激光掩膜微细电解加工机理研究

High efficiency and precision micromachining of stainless steel is a problem for modern manufacturing industry.The high-quality pulsed fiber laser quality beam can realize surface modification treatment on the 304 stainless steel surface by direct writing pattern to form the special layer with anti-corrosive protection. By combining laser surface modification technology and micro electrochemical machining technology, the special layer generated by precision laser surface modification serve as mask layer in electrochemical micromachining to prevent dispersion corrosion, and the complex two-dimensional microstructure can be fabircated by using simple block electrode without photo-lithography, which overcome the defects of surface roughness, cracks and heat affected zone in laser micromachining and the problems of fabricating a micro-electrode and the low efficiency in electrochemical machining with ultra-narrow pulse. In the project, the process of laser phase transition and laser re-melting and laser surface alloying of stainless steel 304 in the the fine laser surface-modification are analyzed to study the mechanism of the role of the special mask play in the laser assisted electrochemical micromachining, and laser thermal conductivity model is established by the finite element method. Through the process test, the parameters are optimized to improve its corrosion resistance. Especially through recursive laser maskings processes, multi-dimensional structure can also be processed.

微小型不锈钢零件的高效、高精度地加工是现代制造业的一个难题。本项目利用光纤脉冲激光器的优质光束可以在304不锈钢表面采用直写方式进行表面改性处理，生成具有抗腐蚀性的保护图案,再将激光表面改性技术与微细电解加工技术相结合，无须光刻掩膜，利用精密激光表面改性生成的具有耐腐蚀特性的表层图案作微细电解加工中的掩膜，通过微细电解加工，利用简单块电极就能生成复杂的二维结构，克服了微细激光加工中表面粗糙度大、有裂纹、产生热影响层等缺陷，也克服了采用超窄脉冲电解加工需要制作微细电极和加工效率低等难题。通过对微细激光表面改性不锈钢304过程中产生的相变、熔凝或激光表面合金化所生成的特殊表面层性能分析，研究该特殊表层在微细电解中起到掩膜作用的机理，利用有限元法建立激光导热模型，通过工艺试验，优化工艺参数，提高其抗腐蚀能力，实现激光掩膜化微细电解加工，尤其可经多次激光掩膜化处理，可以加工多层立体结构加工。

微小金属零件制作是现代制造急需解决的难题，微细电解加工和微细激光加工在微细加工中存在各自的优缺点。本项目将激光打标与微细电解加工复合，进行激光掩膜微细电解复合加工。利用激光打标在不锈钢304表面制有一定形状的掩膜微织构，提高304不锈钢表面耐腐蚀性，用激光掩膜图案为保护掩膜，进行微细电解加工，对没有进行激光掩膜的区域进行电解去除，实现典型微小型腔结构的高效加工。根据激光掩膜微细电解加工原理，研发了一套激光掩膜微细电解加工装置。利用X射线光电子能谱XPS分析（X-ray photoelectron spectroscopy analysis, XPS）不锈钢激光掩膜层表面特性，利用X射线衍射分析(X-ray diffraction analysis, XRD)方法分析激光掩膜层抗腐蚀性能机理，对激光掩膜微细电解复合加工机理展开研究。不锈钢表面激光掩膜形成的Fe、Cr等氧化物是在后继的电解加工中产生掩膜保护作用的主要因素。为了探索影响加工精度的因素，使激光掩膜微细电解加工成为微细加工的一种方法，对激光掩膜重叠率、激光功率、不锈钢表面激光织构从超亲水到超疏水的状态改变等因素对抗蚀性能的影响进行分析。此外，激光掩膜过程中，激光焦点扫描加热304不锈钢，在其表面出现相变，随着光纤激光能量密度加大，激光打标会使不锈钢表面层瞬间熔化，再快速冷却、凝固，生成熔凝金属薄层，由于骤热骤冷过程，形成熔凝层，会使不锈钢熔凝层中金相组织晶粒细化，增强不锈钢表层耐蚀性。根据激光掩膜熔凝理论分析，建立激光熔凝的物理过程的数学模型；利用有限元方法，进行激光直写熔凝温度场数值仿真及工艺参数研究。通过激光掩膜微细电解加工工艺试验，研究分析了激光功率、加工电压、电解液浓度、加工脉冲电源的占空比是影响激光掩膜微细电解复合加工不锈钢型腔加工精度的影响。最后，通过多次激光掩膜微细电解加工可以增加加工凹模型腔的深度，本课题通过3次激光掩膜微细电解加工加工出深20µm左右的典型结构微小凹腔样件。