The High Temperature Oxidation Behavior And Structure Characte Rization Of Co-Mn Scale Coating Prepared By HEMAA For SOF C Interconnect

As global energy challenges grow, alternative energy technologies are being investigated,such as fuel cells. Solid Oxide Fuel Cells(SOFCs) provide the advantages of high energy conversion efficiency, low pollution, fuel flexibility and both portable and stationary application. High material cost and need for longer material lifespan still impede the wider use of SOFCs.To produce substantial voltage, planar SOFCs are joined into stacks using interconnects.Interconnects both separate and connect each individual fuel, separating gas flow and conducting current. For medium-temperature SOFCs that operate at lower than 800℃, metal alloys are being considered to be applied in the interconnect, particularly ferritic stainless steel. Ceramic coatings are being explored to improve the surface conductivity over time and significantly reduce Cr volatility from the steel. In addition, the coating must have a matching coefficient of thermal expansion(CTE) and be compatible with electrode and seal materials.(Co,Mn)3O4 spinel coating is more promising,which has been prepared by various techniques,resulting in different thicknesses, compositions and micro-structures.In this study, Co-10Mn、Co-40Mn、Co-10Mn/Co、Co-40Mn/Co、Co-8Mn-2Dy/Co、Co-38Mn-2Dy/Co coating were firstly prepared on 304 SS by high energy micro-arc alloying(HEMAA). Coated-samples were subsequently pre-oxidized in 800℃ air for 2h to develop spinel protective coating.Ultimately, oxidation behaviors were evaluated as a function of exposure to air and air-10%H2O at 800℃,respectively. The main results of this paper were as fellows:The most available deposition parameters were obtained by testing repeatedly and the effect of each parameter on mass change were analyzed in the meantime.SEM of presented the single deposition point was splashing with low-lying center and swelling edge.Deposition-coating was consisted of massive single points,one piling on another. The XRD result showed deposition-coating was made of cubic Co.Mn was not distributed evenly in deposition-coating, but concentrated in strips or blocks. To get thermal growth oxide-coating, the best parameters of pre-oxidation were gained by comparing different values,including the oxidation temperature and oxidation time. High oxidation-temperature will lead to the spallation of oxide-coating,and discontinuous oxide-coating will be produced in short oxidation-time. The effect of Co transition layer,different ratio of(Co,Mn)and rare earth element Dy on preparation of spinel coating were studied to make the coatingmore continuous and compact.The oxidation kinetics curves of the coated-samples and bare 304 SS in 800℃air were obtained.The oxidation speed of coated-samples were faster than bare 304 SS initially,which was raised to the formation of spinel coating. Oxidation gain gradually become slow and stop finally, concluding that(Co,Mn) spinel coating could improve high-temperature oxidation resistance effectively. In the test of SOFC cathode environment,adhesion was improved in wet air. Pre-oxidation could make corrosion resistance better in wet air.