Abstract
SS347 is one of the 18-8 series austenitic stainless steels. The major improvement for this kind of stainless steel is to add alloying elements of Nb and Ta. The purpose of adding these elements is to prevent the precipitation of carbide and the consequent sensitization of the steel. Although SS347 is usually designed for utilizing in the high temperature and corrosive environment, improper heat treatment would decrease the corrosion resistance of SS347. We use the double-loop electrochemical potentiokinetic reactivation (DL-EPR) to study the effect of heat treatment temperature on the sensitization behavior of SS347. Two phenomena were observed as follows: 1. Degree of sensitization of SS347 undergoing 550℃ and 850℃ heat treatment wouldn't change as the sensitization time increases. Low carbon diffusion rate limits the formation of chromium carbides at 550℃. Niobium catches more carbon atoms to prevent the formation of chromium carbides at 850℃. 2. Degree of sensitization of SS347 undergoing 650℃ and 750℃ heat treatment would increase linearly as the sensitization time increases. D.O.S. is the result of a balance between the rate of the precipitation of chromium carbide and the rate at which the chromium-depleted zones are eliminated by diffusion.