Effects of discharge status in AE-EDM of 8YSZ ceramic

Thermal-barrier-coated superalloys (TBCs) is generally used to make hot-end components such as aero-engine blade, because of its excellent thermal insulation and thermal shock resistance. The film cooling hole technology is applied on blade made of TBCs, which can further improve the service life and performance of aero-engine. However, it is difficult to realise one-step machining with traditional cutting techniques due to the high brittleness of TBCs. Electrical discharge machining (EDM) can not only machine any conductive materials, but also realise the machining of insulating materials. However, the properties of insulating ceramic materials are different with that of conductive materials. Existing discharge status detection mechanisms cannot effectively identify the EDM discharge status of insulating ceramic coating. Hence, in this study, discharge status of 8 mol.% Y2O3-stabilized zirconium (8YSZ) ceramic coating is investigated via assisting electrode method. Experiments with single-factor are carried out to investigate the effects of discharge status on gap erosion characteristics of 8YSZ ceramic with different peak current and pulse duration. The experiments result showed that discharge statuses of 8YSZ ceramic coating were dominated by low resistance discharge rate and high resistance discharge rate, the total discharge rate varied with low resistance discharge rate. Adjusting discharge gap with servo reference voltage, the total discharge rate increased with increasing low resistance discharge rate.