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The effects of process parameters on the microstructures and properties of the laser-assisted epitaxial growth layer are of great significance for the repair of nickel-based single-crystal blades. This work investigated the microstructures and properties of the epitaxial-growth laser-assisted nickel-based single-crystal superalloy. The effects of scanning path, laser power, scanning velocity and heat treatment on the microstructures and hardness of the laser-assisted epitaxial growth layer were explored. The microstructures of the epitaxial-growth samples are the same, starting from the bottom with a continuous columnar dendrite. The dendrites transform into isoaxial crystals when growing to a certain height. The scanning path, laser power, and scanning velocity mutually influence the sample's microstructures. The columnar crystal structure is very stable. Even the epitaxial-growth layer undergoes post-heat treatment, while the isoaxial crystal structure would be coarsened and the hardness decreases, but the subsequent aging treatment leads to an increase in hardness. These findings will greatly help improve the repair effect of single-crystal superalloys.

Fretting wear has an adverse impact on the fatigue life of turbine blade roots. The current work is to comparatively investigate the fretting wear behaviour of the nickel-based superalloy surfaces produced by polishing and creep-feed profile grinding, respectively, in terms of surface/subsurface fretting damage, the friction coefficient, wear volume and wear rate. Experimental results show that the granulated tribolayer aggravates the workpiece wear, while the flat compacted tribolayer enhances the wear resistance ability of workpiece, irrespective of whether the workpiece is processed by polishing or grinding. However, the wear behaviors of tribolayers are different. For the polished surface, when the normal load exceeds 100 N, the main defects are crack, rupture, delamination and peeling of workpiece materials; the wear mechanism changes from severe oxidative wear to fatigue wear and abrasive wear when the loads increase from 50 to 180 N. As for the ground surface, the main wear mechanism is abrasive wear. Particularly, the ground surface possesses better wear-resistant ability than the polished surface because the former has the lower values in coefficient friction (0.23), wear volume (0.06×106 μm3) and wear rate (0.25×10-16 Pa-1). Finally, an illustration is given to characterize the evolution of wear debris on such nickel-based superalloy on the ground surface.

K444 nickel-based superalloy is an important material to manufacture the gas turbine due to its excellent mechanical properties at high temperatures and corrosion resistance. Currently, grinding is the mostly used method for the surface finish of the K444 alloy components. However, few studies worked on the effects of the abrasive tool wear on the ground surface characteristics and corrosion properties of K444 alloy. This study uses two different-type alumina abrasive tools, i.e., white alumina (WA) and microcrystalline alumina (MA) wheels, to grind the K444 alloy. The influence of the alumina abrasive tool wear on ground surface characteristics and corrosion resistance performance are investigated. It is discovered that the MA wheel presents a slighter wheel wear and higher self-sharpening than the WA wheel. Compared to the WA wheel, the MA wheel has less material adhesion, which leads to a better surface finish. In the corrosion testing, the maximum corrosion depth is 80 μm in the surface ground by the MA wheel but 100 μm in the surface ground by the WA wheel, which demonstrates that the MA wheel grinding benefits the surface corrosion resistance of K444 alloy. Therefore, this study could provide a guide to selecting the abrasive tools and optimizing the grinding process of the K444 alloy.

Fluidized Carbon Bed Cooling (FCBC) is an innovative investment casting process for directional solidification of superalloy components. It takes advantage of a fluidized bed with a base of small glassy carbon beads for cooling and other low-density particles that form an insulating layer by floating to the bed surface. This so-called “Dynamic Baffle” protects the fluidized bed from the direct heat input from the high-temperature heating zone and provides the basis for an improved bed microstructure. The prerequisites for a stable casting process are stable fluidization conditions where neither collapse of the bed nor particle blow out at excessive bubble formation occur. This work aimed to investigate the fluidization behavior of spherical carbon bed material in argon and air at temperatures between 20 to 350 °C. Systematic studies at reduced pressures using the FCBC prototype device were performed to understand the stable fluidization conditions at all stages of the investment casting process. The particle shape factor and size distribution characterization and the measurement of the powder’s minimum fluidization velocity and bed voidage show that this material can be fully utilized as a cooling and buoyancy medium during the FCBC process.

(γ’+β) two-phase Ni-Al is a promising high-temperature protective coating material used on Ni-base superalloys since it has good interfacial compatibility with superalloys due to the low Al content compared to single-phase β-NiAl. In this paper, we aim to improve the oxidation resistance, whereby Ni-34Al-0.1Dy, a (γ’+β) two-phase Ni-Al alloy, was treated by laser shock processing (LSP) and the oxidation behavior at 1150 °C was investigated. The results showed that after oxidation, Al2O3 scale formed on the original β phase of the untreated alloy with a small grain size (200-800 nm), while for the LSP-treated samples, the scale grown on the original β phase was dominantly composed of larger Al2O3 grains with a size of 2-3 μm. The distinction was attributed to the promotion of θ-Al2O3 to α-Al2O3 transformation induced by the LSP, because the dislocation density, as well as surface roughness, were increased during LSP treatment which can provide heterogeneous nucleation sites for α-Al2O3. In addition, the larger-size Al2O3 particles, derived from the direct conversion of needle-like θ-Al2O3 in the initial oxidation stage, could rapidly overspread the whole β phase surface thus reducing the scale growth rate.

In this study, functionally graded foam made of Inconel 625 superalloy was successfully produced using the template replication method, with open-cell polyurethane foams as a precursor. The products have a similar pore morphology as the templates and adjacent layers were successfully sintered together by particle bonding. Sound absorption experiments on graded metallic foams reveal that the sound absorption at particular frequency ranges can be improved by various permutations of foam layers. For graded foam of two distinct pore sizes, a mathematical equation was proposed to predict the location of the intersection point of the sound absorption curves, thereby aiding in graded foam design. An increase in sound absorption coefficients by resonance-like effects can be introduced before the intersection points by placing the foam layer of smaller pore size nearer to the sound source. The sound absorption performances can be further customized when the thickness proportion of the pore sizes is changed and when the number of distinct pore sizes used is increased. The sound absorption performance at lower frequencies is generally boosted by resonance-like effects when the layer of foam with the largest pore size is placed furthest from the sound source. Given the same composition of foam with a fixed thickness proportion of pore sizes, one can introduce resonance-like effects to improve the sound absorption performance compared to other permutations while possibly satisfying weight requirements in practical applications. This study provides valuable insights and mathematical guidelines in the design and manufacturing of functionally graded metallic foam for specific applications.

