Mn coating on AISI 430 ferritic stainless steel by pack cementation method for SOFC interconnect applications

Protective/conductive coatings that resist oxide scale growth and reduce chromium migration and evaporation are required to make stainless steel interconnect materials for long-term durable operation of solid oxide fuel cells (SOFCs). To accomplish this, the interconnect can be coated by special spinels for their higher conductivity. In this work, AISI 430 ferritic stainless steel was coated with manganese using the pack cementation method to investigate the oxidation and electrical behaviour at operating conditions of SOFCs. The oxidation behaviour of coated substrates was studied during different types of oxidation tests. Area specific resistance (ASR) of the coated substrates was also tested as a function of temperature and time. The results showed that the formed Mn3O4 and MnFe2O4 spinels improved oxidation resistance by limiting the outward diffusion of Cr cations and the inward diffusion of oxygen anions. These spinels also caused a reduction of ASR for coated substrates (17.4 mΩ cm2) as compared to uncoated substrates(36.1 mΩ cm2) after 200 h of isothermal oxidation at 800 °C.

Research highlights
► Pack cementation of AISI 430 steel in a manganese base pack mixture.
► Formation of Mn3O4 and MnFe2O4 spinels during isothermal oxidation.
► Enhancement of isothermal and cyclic oxidation resistance.
► Enhancement of electrical conductivity of Mn-coated specimens.