Low-temperature oxidation of MoSi2–Si3N4 composites

Abstract

Composites in the MoSi₂ + Si₃N₄ system containing 1.0, 2.5, and 5.0 wt % Si₃N₄ were synthesized by hot pressing at the temperature of 1650°C and the pressure of 30 MPa. Silicon nitride powders of two types of were used as reinforcing additives: one with isometric equiaxed crystals and one with fibrous structure. The samples were characterized by microstructural and phase analyses; the relative density and the flexural strength were determined. Composites with the flexural strength of up to 410 MPa were synthesized. The resistance to low-temperature oxidation of MoSi₂ + Si₃N₄ composites in air at the temperature of 750°C was studied. The increase in the resistance to oxidation of composites with silicon nitride in air compared to pure molybdenum disilicide for both types of silicon nitride powders was established. For all the composites obtained, the parabolic oxidation rate constants were calculated.