Nickel-based Alloys Research Articles

The Effect of Preheating Temperature on the Corrosion Resistance and Porosity Defects Development Behaviour of Ni60A Coating

The laser cladding of nickel-based fusion alloys makes them prone to cracks and defects that affect the overall performance of the coating. In this study, Ni60A coatings were prepared at different preheating temperatures (25 °C, 200 °C, 400 °C and 600 °C). The effect of the preheating temperature of the substrate on the corrosion resistance of the coating as well as on the development of defects were investigated by electrochemical tests and immersion experiments in a 65 wt% H2SO4 solution at 60 °C. The results indicate that preheating the substrate to 200 °C can completely eliminate cracks in the coating and reduce porosity. Preheating leads to a decrease in the corrosion resistance of the coating. The size of the porosity defects is related to the law of longitudinal development of the defects. Porosity defects with diameters smaller than 100 μm have a more pronounced tendency to expand vertically than those with diameters larger than 100 μm.

Microstructure and mechanical properties evolution of 310S and GH3536 in hydrogen metallurgy service

The evolution of microstructure and mechanical properties of 310S austenitic stainless steel and GH3536 nickel-based alloy in hydrogen metallurgy service condition is investigated by conducting heat treatment under high temperature and hydrogen atmosphere. As the annealing time increases at 750 °C, carbide precipitate phases of the σ and μ brittle phases appear in the materials. At 900 °C, the dissolution of carbides induces the dispersion of brittle phases, while the hydrogen content reaching its peak. These brittle phases are still present at defects like grain boundaries at 1050 °C, with the surface of precipitates showing corrosion pits. Materials exhibit increasing strength and hardness initially with temperature and annealing time, followed by a decrease. Meanwhile, fracture elongation shows a positive correlation with temperature but a negative correlation with time. After annealing at 1050 °C for 500 h, GH3536 retains its high-temperature softening behavior and elongation at fracture, demonstrating excellent plastic stability. Furthermore, the mechanism of high temperature and hydrogen affecting metals is expounded, providing reference for the selection and optimization of materials which service in high temperature and hydrogen.

Perbandingan Keutuhan Permukaan Bahan Inkonel 718 dalam Pemesinan Kriogenik dan Kering

Inconel 718 is a nickel-based alloy that has been developed with superior mechanical strength, creep resistance, and corrosion, as well as erosion resistance at temperatures above 649 ˚C. It is suitable to be used for aircraft engine components such as turbine discs. However, it also has low heat conductivity and the presence of hard carbide particles in its alloy worsens the machining conditions with high cutting temperature, and high shear force and promotes work hardening. Thus, this study aims to evaluate the surface integrity of Inconel 718 in terms of surface roughness, plastic deformation, and micro-hardness alterations after the turning process. Cryogenic CO2 cooling was supplied along the cutting process to reduce cutting temperatures and the machining performances were compared with dry machining. The experimental works show that the dry machining resulted in lower surface roughness by up to 42.15% as compared to cryogenic. However, the depth of plastic deformation under dry machining was much more severe than in cryogenic machining driven by higher cutting temperatures and pressure from the worn tool. The depth of plastic deformation became more distinct as the cutting speed increased. While the microhardness alteration of the machined surface was higher under cryogenic machining due to extensive cooling capacity by the CO2 flow. Thus, this study reveals that cryogenic cooling during metal cutting can produce products that have better wear resistance as well as higher surface hardness.

Influence of process parameters on forming quality of largesize nickel-based alloy tubes

In order to improve the forming quality of largesize nickel-based alloy chemical tubes, the influence of different tube specifications and mandrel/tube clearances on the bending forming quality of largesize Hastelloy C-276 alloy tubes was studied. A finite element (FE) analysis model for NC rotary drawing bending (RDB) was established and verified. The results show that with the increasement of the clearance, the wall-thinning ratio [Formula: see text] of different tube specifications gradually decreases, and the wall-thickening ratio [Formula: see text] and ovality [Formula: see text] gradually increase. As the measuring angle increases, the [Formula: see text] of different specifications initially increases and then decreases. The [Formula: see text] exhibits a trend of initially increasing and then decreasing. It is reasonable to take about 1/8 of the wall thickness t for the mandrel/tube clearance. It is of great significance for guiding the bending forming of largesize nickel-based alloy chemical tubes and development of intelligent forming equipment.

