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Field exposure for 5000h combined with weight gain measurement and morphology/composition analysis of oxide film were conducted to examine high temperature oxidation behavior of GH4169 and In617 nickel-based super alloys in SOFC system environment. The In617 alloy has been found to demonstrate excellent oxidation resistance in the SOFC environment because of its high Ni content. An integral and dense NiO oxide film can be developed in the outer layer with a continuous Cr 2 O 3 oxide film formed in inner layer. It indicates that NiO played a crucial role in the formation of an integral and dense oxide film. In contrast, GH4169 alloy failed to develop a continuous and dense oxide film probably due to high Fe content, in which case Fe-dopped chromium oxide (Fe,Cr) 2 O 3 was formed. As a result, the oxide film was loose and porous, leading to relatively poor oxidation resistance. • NiO played a crucial role in the formation of an integral and dense oxide film. • Fe is harmfull for oxidation resistance of nickel-based alloy. • The dopping of Fe in Cr 2 O 3 could result in loose and porous structure of the chromia. [ABSTRACT FROM AUTHOR]

Thin-walled plates are extensively used in the aerospace industry due to their lightweight properties. However, their low rigidity makes them susceptible to deformation and chatter during traditional machining processes, which increases machining complexity and reduces both quality and efficiency. Therefore, this paper proposes an electrochemical machining method involving the use of a rotating body with complex structured windows as the cathode, enabling pure rolling motion on the workpiece surface. Through the action of an electrolyte and an external power supply, the material is removed from the machined surface layer by layer in the form of ions, thus facilitating the manufacture of complex thin-walled plates. Based on the principles of this method, a kinematics model was established to determine the relative position relationship between the cathode and anode during machining. Additionally, an electric field model and a material dissolution model were established to analyze the electric potential distribution and simulate the process of material removal. The simulation results indicate that the trajectory of the cathode windows forms a "V" shape, with the taper angle being independent of the window angle, but decreasing as the cathode diameter increases. Furthermore, it was observed that the use of an insulation coating can effectively reduce stray corrosion on convex structures of the workpiece surface. Based on these simulation results, electrochemical machining experiments were conducted on nickel-based GH4169 plates measuring 600 × 96 mm with a thickness of 3 mm. The results demonstrate that the average thickness of machined workpieces is 1.1 mm, with a thickness error of 0.12 mm. Meanwhile, the surface roughness Ra is 0.778 μm, with a material removal rate reaching 1.01 cm3/min (8271.9 mg/min). Therefore, electrochemical machining proves to be an effective method for manufacturing thin-walled plates. [ABSTRACT FROM AUTHOR]

The effect of six processes including M (milling), G (grinding), MMP (milling and manual polishing), GMP (grinding and manual polishing), MCP (milling and CNC polishing), GCP (grinding and CNC polishing) on surface integrity and fatigue life of GH4169 are studied in this paper. The results show that grinding produce a larger degree of hardening compared to milling, and residual stress of grinding surface and milling surface are respectively compressive and tensile. Polishing can significantly reduce the surface roughness formed by the previous process. Surface tensile residual stress of milling is converted into compressive stress after polishing, while the degree of hardening and residual stress of grinding surface has no significant change after polishing. The roughness, residual stress, and hardening degree of the manual polishing and CNC polishing are similar, but there are many micro surface defects in the manual polishing surface. The fatigue life of GCP, MCP, GMP, and MMP gradually decreases. Therefore, the integration process of GCP can produce better surface integrity including surface roughness, hardening degree, and residual stress distribution. [ABSTRACT FROM AUTHOR]

Direct current (DC) and pulsed DC tungsten inert gas (TIG) additive manufacturing processes were employed to fabricate GH4169 high-temperature alloy specimens. Upon comparing and analysing the two additive manufacturing methods, the evolution of microstructure and mechanical properties of the additively manufactured specimens were discussed. It provided a useful reference for the engineering application of pulsed DC TIG technology. The results showed that the overall forming process of the specimen was relatively stable under the DC TIG additive manufacturing and pulsed DC TIG additive manufacturing processes. The aspect ratio of the deposited layer of the pulsed DC-deposited specimen was relatively low, and the deposited layer of the pulsed DC specimen became flatter, which was conducive to maintaining the stability of the molten pool during the deposition process and improving forming accuracy. The microstructure distribution of the deposited layer from bottom to top was relatively uneven, with columnar dendrites in the bottom layer, cellular crystals in the middle layer, and equiaxed crystals in the top layer. Compared with the DC TIG additive manufacturing of GH4169 high-temperature alloy specimens, the Laves phase of the pulsed DC specimens was significantly reduced, which improved the plasticity and brittleness of the material. [ABSTRACT FROM AUTHOR]

Enhancing the high-temperature oxidation resistance of nickel-based alloys is critical for expanding their industrial applications. Herein, we report a novel strategy for enhancing the high-temperature oxidation resistance of the GH4169 nickel-based alloy by adding small amounts of 304L stainless steel using selective laser melting technology. The oxidation property of GH4169 with various 304L additions (2 wt.%, 4 wt.%, and 6 wt.%) at 900 °C for 45 h was investigated. Results show that the addition of 304L significantly improves the oxidation resistance of GH4169. The thickness of the oxide film and the intergranular oxidation depth of GH4169 with 6 wt.% 304L added are reduced by 61% and 69%, respectively. The addition of 304L increases Cr and decreases Ni in the matrix, which facilitates the formation of a more compact oxide film. The Nb in Laves phase will be increased with 304L addition, which effectively inhibits oxygen penetration and metallic element diffusion.

