Nickel-based Superalloy Research Articles

Influence of process parameters on residual stress in laser metal deposition of nickel-based superalloy

Influence of process parameters on residual stress in laser metal deposition of nickel-based superalloy

Finite Element Analysis of CM247LC Superalloy for Gas Turbine Blade Application

The objective of this article is to conduct a comparative analysis of the various materials used in the production of gas turbine blades. The materials under investigation include CM247LC, Nimonic 80A, and Inconel 738. The selected blade materials are required to demonstrate exceptional resistance to high temperatures and corrosion. It is determined that the most appropriate material for the construction of a gas turbine blade is a nickel-based superalloy. For the purposes of Finite Element Analysis (FEA), the aforementioned materials are defined as nickel-based superalloys. A comprehensive analysis of these materials was conducted using the ANSYS 2024 R2 student edition and a combination of structural and vibrational analyses was carried out. The deformation observed in CM247LC and Nimonic 80A exhibited nearly identical values of 0.965 mm and 0.884 mm, respectively. The results of the vibrational analysis indicated that all materials successfully circumvented the natural frequency as well as the operational natural frequency of 50 Hz, thereby ensuring the safe operation of the gas turbine blade. The findings demonstrated that the CM247LC satisfied both criteria for material selection, making it the most suitable material for gas turbine blade applications when compared to alternative materials. This is due to its comparatively lower deformation despite experiencing a greater magnitude of centrifugal force.

Phase Field Simulation and Experimental Study of Carbide Precipitation Process in Submerged Arc Welding on Descaling Roll

The mechanical properties of surfacing layers are significantly affected by the precipitation and evolution of carbides in nickel-based alloys. At present, the study of carbide precipitation in a Ni-Cr-B-Si surfacing layer is described by using the phase field method. In this paper, the true Gibbs free energy of the M23C6 carbide phase in Ni-Cr-C ternary alloy was established by the CALPHAD method and thermodynamic database. The growth and coarsening process of M23C6 carbide was simulated based on phase field method. The microstructure of M23C6 carbide of Ni-Cr-C alloy at 1373 °C isothermal aging time was observed by scanning electron microscope (SEM). The results show that the growth and coarsening of the precipitated M23C6 carbide phase are undergone through multiple processes during isothermal aging. First, a single precipitate core is formed, and then the single precipitate continues to coarsen and grow, forming a lamellar structure. Two precipitates contact to form a single rod-like structure, and multiple precipitates form slender rod-like structures. Finally, the contacting elongated rod-like structures grow, forming a typical layered eutectic carbide. The precipitation behavior, growth, and coarsening process of M23C6-type carbides in Ni-Cr-B-Si series alloys are explored through phase field simulation and experimental research in this paper. A theoretical basis is provided for the rational control and distribution of carbides in surfacing layers. A reference is also offered for optimizing the nickel-based superalloy materials used for surfacing the surface of descaling rolls.

Interfacial dislocation networks in nickel-based superalloys: The hidden link between moiré patterns and sample sizes

Interfacial dislocation networks in nickel-based superalloys: The hidden link between moiré patterns and sample sizes

Multiscale modeling of oxidation-fatigue damage mechanisms under compressive dwell-fatigue loading conditions for nickel-based single-crystal superalloy

Multiscale modeling of oxidation-fatigue damage mechanisms under compressive dwell-fatigue loading conditions for nickel-based single-crystal superalloy

Crystallographic anisotropy-dependent wear behavior of nickel-based single crystal superalloys across scales

Crystallographic anisotropy-dependent wear behavior of nickel-based single crystal superalloys across scales

Additive Manufacturing of γ' Precipitate-strengthened Nickel-based Superalloy UNS N07001 by Electron Beam Melting: Effects of Post-heat Treatment on Microstructure and Mechanical Properties

Additive Manufacturing of γ' Precipitate-strengthened Nickel-based Superalloy UNS N07001 by Electron Beam Melting: Effects of Post-heat Treatment on Microstructure and Mechanical Properties

Effect of complex stress states on creep rupture life of nickel-based superalloys: Mechanisms and modeling

Effect of complex stress states on creep rupture life of nickel-based superalloys: Mechanisms and modeling

Additively manufactured crack-free nickel-based superalloys with synergistic strength and plasticity via grain refinement and striped oxides inhibition

Solidification cracking seriously hinders the laser powder bed fusion (LPBF) prepared Haynes 230 (H230) superalloy from serving in the aerospace field. In this study, the cracking mechanism of H230 alloy was analyzed in detail and a new H230-La alloy adding La2O3 nanoparticles for cracking elimination was successfully prepared. At the high-angle grain boundary (GB), Si, Al and O elements were enriched to form M5-xSi3-zCx+z silicides and brittle Al-oxides. This led to severe strain concentration at the incompletely solidified GB resulting in solidification cracking. After the addition of La2O3 particles, La2O3 particles reacted with Al and O elements to form LaAlO3 particles, avoiding striped Al-rich oxides at GBs. The La atoms decomposed by La2O3 also promoted the nucleation of M23C6 and relieved GB strain caused by silicides. Moreover, grain refinement caused by heterogeneous nucleation also increased the resistance to crack initiation, thus a crack-free alloy was prepared. The prepared H230-La new alloy exhibited well synergy of strength and plasticity, and the deformation mechanism was transformed from dislocation slip plugging to grain rotational deformation. This study proposes a method to eliminate cracking by in situ inhibition of striped brittle oxide formation in superalloys and helps to broaden the wide range of applications of LPBF-prepared superalloys in the aerospace field.

