Inconel X-750 Research Articles

Effect of Machining Parameters on Turning of Inconel X750 Using PVD Coated Carbide Inserts

It is one of the few studies conducted on the machining of Ni-based Inconel X750 alloy, which has a wide range of applications in the main industries (gas turbines etc.) and aerospace (rotor blades etc.) industries. In this study, cutting tool wear, cutting forces and surface roughness were investigated in dry turning of Inconel X750 super alloy with coated carbide cutting tool. For the determining of the wear types and mechanisms electronic microscope and SEM were used. 4 different cutting speeds (40, 60, 80 and 100 m/min) and 3 different feed rate (0.1, 0.15 and 0.2 mm/rev) values were used in the experiments. The cutting depth was kept constant at 1 mm. According to the results; with increasing feed rate, the value of Fc, Ff and Fp cutting force components increased. The feed rate was significantly influential on Ra. The cutting geometry and the cutting edge sharpness induced by the formation of stable BUE caused Ra to increase. The most suitable parameters for turning the Inconel X750 alloy in terms of all evaluation criteria were the cutting speed of 60 m/min and 0.1 mm/rev.

Microstructural characterization of Inconel X750 alloy used in reactors components

Microstructural characterization of Inconel X750 alloy used in reactors components

Microstructural and Mechanical Evaluations of Transient Liquid Phase Bonded In X-750/BNi-3/SAF 2205

In this study, dissimilar joining between SAF 2205 duplex stainless steel and Inconel X-750 superalloy produced by TLP process was investigated. This process was done at temperature of 1100 °C for different bonding times of 1, 15, 30, 45 and 60 min. The effect of different bonding times on the microstructure and mechanical properties of the welded samples was studied. Microstructure of the samples was analyzed by optical microscopy and scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy. X-ray diffraction analysis was used to determine the formed phases in the bonding area. Microhardness and shear strength tests were done to evaluate the mechanical properties of the joints. It was found that the joint area contains the γ-Ni solid solution, eutectic compounds with intermetallic phases beside precipitated secondary phases. The γ-Ni solid solution, BN, BCN, CrB, Ni3Si and Ni3B were the main phases in the joining area. Maximum microhardness was found in athermally solidified zone, due to the presence of hard and brittle intermetallic and boride phases. The maximum shear strength (368 MPa) was obtained for the sample with the bonding time of 45 min, due to the completion of isothermal solidification and removal of eutectic compounds.

Pristup kombinaciji prirodom inspirisanog algoritma svitaca i ponderisane analize glavnih komponenata kod obrade legure Inconel X-750

Pristup kombinaciji prirodom inspirisanog algoritma svitaca i ponderisane analize glavnih komponenata kod obrade legure Inconel X-750

Performance of micro-drilling of hard Ni alloys using coated and uncoated WC/Co bits

An investigation was conducted into the process of microscale hole drilling, in which commercially available uncoated and TiAlN coated WC/Co drill bits were used for microhole drilling in the Ni-based superalloy Inconel X-750. The life of the drill bits, quality of holes drilled, and the mode of drill bit damage during the machining process were evaluated. In all experiments conducted, wear on the drill bit flute face was not observed and flank face wear was observed instead. Significant adhesive attachment of the workpiece material onto the drill bit was observed on both uncoated and TiAlN coated drill bits. The progression of drill bit damage and the impact of the TiAlN coating on drill bit life and hole quality are discussed.

Experimental investigations into fretting wear and damage mechanisms of Inconel X-750 alloy

Fretting wear characteristics of Inconel X-750 were investigated under the dry test condition. Ball-on-flat contact configuration was subjected to the oscillatory movement at different sliding amplitudes through the different time duration and normal loading. Fretting tests were carried out according to the American Society for Testing and Materials standards (ASTM D6425) by the high frequency linear-oscillation wear test rig SRV 4 at room temperature with ∼60 % relative humidity. Worn surface morphologies in the case of stick, partial slip and gross slip regimes were examined by 3D optical profiler, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The aim of this research is to study the tribological characteristics of the Ni-based Inconel X-750 superalloy, which is widely used in the air lubricated gas foil bearing applications where contacting surfaces are subjected to fretting motion. It is found that the displacement amplitude and normal load had strong effect on the fretting mode and damage mechanism. Wear mechanisms were associated with the plastically sheared asperities and crack nucleation and propagation during the stick and partial slip regimes, respectively. As the displacement increased, the wear modes were switched to adhesion, abrasion, debris oxidation, delamination and plastic deformation during the gross slip condition. Fretting time dependence was critical in the higher displacement amplitudes where the wear volume loss progressed significantly. However, test duration was less consistent in the stick and partial slip regimes where the wear properties remains unchanged over time.

