Inconel Research Articles (Page 1)

Multimaterial additive manufacturing enables the integration of different materials within a single component, allowing for tailored functionality and the reduction of process steps. Among available metal additive manufacturing (AM) techniques, material extrusion of metals (MEX/M) offers a cost-effective and feasible approach for the production of multimaterial parts using a commercial feedstock. This study focuses on the fabrication of green parts composed of pure copper (Cu) and Inconel 718 (IN718), selected for their highly complementary properties: Cu offers excellent thermal conductivity, while IN718 provides outstanding mechanical strength, as well as high corrosion and oxidation resistance. These characteristics make the Cu-IN718 combination particularly attractive for demanding aerospace applications, such as heat exchangers and combustion chambers. A design of experiments approach using response surface methodology was employed to evaluate the influence of key printing parameters, such as nozzle temperature, printing speed, extrusion multiplier, and layer thickness, on the density and dimensional accuracy of green part test specimens. Optimal process parameter sets for each individual material were identified and a corresponding parameter set for the multimaterial combination was subsequently derived. Different geometric features, various material topologies, and two interlocking geometries were analyzed to assess the print quality and geometric accuracy of multimaterial prints. The results were used to derive a set of design guidelines aimed at the manufacturability, reliability, and quality of Cu-IN718 green parts using MEX/M. These guidelines contribute to future standardization efforts in multimaterial extrusion, thus supporting more robust and reproducible production of components via metal AM.

This study investigates the machinability of Inconel 718(IN718) in wire electrical discharge machining(WEDM) using molybdenum wire and demineralized water as the dielectric fluid, aiming to optimize machining efficiency and surface quality. The effects of current, pulse duration (Ton), and pulse interval (Toff) on machining time (MT), material removal rate (MRR), and surface roughness (SR) were analyzed. The overall evaluation criteria (OEC) method was employed to optimize multi-response outputs. Surface morphology was examined through SEM, and elemental analysis was performed using EDS. The results showed that increasing current and Ton enhanced MRR but also led to higher SR due to deeper crater formation. A high Ton combined with insufficient Toff caused process instability, increasing MT and reducing MRR. Conversely, increasing Toff improved surface finish by enhancing debris removal, though excessive Toff slightly reduced MRR. Current was the most influential factor across all responses, as evaluated by ANOVA. Optimal machining conditions, when equal importance was given to efficiency and surface quality in OEC, were identified as 2A current, 40 µs Ton, and 9 µs Toff. SEM analysis revealed that lower discharge energy produced a uniform recast layer with fewer defects, while higher energy resulted in larger globules, micro-pores, and debris accretion. EDS analysis revealed the presence of carbon, oxygen, and molybdenum on machined surface, indicating element migration and possible formation of secondary phases in the recast layer. These findings offer a practical basis for optimizing machining efficiency and surface quality in WEDM of IN718 for high-performance aerospace and thermal applications.

The present study investigates a novel hybrid manufacturing route by synergistically integrating additive manufacturing (AM) and powder metallurgy (PM) to fabricate multi-material metallic components. In this approach, Inconel 718 (IN718) lattice structures were fabricated using Laser Powder Bed Fusion (LPBF), serving as geometrically constrained mould filled with SS316L powder, which was uniaxially compacted and sintered at varying temperatures. IN718–SS316L specimens were analysed for bonding, compatibility and interfacial integrity across sintering temperatures from 1100 °C to 1250 °C. The investigation revealed that elevated sintering temperatures promote interdiffusion of Fe and Ni, as confirmed by EPMA elemental mapping, while also enhancing neck growth and interface consolidation. However, common defects such as partially sintered or unsintered powder, porosity, interfacial cracks and localised over-melting were observed, especially at sub-optimal or excessively high temperatures. Specimen sintered at 1250 °C demonstrated the most uniform bonding with minimal crack density (15.0 cracks/mm²) and the lowest porosity. After polishing, pores ranging from 25.00 μm to 175.05 μm were still predominantly located within the SS316L regions, rather than at the IN718–SS316L interface. The microhardness at the IN718–SS316L interface was measured at 275 ± 4.8 HV, a 30.95% increase compared to typical values reported for conventionally sintered SS316L (∼210 HV). Meanwhile, the IN718 nodal region showed a microhardness of 305 ± 5.5 HV, indicating a well-preserved mechanical profile. The process enables tailored material integration, and with further optimisation in filling strategies, compaction and thermal profiles, offers a promising route for structural applications with graded material properties.

