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Showing papers on "Inconel published in 2019"


Journal ArticleDOI
TL;DR: 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 as discussed by the authors.
Abstract: 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.

306 citations


Journal ArticleDOI
15 Jun 2019-Wear
TL;DR: In this paper, a detailed characterisation of the wear tracks using electron microscopy and surface profilometry revealed a transition in wear mechanism from abrasive wear at room-temperature to oxidative and delamination wear above 600°C.

230 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of solution temperature, time and cooling rate as well as aging hardening on the microstructure and mechanical properties of Inconel 718 (IN718) samples have been produced by selective laser melting (SLM).
Abstract: Inconel 718 (IN718) samples have been produced by selective laser melting (SLM). The effects of solution temperature, time and cooling rate as well as aging hardening on the microstructure and mechanical properties of SLMed IN718 have been studied. It is found that the as-fabricated IN718 is characterized with fine cellular dendrites with Laves phase precipitating in the subgrain boundaries, which is profoundly different from cast and wrought materials and needs different heat treatment schedules. The relationship between the minimum solution time and solution temperature is established and it provides a basis for the selection of solution treatment parameters. In addition, decreasing the cooling rate of solution treatment will contribute to the precipitation of strengthening phases. The precipitation temperatures of γ′ and γ″ are about the same for SLMed and wrought IN718, but the former has a faster aging response. The tensile properties of SLMed IN718 can be tuned in a large range by properly varying the microstructure. The highest elongation of 39.1% can be obtained after solution treatment (water quenching) without aging treatment and the highest yield and tensile strength (1374/1545 MPa) can be obtained after the direct aging treatment. The match of strength and ductility is able to be tailored by controlling the amount of strengthening phases, which can be realized by adjusting the cooling rate of solution treatment and aging time.

133 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied the densification, microstructure and mechanical properties of nano-TiC reinforced Inconel 718 composites processed by selective laser melting (SLM) with variation of laser energy linear density (E).
Abstract: Laser additive manufacturing has demonstrated a promising capability in the simultaneous formation of high-performance nanocomposites with unique microstructure characteristics. The present work studied the densification, microstructure and mechanical properties of nano-TiC reinforced Inconel 718 composites processed by selective laser melting (SLM) with variation of laser energy linear density (E). It revealed that a fully dense TiC/Inconel 718 part was fabricated at a proper E of 300 J/m. On increasing E from 225 to 300 J/m, the nano-TiC reinforcement experienced severe agglomeration to uniform distribution along the grain boundaries and inside the grains of matrix. The morphologies of nano-particles transferred from irregular polygonal to near-spherical shape. The presence of nano-TiC could also accelerate the refinement of columnar dendrites spacing of γ matrix. A high nanohardness of 4.48 GPa, a low coefficient of friction of 0.36 and resultant low wear rate of 3.83 × 10−4 mm3/N⋅m were obtained at E of 300 J/m, showing a significantly improved mechanical performance compared to the SLM-processed unreinforced nickel-based alloys.

115 citations


Journal ArticleDOI
TL;DR: In this article, the authors evaluated the effect of the addition of solid lubricant in vegetal base oil applied by MQL (Minimum Quantity of Lubricant), when turning Inconel 718, with whisker-reinforced ceramic cutting tools (Al2O3 + SiCw).

108 citations


Journal ArticleDOI
TL;DR: Inconel 718 (IN718) superalloy has been fabricated by selective laser melting (SLM) technology, and the effects of the solution and double aging treatment on the microstructures and mechanical properties of the alloy have been studied as mentioned in this paper.

105 citations


Journal ArticleDOI
TL;DR: In this paper, the authors conducted a comprehensive study on the cracking behavior by using optical microscope (OM), scanning electron microscopy (SEM), energy dispersion spectrum (EDS), electron backscatter diffraction (EBSD), X-ray diffraction(XRD), and differential scanning calorimetry (DSC).

