Productivity and Workpiece Surface Integrity When WEDM Aerospace Alloys Using Coated Wires

Following a brief review of recent minimum damage EDM pulse generator developments, experimental data is presented for workpiece productivity & integrity when WEDM Udimet 720 nickel based superalloy and Ti-6Al-2Sn-4Zr-6Mo titanium alloy, using Cu core coated wires (ZnCu50 and Zn rich brass). Up to a 70% increase in productivity was possible compared to when using uncoated brass wires with the same operating parameters. Surfaces measuring ∼ 0.6 μm Ra, with near neutral residual stresses and almost zero recast were produced following two trim passes. Cross-sectional micrographs of specimens following rough machining (∼180mm2/min) showed the recast to be < 7 μm thick (up to 11 μm for uncoated wire), with comparable results for both alloys. Surface cracking, when evident, was restricted to within the recast layer.