Machining Of Superalloys Research Articles

Optimization of Controllable Turning Parameters for High Speed Dry Machining of Super Alloy: FEA and Experimentation

In dry machining, Interference Temperature plays a major role for Tool Wear and change in workpiece properties. Interface temperature and Tool wear are mainly affected by controllable turning parameters such as cutting speed, feed and depth of cut. The research aim of this paper is to minimize tool wear by optimizing controllable turning parameters during high speed dry turning of super alloy Inconel 718. Full FactorialDesign of Experiments is planed with 3 Levels for the purpose. A Finite Element Analysis model is created using Deform 3D software.The FEA outcomes are compared with Experimental results.ANOVAis carried out for the experimental results and mathematical models are developed for both the responses and are used for formulating a multi objective optimization.Multi-objective optimization is carried out using Genetic Algorithm.Satisfactory results are obtained through this research work and can be adopted in Industries.

A Review on Cryogenic Machining of Super Alloys Used in Aerospace Industry

The present work reviews the work done on cryogenic machining of super alloys around the four continents i.e. North America, Europe Asia and Australia. Cryogenic machining has emerged as one of the most effective procedure among the advanced machining techniques for machining super alloys. Along with that, the coating on the tool also plays a crucial role in cryogenic machining. It is found that, North American research focuses on cryogenic machining of innovative materials like shape memory alloys and ceramics. European research focuses on application of cryogenic as well as MQL techniques and studying the different types of wears and surface integrity. Several authors have also presented innovative nozzle geometries which increases cooling efficiency in cryogenic machining. Whereas Asian research focuses on tribological performance of cryogenic coolants using advanced manufacturing techniques like WEDM and using several types of coatings on tools. Australian Research focuses on tool wear and surface roughness of machined surface. More specifically, special attention is given to the main findings obtained over the last couple of years from the various authors collaborative research on cryogenic machining of super alloys, through the experimental investigations.

Process level environmental performance of electrodischarge machining of aluminium (3003) and steel (AISI P20)

Electrodischarge machining (EDM) plays a significant role in the precision machining of super alloys and the die/mould manufacturing industry and hence warrants the study of its environmental impact and sustainability. However, process level data for unconventional machining practices are limited in the available Life Cycle Inventory (LCI) databases. This paper aims to accumulate process level LCI data for EDM and to assess the environmental impact using life cycle analysis. The method of assessment takes insights from ISO 14040 and the CO2PE initiative. Data from industrial case studies relating to diesinking EDM and wire EDM of steel and aluminium alloys are used. Environmental impact is calculated using the resultant LCI data and supplementary data from the Ecoinvent database. The ReCePi endpoint method is used in the impact assessment, enabling comparisons among environmental performances. Recommendations for improvements during the design phase of machine tools and the operational phase of the machines are given.

Investigation of Modified Cutting Insert with Forced Coolant Application in Machining of Alloy 718

In the last decades machining methods have witnessed an advancement in both cutting tools and coolant/lubrication, sometimes in combination with high pressure jet. The aim of this work is to investigate a modified cutting insert with forced coolant application, FCA, how it influences the tool-chip contact in the secondary shear zone and how it affects the tool wear when turning Alloy 718. During the machining process the main and frequent problems are heat generation and friction in the cutting zone, which has a direct impact on the cutting tool life. High pressure jet cooling have headwayed the cutting technology for the last five decades, showing an improvment of tool life, reduced temperature in the cutting zone and better surface integrity of the workpiece. These developments have practically enhanced the capability and quality in machining of superalloys. This paper is an advancement of the previous work, increasing surface area of the insert, with a additional channel design to improve the coolant reachability in the tool-chip contact area on the rake face. The influence in tool wear has been investigated. Through a set of experiments, a channel design insert with forced coolant application, has shown about 24-33% decrease in tool wear compared to only a textured insert. Hybrid inserts with its cooling and channel features have even widened the operational cutting region with significantly less tool wear.