The trade-off between strength and ductility has been an enormous difficulty in the field of materials for an extended time due to their inverse correlation. In this work, friction stir processing (FSP) was for the first time performed to high-strength and high-melting-point Ni-Co based superalloy (GH4068), and enhanced strength and ductility were achieved in FSP samples. At room temperature, the FSP sample demonstrated significantly higher yield strength and ultimate tensile strength (1290 and 1670 MPa) than that of the base material (BM, 758 and 904 MPa) and advanced wrought GH4068 alloy (982 and 1291 MPa), concurrent with high tensile ductility (∼24%). Compared with the BM, 70% higher yield strength of the FSP sample results from the remarkable contribution of grain-boundary and nanotwin strengthening, which has been confirmed by the multimechanistic model studied in this work. More importantly, with increasing temperature, an excellent strength-ductility synergy was obtained at 400 °C, i.e., the yield strength of the FSP sample was increased by more than 50% compared with the BM (from 789 to 1219 MPa); more interestingly, the elongation was also significantly increased from 17.9% in the BM to 28.5% in the FSP sample. Meanwhile, the Portevin-Le Chatelier effect was observed in the engineering stress-strain curve. The occurrence of this effect may be attributed to the interaction between solutes and defects like twins and mobile dislocations. Moreover, the grain refinement mechanism of FSP samples was proved to be discontinuous dynamic recrystallization.

NiCoCr-based multi-component alloys have drawn much attention due to their exceptional ductility and strain hardening capacity. However, insufficient strength-ductility synergy of NiCoCr alloy has always been an issue that prevents it from extensive applications. According to our previous research, the precipitation of γ'' phase can significantly improve the strength-ductility synergy of this alloy system at room temperature. In this study, the effects of V addition on γ'' phase stability and high temperature mechanical properties have been explicitly investigated. The results indicate that V addition can stabilize metastable γ'' phase in this alloy system and prevent it from transforming into stable δ phase at grain boundaries upon 650 °C aging, resulting in improved mechanical properties at elevated temperature. The specific strength of γ''-strengthened multi-component NiCoCr-based alloy can reach up to 86.2 MPa/g•cm−3 at 650 °C, which is higher than those of Ni-based superalloys, IN 939 and Waspaloy. This work provides theoretical guidance for the novel design of γ''-strengthened alloy for high temperature applications.

The stray crystal in the platform region is one of the common main defects in single-crystal superalloy blades. The simple and effective method to eliminate this defect is urgent to be explored. This work found that the Cusp magnetic field can effectively inhibit the stray-crystal formation in the platform. The tendency of stray-crystal formation decreases as the magnetic-field strength increases at a certain withdrawal rate and temperature-gradient. The suppressing effect decreases as the withdrawal rate or the temperature-gradient increases. Finally, the inhibiting mechanism on the stray-crystal formation from the Cusp magnetic field is proposed based on the experiments and the numerical simulation. The magnetic-field application strengthens the flow velocity and changes the flow structure near the liquid-solid interface, and further reduces the radial temperature difference. Accordingly, the secondary dendrites in the heat-conduction undercooled zone expands towards the corner in a faster speed, which reduces the stray-crystal formation in the platform corner. This study provides an effective and simple method for decreasing the stray-crystal formation during the preparation of single-crystal with platform region.

Aero-engine turbine blades may suffer overheating during service, which can result in severe microstructural and mechanical degradation within tens of seconds. In this study, the thermal cycling creep under (950°C/15 min+1100°C/1 min)-100 MPa was performed on a directionally solidified superalloy, DZ125. The effects of overheating and thermal cycling on the creep properties were evaluated in terms of creep behavior and microstructural evolution against isothermally crept specimens under 950°C/100 MPa, 950°C/270 MPa, and 1100°C/100 MPa. The results indicated that the thermal cycling creep life was reduced dramatically compared to the isothermal creep under 950°C/100 MPa. The plastic creep deformation mainly occurred during the overheating stage during the thermal cycling creep. The thermal cycling creep curve exhibited three stages, similar to the 1100°C isothermal creep, but its minimum creep rate occurred at a lower creep strain. The overheating events caused severe microstructural degradation, such as substantial dissolution of γ' phase, earlier formation of rafted γ' microstructure, widening of the γ channels, and instability of the interfacial dislocation networks. This microstructural degradation was the main reason for the dramatic decrease in thermal cycling creep life, as the thermal cycling promoted more dislocations to cut into γ' phase and more cracks to initiate at grain boundaries, carbides, and residual eutectic pools. This study underlines the importance of evaluating the thermal cycling creep properties of superalloys to be used as turbine blades and provides insights into the effect of thermal cycling on directionally solidified superalloys for component design.

A theoretical treatment on the oxide-controlled dwell fatigue crack growth of a γ’ strengthened nickel-based superalloys is presented. In particular, this study investigates the influence of an externally applied load and variations in the γ’ dispersion on the grain boundary oxide growth kinetics. A dislocation-based viscoplastic constitutive description for high temperature deformation is used to simulate the stress state evolution in the vicinity of a crack at elevated temperature. The viscoplastic model explicitly accounts for multimodal γ’ particle size distributions. A multicomponent mass transport formulation is used to simulate the formation/evolution of an oxide wedge ahead of the crack tip, where stress-assisted vacancy diffusion is assumed to operate. The resulting set of constitutive and mass transport equations have been implemented within a finite element scheme. Comparison of predicted compositional fields across the matrix/oxide interface are compared with experiments and shown to be in good agreement. Simulations indicate that the presence of a fine γ’ size distribution has a strong influence on the predicted ow stress of the material and consequently on the relaxation in the vicinity of the crack-tip/oxide wedge. It is shown that a unimodal dispersion leads to reduced oxide growth rates (parabolic behavior) when compared to a bimodal one. Stability conditions for oxide formation are investigated and is associated with the prediction of compressive stresses within the oxide layer just ahead of the crack tip, which become progressively negative as the oxide wedge develops. However, mechanical equilibrium requirements induce tensile stresses at the tip of the oxide wedge, where failure of the oxide is predicted. The time taken to reach this critical stress for oxide failure has been calculated, from which dwell crack growth rates are computationally derived. The predicted rates are shown to be in good agreement with available experimental data.

