PVD Coatings and Technologies

Monday, April 28, 2014 1:30 PM in Room Royal Palm 1-3

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1:30 PM B1-2-1 High-temperature Sputter Deposition of Ti1-xAlxN/TiN Multilayer Coatings on Powder-metallurgical High-speed Steels
Thomas Weirather, Kerstin Chladil (Montanuniversität Leoben, Austria); Bernhard Sartory (Materials Center Leoben Forschung GmbH, Austria); Devrim Caliskanoglu (Böhler Edelstahl GmbH & Co KG, Austria); Rainer Cremer (KCS Europe GmbH, Germany); Werner Kölker (CemeCon AG, Germany); Christian Mitterer (Montanuniversität Leoben, Austria)
Although spinodal decomposition of metastable cubic Ti1-xAlxN-based hard coatings and the underlying mechanisms have been extensively explored, the effect of high deposition temperatures is essentially unknown. It is thus the aim of this work to elucidate structure, properties, thermal stability and wear performance of Ti1-xAlxN/TiN multilayer coatings sputter deposited on powder-metallurgical high-speed steels at substrate temperatures of up to 575°C. Sharper domain boundaries and multilayer interfaces yield increased hardness in the as-deposited state, while the detrimental formation of wurtzite AlN during vacuum annealing is retarded by 50°C according to Rietveld refinement of X-ray patterns. Tribological tests at room temperature and up to 650°C corroborate the high potential of increased coating temperatures, while demonstrating the crucial importance of using a substrate material with adequate hot hardness. Cutting tests verify the high temperature deposition approach to show an increase in tool performance of ~40 %.
1:50 PM B1-2-2 Wear Protective Coating for Cutting Tools Applications Deposited by S3p™
Denis Kurapov, Siegfried Krassnitzer, Theo Bachmann, Jürg Hagmann, Wolfgang Kalss, Mirjam Arndt, Helmut Rudigier (Oerlikon Balzers Coating AG, Liechtenstein)
In this work wear protective coatings for cutting tool applications were produced by novel S3p™ deposition method. S3p™ technology enables scalability of the pulse power density and pulse length. The coating growth was studied with respect to the pulse parameters. The chemical composition of the coatings was investigated by means of energy dispersive X-ray spectroscopy (EDX). The evolution of the growth morphology and crystallographic structure as a function of plasma characteristic was studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The elastic modulus of the coatings was measured by nanoindentation method. The applied pulse power density and pulse length were found to be crucial parameter influencing the phase composition and properties of the coatings. The correlation between coating growth conditions and the cutting performance of the coatings is discussed.
2:10 PM B1-2-3 Internal Oxidation of Nanolaminated Coatings
Yung-I Chen (National Taiwan Ocean University, Taiwan)
Nanolaminated coatings, consisting of alternating gradient concentration, were prepared using co-sputtering deposition by exposing the substrates alternatively under sputter sources. After annealing in oxygen containing atmospheres, internal oxidation has been observed for the nanolaminated coatings, resulting into the formation of an oxidized laminated structure, which consisted of alternating oxygen-rich and deficient layers stacked adjacent to the surface. The forming mechanism for crystalline coatings was proposed as follows: (1) one of the elements should be relatively noble, such as Ru; (2) the coatings show an orientated columnar structure in the as-deposited state, and the elements stack on the substrate with an alternating gradient concentration; and (3) the inward diffusion of oxygen is faster than the outward diffusion of the coating constituents. In this study, thermodynamic and kinetic considerations were examined. Internal oxidation of ternary alloy coatings, Ta–Ru–Zr, was investigated.
2:50 PM B1-2-5 Ion Energy Distributions in DC Arc Plasma from Compound Cathodes
Igor Zhirkov, Oleksiy Vozniy, Johanna Rosen (Thin Film Physics Division, IFM, Linköping University, Sweden)

Arc deposition from compound cathodes is today a common method for synthesis of a wide range of functional multi-element coatings. It is known, that the kinetic ion energy is a crucial plasma parameter for the structural evolution of the film. Therefore, an increased understanding of the plasma generation from compound cathodes is highly motivated. In this work, unfiltered DC arc plasma from Ti-C, Ti-Al, and Ti-Si cathodes were characterized with respect to charge-state-resolved ion energy (velocity). We found that the most likely ion velocity is independent on mass, and hence the same for all ion species and ion charge states originating from the same cathode. Therefore, measured difference in kinetic energies can be inferred to the difference in ion mass, as E=mv2/2. It was also discovered that plasma generated from the cathodes with increased concentrations of C and Si resulted in more energetic ions. This effect may be explained by the “Cohesive energy rule”, where single-element (C) and binary (Ti1-xCx, Ti1-ySiy) phases of higher cohesive energy generally result in increasing ion energies. The collected results are consistent with a gas-dynamic mechanisms of ion acceleration based on pressure gradients, and suggest that the addition of C, and Si into Ti cathodes increase the pressure in the arc spots which in turn lead to increased ion velocities/energies. This is supported by an obtained most likely ion velocity of 1.47, 1.76, and 1.81 (∙104 m/s) for ions from Ti, Ti0.75C0.25, Ti0.75Si0.25, respectively. For Ti ions this correspond to an ion energy of 53.8 eV, 77.1 eV and 81.5 eV, respectively.

