Papers

ICMCTF2005 Session B8-1: Hard and Multifunctional Nano-structured Coatings

Tuesday, May 3, 2005 1:30 PM in Room Golden West

Tuesday Afternoon

Start	Invited?	Item
1:30 PM		B8-1-1 A Review of Multifunctional Wear and Corrosion Resistant Coatings F.M. Kustas (Engineered Coatings, Inc.) Future mechanical systems will need to operate at higher temperatures, higher contact stress, and under adverse environments, which place stringent performance requirements on materials used in moving mechanical assemblies (MMAs) and on surface modification treatments. Recently, multifunctional materials and multifunctional coatings have been proposed as innovative solutions to enhance, and in some cases enable, high performance of these new mechanical systems. Multifunctional coatings are a class of materials that can perform more than one engineering function, such as provide corrosion resistance, wear resistance, and low coefficient of friction. This unique capability results from the selection of coating materials whose inherent properties (e.g., low oxidation rate, low wear factor, etc.) satisfy subsystem operational requirements. In addition to coating material composition, coating architectures are also an important consideration in the development of multifunctional performance. Candidate coating architectures include monolithic construction, nanocomposite co-deposited structures, multilayered designs as well as combinations of these architecture categories. In-situ reaction of constituent coating materials to produce compounds with a unique set of properties not afforded by the starting constituents is another means to enhance surface properties. Examples of multifunctional coating designs will be discussed including cases for engine applications (insulative (low thermal conductivity) surfaces, high-temperature capability, and wear resistance), MMA in aircraft systems (corrosion resistance, rolling contact fatigue resistance, wear resistance, and low coefficient of friction), and aerospace systems (high electrical and thermal conductivities), among others. Relevant examples of multifunctional coating systems and properties from the author’s laboratory will also be presented.
2:10 PM		B8-1-3 Nanocomposite Tribological Coatings Prepared by a Hybrid of Filtered Cathodic Arc and Magnetron Sputtering. Part I: Deposition Process, Coating Structure and Basic Property Characterization V.I. Gorokovsky, C. Bowman, P.E. Gannon, D. VanVorous (Arcomac Surface Engineering, LLC); A. Rutkowski, A.A. Voevodin (Air Force Research Laboratory); R.J. Smith, A. Kayani (Montana State University); V. Shutthanandan (Pacific Northwest National Laboratory) The demand for low-friction and wear resistant components which operate in severe environments has directed attention to advanced surface engineering technologies. The Large area Filtered Arc Deposition (LAFAD) process has demonstrated atomically smooth coatings at high deposition rates over large surface areas¹. In addition to the inherent advantages of conventional filtered arc technology (superhardness, improved adhesion, low density of pin-holes), the LAFAD technology allows functionally graded, multilayer, super-lattice and nanocomposite architectures of multi-elemental coatings via electro-magnetic mixing of two plasma flows composed of different metal vapor ion composition. Further advancement is realized through a combinatorial process using a hybrid filtered arc-magnetron deposition system. In the present study, the basic properties of multilayer and nanostructured TiCrCN/TiCr⁺TiBC composite cermet coatings were deposited by the hybrid filtered arc-magnetron process Coating architecture was designed to provide a best blend of corrosion and wear resistance to steels used in aerospace bearing and gear applications. This coating architecture required a synthesis of a multiphase nanocomposite coating, which was only possible to achieve with the hybrid deposition process. In this process, filtered plasma streams from arc evaporated Ti and Cr targets and from two magnetron sputtered B4C targets were directed to the substrates in the presence of reactive gases. Coatings were characterized using SEM/EDS, RBS and acoustic emission spectroscopy. Coating stress was evaluated on Si wafer substrates using the Stony formula. In addition, coating nanohardness was determined by Berkovich nanoindentation and adhesion by scratch and indentation methods. Coating properties were evaluated for a variety of coating architectures. ¹Vladimir I. Gorokhovsky , Rabi Bhattacharya and Deepak G. Bhat, Surface and Coating Technology, 140 (2) 2001, pp. 82-92.