TiAl alloys are promising structural materials in the field of gas turbine engines, due to their low density and high specific strength. Applying thermal barrier coatings (TBCs) is an effective method to increase the service temperature and lifetime of TiAl alloys. In this work, a YSZ/TiAlCrY bilayer system was fabricated by air and vacuum plasma spray techniques on TiAl alloys. The thermal shock behavior was focused on and compared with the traditional YSZ/NiCrAlY system by means of a water-quenching test at 1100 °C. The results show that the YSZ/TiAlCrY system exhibited excellent thermal cycling lifetime with over 210 cycles, which was almost 3 times that of the traditional YSZ/NiCrAlY system on Ni-based superalloys. The failure mechanism was analyzed based on microstructural observations and residual stress calculations. It is found that without the formation of new brittle phases at the interface and suitable CTE were the key factors for the excellent thermal shock resistance of the YSZ/TiAlCrY system on TiAl alloy substrates.

The wettability of 3 mol% yttria-stabilized zirconia (3YSZ) by molten Cu was noticeably improved by applying a direct current (DC). Furthermore, robust brazing of 3YSZ to a GH3128 superalloy using a Cu filler was achieved within seconds at 1100 °C with the assistance of a DC. When the DC flowed from 3YSZ to GH3128, the shear strength of the joints reached 225 ± 20 MPa at 1 s of energization and increased to 330 ± 30 MPa at 5 s of energization. The formation of Cu51Zr14 at the 3YSZ/Cu interface, the dissolution of Ni into the Cu filler, the dispersive distribution of fine granular (Mo, Cr, W)(Ni, Cu) in the brazing seam and the relief of residual stress by ductile (Cu, Ni) solid solution were crucial for achieving the high-strength joints. This work provides a novel and economical method for ultrafast brazing of zirconia to metals.

Uncontrolled residual stresses have significant effects on the service time and defects of the spun parts. Nowadays, X-Ray Diffraction (XRD) method has been widely used in the residual stress measurement of industry products with different forming processes. The calculated residual stress is usually obtained from the data fitting slope of strain and angle with Ordinary Least Squares (OLS) method. But this fitting method is not always suitable for the big fluctuant data. In this paper, the Weighted Least Square (WLS) method is used for the data fitting and compared with the OLS method. The nickel-based superalloy GH3030 and iron-based superalloy GH1140 are applied in the multi-pass cold spinning experiments. The residual stress distributions of normal, potential crack and wrinkle workpieces are discussed with the grain structure. The results show that WLS method has better goodness of fit compared with OLS method. The residual stress distributions have special relationship with potential crack, wrinkle workpiece and grain structure.

Summary Cermets embrace the high hardness of a ceramic and the good ductility of a metal. Therefore, they potentially meet the ever-increasing demands of new materials for harsh environments in energy generation and conversion. However, cermet sintering faces many challenges, such as metal volatilization, grain coarsening, and poor wettability of the metal with the ceramic, which affect the microstructure and thus mechanical properties. Herein, we apply an ultrafast high-temperature sintering (UHS) method to sinter cermets at a high temperature in only seconds. The high temperature leads to good wettability of the metal with the ceramic, while the short sintering time limits the loss of metal components and accurately controls the grain growth. We demonstrate the UHS method using a model cermet composed of a Ni-based superalloy and aluminum oxide, where we obtain dense microstructure, minimal nickel loss, and uniform grain size. Owing to these merits, good mechanical properties and oxidation resistance are achieved.

The current study demonstrates a well-designed response surface methodology (RSM), based on the generated dataset of finite element method (FEM) to establish an integrated model for simulation of residual stress distribution in a thick thermal barrier coating (TTBC). In this study, typical TTBCs were applied on Hastelloy X Nickel-based superalloy using air plasma spray technique followed by thermal cycling. The recorded stress data of Raman spectroscopy was employed to verify the proposed FEM model. A relatively good agreement was obtained between predicted residual stresses and measured ones. Verified FEM model was used to carry out the parametric studies to evaluate the effects of such various parameters as interface amplitude, wavelength, thermally grown oxide thickness and preheating temperature on the stress distribution in the TTBC during the thermal cycling. The computed data were subsequently used for the development of RSM model. In conclusion, experimentally verified numerical data was used to construct a statistical model based on RSM and successfully used to predict the residual stress distribution field in TTBC during thermal cycling. The obtained results of hybrid FEM- RSM model were in acceptable conformity with Raman spectroscopy measurements.

The effect of specimen thickness on the rupture properties of cast Ni-based polycrystal superalloy M951 was investigated in this paper. The results of the rupture tests in air under 980 ​°C/90 ​MPa revealed that the rupture life and elongation obviously decreased with decreasing specimen thickness. The thin-wall effect for polycrystal superalloy M951 is associated with several factors. First, the surface oxidation and internal nitridation induce the reduction in the load-bearing section, which accelerates the rupture fracture of thin specimens. Second, the combined effect of oxidation and stress at the surface grain boundary facilitates the premature initiation and propagation of the surface cracks in thin specimen. Third, the through-grain boundaries introduce by specimens machining are detrimental for rupture property. A direct comparison of rupture properties of thin-wall samples with different grain morphologies indicate that thin-wall effect can be diminished by avoiding through-grain boundary introduction.

To meet the high demand for ceramic/superalloy composite structural components in various fields, an advanced high-temperature adhesion technique was firstly developed by preparing a novel inorganic/organic hybrid adhesive suitable for ZrO2 and TC4. Chemical bonding started to work at ∼600°C, and became the crucial bonding mechanism at elevated temperatures. The formation of ZrSiO4 and Ti5Si3 at the interfaces of two substrates not only increased the interfacial connection strength, but also formed two gradient layers with a size of ∼2 μm to effectively alleviate the difference of composition and performance between the adhesive and substrates. In the temperature range of 500–900°C, the matching degree of CTE among ZrO2, adhesive and TC4 is higher, and the maximum difference does not exceed 3×10-6 K-1. Meanwhile, the formation of a composite structure containing various ceramics (ZrO2, SiC and ZrB2) and intermetallics (Ni–Si, Al–Ni), and the improvement of structural compactness of adhesive from 500 to 900°C greatly improved the bonding strength to the maximum value of 31.4 MPa at 900°C. Also, the adhesive pretreated at 900°C showed good thermal cycling resistance, and the strength was still higher than 15 MPa after 50 cycles. For cured adhesive, when used directly in an extreme environment, it can provide bonding strength not less than 5 MPa in the whole temperature range, indicating that the adhesive possessed potential emergency repair convenience. This work significantly broadened the application of high-temperature-resistant adhesion technology in the connection of dissimilar ceramics and alloys.

