| 1. |
- 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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| 2. |
- Bolelli, G., et al.
(författare)
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Sliding and abrasive wear behaviour of HVOF- and HVAF-sprayed Cr3C2-NiCr hardmetal coatings
- 2016
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 358-359, s. 32-50
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Tidskriftsartikel (refereegranskat)abstract
- This paper provides a comprehensive characterisation of HVOF- and HVAF-sprayed Cr3C2–25 wt.% NiCr hardmetal coatings. One commercial powder composition with two different particle size distributions was processed using five HVOF and HVAF thermal spray systems.All coatings contain less Cr3C2 than the feedstock powder, possibly due to the rebound of some Cr3C2-rich particles during high-velocity impact onto the substrate.Dry sand-rubber wheel abrasive wear testing causes both grooving and pull-out of splat fragments. Mass losses depend on inter- and intra-lamellar cohesion, being higher (≥70 mg after a wear distance of 5904 m) for the coatings deposited with the coarser feedstock powder or with one type of HVAF torch.Sliding wear at room temperature against alumina involves shallower abrasive grooving, small-scale delamination and carbide pull-outs, and it is controlled by intra-lamellar cohesion. The coatings obtained from the fine feedstock powder exhibit the lowest wear rates (≈5x10−6 mm3/(Nm)). At 400 °C, abrasive grooving dominates the sliding wear behaviour; wear rates increase by one order of magnitude but friction coefficients decrease from ≈0.7 to ≈0.5. The thermal expansion coefficient of the coatings (11.08x10−6 °C−1 in the 30–400 °C range) is sufficiently close to that of the steel substrate (14.23x10−6 °C−1) to avoid macro-cracking
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| 3. |
- Bolelli, G., et al.
(författare)
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Tribology of HVOF- and HVAF-sprayed WC-10Co4Cr hardmetal coatings : A comparative assessment
- 2015
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Ingår i: Surface and Coatings Technology. - : Elsevier. - 0257-8972. ; 265, s. 125-144
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Tidskriftsartikel (refereegranskat)abstract
- his paper provides a comprehensive assessment of the sliding and abrasive wear behaviour of WC–10Co4Cr hardmetal coatings, representative of the existing state-of-the-art. A commercial feedstock powder with two different particle size distributions was sprayed onto carbon steel substrates using two HVOF and two HVAF spray processes.Mild wear rates of < 10-7 mm3/(Nm) and friction coefficients of ≈ 0.5 were obtained for all samples in ball-on-disk sliding wear tests at room temperature against Al2O3 counterparts. WC–10Co4Cr coatings definitely outperform a reference electrolytic hard chromium coating under these test conditions. Their wear mechanisms include extrusion and removal of the binder matrix, with the formation of a wavy surface morphology, and brittle cracking. The balance of such phenomena is closely related to intra-lamellar features, and rather independent of those properties (e.g. indentation fracture toughness, elastic modulus) which mainly reflect large-scale inter-lamellar cohesion, as quantitatively confirmed by a principal component analysis. Intra-lamellar dissolution of WC into the matrix indeed increases the incidence of brittle cracking, resulting in slightly higher wear rates. At 400 °C, some of the hardmetal coatings fail because of the superposition between tensile residual stresses and thermal expansion mismatch stresses (due to the difference between the thermal expansion coefficients of the steel substrate and of the hardmetal coating). Those which do not fail, on account of lower residual stresses, exhibit higher wear rates than at room temperature, due to oxidation of the WC grains.The resistance of the coatings against abrasive wear, assessed by dry sand–rubber wheel testing, is related to inter-lamellar cohesion, as proven by a principal component analysis of the collected dataset. Therefore, coatings deposited from coarse feedstock powders suffer higher wear loss than those obtained from fine powders, as brittle inter-lamellar detachment is caused by their weaker interparticle cohesion, witnessed by their systematically lower fracture toughness as well.
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| 4. |
- Clement, C., et al.
(författare)
-
Corrosion behavior of HVAF- and HVOF-sprayed high-chromium Fe-based coatings
- 2015
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Konferensbidrag (refereegranskat)abstract
- Fe-based coatings with three particular elemental compositions and two different powder particle size were prepared by high-velocity air fuel (HVAF) and high-velocity oxy fuel (HVOF) techniques. The corrosion behavior of which were comparatively studied in 3.5 wt.% NaCl solution. The results indicated that the coatings produced by HVAF process exhibited denser structure with lower porosity. Polarization and electrochemical impedance spectroscopy (EIS) tests indicated that the HVAF coatings provided better corrosion resistance than the HVOF coatings. The presence of defects was significant in HVOF coatings. The investigation illustrated that the corrosion paths initiated and grow through defects of the coating. Furthermore, adding Cr strongly improved the corrosion resistance of the coatings. The results confirmed that the cheap HVAF process could be a potential alternative to HVOF to fabricate Fe-based coatings for industrial applications.
