Papers

ICMCTF2009 Session E4/G4: Coatings for Machining Advanced Materials and Advanced Manufacturing Methods

Thursday, April 30, 2009 8:00 AM in Room California

Thursday Morning

Start	Invited?	Item
8:00 AM		E4/G4-3 Adaptive PVD Coating for Machining of Hard to Cut Materials G. Fox-Rabinovich (McMaster University, Canada); K. Yamamoto (Kobelco, Japan); S. Veldhuis (McMaster University, Canada) New generation of adaptive PVD coating for high performance machining of hard to cut materials is presented. Adaptation during cutting is a complex process that is related to generation of the surface tribo-films with unique protective/lubricious ability in synergy with beneficial structure and properties transformations within the layer of the nano-structured coatings as well. If all these parameters work together then the coating is capable to sustain strongly varying and intensifying external impacts with unattainable tool life. A number of novel adaptive hard coatings is developed best suited for specific applications associated with machining of hardened tool steels as well as aerospace materials such as nickel-based superalloys and Ti-based alloy. Results of long-term research of adaptive TiAlCrN-based coatings (nano-crystalline and nano-multilayered) is presented. Comprehensive investigation of the structural characteristics of the coating is made using XRD, TEM, SEM/EDX. Micro-mechanical properties of the coating such as hardness, micro-hardness dissipation parameter, impact fatigue fracture resistance are studied at RT and elevated temperatures using Micro Materials Test System. Tribological characteristics of the coatings are investigated vs. temperature in contact with corresponding materials. Characteristics of the tribo-films are studied in detail using XPS, EELFAS and EELS methods. Tool life and wear behavior are investigated for specific operating conditions. Wear patterns are indentified. Based on the data obtained some principles of adaptive hard coating development are outlined for specific applications.
8:40 AM		E4/G4-5 Crystalline γ-Alumina Deposited in an Industrial Coating Unit for Demanding Turning Operations K. Bobzin, N. Bagcivan, P. Immich, M. Ewering (RWTH Aachen University, Germany) Crystalline PVD γ-Al₂O₃-coatings offer great potential for their use in high-speed cutting operations. They promise high hot hardness and high oxidation resistance at elevated temperatures. This is important for coatings which are used for machining of materials with low thermal conductivity like stainless steel or Inconel 718 because heat, generated during cutting, can hardly be dissipated by the chip. Because of the prevailing bonding forces of alumina adhesion-related sticking can be reduced, even for dry cutting. Furthermore, the high formation enthalpy of alumina prevents chemical reactions with frictional partners. The present work gives an overview of the deposition of γ-Al₂O₃-thin films on WC/Co-cutting inserts by using pulsed MSIP (Magnetron Sputter Ion Plating) PVD technology. To improve adhesion a (Ti,Al)N bond coat was employed. The samples were analyzed using common thin film test equipment such as scratch test, calo-test , X-ray diffraction, Scanning Electron Microscopy (SEM) and nanoindentation for the mechanical properties. It could be proved, that the developed coatings show excellent premises for their use in cutting operations. In order to proof the coating’s performance, cutting tests were carried out. For drilling operations the difficult-to-machine austenitic steel 1.4301 (X5CrNi18-10) was used. In comparison to a state-of-the-art (Ti,Al)N coating the (Ti,Al)N/γ-Al₂O₃ showed a longer tool life.
9:00 AM		E4/G4-6 Investigating the Performance of TiN and AlTiN Coatings on Milling Cutter Used for Machining Bimetal Steel M. Sarwar, J. Haider (Northumbria University, United Kingdom); M. Persson, H. Hellbergh (SNA Europe, Sweden) Surface engineering of cutting tools (single point or multipoint) through advanced coatings (e.g., TiN) has contributed towards the improvement of tool life, productivity and machining quality¹ by modifying the substrate. New coating species (e.g., AlTiN) are also being developed to further improve the performance of cutting tools². In this study, machining tests were carried out with a Powder Metallurgy High Speed Steel (PM HSS) milling cutter when cutting bimetal (M42 + D6A) steel strips to produce bandsaws. The milling cutter was modified with TiN and AlTiN coatings in order to evaluate their performances. Physical Vapour Deposition (Arc evaporation) technique was used to deposit the coatings after carefully preparing the cutting edges. Failure modes and mechanisms of the milling cutter have been identified by examining the worn cutting edges. Flank wear measurement in the milling cutter teeth was used as the criterion for assessing the performance of coatings. The properties of the coatings were evaluated to correlate with the performance. The product quality of the bandsaw teeth formed by the milling cutter was also studied. The information should be useful for material suppliers, tool designers and tool users. ¹M. Sarwar, D. Gillibrand, S.R. Bradbury, Forces, surface finish and friction characteristics in surface engineered single- and multi-point cutting edges, Surf. Coat. Technol., Vol. 41 (1991) 443-450. ²W. Kalss, A. Reiter, V. Derflinger, C. Gey and J.L. Endrino, Modern coatings in high performance cutting applications, Int. J. Refract. Met. Hard Mater., Vol. 24 (2006) 399-404.
