| 52751. |
- Lyphout, Christophe, 1981
(författare)
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Adhesion strength of HVOF sprayed Inconel 718 coatings
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thermal spray technology in general is nowadays recognized as an industrial process, mature enough to apply coatings on different substrate materials that protect parts against wear, corrosion, heat, or combinations of these. The quality demands on coating homogeneity and adhesion strength are, nowhere more than in the automotive and aeronautic industries, continuously increasing. This was the major reason why the High-Velocity-Oxy-Fuel process was invented. However, adhesion strength is still a limitation of thermal spray processes, specifically in the case of thick coatings, and is a critical property which, sometimes over relatively short time periods, can result in coating spallation.The focus of this study is on High-Velocity-Oxy-Fuel (HVOF) coatings for aerospace applications, where the requirements on coating performance are the toughest. Improving the coating adhesion is, in the aerospace context, necessary to meet new customer demands. Therefore, understanding the relationship between coating adhesion strength and residual stress levels – through the deposit thickness on the one hand and particularly at the interface between coating and substrate on the other – is a prerequisite for any bond strength improvement, and, consequently forms the aim of the current research.The chosen application was the aeronautic repair of Inconel 718 parts comprised of the same material, which is an application with high requirements in terms of adhesion strength. If, in this application, bond strength can be enhanced then permissible repair thickness can be increased.One early finding in the investigation was that, in order to establish the relationship between coating thickness, the residual stress state and adhesion strength, new techniques, methods and algorithms needed to be developed. A method that modifies the standard tensile strength evaluation method ASTM C633, in the sense that gluing is replaced by brazing, was developed alongside a method for determining adhesion shear strength. It was also found that determination of residual stresses by neutron diffraction is a tricky task when a material is to be coated with the same material. Algorithms for the determination of residual stress levels in the coating-substrate interface therefore had to be specifically developed. Residual stresses determined by the Layer Removal Method (MLRM) were compared with the Neutron Diffraction ones in order to be validated.Tentative simulation models were also developed, in order to be able to separate different types of residual stresses, such as thermal mismatch stresses and peening stresses, to be able to predict residual stresses both for single particle impacts and for layer-by-layer coating formation. The developed techniques, methods and models provide valuable tools to evaluate and understand relationships between coating thickness, residual stress states and adhesion strength as well. Additionally, statistical approaches based on the previously developed characterization tools were presented for studying ways in which process parameters can be optimized for enhancing adhesion strength of HVOF sprayed coatings.
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| 52752. |
- Lyphout, Christophe, 1981-, et al.
(författare)
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Characterization of adhesion strenght of HVOF sprayed IN718 coatings
- 2009
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Ingår i: Proceedings of th 22nd Internationa Conference on Surface Modification technolgies - SMT22. Trollhättan, Sweden. - : VALAR Docs. - 9780981706511 ; , s. 11-18
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Konferensbidrag (refereegranskat)abstract
- The tensile adhesion strength of thermally sprayed coating is conventionally evaluated via the ASTM C633-69 standard. The maximum measurable adhesion is then limited by the adhesion strength of the polymer media. High velocity oxy-fuel (HVOF) spraying can exhibit very high bonding strength and thus it is essential to develop an alternative method to evaluate coating adhesion strength. In this work a Modified Tensile Adhesion Test (MTAT) is proposed replacing gluing with induction brazing. The method was evaluated for HVOF sprayed Inconel 718 coatings deposited on Inconel 718 substrates. The effect of induction brazing process and the characteristics of the braze-coating interface was given particular interest. The results indicate that the method is superior to the ASTM C633-69 for characterisation of adhesion of coatings with high bond strength.
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| 52753. |
- Lyphout, Christophe, 1981, et al.
