Ni-based Superalloy Research Articles

Microstructure optimization for improving creep resistance of additively manufactured Ni-based superalloy IN939 through heat treatment

Microstructure optimization for improving creep resistance of additively manufactured Ni-based superalloy IN939 through heat treatment

The hysteresis loop on the near-threshold fatigue crack growth curves generated by stepped load reduction and constant-amplitude loading methods in a Ni-based superalloy

The hysteresis loop on the near-threshold fatigue crack growth curves generated by stepped load reduction and constant-amplitude loading methods in a Ni-based superalloy

Synergistic effects of Pt and Y addition in (Ni, Pt)CrAlY bond coat on oxide spallation resistance and growth of interdiffusion zone between bond coat and Ni-based single crystal superalloy

This study shows the beneficial effect of Pt addition to the (β+γ)-NiCrAlY coating. Adding Y in NiCrAl increases oxide growth kinetics but improves spallation resistance. Pt with Y does not change the oxidation rate compared to only adding Y but significantly reduces spallation when cooled to room temperature. Continuous layers of Al2O3 and Cr2O3, along with other oxides such as YAlO3, NiCr2O4, and NiAl2O4, are observed. Moreover, Pt addition reduces the thickness of the interdiffusion zone where Al goes through an uphill diffusion profile, minimizing Al loss and significantly decreasing the growth of deleterious TCP phases.

Anisotropy cyclic plasticity constitutive modelling for Ni-based single-crystal superalloys based on Kelvin decomposition

Nickel-based single-crystal (SC) superalloys exhibited excellent exceptional mechanical properties at high temperatures due to the elimination of internal grain boundaries, contributed a strong orientation-dependent material response. The anisotropy of SC superalloys was modeled viscoplastically from a macroscopic viewpoint based on the Kelvin decomposition theory [1] which was a decomposition of the stress space according to the elastic matrix eigen-directions to control the viscoplastic flow by Kelvin stress decoupled from each other. Compared to the classical phenomenological macro model, the proposed model effectively captures the slip deformation mechanism of SC superalloys with the inherent ability to simulate anisotropic because of the two criterions framework controlled by Kelvin stress. Compared with others, the proposed model was able to simulate time-dependent inelastic deformation and cyclic deformation behavior under complex loading. The kinematic hardening and isotropic hardening models incorporated microscopic quantities, such as dislocation density and channel phase width, connecting the macroscopic mechanical response with the microscopic state to achieve multiscale constitutive modelling. The parameter identification and finite element implementation were conducted on a SC superalloy [2]. Simulation results demonstrated the accuracy of the proposed model in predicting deformation behavior under various orientations, rate-dependent effects, isothermal and non-isothermal cyclic deformation. Comparison with the classical anisotropic matrix macroscopic phenomenological approaches highlights the superior capability of the proposed model to simulate the orientation-dependent mechanical properties of single-crystal alloys.

The evolution mechanism of ethylene-based and glass-ceramic as composited anti-seepage masking layer for Ni-based superalloy during aluminizing

The evolution mechanism of ethylene-based and glass-ceramic as composited anti-seepage masking layer for Ni-based superalloy during aluminizing

The Effect of Solution Annealing on Additively Manufactured and Hot Isostatically Pressed René 80 Ni-Based Superalloy

The Effect of Solution Annealing on Additively Manufactured and Hot Isostatically Pressed René 80 Ni-Based Superalloy

Optimizing the surface quality of electrochemical machined Ni-based single crystal superalloy via manipulation of phase and dendrite dissolution

The transpassive dissolution behaviors of Ni-based single crystal superalloy in 10 %NaCl, 10 %NaNO3, and mixed solution are investigated by using potentiodynamic polarization, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The alloy exhibits opposite yet complementary dissolution characteristics in NaCl and NaNO3 solutions. The different responses of γ/γ′ phases to Cl− and NO3− contribute to the opposite dissolution behaviors of dendrites and interdendritic regions. The surface flatness is noticeably enhanced in mixed solution due to the synchronous dissolution of the γ/γ′ phases. Our work paves the way for obtaining high-quality surface in electrochemical machining of single crystal superalloys.

