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Etude de l'interaction laser-matière pour la fabrication de pièces à haute valeur ajoutée en céramiques oxydes semi-transparentes par fusion laser sélective sur lit de poudre

Abstract : Selective laser melting of oxide ceramics (Al2O3-ZrO2and Al2O3) is identified as a promising way to produce complex shaped parts with oriented fine microstructures, which would not be achievable by conventional sintering. These lightweight parts, presenting excellent resistance to creep at high temperature and oxidation, would appear as the answer to weight reduction and temperature increasing of turbojet engines, as compared to the usual metal parts coated with porous ceramics. The material/process coupling relies on the controlled addition of an absorber to pure ceramic powders, that compensate the quasi-transparency of these materials to Yb:YAG laser radiation. The effect on optical properties of process parameters, absorbent nature and content, compactness of the powder bed and their influence on manufacturing stability are identified. For this purpose, innovative radiative measurements in reflection and in transmission were carried out during manufacturing and for different operating conditions. These dynamic measurements through an integrating sphere provide information on the laser-material interaction mechanisms taking place in each media and they give access to optical material properties. These measurements enrich an analytical laser-matter interaction model based on the radiation attenuation by the Beer-Lambert law. This model gives a relation between melt pool dimensions, radiative propertiesof the different media (powder bed, substrate and liquid) along with the associated absorption coefficients, the process parameters and powder bed porosity. This model expresses also the apparent melted section within the powder bed, the section of the melted zone within the substrate and the consolidation section within the powder bed. Some of these calculated data are not measurable and usefully contribute to a consolidation model of the powder bed. This model takes into account the material exchanges observed between so-called bare zones (linked to the ejection of powder particles) and consolidation zones. Quantification of these particles exchanges, which have a strong impact on the LBM of these oxide ceramics, allows the definition of a specific manufacturing strategy that compensates for the bare zone formation while avoiding the formation of hot spots. These data collection enables the manufacturing of LBM ceramic oxide parts with reduced porosity and controlled micro-cracking.
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https://pastel.archives-ouvertes.fr/tel-03170259
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Submitted on : Tuesday, March 16, 2021 - 9:16:15 AM
Last modification on : Wednesday, November 17, 2021 - 12:28:40 PM
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  • HAL Id : tel-03170259, version 1

Citation

Liliana Moniz da Silva Sancho. Etude de l'interaction laser-matière pour la fabrication de pièces à haute valeur ajoutée en céramiques oxydes semi-transparentes par fusion laser sélective sur lit de poudre. Matériaux composites et construction. Université Paris sciences et lettres, 2020. Français. ⟨NNT : 2020UPSLM060⟩. ⟨tel-03170259⟩

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