The Effects of Laser Shock Processing on Mechanical Properties of Welded Jionts(Ⅰ)

When a short pulse,high peak power (>10¹³W/m²) laser irradiated to a metel surface,an impulsive wave,which is generated by a high-pressure and high-temperature plasma confined by the transparent medium,propagates into the material interior,thereby inducing strain hardening.We call this surface strengthening technology as "laser shock processing" or "laser shock peening".The laser shock processing(LSP) can improve the surface hardness,tensile strength and gain a compressive stress layer or hardened layer with thickness much lager than that in the case of conventional peening,which is more benefit for the improvement of fatigue properties.In order to study the application of laser shock processing as a post weld treatment technology,the welded beads of a Ni-base super alloy GH30 sheet with thickness of 1.66 mm and a austenitic stainless 1Cr18Ni9Ti with thickness 1.2 mm were shocked by pulse laser,then the surface residue stress,microhardness,ultimate tensile strength and the fatigue life were compared with those without LSP in this paper.The results show that the ultimate tensile strength of GH30 argon arc welded joints was increased by 12% and the fatigue life of 1Cr18Ni9Ti plasma welded joints was increased more than 300% after shocking.