Papers

ICMCTF1999 Session B5: Ion Assisted Deposition and Ion Beam Technologies

Thursday, April 15, 1999 8:30 AM in Room Golden West

Thursday Morning

Start	Invited?	Item
8:30 AM		B5-1 Subplantation Growth of Films Using Ion Beam and Ion Beam Assisted Deposition - Carbon - a Study Case Y. Lifshitz (Soreq NRC, Isreal) The growth of films from hyperthermal (10-1000eV) species is a complex process. It involves penetration to subsurface sites ("subplantation"), collisional energy loss, displacement and sputtering of substrate atoms, migration (thermal or radiation enhanced), formation and relief of stress, formation and breaking of atomic bonds. Carbon, having three different local bonding configurations (sp,sp2,sp3) is an excellent study case to learn the relative significance of each of these processes and their overall effect on the structure and properties of the evolving films. The author’s assessment of the current understanding of the diamondlike carbon growth from hyperthermal species (both by direct impingement or by momentum transfer) will be given. Conclusions relevant for deposition of other materials will also be highlighted.
9:10 AM		B5-3 TiN-Coated Cemented Carbide Treated with a Low Energy High Current Electron Beam (LEHCEB): Micro-structural Studies and Steel Turning Properties. A.J. Perry (A.I.M.S. Marketing, Japan); J.N. Matossian (Hughes Research Laboratories, Inc.); D.I. Proskurovsky (Russian Academy of Sciences, Tomsk, Russia); P. Rice-Evans (University of London, United Kingdom); S.J. Bull, T.F. Page (University of Newcastle, United Kingdom) Sets of cemented carbide cutting tool inserts coated with monolithic TiN by CVD or PVD methods, respectively, have been subjected to a series of pulsed intense electron beam treatments in the energy range 3-5 J.cm^-2. The temperature profiles during the treatment were calculated per Ibmod and Markov codes. Steel cutting tests were run with the treated inserts. The effect of the treatment on the coatings was analyzed by SEM for surface topography and fractographs, SPAS for the vacancy defect population near the surface, AES and SIMS for composition profiles, nanohardness, and classical XRD for phase identification and GIXRD for residual stress and the distribution of microstrain. A selection of the results and their interpretation will be presented.
9:30 AM		B5-4 Surface Hardening of Stainless Steel at Intermediate Temperatures by Plasma Immersion Ion Implantation T. Hoechbauer (Philipps University of Marburg, Germany); K. Volz (University of Augsburg, Germany); M. Rinner (Philipps University of Marburg, Germany); W. Ensinger (Philipps - University of Marburg, Germany) It has been established in the literature that ion implantation into high alloy steels can lead to surface hardening with an improvement in wear resistance. However, this technique has two drawbacks, one being that it is restricted to line-of-sight treatment, the other one that the modified zone is shallow. The shallowness can be overcome by allowing an increased temperature. Three-dimensional bodies can be treated when they are manipulated in the beam. The latter can be avoided when plasma immersion ion implantation is used where the sample is treated from all sides simultaneously with ions extracted from the plasma which envelopes the sample. Owing to the large power input, plasma immersion ion implantation may easily lead to an increased temperature. Therefore, this technique is particularly suitable for filling the gap between ion implantation at low temperatures and plasma nitriding at high temperatures. In the present contribution, results on nitrogen plasma immersion ion implantation of austenitic stainless steels at 40 kV acceleration voltage at intermediate temperatures (typically below 400 °C) are presented. Rutherford backscattering depth profiles show that the incorporated nitrogen may reach depths of microns, depending on the temperature. This results in a reduction of wear as shown by oscillating ball tests. These findings are correlated to phase formation, studied with X-ray diffraction.
9:50 AM		B5-5 Three Dimensional Dose Uniformity of Plasma Immersion Ion Implantation Shown With the Example of Macro-trenches W. Ensinger (Philipps - University of Marburg, Germany); K. Volz (University of Augsburg, Germany); T. Hoechbauer (Philipps University of Marburg, Germany) Plasma Immersion Ion Implantation (PIII) is at present at the border to industrial application, both in semiconductor and in the metallurgical field. Among its main advantages the dose uniformity, also when three-dimensional objects are treated, is often quoted. In order to study the homogeneity of PIII, silicon macro-trenches with different aspect ratios have been treated in an argon plasma. The retained argon dose at the top and bottom of the trenches has been determined by RBS. Already for the widest trench a significant reduction of the implanted argon dose can be found in the trench bottom compared to the top. The situation gets even worse reducing the width of the trench. In order to be also able to look at the situation of the trench sidewalls, the trenches have been lined with Ta foil coated with a 200 nm thick Ta₂O₅film. The colour of Ta₂O₅ is strongly dependent on its layer thickness and therefore it is easily possible to determine the remaining layer thickness after implantation, if parts of the Ta₂O₅ layer have been removed due to sputtering during Ar ion bombardment. This not only yields information on the amount of implanted Ar, but also on the ion incidence angle onto the surface, which is shown to be not at all perpendicular at the sidewalls. The present study shows that there is a retained dose and implanted depth inhomogeneity, if complex shaped objects are treated with PIII. This is explained with the expansion of the plasma sheath during the high voltage pulses.