101 citations


Journal ArticleDOI
TL;DR: In this paper, a nickel-base superalloy Inconel 718 manufactured by selective laser melting (SLM) was investigated with focus on microstructure, orientation-dependent mechanical property and fatigue performance.
Abstract: In the present work a nickel-base superalloy Inconel 718 manufactured by selective laser melting (SLM) was investigated with focus on microstructure, orientation-dependent mechanical property and fatigue performance. Comparative material testing and characterization of the SLM and the forged Inconel 718 revealed significant differences in both microstructures and mechanical properties. The columnar grain structure of SLM alloy leads to the orientation-dependent mechanical properties, which matches the Hall-Petch relation. The inhomogeneous microstructures and slit shaped lack-of-fusion (LoF) defects from the SLM process result in worse fatigue performance and deteriorate the fatigue crack growth behavior.

101 citations


Journal ArticleDOI
TL;DR: In this paper, the feasibility of direct laser metal deposition of Inconel 738 is reported, where cracks evolved during deposition at the substrate/deposit interface and within the deposit along high angle grain boundary for scanning speed of 6 and 12mm/s due to intense residual stress and incipient melting.
Abstract: Inconel 738 is one of the widely used nickel-based superalloys in high-temperature applications, especially in land-based and aerospace gas turbine engines. This paper reports the feasibility of direct laser metal deposition (LMD) of Inconel 738. Cracks evolved during deposition at the substrate/deposit interface and within the deposit along high angle grain boundary for scanning speed of 6 and 12 mm/s due to the intense residual stress and incipient melting. Results showed liquation cracking due to low melting crack boundary γ′ and significant micro-segregation of Al and Ti along the crack boundaries. By maximizing the energy density and by reducing the scanning speed to 3 mm/s, crack-free single wall specimens were successfully manufactured. Microstructural evolution of primary, secondary, grain boundary γ′, MC carbides, and M2B borides in the as-deposited and heat-treat specimens are discussed. Mechanical properties and microstructural development were investigated using tensile testing and scanning electron microscopy. Energy dispersive spectroscopy confirmed significant micro-segregation on various elements along the interdendritic and grain boundaries. X-ray diffraction validated the presence of the observed carbides and boride in the as-deposited and heat-treated samples.

101 citations


Journal ArticleDOI
TL;DR: In this paper, a modified post-deposition homogenization heat treatment was found to be effective in dissolving Laves phase, whereas a standard treatment precipitated δ phase, leading to almost isotropic elevated temperature tensile properties, which meet minimum specifications for conventional cast but not for wrought material.

88 citations


Journal ArticleDOI
TL;DR: Inconel 718 samples were fabricated by selective laser melting (SLM) and the effects of line laser energy densities in the range 0.1-0.3 µm on the microstructure, mechanical properties, and deformation of these samples were investigated as mentioned in this paper.

Journal ArticleDOI
TL;DR: In this paper, the effect of initial microstructure on high cycle fatigue behavior of Inconel 718 superalloy was investigated, where the material was deposited at a 45° (diagonal) and a 90° (horizontal) angle with respect to the loading direction using direct metal laser melting (DMLM).

Journal ArticleDOI
TL;DR: In this article, the morphology and distribution of δ phase in the γ matrix are regulated by pre-designed heat treatment schemes, their effects on tensile properties and stress rupture properties at elevated temperature are discussed.
Abstract: The paper studies comparatively on the microstructures and mechanical performances at elevated temperature of SLM-fabricated Inconel 718 alloy in as-build, SHT 980, SHT 1080, SHT 980 + 1080 heat treated conditions. The morphology and distribution of δ phase in the γ matrix are regulated by pre-designed heat treatment schemes, their effects on tensile properties and stress rupture properties at elevated temperature are discussed. The results show that the specimens of SLM-fabricated Inconel 718 alloy in SHT 980 + 1080 heat treated conditions possess the optimum mechanical performances at elevated temperature, in which the morphology and distribution of δ phase in the γ matrix are the key factors in determining their high temperature performances. The excessive δ phases within grains and along grain boundaries can easily lead to dislocation piling up in the process of tensile test at elevated temperature, causing local stress concentration and microcrack generation in the matrix, further initiating premature failure of parts. However, lack of δ phase will reduce the high temperature strength of grain boundaries and then influence the high temperature mechanical properties. As a result, the suitable heat treatment is used to regulate the precipitation of δ phase and the moderate amount of δ phases precipitate along grain boundaries, further improving high temperature mechanical properties of IN718 alloy.

