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Дисертації з теми "Fusion sélective par laser sur lit de poudre"
Moniz, da Silva Sancho Liliana. "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." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM060.
Повний текст джерелаSelective 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
Massard, Quentin. "Compréhension et maîtrise de la mise en oeuvre en fabrication additive d’aciers à haute teneur en carbone tel que le 100Cr6 par fusion sélective par laser sur lit de poudre." Electronic Thesis or Diss., Ecully, Ecole centrale de Lyon, 2022. http://www.theses.fr/2022ECDL0024.
Повний текст джерелаNowadays, the production of steel parts by additive manufacturing (AM) is a central topic in the world of industry, including automotive. Indeed, the possibilities offered by additive manufacturing are diverse and numerous (weight reduction, complex shapes, ...). 100Cr6 is a high mechanical performance steel, mainly used for the production of ball bearings, due to its high hardness and fatigue resistance. A processability study of 100Cr6 steel produced by selective laser melting on powder bed was first performed. After having characterized the physical and chemical properties of the material, dense and non-cracked samples were produced through a parametric optimization. A post-treatment cycle was defined and plane tensile tests and rotary bending fatigue tests were performed.In order to understand and control the cracking phenomenon of 100Cr6 when used in L-PBF, a thorough metallurgical study (microhardness, optical imaging, SEM, XRD, EBSD) was conducted. The influence of the use of the heating plate on the formation of Bainite and Martensite and their impact on cracking was highlighted.Finally, a recyclability study of the oxidized 100Cr6 powder was carried out through the use of a radiofrequency plasma spheroidization machine. A powder feed rate in the plasma allowing to regenerate the physical and rheological properties of the powder was defined. A cleaning method to improve the chemical properties of the powder was also proposed
Chniouel, Aziz. "Etude de l’élaboration de l’acier inoxydable 316L par fusion laser sélective sur lit de poudre : influence des paramètres du procédé, des caractéristiques de la poudre, et des traitements thermiques sur la microstructure et les propriétés mécaniques." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS379/document.
Повний текст джерелаAdditive Manufacturing (AM) recently became an attractive manufacturing process in several industrial fields such as aeronautics, aerospace and automotive. The exploitation of AM processes for the nuclear industry is currently being studied in different countries. The AM enables the creation of optimized parts with complex geometries impossible to manufacture with conventional processes. This thesis aims to determine the potential contribution of AM processes for the production of metal components for various nuclear applications including future Generation IV reactors. First, the microstructural and mechanical properties of 316L stainless steel parts built by Selective Laser Melting (SLM) process are presented. Three thematics were assessed in this study: the SLM process parameters, the powder characteristics and two post heat treatments (700 ° C-1h and hot isostatic pressing: 1100 ° C-3h under 1800 Bar). Their effects on microstructure and mechanical properties were analyzed. Tensile properties of 316L steel specimens were measured and compared to those of forged 316L steel described in the nuclear field by RCC-MRX standards. The results obtained are superior to those of the standard and comparable to those of a forged steel. This thesis contributes to a better understanding of interactions between the process parameters, the microstructure and the mechanical properties
Chen, Qiang. "Modélisation numérique thermomécanique de fabrication additive par fusion sélective de lit de poudre par laser : Application aux matériaux céramiques." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM004/document.
