Alloy Inconel Research Articles

Role of Activating Flux in Weld Bead Symmetricity during Dissimilar Metal Joining

Ferritic/martensitic steels and austenitic stainless steels are high‐strength steels, and highly recommended in high‐temperature and high‐pressure application. In general, multimetallics with different Inconel alloys are used for joining. This is quite a complex and time‐consuming procedure. The current work demonstrates the efforts made to weld 8 mm‐thick P91 steel and 316L SS plates in a single pass using activating flux tungsten inert gas (A‐TIG) welding process without any interlayers. The main challenge is to get the symmetric weld bead profile. Flux coating is optimized in terms of flux composition, coating density, and coating pattern to get the full penetration with symmetric appearance. The current work discusses the possible cause and their solution of asymmetricity during dissimilar welding. Differential flux coating density is found to be very effective in controlling the arc column shape, fluid flow, and consequently the bead geometry. High coating density is used in the P91 side compared to 316L side. Symmetric weld profile with full penetration is achieved by applying multicomponent flux (33–38% TiO2, 38–43% SiO2, 13–17% NiO, and 8–10% CuO) during A‐TIG welding.

Artificial neural networks-based modelling of effects of cryogenic electrode treatment, nano-powder, and surfactant-mixed dielectrics on wear performance and dimensional errors on superalloy machining

In the present era dominated by Industry 4.0, the digital transformation and intelligent management of industrial systems is significantly important to enhance efficiency, quality, and the effective use of resources. This underscores the need for a framework that goes beyond merely boosting productivity and work quality, aiming for a net-zero impact from industrial activities. This research introduces a comprehensive and adaptable analytical framework intended to bridge existing gaps in research and technology within the manufacturing sector. It encompasses the essential stages of using artificial intelligence (AI) for modelling and optimizing manufacturing systems. The effectiveness of the proposed AI framework is evaluated through a case study on electric discharge machining (EDM), concentrating on optimizing the electrode wear rate (EWR) and overcut (OC) for aerospace alloy Inconel 617. Utilizing a comprehensive design of experiments, the process modelling through an artificial neural network (ANN) is carried out, accompanied by careful fine-tuning of hyperparameters throughout the training process. The trained models are further assessed using an external validation (Valext) dataset. The results of the sensitivity analysis indicated that the surfactant concentration (Sc) has the highest level of influence, accounting for 52.41% of the observed influence on the EWR, followed by the powder concentration (Cp) with a contribution of 33.14%, and the treatment variable with a contribution of 14.43%. Regarding OC, Sc holds the highest percentage significance at 72.67%, followed by Cp at 21.25%, and treatment at 6.06%. Additionally, parametric optimization (PO) shows that EWR and OC overcome experimental data by 47.05% and 85.00%, respectively, showcasing successful performance optimization with potential applications across diverse manufacturing systems.

Processing correlations of laser direct energy deposited Inconel718 based on multi-field numerical simulation

Laser direct energy deposited (LDED) Inconel718 always have problems of non-uniform temperature distribution because of the complex flow of molten pool and layer-by-layer fabrication characterization which directly affected the microstructure and mechanical properties of materials. In this work, Inconel718 revealed a refined grains and a weave structure exhibiting excellent mechanical properties which were superior to those of the conventional casting process were successfully fabricated by adopt a high-precision and intelligent coaxial powder feeding system during the LDED processing. Moreover, based on multi-field numerical simulation method, a two-phase flow model and a transient thermal mechanical deformation model were established to simulate the LDED processing, while takes into account the evaporated mass loss of the inconel718 alloy. The morphology prediction of laser directed energy deposition by multi-physics numerical simulation, the relationship among the laser process parameters, i.e., the laser power, scanning speed and the amount of powder feeding, the temperature filed and the microstructure and mechanical properties of Inconel718 alloy during LDED were investigated and established. The simulated results consistent well with the experimental results. Results shown that the relative density of sample was sensitive to the laser power, the precision and stability of the powder feeding rate. With increasing laser power, the grain size of Inconel718 is refined, and the microhardness and tensile properties of the materials increased. The optimized LDED processing parameters were determined. Evaluating the mechanical properties of the materials LDEDed at a laser power of 600W and a scanning speed of 8.5mms-1 exhibited a high tensile strength of 944±5 MPa and a good elongation of 29 ± 0.5 %. This work suggests that the processing parameters can be optimized to prepare densified materials with excellent mechanical properties.

