Investigation on microstructure and oxidation resistance of Cr-Al-Si coating for carbon/carbon composites by plasma spraying

Cr-Al-Si coating was prepared on the surface of SiC coated C/C composites by the plasma spraying method.The phase composition and microstructure of Cr-Al-Si coating were studied by XRD and SEM.The isothermal oxidation test at 1500℃ was carried out in air.The XRD results show that the outer Cr-Al-Si alloy coating consists of Al3.21Si0.47,Cr3Si and Al2O3.The thickness of the coating was about 120μm,and no penetrable crack was observed in the cross-sectional SEM morphologies of the coating.The oxidation resistance of the single porous β-SiC coating is poor,which can only protect C/C composites from oxidation for 10 h with a mass loss of 10%.After adding the Cr-Al-Si alloy outer coating,the double-layer Cr-Al-Si and SiC show a better oxidation protective ability and 5.3% mass loss of the coated sample after oxidation for 61h.