Plasma Spray Process Modeling for Control: Effect of Torch Inputs on Particle State Distribution

The plasma spray process for depositing thermal barrier coatings is characterized by large variations in particle states that result in corresponding variations of coating microstructure and properties. This paper will deal with process modeling for plasma spray, focusing on the relation between the particle state distributions and torch inputs. The model includes three separate modules: a torch module that maps torch inputs into plasma jet characteristics; a plasma jet module, that models the thermal and momentum development of the jet in atmospheric conditions; and a particle module that predicts the trajectory and thermal history of the particle, including effects of particle phase transitions, collapse of in-flight hollow particles, and internal temperature gradients.   Results will show how critical measures of the distributions of the molten ensemble (volume flux, velocity, centroid) are affected by variations in the torch inputs; implications for implementing measurement and control of particle states will also be discussed.