Papers

ICMCTF2009 Session G6: Coatings, Pre-Treatment, Post-Treatment and Duplex Technology

Tuesday, April 28, 2009 8:00 AM in Room Sunrise

Tuesday Morning

Start	Invited?	Item
8:00 AM		G6-1 Exploring the Potential of Triode Plasma Diffusion Treatments to Improve the Wear Behaviour of Titanium Alloys G. Cassar, A. Leyland, A. Matthews (The University of Sheffield, United Kingdom) Owing to their many attractive properties, nowadays titanium alloys have a wide range of static load-bearing applications. However, there is still concern on their adaptability to use on tribological components. Continued research and development in surface engineering has to some extent improved the wear-resistant capabilities of these alloys. Diffusion-based surface treatments of titanium alloys have received increased attention, but many of these are performed at high temperatures exceeding the β-transformation temperature of the material and/or for excessively long periods of time. This work is focused on developing a cost effective process which will allow the use of titanium alloys for tribological applications even under relatively high loading. The use of low pressure intensified plasmas was shown to allow the diffusion of nitrogen (for example) to generate deeper hardened layers than conventional thermal or diode plasma processes. The process temperature w as limited to 800°C in order to minimize degradation in mechanical properties of the bulk material. The treated specimens were tested and characterized using a variety of techniques using X-ray diffraction, optical microscopy, scanning electron microscopy, microhardness, nanoidentation, reciprocating wear tests and micro-abrasion wear tests. The results obtained indicate that the proposed technique is indeed capable of significantly improving the surface characteristics of Ti alloys.
8:20 AM		G6-2 RF-Plasma Technique for Duplex Coatings on Aluminum S. Meier, M. König, C. Hormann (Fraunhofer Institute for Mechanics of Materials IWM, Germany) An innovative approach to improving behavior of aluminum surfaces and meeting long-term durability requirements of aluminum devices is to design and develop novel systems incorporating duplex diffusion/plasma coating treatments. The composite layers consists of a N-diffusion zone obtained by rf-plasma nitriding, followed by a rf-plasma deposited DLC film. A RF-PACVD processing technology is described that helps to overcome some of the most important limitations of existing technology to generate duplex coatings on technical aluminum substrates. Application of this technique to plasma assisted nitriding of pure aluminum and different aluminum alloys is demonstrated. The influence of the process parameters on the discharge characteristics was examined. Material properties and tribological testing results are shown for both materials.
8:40 AM		G6-3 Plasma Nitrocarburizing and Laser Hardening Duplex Treatment of AISI 4340 Steel V.H. Baggio-Scheid, G.de Vasconcedos, A.J. Abdalla (General-Command of Aerospace Technology, Brazil) The 4XXX steel series are structural steels widely used in automobile and aerospace components. However, when the applications involve wear, a protective coating or surface treatment might be required. In this work the duplex process of plasma nitrocarburizing and laser hardening of AISI 4340 steel was investigated. The plasma nitrocarburizing process was conducted at 773 K during 3 h. Hard cases with 790 HV and 160 µm thickness have been measured. A CO₂ laser with a power density of 70 kW cm^-2 was used for the surface heat treatments. In order to overcome the high reflectivity of the metal, their surface was covered with a thin absorber layer of graphite powder. After the laser irradiation a top graphite layer of about 10 µm was incorporated to the steel surface. Below this graphite coating a diffusion layer with 20 µm thickness and a maximal hardness of 1200 HV has been formed. The heat affected zone extends up to 100 µm towards the matrix. Duplex processes involving combinations of these two treatments were carried out. At all, five different processes have been done: Nitrocaruburizing, Laser hardening with graphite layer, nitrocarburizing plus laser hardening, nitrocarburinzing plus laser hardening with graphite layer, Laser hardening with graphite layer plus nitrocarburizing. The properties of the treated surfaces were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction and by microhardness and wear testing. Influences of the process parameters on the coating properties are analyzed.
