On the Response of Different Particle State Sensors to Deliberate Process Variations

Abstract

Deliberate particle state variations were performed using atmospheric plasma spray (APS) and high-velocity oxy-fuel flame spraying (HVOF) to create a set of first-order process maps. Particle states were measured simultaneously using five in-flight particle sensors: DPV-2000, Accuraspray, SprayWatch, TDS, and SprayCam. While the sensors use similar methods for calculating particle characteristics, absolute values of temperature and velocity were considerably different. Process map trends among sensors are in agreement for the HVOF process, but differ when using plasma spray at high total gas flow conditions. After understanding the stochastic nature of particle detection, an open loop feedback control algorithm was implemented to achieve similar particle states with different hydrogen gas flow rates. The resulting particle state window measured by three different sensors under select fixed hydrogen flow rates was significantly narrowed.

Electrochemical Behavior, Microstructure, and Surface Chemistry of Thermal-Sprayed Stainless-Steel Coatings

“…Accuraspray uses cross-correlation of the particles' signals obtained at two different points spaced by a known distance (2% accuracy). The readers are referred to [19][20][21] for further details on the applications and limitations of these devices. Particle temperatures and velocities were determined at the same stand-off distances at which the substrates were positioned in front of the spray torches.…”

On the dielectric strengths of atmospheric plasma sprayed Al2O3, Y2O3, ZrO2–7% Y2O3 and (Ba,Sr)TiO3 coatings

“…This suggests that some particles could be in semi-molten state or might have started resolidifying due the longer flight time. Further, the Accuraspray-g3 system averages particle data on the whole measurement volume to one single representing value hence, the results derived from accuraspray diagnostics are typically 10-12 % lower than the actual average temperature and velocity values of the particles in the plasma plume [11].…”

Structurally Integrated, Damage-Tolerant, Thermal Spray Coatings

“…As noted earlier, with the advent of optical sensors, it is now feasible to quantify particle temperatures and velocities in real time during spraying. 12 This has allowed both experimental exploration of the process parameters and its effects on particle properties, and it has ensured a high degree of process repeatability and reproducibility. The use of these sensors also enables establishing first-order process maps for TS, where the direct effect of feedstock material, torch hardware, and operating conditions on the spray stream can be visualized.…”