2:30 PM		B8-1-4 Nanocomposite Tribological Coatings Prepared by a Hybrid of Filtered Cathodic Arc and Magnetron Sputtering. Part II: Friction, Wear and Corrosion Protective Properties V.I. Gorokovsky, C. Bowman, P.E. Gannon, D. Van Vorous (Arcomac Surface Engineering, LLC); A. Rutkowski, A.A. Voevodin (Air Force Research Laboratory) Nanostrutured coating architectures were developed to provide a best blend of corrosion and wear resistance for high chromium content steels used in aerospace bearing and gear applications. A hybrid filtered arc-magnetron deposition process was employed to deposit functionally gradient, multilayered, and nanocomposite TiCrCN/TiCr+TiBC cermet coatings on carburized steel substrates. Coatings exhibited an excellent adhesion to the carburized surfaces and had hardness in the range of 23-25 GPa. Tribological properties of the coatings were characterized by sliding friction and reciprocating sliding wear tests in dry and lubricated environments at high contact stresses. Both polyester and perfluoropolyalkylethers (PFPAE) based lubricants were used to evaluate coating performance with neutral and chemically aggressive lubrication. Sliding friction and reciprocating sliding wear tests were performed using modified disk-on-ring and point-on-disk arrangements, respectively. Contact stresses were estimated using the Hertzian contact formula (sliding friction), and through direct measurements of contact areas by SEM (reciprocating sliding). Low-speed ball-on-disk rolling contact fatigue was evaluated at 350°C, using Si₃N₄ balls and PFPAE-based lubricant, at contact stresses of ~3.2 GPa. Wear and corrosion behavior was investigated using SEM/EDS, AFM, profilometry, and optical microscopy. The influence of coating architecture on wear properties was investigated. Multifold improvements of the surface dry and lubricated wear life, reduction of the dry friction coefficient, prevention of corrosion attack from the products of PFPAE lubricant degradation, and improvement of salt-fog corrosion resistance are demonstrated.
2:50 PM		B8-1-5 Interface Smoothening in Multilayers Deposited by Unbalanced Magnetron Sputtering J.C. Cancio (EMPA, Switzerland); F. Levy (IPMC-SB-EPFL, Switzerland); H.-J. Hug, J. Patscheider (EMPA, Switzerland) In order to prepare multilayers consisting of TiN and SiN_x with defined periodicity and composition, bilayers of SiN_x on TiN with individual layer thickness in the nm range were deposited by closed field unbalanced reactive magnetron sputtering. The experiments were carried out at low deposition temperatures (200^oC) and different bias voltages with He additions in the sputtering gas. The layers were characterized with respect to their composition, interface roughness, density and individual layer thickness using X-ray photoelectron spectroscopy, Rutherford Backscattering spectrometry and X-ray reflectometry. The interface roughness became smoother (~0.01 nm) and the layer density approached the theoretical value as He was added to the sputtering gas mixture. The composition of the layers was not affected. The smoothening is attributed to increased adatom mobility promoted by the He bombardment. Due to its low mass He does not cause resputtering while providing additional energy input. This procedure allows the controlled deposition of very thin single layers of high quality in terms of stoichiometry, density and roughness.
