基于激光的增减材复合制造机理及其在微小尺寸复杂内流道结构精密加工中的应用基础研究

The small size complex internal flow passages play the most important roles of many key parts in aeronautics and astronautics, such as solid rocket engine gas diverter valves, aero-engine blades and fuel nozzle. Their dimensional and geometric accuracy, and surface roughness severely affect the hydrodynamics behavior of those key parts. State of the art additive manufacturing processes can create such complex geometries of internal flow passages, and could be the only feasible manufacturing processes with low cost to create such complex geometries in a monolithic part. However the additive manufacturing accuracy is far below traditional subtractive manufacturing accuracy, subject to its intrinsic factors such as laser spot size, metallic particle size and staircase effect. The project is motivated by the problem of producing metal parts with small size high-precision internal flow passages. Hybrid process of additive and subtractive manufacturing, more precisely of selective laser melting and femtosecond laser milling, will be intensively investigated to fabricate such small size high-precision internal flow passages. Two different laser sources are combined in the proposed hybrid process. The fiber laser with 1080nm wavelength is the energy source of deposit/melting materials layer by layer with selective laser melting process, and the femtosecond laser with 800nm wavelength and 100fs pulse width is the energy source to remove/sublimate very little materials from the layered contours during the selective laser melting coalescence. Based on our own intellectual-property rights in dual-wavelength selective laser melting 3D printer, an experiment equipment of the proposed hybrid process will be designed to verify the validity of laser based hybrid process mechanisms. What’s more, the energy transport and transformation in the hybrid process will be explored and quantified, also the controlled interaction mechanisms and process planning for the hybrid process will be reconstructed. Based on the micromachining characteristics of femtosecond laser and our previous works in the dual-wavelength selective laser melting, it is possible not only to fabricate high-precision internal flow passages, but also to design a whole new kind of hybrid manufacturing machine tool.

固体火箭发动机燃气导流阀及航空发动机叶片等关键零件复杂内流道的制造精度水平对航空航天发动机的综合性能指标具有决定性的影响。然而，金属增材制造技术无法实现微小尺寸复杂内流道结构的高精度加工。本项目致力于解决具有复杂内流道结构的金属零件高精度制造基础科学问题，提出基于激光的增减材复合制造工艺方法，即在1080nm波长光纤激光选区熔化分层增材制造零件的同时，采用波长为800nm、脉宽为100fs的飞秒激光减材去除分层轮廓边缘的高精度激光增减材复合制造工艺方法。本项目将在独创的双波长激光选区熔化实验装置的基础上设计复合制造实验装置，研究增减材复合制造工艺机理及高精度复合制造协同控制机制等。飞秒激光的加工特性和课题组近年在双波长激光选区熔化方面的工作不仅说明基于激光的增减材复合制造工艺方法高精度制造微小尺寸复杂内流道结构是可能实现的，并有望发展出新的复合制造关键技术和装备设计理论。

本项目聚焦金属零件增材制造中表面精度较差的关键科学问题，发展了高精度激光增减材复合制造新方法。研制了复合制造实验装置及其控制软件；系统地研究了复合制造协同控制策略及工艺，使得成形件的测面粗糙度降低到了7微米左右；理论上探究了激光增材（SLM）时熔池的行为及脉冲激光减材时的物理过程，并建立了各自过程中的能量传输模型。本项目为工业级高精度增减材复合制造装备的研制提供了理论及技术基础，对金属零件的高精度制造具有十分重要的意义。