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| 5. |
- List, A, et al.
(författare)
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Mechanical properties of cold-sprayed Ti-6Al-4V coatings
- 2013
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Ingår i: Proceedings of the International Thermal Spray Conference. - : ASM International. - 9781632666819 ; , s. 155-160
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Konferensbidrag (refereegranskat)abstract
- Titanium and titanium alloys are of great interest in aerospace and medical industries. Especially, Ti-6Al-4V alloys show a unique combination of high mechanical strength, low density and an outstanding corrosion resistance. However, particularly the high strength restricts industrial processing procedures. Thus, there are increasing demands for powder metallurgical process routes. For pure titanium, cold spraying already proved to be a promising alternative for manufacturing semi-finished products, mainly due to the use of high process gas temperatures and pressures. Nevertheless, due to the higher material strength, the production of Ti-6Al-4V coatings by cold spraying is still challenging, even under higher process parameters. The present study deals with the production and characterization of Ti-6Al-4V coatings produced by cold spraying. All experiments were performed using nitrogen as process gas. By a systematic variation of the spray parameters up to a process gas temperature of 1000°C and a process gas pressure of 5 MPa, the coatings could be tuned for optimum mechanical properties. In addition, attainable coating properties are described in terms of a newly introduced coating quality parameter η, namely the ratio of the particle velocity to the critical velocity, to reveal the most significant influences on coating performance and to give hints for further optimization.
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| 6. |
- Lyphout, Christophe, 1981
(författare)
-
Adhesion and Residual Stress Characterization of HVOF Sprayed Inconel 718 Coatings
- 2008
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Licentiatavhandling (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 increase permissible repair thicknesses. Therefore, understanding the relationship between coating thickness and residual stress levels – particularly in the interface between coating and substrate on the one hand and coating adhesion 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.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 was developed alongside a method for determining adhesion shear strength. It was also found that determination of residual stresses by destructive (Modified Layer Removal Method) and non destructive (Neutron Diffraction) methods is a tricky task when a material is to be coated with the same material. The different techniques, methods and models that have been developed will provide valuable tools in future work to evaluate and understand relationships between coating thickness, residual stress states and adhesion strength as well, additionally, for studying ways in which process parameters can be optimized for enhanced adhesion strength in HVOF sprayed coatings.
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| 7. |
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| 8. |
- Lyphout, Christophe, 1981, et al.
(författare)
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Adhesion Strength of HVOF Sprayed IN718 Coating
- 2011
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Ingår i: Journal of Thermal Spray Technology. - 1059-9630 .- 1544-1016.
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Tidskriftsartikel (refereegranskat)abstract
- The adhesion strength of high velocity oxy-fuel thermally sprayed coatings is of prior importance when thick coatings are to be sprayed for aeronautical repair applications. In this study, relationships between process parameters, particle in-flight characteristics, residual stresses and adhesion strength have been explored. Design of Experiments (DoE) was utilized to identify the most important process parameters that influence coating adhesion strength. Residual stress distributions were determined using the Modified Layer Removal Method (MLRM) and adhesion strength was measured using an in-house developed tensile test. Relationships between process parameters, particle in-flight characteristics, coating microstructure and adhesion strength were established. Particle temperature, particle velocity, substrate preparation and deposition temperature were identified as critical parameters to attain high adhesion strength. Controlling these parameters can significantly improve the adhesion strength, thus enabling thick coatings to be sprayed for aeronautical repair applications.
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| 9. |
- Lyphout, Christophe, 1981-, et al.
(författare)
-
Adhesion strength of HVOF sprayed IN718 coatings
- 2012
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Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 21:1, s. 86-95
-
Tidskriftsartikel (refereegranskat)abstract
- The adhesion strength of high-velocity oxyfuel thermally sprayed coatings is of prime importance when thick coatings are to be sprayed in repair applications. In this study, relationships between process parameters, particle in-flight characteristics, residual stresses, and adhesion strength were explored. The most important process parameters that influence HVOF sprayed IN718 coating adhesion strength on IN718 substrate material were identified. Residual stress distributions were determined using the modified layer removal method, and adhesion strength was measured using an in-house-developed tensile test. Relationships between process parameters, particle in-flight characteristics, coating microstructure, and adhesion strength were established. Particle temperature, particle velocity, substrate preparation, and deposition temperature were identified as critical parameters to attain high adhesion strength. Controlling these parameters can significantly improve the adhesion strength, thus enabling thick coatings to be sprayed for repair applications. © 2011 ASM International.
