Vacuum plasma spraying of MoSi₂ and its composites

Vacuum plasma spraying has been used to fabricate dense MoSi₂ and SiC- and TiB₂-reinforced MoSi₂ composites. The deposits have a high hardness, indentation fracture toughness and flexural strength. It is observed that annealing leads to increases in fracture toughness and flexural strengths due to improved interparticle bonding. The incorporation of reinforcements in the MoSi₂ matrix leads to enhanced fracture toughness and flexural strength, indicating a strong matrix-particle bond. The oxidation resistance of the vacuum-plasma-sprayed MoSi₂ matrix is very good under cyclic and isothermal conditions. Although the incorporation of reinforcement leads to a degradation of oxidation resistance, the SiC-reinforced MoSi₂ composites have a far superior oxidation resistance than do the TiB₂-reinforced MoSi₂ composites.