Machining of a film-cooling hole in a single-crystal superalloy by high-speed electrochemical discharge drilling

Single-crystal superalloys are typical advanced materials used for manufacturing aero- engine turbine blades. Their unique characteristics of high hardness and strength make them exceedingly difficult to machine. However, a key structure of a turbine blade, the film-cooling hole, needs to be machine...

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Bibliographic Details
Published in:Chinese journal of aeronautics 2016-04, Vol.29 (2), p.560-570
Main Authors: Zhang, Yan, Xu, Zhengyang, Zhu, Yun, Zhu, Di
Format: Article
Language:English
Subjects:
Aerospace engines
Drilling
Electrical discharge machining (EDM)
Electrochemical machining (ECM)
Electrodes
Film-cooling hole
High speed
Hybrid technique
Machining
Single crystal
Single crystals
Superalloys
Taguchi methods
Turbine blades
冷却孔
加工效率
合金薄膜
放电
电化学加工
航空发动机
钻井工艺
镍基单晶高温合金
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Summary:Single-crystal superalloys are typical advanced materials used for manufacturing aero- engine turbine blades. Their unique characteristics of high hardness and strength make them exceedingly difficult to machine. However, a key structure of a turbine blade, the film-cooling hole, needs to be machined in a single-crystal superalloy; such machining is challenging, especially considering the increasing levels of machining efficiency and quality demanded by the aeroengine industry. Tube electrode high-speed electrochemical discharge drilling （TSECDD）, a hybrid technique of high-speed electrical discharge drilling and electrochemical machining, provides high machining efficiency and accuracy, as well as eliminating the recast layer. In this study, TSECDD is used to machine a film-cooling hole in a nickel-based single-crystal superalloy （DD6）. The Tagu- chi methods of experiment are used to optimise the machining parameters. Experimental results show that TSECDD can effectively drill the film-cooling hole; the optimum parameters that give the best performance are as follows： pulse duration： 12μs, pulse interval： 30 gs, peak current： 6 A, and salt solution conductivity： 3 mS/cm. Finally, a hole is machined by TSECDD, and the results are compared with those obtained by electrical discharge machining. TSECDD is found to be promising for improving the surface quality and eliminating the recast layer.
ISSN:1000-9361
DOI:10.1016/j.cja.2015.06.021