电泳沉积制备MnCo尖晶石涂层的高温长期稳定性研究

Long-term Stability of MnCo Spinel Coatings Prepared byElectrophoretic Deposition at High Temperatures

采用电泳沉积工艺在不同Cr含量钢表面制备了Mn_(1.5)Co_(1.5)O_(4)尖晶石涂层,探究了温度对Mn_(1.5)Co_(1.5)O_(4)/钢体系的长期稳定性和导电性能的影响。采用X射线衍射(XRD)、扫描电子显微镜(SEM)和4线法电阻(ASR)测试对样品进行表征。结果表明,两步烧结法得到了相对致密性的涂层。在800℃氧化1000 h后,Mn_(1.5)Co_(1.5)O_(4)/钢的氧化速率约为(1~3)×10^(-14)g^(2)·cm^(-4)·s^(-1),随着氧化温度的降低,氧化速率常数下降1~2个数量级。SUS430钢凭借自身较低Cr含量,在Mn_(1.5)Co_(1.5)O_(4)/SUS430样品中形成了更薄的含Cr氧化层。同时,氧化过程中钢中Fe向外扩散促进涂层致密性,最终Mn_(1.5)Co_(1.5)O_(4)/SUS430获得了比Mn_(1.5)Co_(1.5)O_(4)/Crofer22H更低的ASR值。

Spinel coatings Mn_(1.5)Co_(1.5)O_(4) on steels SUS430 and Crofer22H were prepared via electrophoretic deposition,aiming to improve their high-temperature oxidation resistance and electrical conductivity as SOFC interconnector.Afterwards,their oxidation behavior at 700-800℃and electrical conductivity after oxidation were characterized by means of intermittent weighing method,X-ray diffraction(XRD),scanning electron microscope(SEM)and 4-wire electrical resistance tester(ASR).The result showed that relatively dense coatings may be acquired by two-step sintering.The oxidation rate of Mn_(1.5)Co_(1.5)O_(4)/SUS430 oxidized at 800℃ for 1000 h is about(1-3)×10^(-14)g^(2)·cm^(-4)·s^(-1),and the oxidation rate constant decreases by 1-2 orders of magnitude as the temperature decreases.Mn_(1.5)Co_(1.5)O_(4)/SUS430 formed a thinner Cr-containing oxide scale due to its own low Cr content,at the same time,the Fe diffused outward from the substrate steel during the oxidation process to further promote the coating densification.Ultimately,after high temperature oxidation,the Mn_(1.5)Co_(1.5)O_(4)/SUS430 showed ASR values lower than those of the Mn_(1.5)Co_(1.5)O_(4)/Crofer22H.