3:10 PM B1-2-6 Filtered Cathodic Vacuum Arc Processes for Nano-scale Layering of Wear-resistant Structure on High Speed Steel Tools
Alexey Vereschaka, Marina Volosova, Sergey Grigoriev, Anatoly Vereschaka (Moscow State University of Technology (MSUT "STANKIN"), Russian Federation); Andre Batako (Liverpool John Moores University, UK)
This paper presents a development of filtered cathodic vacuum arc formation processes of nano-scale wear-resistant structures to increase life span of high speed steel cutting tools. An attempt is made to increase the efficiency of complex-profile tools made of high speed steel (HSS). This is achieved by depositing wear-resistant complexes (WRC) on the cutting tools using combined catholic vacuum arc deposition processes with filtration of steam-ion flow in a single technological cycle. The wear-resistant coatings have four-component architecture. This includes a thermo-stabilizing layer, which increases the thermal stability of HSS against high temperature creep and thermoplastic deformation at cutting temperatures. This leads to more stable and enduring work of the nano-dispersed multilayer coating, which consists of adhesive underlayer, intermediate and outer layers. This work investigates into the influence of process parameters on the formation of the nano-scale structure of wear-resistant complex coatings and their properties. This allowed defining the optimal conditions for WRC formation, under which the maximum increase of tool life was observed for different cutting regimes. It was found that the tool life of different types of HSS tools coated with the newly developed WRC significantly exceeded the life span of both commercially available uncoated and coated HSS tools.

3:30 PM B1-2-7 Structure and Corrosion Properties of TiN Films Deposited by Combined HIPIMS-DCMS Process
Papken Hovsepian, Arunprabhu Sugumaran, ArutiunP. Ehiasarian (Sheffield Hallam University, UK)

TiN films were deposited using four cathode coating system equipped with power supplies for High Power Impulse Magnetron Sputtering (HIPIMS) and power supplies for Direct Current Magnetron Sputtering (DCMS). In this study, the coatings were produced using different combinations of HIPIMS and standard magnetron sputtering sources. Increasing the number of HIPIMS sources involved in the combined process proved to be an effective tool to manipulate the ionisation degree in the plasma. Optical emission spectroscopy revealed that the intensity ratio of Ti1+:Ti0 in the plasma increased with increasing the number of HIPIMS sources involved in the process from 0.09 to 1.93 for pure DCMS and pure HIPIMS respectively.

TiN coatings phase composition, microstructure texture as well as residual stress, and corrosion properties were studied by number of surface analyses techniques such as X-Ray Diffraction (XRD), Fracture Cross Sectional Scanning Electron Microscopy, (XSEM), Transmission Electron Microscopy, (TEM) as well as RAMAN spectroscopy.

It was revealed that in mixed HIPIMS - DCMS processes the residual stress can be controlled in vide range from -0.21 GPa to -11.35 GPa by smart selection of the degree of HIPIMS utilisation, strength of the electromagnetic field of the unbalancing coils of the machine as well as the bias voltage applied to the substrate.

XSEM analyses revealed that the fracture morphology changes from open columnar to dense almost glassy morphology when the number of HIPIMS sources in the process increases due to the higher ionisation and therefore higher mobility of the condensing species. Furthermore, higher ionisation with HIPIMS dominated processes leads to change in preferred film orientation from (111) to (200).

Significant improvement in corrosion performance was achieved by increasing the number of the HIPIMS sources involved in the process. Raman spectroscopy was used to analyse the nature of the corrosion products as well as to estimate the extent of the corrosion damage. When polarised around Ecorr values (-1 V to + 200 mV), pure DCMS and 1 HIPIMS + 3 DCMS coatings exhibited iron and chromium oxide (Fe2O3, Cr2O3) peaks at ~495 cm-1 and ~ 550 cm-1 in the spectra indicating that the corrosion has reached the substrate. No corrosion products were found in the above potential range for 2 HIPIMS + 2 DCMS and pure HIPIMS coatings demonstrating the advantages of the denser structures.

Mixing HIPIMS with DCMS is also seen as an effective tool for improving the productivity of the deposition process.

3:50 PM B1-2-8 Ternary Carbonitride Coatings deposited by High Power Impulse Magnetron Sputtering
Tina Hirte, Rainer Feuerfeil, Victoria Perez-Solorzano Borragan (Robert Bosch GmbH, Germany); Matthias Scherge (Fraunhofer Institute for Mechanics of Materials, IWM, Germany)

Many recent studies have been investigating ternary carbonitrides including metals or metalloids (like TiCN, NbCN and BCN) for their potential as wear resistant coatings in several applications. The adjustability of their properties, such as hardness, coefficient of friction, wear resistance, and temperature stability is especially promising. Different deposition methods are used to grow thin films for wear protection purposes and it is agreed that structure has a strong influence on their mechanical and chemical properties.

