Search Results (164)

Nickel superalloy Inconel 718 (IN718) is widely employed in harsh environments with prolonged cyclic stresses in the aerospace and energy sectors, due to its corrosion/oxidation resistance and mechanical strength obtained by precipitation hardening. This work investigates the mechanical behavior in fatigue of IN718 manufactured by Additive Manufacturing (AM), specifically by Laser Powder Bed Fusion (PBF-LB), and compares its results with the material produced by forging and rolling. Samples from both processes were subjected to heat treatments of solution and double aging to increase their mechanical strength. Then, tensile, microhardness, microstructural characterization, and uniaxial fatigue tests were performed (with loading ratio R = −1). The results showed that, although the IN718 produced by AM had higher microhardness and a higher tensile strength limit than the forged and rolled material, its fatigue performance was lower. The S–N curve (stress vs. number of cycles) for the material obtained by PBF-LB demonstrated shorter fatigue life, especially under low and medium stresses. The analysis of the fracture surfaces revealed differences in the regions where the crack initiated and propagated. The shorter fatigue life of the material obtained by PBF-LB was attributed to typical process defects and microstructural differences, such as the shape of the grains, which act as points of crack nucleation. Full article

Machining nickel-based superalloys, such as Inconel 718, poses a significant technological challenge due to their high-temperature strength and low thermal conductivity, leading to rapid tool wear. This paper presents a comprehensive comparative analysis of two roughing strategies: high-feed milling and plunge milling, utilizing a unique custom-designed milling head. The primary objective was to evaluate the impact of tool material reinforcement on the process by comparing SiC whisker-reinforced ceramic inserts (CW100) with non-reinforced inserts (CS300). The experiment involved measuring cutting force components, power consumption, and analyzing tool wear progression (VBB) and mechanisms. Results showed that the presence of the reinforcing phase is critical for reducing the axial force component (Fz), particularly in plunge milling, where CW100 inserts achieved a 30–35% force reduction and avoided the catastrophic failure observed in non-reinforced ceramics. Microscopic analysis confirmed that composite inserts undergo predictable abrasive wear, whereas CS300 inserts are prone to brittle fracture and spalling. Multi-criteria optimization using Grey Relational Analysis (GRA) identified high-feed milling with reinforced inserts as the most efficient strategy, while also positioning plunge milling with composites as a competitive, less energy-intensive alternative. Full article

This study was undertaken to investigate the effect of aluminizing on the oxidation of Inconel 718 and Inconel 738LC superalloys. Bare and high-activity chemical vapor deposition (CVD) aluminized Inconel 718 and Inconel 738LC samples were oxidized in air at 925, 1000, and 1050 °C for 200 h. Detailed cross-sectional examinations, elemental analyses, mass change measurements, and X-ray diffraction studies were performed. It was observed that the oxidation resistances of both alloys were significantly improved by the Al₂O₃ scale formed on the NiAl layer that was created on the surfaces of the samples during aluminizing. The beneficial effect of aluminizing was found to be more evident in the case of Inconel 738LC alloy samples which showed lower oxidation rates at all test temperatures. The results have been discussed on the basis of the differences in aluminum contents of the alloys and their effects on diffusion. Full article

