Improved oxidation resistance of coated interconnects at 700ºC

Abstract

Ferritic stainless steels are being considered as potential interconnect materials for solid oxide fuel cells (SOFCs), in part because of their low cost relative to alternatives. These materials are, however, susceptible to degradation over time. A primary source of degradation is spallation or cracking and weight change, which is due to the repeated thermal cyclic oxidation. In this work, AISI 430 ferritic stainless steel was coated with manganese by pack cementation method to investigate the oxidation behavior at operating conditions of SOFCs. The oxidation behavior of coated substrates was studied as a function of time. Cyclic oxidation has been also tested at 700ºC for 50 cycles. Coated substrates oxidation behavior as a function of time showed that the spinels forming (Mn3O4, MnFe2O4) during annealing in isothermal oxidation improved oxidation resistance by limiting the outward diffusion of Cr cation and the inward diffusion of oxygen onion. The weight gain obtained 1.894 mg.cm-2 for uncoated substrates and 0.832 mg.cm-2 for coated substrates after 200 h annealing at 700ºC. Results of cyclic oxidation exhibited that coated substrates demonstrate an excellent resistance against the spallation and cracking.