Hardness and Adhesion Strength Enhancement by Compositional Gradient Structure and Optimization of Ar Partial Pressure for ZrN/Zr/ZrO2 and ZrN/ZrO2 Films Deposited by Reactive Sputtering

Effects of compositionally gradient structure and discharge gas pressure on microhardness and adhesion of ZrN/Zr/ ZrO2/substrate and ZrN/ZrO2/substrate films have been studied. The apparatus used to deposit the films was an UHV-type sputtering machine with a Zr magnetron cathode. The compositional graduation of the films was formed by changing reactive gas flow rate gradually for a constant discharge current in the reactive sputtering. For film prepared, microhardness and adhesion strength were examined. The highest hardness was achieved for a ZrN/ZrO2 film with a gradient interlayer deposited at an Ar partial pressure of 0.4 Pa. The ZrN/ZrO2 or ZrN/Zr/ZrO2 films with interrupted interfaces showed lower microhardnesses compared to the films with gradient interfaces. Although the adhesion strength increased as Ar partial pressure increased, the microhardness decreased. Thus, it was concluded from the experimental results obtained that the ZrN/ZrO2 films with gradient interfaces deposited at a low Ar pressure yielded a high performance as a hard coating.