晶界特征分布对316L不锈钢焊接接头腐蚀行为的影响

Influence of Grain Boundary Characteristic Distribution on Corrosion Behavior of 316L Stainless Steel Welded Joint

采用电子背散射衍射(EBSD)、取向成像显微技术(OIM)和X射线残余应力分析技术,通过电化学试验和浸泡腐蚀试验研究了316L不锈钢焊接接头焊缝和母材的特殊晶界分布和表面残余应力分布,以及溶液温度对其耐蚀性的影响。结果表明:316L不锈钢焊接接头焊缝的低重位点阵(CSL)晶界所占的比例比母材的低45%;焊缝和母材的临界点蚀电位分别为0.26 V和0.40 V;在4%FeCl3溶液中,焊缝的腐蚀速率约为母材的2倍,且随着溶液温度的升高,其腐蚀速率逐渐增大;较低比例的低CSL晶界及高的残余拉应力是焊缝优先发生腐蚀的原因。

Using electron backscatter diffraction(EBSD), orientation imaging microscopy(OIM) and X-ray residual stress analysis technique, electrochemical test and immersion corrosion test were used to study the special grain boundary distribution and distribution of weld and base material of 316 L stainless steel welded joint and surface residual stress distribution, and the influence of solution temperature on its corrosion resistance. The results showed that the proportion of low coincidence site lattice(CSL) grain boundaries in the weld of 316 L stainless steel welded joints was 45% lower than that of the base metal. The critical pitting potentials of the weld and base metal were 0.26 V and 0.40 V, respectively. In 4% FeCl3 solution, the corrosion rate of the weld was about twice that of the base metal, and those corrosion rates increased with the increase of solution temperature. Low CSL grain boundary and high residual tensile stress were the reasons for the preferential corrosion of welds.