Numerical analysis of direct-current (DC) plasma processing for high efficient steel surface modification

Abstract Nowadays, direct-current (dc) non-transferred arc plasma torch has drawn significant interest from both academia and industry due to the capability to process products in an efficient and convenient way. The core of this technology is to clarify and manipulate the arc behavior at the interior of the torch and produces ideal plasma jets for processing. To solve this problem, a quasi-steady axisymmetric model is built to simulate and compare the arc characteristics in different operating conditions and different nozzle structures. The results uncover distinct aspects of the study on arc characteristics, including the detection of the region of primary arc attachment, the effect of changing operating conditions, and the choking effect caused by torch structure. The thermal efficiency focused on processing substrate is also calculated in this paper. The results show that increasing mass flow rate brings better thermal efficiency, whereas improving the arc current value causes the opposite result. Meanwhile, two types of nozzle are discussed by thermal efficiency, and the wide nozzle is chosen for torch optimization due to its high power efficiency. The secondary arc attachment on the metal substrate is discovered, but its effect on the processing could be ignored for the extremely low electric current value.