Multi-Objective Optimization of Machining Process Parameters in Wire-Cut Electric Discharge Machining of Inconel X750 Alloy by Combinatorial Approach

Difficult-to-cut materials, generally high hardness, strength and toughness, are generally difficult to machine in conventional machining. Also tool wear is high in conventional machining processes. Wire Cut Electric Discharge (WEDM) machining is particularly used for machining complex profiles, demanding very high accuracy. The current work focuses on the optimization of roughness of a surface that is machined using WEDM; the process parameters considered for optimization are pulse-on-time (Pon), pulse-off time (Poff), wire feedrate (WFR) and spark gap voltage (SGV). One of the surface integrity aspect is considered as surface roughness (SR) and other related to machining output considered as material removal rate (MRR) for the output responses. The paper presents, a multi-criteria decision making technique, with Grey Relational Analysis (GRA) integrated with Particle Swarm Optimization (PSO) for optimizing the process parameters. Further, confirmation tests that were conducted also validated the improvement in SR and MRR.

Mechanical and Tribological Properties of CrN Coated Inconel X750

Three CrN coatings were deposited on the Inconel X750 through the metal vapor vacuum arc ion implantation and the magnetic filtered cathodic vacuum arc deposition system (MEVVA-FCVA) with the N2 flow rates of 10, 50, and 100 sccm, respectively. The surface morphologies and cross-section morphologies of the CrN coatings were obtained through scanning electron microscopy (SEM) and an optical profilometer. The microstructures of the coatings were characterized through X-ray diffraction (XRD). The hardness and the elastic modulus of the coatings were tested by a nano-hardness tester. The adhesion strength and friction coefficients were investigated through scratch tests and ball-on-disk tests and the wear tracks were tested by the optical profilometer. The experimental results indicate that the CrN coating deposited on the Inconel X750 substrate displays a uniform thickness and a smooth surface. The mechanical properties behaves well as the N2 flow rate varies. The CrN coating significantly reduces the friction coefficient fluctuation and improves the antiadhesion and anti-wear properties of the Inconel X750.

Coupling Multi-Scale Mechanical Testing Techniques with FIB and TEM Characterization to Reveal Mechanisms of Embrittlement of High Dose Inconel X-750

Coupling Multi-Scale Mechanical Testing Techniques with FIB and TEM Characterization to Reveal Mechanisms of Embrittlement of High Dose Inconel X-750

Influence of Distinct Manufacturing Processes on the Microstructure of Ni-Based Metal Matrix Composites Submitted to Long Thermal Exposure

Metal Matrix Composites (MMCs) are known for their remarkable properties, by combining materials from different classes. Ni-based MMCs are a promising group of heat-resistant materials, targeting aerospace applications. A discontinuously reinforced Inconel X-750/TiC 15 vol.% MMC was proposed for use in lighter, creep resistant turbine elements, with the aim to endure service temperatures up to 1073 K (800 °C). However, their microstructural stability at high temperatures for long periods of time remained to be further investigated. To address this need, specimens were produced by both conventional hot pressing and spark plasma sintering, using powders milled by low and high energy processes, followed by long isothermal aging. The treatments were conducted at 973 and 1073 K, for times between 50 and 1000 hours. The resulting samples were investigated with XRD and EDS techniques for phase analysis. In addition, measurements of hardness were made to monitor changes in mechanical behavior. It was found that, for each different manufacturing process, the amount, distribution and size of γ’ and other precipitates notably vary during the overaging process. Consequently, the amount of elements kept in solid solution also shifted with time. Furthermore, the study shows how distinct initial microstructures, resulting from diverse fabrication processes, differently impact the microstructural stability over long times of exposure to high temperatures.

