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To obtain Ni-based oxide dispersion strengthened (ODS) alloys, controlling the amount of Y 2 O 3 addition is crucial. The Inconel 625 with different doping contents of x wt % nano Y 2 O 3 (x = 0.33, 0.66, 1.0) were fabricated by the laser direct energy deposition (LDED), and the effects of nano Y 2 O 3 on the microstructure, microhardness and wear resistance of Inconel 625 alloy were discussed. The results show that under the pinning effect of Y 2 O 3 , the grains of the composites are refined, with a maximum reaching 29 %. Compared to Inconel 625 alloy, The 0.33 wt % Y 2 O 3 /Inconel 625 exhibits higher hardness and doubled wear resistance. However, as the Y 2 O 3 content increases continuously, the wear mass loss in Inconel 625 composites doped with 0.66 wt% and 1.0 wt% Y2O3 increases by 32.3 % and 125.8 %, respectively. The performance degradation is associated with a high dilution rate and newly appearing cracks caused by Y 2 O 3. This work demonstrates that moderate doping of nano-Y 2 O 3 can enhance the wear resistance of Inconel 625 alloy, while excessive doping of Y 2 O 3 would has the opposite effect. [ABSTRACT FROM AUTHOR]

Syngas, mostly hydrogen and carbon monoxide, has traditionally been produced from coal and natural gas, with biomass gasification later emerging as a renewable process. It is widely used in fuel synthesis through the Fischer–Tropsch (FT) process, where the H2/CO ratio is crucial in determining product efficiency and quality. In this sense, this study aimed to reform an emulated syngas resulting from the supercritical water gasification of biomass, tailoring it to meet the H2/CO ratio required for FT synthesis. Conditions resembling dry reforming were applied, using temperatures from 600 to 950 °C and steel wool as a catalyst. Additionally, the effects of Inconel and stainless steel as reactor materials on syngas reforming were investigated. When Inconel was used, H2/CO ratios ranged between 1.04 and 1.84 with steel wool and 1.28 and 1.67 without. When comparing reactions without steel wool performed either in the Inconel or the stainless steel reactors, those using Inconel consistently outperformed the stainless steel ones, achieving CH4 and CO2 conversions up to 95% and 76%, respectively, versus 0% and 39% with stainless steel. It was concluded that the Inconel reactor exhibited catalytic properties due to its high nickel content and specific oxides. [ABSTRACT FROM AUTHOR]

Micro-electro-discharge drilling (μ EDD) is a type of non-traditional machining process used for drilling micro-holes of desired dimensions with a high aspect ratio. But, there are no such research works that could have explained the desired accurate circular shape of micro-holes. The need for a more advanced hybrid machining process to improve the overall efficiency in terms of mainly desired circular shape and radial overcut is evolved. In this research work, an electromagnetic field force-assisted micro-EDM process has been carried out on Inconel 800 with a copper tool of 450 μ m. Experimental results showed that measured metal removal rate and tool wear rate decreased for ascending values of magnetic flux density, peak current and gap voltage, whereas circularity increases linearly with an increase in magnetic flux density and also the effects of magnetic field on circularity of micro-holes on Inconel 800 are more predominant than other parameters. [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]

Superalloys, specifically Inconel 617 (IN617), have distinctive properties, yet it is extremely hard to machine through traditional processes. Electric discharge machining (EDM) has been considered a viable option considering the characteristics and shape intricacy required in the applications of the said alloy. However, EDM's low material removal rate (MRR) impedes its use. Therefore, the machining performance of five different transformer oil (TO) based modified dielectrics and cryogenically treated (CT) tools have been thoroughly investigated herein, which has never been examined so far. A total of 30 experiments were executed employing a full factorial design considering three kinds of electrodes and five different modified dielectrics. CT Cu (CuCT) electrode has given the highest magnitude of MRR (19.65 mm3/min) in the blend of tween 80 and TO, and minimum surface roughness (Rz) 11.0 µm in pure TO. The maximum MRR obtained with the CT electrode is 28% greater in comparison to that recorded for non-treated (NT) electrodes. Among the different electrodes, the CuCT tool performed well in TO-based dielectrics by giving the high MRR compared to the other NT and CT electrodes. CT electrodes yield higher MRR in TO-based dielectrics than kerosene oil (KO) based ones. The highest value of MRR noticed with TO-based dielectric is 20.3% than the maximum MRR noted for the KO-based dielectric. A significant amount of improvement in the MRR (98.56%) and Rz (78.88%) has been observed when the mono-objective optimization is utilized to obtain the optimal set of input variables. Finally, an artificial neural network (ANN) has been modelled to accurately forecast the MRR and Rz value for various input conditions, obviating the necessity for tests, effectively modelling the complicated and nonlinear phenomenon of MRR and Rz. [ABSTRACT FROM AUTHOR]

Non-conventional machining processes are capable of achieving higher performance compared to conventional ones due to their inherent characteristics and higher amount of parameters which can be favorably regulated. Although the correlation between the most important process parameters and process outcome has been already established for a wide range of conditions and workpiece materials, the introduction of new considerations related to the three pillars of sustainability require further investigation on new means for the enhancement of AWJ milling process. As one of the most important parameters in AWJ milling is the abrasive material, the introduction of new materials may offer considerable advantages from different perspectives. Thus, in the present work, a comprehensive investigation on the efficiency of using eco-friendly, mixed abrasives is carried out under various conditions such as different traverse feed rate, abrasive mass flow rate, water jet pressure, jet impingement angle, and mixing ratio. The feasibility of using mixed abrasives is evaluated in terms of achievable depth of penetration, kerf width, kerf taper angle as well as material removal rate (MRR), and cutting efficiency. The findings indicate that among other factors, the mixing ratio plays a noticeable role especially regarding MRR and cutting efficiency and can offer an additional effective means to achieve the desired kerf characteristics in conjunction with other significant parameters such as water jet pressure. [ABSTRACT FROM AUTHOR]

Friction Stir Welding (FSW) has emerged as a prominent technique for joining metallic materials, offering advantages in both similar and dissimilar material combinations. Despite its effectiveness, further advancements are needed to address industry demands and enhance the understanding of the FSW process. Welding nickel-based superalloys like Inconel 718 poses specific challenges, with existing literature suggesting that achieving successful welds requires high axial forces and precise process parameters, limiting its practical application in industries. To tackle these issues, this research proposes the utilization of 3D finite element models integrating multiphysics aspects, encompassing material flow and heat transfer mechanisms such as conduction, convection, and radiation. These models were validated against existing experimental data and employed to analyze temperature and strain distributions within the heat affected zone and weld nugget. The findings offer insights into the impact of various process parameters, including rotational speed, welding speed, normal force, cooling rate, and the effect of induction preheating, on key performance metrics like temperature profiles, grain size distribution, microhardness, and stress evolution. The outcomes underscore a notable correlation between process variables and performance indicators, facilitating a comprehensive understanding of the FSW process dynamics. [ABSTRACT FROM AUTHOR]

