Additive manufacturing (AM) can be used to produce near-net-shape Inconel 718 parts to minimise the material consumption and the machining required for fabricating parts. Compared to wrought Inconel ...718, there are certain characteristics inherent to AM process. These are elongated microstructural grains in the build direction, skin effect and the possibility of semi-finish machining prior to heat treatment. Micro-scratch and end milling tests were used to investigate the impact of these AM specific characteristics on machining performance and compare it with wrought alloy. The analysis demonstrated that directionality, skin effect and heat treatment affect cutting forces and tool wear within the material. Using lubrication can minimise these variations.
Wire + arc additive manufacture (WAAM) was applied to produce INCONEL 718 superalloy (IN718) components in a layer by layer manner; further, interpass cold rolling was introduced to generate ...in-process thermomechanical processing effect during the deposition process. Mechanical testing showed that with rolling applied, the strength of the solution plus aging treated WAAM IN718 was improved from 1056 MPa (unrolled) to 1351 MPa (rolled) which met the wrought standard (1276 MPa), and the material anisotropy was eliminated. The unrolled IN718 featured large columnar grains developing along the building direction, with the length and width as large as 11 mm and 0.8 mm respectively; rolling induced plastic deformation triggered a non-uniform recrystallization upon successive depositions, which produced a recrystallized core with small columnar grains and numerous finely equiaxed grains with the grain size of 12.7 μm. The overall strengthening produced by interpass rolling was attributed mostly (76%) to the rolling induced recrystallization which produced grain size reduction strengthening and created larger grain boundary area to allow more precipitation at the grain boundaries, and partially (24%) due to the improved aging response of the recrystallized grain structure.
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•Wire + arc additive manufacture (WAAM) was applied to deposit IN718.•Microstructure and aging response of WAAM IN718 were studied.•Explanation was given to the inferior strength of WAAM IN718 to the forgings.•Interpass rolling proved to be effective in enhancing the strength of WAAM IN718.
•Provides a new approach for determining the machinability aspects of Inconel 718.•Understanding of the mechanisms created by the milling process of Inconel 718 in dry and MQL environments was ...achieved.•Experimental and predicted data were compared with the machine learning method.•The machine learning method was found to be applicable in machinability experiments.•Considering the machinability properties in milling, it has been determined that the MQL process is effective.
Inconel 718 super alloy, which is widely used in the aerospace industry, has a high fracture resistance, and withstand to high temperatures. The alloy contains mainly Nickel, Chromium and Molybdenum elements in its chemical composition put it among difficult to cut materials. In this context, this study aims to improve the machinability of Inconel 718 superalloy by examining the effect of dry and MQL machining environments while measuring machinability indicators during milling. Tribological aspects considered since the wear, friction and lubrication behavior have a dramatic impact on responses such as tool wear, surface integrity and chip morphology. Microstructural and graphical results were assessed in terms of varying levels of cutting parameters and lubrication conditions. Comparison analysis between MQL and dry media indicated that MQL produces better surface topography and chip morphology, longer tool life in addition to improvement on surface roughness (up to 23.7 %) and cutting temperatures (up to 27.4 %). The root mean square error (RMSE) and coefficient of determination (R2) metrics were utilized to evaluate the findings in the course of machine learning. According to the mean and 95 % confidence interval of RMSE, error rates were found to be good and R2 varied between 67 % and 98 %. Predicted results are in a good agreement with the experimental data which indicated the applicability of machine learning algorithms on sustainable methods of machining.
The coarse columnar grain structure of additively manufactured metals diminishes material performance, hence the transition from columnar grains to equiaxed grains is extensively investigated. The ...microstructure of composite materials and the properties of Inconel 718 are positively influenced by both nano-sized tungsten carbide (nano-WC) and graphene nanoplatelets (GNPs), which act as reinforcing phases. The study employs directed energy deposition (DED) technology for the fabrication of Nano WC/GNPS-IN718 composite materials. Th emicrostructure, wear resistance, and corrosion resistance properties of both Inconel 718 and its composite materials were systemically investigated. The findings discover the microstructure of the composite material consists of γ/M7C3 phases with precipitation of carbides such as (Nb,Ti)C. Utilizing nano WC and graphene as lubricants, and carbides like (Nb,Ti)C as strengthening phases, the composite material exhibits a grain size refinement of approximately 3.36 % compared to IN718. The grain orientation in the XOY plane predominantly aligns along the direction. The Nano WC/GNPS-IN718 composite material exhibited a 1.264-fold increase in average microhardness compared to the IN718 alloy. Notably, the friction coefficient and wear rate were only 77 % and 18.75 %, respectively, of those observed in the IN718 alloy. Furthermore, the corrosion current density of the Nano WC/GNPS-IN718 composite material was 30.8 % of that observed in IN718, with a polarization resistance 4.08 times higher than that of IN718.
