Papers

ICMCTF2009 Session G2-1: Coatings for Automotive and Aerospace Applications

Thursday, April 30, 2009 1:30 PM in Room Sunrise

Thursday Afternoon

Start	Invited?	Item
1:30 PM		G2-1-3 Atmospheric Plasma - Cleaning, Activation and Coating of Materials Surfaces by Openair® Plasma C. Buske (Plasmatreat GmbH, Germany) Since its inception in 1995, Plasmatreat, which today is a globally operating company, has focused on the development of atmospheric-pressure plasma processes. Openair®- Plasma technology is protected internationally by patents and is em-ployed in almost all fields of industrial production. The technique based on a jet principle operates at atmospheric pressure. The jets are operated only with air, possibly also with another desired process gas, and at high voltage. A particular characteristic of the emerging beam of plasma is that it is electrically neutral which greatly extends and simplifies its range of uses. Its intensity is so high that machining speeds of several 100 m/min can be attained. The Openair® Plasma technique is characterised by a threefold action: it activates a surface by selective oxidation processes, eliminates static charge and brings about microfine cleaning. The jet systems employed require neither a complex vacuum chamber nor do they interrupt the production process. The system is capable without restriction of implementation in-line and is compatible with robots, offering extraordinary cost-effective solutions. If a special precursor material is added to the Openair® process, selective nanocoating of surfaces can be accomplished. Whether the aim is to provide protection against corrosion or to facilitate cleaning of a surface, the new PlasmaPlus® technology, developed by Plasmatreat in collaboration with the internationally renown institute Fraunhofer IFAM, is a unique possibility to offer an abundance of differently functionalised layers for selective coating. The properties of these layers can be varied from hydrophilic to hydrophobic by using different precursors and the carbon content of the individual layers can be varied from organic to very inorganic. These properties enable the technology to be customized for different material surfaces like PC,PP,PET and aluminum. The anticorrosive action is particularly effective for aluminium alloys. Due to the small quantities and non-toxicity of the chemicals used in coating the process is highly environmentally friendly. The removal of coatings prior to a recycling process is not required, the coatings can be passed on for recycling together with the substrate material. Since vacuum chambers are not required, the process is especially useful for huge parts or high automated mass production. In December 2007 America’s leading finishing journal Finishing Today Magazine (FTM) honored Plasmatreat with the FTM Innovation Award 2007 in the processing technology category. Plasmatreat received the prize for a revolutionary new environmentally friendly process in the surface pretreatment of aluminium. The Plasmatreat Group has an international presence through technology centers in Germany, the United States and in Japan as well as sales offices around the globe. The presentation will give an overview of this plasma technology as well as the latest results from Fraunhofer Institute for thin film coating.
2:10 PM		G2-1-5 Low Temperature Reactive Magnetron Sputtered nc-Ti(N,C)/a-C:H Coatings for Automotive Applications C. Tsotsos, K. Polychronopoulou (University of Cyrpus); N. Demas (University of Illinois at Urbana-Champaign); M. Baker, Y. Chen (University of Surrey, United Kingdom); K. Kanakis, A. Leyland, A. Matthews (University of Sheffield, United Kingdom); C. Rebholz (University of Cyprus); A.A. Polycarpou (University of Illinois at Urbana-Champaign) Tribological coatings targeted for automotive applications are required to be functionally graded using a different approach to that of coatings developed for cutting tool applications. Depending on the operating environment such coatings do not necessarily require a high hardness but instead an optimal H/E ratio, along with relatively low friction, high corrosion resistance and thermal stability at moderate operating temperatures. 2.5µm thick nc-Ti(N,C)/a-C:H coatings containing ≥ 50% amorphous C:H phase were deposited, using low temperature (~200°C) DC reactive magnetron sputtering, on 100Cr6 steel substrates. The a-C:H phase content was varied with acetylene partial pressure. XPS analysis indicates that the main coating structure is that of TiN with C substituting for N for the crystalline phase and sp² dominant a-C:H phase. TEM analysis is used to characterise the coating structure and ascertain the volume fraction of the a-C:H phase. The me chanical properties are affected by the nc-Ti(N,C)/a-C:H phases volume fraction ratio and the nanoindentation hardness (H) values were measured and found to range from 9 to15GPa and the reduced Young’s modulus values (E) from 80 to 150 GPa. The synthesized coatings were tested using pin-on-disc sliding configuration and the measured friction coefficient values were around 0.2 and survived up to 100 m sliding distance. The performance of the coatings in corrosion resistance tests is greater for predominantly a-C:H coatings. nc-Ti(N,C)/a-C:H coatings are promising candidates for automotive applications offering a lower mismatch in mechanical properties between a relatively low modulus steel substrate and a low modulus low friction topcoat layers.
