Effect of microstructure on high-temperature compressive creep of self-reinforced hot-pressed silicon nitride

An experimental self-reinforced hot-pressed silicon nitride was used to exa mine the effects of microstructure on high-temperature deformation mechanis ms during compression testing. At 1575-1625 degreesC, the as-received mater ial exhibited a stress exponent of 1 and appeared to deform by steady-state grain-boundary sliding accommodated by solution reprecipitation of silicon nitride through the grain-boundary phase. The activation energy was 610 +/ - 110 kJ/mol. At 1450 -1525 degreesC for the as-received material, and at 1 525-1600 degreesC for the larger-grained heat-treated samples, the stress e xponent was >1, Damage, primarily in the form of pockets of intergranular m aterial at two-grain junctions, was observed in these samples.