Decoding physical sensor signals to reveal chip formation and surface deformation: An example in machining nickel-based superalloys

Decoding physical sensor signals to reveal chip formation and surface deformation: An example in machining nickel-based superalloys

Nano-scale microstructural evolution and mechanical property enhancement mechanism during crack inhibition in nickel-based superalloys fabricated by laser powder bed fusion

Nano-scale microstructural evolution and mechanical property enhancement mechanism during crack inhibition in nickel-based superalloys fabricated by laser powder bed fusion

Assessment of dwell-fatigue properties of nickel-based superalloy coated with a multi-layered thermal and environmental barrier coating

A three-layered experimental thermal and environmental barrier coating (TEBC) was deposited using air plasma spraying technology on cylindrical specimens of nickel-based superalloy MAR-M247. TEBC consists of mullite (Al6Si2O13) and hexacelsian (BaAl2Si2O8) upper layer, Y2O3 stabilised ZrO2 interlayer and CoNiCrAlY bond coat deposited on the grit-blasted surface of MAR-M247. The cyclic plastic response and damage mechanisms in uncoated and TEBC-coated MAR-M247 have been studied in isothermal dwell-fatigue tests conducted under strain control with constant strain amplitude at 900 °C. In each cycle, 5-minute dwells were introduced in both tensile and compression peaks of the hysteresis loop. Fatigue hardening/softening curves, stress relaxation curves, cyclic stress-strain curves and fatigue life curves are reported. Ceaseless mild softening has been found in both uncoated and TEBC-coated MAR-M247. TEBC-coated MAR-M247 showed an improved lifetime in the whole range of tested strain amplitudes. Data obtained from stress relaxation curves were used to assess the fraction of creep damage. The generalised damage accumulation rule was used to evaluate damage due to fatigue-creep-environment interaction. A study of the surface relief and internal microstructure using SEM and TEM helped to interpret the specifics of fatigue behaviour of uncoated and TEBC-coated material. The effectiveness of this newly developed TEBC, together with the dwell sensitivity of MAR-M247, were discussed from the perspective relevant to dwell-fatigue cyclic straining.

A novel end-to-end integrated process paradigm for fatigue life improvement in nickel-based superalloy hole structures

A novel end-to-end integrated process paradigm for fatigue life improvement in nickel-based superalloy hole structures

Micro-engraving on modified nickel-base superalloy using a short-pulsed laser source

ABSTRACT The modified nickel-base superalloy is micro-engraved with short pulsed laser with different parameter. The dimensional accuracy of the micro-profiles engraved through laser energy is evaluated through a scanning electron microscope. For the minimum speed of 50 mm per sec, the profile length and breadth have high dimensional stability compared to the average and high scan speed. The optical microscope is used to measure the depth of the micro-profile and the same has been metallurgically processed to read the microstructural changes. A maximum depth of 632 µm for the micro-profile is found with a maximum scan speed of 100 mm per sec at a low power of 2 watts and an average laser frequency of 7 kHz. Therefore, the input process parameters are invariant for the different responses on micro-engraving.

Effect of Interface Relief on the Occurrence of Cracks at the Contact Point of Laser-Direct-Energy-Deposited Copper Alloy and Nickel Base Superalloy

The relevance of the study is related to the need to join dissimilar copper and nickel alloys by laser direct energy and material deposition (LDED). The purpose of research is studying the distribution of elements, structure, and properties of contact zone of nickel-based super alloy and CuCr1 bronze obtained by direct energy and material deposition with preliminary formation of relief of contact surface. For the purposes of research, samples were made from UNS C18200 copper alloy CuCr1 without relief, with a relief of 0.5 mm depth, and with a relief of 1 mm depth. The Ni50Cr33W4.5Mo2.8TiAlNb (EP648) alloy powder was deposited onto the bronze samples with a micro-relief. The deposition was produced by direct injection of energy and material. The influence of interphase interaction of CuCr-chromium carbide system on the possibility of initiation of a crack in the area of carbide secretions is not significant and does not exceed 3.1% according to CIC criterion from the background level for CuCr1 (CIC = 1.54% for CuCr1-Al4C3 interface and CIC = 3.1% for CuCr1-Cr23C6 interface). An X-ray analysis revealed the presence of tensile residual macro-stresses, arising from differences in thermal expansion coefficients in the CuCr1-EP648 interface area, which may be the main cause of crack formation. Cracks are generated and run along the grain boundaries, on which traces of excretion are visible. The contact surface in the CuCr1-EP648 interface area has no visible defects, which indicates the good adhesion of materials when applying an initial layer of EP648 by LDED. The presence of a 0.5-mm micro-relief on CuCr1 has a positive effect on the strength of the connection, as it increases the surface area of the contact CuCr1-EP648 and therefore reduces the contact stress of the breakout.