To effectively reduce residual stresses in GH4169 workpieces, thus enhancing fatigue strength and operational lifespan, this study investigates the influence of spray cooling parameters on surface residual stresses during GH4169 turning in spray cooling conditions, utilizing both simulation and experimental approaches. A simulation model of residual stresses was established using finite element analysis when GH4169 was cut in spray cooling. The effects of spray pressure and flow rate on residual tensile stresses were analyzed. The analysis reveals that with increasing spray pressure, residual tensile stresses show a decreasing trend, gradually stabilizing. Conversely, with an increasing spray flow rate, residual tensile stresses initially decrease and then increase. The turning experiments of GH4169 were conducted under different spray parameters. After the experiment, the workpiece was sectioned and analyzed for residual stresses using X-ray diffraction instrumentation. The value residual stress measured closely matched those of simulation, with a relative error within 6%, validating the accuracy of the simulation model and confirming the appropriateness of parameter settings. These results contribute to the further promotion of spray cooling technology and facilitate the rational selection of spray parameters. [ABSTRACT FROM AUTHOR]

abstractHeat shield is one of the important parts in aero engine, its function is to effectively prevent engine overheating. Under normal operation, the heat shield is subjected to high temperature from the combustion chamber and pressure pulsations inside and outside, and the phase difference of this pulsation pressure results in a very harsh working environment. Based on the experimental results, the approximate equation of the pulsating pressure is established, and the finite element method (FEM) is used to simulate the pulsating pressure. Meanwhile, the mechanical quantities such as thermal stress and mechanical stress are considered comprehensively. Linear elastic fracture mechanics (LEFM), Paris and Forman-Newman-de Koning (FNK) models were employed during the study in order to calculate the fatigue crack propagation life (FCPL) of the heat shield. The results show that the heat shield has an infinite lifetime at a phase difference of zero. As the phase difference increases, the FCPL and critical crack length (CCL) tend to decrease nonlinearly. When the phase difference is π, the FCPL and CCL are the shortest, which are only 3% and 17.1% of those at π/6. This study can provide a reference for the improvement and overhaul of heat shields. [ABSTRACT FROM AUTHOR]

A high entropy interlayer (TiZrHfNb)95Al5 was successfully designed for vacuum diffusion bonding of GH4169 superalloy to Ti2AlNb alloy. The relationships between grain size, grain boundary, lattice mismatch and microhardness, elastic modulus, shear strength and fracture behaviors were revealed. The typical microstructure was Ti2AlNb/B2/Solid solution/(Ti, Zr, Hf)2(Ni, Nb)+(Ti, Zr, Hf)(Ni, Nb) + Solid solution/(Ti, Zr, Hf)(Ni, Nb) + (Cr, Ni, Fe)ss/(Cr, Ni, Fe)ss/Cr-rich(Cr, Ni, Fe)ss/Ni-rich(Cr, Ni, Fe)ss/GH4169. With the holding time increased, the shear strength overall increased and decreased sharply, and the highest shear strength reached 384 MPa at 980 °C for 90 min. The microstructure had anisotropic crystal orientation, and the joints of Zone Ш for 90 min consisted of 92.08 % HAGBs and 7.92 % LAGBs. The residual strains and stresses decreased when the holding time increased. Meanwhile, recrystallisation appeared in Zone Ш, and the increase in the recrystallisation rate led to grain refinement. The lattice mismatch between (Ti, Zr, Hf)(Ni, Nb) and (Cr, Ni, Fe)ss phases was 25.05 %, indicating that the interface was non-coherent, and (Ti, Zr, Hf)(Ni, Nb)+(Cr, Ni, Fe)ss phases were located at an elastic modulus dramatically changed interface. Thus, the cracks easily formed in this interface and led to joint fracture. Moreover, the fracture mechanism was brittle fracture.

TCGH(TC4+GH4169)composite material was prepared by selective laser melting(SLM). The optimum forming process parameters of TCGH composite material were investigated, and the microstructure and mechanical properties of as-deposited samples and heat-treated samples were studied. The results show that the optimum process parameters for fabrication of TCGH composite material are scanning speed of 900 mm/s with laser power of 150 W, and density higher than 99.5%. The addition of GH4169 powder changes the solid phase transformation behavior of TC4 titanium alloy material, and the as-deposited structure shows obvious high temperature solidification characteristics, which makes the forming characteristics of progressive scanning overlap and layer-by-layer scanning accumulation obvious. The original coarse columnar β grain size along the printing direction is significantly reduced, and the tensile strength of the composite is improved. Compared with the as-deposited sample, the microstructure of the heat-treated sample is transformed into a near-equiaxed structure. At the same time, with the increase of heat treatment temperature, the dissolution of the second phase leads to the dominant solid solution strengthening effect of the composite material, which improves the tensile strength and plasticity of the composite material.

GH3536 and GH4169 nickel-based superalloys are widely used in aerospace engines and other hot-end components. In this paper，GH3536 and GH4169 alloy samples were fabricated by optimizing the process parameters using selective laser melting（SLM），the defect characteristics and microstructure of two alloys，as well as the effects of different homogenization temperatures and holding times on microstructure evolution，average grain size，and properties of two alloys were studied. The defect characteristics and microstructure were investigated by OM，SEM，and EDS, et al. The Vickers hardness meter was used to test the alloy’s microhardness. The results indicate that the as-built GH3536 alloy exhibits more defects，including pores，cracks，and lack of fusion， while only pores are present in as-built GH4169 alloy. The melt pool of alloy is eliminated by homogenization treatment，and the grains grow into equiaxed grains. M23C6 are found to distribute within grain boundaries and grain interiors of GH3536 alloy，while NbC are found to distribute within grain boundaries and grain interiors of GH4169 alloy，and the amount of precipitates is significantly reduced with the increase of homogenization temperature. The average grain size of GH3536 alloy is increased by 106.8% from 48.5 μm at 1130 ℃/1 h to 100.9 μm at 1250 ℃/4 h . The grain size of GH4169 alloy is increased by 53.3% from 57 μm at 1080 ℃/1 h to 87.4 μm at 1200 ℃/4 h.The homogenization treatment of GH3536 alloy and GH4169 alloy results in a significant decrease in microhardness of the former，from 262HV to 180-190HV，while the latter shows a significant increase，from 313HV to 430-450HV.