(författare)
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Characterization of Adhesion Strength and Residual Stresses of HVOF Sprayed Inconel 718 for Aerospace Repair Applications
- 2007
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Ingår i: Proceedings of the International Thermal Spray Conference (ITSC), Beijing, China. ; , s. 588-593
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Thermally sprayed Inconel 718 coatings have been deposited by high velocity oxy-fuel (HVOF) spraying on Inconel 718 substrates. The aim of the on-going study is to understand and control the adhesion mechanisms and the residual stress state of the deposit/substrate system, in order to build up thick coatings for maintenance purposes. The coating adhesion strength was evaluated by the standard ASTM C633 tensile test. Coating shear strength was evaluated by the recently developed prEN15340 Shear Test. A modified Layer Removal Method (MLRM) test was carried out to measure residual stresses. The work is a part of an ongoing study for evaluation of relationships between process parameters, residual stress distribution and adhesion strength.
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| 52754. |
- Lyphout, Christophe, 1981, et al.
(författare)
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Influence of substrate preparation on HVOF IN718 coating adhesion strength
- 2011
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Ingår i: Proceedings of the 25th International Conference on Surface Modification Technologies (SMT25).
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Konferensbidrag (refereegranskat)abstract
- In the HVOF spray process, significant peening stresses are generated during the impact of semi molten particles on the substrate. Peening stresses contribute to the density of HVOF coatings, but no systematic study has been carried out to determine in which extent these stresses become beneficial or detrimental to the coating adhesion strength. Neutron Diffraction has been utilized in this work to evaluate the residual stress distribution through different peened surfaces. The investigation was performed on Inconel 718 HVOF coatings sprayed on Inconel 718 substrates for repair application. A Tensile Adhesion Test was developed to measure the resulting coating adhesion strength which normally exceeds the limitation of the standard ASTM-C633 glue test. Combined these experimental techniques yield a deeper understanding of residual stress formation in the HVOF process and thus a tool for process optimization. The relationship between developed stress state at the coating/substrate interface and stress state of the gritblasted substrate prior to spraying is given a particular interest.
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| 52755. |
- Lyphout, Christophe, 1981, et al.
(författare)
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Modeling of Peening Stress in HVOF Sprayed IN718 Coating
- 2011
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Ingår i: Proceedings of the International Thermal Spray Conference ITSC-11.
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Konferensbidrag (refereegranskat)abstract
- Within Surface and Coating Technologies, the High Velocity Oxy-Fuel (HVOF) thermal spray process generates significant peening stresses due to the impact at high velocity of semi molten particles onto the substrate. The level of high kinetic and thermal energy of impinging particles is a key-parameter to understand how residual stresses build up through the whole system during spraying, and to which extend these stresses influence the resulting coating adhesion strength. While an appropriate combination of thermal and peening stresses is beneficial to the deposit bonding, no systematic study has been carried out to determine their respective amplitudes. A numerical Finite Element Analysis (FEA) has been developed to isolate peening stresses from thermal stresses developed into the substrate target, after successive impacts of single particle. The investigation is performed on Inconel 718 feedstock material HVOF sprayed on Inconel 718 substrate. The relationship between the developed stress state at the substrate interface and the impinging particle temperature and velocity is given a particular interest.
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| 52756. |
- Lyphout, Christophe, 1981, et al.
(författare)
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Residual Stresses Distribution Through Thick HVOF Sprayed Inconel 718 Coatings
- 2008
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Ingår i: Proceedings of the International Thermal Spray Conference (ITSC), Maastricht, Netherlands. ; , s. 588-593
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Konferensbidrag (refereegranskat)abstract
- Residual stress build up in thick thermal spray coatings is a property of concern. Coating adhesion to the substrateis influenced by residual stresses that are generated during the coating deposition process. In the HVOF sprayprocess, significant peening stresses are generated during impact of semi molten particles on the substrate. Thecombination of these peening stresses together with quenching and thermal mismatch stresses can be ofsignificant importance. Both numerical Finite Element Method (FEM), to calculate peening, quenching stresses, andexperimental methods, i.e. Modified Layer Removal Method (MLRM) and Neutron Diffraction, have been utilised in this work. The investigation was performed on thick Inconel 718 coatings on Inconel 718 substrates. Combined, these numerical and experimental techniques yield a deeper understanding of residual stress formation in the HVOF process and thus a tool for process optimisation. The relationship between the stress state and deposit/substrate thickness ratio is given particular interest.
