Impact of Selective Laser Melting Additive Manufacturing on the High Temperature Behavior of AISI 316L Austenitic Stainless Steel

International audienceAdditive manufacturing allows production of complex geometries or customized designs that are difficult or impossible to fabricate by conventional means. However, these components have hardly ever been tested in severe conditions corresponding to real functioning at high temperature. The high temperature oxidation of AISI 316L stainless steel additively manufactured by selective laser melting (SLM) has been studied for 100 h at temperatures between 700 and 1000 °C in dry air and compared to that of wrought samples. Thermogravimetric analyses showed slower kinetics for SLM samples than for conventional coupons. In addition, SLM samples exhibit parabolic kinetics for all the studied temperatures, while conventional coupons present complete laws above 800 °C. Parabolic constant rate determined for 900 °C oxidation is one order of magnitude lower for SLM samples (1.73·10−13 g2 cm−4 s−1) than for wrought coupons (1.54·10−12 g2 cm−4 s−1). The resulting activation energy values confirm the better behavior of SLM alloys, in agreement with the formation at their surface of protective chromia Cr2O3. In contrast, additional formation of non-protective iron oxides was observed above 800 °C for the wrought samples. The different behavior could be explained by Cr depletion at the surface of conventional alloy, whereas Cr supply was still insured in the case of SLM material

Microstructure impact on high temperature corrosion behavior of AISI 316L stainless steel additively manufactured by Selective Laser Melting (AM-SLM)

International audienceAdditive Manufacturing by Selective Laser Melting (AM-SLM) is a near-net shape method producing dense and geometrically complex materials from micrometric powders. This process involves complete melting and very high cooling rates who induce a refinement of microstructure, improving the mechanical properties of the material [1,2]. However, the impact of these new microstructures on real functioning properties, like for instance the high temperature durability, needs to be studied. In this purpose, AISI 316L is considered in this work. Samples elaborated by AM-SLM and by conventional metallurgy were oxidized under laboratory air at 900°C for periods up to 3000h. The results highlight better behaviour for AM samples, which present a very good corrosion resistance throughout the 3000 hours. The conventional samples show a good resistance only during the first 1000 hours. These differences were related to the different composition of the oxide layers growing on the surface of the samples during the high temperature ageing: protective chromia for AM-SLM and non-protective iron oxides for conventional samples. To explain these differences of reactivity, several hypotheses were considered. XRD, SEM-EBSD and TEM studies were performed on initial samples in order to evaluate their microstructure, surface mechanical state and crystallographic orientation. The most promising hypothesis seems to be related to the microstructure (probably at nanoscale) of the samples. For AM-SLM coupons, a typical cellular structure was identified by TEM, with a size between 0.2 and 1 µm, corresponding to a very dense network of dislocations, which accumulate forming cell walls. Dislocation might act during the high temperature exposure as short-circuit paths for Cr diffusion from the bulk to the surface allowing the growth of protective scales for long ageing times. Moreover, AM-SLM samples found to contain large quantity of nano-inclusion that might equally influence corrosion behaviour

Study of the Performances of a 3D Printed BPM

International audienceFollowing previous results which have shown that some components built using additive manufacturing (3D printing) are compatible with ultra high vacuum, we have adapted the design of a stripline BPM to the requirements of additive manufacturing and built it. We report here on the design adaptation and on its mechanical and electrical performances

Emissions from metallic powder and high energy-based process - thermal spraying knowledge refresh

International audienceRecently, in different industrials sectors, emissions are subjected to rules and regulations which are coming increasingly stringent and more carefully monitored. And this is where thermal spraying, powder atomization and additive manufacturing come in metal powder and high energy-based processes. These technologies manufacture or use micrometer size feedstock. But the process characteristics as the heat source induces nanoparticle formation. The paper is to address a knowledge refresh on thermal spraying regarding emissions due to the process in relationship with working conditions, personal protection, dust filtration, etc. A survey has been conducted and the results are compared to scientific literature and previous surveys

Exposure to nanoparticles in thermal spraying - Vigilance towards the operator and the outside environment

