Fracture toughness of thermally sprayed MoSi2 composite with different melting indices

Whether the in-situ multiphase doping, especially the metastable phase, makes the thermally sprayed materials tough or brittle is still unknown. In this sense, plasma sprayed MoSi2 composite was accordingly fabricated to investigate the effect of in-situ multiphase doping on the fracture toughness by melting index (M.I.) tuning. The fracture toughness of plasma sprayed MoSi2 composite was improved with M.I. increasing. The maximum fracture toughness can reach to 5.64 MPa m1/2 at a M.I. of 0.59, which was the highest among currently reported single-phase-derived thermally sprayed MoSi2 composites. A large number of metastable β generated in plasma sprayed MoSi2 composite were responsible for such remarkable improvement. The fracture toughness of the plasma sprayed MoSi2 composite, however, would decline as M.I. value exceeded 0.59. Over-heating derived crystallization, which decreased the positive effect of β, caused the fracture toughness deterioration.