ZHANG  Quancai¹, WAN  Hong², ZENG  Fanzheng³, GONG  Jinyu⁴, CAI  Hao⁵, LI  Song⁶

(1. National University of Defense Technology, Changsha 410073, Hunan, China; 2. The 93986 Army, Hotan 848000, Xinjiang, China)

Abstract: The ablative resistance of electrode materials is an important factor affecting the switch stability and service life. In order to improve the ablative performance of graphite electrode, in-situ HfC gradient coating was prepared by using gas permeation method. By means of thermodynamic calculation, preparation of gradient coating and breakdown test, the formation mechanism of HfC coating, preparation technology and ablative performance of the permeable Hf graphite electrode were studied. It was demonstrated that, in the process of graphite permeating Hf, hafnium chloride gas was formed due to the reaction of Hf and NHCl4 at high temperatures, which served as the main substance reacting with graphite to form HfC. By adjusting the initial ratio of the raw materials and controlling the preparation temperature and pressure, about 200 μm permeation layer was formed on the graphite electrode through the in-situ reaction. At breakdown voltage of 24 kV, the jitter of graphite electrode switch was reduced and the ablative performance was enhanced after the surface coating of HfC. Therefore, the stability of the switch was enhanced and the service life of the switch was prolonged.

Key words: graphite; electrode switch; HfC gradient coating