Journal ArticleDOI
TL;DR: In this article, the melting pool characteristics in terms of size and shape and porosity development in laser powder bed fusion-processed Inconel 718 were investigated to determine how laser power and scan speed influence the porosity in the microstructure.
Abstract: The melt pool characteristics in terms of size and shape and the porosity development in laser powder bed fusion–processed Inconel 718 were investigated to determine how laser power and scan speed influence the porosity in the microstructure. The melt pool characteristics developed with both single-track and multilayer bulk laser deposition were evaluated. It was found that the melt pool characteristic is critical for the porosity development. It is shown that the porosity fraction and pore shape change depending on the melt pool size and shape. This result is explained based on the local energy density of a laser during the process. High-density (> 99%) Inconel 718 samples were achieved over a wide range of laser energy densities (J/mm2). A careful assessment shows that the laser power and scan speed affect differently in developing the pores in the samples. The porosity decreased rapidly with the increase in laser power while it varied linearly with the scan speed. A proper combination, however, led to fully dense samples. The study reveals an optimum condition in terms of laser power and scan speed that can be adopted to fabricate high-density Inconel 718 parts using laser powder bed fusion–based additive manufacturing process.

Journal ArticleDOI
TL;DR: In this paper, the effect of oxide, wire source and heat treatment on the mechanical properties of wire + arc additively manufactured (WAAM) INCONEL 718 was systematically evaluated.

Journal ArticleDOI
TL;DR: In this paper, a novel heat treatment (NHT) including higher temperature homogenization at 1150°C for 2.5h and one-time lower temperature aging treatment at 700‌C for 12h is developed, which can overcome the strength-plasticity trade-off of Inconel 718 alloy.

Journal ArticleDOI
TL;DR: In this paper, the microstructures and corrosion resistances of Inconel 718 alloy prepared by selective laser melting (SLM), SLM following various heat treatments, and conventional rolling are studied.
Abstract: The microstructures and corrosion resistances of Inconel 718 alloy prepared by selective laser melting (SLM), SLM following various heat treatments, and conventional rolling are studied. Results show that only Nb element is enriched in interdendritic regions while Fe element is abundant in dendritic trunks for the as-built Inconel 718 alloy. After solution annealing treatment, incomplete recrystallization is observed and distortion energy is released. Increasing the solution annealing temperature from 980 °C to 1020 °C (ST1∼ST3), the morphologies of δ phases turn from needle-like into short platelet shape, which reduces the anodic current density and improves the corrosion resistance compared to other heat-treated samples in 3.5 wt% NaCl solution. Corrosion morphology observation shows that obvious cracking of surface passive film occurs for the SLM, solution annealing plus double aging (SA) and rolled samples, while corrosion pits and micro-cracks appear at the δ phase boundaries of solution-annealed (ST1∼ST3) samples. The surface passive film is smooth for the rolled sample. The corrosion resistance of samples obtained by different processes follows in the order of rolled > ST3 > ST2 > ST1 > SA > SLM. The galvanic coupling effect causes the formation of corrosion pits or cracks between γ matrix and second phases. The high interface energy and lattice misfit may provide driving forces for the preferential dissolution of γ matrix rather than second phases. The inferior corrosion resistance of the as-built Inconel 718 alloy can be significantly improved through solution annealing treatment at 1020 °C.

