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The effect of low‐energy high‐current electron beam (LEHCEB) irradiation on the microstructure and nanohardness of Inconel 718 alloy produced by laser powder bed fusion additive manufacturing is investigated. The LEHCEB irradiation is applied to the alloy at three energy levels, and the resulting microstructural analysis of irradiated surfaces is conducted. The findings from this study demonstrate that the LEHCEB irradiation substantially changes the as‐built microstructure showing intragranular dendrites of different shapes and irregular‐shaped Laves phases. The columnar structure is formed in the modified near‐surface layer as a result of rapid heating and cooling during LEHCEB irradiation. Furthermore, all Laves phases dissolve in the modified layer. Nanoindentation hardness of the irradiated layer of the alloy increases from 593 ± 23 to 693 ± 13 Hv with the highest energy density of 15 J cm−2. This increment is attributed mainly to the dissolution of Laves phases and the formation of an ultrafine columnar structure where the columns are separated from each other by the district regions containing very thin interlayers of a secondary phase and a high amount of dislocations. [ABSTRACT FROM AUTHOR]

To improve the abrasive waterjet drilling procedure for yttrium-stabilized zirconia-coated Inconel 718 superalloy, this study suggests an integrated approach using machine learning and an evolutionary algorithm. The objective is to simultaneously minimize the erosion diameter and taper angle of the drilled holes by identifying the best combination of drilling parameters such as stand-off distance, abrasive flow rate, waterjet pressure, and angle of impact. The machine learning models are developed using the random forest algorithm after tuning its hyperparameters to predict the erosion diameter and taper angle. The multi-verse optimization (MVO) algorithm is used to identify the best combination of drilling parameters. The comparison of results proved the efficacy of MVO over other algorithms. Confirmation experiment results are also in line with the results of MVO, since the percentage of deviation is meager. This integrative approach has the capability of significantly improving aerospace and industrial abrasive waterjet drilling operations. [ABSTRACT FROM AUTHOR]

The application of Inconel-718 ranges from structural components to engine parts such as turbine blades and compressor discs. Inconel-718 is an age-hardenable alloy. We are presenting a comparative tribological study on as-cast and heat-treated Inconel-718 superalloy. The wear behavior of both as-cast and aged Inconel-718 alloy was investigated using a linear reciprocating tribometer at 25 ∘ C, 225 ∘ C, and 450 ∘ C against Si3N4 ball. The heat treatment of Inconel-718 alloy resulted in the improvement of the hardness of the alloy. All the tribological tests were conducted under a constant 20 N normal load. The observed coefficient of friction was found to be decreasing with the increase in temperature. The wear tracks were characterized by a three-dimensional optical profilometer and scanning electron microscopy (SEM). The observed wear volume loss (mm3) of the aged alloy was less than that of the as-cast Inconel-718 alloy. SEM of the worn sample reveals that the main operating wear mechanism at 25 ∘ C is delamination whereas at elevated temperatures of 225 ∘ C and 450 ∘ C, the main operating wear mechanism is abrasion, adhesion, oxidation and spalling. SEM of the counter-surface was also conducted in order to understand the adhesion on its surface and it was found that the adhered oxide contained mainly Ni and Nb oxides. [ABSTRACT FROM AUTHOR]

High-quality metal and alloy powder feedstock for powder metallurgy (PM) and additive manufacturing (AM) is typically expensive due to stringent physical and chemical requirements. The increasing demand for such powders drives innovation toward more sustainable and cost-effective production methods. In this study, we demonstrate the generation of discrete machining chips (MCs) with controlled characteristics during modulation-assisted drilling of Inconel-718 nickel superalloy. To achieve this, a full factorial experimental design, varying modulation frequency (fm) and amplitude (2A) (two factors: fm and 2A, multi-level: 7 and 5, respectively) was used to define discrete and continuous cutting regimes. Furthermore, the effect of individual modulation (fm and 2A) and machining parameters (drill tool diameter, D, and feed rate, h) on the characteristics of MCs was investigated systematically. The findings reveal direct linear relationships between the investigated parameters, i.e., D, fm, and 2A, on chip characteristics: length, width, and thickness, respectively. Specifically, the average chip length was 10–40% smaller than the length of each cutting edge of the drill tool; the average chip width reduces by 17 % when fm increases from 184 to 251 Hz. Similarly, the average chip thickness increases to 80% when 2A increases from 3.6 to 27.5 μm, confirming the generation of MCs having controllable characteristics. As established using a comprehensive comparative analysis, generated MCs (size range: 100–1200 μm) can be used as feedstock directly in press-and-sinter PM and solid-state friction-stir AM technologies. Additionally, the reusability of these MCs can be further enhanced by converting them into finer powder with a well-defined size distribution via ball milling (average particle size < 100 μm having angular morphology, in the present case), promoting a circular economy by repurposing high-value industrial machining waste into useful products. [ABSTRACT FROM AUTHOR]

