An Investigation to Achieve Good Surface Integrity in Wire Electrical Discharge Machining of Ti-6242 Super Alloy

The aim of this study is to investigate the effect of cutting parameters such as pulse-on time (T-on), servo-voltage (U), feed rate (S) and flushing pressure (P) on surface roughness (Ra) when machining Ti-6242 super alloy by WEDM process. The cutting was performed using a brass tool electrode and deionized water as a dielectric fluid. To optimize cutting parameters for surface roughness improvement, Taguchi's signal-to-noise ratio (S/N) approach was applied using L-9 (3 boolean AND 4) orthogonal array and Lower-The-Better (LTB) criteria. Substantially, the findings from current investigation suggest the application of the values 0.9 mu s, 100 V, 29 mm/min, and 60 bar for the cutting parameters T-on, U, S and p, respectively, for producing a good surface finish quality. Electron microscope scanning (SEM) observations have been performed on machined surface for a wide range of cutting parameters to characterize wire EDMed surface of Ti-6242. SEM micrographs indicated that white layer and machining-induced damage characteristics are highly dependent on cutting parameters. For high servo-voltage, decreasing the pulse-on time T-on and feed rate S leads to a strong decrease in the overall machining-induced surface damage. Furthermore, for high levels of servo-voltage and feed rate, it was observed that pulse-on time could play a role in controlling the density of surface microcracks. In fact, the use of low cutting pulse-on time combined with high servo-voltage and feed rate was found to inhibit surface microcracks formation, giving the material surface better resistance to cracking than with high pulse on-time.