The short pulses with very high power density applied in High Power Impulse Magnetron Sputtering (HiPIMS) result in a higher ionization rate of the sputtered material compared to conventional DC magnetron sputtering. Therefore, HiPIMS technology can have a beneficial influence on the film structure and provides a promising approach to tailor the properties of ternary coating systems.

This work focuses on the influence of chamber pressure and nitrogen to argon ratio during the deposition of ternary carbonitride coatings on their composition and structure. The films were grown on high speed steel and silicon substrates with DC-MS and HiPIMS and were characterized using X-ray photoelectron spectroscopy and X-ray diffraction. Topography and morphology were examined by scanning electron microscopy. Furthermore, hardness and adhesion were measured using nano indentation and Rockwell indentation and the correlation with the structure was investigated. The differences in composition, structure and hardness we observed between DC-MS and HiPIMS sputtered coatings are discussed within this publication.

4:10 PM B1-2-9 Laser Assisted and Arc Technologies for Hard Carbon Film Deposition – An Overview from the Beginning up to the Industrial Application
Hans-Joachim Scheibe (Fraunhofer Institute for Material and Beam Technology IWS, Germany)
Pulsed laser assisted and arc methods are preferentialy applied for the generation of a fully ionized plasma with high kinetic ion energy from a solid target material. These are necessary conditions for the deposition of dense hard films with a good adherence to the substrate material, especially for hard amorphous carbon films.

An overview will be given about the development of both technologies during the last 20 years from basic processes in the laboratory scale to the industrial applicable deposition source. Just as well the combination of both technologies in form of the laser assisted pulsed arc deposition process (Laser-Arc) will be presented. The advantages of this combination are presented with resprect of introduction for high volume coating of parts and tools.

Mainly advantages of the Laser-Arc technology are to have a very controlled pulsed arc deposition technology with a high deposition rate (2 µm/h twofold rotating axes of a planetary). By the laser controlling of pulsed arc evaporation a longtime using of the applied rotating graphite cathodes is guaranteed and ta-C films with a thickness up to 10 microns can be deposited. By integration of a filter unit for separation of particles from the carbon plasma, an improved ta-C film quality can be obtained, regarding their roughness, hardness and Young´s modulus with an acceptable loss of the deposition rate.

The nature of the Laser-Arc-Module system is, that this carbon ion source can be integrated in commercial available coating machines, independently of producer.

4:50 PM B1-2-11 Super-hard Tetrahedral Amorphous Carbon Films (ta-C) with Low Internal Stress -The Potential of the Pulsed Laser Deposition Technique
Katja Guenther (University of Applied Sciences Mittweida, Germany); Volker Weihnacht (Fraunhofer IWS, Germany); Steffen Weißmantel (University of Applied Sciences Mittweida, Germany)
Super hard tetrahedral amorphous carbon (ta-C) films have been deposited by: 1) pulsed laser deposition (PLD) using an excimer laser (248 nm wavelength) 2) PLD in combination with laser pulse stress relaxation (PLD – LSR) 3) pulsed laser arc method (ARC) and 4) filtered pulsed laser arc method (fARC). The aim was a comparative study of growth and properties of ta-C films produced by these various production methods. Therefore, ta-C films with the same thickness of 2 μm have been deposited onto polished steel, tungsten carbide and silicon substrates using these different methods. The films were characterized with regard to their morphology, adhesion and hardness by scanning electron microscopy (SEM), scratch testing and nanoindentation, respectively. Both the ARC and PLD methods have in common that large particles (droplets) are incorporated into the films. Our investigations by SEM show that both the size and the number of the droplets are lower for PLD or PLD-LSR films in comparison to ARC films. We will also show how the number of droplets can be reduced by using fARC instead of ARC and will compare the surface roughness of all the films. There are also differences in the film properties. Scratch tests show critical loads of ta-C films on steel substrates between 11 N and 27 N and on tungsten carbide substrates between 30 N and 35 N. The ta-C films produced by PLD and especially by PLD-LSR show clearly different behavior in film failure in the scratch in comparison with the ARC ta-C films, which will be discussed in terms of number and size of droplets, film stress and hardness. Furthermore, hardness measurements will show, that it is possible to produce with all methods equal hardness between 10 GPa and 60 GPa, which can be adjusted by using different deposition parameters. By using the ARC and fARC method it is possible to produce ta-C layers with internal stresses between 1-3 GPa for industrial applications. By using PLD the internal stress is with up to 8-10 GPa higher. This can be reduced near to 0 GPa by using PLD-LSR. The deposition rate of industrial ARC amounts to about 3.6 μm/(h.m2). The plasma filter has a transparency of about 50%, i.e. the deposition rate for fARC is reduced to about 1.8 μm/(h.m2). In comparison, both PLD methods allow at the moment deposition rates up to 0.9 μm/(h. m²). It is shown, that all 4 methods are appropriate to produce the ta-C layers for wear protection of different kinds of tools and sliding components.