Oftentimes, the application of bulk ceramics and ceramic coatings is limited by their poor fracture toughness and low strength. The mechanical properties of ceramics can be significantly improved by the incorporation of fibres, whiskers or particles of high strength, like SiC. Due to the high oxygen content of commercially available SiC fibers in combination with the elevated process temperatures, the SiC decomposes during plasma spraying. Therefore commercial SiC fibres were coated for temporary oxidation protection with C, TiN or Al 2 O 3 . By different agglomeration techniques using an organic binder SiC/Al 2 O 3 composite powders were produced. Powder mixtures consisting of coated fibres and pure alumina as well as agglomerated powders have been successfully sprayed to form deposits. Recent results of the manufacture of SiC fibre-reinforced ceramic composites by plasma spray technology are presented. The properties of the composite coatings are compared to plasma sprayed pure alumina.

Functionally graded materials (FGMs) offer solutions to such engineering problems involving multi-layer systems with large differences in CTE, i.e. thermal barrier coatings, by allowing for a continuous change in the properties over a defined distance, thus minimizing sharp interface effects. By its nature, plasma spraying is well suited to the fabrication of FGMs. However, in order to achieve optimal performance from the material it is necessary to ensure the FGM is uniform in its compositional variation. The deposition efficiency of the particulate species as well as their trajectories will determine the degree of homogeneity of the FGM. It is therefore important that the inter-relationships between the particle size distributions, injection orientation and feed rates are determined. Towards this end, a series of investigations have been carried out to determine the effects of injection orientation on the particle segregation. Analysis of the particle segregation as a function of particle size distribution was then examined in the formation of FGMs. The results indicate that optimal deposition occurs when the various particle species trajectories converge as they approach the substrate.

Thermal spraying of silicon nitride has been considered impossible because the high temperatures involved lead inevitably to decomposition/oxidation of the material. To address these issues, improved silicon nitride-based powders were developed, two of which have been tested as reported in this paper. The powders were applied using low pressure plasma spraying (LPPS) and the resulting coatings characterized based on microhardness, adhesion, and cohesion strength. Phase transformations of the powders during spraying were also investigated and preliminary optimization strategies by statistical variation of plasma spray parameters were tested.

For reasons of the decrease in weight in the industry light cage design materials like aluminum alloys are frequently used. Because the wear resistance of aluminum alloys and/or aluminum generally is not sufficient, an increased wear resistance can be reached by means of particle reinforced aluminum coatings. The installation of ceramic reinforcing components (for example oxide particles) in the ductile metal matrix brings an essential improvement of the wear resistance particularly with regard to abrasion and short time fatigue wear. The results presented in the paper refer to research works concerning thermally sprayed Al - coatings with Al 2 O 3 - and SiC - particles as reinforcement components by vacuum plasma spraying.

The use of aluminum in the automobile engines and other critical parts require a superior surface property of the same. This has led to the development of plasma sprayable surface coatings in the automotive components. To impart the maximum bonding strength, along with hardness to the coatings, an aluminum based composite (Al-SiC) was chosen to be the most suitable. The presence of a hard second phase within a soft matrix improves the wear resistance of the material. The metal matrix composite powders were made by mechanical alloying of 6061 aluminum alloy (particle size 40-60 μm) along with fine SiC particles (≈ 8μm). Content of SiC was varied from 20-75vol% the balance being aluminum alloy. An organic material was used as Process Control Agent to optimize distribution of ceramic within metal matrix. The coatings obtained by plasma spraying the powders were characterized for their microstructure, adherence, wear and other physical properties.

Composite coatings are increasingly applied for the protection against wear in mechanical constructions. Especially, in the case of abrasion these coatings offer the possibility to protect the base material. The matrix is ductile and the reinforcements cause the higher strength and hardness. A research project presented in this paper dealt with the manufacture of carbon-short-fibre-reinforced aluminum composite coatings by vacuum plasma spraying. The basis of the processing is the agglomeration of aluminum powder and carbon fibres. During the spraying process the aluminum melts, covers the fibres, and so, contributes to the creation of the composite coating and/or the composites. The processing times are so short that the damaging formation of carbides can be suppressed mostly. For the creation of free standing bodies it is necessary to find a qualified core material which allows the removing of the sprayed composites. The investigations on the composites are focused on the metallographical judgement regarding the fibre and void content, the fibre distribution, the characterization of the interface as well as the determination of mechanical properties and the wear resistance.

Composite self-lubricating coatings were developed using high-energy plasma spraying (HEPS). These coatings would be potentially used in high contact pressure rolling/sliding systems. The coatings are based on a steel coating deposited by high energy plasma spraying using wire feedstock. Solid lubricants such as graphite and soft metal were investigated. Twin roller rolling/sliding tests were performed at 5% and 35% creep and contact loads of 700 N to 1700 N on a 5 mm contact face. Reduced friction, compared to a steel coating-steel or 1080 wrought steel couple was observed under these rolling-sliding contact conditions.