热障涂层冲蚀后的电火花制孔试验研究

Experimental Study of Drilling Holes Using EDM after Erosion of Thermal Barrier Coatings

电火花加工方法不能直接加工涂覆了热障涂层的高温合金构件。先利用磨料水射流冲蚀去除高温合金表面的热障涂层,形成涂层孔型,再利用电火花加工方法进行金属基体的微小孔加工。涂层孔型底部的金属基体裸露率对后续电火花加工可行性有重要影响。结果表明:电火花加工可行性与金属基体裸露率、残余涂层材料厚度均有很大的关联;在残余涂层材料与金属表面高度差小于理想放电间隙的情况下,金属裸露面积的增加使电火花放电面积和单位时间内的放电能量均增加,可蚀除或剥落更多的残余涂层材料,有助于电火花加工顺利进行;在特定电火花加工条件下,保证金属裸露率达到一定的阈值是实现磨料水射流与电火花组合制孔的必要条件。

Electrical-discharge(EDM)drilling cannot directly be applied to metallic parts coated with ceramics.This study presented a combined process which applies abrasive water jet to drill a blind hole as first stage and followed by using EDM to drill in metallic part.The metal exposure rate in bottom of the eroded blind hole may markedly influence the feasibility of consequential EDM drilling.The results shows that the EDM feasibility is relevant to metal exposure rate and height of residual coating.Increasing metal exposure rate results in increases of discharge area and discharge energy for a certain period of time,and subsequently results in an increase of removal of residual coatings which is helpful to continuous EDM machining.The experiment also revealed that it is necessary to let metal exposure rate to reach a threshold to ensure the EDM feasibility.