2:30 PM		G2-1-6 Gas Flow Sputtering - An Approach to Coat Complex Geometries and Non-Line-of-Sight Areas S. Tang, U. Schulz (German Aerospace Center, Germany) Most PVD techniques are limited in coating complex geometries like turbine blades without additional substrate manipulation. Their application is subject to the Line-of-Sight condition that means they can only coat areas of the substrate which are directly in view to the sputtering or evaporation source and shaded areas can not be coated. If a coating on the whole substrate surface is required, the component has to rotate and process parameters have to be adapted to the requirements. A novel approach to overcome these limits is the innovative Gas Flow Sputtering. This technique combines a hollow cathode glow discharge with an argon gas flow, which supports transportation of sputtered material to the substrate. The mixture of gas and coating material performs a circulation around the contour of the geometry and reaches Non-Line-of-Sight areas. Distribution of coating thickness depends on gas flow kinetics and dynamics. In these investigation different complex geometries such as u-shaped profiles, pipes and turbine blades were coated with pure titanium. The influence of the angle between gas flow direction and substrate surface (angle of impact) on coating thickness distribution, microstructure and crystal orientation was examined by SEM and XRD. To investigate the correlation between gas flow formation and coating thickness distribution some coating procedures were simulated by Computational Fluid Dynamics (CFD). Results show that a stripe or a pipe placed parallel to the gas flow direction is coated over the whole length. Pipes are coated outside as well as inside. The outer diameter of a pipe positioned perpendicular to the gas flow direction is completely covered with material. Interestingly, a coated turbine blade that was not rotated shows a maximum coating thickness at the leading and trailing edge. The microstructure of the coatings is correlated with gas flow and deposition conditions, while the CFD results helped to understand coating growth on complex geometries.
2:50 PM		G2-1-7 Thick Plasma Enhanced PVD Coatings for Weapons Applications S.L. Lee, M. Todaro (US Army ARDEC-Benét Labs); R. Wei, E. Langa (Southwest Research Institute) Plasma-enhanced PVD (physical vapor deposition) process was investigated to deposit thick coating for potential weapon system applications. In the enhanced process, externally generated plasma and substrate biasing were used to deposit coatings on weapon system parts with complex geometry. Tantalum coatings of 200-500µm thickness were sputter deposited on ASTM A723 steel samples cut from curved 120mm smooth bore, and rifled 155mm gun bore sections. SEM showed dense, adhesive, crack-free coatings with improved morphology. XRD showed (110) textured body-centered-cubic tantalum. Fracture tantalum surface showed excellent microvoid coalescence with ductile mode of fracture, resilient to thermal shock cracking. Adhesion tests were performed; including groove test, cyclic pulsed laser heating test, and vented erosion simulator test, simulating the thermal-mechanical-chemical environment of firing. Interior ballistic model of heat load and heat transfer programs were used to simulate the temperature profile for pulsed laser heating test. The plasma enhanced PVD deposition process, the analytic and adhesion test results for thick tantalum depositions on steel, and future potential applications of the techniques will be discussed.
3:10 PM		G2-1-8 Enabling Lightweight, High Load Aero-Bearings J. Avelar-Batista Wilson, S. Banfield (Tecvac Ltd, United Kingdom); B. Karadia, N. Vahegla (Airbus, United Kingdom); P. Smith (Cranfield University, United Kingdom); G. Cassar, A. Leyland, A. Matthews (The University of Sheffield, United Kingdom); J. Housden (TECVAC Ltd, United Kingdom) Environmental and commercial considerations are strongly driving research into weight saving in aircraft. In this research, innovative manufacturing processes were developed to produce lightweight titanium alloy bearings capable of withstanding high bearing pressures. This will enable the replacement of heavier conventional bearing materials with titanium alloy bearings of the same size thereby saving weight. Plasma processing and PVD coating techniques were refined and combined and a sound scientific understanding of the resulting novel processes developed to assure high performance, reliability and repeatability. FEA modelling fed into developments and trials on test samples and small bearings showed the effects on torque and wear by applying progressively greater pressures with the optimum result coating being applied to a full size bearing for full-load simulated aircraft-lifetime tests. The novel treatment has potential applications for many bearings and bearing surfaces throughout aircraft.