STUDIES ON THE SINTERING OF MoSi 2 –Al 2 O 3 CERMETS *

The 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.