Ultrasonic vibration-assisted grinding (UVAG) is an effective and promising method for machining of hard-to-cut materials. This article proposed an ultrasonic vibration plate device enabling the longitudinal full-wave and transverse half-wave (L2T1) vibration mode for UVAG. The characteristics of two-dimensional coupled vibration in different directions were analyzed on the basis of apparent elastic method and finite element method. Furthermore, a correction factor was applied to correct the frequency error caused by the apparent elastic method. Finally, the comparative experiments between the conventional creep-feed grinding and UVAG of Inconel 718 nickel-based superalloy were carried out. The results indicate that the apparent elastic method with the correction factor is accurate for the design of plate device under the L2T1 vibration mode. Compared with the conventional creep-feed grinding, the UVAG causes the reduction of grinding force and the improvement of machined surface quality of Inconel 718 nickel-based superalloy. Furthermore, under the current experimental conditions, the optimal ultrasonic vibration amplitude is determined as 6 μm, with which the minimum surface roughness is achieved.

A three-dimensional high-fidelity particle-scale computational fluid dynamics (CFD) modeling of a selective parallel dual-laser melting (SPDLM) process is developed, on which dynamics behavior of molten pools of Nickel-based superalloy during SPDLM is simulated. The phenomena of wetting, necking, and pores near the overlapping region in the parallel dual-laser molten pools are especially investigated. The simulated results show that the SPDLM process improves the re-melting rate of the molten pool and the wettability of the overlapping region of the SPDLM molten pool, reducing the probability of defects, especially the probability of lack of fusion. Due to the uniform temperature distribution in the overlapping region of the two tracks and the complete melting, the product quality at the overlapping region of the two molten pools can be better guaranteed when the interval between the parallel dual lasers is 2.5 times of the laser beam radius. The results suggest that the SPDLM technique together with appropriate process parameters can not only increase the printing efficiency, but also improve the surface quality of the overlapping area of the two molten pools. The simulated results also reveal the formation mechanisms of pore defects during the selective multi-laser melting process on a mesoscopic scale. This study shows that the proposed particle-scale CFD model provides a high fidelity approach to characterize the molten pool in the SPDLM process and, therefore, is helpful for the optimal process design for the selective multi-laser melting.

In this paper, the effect of rare earth oxide additive on coating material deposited by laser cladding process on various engineering materials has been discussed. The purpose of rare earth oxide additive in the coating composition is to improve the various properties like mechanical, tribological, and chemical properties. The main rare earth oxides are La2O3, CeO2 and Y2O3, which are generally used in laser cladded coatings. The limited amount of addition of these rare earth oxide compound may leads to improvement in hardness, wear and corrosion resistance of coating. The attractive properties of rare earth oxide is grain refinement, conversion of coarse structure to fine dendritic structure, creating grain boundary movement hindrance of dislocation in the material which leads to its application as nutrients in the coating material. The main purpose of coating is to enhance the surface properties of material like hardness, corrosion resistance and wear resistance. When rare earth oxide are added to the coating then it creates extra enhancement in the above properties. The laser cladding is widely used in modern manufacturing technology due to its very attractive properties like good metallurgical bonding with substrate, less dilution, minimum distortion, less heat affected zone and fast solidification and high cooling rate. In this review article the coating developed by laser cladding on various conventional engineering materials like ferrous materials, magnesium alloys, titanium alloys, aluminium alloys and nickel based super alloys with rare earth oxide addition are described.

This study focuses on the transient liquid phase (TLP) bonding of DD5 single-crystal superalloy to CrCoNi-based medium-entropy alloy (MEA) using a BNi-2 filler alloy. The microstructure and mechanical properties of the TLP-bonded DD5/MEA joint were evaluated, and the microstructural evolution mechanism was investigated. The formation of the isothermal solidification zone (ISZ) depended on the diffusion of the melting-point depressants (Si and B elements) from the liquid filler into the DD5 and MEA substrates, as well as the dissolution of the substrates. Boron diffused along the γ channel of DD5 and reacted to form M5B3 boride, herein referred to as the diffusion-affected zone (DAZ I). Similarly, the Cr5B3 boride precipitated in the Ni-rich MEA matrix adjacent to the MEA substrate (i.e., DAZ II). Additionally, a coherent orientation of [0]BCT // [0 1 1]FCC and (0 0 2)BCT // (2 0 0)FCC was detected between M5B3 boride with a body-centered tetragonal (BCT) structure and the face-centered cubic (FCC) matrix. The performance of the joint was dominated by the properties of the bonding seam. As the bonding time increased from 20 to 80 min, the athermal solidification zone (including eutectic microstructure) was gradually replaced by the ISZ exhibiting excellent plastic deformation capability, and the shear strength of the joint was improved. The maximum shear strength (752 MPa) was achieved when the eutectic-free joint was bonded at 1050 °C for 80 min. The fracture morphology revealed a mixture mode, indicating the initiation of cracks in the DAZ II, mainly propagating in the ISZ, and passing through the DAZ I.

To investigate the evaluation method of hydrogen compatibility of A286 superalloy in high pressure hydrogen gas, SSRT tests of hydrogen-charged specimens were conducted at ambient temperature at various strain rates. The relative reduction in area (RRA), one of the ductility parameters, was determined. The hydrogen content in the hydrogen-charged specimen was the same as the equilibrium hydrogen content on the specimen surface at 150 °C in 70 MPa hydrogen gas. The strain rate dependence of RRA was smaller than that of RRA obtained in 70 MPa hydrogen gas at 150 °C. All the hydrogen-charged specimens showed slip-plane fractures in the grains in their cores. However, the specimens in 70 MPa hydrogen gas at 150 °C showed fracture surfaces morphology ranging from dimples to quasi-cleavages and intergranular fractures with decreasing strain rate. These dissimilarities are expected to arise from differences in the hydrogen concentration behaviors of the specimens during the deformation process.

In today's scenario, it is very difficult to machine advanced materials like super alloys with conventional machining process. This paper proposes a study of the machining characteristics i.e. Material removal rate (MRR) and tool wear rate (TWR) of Inconel-600 materials with and without powder mixing in the dielectric of EDM. Taguchi methodology has been used to collect the data. Results shows that With the use of boron carbide as a powder additive, enhance the response parameters. Current is the most dominant factor on both the responses followed by on time and off time. Scanning Electron Microscope (SEM) is used to analyze the surface characteristics.

