Machining Of Nickel-based Superalloys Research Articles

Experimental investigation of the effects of cooling-lubricating methods on the slot milling process of GTD-111 type nickel-based superalloy

Machining of nickel-based superalloys still poses several problems, especially slot milling, because the high work hardening, high metal carbide content and poor thermal conductivity cause the tool to wear quickly, with frequent breakages. This paper has dealt with the investigation of the effects of flood cooling, cryogenic cooling with Liquid Carbon Dioxide (LCO2), and the Minimum Quantity Lubrication and LCO2 combination on the cutting force, tool wear, chip morphology, surface roughness and the width of the milled slots. The authors have developed a new measurement method to measure the edge radius wear as a function of the depth of cut. The importance of this measurement method lies in the fact that at each measurement level, it is possible to determine the degree of wear of each edge radius and the homogeneity of the wear of the tool edges, which allows for determining how close the tool is to failure. Initially, the cooling had a positive effect on the cutting force for both LCO2 and LCO2 + MQL, but towards the end of the machining length, the cutting force was lower for flood cooling. The smallest tool wear resulted from the flood cooling, followed by LCO2 + MQL combination and LCO2. These results suggest that lubricating is more important than cooling for tool life. However, cooling plays a major role in chip breakage and surface quality, and in both cases, the best results were obtained by milling with the LCO2 + MQL combination.

Investigation of parameters and morphology of coated WC tool while machining X-750 using NSGA-II

Nickel-based superalloys have numerous applications in automobile, aerospace, turbine blades, nuclear, oil refinery etc, due to their excellent properties like strength, wear resistance, corrosion resistance and higher creep strength. Because of these properties, modern manufacturing industries need help with the machining of nickel-based superalloys, i.e. hard-to-machine materials. In the present research, Ni-based X-750 alloy is machined with turning operation by a conventional lathe machine using a TiAlN PVD coated tungsten carbide tool at different rotational speed (TRS), depth of cut (DoC) and feed (F) values as input parameters whereas material removal rate (MRR) and tool wear (TW) are the responses of the study. The design of experiments (DoE) is prepared by response surface methodology-based Box-Behnken Design. Analysis of variance (ANOVA) was applied to investigate the percentage contribution of each machining parameter on responses. Non-dominated Sorting Genetic Algorithm-II (NSGA-II) simultaneously optimizes the developed empirical models of MRR and TW. The predicted solutions suggested by NSGA-II are the best solution, and confirmation experiments are conducted on randomly selected parametric settings from these solutions. The optimized set presented by NSGA-II is TRS: 900RPM; DoC: 0.06 mm; F: 0.1 mm rev−1, and the maximum relative error in the case of MRR and TW is in the permissible limit. Scanning electron microscopy (SEM) and Energy dispersive spectroscopy (EDS) are used to investigate the morphology of tool insert before and after machining at optimized value TRS: 900 RPM; DoC: 0.1 mm; F: 0.06 mm rev−1, and it shows the wear marks on the tool, and the Energy dispersive spectroscopy confirms the presence of coating and WC. SEM is used to investigate the morphology of chips formed at different optimized parametric settings.

A Review on Machining of Nickel-Based Superalloys Using Nanofluids Under Minimum Quantity Lubrication (NFMQL)

A Review on Machining of Nickel-Based Superalloys Using Nanofluids Under Minimum Quantity Lubrication (NFMQL)

Machinability Investigation of Nitronic 60 Steel Turning Using SiAlON Ceramic Tools under Different Cooling/Lubrication Conditions.

The machining of nickel-based super alloys is challenging, owing to the generation of high cutting temperatures, as well as difficulty in maintaining dimensional accuracy and minimizing surface roughness, which compels the use of cutting fluids for reducing these issues due to efficient cooling/lubrication strategies. The present work investigates the comparative performance of four cooling/lubrication techniques: dry cutting, wet, minimum quantity lubricant (MQL) and compressed-air modes in turning Nitronic 60 steel using a new-generation SiAlON ceramic inserts. Several machinability parameters were analyzed for performance evaluation. For this purpose, 16 cycles of turning trials were performed based on Taguchi’s L16 orthogonal array experimental design by varying cutting conditions and lubrication modes. MQL exhibits beneficial effects as compared to the other lubrication conditions concerning low cutting force, improved surface finish, decreased cutting temperature, longer tool life, and lower white layer thickness on machined surface. Burr formation on the saw-tooth chip surface, as well as friction, greatly influenced the tool flank wear due to improper cooling and poor lubrication approach in dry, wet, and compressed-air-cooled machining environments in comparison to MQL-machining. From an economical perspective, the tool life in MQL machining improved by 11%, 72%, and 138% in the comparison with flooded, compressed-air, and dry conditions, respectively. The results of the study demonstrate that using the MQL system can help with heat extraction capability, and provide some promising outcomes.