Role of Ti element in the microstructure and corrosion behavior of nickel-based alloy 825

The influence of Ti content on the microstructure and corrosion behavior of nickel-based alloy 825 in acid oil and gas environments was studied. The pitting corrosion behavior and stress corrosion cracking (SCC) behavior of Alloy 825 were investigated using high-temperature and high-pressure immersion tests, electrochemical tests, and slow strain rate tensile tests. Scanning electron microscopy, electron backscatter diffraction, and 3D microscopy were applied to analyze the microstructure and corrosion performance of the samples. The results showed that the number of inclusions and residual strain increased with the increase of Ti content, and strain concentration was found around the inclusions. The rise in inclusions led to lower pitting potential and a narrower passivation interval. In addition, the enhanced SCC susceptibility of the alloy with higher Ti content may also be attributed to the increase in inclusions.

Quantitative assessment of microstructural damage for interior crack initiation and high cycle fatigue life modeling

Axially loaded cyclic tests of a nickel-based alloy were conducted at 550 °C, 630 °C and 650 °C and stress ratios of −1, −0.3 and 0.5 up to high cycle fatigue regime. Multiscale characterizations and quantitative analyses of microstructural damage were carried out to illustrate the physics and mechanics of interior microstructure induced fatigue strength degradation and cracking. Results showed that the fatigue strength increased with the decreases of twin spacing, the size and aspect ratio of carbide, and γ′ phase size. Twin collapse due to slip band-twin interaction was found for the first time and confirmed as a form of crack initiation process, followed by short crack growth forming facets with significant contribution from shear stress. A new mechanistic fatigue life model of interior microstructure induced cracking was established with sound agreement with experimental data. All these combined into a design-manufacturing integrated approach which are capable of ensuring the safe operation and maintenance of service structures in long-life regime.

Effect of purity on solidification structure and micro-segregation in a nickel-based single crystal superalloy

The purity of nickel-based single crystal alloys plays an important role in the final service performance of turbine blades as it impacts the solidification structure, elemental segregation, and inclusions of castings. The highest purity of superalloys studied before was of altogether around 10 ppm of contents of N and O produced by the triple purification process (VIM+ESR+VAR). However, the impact mechanism still remains controversial, and meanwhile whether a lower content of N and O still keeps the impacts on castings is not yet clear due to the lack of raw materials. A superhigh purity of second generation of nickel-based single crystal superalloy DD98M with the sum of N and O contents as low as 4 ppm (hitherto the highest purity of the superalloy as published), home-produced by electron beam smelting (EBS), was put on focus in this work. The effect of three levels of purity (N-doped, commercial, and EBS, corresponding to 21, 10, and 4 ppm for the sum of N and O contents, respectively) on the microstructure evolution (including primary dendrite arm spacing (PDAS), eutectic, micropores, and γ′ phase) and the solute segregation behavior at dendritic scale and nano scale (γ/γ′ interfaces) were systematically studied and the influencing mechanisms were elucidated. The results show that the PDAS decreased from 406 μm to 322 μm with the reduction of O and N from 21 ppm to 4 ppm, which was irrelevant to precipitation of the nitride or oxide inclusions. Instead, it was due to the decrease of diffusion coefficient D or the increase of equilibrium coefficient k, or the decrease of the critical nucleation supercooling and the incubation time of dendrites. The micro-segregation, the number and volume fraction of eutectic, and the number and voltage percentage of shrinkage pores and gas pores were all greatly decreased with the increase of purity. These changes were closely related to the reduction of PDAS and the reduction of fluidity of the remained liquid in the interdendrites during solidification. The morphology and the size of the γ′ phase were independent from the purity, while the segregation of alloying elements at the γ/γ′ interface changed remarkably with the variation of the purity.