Small-hole components of Inconel 718 are widely used in aerospace engineering, medical devices, and other fields. Limited by material properties, its machining efficiency seriously restricts its wide application. The objective of this study is to investigate a novel machining technique for Inconel 718 that integrates ultrasonic machining (UM) and hydrogen embrittlement (HE) treatment. Accordingly, the technique is designated as hydrogen embrittlement-enhanced ultrasonic machining (HEUM). Prior to machining, a stress layer is formed on the surface of the workpiece. To ascertain the fundamental characteristics of Inconel 718, the influences of ultrasonic amplitude, HE time, and HE voltage on the specific material removal rate and surface roughness in the presence of HE were empirically examined. To investigate the material removal process for HEUM, the nanoscratch test and nanoindenter were also conducted with HE samples. Further, the subsurface for HEUAG samples were obtained with SEM. The specific material removal rate under experimental conditions of 10 min and 5 V HE increased by 27.4%. Finally, HEUM is proposed to be used for a 1 mm through-hole with Ra 0.318 μm. A precision hole with a diameter as small as 0.5 mm has been manufactured. [ABSTRACT FROM AUTHOR]

ABSTRACT Furnace components are made from heat‐resistant materials that must withstand the long‐term effects of the atmospheres used during heat treatment. In a nitriding furnace, the atmosphere usually consists of various gaseous media that react not only with the treated parts but also with the furnace equipment. This leads to thermochemical corrosion, even with carefully selected heat‐resistant and stainless steels or nickel‐based alloys. The present research focuses on determining the long‐term effects of ammonia‐containing atmospheres on the metallic furnace materials AISI 309, AISI 314, Alloy 600, and Alloy 601. The materials studied were exposed to numerous nitriding or nitrocarburizing treatments for more than 10 years to investigate the long‐term effects of repeated contact with ammonia‐containing atmospheres. The surface layers of the samples were characterized by several methods to determine the microstructural changes due to nitrogen absorption. A different nitrogen absorption of the metallic furnace materials from the heat treatment atmosphere, depending on the material properties, could be proven by the investigations. [ABSTRACT FROM AUTHOR]

The particle-reinforced CoAlTiWTa refractory high-entropy alloy (RHEA) composite coatings with varying additions of TiC nanoparticles (0%, 2.5%, 5%, and 10% by mass) were deposited on the surface of Inconel 718 superalloy using continuous laser cladding. The phase composition and microstructural characteristics of the RHEA composite coatings were characterized by X-ray diffraction, energy-dispersive spectroscopy, and electron backscattering diffraction techniques. Microhardness distribution and tribological properties at 600 °C were systematically examined. The results show that as the TiC particle content in the coating increases, the hardness and wear resistance of the RHEA composite coating first gradually increase and then decrease significantly. The coating with 5% TiC exhibits the highest hardness and superior high-temperature friction and wear resistance due to laser-induced microstructural refinement and reduced carbide precipitation. When the TiC content reaches 10%, increased agglomeration of TiC particles and grain coarsening lead to a notable decline in hardness and high-temperature tribological performance. The addition of TiC alters the composition of the RHEA matrix, resulting in varying high-temperature friction and wear characteristics of the composite coatings. [ABSTRACT FROM AUTHOR]

Purpose: The need for materials with superior mechanical and physical properties has recently increased. Inconel 718, one of these superalloys, is frequently used in the aviation and space industry. However, during Inconel 718 superalloy machining, cutting tools and cutting fluid were excessively consumed. This study aims to investigate using an innovative and environmentally friendly cutting fluid in milling the Inconel 718 superalloy. Design/methodology/approach: In this study, a Borax- (BX-)added cutting nanofluid was prepared and used for the first time as a coolant in the minimum quantity lubrication (MQL) system of Inconel 718's face milling process. Response surface methodology (RSM) was used to determine the effect of the BX element on cutting performance. Face milling operations were carried out by adding BX elements at 1.5% and 3% at two different rates. Findings: As the BX additive ratio in the cutting fluid used in the MQL system increased, the cutting force values decreased. The lowest cutting force value was measured in the tests with cutting fluid containing 1.5% BX. In addition, a smoother surface was obtained by adding 1.5% BX to the cutting fluid. Furthermore, cutting tool life increased by 20% compared to 0% by 3% BX nanofluid concentration. Originality/value: The study is innovative regarding the material processed, the cutting fluid used and the method used for the aerospace industry. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2024-0191/ [ABSTRACT FROM AUTHOR]

In this study, low Mn content Fe-Mn-Si-based shape memory alloys [Fe-(17-2x) Mn-6Si-xNi-yCr-0.3C (x = 0, 1, 2, 3, 4; y = 0, 1, 3, 5)] were prepared via vacuum arc remelting. The alloys were hot-rolled and solid-solution-treated at 1150 °C for 1 h followed by aging at elevated temperatures. The effects of Cr and Ni addition on the shape memory performance and corrosion resistance of the alloys in 3.5 wt% NaCl solutions were investigated using bending test and potentiodynamic polarization, respectively. It was revealed that the recoverable strain of the alloys remains larger than 2% when 1Ni is replaced with 2Mn and Cr is added. However, it becomes less than 2% in 11Mn and 9Mn alloys because of the easy formation of the α' martensite. The shape memory effect of alloys is highly improved due to the precipitation of fine carbides in the grains by the addition of Cr and after aging treatment at elevated temperatures (≧700 °C). The highest shape recovery ratios of 88.3% for 17Mn0Ni3Cr, 94.0% for 15Mn1Ni3Cr, 94.4% for 13Mn2Ni5Cr, 88.1% for 11Mn3Ni5Cr, and 86.8% for 9Mn4Ni7Cr, respectively, were achieved after 800 °C aging treatment. The strip-like second phase (carbides) forms at the grain boundaries in the Cr-free alloys after 600 °C aging treatment. There are lots of fine carbides (M23C6 and M7C3) precipitated in the interior of the grains at the aging treatments ≧ 700 °C. However, M7C3 is eliminated at 900 °C aging treatment. The corrosion resistance results showed that the corrosion resistance of the alloys is improved by adding Cr. The maximum corrosion potentials (−0.474 V) have been observed for 13Mn2Ni5Cr, and similar mechanisms have been analyzed in all series of alloys. [ABSTRACT FROM AUTHOR]

Creep damage assessment is crucial for ensuring the long‐term reliability of key components operating at high temperatures. However, the existing studies on creep damage are mainly focused on constant loading conditions, while the effect of cyclic loading, which is a common loading mode in practice, remains unclear. In this paper, a series of stress‐controlled cyclic creep tests on the Inconel 718 superalloy were performed to investigate the influence of cyclic loading on creep damage evolution. The ex‐situ microstructural analyses, including fracture surface observations and EBSD measurements, were conducted to reveal the damage mechanisms under cyclic creep conditions. Furthermore, a cavity nucleation and growth model that accounts for the additional cavity closure was developed for the healing effect of cyclic creep damage evolution. The prediction results were consistent with the experimental data of cavity nucleation life and experimental life within a factor of 2. Performing cyclic creep tests under various holding time and stresses.Establishing a cavity nucleation and growth model considering cavity closure.Considering the effect of cyclic loading on creep damage evolution.Revealing the microscopic interactions under cyclic creep conditions. [ABSTRACT FROM AUTHOR]

