ICMCTF2002 Session B1-3: PVD Hard Coatings and Technologies

Friday, April 26, 2002 8:50 AM in Room Golden West

Friday Morning

Start	Invited?	Item
8:50 AM		B1-3-2 Deposition of NbN Thin Films Onto High Speed Steel Using Reactive Magnetron Sputtering for Corrosion Protective Applications M. Fenker, M. Balzer (Forschungsinstitut für Edelmetalle und Metallchemie, Germany); R.V. Büchi (ETH Zürich, Switzerland); H.A. Jehn, H. Kappl (Forschungsinstitut für Edelmetalle und Metallchemie, Germany); J.-J. Lee (Seoul National University, Korea) Niobium nitride is an interesting transition metal nitride with its main application in the fields of superconductivity and wear protection of tool parts. For the latter application NbN is used as one layer component of superlattice coatings. But not much investigations have been done on the corrosion behavior of NbN coated steel substrates, despite the fact that NbN has a very high corrosion resistance in corrosive environments. In this study hard NbN thin films were deposited onto high speed steel (hss) using reactive magnetron sputtering. The experiments were carried out varying the nitrogen partial pressure and the substrate bias voltage. Additionally the effect of intermediate plasma etching of NbN thin films on their film properties was investigated. The corrosion behavior of the NbN/hss samples was studied by potentiodynamic corrosion tests in 0.8 M NaCl solution (pH 7). The corrosion tests revealed that the system NbN/hss has a very broad passivation range with a low current density. Further film properties were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), scratch testing and microhardness measurements. A very high plastic universal hardness could be found for NbN thin films with values up to 47 GPa.
9:10 AM		B1-3-3 Magnetron Sputtered Cubic Boron Nitride Thin Films - A Review J. Ye, S. Ulrich, K. Sell, M. Stüber, H. Holleck (Forschungszentrum Karlsruhe, Germany); W. Kulisch, R. Freudenstein (University of Kassel, Germany) The deposition of cubic boron nitride (c-BN) thin films has been carried out through r.f. magnetron sputtering of an h-BN target under various conditions. The structure and property of the films are characterized and compared with regard to different growth environments like working gases (Ar, N₂, etc.), pressures, and substrate temperatures. In combination with a collection of available data on the magnetron sputter deposition of c-BN, the parameter spaces for the c-BN growth are critically reviewed in terms of the ion energy E_i, the ion to neutral flux ratio F, the ion mass m_i, and the substrate temperature T_s. Two separate sets of well-defined regions suitable for the nucleation and growth of c-BN, respectively, are identified in the F/E_i, F/m_i and F/T_s parameter spaces. Additional influence of film stoichiometry is shown as well. On this basis the nucleation and growth mechanisms of the cubic phase are discussed. With respect to high compressive stresses commonly existed in the deposited c-BN films, recent efforts for the stress reduction and novel growth concepts towards adhesive, thick c-BN films are outlined and evaluated.
9:30 AM		B1-3-4 Amorphous SiC Coatings for WC Cutting Tools A.K. Costa, S.S. Camargo Jr. (Universidade Federal do Rio de Janeiro, Brazil) Silicon carbide is a material that presents suitable properties for coating of mechanical tools but have been quite unexplored up to now. In this work, SiC films were deposited by rf magnetron sputtering onto WC and silicon substrates from a commercial sintered SiC target. After determining the influence of deposition parameters on the properties of the films deposited onto silicon substrates, suitable conditions were chosen to produce high quality 5μm thick films on WC pieces. Mechanical characterization of the films was done by microhardness and residual stress measurements. Low power levels (100W) resulted in the highest hardness values (up to 40GPa) but with low deposition rates (5nm/min) and high film compressive stresses (up to -2.5GPa). On the other hand, high deposition rates (up to 40nm/min), lower stresses (-1GPa) and hardness (25GPa) are obtained at high power levels (400W). Films with the highest hardness were obtained at low argon pressures. A ball-crater apparatus was used to perform both thickness measurements and wear resistance tests. The wear rates of the coated pieces were found to be reduced to less than half of the uncoated ones. Coated and uncoated pieces were submitted to vacuum and atmospheric thermal annealing up to 1000°C. It was observed that uncoated surfaces of WC samples are strongly oxidized by air at temperatures of 600°C or higher, therefore degrading both wear and mechanical properties. On the other hand, SiC coated pieces remained unaffected even at temperatures up to 700°C. For comparison, it was verified that for the same annealing conditions commercial TiN coatings are completely destroyed.
9:50 AM		B1-3-5 Grows of TiN_x Films with Strong (220) Prefered Orientation B. Goncic (The Vinca, Institute of Nuclear Sciences, Yugoslavia); N. Popovic (The Vinca, Institute of Nuclear Sciences, Atomic Physics Laboratory , Yugoslavia); Z. Bogdanov, S. Zec (The Vinca, Institute of Nuclear Sciences, Yugoslavia); M. Zlatanovic (Faculty of Electrical Engineering, Yugoslavia) Titanium nitride thin films were deposited by 2keV argon ion beam reactive sputtering of Ti target onto glass and Si substrates. At low working gas pressure of 1x10-5 mbar, the ambient substrate temperature and film bombardment by argon ions from the beam periphery, the TiNx films of a strong (220) orientation, rarely described in the literature were grown. XRD analysis revealed the increase of TiNx (220) peak intensity with increasing the film thickness, as well as the change of TiNx crystallites dimension and type of internal stresses due to variation of residual gas pressure. The nitrogen partial pressure was changed in a narrow range from 2x10-6 to 5x10-6 mbar at the residual gas pressure of 1x10-6 mbar, 2x10-6 and 3x10-6 mbar. Residual gas pressure was found to have a strong ingluence on the film color appearance, resistivity, crystallite size and internal stresses, the effects attributed to the amount of oxygen containing molecules. The deposition rate was monitored in situ by a light detection resistor that provided the possibility for a qualitative estimation of visible light absorption coefficient of films deposited at the same rate. Low pressure argon beam reactive sputtering was found to be a powerful method for the deposition of TiNx films with a strong (220) orientation.