Analysis on the oxidation behavior of Mo₅Si₃-MoSi ₂/SiC multi-coating at high temperature

To improve the anti-oxidation property of graphite at high temperature，an Mo₅Si₃-MoSi₂/SiC multi-coating was prepared by the chemical vapor reaction (CVR) and slurry method. The structure of the ulti-coating was studied by XRD，SEM and EDS analysis，and the oxidation behavior of the multi-coating at high emperature was investigated by the isothermal oxidation test and thermodynamics calculation. The results show that the Mo₅Si₃ and MoSi₂ phases in the multi-coating are prone to produce the reactions of forming the MoO₃ gas in air at 1823 K and result in the mass loss，while the mass gain in the initial oxidation stage (0～6 h) is primarily attributed to the dominating passive oxidation of SiC. As the main phases of the multi-coating can oxidize and form the SiO₂ glass at high temperature，it enables the coating to have the excellent anti-oxidation ability and thermal shock resistance. After oxidation in air at 1823 K for 20 h and thermal cycling between 1823 K and room temperature 16 times，the mass loss of the coated sample is only 3.78%.