Abstract The investigation of dissimilar metal welds, especially between austenitic stainless steel (SS304L) and Inconel 718 (IN718), is essential for use in challenging environments that demand superior mechanical performance. Current research often overlooks the influence of different heat treatment processes on microstructural and mechanical characteristics, presenting a gap in understanding their implications on joint performance. This investigation employed friction welding to create joints between SS304L and IN718 subjected to two heat treatments before welding: solution treatment (ST) and solutiontreated aging (STA). The materials were characterized through optical and scanning electron microscopy, highlighting the presence of distinct microstructural zones, including fine-grain deformation, thermomechanical affected, and heat-affected zones. Microhardness testing revealed that ST-treated joints exhibited higher hardness values compared to STA, attributed to grain refinement and increased strain hardening. Tensile testing indicated that STAtreated welds, while demonstrating lower yield strength (500 ± 3 MPa) and ultimate tensile strength (665 ± 4 MPa), exhibited greater ductility (15 ± 1%). In contrast, ST joints showed superior mechanical performance, with yield strength at 570 ± 4 MPa and ultimate tensile strength at 710 ± 2 MPa. The failure modes predominantly occurred in the SS304L HAZ (heat-affected zone), underscoring the influence of thermal treatment on joint integrity. This research provides appreciated visions into the impact of thermal and mechanical treatments on microstructural evolution and mechanical properties in dissimilar metal joints, establishing the reliability of friction welding as an effective joining technique for applications in aerospace and high-temperature environments.

Selective laser melting (SLM) allows the production of complex lattice structures with tunable mechanical properties. This study proposes an integrated approach to enhance the mechanical properties of Inconel 718 (IN718) lightweight structures by applying distinct heat treatment protocols and tailoring key printing parameters. Four lattice geometries—body-centered cube (BCC), diamond, inverse woodpile (IWP), and gyroid—were selected for evaluation. Three heat treatment protocols were applied to assess their effect on mechanical behavior. Additionally, the influence of key SLM parameters such as laser power, scan speed, hatch spacing, and layer thickness on structural performance was investigated. By combining process tailoring and post-processing strategies, this work demonstrates a method to improve the mechanical response of complex IN718 lattices. The results highlight significant improvements in yield strength and energy absorption for high-performance applications in aerospace and automotive engineering.

Inconel 718 (IN718) is a nickel-based superalloy that is extensively utilised in the aerospace, automotive, nuclear, and power-generation industries, primarily due to its exceptional high-temperature strength, fatigue and creep resistance, corrosion resistance, and superior weldability. These properties result from optimised thermal and mechanical processing. PBF-LB/M-produced IN718 exhibits characteristic microstructural defects and residual stresses that limit its mechanical properties. The current study systematically examines the effects of various critical post-processing treatments, including stress-relief annealing, Hot Isostatic Pressing (HIP), solution annealing, and ageing treatments, on the microstructure and mechanical properties of PBF-LB/M-manufactured IN718. Furthermore, different combinations of these processes are analysed to explore the potential synergistic benefits, with the possibility of omitting some post-treatments during AM-prepared IN718. The microstructural evolution is investigated using scanning electron microscopy (SEM), complemented by comprehensive mechanical testing, including tensile and hardness tests. The results provide a deeper understanding of the relationship between specific post-processing routes and their impacts on the mechanical performance, supporting the development of optimised treatment strategies for the enhanced reliability and service life of AM-fabricated IN718 components.

Surface texturing with micro- and nano-scale features has emerged as an innovative and robust approach to addressing functional challenges like surface wettability and tribological performance. Among the various techniques, mechanical micro-fabrication stands out for its ability to create highly precise micro-textures in a single step, making it scalable and cost-effective. This study presents a straightforward, one-step mechanical micro-fabrication method such as micro ball-end milling, micro flat-end milling, and micro-drilling for producing micro-dimple patterns on Inconel 625 (IN625) to modify surface topography and enhance wettability. Key parameters, such as texture shape, size, and pitch, were systematically analyzed to evaluate their impact on surface topography. Preliminary findings revealed that the introduction of ordered dimples through micro-milling significantly altered the surface characteristics when compared to untextured surfaces. While the untreated IN625 surface exhibited hydrophobic behavior, micro-texturing transformed it into a hydrophilic surface. The enhancement in wettability was attributed to a combination of factors, including increased surface roughness, texture geometry, and the initial surface condition. Among the different configurations, the untextured surface exhibited the highest contact angle of 101°, whereas the ball-end mill micro-textured surface with the smallest pitch produced the lowest contact angle of 47°.