Superalloys are a group of engineering alloys designed to operate at elevated temperatures, and they find application in various engineering sectors where a high-temperature application is required such as nuclear power plants, steam turbines, and aircraft. There are three important classes of superalloys, that is, iron-based, cobalt-based, and nickel-based superalloys. Among them, nickel-based superalloys find great application at both low and high temperatures due to their higher mechanical strength, good fatigue life, excellent wear, and corrosive resistance. This review article aims to review the tribological studies of the nickel-based Inconel superalloys. The article deals with the systematic studies of wear behavior, wear mechanism, and nanostructured glaze layer formation over the wear surfaces. The effect of load and temperatures influencing the wear rate and wear mechanisms of nickel-based superalloys are also discussed in detail. Along with that, the focus of this review article is to discuss the advancement in the tribological studies of the Inconel-718 superalloy. The development in the Inconel-718 alloys (surface alloying, laser shot peening, composites, microstructure engineering, etc.) to improve wear resistance is also discussed in a systematic manner. This article is expected to assist the researchers in identifying the trend and research gaps so that they can contribute to further tribological developments of nickel-based superalloys. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) is a sustainable process that offers various environmental benefits. However, the parts produced from SLM process require post-processing treatments that increase the energy consumption. Therefore, there is a need for optimization of SLM input parameters to minimize the same. For this purpose, the data set on selectively laser-melted Inconel 718 parts was obtained from the reference. An evolutionary neural net has been employed to model the objective functions: specific energy consumption, relative density and surface roughness in the present study. The neural net strategy was successful in capturing the important trend of the three objectives by achieving a maximum correlation coefficient of 85% in each of them. Subsequently, the trained model is used in tri-objective optimization to yield the optimum input parameters. A close agreement is observed between the predicted optimum parameters and experimentally obtained parameters, proving the formulated strategy to be reliable and effective. [ABSTRACT FROM AUTHOR]

In the laser powder bed fusion (LPBF) process, fast solidification of molten powders and significant temperature gradients generate substantial residual stresses in the build part. The induced residual stresses can result in excessive deformation and potential crack initiation and propagation. Development of a predictive reliable model is thus of paramount importance to predict the induced residual stresses in LPBF process without cost and complexities associated with experimental tests. High-fidelity thermo-mechanical models to predict the residual stresses and distortion in the macro-scale are generally impractical owing to their high level of computational time. Recently, the modified inherent strain methodology has proven to be a viable alternative for predicting residual stresses and distortions efficiently. In this study, a multi-scale finite element-based model of the LPBF process for Inconel-718 is developed utilizing modified inherent strain method to estimate the accumulated stress in the process. The stress formation and inherent strain values were evaluated in a micro-scale deposition considering the effect of LPBF process parameters using Abaqus/standard. The material constitutive models, including kinematic hardening, elastic-perfectly plastic, isotropic hardening, and Johnson–Cook model, and their effect on the evolution of plastic strain were investigated. The precision of the prediction was examined based on the quantity of equivalent layers, employing the agglomeration approach in part-scale analysis and subsequently confirmed experimentally through the fabrication of a printed cantilever beam. The proposed framework showed that the kinematic hardening model performed better than other material models, with an error of less than 6% when compared to experimental measurements. Moreover, the study highlights the significance of selecting the most appropriate material model for future studies involving the integration of advanced artificial neural networks and process parameter optimization to achieve precise and computationally efficient predictions. [ABSTRACT FROM AUTHOR]

Amused with the blissful benefits of micro-textures, researchers consider it a promising option for improving cutting tool performance, especially during machining superalloys. Through this study, the machining performance of two homothetic and six hybrid micro-textured tungsten carbide inserts have been comparatively assessed while dry turning Inconel-718. Dimple and channel micro-textures were the two independent homothetic textures. Dimple and channel micro-textures with 0°, 45°, and 90° orientation angles and a combination of triangle, square, and dimples constituted six different hybrid micro-textures. Micro-textures were fabricated on the rake face of inserts using a Ti-sapphire fired, nanosecond pulsed, infrared fiber laser. Dimple and channel micro-textured tools at 90° texture angle on rake face performed exceptionally well. Improvements in average tool life, cutting forces, and surface finish have been reported. Adhesion and attrition were the predominant forms of tool wear. Chip morphology study revealed long helical and continuous but segmented chips. [ABSTRACT FROM AUTHOR]