Nickel-base superalloys contain high amounts of solutes like Cr, Mo, W, Nb, Ti, etc. These solutes promote the formation of different types of carbide and boride phases that may contain multiple elements. Researchers have mostly discussed the roles of primary elements responsible for the formation of a given carbide/boride phase, often ignoring the role of other solutes on its stability. In the present work, thermodynamic stability of carbide and boride phases in seven commercial superalloys, namely, Alloy 625, Alloy 690, Alloy 718, MAR M246, Rene 100, Udimet 710 and Nimonic 80A, has been studied using the CALPHAD based Thermo-Calc software. The aim of the study was to understand the role of different alloying elements on temperature stability and chemical compositions of equilibrium phases in superalloys. As the accuracy of CALPHAD based predictions depends upon the database used, a detailed examination of its inadequacies has also been carried out to ascertain the limitations of the predicted data. From the calculated equilibrium chemical compositions, major and minor constituents promoting the formation of carbides and borides have been identified. The individual effect of a given solute as well as the synergistic effect of two solutes on the relative thermodynamic stability of carbide/boride phases has been identified using property diagrams and isothermal sections of the temperature-composition diagrams. Most of the simulated results have been found to be consistent with the experimental data available in the literature. From a comparison of the experimental literature and the simulated data of the stable carbide and boride phases in the studied alloys, the interplay of different solutes has been deduced to define conditions under which these phases form, within the limitations of the database used. This study has helped in better understanding of general tendencies of solutes to form different carbide and boride phases in nickel-based superalloys. [ABSTRACT FROM AUTHOR]

Water-cooled wall tubes are susceptible to high-temperature corrosion during service. Applying high-performance coatings via laser cladding on the tube surfaces can significantly enhance corrosion resistance and extend the service life of the tubes, providing substantial economic advantages. This paper prepared Y2O3/IN625 composite coating by means of high-speed laser cladding. Furthermore, the effects of Y2O3 addition on the microstructure evolution, hardness, as well as the high-temperature corrosion behaviors have been systematically investigated. The results show that Y2O3 addition can effectively refine the microstructure of the Inconel 625 coating, but the phase composition has little change. The coating's hardness can also be improved by about 7.7%, reaching about 300 HV. Compared to Inconel 625 coating, the Y2O3-added composited coating shows superior high-temperature corrosion resistance, with the corrosion mass gain decreased by about 36.6%. The denser and tightly bonded Cr-rich oxides layer can be formed adjacent to the coating surface, which plays a predominant role in improving the coating corrosion resistance. [ABSTRACT FROM AUTHOR]

This study analyzes the effects of Post Weld Heat Treatment (PWHT) on the mechanical properties and microstructure of Inconel 617 weldments produced by the Activated Tungsten Inert Gas (A-TIG) welding and Tungsten Inert Gas (TIG) welding. The TIG weld joints considered for this study were in an as-welded condition and underwent two different conditions of heat treatment including 1050∘C for 3 and 5 h, respectively. The A-TIG weld joints studied were the as-welded type and the weldment was heat-treated at 1050∘C for 3 h. The microstructure and the characterization of mechanical properties were performed for all weldments and a comparative assessment was made. Tensile strength and the hardness of the heat-treated samples were considerably higher than that of the as-welded samples. Impact toughness was slightly reduced after PWHT. Improvement in tensile strength could be attributed to the precipitation of the carbides and segregation of Chromium (Cr) and molybdenum (Mo). [ABSTRACT FROM AUTHOR]

Laser-directed energy deposition (L-DED) is an additive manufacturing technique that, in addition to fabricating new parts, is especially adept at creating and repairing thin wall structures. This study explores the effects of the number of infill passes on the microstructure and mechanical properties of Inconel 718 thin walls fabricated by L-DED. The effects of spatially varying cooling rates across both heights above the substrate and through the thickness of the thin wall samples, quantified through a combination of dendrite arm spacing measurements and finite element simulations, revealed that the most rapid cooling occurred at the walls' base under all conditions. The number of infill passes had a significant effect on this behavior, with the no infill pass (P2 sample) condition showing the most uniform cooling rate through its height. Moreover, the microstructure variation resulted in spatially varying hardness ranging from 170 HV in the stainless steel substrate, to ~ 220 HV towards the skin and top of the samples, and finally up to ~ 270 HV in the center of the samples where the cooling rate was the highest. More infill passes (P3 sample with one infill pass and P4 sample with two infill passes) led to higher cooling rates, finer grain structures, and increased hardness, particularly in the central regions of the thin wall samples. Conversely, fewer passes resulted in a more uniform but generally lower hardness throughout the sample. It is concluded that the infill pass strategy is a critical parameter in the L-DED process that directly influences the thermal history and, thus, the resultant microstructure and properties of Inconel 718 thin walls. [ABSTRACT FROM AUTHOR]

This work uses an alumina wheel to investigate the eco-benign grinding for better surface integrity of Inconel 625 (IN 625). To achieve this, applying nanofluids (NFs) with the minimum quantity lubrication (MQL) principle has been adopted, aiming at eco-benign grinding practices. In this work, MoS 2 NFs, MWCNTs NFs and hybrid NFs (prepared by mixing MoS 2 and MWCNTs in a 1:1 ratio) prepared using deionized water as the base fluid have been used. An in-house developed MQL setup is used to aim the NFs inside the grinding zone. The first attempt has been made to grind IN 625 in these environments. The characterisation of NFs in terms of nanofluid stability, dynamic viscosity, thermal conductivity and surface wettability have been performed before their utilization in grinding operations. A comparison has been made between the results obtained from NFs grinding and those from dry and soluble oil-based MQL grinding. It has been found that hybrid NFs provide excellent lubrication and cooling effects, reducing grinding forces and improving surface quality. Moreover, scanning electron microscopy, energy-dispersive spectroscopy and X-ray photon spectroscopy are applied to investigate the ground surfaces under different grinding conditions. Also, residual stress (with the help of X-ray diffraction and electron backscattered diffraction) and microhardness have been determined to gain further insights into the grinding behaviour. The wheel and chip morphology analyses have been performed to support the findings. The findings from this investigation lead to the conclusion that applying nano-MQL improves grinding effectiveness and promotes cleaner grinding outcomes. Hybrid NFs prove especially effective, as the physical synergistic effect enhances and safeguards the surface integrity of the produced ground components. [Display omitted] • This work endorses the grindability improvement of Inconel 625 using nano-MQL. • Thermos-physical and tribological characteristics of developed nanofluids have been investigated. • Ground surfaces have been investigated using SEM, EDS, EBSD, XRD and microhardness techniques. • Findings have been corroborated with the wheel and chip morphology investigations. • Nano-MQL has shown promising results in grindability improvement of Inconel 625. [ABSTRACT FROM AUTHOR]

Most metal turning processes utilize cutting fluids. Despite extensive experimental and analytical studies, the mechanisms of chip formation under consideration of a cutting fluid are still not entirely understood. Due to fluid-structure interaction, simulating wet cutting processes for an extended duration has not been feasible. The primary objective of this study is to utilize a simulation approach to provide additional information about the wet chip formation process in contrast to measurement methods, with a view to drawing conclusions. As methodology the Finite-Pointset-Method (FPM) is employed to simulate the chip formation process for dry, flood and specifically high-pressure cooling conditions during machining of carbon steel C45 as well as nickel-based alloy Inconel 718. Due to the increased relative velocity between workpiece and cutting fluid with the use of high-pressure cooling compared to flood cooling, numerical stability issues are present. Initially, the modeling approach to handle high-pressure cooling conditions is described and validated by an impact test. Subsequently the cutting simulation model is presented in detail and verified by measurements. The simulation results of stress, temperature and plastic strain rate fields are used to elucidate the observed discrepancies between various cutting fluid strategies in detail. These findings suggest explanations for the high efficiency of high-pressure cooling such as a decline of hydrostatic stresses or activation of ductile damaging. [ABSTRACT FROM AUTHOR]

