References of "Lecomte-Beckers, Jacqueline"
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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 detail3-D finite element analysis of laser cladding process. Application to Ti-6Al-4V
Tran, Hoang Son ULg; Brusten, Romain; Paydas, Hakan ULg et al

Scientific conference (2016, May 20)

In this study, a 3-D thermal numerical modelling of laser cladding by powder injection as a repair technology applied to Ti-6Al-4V was developed. In order to implement the movement of the heat source in ... [more ▼]

In this study, a 3-D thermal numerical modelling of laser cladding by powder injection as a repair technology applied to Ti-6Al-4V was developed. In order to implement the movement of the heat source in the model and the addition of material, a C++ programme was developed. Transition refinement elements are used to reduce the number of degrees of freedom. The temperature distribution and its time evolution were computed which allowed the prediction of the heat affected zone and the fusion size of the substrate. Effects of heat source distribution, energy input are investigated. Temperature measurements validate the model. [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 detailStudy of the effect of amino-functionalized multiwall carbon nanotubes on dry sliding wear resistance properties of carbon fiber reinforced thermoset polymers
Pincheira, G.; Montalba, C.; Gacitua, W. et al

in Polymer Bulletin (2016)

This work investigates the effect of multiwall carbon nanotubes (MWCNTs) on the mechanical and tribological behavior of a fiber reinforced composite (FRC). Fiber reinforced composites and nano-engineered ... [more ▼]

This work investigates the effect of multiwall carbon nanotubes (MWCNTs) on the mechanical and tribological behavior of a fiber reinforced composite (FRC). Fiber reinforced composites and nano-engineered FRCs are manufactured by resin transfer molding. In-plane tensile tests, in-plane shear tests and through-thickness compression tests are used to assess the influence of MWCNTs on the material mechanical behavior. Pin on disk dry sliding tests are used to quantify the effect of MWCNTs on the friction coefficient and the specific wear rate. It was determined that (1) MWCNTs have an influence on the improvement on both the through-thickness compression strength and the specific wear rate, and (2) they do not influence the material stiffness, in-plane tensile and shear strengths and the friction coefficient. It is assumed that the observed improvements are due to the demonstrated positive influence of the MWCNTs effect on the matrix/reinforcement interfacial strength and on the matrix fracture toughness. [less ▲]

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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 detailFE modeling of the cooling and tempering steps of bimetallic rolling mill rolls
Neira Torres, Ingrid; Gilles, Gaëtan ULg; Tchuindjang, Jérôme Tchoufack ULg et al

in International Journal of Material Forming (2015)

Numerical simulations enable the analysis of the stress and strain histories of bimetallic rolling mill rolls. The history of rolling mill rolls is simulated by thermo-mechanical metallurgical finite ... [more ▼]

Numerical simulations enable the analysis of the stress and strain histories of bimetallic rolling mill rolls. The history of rolling mill rolls is simulated by thermo-mechanical metallurgical finite element code while considering two steps: post-casting cooling and subsequent tempering heat treatment. The model requires a notably large set of material parameters. For different phases and temperatures, Young modulus, yield limit and tangent plastic modulus are determined through compression tests. Rupture stresses and strains are obtained by tensile tests. Thermo-physical parameters are measured by such experimental methods as dilatometry, DSC (Differential Scanning Calorimetry) and Laser Flash methods. Such parameters as the transformation plasticity coefiicients for the ferrite, pearlite and martensite phases are identified through an inverse method. From the simulation results, the profile of the stresses evolution at different critical times is presented. An analysis of the potential damage is proposed by comparing the predicted axial stress \vith rupture stresses. The perspective of the Ghosh and McClintock damage criteria is also investigated. [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 detailComparison of the wear behavior of high speed steel grades obtained from conventional casting and laser cladding
Hashemi, Seyedeh Neda ULg; Lecomte-Beckers, Jacqueline ULg; Montrieux, Henri-Michel ULg et al

Conference (2015, September)

Tools Steels are alloys which withstand severe mechanical and physicochemical stresses in service. Therefore their alloying design that involved both the original chemical composition and the casting ... [more ▼]

