Micro-milling Inconel Research Articles

Residual stress prediction of micro-milling Inconel 718 thin-walled parts

Residual stress prediction of micro-milling Inconel 718 thin-walled parts

Experimental research on mechanical, material, and metallurgical properties of Inconel 600: Application in elevated temperature environment

Experimental research on mechanical, material, and metallurgical properties of Inconel 600: Application in elevated temperature environment

Prediction of tool wear during micro-milling Inconel 718 based on long short-term memory network

Tool wear is inevitable due to the thermal-mechanical coupling in micro-milling, Micro-milling of difficult-to-cut material Inconel 718 leads to significant flank wear on the cutting tool. Tool wear influences the dimensional accuracy and surface quality of products, and also influences tool life. Tool wear during micro-milling process cannot be obtained by current commercial finite element software directly. This paper presents a tool wear prediction method for micro-milling cutter based on long short-term memory network. Firstly, experiments of micro-milling Inconel 718 are carried out, the cutting forces in three directions, reduction ratio of the tool diameter and the flank wear of the cutting tool are obtained. Then, through correlation analysis, it is found that Fx has the strongest correlation with reduction ratio of the tool diameter, the correlation coefficient is 0.9390, and Fy has the strongest correlation with the flank wear of the cutting tool, the correlation coefficient is 0.9453. Finally, based on the long short-term memory network, a prediction model of reduction ratio of the tool diameter is established with Fx as input. The root mean square error (RMSE), the mean absolute error (MAE) and the mean absolute percentage error (MAPE) are 0.4246, 0.3533 and 2.92 % respectively. And a prediction model of the flank wear of the cutting tool is established with Fy as input. The RMSE, MAE and MAPE are 0.4463, 0.3649 and 0.20 % respectively. The research achieves the prediction of tool wear in micro-milling Inconel 718, which lays a foundation for tool condition monitoring.

Optimization of dead metal zone to reduce cutting forces in micro milling of Inconel 718 using RSM

This study focuses on the mechanism of DMZ (dead metal zone) creation, as well as the impact of cutting edge geometries (sharp, chamfered, double chamfered, and blunt edges), cutting speed, and coefficient of friction on DMZ formation while milling Inconel 718 material (FEM). A non-contact type sensor called a laser doppler vibrometer (LDV) is used to monitor the vibration of rotating surfaces. In current research work, the LDV is used to measure the mill cutter vibration in micro-milling of Inconel 718 in terms of acoustic optic emission signals. A FFT (fast fourier transformer) is used for signals processing in to frequency domain. Design of experiments as per Taguchi, experiments were performed on the alloy at three levels of spindle speeds, depth of cuts, feed rates. Experimental results on the amplitude o vibration of tool along X and Y directions, surface roughness were measured and analysed using response surface methodology. Analysis obtained from the variance was used to recognize the significant parameters which effect the vibration of tool and roughness of surface. RSM was implemented and optimized process parameters for the minimum vibration amplitude and surface roughness.

Statistical Analysis of Surface Roughness, Burr Formation and Tool Wear in High Speed Micro Milling of Inconel 600 Alloy under Cryogenic, Wet and Dry Conditions.

Super alloys offer excellent mechanical and chemical properties at elevated temperatures that make them an attractive choice for aerospace, automotive and chemical processing, and marine applications. These alloys are, however, difficult to machine due to their high strength at elevated temperatures, low thermal conductivity and work hardening. In this study, micro milling of Inconel 600 super alloy has been carried out and the effects of the key input parameters (cutting speed, feed rate, depth of cut) on response parameters (burr formation, surface roughness and tool wear), under various cooling conditions (dry, wet and cryogenic), have been analyzed. High speed micro milling (range up to 80,000 RPM) was carried out, while keeping the feed rate values below and above the cutting edge radius. The Taguchi design of experiments was used during this study. The results have been analyzed using SEM and 3D optical microscopy. Analysis of Variance (ANOVA) revealed that the best surface roughness values can be achieved under cryogenic machining condition with an overall contribution ratio of 28.69%. It was also revealed that cryogenic cooling resulted in the highest tool life with the contribution ratio of cooling conditions at 26.52%.

