The importance of steel chemistry and thermal history on the sensitization behavior in austenitic stainless steels: Experimental and modeling assessment

The sensitization of austenitic stainless steels is dependent on various factors such as chemical composition, heat treatment temperature and time. To study these effects, the degree of sensitization in five austenitic stainless steel compositions that were subjected to isothermal heat treatments in the temperature range 550-820 degrees C has been determined using double loop electrochemical potentiokinetic reactivation testing. The nucleation and growth of grain boundary M23C6 carbides, that are responsible for sensitization, has been modelled with the help of the precipitation and diffusion modules in Thermo-Calc, assuming local multicomponent equilibrium, flux balance at the carbide-matrix interface, to quantitatively predict the Cr depletion. Based on the Cr depletion characteristics, a depletion parameter has been established that can predict sensitization in austenitic stainless steels and predict the effects of individual alloying elements.