Performances of different eco-friendly nanofluid lubricants in the milling of Inconel X-750 superalloy

This study investigated the effects of eco-friendly cutting conditions on machining performance in the milling of Inconel X-750 superalloy. To this purpose, a total of 14 different eco-friendly cutting conditions, including dry, base fluid and three different nanofluids at four different concentrations were tested. Surface roughness, cutting temperature, cutting force, tool wear and tool life were addressed as performance criteria. According to the test results, the use of base fluid increased the machining performance significantly compared to the dry cutting; however, the best results on all performance characteristics were obtained under nanofluid cutting conditions. The optimal concentration for the nanofluids was determined as 0.50 vol% and the hexagonal boron nitride (hBN) nanofluid was shown to be superior to the MoS 2 and graphite nanofluids. • Milling performance of Inconel X-750 under eco-friendly conditions was examined. • Dry, base fluid, hBN, graphite and MoS 2 nanofluid cutting conditions were tested. • Performance criteria included roughness, force, temperature, and tool wear/life. • Nanofluid cutting conditions gave the best results for all performance criteria. • The 0.5 vol% hBN nanofluid provided significant improvement in machining performance.

MULTI RESPONSE OPTIMIZATION OF EDM PROCESS PARAMETERS FOR INCONEL X-750 USING MOORA

Electrical discharge machining (EDM) is used extensively to machine hard to cut materials like nickel, titanium and super alloys with higher dimensional accuracy and surface finish. In this present study, a multi response optimization on the basis of ratio analysis (MOORA) is proposed for finding optimum process parameter of Electrical Discharge machining (EDM) during machining of Inconel X-750 material which is used mostly in thermal erosion process like nuclear plants, aerospace industry. In this study, response surface methodology (RSM) with Box-Behnken approach has been utilized for selecting the appropriate process parameters by using three level four factor (discharge current (Ip), voltage (V), pulse on time (Ton) and pulse off time (Toff)) using tungsten copper electrode (W-Cu). The machining responses considered are material removal rate (MRR), surface roughness (SR) and tool wear rate (TWR). The satisfactoriness of developed mathematical model has been tested with the use of analysis of variance (ANOVA). Further mathematical equations are generated using the statistical software MINITAB 17. The experimental data used for adequate regression model to optimize the process using MOORA. Further the surface characteristics of the machined surface are identified using scanning electron microscope (SEM) and elements with their peak values are revealed with EDX analysis.

Fretting Wear Behavior and Damage Mechanisms of Inconel X-750 Alloy in Dry Contacts

Tribological behavior of the Inconel X-750 alloy disk subjected to fretting against the GCr15 steel ball was investigated in an ambient laboratory air with relative humidity of 55–65%. A high-frequency oscillating Optimol SRV 4 tribometer was employed to execute dry fretting tests in the partial and gross slip regimes under constant 100 N normal load. Tests were carried out for 10, 30, and 90 minutes, and the friction forces vs. displacement amplitudes were monitored during the test duration. Posttest examinations were conducted utilizing advanced tools such as 3D optical surface profiler, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The main objective was to obtain wear scar evolutions, frictional properties, and degradation mechanisms under the different running conditions over time. It was found that fretting wear behaviors of friction pairs were strongly influenced by fretting regimes. Degradation evolutions were greatly influenced by fretting time during partial slip regimes, i.e., evolving from asperity deformation and slight damage to the fatigue crack and material transfer. However, the combination of adhesive, abrasive, delamination, and wear oxidation mechanisms was repeated during the entire gross slip fretting process.

Applying a new push-to-pull micro-tensile testing technique to evaluate the mechanical properties of high dose Inconel X-750

