The Particle In-Flight Characteristics in Plasma Spraying Process Measured by Phase Doppler Anemometry (PDA)

Abstract

Detailed measurements of particle in-flight characteristics have been carried out using a PDA system for benchmarking as well as to provide further information to aid the development of simulation models. The parameters studied included four conditions of primary gas flow rate and carrier gas flow rate. The particle velocities, diameters, and the corresponding volume flux at different locations were obtained. Due to the one port particle injection arrangement, it was noted that particles in general sprayed with an angle (η), deviated from the nozzle axis Z n , to the opposite side of the powder feeder port. The particles would also deviate from the spraying cone axis with a divergence angle (φ). The deviation and divergence angles were examined under different plasma spraying conditions. The measurement data rates at different cross-sectional planes were also obtained so as to compare the results derived from the volume flux measurement and the actual coating on a substrate at the equivalent standoff distance. It was found that the spraying area obtained from the measurement-data-rate increased with downstream distance and a linear relationship between spraying area and distance was also established. Comparing the integrated results, it was noted that the spraying areas derived from the measurement data rate were close to the actual spraying areas obtained from the coordinate measurement machine (CMM) results.

Correlation of Plasma Sprayed Coating Deposition Efficiency with Volume Flux Measurements by Phase Doppler Anemometry (PDA)

“…3a The effective measuring volume of the PDA used was dx = 0.202 mm, dy = 0.092 mm and dz = 0.092 mm. This was the same used by Ma et al [15,16] respectively. The PDA transmitter and receiver probes were mounted on a computer controlled 3-D traversing rig.…”

“…The PDA measurement volume was put under the orifice of the atomizer at a standoff distance of 10 mm, where the sprayed water droplets should assume perfect spherical shape due to the surface tension effect. NiCrAlY and YSZ powders were plasma sprayed under their respective common operation conditions in which a coating with acceptable DE could be produced according to our previous experience [15][16][17], i.e., power current (A), power voltage (V) and powder feeder rate were maintained at 622 A, 317 V and 0.54 · 10EÀ3 Kg/s respectively. The PDA measurement volume was located at the standoff distance of 80 mm from the exit of the plasma torch and on the mean trajectory of the particle plume for the two kinds of powders, where the possibility that particles could be melted was higher.…”

“…In the plasma spray process, the ratio c = v/u was typically lower than five percent [16]. The nearer the measurement point was to the centerline of the plasma torch, the smaller the particle movement trajectory biases from the main flow direction.…”

“…It is only in recent years that the PDA technique was utilized in characterizing the plasma sprayed melted particles [14], and the literature addressing the usage of PDA in the plasma spraying conditions are indeed rare [15,16]. Moreover, PDA seems to have some advantages in measuring the plasma sprayed particles since the powder materials employed for plasma spraying are mostly opaque.…”

Effect of in-flight particle characteristics on the coating properties of atmospheric plasma-sprayed 8mol% Y2O3–ZrO2 electrolyte coating studying by artificial neural networks

“…Although knowledge of mechanisms occurring during plasma spray operation made some very significant progresses over the past years [17,18], the traditional experimental design method is time-consuming. ANN can appear as a pertinent technique for fast optimization compared for example to designs of experiments.…”