Additive and coating technologies, such as high-velocity oxy-fuel (HVOF) thermal spraying and direct metal laser sintering (DMLS), often require extensive post-processing to meet dimensional and surface quality requirements, which remains challenging for nickel-based superalloys such as Inconel 718. This study presents the design and topology optimisation of a cutting tool with a linear cutting edge, capable of operating in turn-milling or turning modes, offering a viable alternative to conventional grinding. A non-optimised tool served as a baseline for comparison with a topology-optimised variant improving cutting-force distribution and stiffness-to-mass ratio. Finite element analyses and experimental turn-milling trials were performed on DMLS and HVOF Inconel 718 using carbide and CBN inserts. The optimised tool achieved significantly reduced roughness values: for DMLS, Ra decreased from 0.514 ± 0.069 µm to 0.351 ± 0.047 µm, and for HVOF from 0.606 ± 0.069 µm to 0.407 ± 0.069 µm. Rz was similarly improved, decreasing from 4.234 ± 0.343 µm to 3.340 ± 0.439 µm (DMLS) and from 5.349 ± 0.552 µm to 4.521 ± 0.650 µm (HVOF). The lowest measured Ra, 0.146 ± 0.030 µm, was obtained using CBN inserts at the highest tested cutting speed. All improvements were statistically significant (p < 0.005). No measurable tool wear was observed due to the small engagement and the use of a fresh cutting edge for each pass. The resulting surface quality was comparable to grinding and clearly superior to conventional turning. These findings demonstrate that combining topology optimisation with a linear-edge tool provides a practical and efficient finishing approach for additively manufactured and thermally sprayed Inconel 718 components. Full article

The distinct solidification behavior of additively manufactured (AM) Inconel 718 (IN718) produces a unique microstructure and precipitation response compared with its conventionally forged counterpart, leading to fundamentally different responses to heat treatment and intermediate-temperature deformation behaviors. In this work, the intermediate-temperature (450–750 °C) deformation mechanisms of laser powder bed fusion (LPBF)-fabricated and forged IN718 alloys were systematically compared under various heat-treatment conditions. Overall, under solution treatment state, the LPBF alloy exhibited fine columnar grains, a high dislocation density, and retained δ phases along the grain boundaries, whereas the forged alloy showed coarse equiaxed γ grains without the δ phase. Under solution + aging (STA) treatment, the δ phase in the LPBF alloy effectively pinned grain boundaries and enhanced flow stress, while in the forged alloy, strengthening was dominated by the uniform precipitation of γ″ and γ′ phases. Owing to Nb consumption by δ-phase formation, the STA-treated LPBF alloy contained fewer γ″/γ′ precipitates and exhibited slightly lower strength than the STA-treated forged alloy. This study demonstrates that the inherent δ phase retention and Nb segregation in LPBF-built IN718 critically influence its precipitation behavior and deformation resistance, distinguishing it from conventionally processed alloys and providing valuable insights for microstructure design in AM-built high-temperature superalloys. Full article

During the heat treatment of nickel-based superalloy (for instance Inconel 718 alloy), the non-isothermal heating and cooling processes significantly influenced precipitation behaviors as well as the final mechanical properties. This study compared the precipitation behaviors and the resulting hardening and softening behaviors of additively manufactured and conventionally forged Inconel 718 alloys under non-isothermal heat treatment processes. The results indicated that additively manufactured Inconel 718 alloy accelerated aging precipitation behavior due to the fine dendritic structure during both heating and cooling processes. As a result, the additively manufactured alloy reached peak hardness of ~480 HV at ~650 °C (~100 °C earlier than the forged alloy’s peak hardness of ~460 HV at ~750 °C) during heating and gained almost constant hardness during cooling. Further, the heating rate significantly affected the precipitation behaviors of γ″ and γ′ phases in both alloys. Slower heating rates provided sufficient time for phase transformation, leading to a more pronounced precipitation., e.g., the volume fraction of precipitates in the SLM alloy increased from 1.5% at 5 °C/min to 5.9% at 0.5 °C/min when heated to 850 °C. During cooling process, the twisted grain boundaries of additively manufactured alloy facilitated the precipitation of δ-phase, which in turn inhibited the formation of γ/γ′/γ″ phase. Both alloys exhibited minimum hardness of ~380–390 HV at 1000 °C due to complete dissolution of strengthening phases. This study provides a comparative understanding of non-isothermal phase evolution in AM and forged Inconel 718, which is critical for optimizing heat treatment in aerospace applications. Full article

