增材制造构件表面激光抛光基础理论和关键技术研究

The surface quality of additive manufacturing based selective laser melting technology (SLM) is difficult to meet the application requirements of assembly, friction and surface roughness, while the traditional polishing technology cannot adapt to the needs of high efficiency, high freedom, no pollution, etc., in SLM forming complex structures. Therefore, the implementation of the research on the theory and key technology of laser polishing on the SLM formed surface is an effective way to solve the problems of weak basic theory and lack of key technologies in this field. To address this concern, this project performs a series of theoretical investigations based on simulation modeling and process explorations based on AM experiments. Firstly, a multi-measurement and multi-level morphological characterization system is established for the SLM surface features, and a parametrically mathematical model for surface topographic feature is constructed. Furthermore, a precise laser heat source model for SLM surface topography and typical material properties is established, and a molten pool dynamics model of laser polishing process is formed to reveal the laser polishing mechanism. Finally, a laser-polishing overall shape prediction model is constructed to approach a process optimization method that comprehensively considers the surface topography and physical and mechanical properties. The successful implementation of this project can systematically solve the scientific problems involved in the laser polishing process for the surface features of SLM forming parts, and also lay a good theoretical and technological foundation for the further application of laser polishing in the field of additive manufacturing.

基于SLM技术的增材制造成形表面质量难以满足具有装配、摩擦或表面粗糙度等功能要求的应用，而传统的抛光技术无法满足SLM成形零件的复杂结构对高效率、高自由度、无污染等的要求。因此，开展SLM成形表面激光抛光理论与关键技术研究，是解决目前该领域基础理论薄弱、关键技术匮乏等难题的有效途径。为此本项目开展一系列基于仿真建模的理论研究和基于成形实验的工艺探索工作。首先面向SLM成形表面特点形成多测度、多层级形貌表征体系，构建表面形貌特征参量化数学模型。其次，建立面向SLM表面形貌特征与典型材料属性的精准激光热源模型，进而建立激光抛光过程的熔池动力学模型，揭示激光抛光机理。最后构建激光抛光整体形貌预测模型，形成综合考虑表面形貌特征和物理力学性能的工艺优化方法。通过项目研究，系统解决面向SLM成形零件表面特征的激光抛光过程所涉及的科学问题，为激光抛光在增材制造领域的进一步应用奠定良好的理论和工艺基础。

随着激光增材制造工业的快速发展及技术的推广应用，对增材制造表面质量控制及后处理工艺提出了更高的要求。激光抛光具有非接触性、高效、无污染等优势，成为提高增材制造构件表面质量的可靠方法之一。本项目基于成形试验工艺探索和仿真建模理论研究，开展了增材制造成形表面激光抛光理论与关键技术研究，具有重要的学术意义和产业化应用前景。项目首先进行了增材制造成形表面的形貌表征及特征提取研究，使用优化的增材制造成形工艺参数、以成形角度为设计变量制备了典型增材制造成形表面，从面、线、点三个维度进行了增材制造成形表面形貌表征和特征提取，给出了表面形貌特征随成形角度的变化规律；开展了激光抛光工艺的试验研究，阐述了增材制造初始表面形貌及抛光工艺参数对抛光后表面形貌及粗糙度的影响规律，建立了激光功率、扫描速度、初始表面形貌与抛光表面粗糙度之间的映射关系模型，获得了以抛光后表面面粗糙度为优化目标的最优抛光工艺参数组合；基于Flow3D软件平台构建了激光抛光过程的热-流动耦合场模型，预测了抛光过程中温度场及熔池随激光功率和扫描速度的变化规律，结合试验结果阐述了不同激光能量及初始表面形貌下的激光抛光作用机理；对比研究了增材制造成形层与抛光层的显微组织、晶粒尺寸、性能及残余应力，给出了抛光层组织、晶粒、性能及残余应力随激光功率及扫描速度的变化规律，研究发现激光抛光层可观察到晶粒细化、小角度晶界占比增加等现象，且激光功率越小，晶粒尺寸越小。