Tools Steels are alloys which withstand severe mechanical and physicochemical stresses in service. Therefore their alloying design that involved both the original chemical composition and the casting route is crucial in order to achieve a tailored microstructure exhibiting enhanced wear performances. Tools steels obtained from conventional casting processes had received lot of attention so far as they yield typical microstructure composed of a quasi-continuous network of coarse grain boundary carbides with grain size ranging between 20 to 200 µm. Direct energy deposition applied to Tools Steels represents a new emerging technique that may allow ultrafine grained microstructures due to the higher cooling rates achieved especially in the solidification range. In this paper, four tool steels grades were studied, one of them being obtained from a conventional casting process and the other ones originated from the direct energy deposition. Differential Thermal Analysis helps enhancing the solidification sequence of the studied alloys, while their microstructure after subsequent heat treatment was characterized by the means of both optical and electron microscopes together with hardness measurements. Tribological tests carried out at room temperature and at high temperature were performed while using a “pin-on-disc” device. Based on the friction coefficient and the wear rate, the wear performances of the tool steel were determined and compared with one another. The influence of metallurgical features (the grain size, or the nature, the size and the distribution of carbides) on the wear behavior was also enhanced. The setting of the wear test parameters together with the microstructure of the studied materials seems to strongly influence the subsequent abrasion and wear mechanisms. [less ▲]

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See detailStudy of the Crystallization Behavior and the Subsequent Martensitic Transformation in a High Chromium Cast Steel submitted to Different Austenitization Temperatures
Tchuindjang, Jérôme Tchoufack ULg; Habraken, Anne ULg; Lecomte-Beckers, Jacqueline ULg

Conference (2015, September)

The crystallization behavior a High Chromium Cast Steel (HCCS) has been determined under Equilibrium conditions with ThermoCalc® software, and under non-Equilibrium conditions through Differential Thermal ... [more ▼]

The crystallization behavior a High Chromium Cast Steel (HCCS) has been determined under Equilibrium conditions with ThermoCalc® software, and under non-Equilibrium conditions through Differential Thermal Analyses (DTA). The results are compared to each other and the differences between the predicted solidification path and the actual one obtained from DTA (Figure 1) are highlighted. The microstructure in the as-cast conditions is characterized while using both scanning electron microscopy (SEM) and hardness measurements. The SEM analysis involves a combination of methods such as backscattered electron observation, energy dispersive spectrometry and backscattered-electron diffraction with X rays, which ensure proper identification of complex solidification carbides and the matrix made of martensite and retained austenite (Figure 2a). Solid state transformations occurring during the heating stage up to the austenitization temperature are studied towards both DTA and dilatometry, especially the dissolution/precipitation reactions. Different austenitization temperatures are considered prior to cooling down to room temperature during dilatometry tests to determine the starting points (Ms) for martensite transformation. In addition a cryogenic quenching within liquid nitrogen is performed which allows the completion of the martensitic transformation (Figure 2b) and help determining the critical point for the end of the martensitic reaction (Mf points). An enhanced discussion based on the influence of the cooling rate and the undercooling is developed to explain the differences that are observed between equilibrium and non-equilibrium conditions, which are mainly related to the solidification sequence and the carbides formed. The influence of the austenitization temperature and the matrix composition/supersaturation on both Ms and Mf points is also discussed. [less ▲]

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See detailCarbides and grain size quantification methods in high speed steel alloys
Tchuindjang, Jérôme Tchoufack ULg; Paydas, Hakan ULg; Hashemi, Seyedeh Neda ULg et al

Conference (2015, July)

High speed steel (HSS) grades are widely used as in highly stressed applications where carbides content promote enhanced mechanical properties together with oxidation and wear resistances. Such a ... [more ▼]

High speed steel (HSS) grades are widely used as in highly stressed applications where carbides content promote enhanced mechanical properties together with oxidation and wear resistances. Such a tribological behaviour is mainly due to the presence of primary carbides. It is thus important to quantify the carbide volume fraction in HSS to correlate this result with the mechanical and tribological properties of the materials. Depending of the steel composition several types of carbides are precipitated in HSS: MC (Nb and V-rich), M2C (Mo and W-rich), Cr-rich M7C3 and some others, depending of the chemical composition. Two groups of HSS were analyzed in this study: cast HSS manufactured by centrifugal casting and cladded HSS manufactured by laser cladding. Depending on the chemical composition and the manufacturing process of the studied material, several methods have been used to quantify the carbide volume fraction and the grain size. [less ▲]

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See detailRapport scientifique et technique final : Tenue à chaud des matériaux métalliques dans des conditions extrêmes - METALEX, Convention n°1217562
Dedry, Olivier ULg; Lecomte-Beckers, Jacqueline ULg; Novello, Frédéric et al

Report (2015)

Le délivrable est la mise au point de deux équipements d’essais et des méthodologies associées permettant d’évaluer la cinétique de dégradation à chaud des matériaux métalliques en conditions extrêmes ... [more ▼]

