带热障涂层叶片气膜孔激光电解组合微细加工新方法及工艺优化模型研究

Thermal barrier coated turbine blade film cooling holes in the aviation engine are important air cooling channels under conditions of high temperature and high pressure. The machining quality of the holes directly determines the service life and stability of turbine blade. They are micro-structure devices and are difficult to be machined. The micro-machining method has become a hot research topic at home and abroad. The defects such as recast layer and micro-cracks in the existing special micro-machining like laser machining are aimed. A new technology of combined micro-machining of laser and electrolysis of thermal barrier coated turbine blade film cooling holes is researched in this project. Only one single presetting cutter is needed from the machining of film cooling hole to its final shape. First of all, nanosecond ultraviolet laser beams passing through the inner hole of tubular electrode directly focus on the surface of workpiece in the electrolyte. The photochemical effect is generated by the multiphoton absorption, and micro-holes on the thermal barrier coatings are milled. Moreover, micro-holes on the nickel based alloy blade are etched by high frequency pulse electrochemical machining. The methods such as small clearance machining (5μm-15μm), side wall insulating tubular electrode and low density compound electrolyte are used in the machining. Thereby, thermal barrier coated turbine blade film cooling holes without recast layer are achieved by the cold machining. At the same time process parameters of combined machining are optimized. It will provide an effective method and approach for micro-machining of thermal barrier coated turbine blade film cooling holes with high quality, high precision and high efficiency. It have important research significance and application prospect.

航空发动机中带热障涂层涡轮叶片气膜孔是高温高压条件下的重要气冷通道，加工质量直接关系到叶片的使用寿命和稳定性，成为难加工微结构器件，其微细加工方法已经成为国内外研究的热点。针对现有激光等特种微细加工存在的再铸层、微裂纹等缺陷，本项目提出带热障涂层叶片气膜孔激光电解组合微细加工新方法，从气膜孔加工到最终成型采用一次对刀，先采用纳秒紫外激光束通过管状电极内孔，在电解液中直接聚焦于工件表面，通过“多光子吸收”产生光化学作用铣削热障涂层微孔；再采用高频脉冲电解加工，通过小间隙加工（5μm-15μm）、侧壁绝缘管状电极以及低浓度酸性电解液等方法刻蚀镍基合金叶片微孔，实现无再铸层带热障涂层叶片气膜孔的冷加工；同时对组合加工工艺参数进行优化。为带热障涂层涡轮叶片气膜孔的高质量高精度高效率微细加工提供一个有效的方法和途经，具有重要的研究意义和应用前景。

项目以航空发动机中对带热障涂层叶片气膜孔的微细加工为研究目标，研究带热障涂层叶片气膜孔激光电解组合微细加工新方法。针对现有激光等特种微细加工存在的再铸层、微裂纹等缺陷。首先，提出电解液射流辅助激光微细加工技术，该技术可以降低再铸层厚度、减少微裂纹数量、消除热影响区高度集中现象；其次，对于激光加工再铸层和电解加工效率低等问题，提出电解液辅助激光加工，进行带涂层合金微孔无再铸层的冷加工；再次，对于电解液辅助激光加工涂层材料微小孔加工技术的不足，进行了激光-电解组合加工技术的初步探索研究、并在此基础上对激光-电解组合加工带热障涂层叶片气膜冷却孔深微孔的加工进行了进一步的研究，验证了组合加工方法的可行性和有效性；最后，对于激光电解加工过程中试验加工参数影响因素很多，且因素之间有交互影响，在电解液辅助激光加工技术研究上，建立了基于响应曲面法的加工工艺回归模型以及基于改进蚁群算法的工艺优化模型，优化工艺参数并实验验证，高效地找出最优实验方案。对于电解加工为解决实际加工中试验次数多、生产成本高、选取加工参数困难等问题，采用改进的动量-自适应学习BP算法构建了BP神经网络预测模型。.在本项目执行期间（2017-2020年），我们认真按照计划任务书开展工作。经过群体成员四年的共同努力,我们在带热障涂层叶片气膜孔激光电解组合微细加工方法、加工数学模型、工艺优化算法和关键技术的一些重要方面取得了实质性的进展，获得了一些有意义的成果，在一些著名的国际刊物和国际会议上发表了一系列论文。深入开展基于激光电解组合微细加工带热障涂层叶片气膜孔的研究，具有重要的研究意义和工程应用价值，将进一步丰富带热障涂层叶片气膜冷却孔高质量高精度高效率的微孔微细加工方法，为激光电解组合加工方法对带热障涂层材料微孔加工的实际应用打下坚实的基础。