The Experts below are selected from a list of 10491 Experts worldwide ranked by ideXlab platform
Filofteia Laura Toma - One of the best experts on this subject based on the ideXlab platform.
-
Demands, Potentials, and Economic Aspects of Thermal Spraying with Suspensions: A Critical Review
Journal of Thermal Spray Technology, 2015Co-Authors: Filofteia Laura Toma, Annegret Potthoff, Lutz-michael Berger, Christoph LeyensAbstract:Research and development work for about one decade have demonstrated many unique Thermal spray coating properties, particularly for oxide ceramic coatings by using suspensions of fine powders as feedstock in APS and HVOF processes. Some particular advantages are direct feeding of fine nano- and submicron-scale particles avoiding special feedstock powder preparation, ability to produce coating thicknesses ranging from 10 to 50 µm, homogeneous microstructure with less anisotropy and lower surface roughness compared to conventional coatings, possibility of retention of the initial crystalline phases, and others. This paper discusses the main aspects of Thermal Spraying with suspensions which have been taken into account in order to produce these coatings on an economical way. The economic efficiency of the process depends on the availability of suitable additional system components (suspension feeder, injectors), on the development and handling of stable suspensions, as well as on the high process stability for acceptance at industrial scale. Special focus is made on the development and processability of highly concentrated water-based suspensions. While costs and operational safety clearly speak for use of water as a liquid media for preparing suspensions on an industrial scale, its use is often critically discussed due to the required higher heat input during Spraying compared to alcoholic suspensions.
-
comparative study of suspension plasma sprayed and suspension high velocity oxy fuel sprayed ysz Thermal barrier coatings
Surface & Coatings Technology, 2015Co-Authors: Ashish Ganvir, Per Nylén, Nicholas Curry, Nicolaie Markocsan, Filofteia Laura TomaAbstract:Suspension Thermal Spraying is a relatively new Thermal spaying technique to produce advanced Thermal barrier coatings. This technique enables the production of much different performance Thermal b ...
-
comparative study on the photocatalytic behaviour of titanium oxide Thermal sprayed coatings from powders and suspensions
Surface & Coatings Technology, 2009Co-Authors: Filofteia Laura Toma, Lutz-michael Berger, D Jacquet, D Wicky, I Villaluenga, Y R De Miguel, J S LindelovAbstract:Abstract This work presents a study of the microstructures and photocatalytic behaviour of titanium oxide coatings obtained by Thermal Spraying of agglomerated nanopowders and suspensions. Fine TiO2 Degussa P25 nanopowder, generally considered as the reference material in photocatalytic applications, was used as the material feedstock. HVOF process and suspension Thermal Spraying were used to prepare photocatalytic titania coatings. The coatings were mainly characterised by means of SEM and X-ray diffraction. The photocatalytic performance was evaluated based on decolouration of the pink dye Rhodamine B and degradation of gaseous acetaldehyde. A lower degree of pollutant degradation was found for deposits prepared by HVOF Spraying of granules due principally to the low content of the photocatalytically active phase, i.e. anatase. Complete photocatalytic degradation of the organic compounds was recorded for the suspension-sprayed coatings. Based on the current results, suspension Thermal Spraying appears to be the better choice for preparing photocatalytically active titanium oxide surfaces for the removal of organic pollutants.
