Effects of loading mode on the critical cracking potential of duplex( α+ γ) stainless steel in a hot chloride solution

Abstract

One of the common characteristics in stress corrosion cracking (SCC) between austenitic and ferritic stainless steels in chloride environments is that cracking occurs at potentials noble to a critical value which has been designated as the critical cracking potential, E[sub cc]. For austenitic stainless steels, E[sub cc] is insensitive to prior cold work with or without the generation of martensite and has been interpreted as the minimum potential for crack propagation. On the other hand, for low interstitial ferritic stainless steels., E[sub cc] is extremely sensitive to microstructural variations induced by small amounts of cold work or grain coarsening. It has been demonstrated that E[sub cc] for the low interstitial ferritic stainless steels, when it is measured at constant load, is that for crack initiation and is determined by the competing rates of generation of a new surface by slip induced film breakdown and repassivation. However, the physical and/or electrochemical meaning for E[sub cc] of duplex stainless steels has not yet been studied. It is the purpose of this work to determine if E[sub cc] for duplex stainless is a potential for crack initiation or one for crack propagation in a hot chloride environment and to examine the effects ofmore » loading modes on the E[sub cc] of these alloys.« less