When plasma spraying operations require high throughput, three-cathode guns may be specified due to their stationary plasma jet and elevated power characteristics, higher feeding rates, and adequate deposition efficiencies compared to one-cathode guns. A new three-anode gun system has been introduced to the market that offers a combination of high power inputs into the plasma as well as stable process conditions. These new guns feature a narrower nozzle outlet diameter compared to multi-cathode designs and they can be used with hydrogen as secondary plasma gas. Both of these characteristics result in higher plasma velocities and net powers. The conceptional designs for two such guns are discussed as well as their suitability for suspension and shrouded plasma spraying.

Up to now no coating systems are marketable in the field of direct hot extrusion, which provide both surface protection of the parts being in contact to the billet (i.e. container and die), and a significant reduction of the frictional losses being induced by the billet passing along the container walls. To dispense the use of lubricants and to enhance the usable forming capacity of the process, different oxide ceramics were given in one suspension and plasma sprayed. The aim is to reach a mixing of the feedstock to obtain deterministic solid solutions of the oxide phases which show a reduction of their coefficient of friction under dry sliding conditions. To reach this goal the high surface-to-volume ratio of feedstock with primary particle sizes below 100 nm was used. By means of X-ray diffraction it could be proven, that the desired phases could be synthesized. The coatings showed a considerable lowering of their frictional coefficient in tribological testings against 100Cr6 in the region of the operation temperatures for the hot extrusion of aluminium alloys. Besides the experimental work the fundamentals of the mixing process of different oxides regarding crystallographic aspects are discussed.

In this study, suspension plasma spraying is used to produce self-lubricating titanium oxide coatings. Certain nonstoichiometric titanium oxide phases, called Magneli phases, exhibit a reduction in friction under dry sliding conditions at elevated temperatures. These phases, however, tend to undergo crystal changes during thermal spraying, resulting in the loss of their good friction behavior. In this work, the goal is to stabilize these phases with suitable lattice substitutions for Ti 4+ . The resulting phases are shown to be homologous to Ti n O 2 n -1 , but have the advantages of a three-component system, making them more thermally stable with a broader area of formation.

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 Sulzer Metco Triplex II gun marks a new generation of three cathode plasma guns. In opposition to conventional single cathode guns, it features a stationary plasma jet. Liquid precursors, wire- and powder shaped spray materials were processed with a modified Triplex II gun under controlled atmosphere and characteristics of the obtained coatings were investigated. A new shroud system was developed to handle susceptible to oxidation and reactive materials such as Ti and B 4 C. A conception of a wire conveyance system enables the handling of three wires of titanium simultaneously. Furthermore a liquid spray material feed system, for the generation of Al 2 O 3 -coating with low porosity based on nanoparticle suspensions, was developed and built. All coatings, which were manufactured by the different procedures, are characterized comprehensively by means of optical microscopy (OM) including interactive image analysis, scanning electron microscopy (SEM) with attached electron dispersive X-ray analysis (EDX) system, X-ray diffraction (XRD) and microhardness.

This presentation gives an overview of a research project of the Institute of Materials Science at the University of Hannover (Germany) focussed on under water plasma spraying (UPS). The aim of this project is to qualify the process for the application of corrosion protective coatings. UPS could be used for maintenance of underwater constructions. Another field of application can be seen in an alternative for atmospheric plasma spraying (APS) in coating shops. Water is an excellent filter for noise and UV radiation. Furthermore, particle polluted water could quite easily be refined so that UPS could show environmental advantages compared to APS. The UPS process is characterized by a low standoff distance and therefore a small plasma spot. A very promising modification of the standard UPS process, which is examined in this project, is shrouded underwater plasma spraying (S-UPS). By adding the shroud to the underwater plasma spray device a large defined cavity could be build up so that spray distances comparable to APS are possible. By variation of the shroud gas in terms of air or inert gas it is possible to reach comparable or even better coating properties then using an APS process.