Surface properties of non-passivated nickel-based alloys in H2O-bearing environments by theoretical calculations: Atomic modification effects from alloying additions

The surface properties of nickel-based alloys with different alloying compositions against aggressively corrosive species were systematically evaluated by using the segregated and non-segregated models designed through first-principles calculations. The presence of typical VIB alloying elements such as chromium (Cr), molybdenum (Mo), and tungsten (W) elements near the nickel surface was identified to significantly enhance the surface adsorption of water molecules (H2O) and their decomposed products (OH, O, and H). The doping patterns and surface electronic structures were found to determine the adsorption diversity of these substances. Consequently, adsorbates containing oxygen were likely to induce the segregation tendencies of these selected alloying elements from the deep area of nickel toward the top-most surface layer (TSL). The electrode potential shifts of the surface Ni atom in the designed alloying systems, compared to the bare Ni (111) surface, were further calculated to identify the beneficial electrochemical performance of alloy surfaces in the absence/presence of various adsorbates. In vacuum, the locations of these alloying elements in the near-surface layers would more increase the electrode potential shifts, thereby delaying the dissolution of Ni atoms from metal substrates. Nevertheless, the presence of adsorbates led to notably negative electrode potential shifts for the Ni (111) surface, among which the decomposed products (hydroxyl and oxygen) were of the most passive effects on corrosion behavior of nickel. The detrimental effects of these adsorbates on surface stability would be effectively alleviated with the aid of atomic VIB alloying elements of nickel-based alloys, especially W segregation to the TSL regardless of the pH in aqueous environments.

Characteristics of Si (C,N) Silicon Carbonitride Layers on the Surface of Ni-Cr Alloys Used in Dental Prosthetics.

Chromium- and cobalt-based alloys, as well as chrome-nickel steels, are most used in dental prosthetics. Unfortunately, these alloys, especially nickel-based alloys, can cause allergic reactions. A disadvantage of these alloys is also insufficient corrosion resistance. To improve the properties of these alloys, amorphous Si (C,N) coatings were deposited on the surfaces of metal specimens. This paper characterizes coatings of silicon carbide nitrides, deposited by the magnetron sputtering method on the surface of nickel-chromium alloys used in dental prosthetics. Depending on the deposition parameters, coatings with varying carbon to nitrogen ratios were obtained. The study analyzed their structure and chemical and phase composition. In addition, a study of surface wettability and surface roughness was performed. Based on the results obtained, it was found that amorphous coatings of Si (C,N) type with thicknesses of 2 to 4.5 µm were obtained. All obtained coatings increase the value of surface free energy. The study showed that Si (C,N)-type films can be used in dental prosthetics as protective coatings.

Evaluation of the Surface Topography of Microfinishing Abrasive Films in Relation to Their Machining Capability of Nimonic 80A Superalloy.

This study investigates the surface topography of microfinishing abrasive films and their machining capability on the Nimonic 80A superalloy, a high-performance nickel-based alloy commonly used in aerospace and gas turbine engine applications. Surface analysis was conducted on three abrasive films with nominal grain sizes of 30, 15, and 9 μm, exploring wear patterns, contact frequency, and distribution. To assess the distribution of grain apexes, Voronoi cells were employed. Results revealed distinct wear mechanisms, including torn abrasive grains and cracked bond surfaces, highlighting the importance of efficient chip removal mechanisms in microfinishing processes. Larger grain sizes exhibited fewer contacts with the workpiece but provided more storage space for machining products, while smaller grain sizes facilitated smoother surface finishes. The research demonstrated the effectiveness of microfinishing abrasive films in reducing surface irregularities. Additionally, surface analysis of worn abrasive tools provided insights into wear mechanisms and chip formation, with the segmentation of microchips contributing to efficient chip removal. These findings underscore the significance of selecting appropriate abrasive films and implementing effective chip removal mechanisms to optimize microfinishing processes and improve surface finishing quality in advanced material machining applications. It is worth emphasizing that no prior research has investigated the microfinishing of components crafted from Nimonic 80A utilizing abrasive films, rendering this study truly unique in its contribution to the field.

