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

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.