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Influence of Laser Peening With and Without Coating on the Surface Properties and Stress Corrosion Cracking Behavior of Laser-Welded 304 Stainless Steel

2021    Irizalp, Simge Gencalp; Koroglu, Burcak Kardelen; Sokol, David

This study aims to investigate the effect of laser peening with (LP) and without coating (LPwC) process on subsurface microstructural evolution, mechanical properties, and stress corrosion cracking (SCC) of laser-welded samples fabricated using 304 stainless steel. SCC behavior of this steel has been studied by the slow strain rate test in air and 3.5wt pct NaCl + 0.5 mol/L H2SO4 solution. Microhardness profiles and metallographic microstructures of the peened and unpeened samples presented and compared. Martensitic transformation is observed by XRD on the surface layer of the peened and unpeened samples. These improvements correlate with the formation of dense deformation bands and work hardening effects resulting from high strain plastic deformation. In unpeened specimens, tensile-type residual stresses arising from the welding process occur. In addition, the LPwC process also induces tensile-type residual stress on the surface. The tensile-type residual stresses on the weld metal and base metal surface as a result of thermal effect are not disruptive for SCC performance because the mechanical effect of LPwC produces an extremely strong work hardening layer just below the surface. As a result, although LPwC offers a combined effect of thermal and mechanical effects on the material, it is an effective and useful method in terms of both mechanical performance and corrosive behavior.