Nimonic 80A is a difficult-to-machine nickel-based superalloy thanks to its superior tensile strength in high temperatures and oxidation resistance. However, cutting fluids applied to improve ...machinability performance during the processing of such materials increase tool life, while at the same time increasing machining costs and causing health and environmental problems. Thus, the present research has been focused on cutting tool life and wear characteristics and analysis of machined surface in turning of Nimonic 80A superalloy under different cutting environments namely dry, air-cooling and oil-spraying method. The performance of the coated tool has been characterized by using optical microscope, SEM and EDS analysis. The results of the tool life and microscopic analysis showed that the oil-spraying method has longer tool life than dry and air-cooling method in turning of Nimonic 80A alloy. Moreover, the volume of material removed has been modeled by response surface method for predicting tool performance under various machining conditions. Lastly, the microstructural and microhardness variations of the machined surface have been evaluated when the cutting tool reaching the wear criterion. The best performance in terms of tool life and surface integrity was obtained at cutting speed of 60 m/min in oil-spraying environment.
Nimonic 80A alloy is widely used in rotor blades, guide vane supports and other aeroengine components. It is exposed to harsh fretting wear and high temperature loads, which reduces the fatigue ...resistance of the components. Laser cladding (LC) technology is utilized to improve structural integrity and fatigue resistance. The aim of the research is to assess the resistance of Nimonic 80A in the very high cycle fretting fatigue (VHCFF) after cladding with Stellite X-40 and In625 + 20 wt% WC. The wear morphology and fracture mechanism of the specimens were studied using scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM). The results show that the crack initiation sites are mainly classified into three types, namely surface initiation, interior initiation, and LC interface initiation. The fretting wear introduces compressive residual stress along the wear depth, as well as the bulk stress, residual stress, and cladding defects all play dominant roles in crack initiation. Especially up to 108 cycles, the glaze oxide layer (GOL) helps to reduce friction coefficient and make the compaction of wear debris easier, inhibiting the crack nucleation. The different distribution of residual stress in on the LC layer and the stronger wear resistance of WC particles lead to the higher fatigue strength and life of the specimen with In625 + 20 wt% WC cladding material compared with the Stellite X-40 ones.
•The substrate metal Nimonic 80A modified by laser cladded with Stellite X-40 and In625 + 20 wt% WC.•The platform appeared in the S_N data for IW specimen for the competition between the crack surface and interior initiation.•The WC particles can enhance the wear resistance and fatigue failure cycles.•As the bulk stress decreases and the Nf > 108, the defects located on the LC interface cause the crack interior initiation.
The objective of the present investigation is to reveal the effects of aggregation kinetics on the nanofluid flow between two revolving plates. Additionally, we have presumed that the upper surface ...of the revolving structure is permeable while the lower one is blessed to move with variable speed. Here we have introduced Nimonic 80A alloy nanoparticles with water as a base liquid. Aggregation kinetics at molecular level has been introduced mathematically to model our work and to explore how aggregation features affect the thermal integrity of the system. Similarity technique guided us to avail non-dimensional form of leading equations. RK-4 method along with shooting technique aids us to solve nonlinear ODEs. Several features of aggregation parameters on velocity and temperature profile have been explored through graphs and tables. Results extract that effective thermal conductivity of aggregated composite increases for nanoparticle volume fraction. Heat transport drops off for radius of gyration factor at lower segment but rises at upper regime.
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The study presents the machinability of Nimonic 80A superalloys depending on the cutting forces in both the turning experiments and simulations by finite element method (FEM) in order ...to approve the precision of the predetermined Johnson-Cook (JC) parameters from our previous study. In the first part of the paper, the turning experiments have been performed on Nimonic 80A superalloy with coated carbide tools to determine the cutting forces namely main cutting force, feed force and radial force. Three different cutting parameters namely depth of cut, cutting speed and feed rate have been used with three levels. The effect levels of the cutting parameters on cutting forces have been also determined with the analysis of variance (ANOVA) at 95% confidence level. Secondly, predetermined JC material model parameters have been inputted into the software running by FEM. Thereafter, the turning simulations have been performed by FEM with the same cutting conditions as experimental ones. According to ANOVA results, depth of cut is the most important parameter on Fc and Ff while feed rate is the most important factor on the Fr. Through the closer results (the mean of 6.45% deviation) of cutting forces between the experiments and simulations, the JC parameters of the material and the boundary conditions of the simulations have been approved with high accuracy.
In order to analyze the evolution of grain size for Nimonic 80A and further controlling the structures and properties of hot deformed parts, a series of isothermal hot compression tests were ...conducted with the height reduction range of 10%–60% under the strain rate range of 0.01–10 s−1 and the temperature range of 1237–1523 K on a Gleeble-3500 thermo-mechanical physical simulator. According to the experimental data, the grain refinement degree was proposed and computed in this work so as to quantitatively analyze the variation of grain size during the whole deformation for Nimonic 80A. The onset strains of DRX initiation (εc) were identified by θ−σ curves (strain hardening rates curves) and their derivative. Then the dynamic recrystallization kinetics model and the dynamic recrystallization grain size model were established based on the results from thermo-simulation experiments and metallographic analysis. After that, the grain refinement degrees of the specimens were proposed and calculated, then the effects of temperature, strain rate and deformation degree on the grain refinement degree were discussed through the metallographs over a wide range of temperatures and strain rates. Finally, the developed models were applied in the finite element simulation model, which implies a good application prospect of the theoretical calculation.