The results from a novel, micro-tensile testing technique, employing a micro-electro-mechanical system, operated in a push-to-pull configuration, to study the effects of radiation damage on Inconel X-750, are presented. Non-irradiated material, along with material irradiated to 67 dpa and 81 dpa at two irradiation temperatures, 120–280 °C and 300–330 °C, is investigated. This testing approach implements a safe, lift-out, extraction method that enables the evaluation of material tensile behavior in specific locations of radioactive components with complex geometries outside of costly hot cell protective environments. Regional cold working and grinding manufacturing processes that go undetected in bulk component testing can be evaluated in parallel with radiation damage effects. Non-irradiated specimens on the order of 1 µm × 1 µm × 2.5 µm taken from center regions of the material unaffected by processing produced yield strengths of 938 MPa and 1043 MPa, in good agreement with the bulk yield strength of Inconel X-750: 972–1070 MPa. Mechanical strengths of material irradiated to 67 dpa decreased by ~75 MPa for material irradiated at 300–330 °C and ~176 MPa for material irradiated at 120–280 °C, compared to the non-irradiated material. However, material irradiated to 81 dpa has practically identical mechanical strengths at the two irradiation temperatures, and these strengths are ~100 MPa greater than those of non-irradiated material. Average ductility of the material decreases more quickly when irradiated at 300–330 °C, from an initial value of ~15% to ~5% after 67 dpa, whereas the ductility of the material irradiated at 120–280 °C remains close to the initial value at 67 dpa and decreases to ~2% after 81 dpa.

Coupling multi-scale mechanical testing techniques reveals the existence of a trans-granular channel fracture deformation mechanism in high dose Inconel X-750

Recent testing has shown that Inconel® X-750 materials have lost strength and ductility following irradiation, which may raise concerns over the structural integrity of the material. Bulk component compression testing shows irradiation temperature has a clear influence on mechanical behaviour; material irradiated at higher temperatures exhibits less ductility compared to material irradiated at lower temperatures. This has been re-affirmed with the most recent large scale compression testing of material irradiated to doses between 70 dpa and 80 dpa. Measuring material yield strength from this data has proven to be challenging, due to the complex geometry of the material and the testing methodology. This work outlines the use of micro-indentation, and novel small-scale micro-mechanical testing to measure the mechanical properties of neutron irradiated Inconel X-750 material. The results and conclusions provide valuable insights into the mechanical property evolution, and embrittlement of the material. Microhardness and micro-mechanical testing have confirmed that material irradiated at lower temperatures has a lower yield strength, lower critical resolved shear stress (CRSS), and higher plasticity. The current results confirm the existence of an additional mechanism of crack initiation not previously considered for Inconel X-750 material. In addition to intergranular fracture, re-examination of component-scale test fracture surfaces also reveals that some portion of the component fails via transgranular, faceted pathways. Transmission electron microscopy (TEM) of deformed micro-tensile specimens has confirmed channel fracture. When subject to a slip band or dislocation channel, helium bubbles within the grain interior shear along the slip direction and coalesce prior to shearing the ligaments between the bubbles. The two deformation mechanisms are expected to interact in the bulk material. When discrete flow localization events (dislocation channels) intersect compromised grain boundaries decorated with helium bubbles, they will be expected to produce significant stresses which drives fracture propagation along the grain boundary.

Fretting Wear Behavior and Damage Mechanisms of Inconel X-750 Alloy in Dry Contact Condition.

Frictional and fretting wear behaviors of Inconel X-750 alloy against GCr15 steel ball were investigated in dry contact condition with ∼60% air humidity. Fretting tests were run at the high frequency tribosystem SRV 4 in room temperature and ball-on-flat contact configuration were adopted with the relative oscillatory motion of small displacement amplitude (40 μm). Sliding regimes, wear volumes, frictional properties, and material damage mechanisms were studied with regard to different normal loading and test durations. After the tests, the worn surface morphologies were analyzed by three-dimensional (3D) optical surface profiler, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) to distinguish fretting running conditions and material responses for different test cases. It was found that the material removals by abrasive and adhesive wear, debris formation and oxidization, and wear delamination were the main damage mechanisms under the lower normal load where the full slide or gross slip regime (GSR) was dominant between the contact surfaces. On the other hand, fretting regime was found to be a stick-slip or a partial slip at greater loads where damage mechanisms were correlated with deformed asperities, fatigue cracks, and thick layer removal due to highly concentrated cyclic stresses. Time dependence was crucial during GSR where the wear volume increased substantially; however, the wear volumes and scars sizes were consistent over time because of stick-slip effects under the higher normal load.

