Deposition of CrN coatings by current-modulating cathodic arc evaporation

Conventional cathodic arc evaporation (CAE) suffers from macroparticle contamination and excessive heat load on the substrates, resulting from the energetic ion flux emitted from hot cathode spots. In this study, a low frequency current-modulating controller was used to modulate the arc currents in high-low cycles. The deposition is conducted primarily during the high-current cycles, while a minimum background-current is maintained to sustain the arc discharge. Cathodes can be operated at currents lower than in the continuous CAE process. Macroparticle ejection is reduced substantially due to the effective cathode cooling. The preferred orientation of CrN changes from Cr2N (211) to CrN (111) by reducing heat load on substrates. The residual stress of CrN coatings is reduced from 3.8 GPa to 3.0 GPa in a current-modulating CAE process. The critical load of CrN deposited by the current-modulating CAE process is 78 N, which is comparable with that of CrN deposited by the continuous CAE process. Fracture toughness and film adhesion were significantly improved by the current-modulating mechanism, leading to a prolonged wear life of CrN coatings by three times. Results of this study provide a practical and effective way to operate CAE process with reduced substrate temperature, reduced coating roughness, and improved film adhesion.