THE METHOD OF LASER-SUSTAINED ARC IGNITION

The method of laser-assisted vacuum arc deposition (laser-arc) was developed to effectively produce high-quality coatings, especially multilayer coatings with a reduced number of droplets. The efficiency of this method depends mainly on the ignition probability of the vacuum arc discharges. In the present work, the process of arc initiation by laser irradiation is studied and the influencing factors such as power density of laser irradiation, target material, and electrode configuration are discussed. It is shown that a high ignition probability (p > 50%) on such coating materials at Ti, TiC, TiN, and C can be guaranteed with a laser power density of about 108 W/cm2, which can be achieved with a low-cost Nd-YAG pulse laser. Measurements of the plasma current preceding the arc ignition and microscopic investigations of the erosion pattern caused by the laser irradiation suggest that the process of plasma-sustained arc ignition (unipolar arcing) plays an important role during the buildup phase of the vacuum arc discharge.