Investigation of surface integrity in dry machining of Inconel 718

Machining of advanced aerospace materials have grown in the recent years although the diffucult-to-machine characteristics of alloys like titanium or nickel-based alloys cause higher cutting forces, rapid tool wear, and more heat generation. Therefore, machining with the use of cooling lubricants is usually carried out. To reduce the production costs and to make the processes environmentally safe, the goal is to move toward dry cutting by eliminating cutting fluids. This objective can be achieved by using coated tool, by increasing cutting speed, and by improving the product performance in term of surface integrity and product quality. The paper addresses the effects of cutting speed and feed on the surface integrity during dry machining of Inconel 718 alloy using coated tools. In particular, the influence of the cutting conditions on surface roughness, affected layer, microhardness, grain size, and microstructural alteration was investigated. Results show that cutting conditions have a significant effect on the parameters related to the surface integrity of the product affecting its overall performance.     

Grey-RBF-FA method to optimize surface integrity for inclined end milling Inconel 718

Performance and service life of aerospace component are significantly influenced by surface integrity, especially for cyclically loaded thin-walled structure component. This work focuses on the surface roughness and residual stress of machined surface, which are considered the most important indications of surface integrity, for inclined end milling Ni-based superalloy Inconel 718. The purpose is to minimize surface roughness and maximize compressive residual stress by optimizing the cutter geometry. Based on the grey relational analysis (GRA), an integrated multi-objective optimization approach with the radial basis function (RBF) neural network and the firefly algorithm (FA) is developed. The end-tooth rake angle, end-tooth relief angle, and helix angle are selected as design factors, while the residual stress and the 3D surface roughness are taken as performance characteristics. The orthogonal array L16 (4³) is employed to generate sample data set. Then, the GRA is introduced to search the most influential factor by the grey relational grade (GRG). Subsequently, the proposed grey-RBF-FA method is applied to the multi-objective optimization problem. After calculating the GRG, the RBF network is used to relate the GRG with cutter geometric parameters. The test data show the RBF model has a low prediction error of 11.11%. Finally, the FA is utilized to search the optimal parameter-level combination. Validation experiments show that, compared with the original GRA, the proposed method further greatly improves the surface roughness and residual stresses in both directions by 1.20 μm, 249.1 MPa, and 176.5 MPa, respectively. The developed approach is proved to be feasible and can be generalized for other multi-objective optimization in manufacturing industry.     

Experimental investigation on high-efficiency grinding of Inconel 718 with heat pipe grinding wheel

Grinding heat is a significant problem for grinding difficult-to-machine materials such as nickel-based superalloys, which restricts their applications. A majority of existing cooling methods ensure cooling by simply increasing the volume of coolant. However, lubricants often lose efficacy due to film boiling and have adverse health and environment effects. To dissipate grinding heat in the contact zone and guarantee workpiece surface quality, a novel cooling method that dissipates grinding heat assisted by forming rotating heat pipe inside the grinding wheel (HPGW) is proposed. Tests were performed to determine its heat transfer capacity in high-efficiency grinding of Inconel 718 alloy. The results show that grinding with HPGW leads to lower grinding temperatures and lower thermal damages to the workpiece when compared to grinding with non-HPGW. Better heat transfer capacity of HPGW is explained by heat transfer resistance analysis for both grinding wheels. The analysis proves that the value of HPGW is one order of magnitude lower than non-HPGW. Furthermore, in-depth studies of the ground surface showed no changes in microstructure or microhardness for the workpiece when using HPGW, whereas different degrees of burn were seen as indicated by different temper colors and corresponding changes in microstructure and microhardness.     

Improving surface integrity in finish machining of Inconel 718 alloy using intelligent systems

In machining of hard materials, surface integrity is one of the major customer requirements which comprise the study of the changes induced to the workpiece. Surface roughness and residual stress are often considered as the most significant indications of surface integrity. Inducing tensile residual stress during the machining processes is a critical problem which should be avoided or minimized to obtain better service quality and component life. This problem becomes more evident in the presence of rough machined surface because fatigue life of manufactured components might be decreased significantly. Inconel 718 superalloy is one of the hard materials used extensively in the aerospace industries. It is prone to tensile residual stress in machined surface. Thus, controlling and optimizing residual stress and surface roughness in machining of Inconel 718 are so needed. Intelligent techniques based on the predictive and optimization models can be used efficiently for this purpose. In this study, the optimal machining parameters including cutting speed, depth of cut, and feed rate were accessed by intelligent systems to evaluate the state of residual stress and surface roughness in finish turning of Inconel 718. The results of experiments and analyses indicated that implemented techniques in this work provided a robust framework for improving surface integrity in machining of Inconel 718 alloy. It was shown that cutting speed has more effect on surface integrity than other investigated parameters. Also, depth of cut and feed rate were found in the moderate range to obtain satisfactory state of tensile residual stress and surface roughness.     

