On Potential Application of Coated Ferritic Stainless Steel Grades K41X and K44X in SOFC/HTE Interconnects

The paper will present the high temperature properties of K41X and K44X ferritic alloys, in particular oxidation behavior in isothermal and cyclic conditions under operating atmosphere. The positive effect of the addition of a protective coating on these steel grades in terms of oxidation resistance will then be presented. Most of the studied coatings are Mn-Co spinels deposited by sol-gel, atmospheric plasma spray or electroplating, their aim being to limit the chromium evaporation and to fit the severe performance requirements. They lead to low and stable contact resistance, which is a requirement necessary for long-term SOFC/HTE operation: for example a contact resistance of 22 mΩ.cm2 was obtained after 3500h at 800°C in air with MnCoFe spinel coating. In this respect, K41X was recently chosen to be tested for the 3rd generation stacks of SOFC in the European project "REAL SOFC" or THE prototypes in French ANR projects