Mechanically activated combustion synthesis of molybdenum borosilicides for ultrahigh-temperature structural applications

• Mechanical activation has enabled combustion synthesis of Mo5SiB2 based materials.
• For the first time, the fabrication of Mo5SiB2–TiB2 material has been reported.
• Among the obtained materials, Mo5SiB2–TiB2 exhibits the best oxidation resistance.

The thermal efficiency of gas-turbine power plants could be dramatically increased by the development of new structural materials based on molybdenum silicides and borosilicides, which can operate at temperatures higher than 1300 °C with no need for cooling. A major challenge, however, is to simultaneously achieve high oxidation resistance and acceptable mechanical properties at high temperatures. Materials based on Mo5SiB2 (called T2) phase are promising materials that offer favorable combinations of high temperature mechanical properties and oxidation resistance. In the present paper, T2 phase based materials have been obtained using mechanically activated self-propagating high-temperature synthesis (MASHS). Upon ignition, Mo/Si/B/Ti mixtures exhibited a self-sustained propagation of a spinning combustion wave, but the products were porous, contained undesired secondary phases, and had low oxidation resistance. The “chemical oven” technique has been successfully employed to fabricate denser and stronger Mo5SiB2–TiC, Mo5SiB2–TiB2, and Mo–Mo5SiB2–Mo3Si materials. Among them, Mo5SiB2–TiB2 material exhibits the best oxidation resistance at temperatures up to 1500 °C.

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