Effects of plasma-related input parameters on fluctuation and coating characteristics in APS – Towards a transdisciplinary integration of technical assessments and human knowledge-driven evaluations

Atmospheric plasma spraying (APS) is characterized by complex interactions between input, process and output variables. The selection of input parameters relies heavily on human expert knowledge. Therefore, knowledge concepts and relations were assessed to provide support for the multiple-criteria decision task. When using non-cascaded torch systems, significant plasma fluctuations occur and affect coating quality. High-frequency fluctuations can only be detected by suitable diagnostic systems and interpreted by experienced APS operators. In this study, the state of the plasma plume (area, length, fluctuation) is investigated depending on total flow rate (50 vs. 65 l/min) and the H₂ content of plasma gases (17, 20 and 23 vol.-%) using high-speed camera pictures. To evaluate plasma fluctuation effects, particle temperature and velocity as well as resulting coating properties (porosity, hardness, sliding wear resistance) are determined for two ceramic systems). Results show that total flow rate and the H₂ content influence plasma fluctuation and melting state of particles resulting in varying coating properties.