| 1. |
- Asala, Gbenga, et al.
(author)
-
Analysis and constitutive modelling of high strain rate deformation behaviour of wire-arc additive-manufactured ATI 718Plus superalloy
- 2019
-
In: The International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 103:1-4, s. 1419-1431
-
Journal article (peer-reviewed)abstract
- A fundamental prerequisite for obtaining realistic finite element simulation of machining processes, which has become a key machinability assessment for metals and alloys, is the establishment of a reliable material model. To obtain the constitutive model for wire-arc additive-manufactured ATI 718Plus, Hopkinson pressure bar is used to characterise the flow stress of the alloy over a wide range of temperatures and strain rates. Experiment results show that the deformation behaviours of as-deposited ATI 718Plus superalloy are influenced by the applied strain rate, test temperature and strain. Post-deformation microstructures show localised deformation within the deposit, which is attributable to the heterogeneous distribution of the strengthening precipitates in as-deposited ATI 718Plus. Furthermore, cracks are observed to be preferentially initiated at the brittle eutectic solidification constituents within the localised band. Constitutive models, based on the strain-compensated Arrhenius-type model and the modified Johnson-Cook model, are developed for the deposit based on experimental data. Standard statistical parameters, correlation coefficient (R), root-mean-square error (RMSE) and average absolute relative error (AARE) are used to assess the reliability of the models. The results show that the modified Johnson-Cook model has better reliability in predicting the dynamic flow stress of wire-arc-deposited ATI 718Plus superalloy. © 2019, Springer-Verlag London Ltd., part of Springer Nature.
|
|
| 2. |
- Fan, Wei, et al.
(author)
-
A review on cutting tool technology in machining of Ni-based superalloys
- 2020
-
In: The International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media Deutschland GmbH. - 0268-3768 .- 1433-3015. ; 110:11-12, s. 2863-2879
-
Journal article (peer-reviewed)abstract
- In this paper, a state-of-the-art review on cutting tool technology in machining of Ni-based superalloys is presented to better understand the current status and to identify future directions of research and development of cutting tool technologies. First, past review articles related to the machining of Ni-based superalloys are summarized. Then machinability of superalloys is introduced, together with the reported methods used in cutting tool design. The current researches on cutting tools in the machining of superalloys are presented in different categories in terms of tool materials, i.e., carbide, ceramics, and Polycrystalline cubic boron nitride (PCBN). Moreover, a set of research issues are identified and highlighted to improve the machining of superalloys. Finally, discussions on the future development are presented, in the areas of new materials/geometries, functional surfaces on the cutting tool, and data-driven comprehensive optimization.
|
|
| 3. |
- Pant, Prabhat, 1990-, et al.
(author)
-
Mapping of residual stresses in as-built Inconel 718 fabricated by laser powder bed fusion : A neutron diffraction study of build orientation influence on residual stresses
- 2020
-
In: Additive Manufacturing. - : Elsevier B.V.. - 2214-8604 .- 2214-7810. ; 36
-
Journal article (peer-reviewed)abstract
- Manufacturing of functional (ready to use) parts with the powder bed fusion method has seen an increase in recent times in the field of aerospace and in the medical sector. Residual stresses (RS) induced due to the process itself can lead to defects like cracks and delamination in the part leading to the inferior quality of the part. These RS are one of the main reasons preventing the process from being adopted widely. The powder bed methods have several processing parameters that can be optimized for improving the quality of the component, among which, build orientation is one. In this current study, influence of the build orientation on the residual stress distribution for the Ni-based super-alloy Inconel 718 fabricated by laser-based powder bed fusion method is studied by non- destructive technique of neutron diffraction at selected cross-sections. Further, RS generated in the entire part was predicted using a simplified layer by layer approach using a finite element (FE) based thermo-mechanical numerical model. From the experiment, the part printed in horizontal orientation has shown the least amount of stress in all three directions and a general tendency of compressive RS at the center of the part and tensile RS near the surface was observed in all the samples. The build with vertical orientation has shown the highest amount of RS in both compression and tension. Simplified simulations results are in good agreement with the experimental value of the stresses. © 2020 The Authors
|
|
| 4. |
- Pouranvari, M., et al.
