Surface Sputtered Modification And High Temperature Oxidation Behavior Of Low Cr Fe-Ni Base Alloy

The interconnect is a critical component of solid oxide fuel cells (SOFCs). With the reduction of SOFC operating temperatures to the range of600-800℃, it is possible to employ cost-effective high temperature oxidation resistant alloys as SOFC interconnects to reduce the cost of a cell stack. However, the major weaknesses of Cr2O3-forming alloys are Cr vaporization. This problem limits the commercial application of SOFC.According to the research results of the former, surface modification was carried out for the low Cr Fe-Ni base alloy containing0.36%Si by means of magnetron sputtering method. The sputtered coating with columnar crystals was obtained on the cast alloy. The main work focuses on the systematic study on the thermal expansion behavior of cast alloy, oxidation behavior of sputtered coating and area specific resistance (ASR) of the oxide in air at800℃. The following conclusions are achieved:(1) The thermal expansion behavior of cast alloy matched with other components of SOFC, which can meet the requirement of a cell stack.(2) Sputtered coating has a good performance in the oxidation experiment. A double-layer oxide structure with a main CoFe2O4spinel outer layer and a protective Cr2O3inner layer was formed on the surface upon thermal exposure in air at800℃. Mass gain of sputtered coating after oxidation for12weeks is only3.04mg/cm2because of its good oxidation resistance. The existence of the spinel outer layer can block the volatilization of Cr2O3.(3) The ASR of oxides formed on the surface of sputtered coating after oxidation for12weeks in air at800℃is only31.97mΩ·cm2. It is lower than0.1Ω·cm2which metallic interconnects require.