors in improving the hot corrosion resistance of Inconel 690. The CRS layer and microhardness layer are another key factor in preventing the cracking of the oxide film to enhance the hot corrosion resistance. Under extreme conditions, the hot corrosion resistance of LSPed specimens is still better than that of unLSPed specimen.