| 1. |
- Fisk, Martin, 1981-, et al.
(author)
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Modelling of induction hardening in low alloy steels
- 2018
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In: Finite elements in analysis and design (Print). - : Elsevier. - 0168-874X .- 1872-6925. ; 144, s. 61-75
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Journal article (peer-reviewed)abstract
- Induction hardening is a useful method for improving resistance to surface indentation, fatigue and wear that is favoured in comparison with through hardening, which may lack necessary toughness. The process itself involves fast heating by induction with subsequent quenching, creating a martensitic layer at the surface of the workpiece. In the present work, we demonstrate how to simulate the process of induction hardening using a commercial finite element software package with focuses on validation of the electromagnetic and thermal parts, together with evolution of the microstructure. Experiments have been carried out using fifteen workpieces that have been heated using three different heating rates and five different peak temperatures resulting in different microstructures. It is found that the microstructure and hardening depth is affected by the heating rate and peak temperature. The agreement between the experimental and simulated results is good. Also, it is demonstrated that the critical equilibrium temperatures for phase transformation is important for good agreement between the simulated and experimental hardening depth. The developed simulation technique predicts the hardness and microstructure sufficiently well for design and the development of induction hardening processes.
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| 2. |
- Haas, Sylvio, et al.
(author)
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Correlation of precipitate evolution with Vickers hardness in Haynes® 282® superalloy : In-situ high-energy SAXS/WAXS investigation
- 2018
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In: Materials Science & Engineering. - : Elsevier BV. - 0921-5107 .- 1873-4944 .- 0921-5093 .- 1873-4936. ; 11, s. 250-258
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Journal article (peer-reviewed)abstract
- The aim of this work is to characterize the precipitation kinetics in Haynes® 282® superalloys using in-situ high-energy Small Angle X-ray Scattering (SAXS) together with Wide Angle X-ray Scattering (WAXS). The phases identified by WAXS include γ (matrix), γ′ (hardening precipitates), MC (metallic carbides), and M23C6/M6C (secondary metallic carbides). The γ'-precipitates are spheroids with a diameter of several nanometres, depending on the temperature and ageing time. From the SAXS data, quantitative parameters such as volume fraction, number density and inter-particle distance were determined and correlated with ex-situ Vickers microhardness measurements. The strengthening components associated with precipitates and solid solutions are differentiated using the measured Vickers microhardness and SAXS model parameters. A square root dependence between strengthening attributable to the precipitates and the product of volume fraction and mean precipitate radius is found. The solid solution strengthening component correlates with the total volume fraction of precipitates.
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