Autogenous joints of Inconel-718 to AISI-316L sheets produced using the electron beam welding process were subjected to defect analysis by the X-ray computed tomography technique. Such investigations revealed variations in undercut and porosity formation tendencies for change in weld processing conditions. The undercut rate has been found to be effectively reduced for the double-side pass and oscillating beam (infinity pattern) conditions. An increase in welding speed from 750 to 1500 mm/min has resulted in the formation of finer pores and reduced its count by 35%. For the same heat input rate, the double-side pass joint has reported formation of uniformly distributed pores with an 80% reduction in number. Compared to static beam joints, the oscillating beam welds have reported an extensive decrease in porosity content (62–87%) and pore-size distribution. The triangular and infinity patterns have reported a more efficient reduction in porosities and size distribution than other patterns. [ABSTRACT FROM AUTHOR]

This study establishes a novel printability criterion for Inconel-718 parts by laser power bed fusion. For this purpose, the regions with D/t ≤ 1.15, L/W > 2.1, and W/D = 2.0 have been identified with lack-of-fusion, balling, and keyhole defects. Regimes within the processing maps related with defects have been regarded as a melt pool geometry function, derived using a FEM model with temperature-dependent thermophysical properties. The data was collected, via design of experiment technique, using validated simulation model. Following that, the acquired data was utilized to train and test a machine learning model based on a backpropagation artificial neural network (ANN). By linking melt pool dimensional ratios to defects, the validated ANN model was used to produce processing maps. The processing maps were validated using experimental analyses, which revealed a consistent correlation between experiments and simulations. The proposed processing maps can be utilized to quickly quantify the Inconel-718 parts generated by the LPBF. [ABSTRACT FROM AUTHOR]

Studying the specific energy during material removal mechanism at micro-scale provides a better understanding of energy transition between different material removal regimes. Modeling of specific energy into components of sliding, plowing and cutting helps to analyze the influence of grain properties process parameters, and mechanical properties on energy transition between different phases of material removal. Present research put forth the comprehensive model of specific energy consumption for abrasive cut off operating based on the individual models of primary and secondary rubbing energies, specific plowing energy and specific cutting energy. Materials of SS201, Inconel 718, Al 1100, Al 7075 and oxygen free copper (OFC– C10100) have been employed while cutting with semi super abrasive cubitron cut off wheel. Model validation on experimental data revealed that triangular shape of cubitron grits significantly influenced the plowing energy and played an important role in energy transition between different material removal regimes. Moreover, cutting conditions and material properties also affected the overall specific energy consumption, dominance of particular specific energy components and machinability of the materials.

The hard-to-cut material nickel-base Inconel-718 is used in large quantities in the aerospace industry and defense industry because the Inconel-718 has good mechanical strength at high temperatures, but the tool is likely to wear in the cutting processes. In this study, chip color and features were employed to predict tool lives because the chips are the closest to the cutting tool in the shear zone during the cutting processes, which can more authentically reflect the phenomenon of tool wear. The changes in chip color and geometric shape were extracted and digitized, and the prediction method employed a two-stage model. In Stage 1, a convolutional neural network (CNN) was used for chip condition classification and validation, and in Stage 2, back propagation neural network (BP) was employed to predict the tool wear. The result showed that when the Google-Net and ResNet50 network models were adopted for CNN chip feature recognition, with the confusion matrix of multi-classification for validation, the recognition precisions were 66.7% and 88.9%, respectively. The modeling and prediction were performed in the BP neural network; the chip chromaticity, chip thickness, and chip width were employed as input features, and the precision was enhanced by multi-fusion features. Finally, the mean absolute percentage error values for heavy cutting were 17.11%, medium cutting at 5.45%, and small cutting at 9.02%, indicating that the CNN-BP prediction model has good forecast accuracy, thus providing a new model prediction form for tool life. [ABSTRACT FROM AUTHOR]