(author)
-
On the Inability of the Moving Interface Model to Predict Isothermal Solidification Time During Transient Liquid Phase (TLP) Bonding of Ni-Based Superalloys
- 2022
-
In: Metallurgical and Materials Transactions. A. - : Springer Nature. - 1073-5623 .- 1543-1940. ; 53:1, s. 126-135
-
Journal article (peer-reviewed)abstract
- Understanding diffusion-induced isothermal solidification time during transient liquid phase bonding is vital in producing intermetallic-free robust joints. The isothermal solidification completion time is overestimated by the existing analytical models, even by the closest one to the real bonding conditions, known as the moving interface model. It was found that the boride formation in the diffusion affected zone of Ni-based superalloy upon using B-containing filler metals is one of the reasons behind the inability of the moving interface model to predict the isothermal solidification completion time accurately, which has received scant attention in the literature. Moreover, simplified assumptions in deriving the moving interface model such as constant interfacial solute concentration, which is only valid for binary systems, along with the independency of diffusion coefficient to concentration introduce errors when estimating the isothermal solidification time using the moving interface model. The significant discrepancy between the predicted and experimentally obtained isothermal solidification times reinforces the idea that the existing moving interface analytical model needs to be modified.
|
|
| 5. |
- Zhao, Wenyue, et al.
(author)
-
Tuning the plasticity of Ni-Mo solid solution in Ni-based superalloys by ab initio calculations
- 2017
-
In: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 124, s. 100-107
-
Journal article (peer-reviewed)abstract
- The generalized stacking fault energies of face centered cubic Ni-Mo solid solutions are calculated using the exact muffin-tin orbital method in combination with coherent potential approximation. The alloying of Mo in Ni is found to decrease the intrinsic stacking fault energy of the solid solution from 150 mJ/m2 (pure Ni) to 50 mJ/m2 (17.5 at.% Mo) almost linearly. At the same time, the unstable stacking fault energy (the unstable twin fault energy) of the Ni-based solid solution increases (decreases) in a small extent with increasing Mo concentration. Three different twinnability measures are adopted and all indicate a substantially enhanced twinning mechanism in Ni-Mo solid solutions with increasing concentration of Mo. The weaker Ni-Ni bonding at high Mo concentrations is considered to be the main mechanism behind the disclosed phenomena. Segregation of Mo to the fault plane is proved to have strong effect on the generalized stacking fault energy of Ni-based solid solution.
|
|
| 6. |
- Zhu, Z., et al.
(author)
-
Isolation of optimal compositions of single crystal superalloys by mapping of a material's genome
- 2015
-
In: Acta Materialia. - : Elsevier BV. - 1359-6454 .- 1873-2453. ; 90, s. 330-343
-
Journal article (peer-reviewed)abstract
- The multicomponent composition space pertinent to the single crystal nickel-based superalloys is mapped and searched, using computational modelling. A resolution of 0.1 wt.% for the alloying elements is assumed, consistent with manufacturing practice. Databases are constructed of alloy compositions which are predicted to be of promising microstructural architecture: e.g. equal fractions of the γ and γ′ phases. These may be regarded as maps - one might term them genomes - of this class of structural alloy. By combining the databases with additional composition-dependent property models, it is demonstrated that compositions can be identified which - subject to the accuracy and limitations of the sub-models - are likely to prove optimal, e.g. on the basis of their creep resistance, density and cost. The methods circumvent the need for the traditional empirically-driven approaches to alloy design.
|
|
| 7. |
- Ajay, A., et al.
(author)
-
Hot corrosion behavior of solution precursor and atmospheric plasma sprayed thermal barrier coatings
- 2015
-
In: Corrosion Science. - : Elsevier Ltd. - 0010-938X .- 1879-0496. ; 98, s. 271-279
-
Journal article (peer-reviewed)abstract
- Hot corrosion behavior of solution precursor plasma spray (SPPS) thermal barrier coating (TBC) in molten salt mixtures of 90wt.% Na2SO4+5wt.% V2O5+5wt.% NaCl and 50wt.% Na2SO4+50wt.% V2O5 at 900°C is compared vis-à-vis atmospheric plasma spray (APS) coating. APS TBCs show better hot corrosion resistance than SPPS TBCs in both the salt mixtures. The vertical cracks in SPPS coatings, meant for strain tolerance and high thermal cycling life, serve as channels for transporting salts across the coating to bond coat/top coat interface and accelerate failure. © 2015 Elsevier Ltd.
|
|
| 8. |
- Ananthanarayanan, Durga, et al.
