Nazlim Bagcivan

Time resolved optical emission spectroscopy of an HPPMS coating process

This paper deals with the time resolved optical emission spectroscopy of a high power pulse magnetron sputtering (HPPMS) physical vapour deposition coating process. With an industrial coating unit CC800/9 HPPMS (CemeCon AG, W?rselen) a (Cr,Al,Si)N coating was deposited. During the coating process, an absolute calibrated Echelle spectrometer (ESA-3000) measured the intensities of the spectral lines of chromium (Cr), aluminium (Al) and molecular bands of nitrogen (N2). Time resolved measurements enable us to calculate different parameters such as the average velocity of sputtered Al and Cr atoms or the internal plasma parameters electron density ne and electron temperature kTe with a time resolution of 20??s. With these parameters, we determine the ionization rates of Al, Cr, Ar and Kr atoms and the deposition densities of Al and Cr atoms. Thus simulated deposition densities of 1.75 ? 1020?m?2?s?1 for chromium and 1.7 ? 1022?m?2?s?1 for aluminium are reached.

Deposition of Oxides as Tool Protection for Large Thixoforming Dies by Using the Pulsed MSIP-PVD Process

Oxide coatings offer great potential for their use in forming operations in the semi-solid state. Advantages of these types of coatings are high resistance against abrasive wear, high hot hardness and low thermal conductivity. Nevertheless deposition by pulsed Magnetron Sputter Ion Plating-PVD for oxide coatings is quite challenging: deposition rates are low and insulating layers on the target surface can cause arcing. On laboratory scale it was possible to deposit γ-Alumina using PVD in a temperature range, where hot working steel can be utilized. The next important step in the development towards an industrial application for larger forming tools is the upscaling process to larger coating units. In this work the process development of oxide coatings on an industrial coating unit for large tools was described. To increase adhesion of oxide top-layer additional bond coats were applied. Different process parameters like oxygen content, total pressure and substrate bias were varied, to improve the performance. The relationship between coating properties and process parameters of the deposited films were characterized by X-Ray-diffraction, Nanoindentation and Scanning Electron Microscopy (SEM). By using reactive pulsed PVD-process it was possible to deposit γ-Al2O3 on large steel tools for semi-solid melt protection. The developed coatings showed for thixoforging processes of X210CrW12 an extraordinary stability in field tests. The lifetime of the permanent moulds was increased by using PVD thin film coatings as a tool protection.

Injection molding of products with functional surfaces by micro-structured, PVD coated injection molds

Molding of micro structures by injection molding leads to special requirements for the molds e.g. regarding wear resistance and low release forces of the molded components. At the same time it is not allowed to affect the replication precision. Physical vapor deposition (PVD) is one of the promising technologies for applying coatings with adapted properties like high hardness, low roughness, low Young’s modulus and less adhesion to the melt of polymers. Physical vapor deposition technology allows the deposition of thin films on micro structures. Therefore, the influence of these PVD layers on the contour accuracy of the replicated micro structures has to be investigated. For this purpose injection mold inserts were laser structured with micro structures of different sizes and afterwards coated with two different coatings, which were deposited by a magnetron sputter ion plating PVD technology. After deposition, the coatings were analyzed by techniques regarding hardness, Young’s modulus and morphology. The geometries of the micro structures were analyzed by scanning electron microscopy before and after coating. Afterwards, the coated mold inserts were used for injection molding experiments. During the injection molding process, a conventional and a variothermal temperature control of the molds were used. The molded parts were analyzed regarding roughness, structure height and structure width by means of laser microscopy.

Impact Behaviour of PtIr-Based Coatings with Different Interlayers for Glass Lens Moulding

Over the last decades demands for optical systems and complex optical products made of glass increased steadily. Precision glass moulding has a great potential for the bulk production of complex lenses with high precision and low costs. To prevent sticking or reactions between hot glass and moulding, and to reduce abrasive wear of the die a protective coating is deposited on the tool. In this research two coating systems suitable for this application are compared by analysing their behaviour under an impact load. The PVD (Physical Vapor Deposition) coating PtIr with two different bond coatings Ni or Cr is analysed. During impact test number of impacts and loads are varied. Compared to industrially used coating system PtIr with a Ni interlayer the adhesion can be improved by using a Cr interlayer. The PtIr-based coating with Cr as bond coating shows an excellent endurance even at very high loads causing Hertzian stresses in the range of 10 14 GPa. An impact load of 600 N which corresponds to a contact pressure of app. 13.2 GPa generates almost no damage after 200,000 impacts.

