Anodic dissolution behavior and microstructure preparation of nickel based superalloy in cryogenic-shielded and laser-assisted electrochemical machining

Abstract

Leading and trailing edges are critical components of blisks, requiring not only high profile accuracy but also “four-zero” processing—free of recast layers, heat-affected zones, micro-cracks, and stray corrosion. The high-precision “shape coordination” manufacturing of these edges has garnered significant attention in the industry. In order to achieve high quality machining of the leading and trailing edges while mitigating stray current corrosion on non-machined surfaces, an innovative cryogenic-shielded and laser-assisted electrochemical machining (CS-LA-ECM) process was proposed for the first time. First, the anodic dissolution mechanism of the CS-LA-ECM process was analyzed using open-circuit potential, potentiodynamic polarization, potentiostatic polarization, and electrochemical impedance spectroscopy. The tests revealed pronounced active, passive, and transpassive behaviors of GH4049 in the CS-LA-ECM process. The passive film formed in the CS-LA-ECM process was richer in Al₂O₃, MoO₃, Fe^2 +/Fe³⁺ ratio, and lacked NiO and MoO₂, indicating a compact structure that enhances corrosion resistance and reduces stray corrosion. Multi-physical field modeling and simulation of the CS-LA-ECM process were conducted to examine the effects of cryogenic shielding and laser-assisted on the machining characteristics. Exploratory experiments demonstrated the successful fabrication of high quality leading and trailing edges on the GH4049 workpieces using the CS-LA-ECM process. Surface analysis showed improvements of 68.3 % in profile accuracy, 15.9 % in surface roughness, and a 81.2 % reduction in stray corrosion compared to conventional ECM process. The results confirm that the CS-LA-ECM process significantly reduces stray corrosion while ensuring high quality machining of leading and trailing edges, making it a promising technique for precision manufacturing in the aerospace industry.