The preheating system is a promising approach to decrease the axial load, improve the weld quality, and enhance the tool life during the friction stir welding (FSW) of high strength material. In the present work, conventional FSW and high-frequency induction heating-assisted friction stir welding (I-FSW) systems were used to join 3 mm thick Inconel 718 plates with a WC-10%Co tool and studied their performances. The welding was carried out at a constant rotational speed of 300 rpm, including varying traverse speeds of 90 mm/min and 140 mm/min and varying preheating temperatures (310 °C, 410 °C, and 700 °C). The results show that good weld joints were possible at high traverse speed (i.e., 140 mm/min) using the I-FSW at low preheating temperature (i.e., 310 °C). Grain refinement in the weld zone with and without preheated FSW led to improved mechanical properties. The increased size of intermetallic phases and carbide particles due to induction preheating in I-FSW was most likely to be responsible for the enhancement of the weld strength. The hardness of the stir zone was increased from 250 HV to 370 HV, and the ultimate tensile strength of the I-FSW joint reaches 740 MPa, which was 98.8% of the base material. The results also revealed that preheating affected the process temperature results lowering the axial force and frictional heat, which improved the tool life. [ABSTRACT FROM AUTHOR]

In this work, an attempt was made to join Inconel 718 by FSW using a tungsten carbide tool. The influence of major operating parameters such as rotational and traverse speed on the thermal history, axial force, mechanical and microstructural properties of welded samples was investigated. To obtain a sound weld joint, lower rotational speed (i.e., 300 rpm) and moderate traverse speed (i.e., 90 mm/min) are preferable. A sound weld joint experienced a joint efficiency of 100.2% and the impact toughness was 84.5%, of the base material. Grain refinement occurs both in the stir zone (SZ) and thermo-mechanical affected zone (TMAZ), with lower rotational speed and increasing traverse speed. The grain refinement leads to the improvement of mechanical properties such as tensile strength, impact toughness and Vickers hardness. XRD analysis revealed the existence of both tungsten and cobalt particles in the weld zone which confirmed the tool wear happened during the FSW. From FESEM and transmission electron microscopy (TEM) investigations, it was observed that the SZ of the sound weld sample revealed the presence of refined grain with secondary phases, which are most likely to be responsible for enhancing weld strength. [ABSTRACT FROM AUTHOR]

The blades in the high-pressure turbine section of engines of modern aerospace and defense industries need to be drilled for pressurization. The milling and drilling of nickel-base material Inconel-718 are likely to create tool wear and tear, so the drilling process of milling is extensively replaced by deep hole electrical discharge machining (EDM). However, EDM creates reaming or overcut phenomenon, so to reduce this, parameter optimization is important. This study used response surface methodology to establish the influencing factors of machining parameters in hole enlargement and machining speed. The experimental results show that the main influencing factor in the nickel-based alloy deep hole EDM is the discharge voltage; the second factor is the discharge current. The hole enlargement of the processed hole without optimization is 60 ~100 μm. The DOE is used for the measurement of hole enlargement and machining speed to design important parameters and to predict experiment data analysis. The half-normal probability graph, Pareto chart, and analysis of variance (ANOVA) are used to learn about the significant factors of parameters and the influence of interaction. The outlet value of optimized parameters was observed to be relatively uniform, and the hole morphology is relatively free of residue stacking. Finally, the inlet and outlet results improved by 17.9% compared with the original parameters. The optimization parameter value predicted by the fitted model was 0.0392 mm, and the optimized upper and lower holes validation experiment machining error was 0.0380 mm, and the values are quite close, proving that this prediction model is accurate. The model prediction of this DOE can enhance the applied technology of deep hole EDM for nickel-based alloy. [ABSTRACT FROM AUTHOR]

Nickel-based superalloys have been extensively used in the aerospace industry due to their excellent mechanical properties at elevated temperatures. The mechanical properties of the Inconel-718 majorly depend on its microstructure which can be controlled using thermomechanical treatments. Machining of the heat-treated Inconel-718 component is very difficult due to very high hardness. This paper investigates the relationship between the material microstructure developed through a thermomechanical process and the machinability through micro-drilling of Inconel-718. In this study, a wide range of microstructures with hardness ranging from 179 HV to 461 HV was achieved by different thermomechanical and heat-treatment processes. Flank wear, thrust force, and burr height analysis were carried out to understand the machining behavior after micro-drilling. Electron back scattered diffraction (EBSD) technique was used to characterize the microstructure. No correlation between grain size and thrust force was observed. However, a clear trend between thrust force and hardness was established. It was also observed through misorientation analysis that the machined surface deforms significantly with material hardness. [ABSTRACT FROM AUTHOR]