Development of a low-frequency vibration–assisted turning device for nickel-based alloys

Development of a low-frequency vibration–assisted turning device for nickel-based alloys

Nanoscale oxide and γ' phase synergistically strengthened nickel-based alloys with varying Al/Ti ratios produced by HIP

In this paper, three nickel-based superalloys with different Al/Ti atomic ratios (1, 1.8 and 16), designated as ODS-1, ODS-1.8 and ODS-16, respectively, were prepared by mechanical alloying (MA) followed by hot isostatic pressing (HIP). The evolution of microstructure and tensile properties of the alloys under varying Al/Ti ratio was analyzed and discussed. The result showed that the size, type and constitution of oxides change with variation of Al/Ti ratio. The average size of the oxides decreases with increasing Al/Ti ratio, which is 15.8 nm for ODS-1, 13.8 nm for ODS-1.8 and 11.8 nm for ODS-16, respectively. The oxides in ODS-1 contain 21.4% Y4Zr3O12, 42.9% Y2TiO5, 21.4% YAM and 14.3% YAP. The oxides in ODS-1.8 consist of 23.5% Y4Zr3O12, 35.3% Y2TiO5, 17.6% YAM and 23.5% YAP. In contrast, only two types of oxides are formed in ODS-16, including 50% Y4Zr3O12 and 50% YAP. As the Al/Ti ratio is increased from 1 to 16, the percentage of Y-Al-O phase increases from 35.7% to 50%, while the proportion of Y-Ti-O phase decreases from 42.9% to 0%. Increasing Al/Ti ratio inhibits the formation of Y-Ti-O phase while promoting the generation of Y-Al-O particles. The finer oxide distribution in ODS-16 is considered to be the main reason for its finer grain size distribution. The bimodal distribution of the γ' phase can be found in all three alloys, but the bimodal distribution feature of the γ' phase in ODS-1 and ODS-1.8 is more significant than that in ODS-16. The average grain size decreases with increasing Al/Ti ratio. The tensile strength at 700 °C is reduced, but the ductility is improved with the increase of Al/Ti ratio. The influence of Al/Ti ratio on the formation of nanoscale oxides and γ' phases are revealed.

A macro-micro approach for identifying crystal plasticity parameters for necking and failure in nickel-based alloy haynes 282

This work develops a two-scales macro-micro approach to address the challenge in calibrating crystal plasticity microstructural models when samples undergo necking prior to fracture. The crystal plasticity models are crucial for predicting the materials’ plastic deformation and failure at the microstructure level, identifying the materials’ intrinsic properties as well as investigating the microstructure-properties relationships. However, after necking occurs, the experimentally measured stress-strain curves fail to reflect the materials ‘true’ stress-strain behavior and cannot be directly fitted into crystal plasticity models. The proposed macro-micro approach employs a top-down strategy to address this challenge, which has been studied with experimental tests on precipitation-strengthened Ni-based superalloy Haynes® 282®. In this approach, a macro rate-dependent anisotropic plasticity model with Voce-type hardening and Rice-Tracey damage law is first utilized to model the deformation and failure of the tensile bar, and calibrated by matching the stress-strain curves, necking strain, and reduction of area. Especially, to match the testing results under different applied strain rates, the rate-sensitivity parameter m and saturation stress in the elasticity model are modified to incorporate dependence on the local strain rate. Then, the ‘true’ stress-strain behaviors are extracted from the necking zone of the macro-model, which are used to calibrate a micro-model with explicit microstructures and governed by an extended crystal plasticity law. The consistency between the micro-model and macro-model are enforced during calibration. The calibration outcomes from the crystal plasticity model elucidate the materials intrinsic properties for slip, hardening, and failure, which is vital for further investigations into the microstructure-properties relationship and for accurate prediction of the material behavior under various test and service conditions.

Direct observation and characterization of a novel long period stacking ordered phase in GH4169 alloy

As is widely recognized, the Long Period Stacking Ordered (LPSO) phase is an important strengthening phase in the rare earth magnesium alloys. The LPSO phase not only enhances the strength of the alloy, but also improves its plasticity, thereby effectively addressing the strength-ductility trade-off phenomenon. Therefore, the preparation of metallic materials containing LPSO phase provides a new idea for designing a new generation of high-strength and high-toughness alloys. In present study, A novel nano-sized LPSO phase is observed and characterized for the first time in GH4169 nickel-based alloy. The results show that the stacking sequence of the LPSO phase is ABCBCBA, which indicates that this LPSO phase has a 6H structure. Meanwhile, the orientation relationships between LPSO phase and the Ni matrix are (11–1)γ//(0006)LPSO and [011]γ//[2-1-10]LPSO.