In this work, a crystal plasticity (CP)-based continuum modeling approach is employed to investigate the interaction between dislocations and coherent γ″ precipitates in the Inconel 718 (IN718) superalloy. A finite element (FE) model is developed to accurately represent realistic microstructures in IN718, specifically incorporating a disk-shaped precipitate embedded within a matrix phase. A length-scale-dependent CP modeling simulation informed by molecular dynamics (MD) findings is conducted. The results indicate that the three γ″ variants behave differently under uniaxial loading conditions, altering the deformation process in the γ phase and leading to significant strain and stress heterogeneities. The presence of dislocation shearing in the γ″ variants reduces the localization of strain and dislocation densities in the adjacent γ phase. The strain gradient-governed geometrically necessary dislocation (GND) density plays a dominant role in influencing strain hardening behavior. The length scale effect is further quantified by considering four different precipitate sizes, with the major axis ranging from 12.5 nm to 100 nm. The findings show that smaller precipitate sizes result in stronger strain hardening, and the size of γ″ precipitates significantly alters GND density evolution.

To address the graphitization of diamond induced by high temperatures during laser cladding of diamond-reinforced composites, this study proposes a laser cladding method utilizing Inconel 718 (IN718) nickel-based alloy as a transition layer which has a lower melting point than the substrate of 45# steel. And then, in order to analyze the detailed characteristics of the samples, scanning electron microscopy (SEM), EDS, Raman spectral analyzer, super-depth-of-field microscope, and friction tests were used. Experimental study and the test results demonstrate that the IN718 transition layer enhances coating performance through dual mechanisms: firstly, its relatively low melting point (1392 °C) reduces the molten pool's peak temperature, effectively suppressing thermal-induced graphitization of the diamond; on the other hand, simultaneously it acts as a diffusion barrier to inhibit Fe migration from the substrate and weaken Fe-C interfacial catalytic reactions. Microstructural analysis reveals improved diamond encapsulation and reduced interfacial sintering defects in coatings with the transition layer. Tribological tests confirm that samples with the transition layer L exhibit lower friction coefficients and significantly enhanced wear resistance compared to those without. This study elucidates the synergistic mechanism of the transition layer in thermal management optimization and interfacial reaction suppression, providing an innovative solution to overcome the high-temperature damage bottleneck in laser-clad diamond tools.

ABSTRACT Electric-arc-directed energy deposition (Arc-DED) revolutionises 3D metal printing by overcoming powder-based processes’ size and production rate limitations. While powder-based processes are constrained by small build chambers and 3–30 micron layer heights, Arc-DED allows for unlimited build scales and 3 mm layer heights, achieving up to 100 times faster deposition rates. Unfortunately, the high energy needed for these rates and thicknesses intensifies the heating and cooling cycles inherent to Arc-DED. This causes significant variations in microstructural and mechanical properties, limiting its use for advanced alloys. This study introduces a conformal top cooling method to regulate the chaotic thermal environment of Arc-DED deposition and produce as-deposited Inconel 718 (IN718) material equivalent to the solutionized condition. The concept is experimentally investigated using cold metal transfer (CMT) of IN718. The role of microstructural and phase uniformity during material production is discussed, material performance in as-deposited and heat-treated conditions is evaluated, processing-property relationships are investigated, and applicability to other materials is addressed. Results show a 45% reduction in process time due to improved thermal management, translating to as-processed microstructural uniformity. Homogeneity in grain growth, controlled phase development, and mechanical testing suggest an as-processed solutionizing effect, with minimised impact of specimen orientation after heat treatment.

In order to clarify the deformation mechanism of Inconel 718 (IN718) alloy at the grain scale during tensile deformation, the deformation behaviors of IN718 alloy were investigated at 650 °C using an in situ electron backscatter diffraction (EBSD) tensile testing method. The evolution of grain morphology, crystallographic orientation, activated slip systems, grain boundaries evolution, and strain-induced misorientation were systematically analyzed during the tensile test. The results showed that the grains were elongated along the tensile direction, and the grain boundaries also became significantly curved. Meanwhile, the EBSD studies illustrated that the changes in local misorientation within individual grains were non-uniform and generally began at the grain boundaries. The low-angle grain boundaries (LAGBs) were first formed near the high-angle grain boundaries (HAGBs) and gradually expanded into the interior of the grains. The activation of the slip system and the Schmid factor were characterized and calculated based on the slip traces on the deformed grain surface. The evolution of local strain within the grains was evidenced by a kernel average misorientation (KAM) map. Finally, the plastic deformation mechanism at the grain scale was discussed in detail based on our experimental results.

