ICMCTF2013 Session B2-1: CVD Coatings and Technologies

Thursday, May 2, 2013 8:00 AM in Room Royal Palm 4-6

Thursday Morning

Start	Invited?	Item
8:00 AM	Invited	B2-1-1 New Developments in the Field of CVD Hard Coatings Ingolf Endler (Fraunhofer IKTS, Germany) Since 40 years CVD hard coatings have been applied widely as wear-resistant coatings for cutting tools. After an intensive development of new CVD coatings in the first years the research activities declined in the nineties. The research shifted more and more to the development of novel PVD coatings as TiAlN and nanocomposite coatings. However CVD coatings still dominate as wear-resistant coatings for hard metal cutting tools on the market. Due to the increase of high speed and dry cutting as well as emerging new workpiece materials the metalworking industry has a growing demand on high performance tools. This fact has also been favoring an increase in the research and development of new CVD hard coatings in the last years. There are complex requirements to hard coatings because of high thermal and mechanical loads at the cutting edge of the insert. Modern hard coatings must offer high hardness as well as high oxidationn resistance and they should be inert to the workpiece material at elevated temperatures. First the state of the art of CVD methods and coatings is considered. Following novel CVD coatings are presented and also research trends. New CVD coatings with a high application potential are aluminum-rich TiAlN and TiAlCN as well as TiSiCN nanocomposite coatings. These novel CVD coating types exhibit a high hardness between 30 GPa and 40 GPa and an oxidationn resistance up to 900°C. Furthermore the progress in the development of alumina coatings will be described. Finally the potential of these new coatings for the design of new CVD coating systems will be shown.
8:40 AM		B2-1-3 CVD Ti_1-xAl_xN Coatings for Mass Production Helga Holzschuh, Werner Buergin (SuCoTec AG, Switzerland) Over the last 20 years Ti_1-xAl_xN coatings were the domain of PVD. Published in 2008 the first cubic Ti_1-xAl_xN coatings containing high Al (x>0.8) were developed in a lab scale CVD system. Remarkable wear behavior and properties were reported. In 2011 a tool manufacturer succeeded to develop an in house CVD process to produce CVD Ti_1-xAl_xN coated inserts. They reported high Al-content (>70%), high hardness, a phase mixture of cubic and hexagonal and excellent cutting results. We now report on Ti_1-xAl_xN results achieved with the first commercially available CVD systems SCT600 and SCT400 which can coat up to 15’000, respectively 8’000 pcs. ½”inserts per batch . The newly developed NH₃ module proved its capability to coat homogenously single phased cubic Ti_1-xAl_xN in medium temperatures and Al contents >70%. By varying the gas parameters phases of the Ti_1-xAl_xN coatings could be tailored (pure cubic, mixed cubic and hexagonal) while keeping the Al-content high. The coated samples were characterized in terms of structure, composition, physical and mechanical properties.
9:00 AM		B2-1-4 The Development of a CVD Material for Thermally Oxidative Environments with High Hydrophobicity and Oleophobicity, and Good Wear Resistance with a Low Friction Coefficient David Smith, James Mattzela, Paul Silvis (SilcoTek Corporation, US) There is a significant need within a variety of applications for surfaces that exhibit and maintain high hydrophobicity, oleophobicity and good wear resistance with a corresponding low coefficient of friction after exposure to environments of high thermal stress in oxidative environments. Examples include areas such as fuel delivery and exhaust systems, and heat transfer systems. With modifications of a commercially available CVD process, a new material is being evaluated for the above characteristics, before and after exposure to 450°C in air. A variety of surface evaluation methods will be discussed, including the use of tensiometer and goniometer data for contact angle analysis, surface FT-IR microscopy and X-ray photoelectron spectroscopy for material composition analysis, potentiometric information for electrochemical and corrosion resistance analysis, and pin-on-disc data for wear resistance and friction coefficient evaluation. The method of deposition will also be discussed, as it allows for the deposition on to complex three-dimensional configurations, in bulk quantities, and on to parts of significant size.
