Applications of Quasi-Steady Magneto-Plasma-Dynamic Arcjets to Ceramic Coatings

Abstract

For applications of quasi-steady magneto-plasma-dynamic (MPD) arcjets to material processing, an MPD arcjet with a cathode covered with ceramic materials was developed. In 100-shot operations at 5-10 kA, the ablation rates of the ceramic covers ranged from 2.5 to 5.0 mg/shot. The front velocities of ablated Al atoms inferred with a streak camera were much higher than velocities of 200-500 m/s for conventional plasma torches for material processing. This is effective for deposition of rigid films adhering strongly to substrate surfaces. The SEM photographs showed that a dense uniform film was deposited near the center of the substrate. From the XPS spectra, the peak area ratio of Ti/Al for the coating film almost equaled that for the cross section, and the valence numbers of Al and Ti did not change.