激光辅助微切削在非晶态NiP模具表面制备周期性微纳结构的加工机理研究

Electroless NiP plating with various micro-/nanostructures is a widely used mold material for mass production of optical glass and resin components. In recent years, miniaturization and functionalization of industrial components have been developing very quickly, which gives more critical requirements for manufacturing technologies of these molds. Higher machining precision, smaller and more complicated structures are required. In the present research, a new laser assisted micro-cutting technology will be further studied for fabricating periodical micro-/nanostructures on the amorphous NiP plating, which will focus on how to decrease surface defects and edge burrs by optimizing parameters of laser irradiation and cutting. Simulation and experiments will be carried out simultaneously. The thermal softening effect of laser irradiation will be studied firstly; the crystallization of amorphous NiP alloy will be investigated; the change of NiP microstructures and its relationship to its mechanical properties will be analyzed. Then, simulation of cutting processes of periodic pyramid structures will be carried out; the influence of thermal effect and the change of materials properties on materials removal mechanisms will be evaluated. At the same time, the experimental fabrication processes of V grooves and periodic pyramid structures will be carried out; the quality of machined surfaces will be evaluated according to the machining conditions; the formation, flow and evacuation of cutting chips and their morphology will be investigated by considering the change of properties of NiP plating under laser irradiation. Finally, the mechanisms of the laser assisted micro-cutting process on amorphous NiP plating and the optimized machined conditions will be concluded.

具备各种微结构的NiP模具工业上被广泛的应用于玻璃和树脂类光学器件的模压成型制造。随着器件小型化和功能化的快速发展，对加工制造精度、表面微结构的尺寸和复杂程度的要求逐步提高，模具的切削加工质量成为了制约器件性能提高的一个瓶颈。本项目在前期工作的基础上，拟深入研究采用激光辅助微切削减少NiP镀层加工中易产生的表面缺陷和边缘毛刺，制备高质量的周期性微纳结构。采用模拟和实验相结合，研究控制激光照射对工件材料的热效应，研究非晶态NiP的结晶化转变，控制热效应对镀层显微组织结构和力学性能的影响；建立周期性微结构的切削加工模型，模拟研究热效应和材料属性变化对材料去除机理的影响；进行V漕和周期性金字塔结构的加工制备，研究激光照射及切削加工的工艺参数对加工质量的影响规律，观测切屑的形成、流动排出和形貌特征，分析材料属性变化引起的材料去除机理变化；通过上述研究，解明加工机理，得出最优化的加工工艺。

非晶态NiP镀层硬度高、耐磨耐腐蚀性好，使得非晶态NiP模具被广泛的应用于玻璃和树脂类光学器件的模压成型制造。但是随着器件小型化和功能化的快速发展，对模具加工制造精度、表面微结构的尺寸和复杂程度的要求逐步提高，宏观尺度下可忽略的微小缺陷在微观尺度都会严重影响光学器件的性能，所以微切削加工质量成为了制约微小器件性能提高的一个瓶颈。前期工作中发现激光辅助切削加工可以减少非晶态NiP的加工缺陷，但是鉴于非晶态与晶态材料在原子排列上存在的本质区别，无法直接用晶态材料的加工变形特性来理解激光辅助非晶态材料加工过程中表面缺陷和边缘毛刺减少的机理。因此，本项目采用模拟和实验相结合的方法，展开对激光辅助微切削非晶态NiP模具材料去除机理的研究。建立了纳秒激光辐照三维传热模型并研究了激光照射条件对NiP的温度梯度的影响规律。通过步进切削实验阐明了非晶态NiP合金切削加工过程中材料变形的变化规律，观测切屑的形成、流动排出和形貌特征发现非晶态NiP合金在压应力下具有较好的形变能力，但在切削出口处承受拉应力时剪切带传播易失稳而快速传播，使得材料表现为宏观的脆性断裂；通过激光辅助切削实验研究了相应的热效应对切削过程的影响，发现当激光辐照温度在非晶合金的玻璃转变温度附近时能较好的软化材料降低出口处的拉应力，从而可以最大程度减少表面缺口。但是激光辐照温度过低时材料不会软化，温度过高时材料发生熔化都达不到理想的加工效果。最后，通过上述研究，得出激光辐照条件与切削速度、切削深度最优化的加工工艺。本项目的研究成果可用于指导激光辅助切削非晶合金加工中激光参数与加工参数的设置，以获得无缺口破坏的表面，得到具有纳米精度的微结构模具。