ABSTRACT Nickel-based superalloys are extensively used in different high-temperature applications due to their excellent strength and performance at high temperatures, such as gas turbines. However, the properties of these alloys vary significantly with changing the manufacturing methods. Additive manufacturing is a new and advanced manufacturing technique that can produce metallic components with great precision, accuracy, and close tolerance. This work focuses on investigating the performance of additively manufactured Inconel (IN) 718 by laser bed powder fusion technique (LPBF) in 1 M HNO3. Open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and Tafel polarization curves (TPC) have been used to assess the corrosion behaviour of IN 718 in 1 M HNO3. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) are employed to know the qualitative effects of corrosion on the surface of IN 718. X-ray photoelectron spectroscopy (XPS) has been used for depth profiling of IN 718 elements to understand the localised corrosion behaviour of IN 718. The results show that additively manufactured IN 718 can be successfully used in strong corrosive and acidic environments.

Abstract Cold metal transfer (CMT) has emerged as a highly promising method for directly producing or repairing high-performance metal components. Induced fabrication defects, like porosity and heterogeneous microstructures, impact part quality and mechanical performance. Investigating a high-efficiency CMT-based wire-arc direct energy deposition method is important for manufacturing high-quality, super duplex stainless steel 2507 (SDSS2507)–Inconel 718 (IN718) parts. Ultrasonic vibration has been used to enhance part performance in melting material solidification procedures. Few studies exist on using ultrasonic vibration in CMT-based wire-arc direct energy deposition for dissimilar SDSS2507–IN718 part production. This research proposes the use of ultrasonic vibration (UV)-assisted CMT-based wire-arc direct energy deposition to manufacture dissimilar SDSS2507–IN718 parts to potentially decrease fabrication faults. Experimental studies are carried out to examine the impact of ultrasonic vibration on the microstructures and mechanical properties of parts manufactured using CMT. The findings demonstrated that the application of ultrasonic vibration improved the microstructure, leading to an average grain size of 4.59 µm. Additionally, it effectively fragmented the harmful Laves precipitated phase into small particles that were evenly distributed. Consequently, the yield strength and ultimate tensile strength (UTS) of the fabricated dissimilar SDSS2507–IN718 parts were improved. The microhardness increases from an average of 302 HV to 335 HV, reflecting an 11% gain, at SDSS2507; from 233 HV to 265 HV at the Interface, indicating a 14% increase; and from 249 HV to 270 HV at IN718, demonstrating a 9% enhancement.

PurposeThe quality of Inconel 718 (IN718) from selective laser melting (SLM) is prerequisite for its application, and meeting required tensile properties is particularly important. This study aims to realize both mechanical property prediction and process parameter selection of SLM-ed IN718 by taking full advantage of their process-tensile property data mined from literature.Design/methodology/approachExtensive data of interest are mined from literature, among which the missing data are then imputed by fitting Gaussian mixture model via expectation maximization. Forward/backward predictive models for predicting the unknowns in tensile properties (ultimate tensile strength, yield strength, elongation) along horizontal and vertical directions and key process parameters (laser power, scanning speed, hatch spacing, layer thickness) are built through Bayesian network.FindingsNone of the experiments from literature has complete data of the four key process parameters and three tensile properties along two directions. Satisfactory accuracies are obtained for both data imputation for the missing values in the mined literature data with an average R2 of 0.64 and forward/backward prediction of process-tensile property with an average R2 of 0.58/0.54. The data imputation and predictive models are also tested with consistent prediction accuracies.Originality/valueForward/backward process-tensile property predictive models of SLM-ed IN718 with satisfactory performance can be obtained after data imputation for the mined literature data. Such models consider more process parameters (four key process parameters) and properties (three tensile properties along two directions), which also cover wider ranges than any individual studies through a less costly while effective approach.

The characteristics of laser powder bed fusion (L-PBF) Inconel-718 (IN-718) differ from those of its wrought counterpart because of the rapid heating and cooling cycles involved during the process. Heat treatments are performed to enhance the characteristics of L-PBF IN-718 components before their suitability for practical applications. This investigation explores the influence of phase transformation-induced changes in the microstructure and thereby the machinability (specifically micro-turning) of L-PBF IN-718. Additionally, a comparison is made with its conventional counterparts (wrought specimens). The anisotropic characteristic of L-PBF IN-718 is only marginally affected by the standard double aging (DA) heat treatment. However, DA substantially impacts the microstructural characteristics, resulting in a notable increase in hardness of 12.2% and 20.7% for wrought and L-PBF IN-718 respectively due to precipitation of the hardening phases γʹ and γ″. Experimental investigations were conducted to study the machining behaviour during micro-turning, focusing on cutting force, tool wear, surface roughness, and chip morphology. Noticeably, heat treatment led to a significant increase in the cutting force (120%), tool wear (67%), and surface roughness (33%) for the L-PBF samples, due to precipitation of γʹ and γ″. Results indicate that to achieve better surface quality, it is recommended to machine the L-PBF specimens at a lower cutting speed whereas the wrought specimens at a higher cutting speed.

