Effect of laser shock peening on microstructure and hot corrosion of TC11 alloy

The effects of laser shock peening (LSP) impacts on microstructure, surface residual stress, micro-hardness and hot corrosion behavior of TC11 alloy were investigated. Results indicate that a large number of crystal defects such as dislocation cells, dislocation walls, dislocation arrays, high dense dislocation tangles and mechanical twins were gained on the surface of TC11 alloy after LSP. Furthermore, the coarse grains in the surface of the specimen have been refined to the nano-grains after multiple LSP impacts. LSP can induce high-amplitude compressive residual stresses on the surface. The maximum compressive residual stress is - 593 MPa with a 200 mu m deep affected layer after 7 LSP impacts. The corrosion surface investigated by X-ray diffraction (XRD) revealed that the corrosion products mainly consist of TiO2, Al2O3, NaAlO2 and Na2TiO3. The oxide protective layer of the specimen treated by 7 LSP impacts is homogeneous and compact without obvious crack, spalling and pits. The dense oxide layer is beneficial to improve the hot corrosion resistance which is contributed to LSP induced crystal defects, nano-grains and high-amplitude compressive residual stresses. The minimum weight loss of the hot corrosion specimen treated by 7 LSP impacts was 1.08 mg/cm(2), which was much lower than that of the untreated specimen (11.87 mg/cm(2)).