Multi-layered structural designs of MoSi₂/mullite anti-oxidation coating for SiC-coated C/C composites

The gradient and laminated multi-layered MoSi₂-mullite coatings were prepared with similar thickness by supersonic atmosphere plasma spraying (SAPS) on SiC coated C/C composites to analyze the effects of the two multi-layered structure on the oxidation resistance of SAPS MoSi₂ coating under high temperature environment. Unexpectedly, the gradient multi-layered design showed almost no positive effect on the protective performance improvement in comparison to the monolayer MoSi₂ coating. The laminated multi-layered design remarkably improved the oxidation resistance at 1500 °C, up to 226 h, as well as the thermal shock resistance to 30 thermal cycles with only half the mass loss of the monolayer one. Such obvious improvement in the laminated MoSi₂/mullite multi-layered coating was attributed to the effect of macroscopic interfaces on the auxiliary self-healing and the change of thermal stress field, which were conducive to hindering further crack prolongation.