Effect of ion implantation on the grain boundary strength of heat treated Inconel X750

Bending tests performed with notched cantilever micro-beams were used to measure the initiate of plastic deformation from grain boundaries in Ni+ and He+ implanted Inconel X750. Whereas the local grain boundary yield stress followed a complex nonlinear dependence upon grain boundary misorientation angle up to about 60⁰, it showed a simpler continuous decreasing dependence upon grain boundary energy. This suggests that the grain boundary strength of the heat treated Inconel X750 alloy, in all conditions tested, is related to the grain boundary energy and decreases as the energy increases. Both Ni+ and He+ ion implantation increased the local grain boundary yield stress over the complete range of boundary misorientation investigated. We attribute this to the strengthening effect resulting from segregation of ion-induced crystal defects and helium bubbles/cavities to the grain boundaries. Our data suggest that the strengthening effect from 5000 appm He+, implanted at 25 °C, is significantly higher than what is produced by 1 dpa crystal damage associated with Ni+ implantation at 25 °C. Analysis of these findings in terms of a dispersed barrier hardening model illustrate that accumulated helium is more effective than irradiation-induced crystal defects, such as stacking faults tetrahedra and small dislocation loops, at preventing dislocation nucleation and/or movement from grain boundaries in the heat treated Inconel X750 alloy.

Application of Taguchi-Response surface analysis to optimize the cutting parameters on turning of Inconel X-750 using Nanofluids suspended Al2O3 in coconut oil

Inconel X-750, a nickel-chromium alloy, is found as a component in applications of the airframe and hot-air duct system. This paper presents the effect of different nanofluids (NF) concentration along with cutting speed and federate on Fz: cutting force, Ra: surface roughness and Vba: tool wear with the application of vegetable oil NF on turning of Alloy 750. The NF and vegetable oil taken for present investigation are nAl2O3 and coconut oil. Experimental is carried out using L9 orthogonal array and turned with PVD (AlTiN) coated carbide inserts. From the experimental research, 1.00% nAl2O3 nanofluids in coconut oil along with cutting speed of 87m/min and 0.14 mm/rev feed rate has proved the better machining performance to minimize the responses. Based on optical micrograph analysis, abrasion, adhesion and small BUE wear are three modes of wear mechanisms. Ribbon chips are produced with a different diameter, and curl diameter is increased with the increment of percentage concentration on turning of Inconel X-750.

Helium bubble nucleation at grain boundaries and its influence on intergranular fracture

ABSTRACTAn in-depth understanding of the formation of intergranular helium bubbles and its relation to embrittlement is an important issue in the nuclear industry. In this paper, a thermodynamic model is developed to analyze the nucleation of intergranular helium bubbles. Microstructural observation using scanning electron microscopy and electron backscatter diffraction gives a detailed description for the relation between the bubble formation and the grain-boundary (GB) misorientation in helium-implanted nickel and Inconel X750. The theoretical and the experimental results confirm that the nucleation of intergranular helium bubbles is GB structure-dependent, the helium-to-vacancy ratio plays an important role in the bubble precipitation, and the interfacial tension of bubbles cannot be approximated to be the interfacial energy. The bubble-induced intergranular embrittlement in a polycrystal is modelled. The GB misorientation distribution, the intergranular bubble nucleation and growth and the GB connectivity are the key factors affecting the GB fracture toughness. The hoop ductility of the cladding tubes containing helium is analyzed. The hoop stress-induced increase in the GB energy promotes the precipitation of bubbles at the radial GBs and lead to the loss of tube ductility. Based on this work, the complicated correlation among the intergranular helium bubbles, the GB structure, the helium concentration, the applied stress and the helium embrittlement is clarified.

Radiation damage to Ni-based alloys in Wolsong CANDU reactor environments

Abstract Radiation damage due to neutrons has been calculated in Ni-based alloys in Wolsong CANDU reactor environments. Two damage parameters are considered: displacement damage, and transmutation gas production. We used the SPECTER and SRIM computer codes in quantifying radiation damage. In addition, damage caused by Ni two-step reactions was considered. Estimations were made for the annulus spacers in a CANDU reactor that are located axially along a fuel channel and made of Inconel X-750. The calculation results indicate that the transmutation gas production from the Ni two-step reactions is predominant as the effective full power year increases. The displacement damage due to recoil atoms produced from Ni two-step reactions accounts for over 30% out of the total displacement damage.