THE EFFECTS OF PRECOATING AND BIAS VOLTAGE ON THE ADHESION OF REACTIVE ARC EVAPORATED TIN AND ZRN COATINGS

The effects of precoating and bias voltage on adhesion have been studied for reactive arc evaporated TiN and ZrN coatings on high speed steel. Pure Ni, Ti, and Zr interlayers were precoated as single or double layers with different thicknesses prior to the deposition of the compound coatings. The adhesion was evaluated by comparing acoustic signals through the scratch test method with incremental applied load. Precoating with a double layer significantly enhanced the adhesion of both TiN and ZrN coatings. A single interlayer precoating also produced an effective improvement of adhesion. The improvement was more pronounced for thicker single interlayers of Ti and Ni in TiN coating. Adhesion was also improved with increasing negative bias voltage for TiN coating without interlayer precoating. The mechanism for the improvement of adhesion by precoating is proposed to be stress accomodation in the interlayer.