非金属夹杂物对439M耐点蚀性能的影响

利用电化学实验和扫描电镜(SEM)结合能谱仪(EDS)分析研究了非金属夹杂物对钛、铌双稳定439M铁素体不锈钢耐点蚀性能的影响。动电位阳极极化实验结果表明,没有或者少夹杂物区域为工作电极的试样439M-Part击穿电位为813mV,比整个区域为工作电极的试样439M-Whole的击穿电位高出了约600mV。SEM结合EDS分析显示:试样439M-Whole的点蚀坑呈不规则形貌,主要发生于(Ti,Ca,Al)2O3复合夹杂物上,这是钝化膜表面不均匀和点蚀坑内的自催化反应共同作用的结果;而试样439M-Part的点蚀坑则位于(Ti,Nb)(C,N)夹杂物周围。研究表明,夹杂物周围有铬的偏析并形成铬的化合物,其周围出现贫铬区,引发点蚀。

Effect of non-metallic inclusions on pitting corrosion resistance of ferritic stainless steel 439M

Effect of non-metallic inclusions on pitting corrosion resistance of Ti+Nb dual stablized ferritic stainless steel 439M was investigated using electrochemical tests and scanning electron microscope (SEM) combining with energy dispersive spectroscopy (EDS) analysis. The results of potentiodynamic anodic polarization tests show that the pitting potential of inclusion-free area (439M-Part) is 813mV, and higher than that of whole sample (439M-Whole) by about 600mV. SEM observation and EDS analysis reveals that the pits with irregular shape for sample 439M-Whole initiate from (Ti,Ca,Al)2O3 complex inclusions, which is attributed to the co-effection of inhomogeneous passive film and self-catalyzed reaction of pits. Whereas, the pits of sample 439M-Part initiate from the area around (Ti,Nb)(C,N) inclusions due to Cr segregation aroud the inclusions, which leads to the appearance of Cr depletion zone around the compounds.