Thermal reaction of SiC films with Mo, Re and Mo–Re alloy

Abstract

Solid-state reactions between SiC films and pure Mo or Re metal substrates on thermal annealing between 1373 and 1873 K for various durations have been investigated. The behaviour of Mo–47.5Re/SiC couple was also examined to establish the effect of the mix on stability. SiC coatings were deposited on metallic wires by hot filament rapid chemical vapour deposition from a gas mixture of tetramethylsilane (TMS) and hydrogen at 1373 K under normal pressure. The interface zones were characterized using optical microscopy, X-ray diffraction, and electron probe microanalysis. All analyses reveal that SiC reacts with substrates. The formation of a rhenium silicide was established on pure Re whereas a carbide and a silicon carbide containing molybdenum were formed on pure Mo. The diffusion kinetics were established from the thicknesses of reaction zones as a function of annealing durations. The outstanding fact of this work was the higher degree of reactivity observed on Mo–47.5Re alloy in comparison with pure Mo or Re as if there is a synergic effect. The apparent activation energy determined on pure Mo, pure Re and Mo–47.5Re substrates are equal to 64, 99 and 74 kcal mol −1, respectively.