Design Of The Double-anode Plasma Spray Torch And Tests On It

A double-anode plasma spray torch is designed in this paper because the reliability and reproducibility of plasma sprayed coatings are imperfect and several kinds of gases have to be used in the traditional plasma spray process. The torch can solve these problems by elongating the arc. Comprehensive tests about the torch are carried out.In the paper, the structure and the design idea of the torch are thoroughly stated. The problems of insulation and sealing of the two anodes, which are water-cooled together, are successively solved, and a practical structure in the engineering is presented which greatly improve the capability of the plasma torch.The results of the tests show that the static characteristics of the arc climb up obviously, which illuminate that the gas in the arc is well ionized and the ampere density is high. The arc voltage fluctuation amplitude (peak-to-peak) represents less than 10% of the mean level, which is markedly small compared with the traditional torch. The Fourier transition of the arc voltage waveforms shows that the fluctuation of them is mainly attributed to the fluctuation of power supply, while the motion of arc root has little effect on them. When pure Ar is used as arc gas, the enthalpy of the torch is higher than that of the traditional one. The values of the audio pression behind the torch, with a distance of 90cm, is lower than 105dB. In the frequency domain, the sound signal characteristics is broad band and a maximum peak occurs at the same frequency (about 4-6kHz).The FeCrBSi coatings with higher quality can be obtained by using the double-anode spray torch with a small power (9.8kw). By using pure Ar as arc gas, the torch can spray AlaOa coatings, but the current used here could be lower than that used by traditional torch.