Comparison of sustainable cooling/lubrication strategies for drilling of wire arc additively manufactured Inconel 625

Machining Inconel presents significant challenges due to the material's high strength, hardness, and heat resistance. These properties often result in accelerated tool wear, modest surface finish, and increased energy consumption during machining processes. Despite its widespread use in industries, the machining of Inconel alloys remains a persistent bottleneck in manufacturing operations. In this study, we focus on drilling rather than milling of Inconel 625, a commonly used nickel-based superalloy, due to its specific relevance in various industrial applications. Drilling operations are critical in numerous contexts, including the fabrication of aerospace components, where precision, hole quality, and efficiency are paramount. Therefore, this study aims to improve machinability of wire arc additively manufactured Inconel 625 by fabricating it with two different travel speeds, 175 mm/min and 185 mm/min as well as by drilling the fabricated Inconel 625 using recently developed sustainable lubrication/cooling strategies, i.e. electrostatic minimum quantity lubrication (EMQL) and cryogenic LCO2. The results show that the sample built with 185 mm/min produces less tool wear, surface roughness, thrust force and power consumption. The use of LCO2 results in approximately 35 % less tool wear, 27 % less surface roughness, 15 % less thrust force, and 4 % lower power consumption compared to EMQL for the sample built at 185 mm/min.

Inhibition of interfacial cracks in 304L-Inconel718 bimetal fabricated via laser powder bed fusion

Multi-material additive manufacturing is crucial for intricate component fabrication, yet challenges, such as interfacial cracks and weak bonding, persist. This work investigated the laser powder bed fusion (L-PBF) of bimetallic components (stainless steel 304L-nickel-based alloy Inconel718) crucial in aerospace and nuclear applications. It is found that the interfacial cracks predominantly occur within the compositional transition zone where the proportion of 304 L is between 45 wt% and 75 wt%, characterized by brittle Laves phases along grain boundaries. Experimental and finite element simulations of melt pool reveal that a higher ratio of temperature gradient (G̅) to the grain growth rate (R̅) (G̅/R̅) results in straight grain boundaries with underdeveloped secondary dendrites. This leads to the formation of continuous liquid film and strip-like Laves phase at grain boundaries, causing interfacial cracks during L-PBF. To suppress these cracks, this work proposes manipulating grain boundaries into a tortuous morphology through promoting the growth of secondary dendrites. By controlling the G̅/R̅ ratios below the critical value (<147.9×106 K∙s/m2) and combining with a high cooling rate (G̅×R̅) during L-PBF, a well-developed secondary dendritic structure and grain refinement are achieved, significantly enhancing grain boundary tortuosity and forming discretely distributed Laves phases. As a result, interfacial cracks are completely suppressed, enabling the successful manufacturing of crack-free 304L-Inconel718 bimetallic components. The approach of tailoring the distribution of brittle precipitates through manipulating grain boundary morphology proposed in this work provides a novel and practical pathway for inhibiting cracks in multi-material additive manufacturing.

An experimental investigation on transpiration cooling with phase change subjected to non-uniform flame

Transpiration cooling with phase change is promising for thermal protection of scramjet engine due to the combined advantages of latent heat absorption of coolant and thermal insulation of gas film. Previous investigations primarily focused on the transpiration cooling subjected to uniform incoming flow. However, few investigations have revealed the effect of the non-uniformity of high-temperature flame on transpiration cooling with phase change. Moreover, the effect of porosity on transpiration cooling performance was seldomly mentioned. Herein, we experimentally investigate the transpiration cooling in porous media of alloy (Inconel 600) with deionized water as the coolant subjected to the non-uniform high-temperature flame. Moreover, the effects of porosity and type of transpiration material on cooling are investigated. Results show that when the injection rate is less than 16 %, local overheating occurs on the surface of the porous materials. The overheating phenomenon occurs earlier at lower injection rates. Moreover, the decrease in porosity of the transpiration material will lead to increases of the surface temperature and top/back surface temperature difference, as well as decreases of top-surface temperature non-uniformity and cooling efficiency. In addition, for the different porous materials with similar thermal conductivity, the specific surface area exhibits a dominant factor in transpiration cooling.

