a plasma - activated cvd process provides improved adhesion of the coated surface layers and employs , as the plasma exciting source , a pulsed direct voltage and a residual direct voltage which remains during the pulse intervals . the residual direct voltage is equal to or greater than the lowest ionization potential of the gases participating in the cvd process , but is no more than 50 % of the maximum value of the pulsed direct voltage . the total thickness of the layer does not exceed 30 μm and the temperature of the basic tool body during the coating process is reduced , compared to prior art plasma cvd processes , and ranges from between 400 ° to 800 ° c ., and is preferably kept below 600 ° c .