热输入对不锈钢激光搭接焊接头晶间腐蚀敏感性的影响

Effects of heat input on the intercrystalline corrosion sensitivity of laser overlapped welded stainless steel joints

利用双环电化学动电位再活化法研究了激光焊接热输入对奥氏体不锈钢激光搭接焊接头晶间腐蚀敏感性的影响,并通过X-射线衍射仪、扫描电子显微镜及能谱仪分析了激光搭接焊接头的相组成与主要合金成分.结果表明,不锈钢激光搭接焊接头的晶间腐蚀敏感性高于母材,且随着激光热输入的增加,焊接接头的阳极极化曲线钝化区间逐渐变窄,维钝电流密度增大,再活化率Ra=Ir/Ia增大,接头的晶间腐蚀敏感性增加.与焊缝金属相比,焊接热影响区的晶间腐蚀倾向更为明显,成为接头中耐晶间腐蚀性能最薄弱的部位,而在晶界上析出M23C6导致晶界贫铬是晶间腐蚀敏感性增加的主要原因.

Effects of heat input on the intercrystalline corrosion sensitivity of laser overlapped welded stainless steel joints were studied by double-loop electrochemical potentiokinetic reactivation (DL-EPR) method. The phase composition and the main alloy composition of the joints were examined with X-ray diffractometer, scanning electron microscopy and energy dispersive spectrometer. The results indicated that the intercrystalline corrosion of the joints was more sensitive than that of base metal. Increasing the heat input, the passivation range of the anode polarization curves was gradually narrowed, the maintaining passivity current density and the reactivation rate was increased, which indicated that the intercrystalline corrosion sensitivity was increased. Compared to the weld seam, the intercrystalline corrosion tendency of the heat affected zone was more obvious. The heat affected zone was the weakest zone of the joint in the performance of intergranular corrosion resistance, and the main reason of the increased intercrystalline corrosion sensitivity was grain boundary poor chromium because of M23C6 separated out on the grain boundary.