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| 10. |
- Lyphout, Christophe, 1981
(författare)
-
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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| 11. |
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| 12. |
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| 13. |
- Lyphout, Christophe, 1981, et al.
(författare)
-
Characterization of Adhesion Strength and Residual Stresses of HVOF Sprayed Inconel 718 for Aerospace Repair Applications
- 2007
-
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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| 14. |
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| 15. |
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| 16. |
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| 17. |
- Lyphout, Christophe, 1981, et al.
(författare)
-
Influence of substrate preparation on HVOF IN718 coating adhesion strength
- 2011
-
Ingår i: Proceedings of the 25th International Conference on Surface Modification Technologies (SMT25).
-
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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| 18. |
- Lyphout, Christophe, 1981-, et al.
(författare)
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Internal Diameter HVAF Spraying for Wear and Corrosion Applications
- 2014
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Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 24:1-2, s. 235-243
-
Tidskriftsartikel (refereegranskat)abstract
- Electrolytic hard chrome (EHC) methods are still widely utilized in the printing, automotive and off-shore industries. Alternative methods to EHC have been widely developed in the past decade by conventional HVOF processes and more recently HVAF systems, which are processing at higher kinetic energy and more particularly at lower temperature, significantly increasing wear and corrosion resistance properties. A dedicated internal diameter HVAF system is here presented, and coatings characteristics are compared to the one obtained by standard HVAF coatings. Specially R&D designed fixtures with inside bore of 200 mm have been manufactured for this purpose, with a possibility to spray samples at increasing depth up to 400 mm while simulating closed bottom bore spraying. WC-based and Cr3C2-based powder feedstock materials have been deposited onto high-strength steel substrates. Respective coating microstructures, thermally induced stresses and corrosion resistance are discussed for further optimization of coating performances. The fact that the ID-HVAF system is utilized both for spraying and gritblasting procedures is also given a particular interest.
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| 19. |
- Lyphout, Christophe, 1981-, et al.
(författare)
-
Mechanical Property of HVOF Inconel 718 Coating for Aeronautic Repair
- 2014
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Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 23:3, s. 380-388
-
Tidskriftsartikel (refereegranskat)abstract
- The module of elasticity is one of the most important mechanical properties defining the strength of a material which is a prerequisite to design a component from its early stage of conception to its field of application. When a material is to be thermally sprayed, mechanical properties of the deposited layers differ from the bulk material, mainly due to the anisotropy of the highly textured coating microstructure. The mechanical response of the deposited layers significantly influences the overall performance of the coated component. It is, therefore, of importance to evaluate the effective module of elasticity of the coating. Conventional experimental methods such as microindentation, nanoindentation and four-point bending tests have been investigated and their results vary significantly, mainly due to inhomogeneous characteristics of the coating microstructure. Synchrotron radiation coupled with a tensile test rig has been proposed as an alternative method to determine the coating anisotropic elastic behavior dependence on crystallographic orientations. The investigation was performed on Inconel 718 (IN718) HVOF coatings sprayed on IN718 substrates. Combining these experimental techniques yield a deeper understanding of the nature of the HVOF coating Young’s modulus and thus a tool for Design Practice for repair applications. © 2013 ASM International.
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| 20. |
- Lyphout, Christophe, 1981, et al.
(författare)
-
Modeling of Peening Stress in HVOF Sprayed IN718 Coating
- 2011
-
Ingår i: Proceedings of the International Thermal Spray Conference ITSC-11.
-
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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| 21. |
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| 22. |
- Lyphout, Christophe, 1981-, et al.
(författare)
-
Relationships between process parameters, microstructure, and adhesion strength of HVOF sprayed IN718 coatings
- 2011
-
Ingår i: Journal of thermal spray technology (Print). - 1059-9630 .- 1544-1016. ; 20:1-2, s. 76-82
-
Tidskriftsartikel (refereegranskat)abstract
- Fundamental understanding of relationships between process parameters, particle in-flight characteristics, and adhesion strength of HVOF sprayed coatings is important to achieve the high coating adhesion that is needed in aeronautic repair applications. In this study, statistical Design of Experiments (DoE) was used to identify the most important process parameters that influence adhesion strength of IN718 coatings sprayed on IN718 substrates. Special attention was given to the parameters combustion ratio, total gas mass flow, stand-off distance and external cooling, since these parameters were assumed to have a significant influence on particle temperature and velocity. Relationships between these parameters and coating microstructure were evaluated to fundamentally understand the relationships between process parameters and adhesion strength. © 2010 ASM International.
