Microstructure and oxidation mechanism of multiphase Mo–Ti–Si–B alloys at 800 °C

Highlights: • Microstructure evolution was analyzed for three Mo–Ti–Si–B alloys. • Suppressing the volume fraction of Mo₃Si is an effective way to prevent pesting. • Site-specific microstructure of the oxide scale was observed. • Interactions between constituent phases contributed to the oxidation resistance. Three Mo–Ti–Si–B alloys with compositions of 50Mo–20Ti–20Si–10B, 40Mo–30Ti–20Si–10B and 30Mo–40Ti–20Si–10B (at.%) were designed and prepared by arc-melting. Microstructure evolution at 1600 °C and oxidation mechanism at 800 °C of these alloys were analyzed. 50Mo–20Ti–20Si–10B suffered from pesting because of a large volume fraction of Mo₃Si, which produced porous products with severe volume expansion. Both 40Mo–30Ti–20Si–10B and 30Mo–40Ti–20Si–10B have better oxidation resistance. It can be inferred that during long-term oxidation, interactions between constituent phases contributed to the overall oxidation resistance of the alloys.