Metallurgical and mechanical properties of trimetallic functionally graded material fabricated by wire arc additive manufacturing

This study explores the fabrication of a trimetallic functionally graded material (FGM) using stainless steel (ER316L), duplex steel (ER2205), and Inconel 718 (IN718) through a gas metal arc welding (GMAW) based wire arc additive manufacturing (WAAM) process. The metallurgical examination reveals the large columnar austenitic grains and δ-ferrite phase at the grain boundaries along the built direction in the stainless-steel zone. At the interface of ER2205-IN718, a distinct boundary is observed due to the different alloy compositions. Scanning electron microscopy (SEM) shows metal carbide of nickel (Ni), molybdenum (Mo), and niobium (Nb) along the grain boundaries and nodular-shaped Lave phases in the IN718 zone. The energy dispersive spectroscopy (EDS) analysis reveals a gradual variation of Ni and Fe content, indicating the successful fabrication of the FGM. The mechanical characterization reveals that the hardness of the developed FGM steadily increases from bottom to top. However, at the ER2205-IN718 interface, it experiences a sharp decrease, followed by a subsequent increase within the IN718 zone. The tensile test demonstrated an increase in tensile strength along the built direction, accompanied by a reduction in strain. Notably, the minimum strain observed in the developed FGM is approximately equal to that of IN718 alloy.

Re-heat treatment effect on the microstructure and mechanical properties of the Inconel 706 alloy for repair

Although the understanding of microstructure and mechanical property changes in re-heat-treated Inconel alloys is important to evaluate the performance of repaired components, recent research has mainly focused on the heat treatment effect of as-fabricated products. Thus, in this work, the performance change of the used Inconel 706 rotor-disks under varying re-heat treatment conditions was investigated. Because of the heat exposure of the used rotor-disk component, a high fraction of plate-like η phase (6.36%) and compact γ'/γ" co-precipitate structure were initiated in the as-received sample. After re-heat treatment, η phase dissolution breakage and compact to non-compact γ'/γ" co-precipitate structure transition occur, resulting in mechanical properties changes of the Inconel 706 alloy. As a result, η phase fraction affects the tensile strength and ductility of Inconel 706 alloy, while the non-compact γ'/γ" co-precipitate structure in the matrix degrades the creep lifetime. These results indicate that re-heat treatment during the repair of operated components induces microstructural and mechanical properties changes. However, to investigate the detailed history of used Inconel 706 components, additional research on the microstructural degradation during operation of Inconel components is required.

High-speed perforation of IN718 plates by spherical TC4 Ti alloy projectiles: Experiments and modeling

Data and knowledge on ballistic performance of Inconel-718 (IN718) alloy is critical for evaluating the resistance of turbine blades against foreign object impacts in aeronautical and astronautical industries. Ballistic perforation experiments (impact velocity 480 ms−1 to 1340 ms−1) with TC4 spherical projectiles (5-mm-diameter) are conducted on IN718 target plates (2-mm-thick) in this work, along with high-speed photography. The IN718 plates show multiple deformation and failure modes (bulging, dishing, petaling and plugging). The ballistic limit velocity for the investigated projectile/target combination is 823 ms−1. Postmortem material characterizations (optical photography, scanned electron microscopy and energy dispersive spectrometry) are conducted on recovered projectiles and bullet hole inner walls, and the observations indicate adiabatic shearing, surface melting and abrasion of projectile material. A finite element model based on the Johnson–Cook constitutive model and failure criterion is established, and reproduces the ballistic experiments. Dimensionless analyses are conducted on the dimensions of postmortem projectiles and bullet holes, and the projectile residual velocity/mass. On the basis of experimental observations and theoretical analysis of the projectile dynamics, the whole perforation process is divided into three stages (the entering, cratering and plugging stages). A multi-stage analytical model on perforation is then developed considering the effects of cavity expansion, projectile deformation and abrasion, and can well predict the projectile dynamics during entering and cratering stages.

An Investigation into Sheet-Inconel 718 Forming with Flexible and Metal Tools-Simulation and Experiment.