Abstract This study attempts to elucidate the quasi-isotropic behavior observed in laser-based powder bed fusion of Inconel 718 (IN718) alloy. This effort emphasizes the effect of laser process parameters on crystal orientation and subsequent mechanical behavior. The plate-type IN718 rectangular coupons were deposited using a laser powder bed fusion technique with a volumetric energy density of 66.29 J/mm3 and a scanning strategy of 67 deg rotational between each consecutive layer. These coupons were solution-treated, and subsequently, precipitation-hardened. Quasi-isotropic mechanical properties were observed in the coupons through tensile experiments performed along 0 deg and 90 deg to the building direction. Electron backscattered diffraction studies have indicated the development of an <001> orientation in the as-built and precipitation-hardened coupons. But, the solution-treated coupons deviated from the ideal <001> orientation. However, X-ray diffraction studies revealed the presence of a weak cube texture for all thermally-treated conditions. The scanning strategy and volumetric energy density led to the development of the weak cube texture in the as-built sample, which is thus implicated in the quasi-isotropic mechanical properties in the printed coupons.

This study investigates the microstructure and mechanical properties of Inconel 718 (IN718) manufactured via electron beam melting (EBM). The EBM‐processed IN718 exhibits a unique grain structure with columnar grains along the build direction (BD) and equiaxed grains perpendicular to it. Contrary to typical solidification textures, the strongest texture intensities are observed for (110) and (111) orientations, attributed to in situ δ phase precipitation during high‐temperature processing. The microstructure notably lacks cellular structures common in additively manufactured materials, instead featuring δ phase formed through in‐situ aging. A tailored heat treatment strategy is developed to control δ phase precipitation at grain boundaries, mitigating grain boundary sliding (GBS). This treatment results in <100> texture and large columnar grains, leading to a twofold increase in yield strength compared to the as‐printed (AP) condition. Interestingly, the AP EBM IN718 shows no signs of dynamic strain aging (DSA), distinguishing it from conventionally processed IN718. This comprehensive analysis of microstructure, texture, and mechanical behavior provides valuable insights for optimizing EBM processing and heat treatment of IN718 for enhanced performance in high‐temperature applications.

An in-depth understanding of the texture formation in melt pools allows for the modification of the surface layer microstructure and corresponding material properties, providing an opportunity to integrate laser surface re-melting into metal additive manufacturing. This study investigates crystallographic texture formation at different cooling rates in single melting tracks on the Inconel 718 (IN718) plate produced by laser surface re-melting. The cooling rate varies from 2.31 × 105 °C/s to 9.56 × 105 °C/s with the increase in scanning rates from 400 mm/s to 1200 mm/s, measured by recently developed real-time temperature monitoring of melt pools. Columnar grains are dominant, with distinct crystallographic textures forming in the melt pools. At a slower scanning speed, the keyhole mode shows three different textures forming at different depths (crystallographically layered structure), while, at a faster scanning speed, the conduction mode shows only random grain orientation. There are no pores/voids detected, and the columnar grain morphology and columnar grain width (8.6 μm to 12.4 μm) follow the analysis framework in terms of thermal gradient and solidification rate analysis. This implies that laser surface re-melting provides the potential to modify the surface structure from a random grain orientation to a crystallographically layered structure.

From an economic and sustainability point of view, repair is considered a promising alternative for high value-added aeronautical materials. In this study, laser metal deposition (LMD) was used for simulating the repair of damaged Inconel 718 (IN718) parts. Grooves were machined in IN718 substrates using abrasive water jet (AWJ) and filled with powdered IN718 alloy. Based on these results, a set of optimal LMD process parameters were selected for depositing material layers on milled substrates with various of roughness and texture levels induced by AWJ machining to evaluate the effect of surface preparation on repair quality. The substrate-deposit repair interfaces were characterized using microscopic analysis and multi-scale hardness tests. The results showed the influence of scan speed on the height of the weld bead, while increasing laser power and scan speed were both found to increase weld bead height. Dilution increased with a decrease in scan speed. Additionally, repair quality was found to be independent of the different surface conditions. Overall, the repairs exhibited excellent weldability, and were free of cracks and lack-of-fusion defects. Furthermore, microhardness measurements yielded higher values of hardness in the deposit area than in the substrate for all repairs.

Effect of feedstock bimodal powder design and cold isostatic pressing on the mechanical behavior of binder jetting additive manufactured Inconel 718 superalloy