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•The addition of nano WC and graphene nanosheets promotes grain structure transformation, enhancing composite performance.•(Nb, Ti)C precipitates serve as strengthening phases, boosting material properties.•Nanomaterials refine grain structure, markedly improving properties compared to pure materials.•Composite materials demonstrate notable enhancements in wear and corrosion resistance over pure materials, thanks to the incorporation of nanomaterials, ensuring reliable performance in extreme conditions.
Serious wear can easily occur in traditional abrasive belts during grinding nickel-based superalloy components. To find an abrasive belt with excellent wear resistance and surface finishing, this ...study uses electroplated diamond abrasive belt (EDAB) to grind Inconel718, and investigates its wear evolution and corresponding grinding surface integrity. It was revealed that EDAB showed stable grinding performance, and the wear mechanism in initial, steady, and final wear stage was primarily micro cleavage fracture, macro cleavage fracture and adhesive wear, respectively. As EDAB wore, ground surface roughness gradually decreased and reached a minimum of Ra0.5 µm, and subsurface crystalline grains of Inconel718 were refined. Furthermore, the abrasive belt wear was significantly reduced and the surface integrity was improved using low-hardness contact wheels.
•Electroplated diamond abrasive belt is used to grind Inconel718.•Electroplated diamond abrasive belt shows excellent wear resistance.•Surface integrity of Inconel718 is improved as abrasive belt wear increases.•Low-hardness contact wheel significantly reduces adhesive belt wear.
Inconel 718 is one of the most commonly employed alloys for metal additive manufacturing (MAM) and has a wide range of applications in aircraft, gas turbines, turbocharger rotors, and a variety of ...other corrosive and structural applications involving temperatures of up to ∼700 °C. Numerous studies have investigated different aspects of the mechanical behaviour of additively manufactured (AM) Inconel 718. This study analyses the observations from more than 170 publications to provide an unbiased engineering overview for the mechanical response of AM Inconel 718 (and its variations and spread among different reports). First, a brief review of the microstructural features of AM Inconel 718 is presented. This is followed by a comprehensive summary of tensile strength, hardness, fatigue strength, and high-temperature creep behaviour of AM Inconel 718 for different types of MAM techniques and for different process and post-process conditions.
In this paper, a powder feeding laser additive manufacturing technology has been used for fabricating the Inconel 718 super-alloy. Laves phases of different sizes and morphologies have been obtained ...by using three types of heat treatments. The influence of Laves phases on the room temperature tensile properties of laser additive manufactured Inconel 718 has been investigated. The results show that small and granular Laves phase can be gained after heat treatment at 1050 °C for 15 min (S-15 sample). When the holding time extends to 45 min, the morphologies of Laves phases basically remain unchanged while its volume fraction further decreases (S-45 sample). Nevertheless, irregular and long-striped Laves phases still exist in the samples only after direct aging heat treatment (DA sample). The room temperature tensile results reveal that the S-15 samples have better tensile strength and ductility than that of S-45 samples. Besides, the DA samples with irregular and long-striped Laves phases show the lowest tensile strength and ductility. Hence, a certain amount of small and granular Laves phases are presumably beneficial for the room temperature tensile properties of Inconel 718. Moreover, a model has been established to describe the fracture of the Laves phase. On the basis of the fracture model, the critical stress needed for the fracture of long-striped Laves phases is lower than that needed for the fracture of granular Laves phases. Therefore, the former generally suffered internal fracture while the latter often fail by interfacial decohesion. Through influencing the volume fraction, the size and the distribution of γ" phase, the effect of the Laves phases on the room temperature tensile property is achieved. Furthermore, a yield strength model has been developed to reveal this influence in terms of numbers. The yield strength increments caused by grains, solution elements and γ′ phase are almost the same for the three kinds of samples. The differences of the yield strength are mainly caused by γ" phase. In addition, in terms of ductility, granular Laves phases are more favorable than long-striped Laves phases.