The article presents the results of numerical simulations and experimental tests of plastic forming sheets made from the difficult-to-deform nickel alloy Inconel 718 with a thickness of 1 mm, using punches made from elastomeric materials with hardness 50-90 Shore A and steel dies. Elastomeric stamps were created in the form of five layers with a diameter of 160 mm. The influence of the hardness of the elastomeric punches on the geometry of the elements obtained was determined. The dies were made from 90MnCrV8 steel with a hardness of over 60 HRC. Their task was to obtain the expected shape of the element while generating various stress states in specific areas of the semi-finished product. The research was carried out using an original device whose operating principle was based on the Guerin method. The shape and dimensions of the elements made from Inconel 718 nickel alloy were determined by optical 3D scanning. The geometry of the drawpiece showed a significant impact of the hardness of the layered elastomer matrices on the degree of shape reproduction. The results obtained from numerical modeling were confirmed by the results of experimental tests. It has been shown that the hardness of the elastomeric material used for punches for plastic forming Inconel 718 nickel alloy sheets should be adapted to the shape of the drawpiece. It was also found that one of the important aspects of plastic forming sheets using the Guerin method is the tendency to obtain a diversified shape of the final elements.

Influence of Chloride Concentration on Fretting Wear Behavior of Inconel 600 Alloy.

The nickel-based alloy Inconel 600, strengthened by solution treatment, finds extensive application as a heat exchange pipe material in steam generators within nuclear power plants, owing to its exceptional resistance to high-temperature corrosion. However, fretting corrosion occurs at the contact points between the pipe and support frame due to gas-liquid flow, leading to wear damage. This study investigates the fretting wear behavior and damage mechanism of the nickel-based alloy Inconel 600 and 304 stainless steel friction pairs under point contact conditions in a water environment. Characterization was performed using laser confocal scanning microscopy and scanning electron microscopy equipped with energy-dispersive spectroscopy. Results indicate that the friction coefficient remains consistent across different chloride ion concentrations, while the wear volume increases with increasing chloride concentrations. Notably, friction coefficient oscillations are observed in the gross slip regime (GSR). Moreover, the stability of the oxide layer formed in water is compromised, diminishing its protective effect against wear. In the partial slip regime (PSR), friction coefficient oscillations are absent. An oxide layer forms within the wear scar, with significantly fewer cracks compared to those within the oxide layer in the GSR. It is worth noting that in GSR, the friction coefficient oscillates.

Analysis of structure and strength properties of heat‑resistant iron‑chromium‑nickel (Inconel 718) alloy obtained using secondary metal powder composition in direct laser deposition

This work presents investigations on the structure, chemical analysis, and strength properties of deposited metal using two types of metal powder compositions, namely the primary powder and the residuals (secondary) of the heat‑resistant ironchromium‑nickel alloy Inconel 718.Based on the obtained results, the causes of the formation of a fine‑cellular‑dendritic directional structure with needle and dendritic morphology were determined, as well as the decrease in heat resistance of the deposited material from the secondary powder of the heat‑resistant iron‑chromium‑nickel alloy Inconel 718 at elevated temperatures.

Minimization of residual stress, surface roughness and tool wear in Electro Discharge Machining of inconel 625

Electro Discharge Machining (EDM) is a well-known non-traditional machining technique which is widely used to make die castings and turbine blades out of difficult-to-cut materials like Inconel 625. The machined part's surface quality and dimensional accuracy are affected by the EDM electrode's wear. Moreover, surface roughness and residual stress augmentation of EDM-machined components can reduce the workpiece's lifespan by decreasing the fatigue life of machined parts. To enhance the precision and durability of EDM machined components, residual stress, tool wear, and surface roughness should be evaluated and minimized. The majority of published research works for the assessment and optimization of EDM machining parameters are based on experimental works which are limited to testing, workpiece materials, and machining conditions. In order to improve the quality of machined surfaces and reduce tool wear and residual stress during Inconel 625 EDM processes, a virtual machining approach has been developed in the research work. To predict the cutting temperature during EDM operations, the modified Johnson Cook model of Inconel alloys is used. The finite element approach is then used to calculate the generated residual stress during the EDM process. The proposed virtual machining approach is also applied in order to predict the surface roughness of EDM machined parts. To minimize the residual stress, tool wear, and surface roughness during EDM operations of Inconel 625, the machining parameters of gap voltage, peak current, pulse-off time, and pulse-on time are optimized using the Taguchi optimization approach. Experiments and simulations are then conducted to verify the developed virtual machining system in the study. So, using the optimal machining parameters, the residual stress, surface roughness of machined items and wear of EDM electrode are minimized by 24.5 %, 25.4 %, and 25.4 % respectively. Thus, the quality and reliability of components made using EDM processes may be enhanced by the suggested virtual machining system.