Journal ArticleDOI
TL;DR: In this article, the effect of scanning strategy, i.e., bidirectional scanning without (SS-X) and with a 90°-rotation (SS -XY) for every layer, on mechanical properties of Inconel 718 fabricated by selective laser melting (SLM) was investigated.
Abstract: The effect of scanning strategy, i.e. bidirectional scanning without (SS-X) and with a 90°-rotation (SS-XY) for every layer, on mechanical properties of Inconel 718 fabricated by selective laser melting (SLM) was investigated. The results show that tensile strength and fatigue strength of SS-X specimens are superior to that of the SS-XY ones. Such excellent mechanical properties of the SS-X specimens at room temperature were found to mainly result from the processing-induced fine grain structures compared with void size, crystalline orientation or dendrite structure.

Journal ArticleDOI
TL;DR: In this article, selective laser melting (SLM) was used to construct 316L stainless steel and Inconel 718 (IN718) multi-material parts and their interfacial characteristics and mechanical properties were investigated by optical microscopy and scanning electron microscopy, energy dispersive spectroscopy, electronic universal testing machine and microhardness tester.
Abstract: The multi-material selective laser melting (SLM) technology has been widely studied in recent years. In this paper, 316L stainless steel (316SS) and Inconel 718 (IN718) multi-material parts were manufactured by SLM and their interfacial characteristics and mechanical properties were investigated by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, electronic universal testing machine and microhardness tester. The interface metallograph and higher comprehensive mechanical performance with elasticity modulus (103 ± 3 MPa), elongation (28.1 ± 2%) and ultimate tensile strength (596 ± 10 MPa) proved good metallurgical bonding at the interfaces (∼100 μm) between 316SS and IN718. Nevertheless, some cracks and holes, which were found at or near the interfaces, suggested special SLM processing parameters (such as laser power, laser scanning speed, layer thickness, hatch spacing, remelting, fabrication sequence and layers of interface) should be applied at the interfaces.

Journal ArticleDOI
TL;DR: In this paper, the microhardness of Ni-based superalloy Inconel 718 clads was compared to the values from a computational thermo-fluid dynamics (CtFD) model.
Abstract: Process−property relationships in additive manufacturing (AM) play critical roles in process control and rapid certification. In laser-based directed energy deposition, powder mass flow into the melt pool influences the cooling behavior and properties of a built part. This study develops predictive computational models that provide the microhardness of AM components processed with miscible dissimilar alloys, and then investigates the influence of varying process parameters on properties in experiments and modeling. Experimentally-determined clad dilution and microhardness results of Ni-based superalloy Inconel 718 clads deposited onto 1045 carbon steel substrates are compared to the values from a computational thermo-fluid dynamics (CtFD) model. The numerical model considers the fluidic mechanisms of molten metal during powder deposition and the resulting transient melt pool geometry changes. The model also handles the change in thermo-physical properties caused by the composition mixture between the powder and substrate materials in the melt pool. Based on the computed temperature and velocity distributions in the melt pool, cooling rate, dilution of the melt pool and microhardenss are evaluated. The capability to predict thermal histories in such models is calibrated and validated with experimental thermal imaging and microstructures of additive manufactured clads. In addition, the roles of cooling rate and alloy composition on the microhardness are examined. The results show that variation in microhardness is dominated by composition mixture between the powder and substrate materials, rather than cooling behavior or dendrite arm spacing at liquid-solid interface in laser deposited Inconel 718 on AISI 1045 carbon steel.

Journal ArticleDOI
TL;DR: In this paper, the microstructure evolution, hardness, adhesive strength and tensile strength were investigated systematically on the cold-sprayed and heat-treated Inconel 718 alloy.

Journal ArticleDOI
TL;DR: In this article, the authors investigated dissimilar metal weldments between P91 steel and AISI 316 stainless steel fabricated by activated TIG welding (A-TIG) with and without the use of interlayers of Incoloy 800 and Inconel 600.

