Towards a Complete Model of DC Plasma Spray Process

DC Plasma spraying of metals and ceramics is extensively used in many industries, especially in aerospace industry.  This is a common method employed for protection of components exposed to challenging environments. 

The plasma coating process has three distinct regions: a) plasma torch where an arc is struck between a cathode and anode; b) plasma jet region where powders are injected into the jet; and, c) substrate region where molten, semi-molten, and solid particles impinge on it to form a protective coating. In order to predict the microstructure of the coating, all these three regions have to be modelled.  This seminar presents the different challenges and the state-of-the-art in modelling these three regions.

Modelling of flow, temperature, and electromagnetic fields within the torch is inherently 3-dimensional, turbulent and, because of the arc-root movement, time-dependent. In this part, it is proposed to employ the measured voltage fluctuations of the arc and develop a realistic 3-D model of the different fluctuating fields within the torch.

Plasma jet fluctuations predicted at the torch exit will be considered in the second region and the effect of such fluctuations on particle heating and acceleration history will be discussed.  

Once the state of particles at the substrate is known, deposition of the droplets will be presented. Impact of the drops on surfaces is inherently 3-dimensional, time dependent and involves solidification. Results of the impact which are based  on the volume-of-fluid (VOF) method as well as smooth-particle hydrodynamics (SPH) will be discussed.