Effect of the O2 dissociation degree on the rate of anodic evaporation of Al in a low-pressure arc

The results of probe diagnostics and optical emission spectroscopy of Ar-O2 plasma of a low-pressure arc generated under anodic evaporation of Al and an increased (0.32 – 0.48) degree of O2 dissociation are presented. It is shown that an increase in the degree of O2 dissociation at a constant gas flow into the discharge gap leads to a significant (more than 1.5 times) decrease in the density of the evaporated atoms flux and a corresponding decrease in the coating deposition rate. The observed effect is due to the accelerated growth of the oxide film on the melt surface, which leads to the limitation of the flow of evaporated Al atoms by the rate of diffusion through the alumina.