Use of powder metallurgy (PM) compacted electrodes for electrical discharge surface alloying/modification of Ti–6Al–4V alloy

Following a brief summary of the electrical discharge surface alloying process and key publications, the paper details experimental results when alloying α–β titanium Ti–6Al–4V, using both solid and powder compacted copper electrodes with a commercial water-based dielectric fluid. At the discharge energies employed, recast layer thickness varied from ∼4 to 11 μm with thicker and rougher layers evident when using positive tool electrode polarity. All layers were in general discontinuous, however those produced with negative polarity were more uniform, especially when using solid electrodes. The hardness of the recast varied between ∼200 and 1100HK0.025 compared to the bulk material ∼365HK0.025. Glow discharge optical emission spectroscopy showed that the percentage of copper transferred from the solid electrodes to the workpiece was up to ∼29 at%, while for the powder compact electrodes the level was significantly higher, with the 32 MPa pressed pellets giving ∼78 at% at the surface.