July/August_AMP_Digital

iTSSe TSS A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U L Y / A U G U S T 2 0 2 0 5 9 iTSSe TSS small particle size, high velocity, and low temperature. While two-color optical pyrometers, one-color cameras, and spec- troscopic techniques have been widely used in thermal spray processes, the low particle temperatures in CS do not permit use of these tools. Recent preliminary work offers the fundamentals of a novel technique to measure CS particle temperature using a high-speed infrared camera [24] . Successful results were ob- tained for large spherical titanium particles traveling at 200 m/s at the exit of a CS nozzle. A high-speed mid-wave in- frared camera was used along with a real-time calibration technique. As shown in Fig. 6, particles exiting the CGDS noz- zle were successfully identified and their low temperature de- tected. Work is currently underway to extend the technology to smaller and faster particles that would allow in-line particle temperature monitoring. The CS process involves low particle temperatures— compared to other thermal spray processes—leading to a solid-state deposition process. Nevertheless, increasing and controlling particle impact temperature seems to be beneficial for process performance and coating properties, and process parameters can be optimized to maximize these benefits. The (a) (b) Fig. 6 — Particle in-flight temperature detection after spray nozzle exit using high-speed infrared camera. (a) Experimental set-up and (b) experimental particle temperature data. FEATURE 9