9:20 AM		E4/G4-7 Process Variability in Honing of Cylinder Liner with Vitrified Bonded Diamond Tools L. Sabri (Renault, France); S. Mezghani, M. El Mansori (Arts et Métiers Paris Tech, France) A fundamental investigation is reported on the variability in honing behaviour due to stone inconsistency and nature of its properties. The conventional abrasives used in honing are indeed bodies consisting of Silicon Carbide grits and Vitrified Bond bridge (VBSC). Theses stones are soft and have an openness structure for a permanent “resharpening” of grains and high chip accommodation. Even if VBSC stones produce high surface quality, they are not suitable for high production usage. The use however of superabrasives stones such as Metallic Bonded Diamond (MBD) sticks fulfil the tool life requirement but generate some background texture harmful for the reciprocating mechanical components of the engine. This study discusses the honing process variability with Vitrified Bonded Diamond (VBD) stones compared to the VBSC one. An experiment test rig is developed consisting of industrial honing machine instrumented with sensors to measure spindle power, expansion pressu re and honing head displacement. Microchips and honed surfaces are also investigated with Scanning Electron Microscopy (SEM). Moreover, a surface multi-scale characterization approach is introduced to assess deeply the effects of stone’s properties on the quality of honed surfaces. The results show a large influence of the expansion velocity in correlation to the depth of indentation per grit. Considerable variability in honing behaviour observed is related to the mechanics of the process.
9:40 AM		E4/G4-8 Influence of Nanostructured CVD Diamond Coatings During Dry Turning of a SiC Particle-Reinforced Metal Matrix Composite A. Kremer, M. El Mansori (Arts et Métiers Paristech, France) This paper reports on a experimental test program to study the effect of the coating structure associated with the machining of a particle-reinforced metal matrix composite (PRMMC). The composite materials investigated were respectively a 5%, 15% and 25% by volume SiC particle-reinforced A2009 aluminium alloy. The machining of these materials is indeed very difficult due to the abrasive effect of the ceramic reinforcement upon the cutting tool. In this work, the ability of coated tungsten-carbide tools with nanostructured CVD diamond coatings to cut PRMMC components is discussed during dry machining. The performances of three different structures of CVD diamond coating are then considered using classical parameters (cutting forces, tool life, residual stress) and innovative criterion such as dust emission. The results show that in spite of their similar thickness, the coatings have various performances. The tool life was varied in a ratio of 1 to 6 irrespectively to the cumulative wear evolution which was monitored in situ with a power measurement and quantified ex situ using a white light interferometer.
10:00 AM		E4/G4-10 Coating Thickness Effects on Diamond Coated Cutting Tools F. Qin, Y. Chou (The University of Alabama); D. Nolen, R. Thompson (Vista Engineering) CVD-grown diamond films are finding applications as a coating for cutting tools. Even though use of conventional diamond coatings seems to be established in the cutting tool industry, selections of proper coating thickness for different machining operations have not been known. Coating thickness affects the characteristics of diamond coated cutting tools in different perspectives that critically and mutually, in a complex way, impact the tool performance in machining. In this study, coating thickness effects on the deposition residual stresses, particularly around a cutting edge, and on coating failure modes were numerically investigated. On the other hand, coating thickness effects on tool surface smoothness and cutting edge radii were experimentally compared. In addition, machining Al matrix composites using diamond coated tools with varied coating thicknesses was conducted to evaluate the effects on cutting forces, part surface finish and tool wear. The results are s ummarized as follows. (1) Increasing coating thickness will increase the residual stresses at the coating-substrate interface. (2) On the other hand, increasing coating thickness will generally increase the resistance to surface cracking and delamination. (3) Thicker coatings have a higher surface roughness and naturally enlarged edge radii, which tend to increase the machining load on the tool surface. (4) Preliminary results show a non-monotonic relation between the coating thickness and diamond coated tool performance.