The Influence of nc-AlCrTiN/α-BN Coatings on Increasing the Durability of WC/Co Cutting Inserts in the Inconel Alloy Machining Process.

Anti-wear coatings obtained through PVD methods may significantly increase the durability of cutting tools by impacting their wear mechanisms. This study presents and discusses the results of studies on the impact of the thermal conductivity of PVD coatings on the intensity of the built-up edge (BUE) and built-up layer (BUL) formation in Inconel 600 alloy machining processes. The authors determine the microstructure, phase structure, mechanical properties (hardness, Young's modulus, and adhesion), and thermal conductivity of different PVD coatings selected for the purpose of the study and varying in terms of conductivity-i.e., AlCrTiN and AlCrTiN/BN. Machining processes were carried out under controlled conditions using VBGT160404-M3 cutting inserts with AlCrTiN and AlCrTiN/BN coatings deposited on their surface. The authors prove that the adjustment of the thermal conductivity of PVD coatings to the thermal conductivity of the tool and machined materials can help change the direction of heat flow to cool the cutting zone more effectively. The study results presented in this article show that the deposition of the AlCrTiN/BN coating reduces the friction wear on the tool flank by over 70% and lowers the intensity of BUE and BUL formation processes on the face by 10%, compared to the AlCrTiN coating.

Effects of Solution Treatment on Microstructure and Properties of Inconel600 Alloy

Effects of Solution Treatment on Microstructure and Properties of Inconel600 Alloy

Optimization of the grain boundary network and tensile properties of powder metallurgy-hot isostatic pressed Ni-based alloy Inconel 625

Powder metallurgy-hot isostatic pressing (PM-HIPing) is an advanced manufacturing technology for large-sized and complex-shaped components for nuclear applications. In the present study, a novel PM-HIPing strategy was proposed to optimize the grain boundary network and tensile properties of Ni-based alloy Inconel 625, and it was verified by a series of experiments. Samples with 69 % and 74 % of coincidence site lattice (CSL) grain boundaries were obtained when the narrow-size ranged powder was consolidated at 1140 °C and 1180 °C, respectively. The fraction of CSL grain boundaries was further increased to ∼78.5 % after a high temperature solution treatment. Room temperature yield strength and ultimate tensile strength of PM-HIPed alloy 625 were comparable to that of the wrought specimens, elongation of the specimens was ∼56–60 %, the samples all featured with dimple ductile dominant fracture mode.

Feasibility of clearance level electrolytic decontamination of simulated radioactive Ni-based alloy

Many countries are in the process of decommissioning their nuclear power plants. These power plants contain valuable metals, including Inconel alloys, which are often only contaminated on the surface. Metals are typically decontaminated using laser ablation. However, electrolytic decontamination is a simpler and less expensive solution. Our investigation aimed to develop a method for decontaminating Inconel alloy contaminated with Co to clearance level for recycling and reuse. This study focused on the electrolytic decontamination of Ni-0.2 wt.% Co alloy, identified as a potential replacement for the radioactively contaminated material. Molten LiCl-KCl-NiCl2-CoCl2 (500 °C) was used as the electrolyte in the experiments and the potential recyclability of the used electrolyte was examined. In the absence of CoCl2 in the electrolyte, the decontamination factor is 1.38E8 after the third cycle of electrolytic decontamination. Considering that the decontamination factor corresponding to the clearance level is 1.27E7, three cycles of electrolytic decontamination are considered to be sufficient. Additionally, an investigation of the possibility of recycling the used electrolyte showed that the solidified products formed after vacuum distillation were LiCl, KCl, and Co oxide with traces of Ni oxide. ICP analysis of the LiCl and KCl collected after vacuum distillation revealed that the concentration of Co was less than 0.1 ppm, which suggests that the used electrolyte can be recycled. These findings are expected to offer valuable insights into the electrolytic decontamination process, its limitations, and potential applications in the processing of nuclear waste.

