Study of cutting deformation in machining nickel-based alloy Inconel 718

During the process of high-speed machining nickel-based alloy the material presents serrated chips. An experiment involving quick-stop device was conducted. The chip root obtained in the experiment was presented in a metallographic graph. Through the analysis of metallographic graph, the physical features showed that shear angle is reduced and shear plane is converted into shear body when serrated chips formed were analyzed. Conditions under which a crack appeared and adiabatic shear that occurred were also analyzed. Based on the research, shear strain, shear strain rate and shear stress model in the adiabatic shear band were established. The effects of cutting parameters on character of the serrated chip were studied through observing chip metallographic graph.     

Modelling tool wear in cemented-carbide machining alloy 718

Tool wear is a problem in turning of nickel-based superalloys, and it is thus of great importance to understand and quantitatively predict tool wear and tool life. In this paper, an empirical tool wear model has been implemented in a commercial finite element (FE) code to predict tool wear. The tool geometry is incrementally updated in the FE chip formation simulation in order to capture the continuous evolution of wear profile as pressure, temperature and relative velocities adapt to the change in geometry. Different friction and wear models have been analysed, as well as their impact on the predicted wear profile assessed. Analyses have shown that a more advanced friction model than Coulomb friction is necessary in order to get accurate wear predictions, by drastically improving the accuracy in predicting velocity, thus having a dramatic impact on the simulated wear profile. Excellent experimental agreement was achieved in wear simulation of cemented carbide tool machining alloy 718.     

Effect of machining parameters and cutting edge geometry on surface integrity of high-speed turned Inconel 718

Stringent control on the quality of machined surface and sub-surface during high-speed machining of Inconel 718 is necessary so as to achieve components with greater reliability and longevity. This paper extends the present trend prevailing in the literature on surface integrity analysis of superalloys by performing a comprehensive investigation to analyze the nature of deformation beneath the machined surface and arrive at the thickness of machining affected zone (MAZ). The residual stress analysis, microhardness measurements and degree of work hardening in the machined sub-surfaces were used as criteria to obtain the optimum machining conditions that give machined surfaces with high integrity. It is observed that the highest cutting speed, the lowest feedrate, and the moderate depth of cut coupled with the use of honed cutting edge can ensure induction of compressive residual stresses in the machined surfaces, which in turn were found to be free of smeared areas and adhered chip particles.     

Microstructures forming in friction welding of Inconel 718 alloy – joint performance and its controlling factors in friction welding of Inconel 718 alloy

Microstructures forming in the friction welding of Inconel 718 alloy have been investigated in order to understand the phenomena occurring during the welding process and to determine the factor controlling the joint performance from a metallographic point of view. In the interfacial zone, liquation microstructures characterized by a eutectic structure consisting of γ and Laves phases, and Nb-rich microstructures along the grain boundary (Nb-rich GB microstructures) were observed, and their amounts increased with the friction time and pressure. The volume fractions of these liquation structures were greater in the flash than in the interfacial zone, suggesting that the liquid phase was preferentially expelled into the flash by friction pressure, compared with the solid phase. Since the liquid phase was rich in Nb, this preferential expulsion of the liquid phase caused the depletion of Nb, a major element for the precipitation hardening of the alloy. The depletion of Nb brought about a decrease in the hardness in the interfacial zone after a post-weld heat treatment for precipitation hardening. Thus, although the friction bonding is a solid state welding process, the liquation occurs in the weld of Inconel 718 alloy having a wide solid–liquid coexisting temperature range, and has a significant influence on the joint performance.     

Investigation of machining performance in high pressure jet assisted turning of Inconel 718: A numerical model

This study aims at investigating the effects of high-pressure jet assistance (HPJA) in rough turning of Inconel 718. A finite element (FE) model for orthogonal machining has been developed in order to reach additional data, compare trends to the experimental ones and understand the influence of the jet on the cutting process. Mechanical and thermal loads induced by the jet are considered. Consequences on the primary and secondary shear zones, chip formation and tool rake face have been studied on a whole pressure range (30-130 MPa) and compared to dry cutting. It is shown that the jet is able to decrease the cutting forces, chip radius and tool-chip contact length. Contact pressure and temperature fields on the cutting tool are also reduced as well as the sticking part of the contact zone. Authors confirmed that the effects of convection are able to change and even amplify the influence of the pure mechanical load induced by the jet.     

