PROCESS FOR THE HOT ISOSTATIC COMPRESSION OF SILICON NITRIDE BODIES REINFORCED WITH CARBIDE FIBRES AND CARBIDE WHISKERS

摘要

Process for the hot isostatic compression (HIC) of silicon nitride bodies reinforced with carbide fibres and carbide whiskers. The process is characterized by the fact that the HIC is carried out without encapsulation of the pre-sintered, unpressurized mould, at temperatures of between 1000 and 3000 DEG C in a controlled nitrogen atmosphere under a nitrogen partial pressure, corresponding to the equation (I), in which PN2 signifies N2 partial pressure, and Ts signifies the temperature in DEG K. The lower limit of partial pressure is represented by the following values: a = 872 213, b = 405.6 and c = -16.6. The upper limit of partial pressure, depending on the carbide used, is represented by the following values: (II). Said process enables maximal compression to be achieved even at relatively low temperatures, at a low nitrogen partial pressure but high total gas pressure, without destroying the carbide fibres or carbide whiskers.