The Wear of Cutting Pellets Coated with TiAlN During Machining of a Cobalt Superalloy (FSX-414)

For the machining of superalloys, unconventional methods such as electroerosion, electrochemistry and others are frequently used due to the hardness of the material. Although, for some other operations, theconventional machining is essential. Because of their high hardness and improved mechanical properties, these superalloys require specific materials means such as machines and tools. To get an idea of the behavior of such a material in particular fields such as gas turbines, nuclear reactors, the industrialists have been interested for many years in the development and characterization of new materials to optimize the wear of the cutting tools and produce at a lower cost. In this context, the study of the tribological behavior of the cobalt-based superalloy FSX-414 standard 9001F in contact with the TiAlN-coated carbide inserts provides important information in the case of the turbine blade industry. The article discusses the productivity of gas turbine blades of the thermal power plant electricity production. The material to be machined is a superalloy which requires a carbide tool with adequate coating (TiN, TiC, TiAlN, TiCN...). This research eté preceded by an article about the couple material / tool (FSX-414 / TiN coated carbide). A comparison of results has been made to optimize the cutting process and start production with lower cost. The lifetime of the cutting tool is mainly related to the development of two types of wear: flankwear of the sidewall and crater wear. This phenomenon of wear seems to be progressive, it develops during the cutting, which affects the quality of the machining, the productivity, and in particularly it may lead to the destruction of the tool in case of excessive wear. For the measurement of wear, an indirect method is used by coupling a Touptek photon camera to a microscope and capture the image to be processed by Toupview analysis software. It has been shown that the coating is the most influential parameter, followed by the sliding velocity. In this context, a focused research on the wear of TiAlN-coated Platelets in contact with this superalloy which is resistant to wear at high temperature has been developed.

Study on the Shear Angles<i> </i>in High Speed Machining of Powder Metallurgy Superalloy

High efficiency and high speed are the development directions of modern manufacturing technologies. In the last two decades, high speed machining is successfully applied in cutting steel and alumina alloy, due to its unique advantages. However, it is not yet prevalent in powder metallurgy (PM) superalloy machining. This work focuses on the shear angles and influencing rules in high speed machining PM nickel based superalloy, in order to provide reliable theoretical and practical methods in high efficiency/speed machining this kind of material in production practice.

An investigation on surface burn during grinding of Inconel 718

Grinding nowadays is extensively used for machining of superalloys. Inconel 718 is a Ni-based superalloy which is known as difficult to grind material (DTG) due to its inherent properties like high hardness, high hot strength, severe strain hardening and low thermal conductivity. In the present work, grindability of Inconel 718 using conventional abrasive grinding wheels has been experimentally explored. Ground surfaces have been characterized after grinding with silicon carbide (SiC) and alumina (Al2O3) wheels under dry condition. Surface integrity of the ground product has been studied using surface characterization techniques like Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Further, the surface behavior of the ground surface has been investigated using microscopic images, micro-hardness tests, and surface roughness measurements. The major conclusion of the present work is that Inconel 718 can be ground more efficiently using alumina grinding wheels compared to the SiC grinding wheel. In the case of SiC wheel, it has been found that the severe attritious wear of the wheel took place primarily due to the chemical reaction between SiC grits and workpiece material at a higher grinding temperature. The mechanism for such attritious wear has been studied, and it appears to be a dissociation of SiC at higher temperature.

Damage of PVD-Coated Cutting Tools Due to Interrupted Cutting of Ni-Based Superalloys

Ni-based superalloys are typically difficult-to-cut materials. During machining, the cutting forces and temperatures of these superalloys are generally higher than those of other materials. Therefore, the tool life of the coated carbide cutting tools used for superalloy machining is shortened. This study evaluates the damage of the coated end mills during interrupted cutting of alloy 718 and finds the coating properties necessary for improved cutting of Ni-based superalloys. Damage of the PVD-TiN-coated cutting tools was observed by scanning electron microscopy and transmission electron microscopy of the surfaces and cross sections. In addition, friction forces were measured during turning for some coatings, and hardness of the coatings was measured after annealing. Plastic deformation of the coating and crack formation was shown to occur at the coating cross section. In addition, we determined that the major factor for the damage was high friction force between the coating surface and work material at high temperatures. In summary, coatings with stability at high temperatures and low friction forces during machining can reduce the damage of coated cutting tools, thus increasing the tool life.