Le délivrable est la mise au point de deux équipements d’essais et des méthodologies associées permettant d’évaluer la cinétique de dégradation à chaud des matériaux métalliques en conditions extrêmes (combinaison des effets de la température et de la corrosion). Les milieux corrosifs seront essentiellement constitués par des sels fondus. Deux milieux sont envisagés : les condensats agressifs qui affectent les incinérateurs de déchets ménagers et industriels (mélanges de sels liquides/solides en milieu oxydant) et les fluides caloporteurs des futures centrales électriques à tour solaire (mélanges de sels fondus en milieu inerte ou légèrement oxydant). Les domaines de température étudiés seront compris dans l’intervalle 300-650°C. Les matériaux étudiés dans le cadre de cette recherche sont destinés à la construction d’unités pour lesquelles le constructeur doit fournir une garantie longue durée, à titre d’exemple, pour une chaudière en centrale thermique, il est requis 25 ans de garantie. Les données quantitatives fournies aux constructeurs permettront d’évaluer la qualité et les quantités de matériaux à mettre en oeuvre. [less ▲]

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See detailDevelopment of quantification methods applied to HSS alloys for carbides volume fraction and grain size assessments
Tchuindjang, Jérôme Tchoufack ULg; Paydas, Hakan ULg; Hashemi, Seyedeh Neda ULg et al

Poster (2015, July)

High speed steels (HSS) are used in applications where enhanced mechanical properties together with hot oxidation and wear resistances are required. Such an improved physico-chemical behaviour is mainly ... [more ▼]

High speed steels (HSS) are used in applications where enhanced mechanical properties together with hot oxidation and wear resistances are required. Such an improved physico-chemical behaviour is mainly due to the presence of primary carbides within the microstructure. Depending of the initial chemical composition several types of carbides can precipitate in HSS such as MC (Nb and V-rich), M2C (Mo and W-rich), Cr-rich M7C3, etc. Two groups of HSS were analysed in this study, which are the so-called cast HSS grades that are manufactured by a centrifugal casting process and the cladded HSS manufactured by laser cladding. Purpose: Quantify the carbide volume fractions and the grain size within HSS grades in order to set correlations between the microstructure and both the mechanical and the tribological properties of the materials. Findings: The metallurgical features such as carbides nature and shape have been determined that are related to the manufacturing process of the studied material, and several methods have been used to quantify the carbide volume fractions and to assess the grain size. [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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See detailDetermination of Stress and Strain Fields in Cast and Heat Treated Bimetallic Rolling Mill Rolls
Neira Torres, Ingrid; Tchuindjang, Jérôme Tchoufack ULg; Sinnaeve, Mario et al

in Proceedings of the Iron & Steel Technology Conference and Exposition (AISTech 2015 & ICSTI) (2015, May)

Efficient work rolls for Hot Strip mill roughing stands are usually produced as bimetallic spun cast rolls with a core material made of Spheroidal Graphite Iron (SGI) and a shell material made of High ... [more ▼]

Efficient work rolls for Hot Strip mill roughing stands are usually produced as bimetallic spun cast rolls with a core material made of Spheroidal Graphite Iron (SGI) and a shell material made of High Chromium Steel alloy, semi-High speed steel or adapted High Speed steel chemistry. In this paper, the evolution of stress fields and microstructure during post casting cooling and subsequent heat treatment of a standard high chromium steel is targeted. This knowledge is a first step to analyze the different events that could happen during these production stages and provides the residual stress fields as well as the final roll microstructure which are interesting data for roll service life. As far as roughing mill work rolls for roughing mills are concerned, current trends in terms of work roll design are forcing the roll producer to go towards higher usable shell thicknesses or increased residual shell thickness after scrap diameter in order to delay potential fatigue phenomena at the shell-core interface. One important parameter could not be evaluated in this study, it concerns the pollutions of the core material by alloying elements of the shell during production, which could affect to some extent the mechanical properties and microstructure of the core. The macroscopic thermo-mechanical-metallurgical Finite Element model used to perform simulations, takes into account coupled effects. Input data parameters are identified by experimental tests such as compression tests at constant strain rate and numerical procedures such as inverse method. After the model presentation, the material data set is commented. Whole experimental campaign could not be presented, however interested readers are referred to [1] where more details on the material study of High Chromium Steel alloy can be found. The section of simulation results show the phase transformation histories and stress profiles of a typical roll of diameter 1.2 m and shell thickness of 0.08 m. An additional sensitivity analysis of the results to some material data such as induced plasticity transformation coefficient and shift of the martensitic transformation start temperature parameters is reported. Finally, some conclusions analyze the interest and drawbacks of the described model and its results. [less ▲]

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