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

摘要

A chromium silicide-chromium carbide (Cr_3Si-Cr_7C_3) outer layer mainly composed of Cr_3Si, Cr_7C_3, and a small amount of Cr_3C_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_3Si-Cr_7C_3 outer layer showed folded ridge morphology. The width of the largest microcracks on the outer layer of the Cr_3Si-Cr_7C_3/SiC/SiC coating was only one forth of that on the outer layer of the SiC/SiC/SiC coating. The Cr_3Si-Cr_7C_3/SiC/SiC coating showed significantly enhanced oxidation protection compared to the SiC/SiC/ SiC coating. After oxidation for 10 h, the Cr_3Si-Cr_7C_3/SiC/SiC coated composite showed nearly the same failure behavior and residual flexural strength as that of the as-received composite.