Crystal plasticity modeling and analysis for the transition from intergranular to transgranular failure in nickel-based alloy Inconel 740H at elevated temperature

The precipitation-strengthened Nickel-based alloy Inconel® 740H® (IN740H) exhibits increased ductility at higher applied strain rates during quasi-static tensile tests at an elevated temperature of 760 °C. The examination of fracture surfaces in this context reveals a noteworthy transition of underlying fracture mechanisms from transgranular to intergranular fracture as the applied strain rate decreases from 1×10−3/s to 0.83×10−4/s. To thoroughly understand the mechanical response of IN740H under these conditions, this study develops a crystal plasticity finite element (CPFE) model. This model incorporates various deformation mechanisms including dislocation slips, climb, and grain boundary sliding, which are relevant to the test conditions. The model is calibrated using data from both tensile tests at different strain rates and creep tests across a broad stress range at 760 °C, enabling the accurate determination of model parameters for each mechanism. Simulation results well captured the experimental observations of different failure modes. At higher strain rates, the model shows a dominance of dislocation slip leading to heterogeneous plastic deformation and formation of transgranular shear bands causing the failure, while at lower strain rates, an increased activity of grain boundary sliding causes grain boundaries crack leading to intergranular failure.

Enhancement of spectral model transferability in LIBS systems through LIBS-LIPAS fusion technique

BackgroundLaser-induced breakdown spectroscopy (LIBS) is extensively utilized a range of scientific and industrial detection applications owing to its capability for rapid, in-situ detection. However, conventional LIBS models are often tailored to specific LIBS systems, hindering their transferability between LIBS subsystems. Transfer algorithms can adapt spectral models to subsystems, but require access to the datasets of each subsystem beforehand, followed by making individual adjustments for the dataset of each subsystem. It is clear that a method to enhance the inherent transferability of spectral original models is urgently needed. ResultsWe proposed an innovative fusion methodology, named laser-induced breakdown spectroscopy fusion laser-induced plasma acoustic spectroscopy (LIBS-LIPAS), to enhance the transferability of support vector machine (SVM) original models across LIBS systems with varying laser beams. The methodology was demonstrated using nickel-based high-temperature alloy samples. Here, the area-full width at half maximum (AFCEI) Composite Evaluation Index was proposed for extracting critical features from LIBS. Further enhancing the transferability of the model, the laser-induced plasma acoustic signal was transformed from the time domain to the frequency domain. Subsequently, the feature-level fusion method was employed to improve the classification accuracy of the transferred LIBS system to 97.8 %. A decision-level fusion approach (amalgamating LIBS, LIPAS, and feature-level fusion models) achieved an exemplary accuracy of 99 %. Finally, the adaptability of the method was demonstrated using titanium alloy samples. Significance and noveltyIn this work, based on plasma radiation models, we simultaneously captured LIBS and LIPAS, and proposed the fusion of these two distinct yet origin-consistent signals, significantly enhancing the transferability of the LIBS original model. The methodology proposed holds significant potential to advance LIBS technology and broaden its applicability in analytical chemistry research and industrial applications.

A laser powder bed fusion–based methodology for repairing damaged nickel-based turbine blades: Investigation of interfacial characteristics and hot isostatic pressing treatment

This study presents a methodology for repairing a damaged nickel-based turbine blade via laser powder bed fusion (LPBF) additive manufacturing. Specifically, the CM247LC nickel-based alloy was utilized to repair a damaged SRR99 nickel-based blade with LPBF, followed by hot isostatic pressing (HIP) post-treatment. The LPBF repair process achieved crack-free metallurgical bonding at the CM247LC/SRR99 interface with large epitaxially grown grains. Furthermore, HIP facilitated the formation of γ/γ’ phases with comparable dimensions at the interface as well as in the CM247LC and SRR99 regions through recrystallization. Additionally, the columnar grains in the LPBF-printed CM247LC region transformed into coarse equiaxed grains after HIP, accompanied by precipitation of nanoscale Hf-rich carbides. Meanwhile, microcracks in the LPBF-printed CM247LC region and shrinkage pores in the cast SRR99 region were effectively eliminated. The LPBF-printed CM247LC exhibited an 8.62% higher hardness compared to that of SRR99. The repaired samples showed an ultimate tensile strength of 791 MPa, with fracture occurring at the SRR99 side, indicating a reasonable metallurgical bonding strength at the CM247LC/SRR99 interface. The findings offer a novel alternative for the industrial application of repairing damaged nickel-based turbine blades.

