Temperature Measurements of In-flight Particles in Suspension Plasma Spray

Suspension plasma spray (SPS) is currently going through a transition phase from research and development to daily use on the production floor. Further efficient operation of the SPS process depends on improvement of its repeatability and reproducibility. This objective can be achieved by using a diagnostic system to monitor and control key parameters that influence the coating microstructure. Among those parameters, temperature of the in-flight particles is one of the most critical. However, the small size of the sprayed particles and the radiation from the plasma do represent a significant challenge. In this study, a two-color pyrometric method was used to measure the temperature of the in-flight particles. The precision of the measurement was improved by reducing the effect of plasma radiation via proper filtering of undesirable wavelengths. The particle temperature was measured under different SPS conditions to assess the accuracy of the measurement with the new approach.