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Electron beam welding of GH4169 and Ni is required in the manufacture of the regenerative cooling system of the liquid rocket motor. The thermoelectric effect is observed during the welding of dissimilar metals; however, there has been a lack of investigation into the influence of this effect on electron beam welding joint formation and its dependence on test plate thickness. The thermoelectric effect of electron beam welding between GH4169 and Ni with varying thicknesses, as well as the influence of induced magnetic fields on electron beam trajectories, are investigated through the establishment of a numerical model incorporating thermal-electric-magnetic coupling.The results show that when the test plate increases from 2.5 mm to 10 mm the peak current density increases from 5.1 × 106 A/m2 to 7.6 × 106 A/m2, and the maximum magnetic flux density increases from 1.49× 10−2 T to 1.77 × 10−2 T. The increase in magnetic flux density results in a greater displacement of the electron beam spot away from the interface between the two materials, thereby causing incomplete fusion defects in the joints. This study elucidates the fundamental physical principles underlying the occurrence of incomplete fusion defects in electron beam welding joints, thereby furnishing essential theoretical underpinnings for enhancing the quality of dissimilar metal electron beam weld joints.

GH4169 nickel-based high-temperature alloy demonstrates excellent mechanical, chemical, thermal shock, and mechanical load resistance properties. However, it is typically a difficult-to-machine material. Ultrasonic vibration–assisted milling can effectively solve the machining challenges of GH4169 nickel-based high-temperature alloy and improve surface integrity. Herein, the motion model of the tool-tip under ultrasonic vibration assistance is established. The tool-tip motion trajectory and chip separation law are analyzed. The effect of ultrasonic vibration on surface integrity is investigated through ultrasonic vibration–assisted milling experiments. The results show that residual surface stress stimulates at high milling speed, depth of cut, and feed rate, while it progressively decreases with ultrasonic amplitude. The machined surface hardening enhances with the addition of ultrasonic amplitude. The machined surface roughness increases with the growth of milling speed, feed rate, and ultrasonic amplitude, and decreases with the rise of cutting surface roughness increases with the addition of milling speed, feed rate, and ultrasonic amplitude, and falls with the rise of cutting depth. [ABSTRACT FROM AUTHOR]

In this study, the wear resistance of micro-textured tools was explored. Micro-textured tools with different morphologies were used in turning GH4169 during spray cooling. The tool wear on the rake face of the different micro-texture morphologies was investigated through simulation and experiments. Firstly, based on the existing research on bionics, micro-textures with five different morphologies were designed on the rake face of carbide tools. A simulation model of cutting GH4169 during spray cooling was established, and the tools with designed micro-textures were used in it. The influence of the different micro-texture morphologies on the tool wear was analyzed. Secondly, the designed micro-textured tools with five different morphologies were produced using a femtosecond laser. Cutting experiments were conducted using the micro-textured tools during spray cooling. The wear area of the rake face was measured based on the infinitesimal method, and the optimal morphology with the best anti-wear ability was obtained. This study provides technical support for the design and development of micro-textured tools with an improved cutting performance, and contribute to the promotion and application of micro-textured tools. [ABSTRACT FROM AUTHOR]

Nickel-based superalloys (GH4169) are a typical difficult-to-machine material with poor thermal conductivity and severe work hardening. They are also prone to poor surface quality, severe tool wear, and poor machinability, which affect their performance. In this paper, an experimental study of GH4169 ultrasonic elliptical vibratory ultra-precision cutting was carried out. The experimental results show that ultrasonic elliptical vibratory cutting (UEVC) significantly reduces surface roughness and improves surface quality compared to conventional cutting (CC). The effects of cutting parameters such as cutting speed, feed rate, cutting depth, ultrasonic amplitude, and tool nose radius on the surface roughness of GH4169 workpieces were further investigated in UEVC. Based on the analysis of the experimental data, the optimal combination of parameters for GH4169 ultrasonic elliptical vibration ultra-precision cutting was determined: cutting speed of 3 m/min, feed rate of 16 μm/rev, cutting depth of 2 μm, ultrasonic amplitude of Ay = 3.0 μm, Az = 0.8 μm, and a tool nose radius of 0.8 mm. This parameter combination improves the machining quality of GH4169 and provides a valuable reference for the subsequent development of ultrasonic elliptical vibratory cutting for other difficult-to-machine materials.

Cross wedge rolling process provides a new way with short production chain and precise control for high-performance blade preforming used in aeroengine, but the issue of central damage needs to be paid attention and investigated. Therefore, this paper aims to understand the formation mechanism of central damage on CWR of GH4169 alloy. The uniaxial hot tensile test and CWR experiments were carried out to explore the high-temperature deformation behavior of GH4169 alloy, as well as the central damage of GH4169 alloy CWR process. Moreover, the finite element model was established and used to analyze the evolution of stress and strain at different position. The results showed that central part of the workpiece is in the state of higher stress triaxiality η, which is easy to cause damage. And the micro-holes in the center of workpiece mainly nucleated around the detached NbC carbide. Meanwhile, the first principal stress σ 1 and the maximum shear stress τ max are the dominant factors which affect the central damage. Therefore, a novel damage criterion suitable for CWR of GH4169 alloy was developed with considering the effect of stress triaxiality η and the sensitivities of deformation temperature and strain rate on the central damage evolution. In addition, initial forming temperature T0 is the most important factor affecting the central damage, and the maximum area reduction φ and rolling speed n are related to the initial deformation temperature T0. And in order to inhibit the damage, the initial forming temperature should be controlled below 1020℃, and the area reduction and rolling speed should not be higher than 55% and 10r/min, respectively. [ABSTRACT FROM AUTHOR]

