The Effect of Tungsten Addition on the Oxidation Behavior of Fe-22Cr-0.5Mn Ferritic Stainless Steel

Abstract

The effect of tungsten addition to Fe-22Cr-0.5Mn ferritic stainless steel on the oxidation, electric property and Cr evaporation was investigated for application to the solid oxide fuel cell (SOFC) interconnect. Mass gain was measured at 800oC to evaluate the oxidation rate and a 4-probe DC method was used to measure the area specific resistance (ASR). Cr evaporation rate was evaluated by the condensation method. Addition of 4 wt% W reduced the oxidation rate of Fe-22Cr-0.5Mn steel. The evaporation rate of Cr vapor species and ASR were also reduced. Chi (χ) phase, which precipitated at the grain boundary near the interface between the oxide layer and substrate steel, seems to be responsible for suppressing the fast diffusion of Cr, so that the surface Cr content was reduced while Mn content was increased. This reduced Cr content at the surface is responsible for the lower Cr evaporation rate and ASR.