9:20 AM		B2-1-5 Phase Selective Deposition of α-Al₂O₃ by Thin Layers of TiO₂ Mats Boman, Mattis Fondell, Sara Munktell (Uppsala University, Angstrom Laboratory, Sweden); Oscar Alm, Tommy Larsson (Seco Tools AB, Sweden) The industry of metal cutting is under constant development. New machines with higher cutting speed and new materials that require more advanced cutting tools are two reasons for this. A cutting tool needs to be tough, wear resistant, deformation resistant and stable at high temperatures. Today most cutting tools for different kinds of steels and other types of metals are constructed with a hard but tough bulk material and a multilayer coating of hard and stable ceramics. Often a bulk material of cemented carbide and coatings of titanium carbon-nitride and aluminum oxide are used. To further enhance the properties multilayer coatings are deposited on the tool.There are two different techniques often used to create these kinds of hard coatings; chemical vapour deposition (CVD) and physical vapor deposition (PVD). CVD is used to deposit the titanium carbonnitride and the aluminum oxide coatings. A material that has proven useful in the harsh environment of metal cutting is aluminium oxide. Aluminum oxide shows great properties in wear resistance, toughness and deformation resistance at high temperatures. The most common phases of aluminium oxide usually obtained in the CVD process are α-Al2O3 and κ-Al2O3. The thermodynamically stable phase is α-Al2O3. If a cutting tool is coated with κ-Al2O3 the film may undergo phase transformation during the cutting process which could reduce the durability of the tool coating and therefore α-Al2O3 is the desired phase. Aluminum oxide is usually combined with layers of titanium carbonitrides. Ti(C,N) which has complementary wear properties to aluminum oxide making it widely used on metal cutting tools. It has proven to be a difficult task to deposit α-Al2O3 on Ti(C,N) with CVD as the phase obtained is mainly κ-Al2O3. In this investigation phase selective growth of α-Al2O3 is demonstrated by thin interlayers of TiO2 deposited by atomic layer deposition.
9:40 AM		B2-1-6 Influence of the N/Al Ratio in Gas Phase on the Crystalline Quality of AlN Grown by HTCVD on c-sapphire. Raphaël Boichot, Nicolas Coudurier (Grenoble INP, France); Elisabeth Blanquet, Michel Pons (CNRS, France) The availability of industrial-grade quality and cheap AlN templates is currently a major concern for optoelectronic industry. A solution could be to produce epitaxial AlN layers by high temperature chemical vapor deposition (HTCVD) directly grown on c-sapphire, one of the cheapest UV/visible transparent substrate. The main difficulty is that in addition to the fact that the lattice mismatch between c-sapphire and AlN is high (13.3 %), leading to strain and cracks in the grown layer, the initial sapphire surface is not stable in HTCVD conditions (H2 etching or NH3 nitridation at temperature above 1200°C). Many studies attempted to optimize epitaxial growth of AlN on sapphire c-plane using AlCl3 and NH3 as precursors. The most promising way is to protect the sapphire surface with a controlled nucleation/nitridation layer grown at low temperature (below 1200°C) and low growth rate [1] prior the deposition at high temperature (typically 1500°C). Another solution is to control precisely the N/Al ratio in the gas phase during growth. Previous studies [2] concluded that the optimal N/Al ratio in gas phase for AlN epitaxial growth on various substrates was about 1.5. The main issue is that in all previous experiments, the N/Al ratio influence was investigated whereas growth rate and layer thickness also varied. On the other hand, kinetic modeling of AlN growth rate is available [3], so that a study of the influence of N/Al ratio at constant thickness and constant growth rate is possible without any time-consuming growth rate calibration experiments. This study focuses on the influence of the N/Al ratio in gas phase at constant growth rate and thickness. The influence of layer thickness at constant growth rate and layer growth rate at constant thickness is also discussed. Finally, the addition of a protective by different ways (two steps growth or continuous growth) is studied. This study leads to the synthesis of 5 µm AlN templates grown at 5 µm/h with a crystalline quality of 460 arcsec for the FWHM 0002 reflectivity, exhibiting no cracks on two inches sapphire wafers. The photoluminescence spectra and TEM interface image of some samples are also presented. [1] M. Balaji, A. Claudel, V. Fellmann, I. Gélard, E. Blanquet, R. Boichot, A. Pierret, B. Attal-Trétout, A. Crisci, S. Coindeau, H. Roussel, D. Pique, K. Baskar, M. Pons, Journal of Alloys and Compounds 526 (2012) 103. [2] A. Claudel, E. Blanquet, D. Chaussende, R. Boichot, B. Doisneau, G. Berthomé, A. Crisci, H. Mank, C. Moisson, D. Pique, M. Pons, Journal of Crystal Growth 335 (2011) 17. [3] R. Boichot, A. Claudel, N. Baccar, A. Millet, E. Blanquet, M. Pons, Surface and coatings Technology, 205 (2010) 1294.
