Advanced magnetron sputter technique for depostion of superhard a-C:H coatings

Superhard amorphous hydrogenated carbon (a-C:H) coatings were prepared in a large scale batch coater equipped with four targets and electromagnetic coils. To improve the adhesion, different interlayer systems, e.g., from chromium or tungsten carbide were used. The a-C:H coating deposition was carried out working with varying parameters of substrate bias, acetylene flow and coil currents. The highest hardness values were reproducibly measured with up to 50 GPa. The coatings characterization was done by Scanning Electron Microscopy (SEM), Secondary Ion Mass Spectroscopy (SIMS) and Raman spectroscopy as well as by hardness and wear tests. The hardness clearly depends on the hydrogen contents and the hardest coatings could be prepared at about 10 atom %. Reasons for this behavior will be discussed considering the effects of the most essential process parameters. To achieve optimum adhesion for components or tools, respectively, different types of interlayers were applied. HIPIMS steps allowed additional process modifications influencing coating properties, especially the adhesion.