A fused glass coating for oxidation protection of Mo–W–ZrO2 cermet

• Anti-oxidation coating of borosilicate glass was developed for the Mo–W–ZrO2 cermet.
• Compactness, volatility and adhesion of the coating were discussed.
• We study the oxidation resistance of the coating for the cermet.
• Good anti-oxidation for the cermet at 400–1000 °C was verified by the application test.

Mo–W–ZrO2 cermet is suitably used for the liquid steel temperature sensor due to its excellent erosion resistance, good thermal shock resistance and high-temperature strength. However, it is easily oxidized in the firing process of the sensor below 1000 °C, which limits its application. In this work, a continuous coating of borosilicate glass was developed to prevent the cermet from oxidizing by a two-step process. Raw materials of borax and potash feldspar were initially fused at 1200 °C and ground into powder. Then, the slurry of the powder and ethyl alcohol was applied to the cermet and fused at 1000 °C. Results showed that the coating had an amorphous nature and low volatility (0.39% weight loss up to 1000 °C), which exhibited good continuity and adhesion to the cermet. Moreover, no matter whether the coating was in a non-molten or molten state (800 or 1000 °C), it had good oxidation resistance. According to the application test in the firing, the coating could protect the cermet from oxidation at 400–1000 °C. The method of fused glass coating may have important implications for other oxidation resistance in a wide temperature range, especially at low temperatures.