Papers

ICMCTF2009 Session G2-2: Coatings for Automotive and Aerospace Applications

Friday, May 1, 2009 8:00 AM in Room Sunrise

Friday Morning

Start	Invited?	Item
8:00 AM		G2-2-1 TiN Multilayer Systems for Compressor Airfoil Sand Erosion Protection A. Feuerstein, A. Kleyman (Praxair Surface Technologies, Inc.) Frequently, aircraft, tank and helicopter gas turbine engines are operated in a desert environment where the gas turbine compressor rotor blades and vanes are exposed to erosive media such as sand and dust. These erosion effects lead to increased fuel consumption, efficiency loss, and can cause damage to compressor and turbine hardware. Erosion resistant coatings such as TiN, TiCN, TiZrN, TiZrCN, TiAlN and TiAlCN, applied by cathodic arc physical vapor deposition or other PVD processes, can be used to prolong the life of compressor airfoils in a sand erosion environment. Praxair Surface Technologies, Inc. has developed unique multilayered TiN coating systems with optimized erosion resistance compared to conventional mono block layers. The multilayer structure can be tailored to the respective erosion media particle size distribution. The key features of two selected coating architectures are outlined. Selected erosion performance data with different erosion media are presented. The aspects of high quality mass production are addressed.
8:20 AM		G2-2-2 Lubricated PVD Coatings for Automotive Applications K. Bobzin, N. Bagcivan, N. Goebbels, K. Yilmaz (RWTH Aachen University, Germany); B.-R. Hoehn, K. Michaelis, M. Hochmann (University of Munich, Germany) The demand on a better efficiency and higher performance under environment friendly aspects is an actual trend for automotive applications and machine components. This demand can be achieved by vacuum coatings such as DLC (Diamond like Carbon), which offer excellent results in e.g. fuel injection systems, piston pins, cam follower, gears and bearings. At the beginning the focus of DLC coatings was mainly on dry lubrication capability. Nowadays this kind of coating become very interesting for lubricated tribological contacts, because of their excellent tribological performance under boundary lubrication, which provides low friction losses and high wear resistance. In addition to DLC, the CrAlN coatings promise also performance increase especially for the lubricated tribological contacts, where high ductility and wear resistance is needed. Surface properties of DLC and CrAlN coatings are not analogous to uncoated steel surfaces; thereby their wettability with lubricants is different than conventional steel surfaces. Hence finding an optimal PVD coating/lubricant pair is still a challenge with regard to improvement of system performance and efficiency. In this research the wettability of the PVD coatings with different lubricants and the effect of the wettability on tribological behavior are investigated. The PVD coatings are WC/C and CrAlN, the lubricants are Polyalphaolefin, Polyglycol, synthetic ester and mineral oil, which are mixed with additives ZnDTP, MoDTP and S-P. The wettability of the PVD coatings with lubricants was determined by means of spreading coefficient and adhesion energy. For the tribological tests two different types of Tribometer, Pin on Disk and Twin Disk Tribometer are used. The Pin on Disk Tribometer delivers elementary information about the tribological performance of the PVD coatings with lubricants, whereas the twin disk Tribometer simulates the different working points of PVD coated gears for lubricated applications. By measuring friction coefficients, the tribological behavior of PVD coatings with the lubricants for different working points, such as different Hertzian pressure, slip velocity and lubricant temperature, are determined. The wear rates of the PVD coatings are measured and the tribological results are compared with the wettability. It is found that the wettability of the PVD coated surface can be optimized by means of adapting the adhesion energy, which in return leads to optimized friction behavior.
8:40 AM		G2-2-3 Multiphase Wear and Erosion Resistant Coatings for Aerospace Applications J. Nainaparampil, A.K. Rai, R. Bhattacharya (UES Inc.) Sand, pollutants, and moisture may all affect the smooth functioning of a Gas Turbine (GT) engine. Since present day designs look for increased efficiency, lightweight and high temperature operation the choice of materials systems is limited. Since Ti, Ni and their alloys fulfill most of the requirements, critical engine parts are made of these alloys. Protective coatings are needed to enhance the erosion resistance of these components. A tough, super adherent, hard and chemically stable protective coating with high temperature resistance can preserve the design tolerances and surface finish. In this work, a nano-structured TiN based composite thin film with varied architecture is deposited with direct arc vacuum evaporation and used as a protective coating for Ti6Al4V and Inconel 718 substrates. The mechanism used to attain the protection is the manipulation of hardness to elastic modulus ratio, which in turn determines the resistance