Preparation and oxidation resistance of mullite/SiC coating for carbon materials at 1150 °C

To protect carbon materials from oxidation, mullite/SiC coatings were prepared on graphite by chemical vapor reaction (CVR) and slurry sintering. The XRD analyses show that the phase of the outer-layer coating is composed of SiO2 and mullite, and the inner-layer coating is mainly composed of β-SiC. The anti-oxidation behavior of the coating and the Rockwell hardness (HRB) of the coating after oxidation were investigated. The oxidation test shows that the as-prepared multi-layer coating exhibits excellent anti-oxidation and thermal shock resistance at high temperature. After oxidation at 1150 °C for 109 h and thermal shock cycling between 1150 °C and room temperature for 12 times, the mass gain of the coated sample is 0.085%. Meanwhile, the indentation tests also demonstrate that the as-prepared coating has good bonding ability between the layers.