Electrical Discharge Machining of Nickel-based Superalloys: A comprehensive review

Electrical Discharge Machining of Nickel-based Superalloys: A comprehensive review

Investigation of the Influence of Tool Rake Angles on Machining of Inconel 718

It is essential for superalloys (e.g., Inconel 718) to obtain an anticipated surface integrity after machining, especially for safety critical areas (e.g., aerospace). As one of the main characteristics for cutting tools, the rake angle has been recognized as a key factor that can significantly influence the machining process. Although there are large research interests and outcomes in the machining of nickel-based superalloys, most of them focus on the surface integrity and macroscale temperature observation, whereas the temperature distribution in the tool rake face is not clear. Thus, it is necessary to investigate the basic role of rake angles and the tool–workpiece interaction mechanism to determine the machining condition variations and surface integrity. In the present study, both experimental and numerical methods are employed to explore the cutting force, thermal distribution, and shear angles during the process and the metallurgy characteristics of the subsurface after machining, as well as the mechanical properties. The research has emphasized the importance of rake angles on both the cutting process and machined surface integrity, and has revealed the microscale temperature distribution in the tool rake face, which is believed to have a close relationship with the tool crater wear. In addition, it is clearly presented that the surface generated with positive rake angle tools generates the minimum subsurface deformation and less strain hardening on the workpiece.

Tool wear characteristics in rough turning of Inconel 718 with coated carbide tool under conventional and high-pressure coolant supplies

The machining of nickel-based superalloys is often challenging due to their excellent physical properties. High-temperature gradients are generated at the cutting zone, which accelerates the tool wear and impairs its performance. However, introducing high-pressure coolant (HPC) lubrication has been shown to improve both the tool life and surface integrity. In this investigation, attention has been mainly focused on the tool wear characteristics in the rough turning of Inconel 718. The longitudinal turning experiments have been conducted under conventional and HPC lubrication with two cutting speeds. Coated carbide inserts have been analyzed using several techniques including scanning electron microscopy, energy-dispersive X-ray spectroscopy, and 3D scanning. The experimental procedure has embraced the tool life, the tool wear, the generated forces, and the wear mechanisms. The examination of the worn tool surfaces demonstrates that although the depth of cut notching is more pronounced, it is possible to reduce the flank wear by using HPC lubrication. The results also highlight a marginal reduction in cutting and axial forces, a good chip fragmentation, and a significant improvement of the tool life. Furthermore, the investigations show that the wear mechanisms are strongly influenced using HPC under the various investigated cases.

A study on machinability of nickel based superalloy using micro-textured tungsten carbide cutting tools

In this research, an investigation on machinability of nickel-based superalloy (Inconel 600) under the influence of textured tungsten carbide cutting tools is conducted. Two main machinability indicators, namely, wear and life, have been investigated. Three types of micro-texture patterns i.e. dimples, lines and splines are laser engraved on the flank face of the cutting tool. Experiments are done with different cutting velocities, feed rate and depth of cut considering the texture pattern one among the input parameters. Firstly, while machining Inconel 600 with plain (non-textured) tungsten carbide cutting tool, it is investigated that at low velocity, the cutting nose caused damage due to abrasion and friction between the tool-chip interface. Severity in tool edge has increased along with adhesive wear and built-up edge at the cutting radius with increase in velocity. Thereafter, using textured on the tools, it is observed that the cutting tool wear resistance has tremendously increased with different textured patterns due to significant reduction in friction and heat. At low velocity (50 m min−1) the tool wear measured is in the range of 100–150 μm and maximum of 394 μm at high cutting velocity of 150 m min−1. The tool life was calculated using Taylor’s equation based on Gaussian method. Tool lives for dimple and line textures are found superior. It is concluded that textured tools have potential to machine hard materials like Inconel superalloys with longer tool life.

