Laser surface melting of nickel-based alloy reduces nickel release in the primary cooling system of a nuclear power plant

The surface of Ni-based alloy 690 was treated using a sub-microsecond pulsed laser in order to reduce the amount of nickel released when the surface is exposed to the primary cooling system of pressurized water nuclear reactors. A 2D array of laser treatment parameter sets was investigated. The results on sample surfaces was characterized using interferometric microscopy, Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectrometry (GDOES) and X-ray Photoelectron Spectrometry (XPS). The treatment leading to a continuous and defect-free chromine surface having the minimum nickel content over about the first two nanometers and no subsurface chromium depletion was selected for the nickel release test. This selection criterion proved to be very efficient as the total amount of nickel released in a standard qualification test using a simulated primary coolant was reduced, compared to a non-treated surface, by a factor of 7 during the heating phase and by a factor of 3.7 on average over the whole month-long test

Emerging processes for metallurgical coatings and thin films

Innovation in thin-film deposition processes, thermal spraying and cladding technologies mostly rely on evolutions of their previous iteration. Along with other examples, five case studies of emerging elaboration processes for metallurgical coatings are described coupled with their applications. In the frame of the lifetime extension of components exposed to aggressive media or their functionalization, this article depicts all the developments of the detailed processes. Physical vapor deposition (PVD) of coatings with exceptional properties is possible thanks to sources generating highly ionized metallic vapors. The control of the average energy per incident species and particularly metallic ions strongly influences the characteristics of the deposited layer obtained, for example, with HiPIMS (High Power Impulse Magnetron Sputtering). While PVD techniques are mainly directive regarding the growth of the coating, chemical vapor deposition (CVD) processes manage to homogeneously coat complex 3D shapes. The use of specific precursors in DLI–MOCVD (Direct Liquid Injection – MetalOrganic CVD), carefully selected from the whole metalorganic chemistry, allows one to efficiently treat heat-sensitive substrates and broadens their application range. The third detailed example of emerging technology is suspension plasma spraying (SPS). Projection of various solutions containing nanoparticles leads to the growth of unusual morphologies and microstructures and to the generation of porous coatings with multi-scaled porosity. On the other hand, cold-spray uses metallic powders with higher granulometry and does not modify them during the deposition process. As a result, high-purity and dense materials are deposited with properties similar to those of wrought materials. Whereas cold-spray is suitable only for ductile metals, laser cladding can be applied to ceramics, polymers and of course metals. Laser cladding is a key technology for advanced metallurgical engineering and alloy development due to its capability for functionally graded materials production and combinatorial synthesis

Synthèse par pyrolyse LASER et caractérisation de nanoparticules à base d'oxyde de titane et application

TOURS-BU Sciences Pharmacie (372612104) / SudocSudocFranceF

Growth of micrometric oxide layers for the study of metallic surfaces decontamination by laser

The nuclear industry produces a wide range of radioactive waste in term of level of hazard, contaminants and material. For metallic equipment like steam generators, the radioactivity is mainly located in the oxide surface. In order to study and develop techniques for dismantling and for decontamination in a safe way, it is important to have access to oxide layers with a representative distribution of non-radioactive contaminants. We propose a method of formation of oxide layer on stainless steel 304L with europium (Eu) as contaminant marker. In this method, an Eu-solution is sprayed on the stainless steel samples. The specimen are firstly treated with a pulsed nanosecond laser and secondly the steel samples are exposed to a 600°C furnace for various durations in order to grow an oxide layer. The oxide structure and in-depth distribution of Eu in the oxide layer are analysed by scanning electron microscopy coupled with energy dispersive X-ray microanalyzer, and by glow discharge optical emission or mass spectrometry. The oxide layers were grown to thicknesses in the range of 200 nm to 4.5 μm regarding to the laser treatment parameters and the heating duration. These contaminated oxides have a ‘duplex structure’ with a mean weight percentage of 0.5% of europium in the volume of the oxide layer. It appears that europium implementation prevents the oxide growth by furnace but has no impact on laser heating. These oxide layers are used to study the decontamination of metallic surfaces such as stainless steel 304L using a nanosecond pulsed laser

Numerical Modeling of melt pool in the powder bed fusion processes

Ecole d'étéInternational audienc

Activated twinning variant determination in cold-rolled 316L stainless steel by effective Schmid factor analysis

International audienceA method is proposed to determine accurately the activated twinning variant during the cold-rolling of 316L stainless steel parts produced by L-PBF (Laser Powder Bed Fusion) from EBSD datas. The twinning variant selection is carried out by Schmid factor (SF) computations, using an effective Schmid factor for cold-rolling specifically. Schmid factor was proven to be a relevant parameter to predict the experimentally activated twinning variant. Additionally, cold-rolling deformation is shown to be composed by a strong compression component, along with a minor traction component. The effective Schmid factor is then modified accordingly to ensure a better prediction of twinned grains. Moreover, twinning Schmid factor analyses in traction and compression provide valuable information on the twinning activation regarding textured materials such as L-PBF 316L steel

Procédés d'insertion de dopants dans poudre industrielle INCO718 = ODS (Oxide Dispersion Strengthened,) pour fabrication LPBF (SLM) pour des applications nucléaires

International audienceLes alliages à base de Ni sont des matériaux prometteurs pour le nucléaire en raison de leur excellente résistance mécanique sous haute température et de leur bon comportement dans des environnements corrosifs ou oxydants. Cependant, en raison de la complexité de ses composants, les techniques de traitements conventionnelles sont limitées. De nouvelles technologies, élaboration à base de poudre métalliques, permettent d'élargir les possibilités de conception, de s'affranchir des problèmes de soudabilité, en particulier la fusion laser en lit de poudre (LPBF). Les performances mécaniques remarquables de l'Inconel 718 sont obtenues par le renforcement de la phase de matrice γ en solution solide, la précipitation γ' et γ''. Cependant l'ajout d'oxyde peuvent permettre d'augmenter les performances des matériaux. Dans cette étude nous nous sommes intéressés à l'influence de l'ajout d'Y2O3 sur la microstructure de l'Inconel 718. L'intégration de particules d'oxyde nanométriques dans une matrice relativement ductile n'est pas facile à réaliser. Afin de résoudre ce problème, divers procédés d'insertion ont été essayés, notamment le procédé MA (mécanosynthèse), le mélange par turbula et le dépôt d'oxyde par PVD. De plus, l'ajout d'oxyde nécessite une adaptation des paramètres du procédé LPBF. Les principaux paramètres tels que la vitesse du processus, la puissance du laser, la distance de hachage et les stratégies de balayage sont pris en compte pour chaque processus d'insertion d'oxyde. Enfin, les macro et microstructures sont analysées et des conclusions sont données sur les potentialités et les limites de chaque condition de fabrication

Melt pool modelling for additive manufacturing (MOBAFA)

Advanced coursesInternational audienc

Melt Pool Modelling for Additive Manufacturing (MOBAFA)

International audienc

Melt Pool Modelling for Additive Manufacturing (MOBAFA)

International audienc