Microstructure, properties and toughening mechanisms of MoSi2@ZrO2 core shell composites prepared by spark plasma sintering

MoSi2 is the most potential high temperature structural materials that can be used in aerospace and aviation industry. But its fracture toughness is low and its low temperature oxidation resistance is poor, which limits its application. To solve these problems, novel MoSi2@ZrO2 core-shell composites were prepared by spark plasma sintering (SPS) at 1300 °C⁓1500 °C. The influences of sintering temperatures on the microstructures, mechanical properties and tribological properties of the composites were studied. It was found that the relative density, Vickers hardness, bending strength and fracture toughness of the composites first ascended and then descended with the sintering temperature rising from 1300 °C to 1500 °C. As the sintering temperature reached 1400 °C, the maximum relative density, the maximum Vickers hardness, the maximum bending strength and the maximum fracture toughness of the composite material achieved 97.5%, 1103 HV, 540 MPa and 7.96 MPa·m1/2, respectively. Additionally, the friction coefficient of the composite materials first descended and then ascended with sintering temperature rising. As the sintering temperature reached 1400 °C, the minimum friction coefficient was about 0.355. Moreover, we analyzed the relations between the mechanical properties and microstructure. The toughening mechanisms of the MoSi2@ZrO2 composites were also discussed. In addition, during cyclic isothermal oxidation at below 600 °C, weight gains of the MoSi2@ZrO2 composites evidently decreased, compared with that of pure MoSi2, proving better low-temperature oxidation resistance.