电化学去毛刺技术在航空产品中的应用

阐述了电化学去毛刺技术的加工能力、工艺过程及电极的结构。     

冰层辅助对电火花-电解复合穿孔的影响

电火花-电解复合穿孔(ECDD)加工方法有望实现难加工材料涡轮叶片气膜冷却孔无重铸层高效加工,为了进一步提升小孔孔壁的加工质量,提出了在工件底部填充冰层的电火花-电解复合穿孔加工新方法。分析了冰层辅助对复合加工过程中两极之间电流电压的波形、复合穿孔的加工效率、小孔的出入口孔径、孔壁重铸层去除等的影响,进行了冰层辅助与无冰层辅助电火花-电解复合穿孔对比试验。试验表明:冰层辅助加工可以在小孔穿透之后形成充分的反向冲液,有效地解决小孔穿透之后的漏液问题。在增加底部停顿时间的基础上,即小孔穿透后管电极到达预设深度继续停留一段时间,延长管电极对孔壁的电解作用时间,可以显著提高重铸层的去除效果,有望实现小孔整个孔壁重铸层的完全去除。     

叶片型面精密振动电解加工工艺研究

采用电解加工工艺对叶片型面进行加工,可以有效提高发动机叶片加工效率,降低生产成本。针对GH4169G合金叶片型面,开展了精密振动电解加工试验研究。结果表明:高频脉冲电流和阴极机械振动具有改善极间流场特性、降低阳极钝化和阴极的产物吸附的作用,可以大幅改善加工效果;采用参数组加工电压15V、阴极振动频率25Hz、开通角度Ra 150°~195°、脉冲频率3000Hz时,获得最优的型面加工质量,型面轮廓度为-0.012~+0.013mm,表面粗糙度值为0.51μm,证明精密振动电解加工工艺满足叶片型面的加工要求。     

旋印电解加工

航空发动机机匣是航空发动机重要的连接、承载部件,它结构复杂、刚性弱、材料难加工,目前存在加工变形严重、壁厚精度差等制造难题,已成为制约新型航空发动机研制和生产的瓶颈。针对薄壁机匣的制造需求,本文提出了旋印电解加工技术,该技术采用回转体电极作为阴极工具,通过工件与工具的同步对转对阳极工件逐层精确溶解去除,实现薄壁机匣的无变形精密加工成形。研究揭示了旋印电解加工阳极成形规律、难加工材料脉动态溶解机理、电解液流场分布特性等基础科学问题,突破了阴极工具设计、钛合金点蚀抑制、流场优化设计等关键技术,研制出具有自主知识产权的大型旋印电解机床,实现了大型薄壁机匣的高效精密加工,为新型航空发动机的研制和生产提供了重要的技术支撑。     

振动进给,脉冲电流提高电解加工精度的探讨

分析了电解加工工艺目前的应用状况，介绍了一种电解加工新技术－振动进给，脉冲电流电解加工，结合试验，分析论证了此加工方式提高电解加工精度的机理，（１）加工间隙及电流周期性变化，从而减小了实际等效加工间隙，有利于提高加工精度；（２）加工，冲刷的交替性改善了加工过程，有利于采用小间隙加工，这种加工技术将有画于提高电解加工精度，扩大电解加工应用范围。     

油溶性缓蚀剂的乳状液评定方法

采用乳化液的形式对油溶性缓蚀剂进行研究，通过在缓蚀剂的乳化液中测量金属的稳态极化曲线，进而评价缓蚀剂的优劣，克服了油溶性缓蚀剂由于不溶于水，从而不能配成电解质溶液对其进行电化学研究的局限性。     

Wire electrochemical machining with axial electrolyte flushing for titanium alloy

Titanium and its alloys have found very wide application in aerospace due to their excellent characteristics although their processing is still a challenge. Electrochemical machining is an important issue in the fabrication of titanium and titanium alloys. Wire electrochemical machining (WECM) is mainly used for workpiece cutting under the condition of different thickness plates. It has a great advantage over wire electro-discharge machining, which is the absence of heat-affected zone around the cutting area. Moreover, the wire electrode in WECM could be used repetitively because it is not worn out. Thus, much attention has been paid to WECM. The effective way of removing electrolysis products is of importance to WECM. In this paper, the axial electrolyte flushing is presented to WECM for removing electrolysis products and renewing electrolyte. The Taguchi experiment is conducted to optimize the machining parameters, such as wire feedrate, machining voltage, electrolyte concentration, etc. Experimental results show that WECM with axial electrolyte flushing is a promising issue in the fabrication of titanium alloy (TC1). The feasibility of multi-wire electrochemical machining is also demonstrated to improve the machining productivity of WECM.     