Journal ArticleDOI
TL;DR: In this paper, a multiscale investigation of the microstructures and mechanical properties of Inconel 718 fabricated by selective laser melting (SLM) was performed on the as-SLM and heat-treated (HT) samples at various build locations.

Journal ArticleDOI
TL;DR: In this article, the variation in tensile properties of Inconel 718 at varying angles with respect to build direction was investigated, and it was found that a preferred grain texture and twinning orientation that aligns with the build direction may contribute to the anisotropic enhancement in ductility.
Abstract: The production of components via selective laser melting (SLM) metal additive manufacturing results in microstructures unique to the process that are highly dependent on laser processing parameters and orientation of part geometry relative to the build direction. This study investigates the variation in tensile properties of SLM Inconel 718 at varying angles with respect to build direction. ASTM E8 tensile specimens were built in XY, Z, and B+45 from Z orientations to near-net shape, HIP and heat treated, and tensile tested at room temperature. Orientation dependence of mechanical properties was observed; Z samples had the lowest strength and highest elongation, while XY samples had the highest strength and lowest elongation. Optical, SEM, and EBSD analysis were conducted to probe for microstructure variation that could be the cause of the difference in mechanical properties. Analysis of pole figures and grain maps suggests a preferred grain texture and twinning orientation that aligns with the build direction, which may contribute to the anisotropic enhancement in ductility.

Journal ArticleDOI
TL;DR: In this article, the microstructure and hardness of Inconel 718 parts fabricated with selective laser melting were investigated and the results demonstrated the effects of homogenization and consequently the effect of aging on the micro structure and hardness.
Abstract: The microstructure and hardness of solid solution heat treated (ST) and precipitation hardened Inconel 718 parts fabricated with selective laser melting are investigated. The temperature range for the ST is between 970 and 1250 °C, while the two-step precipitation hardening was done at 760 and 650 °C, each for 10 h. The result demonstrates the effects of homogenization and consequently the effects of aging on the microstructure and hardness of the samples studied. Complete recrystallization occurred for the specimens ST at and higher than 1180 °C. The grain structures of ST specimens qualitatively appear identical with those specimens ST and aged, implying that aging does not induce noticeable changes in the grain structures. Precipitation hardening generates uniformly distributed good yield of ellipsoidal γ″ precipitates with average size of minor and major axis of 11–17 nm and 48–81 nm, respectively. In addition, smaller quantities of γ′ precipitates with an average size of 24 nm are observed for the aged specimens. Increasing the hold time of ST for a particular temperature leads to coarsening of γ″ precipitates, which have a negative impact on the hardness of the material. After aging, the hardness of the specimens is increased by 32–43% relative to that of the as-printed specimen. The increments in hardness for the specimens ST at and lower than 1100 °C (and aged) are the result of the combined effects of hardening precipitates and strain associated with the lattice defects, such as dislocation networks and subgrain boundaries that remain undissolved. The microstructures of the specimens ST at higher temperatures (e.g., 1250 °C) have attained minimal lattice defects due to completed recrystallization. Hence, the increment in hardness for these specimens after aging is mainly due to the hardening precipitates. Needle-shaped δ phase is also precipitated along/near grain boundaries during solid solution heat treatment at 970 °C. Formation of δ phase can consume a lot of Nb, which otherwise be used for the precipitation of hardening phases.

Journal ArticleDOI
TL;DR: In this paper, the effect of solution ageing and hot isostatic pressing treatments on the high-temperature (900, 1000)°C) oxidation of selective laser melted Inconel 718 alloy was studied.