切削Inconel718表面粗糙度的试验研究

利用涂层硬质合金刀具对Inconel 718进行了高速切削试验,对不同切削参数下刀具的切削用量及刀具磨损对工件表面粗糙度的影响进行了研究。分析结果表明进给量对已加工表面的粗糙度影响最大,切削深度次之,切削速度最小;刀具进入正常磨损阶段后,表面粗糙度减小,处于最佳的切削状态。     

A review on the progress towards improvement in surface integrity of Inconel 718 under high pressure and flood cooling conditions

Self-conditioning performance of polishing pad is an important characteristic to influence processing efficiency and service life in chemical mechanical polishing (CMP). The slurry can react with the pad surface, which affects its self-conditioning performance in fixed abrasive polishing process. Wear ratio of wafer material removal rate (MRR) and pad wear rate is introduced to evaluate self-conditioning performance of fixed abrasive pad (FAP). To clear the effect of chemical additive on FAP self-conditioning, wear ratio, FAP surface topography, friction coefficient, and acoustic emission signal of polishing process were investigated in fixed abrasive polishing of quartz glass with ferric nitrate, ethylenediamine (EDA), and triethanolamine (TEA) slurry, respectively. Results indicate that TEA slurry can provide excellent self-conditioning of FAP in fixed abrasive polishing of quartz glass. MRR and wear ratio maintain high levels during the whole polishing process. Friction coefficient and acoustic emission signal are more stable than that of the other two chemical additives. An appropriate amount of TEA, which is beneficial to enhance MRR and extends service life of FAP, is added in the polishing slurry to improve FAP self-conditioning in fixed abrasive polishing process.     

Study of surface quality in machining nickel-based alloy Inconel 718

In machining operation, the surface quality is one of the most important requirements for many workpieces. Because of the special physical and chemical properties, good-machined surface quality becomes a key issue to solve in machining Inconel 718. In this paper, PVD-TiAlN-coated carbide tools were used to turn Inconel 718. Based on observing the tool wear and machined surface morphology, the main factors affecting surface quality at different cutting speeds were analyzed. The optimal cutting temperature was calculated, according to the above analysis and Archard adhesion wear model, and further cutting parameters optimization was conducted, on the basis of the proposed optimal cutting temperature. The optimized cutting parameters based on optimal cutting temperature can be considered to improve surface quality.     

用于加工Inconel718的切削刀具发展现状

镍基高温合金Inconel718具有熔点高、热传导率低、加工硬化现象严重的特点,被认为是最难加工的金属材料之一。近年来,随着航空航天、能源动力技术的飞速发展,Inconel718高温合金的应用越来越多,其高速、高效切削的加工需求也日益扩张,其切削工艺的制定、尤其是切削刀具的选择越来越重要。本文综述了常用于加工In-conel718的刀具(高速钢、硬质合金、陶瓷、立方氮化硼)及其涂层刀具的加工性能,分析了不同涂层对于刀具寿命和工件表面质量的影响,对硬质合金刀具和陶瓷刀具作了详尽的对比分析。最后,对高速钢、陶瓷、硬质合金和立方氮化硼刀具切削Inconel718的应用情况进行了总结,给出了Inconel718高温合金切削加工刀具选择的有益参考。     

Incone1718镍基高温合金的切削性能仿真

在考察Inconel718镍基高温合金的化学成分和有关性能的基础上,通过Deform-3D软件对其进行车削仿真,分析影响Inconel718镍基高温合金切削性能的主要因素,给出其最佳的切削速度、进给量和背吃刀量的组合.研究了不同换热系数和刀-屑摩擦因数对Inconel718镍基高温合金切削性能的影响,找到了恰当的冷却润滑方式.     

镍基合金Inconel718可切削加工性的试验研究

Inconel718是一种高强度耐热镍基合金,具有优良的高温强度、高温硬度和耐蚀性,在高温条件下能长期工作,已被广泛地应用于宇航工业、航空工业的涡轮发动机和相关零件的制造。分析Inconel718的机械性能、微观组织结构及其对切削加工性能的影响并进行了相关的试验验证,在试验数据的基础上,研究Inconel718中含碳量对切削过程中刀具磨损的影响。试验结果表明,Inconel718中含碳量在刀具后刀面磨损中起着非常重要的作用,Inconel718合金中含碳量越高,合金中所含的细微硬质夹杂物也越多,在切削过程中使刀具产生严重的后刀面磨粒磨损,从而降低材料的切削加工性。     

基于MQL的超声椭圆振动微切削Inconel718的机理研究

研究不同切削条件下的超声椭圆振动(Ultrasonic elliptical vibration,UEV)对Inconel718微切削性能的影响规律,讨论微量润滑(Minimum quantity lubrication,MQL)和UEV切削对加工性能的影响机理.针对微量润滑切削时的不同喷嘴角度,提出一种新的换热模型,...     

