Papers

ICMCTF2005 Session B7-3: Properties And Characterization of Hard Coatings And Surfaces

Tuesday, May 3, 2005 8:30 AM in Room Golden West

Tuesday Morning

Start	Invited?	Item
8:30 AM		B7-3-1 Synthesis and Mechanical Evaluation of New Quaternary Ti-Cr-Si-N Coatings Deposited by a Hybrid Method of Arc Ion Plating and Sputtering Techniques D.K. Lee, D.S. Kang, K.H. Kim, P.K. Song, Y. Shigesato (Pusan National University, South Korea) New quaternary Ti-Cr-Si-N coatings were synthesized onto steel substrates (SKD11) and Si wafers using a hybrid method of arc ion plating (AIP) and sputtering techniques. For synthesis of Ti-Cr-Si-N coatings, the Ti-Cr-N coating process was performed substantially by a multi-cathodic AIP technique using Cr and Ti targets, and Si could be added by sputtering Si target during Ti-Cr-N deposition. In this work, comparative studies on microstructure and evaluation of mechanical properties between Ti-Cr-N and Ti-Cr-Si-N coatings were conducted. As the Si was incorporated into Ti-Cr-N coatings, the Ti-Cr-Si-N coating showed further increased hardness value of approximately 45 GPa than one of 30 GPa for Ti_1-x-Cr_x-N ( X-0.3 ) coating. The oxidation behavior of Ti-Cr-Si-N coating was conducted between 500 and 1000â"f in atmospheric air, and the quaternary Ti-Cr-Si-N coatings showed further enhanced oxidation resistance than ternary Ti-Cr-N coatings. The average friction coefficient of Ti-Cr-Si-N coatings gradually decreased with increase of Si content in Ti-Cr-N coatings.
8:50 AM		B7-3-2 Oxidation of Arc-Evaporated Al_xCr_1-xN Coatings A.E. Reiter (Balzers Ltd., Liechtenstein); R. Kaindl, R. Tessadri (University of Leboen, Austria); C. Mitterer (University of Leoben, Austria) The recently introduced Al_xCr_1-xN coatings are characterized by superior thermal stability and oxidation resistance. Although several studies on the microstructure and mechanical properties of these coatings have been published, the oxidation behavior and mechanisms for high Al-containing coatings have not yet been investigated. Within this work, the oxidation of arc-evaporated Al_xCr_1-xN coatings was investigated as a function of the Al content. Coatings were deposited onto cemented carbide using an industrial-scale arc-evaporation system (Balzers RCS) and alloyed Al/Cr targets yielding Al_xCr_1-xN coatings ranging from x = 0.2 to x = 0.7. Heat treatments in air and argon atmosphere were conducted in the temperature range between 900°C and 1100°C. In order to determine elemental distribution and the phases present within the coating and the oxide layers, SIMS and XPS depth profiling, XRD, and Raman spectroscopy were performed. After annealing in argon atmosphere, Cr was found to segregate to the coating surface as a result of the decomposition of the CrN phase into Cr₂N and finally Cr. Simultaneously, Al depletion was observed for the Cr-enriched region. Contrary, no evidence for CrN decomposition was found after annealing in air. A protective Cr₂O₃-rich layer was formed on top of the coatings for all compositions investigated. For high Al contents, a tendency for forming an additional Al₂O₃-rich layer below the Cr₂O₃-rich layer was observed. These protective oxide layers prevent the AlCrN decomposition observed after annealing in inert atmospheres.
9:10 AM		B7-3-3 The Effect of Multilayers on the Residual Stress in Chromium Nitride Coatings Deposited on Cemented Carbide by Physical Vapour Deposition F. Keely, S. Chowdhury, M.T. Laugier (University of Limerick, Ireland) Residual stresses present in chromium nitride coatings on cemented carbide substrates have been investigated using X-ray diffraction (XRD) and from indentation testing. The chromium nitride coatings were deposited in layers 1.5 mm thick by means of reactive electron beam evaporation of Cr in a nitrogen atmosphere and were found to be mainly Cr₂N with small amounts of CrN detected by XRD. A triaxial stress state was found from XRD. In-plane coating stresses were compressive and exceeded thermal stresses computed using values of Young's modulus determined from nanoindentation by a factor of around three. Increasing the number of layers was not found to have an effect on stress values.
