New findings on intergranular corrosion mechanism of stabilized stainless steels

Number of different sets of stabilized both ferritic and austenitic stainless steels with various alloying elements were evaluated to verify new findings on the intergranular corrosion mechanism. The intergranular segregation and precipitation were analyzed by using a transmission electron microscopy with an energy dispersive X-ray spectroscopy and a laser assisted three-dimensional atom probe. On the basis of the current result, it is newly proposed that the intergranular corrosion occurring in the stabilized both ferritic and austenitic stainless steels is induced by Cr-depletion due to segregation of un-reacted Cr atoms around carbides of stabilizer elements (Ti or Nb) along the grain boundary, but not due to formation of Cr-carbide. A prevention method for this type of intergranular corrosion is also suggested after critical evaluation on the effect of Cr, C, and Ni.