ICMCTF1998 Session D4/E5: Properties and Applications of Diamond, Diamondlike and c-BN Coatings

Wednesday, April 29, 1998 1:30 PM in Room Forum/Senate/Committee
Wednesday Afternoon

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1:30 PM D4/E5-1 Tribological and Mechanical Properties of CNx Thin Films
M.Y. Chen, D.J. Kramer (Air Force Research Laboratory)
Carbon nitride compounds offer great potentials for protective, wear, and optical applications. Reactive magnetron sputtering with and without the assistance of an electron cyclotron resonance source have been used to deposit CNx thin films. The level of nitrogen content was varied by changing the growth condition. Pin-on-disc experiments were performed between 440C stainless steel pins and CNx-coated 440C substrates at 0.1 m/s sliding velocity and 1 N load. The effects of process variables and interface modification on friction and wear rate were examined. Mechanical properties including hardness, modulus and elastic response of CNx films were obtained from nanoindentation. Comparisons of these properties between CNx and DLC films deposited by this technique will be presented.
1:50 PM D4/E5-2 In Situ Diagnostics of c-BN Film Gowth by IR Reflection Spectroscopy
K.-L. Barth, A. Neuffer, P. Scheible, L. Ulrich, A. Lunk (University of Stuttgart, Germany)

Cubic boron nitride (c-BN) layers were deposited on silicon by a plasma activated process in a hollow cathode arc deposition device. The plasma parameters were measured by Langmuir probe diagnostics and the growth process is analyzed by in situ polarized infrared reflection spectroscopy.

The s-polarized infrared reflectance spectra of a growing BN film shows the structure of the in-plane vibration of sp2 bonded BN at 1370 cm-1 after a time delay t1. The out of plane vibration at 780 cm-1 can be observed too with a time delay t2. The signature of the cubic phase can be detected later on with a time delay t3. The time delays t1 - t3 depend on deposition conditions with the bias voltage as the most important parameter.

Starting at deposition conditions where c-BN layer growths the shift of the c-BN peak and the ratio of the peak heights c-BN/h-BN were investigated in situ in dependence of deposition time and bias voltage (DC and RF). Applying DC bias to the substrate the h-BN peak appears at -275 V. Applying RF the corresponding bias voltage becomes lower.

By simulation of the spectra, the damping constant of the c-BN oscillator was estimated to be 170 cm-1, nearly independent of the thickness. The transverse optical mode frequency of the c-BN phonon starts at 1090 cm-1, decreases to a minimum of 1070 cm-1 at a film thickness of 300 nm and increases at higher thicknesses. Up to a film thickness of 300 nm the oscillator strength increases from 5x105 cm-2 to 22x105 cm-2 and remains constant during further growth.

2:10 PM D4/E5-3 Influence of Water Vapour and Oxygen on the Tribological Behaviour of Diamond Coatings / Steel Couple
M Schmitt, T. Le Huu (National Polytechnics Institute of Lorraine, France); M. EL Mansori, D. Paulmier (ERMES, France); A. Grabcheko (Kharkov State Polytechnical University, Ukraine); A.G. Mamalis (National Technical University of Athens, Greece)

Tribological properties of diamond coatings depend on a lot of parameters especially on the elaboration processes, the nature of the counterface and the environment.

This paper presents a study of a diamond coating deposited by flame process on a tungsten carbide pin and rubbing on a steel disc under different environments : air, water vapour, oxygen and argon with pressure variations.

The deposition conditions were chosen to obtain the growth of the diamond crystals following the {111} direction.

Concerning the friction coefficient, it appears that it increases with the pressure of oxygen and water vapour to a limit value, whereas the wear rate of the steel disc continues to increase with pressure.

Analyses from the disc, the pin surface and the wear debris are presented to explain the interactions between diamond and steel in the machining conditions and highlight the transfer mechanisms.

This behaviour of the diamond coating / steel couple is explained together by the evolution of the oxygenated terminal bondings on the surface of the diamond, by the growth of the oxide layer on the steel disc surface and the role, the composition of the wear debris and the manner which these are evacuated from the interface.

2:30 PM D4/E5-4 Characteristics of Carbon Nitride Films Synthesized by Chemical Vapor Deposition
S.P. Wong, D. Chen, N. Ke, W.Y. Cheung, R.W.M. Kwok (The Chinese University of Hong Kong, China)
Carbon nitride films have been synthesized by UV-light assisted hot filament chemical vapor deposition in a mixture gas ambient of N2 and CH4. The optical, mechanical and structural properties of these films deposited at various CH4 partial pressures and bias voltages have been studied. The N/C atomic ratio and the various carbon nitride phases in these films were analyzed using X-ray photoelectron spectroscopy. The carbon-nitrogen bonding structures were studied by Fourier transform infrared absorption and the spectra showed that bands appeared at 1500, 1630 and 2200 cm-1 corresponding to C-N, C=N and C?=N stretching vibration of carbon-nitrogen bonds. TEM and XRD were used to determine the structures and crystalline phases of the films. Vickers hardness Hv and Young's modulus of these samples have also been measured. The dependence of the nitrogen content and the relative abundance of the various carbon nitride phases in the films on CH4 partial pressure will be presented. The results also showed that UV-light irradiation has played an important role in the formation of β-C3N4 structure by reducing the activation energy of the process. The effect of substrate bias voltage on the structure of the films will also be discussed.
2:50 PM D4/E5-5 Cutting Applications of DLC, Hard Carbon and Diamond Films
K.M.B. Vandierendonck, E.M.F. De Mulder, M. Van Stappen (WTCM; Centre for Scientific and Technical Research in Metal Manufacturing)

Due to their high hardness and low friction coefficient amorphous hard carbon "HC", diamondlike carbon"DLC" and diamond coatings have great potential for dry cutting operations. It is however not always clear which coating should be chosen for which application. The main differences between the films can be found in their hardness (respectively 5000-8000HV, 2500HV and 10000HV), their morphology (HC: amorphous, DLC : amorphous and diamond crystalline) and their thermal stability (HC : 600°C, DLC : 250°C and diamond 700°C).

. The films have been characterized with Raman spectroscopy (determination sp2 - sp3 content), Vickers hardness measurement and scanning electron microscopy "SEM"measurements (thickness and morphology). The three coatings have been deposited on end-mills (both hardmetal and HSS (no diamond)) and on turning inserts (hardmetal). The coatings have been evaluated for a turning application of a metal matrix composite AlSiC (20%SiC), for a turning application of graphite and for a milling application of AlMgSi0.5. Wear analyses have been performed with SEM. These lead to recommendations on the use of the three coatings for dry cutting applications.

3:10 PM D4/E5-6 Stress Issues in Wafer-Scale CVD Diamond Fabrication
H. Windischmann (Norton Diamond Film)
Because of the unfavorable mechanical properties of diamond, the source and type of stress must be identified and magnitude controlled at every stage of the CVD diamond deposition process to develop a high yield, wafer-scale fabrication process. This paper reports on the defects and stresses encountered in CVD diamond deposition by DC arc jet. By implementing tight process control and making a judicious selection of substrate material, DC arc jet technology is capable of producing 175 mm diameter wafers at high yield with uniform properties.
Time Period WeA Sessions | Abstract Timeline | Topic D Sessions | Time Periods | Topics | ICMCTF1998 Schedule