浅谈复合电解加工技术研究现状

在日新月异的现代加工技术的发展下,单一的电解加工技术已经不能满足人们的加工要求,为了弥补其不足,复合电解加工技术应运而生,本文介绍了两种复合电解加工技术及其研究现状。     

电化学溶解高温合金研究进展

电化学溶解合金工艺在高温合金的回收与电解加工领域得到了广泛应用,受到相关领域从业人员的广泛关注。本工作主要概述了电化学溶解合金工艺在高温合金回收和加工领域的应用现状,归纳了不同实验参数对电解效率的影响,分析了当前研究存在的问题,展望了电化学溶解高温合金工艺未来的研究热点。     

复杂孔电解液系统设计与试验验证

复杂孔进行一次到位的高效率加工是电解加工领域研究的热点问题,对于那些大口径、形状复杂的零件,由于其管身长,加工时间长,加工电流大,随着内反应进行,蚀除的产物增多,在进行深孔电解加工时,维持电解液池中电解液的浓度、温度和清洁度的稳定比一般电解加工更为迫切。针对深孔材料选择了电解液,进行了电解液池的布局设计,对系统所采用的6台两种不同类型的泵、净化装置、冷热交换器进行选型和安装原理分析。通过试验说明一套合理的电解液系统对最终零件产品的成型起着非常关键的作用。     

超纯水电解加工机理及工艺基础

引言 超纯水电解加工是在常规电解加工原理的基础上,利用超纯水作电解液,并采用强酸性阳离子交换膜来提高超纯水中OH-离子的浓度,使电流密度达到足够去除材料的一种新型电解加工工艺方法.     

电解加工对TC17钛合金表面完整性及振动疲劳性能的影响

对比了机械加工和电解加工对TC17钛合金表面完整性及振动疲劳性能的影响。结果显示,经过电解加工的TC17钛合金表面不存在明显的晶粒细化或破碎的变形层,表面残余应力普遍呈现为压应力状态,并且变化较平稳。电解加工试样的室温振动疲劳寿命高于机械加工试样,可能与电解加工试样的表残余应力和晶粒取向较优有关。     

电解加工-振动光饰对TC17钛合金表面完整性及力学性能的影响

先对TC17钛合金进行电解加工,再进行振动光饰。采用扫描电镜、白光干涉三维形貌仪和残余应力分析仪分析了电解加工和振动光饰后TC17钛合金的表面完整性,通过室温拉伸试验和室温振动疲劳试验检测了其力学性能。结果显示,经过电解加工和振动光饰处理后,TC17钛合金表面平整,粗糙度大幅降低,并呈现较大的残余压应力状态。由于表层只发生极小的塑性变形,因此TC17钛合金晶粒取向几乎不受影响。电解加工+振动光饰试样的室温拉伸性能与电解加工试样相当,但前者的室温振动疲劳性能优于后者。     

电解加工对GH4169G高温合金表面完整性和力学性能的影响

对比了机械加工和电解加工对GH4169G高温合金表面完整性和力学性能的影响。结果显示,经过电解加工的GH4169G高温合金表面不存在明显的晶粒细化或破碎的变形层,其在深度方向的表面残余应力变化幅度较小,基本保持在100 MPa以内。电解加工试样的高温持久性能与机械加工试样相当,前者的室温振动疲劳寿命低于后者,可能与电解加工试样的表面粗糙度较高有关,但都在同一数量级。     

SiC微粒辅助掩膜电解加工金属微孔阵列结构的研究

针对掩膜电解加工(TMECM)金属微孔阵列结构存在定域性差、微孔孔径的加工精度及刻蚀深度难以满足要求的问题，提出了SiC微粒辅助掩膜电解加工(PA-TMECM)的方法。研究了SiC微粒直径、质量浓度及电解液流量对304不锈钢表面微孔阵列结构加工效果的影响，探讨了微粒辅助掩膜电解加工的作用机制。实验结果表明：当SiC微粒质量浓度为6 g/L、直径为40μm、电解液流量为3 000 mL/min时，加工定域性最佳，蚀刻因子为3.52。在微粒辅助掩膜电解加工过程中，微粒通过持续、高频的冲击作用有效去除了阳极表面的电解产物，增大了微孔刻蚀深度，限制了侧向刻蚀，最终提高了掩膜电解加工的定域性。     

航空发动机气膜冷却孔的电解加工

以航空发动机涡轮叶片常用材料 Inconel718高温镍基合金为基材进行电解加工(ECM)，得到气膜冷却孔。通过几组交叉实验，分析了加工电压、电解液NaNO3含量、工具电极进给速率3个工艺参数对加工过程稳定性、加工精度和加工效率的影响，得到电解加工的最优工艺参数为：电解液中NaNO3的质量分数10%，加工电压10 V，工具电极进给速率7μm/s，电解液流量10 mL/min。在该工艺条件下，加工过程稳定，效率高，精度好。     