Prediction of Tool Wear during Micro-milling Inconel 718 Thin-walled Parts

Prediction of Tool Wear during Micro-milling Inconel 718 Thin-walled Parts

Prediction of tool wear during micro-milling Inconel 718 thin-walled parts

Prediction of tool wear during micro-milling Inconel 718 thin-walled parts

Tool wear mechanism of micro-milling Inconel 718 thin wall

Tool wear mechanism of micro-milling Inconel 718 thin wall

Tool wear mechanism of micro-milling Inconel 718 thin wall

Tool wear mechanism of micro-milling Inconel 718 thin wall

Deflection prediction of micro-milling Inconel 718 thin-walled parts

There has been a great increase in the applications of micro thin-walled parts in many fields, such as medical devices, aerospace and so on. The requirement of machining dimensional accuracy for micro thin-walled parts is very high. Inconel 718has the advantages of high strength and corrosion resistance, which can meet the requirements of micro thin-walled parts under poor applying working conditions. However, it is difficult to machine. Micro-milling is a potentially effective processing technique for processing Inconel 718 thin-walled parts. Because of the low rigidity, deflection of Inconel 718 thin-walled parts is easy to occur in micro-milling process, which affects the machining accuracy. So far, the research on the deflection of micro-milling Inconel 718 thin-walled parts is still blank. In this paper, a method of deflection prediction of micro-milling thin-walled parts is proposed. Firstly, a simulation model of micro-milling Inconel 718 thin-walled parts process is established, which realizes the prediction of milling force. Then, by using element birth/death technique, a deflection prediction model of micro-milling thin-walled parts is built based on the predicted value of milling force output by the simulation model, which achieves the more efficient and accurate deflection prediction of micro-milling thin-walled parts. Finally, the correctness of the built simulation model of micro-milling thin-walled parts process as well as the deflection prediction model of micro-milling thin-walled parts are verified by experiments. The research provides a feasible way for deflection prediction of micro-milling thin-walled parts, and lays foundation for deflection suppression and machining accuracy improvement of micro-milling thin-walled parts to a certain extent.

Simulation of micro-milling Inconel 718 considering scale effect

To study the scale effect during micro-milling process, we establish a modified Johnson-Cook (JC) constitutive model to describe the strengthening behavior of materials on microscale based on the theory of strain gradient plasticity. The VUMAT constitutive subroutine of Inconel 718 is programmed. The radius of the tool edge and its influence on the rake angle are considered. Based on the modified JC constitutive equation, the simulation of micro-milling Inconel 718 process is achieved. The micro-milling Inconel 718 experiments are conducted. The accuracy of the simulation of micro-milling Inconel 718 process considering scale effect is verified by comparing cutting force from experiments with simulation outputs based on the traditional as well as modified JC constitutive equation. It is proved that the simulation outputs of the micro-milling process based on the modified JC constitutive equation are more consistent with the experimental results.

Investigation on laser-induced oxidation assisted micro-milling of Inconel 718

Poor surface quality and rapid tool wear are the main problems in micro-cutting of Inconel 718. In this study, a novel hybrid machining method named laser-induced oxidation assisted micro-milling is proposed to solve the aforementioned problems. A loose oxide layer and a relatively flat sublayer are formed on the material after laser irradiation. Under optimized laser parameters with a scanning speed of 1 mm/s and an average laser power of 4.5 W, the thicknesses of the oxide layer and the sublayer are 24 and 18 μm, respectively. The influence of cutting parameters on milling force, surface roughness, surface quality, and top burr size is studied in detail. Cutting force and thrust force in the proposed hybrid machining process are lower than those in the conventional micro-milling. Results show that for the investigated range of parameters, the optimal feed per tooth and depth of cut in the hybrid process are 3 μm/z and 3 μm, respectively. When using the optimal parameters, the surface roughness of the machined slot bottom is 108.5 nm. The top burr size on the up-milling side and the down-milling side is 26.8 and 36.2 μm, respectively. In addition, the tool wear mechanism is coating delamination in hybrid process, whereas chipping, coating delamination, tool nose breakage, and adhesion are the main tool wear mechanism in the conventional micro-milling. For the same amount of material removal, the proposed hybrid process can decrease the tool wear and enhance the service life of the micro-end mill as compared to conventional micro-milling.