-
comparison of the photocatalytic behavior of tio2 coatings elaborated by different Thermal Spraying processes
Journal of Thermal Spray Technology, 2006Co-Authors: Filofteia Laura Toma, Ghislaine Bertrand, Christian Coddet, Dmitry Sokolov, Didier Klein, Cathy MeunierAbstract:This paper proposes a comparative study on the microstructure and photocatalytic performances of titanium dioxide coatings elaborated by various Thermal Spraying methods (plasma Spraying in atmospheric conditions, suspension plasma Spraying, and high-velocity oxyfuel Spraying). Agglomerated spray dried anatase TiO2 powder was used as feedstock material for Spraying. Morphology and microstructural characteristics of the coatings were studied mainly by scanning electron microscopy and x-ray diffraction. The photocatalytic behavior of the TiO2-base surfaces was evaluated from the conversion rate of gaseous nitrogen oxides (NOx). It was found that the crystalline structure depended strongly on the technique of Thermal Spraying deposition. Moreover, a high amount of anatase was suitable for the photocatalytic degradation of the pollutants. Suspension plasma Spraying has allowed retention of the original anatase phase and for very reactive TiO2 surfaces to be obtained for the removal of nitrogen oxides.
Christian Coddet - One of the best experts on this subject based on the ideXlab platform.
-
Laser surface texturing (LST) treatment before Thermal Spraying: A new process to improve the substrate-coating adherence
Surface and Coatings Technology, 2010Co-Authors: A. Lamraoui, Sophie Costil, Cécile Langlade, Christian CoddetAbstract:There are a number of widely used texturing techniques, as etching, electrical discharge and abrasive blasting (sandblasting) which combine quality and optimised processing time. The process allows the ablation, fusion and/or vaporization, and finally substrate texturing in only one step by means of a concentrated energy bean in a focused spot. A pulsed Nd:YAG laser (1.064. ??m radiation, 120 ns) with repetitive scans has been used to texture aluminium AL 2017 substrates. During the process, several laser parameters as scanning rate, distance between the laser impacts, frequency of the impulses and incident power have been studied to achieve NiAl coatings. Optical and scanning electron microscopy, and optical 3D profilometry were used to characterize the surface texture. Mechanical testing allowed evaluating the toughness and adhesion of the deposit. Surface texturing inducing holes on the substrate surface, coating adherence produced by Thermal Spraying mainly depends on the geometry of the texture (depth and diameter of holes) as well as on the distribution throughout the treated surface. ?? 2010.
-
microstructure and magnetic properties of fe si based coatings produced by hvof Thermal Spraying process
Journal of Alloys and Compounds, 2007Co-Authors: M Cherigui, N Fenineche, Gang Ji, Thierry Grosdidier, Christian CoddetAbstract:Abstract In this work, the Fe–Si based Thermal sprayed coatings were synthesized using HVOF in order to obtain ferromagnetic materials. Ultra-fine grain Fe–Si based coatings were synthesized by HVOF Thermal Spraying using nanostructured powders obtained from mechanical milling. Magnetic measurements revealed a soft magnetic character for all the coatings. Additions of boron, niobium and copper which can be regarded as non-magnetic inclusions caused a slight increase of coercivity. In order to investigate the stability of the magnetic properties of Thermal spray deposits during their application, relaxation heat treatments was carried out. The result shown the high Thermal stability in magnetic properties of the deposits and allow to using these deposits in several magnetic applications even to high temperatures.
-
comparison of the photocatalytic behavior of tio2 coatings elaborated by different Thermal Spraying processes
Journal of Thermal Spray Technology, 2006Co-Authors: Filofteia Laura Toma, Ghislaine Bertrand, Christian Coddet, Dmitry Sokolov, Didier Klein, Cathy MeunierAbstract:This paper proposes a comparative study on the microstructure and photocatalytic performances of titanium dioxide coatings elaborated by various Thermal Spraying methods (plasma Spraying in atmospheric conditions, suspension plasma Spraying, and high-velocity oxyfuel Spraying). Agglomerated spray dried anatase TiO2 powder was used as feedstock material for Spraying. Morphology and microstructural characteristics of the coatings were studied mainly by scanning electron microscopy and x-ray diffraction. The photocatalytic behavior of the TiO2-base surfaces was evaluated from the conversion rate of gaseous nitrogen oxides (NOx). It was found that the crystalline structure depended strongly on the technique of Thermal Spraying deposition. Moreover, a high amount of anatase was suitable for the photocatalytic degradation of the pollutants. Suspension plasma Spraying has allowed retention of the original anatase phase and for very reactive TiO2 surfaces to be obtained for the removal of nitrogen oxides.
