Plasma CVD process for coating a basic tool body

A plasma-activated CVD process for coating a basic tool body with at least one surface layer comprised of at least one hard substance selected from the group consisting of carbides, nitrides, and carbonitrides of titanium and zirconium, the plasma-activated CVD process comprising:

• a. positioning a basic tool body in a CVD chamber having means for supplying direct voltage thereto, the basic tool body being connected to the direct voltage supplying means as a cathode thereof;
• b. introducing into the CVD chamber a reactive gas mixture comprised of a nitrogen-containing substance, a carbon-containing substance, and at least one compound containing at least one of titanium and zirconium;
• and
• c. exciting plasma formation at the basic tool body and coating same by chemical vapor deposition by applying a pulsed direct voltage having a residual direct voltage thereto, the residual direct voltage having a magnitude which is at least equal to the lowest ionization potential of any gas in the reactive gas mixture but not exceeding 50% of the maximum value of the pulsed direct voltage,
• wherein the CVD chamber has a temperature ranging from 400.degree. to 800.degree. C. and a pressure ranging from 10 to 1,000 Pascal during step (c).