Thin elemental coatings of yttrium, cobalt, and yttrium/cobalt on ferritic stainless steel for SOFC interconnect applications

Thin elemental coatings of Y, Co, and Y/Co on a commercial ferritic stainless steel (AISI444) were investigated for their effects on the growth kinetics and area specific resistance (ASR) of the scale formed at 800 °C. After oxidation for 1000 h, the ASR value of the Y-coated AISI444 was less than that of the corresponding uncoated sample by the factor of two, because of a significant retardation of scale growth. The Co coating also resulted in a decrease of the ASR value even though it significantly accelerated the scale growth. The effects of the Y and Co coatings on scale growth were associated with the growth kinetics of the chromia sublayer in the scale. The Y coating was most effective for solid oxide fuel cell (SOFC) interconnect applications because of the relatively low and stable ASR value with the lapse of oxidation time.