Повний текст джерелаThe application of SLM process is limited by the difficulty of process control. Its application to ceramics is especially challengeable due to their weak absorption to laser and weak resistance to thermal shock. The mastery of this process requires a full understanding of heat transfer, fluid dynamics in melt pool and solid mechanics. In this work, we propose a numerical model for the simulation of SLM process applied to ceramics. The model is developed at the track scale and with the assumption of continuous powder bed. It is based on level set method and multiphase homogenization, with which we are able to follow the evolution of gas/material interface and phase transformation. Simulations are performed to study the influence of material properties and process parameters on temperature, melt pool shape, fluid dynamics and solid mechanics. Apart from the laser power and scanning speed, material absorption is also found to be important to the thermal behavior and the melt pool shape. With the fluid dynamics, convex shape of track cross section is achieved under surface tension. Besides that, liquid droplets collapsing formed by the melting of powder create melt pool instability when falling, thus leading to track irregularity after solidification. The Marangoni effect, caused by surface tension gradient at gas/material interface, is investigated. Its influence on temperature distribution, melt pool shape and track regularity is recognized. One interesting finding is the smoothing effect of track surface with negative ∂γ/∂T. When combine surface tension with scanning speed, track surface becomes more irregular with the increase of scanning speed. The well-known balling effect is reproduced with high scanning speed. This can be helpful to find the regime for regular track shape with given laser power and scanning speed. Cracking defect is deleterious in additive manufacturing. The use of an auxiliary laser can help to avoid this defect by decreasing the maximum tensile stress. The process mode of this auxiliary laser remains an interesting subject to be studied and some guidelines have been given by the presented simulations. The model is validated by the comparison of melt pool shape with experiments under different process conditions. Simulations can also reveal the tendency of track surface variation for certain cases. By the application to multi-track deposition, the influence of hatch distance on layer surface, temperature and stress evolution is emphasized
François, Mathieu. "Conception pour la fabrication additive, par fusion laser sur lit de poudre, de composants hyperfrequences." Thesis, Paris, HESAM, 2020. http://www.theses.fr/2020HESAE008.
Повний текст джерелаFor many years, passive microwave waveguide components have been used in communication systems, particularly for antenna feed chains. This kind of radiofrequency equipment is already widely operational in various fields such as satellite communications, radars, space observations, etc. Because of their low loss as well as their high energy management capacity. However, the emergence of new technologies and the significant degree of competition that occurs within the defense market, customers are increasingly calling for lower-cost products, shorter lead times, with requirements equally high.Over the past years, several institutions and industries have become more and more interested in additive manufacturing processes for passive waveguide components. Without any need for raw material or dedicated tools, additive technologies bring some new design perspectives. In particular, the addition of material layer by layer promotes the manufacture of monolithic parts, which would contribute to lighten the weight of antennas and save time and costs. On the other hand, it offers additional degrees of freedom during the design stage, encouraging the development of complex and innovative architectures, resulting in increased performance, which would be unachievable by conventional techniques. As such, additive manufacturing has been identified as being able to play a crucial role in the development of this type of part.However, like any other manufacturing process, additive processes involve several physical phenomena and so have their own manufacturing specificities and constraints to consider during the design phase to benefit fully from all the potential of additive manufacturing. Combined with the microwave requirements, the designer must then be able to identify the correlation between design, process and electromagnetic to guarantee a quality part conforming to the specifications.The objective of this study is twofold. The first one consists of identifying the specificities of the laser beam melting process with a major influence on electromagnetic properties, in order to be able to pay special attention during the design phase. The second concerns the development of a method that incorporates the constraints and opportunities of additive manufacturing while meeting the objectives arising from the microwave specifications
Vinson, Pierre. "Fusion sélective par laser de lits de poudre : Étude sur le recyclage de la poudre et détection de défauts au cours de la fabrication par imagerie thermique." Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0068.
Повний текст джерелаDirect and additive manufacturing regroups several new technologies that are very different from conventional manufacturing processes such as casting. Aeronautic and space industries are really interested in those new processes such as the selective laser melting of metallic powder beds know as the SLM process. This PhD thesis report will show the issues of additive manufacturing and will describe some processes. A bibliography study has been done on two aeronautical alloys used in this work: titanium alloy TA6V and nickel-based superalloy Nimonic 263. This work also presents powder characterization (granulometry, morphology chemical composition) for the gas atomized powder. Besides, study has been done on the recyclability of the TA6V powder for the SLM process, for the powder itself and the mechanical properties of parts built from recycled powder. Moreover, this works deals with a powder bed consolidation model to estimate the productivity of the process. Then, a parametric and thermal study has been done on the Nimonic 263. The coaxial system for thermal visualization is described such as the image processing algorithm used. Finally, this reports deals with the study of thermal signature of typical SLM defects
Masmoudi, Amal. "Modélisation et développement expérimental du procédé de fabrication additive par fusion laser sélective d'un lit de poudre métallique : influence de la pression de l'atmosphère." Thesis, Belfort-Montbéliard, 2016. http://www.theses.fr/2016BELF0287/document.