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| 23. |
- 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
-
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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| 24. |
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| 25. |
- Lyphout, Christophe, 1981-, et al.
(författare)
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Screening design of hard metal feedstock powders for supersonic air fuel processing
- 2014
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 258:15 November, s. 447-457
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Tidskriftsartikel (refereegranskat)abstract
- Replacement of Electrolytic Hard Chromium (EHC) method by Thermal Spray Technology has shown a growing interest the past decades, mainly pioneered by depositing WC-based material by conventional HVOF processes. Lower thermal energy and higher kinetic energy of sprayed particles achieved by newly-developed Supersonic Air Fuel system, so-called HVAF-M3, significantly reduces decarburization, and increases wear and corrosion resistance properties, making HVAF-sprayed coatings attractive both economically and environmentally. In the present work, a first order process map has been intended via a full factorial Design of Experiments (DoE) to establish relationships between powder feedstock characteristics, such as primary carbides grain size, binder grain size and powder strength, and coatings microstructure and mechanical properties. A second order process map was then established to study possible correlations between the deposit microstructural properties and their respective abrasion/erosion wear and corrosion performances.
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| 26. |
- Lyphout, Christophe, 1981-, et al.
(författare)
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Screening Design of Supersonic Air Fuel Processing for Hard Metal Coatings
- 2014
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Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 23:8, s. 1323-1332
-
Tidskriftsartikel (refereegranskat)abstract
- Replacement of electrolytic hard chromium method by thermal spray technology has shown a growing interest in the past decades, mainly pioneered by depositing WC-based material by conventional HVOF processes. Lower thermal energy and higher kinetic energy of sprayed particles achieved by newly developed Supersonic Air Fuel system, so-called HVAF-M3, significantly reduces decarburization, and increases wear and corrosion resistance properties, making HVAF-sprayed coatings attractive both economically and environmentally. In the present work, full factorial designs of experiments have been extensively utilized to establish relationships between hardware configurations, process and engineering variables, and coatings properties. The relevance of those process factors is emphasized and their significance is discussed in the optimization of coatings for improved abrasion wear and corrosion performances. © 2014 ASM International.
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| 27. |
- Lyphout, Christophe, 1981-, et al.
(författare)
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Tribological Properties of Hard Metal Coatings Sprayed by High Velocity Air Fuel Process
- 2015
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Ingår i: Proceedings of the International Thermal Spray Conference. - : ASM International. ; , s. 761-766
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Konferensbidrag (refereegranskat)abstract
- Lowering the thermal energy and increasing the kinetic energy of sprayed particles by newly developed HVAF systems can significantly reduce material decarburization, and increases sliding wear and corrosion resistance of hard metal coatings, making HVAF coatings attractive both economically and environmentally over its HVOFs predecessors. Two agglomerated and sintered feedstock powder chemistries, respectively WC-Co (88/12) and WC-CoCr (86/10/4), with increasing primary carbides grain size from 0.2 to 4.0 microns, have been deposited by the latest HVAF-M3 process onto carbon steel substrates. Respective dry sliding wear behaviours and friction coefficients were evaluated at room temperature via Ball-on-disk (ASTM G99-90) wear tests against Al2O3 counterparts, and via Pin-on-disk (ASTM G77-05) wear tests against modified martensitic steel counterparts in both dry and lubricated conditions. Sliding wear mechanisms, with formation of wavy surface morphology and brittle cracking, are discussed regarding the distribution and size of primary carbides. Corrosion behaviours were evaluated via standard Neutral Salt Spray (NSS), Acetic Acid Salt Spray (AASS), accelerated corrosion test and electrochemical polarization test at room temperature. Optimization of coating tribological properties are discussed regarding the suitable selection of primary carbide size for different working load applications
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| 28. |
- Lyphout, Christophe, 1981-, et al.
