Mo-si-B alloys oxidation protective coating for sic-coated carbon/carbon composites

A novel Mo-Si-B double-layer coating was prepared for the carbon/carbon (C/C) composites by pack cementation in an argon atmosphere. The structures of the double-layer coatings were characterized by XRD and SEM. The as-received coating shows an excellent oxidation resistance at high and intermediate temperature. It could effectively protect C/C composites from oxidation for 30 h with a weight loss of 0.9% in air at 1873 K, and for 25 h with a weight loss of l.7% at 1173 K. The oxidation protective coating was principally due to producing eutectic glass film for decreasing oxygen diffusing through the penetrable cracks in the coating.