On the feasibility of a reduction in cutting fluid consumption via spray of biodegradable vegetable oil with compressed air in machining Inconel 706

Superalloys, such as Inconel 706, have extensive applications in aerospace and turbine manufacturing industries owing to their exceptional characteristics, especially high corrosion resistance and stability in elevated temperatures. However, they usually suffer from low coefficient of heat transfer, which can put them in the category of hard-machining alloys. Therefore, utilizing a cutting fluid is the indispensable part of superalloy machining process. Investigating the feasibility of reducing or even removing the cutting fluid plays a crucial role in the machining, since it may induce high machining costs, detrimental impacts on environment and endanger human health. In the present article, influences of machining parameters on forces, surface roughness and tool tip temperature were investigated in two modes of utilizing fluid, which were flood mode and spraying with compressed air, in order to reduce or eliminate the cutting fluid from turning process of Inconel 706. The results revealed that spray mode of cutting fluid in combination with compressed air can ameliorate the heat transfer problem. Moreover, in all of the experiments with spray mode, cutting forces, surface roughness and temperature of cutting area were significantly lower than using fluid with flood mode. This can result in a remarkable decrease in consumption of cutting fluid, which in turn, can solve the environmental issues. Furthermore, during machining with using cutting fluid in spray mode, it is possible to monitor the temperature of machining area via thermal imager in order to have an appropriate control over machining process. Eventually, optimum values of machining parameters were proposed for machining with spray mode of cutting fluid.

Parametric modeling and optimization for wire electrical discharge machining of Inconel 718 using response surface methodology

Inconel 718 is a high-nickel-content superalloy which possesses excellent strength at elevated temperatures and resistance to oxidation and corrosion. This alloy has wide applications in the manufacturing of aircraft engine parts such as turbine disks, blades, combustors and casings, extrusion dies and containers, and hot work tools and dies, but the inherent problems in machining of superalloys with conventional techniques necessitate the use of alternative machining processes. The wire electrical discharge machining (WEDM) process has been recently explored as a good alternative of conventional machining methods, but there is lack of data and suitable models for predicting the performance of WEDM process particularly for Inconel 718. In the present work, empirical modeling of process parameters of the WEDM has been carried out for Inconel 718 using a well-known experimental design approach called response surface methodology. The parameters such as pulse-on time, pulse-off time, peak current, spark gap voltage, wire feed rate, and wire tension have been selected as input variables keeping others constant. The performance has been measured in terms of cutting rate and surface roughness. The models developed are found to be reliable representatives of the experimental results with prediction errors less than ±5 %. The optimized values of cutting rate and surface roughness achieved through multi-response optimization are 2.55 mm/min and 2.54 μm, respectively.

Study on Application of Grey Prediction Model in Superalloy MAR-247 Machining

Superalloy MAR-247 is mainly applied in the space industry and die industry. With its characteristics of mechanical property, fatigue resistance, and high temperature corrosion resistance, therefore, it is mainly applied in machine parts of high temperature and corrosion resistance, such as turbine blades and rotor of the aeroengine and turbine assembly in the nuclear power plant. However, considering that its properties of high strength, low thermal conductivity, being difficult to soften, and work hardening may reduce the life of cutting-tool and weaken the surface accuracy, the study provided minimizing experiment occurring during milling process for superalloy material. As a statistical approach used to analyse experiment data, this study used GM(1,1)in the grey prediction model to conduct simulation and then predict and analyze its characteristics based on the experimental data, focusing on the tool life and surface accuracy. Moreover, with the superalloy machining parameters of the current effective application improved grey prediction model, it can decrease the errors, extend the tool life, and improve the prediction precision of surface accuracy.

Effect of Wire Materials on Cutting Performance of WEDM for Machining of Inconel Superalloy

The machining of superalloys has put really a challenge for technologists and researchers. The conventional techniques of machining do not give satisfactory performance for machining of superalloys. In this paper, the results of an experimental study for cutting of Inconel 718 superalloy with wire electrical discharge machining (WEDM) have been presented. Three different wire materials along with important input process parameters namely peak current, servo voltage, pulse on time and pulse off time have been selected. The effect of these parameters on material removal rate has been investigated by using well know experimental technique called response surface methodology. The experimental results indicate that zinc-coated brass wire is most suitable for Inconel 718. An empirical model has been developed for correlating input parameters and material removal rate for zinc-coated brass wire. Analysis of variance has also been presented.