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| 52757. |
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| 52758. |
- Lyseid Authen, Thea, 1993, et al.
(författare)
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A comparison on the use of DEHBA or TBP as extracting agent for tetra- and hexavalent actinides in the CHALMEX Process
- 2022
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 331:12, s. 5137-5145
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Tidskriftsartikel (refereegranskat)abstract
- The Chalmers Grouped ActiNide EXtraction process is a solvent extraction process for the homogeneous recycling of spent nuclear fuel. The use of TBP for the extraction of tetra- and hexavalent actinides can be problematic for several reasons, including troublesome degradation products causing crud formation, decreased extraction yield and the possibility of explosive red oil reactions. Here, the substitution of TBP by a N,N-dialkyl monoamide, DEHBA, is investigated. The findings suggest that DEHBA can be a suitable extracting agent for use in the CHALMEX solvent, although identified drawbacks need to be further investigated.
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| 52759. |
- Lyseid Authen, Thea, 1993
(författare)
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Advances in the Application and Understanding of the CHALMEX FS-13 Process
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the last year, the European demand for electricity has increased and at the same time, the production of planned electricity generation has decreased due to unexpected weather conditions and war. Combined with a limited capability to store energy, low-carbon energy producers such as nuclear power is getting renewed attention in many countries. While having benefits such as reliable, clean, affordable and safe electricity production, the main concerns regarding nuclear power usually refer to the extremely long-lived and radiotoxic final waste. The main contributor to the long-lived radiotoxicity of the spent fuel is Pu and the minor actinides (Np, Am, Cm). The Chalmers Grouped ActiNide EXtraction (CHALMEX) process is a solvent extraction process for the recycling of minor and major actinides as a group, from spent nuclear fuel. By recycling the actinides, and using them as fuel in fast reactors, one can significantly reduce both the overall environmental impact of the nuclear fuel cycle, the lifetime- and the radiotoxicity of the final waste. By combining the extractants TBP with CyMe4-BTBP in the diluent FS-13, the CHALMEX solvent has been shown to have preferential physical properties for use in industrial processes. Separation of the actinides from a spent fuel solution is achieved in only 8 process stages. The co-separation of specific fission products is reduced by the use of masking agents and scrubbing stages. Overall, low degrees of fission product contamination is found in the actinide product stream (<1.5%).The kinetics of the system has also been shown to be compatible with contacting in centrifugal contactors. Despite observation of phase entrainment under certain conditions in a centrifugal contactor, the CHALMEX process is a promising process for the actinide separation from spent nuclear fuels.
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| 52760. |
- Lyseid Authen, Thea, 1993, et al.
(författare)
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An overview of solvent extraction processes developed in Europe for advanced nuclear fuel recycling, Part 2 — homogeneous recycling
- 2022
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Ingår i: Separation Science and Technology. - : Informa UK Limited. - 1520-5754 .- 0149-6395. ; 57:11, s. 1724-1744
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Forskningsöversikt (refereegranskat)abstract
- The hydrometallurgical separation concepts for the recycling of irradiated nuclear fuels developed in Europe are presented and discussed. Whilst Part 1 of the review focused on concepts for heterogeneous recycling of minor actinides, this article focuses on group recycling of transuranic actinides, which would support homogeneous recycling scenarios. Most of these concepts were developed within European collaborative projects and involve solvent extraction processes separating all the actinides (U-Cm) in two cycles. The first cycle uses a monoamide extractant to recover uranium leaving all the transuranic actinides in the aqueous raffinate with the fission products. The second cycle aims for a group recovery of the transuranium elements and several strategies have been proposed for this stage. In this review article, the various solvent extraction processes are summarised and the key features of the process schemes are compared.
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