热处理对Inconel718合金组织及力学性能的影响

针对Inconel 718合金的不同用途,分析研究了4种常用热处理工艺对Inconel 718合金组织和力学性能的影响。结果表明:固溶温度超过1020℃时,奥氏体晶粒显著长大。合金中主要析出相有MC、δ、γ’和γ″相。δ相沿晶界分布,1025℃固溶时呈颗粒状少量析出;950℃固溶时呈块状大量析出;直接时效时呈网状不连续分布。同时,δ相对合金的晶粒度影响较大,且其析出数量和形态决定了合金的韧塑性,γ″、γ’相的析出量和尺寸与晶粒尺寸决定了合金的强度变化。     

An analytical model to predict specific shear energy in high-speed turning of Inconel 718

Machining of Inconel 718 at higher cutting speeds is expected to provide some relief from the machining difficulties. Therefore, to understand the material behavior at higher cutting speeds, this paper presents an analytical model that predicts specific shearing energy of the work material in shear zone. It considers formation of shear bands that occur at higher cutting speeds during machining, along with the elaborate evaluation of the effect of strain, strain rate, and temperature dependence of the shear flow stress using Johnson–Cook equation. The model also considers the ‘size-effect’ in machining in terms of occurrence of ‘ploughing forces’ during machining. The theoretical results show that the shear band spacing in chip formation increases linearly with an increase in the feedrate and is of the order of 0.2–0.9 mm depending upon the processing conditions. The model shows excellent agreement with the experimental values with an error between 0.5% and 7% for various parametric conditions.     

Tool-life and wear mechanisms of CBN tools in machining of Inconel 718

The demand for increasing productivity when machining heat resistant alloys has resulted in the use of new tool materials such as cubic boron nitride (CBN) or ceramics. However, CBN tools are mostly used by the automotive industry in hard turning, and the wear of those tools is not sufficiently known in aerospace materials. In addition, the grade of these tools is not optimized for superalloys due to these being a small part of the market, although expanding (at 20% a year). So this investigation has been conducted to show which grade is optimal and what the wear mechanisms are during finishing operations of Inconel 718. It is shown that a low CBN content with a ceramic binder and small grains gives the best results. The wear mechanisms on the rake and flank faces were investigated. Through SEM observations and chemical analysis of the tested inserts, it is shown that the dominant wear mechanisms are adhesion and diffusion due to chemical affinity between elements from workpiece and insert.     

K418合金表面激光再制造Inconel718高温合金涂层性能研究

针对K418高温合金叶轮高温、高转数工况下形变超差大,再制造成形层力学性能降低的领域研究热点,基于波形可调制脉冲激光优化工艺,再制造Inconel718高温合金成形层。采用金相显微镜、SEM、XRD、EDS、显微硬度计对该合金涂层的显微组织形貌、相结构、界面成分分布、基本力学性能进行研究。结果表明:涂层与基体间为致密的冶金结合,涂层中部为粗大的树枝晶,与激光扫描方面成30o^45o角,由涂层中部到顶部及底部,分别退化为等轴晶和胞状晶;成形层显微硬度为4100~4400 MPa,略高于基体;晶内及晶间析出少量Laves相,减少了对成形层硬脆性的影响;摩擦磨损系数较基体略有降低,但仍符合再制造要求。     

磷硼复合添加对Inconel 718合金铸态组织及均匀化处理参数的影响(英文)

研究磷硼复合添加对Inconel 718高温合金铸态组织及均匀化处理参数的影响。结果表明:磷硼的加入促进块状Laves相的形成。由于硼在最后残余液相中大量富集,形成一种富含Nb、Mo和Cr的含硼相。根据DSC和电子探针分析结果,确定磷硼复合添加Inconel 718高温合金的凝固顺序为L→L+γ→L+γ+MC→L+γ+MC+Laves→γ+MC+Laves+含硼相。由于低熔点含硼相的存在,磷硼复合添加Inconel 718高温合金的均匀化处理温度应比标准Inconel 718合金低至少40°C。     

