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See detailOn the Elaboration of Metal-Ceramic Composite Coatings by Laser Cladding
Mertens, Anne ULg; L'Hoest, Thibaut; Magnien, Julien et al

in Materials Science Forum (2017), 879

This paper reports on a preliminary investigation into the elaboration, by the additive process known as laser cladding, of composite coatings with a matrix of stainless steel 316L reinforced with varying ... [more ▼]

This paper reports on a preliminary investigation into the elaboration, by the additive process known as laser cladding, of composite coatings with a matrix of stainless steel 316L reinforced with varying contents of tungsten (WC) or silicon carbides (SiC) particles. Laser cladding is characterised by ultra-fast solidification and cooling rates, thus giving rise to ultra-fine out-of-equilibrium microstructures and potentially enhanced mechanical properties. Both types of composite coatings – i.e. with SiC or WC ‒ are compared in terms of their microstructures and hardness. Special attention is given to the dissolution of the carbides particles and to interfacial reactions taking place between the particles and the metallic matrix. [less ▲]

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See detailAdditive Manufacturing of Metallic Materials: An Introduction
Mertens, Anne ULg

Learning material (2016)

This powerpoint presentation was used as teaching material in a seminar given as part of the course “Ingénierie des matériaux métalliques”. Following on a general introduction to additive manufacturing of ... [more ▼]

This powerpoint presentation was used as teaching material in a seminar given as part of the course “Ingénierie des matériaux métalliques”. Following on a general introduction to additive manufacturing of metallic materials, it outlines some important current issues in the development of additive technologies, by reporting on two case studies into the processing (1) of a single material system (i.e. Ti alloy Ti-6Al-4V) and (2) of a multimaterial system (i.e. a metal matrix composite). The first case study on Ti-6Al-4V reviews issues related to the dimensional accuracy of the produced components, as well as the control of their microstructures and usage properties. The second case study provides an introduction to metal matrix composites with a particular attention for the process known as laser cladding, focusing on the relationships between the thermal history during the production of a composite coating, and the resulting microstructure and properties, with special attention to the dissolution of ceramic particles (e.g. carbides) and to interfacial reactions taking place between the particles and the metallic matrix. [less ▲]

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See detailLaser Additive Manufacturing of Metal Matrix Composites
Mertens, Anne ULg

Learning material (2016)

Current trends in the mechanics and energy industries impose increasing demands on metallic materials, combining elevated service temperatures and severe mechanical solicitations. Metal matrix composite ... [more ▼]

Current trends in the mechanics and energy industries impose increasing demands on metallic materials, combining elevated service temperatures and severe mechanical solicitations. Metal matrix composite coatings with ceramic reinforcements are good candidates in view of fulfilling the requirements for an improved mechanical durability, and for other complex functions (e.g. self-lubrication, biocompatibility...). First of all, this paper provides an introduction to metal matrix composites with a particular attention for the process known as laser cladding that appears as a promising technology for making composite coatings. In this process, a (mixture of) metallic powder(s) is projected onto a substrate through a nozzle and simultaneously melted by a laser beam. Laser cladding is characterised by ultra-fast solidification and cooling rates, thus giving rise to ultra-fine microstructures and potentially enhanced mechanical properties. The paper thus focuses on the relationships between the thermal history during the production of a composite coating, and the resulting microstructure and properties, with special attention to the dissolution of ceramic particles (e.g. carbides) and to interfacial reactions taking place between the particles and the metallic matrix. [less ▲]

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See detailOn the effect of microstructural anisotropy on the mechanical and thermophysical properties of Ti6Al4V processed by Laser Beam Melting
Mertens, Anne ULg; Paydas, Hakan ULg; Rigo, Olivier et al

Conference (2016, August 05)

Laser beam melting (LBM) is a strongly directional process in which a metallic powder is deposited layer by layer in a powder bed and molten locally according to the desired shape. When processing Ti6Al4V ... [more ▼]

Laser beam melting (LBM) is a strongly directional process in which a metallic powder is deposited layer by layer in a powder bed and molten locally according to the desired shape. When processing Ti6Al4V, it is well known that the latest layer tends to solidify epitaxially on the previous layers, thus giving rise to elongated columnar primary β(BCC) crystals extending over several successive layers. These primary β grains then transforms into the α(HCP) structure upon cooling. The present work aimed at studying the microstructural anisotropy of LBM Ti6Al4V, as well as its consequences on the mechanical and thermophysical properties (i.e. thermal expansion and thermal conductivity). In order to gain a deeper undestanding of thermal phenomena in the LBM of Ti6Al4V, great care was also taken to characterize the thermophysical properties over a wide temperature range from room temperature. [less ▲]