10:00 AM		B2-1-7 Growth of HfC and Nanostructured Multilayer HfC/SiC Coatings by DLICVD Guillaume Boisselier, Francis Maury (CIRIMAT, France); Frédéric Schuster (CEA-Saclay, France) Nanostructured refractory multilayer coatings exhibit high protective performances under extreme environment. They are deposited by different processes in alternating the growth of each layer. To develop CVD processes industrially viable each component should grow at the same temperature and pressure, and the multilayer architecture is achieved by controlling alternatively the composition of the gas phase. Thus the key point is to select molecular precursors which decompose under identical conditions. On the other hand, the pulsed direct liquid injection (DLI) of precursors is an emerging technology to feed with high vapor flow rate CVD reactors, which offers new opportunities for metallurgical coatings. Recently (ICMCTF 2012), SiC coatings were grown by DLICVD starting with a solution of polysilaethylene (PSE) in toluene as single-source precursor. The growth was achieved in the temperature range 700- 800 °C at a total pressure of 50 Torr. These ceramic coatings were amorphous, very dense and exhibited an Si:C atomic ratio close to 1:1. As salient feature, the coatings had many microcracks through the coating to the substrate of graphite or Si. The microcracks resulted from high tensile intrinsic stresses induced by the growth mechanism that was essentially a densification with hydrogen release from the growing layer. Here, in the same hot-wall reactor and using comparable conditions, HfC coatings were deposited by injection of a solution of Cp₂HfMe₂ in toluene under H₂ partial pressure. These coatings are very dense, crack-free, nanocrystalline and C-rich. They exhibit a very smooth surface morphology (Ra < 6 nm) and the growth rate can reach 5 µm/h. HfC/SiC multilayer coatings were deposited at 750 ° C by combining alternatively both chemical systems. Coatings with a thickness of approximately 5 µm have been prepared and characterized. Each HfC and SiC layer had the same thickness and the bylayer period was varied between 400 and 100 nm, which corresponded to a number of individual layers between 26 and 100, respectively. In this last case, a nanostructuration of the coating was achieved since the thickness of each individual layer was only 50 nm. Interestingly, a self-healing of SiC cracks occurs during the growth of the multilayer coating as a result of a good infiltration and conformal coverage of HfC and other layers within cracks until clogging. Preliminary properties are also reported and discussed.
10:20 AM		B2-1-8 Industrial Scale Production of HFCVD Diamond Coatings Oliver Lemmer, Christoph Schiffers, Martin Frank, Biljana Mesic (CemeCon AG, Germany); Martin Rüffer (DiaCCon GmbH, Germany); Stefan Rosiwal (University Erlangen-Nürnberg, Germany) The extraordinary properties of diamond coatings produced by hot filament chemical vapor deposition (HFCVD) make it suitable for a broad spectrum of applications. A unique coating machine allows deposition of diamond coatings with different properties and numerous types of substrates in an industrial scale. This is achieved by highly versatile filament arrays, substrate fixtures and process parameters.The polycrystalline and nanocrystalline diamond coatings on cutting tools are well established not only for machining graphite, printed circuit boards (PCB) and extremely abrasive aluminum-silicon and titanium-aluminum alloys but also for machining of challenging composite materials such as carbon fiber reinforced plastics (CFRP) for aerospace applications. Nanocrystalline diamond is one of the most interesting materials for micro-mechanical systems and MEMS devices. Large scale deposition of diamond films on silicon and on wear parts in an industrial scale have been developed. Boron doped diamond coatings can be used as electrode material for different electrochemical applications such as electrochemical synthesis or waste water treatment. Homogenous large area electrodes were produced using the same set up. Nanocrystalline self-supporting diamond foils, e.g. for erosion protection, were produced on appropriate templates and afterwards stripped-off. Despite the pure covalent bond and highest hardness the diamond foil is very flexible and easy to handle. This enables the application of diamond coating on temperature sensitive substrates.