10:30 AM		B5-7 Formation of Hafnium Nitride Films by Ion Beam Assisted Deposition K. Volz (University of Augsburg, Germany); B. Enders (Philipps University of Marburg, Germany); M. Kiuchi (Osaka National Research Institute, Japan); W. Ensinger (Philipps - University of Marburg, Germany) Hafnium nitride is a ceramic matrial which is of interest due to its tribological and corrosion performance. HfN films have been formed by electron beam evaporation of hafnium under simultaneous nitrogen bombardment on silicon wafers as well as on stainless steel samples. The samples have been analyzed by RBS for their composition. X-ray diffraction and cross-section transmission electron microscopy have been applied in order to determine phase composition and microstructure. Without ion irradiation, an oxgen rich, polycrystalline hafnium film is formed on the substrate, which is composed of columnar grains with open grain boundaries. These films are therefore not well suited for corrosion applications. Ion irradiation with an energy of 10 keV results in the formation of a finecrystalline hafnium nitride film on the substrates. The phase formed is the cubic HfN. The morphology of the polycrystalline HfN is still columnar, but the grain boundaries are no more open, resulting in a much better corrosion performance.
10:50 AM		B5-8 Titanium Carbide Coatings Deposited by Reactive Ion Beam Assisted, Electron Beam-Physical Vapor Deposition (EB-PVD) D.E. Wolfe, J. Singh (The Pennsylvania State University) Hard coatings are applied to various materials to extend the life and improve the performance of cutting tools under wear conditions. Titanium carbide has long been know to be a hard, wear resistant material with excellent wear-resistance in the machining and cutting of stainless and tool steels. Titanium carbide (TiC) was successfully deposited on 304 stainless steel by reactive ion beam-assisted electron beam-physical vapor deposition. The hardness values ranged from 1100 3500 VHN depending on the processing conditions. The surface morphology and degree of texturing were correlated with the processing conditions. By growing the films with a specific orientation to the cutting surface, the wear-resistance of the coating should be improved. The wear rates and friction coefficients of TiC deposited on 304 stainless steel were determined using a ball on-disc tribology tester. Scanning electron microscopy, x-ray diffraction, electron probe microanalysis, and tribology were used to characterize these films.
11:10 AM		B5-9 On the Mechanism of Improvement of TiN-coated Tool Life by Nitrogen Implantation S.J. Bull (University of Newcastle, United Kingdom); Y.P. Sharkeev, S.V. Fortuna (Russian Academy of Sciences, Russia); A.J. Perry (Kyoto University, Japan) For some time now it has been known that the life of TiN-coated tools can be improved by a post coating ion implantation treatment. However, despite many studies showing the effectiveness of the treatment the mechanism by which such improvements occur are not well understood. Nitrogen implantation of both PVD TiN and CVD TiN can produce a hardening at low doses but this is often followed by a softening as the dose increases which has been attributed to amorphisation. Given the metallic nature of the bonding in TiN this mechanism is unlikely and so in this study we have used a combination of transmission electron microscopy and atomic force microscopy to characterise the microstructure of implanted PVD TiN coatings on WC/Co and related these to mechanical property measurements (nanoindentation, residual stress, etc.) made on the same samples. Ion implantation leads to a reduction in the grain size of the TiN in the implanted zone rather than any amorphisation. The softening could be due to the presence of a layer of bubbles generated by the very high implantation doses used. These results are discussed in light of the machining performance of the implanted coatings
11:30 AM		B5-10 Aqueous Corrosion Behavior of Molybdenum and Chromium Nitride Coatings Produced by Ion Beam Assisted Deposition J.D. Demaree (U.S. Army Research Laboratory); G.P. Halada, C.R. Clayton (State University of New York at Stony Brook) Hard nitride coatings produced by Ion Beam Assisted Deposition (IBAD) are candidates to replace electroplated chromium in a number of tribological applications. Previous studies have shown that IBAD is capable of depositing hard nitride coatings with wear resistance equal to or exceeding that of electroplate, but the corrosion behavior of these IBAD coatings has not been fully characterized or optimized. The IBAD coating systems under consideration may contain a mixture of phases, ternary nitride phases, or even graded interfaces with adhesor layers on the underlying substrate, all of which can lead to a complex corrosion system which must be understood in order to maximize the coating durability. In this study, coatings of Cr_xN_y, Mo_xN_y, and Cr_xMo_yN_z have been synthesized with IBAD, using 1200 eV nitrogen ions and thermal vapor deposition. The composition and thickness of the coatings were examined using Rutherford backscattering spectrometry (RBS) and x-ray photoelectron spectroscopy (XPS) before removing from the high vacuum system. The aqueous corrosion behavior of the alloys was then studied by electrochemical techniques, and the surface chemistry examined using angle-resolved XPS. The effect of nitrogen content on the formation of oxyanions will be discussed, as will the design of coating chemistry to produce self-healing coatings with maximized resistance to corrosive environments.