Laser surface alloying of Hastelloy X superalloy with Amdry 365 powder: Microstructural evolution and microhardness

Laser surface alloying is a surface modification technique that melts coat powder and substrate with high laser power density. This study aims to improve the properties of Hastelloy X, a Ni-based superalloy used for gas turbine components, by applying a NiCoCrAlY coating using laser surface alloying. The purpose of this study was to investigate the process parameters including laser scanning speed, laser power, and stand-off distance on the microstructure and microhardness of the alloying zones. The findings indicate that different microstructures were formed in different alloying zones such as cellular, columnar, and equiaxed. The results also revealed the presence of β and γ phases in the dendritic and interdendritic regions. The microhardness at the interface was higher than that of the other alloying areas due to the increased content of the Mo element. This study concluded that the properties of Hastelloy X can be improved by using NiCoCrAlY powder through a laser alloying process.

Investigation of EDM erosion behavior for Ni-based superalloy using experimental and machine learning approach

The rapid growth of the global population and the consequent increase in manufacturing activities have heightened the need for sustainable practices to protect the environment. Non-traditional manufacturing processes, such as electric discharge machining (EDM), often use oil-based dielectric fluids like kerosene, which emit toxic fumes and aerosols, contributing to environmental pollution. To address this, the reuse of waste cooking oil (WCO) as a dielectric fluid in EDM presents a promising solution. This method not only tackles the issue of waste oil disposal but also supports the circular economy by repurposing waste materials. EDM, frequently criticized for its low cutting rates, can be enhanced by using nitrogen assisted modified Cu electrodes (cryogenically treated (CT)). This study focused on machining the difficult-to-cut nickel-based superalloy, IN718 by incorporating Sillimanite nano-powder with Span-60 (S-60). The erosion performance characteristics such as material removal rate (MRR), electrode wear rate (EWR), and accuracy index (AI) were evaluated. An artificial neural network (ANN) was employed to predict and correlate experimental and predicted values. Significant improvements were achieved using the non-dominated sorting genetic algorithm (NSGA-II) in the confirmation investigations. With a non-treated (NT) Cu electrode, the confirmatory experiments showed a 79.81 % increase in MRR, an 18.99 % decrease in EWR, and a 0.89 % improvement in AI. For the CT Cu electrode, MRR increased by 85.48 %, EWR decreased by 32.90 %, and AI improved by 0.53 % when using optimal processing parameters. This study demonstrates the potential for significant environmental and performance benefits in EDM by reusing WCO and optimizing electrode treatments.

Simulation and experimental investigation of grain structure, residual stress,γ′ phases in single crystal blade

Ni-based superalloy turbine blades have been required components in contemporary aero-engine. Knowing the solidification behavior, residual stress at grain defects, and microstructure of directionally solidified turbine blades is a required condition to improve the service performance of directionally solidified turbine blades. Firstly, the temperature field evolution of the blade under the withdrawal rate of 3 mm/min was studied. The deviations in temperature distribution in the high-rate solidification (HRS) procedure, particularly near the platform, can lead to transformations in the mushy zone, potentially resulting in solidification defects. Secondly, the grain growth of hollow turbine blades was calculated using the cellular automaton-finite factor method. The simulated grain framework was essentially consistent with experimental results. A method of process bar addition based on physical field distribution is also proposed. This method involves designing a combination of one Y-shaped and two I-shaped rods to decrease the cooling rate of blade edges and eliminate stray grains (SG). Then, the residual stress distribution at the locations of stray grains and low-angle grain boundaries (LAGBs) was analyzed before and after the addition of process bars. Finally, discussions were held regarding the distribution of γ′ phases in grain defects and blades.

Effect of Protective Coating Layer and Overlapping Factor on the Microstructure and Mechanical Properties of Rene-80 Ni-Based Superalloy in Laser Shock Peening Process

Effect of Protective Coating Layer and Overlapping Factor on the Microstructure and Mechanical Properties of Rene-80 Ni-Based Superalloy in Laser Shock Peening Process

Investigation on non-uniform oxidation behaviour in dendritic and interdendritic regions in a single-crystal Ni-based superalloy

Investigation on non-uniform oxidation behaviour in dendritic and interdendritic regions in a single-crystal Ni-based superalloy

Cooling and Lubricating Strategies for INCONEL® Alloys Machining: A Comprehensive Review on Recent Advances

