New requirements for modern component part surfaces increasingly demand improvements over friction coefficients in the sense of a reduction of friction losses. A substantial control factor in terms of lower friction and wear is the use of coating solutions such as thermal spray coatings. In practice, the application of coatings by means of thermal spray is more and more often used for influencing tribological matching. However, surface microstructuring might represent an additional, further reaching solution for wear and friction behaviour improvements of tribologically high-stressed surfaces. The aim of the reported research project is the development of atmospheric plasma sprayed (APS) coatings with an inherent porous microstructure and surfaces with stochastically distributed nap volumes (from cut pores) regarding lubricant retention and -distribution in running surfaces of friction-type bearings. Subject of these investigations are in particular thermomechanically highly loaded hydrodynamic tribological matchings, amongst others by the example of a piston ring/cylinder system in engine blocks. The use of special fractioned Fe-base powders enables the production of a new type of coatings with an inherent porous microstructure, which offer advantages due to constantly regenerating their surface topology under wear, and maintain employment in tribological systems with increased loads due to optimized lubricant retention and distribution. Hence, this project has an emphasis on the design of optimal nap sizes in coating surface structure in dependence on the hydrodynamical load, as well as on investigations for the controllability of nap volumes by the design of suitable processes.

Thermal spraying for joining and filling of aluminum substrates under atmospheric conditions represents an enrichment in soldering technology. In a respective process, rod-, wire- or cored wire type, zinc-aluminum-based spray materials are applied for joining components or area filling of substrate and fused simultaneously. The advantages, in contrast to soldering, result from the direct application of the spray material, in particular also in constraint positions, and an uncomplex processing, which enables a conditioned inline capability and the use as a comparatively simple procedure for construction-site services or repairs. The aluminum substrate surface and spray material passivation, which would prevent a successful fusing, can be effectively suppressed by the use of a flux in the cored wires as well as straight on the substrates or a brushing activation.

The Goal of this research project is the development of a thermal spray technique for production of layers with high SiC content. Due to its physicochemical characteristics, silicon carbide (SiC) is a material which is particularly well suited as a component of wear-protection layers [1]. In thermal spray, however, silicon carbide can not be processed easily, since it disintegrates and sublimates into the gaseous phase at the prevailing high process temperatures under atmospheric conditions. In this project, SiC-phases of the spray layers are to be in-situ synthesized from silicon and carbon-containing substances during the spray process. Silicon containing solids are to be brought into reaction with carbon-containing solids, liquids and gases. For economic reasons, this technique is aimed at using low-priced basic materials to be processed by flame- and plasma spraying techniques with only slight modifications to existing atmospheric spraying equipment; thus the said SiC coatings might become an alternative to assigned hard material coatings. In this first step the technologic-mechanical potential and thus the feasibility and usability of a yet to develop coating system by different synthesis routes should be evaluated.

Modern thermal spray processes require wide use of diagnostics to gather an extensive process understanding. Today's diagnostic results provide the basis for future designs and advancements, particularly and increasingly on basis of computational approaches. Due to the measuring area in the square centimeter range and its quick and accurate results, the Particle Image Velocimetry (PIV) represents an enriching for thermal spray process diagnostics. Our experimental results obtained from PIV are in accordance to present theoretical and empirical derivations of some kinematic parameters of thermal spray processes. Beneath verification of well-known dominant parameters (for example powder fraction or carrier gas mass flow), this procedure enables the detection and characterization of ancillary influences on the process due to its high accuracy. By statistical analysis of our experiments, using multiple parameter variations per experiment according to the technique of "Design of Experiments" (DoE), we possibly found some hints on interactions between ancillary parameters which shall be analysed in further works carefully. In combination with detailed simulations on plasma - particle interactions and powder injection it should be possible to develop methods for thermal spray processes to minimize the particle flow expansion for an optimization of deposition rate and energy efficiency in the future.