Friction and high temperatures greatly affect the hardness and processing efficiency of superalloys. Therefore, it is important to provide a coating on their surfaces with a hard layer. In this study, pack boronizing was applied on Inconel 601 to improve its microstructure and tribological properties. In this regard, tribological tests were performed under MQL, nano-MQL1 (MQL + CuO), and nano-MQL2 (MQL + TiO2) environments. The research results showed that the lowest wear depth, friction force, coefficient of friction (CoF), and volume loss values were obtained in pack-boronized Inconel 601 in a nano-MQL2 environment. In the nano-MQL2 environment, the wear depth decreased by 17.81% (from 57.922 µm to 47.605 µm) with package-boronized Inconel 601 compared to as-received Inconel 601 at a 45 N load. Pack-boronized Inconel 601 experienced an average reduction of 30.23%, 41.60%, and 52.32% in friction force when switching from dry to MQL, nano-MQL1, and nano-MQL2 environments, respectively. It was also observed that the coefficient of friction (CoF) and volume loss values decreased with pack boronizing in an MQL/nano-MQL environment. In a nano-MQL2 environment at 15 N load, volume losses for as-received and boron-coated Inconel 601 were determined as 0.288 mm3 and 0.249 mm3, respectively (13.54% decrease). The findings of this study demonstrate that pack boronizing and MQL and nano-MQL techniques enhance the tribological characteristics of Inconel 601 alloys. [ABSTRACT FROM AUTHOR]

This work investigates the characterization of a cryo-processed AlTiN-coated tool and its turning characteristics for Inconel 600. The microhardness was enhanced by 3.68% under cryo-treatment when compared with the as-received condition of the inserts because of the wear-protective coating formed on the surfaces of the cutting tool. This was confirmed through EDS elemental analysis of carbon element growth and change in chemical composition, as well as XRD phase analysis. Next, this work studied the influence of cryo-treated inserts on roughness and mechanism of wear during turning Inconel 600 using varying cutting velocities (37, 60, and 100 m/min) under dry conditions. The output responses revealed that the use of cryo-treated tools reduced the roughness of the product by 11–27% and the rate of tool wear when compared with the untreated conditions. Due to these enhanced properties with cryo-treated conditions, it remains a suitable cutting tool for a significant contribution to sustainable machining toward dry cutting of aerospace alloys. [ABSTRACT FROM AUTHOR]

This paper describes the principles of obtaining wear-resistant coatings based on titanium diboride that are deposited on the cutting tool for use in the machining of chromium–nickel alloys. The spark plasma sintering of samples from the TiB2/Ti powder composition was studied, and the influence of sintering modes on the characteristics of the ceramic targets was analyzed. The regularities of the magnetron sputtering of sintered targets were revealed. The dependences of the physical and mechanical properties of coatings formed on hard alloy substrates on deposition conditions were established. The wear resistance of carbide samples with TiB2-based coatings under friction-sliding conditions and coated carbide ball-end mills in milling Inconel 718 chromium–nickel alloy that is widely used in the industry was assessed. [ABSTRACT FROM AUTHOR]

The purpose of this research was to create a predictive model for a medium-speed wire electrical discharge machine (WEDM) utilizing an artificial neural network (ANN). Medium-speed WEDM experiments were developed based on the I-optimal mixture design for machining, the Inconel 718 superalloy. During the experiment, the input parameters were the spark ontime, spark offtime, wire feed, and current, with the material removal rate (MRR) and surface roughness (Ra) selected as performance indicators. The ANN model was trained on experimental data and built using a feed-forward backpropagation neural network with a (4-8-2) structure and the Bayesian regularization (BR) learning approach. The model correctly predicted the relationship between the medium-speed WEDM's primary process parameters and machining performance. An integrated ANN model and the Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) were used to determine the ideal parameters for the MRR and Ra, resulting in a set of Pareto-optimal solutions. The confirmation experiment revealed that the mean prediction error between the experimental and ideal solutions had a maximum error percentage of 1% for the MRR and 2% for the Ra, which are within acceptable ranges. This showed that the best process–parameter combinations were better for the MRR and Ra. [ABSTRACT FROM AUTHOR]

This article delves into optimizing and modeling the input parameters for the selective laser melting (SLM) process on Inconel 625. The primary aim is to investigate the microstructure within the interlayer regions post-process optimization. For this study, 100 layers with a thickness of 40 µm each were produced. Utilizing the design of experiments (DOE) methodology and employing the Response Surface Method (RSM), the SLM process was optimized. Input parameters such as laser power (LP) and hatch distance (HD) were considered, while changes in microhardness and roughness, Ra, were taken as the responses. Sample microstructure and surface alterations were assessed via scanning electron microscopy (SEM) analysis to ascertain how many defects and properties of Inconel 625 can be controlled using DOE. Porosity and lack of fusion, which were due to rapid post-powder melting solidification, prompted detailed analysis of the flaws both on the surfaces of and in terms of the internal aspects of the samples. An understanding of the formation of these imperfections can help refine the process for enhanced integrity and performance of Inconel 625 printed material. Even slight directional changes in the columnar dendrite structures are discernible within the layers. The microstructural characteristics observed in these samples are directly related to the parameters of the SLM process. In this study, the bulk samples achieved a microhardness of 452 HV, with the minimum surface roughness recorded at 9.9 µm. The objective of this research was to use the Response Surface Method (RSM) to optimize the parameters to result in the minimum surface roughness and maximum microhardness of the samples. [ABSTRACT FROM AUTHOR]

The chemical composition of alloy 718 powder was optimized to suppress a solidification cracking in the additive manufactured part by the laser metal deposition method. The relationship between the condition of additive manufacturing and defects was evaluated. A lack of fusion was observed on the low heat input (low energy density), and the solidification cracking occurred on the high heat input (high energy density). The powder composition of alloy 718 was attempted to be optimized from a theoretical approach of the solidification cracking susceptibility. It was found that Si and B had a significant influence on the solidification cracking, therefore a preventive powder with reduced Si and B was developed. The effects of Si and B on solidification cracking were compared by reproducing the solidification conditions during additive manufacturing and evaluating the solidification brittle temperature range (BTR) using the Varestraint test. It was found that the BTR of the preventive material was smaller, and the solidification cracking susceptibility was improved. In addition, the solidification cracking did not occur in additive manufacturing using the preventive powder. In other words, it is suggested that the countermeasure for weld solidification cracking leads to the prevention of solidification cracking in additive manufacturing directly, and the effectiveness of the optimization of powder composition was verified. [ABSTRACT FROM AUTHOR]