9:30 AM		B7-3-4 CrN-Ag Self-Lubricating Hard Coatings C.P. Mulligan (Benet Laboratories); D. Gall (Rensselaer Polytechnic Institute) CrN-Ag composite films, 2-5 µm thick, were deposited by reactive sputtering on Si and stainless steel substrates in a 3 mTorr pure nitrogen atmosphere at 500°C. Layer compositions of 0, 3, 15, and 33 atomic percent Ag were obtained by adjusting the relative power to the 3-inch Ag and Cr targets. The layers exhibit a dense, homogeneous microstructure with a columnar morphology. In the as-deposited condition, the Ag is distributed evenly throughout the CrN matrix. The coatings were vacuum annealed for t_a = 5 - 60 minutes at temperatures ranging from T_a = 600 - 700°C, to study the lubricant-transport to the surface. The surface structures of the 3 and 15 at. % Ag samples are nearly unaffected by the annealing. However, distinct surface modifications were noted in the 33 at. % samples: Ag diffuses out of the matrix and forms loosely bound surface particles with diameters ranging, as a function of T_a and t_a, from 50 - 1000 nm. Statistical analysis of the particle size and separation distributions, which exhibit peaks at 200 - 300 nm and 250 - 500 nm, respectively, provide insight into the kinetics and mechanisms for the Ag transport to the surface. Compositional changes, measured by energy dispersive x-ray spectroscopy, show the depletion of Ag from the CrN matrix due to diffusion to the surface. Tribological testing via micro-indentation, micro-scratch, and pin-on-disk wear testing indicate that the CrN acts as the hard matrix material for wear resistance and the co-deposited silver functions as the solid lubricant.
9:50 AM		B7-3-5 Magnetron Sputtered Nanocrystalline Metastable f.c.c. (Cr,Si)N Coatings S. Ulrich, M. Stüber, H. Leiste (Forschungszentrum Karlsruhe, Germany) On the basis of thermodynamic calculations and estimations chromium silicon nitride coatings in a nanocrystalline metastable f.c.c. structure have been deposited by non-reactive and reactive r.f. magnetron sputtering of a chromium silicon nitride target in a pure argon and a pure nitrogen plasma, respectively. The chemical composition was determined by means of microprobe analysis. The constitution of the films has been examined by X-ray and electron diffraction as well as by transmission electron microscopy. The mechanical properties such as Vickers hardness, elastic modulus and residual stresses have been determined in dependence on the substrate bias and gas composition during deposition. The interface between the hard metal substrate and the (Cr,Si)N functional top-layer was improved by an optimized 2-layer adhesion layer system. This optimized multifunctional 3-layer system shows a Vickers hardness of 2600 HV0.05 and a critical load of failure in the scratch test of 85 N.
10:10 AM		B7-3-6 Oxidation Behavior and Morphology of Cr_xAl_yY_zN, Cr_xAl_yB_zN, Cr_xAl_ySi_zN - PVD Coatings H. Scheerer, B.C. Schramm, H. Hoche, E. Broszeit, E. Abele, C. Berger (Darmstadt University of Technology, Germany) The present study examines the potentials of newly developed Cr_xAl_yY_zN, Cr_xAl_yB_zN and Cr_xAl_ySi_zN- PVD coatings concerning to their oxidation behavior. The aim of developing such chromium-aluminum based coatings is to create a thermal barrier film and thus redirecting the heat from work piece and tool into the chip during dry machining operations. Due to their high proposed oxidation resistance, Cr_xAl_yN coatings with different Yttrium, Boron or Silicon contents were deposited onto notched bar impact specimens. To characterize the oxidation behavior, the coated notched bar impact specimens were heat treated at different temperatures. SEM examinations of the cross sections reveals the thickness of the oxidized layer and the morphology of the coatings. The coating composition and the depth profile of the as-deposited and thermally treated films has been further analyzed with Glow Discharge Optical Emission Spectroscopy (GDOES). Mechanical investigations such as hardness, scratch adhesion and ball cratering supplement the coating characterization.
