Multilayer diamond coatings on silicon carbide

Multilayer composite diamond coatings on SiC substrates with improved adhesion and wear resistance have been developed. The coatings consist of a first layer of discontinuous diamond crystallites which are anchored to the SiC substrates by an interposing layer of TiC or TiN films. A top layer of continuous diamond film is grown epitaxially on the first layer. The diamond films and TiC or TiN films were deposited using hot filament chemical vapor depostion and laser physical vapor deposition, respectively. The diamond films were characterized by scanning electron microscopy and Raman spectroscopy. Adhesion of the diamond coatings to SiC seal ring substrates was investigated by using overlap polishing with diamond paste or by wear test against Al-12.5%Si alloy. The results show that, after introducing an interposing layer, the internal thermal stresses are reduced so that the adhesion of diamond coatings on the SiC substrates is improved significantly.