Laser powder bed fusion of oxide dispersion-strengthened IN718 alloys: A complementary study on microstructure and mechanical properties

In this study, two new grades of oxide dispersion strengthened (ODS) Inconel 718 (IN718) alloys were designed by the thermochemical CALPHAD method and produced by laser powder bed fusion (LPBF) technique. Alloys designated as IN718-YF and IN718-YFH, that consist Y2O3–FeO and Y2O3–FeO–Hf, respectively, were fabricated with >99.9 % densification using optimized process parameters. CALPHAD calculations were highly consistent with experimental findings, highlighting the formation of Al-containing Y–Ti–O and Y–Hf–O nano-oxides in both alloy types. Texture analyzes revealed no significant texture development in as-built (AB) or heat-treated (HT) alloys. Heat treatment was applied at 1050 °C for 1 h to enhance nano-oxide density. The nano-oxide number density remained similar in IN718-YF while it decreased in IN718-YFH alloy as a result of carbide formation after the heat treatment. Besides, formation of secondary γ′ particles was observed in the IN718-YFH/HT alloy. Even though the yield strengths of IN718-YF and IN718-YFH alloys in both AB and HT conditions were similar, the ductility of IN718-YFH was ∼50 % less in almost all conditions compared to the ductility of IN718-YF. This has been shown to be as a result of irregular shaped micron-sized Y-Hf-O oxides, martensite formation in AB condition, increased amount of carbides and existence of secondary γ′ particles in HT condition in IN718-YFH. High density of stacking faults (SF) forming at the interface of the nano-oxides have been detected in IN718-YF alloys. Besides dislocation/nanoparticle interactions, SFs which are responsible for the delocalization of the deformation improve the ductility of IN718-YF alloys. Overall, high temperature mechanical tests exhibit that both alloys have higher strength with improved ductility compared to the standard IN718 alloys, indicating the contribution of the nano-oxides.

Multi-functional Inconel 625 micro-machining and process optimization using ANFIS

The primary objective of this study is to develop an adaptive neuro-fuzzy inference-based system (ANFIS) that assesses the ideal parameters and impact of the micro-electro-discharge machining (Micro-EDM) technique on surface roughness (SR). In this work multi-functional Inconel alloy specimens were machined using micro-elector-discharge machining (Micro-EDM) with zinc-coated copper electrodes in a graphite nano abrasive submersion medium. An ANFIS and Taguchi design of experiments (DOE) was employed to evaluate the Micro-EDM method. The study utilized Taguchi's L9 mixed orthogonal arrays (OA) to consider three process variables, namely open voltage (V), capacitance (C), and powder concentration (CP). ANOVA analysis was conducted to identify important process variables and evaluate their influence on surface properties. The experimental results showed that all approaches were effective in representing the process. Based on the results of the response surface methodology (RSM) and ANFIS predictions, the correlation coefficients (R2) of the experimental roughness were 0.995649 and the root mean square error (RMSE) value was 1.01226e-06, respectively. The results obtained indicate a strong alignment between the predicted and experimental values, effectively fulfilling the proposed objective. These findings hold significant potential for practical applications in the Micro-EDM industry, particularly in the machining of Inconel alloy.

Crystal plasticity modeling and analysis for the transition from intergranular to transgranular failure in nickel-based alloy Inconel 740H at elevated temperature

The precipitation-strengthened Nickel-based alloy Inconel® 740H® (IN740H) exhibits increased ductility at higher applied strain rates during quasi-static tensile tests at an elevated temperature of 760 °C. The examination of fracture surfaces in this context reveals a noteworthy transition of underlying fracture mechanisms from transgranular to intergranular fracture as the applied strain rate decreases from 1×10−3/s to 0.83×10−4/s. To thoroughly understand the mechanical response of IN740H under these conditions, this study develops a crystal plasticity finite element (CPFE) model. This model incorporates various deformation mechanisms including dislocation slips, climb, and grain boundary sliding, which are relevant to the test conditions. The model is calibrated using data from both tensile tests at different strain rates and creep tests across a broad stress range at 760 °C, enabling the accurate determination of model parameters for each mechanism. Simulation results well captured the experimental observations of different failure modes. At higher strain rates, the model shows a dominance of dislocation slip leading to heterogeneous plastic deformation and formation of transgranular shear bands causing the failure, while at lower strain rates, an increased activity of grain boundary sliding causes grain boundaries crack leading to intergranular failure.