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See detailAlumina and zircon refractory ceramic molds fabrication by additive methods for metal alloys casting
Bister, Geoffroy; Hautcoeur, Dominique; Deschuyteneer, Dorian et al

Conference (2016, July 19)

Traditional processes for the foundry molds fabrication need numerous and rather time consuming steps. These processes are not really adapted to small series or prototypes. The research project exposed in ... [more ▼]

Traditional processes for the foundry molds fabrication need numerous and rather time consuming steps. These processes are not really adapted to small series or prototypes. The research project exposed in this contribution proposes an alternative method combining the advantages of molding (free formulation of metal alloys, economy on material and on time of machining) with those of the additive processes (short steps between 3D-model and final product, very complex geometries available). For short series the selective laser melting process (SLM) allows the building of molds in a very short time compared to the traditional investment casting method. This technique also permits the unique advantage to control the design of the shell thickness and structure in order to have a better control of the thermal fluxes during metal cooling. This would potentially ensure a better control of the casting defaults. In this presentation, molds built with alumina and zircon as raw materials will be presented. Two metallic alloys have been tested in order to validate alumina and zircon as mold materials; the first, AlCu4MgSi chosen as low melting point alloy reference and the second, stainless steel 316L, as high melting point alloy reference [less ▲]

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See detailOn the role of interfacial reactions, dissolution and secondary precipitation during the laser additive manufacturing of metal matrix composites - A Review
Mertens, Anne ULg; Lecomte-Beckers, Jacqueline ULg

in Shishkovsky, I.V. (Ed.) New Trends in 3D Printing (2016)

Since current trends in the transportation, energy or mechanical industries impose increasingly demanding service conditions for metallic parts, metal matrix composites (MMC) are the object of a growing ... [more ▼]

Since current trends in the transportation, energy or mechanical industries impose increasingly demanding service conditions for metallic parts, metal matrix composites (MMC) are the object of a growing interest. Powder-based laser additive manufacturing, that allows to make parts with complex shapes, appears particularly adapted for the production of MMCs. This paper reviews the current state-of-the-art in the production of MMCs by additive processes, with the aim of assessing the potentials and difficulties offered by these techniques. Two main processing routes are envisaged i.e. (1) the processing of ex-situ composites in which the reinforcing phase as a powder – often of ceramic particles − is directly mixed with the powder of the matrix alloy, and both powders are simultaneously processed by the laser. (2) Alternatively, the reinforcing phase can be produced in-situ by a chemical reaction during the fabrication of the composite. For both processing routes, a careful control is needed to overcome challenges brought e.g. by the behaviour of the reinforcement particles in the laser beam, by changes in laser absorptivity or by the dissolution of the reinforcing particles in the molten metal, in order to produce metal matrix composites with enhanced usage properties. [less ▲]

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See detailMicrostructural evolution during the heat treatment of Laser Beam Melted AlSi10Mg
Mertens, Anne ULg; Dedry, Olivier ULg; Reuter, David et al

Conference (2016, June 01)

Al alloy AlSi10Mg processed by Laser Beam Melting (LBM) exhibits a much finer microstructure than its cast counterpart due to the ultra-fast cooling rates imposed in the LBM process. One important ... [more ▼]

Al alloy AlSi10Mg processed by Laser Beam Melting (LBM) exhibits a much finer microstructure than its cast counterpart due to the ultra-fast cooling rates imposed in the LBM process. One important consequence of this microstructural refinement is that a classical T6 age hardening heat treatment will not have the same effect on LBM AlSi10Mg when compared with cast AlSi10Mg. Indeed, a previous study by the present authors has shown that heat treating LBM AlSi10Mg at 510°C for 6 hours followed by a second isothermal hold at 170°C for 6 hours brought a marked improvement of the yield stress by 30% and of the elongation at break by 220%. However, this was achieved at the expense of a decrease in both hardness and ultimate tensile strength. A better understanding of the underlying phenomena is needed in order to optimize the heat treatment of LBM AlSi10Mg. The present work hence aims at investigating in more depth the microstructural evolution induced upon heat treating LBM AlSi10Mg. Changes in texture as well as in the distribution of Si-rich precipitates (size, morphology...) have been studied, with a particular attention to those changes taking place during the first step of the heat treatment at the higher temperature of 510°C. [less ▲]

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See detailOn the laser additive manufacturing of metal matrix composites
Mertens, Anne ULg; L'Hoest, Thibaut; Lecomte-Beckers, Jacqueline ULg et al

Conference (2016, May 27)

This paper reviews the challenges and opportunities related to the production of of metal matrix composites (MMCs) and functionally graded materials (FGMs) by additive manufacturing laser-based ... [more ▼]

