Quantitative analysis of Cr-depleted zone morphology in low carbon martensitic stainless steel using FE-(S)TEM

A new type of intergranular stress corrosion cracking (IGSCC) has been observed in low carbon martensitic stainless steel at heat affected zone (HAZ). Nano level microstructural analysis was carried out to investigate IGSCC factors. It was found that cracks propagate along prior austenite grain boundaries where a row of carbides had been formed. Cr-depleted zones at the grain boundaries were characterized by a STEM-EDX analysis and that morphology was obtained by deconvoluting this results. It is concluded that Cr-depleted zones only a few nanometers in width are enough to cause IGSCC at HAZ in this steel under certain circumstances.