Abstract Turbine blades in hydropower plants have to withstand the most severe seasonal loading conditions when the river water is heavily loaded with sediments. Welded blade surfaces are considered state of the art, but they cannot withstand the aggressive, eroding and abrasive loading conditions in the major rivers in China. Once a year there is flooding with a maximum amount of sediment in the river water. This is why coating systems with maximum wear resistance must be developed, examined, produced and tested over a maximum period of time. In this article, the wear results of various coating systems examined in a special test facility are described in order to obtain comparable results from several proposed coating systems together with material classification tests. Paper includes a German-language abstract.

Abstract This paper evaluates four tungsten carbide basecoats produced by thermal spraying with a high speed flame spraying system as potential candidates to replace hard chrome in applications subject to abrasive and/or corrosive conditions. It investigates the potential of using WC-based cermet coatings deposited using high velocity oxy-fuel thermal spraying to replace electrodeposited hard chromium. The paper shows that WC-based thermally sprayed coatings are available to replace hard Cr in many applications. Salt spray tests and electrochemical measurements in synthetic sea water showed that the Cr-containing coatings had the highest corrosion resistance. These results indicated that 10Co-4Cr-WC could be the best coating candidate for conditions in which both abrasion and corrosion are present. Paper includes a German-language abstract.

Abstract TiC-based coatings sprayed by different processes, such as detonation gun spraying, high velocity oxy-fuel spraying, atmospheric plasma spraying (APS), and vacuum plasma spraying, using agglomerated and sintered powders have been actively developed over the years. This development is based on the high technical and engineering potential of the hard phase TiC. This paper describes the results of basic studies of the APS for various alloying steps in the production of TiC base coatings from agglomerated and sintered powders as well as the results of the application of APS coatings on piston rings. Paper includes a German-language abstract.

Abstract This article attempts to predict the temperature, state and velocity of Tribaloy 800 particles by means of numerical modeling. It aims to identify parameters that have a significant influence on the inflight particle characteristics for Argon/Hydrogen plasma sprayed Tribaloy 800, and to compare predicted air entrainment and particle residence times between Argon/Hydrogen and Argon/Helium plasma gas mixtures. The effect of spray parameters (primary-, secondary- carrier gas mass flows, current, spray distance and nozzle diameter) on the particle in-flight characteristics (velocity and temperature) and their interactions are studied by a two level fractional factorial experiment applied on the simulations. A comparison between argon Argon/Hydrogen and Argon/helium plasm gas mixtures is made in order to investigate whether the coating oxidation level can be reduced using Argon/Helium. Finally, the correlation between the modeled parameters and the application microstructure is studied. Paper includes a German-language abstract.

Abstract Co-based alloys are used extensively in applications requiring good wear resistance, corrosion and heat resistance. This paper presents the wear data of Co-based plasma sprayed coatings for aeronautical applications at temperatures up to 750 deg C, evaluated in a pin-on-disk unit. Investigation of the coating structure and the wear mechanisms revealed the processing-structure-functionality relationships. The analysis of the tribological results was supported by structure, microhardness and X-ray diffraction studies of the coatings. An SEM examination of the wear marks revealed the predominantly active wear mechanisms in each case. Paper includes a German-language abstract.

Abstract A promising technique to increase the portions of hard metal and hence the wear resistance of components is the coating with more wear-resistant hard metals by thermal spraying. The development of suitable coatings includes the selection of substrates, preliminary treatment of substrates, selection of powders, spraying techniques, spraying parameters, coating and quality characterisation. Examined were variants of high velocity oxy-fuel flame spraying CDS (Continuous-Detonatio-Spraying), DJH (Diamond-Jet-Hybrid 2700) and the wear resistance with 3-body-wear. The results confirm that substrates coated by DJH hard metal (e.g. with WC 86 Co10 Cr4) in comparisation with uncoated substrates (16MnCr5, case-hardened, hardness 65 HRC) have a specific wear by 3-body-wear-test which is many times lower then without coating. Paper text in German.