Journal ArticleDOI
Mang Ni1, Shichao Liu1, Chao Chen1, Ruidi Li1, Xiaoyong Zhang1, Kechao Zhou1 
TL;DR: In this paper, the authors evaluated the microstructural evolution and mechanical properties of a selective laser melting (SLM) fabricated Inconel 718 (IN718) alloy under solution-aging treatment.
Abstract: This study evaluates the microstructural evolution and mechanical properties of a selective laser melting (SLM) fabricated Inconel 718 (IN718) alloy under solution-aging treatment. It was demonstrated that the fraction of low angle grain boundaries (LAGBs) and the aspect ratio of the grains decreased with the increase of the solution temperature, while the average grain size increased after solution treatment. Aging treatment promoted full precipitation of the strengthening phase. The fraction of the γ′ and γ′′ phases exceeded 45.5% compared to 24% of the as-fabricated alloy. Heat treatment also eliminated the anisotropic mechanical properties of the SLM-processed IN718, as the columnar grains transformed to equiaxed grains with the increase of the solution temperature. High strength (1500 MPa) with good elongation was obtained in the low temperature solution- and double aging-treated IN718 alloy, which was attributed to the combination of hierarchically heterogeneous microstructures (solidification enabled sub-micron cellular structure and large fraction of LAGBs) formed in the SLM process and the full precipitation of the γ′ and γ′′ phases in the aging treatment. Furthermore, this study demonstrated that mechanical properties similar to those of wrought alloy can be produced in SLM-processed precipitation-hardened alloys by direct aging treatment without the energy-intensive solution treatments.

Journal ArticleDOI
01 Aug 2019-Vacuum
TL;DR: In this article, a process window is developed for fabricating thin walled Inconel 718 (IN718) structures for Laser Additive Manufacturing using Directed Energy Deposition (LAM-DED).

Journal ArticleDOI
TL;DR: In this paper, the influence of incline angle on the microstructure, tensile and corrosion response of Inconel 718 (IN 718) samples fabricated via selective laser melting (SLM) with build directions ranging from 0° to 45°.
Abstract: In this work we studied the influence of incline angle on the microstructure, tensile and corrosion response of Inconel 718 (IN 718) samples fabricated via selective laser melting (SLM) with build directions ranging from 0° to 45°. Results reveal that the fraction of Laves phase increases with increasing incline angle and the -direction of crystals align along the vertical direction in the samples fabricated with different incline angles. Tensile tests of the printed samples were performed at room temperature and the results showed that the yield strength and ultimate tensile strength increase with increasing incline angle. The highest strength was obtained for the sample with an incline angle of 45°. However, the ductility remains relatively independent of the incline angle. The dependence of microstructure and tensile behavior on the incline angle was rationalized in terms of the temperature gradient during deposition and the ensuing anisotropy in the crystal orientation. The corrosion resistance of SLMed IN 718 in 3.5% NaCl solution increased slightly with increasing incline angle, and this behavior was attributed to the changes in crystallization texture and grain boundary density.

Journal ArticleDOI
TL;DR: The microstructure of as-built SLM Inconel 718 was investigated at different length scales using optical microscopy, scanning electron microscope, and transmission electron microscopy (TEM).
Abstract: Nickel-based Inconel 718 is a very good candidate for selective laser melting (SLM). During the SLM process, Inconel 718 develops a complex and heterogeneous microstructure. A deep understanding of the microstructural features of the as-built SLM material is essential for the design of a proper post-process heat treatment. In this study, the microstructure of as-built SLM Inconel 718 was investigated at different length scales using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Electron backscatter diffraction (EBSD) was also used to analyze the grain morphology and crystallographic texture. Grains elongated in the build direction and crossing several deposited layers were observed. The grains are not constrained by the laser tracks or by the melt pools, which indicates epitaxial growth controls the solidification. Each grain is composed of fine columnar dendrites that develop along one of their axes oriented in the direction of the local thermal gradient. Consequently, prominent crystallographic texture was observed and the dendrites tend to grow to the build direction or with occasional change of 90° at the edge of the melt pools. At the dendrite length scale, the microsegregation of the alloying elements, interdendritic precipitates, and dislocations was also detected.