This study aims to present the comparison between 2 different nickel-based superalloy materials, rene 41 and waspaloy through their application in designing a high-pressure (HP) turbine blade for a turboshaft engine. NACA 4-digit airfoil profile has been used to create the airfoil for the HP turbine blade. MATLAB software is used to create a graphical user interface for the selection of various parameters used to define the airfoil profile including the NACA airfoil number, angle of attack, number of grid points, grid type, trailing edge type, chord length, and the plot style. For this study, NACA 9618 airfoil is used to model a single HP turbine blade. Numerical flow analysis using vortex panel method (VPM) is carried out on the airfoil to obtain the flow characteristics. Further, several types of failure methodologies occurring in the turbine blades and standard industrial methods used to reduce failure cycles are discussed. Comparisons are carried out showing precipitation-hardened rene 41 exhibiting relatively larger Von-Mises stress values in comparison with age-hardened waspaloy at elevated temperature for thermo-mechanical loading in the blade structure. Steady-state simulation at 39,000 rpm yields maximum temperature values of 1056 °C and 1220 °C for rene 41 and waspaloy respectively, also yielding relatively close values for critical displacement at the shroud section of the blade. Analysis models are proposed to determine the effect of mechanical and thermal loads on the high-pressure turbine blade design.

In current exploration, a die-sinking EDM technique on two various Ni based alloy materials (Alloy 625, Alloy 718) were planned to optimize numerous performance attributes depends on Taguchi method. Nickel based Super alloy like Alloy 625 and Alloy 718 are mostly used in aerospace, marine, nuclear industries due to its remarkable chemical and mechanical properties. Experimentation have been proposed by Taguchi’s design to see impact of four input process machining factors like pulse on time, off time, current and tool rotation on material removal rate, electrode wear rate, average surface roughness and overcut. A combined route of optimization of satisfaction function with Taguchi method was used for the multiple performances optimization. The optimum and most cogent parametric setting for machining was obtained at: [pulse on time = 100 µs, pulse off time = 50 µs, current = 17A, tool rotation = 825 rpm] for alloy 625; [pulse on time = 300 µs, pulse off time = 75 µs, current = 14A, tool rotation = 925 rpm] for alloy 718.

Fabrication of thin-wall components using the laser powder bed fusion (LPBF) additive manufacturing (AM) technology was investigated for two “hard-to-weld” high gamma prime Ni-based superalloys RENE 65 (R65) and RENE 108 (R108). Simple block parts with wall thicknesses of 0.25 mm, 1.00 mm, and 5.00 mm are printed using a bidirectional laser scanning strategy without layer-wise rotation. Parts with walls thinner than 5 mm fail before reaching the designated build height. Results indicate that reduction of limiting build height (LBH) corresponds to the reduction of part thickness and is unaffected by alloy composition. On the contrary, the number of internal micro-cracks along columnar grain boundaries in the build direction (BD) increases with part thickness and is significantly higher in R108 than R65. These findings suggest that reduced LBH in parts with thinner walls is not caused by internal micro-crack formation. Fractography and finite element analysis (FEA) of the in-process thermal stresses show that the LBH trend is not explained by the conventional cracking mechanism. Simulations suggest that part thickness affects stress distribution leading to more substantial distortion and consequent failure to add layers for continued fabrication of thinner parts.

This work reports on the performance of eco-friendly spray-based approach employing vegetable oils to precision machine nickel based superalloy Inconel 718. Taguchi L9 (33) orthogonal array was used to evaluate two vegetable oils namely sunflower and castor oil for turning operation and their performance was compared with dry machining mode. Three levels of cutting speed (30, 50, 70 m/min.), feed rate (0.168, 0.281, 0.393 mm/rev.) and air pressure (2, 3.5, 5 bar) were used while keeping constant depth of cut (1) mm and spray standoff settings (50 mm). Tool wear, surface roughness and machined surface integrity were taken as response parameters. Tool wear analysis was further supplemented with scanning electron microscopy (SEM). The effects of the input variables on response parameters were quantified by analysis of variance (ANOVA). It was found that feed rate is the most contributing factor for surface roughness with a contribution of 95.71%, 97.86% and 93.19% for MQLSO, MQLCO and dry machining conditions respectively. As for the tool wear, cutting speed is the most contributing factor with a contribution of 76.55%, 80.87% and 69% for MQLSO, MQLCO and dry machining conditions respectively. Minimum tool wear was obtained with sunflower oil with lowest feed rate (0.168 mm/rev.) and cutting speed (30 m/min.) combination. Further insight on worst and least tool wear conditions via SEM images indicate grooving, incidences of adhered material and attrition/chipping to be observable for dry machining condition. On the other hand, lesser incidences of adhered chips and uniform wear which extended up-to the tool nose was observed for least tool wear condition obtained with MQLSO indicting its effectiveness. The minimum values for tool wear (116 μm) and surface roughness (0.43 μm) as obtained with MQLSO, were 26% and 52.09% better (respectively) when compared to the dry machining at same conditions. In the context of surface integrity, a strain hardened layer extending up to the depth of 270 μm was observed at optimum machining parameters. Approximately, 16% higher hardness value was observed closer to the machined surface, than that of bulk material.

This paper aims to propose a creep life evaluation method considering the effect of crystallographic orientation. First, the maximum Schmid factor of {111} 〈112〉 and the corresponding lattice rotation angle were introduced to form an “orientation factor”. Then the equivalent stress was calculated by multiplying this factor and the nominal stress. Latterly, the Larson-Miller Parameter (LMP) method was adopted as the rupture life evaluation criteria, in which the input variable was the equivalent stress instead of the nominal stress. All the predictions showed high accuracy when the proposed method was applied to Mar-M247, SC7-14, CMSX-2, Alloy454, CMSX-4 and DD6. Finally, the applicable temperature ranges of the orientation-dependent method (using equivalent stress) and the traditional LMP method (using nominal stress) were discussed. The results show that only the Orientation-Dependent (OD) method is reliable at intermediate temperatures (760–850 °C) because the orientation has significant effect on the stress rupture life, while the influence of orientation is considerably reduced at high temperatures. Both methods provide precise predictions in this situation, and the LMP method should be favored since it is much easier to implement.