10:30 AM		B7-3-7 Nanocomposite AlTiNCO Coatings Deposited by the Reactive Cathodic Vacuum Arc Evaporation J. Vetter (Metaplas Ionon, Germany); T. Ishikawa, N. Shima (Hitachi Tool Engineering Ltd., Japan) AlTiNCO coatings were deposited using reactive vacuum arc evaporation. The coatings were deposited with different coating architectures including monolayers and multilayer structures. Variations in microstructure (obtained by XRD), morphology (studied by SEM) and chemical composition (determined by EDS) were correlated to mechanical properties (residual stress, microhardness). It could be shown by high-resolution transmission electron microscopy (TEM) that nanocrystalline phases are present consisting of phases with higher carbon contents and phases with lower carbon contents. The estimated grain sizes and grain boundary sizes are in the range of 2 to 12 nm. More investigations were made by RAMAN spectroscopy and EELS to characterize the nanocomposite structure. Selected cutting results are presented.
10:50 AM		B7-3-8 Real-Time In-Situ Growth Study of TiN and TiC_xN_y Based Superhard Nanocomposite Coatings using Spectroscopic Ellipsometry P.M. Jedrzejowski, A. Amassian, E. Bousser, J.E. Klemberg-Sapieha, L. Martinu (Ecole Polytechnique de Montreal, Canada) Spectroscopic ellipsometry is a very powerful method for assessing the optoelectronic properties of materials and for in-situ monitoring of film growth. In this work, we investigate the growth mechanisms of TiN-based hard and superhard nanocomposite (nc) coatings, namely TiN, nc-TiN/SiN_1.3, and novel nc-TiC_xN_y/SiCN. These materials were synthesized by plasma enhanced chemical vapor deposition (PECVD) from TiCl₄/CH₄/SiH₄/N₂ gas mixtures at an intermediate substrate temperature of 500 °C. The materials' optical properties were modeled using mixed Drude (intraband) and Lorentz (interband) electronic absorptions. It allowed us to evaluate, in real-time, the evolution of the electrical properties. The resistivity was described on the basis of existing models as a function of electron scattering due to phonons, point and line defects (grain boundaries), and surface effects. The films' electrical properties were confirmed by direct four-point measurements and interpreted in terms of evolution of their microstructure and chemical composition.
11:10 AM		B7-3-9 Syntheses and Mechanical Properties of TiAlC_xN_1-x Coatings Deposited by Arc Ion Plating C.S. Jang, J.H. Jeon, P.K. Song, Y. Shigesato, K.H. Kim (Pusan National University, South Korea) Quaternary TiAlC_xN_1-x coatings were deposited on WC-Co substrates by Arc Ion Plating (AIP) method using TiAl (50 at.% Al) alloy target in CH₄/N₂/Ar gases mixture at fixed TiAl arc current of 60A and deposition temperature of 300°C. The carbon content of TiAlC_xN_1-x coatings was linearly increased with increasing CH₄/N₂ gas flow rate ratio. The microhardness of TiAlC_xN1-x coatings increased from ~20 GPa of TiAlN to ~38 GPa with carbon content increased. In this work, the microstructure and mechanical properties of TiAlC_xN_1-x coatings were systematically investigated.
11:30 AM		B7-3-10 Characterisation and Applications of Cr-Al-N Coatings E. Spain, J.C. Avelar-Batista, M. Letch, J. Housden (Tecvac Ltd., United Kingdom) There are an increasing number of applications for hard coatings in engineering where both high oxidation resistance and high hot hardness are required. A way to solve this problem is to use hard ceramic coatings which are a combination of more than one metal, this way the coating performance will benefit from the combined mechanical properties of the metals present. In this study, Cr-Al-N coatings were deposited on AISI M2 steel substrates and 1/4 inch HSS drills by means of Electron Beam Plasma Assisted Physical Vapour Deposition (eB-PAPVD). For comparison, Ti-N and Ti-Al-N samples were also prepared by the same method, for all the depositions the coating temperature was below 773 K. Indention tests, scratch tests, wear tests and hardness measurements were performed to characterise the mechanical properties of the coatings. Glow Discharge Optical Emission Spectroscopy (GDOES) was used to determine the composition of the coatings deposited. Along with the laboratory tests, industrial applications were also used to evaluate the performance of the coatings, these applications included both drilling and punching. The results from both the laboratory characterisation and industrial applications showed that Cr-Al-N performs exceptionally well compared to the industry standard of Ti-N and Ti-Al-N.