High-efficiency electrical arc machining of tantalum–tungsten alloy: Mechanism, microstructural evolution, and surface modification for precision finishing

Abstract

Tantalum–tungsten (Ta–W) alloys are widely used in extreme environments due to their exceptional thermal stability, mechanical strength, and corrosion resistance. However, their high hardness and melting point make them extremely difficult to machine. To overcome the limitations of traditional mechanical—which often suffer from low efficiency and poor process stability—this study pioneers the application of high-efficiency electrical arc machining (EAM) to the rough machining and surface modification of Ta–W alloys. A coupled thermo-mechanical model is developed to correlate discharge energy with the depth of the heat-affected zone (HAZ), grain size evolution, and surface hardness degradation. Real-time arc dynamics are captured via high-speed imaging, and microstructural transformations are systematically analyzed using electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and nanoindentation techniques, revealing evident recrystallization, grain coarsening, and thermal softening. Experimental results show that under 30 V, a maximum material removal rate (MRR) of 11,869.88 mm³ /min is achieved, while the relative electrode wear ratio (REWR) is reduced to 1.86 %. Meanwhile, the surface hardness in the HAZ decreases by over 60 %, dropping from 2.4–2.9 GPa in the base material to 0.84 GPa. Friction and wear testing further indicate that the arc-modified surface exhibits improved machinability, providing a favorable foundation for subsequent precision processing.