In the industrial cutting of alloy GH4169, high cutting force and temperature have always been important factors affecting machining quality and efficiency. In view of this, this study aims to improve the cutting performance of the alloy GH4169, and special attention was given to the changes in cutting force and temperatures under different parameters with ceramic turning experiments, and the optimal cutting parameters were determined based on orthogonal experimental design. The work findings indicate that the resultant force initially increased and then declined with the increase of cutting speed, while it showed increasing trend with the increased of both feed rate and depth of cut. Meanwhile, cutting temperature was positive related to both the cutting speed, feed rate and depth of cut. Based on the range analysis and variance analysis, the depth of cut had the greatest impact on the resultant force and cutting temperature, followed by cutting speed and feed rate, and only the depth of cut significantly affected the changes in resultant force and cutting temperature. Finally, an optimal cutting condition with the lowest resultant force and temperature was determined, where cutting speed is 150 m/min, feed rate is 0.05 mm/r, and depth of cut is 0.1 mm. It is proposed to be used in the industrial machining of alloys GH4169 for the grater product quality and benefits. [ABSTRACT FROM AUTHOR]

The corrosion behavior of Ni-based superalloy GH4169 in the marine environment was simulated and investigated by the alternation of intermediate temperature salt spraying and the marine atmosphere. The results suggested that promoted corrosion caused by intermediate temperature NaCl spraying was primary and severe in the form of an over-parabolic weight gain while a weight loss in marine atmosphere. After long-term exposure, corrosion further invaded the matrix alloy and resulted in severe internal corrosion. The corrosion preferentially occurred at the vertices of NaCl particles and led to the consumption of Cr2O3. A complex mixture of Cr2O3, NaCrO2, and Na2CrO4 was thus caused and evolved under the “active oxidation” mechanism. Accordingly, actual corrosion behavior of aircraft engine blades serviced and parked in the marine environment was revealed in the work.

This study explores the performance of micro-textured tools when cutting GH4169 during spray cooling. First, the morphologies of the micro-textures were selected according to the simulation and experiments. Secondly, cutting experiments were carried out during spray cooling. As appropriate for each experiment, regression models of cutting force, cutting temperature, or tool wear area were established, and variance analysis was conducted. The cutting force, cutting temperature, and tool wear area functions were obtained from the respective regression models. Based on these functions, the micro-texture parameters were optimized using the response surface method with the cutting force, cutting temperature, and rake face wear area as the objectives. Finally, a full factor experiment on the micro-texture parameters was designed using Minitab, and cutting experiments were conducted using micro-textured tools with these parameters. Taking a relatively low cutting force, cutting temperature, and tool wear as the objectives, a genetic algorithm multi-objective optimization model for the micro-texture parameters of the tools was established, and the model was solved using the NSGA-II algorithm to obtain a Pareto solution set and micro-texture parameters with a good, comprehensive cutting performance. The micro-texture morphology and parameters obtained in this study can also be used for cutting other high-temperature alloy materials with similar properties to GH4169. This research method can also be used to optimize micro-textured tools for cutting other materials. [ABSTRACT FROM AUTHOR]

The GH4169 superalloy has the characteristics of high strength, strong thermal stability, large specific heat capacity, small thermal conductivity, etc., but it is also a typical hard-to-cut material. When cutting this material with ordinary cutting tools, the cutting force is large, and the cutting temperature is high, which leads to severe tool wear and short service life. In order to improve the performance of tools when cutting GH4169, reduce the cutting temperature, and extend the service life of the tool, micro-textured tools were used to cut GH4169 in spray cooling. The effects of micro-texture morphology and dimensional parameters on cutting temperature were analyzed. Firstly, tools with micro-textures of five different morphologies were designed near the nose on the rake face of the cemented carbide tools. The three-dimensional cutting models of the micro-textured tools with different morphologies were established by using ABAQUS, and a simulation analysis was carried out. Compared with the non-textured tools, the micro-texture morphology with the lowest cutting temperature was selected according to the simulation results of the cutting temperature. Secondly, based on the optimized morphology, tools with micro-textures of different size parameters were designed. When cutting GH4169, the cutting temperature of the tools was simulated and analyzed, and the size parameters of the micro-textured tools with the lowest cutting temperature were selected as well. Finally, the designed micro-textured tools were processed and applied in cutting experiments. The simulation model was verified in the experiments, and the influence of size parameters of micro-textures on the cutting temperature was analyzed. This paper provides a theoretical reference and basis for cutting GH4169 and the design and application of micro-textured tools. [ABSTRACT FROM AUTHOR]

This research delves into the hot deformation characteristics of as-cast GH4169 superalloy, incorporating a substantial proportion of recycled material. Through conducted hot compression tests across a range of temperatures (900–1100 °C) and strain rates (0.005–1 s−1), the study aims to elucidate the deformation behavior under these conditions. By integrating microstructural observations, the optimal hot processing window has been determined, and the factors influencing the thermal activation energy have been thoroughly discussed. The intrinsic model and the dynamic recrystallization volume fraction model have been developed by analyzing the stress-strain curves of the as-cast GH4169 alloy. The flow stresses exhibit a systematic evolution with changes in deformation temperature and strain rate, highlighting significant work-hardening characteristics. The thermal processing maps reveal that a strain rate of 0.005–0.011 s−1 and a deformation temperature of 1030 °C to 1100 °C constitute the optimal processing interval for the as-cast GH4169 alloy. This interval is found to be more confined compared to that of the homogenized alloy. The activation energy for hot deformation across different states of the GH4169 alloy is ranked as follows: homogenized state, forged state, forged solid solution state, and as-cast unhomogenized state. The results of this study not only provide a theoretical basis for the application of as-cast GH4169 alloy in the actual forging process of billets, but also provide scientific guidance for the optimization of production costs in the future. [Display omitted] • Dendrite and recrystallization evolution for as-cast GH4169 under hot deformation were established, explaining the mechanism. • The activation energies of GH4169 alloy in different states were quantified and analyzed for their differences. • GH4169 alloy's hot deformation activation energy ranks: homogenized, forged, forged solid solution, as-cast unhomogenized state. • Constitutive equations for GH4169 in the initial dendrite state were established, determining its optimal processing window. [ABSTRACT FROM AUTHOR]