A review of developments towards dry and high speed machining of Inconel 718 alloy

The increasing attention to the environmental and health impacts of industry activities by governmental regulation and by the growing awareness in society is forcing manufacturers to reduce the use of lubricants.In the machining of aeronautical materials, classified as difficult-to-machine materials, the consumption of cooling lubricant during the machining operations is very important. The associated costs of coolant acquisition, use, disposal and washing the machined components are significant, up to four times the cost of consumable tooling used in the cutting operations. To reduce the costs of production and to make the processes environmentally safe, the goal of the aeronautical manufacturers is to move toward dry cutting by eliminating or minimising cutting fluids. This goal can be achieved by a clear understanding of the cutting fluid function in machining operations, in particular in high speed cutting, and by the development and the use of new materials for tools and coatings. High speed cutting is another important aspect of advanced manufacturing technology introduced to achieve high productivity and to save machining cost. The combination of high speed cutting and dry cutting for difficult-to-cut aerospace materials is the growing challenge to deal with the economic, environmental and health aspects of machining.In this paper, attention is focussed on Inconel 718 and recent work and advances concerning machining of this material are presented. In addition, some solutions to reduce the use of coolants are explored, and different coating techniques to enable a move towards dry machining are examined.     

热处理对激光选区熔化成形Inconel 718合金显微组织结构和力学性能的影响

主要研究了激光选区熔化(selective laser melting,SLM)成形Inconel 718合金经固溶时效(SA)、均匀化+固溶时效(H+SA)、热等静压+固溶时效(HIP+SA)3种热处理后显微组织结构的转变与力学性能之间的关系.结果表明,沉积态试样的晶粒内部存在大量树枝晶结构,枝晶间析出了大量硬脆La...     

热处理对激光选区熔化制备Inconel 718合金组织和拉伸性能的影响

采用激光选区熔化工艺(SLM)制备了Inconel 718合金,并对合金分别进行了1050 ℃×1 h固溶和1050 ℃×1 h固溶+720 ℃×8 h+620 ℃×8 h双级时效热处理。结合微观组织、拉伸性能和断裂特征分析,研究了热处理工艺对SLM制备的Inconel 718合金组织和力学性能的影响。结果表明:固溶处理后合金内Laves相溶解,位错密度显著降低,材料的强塑性匹配较打印态得到良好的改善。经过时效热处理后,γ′和γ″强化相析出使合金强度大幅度提高的同时,保留了一定的塑性。     

Mechanisms involved in the improvement of Inconel 718 machinability by laser assisted machining (LAM)

The aim of the present research work has been to gain a broader understanding of how or why laser assisted machining (LAM) improves machinability of Inconel 718, a hard-to-machine material of interest in the aeronautic industry. This has been accomplished by, first, running short run tests to determine the laser parameters and configuration for which highest force reductions are obtained and also to determine the effect of cutting parameters (feed, cutting speed and depth of cut) on force reduction. Secondly, long run tests have been performed in order to analyze process variables such as cutting forces, tool wear and surface roughness. Temperatures and hardness have been also measured in order to gain a broader perspective of the process.Experimental results have demonstrated that LAM improves machinability of Inconel 718 since machining forces and final surface roughness are reduced. The novelty reached with the present research work is the identification of three mechanisms associated to the laser heating as the responsible of this machinability improvement: material yield strength reduction, material base hardness reduction (only in precipitation hardened Inconel 718) and elimination of the work hardening generated in previous machining passes. The reduction of the work hardening leads also to a lower notch wear that limits the risk of sudden failure of the cutting tool and thus the wear mode is changed to flank wear, which leads to a controllable tool life and better surface roughness.     

