The characteristics of cathode spots in removing oxide layer on metal surface by vacuum arc

Vacuum arc descaling technique mainly utilizes the high energy density property and the selective motion property of cathode spots. Cathode spots play a vital role in removing the oxide layer on metal surface. In this paper, the characteristics of cathode spots during the descaling process are investigated experimentally. Experiments are conducted in a vacuum chamber with a protect argon gas pressure of 10Pa. The vacuum arc circuit and the electrode gap distance are set to 200A and 10mm, respectively. The images of cathode spots during the descaling process are photographed by a high speed digital camera with an exposure time of 2μs. Experiment results indicate that during the descaling process, cathode spots exhibits some particular characteristics. One of the most representative characteristics is the contract motion of cathode spots during the descaling process. Cathode spots initially form on the rim of the cathode surface with oxide layer, then they moves gradually towards the center of the cathode in a contract manner. The photos of the cathode surface after descaling are also analyzed.