A noncontact machining process such as electrical discharge machining (EDM) is generally employed for machining electrically conductive materials irrespective of its hardness. However, the process becomes unstable and slow when deep features are to be machined. Furthermore, the standard dielectric-based EDM process is unable to meet the requirements of today's fast moving manufacturing industry. Therefore, in this study the authors present the development of a novel super dielectric which is used in the EDM drilling process, and experimentally demonstrate how the machining efficiency in the drilling of a deep hole is improved significantly. In addition the effect of super dielectric fluid on the plasma current is presented and the experimental observations have been validated through the plasma physics theory. The efficiency of the super dielectric-based EDM process is experimentally validated with the successful drilling holes of aspect ratio more than 100 in Inconel 718 within 6 minutes. [ABSTRACT FROM AUTHOR]

In the present work, Inconel-718 (IN718) coating was developed on a gray cast iron (C.I) substrate by utilizing a high-velocity oxy-fuel spray technique. The microstructural analysis was performed to know the topological characteristics of the deposited IN718 coating. Corrosion testing of bare and coated samples was carried out at an ambient temperature in a NaCl solution (3.5 wt.%) using potentiodynamic polarization technique. The kinetics of corrosion and surface characteristics of the as-sprayed and corroded coatings were studied by scanning electron microscopy/energy-dispersive spectroscopy techniques. The different phases in the feedstock powder and as-sprayed coating were determined through X-ray diffraction analysis. The reported average microhardness value of the developed IN718 coating was 563 ± 15 HV0.2. The increased hardness of the IN718 coating is credited to the existence of Mo and Ti elements in the IN718 coatings. Corrosion testing showed that the IN718 coating exhibited the maximum corrosion resistance compared to a C.I. substrate due to a stable passive layer in the IN718 specimen. [ABSTRACT FROM AUTHOR]

• A rotational Euler–Bernoulli beam (REB) model is proposed for gundrill shaft. • 1st critical RPM in gundrilling increases as coolant pressure and RPM increase. • The optimized machining parameters for coolant pressure and RPM are found. • Straightness can be improved by increasing the 1st critical RPM of gundrill shaft. • A straighter hole (8 mm) in tolerance is achieved in gundrilling of Inconel-718. A dynamic model for multispan rotating gundrill shaft with thrust force and coolant pressure is proposed using rotational Euler–Bernoulli beam model (REB) through energy approach. From the numerical simulation, it is found that the 1st critical RPM of the rotating gundrill shaft increases tremendously as coolant pressure increases. The proposed model is incorporated with a straightness model. Experimental verification for the proposed model is presented. It is found that by using the combination of higher pressure (2000 psi) and rotational speed (1600 rpm), a straighter hole within industrial tolerance is achieved in gundrilling of Inconel-718. [ABSTRACT FROM AUTHOR]

Precise machining of advance material like Inconel-718 is an emerging need. Selection of an appropriate optimal range of cutting parameters is quite essential to achieve the high-quality cut and is a challenging task within this domain of study. The aim of this research is to develop a robust prediction model, which can suggest the desired range of cutting parameters for accomplishing better cutting quality, precision, and geometrical accuracy. Experiments have been performed on a 300 W (CNC-PCT 300) pulsed Nd: YAG laser cutting system at various levels of input cutting parameters, namely gas pressure, standoff distance, cutting speed, and laser power. Thereafter, response surface methodology has been adopted to develop mathematical models in terms of aforementioned input cutting parameters for geometrical quality characteristics: top kerf width and bottom kerf width. These developed models have been validated by comparing the predicted values with the experimental ones. Further, these models have been optimized using the multiobjective genetic algorithm in order to ascertain the optimal range of cutting parameters pertaining to better quality cut with high precision and geometrical accuracy. [ABSTRACT FROM AUTHOR]

