Dense, fine-grain Mo-Si-B alloys from nitride-based reactions

Mo-Si-B intermetallic alloys have the potential to possess the oxidation resistance and mechanical properties required for the next generation of jet turbine engine blades. In a novel approach, three-phase alloys of α-Mo, Mo 3 Si (A15), and Mo 5 SiB 2 (T2) have been produced through the reaction of molybdenum, Si 3 N 4 , and BN powders. Formation of the intermetallics was examined by thermo-gravimetric and x-ray diffraction analysis. Densities of 94% of theoretical were achieved from pressureless sintering at 1,600°C. Microstructure examination using scanning electron microscopy and electron backscatter diffraction analysis shows that this powder metallurgy approach yields a fine dispersion of intermetallics in a molybdenum matrix with grain sizes on the order of 1–4 µm. The formation of Mo-Si-B alloys from the nitride-based reactions uses standard powder processing methods and provides a method for creating these materials in a much less complex and expensive manner than has been previously demonstrated.