Improving profile accuracy and surface quality of blisk by electrochemical machining with a micro inter-electrode gap

Abstract

Electrochemical machining (ECM) has emerged as an important option for manufacturing the blisk. The inter-electrode gap (IEG) distribution is an essential parameter for the blisk precise shaping process in ECM, as it affects the process stability, profile accuracy and surface quality. Larger IEG leads to a poor localization effect and has an adverse influence on the machining accuracy and surface quality of blisk. To achieve micro-IEG (<50 μm) blisk finishing machining, this work puts forward a novel variable-parameters blisk ECM strategy based on the synchronous coupling mode of micro-vibration amplitude and small pulse duration. The modelling and simulation of the blisk micro-IEG machining have been carried out. Exploratory experiments of variable-parameters blisk ECM were carried out. The results illustrated that the IEG width reduced with the progress of variable parameter process. The IEG width of the blade’s concave part and convex part could be successfully controlled to within 30 μm and 21 μm, respectively. The profile deviation for the blade’s concave surface and convex surface are 49 μm and 35 μm, while the surface roughness reaches Ra = 0.149 μm and Ra = 0.196 μm, respectively. The profile accuracy of the blisk leading/trailing edges was limited to within 91 μm. Compared with the currently-established process, the profile accuracy of the blade’s concave and convex profiles was improved by 50.5 % and 53.3 %, respectively. The surface quality was improved by 53.2 % and 50.9 %, respectively. Additionally, the machined surface was covered with small corrosion pits and weak attacks of the grain boundary due to selective dissolution. Some electrolytic products were dispersed on the machined surface, and their components were mainly composed of the carbide and oxide products of Ti and Nb elements. The results indicate that the variable-parameters strategy is effective for achieving a tiny IEG in blisk ECM, which can be used in engineering practice.