Nickel-based superalloy Inc-718 has become an indispensable alloy in critical sectors, especially in the aerospace industry, thanks to its unique characteristics. However, some properties of the alloy (especially low thermal conductivity and hot hardness) cause difficulties in its machinability. For this reason, comprehensive studies to improve the machinability of Inc-718 alloy by considering the microstructural properties are guiding. In this context, the present study uses various methods to increase the machinability efficiency of Inc-718, while also investigating their effect on microstructural properties. Firstly, the effect of the pre-heating process (hot), pure-MQL (PMQL), nanofluid-MQL (NMQL), and hybrid methods (hot+PMQL and hot-NMQL) on the surface roughness, cutting forces, tool wear, vibration, and temperature was investigated while milling Inc-718 surfaces. Then the utilization of Electron Backscatter Diffraction (EBSD) facilitated a comprehensive examination of microstructural behavior, with a specific focus on Euler-colored maps and phase distribution maps, providing valuable insights into the material's behavior under distinct milling conditions. As a result, hot+PMQL, hot+SiC-NMQL, and hot+Al 2 O 3 -NMQL provided an important contribution to the improvement of machinability characteristics. Also, it was seen that in EBSD analysis, a limited area is affected by heat in the hot machining environment. The crystal orientations of the pre-heated and hybrid machined Inc-718 alloy are highly similar to that of the dry-machined alloy. This similarity indicates that the removal of the heated layer from the workpiece during the milling process contributes to the preservation of the microstructure. [ABSTRACT FROM AUTHOR]

Selection of an appropriate optimal range of cutting parameters during the machining of Inconel-718 is quite essential to achieve the high-quality cut and is a challenging task within this domain of study. The aim of this research is to develop a robust prediction model which can suggest the desired range of cutting parameters for accomplishing better cutting quality, precision, and geometrical accuracy. Experiments have been performed on a 300 W (CNC-PCT 300) pulsed Nd: YAG laser cutting system at various levels of input cutting parameters, viz., gas pressure, standoff distance, cutting speed, and laser power. Thereafter, the artificial neural network technique has been adopted to develop mathematical models in terms of aforementioned input cutting parameters for geometrical quality characteristics: Top Kerf Width, Bottom Kerf Width, and Kerf Taper. These developed models have been validated by comparing the predicted values with the experimental ones. Furthermore, these models have been optimized using a multiobjective genetic algorithm and particle swarm optimization techniques, in order to ascertain the optimal range of cutting parameters pertaining to better quality cut with high precision and geometrical accuracy. [ABSTRACT FROM AUTHOR]

Inconel-718 is a nickel based super alloy and is extensively in use for working at very high temperature (upto 2000 °C) such as aero engine gas path equipment, nuclear equipment etc. Drilling micro size hole in such material with laser beam has been a proven choice and laser drilling process produces geometrically and dimensionally improved hole. Hole geometrical features can be improved further if laser drilling system operated at optimal input parameter setting. This paper experimentally investigates the behavior of hole geometrical features hole circularity and hole taper in laser trepan drilling of Inconel -718 sheet. Optimal value of laser input parameters for improved hole circularity and reduced hole taper have been suggested with the help of computational intelligence technique particle swarm optimisation. The effect of each laser input parameter on hole quality characteristics are also discussed and demonstrated graphically. Finally the experimental validation of the predicted results has been carried out. [ABSTRACT FROM AUTHOR]

In the present work, fracture forming limit diagram (FFLD) of two different solution treated i.e. 970 °C (HT970) and 1070 °C (HT1070) Inconel-718 sheets were evaluated by carrying out stretch forming experiments. The obtained failure limiting strains were then transformed into effective plastic strain versus triaxiality locus (ƞEPS-FFLD) and major versus minor principal stress space (σ-FFLD). It was observed that the HT1070 material possessed higher ƞEPS-FFLD and lower σ-FFLD indicating improved formability with reduced deformation load. In order to predict the fracture, six different ductile fracture models incorporating anisotropic properties were calibrated with experimental data. Among all the models, Oh model showed comparatively better prediction with an average absolute error of 10.2% and 10.1% for HT970 and HT1070 materials respectively. However, the model was not able to capture the fracture limits along complete triaxiality path ( 0.33 ≤ η ≤ 0.66 ). Therefore, finite element (FE) analysis of deep drawing and stretch forming processes were performed incorporating experimentally evaluated ƞEPS-FFLD and σ-FFLD. The formability in terms of fracture location, limiting draw ratio, wrinkling evolution, thickness distribution, and limiting dome height were predicted successfully using Hills-48 plasticity theory. Also, the microhardness at critical regions of deformed cups was determined and the maximum hardness was found at cup junction of HT970 material especially in case of hemispherical dome cups. Thus, it was suggested that the deep drawn components of HT970 material have better part performance as compared to that of HT1070 material. [ABSTRACT FROM AUTHOR]