Abstract This paper describes the development of novel engineered surfaces based on thermal spray coatings for sliding wear resistance under conditions of high loading and starved lubrication. As specific examples, piston ring elements for internal combustion engines and radial bearings for medium-lubricated pumps are discussed. The properties of two coatings, SUME SOL 220 and SUME SOL 320, are compared with existing materials and coatings. It was found that SUME SOL 220 exhibited excellent sliding wear resistance under boundary (oil) lubrication. As a consequence, they are considered as attractive candidates for piston ring applications in heavy duty engines. For more corrosive applications, such as encountered in sea water environments, the SUME SOL 320 coating exhibited superior combinations of sliding wear and corrosion resistance. Paper includes a German-language abstract.

Abstract Using a DC-plasmajet amorphous and nanocrystalline Si-C-layers are synthesized from chloromethylsilanes on various substrate materials. Though most of the layers show granular morphologies with cluster diameters between 25 and 400 nm depending on the process parameters, coatings with a dense or columnar morphology and with a smooth surface can be synthesized as well. XRD analyses verify β-SiC crystals with an average diameter of 5 nm. In some samples produced from carbon rich precursors also graphite is detected. Depending on the substrate material and the process parameters deposition rates up to 1,300 µm/h are obtained. Apart from silicon and carbon the coatings convey oxygen and chlorine verified by EDX. Coatings removed from the substrate can withstand several bending cycles (45°) without any visible indication of failure. Paper text in German.

Abstract Diamond films have been deposited on WC - 6% Co hard metal tools by the DC plasma jet CVD synthesis. The parameters of the process (gas composition, temperature of the gas phase and the substrate, process pressure) as well as of the substrate surface (material, pretreatment) are related to the diamond film growth. For machining abrasive materials the hard and wear resistant diamond coatings must adhere good to the substrate. The wear behaviour of thin diamond films on hard metals under cavitation treatment has been examined. Thus the conditions of diamond synthesis have been varied especially concerning the coating duration and the process pressure and engineering. The cavitation test reacts more sensitive to coating defects of pm size than the conventional testing methods (scratch test, indenter method) and considers the microstructure of the material. Paper text in German.

Abstract The improvement of the tribologic characteristics of surfaces is an important application of thermal sprayed coatings. Also various ranges of application demand good antiadhesive characteristics. The tribologic and antiadhesive characteristics of fluorine containing polymers are very good. Since furthermore those polymers have the highest thermal resistance of all plastics it has been investigated if those polymers can be integrated in thermal sprayed oxide and carbide coatings. The aim was to improve the tribologic and antiadhesive characteristics. The processes Plasma- and HVOF-spraying have been used to apply the coatings. The polymers in the coatings were detected by examinations with the light-optical and the scanning electron microscope. To heighten the contrast for the light microscopy examinations the metallographic sections of the specimens were physically contrasted. To clearly identify the different phases with the scanning electron microscope EDX-analyses have been carried out. Samples have been tested to investigate the mechanical characteristics of the coatings. Paper text in German.

Abstract This paper provides results from experimental studies with regard to novel, thermally sprayed coatings for tribological applications, which consist of mechanical mixtures of cast iron powders (2.16% by weight C and 5.18% by weight Si) and solid lubricant (calcium fluoride or iron oxide) produced in an amount of 10 to 20% by volume. It was established that a basic phase of initial cast iron powder and detonation coatings is gamma-Fe and it is alpha-Fe in plasma coatings. Oxide inclusions which are products of cast iron oxidation are observed in coatings structure. Metallographic investigations showed an uniform distribution of solid lubricant inclusions in a metallic-matrix of coatings. Tribotechnical tests of coatings containing 20 vol. % calcium fluoride carried out in conditions of room temperature indicated that the best antifriction properties were obtained for coatings with calcium fluoride additions which were sprayed by supersonic air-gas plasma method. Paper includes a German-language abstract.