Atmospheric pressure plasma jet assisted micro-milling of Inconel 718

Nickel-based superalloy Inconel 718 is one of the hardest materials owing to its high hardness and additional physical properties. It is the most commonly used superalloy in gas turbine, aerospace, and automobile sectors. Micro-milling is generally employed for precision manufacturing of tiny structures, but it is difficult to obtain good surface quality with micro-milling Inconel 718 because of its excellent mechanical properties like high strength and hardness. Atmospheric pressure cold plasma jet can effectively improve surface wettability without changing surface micromorphology, which is expected to have positive lubricating effects in micro-machining of difficult-to-cut materials. In addition, minimum quantity lubrication can induce coolants into the machining area more efficiently, and is especially appropriate for micro-machining. In this paper, we propose a composite micro-milling method combining plasma jet and minimum quantity lubrication to machine Inconel 718. The effect of plasma jet on machinability is investigated by performing micro-milling experiments under different atmospheres (dry, nitrogen jet, plasma jet, minimum quantity lubrication, and plasma + minimum quantity lubrication). Surface roughness, cutting forces, and residual stress are the measures using corresponding techniques. The results indicate that the atmospheric pressure cold plasma jet can efficiently improve surface quality and reduce cutting forces of Inconel 718.

A study on effect of dead metal zone on tool vibration, cutting and thrust forces in micro milling of Inconel 718

Inconel 718 is a nickel-based super alloy, its characteristics pose more complex in micro machining. Aim of the present study is to investigate effect of process parameters and tool parameters on the dead metal zone (DMZ) geometry and length of shear plane and further on cutting force, thrust force and amplitude of cutter vibration. In the present study, mechanistic models were integrated with finite element method (FEM) simulation to predict cutting force and thrust force in micro milling of Inconel 718. Numerical simulation was carried out to estimate size of DMZ and its angles for all the experiments. Simulation results were used in the mechanistic models to estimated cutting force and thrust force. Series of experiments were carried out on the Inconel 718 at different levels of process and tool parameters and cutting forces were measured. Comparison between the predicted values of cutting forces and thrust forces with experimental results shown a good agreement. Effect of process and tool parameters on size of DMZ and length of shear plane was studied. Further, effect of DMZ and length of shear plane on cutting force, thrust force and amplitude cutter vibration was studied. Feed per tooth and cutter nose radius have significant effect on length of shear plane and length of DMZ side respectively. The parameters were optimized as 4500 rpm of cutting speed, 10 μm per tooth of feed, 0.12 mm of cutter nose radius and 6.8485° of rake angle for minimum side length of DMZ and length of shear plane in order to reduce cutting force, thrust force and amplitude of cutter vibration.

The effect of cutting parameters on micro-hardness and the prediction of Vickers hardness based on a response surface methodology for micro-milling Inconel 718

The poor characteristics of Inconel 718, such as large plasticity, low thermal conductivity, and sensitivity to the strain rate, lead to serious problems in its micro-milling, particularly its work hardening, which lowers the fatigue and the corrosion resistance of micro parts and accelerate tool wear. Therefore, the studies pertaining to work hardening caused by micro-milling of Inconel 718 are needed. This paper studies the influence of cutting parameters, including the spindle speed, the feed rate per tooth, and the axial cutting depth, on surface Vickers hardness and predicts the Vickers hardness of the machined surface on Inconel 718. The authors adopt response surface methodology to build the Vickers hardness prediction model and rank the parameters based on their influences on surface Vickers hardness of micro-milled Inconel 718. According to our analyses, the spindle speed has themost influence on Vickers hardness, the axial cutting depth has an intermediate influence, and the feed rate per tooth has the least influence. A significant interactive influence between the spindle speed and the feed rate per tooth exists. The study could support the appropriate selection of cutting parameters in improving the characteristics of surface work hardening thereby the quality of the final product.

The flank wear prediction in micro-milling Inconel 718

PurposeCutting tool wear is known to affect tool life, surface quality, cutting forces and production time. Micro-milling of difficult-to-cut materials like Inconel 718 leads to significant flank wear on the cutting tool. To ensure the respect of final part specifications and to study cutting forces and tool catastrophic failure, flank wear (VB) has to be controlled. This paper aims to achieve flank wear prediction during micro-milling process, which fills the void of the commercial finite element software.Design/methodology/approachBased on tool geometry structure and DEFORM finite element simulation, flank wear of the micro tool during micro-milling process is obtained. Finally, experiments of micro-milling Inconel 718 validate the accuracy of the proposed method for predicting flank wear of the micro tool during micro-milling Inconel 718.FindingsA new prediction method for flank wear of the micro tool during micro-milling Inconel 718 based on the assumption that the wear volume can be assumed as a cone-shaped body is proposed. Compared with the existing experiment techniques for predicting tool wear during micro-milling process, the proposed method is simple to operate and is cost-effective. The existing finite element investigations on micro tool wear prediction mainly focus on micro tool axial wear depth, which affects size accuracy of machined workpiece seriously.Originality/valueThe research can provide significant knowledge on the usage of finite element method in predicting tool wear condition during micro-milling process. In addition, the method presented in this paper can provide support for studying the effect of tool flank wear on cutting forces during micro-milling process.

