Microstructural and compositional investigations of surface-nitrided silicon carbide ceramics

Hot isostatically pressed SiC ceramics were nitrided at a N2-pressure of 200 MPa and a temperature of 1850 °C for 1 h. The microstructures were investigated by scanning electron microscopy and transmission electron microscopy. A continuous nitride layer was observed in the near-surface region, where Si3N4 was formed between SiC grains. The nitride-layer thickness was determined to be approximately 14 μm by proton elastic backscattering spectrometry. The depth distribution of elements Si, C and N was quantitatively evaluated by Auger electron spectroscopy, which showed that the N concentration was nearly maintained at the same fraction in the nitride layer.