Abstract INCONEL® alloys are Ni-based superalloys with superior mechanical properties for extremely high temperature (T) applications. These alloys present significant challenges: they are difficult-to-cut materials due to the low thermal conductivity (k), severe work hardening and elevated surface hardness. They are widely used in applications that require good dimensional stability; however, built-up edge (BUE) followed by premature Tool Wear (TW) are the most common problems when applying conventional machining (CM) and hybrid machining processes, i.e. Additive Manufacturing (AM) followed by milling, resulting in a meagre final product finishing. Regarding cooling/lubricating environments, a miscellanea of methods can effectively be applied to INCONEL® alloys, depending on their advantages and disadvantages. It is imperative to refine the machining parameters to enhance the performance outcomes of the process, particularly concerning the quality and cost-effectiveness of the product. This current review intends to offer a systematic summary and analysis of the progress taken within the field of INCONEL® CM and the various cooling/lubricating methods over the past decade, filling a gap found in the literature in this field of knowledge. A Systematic Literature Review (SLR) approach was employed in this study, aiming to identify pertinent papers within the cooling and lubricating strategies for INCONEL® alloys machining. The most recent solutions found in the industry and the prospects from researchers will be presented, providing significant insights for academic researchers and industry professionals. It was found that selecting cooling methods for INCONEL® machining requires careful consideration of various factors. Each lubrication environment utilized in traditional INCONEL® machining methods offer unique advantages and challenges regarding the different outcomes: TW, Tool-Life (TL) and/or surface quality assessment; nevertheless, cryogenic cooling by CO2(l) and N2(l) highlights as the better cooling environment to improve the machined surface quality.

Modified crystal plasticity constitutive model considering tensorial properties of microstructural evolution and creep life prediction model for Ni-based single crystal superalloy with film cooling hole

Accurate assessment of the creep life of film cooling hole structures is critical for long-life design and safe operation of aero engines and gas turbines. Firstly, through the high temperature creep experiment of nickel-based single crystal superalloy with film cooling hole, the microstructure evolution process under multiaxial stress state around film hole is characterized. Then, considering the directional effect of rafting structure and the influence of multiaxial stress, a fourth-order tensor is used to describe the evolution of γ phase width, and the microstructure evolution model accounting for multi-axial stress states is established. The microstructure evolution is coupled into the crystal plasticity constitutive model by Orowan stress. Meanwhile, based on continuous damage mechanics, a new multiaxial damage evolution law is established by introducing a multiaxial ductility factor into the constitutive model. The improved crystal plasticity constitutive model can effectively predict the microstructural evolution under multiaxial stress conditions. Furthermore, the combination of the modified crystal plasticity constitutive model and the critical distance method considering stress gradients is used for life prediction of film cooling hole structures. The prediction results show the effectiveness and necessity of considering the microstructure evolution in the life prediction.

Understanding Environmental Barrier Coating Lifetimes and Performance for Industrial Gas Turbines

Abstract Hydrogen or hydrogen blend fuels are expected to replace natural gas in land-based industrial gas turbines (IGTs) to support a greener power economy. Silicon carbide (SiC) base ceramic matrix composites (CMCs) are considered for replacement of Ni-based superalloys to facilitate future efficiency improvements. SiC CMCs require environmental barrier coatings (EBCs) to mitigate volatilization from high-temperature steam, thus making the EBC lifetime critical information for identifying CMC component lifetimes. The goal of this project is to determine the maximum bond coating temperature underneath the EBC for achieving an IGT component lifetime goal of 25,000 h, which is far greater than current CMC component lifetime requirements for aeroturbine applications. To provide data for the lifetime model, laboratory testing used atmospheric plasma-sprayed rare-earth silicate EBCs on monolithic SiC substrates with an intermediate Si bond coating. Specimens exposed to 1-h thermal cycles in flowing air–steam environments and reaction kinetics were assessed from 700 °C to 1350 °C by measuring the thickness of the thermally grown silica scales. The silica growth and phase transformation appear critical in predicting EBC lifetime and several strategies have been explored to reduce the oxide growth rate and improve EBC durability at elevated temperatures. Advanced characterization using Raman spectroscopy has helped clarify this system.

