In-Flight particle measurements of twin wire electric arc sprayed aluminum

A real-time, nonintrusive measurement technique was successfully applied to a Tafa Model 9000 (TAFA Incorporated, Concord, NH) twin wire electric arc thermal spray system to simultaneously measure particle size, velocity, and temperature within the spray plume. Aluminum wire was sprayed with the current varied from 100 to 300 amp, and the gun pressure (air flowrate) varied from 40 to 75 psia. For all cases, the average sizes of the molten aluminum particles along the spray centerline range from 33 to 53 mm. The particles accelerate to peak velocities between 130 and 190 m/s, then decelerate slightly as they travel downstream. The average centerline particle temperature ranges from 2004 to 2056 °C, and the temperature profile remains fairly flat throughout transport to the substrate. A stagnation pressure probe was used to quantify the gas flow regime in the unladen jet. The wires were found to have a pronounced effect on the flow, resulting in a complex three-dimensional flowfield with mixed regions of subsonic and supersonic flow.