Ultrafast drilling of Inconel 718 using hybrid EDM with different electrode materials

In recent years, the popularity of nickel-based super alloys has been on the rise due to their widespread application in oil and gas, aerospace and automobile, marine and biomedical industries. The unique combination of superior mechanical and chemical properties like hardness, strength, temperature and corrosion resistance is responsible for the extensive application of these alloys. However, these properties pose challenges during the conventional machining of nickel-based super alloys. The low thermal conductivity and high work-hardening characteristics of Inconel 718 make it difficult to machine. To overcome the aforementioned problem, a hybrid non-contact electrical discharge and arc-machining process has been employed. In this process, an additional DC power supply is employed in conjunction with the normal EDM-pulsed power supply. Furthermore, the selection of proper electrode material plays an important role in defining the machining performance. In this study, in order to select a suitable electrode material for the newly developed process, several experimental investigations have been conducted with three different electrode materials, namely brass, copper (Cu) and copper tungsten (CuW). The results have shown that, for all the current settings, brass electrode provides the highest material removal rate (MRR), followed by Cu and CuW electrodes. However, CuW exhibited the lowest electrode wear rate (EWR). Moreover, the average surface roughness and surface characteristics of the electrodes after machining were investigated as well. Based on all the performance parameters, CuW appears to be the best choice for the hybrid process to machine Inconel 718.

Modeling and optimizing of cutting force and surface roughness in milling process of Inconel 738 using hybrid ANN and GA

Super-alloys have high thermal and mechanical strength and are widely used for heat exchangers, turbine blades, and other parts which work under severe creep conditions. Machinability of these alloys is directly affected by mechanical and physical properties. In addition, cutting force and surface roughness are two important factors in machinability of alloys. Hence, numerous studies have been conducted in order to illustrate their influences. However, among these alloys, the machining of Inconel 738 has been less studied. Milling parameters such as cutting speed, feed rate, the axial depth of cutting, and coolant have the most effects on machinability of nickel-based super-alloys. Therefore, in this research, they are considered as input parameters for investigation of milling of Inconel 738. The present study utilizes artificial intelligence as an effective method for predicting milling forces and surface roughness based on experimental results. To investigate the behavior of this alloy, four levels for the two former input parameters and two levels for the two other, totally 64 experiments, were fulfilled and studied. Based on the experimental results, the effect of input parameters on the outputs, that is, cutting force and surface roughness, was investigated, and then, neural network for modeling and predicting and genetic algorithm for the optimization of the outputs have been utilized. The optimized artificial network, which was obtained in this research, is useful for prediction of machining force and surface roughness of milling based on the values of cutting speed, feed rate, and the axial depth of cutting, for wet and dry milling of Inconel 738.

OPTIMUM FLANK WEAR OF TiAlN-COATED TOOL: TOWARD PRODUCTIVE ROUGH CUTTING OF INCONEL 625

Long tool life and high material removal rate (MRR) are the two essential requirements in rough cutting of materials. The rapid rate of the flank wear propagation in machining of nickel-based superalloys has induced the utilization of low cutting parameters when the goal was set to maximize the tool life based on the machining time or cutting length. However, this method may not provide an effective rate for the material being cut. This work presents two mathematical models to find the optimum cutting parameters results for the minimum flank wear and maximum MRR. Experimental tests were carried out based on the central composite design (CCD) in rough cutting of Inconel 625 by using TiAlN-coated insert. Maximum flank wear was measured to determine the tool wear propagation. The wear mechanisms which contribute in the tool wear were analyzed by using scanning electron microscope (SEM) to evaluate the effects of cutting parameters on the flank wear propagation. The results showed that cutting speed and depth of cut had the most significant effect on the tool wear. However, optimum cutting condition was achieved by reducing the cutting speed when feed rate and depth of cut maintained at the highest level. This was associated to the interaction of cutting speed and depth of cut, and predominant of abrasion and notching at their highest levels, respectively.

Performance Evaluation of Vegetable Oil-Based Nano-Cutting Fluids in Environmentally Friendly Machining of Inconel-800 Alloy.

