Silicon Carbide Whisker Stability During Processing of Silicon Nitride Matrix Composites

The effects of two different sources of SiC whiskers on the chemistry and microstructure of the SiC‐whisker—Si 3 N 4 composites were evaluated using scanning transmission electron microscopy. Analyses were performed after presintering in N 2 and after encapsulated hot isostatic pressing. Significant differences in the porosity, α‐ to β‐Si 3 N 4 conversion, and whisker degradation were observed after presintering. It was also noted that whiskers containing surface iron impurities were converted to Si 3 N 4 during processing. Whiskers from the source having low surface iron exhibited little reaction. After hot isostatic pressing, some oxidation of the cleaner whiskers was observed.