The evolution of the rapid prototyping with the emergence of the Industry 4.0 brings the new challenges in the field of additive manufacturing. The additive manufacturing eliminates the various process incorporated in conventional manufacturing such as casting, machining and welding. Therefore, the additive manufacturing reduces the manufacturing cost, labours and produce complex shapes easily. The additive manufactured Inconel 718 super alloy is widely used in various fields such as medical application, automobile and air crafts for its mechanical strength and corrosion resistance. The mechanical study of this material may cause most expansive, time consuming process and material wastage. The study is mainly focused to minimized expenditure and material wastage due to conventional testing process. In this paper, the additive manufactured Inconel 718 super alloy is evaluated through CAE software. For investigation, the direct metal laser sintering (DMLS) processed material and their corresponding mechanical properties are considered as a base data. All the models are meshed fine elements in hex shape to improve the accuracy of testing. Boundary condition applied as per ASTM standard for tensile (ASTM E8), erosion (ASTM G76) and impact (ASTM E23). Experimentation such as axial loading, impact loading and solid particle erosion studies are performed. Subsequently, the simulated results are compared with conventionally tested material for data interpretations. The analytical result for DMLS alloy has tensile strength is 1125 MPa and impact strength of 23.30 J; and the commercial alloy has tensile strength of 1252 MPa and impact strength 25.33 J respectively. As a research finding, it has been confirmed that the result achieved through simulated modelling for DMLS processed Inconel718 is very close and with negotiable difference for the conventional Inconel 718 material.

Nowadays, thermal condition and solute field are considered as the potential dominant factors controlling competitive grain growth during directional solidification process. However, the controlling modes and critical conditions of competitive grain growth have been drastically debated over the past two decades. In this work, thermal condition and solute field are combined to study the competitive grain growth in the converging case by experimental observation and numerical simulation of bicrystal samples. We find the competitive grain growth is controlled by the cooperative effect of thermal condition and solute field, and the controlling modes are related to the bicrystal misorientation between favorably and unfavorably oriented grains. When the unfavorably oriented grain is low misoriented, unfavorably oriented grain dominates grain selection, and the competitive grain growth performs as solute field domination. However, with the increase of unfavorably oriented grain's misorientation, the grain selection converts into favorably oriented grain domination, and the competitive grain growth changes to thermal condition domination. To explain these abnormal transformation phenomena, we propose a misorientation dependent thermal condition-solute field cooperative domination model and identify the critical conditions by a critical misorientation (θcm). According to dynamic equation of dendrite growth, we calculate the critical misorientation θcm to prove this model. The theoretical calculation results agree well with the experimental results.

Ni-based superalloys have various uses in the automotive, marine, and aerospace industries, owing to their oxidation and heat resistance. Machinability characteristics are obtained by actual machining trials, which is a time-consuming and costly technique. The current project's goal is to study and simulate nickel-based superalloy turning. The Inconel 718 material is considered in the study. The results were obtained using the ANSYS finite element (FE) tool. The machinability features obtained through FE simulation are compared to experimental results published in the literature. The Design of Experiments (DOE) tool is adopted in this study to design the experiments and analyze the cutting variables for the tool-tip temperature and cutting forces in turning of nickel-based superalloy.

Functionally grading material composition in laser powder bed fusion (LPBF) provides the potential for complex components with spatially tailored properties. Novel LPBF machine technology is described addressing a combination of the significant challenges for multiple material fabrication including grading in both the vertical and horizontal directions, clearing of unwanted powder compositions from previous layers, local processing parameter changes, grading of materials with disparate melting temperature and demonstration of complex geometries with graded composition. Multi-directional graded composition components are presented for titanium to tantalum and nickel-based superalloy 718 to copper-alloy GRCop-42, demonstrating the potential for tailored, location specific functionality.

WEDM commonly used in numerous industries, including as aerospace and aeronautics, to make superior-quality products at minimal cost and weight while maintaining high accuracy and precision. The prime concern of this research is to explore the different research work accomplished by different researchers on WEDM of Nickel based superalloys. It also revealed the use of machine learning algorithm and advance optimization techniques used to evaluate the WEDM of Nickel based superalloys. Furthermore, this research also examines the influence of various process parameters of WEDM of Nickle based super alloys on response variables. The Pulse-on time (Ton) and pulse-off time (Toff), peak current (IP), gap voltage (Vg), flushing pressure (PF), wire feed (WF), and wire tension (WT) are process parameters, can be used to improve performance indicators as Material Removal Rate (MRR), Tool Wear Rate (TWR), cutting speed (CS), & Surface Roughness (SR). The study also examines the direction of research in the field of WEDM in the future.

Application of Inconel 718 cylinders have been uprising with the up gradation of requirement of super alloys in this advance technological world. Although Inconel 718 possesses superior mechanical properties resulting into excellent performance in extreme environmental conditions but on the other hand make it difficult to machine and finish with available machining processes. This investigation has been used for the analysis of material removal of Inconel 718 cylinder using magnetic abrasive finishing process assisted with chemical etching. Finishing process has been conducted on 155 mm long and 5.7 mm thick Inconel 718 cylinder under specified investigating variable parameters such as duration of processing, work pole gap, abrasive weight percentage, and size of abrasive particles and concentration of etchant keeping certain factors as constant like rotational speed, etching temperature. Impact of processing variables represent through surface microstructure.

With the progression of technology, demands of super alloys have been increased dramatically. One such super alloy is Inconel-718. Although, it is having an extensive application in aerospace industries, steam power plants and oil and gas refineries due to possession of some stringent properties like hot hardness, resistance to wear, high strength. Possession of these rigorous characteristics makes it hard to finish this alloy with the conventional finishing processes almost impossible. So the present work focuses on the predominant role in Industries by giving an edge on surface finishing with more precision and accuracy. To establish the process experimental setup and magnetic tool have been created for chemical assisted magnetic abrasive finishing process to inspect the enhancement in internal roundness of Inconel-718 cylinder. The processing unit has been installed on the lathe machine. Experiments have been performed on Inconel-718 cylinders with 5.7 mm in thickness, 155 mm in length. The experiments have been planned by means of Response surface methodology. Results of the experiments have been analysed with the help of analysis of variance. It has been found that with the operating parameters having specified values like duration of processing-80 mins, Pole work gap-4 mm, and abrasive weight percentage-30%, size of abrasive particle- 40 µm and concentration of Etchant- 700 gm/litre internal roundness improvement percentage for Inconel 718 cylinder is achieved as 42.86%.