不同封闭工艺对2195铝锂合金环保型阳极氧化膜耐蚀性能影响

针对轻量化航天装备的可靠性服役对2195铝锂合金提出的高耐蚀性需求,采用环保型硫酸己二酸(50 g/L硫酸和10 g/L己二酸)溶液体系在2195铝锂合金表面制备阳极氧化膜,对所得的膜层通过沸水封闭、铬酸盐封闭、镍盐封闭和铈盐封闭4种封闭工艺进行后处理,并利用扫描电子显微镜、动电位极化曲线、电化学阻抗谱等方法对膜层表面的显微形貌和耐蚀性能进行表征。结果表明:相较于未封闭的阳极氧化膜,4种封闭工艺均提高了膜层的耐蚀性能,其中镍盐封闭后对基体的钝化效果最好,铬酸盐封闭次之,沸水封闭和铈盐封闭对膜层防腐性能提升有限。对电化学阻抗谱的进一步解析表明,4种膜层阻挡层电阻Rb均在105Ω·cm2数量级,膜层耐蚀能力主要来自于被水合及沉淀物充分填充的多孔层内部,相应的电阻Rp2的数值大小依次为镍盐封闭铬酸盐封闭沸水封闭≈铈盐封闭。     

Exploration life support technology challenges for the Crew Exploration Vehicle and future human missions

As NASA implements the U.S. Space Exploration Policy, life support systems must be provided for an expanding sequence of exploration missions. NASA has implemented effective life support for Apollo, the Space Shuttle, and the International Space Station (ISS) and continues to develop advanced systems. This paper provides an overview of life support requirements, previously implemented systems, and new technologies being developed by the Exploration Life Support Project for the Orion Crew Exploration Vehicle (CEV) and Lunar Outpost and future Mars missions. The two contrasting practical approaches to providing space life support are (1) open loop direct supply of atmosphere, water, and food, and (2) physicochemical regeneration of air and water with direct supply of food. Open loop direct supply of air and water is cost effective for short missions, but recycling oxygen and water saves costly launch mass on longer missions. Because of the short CEV mission durations, the CEV life support system will be open loop as in Apollo and Space Shuttle. New life support technologies for CEV that address identified shortcomings of existing systems are discussed. Because both ISS and Lunar Outpost have a planned 10-year operational life, the Lunar Outpost life support system should be regenerative like that for ISS and it could utilize technologies similar to ISS. The Lunar Outpost life support system, however, should be extensively redesigned to reduce mass, power, and volume, to improve reliability and incorporate lessons learned, and to take advantage of technology advances over the last 20 years. The Lunar Outpost design could also take advantage of partial gravity and lunar resources.     

Modeling and Experimental Investigation of Laser Drilling with Jet Electrochemical Machining

As two kinds of defects, recast layers and spatters, commonly accompanied by laser-drilled holes always prevent the laser drilling technique from extending its applications in aerospace and aircraft industries, therefore, a novel hybrid process incorporating laser drilling with jet electrochemical machining (JECM-LD) has been developed to solve these problems as well as improve the overall quality of laser-drilled holes. It is executed by directing an electrolyte jet coaxially aligned with a laser beam onto the workpiece surface. During the process, the electrolyte jet produces electrochemical reaction with the surface material, effective cooling of it and carries away the process scraps. A two-dimensional mathematical model is proposed to describe the shape of the holes machined by JECM-LD. The model is verified through comparison between the results from simulation and those from experiments conducted on the test pieces made of 321 stainless steel 0.5 mm thick processed by the pulsed Nd:YAG laser at second harmonic wavelength. An examination of the experimental results under an optical microscope discovers that, by contrast with the laser drilling in air, the JECM-LD has effectively removed the recast layers and spatters, but its efficiency dropped by about 30%.