Mechanism analysation and parameter optimisation of electro discharge machining of titanium-zirconium-molybdenum alloy

Titanium-zirconium-molybdenum (TZM) alloy is one of the most widely used molybdenum based high temperature alloys which is difficult-to-machine even for the non-traditional process. Throughout this research, a special phenomenon was disclosed and the material removal mechanism of TZM in EDM was studied based on single discharge experiments and FEM methods. When machining TZM with EDM, the crater diameter is much smaller than the plasma affected region, especially in the case of small discharge current. The single discharge experiment result showed that the crater size increases with the rising of the peak current but insensitive to the pulse duration when the discharge current is small. The reason that causes this phenomena is analyzed by analyzing the current density distribution along with plasma radius and considering the influence of TZM's special thermal physical properties, such as high melting point and good thermal conductivity. Additionally, a single discharge thermal erosion simulation based on time integration effect (TIE) method was conducted to support the explanation above as well as to investigate the temperature distribution on the workpiece. According to the results of the mechanism analyzation, difference machining characteristics and effects were presented for ED-machining of TZM material. In order to improve the machining performance, the Box-Behnken method was implemented to optimize the parameters. Last, a TZM hot-gas valve with complex internal flow channels was machined as a means to verify the findings of this research.