新型内齿轮精锻模设计

汽车、拖拉机变速箱内齿轮因形状所致无法切削加工，且难以用传统的锻造工艺进行生产，因此采用电解加工工艺，生产效率低，内齿强度低、精度差、寿命低，电解废液污染环境。本文提出快档齿轮热精锻成形的实用模具结构，论述了模具结构原理和模具齿形设计加工方法。该模具采用强力脱模装置，使锻件在锻击结束瞬间立即脱离凸模。彻底解决了热锻件将凸模抱死这一关键技术问题。     

Calculation of temperature transients in pulse electrochemical machining (PECM)

Pulse Electrochemical Machining (PECM) is a manufacturing process which provides an economical and effective method for machining hard materials into complex shapes. One important drawback of ECM is the lack of quantitative simulation software to predict the tool shape and machining parameters necessary to produce a given work-piece profile. Calculating temperature distributions in the system allows more accurate simulations, as well as the determination of the thermal limits of the system. In this paper temperature transients over multiple pulses are calculated. It is found that the way the system is modeled has a great impact on the temperature evolution in the thermal boundary layer. The presence of massive electrodes introduces extra time scales which may not be negligible. It is advantageous to identify the thermal time scales in the system, to see whether the heat produced during separate pulses will accumulate or not during the process. The occurring thermal time scales in the system are discussed in detail.     

The use of a segmented tool for the analysis of electrochemical machining

A planar workpiece/planar segmented tool experimental configuration has been used to collect current–time data for the electrochemical machining (ECM) of Inconel 718 (In718) and stainless steel (SS316). As with previous measurements, theoretical analysis of the chronoamperometric data has been used to obtain values for the characteristic parameters of ECM under characteristic machining conditions, but the segmented tool allows this for each segment. These parameters are the valency, n, and k, from which the minimum voltage required to initiate machining, V ₀, and the electrolyte conductivity, can be obtained. The variation of n, V ₀ and between segments enables ECM conditions along the flow path length to be probed. Measurements on In718 in nitrate electrolyte have shown a small increase in electrolyte conductivity along the flow path. Tool segments which overlap the workpiece ends have been employed to measure edge effects in the ECM process; no significant edge effects were found when machining In718 in nitrate. The temporal and spatial dependences of a change in valency previously observed during the machining of SS316 have also been studied for the first time. Regions of low valency (n = 2.1) dissolution (downstream) and high valency (upstream, n = 3.0) dissolution were observed, with an intermediate region with monotonically decreasing valency where 3.0 > n > 2.1.     

The effect of substrate surface integrity on the surface properties of TiCrN coating applied via the CAE-PVD method

This study aims to investigate how the predeposition machining processes such as magnetic grinding, turning machining, and wire electrical discharge machining can influence the surface properties including electrochemical and tribological behavior of TiCrN nanostructured coating applied on Mo40 steel substrate. A physical vapor deposition technique using cathodic arc evaporation was used to apply the coating. The crystallographic phases and the microstructure of the coating were studied by X-ray diffraction and scanning electron microscope, respectively. Rockwell-C, electrochemical impedance spectroscopy and potentiodynamic polarization, and pin-on-disk wear tests were employed to evaluate the adhesion strength, corrosion behavior, and tribological property of specimens, respectively. The electrochemical results after 24 h of exposure to 3.5 wt% NaCl solution showed that TiCrN coating pretreated with a turning process with polarization resistance of about 3525.32 Ω.cm² had the best corrosion resistance among all specimens. This was because of the improvement of the smoothness, surface quality, and adhesion after the turning process. On the other, the friction coefficient of the grounded sample is less than that of other ones. This is probably due to its higher adhesion strength and higher surface smoothness.     

Time averaged temperature calculations in pulse electrochemical machining, part II: numerical simulation

Simulation of the temperature distribution and evolution during pulse electrochemical machining can be a computationally very expensive procedure. In a previous part of the work [Smets et al. J Appl Electrochem 37(11):1345, 2007] a new approach to calculate the temperature evolution was introduced: the hybrid method, which combines averaged and pulsed calculations. The averaged calculations are performed by time averaging the boundary conditions and the bulk heat sources of the system. The timesteps used during the averaged calculations are then no longer dictated by the pulse characteristics. Using this approach, computationally very cheap, yet satisfactory results can be obtained. The analysis in the previous part of the work was obtained from analytical solutions on simplified models. In this part, the more general case is solved numerically. Multiple geometries are simulated and analyzed and methods are compared. Very satisfactory, yet cheap results are obtained.     

