Oxidation behavior and microstructural evolution of plasma sprayed La2O3-MoSi2-SiC coating on carbon/carbon composites

Abstract

Improving the efficiency and service-life of high-temperature coatings in a cost-effective way has always been capturing more attention. In this study, we developed a multiphase La2O3-MoSi2-SiC (LO-MS) composite coating using an efficient supersonic atmospheric plasma spraying (SAPS) to protect carbon/carbon (C/C) composites against oxidation. Isothermal oxidation evaluation of LO-MS coating was carried out at 1473 K and 1773 K. A lower mass loss at 1773 K for 100 h with 6.42 mg·cm−2 than that of 1473 K with 10.93 mg·cm−2 indicated that a superior oxidation resistance of LO-MS coating at 1773 K relative to 1473 K, which might be attributed to the decreased viscosity of SiO2-rich glass scale at 1773 K and their good healing effect for cracks. Moreover, thermogravimetric analysis showed that the LO-MS coating provided a sufficient protection for C/C composites in a wide temperature range from 373 K to 1673 K. The continuous La-Si-O compound scale served as a barrier layer to effectively block the inward infiltration of oxygen.