Metallurgical Investigation and Failure Analysis in GTD-111 Stage 2 Buckets From an Industrial F-Class Gas Turbine

Abstract A utility experienced cracking in multiple stage 2 buckets (S2Bs) in a large F-class power generation gas turbine after only 7348 h and 31 starts following a standard repair and rejuvenation heat treatment cycle. The blades were cast from a directionally solidified (DS) superalloy and the cracking was found in the shroud section of the blade in the Z-notch region. A detailed failure investigation was conducted to determine the failure mechanism and most likely contributing factors to root cause in terms of design, operation, fabrication, and metallurgy. Three blades, two with visible cracks and one without cracks, were subjected to nondestructive and destructive evaluation. Methods consisted of visual inspection, three-dimensional scanning, physical measurements, chemical analysis, optical metallography, LED surface topological evaluation, and scanning electron microscopy. The failure mechanism was determined to be due to creep with damage propagating along the grain boundaries in a high stress concentration area. Evaluation of precipitate structure and size also confirmed this area exhibited the highest temperature during operations. High temperature creep testing was also conducted in material from the two different casting houses to confirm metallurgical risk did not have a significant impact on creep performance. An evaluation of the operational profile of an entire fleet of GE 7FA units showed that the failed 7F.03 S2Bs were in the highest operating temperature base loaded units. The findings from this work will help better define key factors that influence the high temperature performance of nickel-base superalloys used in the hot section of industrial power generating turbines.

Using a Combined FE-CA Approach to Investigate Abnormally Large Grains Formed by the Limited Recrystallization Mechanism in a Powder Metallurgy Nickel-Based Superalloy

Using a Combined FE-CA Approach to Investigate Abnormally Large Grains Formed by the Limited Recrystallization Mechanism in a Powder Metallurgy Nickel-Based Superalloy

Accelerating homogenization kinetics and enhancing hot-workability of as-cast nickel-based superalloy via prior hot-deformation

Accelerating homogenization kinetics and enhancing hot-workability of as-cast nickel-based superalloy via prior hot-deformation

Microstructural Evolution and Oxidation Resistance of Fe-30Ni-15Cr Alloy for Internal Combustion Engine Valves Under Long-Term High-Temperature Exposure and Heat Treatment

Iron–nickel-based superalloy is an ideal substitute for the expensive Inconel 625 and Inconel 751 alloys. To elucidate the evolution of the microstructure and properties of Ni30 alloy under different thermal treatment conditions, a systematic study was conducted on the microstructural transformation of the alloy’s strengthening γ′ phase following solution treatment and aging, as well prolonged exposure at 750 °C, and the oxidation behavior of the Ni30 alloy was examined. During prolonged thermal exposure, grain growth occurs mainly in the initial stage, and after 200 h, the prolonged exposure time leads to a significant coarsening of γ′ precipitates, whose area fraction increases by more than 10 times compared to their unaged state. After 100 h of aging, the alloy reaches a peak tensile strength of 1270 MPa and a yield strength of 820 MPa; after 2000 h, the alloy maintains a relatively high strength with a slight decrease in ductility. The oxidation kinetic curve of Ni30 alloy follows the quasi-parabolic oxidation law at 750 °C, and its oxidation rate is consistently lower than 0.1 g·m−2·h−1 throughout the whole oxidation process, which indicates that it has excellent oxidation resistance. The external oxide layer of Ni30 alloy shows a bilayered structure, and no obvious surface porosity or flaking of oxidation products were observed throughout the high-temperature oxidation test. This study not only contributes to the improvement of material properties, but also promotes innovation and development in the field of high-temperature engineering applications that will help to meet the increasingly stringent requirements of high-temperature working environments.

Review of the Microstructural Impact on Creep Mechanisms and Performance for Laser Powder Bed Fusion Inconel 718.

Inconel 718 (IN718) is a polycrystalline nickel-based superalloy and one of the most widely used materials in the aerospace industry owing to its excellent mechanical performances at high temperatures, including creep resistance. Interest in additively manufactured components in aerospace is greatly increasing due to their ability to reduce material consumption, to manufacture complex parts, and to produce out-of-equilibrium microstructures, which can be beneficial for mechanical behavior. IN718's properties are, however, very sensitive to microstructural features, which strongly depend on the manufacturing process and subsequent heat treatments. Additive manufacturing and, more specifically, Laser Powder Bed Fusion (LPBF) induces very high thermal gradients and anisotropic features due to its inherently directional nature, which largely defines the microstructure of the alloy. Hence, defining appropriate manufacturing parameters and heat treatments is critical to obtain appropriate mechanical behavior. This review aims to present the main microstructural features of IN718 produced by LPBF, the creep mechanisms taking place, the optimal microstructure for creep strength, and the most efficient heat treatments to yield such an optimized microstructure.