The surface structure during pulsed ECM of iron in NaNO3

During electrochemical micro machining (ECMM) metals are electrochemically dissolved at very high current densities up to 100 A/cm² in aqueous electrolytes like NaNO₃ or NaCl. Different anode processes take place during the electrochemical machining (ECM) process of iron in NaNO₃. Iron is dissolved as Fe²⁺ and Fe³⁺ and oxygen evolution appears. The different reaction products are analysed quantitatively and time resolved for pulses 10 ms ≤ t_pulse ≤ 5000 ms under ECM conditions by a combination of our flow-through-microcell with an UV-vis-spectrometer and a pulse generator. The surface structure during pulsed ECM and the appearance of the machined surface is shown in dependence of the pulse length and the prepolarisation of the electrode. Crucial for the obtained results are the build-up and removal of the oxides, as well as the polishing film. The model for stationary ECM conditions is extended to a time resolved model.     

陶瓷零件的加工方法

工程陶瓷具有极高的硬度、良好的耐磨性和耐腐蚀性以及脆性大等特点，属于难加工材料，特别是加工高精度、形状复杂的构件非常困难。陶瓷材料作为工程材料的大规模推广应用，在很大程度上取决于陶瓷零件加工技术的发展。笔者综述了陶瓷零件的加工方法及最新进展。     

Experimental study on laser assisted ultrasonic elliptical vibration turning (LA-UEVT) of 70% SiCp/Al composites

SiC_p/Al composites are more and more used in aerospace, military industry and other industries. However, the surface integrity of materials is poor, and the cutting force is large as the anisotropy of materials in the traditional machining (TM) process, which hinders the application of ceramic particle reinforced metal matrix composites. With the requirement of high dimensional accuracy, high efficiency and low damage for materials in these fields, non-traditional machining technology has become a research hotspot. Laser assisted machining (LAM) is a non-contact special machining method. Its advantages in machining SiC_p/Al composites have been proved by experiments, but there are still processing defects such as thermal cracks. Therefore, to further improve the machining quality of 70% SiC_p/Al composites with high volume fraction, a new machining method combining ultrasonic elliptical vibration turning (UEVT) and laser heating assisted turning (LAT) is proposed. High frequency intermittent machining and the adjustment of laser temperature influence on materials can be realized by adjusting the ultrasonic amplitude. Combining the characteristics of the two processing techniques, the feasibility study of the new machining method was studied by turning experiments. In this paper, compared with TM and LAT, the removal mechanism of materials and the effects of different laser heating temperatures and ultrasonic vibration on cutting force, surface quality, subsurface damage and chip morphology are explored. The results show that LA-UEVT can effectively reduce the cutting force and surface roughness, improve the plastic removal ability, and inhibit surface and subsurface damage. And the material removal process is mainly in the form of small particle crushing and particle pressing, which improves the stability of cutting force in the cutting process.     

Composite machining damage quantification using thermoelastic stress analysis

A new experimental method is presented for quantifying machining damage in polymer matrix composites. The method consists of capturing infrared images of machined samples and using thermoelastic stress analysis to quantify damage from the machining event. A modified stress concentration factor is presented as an easily measured and useful damage parameter. Circular holes were drilled into the center of plate specimens fabricated from a commercially available glass fiber reinforced composite. A standard drill bit, brad point drill bit, and abrasive water jet machining were the three machine tools investigated. Infrared images were used to quantify the machining damage by assigning a thermoelastic stress analysis based stress concentration factor (mSCF) to each machined hole. The mSCF was then used to rank the damage inherent to each machining method. Optical and electron microscopy were utilized to identify the types of damage associated with the three machining methods. Finally, each sample was fatigued to failure to substantiate the IR results. The ranking of damage based upon the mSCF was in good agreement with the fatigue lifetime rankings: higher mSCF is associated with shorter fatigue lifetimes.     

Statistical Analysis of Experimental Parameters in Ultrasonic Machining of Tungsten Carbide Using the Taguchi Approach

The objective of this paper is to study the influence of operating parameters of ultrasonic machining of tungsten carbide on the machining characteristics. The effectiveness of the ultrasonic machining process with tungsten carbide is evaluated in terms of the material removal rate and the surface finish quality of the work piece produced. Tungsten carbide as a super hard and high wear-resistant material has been used widely in industries. Powder metallurgy technology is the common method for producing tungsten carbide components. However, this method is obviously too costly and time consuming for small quantity production, such as product prototyping. It is expected to make the prototypes by a material removal process, such as ultrasonic machining. In this paper, an experimental study on the ultrasonic machining of tungsten carbide is presented using a systematic approach. Practical aspects are given on the characteristics of tungsten carbide as functions of the type of abrasive slurry, their size and concentration, nature of the tool material, and the power rating of the machine. The optimum combination of various input factors for the ductile chip formation in the machining of tungsten carbide has been determined by applying the Taguchi approach and the F -test.