The adoption of artificial intelligence (AI) in industrial manufacturing lags behind research progress, partly due to smaller, imbalanced datasets derived from real processes. In non-destructive aerospace testing, this challenge is amplified by the low defect rates of high-quality manufacturing. This study evaluates the use of synthetic data, generated via multiresolution stochastic texture synthesis, to mitigate class imbalance in material defect classification for the superalloy Inconel 718. Multiple datasets with increasing imbalance were sampled, and an image classification model was tested under three conditions: native data, data augmentation, and synthetic data inclusion. Additionally, round robin tests with experts assessed the realism and quality of synthetic samples. Results show that synthetic data significantly improved model performance on highly imbalanced datasets. Expert evaluations provided insights into identifiable artificial properties and class-specific accuracy. Finally, a quality assessment model was implemented to filter low-quality synthetic samples, further boosting classification performance to near the balanced reference level. These findings demonstrate that synthetic data generation, combined with quality control, is an effective strategy for addressing class imbalance in industrial AI applications. Full article

Inconel 718 is a Ni-based superalloy with excellent corrosion resistance, heat resistance, high-temperature strength and high creep resistance. It is also known to be a difficult-to-machine material. Conventional machining methods have not only low machining efficiency, but also high cost and low versatility using CBN and ceramic tools, so cost reduction and highly efficient machining by substituting relatively inexpensive cemented carbide tools are required. Some results on the tool life in milling for intermittent cutting for Inconel 718 superalloy have been reported, and the tool life has been considered a problem. Therefore, there is a need to clarify the basic characteristics of milling, such as tool wear and adhesion conditions, and to identify long tool life and highly efficient cutting conditions in order to achieve highly efficient milling of Inconel 718 superalloy. In this study, the milling of Inconel 718 superalloy was conducted using an end mill with a constant depth of cut, and milling efficiency was defined as the table feed rate of the milling machine in mm/min. The tool wear, welding condition, and surface roughness of the workpiece were evaluated according to the combination of cutting speed and feed rate per edge, with a milling efficiency of 800 mm/min. The experimental results showed that with the combination of a cutting speed of 10.33 m/min and feed rate of 0.4 mm/tooth, and the combination of 20.65 m/min and 0.4 mm/tooth, when there was a lower cutting speed and higher feed rate per edge, less weld detachment occurred, less progression of flank wear, and less chipping occurred, and the tool edge was more stable. It was also confirmed that, by keeping the cutting speed constant and increasing the feed rate per edge, both long tool life and highly efficient milling were possible under the above conditions. Full article

The turbine mortise is a critical structural feature of turbine disks, and its manufacturing quality directly determines the performance and service life of aircraft engines. With the increasing application of advanced nickel-based superalloys, severe tool wear in conventional mechanical broaching of turbine mortises has emerged as a key limitation, substantially elevating production costs. Electrochemical broaching (ECB), which removes material through anodic dissolution reactions, eliminates tool wear and thus offers low cost and efficiency advantages, making it a promising method for turbine mortise fabrication. In this study, COMSOL Multiphysics 6.2 was employed to simulate the multiphysics field comprising the electric field, flow field, temperature field, bubble ratio, and dynamic mesh and elucidate the evolution of the electric field during the ECB process. ECB experiments of specimens on Inconel 718 were conducted under different feed speeds. On this basis, optimal processing parameters were identified. The results of the mid-position ECB experiments revealed five distinct dissolution states: pre-processing, pre-transition, stable dissolution, post-transition, and post-processing stages. A material dissolution mechanism model for the ECB process was established. Finally, fir-tree turbine mortises were successfully manufactured on Inconel 718 using a self-developed specialized electrochemical machining system at a feed speed of 70 mm/min. The mortise profile demonstrated dimensional deviations of (+16 to −21) μm, with working surface variations maintained within ±5 μm. The machined surfaces exhibited uniform and dense morphology with a surface roughness of Ra 0.275 μm. Three sets of mortise specimens processed under identical parameters showed excellent consistency, presenting a maximum deviation in profile removal thickness of +4.1 μm. The tool cathode was repeatedly reused without any detectable wear. Full article

