Muti-angle Characterization Methods and Damage Mechanism of Single Crystal Superalloy Caused by EDM Drilling

This paper studies the damage behavior of various process parameters of electrical discharge machining (EDM) drilling processes on the new-generation single crystal superalloys, through 25 orthogonal experiments with the changes of processing current, pulse width and pulse interval. The effect of different damage caused by drilling was characterized by laser confocal microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter (EBSD) and other characterization methods. The results show that the machining current has the most significant effect on the roughness of hole wall and the thickness of remelted layer, followed by the pulse width and the weakest effect of pulse interval. Based on the test results, a multi-angle evaluation methods of gas film pore damage were formed to perform the characterization in the aspects of roundness, taper, hole inner wall roughness, hole inner wall morphology, remelted layer thickness distribution, remelted layer microstructure, remelted layer composition, etc. The thickness and formation process of the remelted layer was evaluated by the method of orthogonal calculation at multiple locations, extreme difference of multiple measurements, and the area method. Finally, the damage mechanism of advanced single crystal superalloy by EDM drilling was proposed.