Investigation of the effect of SiC additions on the high-temperature oxidation behavior of combustion-synthesized MoSi2

Abstract

In this study, the effect of the weight percentage of SiC on the high-temperature oxidation behavior of MoSi2-Xwt. % SiC composite (X = 0, 10, 20, 30) was studied. The composites were produced from elemental powder compacts of molybdenum, silicon and carbon (where applicable) by combustion synthesis and subsequent sintering method. Additionally, a series of each synthesized powder was mixed with 5 wt% bentonite and consequently sintered. The sintered specimens were then subjected to oxidation at 1100 °C. Microstructure and phase analysis of the oxidized samples were investigated by X-ray diffraction (XRD) and a scanning electron microscope equipped with energy-dispersive spectroscopy (SEM-EDS). Surface and cross-sectional examinations of the samples after oxidation revealed that all samples possessed good oxidation resistance in the way that no spallation was observed between the oxide layer and the substrate. The highest oxidation resistance at 1100 °C was observed in the sample with MoSi2 (without SiC) containing bentonite (AB0). This sample showed only 0.75% weight gain after 50 h of oxidation, which is probably due to the effective role of bentonite in decreasing the open porosities, and further reducing the oxygen penetration path during the oxidation process.