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The fatigue behaviour of notched and unnotched specimens produced by additively manufactured Inconel 718 were analysed in the as‐built and heat‐treated conditions. The surfaces display high roughness and defects acting as fatigue initiation sites. In the as‐built condition, fine subgrains were found, while in in the heat‐treated state, the subgrains were removed and the dislocation density recovered. SN‐curves are predicted based on tensile properties, hardness and defects obtained by fractography, using the urn:x-wiley:ffe:media:ffe13300:ffe13300-math-0001‐method. © 2020 The Authors. Fatigue & Fracture of Engineering Materials & Structures published by John Wiley & Sons Ltd This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

In this study, Ni-based Inconel 718 coatings were additively manufactured on the surface of AISI H13 work tool steel by electro-spark deposition (ESD). Some of the electro-spark deposited samples were boronized at 1000 ? for 5 h to evaluate the effects of boronizing on microstructure, high-temperature wear, and corrosion resistance. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), 2D pro-filometry, wear and electrochemical corrosion testing was used to characterize the surfaces, microstructures, microhardness, some mechanical properties, high-temperature wear, and corrosion resistance of the applied coatings. Wear tests were performed at room temperature and 650 ?, and corrosion tests were performed in 3.5% NaCl at room temperature, considering the applications of AISI H13 and Inconel 718 alloys. The characterization studies showed evidence of microcracking and oxidation in the as-deposited Inconel 178 coatings. In the boronized Inconel 718 coatings, the oxides and microcracks were slightly reduced. The hardness of the boronized Inconel 718 coating was increased to about four times the hardness of the as-deposited Inconel 718 coating, and this significantly improved its wear resistance. The highest wear resistance was achieved with the boronized coating, while the best corrosion resistance was obtained with the as-deposited coating. The improvements in wear resistance provided by boronizing have the potential for expanding the applications of Inconel 718 coatings in machine components.

Since there is no report on the influence of machining depth on electron beam melting (EBM) parts, this paper investigated the role of superficial defects and machining depth in the performance of EBM made Inconel 718 (IN718) samples. Therefore, as-built EBM samples were analyzed against the shallow-machined (i.e., only removal of outer surfaces) and deep-machined (i.e., deep surface removal into the material) parts. It was shown that both as-built and shallow-machined samples had a drastically lower yield strength (970 ± 50 MPa), ultimate tensile stress (1200 ± 40 MPa), and ductility (28 ± 2%) compared to the deep-machined samples. This was since premature failure occurred due to various superficial defects. The superficial defects appeared in two levels, as (1) notches and pores on the surface and (2) irregular pores and cracks within the subsurface. Since the latter occurred down to 2 mm underneath the surface, shallow machining only exposed the subsurface defects to outer surfaces. Thus, the shallow-machined parts achieved only 68% and 8% of UTS and elongation of the deep-machined parts, respectively. This low performance occurred to be comparable to the as-built parts, which failed prematurely due to the high fraction surface voids and notches as well as the subsurface defects.

Additively manufactured components are likely to contain defects deriving from the manufacturing process. They are also likely to be designed with high geometric complexity (including notches), due to very few design-limitations. In order to understand the influence of these two types of geometric features, we here investigate as-built Inconel 718 specimens produced by selective laser melting under quasi-static and cyclic loading. Notched and unnotched specimens are considered, and the main emphasis is set on the influence of the defects and on how they influence the failure locations at different load levels.

In this study, the effects of cutting tool type (Ct), cutting speed (Vc), feed rate (f) and drill bit angle (A) on the average surface roughness (Ra) were investigated in the drilling of Waspaloy superalloy with coated and uncoated solid carbide drills. Experimental studies were performed in the orthogonal array of L18 (21 × 33) by using Taguchi method. A second order predictive equation was developed with Linear Regression Analysis and coefficient of correlation for Ra calculated as R2 = 96.9%. The most effective parameters on Ra were determined as A, f, Vc and Ct with 49.44%, 15.0%, 14.45% and 13.47% contribution ratios, respectively. Ra surface roughness values increased with the increasing tool wear. In this study, the chip formation and tool wear were also evaluated. Three types chip formation such as spiral chip, string chip and short chip were observed in the drilling of Waspaloy with solid carbide drills.

International audience; An experimental program was performed to determine the rheology and influence of niobium additions to high-purity nickel on dynamic-recrystallization behavior during hot working. Various high-purity alloys were prepared (pure Ni and Ni-0.01, 0.1, 1, 2, 5 and 10 wt% Nb) and deformed to high strains by hot torsion to characterize the mechanical behavior within the temperature range from 800 to 1000 degrees C at (von Mises equivalent) strain rates of 0.03, 0.1 and 03 s(-1). A simple analytical method was proposed for predicting the strain-hardening and dynamic-recovery parameters in the classical Yoshie-Laasraoui-Jonas equation. By the means, the effect of niobium solutes on plastic flow was determined, thus enabling a reasonable fit for the flow curves for the entire range of solid solution Ni-Nb alloys. (C) 2013 Elsevier B.V. All rights reserved.

It has been observed that considerable attention has been given to the use of cBN and/or ceramic tools for achieving better performance in the machining of superalloy Inconel 718. However, their cost limits the use in the engineering applications. In this article, the performance of multicoated TiN/TiAlN (PVD) coated and TiN/Al 2O 3/TiCN (CVD) coated tungsten carbide tools were investigated while high speed turning (HST) of superalloy Inconel 718. The effect of coating materials on cutting force, cutting temperature, vibration, and acoustic emission were recorded, analyzed, and reported. From the experimental results it has been found that TiN/Al 2O 3/TiCN (CVD) coated tool outperformed the TiN/TiAlN (PVD) coated tool in terms of machinability parameters such as cutting force and cutting temperature. From the fast Fourier transform (FFT) analysis of the vibration signals it was observed that the vibrations were less in case of the CVD coated tool than in case of the PVD coated tool. � 2012 Copyright Taylor and Francis Group, LLC.