This paper presents the results of experimental investigation of the effects of three cooling strategies (minimum quantity lubrication (MQL), cryogenic cooling using liquid nitrogen (LN2), and combined (MQL + LN2)) and three tool coatings (uncoated and AlTiN- and GMS2-coated) on cutting force components (Fx, Fy, Fz); the resultant cutting force, Fr; and cutter tooth frequency in peripheral high—speed end milling of Inconel-718 to improve machinability and reduce cost. All the experiments were conducted on a Cincinnati Milacron Sabre 750 vertical machining center (VMC), equipped with Acramatic 2100 CNC controller using uncoated and AlTiN- and GMS2-coated solid carbide bull-nose helical end mills of 12.7 mm (0.5 in.) diameter, and 0.762 mm (0.03 in.) corner radius. Each experiment consisted of eight passes, each pass of 76.2 mm (3 in.) cutting length. Axial and radial depths of cut, cutting speed, and material removal rate were kept constant for all experiments. The experimental results show that uncoated end mills generated lowest resultant cutting forces, whereas GMS2-coated end mills generated highest resultant cutting forces under all cooling strategies. MQL cooling strategy generated lowest resultant cutting forces, whereas LN2 cooling strategy generated highest resultant cutting forces for all end mill coatings. Using LN2 cooling strategy alone is not recommended for machining Inconel-718 due to high cutting forces and vibrations. Uncoated end mills under MQL cooling strategy generated the lowest cutting forces and are recommended for machining Inconel-718, whereas GMS2-coated end mills under LN2 cooling strategy generated highest cutting forces. [ABSTRACT FROM AUTHOR]

Inconel-718 has found high demand in different industries due to their superior mechanical properties. The traditional cutting methods are facing difficulties for cutting these alloys due to their low thermal potential, lower elasticity and high chemical compatibility at inflated temperature. The challenges of machining and/or finishing of unusual shapes and/or sizes in these materials have also faced by traditional machining. Laser beam cutting may be applied for the miniaturization and ultra-precision cutting and/or finishing by appropriate control of different process parameter. This paper present multi-objective optimization the kerf deviation, kerf width and kerf taper in the laser cutting of Incone-718 sheet. The second order regression models have been developed for different quality characteristics by using the experimental data obtained through experimentation. The regression models have been used as objective function for multi-objective optimization based on the hybrid approach of multiple regression analysis and genetic algorithm. The comparison of optimization results to experimental results shows an improvement of 88%, 10.63% and 42.15% in kerf deviation, kerf width and kerf taper, respectively. Finally, the effects of different process parameters on quality characteristics have also been discussed. [ABSTRACT FROM AUTHOR]

The Inconel-718 is one of the most demanding advanced engineering materials because of its superior quality. The conventional machining techniques are facing many problems to cut intricate profiles on these materials due to its minimum thermal conductivity, minimum elastic property and maximum chemical affinity at magnified temperature. The laser beam cutting is one of the advanced cutting method that may be used to achieve the geometrical accuracy with more precision by the suitable management of input process parameters. In this research work, the experimental investigation during the pulsed Nd:YAG laser cutting of Inconel-718 has been carried out. The experiments have been conducted by using the well planned orthogonal array L 27 . The experimentally measured values of different quality characteristics have been used for developing the second order regression models of bottom kerf deviation (KD), bottom kerf width (KW) and kerf taper (KT). The developed models of different quality characteristics have been utilized as a quality function for single–objective optimization by using particle swarm optimization (PSO) method. The optimum results obtained by the proposed hybrid methodology have been compared with experimental results. The comparison of optimized results with the experimental results shows that an individual improvement of 75%, 12.67% and 33.70% in bottom kerf deviation, bottom kerf width, and kerf taper has been observed. The parametric effects of different most significant input process parameters on quality characteristics have also been discussed. [ABSTRACT FROM AUTHOR]

