STUDIES ON THE SINTERING OF MoSi2–Al2O3 CERMETS*

AbstractThe porosity of hydrogen-sintered bodies composed of molybdenum disilicide and alumina has been studied as a function of alumina content and grain size. It is found that oxidation-resistant bodies can be made if the grain size of the constituents is ∼ 10 μ or less, although the bodies are fairly weak.In addition, samples were sintered in dissociated ammonia and compared with those sintered in hydrogen. It became apparent that samples sintered in dissociated ammonia underwent a particularly severe form of attack when exposed to air at high temperatures. This is attributed to the formation, during sintering, of Si3N4, a phase which decomposes at high temperature in air when enclosed in the cermet bodies.