A particle image velocimetry investigation of in-flight and deposition behaviour of steel droplets during electric arc sprayforming

Gas and Fe–0.8 wt.% C droplet dynamics during electric arc spraying have been characterised using particle image velocimetry (PIV). This study has shown that the flow of N2 atomising gas was well-collimated, with an exit velocity of 255 m s−1, decaying to 75 m s−1 at an axial distance of 150 mm, where the jet diameter was ∼50 mm. The presence of atomised steel droplets increased spray divergence. Droplet mode velocity measurements equalled the gas-only velocity measurement of ∼120 m s−1 at an axial distance of 95 mm, and then further increased to 135 m s−1 at 150 mm. Close to the substrate, droplet splashing dominated the flow field with upward and then lateral flow of splashed droplets. In the presence of a vertical step feature, the flow field became complex, with some splash droplets having trajectories that caused secondary deposition on the vertical step wall.