Nickel-based alloys, including Inconel 718 and alloy 625, are indispensable in industries such as aerospace, marine, and nuclear energy due to their exceptional mechanical strength, high-temperature performance, and corrosion resistance. However, these very properties pose severe machining challenges, such as accelerated tool wear, poor surface finish, and high cutting forces. Although several studies have investigated coatings, lubrication strategies, and process optimization, a comprehensive and up-to-date integration of these advancements is still lacking. To address this gap, a systematic review was conducted using Web of Science and Scopus databases. The inclusion criteria focused on peer-reviewed journal and conference articles published in the last eleven years (2014–2025), written in English, and directly addressing machining of nickel-based alloys, with particular emphasis on tool coatings, lubrication/cooling technologies, and machinability optimization. Exclusion criteria included duplicate records, non-English documents, papers lacking experimental or modeling results, and studies unrelated to tool life or coating performance. Following this screening process, 101 high-quality articles were selected for detailed analysis. The novelty of this work lies in synthesizing comparative insights across TiAlN, TiSiN, and CrAlSiN coatings, alongside advanced lubrication methods such as HPC, MQL, nano-MQL, and cryogenic cooling. Results highlight that CrAlSiN coatings retain hardness up to 36 ± 2 GPa after exposure to 700 °C and extend tool life by 4.2× compared to TiAlN, while optimized cooling strategies reduce flank wear by over 30% and improve tool longevity by up to 133%. The integration of coating performance, thermal stability, and lubrication effects into a unified framework provides actionable guidelines for machining optimization. The study concludes by proposing future research directions, including hybrid coatings, real-time process monitoring, and sustainable lubrication technologies, to bridge the remaining gaps in machinability and promote industrial adoption. This integrative approach establishes a robust foundation for advancing machining strategies of nickel-based superalloys, ensuring improved productivity, reduced costs, and enhanced component reliability. Full article

Inconel 718, which is a high-performance superalloy, is known for its strength under elevated temperatures and corrosive conditions. However, boosting the durability of this alloy in challenging industrial environments is required. Accordingly, this study investigates the effect of rare-earth Cerium (Ce) additions (0.1–0.4 weight percent (wt.%)) on the microstructure, thermal stability, and corrosion resistance of Inconel 718 superalloy synthesized via powder metallurgy. The alloys were comprehensively characterized following sintering and annealing treatment. The results demonstrate that an addition of 0.2 wt.% Ce is optimal, leading to a refined microstructure and significantly improved high-temperature thermal stability. The 0.2 wt.% Ce alloy demonstrated superior thermal stability, with a lower rate of mass gain observed at temperatures up to 1200 °C. This improvement is attributed to Ce promoting a more stable and protective surface oxide layer. Most notably, the annealed (1000 °C/2 h) 0.2 wt.% Ce alloy exhibited a dramatic enhancement in corrosion resistance, as evidenced by a corrosion current density (I_corr) of 3.690 × 10⁻⁶ A/cm², which is over an order of magnitude lower than the baseline Inconel 718. In summary, this work establishes that a minor 0.2 wt.% Ce modification is an effective strategy for substantially improving the durability of Inconel 718 for demanding applications. Full article

Inconel 718 is a nickel-based superalloy that has a wide range of applications in the industries that require corrosion resistance or high-temperature resistance. It is well known that parts display internal stresses, anisotropy, and alloying element segregation after the selective laser melting (SLM) process. A homogenization heat treatment, which reduces internal stresses and homogenizes the material structure, can resolve these shortcomings. The present study focuses on the impact of this heat treatment on the microstructure of the Inconel 718 material produced by SLM. The research results indicate that this heat treatment improves both the material microstructure and mechanical performance by lessening the microstructural inhomogeneities, dissolving the Laves phases, and promoting grain coarsening. The findings of this study can contribute to the optimization of post-fabrication strategies for Inconel 718 parts fabricated by SLM. Full article

