Preparation Of CeO₂ And CeO₂/FeCoNi Coating On Stainless Steel And Its High-temperature Performance

With the improvement of solid oxide fuel cell(SOFC),the operating temperature has been reduced to 600?800?.Ferrite stainless steel(FSS)can be used as SOFC interconnect with the advantages of excellent manufacturability and economic cost.However,there are two problems to be resolved for the FSS.Firstly,with the increase of oxidation,the thickness of Cr₂O₃ sustainedly increases which reduced electrical conductivity of interconnect.Secondly,poisoning of porous cathode caused by Cr element evaporation must result in degradation of cell performance.At present,the main solution is to apply a protective coating on the surface of interconnect to improve the oxidation resistance of the FSS and inhibit the diffusion of Cr element.CeO₂ was deposited on the surface of SUS430 FSS by dipping and thermal decomposition method.In addition,FeCoNi coating was deposited by magnetron sputtering on the CeO₂ deposited steel.The oxidation behavior of CeO₂ and CeO₂/FeCoNi coated steel at 800? in air was investigated via X-ray diffraction(XRD),scanning electron microscopy(SEM).The scale area specific resistance(ASR)of oxidized samples was measured using four probes direct current(DC)technique.The results indicated that:The oxidation mechanism of stainless steel substrate can be changed by the dispersion distribution of CeO₂ in Cr₂O₃ layer,which reduces oxidation gain rate and improveds the adhesion between oxide layer and substrate.Due to the out-diffusion of Mn element,(Mn,Cr)₃O₄ spinel phase is formed outside Cr₂O₃.The ASR of surface scale formed on the CeO₂ deposited steel after oxidation for 15 weeks is 43.20 m?·cm².For CeO₂/FeCoNi coated steel after oxidized for 300h,the surface scale has shown a multi-layered structure with a inner layer of Cr₂O₃,a middle layer of(Ni,Co)O layer and outer layer of(Fe,Co,Ni)₃O₄ spinel.The dispersive distribution of CeO₂ in Cr₂O₃ layer can improve the oxidation resistance and the adhension between oxide layer and substrate and prevent Cr diffusion.The ASR of surface scale formed on the CeO₂/FeCoNi coated steel after oxidation for 300h is 12.42 m?·cm².The surface deposition of CeO₂/FeCoNi coating can effectively improve the performance of interconnect.