Employing preheating- and cooling-assisted technologies in machining of Inconel 718 with ceramic cutting tools: towards reducing tool wear and improving surface integrity

The International Journal of Advanced Manufacturing Technology - This paper is motivated by the fact that machining of Inconel 718 involves rapid tool wear and poor surface integrity. We...     

电火花成型加工Inconel 718电极损耗及材料去除率研究

采用正交实验方法用铜电极对Inconel718合金材料进行电火花加工研究,研究了不同的加工参数(电流、周率、效率、间隙电压)对电火花加工Inconel718材料过程中的电极损耗和材料的去除率的影响,并对实验结果进行了主效应分析以及方差分析。结果表明:材料去除率随着电流和周率的增大而增大,电极损耗随着周率的增大而减小。在加工参数电流为10A,周率为100μs,效率为80%,间隙电压20V时获得较高的材料去除率;加工参数在电流为4A,周率为200μs,效率为20%,间隙电压20V时获得较小的电极损耗。     

Cutting data correction in Inconel 718 turning

The paper presents research work concerning difficult-to-cut materials turning and chipbreakers reliability in local operating features. Inconel 718 alloy was used as a sample material and two different chipbreakers were tested. The aim of the research was to check the efficiency of chipbreakers in the area of applications recommended by tool manufacturers. As a result, the algorithm for cutting data selection and correction which combines experiments and simulation processes concerning chip breakage effectiveness was built. To estimate chip forms in tests, the visual system equipped with a high-speed camera was used. The cutting forces measuring system provided information for verification of simulation results. The simulation based on the FEM was applied to estimate chip groove filling. Distributions of temperature and stresses on the tool rake face in the function of distance from the cutting edge were calculated. The paper gives recommendations for cutting data correction to achieve acceptable chip forms.     

Machinability investigation of Inconel 718 in high-speed turning

This article presents an approach based on wavelet correlation modelling for health state monitoring of fluid dynamic bearings in brushless DC motors. This approach involves two stages: (1) extracting of features from the motor-stator current signatures by analysing discrete wavelet transform coefficients; and (2) building of the simplest correlation model between the extracted features and the bearing wear using a multivariable regression technique. The correlation model can be used to detect and predict the bearing wear of brushless DC motors. Experiments were carried out using brushless DC motors with fluid dynamic bearings to verify the proficiency of this approach. Good agreement between the prediction result and the real motor health condition demonstrated the viability of the approach for bearing prognostic applications. The correlation equations obtained have acceptable detectability and accuracy based on a desired 95% level of confidence.     

Finite element analysis of laser inert gas cutting on Inconel 718

Inconel 718 has high strength, which makes it difficult to cut using conventional cutting methods. In the present study, the laser inert gas cutting of Inconel 718 was simulated by finite element analysis software ANSYS. Finite element method was used to predict thermal stress and kerf width formation during the laser cutting process. ANSYS Parameter Design Language was used to model the Gaussian-distributed heat flux from the laser beam acting on the workpiece. The removal of melted material during laser cutting to form the kerf width was modeled by employing the element death methodology in ANSYS. In addition, laser cutting was simulated at continuous wave (CW) and the effects of laser power and cutting speed on kerf width were investigated. A series of experiments were carried out to verify the predictions. The temperature fields on the workpiece were measured using thermocouples. The kerf width size was measured using a profile projector, whereas the metallurgical and morphological changes at the cutting edge were examined using scanning electron microscopy. A good correlation was found between the simulation and experimental results.     

基于实验Inconel718正交切削有限元仿真分析

为研究犁削效应和前刀面粘压对Inconel718切削过程的影响.基于正交切削实验建立Inconel718有限元切削模型,模型结果同实验值对比以验证模型可靠性.通过改变刀具圆角半径和负前角参数,提取并比较不同的切削力时域曲线和刀具温度,分析犁削效应和前刀面粘压.研究表明犁削效应提高进给力数值,刀具圆角半径由0变为5μm,Inconel718切削进给力均值提高7％：前刀面粘压提高刀具和切屑温度,有利于切屑分离.但刀具负前角为-20＆#176;,切削加工不稳定.     

高速车削Inconel 718切削力的试验研究

为了研究高速切削Inconel 718的切削力经验公式和各切削参数对切削力的影响显著程度,应用涂层硬质合金刀具对Inconel 718进行了正交车削试验,得到了硬质合金刀具车削Inconel 718的切削力经验公式。分析结果表明:对切削力影响最大的因素是进给量,切削深度和切削速度对试验结果的影响依次减弱。用涂层硬质合金刀具KC5510精车Inconel 718时,采用小进给量、小切削深度、高切削速度可以得到小的切削力,取得良好的切削效果。