Investigation on in-flight particle velocity in supersonic plasma spraying

摘要

In-flight particle velocity and flux distribution were measured using CCD thermal spray monitor system during supersonic plasma spray processing with nano-structured Al2O3-TiO2 feed stocks. According to the results of particle flux measurement, the largest radian of the divergent particle stream is about 0.2. Within the measuring range, top speed of in-flight particles reached 800m/s. Particle acceleration was accomplished within 4cm down stream of the nozzle. Average particle velocity （about 450m/s） exceeded local sound speed （340m/s） even at a mean standoff distance of 17cm. With increasing mean standoff distance, average velocity of in-flight particle decreased according to a parabolic rule approximately. Image diagnosis showed that the result of in-flight particle velocity measurement is credible.