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 alpha-beta titanium Ti-6A1-4V, 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 similar to 4 to 11 Rm with thicker and rougher layers evident when using positive toot 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 similar to 200 and 1100HK(0.025) compared to the bulk material similar to 365HK(0.025). Glow discharge optical emission spectroscopy showed that the percentage of copper transferred from the solid electrodes to the workpiece was up to similar to 29 at %, while for the powder compact electrodes the level was significantly higher, with the 32 MPa pressed pellets giving similar to 78 at % at the surface. (C) 2007 Elsevier B.V. All rights reserved.