Industrial applications of CrN (PVD) coatings, deposited at high and low temperatures

Industrial applications of CrN (PVD) coatings are entering an expanding but selective range of mass manufactured goods. They may be prepared as single, low and high temperature CrN coatings and double TiN + CrN coatings. In this work, depositions of CrN at high temperatures were performed by a low voltage thermionic are in a BAI 730M apparatus, while at low temperatures (below 250 degrees C), the plasma-beam sputtering process in a SPUTRON apparatus was used. We studied the following critical parameters that influence the quality of the coatings and applied the performance tests used in industrial practice: adhesion and scratching coefficient, microhardness, surface topography, oxidation and corrosion resistance. The performance tests were made with the assistance of technicians as well as in 12 Slovenian factories. CrN coatings were deposited at 480 degrees C for wear and corrosion protection in cold forming and cutting of copper in commutator manufacturing, in forming of aluminium components in automotive production and for surface improvement of moulds (made of H11 steel) in Al-Si die casting under pressure. Deposition temperatures of 180-220 degrees C, obtained in the SPUTRON apparatus, were required to improve cold forming tools made of alloyed tool steels (e.g. D2 and D3). The lowest obtainable temperature of 140 degrees C in the SPUTRON gave a CrN coating of high quality for practical use. These coatings were used to protect electrodeposited and electropolished nickel moulds (models) in artificial teeth production. Double TiN+CrN coatings were used as a highly abrasive resistant coating in the production of rotors (in the electromotor industry), and in cold forming and forging in mass manufacturing of screws. The results and performance tests were compared with the available data, mostly published on forming, milling, deep drawing of copper, nickel and titanium and their alloys, and on die casting of aluminium and Al-alloys. (C) 1997 Elsevier Science S.A.