The aim of this paper was to develop and verify a method for evaluating the high-performance milling of Inconel 718 alloy under accelerated tool wear conditions. The method considered parameters such as cutting-force components, total machine power consumption, cutting-edge wear, and material removal rate. The study compared high-feed milling and plunge milling, using sets of cutting parameters that are appropriate for both techniques. The results indicate that high-feed milling was more efficient, achieving higher material removal rates and lower tool wear. On the other hand, plunge milling was characterized by a lower axial force component (Fz), which can positively affect machining accuracy. The paper highlights that the proposed evaluation method can also be applied to other hard-to-machine materials, and plunge milling offers a competitive alternative for roughing operations in the milling of Inconel 718 alloy. [ABSTRACT FROM AUTHOR]

Nickel-based superalloys, like Inconel 718, are very attractive metals for aerospace applications due to their excellent mechanical properties and thermal stability. However, these materials pose a significant challenge to the metal machining industry due to their very low machinability, especially in terms of reduced tool life because of the high heat generated during cutting. Nevertheless, it can be improved using high-performing tools that retain their hardness when exposed to high temperatures, such as ceramic tools. In this context, the study aims to compare the performance of two advanced ceramic tools, namely an alumina ceramic tool reinforced with SiC whiskers and a Bidemics™ one, when turning Inconel 718 at different cutting speeds, using as a baseline a conventional coated cemented carbide tool. First, the three inserts were characterized in terms of topography, thermal conductivity, and hot hardness to fully understand their operational behavior. Then, turning trials were conducted showing that both the ceramic tools outperform the coated carbide one in terms of tool life, with Bidemics™ demonstrating the best performance among all. This can be ascribed to its very high hardness maintained even at high temperatures, as well as its moderate thermal conductivity. [ABSTRACT FROM AUTHOR]

The deposition of agglomerated hydroxyapatite (HAp) powders by low-pressure cold spray has been a topic of interest in recent years. Key parameters influencing the deposition of HAp powders include particle morphology and impact kinetic energy. This work examines the deposition of HAp powders on various metal surfaces to assess the impact of substrate properties on the formation of HAp deposits via cold spray. The substrates studied here encompass metals with varying hardness and thermal conductivities, including Al6061, Inconel alloy 625, AISI 316 stainless steel, H13 tool steel, Ti6Al4V, and AZ31 alloy. Single-track experiments offer insights into the initial interactions between HAp particles and different substrate surfaces. In this study, the results indicate that the ductility of the substrate may enhance HAp particle deposition only at the first deposition stages where substrate/particle interaction is the most critical factor for deposition. Features on the substrate associated with the first deposition sprayed layer include localized substrate deformation and the formation of clusters of HAp agglomerates, which aid in HAp deposition. Furthermore, after multiple spraying passes on the various metallic surfaces, deposition efficiency was significantly reduced when the build-up process of HAp coatings shifted from ceramic/metal to ceramic/ceramic interactions. Overall, this study achieved agglomerated HAp deposits with high deposition efficiencies (30–60%) through single-track experiments and resulted in the preparation of HAp coatings on various substrates with thickness values ranging from 24 to 53 µm. These coatings exhibited bioactive behavior in simulated body fluid. [ABSTRACT FROM AUTHOR]

Present study investigates isothermal annealing behavior of prior cold-worked Inconel 601 (aka, IN 601) sheets. The study comprehensively covers the annealing response of the material over wide cold-reduction and temperature ranges. Using structural characterization and mechanical testing, the study tracks strain-hardening, strain-aging, recovery, and recrystallization stages of IN 601 sheets as a function of degree of cold-reduction and annealing temperature. Using X-Ray diffraction analysis, hardness measurements, and tensile tests, the study reveals that prior cold-worked IN 601, irrespective of the degree of cold-reduction, consistently exhibits strain-aging during low-temperature (~ 0.4Tm) annealing. The investigation establishes that the 'recovery stage' is preceded by 'strain-aging-stage' during which the alloy exhibits superior strength and hardness than the strain-hardened and recovered states. Based on the thermomechanical experimental results, the current work proposes a recrystallization map that integrates the 'strain-hardening' and 'strain-aging' stages with the recovery and recrystallization stages. Additionally, microstructural analysis and SEM-EBSD analysis presented in this work indicate that, by suitably controlling strain-hardening and the recrystallization annealing, a refined microstructure comprising high aspect-ratio grains having high-angle grain-boundaries can be obtained that may improve both fatigue and creep properties of IN 601 sheets. [ABSTRACT FROM AUTHOR]

This study investigates the effect of four major process variables viz. laser power, scanning speed, hatch distance and powder bed thickness on the densification behavior of Inconel 718 (IN718), with a view to obtain defect free builds during laser powder bed fusion (L-PBF) process. In order to determine the causes of defect generation, samples with different process variables were printed and examined microstructurally. Samples printed as per Taguchi's L9 orthogonal array have exhibited different types of microscopic defects such as porosity, lack of fusion (LOF) and cracks. Based on detailed study, the optimized process parameters for obtaining defect free IN718 builds were found to be with a laser power of 320 W at a scanning speed of 850 mm/s and a hatch distance of 0.11 mm. LOF and un-melted tracks have formed at low volume energy density (VED) while porosity was found at high VED values. Cracks are most evident in XZ plane, and the formation of such cracks is high at high laser power and scanning speed. Although VED represents the energy input to the process, it should no longer be considered a process parameter, as multiple combinations of input process variables with different performance characteristics can result in the same value. This aspect has been demonstrated in this paper with experimental data. A Modified Taguchi's approach has been followed in this study to develop empirical relationships to the performance characteristics (density), in terms of process variables and demonstrated their validity through comparison of test data. The method suggests few tests as per the orthogonal array and provides complete information for all combinations of levels and process variables. This method also provides the estimated range of output responses so that the scatter in the repeated tests can be assessed prior to the tests. [ABSTRACT FROM AUTHOR]

One potential eco-friendly variant of electro-discharge machining is dry electro-discharge machining (EDM), in which the liquid hydrocarbon–based dielectric is substituted with a gaseous medium. The primary challenge associated with dry EDM is the excessive dissipation of heat within the machining gap, which restricts its utilisation only to a microscale machining. Consequently, further modifications to the underlying mechanism of the process are being undertaken with the aim of efficient industrialising it on a larger scale. In the present study, a novel approach is proposed to enhance the efficiency of dry-EDM process while using carbon dioxide as a gaseous medium together with introducing additional external workpiece cooling with deionised water. A series of experiments were conducted to determinate the impact of external workpiece cooling with deionised water and the main machining parameters, namely pulse-on time and current intensity gas pressure, on the material removal rate, working electrode wear, and surface integrity of Inconel 625 during EDM in milling kinematics. The results demonstrated that, under the same machining parameters, the wear of the working electrode, the surface roughness, and the thickness of the recast layer were significantly reduced in the EDM with external workpiece cooling in comparison to the dry-EDM process without water cooling. Furthermore, the EDM with coolant exhibited superior performance in comparison to the dry-EDM process due to the fact that there were fewer changes in the surface morphology and chemical composition of the machined material. [ABSTRACT FROM AUTHOR]

