Numerical Simulation of Plasma Jet Characteristics under Very Low-Pressure Plasma Spray Conditions

Plasma spray-physical vapor deposition (PS-PVD) is an emerging technology for the of uniform and large area coatings. As characteristics plasma jet are difficult to measure in whole chamber, computational fluid dynamics (CFD) simulations could predict temperature, velocity pressure fields. However, as PS-PVD generally operated at pressures below 500 Pa, a question rises about validity CFD predictions that based on continuum assumption. This study dealt with system either argon-hydrogen low-power (<50 kW) or argon-helium high-power (≥50 kW). The effect net arc power chamber local gradient Knudsen number (Kn) was systematically investigated. Kn found be lower than 0.2, except region corresponding first expansion shock wave. peak value this decreased rapidly increase width pressure. Based results study, introduced detecting conditions where approach valid under time reasonably used determine process parameter window study.