The combination of Ni3Al-based superalloy and S31042 steel could meet service requirement of different parts in nuclear power units. To broaden the application of Ni3Al-based alloy, vacuum diffusion bonding with S31042 austenitic heat-resistant steel was studied in this work. Different thicknesses (2, 5, 10, 15, 30 μm) of pure Ni interlayer were adopted to obtain a sound bonded joint. Result shows that the formed AlN phase in bonding process hindered atom diffusion and deteriorated joint properties. When interlayer thickness is 15 μm, the joint strength reached 96% of Ni3Al-based alloy, meanwhile elongation was 320% of Ni3Al-based alloy and 62% of S31042 alloy. The less AlN phase, uniform precipitation of γ′ phase and grain boundary intermigration behavior in two substrates contribute to the high strength and elongation of joint. The prevailing mechanism of the dissimilar joint bonded by 15 μm interlayer is ductile fracture. However, the fracture with low elongation showed the equiaxial pot and intergranular torn edges in other bonded samples due to the typical dual-phase structure in interlayer.

To facilitate the repairing and connecting processes for titanium superalloys, an advanced high-temperature resistant adhesive that can be converted to a composite of intermetallics and ceramics was prepared by modifying aluminum phosphate-based adhesive with various additives. The composition evolution of the adhesive, the structure changes in the bonding layer, the reaction process at interfaces and the fracture mode of joints are comprehensively studied to explore the bonding mechanism. The results showed that the chemical bonding based on the formation of TiSi and Ti5Si4 started to work at 600 °C, and became the crucial bonding mechanism at higher temperatures. A diffusion reaction layer with size up to 6 μm effectively alleviated the difference of composition and performance between alloy substrate and adhesive. From RT to 900 °C, the coefficient of thermal expansion (CTE) of adhesive matched well with that of alloy substrates, and the difference of their CTE was always lower than 2 × 10−6 k−1. The bonding strength reached ~16 MPa after pre-treatment at 900 °C without pressure, and remained over 13 MPa within the common operating temperature range (400–600 °C) of TC4 alloys. Without any pre-treatment, the adhesive could still provide above 5 MPa in range of RT-600 °C.

This paper aimed to design and optimize the structure of a thick thermal barrier coating by adding graded layers to achieve a balance between high thermal insulation capacity and durability. To this end, conventional TBC, conventional TTBC, and functionally graded TTBCs were deposited on the superalloy substrate by air plasma spraying. To determine the quality of the bond strength of the coatings, the bonding strength was measured. The durability of coatings was evaluated by isothermal oxidation and thermal shock tests. Then, at a temperature of 1000 °C, the thermal insulation capacity of the coatings was carried out. The microstructure of the coatings was characterized by a scanning electron microscope. The results showed that the thickness of the TGO layer formed on the bond coat in the conventional TBC and TTBC under the oxidation test at 1000 °C after 150 h was 2.79 and 2.11 μm, respectively, whereas, in the functionally graded TTBC samples, no continuous TGO layer was observed as a result of internal oxidation. The functionally graded TTBC presented higher durability than conventional TTBC due to improved bonding strength, thermal shock resistance, and the lack of a TGO layer at the bond/top coat interface. Also, the thermal insulation capacity of the functionally graded TTBC (with 1000 μm thickness of YSZ coating) was better than TTBC.

Hot cracking is a severe defect that occurs during the repair or manufacturing of directionally solidified superalloy by laser metal deposition. In this study, the hot cracking sensitivity of a directionally solidified superalloy, IC10 alloy, in the laser surface re-melting was evaluated and the effects of heat input on the hot cracking was investigated. It is found that the crack number density and the crack length density first increase and then decrease with the increase of heat input under studied conditions, and the crack-free re-melted sample can be achieved under the heat input of 50 J/mm. Meanwhile, the cracks display a typical characteristic of liquation cracks. The formation of liquid film can be ascribed to the liquation of γ-γ' eutectic phases, γ' phases and carbides. The liquation height and the maximum width of liquid channel increase with the increase of heat input, and they are used to describe the capability of liquid feeding. Furthermore, the driving force for crack initiation and propagation induced by thermomechanical conditions are also discussed. These findings provide technical support for achieving successful repair or manufacturing methods of the non-weldable directionally solidified superalloys.

Directed energy deposition has been used to repair superalloy components in aero engines and gas turbines. However, the microstructure and properties are generally inhomogeneous in components because of the different processing histories. Here, the microstructures and wear behavior of different zones (substrate, HAZ, and deposit) are investigated for the IC10 directionally solidified superalloy repaired by the directed energy deposition process. It is found that the microstructure of the deposited layers is strongly textured with a -fiber texture in the building direction, and the texture intensity is continuously increased along the building direction. Two kinds of γ′ phase (primary and secondary γ′ phase) can be found in the heat-affected zone (HAZ), and the average size of primary γ′ phase is smaller than that in the substrate due to liquation. In the deposit layers, the size of γ′ phase is much smaller than those in the substrate and the primary γ′ phase of HAZ; both size and the fraction of the γ′ phase decreases with the increase of building height. The wear rate of the substrate is the smallest, indicating the best wear resistance; while the wear rate of HAZ is the largest, indicating the worst wear resistance in the repaired sample. The wear rates in the deposit layers increase from the bottom to the top zones, showing a decreasing wear resistance. Abrasive wear is found to be the dominant wear mechanism of the repaired alloy, and the resistance to which is closely related to the fraction of γ′ phase in the microstructure. The understanding of the influence of microstructure on wear resistance allows for a more informed application of inhomogeneous superalloy components repaired by directed energy deposition in industry.

The hot components of a gas turbine are susceptible to damage in the high-temperature environment of turbine engine operation. Given that these components are relatively costly to manufacture, they are often repaired than replaced when damaged. Fusion welding is an economical method for repairing the damaged components of a gas turbine. This research examines the roles of heat input, pass number and layer number on the intergranular liquation cracking of the Inconel-939 (IN-939) precipitate nickel base superalloy during tungsten arc welding. Several specimens were welded with IN-625 filler alloy under argon gas by following the Taguchi method and an L8 array. These specimens were then characterized via metallographic investigations and hardness measurements. Results show that, during welding, the IN-939 heat-affected zone (HAZ) is acutely prone to cracks that propagate along the grain boundaries. Moreover, layer number, heat input and pass number significantly influence the microstructure and liquation cracking of HAZs with impact percentages of 72.37%, 22.17% and 4.84%, respectively.

