Formation of Ti(OCN) Layers Under Glow Discharge Conditions

Abstract
By using a gaseous mixture composed of tetraisopropoxytitanium, nitrogen and hydrogen in PACVD process, we obtain Ti(OCN) layers of a good performrance properties, such as a high hardness and good resistance to corrosion and to frictional wear. The optimum temperature of the process is 500°C. At higher temperatures, the surface microhardness decreases. When the process is carried out at 700°C, a surface layer which contain titanium cannot be obtained, only a diffusive oxycarbonitrided layer forms. Spectral investigations by optical emission spectroscopy have shown that the active particles that take part in the formation of the Ti(OCN) type layer are titanium ion Ti, nitrogen particles : N, N₂, NH, oxygen atoms and CN radicals coming from the gaseous atmosphere and also nitrogen from the pre-nitrided substrate.