Preparation Of Mn-Cu Spinel Coating On The Surface Of Stainless Steel And Study Of Its Electrical Performance

Ferritic stainless steels become the first choice for solid oxide fuel cell(SOFC)metallic interconnect due to the advantages including low cost,coefficient of thermal expansion match with other cell components,high temperature oxidation resistance,and acceptable electrical properties of the surface scale.However,the evaporation of Cr2O3 poisons the cathode,and leads to the degradation of cell performance.In previous study,Mn-Cu alloy(the atomic ratio of Mn to Cu is 1:1)coating was deposited on SUS430 stainless steel by DC magnetron sputtering,followed by high temperature oxidation to convert the metallic coating to(Mn,Cu)3O4 spinel oxides.Nevertheless,the outer surface of the spinel coating contains some CuO.To resolve this problem and get more pure(Mn,Cu)3O4 spinel coating,the sputered alloy target of Mn1.7Cu1.3(atomic ratio)was chosen.In this work,the oxidation behavior of the Mn1.7Cu1.3-coated steel was investigated.The morphology,phase structure and electrical performance of the surface scale were characterized.The results indicated that:(1)During the early stage of the oxidation for coated steel,Mn was firstly oxidized and generated MnO and Mn3O4.Then Cu was oxidized and generated CuO.Since the oxide of Mn and Cu couldn’t prevent the inward diffusion of O,Cr in the steel occur selective oxidation at the interface of the surface scale and the steel.With the process of the oxidation,(Mn,Cu)3O4 spinel phase was formed due to the reaction between CuO and Mn oxide.(3)The mass gain of the coated steel was obvious during the first week,and then it was similar to that of the steel substrate.After the first week,the masss gain just increased slightly with increasing time.(3)A double-layer oxide scale was developed on the surface of the coated steel,consisting of an outer layer of(Mn,Cu)3O4 spinel and an inner layer of oxide rich in Cr.(4)The(Mn,Cu)3O4 spinel layer not only suppressed the outward migration of the Cr,but also improved the electrical conductivity of the surface scale.