Al2O3–mullite–SiC–Al4SiC4 multi-composition coating for carbon/carbon composites

Abstract A new type of oxidation-protective multi-composition coating for carbon/carbon (C/C) composites has been produced by a pack cementation technique in an argon atmosphere. XRD analyses shows that the phases of the composite coating are composed of Al 2 O 3 , mullite, SiC and Al 4 SiC 4 , and the bonding layer between the coating and C/C composites are composed of Al 4 C 3 , SiC and Al 4 SiC 4 . It is found by SEM surface observation and EDS area scanning analyses that the coating has two kinds of surfaces that are distinctly different in element content of Si and C. In the meantime, cross-section SEM observation of the coating also displays a dense microstructure. Oxidation test shows that the as-prepared coating characterized by excellent thermal shock resistance on the surface of C/C composites during exposure to an oxidizing atmosphere at 1773 K could effectively protect the C/C composites from oxidation for 41 h.