The Effect of Shot Blasting Abrasive Particles on the Microstructure of Thermal Barrier Coatings Containing Ni-Based Superalloy

Grit particles remaining on the substrate surface after grit blasting are generally considered to impair the thermal performance of thermal barrier coatings (TBCs). However, the specific mechanisms by which these particles degrade the multilayer structure of TBCs during thermal cycling have not yet been fully elucidated. In this study, the superalloy substrate was grit-blasted using various processing parameters, followed by the deposition of thermal barrier coatings (TBCs) consisting of a metallic bond coat (BC) and a ceramic top coat (TC). After thermal shock tests, local thinning or discontinuities in the thermally grown oxide (TGO) layer were observed in TBCs where large grit particles were embedded at the BC/substrate interface. Moreover, cracks originated at the concave positions of the TGO layer and propagated vertically towards BC; these cracks may be associated with additional stress imposed by the foreign grit particles during thermal cycling. At the BC/substrate interface, crack origins were observed in the vicinity of large grit particles (~50 μm).

Effect of molybdenum addition on precipitate coarsening kinetics in Inconel 740H: A phase-field study

Inconel 740H (IN740H) has emerged as an important candidate for the advanced ultra-supercritical (AUSC) steam turbines due to its superior microstructural stability and creep resistance under service conditions. In the present work, we have reparameterized a multicomponent Ni-based superalloy (IN740H) into an equivalent ternary Ni-Al-Mo superalloy, based on the partitioning coefficients of the elements, using the thermodynamic database (CALPHAD). We use this thermodynamic description to employ a quantitative phase-field model to assess the long-term stability of γ′ precipitates in IN740H utilizing GPU-based supercomputing architecture. The assessment helps us to enhance our understanding of the effect of the atomic diffusivity of Mo on coarsening kinetics of the γ′-precipitates in equivalent ternary Ni-Al-Mo superalloy. Investigation reveals that our phase-field model can accurately predict the experimentally observed coarsening kinetics in IN740H.

Changing the Structure of a Single-Crystal Ni-Based Superalloy During Its High-Temperature Salt Corrosion at 750°C

Changing the Structure of a Single-Crystal Ni-Based Superalloy During Its High-Temperature Salt Corrosion at 750°C

Effect of carbon content on the microstructure and stress rupture properties of a 4th-generation nickel-based single crystal superalloy

The balance between the stress rupture properties and castability of a 4th-generation Ni-based single crystal superalloy can be achieved by addition of appropriate carbon content. In this work, the effects of carbon content on the microstructure and stress rupture properties of a 4th-generation Ni-based single crystal superalloy were investigated in detail. The results showed that minor carbon addition could aggravate the dendrite segregation, while the addition of carbon had no obvious effect on the rafting and distortion of γ′ phase during stress rupture deformation. At 760 °C/810 MPa and 1100 °C/210 MPa, the stress rupture lives of the three experimental alloys initially increased and subsequently decreased with the increasing carbon content. However, under condition of 1140 °C/137 MPa, the increased carbon content resulted in the reduction of the stress rupture lives of alloy. It was discovered that minor carbon elements addition (0.045 wt%) can promote formation of interfacial dislocation networks and improve creep resistance at high temperatures. At intermediate temperature, the introduction of carbon could reduce the stacking fault (SF) energy of γ matrix, thus facilitating the formation of SFs in γ matrix. The M6Cgranular carbides precipitated at high temperature, which was considered to be beneficial to stress rupture properties.

Microstructure and Fatigue Behavior of PM-HIPed Ni-Based Superalloys and Martensitic Tool Steels: A Review

Hot isostatic pressing (HIP) is a near-net shape powder metallurgy (PM) technique, which has emerged as an efficient technique, offering precise control over the microstructure and properties of materials, particularly in high-performance alloys. This technology finds applications across a wide range of industries, such as aerospace, automotive, marine, oil and gas, medical, and tooling. This paper provides an overview of powder metallurgy and hot isostatic pressing, covering their principles, process parameters, and applications. Additionally, it conducts an analysis of PM-HIPed alloys, focusing on their microstructure and fatigue behavior to illustrate their potential in diverse engineering applications. Specifically, this paper focuses on nickel-based superalloys and martensitic tool steels. The diverse microstructural characteristics of these alloys provide valuable insights into the PM-HIP-induced fatigue defects and properties.