大型钛合金薄壁回转体零件精密对转电解加工基础研究

Counter-rotating electrochemical machining (CRECM) is a new ECM method, in which a revolving cathode tool is typically used to rotate relative to the anode workpiece at the same rotational speed. The materials can be removed gradually and evenly during the counter rotating motion of the electrodes. Compared with the existing processing technology, this method has its unique advantages for the machining of thin-walled revolving parts with complex surface such as the aero-engine casings，and has important application value. In CRECM, as the current density for a specific point on the anode workpiece is in a low-frequency and low-duty-cycle pulse state, the anodic dissolution of titanium alloy becomes unusual, which will affect the machined surface quality. In addition, the surface of convex structure will suffer serious stray corrosion during the counter rotating process, leading to a poor machining accuracy. In order to improve the surface quality and machining accuracy, the anodic dissolution behavior of titanium alloy and the stray corrosion process in CRECM will be intensively investigated. The electrochemical dissolution mechanism of titanium alloy under the low-frequency and low-duty-cycle pulse will be revealed, and the control mechanism for surface quality during the CRECM process of titanium alloy will be mastered. The dynamic distribution characteristic of the electric field and the stray corrosion process on the surface of convex structure will be clarified. A high-potential auxiliary anode will be used to regularize the electric field distribution, and thereby reduce the stray corrosion on the surface of convex structure. The study in this project will significantly improve the surface quality and machining accuracy of titanium alloy thin-walled revolving part, and lay the foundation for the rapid promotion of CRECM technology for titanium alloy.

对转电解加工采用回转体工具电极，通过工件与工具同步对转方式实现材料的逐渐均匀蚀除，对于机匣等复杂型面薄壁回转体零件加工有着独特的优势，具有重要的应用价值。在钛合金回转体零件对转电解加工中，由于工件运动，使得阳极特定点处于低频、低占空比脉冲加工状态，会导致钛合金溶解行为异常，影响加工表面质量；阳极凸台表面在对转过程中又会受到严重杂散腐蚀，导致凸台成型精度差。为提高钛合金对转电解加工表面质量和凸台成型精度，本项目将深入开展钛合金材料在对转过程中的电化学溶解特性及凸台表面杂散腐蚀过程研究，揭示低频、低占空比脉冲下钛合金电化学溶解机理，掌握钛合金对转电解加工表面质量控制机制，明晰电场动态分布特性及凸台杂散腐蚀特点，并提出高电位辅助阳极电场调控方法，实现凸台表面杂散腐蚀的有效抑制。本项目研究将显著提高钛合金薄壁回转体零件对转电解加工的表面质量和成型精度，为钛合金对转电解加工技术的迅速推广奠定基础。

机匣是典型的大型薄壁回转体零件，是航空发动机的核心部件，普遍存在加工变形严重、壁厚精度差等制造难题。对转式（也称旋印）电解加工通过工件与工具的同步对转实现材料逐层溶解，对于薄壁回转体的变形和壁厚控制具有原理上优势。然而，在钛合金旋印电解加工中，阳极溶解处于低频、低占空比脉冲加工状态，存在异常溶解现象，加工表面质量差；阳极凸台表面存在严重杂散腐蚀，凸台成型精度有待提升。本项目通过深入系统的研究，揭示了钛合金在低频、低占空比脉冲下的电化学溶解机理，提出辅助电极电场调控方法消除了点蚀现象，显著提升了加工表面质量；建立回转体表面电场分布等效模型和电化学溶解数学模型，掌握了非稳态间隙演变规律和凸台轮廓演变规律；通过施加辅助电极和非金属层屏蔽等创新方法，有效抑制了凸台表面的杂散腐蚀，显著提升了凸台成形精度；揭示了间隙内流场动态演变规律，提出复杂变间隙内电解液流场调控策略，保证了加工过程的稳定性；研制出国内外首台具有自主知识产权的大型薄壁机匣旋印电解加工试验系统，实现了钛合金薄壁机匣样件的高效精密加工。本项目研究显著提升了钛合金薄壁回转体零件的表面质量和成型精度，为新型高推重比航空发动机的研制提供重要的技术支撑。