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ABSTRACT
Vacuum Are Spraying (VAS) represents a promising method to deposit highly pure, dense and corrosion resistant coatings of reactive materials such as titanium or tantalum. Following an introduction to the problems of vacuum arc spraying, stability criteria for the process will be examined. Moreover, a theoretical description of the arc phenomena will be undertaken. This model allows the calculation of arc length in dependence on pressure, voltage and the kind of atomizing gas, The results obtained from these calculations enable the development of a new vacuum arc spraying gun which allows stable operation down to chamber pressure of 85 hPa. The influence of two main process parameters, chamber pressure and spray distance, on the structure of titanium coatings will be examined. Moreover, roughness, hardness and gas content measurements of the titanium coatings gave information about the coating built up conditions. Optimized titanium coatings revealed no open porosity and a good corrosion resistance to HNO3 and H2SO4 Furthermore, a new concept for vacuum arc spraying with a single wire will also be introduced.