Surface Integrity and Oxidation of a Powder Metallurgy Ni-Based Superalloy Treated by Laser Shock Peening

Laser shock peening (LSP) is a mechanical surface treatment which can induce large compressive residual stresses and microstructural changes in a material by using repetitive shocks from laser pulses. In this work, the surface integrity (surface microstructure, topography, hardness and residual stress) of a LSP-treated powder metallurgy Ni-based superalloy was investigated for the first time. LSP treatment introduced large plastic deformation especially at a depth of about 100 μm from the surface, which increased the local hardness. The residual stress from the surface to the interior of the sample was investigated by synchrotron x-ray diffraction. The maximum compressive stress reached 400 MPa at the surface, while the depth of the compressive stress is about 0.7 mm. Lastly, the oxidation behavior of the treated and untreated samples was evaluated by thermal exposure at 700°C for 312 h. The LSP treatment decreased the thickness of the oxide layer, thereby showing improved oxidation resistance.