The following contribution deals with carbide composite powders. These composite powders were made by the SHS-process. The present work is a result of a co-operation between the Institute for Powder Metallurgy Minsk (PMI) and the Department of Composites and Surface Technology at the Chemnitz University of Technology (TUC). The main aspect of this research activity is the improvement of the wear protection due to the deposition of the composite coatings. Paper text in German.

HVOF-sprayed stainless steel coatings are potential candidates for protection against water corrosion. However, the process parameter "window" leading to acceptable corrosion behavior has yet to be determined. With potentiodynamic tests, this paper examines the corrosion behavior of metallic, thermally sprayed coatings under carefully controlled conditions in order to gain an insight into their performance "in service". The influence of the variations in the fuel:oxygen ratio, in the total gas volume and in the spraying distance, on the corrosion process of HVOF-sprayed stainless steel coatings on steel substrates with a low carbon content is determined by means of potentiodynamic measurements. The results are correlated with a characterization of the microstructure to understand the influence and role of oxide content, porosity, and coating morphology. Some comparisons with VPS coatings are also made. Paper includes a German-language abstract.

This paper investigates the oxidation that occurs during the flight movement of a powder particle and during the spatter solidification in the thermal spray process. The effects of oxidation on droplet flattening, on the mechanical and thermal interactions between spatter and substrate, on spatter morphology, on porosity, and on adhesion are studied. The influence of wetting and oxygen dissolution is analyzed. The experimental results show that during High Velocity Oxy-Fuel spraying of the chromium carbide-nickel-chromium powder, the relative mass of chromium oxide in the coating is about 4.95%. The theoretical results agree well with the experimental observations. Paper includes a German-language abstract.

This paper examines WC based coatings with high-alloy binders with regard to their structure, corrosion behavior and wear. The coatings are compared to conventional coatings with respect to corrosion and wear. The coatings were made using HVOF spraying of various powders. All powders examined were produced by agglomeration/sintering, that is by agglomeration of metal particles with WC particles and subsequent sintering. Some powders have been made using pre-alloyed metal particles. The paper also examines a mixture of ceramic-metallic powder and purely metallic powder. Various methods are used to characterize the powders and coatings. Paper includes a German-language abstract.

In this paper, a simple cutting method is used to examine the changes in wear resistance of four thermally sprayed coatings, two yttrium stabilized zirconia, and two aluminum oxides using a heat treatment. These changes were correlated with the changes in the microstructure of the application layers, which were characterized using intrusion porosimetry, scanning electron microscopy, and small-angle neutron scattering. Analysis of the results shows that changes in wear resistance are believed to have been caused by changes in the shape and surface area of the voids caused by sintering as well as crystallographic phase changes. Paper includes a German-language abstract.

In order to be suitable for food processing application, besides having the usual characteristics as high adhesion, high cohesion, high compactness and maximum hardness and wear resistance, the thermal spray coating should not release foreign substances, as prescribed by the international standards. This paper defines a very strict procedure according to valid EC and FDA standards in order to test the compatibility of the coating with the food. It discusses the applicability of this test method, in which a contact is created between a food-simulating solvent and the thermally sprayed coating to be analyzed. The inert nature of the drawn migration cell, the adopted time-temperature conditions and the characterization of the coating before and after the migration test are discussed. Paper includes a German-language abstract.