Structure and mechanical properties of vacuum arc-deposited NbN coatings

V. N. Zhitomirsky*, I. Grimberg, L. Rapoport, N. A. Travitzky, R. L. Boxman, S. Goldsmith, A. Raihel, I. Lapsker, B. Z. Weiss

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Thin NbN coatings were deposited using a vacuum arc plasma gun connected to a straight plasma duct, with an imposed axial magnetic field. The substrates were cemented carbide bars having a composition of 90% WC, 1.8% TaC, 0.2% NbC, and 8% Co. The influence of the nitrogen pressure in the deposition system, which was in the range of 0.13-2 Pa, on the structure, phase composition, microhardness, and scratch critical load of the coatings was studied. It was shown that for nitrogen in the pressures range of 0.13-0.4 Pa the coating is composed of a mixture of two phases: hexagonal β-Nb2N and cubic δ-NbN, whereas at pressures of 0.67 Pa and above single-phase δ-NbN with a NaCl type structure was obtained. In most cases the coatings consisted of randomly oriented equiaxial grains. A maximum microhardness of 42 GPa was obtained for the two-phase coatings deposited at a nitrogen pressure of 0.4 Pa. However the maximal critical load of 95 N was obtained with the homogeneous δ-NbN coatings, deposited at a nitrogen pressure of 0.93 Pa, while the coatings with the hexagonal β-Nb2N phase had a much lower critical load (50 N). The NbN coatings with the highest critical load exhibited an average Vickers microhardness of 38 GPa.

Original languageEnglish
Pages (from-to)134-142
Number of pages9
JournalThin Solid Films
Volume326
Issue number1-2
DOIs
StatePublished - 4 Aug 1998

Keywords

  • Mechanical properties
  • NbN coatings
  • Vacuum arc plasma gun

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