-
ceramic fluoropolymer composite coatings by Thermal Spraying a modification of surface properties
Surface & Coatings Technology, 2005Co-Authors: C. Mateus, Sophie Costil, Rodolphe Bolot, Christian CoddetAbstract:Abstract Even if polymer coatings are widely used for industrial applications, their performances are often limited by a poor scratch resistance or a high water and gas permeability. To overcome such limitations, the composite coating of ceramics with polymer can be a solution to be adopted. Thermal Spraying may help to achieve this objective, thanks to its ability permitting to deposit many kinds of materials with an important range of coating thicknesses. The aim of this paper is to develop composite coatings (fluoropolymer/ceramic) by plasma spaying. Due to different Thermal characteristics of the initial materials (PTFE or PFA polymers and Al 2 O 3 –TiO 2 ceramic), three types of powders injections are elaborated. To compare these three conditions, microstructure, surface wettability and wear resistance deposits behaviour were characterized. Al 2 O 3 –TiO 2 /fluoropolymer (PTFE or PFA) composite coatings are characterized by a well-melted ceramic matrix in which rounded polymer particles are randomly distributed. The as-sprayed polymer particles kept at the coatings surface can however be spread thanks to a Thermal treatment at 350 °C during 15 min. Unlike the PFA, a large PTFE loss was noticed during the Spraying process. Thus, the highest polymer/ceramic ratio is observed in the coatings made with the separated injection of the Al 2 O 3 –TiO 2 and PFA powders. The lowest friction coefficient is also measured for this coating.
-
effects of the spray angle on splat morphology during Thermal Spraying
Surface & Coatings Technology, 1997Co-Authors: Ghislain Montavon, Sanjay Sampath, C C Berndt, H Herman, Christian CoddetAbstract:Abstract The effects of spray angle on the morphology of Thermally sprayed particles impinging on polished substrates have been studied by implementing several statistical tools (i.e., Gaussian analysis, Weibull distribution and the t -test). Nickel-based alloy (Astroloy) particles were vacuum plasma-sprayed onto copper plates at normal (i.e., 90 °) and several off-normal spray angles (i.e., 75, 60, 45 and 30 °). Different geometric shape factors (i.e., referring to an equivalent diameter, elongation factor and degree of splashing) were determined using image analysis. The spray angle had a strong effect on these geometric properties, in particular on the elongation factor of the shapes.
Ghislain Montavon - One of the best experts on this subject based on the ideXlab platform.
-
application of robot offline programming in Thermal Spraying
Surface & Coatings Technology, 2012Co-Authors: Sihao Deng, Zhenhua Cai, Dandan Fang, Hanlin Liao, Ghislain MontavonAbstract:Abstract Nowadays, robot manipulators have already been widely used in Thermal Spraying. They can be programmed in two ways: online and offline programming. The first programming method is easy to operate but difficult to guarantee the quality of coatings, especially for some complex workpieces. The offline programming technology is a good solution that can overcome the online programming tolerances by using the CAD files of the workpiece. The purpose of this study is to introduce the current applications of offline programming technology in Thermal Spraying, including some popular methods of path generation, process simulation, robot kinematics optimization, etc. In the last part of this paper, two examples of offline programming in Thermal Spraying were presented which refer to the trajectory optimization on a workpiece with a great angle and path generation on the complex workpiece with external axis. The simulations and experiments have proved that offline programming can effectively improve the production efficiency and coating quality.