10:40 AM		B2-1-9 Gradient of Tribological and Mechanical Properties of Diamond-like Carbon Films Grown on Ti6Al4V Alloy with Different Condition of Interlayer Preparation Patrícia Silva, Gislene Martins, João Machado, Evaldo Corat (Instituto Nacional de Pesquisas Espaciais (INPE), Brazil); Vladimir Trava-Airoldi (Instituto Nacional de Pesquisas Espaciais (INPE, Brazil) Ti6Al4V alloy are used on advanced aerospace systems, as a biomaterials, etc., because of their properties like high strength to weight ratio and excellent corrosion resistance and biocompatibility compared to many other metal alloys. In order to improve such applications, it is necessary to improve its tribological and mechanical properties and a good choice is the deposition of diamond-like carbon (DLC) coating with very high adhesion. DLC films are well known for their low friction, high hardness and good wear resistance. The adhesion between a DLC coating and Ti6Al4V alloy can be enhanced by the application of an interlayer of diverse materials. In this work, it was used a silicon interlayer that was deposited with different controlled ion energy, generating singular ion subimplantation profiles on the titanium alloy substrate. The DLC films were deposited using a modified PECVD pulsed-DC discharge under controlled conditions to obtain maximum hardness, minimum stress and maximum deposition rate. Tribological and mechanical tests were made to observe the friction and wear gradient of the samples. The tribometer was adjusted for ball-on-plate mode, in the reciprocating manner, in a humidity of 26 ± 2% RH and a temperature of 25 ± 1 ºC. The scratching tests were made in order to study the adhesion of DLC coatings on Ti6Al4V alloy as a function of silicon interlayer parameters of obtaining. The samples were also characterized by micro and nano-identation to observe the hardness profile, and Raman spectroscopy to verify the structural arrangement of carbon atoms. It was observed that the adhesion between DLC film and substrate is strongly related to gradient of mechanical and tribological properties of the substrate from the bulk to the surface.
11:00 AM		B2-1-10 Selected Aspects of Technology Development of Ceramic Coatings Obtained by Microwave Plasma Enhanced Chemical Vapor Deposition Lucjan Swadzba, Bartosz Witala (Silesian University of Technology, Poland); Radoslaw Swadzba (Institute for Ferrous Metallurgy, Poland); Marek Hetmanczyk, Grzegorz Moskal, Boguslaw Mendala (Silesian University of Technology, Poland); Lukasz Komendera (AVIO Poland sp. z o.o., Poland) The increase in engine efficiency, reduced gas emissions of NOx, SOx into the atmosphere, as well as noise reduction is achieved by increasing the temperature of the gas turbine components which have to be protected with TBCs (Thermal Barrier Coating) with low thermal conductivity separating the elements from the hot gas stream. Currently in the aerospace industry two main technologies of TBC deposition are used on a large scale: plasma spraying method APS (Air Plasma Spraying) and a method of physical vapor deposition EB-PVD. There is a need to develop alternative technologies for EB-PVD method, creating the possibility of obtaining columnar structure of TBCs with the durability and thermal conductivity properties at least as good as the in EB-PVD method with less investment costs. In the literature, the proposed technology is an alternative method of CVD (Chemical Vapour Deposition). CVD technology consists in placing the coated components in the chamber which is heated to the process temperature after which the gaseous precursors are formed in the external generators. There are three main technologies used for the preparation of ceramic layers: MOCVD, MPECVD and LCVD. The paper will be presented experimental apparatus for the production of ceramic coatings developed at the Silesian University of Technology. The results of the first tests of ceramic coating deposition using CVD technology assisted by plasma energy generated by microwaves will be presented. These processes utilizes chloride precursors formed in the outer gas generators.