Deposition and modeling of hard, wear-resistant Si-C-N coatings

Hard, wear-resistant Si-C-N coatings were produced via a thermal plasma chemical vapor deposition process in a triple torch reactor. Vaporized hexamethyldisilazane (HMDSN) and nitrogen and/or hydrogen gases were dissociated through the argon plasma as additional reactants. Several Si-C-N coatings were synthesized with varying reactant flows and substrate temperature. Film composition, morphology, and mechanical performance were examined. Hardness and elastic modulus increased with decreasing N:H gas ratio, decreasing roughness, and the inclusion of nanocrystallites. A kinetic reaction mechanism determined that the atomic species primarily existed in the substrate boundary layer. The Damköhler number was calculated to predict the necessary reactant composition for morphologically smooth films.