The GH4169 Ni-based superalloy is prepared by wire arc additive manufacturing and the sizes and morphologies of Laves phases under different heat treatment strategies are obtained to further investigate the influence of residual Laves phases on the tensile properties of the superalloy. After the solution treated at a higher 1150 °C and followed by aging, the Laves phase is completely dissolved, with limited δ phase with varying sizes distributed at the grain boundaries. While for lower 1020 °C solid solution heat treatment temperature, the Laves phase in the sample changes from chain-like to particle-like shapes by partially dissolving, and the needle-like δ phase exists around the particle-like Laves phase. Such residual "Laves + δ" impede high-temperature tensile crack propagation, significantly enhancing plasticity. This mechanism makes the lower temperature solid solution treated sample exhibit similar tensile stress but ∼2 times of elongation when compared to the sample treated by higher solid solution. • Novel Heat treatment strategy to benefit from dense Laves phase in WAAM GH4169. • Lower solutionized treatment forms bulk Laves phase surrounded by needle δ phase. • Laves/δ structure rises the plasticity without lower the strength at high temperature. • Micro-cracks initiate inside residual Laves phase and inhibit by surrounding δ phase. [ABSTRACT FROM AUTHOR]

In this study, the wear resistance of micro-textured tools was explored. Micro-textured tools with different morphologies were used in turning GH4169 during spray cooling. The tool wear on the rake face of the different micro-texture morphologies was investigated through simulation and experiments. Firstly, based on the existing research on bionics, micro-textures with five different morphologies were designed on the rake face of carbide tools. A simulation model of cutting GH4169 during spray cooling was established, and the tools with designed micro-textures were used in it. The influence of the different micro-texture morphologies on the tool wear was analyzed. Secondly, the designed micro-textured tools with five different morphologies were produced using a femtosecond laser. Cutting experiments were conducted using the micro-textured tools during spray cooling. The wear area of the rake face was measured based on the infinitesimal method, and the optimal morphology with the best anti-wear ability was obtained. This study provides technical support for the design and development of micro-textured tools with an improved cutting performance, and contribute to the promotion and application of micro-textured tools.

GH4169 superalloy and Si3N4 ceramics were vacuum-brazed with AgCuTi+Cu foam composite filler. The effect of brazing temperature on the microstructure and mechanical properties of the GH4169/Si3N4 joint was studied. The results show that the interface microstructure of the GH4169/Si3N4 joint is the GH4169 superalloy/TiCu+Ti2Ni+TiCu2+Ag(s, s)+TiCu4+Cu(s, s)+TiN+Ti5Si3/Si3N4 ceramics. With the increase in brazing temperature, the element diffusion between the base metal and the brazing filler intensifies, and the interfacial reaction layer thickens, which is conducive to the improvement of shear strength. At 850 °C, the maximum shear strength of the joint is 196.85 MPa. After further increases in the brazing temperature, Cu foam dissolves completely, and the Ti-Cu intermetallic compounds increase, which is harmful to the shear strength due to the increases in the brittle phase. However, when the brazing temperature reaches 910 °C, the shear strength of the brazing joint slightly increases under the combined effect of the Ti-Cu intermetallic compounds and the thickness of the reaction layer. [ABSTRACT FROM AUTHOR]

Ceramic cubic boron nitride (CBN) wheel is widely used in grinding field for its superior grinding performance. The random grain orientation of CBN grinding wheel with ceramic bond affects its grinding performance to a certain extent. In this paper, magnetically controlled ceramic CBN grinding wheel was prepared by magnetic field and sintering process. In order to improve the magnetic conductivity of the abrasive grains, nickel-plated CBN was used to replace the abrasive particles. It was found that the direction of the abrasive particles could be effectively controlled by adjusting the strength and properties of the magnetic field, so that the abrasive particles presented a chain distribution under the magnetic field. The experimental results showed that the nickel-plated CBN abrasive grains have good orientation and chain distribution in the bond power by using alternating magnetic field. Finally, experiments were carried out to study the grinding of GH4169 with magnetically controlled ceramic CBN grinding wheel, and the experimental results were compared with common ceramic CBN grinding wheel. It was confirmed that the grinding temperature and grinding force of GH4169 with magnetically controlled ceramic CBN grinding wheel were slightly lower than that of common grinding wheel, and the grinding surface quality is better than that of ordinary grinding wheel. In this paper, the method of preparing ceramic CBN grinding wheel with controllable grain orientation was established, and the system of evaluating the grinding wheel performance was constructed. It enriched the preparation process of ceramic bond CBN grinding wheel, and would have important significance for further expanding the application of ceramic CBN grinding wheel. [ABSTRACT FROM AUTHOR]

The widely used GH4169 alloy can meet various application through different heat treatment methods. In order to investigate the effect of heat treatment method on crack resistance at elevated temperature, fatigue crack growth tests of direct aging heat-treated GH4169 alloy (DA-GH4169) and standard heat-treated GH4169 alloy (SHT-GH4169) were performed at 650 °C in air. Under 10 Hz sinusoidal waveform, the fatigue crack growth rate of DA-GH4169 is slightly higher than that of SHT-GH4169 at low- Δ K Paris regime. The rates become close as Δ K increased. Under 0.5 Hz triangular waveform, the fatigue crack growth rate of DA-GH4169 is always higher than that of SHT-GH4169 in the tested Δ K scope. The change of fracture morphology from intergranular to transgranular in the Paris regime was observed for two GH4169 alloys. It is attributed to the interaction of cyclic plastic damage and dynamic embrittlement at crack tip, which is influenced by load, microstructure and frequency. Completely different propagation modes were found in the near-threshold region. While intergranular δ phases mildly inhibit grain boundary oxidation in the Paris regime, the transgranular propagation induced by intergranular δ phases in the near-threshold region is responsible for lower threshold. [ABSTRACT FROM AUTHOR]

