Physical vapor deposition of thick Cr and its carbide and nitride films by hollow‐cathode discharge

Approaches to a dry process of hard Cr plating to overcome industrial pollution problems should be extensively investigated for many possible applications. Deposition by using a hollow‐cathode discharge (HCD) gun, however, is one of the potential solutions; HCD generates very high density plasma between the substrate and the evaporation source. The plasma also serves to produce compound chemical films when reactive gas is properly introduced during deposition. Ductile Cr films are obtained in a variety of substrate temperatures ranging from 20° to 670 °C and an applied negative voltage from 0 to −200 V to the substrate. Hardness, corrosion resistance, and surface roughness are closely related to the experimental parameters. Hard carbide and nitride are formed by introducing acetylene and nitrogen, respectively, to a partial pressure around 1×10−4 Torr (1.33×10−2 Pa) mixed in argon of 7.5×10−4 Torr (0.1 Pa); hollow‐cathode discharge with or without a negative bias voltage gives a sound film at a relatively low substrate temperature of 350 °C or higher. These films have high micro Vickers hardness between 1100 to 1800 and 1200 to 1600 for carbide and nitride, respectively. The carbide and the nitride films show reasonably good corrosion resistance and good adhesion to steel substrates.