An interlaboratory study for assessing repeatability and reproducibility of the data generated by rotating drum powder rheometers (Part 1: Granudrum)

The National Institute of Standards and Technology (NIST) organized an interlaboratory study to assess the repeatability and reproducibility of the data generated by two commercially available rotating drum powder rheometers namely, Granudrum and Revolution Powder Analyzer. Part 1 of this interlaboratory study focuses on the Granudrum rheometer. In total, thirteen laboratories comprised of industry, academia, and a national laboratory participated in this study. A nickel-based alloy, a titanium alloy, and a stainless-steel alloy in powder forms were tested, and an analysis of variance (ANOVA) model was used to rank the contributions of the study factors to the observed variability in the data. First, a maximum of five study factors were considered: material, sample, rotation speed, test, and participant (lab), which provides the ability to assess interactions, such as between lab and rotation speed and lab and material. The ANOVA results indicate that the ‘Flow Angle’ data showed 6% of its variation attributable to repeatability and 5% to reproducibility, whereas the ‘Cohesive Index’ data showed 21% of its variation attributable to repeatability and 17% to reproducibility. Next, because using the different rotation speeds and materials can add significant variability to the overall data, we also present separate ANOVA results for each combination of rotation speed and material. These results provide further insight into the repeatability and reproducibility of the Granudrum-generated data.

Rapid L-PBF printing of IN718 coupled with HIP-quench: A novel approach to manufacture and heat treatment of a nickel-based alloy

There has been a growing interest in additive manufacturing in recent years, with researchers actively working on improving component quality through adjustments to printing parameters, lead time, and productivity. Rapid L-PBF printing has emerged as an attractive approach to expedite component manufacturing. However, employing a rapid building strategy may lead to additional internal flaws, which can be addressed during a Hot Isostatic Pressing (HIP) cycle. In this study, Inconel 718 was L-PBF printed using two distinct strategies: one involving the creation of a dense 1 mm shell with loosely packed powders in the core and the other utilizing different sets of printing parameters for the shell and core, respectively. These strategies resulted in a 60% and 45% printing time reduction, respectively, compared with the time requirement for printing same-size cubic samples with optimized parameters. Additionally, full densification and porosity elimination were achieved through a HIP-quench approach, obviating the need for further heat treatment. The study presents the final microstructures and retained flaws, along with assessing the degree of recrystallization via EBSD analysis and evaluating mechanical properties using hardness measurements and compression tests.

Wear Resistance Evaluation of Self-Fluxing Nickel-Based Coating Deposited on AISI 4340 Steel by Atmospheric Plasma Spray

Materials with enhanced wear resistance are constantly in high demand. Nickel-based self-fluxing materials deposited by atmospheric plasma spraying (APS) have feasible wear resistance performance. This study aimed to evaluate the results of a nickel-based self-fluxing alloy coating deposited on AISI 4340 steel substrate using APS. Additionally, the temperature at which the remelting process achieved optimal results was investigated. The AISI 4340 steel substrate samples were coated with a self-fluxing NiCrBSiCFe powder by APS. The post-coating remelting process was performed in a controlled atmosphere tube furnace at 900, 1000, and 1100 °C. Microstructural analysis was carried out by Scanning Electron Microscopy (SEM) before and after remelting. The estimated porosity of the as-sprayed sample was 3.28%, while the remelted coating sample at 1100 °C had only 0.22% porosity. Furthermore, a microhardness measurement was conducted, and the best condition yielded an average value of 750 HV0.5. Tribological tests were performed to evaluate the coefficient of friction and wear rates, revealing that at 1100 °C, the as-sprayed coating had a wear rate of 9.16 × 10−5 [mm3/(N*m] and the remelted coating had 4.106 × 10−5 [mm3/(N*m]. The wear-loss volume was determined to be 14.1 mm3 for the as-sprayed coating sample and 3.6 mm3 for the remelted coating at 1100 °C.