Measurement and application of arc separability in plasma arc

The authors recently demonstrated that the arc plasma and electron flow in an arc could be separated. This separability provided the foundation to develop an ability to adjust the heat and arc pressure distribution without changing the current. To better understand this property, a novel system was developed based on the split anode. The distribution of the pressure and heat from the separated arc plasma was analyzed quantitatively. It was verified that the arc pressure mainly concentrated in the arc plasma. Also, the heat input from the arc plasma exceeded that from the eletron flow. To explore possible applications of this separability, a novel process, namely, separated plasma transferred arc weld surfacing (SPTAWS) is proposed. Grade D steel workpieces were hardfaced using this process. As the separated electron flow increased, the heat-affected zone (HAZ) of the deposited bead was reduced. The microstructure with SPTAWS was found to be better than with conventional plasma transferred arc weld surfacing (PTAWS), especially in the fine-grain zone. The grain is more refined and uniform.