Amorphous carbon nitride hard coatings by multistep shielded arc ion plating

Hard amorphous carbon nitride (a-C:N) films fabricated by shielded arc ion plating break into pieces because of the large compressive stresses in the films when the film thicknesses are more than 200 nm. In the application of these films to practical hard coatings, the development of a technique to grow thicker films (over 1 μm) is necessary. In this study, we developed a multistep ion plating technique to grow thick hard multilayer films. We formed a-C:N multilayers with a total thickness of more than 1 μm on Si (100) and high speed steel (SKH9) substrates by stacking hard and soft films alternately in order to relax the large compressive stress in the hard film. The multilayers are extremely hard (Knoop hardness: 3200) and neither break into pieces nor peel off substrates spontaneously.