Low-temperature electrochemical machining of titanium alloys: A universal approach for phase-uniform dissolution and improved surface integrity

Abstract

Titanium alloys have become indispensable materials in the aerospace engine industry owing to their superior mechanical properties. Aerospace engines operate under extreme conditions, placing stringent demands on the surface integrity of titanium alloys. Although electrochemical machining (ECM) offers numerous advantages for machining difficult-to-cut materials, challenges remain, such as inconsistent dissolution rates of the α and β phases and unsatisfactory surface quality during titanium alloy machining. This study presents a novel low-temperature ECM approach that achieves unparalleled phase uniformity and surface integrity in aqueous electrolyte solutions, while providing insights into the underlying mechanism. Notable phenomena and key technical breakthroughs are as follows: First, low temperatures reverse the contact potential difference between the α and β phases on the TA15 alloy surface, effectively mitigating galvanic corrosion and promoting uniform nanoscale dissolution of the α and β phases. Second, under low-temperature conditions, the passive film has been demonstrated to exhibit instability and insufficient corrosion resistance, leading to its faster removal during ECM. Furthermore, low-temperature ECM has been proved to be universal, consistently achieving surface roughness values between Sa 0.23 μm and Sa 0.36 μm across various titanium alloys and different ECM processes. These values are significantly lower than the surface roughness values of Sa 1.32 μm to Sa 4.81 μm obtained in high-temperature ECM. The low-temperature ECM method effectively overcomes the challenges associated with surface quality and integrity in the ECM of titanium alloys, thereby enhancing the performance of aerospace engine components and making it a promising technique in the aerospace industry.