Oxidation behavior of pre-oxidized ferritic stainless steel interconnect with Mn1.7Cu1.3 coating by magnetron sputtering

摘要

Solid oxide fuel cells (SOFCs) for stationary, transportation and portable power generation have been extensively attracted due to their high energy conversion efficiency, environmentally benign emissions and fuel flexibility. However, some critical issues continue to impede widespread implementation. One of the hurdles related to materials is interconnects, which physically connect individual fuel cells into electric series, separate fuel and oxidant gases. With the reduction of SOFCs operating temperature, Cr_2O_3-forming alloys such as ferritic stainless steels have been widely used as intermediate temperature (600-800°C) planar SOFC interconnect. One challenge for them is the evaporation of Cr_2O_3, leading to the cathode Cr-poisoning. To solve this problem, some coatings have been developed including spinel coatings such as (Mn,Cu)_3O_4 due to its high electrical conductivity and coefficient of thermal expansion (CTE) match with other cell components. In this work, Mn_(1.7)Cu_(1.3) coating was deposited on the pre-oxidized ferritic stainless steel SUS 430 by means of magnetron sputtering, followed by thermal exposure in air at 800°C corresponding to the SOFC cathode environment in order to convert Mn_(1.7)Cu_(1.3) coating into (Mn,Cu)_3O_4 spinel. The early-stage and long-term oxidation behaviors of the pre-oxidized steel with Mn_(1.7)Cu_(1.3) coating were investigated in air at 800°C, and the oxidation mechanism was discussed.