9:00 AM		G6-4 Dedicated Coatings for High Precision Cutting Tools – Coating Design and Architecture Adjusted with Most Modern Process Technology T. Leyendecker, R. Cremer (CemeCon AG, Germany) Metal-Ion-Sputtering as well as Diamond coating technology are essentially strong tools for creating designed coatings. In some segments "coatings off-the-shelf" may be still appropriate, but steadily increasing demands in performance and specialized operations and workpiece-materials require more and more adapted tools and tailored coatings. Moreover each machining operation, whether drilling, turning, milling, reaming, threading, gear cutting or grooving has different needs. The dedicated coatings are developed in a defined and reproducible process consisting of: - Definition of the objective - Determining of coating specifications - Production of test tools, evaluation and, if necessary, optimization - Finalization of the specifications Tool micro- and macro-geometry as well as tool material are closely related to the corresponding coating. Nowadays coating is a complex but controlled process merging different elements und steps, like pre-treatment, coating material, coating thickness, tolerance, color, post treatment and others. Only for sputtered coatings all compounds and combinations of metals and non-metals in different structures are possible. New technologies like HPPMS (High Power Pulsed Magnetron Sputtering) can produce unsurpassed high coating-adhesion and -smoothness.
9:40 AM		G6-6 Edge Honing for High Performance Drilling Operations M. Maes (KOMET GROUP GmbH, Germany) Modern machining processes are exposed to an enormous pressure regarding their cost efficiency. Only highly efficient processes like High Speed Cutting (HSC), High Performance Cutting (HPC), High Hard Cutting (HHC) are able to survive within these countries. Also new high-tensile constructive materials like Sibodur 700-1, Austempered Ductile Iron (ADI), Compact Graphitic Iron (CGI) and glass fibre reinforced plastics that are used in the automotive and aerospace industry require new demands for tooling concepts. High performance cutting tools are the key to enable this demand for cost effective machining processes and machinibility of these high-tensile materials. Therefore tool suppliers have to generate durable tool concepts that also allow high material removal rates to sustain cost effective machining. Within this presentation, tool concepts are presented that focus on high performance drilling. The carbide inserts used are optimised for this machining purpose with respect to substrate and coating. It is well known that the cutting edge radius has a tremendous effect on both edge toughness and cutting forces. Therefore the cutting edge was prepared with different radii to evaluate suitability for several drilling operations. The effect of the cutting radius on machining performance and cutting forces is evaluated within this presentation.
10:00 AM		G6-7 Process Temperature and Post Annealing Effects on Microstructure and Mechanical Behavior of the Sputtering Ni-P-Al Coatings Y.M. Su, J.C. Wu, F.B. Wu (National United University, Taiwan) The Ni-P-Al ternary coatings were fabricated by magnetron sputtering technique with composite target design. The effects of thermal treatments, including post annealing and deposition temperature, on phase transformation phenomenon and related mechanical properties were investigated. The as-deposited coatings produced under process temperature below 475°C showed an amorphous/nanocrystalline microstructure. Significant recrystallization of Ni matrix and precipitation of Ni-P and Ni-Al compounds were observed for the coatings manufactured under high sputtering temperature of 500 to 600°C. In comparison, the amorphous Ni-P-Al coatings were post-annealed at 500 to 600°C in vacuum environment. The amorphous feature of the Ni-P-Al coating remained under a high annealing temperature of 550°C, showing a better thermal stability as compared to those fabricated under high process temperatures. Furthermore, the hardness and indentation behavior of the coating under various thermal histories were evaluated. Superior hardness and mechanical behavior were found for the post-annealed Ni-P-Al coatings due to volumetric constrain of recrystallization and precipitation. On the other hand, the overaged phenomenon and subsequent degradation in hardness were found for the Ni-P-Al coatings fabricated under high temperature deposition processes. The phase transformation mechanisms of the coatings through different thermal treatments were intensively discussed.