Formation of a diamond coating on a substrate, e.g. tools and precision components, comprises subjecting the substrate to a reactive gas mixture exited by a vacuum atmosphere by a plasma discharge

摘要

Process for forming a diamond coating on a substrate comprises subjecting the substrate to a reactive gas mixture exited by a vacuum atmosphere by a plasma discharge. The plasma discharge comprises a plasma beam (14) in an evacuated vessel (16) formed between a cathode chamber (1) and an anode (2). The reactive gas mixture comprises a reactive gas and a working gas. The evacuated vessel is pumped out using a pumping arrangement (15). The hydrogen concentration of the gas mixture is 0-45 vol.%. Preferably the hydrogen concentration of the gas mixture is selected so that the diamond coating has an average crystal size of less than 50, preferably 1-30 nm, and the substrate temperature is 300-750 deg C. The concentration of the reactive gas in the gas mixture is 0.1-85 vol.%. The reactive gas contains hydrogen, carbon-containing gases and nitrogen-containing gases, especially nitrogen. The working gas contains a noble gas. The plasma beam is formed as a low voltage arc discharge, preferably as a high current arc discharge.