Effect of Ti addition on the electric and ionic property of the oxide scale formed on the ferritic stainless steel for SOFG interconnect

摘要

Ferritic stainless steels with Ti addition are considered as promising candidates for SOFC interconnect application. In this study, the effect of Ti addition on the electrical conductivity and Cr evaporation resistance was discussed in terms of microstructure and ionic property of the oxide scale by using TEM analysis and asymmetry polarization method. Ti addition induced the generation of ionic defects in the oxide layer and modified the growth kinetics of Cr_2O_3 and MnCr_2O_4, but in different manner depending on Ti amount. Ti content in a range of 0.05-0.07 wt% was effective for reducing the oxidation rate and electrical resistance. Addition of 1 wt% Ti promoted fast Cr_2O_3 growth due to the excess ionic defect in Cr_2O_3 matrix. However, the formation of the outermost MnCr_2O_4 layer was accelerated by Ti segregation near the scale/alloy interface and it reduced Cr evaporation effectively. Co-addition of a small amount of Ti and La enhanced Ti segregation without generation of excess ionic defect and improved both the electric conductivity and Cr evaporation resistance.