Experimental Study on the Design and Characteristics of a Laminar Plasma Torch With Medium Working Power and its Applications for Surface Hardening

Abstract

Due to its favorable temperature and velocity distributions, a lamina plasma jet, generated by a laminar plasma torch (LPT), is superior to a turbulent plasma jet on some applications. However, most of the reported LPTs usually work at a relatively low output power with a relatively low arc voltage and thermal efficiency, limiting its capability in the applications such as the surface hardening, synthesis of nanoparticles, remanufacturing of large components, and so on. Therefore, this article aims at designing an LPT with medium level output power and a relatively low arc current but a high thermal efficiency. The characteristics and applications of the proposed LPT have been obtained by experiments. The experimental results show the following characteristics: 1) the mean arc voltage of the proposed LPT is higher than 190 V with a maximum working power larger than 25 kW; 2) its mean thermal efficiency and jet length arrive at 50% and 450 mm, respectively; 3) the experimental data of the proposed LPT were used to fit its theoretical characteristics by using the least squares method. According to these fitted curves, the theoretical characteristics of the proposed LPT at a specified working conditions can be predicted; and 4) in addition, the surface of 45# steel was hardened by using the laminar plasma jet to obtain a hardening surface. The maximum hardness of the treated substrate arrives at about 600 HV, which is three times of the untreated substrate.