Oxidation protective silicon carbide coating for C/SiC composite modified by a chromium silicide-chromium carbide outer layer

A chromium silicide-chromium carbide (Cr₃Si-Cr₇C₃) outer layer mainly composed of Cr₃Si, Cr₇C₃, and a small amount of Cr₃C₂ was prepared on a SiC coated carbon fiber reinforced silicon carbide (C/SiC) composite using a Powder Immersion Reaction Assisted Coating (PIRAC) method. The Cr₃Si-Cr₇C₃ outer layer showed folded ridge morphology. The width of the largest microcracks on the outer layer of the Cr₃Si-Cr₇C₃/SiC/SiC coating was only one forth of that on the outer layer of the SiC/SiC/SiC coating. The Cr₃Si-Cr₇C₃/SiC/SiC coating showed significantly enhanced oxidation protection compared to the SiC/SiC/SiC coating. After oxidation for 10h, the Cr₃Si-Cr₇C₃/SiC/SiC coated composite showed nearly the same failure behavior and residual flexural strength as that of the as-received composite.