Net emission of ArH2He thermal plasmas at atmospheric pressure

International audienceThe Net Emission Coefficient (NEC) has been calculated for Ar-H 2 -He thermal plasmas and for a temperature range from 5000K to 30000K. The plasma is supposed to be in Local Thermodynamic Equilibrium (LTE) at atmospheric pressure. This study takes into account the radiation resulting from the atomic continuum, the molecular continuum, and the atomic lines. A particular attention has been paid to the treatment of helium lines broadenings. The results of net emission coefficients are presented for pure gases and Ar-H 2 -He mixtures. Radiation is weak in pure helium at low temperatures because of the high ionization energy of this species. On the opposite, at very high temperature, the influence of hydrogen tends to decrease because ionic lines do not exist for this last species. Finally, a small proportion of helium in Ar-H 2 mixtures does not change the net emission coefficient because of the weak intensity of the helium lines

Analyse par simulation de l’interaction entre un jet plasma et des gouttes de suspension colloïdale : application à la projection plasma de nanomatériaux

L'objectif de ce travail consiste à modéliser les interactions hydrodynamiques, thermiques et physico chimiques entre un jet de plasma à haute température et un jet liquide chargé en particules nanométriques. La projection plasma de nanomatériaux est une voie industrielle qui permet d'obtenir des dépôts denses épais (environ dix microns, voire plus) aux propriétés accrues. Ce procédé fait l'objet de recherches approfondies tant les potentialités industrielles sont nombreuses. Sa modélisation requiert de scinder l'écoulement à plasma en zones géographiques correspondant aux étapes du procédé : -l'injection de la phase porteuse des particules dans laquelle le jet continu ou les trains de gouttes viennent pénétrer le jet de plasma et donner lieu à la fragmentation primaire et secondaire de la phase liquide. Des travaux antérieurs ont porté sur cette étape. -L’évaporation de la phase porteuse -Les interactions particule/plasma -L’étape d'impact et de fabrication du dépôt que nous n’étudierons pas. La fabrication du revêtement dépend fortement des étapes précédentes. A partir des travaux précédents, nous modéliserons l'évolution thermocinétique des gouttes et particules sur des échelles allant du micron au millimètre avec les mécanismes spécifiques liés au changement de phase liquide/solide, à la mouillabilité sur les particules solides, aux lignes triples et à l'interaction particule/écoulement di/triphasique. Il s'agira de simuler à une échelle locale les écoulements multiphasiques et les transferts de chaleur, par des méthodes VOF et un modèle 1 fluide compressible, et d'étudier l'évolution thermocinétique des particules et de la phase porteuse. L’intérêt de ce travail est de fournir des éléments de compréhension du procédé et de contrôle des propriétés du dépôt

Microstructure and indentation mechanical properties of YSZ nanostructured coatings obtained by suspension plasma spraying

[EN] A commercial nanosuspension of yttria-stabilised zirconia (YSZ) was successfully deposited on austenitic stainless steel substrate by suspension plasma spraying technique (SPS). A SG-100 torch with internal radial injection was used for the spraying. The pneumatic system transported the feed suspension from the containers to the plasma torch. In order to study the effect of the spraying parameters, a factorial model was used to design the experiments, changing both spraying translation speed and suspension flow rate. The coating microstructure was characterised by FEG-SEM. All coatings displayed a two-zone microstructure formed by nanometre-sized particles surrounded by fully molten areas. Moreover, crystalline phases were determined by XRD and Raman spectroscopy. Mechanical properties were also determined using nanoindentation technique. Nanoindentation tests showed a bimodal distribution of the mechanical properties (hardness and Young's modulus) which is related to the two zones (molten and partially molten) present in the coatings. (C) 2012 Elsevier B.V. All rights reserved.This work has been supported by the Spanish Ministry of Science and Innovation (project MAT2009-14144-C03) and the Research Promotion Plan of the Universitat Jaume I, action 2.1 (ref. E-2011-05) and action 3.1 (ref. PREDOC/2009/10). The authors are grateful to Leszek Łatka for his help in plasma spray experiments.Carpio, P.; Rayón Encinas, E.; Pawlowski, L.; Cattini, A.; Benavente Martínez, R.; Bannier, E.; Salvador Moya, MD.... (2013). Microstructure and indentation mechanical properties of YSZ nanostructured coatings obtained by suspension plasma spraying. Surface and Coatings Technology. 220:237-243. https://doi.org/10.1016/j.surfcoat.2012.09.047S23724322

Sliding Wear Response of Nanostructured YSZ Suspension Plasma-Sprayed Coating

Nanostructured yttria-stabilized zirconia coatings for applications in high-temperature environments can be deposited by suspension plasma spraying (SPS) techniques. The present research has been conducted in order to study the sliding wear response of a SPS ZrO2–8% mol. Y2O3 coating (75 lm in thickness) deposited onto a Haynes 230 substrate, using pin-on-disc tests. Some of the coated samples were subsequently heat-treated for 1 h at 300 and 600 !C. Samples characterization prior and after the wear tests was carried out by SEM, EDS, XRD and optical profilometry techniques. Instrumented indentation was employed to determine elastic modulus and hardness. The results have shown that the as-sprayed and heat-treated samples experienced severe wear (10213 m3/Nm) and the worst wear performance corresponded to the sample heat treated at 600 !C. Such a behavior could be related to both the structural changes that took place during heat treatment and the nature and level of the residual stresses in the coatings. In general, the morphologies of the wear tracks observed by SEM have shown a smoothing of the surface, brittle fracture, smearing and grain pull-out

Double nano / micro ceramic layer as protective coating on thin metal substrate for long-term service

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