Understanding multi-arc plasma spraying

Multi-arc plasma spraying systems promises several advantages in comparison to the conventional single-arc systems. However, some of the underlying fundamentals of the multi-arc plasma spraying are still poorly understood. Intensive numerical research which has been conducted to identify the fundamentals of conventional single-arc plasma spraying has not been applied to multi-arc plasma spraying process yet. A comprehensive numerical research to understand the behavior of the plasma columns in the plasma torch as well as that of powder particles in the plasma jet in multi-arc plasma spraying were the subjects of this thesis. In this study, the focus was set to the influence of relevant numerical aspects and model assumptions on the numerical results. The models which are necessary to analyze the plasma and particle behavior in multi-arc spraying systems have been subjected to intensive verification with respect to the underlying model assumptions and numerical aspects. Subsequently, the prediction powers of the models have been evaluated by comparing the results of the developed models with the results of advanced diagnostic systems. General characteristics of plasma columns within and outside of the spraying system as well as particle behaviors in the plasma jet have been analyzed using developed numerical models. Furthermore, the possible application areas of the developed models have been introduced exemplarily. Good accuracy of the models regarding the predicted plasma jet characteristics and particle temperatures and velocities is evident. Due to the stable behavior of the plasma columns, modeling of multi-arc spraying systems promises accurate description of the process and a high predicting power allowing a successful deployment of the developed models with the purpose of designing and optimization of process and injection parameters.