This paper deals with the development and characterization of an Inconel 625 (IN625) reinforced with 2 wt.% of sub-micrometrical TiC particles produced by the laser powder bed fusion (LPBF) process. IN625 and IN625 2 wt.% TiC microstructural evolution was evaluated in the as-built, solution-annealed (2 h at 1150 °C), and prolonged heat-treated (2 h at 1150 °C + 100 h at 1000 °C) conditions. The IN625 and IN625 + TiC samples were successfully produced with low residual porosity (<0.15%). In the as-built conditions, both materials developed mainly columnar grains elongated to the building direction with melt pools, fine dendric structures, and small fractions of recrystallized grains. Some TiC segregations were observed in the composite, preferentially located at the melt pool boundaries. The heat treatments led to a different microstructural evolution between the base alloy and the composite. After solution annealing, the IN625 alloy was subjected to full recrystallization with a drastic reduction in hardness. Afterward, the prolonged thermal exposures for 100 h at 1000 °C provoked the formation of carbides, increasing the hardness. On the contrary, the composite retained the as-built microstructure with columnar grains in the solution-annealed and prolonged heat-treated conditions, revealing a limited formation and growth of carbides, thus resulting in a reduced hardness variation. The addition of TiC inside the IN625 enhanced the microstructural stability of the composite, preventing the recrystallization and the growth of phases occurring under prolonged thermal exposures. The current study therefore reported the effect of TiC particles on the microstructural stabilization of LPBFed IN625, with a peculiar focus on the prolonged thermal exposure at 1000 °C. [ABSTRACT FROM AUTHOR]

The Inconel 718 superalloy, a precipitation-hardenable material, is of particular interest for applications involving components operating under extreme conditions due to its excellent mechanical properties, high corrosion resistance at temperatures up to 700 °C, and good workability. At high temperatures, thermal transfer processes are crucial for temperature distribution across the component's section, structural transformations, and variations in the alloy's properties. The history of accidental overheating events is critical for the microstructure and properties of the alloy. Studies on thermal transfer in the Inconel 718 alloy available in the literature typically focus on the alloy in its as-delivered state. The experimental research presented in this paper examines the influence of repeated overheating history on the thermal diffusivity of the alloy. [ABSTRACT FROM AUTHOR]

In this study, dissimilar structures of 316L and Inconel 625 were fabricated using wire and arc additive manufacturing with the cold metal transfer plus pulse mode (CMT+P). Based on various arc scanning strategies, including single-layer and multi-layer deposition, in vertical and horizontal building directions, the evolution of interface microstructure and mechanical properties of additively manufactured heterogeneous structures were studied. The microstructure analysis showed that during single-layer deposition, both 316L and Inconel 625 formed dendrites and columnar crystals. During the multi-layer deposition process, the 316L material solidified to form a dual-phase microstructure consisting of austenite and ferrite, whereas the Inconel 625 primarily formed an austenite microstructure. The segregation of elements such as Nb and Mo occurred at the interface, resulting in the formation of numerous precipitated phases at the grain boundary. At the interface of the vertically deposited sample, the inadequate diffusion of elements resulted in the formation of a transition layer in the microstructure. The microhardness of the deposited Inconel 625 layer was approximately 215 HV, while the microhardness of the deposited 316L layer ranged from 170 to 200 HV. The tensile strength and elongation rate of the horizontally deposited samples were higher than those of the vertically deposited structure. Both the tensile strength and elongation rate of the multilayer deposited structure were reduced due to the presence of numerous interfaces. The maximum tensile strength and elongation rate of horizontal single-layer samples were 488.57 MPa and 43.53%, respectively. The average tensile strength and elongation of vertical multi-layer samples were 387.26 MPa and 17.79%, respectively. Results showed that the mechanical properties of the SS316L/Inconel 625 heterogeneous structure in wire and arc additive manufacturing are clearly influenced by the deposition strategies and interface orientation. [ABSTRACT FROM AUTHOR]

We present an efficient approach to quantify the uncertainties associated with the numerical simulations of the laser‐based powder bed fusion of metals processes. Our study focuses on a thermomechanical model of an Inconel 625 cantilever beam, based on the AMBench2018‐01 benchmark proposed by the National Institute of Standards and Technology (NIST). The proposed approach consists of a forward uncertainty quantification analysis of the residual strains of the cantilever beam given the uncertainty in some of the parameters of the numerical simulation, namely the powder convection coefficient and the activation temperature. The uncertainty on such parameters is modelled by a data‐informed probability density function obtained by a Bayesian inversion procedure, based on the displacement experimental data provided by NIST. To overcome the computational challenges of both the Bayesian inversion and the forward uncertainty quantification analysis we employ a multi‐fidelity surrogate modelling technique, specifically the multi‐index stochastic collocation method. The proposed approach allows us to achieve a 33% reduction in the uncertainties on the prediction of residual strains compared with what we would get basing the forward UQ analysis on a‐priori ranges for the uncertain parameters, and in particular the mode of the probability density function of such quantities (i.e., its "most likely value", roughly speaking) results to be in good agreement with the experimental data provided by NIST, even though only displacement data were used for the Bayesian inversion procedure. [ABSTRACT FROM AUTHOR]

Purpose: The nickel-based alloys Inconel 625 and Inconel 718 stand out due to their high strength and corrosion resistance in important industries like aerospace, aviation and automotive. Even though they are widely used, current techniques of producing materials that are difficult to cut pose several problems from a financial, ecological and even health perspective. To handle these problems and acquire improved mechanical and structural qualities, laser powder bed fusion (LPBF) has been widely used as one of the most essential additive manufacturing techniques. The purpose of this article is to focus on the state of the art on LPBF parts of Inconel 625 and Inconel 718 for microstructure, mechanical behavior and postprocessing. Design/methodology/approach: The mechanical behavior of LPBF-fabricated Inconel is described, including hardness, surface morphology and wear, as well as the influence of fabrication orientation on surface quality, biocompatibility and resultant mechanical properties, particularly tensile strength, fatigue performance and tribological behaviors. Findings: The postprocessing techniques such as thermal treatments, polishing techniques for surface enhancement, mechanical and laser-induced peening and physical operations are summarized. Originality/value: The highlighted topic presents the critical aspects of the advantages and challenges of the LPBF parts produced by Inconel 718 and 625, which can be a guideline for manufacturers and academia in practical applications. [ABSTRACT FROM AUTHOR]

This review sets out to investigate the detrimental impacts of hydrogen gas (H2) on critical boiler components and provide appropriate state-of-the-art mitigation measures and future research directions to advance its use in industrial boiler operations. Specifically, the study focused on hydrogen embrittlement (HE) and high-temperature hydrogen attack (HTHA) and their effects on boiler components. The study provided a fundamental understanding of the evolution of these damage mechanisms in materials and their potential impact on critical boiler components in different operational contexts. Subsequently, the review highlighted general and specific mitigation measures, hydrogen-compatible materials (such as single-crystal PWA 1480E, Inconel 625, and Hastelloy X), and hydrogen barrier coatings (such as TiAlN) for mitigating potential hydrogen-induced damages in critical boiler components. This study also identified strategic material selection approaches and advanced approaches based on computational modeling (such as phase-field modeling) and data-driven machine learning models that could be leveraged to mitigate potential equipment failures due to HE and HTHA under elevated H2 conditions. Finally, future research directions were outlined to facilitate future implementation of mitigation measures, material selection studies, and advanced approaches to promote the extensive and sustainable use of H2 in industrial boiler operations. [ABSTRACT FROM AUTHOR]