In this study, high-temperature uniaxial tensile tests were performed on IN718 superalloy samples fabricated using Wire Arc Additive Manufacturing (WAAM) and compared to wrought IN718 superalloy samples. The mechanical properties and Portevin–Le Chatelier (PLC) behavior of WAAM IN718 were analyzed, with particular attention paid to its anisotropy and differences from its wrought counterpart. WAAM specimens were obtained from three distinct orientations within the printed blocks. The results indicated that WAAM IN718 exhibited a higher yield strength but reduced failure elongation compared to wrought IN718. Among the WAAM samples, the yield strength was highest in the transverse direction, followed by the in-depth direction, and lowest in the growth direction. Post-aging treatment significantly increased the yield strength of WAAM IN718. WAAM IN718 showed a larger critical strain for the onset of serrated flow and smaller stress drop amplitudes compared to wrought IN718 under the PLC effect. Furthermore, as the strain rate decreased, PLC serrations in WAAM specimens from the in-depth direction transitioned from type A to type C. Conversely, specimens from the growth direction maintained type B serrations at a strain rate of ${10}^{-4}{\mathrm{s}}^{-1}$. This study also examined potential factors influencing the differences in PLC behavior and conducted an analysis of the fracture surfaces across various specimens. Full article

While the machining of Inconel 718 has been widely studied, its cast counterpart Inconel 713LC remains underexplored, despite its relevance in high-temperature aerospace and energy components. This work presents a comprehensive investigation of dry milling behavior in Inconel 713LC, focusing on the interplay between tool wear, cutting forces, surface integrity, and chip formation across a broad range of cutting parameters. A stable process window was identified: 30–50 m/min cutting speed and 0.045–0.07 mm/tooth feed, where surface roughness remained below Ra 0.6 µm and tool life exceeded 10 min. Outside this window, rapid thermal and mechanical degradation occurred, leading to flank wear beyond the 550 µm limit and unstable chip morphology. The observed trends align with those in Inconel 718, allowing the cautious transfer of established strategies to cast alloys. By quantifying key process–performance relationships and validating predictive models for tool life and cutting forces, this study provides a foundation for optimizing the dry machining of cast superalloys. The results advance sustainable manufacturing practices by reducing reliance on cutting fluids while maintaining surface and dimensional integrity in demanding applications. Full article

Inconel 617 is a nickel-based superalloy that is a primary candidate for use in next-generation nuclear applications such as the Gen IV Molten Salt Reactor (MSR) and Very-High-Temperature Reactor (VHTR) due to its corrosion and oxidation resistance and high strength in elevated temperatures. However, Inconel 617 machinability is poor due to its hardness and tendency to work harden during manufacturing. While the machinability of its sister grade, Inconel 718, has been widely studied and understood due to its applications in aerospace, there is a lack of knowledge regarding the behaviour of Inconel 617 in machining. To address this gap, this paper investigates the influence of cutting parameters in the turning of Inconel 617 and compares the impact of Minimum Quantity Lubrication (MQL) turning against conventional coolant. This investigation was performed through three distinct studies: Study A compared the performance of commercial coatings, Study B investigated the influence of cutting parameters on the surface finish, and Study C compared the performance of MQL to flood coolant. This work demonstrated that AlTiN coatings performed the best and doubled the tool life of a standard tungsten carbide insert compared to its uncoated form. Additionally, the feed rate had the largest impact on the surface roughness, especially at high feeds, with the best surface quality found at the lowest feed rate of 0.075 mm/rev. The utilization of MQL had mixed results compared to a conventional flood coolant in the machining of Inconel 617. Surface finish was improved as high as 47% under MQL conditions compared to the flood coolant; however, work hardening at the surface was also shown to increase by 10–20%. Understanding this, it is possible that MQL can completely remove the need for a conventional coolant in the machining of Inconel 617 components for the manufacturing of next-generation reactors. Full article