Macrosegregation at the interface in Multi-Material (MM) structures fabricated by Selective Laser Melting (SLM) has evidenced deleterious effects on interfacial bonding reliability, but its fundamental understanding is less revealed. Therefore, this work vertically prepared MM parts of H13 tool steel and IN625 superalloy by SLM, as an example, to explore the interfacial macrosegregation mechanism. According to the mechanism, a liquid layer of unmixed H13 can exist at the molten pool bottom due to the no-slip boundary condition in fluid mechanics and solidifies as an H13 macrosegregation beach. Considering the higher liquidus temperature of H13 (1483 °C) than IN625 (1300 °C), a region cooler than the H13 solidification temperature exists within the IN625 molten pool; therefore, when the melted but unmixed H13 liquid is entrained into the cooler region by fluid flows, it can solidify quickly, forming H13 macrosegregation peninsulas/islands. The laser melting+remelting strategy developed to mitigate interfacial macrosegregation reveals its significant contribution to efficient migration of H13 into IN625 molten pools in a layer-by-layer manner, forming a broad interface. As the direct reflection of interfacial macrosegregation, the microstructure experiences a cellular-columnar-cellular transition across the H13/IN625 interface. Even a peninsula with H13 microstructural features is observed in an IN625 molten pool, verifying the rapid solidification of intruded H13 in IN625. Finally, the microhardness values with varying standard deviations across the interface successfully evaluate the interfacial macrosegregation on a macro-scale. These results can provide theoretical support to mitigate interfacial macrosegregation and benefit the development of MM structures with good interfacial bonding reliability by SLM.

Cobalt is an important strengthening element in superalloys, but its effect on 718 alloy family has rarely been studied and reported, and it is difficult to understand the controversy policy for controlling the Co content in the alloys such as 718 and 718 Plus. Therefore, the function of Co on the precipitation of 718 family alloy has been investigated in a reference alloy, in which 1.2 wt.% Al was added into the 718 base composition for raising the sensitivity of precipitation to the composition variation. It was found that the Co additions favored the intergranular Laves precipitation and refined the grains. The thermodynamic calculation showed that the range of the precipitation temperature was enlarged by the Co additions, and the peak temperature of the Laves precipitation was located around 980 °C. Unexpectedly, the Co addition increased the volume fraction of γ′ while decreased the volume fraction of γ″ precipitations. It was revealed by analyzing the distribution of elements in the microstructures of the as cast experimental alloys that the Co addition increased the solubility of Nb while hardly changed the solubility of Al in the γ matrix. It is apparent that the Co addition influenced the precipitations of γ′-Ni3Al and γ″-Ni3Nb by affecting the solubility of Al and Nb in the γ matrix and the precipitates of Nb-rich and Al-poor Laves phase. Accordingly, the controlling policy of Co content in alloys 718 and 718 Plus is discussed in the text.

Inconel 718 (IN-718) is a nickel-based alloy, mostly used in the aeroengine applications due to its good mechanical strength and resistance to corrosion. However, it is amenable to alloying segregation and Laves phase growth in fusion zone (FZ) which severely deteriorates the strength and corrosion resistance of IN-718 joints. To overcome this problem, InterPulsed TIG (IP-TIG) welding process, characterized by high frequency current pulsation and arc constriction, was attempted to join thin sheets of IN-718 alloy. The 3D graphs of response surfaces were built to establish the optimized welding parameters for maximizing the joint strength. The parametric mathematical equation was constructed to predict the strength of IN-718 joints. The mathematical equation was also built to predict the tensile strength from Laves phase. The potentiodynamic corrosion test was done in a 3.56 wt.% NaCl solution for the selected joints to determine the corrosion behavior of IN-718 joints. The IP-TIG welded IN-718 joints exhibited 99.20% of base metal strength and superior corrosion resistance at optimized condition of welding parameters. This refers to the refining of FZ dendritic structure which aids in minimizing the Laves phase. The IN-718 joints developed using optimized IP-TIG parameters exhibited 22–32% higher strength and superior corrosion resistance than TIG welded IN-718 joints and comparable to EBW and LBW IN-718 joints.

Fusion welding of nickel-based superalloys with a total Al and Ti content of more than 6% has always been challenging. The reason for this is the occurrence of solidification and liquation cracks during welding. Investigating the mechanisms of formation of these two types of cracks can increase the theoretical and practical insight necessary to achieve a welded alloy without cracks. The objective of this research was to look at the link between solidification and liquidation fractures in Nd:YAG pulsed-laser welded GTD-111 nickel-base superalloy joints. The reason for choosing the pulsed-laser method is the mechanism of continuous welding of the pulses and the creation of separate microstructural zones due to the high liquation and solidification speed. Liquation cracks in the partially melted zone (PMZ) of base metal were shown to be significantly associated with solidification cracks in the weld metal, according to the findings. Liquation cracks in PMZ act as a strong place to create and extend solidification cracks. It was also observed that with increasing pulse frequency, the tendency to form both types of cracks decreases due to the increased tendency to back-filling.

Inconel 738 LC samples were fabricated using laser powder bed fusion under continuous-wave and pulsed-wave modes. Microstructure, surface quality and mechanical properties were compared to evaluate the printing quality between these 2 laser beam modes. The results show that the application of pulsed wave could effectively eliminate cracking in the as-fabricated sample, despite 0.046% porosity generated. Further microstructure analysis revealed that the refinement of grains by the pulsed-wave laser beam was the main contributor in eliminating the cracks. And this refinement was ascribed to the higher cooling rate under the discontinuous radiation of laser beam proofed by the numerical simulation. And the pore formation was related to Rayleigh instability and residual bubbles in the sample under the pulsed-wave mode, while pores were less detrimental to the mechanical properties than cracks. Therefore, the part under the pulsed-wave mode exhibited superior mechanical performance compared to that under the continuous-wave mode.

A novel low-density nickel-based single-crystal superalloy was prepared and the effect of solution treatment on the creep deformation mechanism was systematically investigated. The results reveal that the creep life increases with the increase of solution treatment time, which can be ascribed to microstructural homogenization. However, when the solution treatment time exceeds a threshold limit, the relative proportion of undesirable defects significantly increases, which accelerates the failure and compromises the creep life. The homogenization of the composition leads to the precipitation of a more homogenized γ′ phase and, in turn, results in a more uniform and dense dislocation network, thus hindering the dislocation movement and improving the creep life. The undesirable defects may lead to the stress concentration and weaken the effect of the dislocation network, thus accelerating the creep process and the dislocation are more likely to shear into the γ′ phase. In general, the current study provides guidance for selecting a more reasonable solution treatment time to improve the creep strength.