Coupled thermal and mechanical analyses of micro-milling Inconel 718

Micro-milling forces, cutting temperature, and thermal–mechanical coupling are the key research topics about the mechanism of micro-milling nickel-based superalloy Inconel 718. Most current analyses of thermal–mechanical coupling in micro-milling are based on finite element or experimental methods. The simulation is not conducive to revealing the micro-milling mechanism, while the results of experiments are only valid for certain machine tool and workpiece material. Few analytical coupling models of cutting force and cutting temperature during micro-milling process have been proposed. Therefore, the authors studied coupled thermal–mechanical analyses of micro-milling Inconel 718 and presented a revised three-dimensional analytical model of micro-milling forces, which considers the effects of the cutting temperature and the ploughing force caused by the arc of cutting edge during shear-dominant cutting process. Then, an analytical cutting temperature model based on Fourier’s law is presented by regarding the contact area as a moving finite-length heat source. Coupling calculation between micro-milling force model and temperature model through an iterative process is conducted. The novelty is including cutting temperature into micro-milling force model, which simulates the interaction between cutting force and cutting temperature during micro-milling process. The established model predicts both micro-milling force and temperature. Finally, experiments are conducted to verify the accuracy of the proposed analytical method. Based on the coupled thermal–mechanical analyses and experimental results, the authors reveal the effects of cutting parameters on micro-milling forces and temperature.

Strain Hardening Properties and the Relationship Between Strain and Hardness of Inconel 718

In micro-milling of Inconel 718, work hardening occurs and the strain hardening properties as well as the relationship between strain and hardness of Inconel 718 remain unclear. The quasi-static tensile tests are conducted in this paper. Through the experiments, the strength coefficient K and the strain-hardening exponent n in Hollomon formula, which describes the relationship between strain and stress of a material, are calculated. After the measurements of the micro-hardness of Inconel 718 under different plastic deformations, the relationship between micro-hardness and strain of Inconel 718 is established. This relationship is valuable in computation of the hardness based on the stress state of Inconel 718 and it also extends the application of the commercial finite element analysis software such as ABAQUS, since it tracks stress state but cannot acquire the hardness of the machined surface. The proposed equation then calculates the hardness value based on the simulation output of stress in the software. [Submitted 18 July 2017; Accepted 28 November 2017]

Modelling and optimisation of cutting parameters on surface roughness in micro-milling Inconel 718 using response surface methodology and genetic algorithm

In recent years, micro-milling techniques have attracted great attention and interest from academia and industry. Inconel 718 is a nickel-based superalloy with good tensile, fatigue, creep and rupture strength and can find great application in nuclear and aerospace industry. In this paper, the response surface methodology (RSM) was applied to develop the model for predicting surface roughness in micro-milling Inconel 718. The magnitudes of cutting parameters affecting the surface roughness, which were depth of cut, spindle speed, and feed rate, were analysed by the analysis of variance (ANOVA). The validity of the surface roughness prediction model was proved due to the tiny error between the measured values and the prediction results. Then, genetic algorithm (GA) was used to determine the optimal cutting parameters achieving minimum surface roughness in micro-milling Inconel 718 process. All experiments show that the optimised results agree well with the test ones.

Effects of cutting parameters on temperature and temperature prediction in micro-milling of Inconel 718

Inconel 718 is a kind of typical difficult-to-machine material. Micro-milling technology is an effective method for fabricating micro parts of Inconel 718. The change rules of micro-milling temperature differ from those of the traditional processing, which will affect the surface integrity of the workpiece and the tool life of the micro-milling cutter in different ways. To ascertain the effects of cutting parameters on cutting temperature during micro-milling Inconel 718 and achieve the prediction of cutting temperature, some micro-milling experiments are conducted based on the response surface method. The independent and interaction effects of the spindle speed, feed per tooth and axial cutting depth on cutting temperature are investigated. A micro-milling temperature prediction model is established based on the experiment results. The maximum prediction error is 5.3% and the average prediction error is 2.6%. Finally, the accuracy of the proposed model is validated through experiments of micro-milling Inconel 718.