to high-speed impact erosion¹. This can be achieved by incorporating a hard ceramic phase with an amorphous or ductile phase of another soft material. Hard and tough films have been developed by numerous researchers in the past mainly by mixing two types of material systems. A) nc-MeN/a-nitride, boride (e.g. a-Si₃N₄, a-TiBN, etc.) b) nc-MeN/metal (e.g. Cu, Ni, Y, Ag, Co, etc.) where Me stands for any transition metal, and ’a’ stands for amorphous. The ductile/amorphous component forms the separation medium between the ceramic hard phases.. Manipulation of toughness can be achieved by proper selection of the ductile/amorphous phase and overall microstructure of the films. High temperature, high speed erosion data coupled with toughness and hardness values of these films will be presented. Results from Tribological characteristics and Microstructure study will also be presented. An attempt is made to correlate the results with existing models of toughening mechanisms. ¹S. Veprek, P. Nesla´dek , A. Niederhofer , F. Glatza, M. Jılek, M. Sıma, Surface and Coatings Technology 108–109 (1998) 138.
9:00 AM		G2-2-4 Investigations on the Interfacial Strength of Chromium Adhesion Layers in DLC Coating Systems for High Load Applications J. Schaufler, K. Durst (University Erlangen Nürnberg,, Germany); R. Mertens (Oerlikon Balzers AG, Liechtenstein); M. Göken (University Erlangen Nürnberg, Germany) DLC coatings play an important role in many high load applications. Their unique properties such as hardness, low friction coefficient and chemical inertness make them suitable for such applications. During service, the interfacial strength between the coating and the substrate is of a great importance. A chromium - chromiumcarbide adhesion layer is frequently used to enhance the adhesion between the coating and the steel substrate. However, the structure and quality of these adhesion layers mainly depend on the conditions and parameters of the deposition process. The interfacial strength and quality is usually determined by a Rockwell-C indentation test, using the cracking patterns to qualify the interfacial strength. In this work a detailed structural characterization of various adhesion layers with different interfacial strength, ranging from poor to very good has been conducted. This characterization includes TEM investigations of the microstructure in combination w ith EDX analysis. The internal stresses in the coating systems were measured with a cantilever deflection method, using a focused ion beam workstation. The residual damage zone around the indentation is analyzed in FIB cross sections and with a TEM. There it is found, that the analyzed weak coating system mainly fail in the chromiumcarbide zone, whereas the adhesion layer with the strong interfacial strength shows a great stability against internal cracking. By analyzing the failure mechanism a crosslink between the microstructure, the internal stress and the interfacial strength of the coating systems can be determined.
9:20 AM		G2-2-5 Innovative Surface Technologies for Advanced Automotive Applications: From Super-Hard and –Low Friction Coatings to Super-Fast Surface Treatments A. Erdemir, O.L. Eryilmaz, G. Kartal (Argonne National Laboratory); K. Kazmanli, S. Timur, M. Urgen (Istanbul Technical University, Turkey) During last decade or so, there has been an overwhelming interest in the development and diverse utilization of super-hard and –low friction coatings for a wide range of automotive applications. Within the same period, great strides have been made in deposition technologies by which these multifunctional coatings are produced. With these advances, it is now possible to produce nano-composite and/or –layered coatings that can meet the ever increasing property and performance requirements of advanced automotive applications. In this paper, we will concentrate primarily on the design and development of super-hard and low-friction nano-composite coatings that can make a huge positive impact on the fuel efficiency and durability of advanced engine systems that are subjected to increasingly more severe applications conditions than before. Specifically, we will introduce a crystal-chemical model that can help identify the kinds of coating ingredients that are needed in suc h nano-composite architectures for achieving ultra-low friction and wear on lubricated surfaces. Recent results from bench-top and fired engine tests will be presented in support of much superior tribological properties for these designer coatings over a broad range of sliding conditions. Surface treatments (like, nitriding, carburizing, and boriding) are used extensively by industry in all types of engine components despite being very time and energy consuming. In this presentation, we will also present very briefly a super-fast surface treatment process which can complement or displace some or all of the existing surface treatment processes. Initial results from selected engine parts and their tribological properties will be presented and the future outlook for both the super-hard coatings and super-fast surface treatment technologies will be provided.