Selected diagnostic methods for the plasmaspray process

Thermal spray is a widespread technology in order to modify surfaces by applying various types of coatings. Due to the diverse possibilities and the strong turnover in this industrial branch, plasma spray is utilised not only in SME's but also in large companies. Research activities in this field concentrate on assuring or improving the quality and on reducing the costs. One important step in order to improve the coatings with regard to these aspects was the introduction of the process-accompanying control using diagnostic systems. These consider a few important parameters which were identified by means of previous research with, in part, very complicated and cost-intensive systems. A few of these diagnostic systems which are necessary for parameter identification are introduced in this paper. In this respect, the entire spray system is investigated by means of spectroscopic investigations on the free plasma jet, the analysis of shadow images for particle characterisation and the investigation of the coatings using a new profilometer. In addition to the significance of the individual diagnostic systems, it is shown how the measurements portray the overall process.