Low vacuum enhanced expansion of a supersonic arc plasma plume

A novel expansion and super long plasma plume at low vacuum conditions (200 Pa–10000 Pa) has been developed to deposit the ceramic thermal barrier coating (TBC) for aircraft engines. The maximum length of the Ar–He plasma plume is 1900 mm when the plasma torch operates at a chamber pressure of 200 Pa and an input power of 64 kW (I = 2000 A). Meanwhile, the radial expansion of the plasma plume is 90 mm in an axisymmetric plane at the same condition. The maximum substrate temperature ranges from 1100 °C to 1250 °C when the plasma plume impinges perpendicularly on the graphite substrate at the distance from 800 mm to 1500 mm. It is also found that the Mach number of the plasma flow is 3.4. The numerical simulation predicts the maximum velocity and temperature of the plasma plume are 6474.8 m/s and 12823.7 K, respectively.