Recently, the application of nano-cutting fluids has gained much attention in the machining of nickel-based super alloys due their good lubricating/cooling properties including thermal conductivity, viscosity, and tribological characteristics. In this study, a set of turning experiments on new nickel-based alloy i.e., Inconel-800 alloy, was performed to explore the characteristics of different nano-cutting fluids (aluminum oxide (Al2O3), molybdenum disulfide (MoS2), and graphite) under minimum quantity lubrication (MQL) conditions. The performance of each nano-cutting fluid was deliberated in terms of machining characteristics such as surface roughness, cutting forces, and tool wear. Further, the data generated through experiments were statistically examined through Box Cox transformation, normal probability plots, and analysis of variance (ANOVA) tests. Then, an in-depth analysis of each process parameter was conducted through line plots and the results were compared with the existing literature. In the end, the composite desirability approach (CDA) was successfully implemented to determine the ideal machining parameters under different nano-cutting cooling conditions. The results demonstrate that the MoS2 and graphite-based nanofluids give promising results at high cutting speed values, but the overall performance of graphite-based nanofluids is better in terms of good lubrication and cooling properties. It is worth mentioning that the presence of small quantities of graphite in vegetable oil significantly improves the machining characteristics of Inconel-800 alloy as compared with the two other nanofluids.

Nd:YAG Pulsed Laser Assisted Machining of AMS 5708 Waspaloy Alloy

Due to very high strenght, low thermal conductivity, and high work hardening rate, the machinability of nickel-based superalloys is poor at room temperature. Laser-assisted machining (LAM) can provide a better aspect of machining such alloys. Since the wavelength of Nd:YAG laser is about 1/10th of that of CO2 laser, absorption and heating efficiency of Nd:YAG laser is much higher on metals and especially superalloys. Transmission of Nd:YAG laser through fiber optics to the heating point on the workpiece is a simple task during machining. This makes the LAM process more convenient and practical than the CM process. In this study a model is introduced for LAM of waspaloy, and its machinability is evaluated in terms of ease of material removal. Also, a temperature generation model is introduced for the Nd:YAG laser beam. Furthemore, wear behavior of an uncoated tungsten carbide and the formed chips were compared during the LAM and the CM of waspolay. To study the wear mechanism, the worn cutting tool was studied via scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). The formed chips were also evaluated via SEM and optical microscopy. Based on the results, the optimum LAM conditions were obtained at a cutting speed of 24 m/min and a feed rate of 0.06 mm/rev when a 400 W laser mean power and 80 Hz frequency are applied. Under these conditions, the temperature ahead of the cutting tool edge on the surface of workpiece was estimated to be 524°C. In comparison with CM, a significant improvement in tool wear and a better chip morphology were achieved through LAM, and also specific cutting energy and surface roughness were reduced by 25 and 20%, respectively.

Modeling of the microstructure alteration induced by hard turning of Inconel 718

The machining of nickel-based superalloys used for aeronautical applications generates damage, deformation, and carbide cracking in machined surface and subsurface layers as a result of microstructural heterogeneities which reduce the fatigue life of aeronautic machined components. In this study, Inconel 718 was hard turned with a carbide tool using different cutting conditions according to a Roquemore 311B hybrid design of experiments (DOE) method. The main objective of the study was to model the effect of cutting parameters on the evolution of the microstructure and to accurately predict the alterations induced by machining, especially the deformed layer thickness (DL) and the average number of cracked carbides (ACC). The material removal rate (MRR) and the deformation power (E) were calculated in order to obtain a strong correlation between controlled cutting parameters and microstructure alterations. Damages were quantified using a confocal laser-digital microscope and were validated with the proposed models. These models showed a direct relation between both MRR and E with DL and ACC, with good prediction at a 95% confidence interval (CI).

Influence of tribological properties on the performance of uncoated, CVD and PVD coated tools in machining of Incoloy 825

The influence of tribological properties of coated tools on performance during machining of nickel-based super alloy is not well reported. The current study comparatively evaluated tribological properties of tools coated with chemical vapour deposition (CVD) and physical vapour deposition (PVD) with reference to their uncoated counterpart. The same cutting tools were then utilised in machining of Incoloy 825. Adhesion, attrition, edge chipping and notch wear were prominent wear mechanism of uncoated followed by CVD coated tool. However, PVD coated tool outperformed the others. This might be attributed to excellent tribological properties of TiAlN/TiN multilayer coating. Anti-friction and anti-sticking property of TiN and good toughness due to multilayer configuration in combination with thermally resistant TiAlN phase are the primary contributing factors.