The hot deformation behaviour of the GH4169 alloy in two different initial states (homogeneous and mixed-crystal states) was investigated by performing isothermal compression tests at different strain rates (0.01-1 s−1) and deformation temperatures (1050-1150 °C). Hot-working diagrams were established for both alloy types, and the microstructural evolution in both alloy types during hot deformation was analysed to determine the corresponding deformation mechanism. The experimental results showed that the peak stress of the homogeneous alloy was lower than that of the mixed-crystal alloy for the same temperature and strain rate. Based on the processing maps, the flow instability domain of the homogeneous alloy exceeded that of the mixed-crystal alloy. The optimal processing parameters of the homogeneous alloy were 0.01-0.1 s−1/1050-1100 °C, and 0.01-0.1 s−1/1050-1080 °C (at a lower strain state) or 1100-1150 °C (at a higher strain state) was optimal for the mixed-crystal alloy. Microstructural analysis revealed that the differences in the hot deformation behaviour of the homogeneous and mixed-crystal alloys were caused by the different initial grain sizes and dynamic recrystallization (DRX) mechanisms. The main DRX nucleation method of the homogeneous alloy was discontinuous DRX, whereas that of the mixed-crystal alloy was continuous DRX and discontinuous DRX. [ABSTRACT FROM AUTHOR]

Ni-based superalloy GH4169 is widely demanded in the aerospace industry because of its excellent properties. However, the cutting of GH4169 at normal temperature has many challenges, such as tool wear, machining accuracy, and production efficiency. Cryogenic cutting has been an advanced method in assisting material removal machining. This paper focused on the cryogenic cutting performance of GH4169 at different initial temperatures, namely, 20 °C, −30 °C, −80 °C, and –130 °C. Firstly, the cryogenic mechanical properties of GH4169 were obtained by the Hopkinson pressure bar test at speed of 12 m/s and 18 m/s. The obtained data was used to analyze the cryogenic cutting performance of GH4169 at evaluated temperatures. The single factor milling experiments of GH4169 were carried out at room temperature and evaluated cryogenic levels, and the cutting performance in terms of cutting chips, cutting forces, and tool wear was investigated. The results showed that cryogenic cooling at −130 °C could increase the shear yield strength of the GH4169 by around 19.80% and the length of the cutting chip decreased monotonically by 53.45% compared with the length at room temperature. However, the cutting forces were not monotonically decreased. The cutting forces increased with the decrease of temperature when the initial temperature varied from 20 to −80 °C. However, when the initial temperature further dropped to –130 °C, the cutting forces were reduced by 30.60% for Fx, 24.02% for Fy, and 16.15% for Fz, respectively. Similarly, tool wear at the rake face and flank face is the most severe at –80 °C and the least at –130 °C. The average wear bandwidth at room temperature is 92.06 μm and decreases to 83.358 μm at –130 °C, which is reduced by 9.45%. [ABSTRACT FROM AUTHOR]

This study explores the performance of micro-textured tools when cutting GH4169 during spray cooling. First, the morphologies of the micro-textures were selected according to the simulation and experiments. Secondly, cutting experiments were carried out during spray cooling. As appropriate for each experiment, regression models of cutting force, cutting temperature, or tool wear area were established, and variance analysis was conducted. The cutting force, cutting temperature, and tool wear area functions were obtained from the respective regression models. Based on these functions, the micro-texture parameters were optimized using the response surface method with the cutting force, cutting temperature, and rake face wear area as the objectives. Finally, a full factor experiment on the micro-texture parameters was designed using Minitab, and cutting experiments were conducted using micro-textured tools with these parameters. Taking a relatively low cutting force, cutting temperature, and tool wear as the objectives, a genetic algorithm multi-objective optimization model for the micro-texture parameters of the tools was established, and the model was solved using the NSGA-II algorithm to obtain a Pareto solution set and micro-texture parameters with a good, comprehensive cutting performance. The micro-texture morphology and parameters obtained in this study can also be used for cutting other high-temperature alloy materials with similar properties to GH4169. This research method can also be used to optimize micro-textured tools for cutting other materials.

The GH4169 superalloy has the characteristics of high strength, strong thermal stability, large specific heat capacity, small thermal conductivity, etc., but it is also a typical hard-to-cut material. When cutting this material with ordinary cutting tools, the cutting force is large, and the cutting temperature is high, which leads to severe tool wear and short service life. In order to improve the performance of tools when cutting GH4169, reduce the cutting temperature, and extend the service life of the tool, micro-textured tools were used to cut GH4169 in spray cooling. The effects of micro-texture morphology and dimensional parameters on cutting temperature were analyzed. Firstly, tools with micro-textures of five different morphologies were designed near the nose on the rake face of the cemented carbide tools. The three-dimensional cutting models of the micro-textured tools with different morphologies were established by using ABAQUS, and a simulation analysis was carried out. Compared with the non-textured tools, the micro-texture morphology with the lowest cutting temperature was selected according to the simulation results of the cutting temperature. Secondly, based on the optimized morphology, tools with micro-textures of different size parameters were designed. When cutting GH4169, the cutting temperature of the tools was simulated and analyzed, and the size parameters of the micro-textured tools with the lowest cutting temperature were selected as well. Finally, the designed micro-textured tools were processed and applied in cutting experiments. The simulation model was verified in the experiments, and the influence of size parameters of micro-textures on the cutting temperature was analyzed. This paper provides a theoretical reference and basis for cutting GH4169 and the design and application of micro-textured tools.

