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TiN hard coatings have been prepared by unbalanced magnetron (UBM) sputtering and cathodic arc deposition using uni- and bipolar pulsed bias voltages. For UBM sputtering using a unipolar pulsed bias voltage the average substrate bulk temperature Ts was reduced to 220 °C without considerable loss of microhardness and adhesion by variation of the pulse parameters. Determination of the average energy Ep delivered to the growing film per deposited particle leads to values lower than the critical transition energy (150 eV atom-1) between open porous and dense coatings. Using a bipolar pulsed bias voltage Ts decreased with increasing duration ton+ of the positive bias pulse. It was found that Ep increased with increasing ton+ up to values found for d.c. bias voltage. The coatings prepared using a bipolar pulsed bias voltage at low Ts are dense and in compressive stress with acceptable microhardness and adhesion. First results of the investigation of TiN coatings prepared by cathodic arc deposition using unipolar pulsed bias are given.
An attempt was undertaken to obtain a better understanding of the tribological properties of two wear-resistant coatings on tool steel by structural and microchemical analysis of wear particles using a transmission electron microscope. Coatings were deposited by physical vapor deposition and plasma-assisted chemical vapor deposition techniques and tribological properties were derived from reciprocating sliding tests of the coatings against alumina balls. Three types of wear particles were identified by electron diffraction and energy dispersive X-ray spectroscopy: nanocrystalline rutile (TiO2), nanocrystalline graphite and microcrystalline graphite. Low coefficients of friction, of the order of 0.2, were attributed to the formation of solid lubricant films of sub-stoichiometric TiO2-x Magnéli phases and/or graphite.
Instrumented indentation test for hardness and materials parameter from millinewtons to kilonewtons
(2002)
The ISO/DIS 14577 Metallic materials - Instrumented indentation test for hardness and
materials parameters Part 1-3 (IIT) concerns test forces up to 30 kN. The paper reports on
IIT at test forces ranging from 0.002 N to 1000 N on non magnetizable steel X8 CrMnN 18-
18 (1.386) with well polished surface using Vickers indenter and four hardness machines of
different design (Nano Indenter XP, Fischerscope H 100, Zwick Z005 with Universal
hardness head and a laboratory four-column set up materials testing machine) according to
the standard. Using mostly identical test parameters the results of the different machines are
almost in good agreement. Estimated small differences are caused by the different
uncertainties of the used machines and by different methods of mathematical analysis of the
detected raw data.
In the last years, a lot of research work has been performed in the field of surface coatings and thin films technology, often supported by governmental research programs, as i.e. in Germany, the Thin Film Technology and OSTec research programs. But up until now, there is still a lack in transfer of this large amount of knowledge created by research activities on to industrial application and commercialization. To overcome this problem, a new web based information system has been developed (http://www.schichttechnik.net), which in a first step will make the whole content of the German OSTec research program (approx. 180 research reports) of the last 10 years available. In further steps, data from products of coating suppliers and other research programs will be taken into account. The database contains the following sections: definition of the coating system, deposition equipment, deposition processes, application properties, test procedures and test equipment, information about standardization and base information about coating processes etc. It will be possible to search for coatings by material properties and functions of coatings, considering also restriction on the substrate. In addition, searching regarding combination of properties, e.g. for wear-resistant, conductive, decorative coatings etc. will also be possible.
The chemical and microstructural changes occurring during braking simulation tests at the surface of a conventional brake pad material were investigated mainly by scanning and transmission electron microscopy and surface analytical techniques. It can be shown that patches of a third body material develop, comprising a compositional mix of all constituents of the pad and iron oxides from the disk. Milled debris particles still have the crystal structure of barite, the major phase of the pad material, but the grain size is reduced drastically to the nanometer scale. The major wear mechanism is delamination of filler particles from the organic binder, supported by local degradation of the phenolic resin during asperity heating. Quartz crystals are preserved thereby adopting the function of primary contact areas.