AVS 52nd International Symposium
    Advanced Surface Engineering Tuesday Sessions
       Session SE-TuM

Paper SE-TuM1
Structure and Properties of TiBN Coatings Deposited by Reactive Arc Evaporation

Tuesday, November 1, 2005, 8:20 am, Room 201

Session: Hard Coatings and Wear Mechanisms of Protective Coatings
Presenter: J. Neidhardt, University of Leoben, Austria
Authors: J. Neidhardt, University of Leoben, Austria
C. Mitterer, University of Leoben, Austria
Zs. Czigány, Research Institute for Technical Physics and Materials Science, Hungary
M. O'Sullivan, Plansee AG, Austria
Correspondent: Click to Email
TiBN based coating systems have been shown to have a high potential as wear protective coating owing to their outstanding mechanical properties as well as their chemical and thermal stability. However, the industrial scale synthesis has been very limited so far, presumably due to the sensitivity of the target materials and the therefore low deposition rates as well as the commonly high intrinsic stresses. This study reports, thus, on high-rate (30 - 40 nm-min@super -1@) TiBN coating deposition by reactive arc evaporation in a commercial Balzers Rapid Coating System at different N@sub 2@ partial pressures. Decreasing the bias voltage to -20V is shown to reduce the intrinsic stress and in turn to improve the adhesion on various substrates, e.g. high speed steel and (100) Si. XRD as well as high-resolution transmission electron microscopy in combination with selected area electron diffraction revealed that all coatings contain fcc crystallites, whereas the increasing lattice parameter at lower N@sub 2@ partial pressures indicates a supersaturated solid solution of B in fcc TiN. At higher N@sub 2@ partial pressures an amorphous BN phase forms, whereas its extent scales with the N@sub 2@ fraction. Nano-indentation revealed a maximum in hardness at approximately 40 GPa for the TiBN single phase solid solution which drops to 22 GPa for the coating grown in pure N@sub 2@. Ball-on-disc tests against alumina at 5N showed that the high hardness of the single phase material results in a by one order of magnitude reduced wear coefficient with respect to the coating containing the additional amorphous phase, even though the coefficient of friction remained constant at 0.7 to 0.8