Metallurgical and mechanical characterization of surface and subsurface regions in broached and shot-peened fir-trees in an industrial gas turbine disc made of Inconel-718 were carried out. High resolution scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectrometry (EDS), electron backscatter diffraction (EBSD), X-ray diffraction, optical microscopy, and microhardness instruments were employed for qualitative and quantitative assessment of alterations at surface and subsurface levels. Five specific locations along the broached and shot-peened path were selected and thoroughly examined. Original metallography methods were developed to clearly and reliably reveal microstructure constituents. Special emphasis was placed on the generated defects in view of the manufacturer's quality indices, formation mechanisms of defects, and their potential impact on the service capability of the disc. Also, advanced analysis of the EBSD data allowed assessment of the deformed layer thickness as well as the misorientation angle and grain size variations from the broached and shot-peened surface towards the bulk parent material (PM). Furthermore, through successive material removal by electropolishing, measurement of residual stresses as a function of depth from the surface was performed by the sin 2 Ψ method. The obtained results are analyzed in terms of impact of the processing conditions on the evolution of microstructure, microhardness, and residual stresses. The findings are also related to the geometrical location in the disc. [ABSTRACT FROM AUTHOR]

In the present study, corrosion behavior of microwave welded Inconel-718 at various conditions was investigated. Welding of Inconel-718 in 980 °C solution-treated condition was performed using microwave hybrid heating technique. The microwave welds were subjected to post-heat treatment for improving its microstructure and mechanical properties by solubilizing the Nb-enriched Laves phase. The microstructural features of the fabricated welds at various conditions were investigated through scanning electron microscopy. The electrochemical testing results revealed that Inconel-718 welds were galvanic corroded when they were anodically polarized in 3.5 wt.% NaCl solution at 28 °C. The difference in the corrosion potentials between the base metal (BM) and fusion zone (FZ) in an Inconel-718 weld was the main factor for galvanic corrosion. The highest corrosion was occurred in the as-welded/aged weldments, followed by 980 °C solution-treated and aged weldments, as-welded specimen, and 1080 °C solution-treated and aged (1080STA) weldments. The least galvanic corrosion was occurred in the 1080STA specimens due to almost uniform microstructure developed in the weldment after the treatment. Thus, it was possible to minimize the galvanic corrosion in the microwave welded Inconel-718 by 1080STA treatment which resulted in reducing the difference in corrosion potentials between the BM and the FZ. [ABSTRACT FROM AUTHOR]

This study aims at investigating the effect of cutting speed, feed rate and depth of cut on surface roughness, microstructure of machined part and tool wear in dry rough turning of Ni superalloy Inconel-718 using PVD coated (TiAlN + TiN) carbide tool inserts. Taguchi's method for optimization of machining parameters (vc = 40-60 m/min, f = 0.05-0.1 mm/rev and d = 0.25-0.5 mm) was used. A Finite Element (FE) model of the tool geometry was developed in order to understand the trends of deformation and shear stress induced due to mechanical loads during orthogonal machining. Regression equations versus the cutting parameters were obtained for surface finish and tool wear. Changes in microstructure were found to be negligible. The investigation suggested that for PVD coated (TiAlN + TiN) carbide tool inserts, cutting speed of 60 m/min, feed rate of 0.05 mm/rev and depth of cut of 0.5 mm were optimum for producing the best cutting results. [ABSTRACT FROM AUTHOR]

In this paper effect of electron beam welding heat input on the microstructure and mechanical properties of Inconel 718 was studied. Sheet of 2 mm thickness was used with an average grain size of 30 μm. Five different heat inputs ranging from 36 J/mm to 180 J/mm were used to make full penetration welds. Welding current was varied from 18 mA to 90 mA and other welding parameters were kept constant. Change in heat input altered the geometry of the weld (width to depth ratio) and the microstructure of fusion zone (FZ) and heat affected zone (HAZ) also changed. As the heat input increased the interdentric spacing in FZ was increased from 3.5 μm to 6 μm. Grain boundary liquation was found in all the welds. Intensity of liquation increased with decrease in heat input and the microfissuring was observed only in the lowest heat input weld. Change in heat input did not significantly affect the tensile properties of the weld. [ABSTRACT FROM AUTHOR]

Abstract: Inconel-718 powder was thermal sprayed on mild steel substrate utilizing APS (air plasma spray) thermal spraying facility. Coatings of thickness 200μm and 250μm were produced by APS using powders of average particle size 50μm. Developed coatings were subjected to microstructure studies, microhardness test and slurry erosive wear studies in 3.5% NaCl media. Microstructural studies reveal uniformity of Inconel-718 coating with good bond and minimal porosities. The surface hardness of developed coatings were higher than that of the substrate and increases with increase in coating thickness. The slurry erosive wear resistance of developed coatings are superior than that of uncoated mild steel substrate. SEM studies on the slurry eroded surfaces of both uncoated mild steel and Inconel-718 coating have been carried out. [Copyright &y& Elsevier]