SHS Metallurgy of Binary Silicides (MoW)Si2 for Sintering Composite Materials

Resumo

The regularities of synthesis by the SHS metallurgy method of cast materials in the Mo-W-Si system are studied. The experiments were carried out in SHS reactors with a volume of 3, 20 and 30 L under the pressure of an inert gas (argon) P = 5 MPa. In the experiments, high-calorie mixtures of molybdenum (6) and tungsten (6) oxides with aluminum and silicon were used. Thermodynamic calculation of combustion parameters of the initial systems according to the Thermo program showed that they have high adiabatic combustion temperatures exceeding the melting points of the initial reagents and final products of synthesis. Studies have shown a strong effect of the ratio of the initial reagents on the regularities of synthesis. Cast (ingots) single-phase disilicides of molybdenum (MoSi₂) and tungsten (WSi₂), as well as their solid solutions MoSi₂–WSi₂, are obtained with any given ratio between them. Their microstructure and elemental and phase composition were investigated. Optimal modes of mechanical conversion of the obtained ingots of the target products into the powders of the required fractions are developed. The influence of the composition of composites on the strength and oxidation of sintered samples in air at different temperatures was studied. It was shown that sintered composites from MoSi₂–WSi₂ solutions have higher strength and are less susceptible to oxidation compared to ceramics obtained by solid-phase sintering from powders of individual MoSi₂ and WSi₂.