Self-adjusting EDM/ECM high speed drilling of film cooling holes

In order to reduce the thickness of recast layer and improve the surface quality of film cooling holes, a novel high speed self-adjusting electrical discharge machining (EDM)/ electrochemical machining (ECM) approach was developed by applying two independent flushing systems that were able to switch...

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Bibliographic Details
Published in:Journal of materials processing technology 2018-12, Vol.262, p.95-103
Main Authors: Li, Chaojiang, Zhang, Bowei, Li, Yong, Tong, Hao, Ding, Songlin, Wang, Zhiqiang, Zhao, Lei
Format: Article
Language:English
Subjects:
Casting
Cooling
Cooling rate
Drilling
ECM
EDM
Electric discharge machining
Electrochemical machining
Electrostatic discharges
Energy dispersive X ray spectroscopy
Energy transmission
Film cooling
Film cooling holes
Flushing
High speed
High speed machining
Low voltage
Nickel base alloys
Parameters
Recast layer
Surface properties
Thickness
Working fluids
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Summary:In order to reduce the thickness of recast layer and improve the surface quality of film cooling holes, a novel high speed self-adjusting electrical discharge machining (EDM)/ electrochemical machining (ECM) approach was developed by applying two independent flushing systems that were able to switch automatically in the machining process. The new flushing systems used different work-liquids and online dynamically changing discharge parameters. With the change in gap distance and the depth of the hole drilled, the dominant machining mechanism is graduated changed from EDM to electrochemical discharge machining (ECDM) and ECM. The formation mechanism of the recast layer on nickel alloy was investigated by comparing the surface characters of the bulk material and those of the recast layer using transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy (EDS). The results from comparison experiments, in which different discharge parameters and sustaining time were applied, show that this new flushing systems would ensure much better flushing continuity of the working fluid and improve the discharge gap status. In addition, low voltage and current would benefit the ECM process and the removal of recast layer.
ISSN:0924-0136
1873-4774
DOI:10.1016/j.jmatprotec.2018.06.026