The influence of electrical discharge machining (EDM) on thermal barrier coating (TBC) in a two-step drilling of nickel-based superalloy has been studied. The TBC was coated on the superalloy using electron beam physical vapor deposition (EB-PVD). Simulation result shows that the temperature at TBC/metal interface increases with pulse-on time and peak current. The temperature will exceed the melting point of the coating material when using relatively large pulse energy. Experimental result reveals that large pulse-on time or high peak current caused defect such as cracking at coating sidewall and delamination at the TBC/metal interface. For EDM drilling holes with inclined angle, the leading edge had worse condition of debris evacuation, and consequently caused secondary discharge which resulted in melt and spalling of the coating material. In addition, relatively larger pulse-on time and greater peak current might result in greater thermal stress gradient at the interface and subsequently lead to cracking or spalling at the coating layer. Therefore, process conditions of short pulse-on time, longer pulse-off time, and small peak current are recommended for EDM drilling of the EB-PVD coated nickel-based superalloy.

研究了镍基高温合金两步钻孔中电火花加工（EDM）对热障涂层（TBC）的影响。使用电子束物理气相沉积（EB-PVD）将TBC涂覆在高温合金上。仿真结果表明，TBC /金属界面温度随脉冲接通时间和峰值电流的增加而升高。当使用相对较大的脉冲能量时，温度将超过涂层材料的熔点。实验结果表明，较大的脉冲接通时间或较高的峰值电流会导致缺陷，例如涂层侧壁开裂和TBC /金属界面分层。对于具有倾斜角度的EDM钻孔，前缘的碎屑排出条件更差，因此导致二次放电，从而导致涂料熔化和剥落。此外，相对较大的脉冲接通时间和较大的峰值电流可能会导致界面处的热应力梯度变大，从而导致涂层破裂或剥落。因此，对于EB-PVD涂层镍基高温合金的EDM钻孔，建议使用短脉冲接通时间，较长脉冲断开时间和较小峰值电流的工艺条件。