分析右美托咪定静脉泵注在全身麻醉中的应用效果

采用第一性原理计算与实验相结合的方法探究了Cu元素掺杂所造成的元素之间的交互作用对Inconel 718合金Nb偏析的影响。构建了掺杂前后Ni-Fe-Cr-Nb超晶胞模型,计算了掺杂前后各体系的形成热、结合能、态密度、差分电荷密度以及布居分布。计算结果表明,Cu原子的掺杂降低了体系的稳定性;掺杂改变了体系中元素之间的交互作用,影响了原子之间的键合强度及电荷密度分布,Cu的添加增加了基体中Fe原子和Cr原子之间的结合力,但同时也增加了Fe原子和Nb原子之间的排斥力。实验结果表明,微量Cu元素的加入降低了Fe和Cr的偏析,但促进了Nb元素的偏析。第一性原理计算和实验结果表明,Cu掺杂后Nb原子与周围Fe原子间排斥力的增加是Cu促进Nb偏析的本质原因。     

The electrochemical polishing behavior of the Inconel 718 alloy in perchloric-acetic mixed acids

The electropolishing behavior of the Inconel 718 alloy was studied by using rotating disc electrode (RDE) in the HClO₄-CH₃COOH mixed acids with different HClO₄-concentrations. After electropolishing, surface morphologies of RDE specimens were examined with surface profiler, atomic force microscope and scanning electron microscope. According to the surface morphologies observed, three types of anodic dissolution behavior can be characterized in relation to the HClO₄-content in mixed acids; namely, leveling without brightening of the surface in the mixed acids with 10 and 20 vol% HClO₄, leveling and brightening of the surface in the mixed acids with 30 and 40 vol% HClO₄, and a matt and gray surface in the mixed acids with 50 vol% or more HClO₄. Anodic dissolution in the first and second dissolution types follows a mass-transfer controlled mechanism, in which a linear relationship between the reciprocal of limiting-current density and the reciprocal of square root of rotating speed of RDE specimen can be detected. Owing to precipitation of salt film on the polished surface of the Inconel 718 material, saturated dissolved metallic ions could be the chemical species for the mass-controlled mechanism. The salt film, in addition, could enhance the corrosion resistance of the Inconel 718 alloy.     

The effect of water content on the electropolishing behavior of Inconel 718 alloy in perchloric–acetic acid mixtures

The electropolishing behavior of Inconel 718 alloy was studied in perchloric–acetic acid mixtures using a rotating disc electrode. The electropolishing behavior of an Inconel 718 weld, which was prepared with electron beam welding, was also investigated. A leveled but not brightened surface can be achieved when Inconel 718 alloy is potentiostatically polished in the acid mixture with 20 vol.% perchloric acid. Interestingly, a brightening effect could be obtained in this acid mixture by adding 10–50 ml l⁻¹ water or by being at rest at room temperature for several days. When electropolishing in acid mixture with 40 vol.% perchloric acid, leveling and brightening of the Inconel 718 surface can be detected. When electropolished in this acid mixture, the fusion zone of the Inconel 718 weld cannot be leveled together with its nearby base metal. Nevertheless, a good polished surface of the Inconel 718 weld can be achieved with the acid mixture with 20 vol.% perchloric acid by adding 40 ml l⁻¹ of water. Electropolishing was performed in the limiting diffusion current region where the transport of water to the anode seemed to be the rate-determining process.     

基于人工神经网络的机械加工工艺方案的综合评估决策模型的研究

采用了人工神经网络(Artifical Neural Network ANN)技术。提出了一种新型的机械加工工艺方案的综合评估模型，并经实际应用，结果表明该工作是可行的、简易的，可以作为评估的一种有效方法，为机械加工工艺方案的决策打下基础。     

Simulation of aging process of lead frame copper alloy by an artificial neural network

1　INTRODUCTIONThefunctionsofleadframeinelectronicpackingareprovidingchannelsforelectronicsignalsbetweendevicesandcircuits ,andfixingdevicesoncircuitboards.Leadframealloysarerequiredtohavehighstrengthandgoodformabilityaswellashighelectri calandthermalconductivity .Cu basealloysarethemostpopularleadframealloysandareusedinplasticpackagingapplicationduetotheirhighthermalandelectricalconductivityaswellashighstrength[13] .Theaginghardening processinfabricationofleadframecopperalloymakesitpossi…