Papers

ICMCTF2000 Session B2-2: Plasma Assisted Deposition and Thermochemical Treatments

Thursday, April 13, 2000 1:30 PM in Room Golden West

Thursday Afternoon

Start	Invited?	Item
1:30 PM		B2-2-1 New trends in DECR Plasma Technology : Applications to Novel Duplex Treatments and Process Combinations with Extreme Plasma Specifications J. Pelletier, A. Lacoste, Y. Arnal (Centre National de la Recherche Scientifique, France); T. Lagarde (Metal Process, France) After a brief recall of the plasma production and diffusion mechanisms above multipolar magnetic field structures, the possible means of sustaining magnetron discharges are listed. In particular, various designs of DECR (distributed electron cyclotron resonance) plasma reactors are described. At the industrial level, besides gas and pumping distribution, the control of plasma uniformity (up to square meters) is a necessary condition to obtain the desired uniformity of reactive species. Another process parameter, controlled via independent substrate biasing, is the energy distribution function of ions onto surfaces. Ion implantation in the 100 keV range requires large volumes (cubic meters) of very low pressure plasma (below 10^-4 torr), whereas ion bombardment in the very low energy range (a few eV) can only be obtained with quiescent, magnetic field free plasmas exhibiting a very low electron temperature. In contrast, ionization of metallic vapors present in the central volume of a DECR reactor can be enhanced in particular by increasing the electron temperature of the diffusion plasma. The control of plasma parameters in magnetron-like plasmas opens new possibilities for complex treatments associating successive processes with extreme plasma specifications. As examples, thermochemical processing at low ion bombardment energy or via plasma-based ion implantation (PBII) can be performed in DECR plasmas. More generally, plasma assisted deposition (PAD) or PBII & deposition (PBIID), using chemical (CVD) or physical vapor deposition (PVD), can be operated with magnetron-like discharges: PACVD and PBIICVD in DECR plasmas, PAPVD and PBIIPVD in hybrid DECR-magnetron reactors.
2:10 PM		B2-2-3 The Use of Intensified Plasma-assisted Processing to Produce m Phase in AISI 316 Stainless Steel V. Singh (Louisiana State University); E.I. Meletis (Louisiana State University.); K. Marchev (Norton Diamond Film); C.V. Cooper (United Technologies Research Center) Recently, it has been reported that conventional, diode plasma nitriding is capable of producing compound layers which contain single-phase, metastable m in AISI 316l stainless steel following processing in the temperature range from 400 - 480°C [1,2]. Following conventional (plasma) nitriding, the processed alloy was found to be possess high hardness and wear resistance while producing corrosion properties superior to those of the unprocessed alloy. In the present study, processing of AISI 316 has been extended to include intensified plasma-assisted plasma processing (IPAP), in which the processing parameters have been varied in an effort to determine whether and which conditions lead to m phase formation. The structural characteristics of the nitrided layers produced by IPAP have been investigated by x-ray diffraction and pole-figure analysis, nanoindentation in cross section has been performed to determine hardness and elastic modulus profiles, nitrogen concentration profiles have been obtained by electron-probe microanalysis, and wear experiments have been conducted to characterize IPAP-processed 316. Significantly IPAP has been successful in producing single-phase m with high hardness and lattice parameters which are smaller than those reported following diode nitriding. [1] K. Marchev, C.V. Cooper, J.T. Blucher, and B.C. Giessen, Surf. Coat. Technol., 99 (1998) 225. [2] K. Marchev, M Landis, R. Vallerio, C.V. Cooper, and B.C. Giessen, Surf. Coat. Technol, 116-119 (1999) 184.
2:30 PM		B2-2-4 Characterization of Carburized Tantalum Layers Produced by Inductive RF Plasma A. Raveh (University of North Carolina at Chapel Hill); A. Danon, J. Hayon (NRC-Negev, Israel); A. Rubinshtein, R Shneck (Ben-Gurion University, Israel); J.E. Klemberg-Sapieha (Ecole Polytechnique, Canada); L. Martinu (École Polytechnique, Canada) Tantalum surfaces were carburized in a radio-frequency (r.f.) plasma in order to improve its mechanical properties and corrosion resistance. The carburized layers were produced in an inductively coupled r.f. plasma using argon/methane, or argon/methane/hydrogen mixtures, and substrate temperature between 700 and 850degC. The process was performed at a constant flow rate of 100 sccm, while the variable parameters were the gas pressure P (10 -100 mbar), the r.f. power W (0.3 - 2.0 kW), the CH₄ concentration C_CH4 (0.1 - 0.8 vol.%), the hydrogen content C_H2 (1 - 50 vol.%), and the process duration t (3 - 20 h). The microstructure and composition of the layers obtained were characterized by XRD, AES/XPS, and TPD-MS (Temperature Programmed Desorption - Mass Spectrometry). The mechanical properties were studied by microindentation and microscratch techniques, and the corrosion resistance was examined by impedance analysis. For the same treatment time, it was observed that the thickness of the carburized layer and the phase content (TaC or Ta₂C) were different for three distinct ranges of fabrication conditions: (a) W < 1.2 kW and P < 30 mbar, a thin layer of ≤ 1 m m thickness and gradient diffusion profile; (b) 1.4 < W < 1.6 watt and 40 < P < 60 mbar, a thick carbide layer was formed (several m m) consisting of mainly the TaC phase with an uniform chemical composition and the highest hardness (~25 GPa); and (c) W ~ 2.0 kW and/or P ~ 100 mbar carbon films on the treated surface were formed.