Inconel 718 (2 mm thick) was welded using argon and helium gas shielded tungsten arc welding process with a filler metal. Both constant current and compound current pulse modes were applied and the cooling rates calculated. The dependence of Laves phase formation, dendrite arm spacing and niobium segregation ratios in fusion zone on the nature of shielding gases and current was studied. The maximum instantaneous weld cooling rate was achieved for the combination of Helium shielding gas and compound current pulse mode. This ultimately resulted in reduction of laves phase, segregation of niobium and dendrite arm spacing in the fusion zone. � 2013 Elsevier B.V. All rights reserved.

Inconel 718 is widely used in sophisticated engineering applications due to its unique properties such as high oxidation resistance and corrosion resistance even at high temperatures and retains a mechanical strength under these conditions as well. But machining such an exotic material is costly due to the rapid tool wear. An attempt has been made to improve the performance of cemented tungsten carbide (WC-Co, K20) tool through various posttreatments namely cryogenic treatment and controlled heating and oil quenching. The treated tools were evaluated for their properties through microhardness and X-ray diffraction technique (XRD). The treated tools were subjected to machining (turning) of difficult-to-cut material, i.e., superalloy Inconel 718 to check their performance enhancement. Results showed that post-treated tools performed better while machining (turning) of superalloy Inconel 718 indicating that selected posttreatments can be potential posttreatment methods for improving machining ability of cemented tungsten carbide tools. � 2014, Springer-Verlag London.

In nickel-based superalloys, substitutional solute species have a strong impact on in service mechanical properties as well as on oxidation and corrosion resistances. In alloy 718, recent studies carried out by tensile tests highlighted the fact that refractory solute species are able to interact strongly with mobile dislocations during plastic deformation, generating dynamic strain ageing, and, in wide ranges of tests temperatures and strain rates, Portevin-Le Chatelier effect. The precise nature of the substitutional element responsible for such a dynamic interaction is still subject to debate. We addressed this question by means of mechanical spectroscopy studies of alloy 718 and various related alloys corresponding to monitored changes in the chemical composition. Only a single internal friction relaxation peak has been observed for all the studied alloys. By analyzing the damping behavior of these alloys at different imposed solicitation frequencies by sweeping a large temperatures range, the activation energies of the relaxation process and the type of mechanism involved have been determined. The process is a “Zener relaxation” in the alloys, i.e. a substitutional atoms dipole reorientation under applied stress. The results tend to prove that Niobium is not involved in the relaxation process whereas Molybdenum content seems to play an important role in the relaxation intensity.

cited By 2; International audience; Induced changes in the thermoelectric power (TEP) of the Inconel 718 by elastic and plastic strain have been previously reported by López Cuéllar et al. [1]. Now, in this work, the TEP of a nickel-based superalloy Waspaloy with different heat treatments has been followed during stressing tests. In all cases plastic deformation has been attained. TEP measurement variations of ∼160 nV/°C have been attained for a certain heat treatment that produces the desirable γ′ phase, and low changes of TEP are observed for the treatment that does not produce γ′. Like for the Inconel 718, results indicate that TEP of the Wasploy is clearly affected by the elastic and plastic strain induced during tests. The previously proposed model to describe the change in TEP induced by the strain in specimens of Inconel 718 [1], is validated with the Waspaloy superalloy in this work. Thus, these results confirm that the TEP technique is a powerful tool to detect non-desirable states and levels of strain in alloys containing γ′ phase like the Waspaloy and Inconel superalloys. © 2011 Elsevier B.V. All rights reserved.

Superalloy, Inconel 718 is termed as 'difficult to cut' material due to its poor machinability. In order to effectively take advantage of inherent properties such as high temperature resistance, corrosion resistance, creep resistance, and high strength to weight ratio and longer operational life of Inconel 718, it is necessary to improve its machinability. Hence, researchers and industry are working to explore the machinability characteristics of this material particularly with respect to high speed machining (HSM). In these investigations machinability characteristics of Inconel 718 under dry and minimum quantity lubrication (MQL) conditions were evaluated with respect to cutting forces, surface roughness and tool wear using K20 tungsten carbide cutting tool. Moreover, X-ray diffraction analysis of the collected chips was carried out to study the direct effect of dry and MQL cutting conditions to confirm the experimental results obtained. It was observed that machining of Inconel 718 under MQL condition has out performed than the dry condition. The same was confirmed with SEM tool wear analysis and XRD analysis of the chips. Copyright � 2013 Inderscience Enterprises Ltd.

In this paper effect of electron beam welding heat input on the microstructure and mechanical properties of Inconel 718 was studied. Sheet of 2 mm thickness was used with an average grain size of 30 μm. Five different heat inputs ranging from 36 J/mm to 180 J/mm were used to make full penetration welds. Welding current was varied from 18 mA to 90 mA and other welding parameters were kept constant. Change in heat input altered the geometry of the weld (width to depth ratio) and the microstructure of fusion zone (FZ) and heat affected zone (HAZ) also changed. As the heat input increased the interdentric spacing in FZ was increased from 3.5 μm to 6 μm. Grain boundary liquation was found in all the welds. Intensity of liquation increased with decrease in heat input and the microfissuring was observed only in the lowest heat input weld. Change in heat input did not significantly affect the tensile properties of the weld.