Wearing Evaluation in Nickel Super-Alloys Turning for the Development of a Predictive Model for CAM Optimization

Nickel super-alloys are characterized by: high temperatures resistance, high hardness and low thermal conductivity. For this reason they are widely used in critical operating conditions. However, due to their excellent properties, nickel super-alloys are hard to machine. Tool wear is a major problem in nickel super-alloy machining; the high temperature at the tool rake face is a principal wear factor. Flank wear is the most common type of tool wear; it offers predictable and stable tool life evaluation. In this work, the authors present a flank wear evaluation in Inconel 718 turning, in order to develop a predictive model for CAM optimization. An appropriate database has been developed thanks to an experimental activity (VB as a function of: the cutting time T, cutting speed S and feed rate F). The objective of the optimization procedure is to maximize the Material Removal Rate (MRR) under the constraint represented by the flank wear limit. The developed procedure operates directly on the part program code, using the original one as starting point for the application of the knowledge about the wear behaviour. After the optimization phase the given output is represented by a new part program code obtained in accordance with: the maximum MRR within the respect of the wear limit. s and tables etc.

Modeling Static and Dynamic Cutting Forces and Vibrations for Inserted Ceramic Milling Tools

Cutting tools with ceramic inserts are increasingly being used in machining of super alloys typically used in aerospace industry. The ceramic inserts make higher cutting speeds possible due to the higher temperature resistance compared to carbide inserts. However, the success of the process is very sensitive to the right selection of process parameters. In this study, analytical process models for indexable milling tools with round ceramic inserts are presented. These models can be used to determine the cutting parameters for optimum quality and maximum productivity. Firstly, geometry of the insert cutting edges under the effect of angles on the inserts was formulated. Then, an analytical cutting force model was developed. This allows analyzing the effects of the parameters on the cutting forces. A time-domain model was also developed to analyze the dynamic cutting forces and stability limits for the milling process. Afterwards, the models were implemented in a Matlab® GUI to make the applications of the models in the industry easy. Cutting force coefficients, which are needed to calculate cutting forces, were identified from cutting tests with Inconel 718 material. Then, the cutting force model was validated with cutting experiments. After obtaining modal data of the tool via tap testing, dynamic cutting forces and vibrations were simulated by means of the time domain model. A series of simulations was carried out to determine stability limits at certain operating conditions using the time domain model, and stability lobes for the tools under study were plotted.

A Surface Roughness Study for Machining of Udimet500 Superalloy, through Statistical Analysis of Influential Parameters

Superalloy is an alloy that has been developed to be used in processes with high thermal and mechanical stresses and also preserving high surface stabilities. Because of the increase in temperature and wearing of tool tip (even in low cutting speeds), machining of these materials has not developed considerably. Increase in demand for machining of these materials equally increases the need for investigating their manufacturing methods. For this reason, optimal machining of superalloys is very important and is under great investigations. The most important parameter for manufacturing companies is surface roughness. In the present paper, surface roughness of Udimet500 superalloy which is a nickel-based superalloy is investigated. Based on regression analysis, the most influential parameters to surface roughness are obtained and a relation for the roughness with respect to depth of cut, cutting speed, feed rate and lubricant type (CO2, Z1 or dry) is derived.

Analysis of acoustic emission signals and surface integrity in the high-speed turning of Inconel 718

Acoustic emission (AE) signals from the machining deformation zone have been used in the past to monitor and study the cutting tool wear and failure, the chip formation mechanism, and the machined surface quality on work materials other than Inconel 718. The machined surface quality generated during the machining of superalloys is a function of the deformation process that occurred in the machining zone. It is known that the interaction between the machining parameters, the cutting tool, and the work material characteristics govern the deformation process. AE signals are capable of capturing the deformation zone activities and hence it is felt that an analysis of the AE signals during machining could help to determine the quality of the machined surface. Therefore, in this work, the dependence of the machining deformation on the surface generation mechanism was assessed in terms of the energy, number of counts, and mean frequency amplitude of the AE signals. Further, the AE characteristics were analysed as a function of the cutting speed, feed rate, depth of cut, and tool edge geometry. The analysis revealed that the frequency amplitude of the AE signals is influenced by the cutting speed. The feed rate and edge geometry are found to influence the number of counts generated during machining deformation. AE signals with fewer perturbations in the energy and counts profiles indicate a better-quality surface with the least alterations. Thus, in general, the AE signal variations have been found to be useful to correlate abnormal events during machining, such as higher thrust forces, chip form variation, and surface anomalies produced in the machining of Inconel 718.