Повний текст джерелаThe selective laser melting process (SLM) of a metallic powder bed is an innovative process that allows the manufacturing of complex shape parts directly from a CAD file via a complete melting of powder layers deposited successively. During the SLM process, the high laser energy density creates many thermal cycles: melting - vaporization - solidification.The purpose of this work was: 1) to better characterize and understand experimentally the phenomena that occur during the laser beam - powder / molten metal pool interaction and 2) to develop a numerical model taking into account the phenomena of melting and vaporizing of the material and the presence of the surrounding gas in the build chamber.In a first time, considering simple geometries (tracks and surfaces) and 316L stainless steel as material, we studied the interaction between the laser beam, the powder bed and the liquid metal pool using several experimental techniques (spectrometry, calorimetry, ...) in order to understand the nature and the role of the metal vapor generated during the process. The results showed that the vapor has no effect on the transmission of the laser beam energy to the material during the SLM process. Meanwhile it leads to the deposition of condensed vapor and also drag some molten metal droplets.In a second time a numerical model was developed to determine the influence of the pressure of the surrounding environment on the melting process of a powder bed by a laser beam. Parameters characterizing the evolution of the physical properties of the material and of the gaseous medium according to the temperature and pressure were incorporated into the model database. Some material parameters were determined from the literature and others were obtained empirically using specific experimental measurements.Finally, this numerical model, complementing experimental results, was used to treat the main subject of the thesis which is the effect of the surrounding pressure on the SLM process. The model helped to clarify the physical phenomena provided by the change in the pressure level and its validity was checked through experimental measurements
Annovazzi, Alicia. "Contribution à l'étude - interaction laser-matière à différentes pressions résiduelles : Application au procédé micro-fusion laser sur lit de poudre." Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCA024.
Повний текст джерелаThe laser beam melting (LBM) and electron beam melting (EBM) processes are two additive manufacturing technologies allowing the production of metallic parts. The intense energy density provided by the power supply is sufficient in order to melt the material creating a molten pool, and will solidify after cooling. This change of phase which takes place in a very short time, induced complexthermodynamics phenomena. Each of the processes offer advantages that could be interesting to be combined. Hence, a combination of the two technologies has been investigated. The EBM process requiring a rough vacuum in the work chamber, the issue of this work is based on the study of the laser melting at low pressure. Besides the intended combination, the selective laser melting under vacuum pressure can be attractive with the aim of improving the material integrity, in particular on the oxygen-sensitive materials. However, a clear decrease of the process efficiency has been observed. This work includes two parts: a) Firstly, an experimental study of samples fabricability at different pressures conditions is observed. For the same manufacturing parameters, a significant decrease of samples densification is observed in rough vacuum. The parameters volumetric energy density and the laser displacement speed have to beadapted in function of the chamber pressure. b) The second part is an attempt to explain the molten pool motion which change depending on the pressure. This can be achieved with a fast cam allowing the observations of strong instabilities in the powder bed with the denudation zone, and the molten pool with the morphology, for specific laser parameters. These phenomena are more important for residual pressures under 30 mbar. Then, a powder bed pre-sintering for the purpose of ”in-situ” annealing of the materials studied, has shown the beneficial effect during the interaction laser-powder under vacuum. Improvement melt quality and increased manufacturing efficiency have beenachieved
Godineau, Kévin. "Optimisation du pilotage de chaînes opto-mécaniques pour l'exécution de trajectoires en fabrication additive par fusion laser sur lit de poudre." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLN019.