3:10 PM		B8-1-6 Formation of Nano-Multilayered Coatings in Industrial Hybrid Coater and their Cutting Performance S. Kujime, K. Takahara, K. Yamamoto (Kobe Steel Ltd., Japan) Previously, we reported deposition and characterization of nano-multilayer coatings deposited by a hybrid coater, which comprises AIP sources and UBMS sources in the same process chamber. Nano-multilayer coatings were characterized by the stacking sequence of AIP and UBM deposited layer in nanometer range. Their property strongly depends on the modulation wavelength and overall composition of the coating. In this study, nano-multilayered coatings such as TiAlN/SiN, TiAlN/WN and TiAlN/MoN were deposited using an industrial scale AIP and UBM hybrid coater. Modulation structure and composition distribution was investigated under different substrate rotation methods and positions in the chamber. Coatings were deposited by a industrial hybrid coater comprising 6 round arc evaporation sources (3 sources on one wall) and 2 rectangular UBM sources¹. Depositions were carried out in Ar/N₂ atmosphere and arc and UBM sources were operated simultaneously. The structure of TiAlN/SiN multilayer coating was investigated respect to the rotation method (1 or 3-axis planetary rotation). In case of the 3-axis planetary rotation, the thickness of the AIP and UBM deposited layers were not uniform that reflected the complex movement of the substrate against each evaporation source. Whereas a regular periodic structure was observed in case of the 1-axis planetary rotation. However by adjusting input power to the each evaporation source and the rotation speed of rotary table, mechanical properties were able to be equalized. Distribution of the elemental composition depending on the chamber position and cutting performance will be reported. ¹Kohara et al. Surf. Coat. Technol. 185 (2004) 166-171.
3:30 PM		B8-1-7 Manufacture, Microstructure and Mechanical Properties of CrWN and CrN/WN Nanolayered Coatings F.B. Wu, S.-K. Tien, J.G. Duh (National Tsing Hua University, Taiwan) Chromium nitride and tungsten nitride coatings were fabricated in sequence to form a CrN/WN nanolayered coating by rf reactive magnetron sputtering technique with a dual-gun system. Nanocomposite CrWN coating was also manufactured for comparison. The bilayer period (λ) of the coating was controlled from 6 to 24 nm. Alternating elemental distribution of the nanolayered coatings was revealed by the Auger electron spectroscopy (AES) depth profiling analysis. The phase identification revealed that the coatings were composed of CrN and W₂N phases. The CrN/WN nanolayered microstructure was evaluated by scanning and transmission electron microscopy (TEM). Nanoindentation technique was employed to evaluate the mechanical properties, including hardness and Young's modulus. The nanolayered CrN/WN coatings exhibited a high hardness around 30 GPa, which was superior to that of the CrWN coating. The nanolayered structure which confined grains of the nitrides in the nano range was beneficial to the enhancement of the mechanical performance for the multilayer coating.
3:50 PM		B8-1-8 The Crystalline Structure, Hardness and Thermal Stability of AlN-CrN Superlattice Coatings Prepared by D.C. Magnetron Sputtering J.-K. Park (Korea Institute of Science and Technology, Korea); Y.-J. Baik (Korea Institute of Science and Technology, South Korea) Al_1-xCr_xN coatings were known to have good oxidation and wear resistance in comparison to the Ti_1-xAl_xN coatings, and thus has been adopted as coating materials for cutting tools. In AlN-CrN based coatings, however, the mechanical properties such as hardness and wear resistance could be increased by controlling microstructure of the phase. Recently, many kinds of nanomultilayer coatings with superlattice have been widely investigated, because of the excellent mechanical properties such as hardness and corrosion resistance. In this study, the crystalline structure, mechanical properties and thermal stability of AlN-CrN superlattice coatings has been investigated. The AlN-CrN superlattice coatings were deposited on M2 HSS by D.C. magnetron sputtering with two Al and Cr targets. The period of nanomultilayer was controlled by changing rotation speed of substrate holder. Reactive gas of N₂and Ar was used. The crystalline structure and mechanical properties such as hardness, elastic modulus of the obtained coatings were measured. The AlN-CrN superlattice coatings were annealed at different temperature from 700C° to 1000C° to investigate the thermal stability and oxidation resistance of the coatings. The effect of bilayer period on the crystalline structure, mechanical properties and thermal stability of the AlN-CrN suprelattice coatings will be discussed. This research was supported by a grant(code #: 04K1501-01210) from 'Center for Nanostructured Materials Technology' under '21st Century Frontier R&D Programs' of the Ministry of Science and Technology, Korea.