Determination of local deposition efficiency based on in-flight particle diagnostics in plasma spraying

Abstract

Increasing the deposition efficiency (DE) and consequently reducing the manufacturing costs has been always one of the central goals in thermal spraying. Hence, the effect of modifying various spraying parameters on DE has been widely investigated in the literature. However, there has not been a methodology so far to correlate the in-flight particle properties with their DE on the substrate locally. In this study, a method is developed to determine the local deposition efficiency (LDE) of the plasma spraying process based on optical particle diagnostics of the in-flight particles. To this end, the entire free-jet transverse section is divided into several non-overlapping focal planes and the size and velocity of the particles are measured at these focal planes. Furthermore, the in-flight particle temperatures are captured in a measurement grid normal to the gun axis. The experiments are conducted with alumina spray powder and a three-cathode plasma gun. The LDE is calculated based on the spatial distribution of the in-flight particle mass flow rate (PMFR) and the local deposited mass on the substrate. Subsequently, the interdependencies between the in-flight particle properties and the calculated LDE are investigated using a nonlinear regression model.