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•The DRX kinetics and grain size models are established and a concept is introduced to analyze the grain refinement degree.•The influences of temperature, strain rate and strain on grain refinement degree is discussed for the Ni80A.•The developed DRX kinetics and grain size models were applied in the finite element model.
Developing high temperature technology increases the need for high temperature resistant materials. Nimonic 80A alloy is generally preferred due to its high creep resistance, oxidation resistance and ...high resistance to high temperature corrosion. The study determines the tensile constitutive equation (JC parameters) of Nimonic 80 A superalloys. Johnson Cook (JC) model is preferred amongst the various material constitutive equations (Zerille Armstrong, Bordner Partom, JC model). Three different kinds of tensile experiment were performed to identify the model parameters. These are quasi-static tensile experiments applied at room temperatures. These experiments were carried out at 0.001, 0.01 and 0.1 s−1 strain rates. Therefore, the reference strain rate for all experiments was selected to be 10−3. As a second test, tensile experiments were conducted at room temperature at high strain rates (102–103 s−1) using the Split Hopkinson pressure bar (SHPB). Lastly, tensile experiments were conducted at high temperatures (300–900 °C) at 0.001 s−1. It was observed whether all tests are compatible with each other or not, and so five Johnson-Cook (JC) parameters of Nimonic 80 A alloy were identified via the data found from the experiments. After determination of parameters, tensile test simulations by finite element method (FEM) were performed in ANSYS Workbench. As a result, the accuracy of the JC parameters is verified since there is a deviation of %2.84 between the experimental and the simulation results.
•The material tensile constitutive model (Johnson-Cook) of Nimonic 80A superalloy.•Three different types of tensile tests to determine the tensile equation parameters.•The microstructural developments during the all tension tests.•The FE simulations of tensile tests by using JC parameters of Nimonic 80A alloy.•Verification of tensile JC parameters of Nimonic 80A superalloy.
To deeply understand and even describe the evolutions of the low-energy twin boundary density (BLD∑3n) in a thermal-plastic deformation process, an improved twin density model as a function of ...average grain size and stored energy is developed. For Nimonic 80A superalloy, the model is solved based on the EBSD statistical results of grain size and BLD∑3n in the specimens compressed at temperatures of 1273–1423 K and strain rates of 0.001–10 s–1. The corresponding relationships of BLD∑3n with stored energy and grain size varying with temperature and strain rate are clarified by the superimposed contour plot maps. It is summarized that BLD∑3n increases with increasing stored energy and decreasing grain size, and higher BLD∑3n with finer grains corresponds with lower temperatures and higher strain rates. Such relationships are described by the improved twin density model, and the prediction tolerance of the solved model is limited in 2.8%.
A material is considered an alloy if it contains at least two different metals or one metal and one nonmetal. It might be a single phase, a mixture of metallic phases, or an intermetallic compound ...with no clear boundary between the steps. Alternatively, it could be none of these things. Aircraft construction, the military, industry, medicine, and manufacturing are some of the many alloy applications. Aluminium, copper, nickel, stainless steel, and titanium alloys are used in various tools, machines, vehicles, and buildings across multiple fields. As a consequence of these applications, we look at the role that radiative heat transfer plays in the movement of ternary alloys over a melting surface. Furthermore, Nimonic 80A and aluminium alloys (AA7072-AA7075) are combined to make ternary alloys, with Ethylene Glycol as the solvent. The PDEs were obtained by approximating the Navier–Stokes equation using the boundary layer approach under the flow assumptions. This system is translated into ODEs using similarity transformations. A dimensionless system is explained using the bvp4c method. The impacts of the relevant physical parameters are elucidated quantitatively and visually. It is found that, the higher R value indicates a more robust heat transmission to the liquid, resulting in a thicker temperature field. Furthermore, the mixing of more nanoparticles may need more energy, which will result in an increase in the temperature profile.
The fatigue life of metallic materials in the very high cycle fatigue (VHCF) regime is characterized by a large scatter of experimental results. The aim of the present work is to investigate the ...reasons for the scattering of the fatigue life as well as to model its impact statistically. For this purpose crack initiation in the Ni-base superalloy Nimonic 80A was investigated as a function of the number of cycles to failure at different stress amplitudes both in the HCF and the transitional HCF–VHCF regime. According to the experimental observations the fatigue crack initiation depends on the stress amplitude and occurs at twin boundaries and grain boundaries with a large misorientation angle. The application of two analytical approaches for the assessment of the local stress concentration at different grain boundaries is discussed. In particular in the VHCF regime, the misorientation factor developed by Blochwitz et al. (1997), which depends on the misorientation angle between two adjacent grains as well as on the orientation of their boundary with respect to the external load, was used to estimate the stress concentration at the grain boundaries. It was revealed, that the cracks initiate at the grain boundary of maximum misorientation factor calculated for each specimen. Furthermore, the calculated maximum misorientation factor per specimen show a direct relation to the number of cycles to failure and can be used as an additional microstructural information for statistically based fatigue life prediction models.
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