2:50 PM		B2-2-5 Filtered Arc Plasma Immersed Ion Nitriding and Duplex Processing of Large Area Complex Shape Articles V.I. Gorokhovsky (Aromac Plasma Processing Lab, Canada); P. Del Bel Belluz, P. Lidster (Exactatherm, Canada) The ion nitriding of different types of steel in a large area filtered arc plasma immersed environment is investigated. The rate of nitriding vs plasma parameters, such as ion current density, pressure and gas composition are established for several types of steel: 4140 steel, M2 steel, H13 steel. The ion nitriding layer is characterized by structure, thickness, microhardness depth profile, and surface roughness. Ion nitriding by both regular impulse glow discharge and filtered arc plasma immersed process followed by TiN coating. The adhesion and micro hardness of the resulting duplex layers is characterized. Comparison study for regular glow discharge ion nitriding vs filtered arc plasma immersed ion nitriding processes is presented. The results of processing complex shapes are discussed.
3:30 PM		B2-2-7 PCVD Coated Cemented Carbides - 10 years Experience in Industrial Practice H. van den Berg, R. Tabersky, U. König (Widia-Valenite, Essen, Germany) The coating of cemented carbides by using the plasma enhanced CVD technology was developed at WIDIA since 1985. Inserts coated by this process showed in cutting tests tremendous advantages. A coating furnace for the production of large batches was designed and build ¹. In 1989 the new grades of PCVD coated inserts were launched to the market. The plasma enhanced CVD process runs at much lower temperatures than the widely used CVD methods. It combines the advantages of both high temperature CVD and low temperature PVD deposition. It became possible to produce coatings of titanium nitride, titanium carbonitride, titanium carbide and aluminium oxide with high productivity. The Widia-Valenite PCVD grades are used in many metal cutting applications, especially in milling, drilling threading, but also in turning operation. Although there is a strong competition of modern PVD coated grades, the market for the PCVD coated inserts is still growing. The paper deals with experiences gained in the industrial production practice and gives an overview of the great variety of applications in the metal working industry. ¹ { Refractory Metals & Hard Materials, June 1990, p. 69.}
4:10 PM		B2-2-9 Preparation of SiC_xN_y Films by Microwave Plasma from Two Precursors : Comparison of the Incorporation of Carbon and Nitrogen M.P. Delplancke-Ogletree (Université Libre de Bruxelles, Belgium); O.R. Monteiro (Lawrence Berkeley National Laboratory) Thin SiC_xN_y films were prepared in a microwave plasma with various precursors. On one hand, the gas phase made off nitrogen, CH₄ and H₂ etched the silicon substrate and the amorphous sp² carbon to form small crystallites of SiC_xN_y with a low level of carbon incorporation. On the other, the silicon and carbon were provided by a liquid organic precursor, the tetramethylsilane (Si(CH₃)₄) carried by an argon flow and the gas phase made of hydrogen, nitrogen was used to provide the nitrogen and to control the carbon incorporation. In the last case, the carbon incorporation is high while the nitrogen incorporation is low. The films were characterized by scanning and transmission electron microscopy, X-ray diffraction and by Auger electron spectroscopy. The importance of substrate temperature, plasma uniformity, gas phase composition and injection position of the precursors is shown.
