Microstructure and oxidation behaviour of Mo–Si–B–Hf alloys at 800 °C and 1100 °C

The influences of the microstructure evolution and oxidation behaviour of Hf-modified Mo–12Si–12B alloys were systematically studied at 800 °C and 1100 °C. Vickers hardness tests show that the Hf addition increases the hardness of Mo–Si–B–Hf alloys. The oxidation experiments were conducted at 800 °C and 1100 °C for 12 h; the detailed analysis revealed that the formation of HfSiO₄ in Mo–12Si–12B–10Hf alloy can effectively decrease the content of oxygen and make the surface of the oxide layer more complete at 800 °C. At 1100°C, the distinct difference in the expansion coefficient among the oxide films results in the formation of cracks and holes in Mo–12Si–12B–10Hf alloy, so the Mo–12Si–12B–10Hf alloy shows poor oxidation resistance.