Study on the Machinability Characteristics of Superalloy K424 during High Speed Turning

The present paper is an attempt of an experimental investigation on the machinability of superalloy, K424 during high speed turning using different ceramic inserts under different cutting speed and cooling/lubricating condition. The effect of machining parameters on the tool wear was examined through SEM micrographs.The experimental results show that, round Al2O3＋SiCW KY4300R ceramic insert shows the best cutting performance in cutting the superalloy K424 , and it should be used in rather higher speed. Cold nitrogen gas is not recommended when machining nickel-based alloy with ceramic tools. SEM and EDS analysis shows that the ceramic tool was severely controlled by tool nose and depth-of-cut notch wear, followed by flaking and chipping.

A metric for defining the energy efficiency of thermally assisted machining

A significant amount of work has been conducted on thermally assisted machining (TAM) with a great deal being focused on using a laser to deliver the thermal energy. The body of work has shown that preheating of the workpiece (usually localized heating) makes it possible to machine certain structural ceramics with a conventional cutting tool, improves the machinability of superalloys, and improves the micro-end milling of metals. A variety of metrics have been used to ascertain the impact of thermal assistance on the machining of these materials, including specific cutting energy, tool wear rate, surface roughness, residual stress, material removal rate, material removal mechanism, cost, and surface integrity. Combined, these quantities provide a good description of the process as a function of the material removal temperature. However, they do not address the question of how much thermal energy is required to achieve these temperatures and whether there is room for improving the preheating (i.e., reduce cost). This manuscript looks at the flow of energy in TAM in an attempt to determine how beneficial preheating is. Some efficiency metrics are suggested and used to study the data that have been collected to date. The total thermal energy deposited in the workpiece is compared with the theoretical minimum required to heat the removed material in order to determine what percentage of the deposited (i.e., absorbed) energy is actually used in assisting the cutting process. This enables a comparison between cutting processes (e.g., end milling and turning) and operating conditions to determine how efficiently the added thermal energy is being used. Compared to other machinability metrics the thermal energy efficiency is used to evaluate how beneficial preheating is to the machining processes studied. Four sets of data are studied: thermally assisted turning of silicon nitride and partially stabilized zirconia, and micro-end milling of 6061-T6 aluminum and 1018 steel. The specific energy for TAM of silicon nitride is compared with that for grinding of silicon nitride. It is hoped that this paper will spark a debate in the manufacturing community and provide more insight into thermally assisted manufacturing.

Study on the machinability characteristics of superalloy Inconel 718 during high speed turning

The present paper is an attempt of an experimental investigation on the machinability of superalloy, Inconel 718 during high speed turning using tungsten carbide insert (K20) tool. The effect of machining parameters on the cutting force, specific cutting pressure, cutting temperature, tool wear and surface finish criteria were investigated during the experimentation. The machining parameters have been optimized by measuring forces. The effect of machining parameters on the tool wear was examined through SEM micrographs. During high speed turning acoustic emission signal were collected and analyzed to understand the effect of cutting parameters during online. The research work findings will also provide useful economic machining solution by utilizing economical tungsten carbide tooling during high speed processing of Inconel 718, which is otherwise usually machined by costly PCD or CBN tools. The present approach and results will be helpful for understanding the machinability of Inconel 718 during high speed turning for the manufacturing engineers.

Femtosecond Laser Ablation Regimes in a Single-Crystal Superalloy

Femtosecond (fs, 10−15 second) laser ablation of single-crystal nickel-base superalloy CMSX-4 under laser fluences ranging from 0.1 to 160 J/cm2 has been investigated. For comparison, the ablation behaviors of Ni and Ni3Al as individual components of the superalloy have also been studied. Two distinct ablation regimes were observed, dependent on the incident laser fluence. The ablation threshold fluences for these two ablation regimes were determined to be $$ \phi _{{th1}} $$ = 0.30 ± 0.03 and $$ \phi ^{{}}_{{th2}} $$ = 5.3 ± 0.5 J/cm2 in the superalloy. Ablation thresholds for the single-phase Ni and Ni3Al alloys were close to those measured for two-phase superalloy. The two distinct surface morphologies produced by ablation in these regimes were characterized in detail by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The ablation rate equations for the two regimes are presented and the corresponding ablation mechanisms are discussed. The implications for application of fs pulsed lasers to machining of superalloys are also discussed.