Surface conditions and vacuum breakdown characteristics of titanium electrodes lathed by different cutting tool bits and treated by chemical polishing method

In this paper, we investigated the vacuum breakdown characteristics for some kinds of Ti electrodes which have different surface conditions. We focus on the influence of machining by the use of different tool bit, such as a cemented carbide tool bit and a cubic Boron Nitride (cBN) tool bit when the electrodes are manufactured with a lathing machine. Moreover we investigated the influence of the chemical polishing (CP) using the mixed liquid of nitric acid and hydrofluoric acid on the breakdown characteristics. Surface conditions of the electrodes are investigated by an optical microscope. We report on the comparison of the electrical breakdown characteristics of these processed Ti electrodes and treated with chemical polishing. Additionally we treated some of them with vacuum heat treatment at 200 degree centigrade and made the experiments on them. In these experimental results, it is found that chemical polishing to titanium electrode surface is effective in increasing first breakdown fields and earlier saturation of conditioning. But saturated breakdown fields were almost same value for those of the electrodes which are machined the cemented carbide tool bit and CBN tool bit. Additional vacuum heat treatment showed certainly better effects on them.