Preparation and Characterization of Protective LSM Coatings Produced by Atmospheric Plasma Spraying

Abstract

Lanthanum strontium manganite oxides with perovskite structure are widely employed materials for protective coatings on chromium-contained metallic interconnectors in the intermediated temperature solid oxide fuel cells (ITSOFCs). The application of protective coatings is used to decrease the growth of chromium oxide and the evaporation of chromium trioxide and chromium hydroxide from the surfaces of metallic interconnectors. In this study, La0.8Sr0.2MnO3-δ (LSM) protective coatings are produced by the promising atmospheric plasma spraying (APS) technique on the substrates of Crofer 22 H, Crofer 22 APU and SS441 ferritic steels with or without pre-oxidation treatment. The substrates with pre-oxidation treatment were heated to 800°C and dwelled for 12 hrs in air before APS coating process. The cross-sectional micrographs show that the LSM coatings produced by APS technique are quiet dense without penetrating cracks. The XRD results identify that the LSM coatings produced by APS under 50 kW torch power reveal desired perovskite structure without any X-ray detectable second phase. After 600 hrs ageing in air at 800°C, the initial and final ASR values of the coated Crofer 22 APU sample with pre-oxidation treatment are 1.350 and 1.694 mΩcm2, respectively. The measured ASR increasing rate is only about 0.573 μΩcm2/hr. Thus, LSM coating prepared by APS technique can dramatically decrease the growth of chromium oxide to protect the metallic interconnector and the generation of gaseous Cr-contained species to avoid cathode poisoning at the operating temperatures of ITSOFCs.