14 research outputs found
Traitement de surface en continu avec un laser Nd:YAG impulsionnel
This work presents the results of investigations in case of laser cladding with a pulsed Nd:YAG laser. We discuss about the experimental parameters in view to realize single clad and particulary the laser data (energy, frequency, pulse duration). The main results are the clad formation beyond an energy threshold and beyond a threshold pulse duration, the clad behaviour is the same as a clad obtained with a cw laser. Thanks to a cross-section modeling, we compare calculations with experiments and we conclude that the interaction efficiency depends widely on powder spray characteristics
Modélisation de la section de dépôts obtenus par fusion d'une poudre métallique projetée dans un faisceau laser Nd-YAG
This work presents a cross-section modeling of laser claddings by powder spraying
in a cw Nd-YAG laser. We admit a homogeneous temperature repartition inside each
powder particle during interaction time, a material's intern energy variation
equals its absorbed energy and an optical extinction through a powder cloud
following a Beer-Lambert law. Apart the good correlation obtained between model
and experiments, this one shows experimentals data which change widely the
cross-section (power, power feed, scanning speed). And we define and obtain
experimentally an absorption coefficient which is nearly the value of a liquid
metal absorption coefficient.L'objectif de cette étude est la modélisation de la section des dépôts obtenus
lors d'opération de revêtement de surface par projection de poudre dans un faisceau
laser Nd-YAG. Pour ce faire, nous admettons que la répartition des températures au
sein de chaque particule est homogène pendant le temps d'interaction, que la variation
d'énergie interne du matériau est égale à l'énergie absorbée par celui-ci et que
l'atténuation du faisceau au travers du nuage de poudre suit une loi de type
Beer-Lambert. Outre la bonne corrélation obtenue entre le modèle et l'experience,
les paramètres opérationnels qui influent fortement sur le résultat apparaissent
clairement (puissance, débit de poudre, vitesse de travail). Enfin, nous définissons
et obtenons expérimentalement un coefficient d'absorption qui est de l'ordre de
grandeur du coefficient d'absorption d'un métal en phase liquide
Experimental optimisation of a hypervapotron® concept for ITER plasma facing components
Historically developed for cooling of klystron electronic tubes, metallic hypervapotron® prototypes with different width were manufactured for high heat flux plasma facing components (PFC) applications. They were critical heat flux (CHF) tested
Qualification and Post-Mortem Characterization of Tungsten Mock-ups Exposed to Cyclic High Heat Flux Loading
In order to evaluate the option to start the ITER operation with a full tungsten (W) divertor, high heat flux tests were performed in the electron beam facility FE200, Le Creusot, France. Thereby, in total eight small-scale and three medium-scale monoblock mock-ups produced with different manufacturing technologies and different tungsten grades were exposed to cyclic steady state heat loads. The applied power density ranges from 10 to 20 MW/m2 with a maximum of 1000 cycles at each particular loading step. Finally, on a reduced number of tiles, critical heat flux tests in the range of 30 MW/m2 were performed.Besides macroscopic and microscopic images of the loaded surface areas, detailed metallographic analyses were performed in order to characterize the occurring damages, i.e., crack formation, recrystallization, and melting. Thereby, the different joining technologies, i.e., hot radial pressing (HRP) vs. hot isostatic pressing (HIP) of tungsten to the Cu-based cooling tube, were qualified showing a higher stability and reproducibility of the HIP technology also as repair technology. Finally, the material response at the loaded top surface was found to be depending on the material grade, microstructural orientation, and recrystallization state of the material. These damages might be triggered by the application of thermal shock loads during electron beam surface scanning and not by the steady state heat load only. However, the superposition of thermal fatigue loads and thermal shocks as also expected during ELMs in ITER gives a first impression of the possible severe material degradation at the surface during operational scenarios at the divertor strike point
Manufacture of two primary first wall panel prototypes with Beryllium armor for ITER
The aim of this paper is to present the results of a manufacturing program that was implemented to demonstrate the feasibility for manufacturing the primary first wall panels, including a part of R&D work concerning the joining of Beryllium plat