Transient liquid phase (TLP) bonding was used to bond an IN939 superalloy utilizing a traditional, two-step heating process. The bonding process was carried out using BNi-2 foil with a 70-µm thickness as the interlayer in the first step at 1160 °C for 1 min and then at 1120 °C for different isothermal solidification times (50, 65, 80, and 95 min) in the second, also at 1120 °C for 80 min in conventional TLP bonding under vacuum furnace at a pressure of 10-5 torr. All the bonded specimens are then subjected to heat treatment and examined before and after heat treatment. A single-phase (isothermal solidification) was generated at the centerline after 80 minutes using a two-step technique. Due to insufficient bonding times, eutectic-products consisting of (gamma solid-solution), (Cr rich-boride), and (Ni rich-boride phases) formed in the centerline. The diffusion-affected zone also contained blocky- and needle-shaped boride precipitates in addition to the eutectic phases. The Vickers micro-hardness, and shear tests were done on the joints to evaluate their mechanical quality. The duration of isothermal solidification was shortened by using two-step TLP bonding. The hardness profile across the bond area was better than the conventional method and became more uniform after the heat treatment, and the shear strength was 631 MPa, and became 885 MPa after heat treatment, while about 479 MPa with the conventional TLP after heat treatment for the specimen with the isothermal solidification time of 80 min. After being subjected to a two-stage post-bond heat treatment, the microstructure becomes close to the base metals, as a result, a homogenizing microstructure forms across the joint. With increased bonding times, all of the bonds' shear strengths increased, and the hardness distribution across the bond area was better than the conventional technique and following the heat treatment, became more uniform. The bond shear strength was enhanced after the heat treatment because a significant γ-'phase developed in the bond area. [ABSTRACT FROM AUTHOR]

A streamlined sample preparation method for nanomechanical testing is needed to improve the quality of specimens, reduce the cost, and increase the versatility of specimen fabrication. This work outlines an in-plane liftout focused ion beam (FIB) fabrication procedure to prepare electron-transparent specimens for in situ transmission electron microscopy (TEM) nanomechanical testing. Ion etching and electron backscatter diffraction (EBSD) techniques were used to lift out a [110] oriented grain from a neutron-irradiated bulk X-750 alloy. Careful control of voltages and currents ensured precision. Top surface thinning sweeps prevented resurfacing and redeposition while dog-bone geometries were shaped with a 1:4 gauge width-to-milling pattern diameter ratio. Nanotensile testing in the TEM with a picoindenter allowed for the estimation of an ultimate tensile strength of 2.41 GPa, and inspection revealed a high density of bubbles in the X-750 matrix. The proposed fabrication procedure is significant for preparing samples from radioactive materials, studying complex structures that are orientation-dependent, and analyzing desired planar areas. [ABSTRACT FROM AUTHOR]

Due to its exceptional mechanical and chemical properties at high temperatures, Inconel 718 is extensively utilized in industries such as aerospace, aviation, and marine. Investigating the flow behavior of Inconel 718 under high strain rates and high temperatures is vital for comprehending the dynamic characteristics of the material in manufacturing processes. This paper introduces a physics-based constitutive model that accounts for dislocation motion and its density evolution, capable of simulating the plastic behavior of Inconel 718 during large strain deformations caused by machining processes. Utilizing a microstructure-based flow stress model, the machinability of Inconel 718 in terms of cutting forces and temperatures is quantitatively predicted and compared with results from orthogonal cutting experiments. The model's predictive precision, with a margin of error between 5 and 8%, ensures reliable consistency and enhances our comprehension of the high-speed machining dynamics of Inconel 718 components. [ABSTRACT FROM AUTHOR]

Laser-directed energy deposition (LDED) has the advantages of high material utilization, high degrees of freedom and high forming efficiency; consequently, it is applied widely in surface enhancement and repair of damaged parts. There are, however, some defects in the deposition process such as cracks and pores. The assistance of the external energy field is an effective measure to reduce such defects. To study this we deposited a single track clad of Inconel 625 onto the surface of HT300 grey cast iron by laser-directed energy deposition (LDED) with electromagnetic compound field (EMCF) assistance. The geometrical characteristics, microstructure and microhardness of the clad were determined to investigate the influence of the EMCF. The results show that: under the action of the EMCF with high magnetic field strength and high pulse current strength, the geometrical characteristic of the clad changed markedly. The application of the EMCF led to an increase in clad depth and a decrease in clad height, which led to an increase in dilution rate. The geometrical characteristic did not change significantly when the EMCF was small. The application of the EMCF can inhibit the growth of dendrites crystals, facilitates fine grain formation and improves the uniformity of microstructure. The microhardness improved and the range of microhardness decreased significantly under the condition of the EMCF. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to investigate the effect of NaCl solution with different concentrations on impact-sliding fretting corrosion behavior of Inconel 690TT steam generator heat transfer tubes. Design/methodology/approach: The optical 3D profiler was used to measure the wear profile and calculated the wear volume. Corrosion behavior was studied using open circuit potential monitoring and potentiodynamic polarization testing. The morphologies and elemental distributions of wear scars were analyzed using scanning electron microscopy and energy-dispersive spectroscopy. The synergism of wear and corrosion was analyzed according to the ASTM G119 standard. Findings: The corrosion tendency reflected by OCP and the corrosion current calculated by Tafel both increased with the increase of NaCl concentration. The total volume loss of the material increased with concentration, and it was known from the synergism that the volume loss caused by corrosion-enhanced wear accounted for the largest proportion, while the wear-enhanced corrosion also made a greater contribution to volume loss than tangential fretting corrosion. Through the analysis of the material morphologies and synergism of wear and corrosion, the damage mechanism was elucidated. Originality/value: The research findings can provide reference for impact-sliding fretting corrosion behavior of Inconel 690TT heat transfer tubes in NaCl solution with different concentrations. [ABSTRACT FROM AUTHOR]

A physically‐based constitutive modeling framework is proposed for the cyclic deformation and softening of Ni‐based superalloys. The constitutive model accounts for underlying mechanisms of grain size strengthening, dislocation strengthening, solid solution strengthening, and precipitate strengthening, commonly observed in these alloys. A constitutive model is proposed for the shearing of precipitates on their interaction with glide dislocations during cyclic deformation. This is the primary contributor to the experimentally observed cyclic softening behavior in Ni‐based superalloys. Model predictions of the cyclic stress–strain response and the cyclic softening (quantified in terms of the peak stress) are compared with the experimental counterparts for a range of strain amplitudes under fully‐reversed cyclic loading of Inconel 718 (IN 718). Further, model predictions of precipitate size are also compared with the experimentally measured transmission electron micrographs of precipitate sizes at the end of deformation. Concurrence in the cyclic stress–strain response, peak stress, and precipitate size provides validation for our constitutive modeling framework. Highlight: Development of a physically‐based constitutive modeling framework for cyclic deformation.Microstructure‐based strengthening mechanisms are considered in the model.Model incorporated the physical mechanisms of cyclic softening due to precipitate shearing. [ABSTRACT FROM AUTHOR]

