Oxidation behaviour of reaction hot pressed MoSi2–SiC composites at 500°C

Abstract

The oxidation behaviour of a molybdenum disilicide (MoSi2) composite, reinforced with 20 vol.-% silicon carbide (SiC), at 500°C has been investigated and the results have been compared to those of hot pressed monolithic MoSi2 and other MoSi2 based composites. The MoSi2-SiC composite was processed by reaction hot pressing an Mo, Si, and SiC powder mixture at 1500°C, and the composite had around 98% of the theoretical density. The presence of SiC particles does not affect the oxidation behaviour, except the interfaces oxidised at higher rates. The oxidation rate is slow enough in dense composites to prevent pest disintegration. The oxidation products are either an Mo-Si-O compound or Mo5Si3 and SiO2 for exposure up to 120 h, after which MoO3 whiskers and SiO2 phases become predominant. The oxide layer thickness was found to be 10.0 μm,at the most, after 250 h exposure at 500°C.