Influence of Ar/Kr ratio and pulse parameters in a Cr-N high power pulse magnetron sputtering process on plasma and coating properties

Krypton is sometimes used in physical vapor deposition processes due to its greater atomic mass and size compared to argon, which leads to a lower gas incorporation and may have beneficial effects on kinetics of the coating growth. In this paper, the authors investigate the plasma composition and properties of deposited high power pulse magnetron sputtering Cr-N coatings for discharges with various Ar/Kr ratios and for various pulse lengths of 40 μs, 80 μs, and 200 μs, keeping the average discharge power constant. The results show that an addition of Kr influences the discharge process by altering the ignition and peak values of the discharge current. This influences the metal ion generation and growth conditions on the substrate by reducing the nucleation site densities, leading to a predominantly columnar grow. However, the deposition rate is highest for an Ar/Kr ratio of 120/80. The integral of the metal ion and atom emission exhibits the same trend, having a maximum for Ar/Kr ratio of 120/80. By decreasing the pulse length, the deposition rate of coatings decreases, while the hardness increases.

Flow curve determination on dc-MS and HPPMS CrAlN coatings

In this paper, a new method for determining flow curves of thin coatings is tested on the basis of chromium aluminum nitride coatings deposited by direct current and high power pulsed magnetron sputtering physical vapour deposition with a wide range of chemical composition. The flow curves have been determined using the nanoindentation technique with a spherical indenter combined with analytical methods and finite element simulation. Extensive analyses of the FEM simulation also examine the possible influence of the substrate material on the measured flow curves. The results show that different coating flow behaviour have been characterized with this method which can be correlated with material phase appearance in the coating. Suggestions to completely eliminate the substrates influence in experiment or simulation are made.

Metal flow and die wear in semi-solid forging of steel using coated dies

Thixoforging of steels is a potential forming technology, which aims at producing near-net-shaped components with good quality from high strength steels in one forging step. The thixoforging process parameters such as billet temperature, temperature distribution after reheating, argon gas pressure, transportation time and forging load were investigated on the thixoforging of non axis-symmetric parts of steel grade X210CrW12. The experimental and numerical study of the material flow and tool temperature load reveal the areas of intensive tool wear, thus being useful for further tool design. Hardened hot working steel X38CrMoV5-1 as a tool bulk material with protecting thin films of TiAlN/γ-Al2O3 shows good experimental results at 170 forging cycles.

Hybrid Production Systems

While virtual product development allows great freedom in terms of design, actual development processes are rather restricted. Those boundary conditions are at best hardly possible to exert influence on. Therefore, future research has to focus both on the realisation of the concept of one-piece-flow while simultaneously increasing flexibility and productivity and on the technological advancement. Hence, hybridisation of manufacturing processes is a promising approach, which often allows tapping potentials in all the aforementioned dimensions.

Virtual Production Systems

The use of simulation systems is of significant importance for companies in high-wage countries as the requirements of product- and process quality are generally higher than in low-wage countries due to conditions of the market. Since the implementation of simulation tools is not value-adding in the first place, the performance of virtual product development chain must therefore be continuously increased in terms of greater planning efficiency. Research in the field of virtual production systems therefore addresses the following issue.

Influence of the layer architecture of DLC coatings on their wear and corrosion resistance

Abstract In this work, the influence of diamond-like carbon top layers deposited on two different types of layer architecture on wear and corrosion resistance is investigated. Physical vapour deposition coatings with a-C:H top layer of various thicknesses were deposited on plasma nitrided 42CrMo4 by reactive magnetron sputter ion plating. Beneath the top layer, an architecture with and without a-C interlayers was deposited. Investigations using potentiodynamic polarisaton testing in artificial seawater as well as an impact tribometer show that it is possible to protect low-alloy heat treatable steel from both corrosion and wear by using pre-treatment and an appropriate diamond-like carbon coating. Thicker a-C:H top layers as well as the addition of a-C interlayers resulted in an overall improvement in the coating behaviour.