Dry machining of nickel-based super alloy as a sustainable alternative using TiN/TiAlN coated tool

Surface coating has been used to improve sustainability in machining process. Therefore, the role of advanced tool coatings in curtailing the usage of environmentally hazardous cutting fluid (CF) particularly during machining of difficult-to-cut materials needs immediate research attention. In the present work, Incoloy 825, a nickel-based super alloy, has been machined under completely dry environment using a commercially available multilayer (TiN/TiAlN) coated tool obtained using physical vapour deposition (PVD). Various machinability characteristics with primarily emphasis on cutting force (responsible for consumed cutting energy), tool wear (for tool life) and surface quality (surface roughness) have been compared with those obtained with uncoated tool under conventional flood cooling and minimum quantity lubrication (MQL). The results achieved under both rough and finish modes of machining clearly established the use of PVD coated tool under dry environment as a sustainable strategy for achieving green machining.

Machinability of Nickel-Based Superalloy by Abrasive Water Jet Machining

This paper deals with the machinability of nickel-based superalloys using abrasive water jet machining process. The machining studies were carried out with three different parameters such as water jet pressure, traverse speed of jet nozzle, and standoff distance at three different levels. The performances of the process parameters are evaluated by measuring difference in kerf width, kerf wall inclination, and material removal rate (MRR). Further, the surface morphology and material removal mechanisms are analyzed through scanning electron microscope (SEM) images. It is found that water jet pressure is the most influencing factor related to surface morphology and surface quality.

Numerical Simulation of Surface Modification During Machining of Nickel-based Superalloy

Abstract The main objective of this study is to implement a reliable FE model of the orthogonal machining of a Nickel based superalloy for the prediction of microstructural changes occurring during the process. A FE numerical model was properly calibrated using an iterative procedure based on the comparison between simulated and experimental results. A user subroutine was implemented in the FE code to simulate the dynamic recrystallization and consequently the grain refinement and hardness variation when orthogonal cutting of Nickel based superalloy is performed. Thus, Zener-Hollomon and Hall-Petch equations were implemented to predict the grain size and micro hardness, respectively. In addition, the depth of the affected layer was predicted using the critical strain equation. The obtained results proved the adequacy of the proposed model showing a good agreement between the simulated and the experimental results.

Notch wear prediction model in turning of Inconel 718 with ceramic tools considering the influence of work hardened layer

The alumina-based ceramic cutting tools are a kind of promising tools used in machining of heat-resistant-super-alloys, such as nickel-based super alloy, due to its high wear resistance, low thermal expansion and good oxidation resistance up to above 1000°C. Sharp temperature rise mainly caused by excessive plastic deformation as well as the friction in machining of nickel-based super alloys is considered to be the key for rapid tool wear, especially the notch wear, which is the predominant type of catastrophic failure mechanism for the round type ceramic cutting tools. In this study, the wear mechanism of alumina-based ceramic cutting tools during dry turning of Inconel 718 is experimentally investigated. Based on the observation of tool wear, an attempt by employing the hardened layer beneath the workpiece surface is made to explain the occurrence of notch wear. Consequently, a predictive model of notch wear depth considering the influence of work hardened layer is developed. Series of cutting tests are used to validate the proposed notch wear model, and the result indicates that the proposed model is feasible. The contribution of this work can guide the effective control of tool wear by reducing the work hardened layer through the optimization of processing parameters.

Influence of Dry Cut and Tool Wear on Residual Stresses in High Speed Machining of Nickel-Based Superalloy

Machining induced residual stresses were investigated in Inconel 718 prepared by high speed turning under dry cut condition. The influence of cutting tool wear and the use of cutting fluid were studied. By x-ray diffraction measurements, characteristic residual stress distributions with tensile stresses in the top layer and compressive stresses in the layer below were found in all the investigated samples. The magnitude of surface tensile stresses and size of the tension as well as compression zones varied depending on the cutting condition. The application of cutting fluid for turning using new tool has a minor effect, giving a somewhat larger subsurface compressive zone but reducing the surface tensile stresses. Tool flank wear has shown a much stronger effect. While a flank wear of VBmax=0.15 mm enhanced mostly the surface tensile residual stresses, a severer wear of VBmax=0.3 mm greatly increased the thickness of the subsurface compression zone and at the same time resulted in strong stress anisotropy. Microstructural study by electron channelling contrast imaging shows that the observed influence of tool flank wear or cutting fluid on residual stresses are related to different contributions from increased plastic deformation and cutting heat, which changed with the cutting conditions.