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

Abstract A chromium silicide–chromium carbide (Cr 3 Si–Cr 7 C 3 ) outer layer mainly composed of Cr 3 Si, Cr 7 C 3 , and a small amount of Cr 3 C 2 was prepared on a SiC coated carbon fiber reinforced silicon carbide (C/SiC) composite using a Powder Immersion Reaction Assisted Coating (PIRAC) method. The Cr 3 Si–Cr 7 C 3 outer layer showed folded ridge morphology. The width of the largest microcracks on the outer layer of the Cr 3 Si–Cr 7 C 3 /SiC/SiC coating was only one forth of that on the outer layer of the SiC/SiC/SiC coating. The Cr 3 Si–Cr 7 C 3 /SiC/SiC coating showed significantly enhanced oxidation protection compared to the SiC/SiC/SiC coating. After oxidation for 10 h, the Cr 3 Si–Cr 7 C 3 /SiC/SiC coated composite showed nearly the same failure behavior and residual flexural strength as that of the as-received composite.