High-temperature oxidation behavior of plasma-sprayed ZrO₂ modified La-Mo-Si composite coatings

Plasma-sprayed ZrO₂-modified LaB₆-MoSi₂ coating (ZLM) was firstly fabricated on SiC pre-coated carbon/carbon (C/C) composites to obtain an improved oxidation resistance at 1773 K involving long-term oxidation and short-term cyclic oxidation in an atmospheric environment. A crack-free structure in ZLM coating has been established with interlocking adhesion between the layers of coating. It is shown that the specimen with ZLM coating exhibits superior oxidation with the mass loss of 0.96% after 140 h at 1773 K and spallation resistance with the mass loss of 0.61% after 30 thermal cycles between 1773 K and room temperature. These beneficial effects can be attributed to superior integrated structure of the ZLM coating provided by the continuous Zr-La-Si-O protective scale gave rise to the suppression of oxygen diffusion in ZLM coating. Moreover, the formation of “inlaid phases” in the compound glass layer is helpful to consume the crack propagation energy and restrict the spreading of it. Dual protection of the “inlaid structure” and Zr-La-Si-O compound glass film is responsible for the excellent oxidation resistance of the ZLM coating.