激光冲击对不锈钢焊接接头残余应力场的影响

针对不锈钢焊接接头存在残余应力且分布不均匀、容易发生应力腐蚀的问题,采用激光冲击强化对其进行处理,探究激光功率密度和冲击次数对表面残余应力状态的优化作用,并通过应力腐蚀试验验证优化效果。结果表明:随着功率密度增加,表面残余应力明显下降,但下降幅度逐渐减小,功率密度4.24GW/cm2与2.83GW/cm2冲击产生的残余应力相差不大,熔合区还存在残余拉应力,说明高功率密度不足以消除表面残余拉应力;随着冲击次数增加,残余拉应力显著降低,2.83GW/cm2冲击3次之后,残余拉应力完全消除,局部最高应力梯度从54.7 MPa/mm下降到11.7 MPa/mm,获得了高数值、分布均匀的残余压应力层。激光冲击强化后,焊接试样的应力腐蚀断裂时间提高了33.48%,激光冲击强化产生的残余压应力是其应力腐蚀抗性提高的重要原因。

Effect of laser shock processing on residual stress of strain steel welded joints

There exists residual tensile stress in the stainless steel welded joints, which makes the stainless steel welded joints sensitive to stress corrosion cracking. Laser shock processing is used to treat stainless steel welded joints. The effect of laser shock processing on optimization of surface residual stress is researched, and the test of stress corrosion is carried out to examine optimization result. With increasing of laser power density, the surface residual tensile stress decreases, but the increment of the decrease is gradually reduced. For example, when impacted with 4.24 GW/cm2 and 2.83 GW/cm2, the residual stress has not obviously changed; moreover, there still exists residual tensile stress in the fluxional zone. It indicates that residual tensile stress cant be eliminated entirely when impacted individually with high power density. With increasing of the impact times, the residual tensile stress will be eliminated absolutely, and the stress gradient decreases from 54.7 MPa/mm to 11.7 MPa/mm. When treated by laser shock processing, the stress corrosion rupture time of the welded specimen increases by 33.48%, which is attributed to residual compressive stress generated by laser shock processing.