International audienceThe previous survey of the French CaRPE project has shown a lack of information and showed the interest to assess the residual exposure to these particles. This paper presents the results of various sampling operations and emission analyses of plasma spraying equipment. For this purpose, different areas have been targeted, such as at the level of the emissions channeled upstream and downstream of the filtration system, at the workstation level as well as fugitive emissions. Various measurements were carried out: real-time particle size distribution, mass concentration of total suspended dust, heavy metals, sampling characterization by EDX/ MET, etc. The metallic aerosol is mainly composed of nanometric structures. The number concentration is particularly high (between 108 and 109 particles/cm3) downstream the filtration system. Measurements upstream and downstream of the filtration system have made it possible to determine its efficiency, which is greater than 90%. The mass concentration downstream of the filter is ~2.6 mg/m3 while the number concentration remains above 106 particles/cm3. Some recommendations were then derived. Very great vigilance is therefore recommended in order to protect the operator, since we must remember that we are in the presence of a very high concentration of metallic and nanostructured particles

Emissions From Metallic Additive Manufacturing - An Occupational and Environmental Perspective

The additive manufacturing market is rapidly increasing due to a growing maturity of users and a diversity of uses. However, due to their novelty, there are concerns that these technologies can pose specific health and environmental risks. In order to foster the sustainable deployment of these technologies, including the post-treatment, it is necessary to implement adequate safety and environmental management of the used materials and associated by-products. This paper proposes a multi-tier approach to investigate diffuse and channeled emissions so as to propose inherently safe(r) by design processes and adequate safety barriers

Study of the suitability of 3D printing for Ultra-High Vacuum applications

International audienceIn the recent year additive manufacturing (3D printing) has revolutionized mechanical engineering by allowing the quick production of mechanical components with complex shapes. So far most of these components are made in plastic and therefore can not be used in accelerator beam pipes. We have investigated samples printed using a metal 3D printer to study their behavior under vacuum. We report on our first tests showing that such samples are vacuum compatible and comparing pumping time

Projet CaRPE : caractérisation et réduction des émissions des procédés poudres métalliques - hautes énergies

High temperature processes related to metal powders (e.g. atomization, thermal spraying) lead to the production and release of metal particles, which are partly nano-sized. There is a lack of knowledge with respect to the properties of these emissions and with respect to their management (collection, confinement or treatments). The CaRPE project aims at bridging the current knowledge gaps in this area. A network of various stakeholders, both form the private as well as the public sector, will join their efforts to address current challenges in the field of process engineering, process use, emission risk analysis, metrology and clean process design and support a sustainable development of these technologies.Les procédés métallurgiques à haute température (ou « la mise à haute température de métaux par des procédés ») tels que l'atomisation, la projection thermique ou la fabrication additive, entraînent la production d'effluents métalliques particulaires, composés pour partie de nanoparticules. Il existe un besoin en matière de connaissances, tant au niveau des propriétés de ces émissions, qu'en matière de gestion, c'est-à-dire de captage ou confinement, et de traitement. Le projet CaRPE se propose de contribuer à ce développement de connaissances, en rassemblant des acteurs de différentes spécialités (chercheurs en génie des procédés, utilisateurs de procédés, spécialistes de l'analyse de procédés en matière de risque d'émission, et enfin spécialistes en gestion des effluents) afin de répondre aux défis posés et promouvoir un développement toujours plus sûr de ces procédés

Effects of Clozapine on Perceptual Abnormalities and Sensory GatingA Preliminary Cross-Sectional Study in Schizophrenia

International audienceThe aim of the present study was to investigate the effect of second-generation antipsychotics (clozapine or another second-generation antipsychotic) on perceptual abnormalities related to sensory gating deficit. Although clozapine is known to improve sensory gating assessed neuro- physiologically, we hypothesized that patients with schizophrenia treated with clozapine would report less perceptual abnormalities related to sen- sory gating deficit than patients treated with other second-generation anti- psychotics do. Forty patients with a diagnosis of schizophrenia were investigated (10 patients treated with clozapine and 30 patients treated with another second-generation antipsychotic drug). Perceptual abnor- malities were assessed with the Sensory Gating Inventory. Sensory gating was assessed through electroencephalogram with the auditory event- related potential method by measuring P50 amplitude changes in a dual click conditioning-testing procedure. Patients treated with clozapine pres- ent normal sensory gating and report less perceptual abnormalities related to sensory gating than patients treated with other second-generation anti- psychotics do. Although the cross-sectional design of this study is limited because causal inferences cannot be clearly concluded, the present study suggests clinical and neurophysiological advantages of clozapine com- pared with other second-generation antipsychotics and provides a basis for future investigations on the effect of this treatment on perceptual abnor- malities related to sensory gating deficit in patients with schizophrenia