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When Inconel 718 alloy is fabricated by selective laser melting and treated by traditional homogenization plus double aging heat treatment (HA), its strength improves greatly, but ductility ...decreases. A novel heat treatment (NHT) including higher temperature homogenization at 1150 °C for 2 h and one-time lower temperature aging treatment at 700 °C for 12 h is developed, which can overcome the strength-plasticity trade-off of Inconel 718 alloy. The results show that recrystallized grains with annealing twins and ultrafine strengthening phases form in the specimen subjected to the NHT. These microstructures differ from those in as-built and conventional heat-treated samples. Especially the morphology of strengthening phase γ″-Ni3Nb precipitated in the NHT specimen has changed a lot, it seems to be spherical rather than disc-like shape occurred in the traditional heat-treated samples. Consequently, the NHT process increases plasticity by 41%, while maintaining ultimate strength at the same level achieved by the traditional heat treatment. The enhanced ductility is attributed to the annealing twins and recrystallized grains without local strains, while the strength is provided by the smaller precipitates formed in the NHT one-time aging treatment.
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•A novel heat treatment process was proposed for Inconel 718 superalloy.•The morphology of γ″ phase was modified by one-time aging heat treatment.•The recrystallized grains with annealing twins promoted good plasticity.
Cold-worked Inconel 718 alloy has successful applications in turbine engines due to its elevated strength. Otherwise, cold working will bring about the undesired ductility degradation accompanied ...with strength improving. Meanwhile, the susceptibility to δ precipitation is increased with modified morphology. To address these issues, this work aims expressing the effect of cold-rolling on hot ductility and the role of δ phase regarding differential morphologies in tensile behavior of Inconel 718 alloy at 650 °C. The results revealed that the ductility degradation can be attributed to the interactions of necking, microstructure instability and oxidation process tailored by cold-rolling. Nevertheless, appropriate cold-rolling is proved to enhance the resistance to crack propagation. The needlelike δ phase in strain-free structure tightly hindered the migration of horizontal GBs to enhance the strength but promote the intergranular brittle cracking, resulting in the degradation of ductility. In contrast, the δ phase with modified granular morphology in cold-rolled structures showed good deformation compatibility with horizontal GBs, playing a positive role in delaying necking occurrence and impeding crack propagation. In summary, the granular δ precipitation endowed cold-rolled Inconel 718 alloy with a superior combination of strength and ductility at 650 °C.
The current study investigates the effects of a wide range of process parameters on three part properties; density, surface roughness, and surface residual stresses simultaneously for selective laser ...melting of Inconel 718. In addition to the lack of investigations on surface roughness and residual stresses in selective laser melting of Inconel 718, process maps were developed for the selection of the best process parameters to achieve the desired values for the three parameters combined. Five laser powers, six scan speeds and three hatch spacings were chosen from the stable single tracks tests. Based on each property, a 99.5% density or a 2 μm surface roughness or the least surface tensile residual stress of 248 MPa were possible. However, no single process parameter combination was able to achieve good values for all three parameters. Prioritizing density and surface roughness, being crack initiators, over residual stresses for their effect on fatigue failure, it was found that 99.2% density and relatively low roughness of 3.5 μm are feasible at 320 W, 600 mm/s and 0.12 mm hatch spacing. Finally, opposite to the commonly observed columnar grain in Inconel 718, mixed grain structure was obtained at 600 mm/s and 1000 mm/s, indicating reduced anisotropy.
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•Effect of different laser powers and scan speeds on melt pool stability of Inconel 718.•Severe keyhole, balling and melt pool irregularities are identified.•Effect of laser powers, scan speeds and hatch spacing on part density, surface roughness and surface residual stress.•Process maps are developed for selection of process parameters combinations to obtain desired part properties.
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