激光增材-铣削减材应力耦合机制及其对再制造压缩机叶片服役寿命影响

The hybrid manufacturing technology integrating laser additive process and milling subtractive process is an important approach to achieve the remanufacturing of centrifugal compressor blades. At present, it lacks of systematic research on the influence of damage constraint boundary on the residual stress and microstructure of laser additive layer, the coupling interaction mechanism of milling stress and laser additive stress, and its impact on the service life of the remanufactured blade. To this end, the combining method of additive and subtractive tests, theoretical analysis, numerical and simulation calculation will be used in this project. Firstly, mapping relations among constraint boundary, microstructure, as well as residual stress will be established based on stress evolution model of laser additive forming and alloy melted dynamics model. Then, the coupling interaction mechanism of milling stress and laser additive stress will be revealed. Based on this, the active control technology theory of stress will also be proposed. After this, the influence mechanism of microstructure evolution and stress of cutting layer on the fatigue strength of the remanufactured blade will be elucidated. Finally, the process parameters database of damage blade remanufacturing based on laser additive technology- milling subtractive combining technology will be established. By conducting the research work of this project, key scientific issues of blade remanufacture using laser additive and milling subtractive technology will be systematically solved. The outcome of this research will significantly promote the remanufacturing level not only for the compressor blade but also for the mechanical equipment industry.

激光增材-铣削减材复合加工技术是实现离心式压缩机叶片再制造的重要手段。目前尚缺乏损伤约束边界对激光增材成形层残余应力及微/宏观组织结构等性能影响、铣削减材应力与激光增材初始应力耦合作用机制及其对再制造叶片服役性能影响等的研究。为此，使用增/减材试验、理论分析及数值/仿真计算相结合的方法开展研究。首先，基于激光增材成形应力演变模型及合金熔凝动力学模型建立约束边界-成形层微观结构-残余应力分布之间的映射关系；其次，揭示激光增材-铣削减材应力耦合作用机理，提出基于应力耦合机制的激光增材成形层应力主动控制工艺理论；再次，阐明微观组织演变及加工应力影响层对再制造叶片疲劳强度的影响机理；最后，建立基于激光增材-铣削减材复合技术的损伤叶片再制造工艺参数数据库。通过本项目研究解决激光增材-铣削减材技术应用于压缩机叶片再制造中存在的关键科学问题，对于提升我国压缩机叶轮及机械装备再制造水平具有重要科学意义。

本课题提出基于铣削减材的激光增材成形层应力主动控制方法。残余应力对激光增材成形层裂纹敏感性、疲劳强度等有显著影响。目前激光增材成形残余应力控制主要通过优化激光工艺参数、改善膨胀系数等物理力学性能、改善元素组成等手段，本课题提出基于铣削减材的激光增材成形层应力主动控制工艺方法，通过铣削减材加工主动控制激光增材成形层近表层应力状态，实现成形层性能及生产效率兼顾。此外，考虑到激光在增材过程中穿透性和热能衰退特性建立精确热源模型，建立了考虑大温度梯度下材料非均匀性热胀冷缩及塑性热应力的非线性瞬态激光增材仿真模型；研究获得了不同输入功率及不同的功率输入方式对激光增材熔池峰值温度影响及成形件残余应力分布、最大残余应力影响规律；研究获得了扫描路径、扫描速度、扫描时间间隔等对激光增材热循环、温度梯度及最大残余应力的影响规律；通过霍普金森压杆试验建立了典型增材成形材料的J-C本构模型及修正J-C本构模型；建立了典型增材成形材料的铣削减材加工有限元模型，揭示了激光增材与铣削减材的应力耦合机理。基于铣削减材的激光增材成形层应力主动控制方法的研究价值在于从传统控制方法之外入手，使用必要的铣削减材加工来主动控制增材成形层应力，实现性能与效率兼顾。由于大量热输入激光增材成形层一般为残余拉应力，铣削减材在加工表面产生机械载荷和热载荷，引入的应力状态因加工工艺而异，因此揭示激光增材初始应力与铣削减材加工应力耦合作用机理，通过铣削减材改善增材成形层近表层残余应力状态，对实现基于铣削减材的增减材复合制造应力主动控制具有重要科学意义。