This paper reviews the challenges and opportunities related to the production of of metal matrix composites (MMCs) and functionally graded materials (FGMs) by additive manufacturing laser-based technologies. Special attention is given to issues such as the stability of the reinforcement particles under the laser beam, particles’ dissolution in the metallic melt pool and interfacial reactions between the particles and the metallic matrix. Illustrations are taken from a preliminary investigation, by the MMS Unit, into the laser cladding of stainless steel + carbides composite coatings, as well as from the open scientific literature. [less ▲]

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See detailUnderstanding the effect of thermal treatments on the ductility of LBM AlSi10Mg
Mertens, Anne ULg; Dedry, Olivier ULg; Lecomte-Beckers, Jacqueline ULg et al

Conference (2016, May 26)

This communication reviews the additive manufacturing activities of the MMS Unit, University of Liège, with a particular focus on the study of post-processing treatments of Al alloy AlSi10Mg. Al alloy ... [more ▼]

This communication reviews the additive manufacturing activities of the MMS Unit, University of Liège, with a particular focus on the study of post-processing treatments of Al alloy AlSi10Mg. Al alloy AlSi10Mg processed by Laser Beam Melting (LBM) exhibits a much finer microstructure than its cast counterpart due to the ultra-fast cooling rates imposed in the LBM process. One important consequence of this microstructural refinement is that a classical T6 age hardening heat treatment will not have the same effect on LBM AlSi10Mg when compared with cast AlSi10Mg. Indeed, a previous study by the present authors has shown that heat treating LBM AlSi10Mg at 510°C for 6 hours followed by a second isothermal hold at 170°C for 6 hours brought a marked improvement of the yield stress by 30% and of the elongation at break by 220%. However, this was achieved at the expense of a decrease in both hardness and ultimate tensile strength. A better understanding of the underlying phenomena is needed in order to optimize the heat treatment of LBM AlSi10Mg. The present work hence aims at investigating in more depth the mechanical and microstructural evolution induced upon heat treating LBM AlSi10Mg. [less ▲]

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See detailOn the Laser Cladding of Ti Alloy Ti-6Al-4V with Low Laser Power
Mertens, Anne ULg; Paydas, Hakan ULg; Tchuindjang, Jérôme Tchoufack ULg et al

in Ventakesh, V.; Pilchak, A.L.; Allison, J.E. (Eds.) et al Proc. of the 13th World Conference on Titanium (2016, May 06)

Laser cladding is an economic layer-by-layer near-net-shape process for the production and the repair of metallic parts. In this process, a metallic powder is projected onto a substrate while being molten ... [more ▼]

Laser cladding is an economic layer-by-layer near-net-shape process for the production and the repair of metallic parts. In this process, a metallic powder is projected onto a substrate while being molten by a laser beam. Laser sources with fairly high power – i.e. typically 2kW − are often used to ensure short building times and high productivity. However, this approach has limitations. Indeed, it is very difficult to produce thin walls at high laser power. Moreover, an increase of the incident energy may give rise to a relatively coarser microstructure, and this will in turn affect the mechanical properties of the component. In order to address these issues, this paper aims at assessing the potential of a laser source with a lower maximum power of 300W to enhance the flexibility of the process. Two types of samples – i.e. thin walls or bulk deposits − were produced at low laser power from alloy Ti-6Al-4V. Their geometry, microstructures and local hardness are characterised and correlated with the thermal history experienced during fabrication. [less ▲]

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See detailRAPPORT FINAL - Portefeuille de projets TipTopLam
Gravet, Denis; Carton, Marc; Contrepois, Quentin et al

Report (2016)

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See detailRefractory ceramic molds fabrication by additive methods for low and high melting point metal alloys casting
Bister, Geoffroy; Deschuyteneer, Dorian; Hautcoeur, Dominique et al

Conference (2016, March 23)

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See detailLocal thermal history during the laser additive manufacturing of steel
Mertens, Anne ULg; Hashemi, Seyedeh Neda ULg; Tchuindjang, Jérôme Tchoufack ULg et al

Conference (2016, February 09)

Laser additive manufacturing techniques – such as laser cladding − were developed in the late 1990s as economic layer-by-layer near-net-shape processes allowing for the production or restoration of ... [more ▼]

Laser additive manufacturing techniques – such as laser cladding − were developed in the late 1990s as economic layer-by-layer near-net-shape processes allowing for the production or restoration of complex metallic parts. These techniques are characterised by ultra-fast solidification and cooling rates, thus giving rise to ultra-fine out-of-equilibrium microstructures with potentially enhanced mechanical properties. However, the general quality of a component, as well as its dimensional accuracy, microstructure and final usage properties are strongly influenced by the local thermal history experienced during fabrication. As a consequence, a deeper understanding of the influence of the various processing parameters on the local thermal history during fabrication is of paramount importance, and it can only be reached by combining detailed experimental studies and modeling. Keeping this in mind, the present paper reviews on-going investigations carried out in the Metallic Materials Science Unit of the University of Liege in the laser additive manufacturing of HSS and of stainless steel 316L. [less ▲]

