Design of a plasma spray torch of elongating arc and the arc voltage tests on it

A plasma spray torch of elongating the arc was designed in order to overcome the shortcomings that the reliability and reproducibility of plasma sprayed coatings are imperfect in the traditional plasma spray process. The torch can bring higher arc voltage with lower fluctuation by elongating the arc. The problems of insulation and sealing of the two anodes, which are water-cooled together, are successively solved. A practical structure in the engineering was presented which greatly improves the capability of the plasma torch. The results of the tests show that the arc voltage fluctuation amplitude (peak-to-peak) represents almost 10% of the mean level. 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.