(author)
-
Grain Structure Prediction for Directionally Solidified Superalloy Castings
- 2020
-
In: JOM. - : Springer Nature. - 1047-4838 .- 1543-1851. ; 72:5, s. 1785-1793
-
Journal article (peer-reviewed)abstract
- A highly parallelized mesoscale solidification model based on a cellular automaton method was coupled with a macroscale process model to predict grain structure during directional solidification. The macroscale thermal model and a nucleation parameter (maximum nucleation density) for René N500 were verified and calibrated using temperature profiles obtained via thermocouples in step-geometry castings and grain structures analyzed by electron backscatter diffraction (EBSD), respectively. The calibrated model was then applied to a laboratory-scale turbine blade to predict its grain structures. The predicted grain sizes agreed with experimental measurements under different casting conditions. The established bulk nucleation parameter based on the simple geometry can be directly transferred to complex geometries. Grain calculations without accurate estimations of nucleation on the chill plate can still provide reasonably good predictions. Overall, a viable path to calibrate model inputs for grain structure models based on simple geometry, where faster iterations can be achieved, is demonstrated.
|
|
| 9. |
- Andersson, Joel, 1981-
(author)
-
Fabrication and Weldability Aspects of Ni- and Ni–Fe Based Superalloys : A Review
- 2023
-
In: Proceedings of the 10th International Symposium on Superalloy 718 and Derivatives. - : Springer Cham. - 9783031274473 - 9783031274497 ; , s. 659-696
-
Conference paper (peer-reviewed)abstract
- Superalloys are commonly used in structural components of aero-engines. Superalloys in general, Ni- and Ni–Fe-based superalloys, belong to an important group of materials used in aerospace applications. Fabrication and associated weldability aspects of structural components for the hot section of aero-engine gas turbines continue to be of high importance to the manufacturing industry within this discipline. Cracking and specifically hot cracking as well as strain age cracking is a serious concern during the welding and additive manufacturing (AM) of these structural components. The cracking phenomena can occur during welding, AM or subsequent heat treatment of precipitation-hardening superalloys. The cracking behaviour can be influenced by several factors, i.e., chemical composition in terms of hardening elements and impurities, the microstructure of base material, and weld zone, together with corresponding welding, AM and post-treatment process parameters. This paper provides a review of Ni- and Ni–Fe-based superalloys concerning fabrication and weldability aspects within the context of structural components of aero-engines. Also, the paper offers insight and analyses to research publication data of welding and AM of superalloys in the context of annual publication developed over the years as well as specific contributions from countries, affiliations, and specific researchers.
|
|
| 10. |
- Andersson, Joel Håkan, 1981, et al.
(author)
-
Hip-densification of alloy 718 and ati 718Plus®
- 2014
-
In: 8th International Symposium on Superalloy 718 and Derivatives 2014; Pittsburgh; United States; 28 September 2014 through 1 October 2014. - Hoboken, NJ, USA : John Wiley & Sons, Inc.. - 9781634396424 ; , s. 425-435
-
Conference paper (peer-reviewed)abstract
- Cast Alloy 718 and ATI 718Plus® have been investigated to disclose their ability to develop Hot Isostatic Pressing (HIP) porosity which may form as a consequence of the casting process. Artificial defects were manufactured in cast Alloy 718 and ATI 718Plus® block and sealed by electron beam welding prior to the HIP treatment which was carried out at three different temperatures, namely; 1120 °C, 1165 °C, and 1190 °C at a pressure of 100 MPa. It was seen that there are no significant difference in the ability to heal pores in between cast Alloy 718 and ATI 718Plus®. No major difference in between the three different temperatures were disclosed whereas the size of the pore seem to have the biggest impact on the ability to heal, which was supported by careful SEM characterization and by simplified calculations considering two different sizes of pores.
|
|