(författare)
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Tribological Properties of Hard Metal Coatings Sprayed by High-Velocity Air Fuel Process
- 2016
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Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 25:1-2, s. 331-345
-
Tidskriftsartikel (refereegranskat)abstract
- Lowering the thermal energy and increasing the kinetic energyof hard metal particles sprayed by the newly developed HVAF systems can significantly reduce their decarburization, and increases the sliding wear and corrosion resistance of the resulting coatings, making the HVAF technique attractive, both economically and environmentally, over its HVOF predecessors. Two agglomerated and sintered feedstock powder chemistries, WC-Co (88/12) and WC-CoCr (86/10/4), respectively, with increasing primary carbides grain size from 0.2 to 4.0 microns, have been deposited by the latest HVAF-M3 process onto carbon steel substrates. Their dry sliding wear behaviors and friction coefficients were evaluated at room temperature via Ball-on-disk (ASTM G99-90) wear tests against Al2O3 counterparts, and via Pin-on-disk (ASTM G77-05) wear tests against modified martensitic steel counterparts in both dry and lubricated conditions. Sliding wear mechanisms, with the formation of wavy surface morphology and brittle cracking, are discussed regarding the distribution and size of primary carbides. Corrosion behaviors were evaluated via standard Neutral Salt Spray, Acetic Acid Salt Spray, accelerated corrosion test, and electrochemical polarization test at room temperature. The optimization of the tribological properties of the coatings is discussed, focusing on the suitable selection of primary carbide size for different working load applications. © 2015 ASM International
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| 29. |
- Nylén, Per, 1960-, et al.
(författare)
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Relationships between Process Parameters, Microstructure and Adhesion Strength of HVOF Sprayed IN718 Coating
- 2010
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Ingår i: Proceedings of the 2010 International Thermal Spray Conference. - : Springer Science and Business Media LLC. - 9783871555909 ; , s. 1-7
-
Konferensbidrag (refereegranskat)abstract
- Fundamental understanding of relationships between process parameters, particle in-flight characteristics, and adhesion strength of HVOF sprayed coatings is important to achieve the high coating adhesion that is needed in aeronautic repair applications. In this study, statistical Design of Experiments (DoE) was used to identify the most important process parameters that influence adhesion strength of IN718 coatings sprayed on IN718 substrates. Special attention was given to the parameters combustion ratio, total gas mass flow, stand-off distance and external cooling, since these parameters were assumed to have a significant influence on particle temperature and velocity. Relationships between these parameters and coating microstructure were evaluated to fundamentally understand the relationships between process parameters and adhesion strength.
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| 30. |
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| 31. |
- Vijay, Sudarshan, et al.
(författare)
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Surface characteristics investigation of HVAF sprayed cermet coatings
- 2019
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 493, s. 956-962
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Tidskriftsartikel (refereegranskat)abstract
- Superhydrophobic surfaces that are durable and can be easily manufactured are of high interest for many industrial applications. Measuring and understanding roughness in the context of superhydrophobicity is the first step in creation of a surface that does not require activation to be hydrophobic. In this study, the as sprayed surface of different cermet (WC-10Co4Cr and Cr3C2-25Ni20Cr) coatings produced by High Velocity Air Fuel (HVAF) spraying – have been investigated to assess their wetting ability. In order to address the challenges raised by the specific roughness profile of thermal spray surfaces, two routes have been adapted and used for surface characteristics analysis i.e. statistical and fractal. Results show that both methods have a strong correlation to wettability. Roughness parameters Sdq and Sdr show good correlation with advancing contact angle. Hausdorff Dimension of a sub-micrometer profile shows good relation with the contact angle and provides information for state of the droplet. To determine how to increase the contact angle of the coating surface, coating parameters such as CGS Density have been correlated with Hausdorff Dimension. Both methods provide good understanding in terms of wettability of rough cermet surfaces. © 2019 Elsevier B.V.
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| 32. |
- Vijay, S., et al.
(författare)
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Wetting properties of ceramic reinforced metal matrix composites on varied roughness profiles
- 2017
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Ingår i: Proceedings of the International Thermal Spray Conference & Exposition (ITSC 2017). - New York : Curran Associates, Inc.. - 9781510858220 ; , s. 537-542
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Konferensbidrag (refereegranskat)abstract
- Superhydrophobic surfaces are of great importance in many industrial applications, especially where components are exposed to wet environments and low temperatures.Texturing of surfaces to reach superhydrophobicity can be achieved by thermal spraying technology, which is an attractive coating method as it is cheap, flexible and can employ a large range of feedstock materials. In this study, ceramic reinforced metal matrix composite (WC-CoCr) powders were sprayed using High Velocity Air Fuel method. They were varied based on their powder parameters such as carbide grain size, binder grain size and powder strength. The purpose was to investigate their hydrophobic characteristics and how these are influenced by different roughness profiles. The wetting properties such as contact angle and contact angle hysteresis were first investigated for the as-sprayed coatings. The roughness properties and Hausdorff Dimension were then related to the wetting properties. Aside from as-sprayed coatings, the effect of roughness and inherent wetting characteristics were studied by investigating the coating surface after grit blasting and polishing. Results show that powder parameters can lead to designing surfaces with higher surface roughnesses and thus having higher contact angles. It was also shown that surface composition of cermets has an impact on wettability, with the binder accounting for wetting characteristics and carbides accounting for roughness.
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