Dependency of the pulse dynamic electrochemical machining characteristics of Allvac 718 plus in NaNO3 solution on the machining paraments

Abstract

Pulse dynamic electrochemical machining (PDECM) is an innovative electrochemical machining technique that significantly enhances machining precision. It is considered a promising method for manufacturing the blisks of next-generation aircraft engines. Allvac 718 Plus (ATI718 Plus), a new generation nickel-based superalloy, is an essential material for these blisks due to its exceptional performance under high-temperature and high-pressure conditions. This study aims to investigate the electrochemical dissolution characteristics of ATI718 Plus under various PDECM parameters. Potentiodynamic polarization experiments revealed that ATI718 Plus exhibits a complex dissolution behavior characterized by distinct passivation and transpassivation stages. Electrochemical impedance spectroscopy (EIS) further confirmed the superior protective capabilities of the oxide film, suggesting it has a bilayer structure with an outer porous layer and an inner dense layer. X-ray photoelectron spectroscopy (XPS) analysis validated this hypothesis by accurately identifying the proportions of various metal oxides within the film. Subsequently, PDECM experiments were conducted on ATI718 Plus under different duty cycles, vibration frequencies, and applied voltages. The relationships between these processing parameters and the machining quality of ATI718 Plus were explored by examining the post-processing microstructure, surface roughness, material dissolution rate, and machining precision. Finally, an ATI718 Plus blade was machined using the optimized parameters, achieving a residual deviation of 0.065 mm and a surface roughness of 0.373 μm, meeting the design requirements of the blade.