A study of electrodischarge machining–pulse electrochemical machining combined machining for holes with high surface quality on superalloy

Ning Ma,Mingqian Gao,Ganlin Liu,Wenji Xu,Xiaolong Yang,Jinlong Song

doi:10.1177/1687814015618630

Abstract

Noncircular holes on the surface of turbine rotor blades are usually machined by electrodischarge machining. A recast layer containing numerous micropores and microcracks is easily generated during the electrodischarge machining process due to the rapid heating and cooling effects, which restrict the wide applications of noncircular holes in aerospace and aircraft industries. Owing to the outstanding advantages of pulse electrochemical machining, electrodischarge machining–pulse electrochemical machining combined technique is provided to improve the overall quality of electrodischarge machining-drilled holes. The influence of pulse electrochemical machining processing parameters on the surface roughness and the influence of the electrodischarge machining–pulse electrochemical machining method on the surface quality and accuracy of holes have been studied experimentally. The results indicate that the pulse electrochemical machining processing time for complete removal of the recast layer decreases with the increase in the pulse electrochemical machining current. The low pulse electrochemical machining current results in uneven dissolution of the recast layer, while the higher pulse electrochemical machining current induces relatively homogeneous dissolution. The surface roughness is reduced from 4.277 to 0.299 µm, and the hole taper induced by top-down electrodischarge machining process was reduced from 1.04° to 0.17° after pulse electrochemical machining. On account of the advantages of electrodischarge machining and the pulse electrochemical machining, the electrodischarge machining–pulse electrochemical machining combined technique could be applied for machining noncircular holes with high shape accuracy and surface quality.

Highlights

Under the effect of high temperature and load, the performance and reliability of turbine rotor blades are directly related to the performance, durability, reliability, and life of aero engines.[1]
It can be seen that inner-wall surface of the hole is rough and many micropores exist after electrodischarge machining (EDM) processing, while the inner-wall surface becomes smooth after Pulse electrochemical machining (PECM)
EDM-PECM combined machining technique was applied for machining noncircular holes on the superalloy, which is widely used in aero engine but difficult to process

Summary

Introduction

Under the effect of high temperature and load, the performance and reliability of turbine rotor blades are directly related to the performance, durability, reliability, and life of aero engines.[1]. Based on the advantages of ECM and the disadvantages of recast layer caused by EDM, EDM-ECM combined technology could be applied in machining holes or special-shaped microholes on high-strength parts.[10,11,12,13,14] For instance, Chung et al.[11] and Nguyen et al.[12] successfully machined microholes with high surface quality by EDM process using the low-resistivity deionized water as the dielectric fluid.

Results

Conclusion