Повний текст джерелаIn metal additive manufacturing by laser powder bed fusion, the geometry and mechanical characteristics of the produced parts are generated during the manufacturing process. These two aspects are greatly influenced by the laser spot trajectories, and by the control of the energy provided to the powder locally. The numerical control system, whose purpose is to generate instructions to be sent to actuators, has therefore a significant impact on the quality of the parts produced.This work proposes to study the local impact of the operations carried out in the numerical control on both the trajectories executed and the energy provided to the material. In the literature, few studies have addressed these aspects in additive manufacturing. For this reason, an experimental platform is implemented and used to analyze and better understand the operations currently implemented in industrial numerical controls.First, a mathematical model representative of the machine geometry is established. This model converts the laser spot trajectories into instructions for actuators. The model developed is used to improve the calibration step of the machines. Once the system is calibrated, the instructions sent to the actuators are studied. The various processes carried out in the industrial numerical control are analysed, limitations are highlighted and several proposals for improvements are implemented. All these developments are then used to precisely control the energy supplied to the material in the case of certain trajectories adapted to the process. The scientific developments proposed in these works are all validated experimentally on an additive manufacturing machine or on the test bench developed. The work carried out makes it possible to envisage many perspectives concerning the improvement of the treatments carried out inside the numerical control in additive manufacturing
Salvan, Claudia. "Alliage de cuivre à durcissement structural mis en œuvre par fusion laser sur lit de poudre : lien entre microstructure et propriétés mécaniques, thermiques et électriques." Thesis, Université Grenoble Alpes, 2021. http://www.theses.fr/2021GRALI013.
Повний текст джерелаThe CuCrZr is a precipitation hardening alloy, used for its good electrical and thermal properties combined to high mechanical properties. Using additive manufacturing technologies, and more precisely the laser powder bed fusion (L-PBF) process, offers the possibility to build highly complex parts for the conception of compact and efficient heat exchangers. However, the high optical reflectivity of the alloy at the standard laser wavelength added to the high thermal conductivity of the alloy require the use of a high energy density during the fabrication. Regarding the environmental cost and the risk of machine damage, this is not always a desirable choice.The research aimed to (i) reduce the optical reflectivity of the powder by a controlled particle oxidation, (ii) optimize the process parameters in order to build dense part using the different powers available on two machines, (iii) compare the L-PBF CuCrZr microstructure, before and after heat treatment to wrought and HIP (hot isostatic pressing) CuCrZr and (iv) explain the L-PBF CuCrZr mechanical behavior relying on SEM-EBSD and TEM microstructural characterization through the discussion of the different hardening mechanisms via a mechanical model.This work shows the link between the chemical composition and the thickness of the oxide layer on particles, and the powder optical reflectivity and flow properties. This thesis presents L-PBF CuCrZr microstructural, mechanical (hardness and traction at 20°C and 250°C), electrical and thermal properties before and after two heat treatments (the first one is composed of a solution annealing, a water quench and an age hardening steps and the second one is only composed of a direct age hardening), compared with CuCrZr references properties. We have shown that a direct age hardening on L-PBF materials provides high mechanical properties (184 HV1 hardness, Rp0.2=527 MPa, Rm=585MPa) while keeping a good elongation (14%), electrical (42 MS.m-1) and thermal properties (375 W.m-1.K-1 at 100°C). Those results are explained by (i) the presence, in the as built L-PBF part, of a supersaturated solid solution with all the Cr dissolved, allowing, after direct age hardening to have a high nano-precipitates density, and thus a high precipitation hardening, (ii) the presence of a high dislocations density linked to the characteristical presence of solidification cells in the as built state, and widely preserved thanks to the direct age hardening heat treatment