The microstructure and tensile properties of GH4169 alloy fabricated by wire-fed electron beam directed energy deposition (EB-DED) were investigated in both as-deposited (As-Dep) and homogenization plus double aging heat treatment (HA) condition. The results show that thermal cycling caused an aging effect in the As-Dep samples, resulting in the precipitation of the γ'/γ" phases in close proximity to the Laves phase. The dissolution behavior of Laves phase in GH4169 alloy at various homogenization heat treatment temperatures and holding times was studied. Based on experimental results and Johnson-Mehl-Avramie-Kolmogorov (JMAK) analysis, the dissolution activation energy of Laves phase was calculated as 218.2 kJ/mol. The heat treatment regime utilized in HA treatment consisted of 1150 °C × 60 min/WC + 720 °C × 8 h/FC to 620 °C × 8 h/WC. After HA treatment, most of the Laves phases were dissolved and the γ'/γ" phases were precipitated. The mechanical properties of HA samples are superior to those of As-Dep samples. The morphology, distribution and evolutionary mechanism of the Laves phase, γ'/γ" phases are discussed and analyzed. • Thermal cycling caused an aging effect during wire-fed electron beam directed energy deposition (EB-DED) of GH4169 alloy. • The dissolution mechanism of Laves phase was revealed. • A homogenization plus double aging heat treatment (HA) schedule is developed for the EB-DED GH4169 alloy. • The enhancement of mechanical properties highlights the strengthening effect of HA. [ABSTRACT FROM AUTHOR]

[Display omitted] • A high entropy interlayer (TiZrHfNb) 95 Al 5 was successfully designed for diffusion bonding of GH4169 to Ti 2 AlNb. • The relationships between grain characteristics, lattice mismatch and mechanical properties, fracture mechanisms were revealed. • The major cracks located at the elastic modulus dramatically changed interface, i.e., the no-coherent interface. • The highest shear strength reached 384 MPa at 980 °C for 90 min. A high entropy interlayer (TiZrHfNb) 95 Al 5 was successfully designed for vacuum diffusion bonding of GH4169 superalloy to Ti 2 AlNb alloy. The relationships between grain size, grain boundary, lattice mismatch and microhardness, elastic modulus, shear strength and fracture behaviors were revealed. The typical microstructure was Ti 2 AlNb/B2/Solid solution/(Ti, Zr, Hf) 2 (Ni, Nb)+(Ti, Zr, Hf)(Ni, Nb) + Solid solution/(Ti, Zr, Hf)(Ni, Nb) + (Cr, Ni, Fe) ss /(Cr, Ni, Fe) ss /Cr-rich(Cr, Ni, Fe) ss /Ni-rich(Cr, Ni, Fe) ss /GH4169. With the holding time increased, the shear strength overall increased and decreased sharply, and the highest shear strength reached 384 MPa at 980 °C for 90 min. The microstructure had anisotropic crystal orientation, and the joints of Zone Ш for 90 min consisted of 92.08 % HAGBs and 7.92 % LAGBs. The residual strains and stresses decreased when the holding time increased. Meanwhile, recrystallisation appeared in Zone Ш, and the increase in the recrystallisation rate led to grain refinement. The lattice mismatch between (Ti, Zr, Hf)(Ni, Nb) and (Cr, Ni, Fe) ss phases was 25.05 %, indicating that the interface was non-coherent, and (Ti, Zr, Hf)(Ni, Nb)+(Cr, Ni, Fe) ss phases were located at an elastic modulus dramatically changed interface. Thus, the cracks easily formed in this interface and led to joint fracture. Moreover, the fracture mechanism was brittle fracture. [ABSTRACT FROM AUTHOR]

It is critical to optimize the cutting parameters in order to increase the machining efficiency as much as possible while ensuring tool life. Therefore, a model of tool wear in the turning process is established to predict tool wear at any time under various cutting conditions. Thereby, a model of tool life is derived. Considering the influence of uncertain parameters on turning processing, a reliability-based optimization model of turning is established, and the optimization model is solved by the sequential optimization and reliability assessment(SORA)method to obtain the optimal cutting parameters. Finally, an example verifies the advantage and feasibility of this method in the parameter optimization of turning nickel-based superalloy GH4169. [ABSTRACT FROM AUTHOR]

GH4169 alloys were manufactured by selective laser melting (SLM). The microstructure evolution and tensile properties of GH4169 alloys during hot isostatic pressing(HIP) and heat treatment(HT) process were analyzed by OM,SEM,EBSD and TEM. The results show that the grains of the as-deposited samples in the building direction are columnar, exhibit very fine cellular-dendritic structure with fine Laves phases precipitating in the interdendritic region. Most of porosities and Laves phases disappear after HIP, and the microstructure parallel to the building direction is transformed into equiaxed grains. Short rod-like δ phases are precipitated along grain boundaries after annealing at 980 ℃ for 1 h. The tensile properties at room temperature and 650 ℃ of specimens after HIP and HT are higher than those of the standard requirements for the forgings, and the temperature has a little influence on the fracture mode.

Taking GH4169 alloy large-size bar as research object, combined with the manufacturing process of the bar, the stress rupture properties of the specimens with different grain sizes were analyzed by means of OM, FE-SEM, EBSD and TEM. The results show that under the high temperature and stress of the long-lasting test, various grain size samples exhibit different stress rupture properties and grain orientation evolution. When the grain size is small, some orientation of〈101〉obviously rotates to 〈001〉or 〈111〉orientation where deformation and fracture occur. Besides, the coordination of macroscopic deformation of fine grain is better. These promote the effective release of stress concentration and then better plasticity. But the diffusion creep caused by more grain boundaries in the fine grain sample is unfavorable to the high temperature strength and cracks are prone to nucleate and expand at the grain boundary adjacent to the hard orientation of 〈111〉, thus the rupture life is reduced. In addition, the deformation of the fine grain sample is larger, mainly concentrated at grain boundaries, and the number fraction of large angle misorientation is more, which is easy to crack and reduce the life.

