Laser shock peening enhanced corrosion properties in a nickel based Inconel 600 superalloy

Abstract

Laser peening without coating (LPwC) is an advanced surface modification treatment applied nowadays for many of the industrial alloys, as it tremendously enhance the fatigue and corrosion properties. We report the influence of LPwC on residual stresses, hardness, microstructure, surface roughness and topography of a nickel based superalloy, Inconel 600. LPwC parameter optimization for Inconel 600 that results in larger and deeper compressive residual stresses with relatively smaller surface roughness was carried out. It was noted with optimized LPwC condition that maximum compressive residual stresses was nearly −672 MPa and depth of work-hardening was about 1400 μm, with slight increase in the hardness with a case depth of about 400 μm. The 3D topography indicated roughening at LPwC treated surface and represented the column or steps like feature whilst the average roughness was found to be smaller (≤1 μm). Grain refinement was not observed. The corrosion resistance of LPwC specimen showed tremendous increase with a 106 fold decrease in corrosion rate from that of untreated condition. Consequently, larger and deeper pits were observed in the case of untreated specimen while LPwC treated specimen showed no pitting. The chemical composition and chemical state analyzed with XPS indicated a better passivation of the surface film on LPwC specimen.