炭化ケイ素セラミックスの表面窒化

抄録

The purpose of this paper is to modify the surface of ceramics by nitridation using NH₃ gas at low temperature. Two kinds of SiC specimens, sintered and reaction bonded, were used. In evaluation, surface layers were analyzed by ESCA and thin film X-ray diffraction, and mechanical properties were studied by micro Vickers hardness and scratch test. More nitrogen penetrated in the reaction bonded specimen treated at higher temperature. The maximum penetration depth of nitrogen was about 100Å in reaction bonded SiC treated with NH₃ gas at 900°C. The formation of Si₃N₄ and the change from 12H-SiC to 8H-SiC were detected by ESCA spectra and thin film X-ray diffraction. On the other hand, Vickers hardness and critical load by scratch test increased with increasing nitrogen on the surface of specimens. The maximum increase in Vickers hardness was 42% for reaction bonded SiC. The strain on the nitridated surface of SiC ceramics is possibly responsible for these phenomena.