Arc sawing of nickel based superalloys in aqueous electrolytes

Abstract Arc sawing (AS) is a non-conventional machining process that utilises an arc to melt and vaporise workpiece material. A low voltage, high current supply is employed to produce a continuous arc in either an electrolyte or in air. Machinability is enhanced with highly conductive electrolytes, such as sodium silicate. The paper details AS machinability work on Inconel 718 and compares the performance of four aqueous electrolytes, namely sodium silicate, sodium chloride, potassium chloride and sodium sulphate in submerged cutting. Conductivity levels ranging from 14 870 to 24 020 μS/cm are investigated. Data presented includes material removal rate (MRR), kerf width and power consumption. Workpiece surface integrity analysis includes surface roughness (Ra) results and subsurface microstructural information from sectioned, mounted and polished samples together with microhardness data. The heat affected zone for all the electrolytes was typically 40–70 μm deep. The use of sodium silicate electrolyte produced the highest MRR of 7.051 cm 2 /min at the lowest power consumption of 2.625 kW and the lowest tool wear ratio of 6.2 : 1. When using sodium chloride, workpiece surface roughness ranged from 5.44 to 12.53 μm perpendicular to the lay.