In this investigation, titanium layers with different titanium nitride phases are deposited via reactive gas plasma spraying using a statistical design-of-experiments approach to determine the effect of process parameters on coating properties. The layers are characterized by various means, showing how nitrogen concentration in the plasma gas, spraying pressure, and substrate temperature correspond with coating hardness, porosity, and nitriding levels. The values of all layer properties were found to increase with increasing nitrogen content in either the plasma gas or spraying atmosphere. Paper includes a German-language abstract.

Plasma spraying is known to be one of the main promising processes for the manufacturing of Ti/SiC long fiber composites. However, some improvements remain to be done for this process to be applied in a routine industrial route. These include: oxygen contamination of the sprayed material through that of Ti particles before and during spraying damaging of fibers due to a high level of thermal stresses induced at the spraying stage adequate deposition of Ti-based powder to achieve a low-porosity matrix and good impregnation of the fiber array. This contribution deals with work in the 3 previously mentioned fields, which resulted in a whole 3-fold study of the process. Oxidation was studied using electron microprobe analysis of elementary particles quenched and trapped into a closed box at various given flight distances. Oxygen diffusion phenomena within the particles are discussed from a preliminary theoretical approach coupled with experimental data. Isothermal and thermo-mechanical calculations were made using ABAQUS code to determine stresses arising from contact of a liquid Ti-6Al-4V particle onto a SiC fiber. On a higher scale, i.e. that of the sprayed powder flow, a 2-dimensional original model simulating the deposition of droplets onto a substrate was developed. This model is based on a lattice-gas automaton which reproduces the hydrodynamical behavior of fluids.

A concurrent fibre winding and low pressure plasma spraying (LPPS) process has been developed to manufacture multiple fibre reinforced titanium matrix composite (TMC) rings in a single spraying operation. Optimisation of the LPPS parameters has been successively performed for two different sizes of Ti-6Al-4V powders by experimental design and statistical analysis, which provided minimum porosity and surface roughness for both powders. The most important LPPS parameters affecting porosity and surface roughness of deposits were Ar gas flow rate and chamber pressure. During TMC manufacture, the coarse Ti-6Al-4V powder spraying provided enhanced infiltration between fibres but caused degradation of fibre tensile strength, as well as a rough ring surface. The fine Ti-6Al-4V powder gave no significant degradation of fibre strength and a relatively smooth ring surface. Four-ply SiC fibre reinforced TMCs manufactured by the spray-wind process have also been evaluated in terms of porosity, fibre distribution and fibre damage.

In this investigation reactive plasma spraying was used to produce wear resistant coatings of Ti-carbides/titanium or Ti-nitrides/titanium composites. Ti-powders with different powder size distributions were used as raw materials. Methane and nitrogen were used as reactive gases to form carbides and nitrides. A reactor was adapted to the plasma gun F4 of a Sulzer Metco vacuum plasma spraying equipment to increase the degree of the expected reactions. Phase analysis and micrography of the coatings reveal that the Ti-hardphases were synthesized during spraying and embedded in the titanium matrix. The in situ synthesized hardphases show different forms and sizes. Most of them are non-stoichiometry. Compared to the titanium coating the coatings produced by reactive plasma spraying are much harder and more resistant against both sliding and abrasive wear.