In order to obtain the ideal surface residual stress of GH4169 milling surface,the optimal interval division method of milling process parameters was proposed,and the orthogonal test of GH4169 milling was designed.The order of the influence of the process parameters on the residual stress was determined by the experiment results and the change trend of the residual stress with the increasing of the process parameters was analyzed.The optimal intervals of process parameters were determined according to the proposed method,and the reliability of the optimized interval was verified by experiments.

To investigate the microstructural evolution of wrought-nickel-based superalloy GH4169 from the original ingot to the finished product of manufacturing processes, different kinds of etchants and etching methods were used to show the fine precipitates and their morphologies. The obtained microstructures can vary in size, type, distribution, location, formation, and interactions of multiple phases, which were observed and analyzed by optical microscopy (OM), scanning electron microscopy (SEM), and an energy dispersive spectrometer (EDS). The dendrite segregation behavior of as-cast superalloy GH4169 was investigated. In addition, the microstructural evolution mechanism of second-phase particles during dynamic recrystallization was analyzed. This work sheds light on the evolution of the second-phase structure of nickel-based superalloys during the preparation process, providing guidance for process development and visual interpretation of the relationships between microstructure and properties.

A high entropy interlayer (TiZrHfNb) 95 Al 5 was designed for vacuum diffusion bonding of Ti 2 AlNb to GH4169. The influence of bonding temperature on the interfacial microstructure morphology, mechanical properties and fracture behaviour of the resultant joints was investigated. The evolution of microstructure and fracture mechanism were revealed. The typical interface microstructure of Ti 2 AlNb/B2/Solid solution/(Ti, Zr, Hf) 2 (Ni, Nb)+(Ti, Zr, Hf)(Ni, Nb)+(Ti, Zr, Hf)(Ni, Nb) 2 +Solid solution/(Ti, Zr, Hf)(Ni, Nb)+(Cr, Ni, Fe) ss /(Cr, Ni, Fe) ss /Cr-rich(Cr, Ni, Fe) ss /Ni-rich(Cr, Ni, Fe) ss /GH4169 was formed. As the bonding temperature increased, the thickness of interfacial reaction layer gradually increased, and the shear strength gradually increased until 980 °C, then decreased sharply. The highest shear strength reached 376 MPa at 980 °C for 90 min. The highest microhardness region of 11.79 GPa existed on the GH4169 side, which was mainly composed of (Ti, Zr, Hf)(Ni, Nb) and (Cr, Ni, Fe) ss phases. Meanwhile, the elastic modulus dramatically changed interface formed near this region. The fracture surface morphology indicated typical brittle fracture characteristics such as cleavage steps, transgranular fracture and intergranular fracture. According to the fracture analyses, major cracks initiated in the (Ti, Zr, Hf)(Ni, Nb) phase+(Ti, Zr, Hf) 2 (Ni, Nb) phase and gradually extended to the (Cr, Ni, Fe) ss phase. Thus, the major crack emerged region was located at the elastic modulus dramatically changed interface. • Ti 2 AlNb alloy was diffusion bonded to GH4169 alloy by using (TiZrHfNb) 95 Al 5 high entropy interlayer. • The maximum shear strength of 376 MPa reached in the bonding temperature of 980 °C and holding time of 90 min. • The relationship between the interfacial microstructure and the fracture behaviour was examined. • The major crack emerged region was located at the elastic modulus dramatically changed interface. [ABSTRACT FROM AUTHOR]

In this work, GH4169 dovetail specimens were coated on both sides with a bonded solid lubricant coating. Fretting fatigue tests were carried out at 500 °C and compared with untreated dovetail specimens. The results showed that the fretting fatigue life of the coated specimens was increased by about 41.4% compared to the untreated specimens. This is attributed to the inherent shear properties of the two-dimensional material and its uniform adsorption at the friction interface, which provides excellent lubrication, significantly reduces the interfacial shear, effectively inhibits early crack initiation, and to a certain extent promotes crack closure to slow down the crack propagation rate. This study further demonstrates that interfacial lubrication has a positive effect on the enhancement of fretting fatigue life. [ABSTRACT FROM AUTHOR]

Establishing a fatigue life prediction model considering the machined surface state is of great significance to improve fatigue life prediction accuracy. Fatigue tests with different machined surface states of GH4169 alloy were conducted firstly. The influence of surface state parameters on the fatigue life was analyzed. Then, the machined surface stress concentration factor and residual stress were introduced into the fatigue crack initiation and propagation models. Finally, the fatigue life prediction model of GH4169 material considering the surface states was established. The prediction results based on the proposed model are almost within a factor of two scatter band of the test results. [ABSTRACT FROM AUTHOR]

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The nickel-based superalloy GH4169 is widely applied in the aviation industry due to its outstanding mechanical properties. However, many blades of GH4169 are still produced by milling and manual polishing, which is costly and unreliable. In this article, GH4169 superalloy components manufactured with combination processes of milling, grinding, and polishing were comparatively studied involving surface integrity and fatigue performance. Test results indicate that the final polishing is the most dominant process that influences the high-cycle fatigue life of GH4169 components. Samples produced via cubic boron nitride grinding and numerical control polishing with a diamond-rubber wheel exhibit fatigue limits of 150 MPa higher than the milled and manually polished samples. Cubic boron nitride grinding induces a considerable compressive residual stress profile with a magnitude of -930 MPa and a depth of 200 μm. Milling induces a typical "hook" residual stress profile with 318 MPa at the surface. Polishing affects the machined surface by two ways, the removal effect and the squeezing effect. The squeezing effect induces a shallow compressive residual stress with approximately −1000 MPa, therefore improves the surface condition. However, inevitable omissions, scratches, texture disorders, and knock marks in hand-polishing are the main causes of the unstable high-cycle fatigue life of hand-polished components. [ABSTRACT FROM AUTHOR]