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See detailFLYCOAT - Programme d'excellence : Rapport scientifique et technique 1°phase 1er Mars 2015 au 29 Février 2016
Dedry, Olivier ULg; Mertens, Anne ULg; Lecomte-Beckers, Jacqueline ULg

Report (2016)

Le projet FLYCOAT innovera dans les domaines suivants : - Résistance à l’usure : améliorer les revêtements existants par des procédés de fabrication innovants, pour répondre à des propriétés spécifiques ... [more ▼]

Le projet FLYCOAT innovera dans les domaines suivants : - Résistance à l’usure : améliorer les revêtements existants par des procédés de fabrication innovants, pour répondre à des propriétés spécifiques, comme la tenue à l’érosion et à l’impact (grêle, gravillonnage) - Protection anti-corrosion : obtenir des performances équivalentes aux systèmes actuels en l’absence de chromates - Propriétés électriques : conférer des propriétés antistatiques - Propriétés thermiques : améliorer la résistance à la thermo-oxidation et au cyclage thermique. - Résistance aux liquides aéronautiques. [less ▲]

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See detailCurrent issues in the processing of Ti alloy Ti6Al4V by laser additive manufacturing techniques
Mertens, Anne ULg

Learning material (2015)

This powerpoint presentation was used as teaching material in a seminar given as part of the course “Advanced Manufacturing technologies” at Université catholique de Louvain. It outlines important current ... [more ▼]

This powerpoint presentation was used as teaching material in a seminar given as part of the course “Advanced Manufacturing technologies” at Université catholique de Louvain. It outlines important current issues in the development of additive technologies for the processing of metallic materials in general, and particularly of Ti alloy Ti-6Al-4V. This includes issues related to the dimensional accuracy of the produced components, as well as the control of their microstructures and usage properties. [less ▲]

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Peer Reviewed
See detailLaser cladding as repair technology for Ti6Al4V alloy: Influence of building strategy on microstructure and hardness
Paydas, Hakan ULg; Mertens, Anne ULg; Carrus, Raoul et al

in Materials & Design (2015), 85

Laser cladding is a metal deposition technique used to fabricate or repair components made from high value metallic alloys. In the present work Ti-6Al-4V deposits with variable thickness are made to ... [more ▼]

Laser cladding is a metal deposition technique used to fabricate or repair components made from high value metallic alloys. In the present work Ti-6Al-4V deposits with variable thickness are made to assess the use of laser cladding as a repair technology. Both the effect of the building strategy (BS) and the incident energy (IE) on the metallurgical characteristics of the deposits in relation to their complex thermal history have been studying. It is shown that for the configuration consisting in a decreasing track length (DTL) under high IE, a gradient of cooling rate exists that leads to the presence of different phases within the microstructure. Conversely homogeneous microstructures are present either for the configuration with a constant track length (CTL) under high IE, and for the strategy obtained from a DTL under low IE. Depending on the possible heat accumulation the nature of the phases are determined together with hardness maps within the deposits. Some qualification criteria are set prior to tensile tests to selected the adequate candidate-deposit that does not weaken the cladded material when it is stressed. A thermo-metallurgical scheme is proposed that helps understanding the effect of both the BS and the IE on the microstructure. [less ▲]

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See detailProduction of alumina foundry moulds by additive manufacturing for low and high melting points alloys prototypes
Bister, Geoffroy; Deschuyteneer, Dorian; Hautcoeur, Dominique et al

Poster (2015, October 26)

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See detail2D Thermal model of powder injection laser cladding of high speed steels (HSS)
Hashemi, Seyedeh Neda ULg; Gilles, Gatën; Tomé Jardin, Ruben Antonio ULg et al

Conference (2015, October 23)

A two-dimensional multi-layer model for the transient temperature field analysis of Laser cladding process is developed. This model allows studying the thermal field of the multilayer deposits during ... [more ▼]

A two-dimensional multi-layer model for the transient temperature field analysis of Laser cladding process is developed. This model allows studying the thermal field of the multilayer deposits during their development by laser, and the "flat" substrate on which the deposition is carried. [less ▲]

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See detailTipTopLam - Rapid manufacturing laser de pièces en titane (2008-2015), volet 1: Caractérisation microstructurale
Carton, Marc; Contrepois, Quentin; Mertens, Anne ULg et al

Report (2015)

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