Tool surface texturing is a new sustainable method for machining hard-to-machine materials. The present study focuses on the new honeycomb texture (mimic of bee's honeycombs) containing hexagons forming between thin vertical walls. The important novelty in this work is the cutting performance of honeycomb texture on Inconel 713C was examined under cutting parameters and different cooling conditions: dry untextured (T1), dry textured (T2) tool, impregnated solid lubricant (hexagonal boron nitride (hBN)) textured tool (T3), MQL (coconut oil) with textured tool (T4), and NMQL (0.20 wt.% hBN + coconut oil) with textured tool (T5). Compared to plain tools, NMQL to honeycomb texture reduced flank wear by 53.2%, roughness by 43.2%, turning force by 27%, and cutting temperature by 47.7%. Honeycomb texture with MQL (T4) and NMQL (T5) reduces flank surface Ni element diffusion during turning. Nanofluid-textured inserts (T5) demonstrated higher shear angles, lower chip curl diameter, and shorter tool-chip contact length than other conditions. [ABSTRACT FROM AUTHOR]

The inferior creep ductility of Inconel 718 (IN718) fabricated by selective laser melting (SLM), which is unable to meet aerospace material specification (≥4%), limits its engineering application. Despite persistent optimization efforts in the SLM process and post-heat treatment, this issue remains unresolved. This study involved SLM fabrication of the modified IN718 with trace amounts of LaB6 and/or P, followed by homogenization and double aging heat treatment. The addition of trace LaB6 notably influenced the recrystallized grain structure and carbide precipitation at grain boundaries, while trace P addition had minimal impact. All samples exhibited similar γ′ and γ″ strengthening precipitates. Creep tests conducted at 650°C/690 MPa revealed that the individual modification of LaB6 showed limited improvement in creep performance and P showed no improvement, but the combined addition of LaB6 and P led to a substantial enhancement in creep performance, especially reaching as high as 8.6% creep strain. This remarkable improvement in creep ductility is unlikely to arise from the altered grain structure and grain boundary precipitates induced by LaB6 but predominantly arises from the synergistic effect of P and B in enhancing resistance to crack propagation during the third stage of creep. [ABSTRACT FROM AUTHOR]

Consumption of energy in any manufacturing operation contributes significantly to the ultimate production cost. The study is focused on optimising various CNC milling input variables like depth of cut, round edge radius, feed rate and spindle speed during machining of Inconel 625 alloy for responses such as power consumption, axial force, torque and surface roughness. The experimental results are optimised with MOGA and RSM approaches. It is observed that increases in spindle speed, depth of cut, feed rate and round edge radius increased power consumption, axial force, torque and surface roughness. Optimum machining parameters for MOGA were depth of cut: 0.299 mm, round edge radius: 25 µm, feed rate: 197.31 mm/min and spindle speed: 3000 rpm and output responses were power consumption 1199.63 W, surface roughness 2.16 µm, axial force 176.15 N and torque 0.336 Nm. For RSM, optimum machining parameters were depth of cut: 0.1 mm, round edge radius: 61.36 µm, feed rate: 172.72 mm/min and spindle speed: 3000 rpm and output responses are power consumption 1124.53 W, surface roughness 0.3438 µm, axial force 166.53 N and torque 0.132 Nm with composite desirability of 0.8421. Impact of individual input parameters on response has been examined using 3D surface view. [ABSTRACT FROM AUTHOR]

The conventional machining of the widely used nickel-based superalloy Inconel 625 is challenging since it exhibits high strength at elevated temperatures. Cryogenic machining is an effective cooling technique to extract the heat developed during machining and enhance the machining performance of superalloys by eliminating the high-temperature related machining obstacles. The maximum machining performance of cryogenic machining can be achieved by optimising the input parameters considered for the study. This work attempts to improve the cryogenic machining performance of Inconel 625 using grey relational analysis. Multiple responses that are having the most significance on the performance of the machining such as main cutting force, tool wear and surface roughness were considered to optimise the process. The experiments were designed on the basis of the orthogonal array. Taguchi's L9 design with three levels of cutting speed, feed and depth of cut was considered for conducting the experiments. A cutting speed of 60 m/min, feed of 0.05 mm/rev and depth of cut of 0.2 mm were obtained as the optimal parameters. The analysis of modes of wear and morphology of chips was also conducted using SEM imaging to understand the wear mechanisms and machining performance at the optimal level under cryogenic cooling. [ABSTRACT FROM AUTHOR]

This study identified a cracking that occurred continuously in the built direction of an additive manufactured part of alloy 718 by the laser metal deposition method and clarified the cracking behavior. The solidification microstructure of alloy 718 was evaluated by EDS, EPMA, and extraction residue, and it was found that Laves phase, Ti carbides, and Al oxides were formed between the dendrite microstructures. A fracture surface analysis of the cracks revealed that the cracking in the additive manufacturing was hot cracking associated with the liquid film and that the cracking occurred along the grain boundaries. The fracture surface at the beginning of the cracking showed a solidification cracking fracture surface. The experimental investigation for crack propagation during additive manufacturing and the analytical evaluation of the mechanical state around the cracking using thermal elastic-plastic analysis elucidated the cracking behavior during additive manufacturing. If the cracking exists at the fusion boundary, it is suggested that the cracking initiates from the solid-liquid interface towards the solidification direction. Moreover, tensile strain occurred around the cracks during additive manufacturing, particularly the strain was biggest at the crack edge on the fusion boundary. Therefore, the continuous cracking that occurred beyond each layer in the additive manufacturing of alloy 718 in this study can be considered solidification cracking, and its behavior can be further explained as a notch extension cracking that starts from the solidification cracking and continuously occurs in the solid-liquid coexistence temperature region. [ABSTRACT FROM AUTHOR]

This study focused on producing metal matrix composite (MMC) coatings on Ti–6Al–4V alloy through laser surface alloying using a novel combination of Inconel 625 and SiC precursor materials. Various ratios of alloying powders were examined to evaluate surface properties such as microhardness, wear resistance, and friction coefficient, along with analyzing the phase composition and microstructure of the coatings. The in situ synthesized MMC coatings exhibited the presence of α-Ti, NiTi, NiTi2, and TiC phases. Additionally, Ti5Si3 and α-Ti/Ti5Si3 eutectic structures were observed when the SiC content exceeded 20%. In comparison to the titanium substrate, the MMC coating significantly enhanced microhardness by over threefold and reduced wear by 95%. However, it was crucial to carefully select the appropriate combination of alloying powders to avoid a substantial decrease in friction performance and excessive formation of cracks. Through a comparative analysis of experimental results, the optimal precursor material composition was identified as 85% Inconel 625 and 15% SiC. This study demonstrated the effective utilization of Inconel 625 and SiC alloying materials to enhance the surface properties of titanium alloys, thereby expanding their application in challenging environments. [ABSTRACT FROM AUTHOR]

Inconel 625 deposited metal was prepared by gas metal arc welding. The solid solution treatment temperature was set at 1140 °C for 4 h using the DSC test method, followed by secondary aging at 750 °C/4 h and 650 °C/24 h. The specimens in the prepared state and after heat treatment were subjected to high temperature tensile at 600 °C, respectively. The fracture morphology, thermal deformation behavior, and strengthening mechanism of the samples in different states were analyzed. The results showed that the stress–strain curves of the deposited metals exhibited obvious work-hardening behavior at 600 °C. The solid solution and aging heat-treated samples have higher tensile and yield strength, but the plasticity is obviously lower than that of the deposited metal. It was also found that the γ″ phase and M23C6 carbides, as well as the continuous stacking faults in the alloy, were the main reasons for the increase in tensile strength of the solution and aging heat-treated sample. [ABSTRACT FROM AUTHOR]