4:30 PM		B2-2-10 Deposition of Multicomponent Coatings Including Elements of B, C, N, O, Al, Si, Ti and Zr on Cemented Carbides Using Plasma Enhanced CVD R. Tabersky, H. van den Berg, U. König (Widia-Valenite, Essen, Germany) Up to now the high temperature CVD technology is the dominant coating technique in hardmetal industry. Current innovations of Widia/Valenite in the CVD field also show potentials for the future ¹. But for metal cutting applications with high requirements to toughness and stability of the cutting edges coating processes working at lower temperatures are more favorable. Beside of the different PVD techniques the pulsed DC-mode PCVD process developed by Widia/Valenite was a special approach in this direction ², ³. This coating technique has been successfully applied since many years for all types of hardmetal inserts and the number of applications is still growing. Among the low temperature methods for the deposition of hard coatings the plasma enhanced CVD (PCVD) shows some particular characteristics. The coatings grow by chemical processes, governed by the thermodynamic of the reactions and their kinetics and modified through the presence of a glow discharge plasma. In general it results to fine grained materials with well defined stoechiometry. But in contrast to the high temperature CVD, where in many cases the thermodynamical most stable phase is growing, with PCVD it is possible to synthesize a greater variety of coating materials. We have studied the PCVD of many systems of the elements of B, C, N, O, Al, Si, Ti and Zr, getting a large variety of hard coatings. Thus it was possible to deposite coatings in the composition range of Ti-Zr-C-N, Ti-Al-Si-C-N and B-C-N. Some of these show remarkable properties. In combination with new hardmetal grades and tool geometries these coatings can help to meet the current and future demands in metal cutting operations. ¹ H. Westphal, V. Sottke, R. Tabersky, H. van den Berg, U. König, Proceed. 14th Int. Plansee Seminar 1993, Vol. 3 (1997), C7, 55-62} ² U. König, R. Tabersky, H. van den Berg, Surface and Coatings Technology, 50 (1991) 57-62} ³ R. Tabersky, H. van den Berg, U. König, Int. J. of Refractory Metals & Hard Materials 14 (1996) 79-84}
4:50 PM		B2-2-11 CVD of TiC_x/a-C-layers Under DC-pulse Discharge A. Leonhardt, H. Liepack, K. Bartsch (Institut für Festkörper- und Werkstofforschung Dresden, Germany) Hard layers consisting of TiC_x and amorphous carbon have been co-deposited from CH₄-TiCl₄-H₂-Ar gas mixtures by plasma CVD varying the C concentration in a wide range. The layers were characterized with respect to their composition, structure and some properties essential for mechanical applications. Especially, the influence of the CH₄/TiCl₄ ratio on the layer constitution and behaviour was investigated. Up to a very high hydrocarbon content the excess carbon forms an amorphous matrix. Any graphite could not be detected by electron diffraction in the layers. With increasing carbon concentration also the hydrogen incorporation in the amorphous matrix increases in the case of H₂ containing deposition gas mixtures. TEM investigations demonstrated a homogeneous distribution of the TiC_x crystallites and a grain size of about 4 - 5 nm. The layers are textureless and with increasing amorphous carbon content the surface roughness decreases. The microhardness depends on the excess of carbon and, probably, the content of the dissolved hydrogen. If the deposition process is realised without any additional H₂ in the gas phase, the microhardness increases strongly (> 4000 HV[0.05]). A maximum of microhardness was observed at 60 at% carbon in the coatings. The elastic modulus shows a similar behaviour and corresponds to a value of 520 GPa for the maximum. Stress measurements by XRD and the beam bending method revealed generally that a high compressive stress occurs in stoichiometric TiC layers in comparison with in TiC_x/a-C layers. Nevertheless, all composite layers showed a low adhesion on different substrates. An improvement could be achieved by pre-deposition of suitable interlayers. The low friction coefficient and the favourable surface roughness make PACVD-TiC_x/a-C-layers to be a good candidate for sliding wear applications.
5:10 PM		B2-2-12 Tungsten and Tungsten Carbon Multilayers Deposited by Inductively Coupled Plasma Source P. Colpo (European Commission Joint Research Centre, Italy); P Sauvageot (IHCP, Italy); G. Ceccone, N Gibson, F. Rossi (European Commission Joint Research Centre, ITALY); P. Monge-Cadet (Turbomeca, France) This work deals with the deposition of tungsten and carbon tungsten multilayers by Inductive Plasma enhanced CVD. A metallic slotted Faraday shield is arranged within the plasma chamber to prevent electrically conductive film deposition on the dielectric chamber wall which would screen the electromagnetic field. Tungsten deposition has been performed from WF₆ diluted in argon and hydrogen. Carbon tungsten films are obtained in adding methane or acetylene to the mixture. The process temperature were below 400 C. The corresponding film microstructure characteristics were investigated by SEM/EDX; XRD was used to assess the coating crystal structure, whereas the carbon content of the WC films was investigated by AES and XPS. The mechanical properties of the films have been assessed by nanoindentation. Measurements show that biasing the substrate increases the tungsten hardness from 5 to 20 GPA ant that the hardness of the WC films depends strongly on the carbon contents of the films. Correlation between the deposition parameters, such as the gas composition, RF bias, and RF power, and coating properties have been investigated. Comparison of WC film obtained by CH₄ and C₂H₂ is performed.