Preparation of MoSi2-SiB6 oxidation inhibition coating on graphite by spark plasma sintering method

To enhance the oxidation inhibition ability of the MoSi2 coating by forming stable borosilicate glass layer, MoSi2-SiB6 coatings with different components were prepared by spark plasma sintering method. In order to eliminate the interference caused by the oxidation loss of carbon substrate on the weight change law of coatings, the coating samples and corresponding standard ceramic samples were simultaneously prepared. The oxidation inhibition evaluation system of the coatings was established based on the Standard sample-Coating sample-Substrate sample data collection mode. Although MoSi2 presents higher inerting effect than that of SiB6, the 60%MoSi2–40%SiB6 coating presents the best oxidation protection efficiency, whose value is 99.6%. The oxidation rate curve and the active factor of the 60%MoSi2-40%SiB6 coating is the most stable and lowest, indicating the lowest oxidation consumption degree. An intact compound glass layer was generated on the surface of the 60%MoSi2-40%SiB6 coating, which present less micropores and microcracks. The thickness of the glass layer formed on the surface of the 60%MoSi2-40%SiB6 coating is only about 25 μm, with whose protection the average oxygen permeability of the coating is only 1.39% and the carbon loss rate is only 0.109 ± 0.022 × 10−6 g·cm−2·s−1. An inner glass layer generated at the interface between the coatings and carbon substrate, building double protective mode and weaken the oxidation consumption of the carbon substrate. •MoSi2-SiB6 coatings were prepared by spark plasma sintering method.•Oxidation inhibition evaluation system of the coatings was established.•The addition of 40%SiB6 results in the minimum oxygen permeability of the glass.•Double glass layer was generated on the surface and the substrate interface.•MoSi2 presents higher inert effect than SiB6 to inhibit the oxidation consumption.