-
latest developments in suspension and liquid precursor Thermal Spraying
Journal of Thermal Spray Technology, 2010Co-Authors: Pierre Fauchais, Ghislain MontavonAbstract:The interest to manufacture onto large surfaces thick (i.e., 10-20 μm, average thickness) finely structured or nanostructured layers is increasingly growing since the past 10 years. This explains the interest for suspension Thermal Spraying (STS) and solution precursor Thermal Spraying (SPTS), both allowing manufacturing finely structured layers of thicknesses varying between a few micrometers up to a few hundreds of micrometers. STS aims at processing a suspension of sub-micrometer-sized or even nanometer-sized solid particles dispersed in a liquid phase. The liquid phase permits the injection of particles in the Thermal flow (i.e., due to their size, a carrier gas cannot play this role). SPTS aims at processing a solution of precursors under the same conditions. Upon evaporation of the liquid phase, the precursor concentration increases until precipitation, pyrolysis, and melting of small droplets occur. Compared to conventional Thermal spray routes, STS and SPTS are by far more complex because fragmentation and vaporization of the liquid control the coating build-up mechanisms. Numerous studies are still necessary to reach a better understanding of the involved phenomena and to further develop the technology, among which are injection systems, suspension and solution optimizations, spray kinematics, etc. This review presents some recent developments and our present knowledge in this field together with the available tools implemented to characterize the plasma-liquid interaction and the coating formation.
-
Thermal and Cold Spray: Recent Developments
Key Engineering Materials, 2008Co-Authors: Pierre Fauchais, Ghislain MontavonAbstract:Thermal Spraying consists in a technology aiming at producing coatings whose thicknesses range from 10 μm to a few millimeters onto mechanical components to confer them specific and unique functional properties, such as wear and corrosion resistances, friction coefficient adaptation, Thermal and electrical insulation, biocompatibility, repair, etc., among the principals. Thermal Spraying consists in injecting in a viscous enthalpic jet (animated by a momentum) powder with particles which average size ranges from 0.01 to 100 μm. These particles are melted and simultaneously accelerated towards the surface of the part to be covered. They form, after impact, spreading and solidification, near-circular lamellae the stacking of which form the coating. Due to the versatility of the available processes exhibiting a wide range of enthalpic and momentum contents, virtually any kind of material exhibiting congruent melting behavior can be processed, from alloys and ceramics to polymers, ever since its melting temperature differs from its vaporization or decomposition temperature by at least 300 K and that it can be processed previously under the form of powder particles or wires. Thermal spray techniques offer the unique capability to manufacture a large variety of coatings on components of a large variety and geometry. However, Thermal Spraying constitutes a special process for which the coating service properties derive mostly from the structure and indirectly from the selection of the operating parameters. Very significant improvements over the past years permitted to diagnose the in-flight particle characteristics, mostly in terms of velocity and temperature. Recently, these new capabilities have made possible the development of on-line process controls. This should participate to a drastic increase in coating reliability. In conventional Thermal Spraying processes, a pulverulent feedstock (i.e., powder particles) is injected within the plasma jet via a carrier gas. This approach does not permit to process small diameter particles; i.e., nano-sized particles, which could permit to form finely grained coatings. Replacing gas by liquid to carry particles offer the unique possibility to process nano-sized particles. Cold gas Spraying may appear as an alternative process to reach the same goal. Indeed, Thermal spray processes experienced very significant developments over the past years, opening new doors to manufacture coatings with a high reliability and superior properties. This papepr indend at presenting some of those developments.
-
effects of the spray angle on splat morphology during Thermal Spraying
Surface & Coatings Technology, 1997Co-Authors: Ghislain Montavon, Sanjay Sampath, C C Berndt, H Herman, Christian CoddetAbstract:Abstract The effects of spray angle on the morphology of Thermally sprayed particles impinging on polished substrates have been studied by implementing several statistical tools (i.e., Gaussian analysis, Weibull distribution and the t -test). Nickel-based alloy (Astroloy) particles were vacuum plasma-sprayed onto copper plates at normal (i.e., 90 °) and several off-normal spray angles (i.e., 75, 60, 45 and 30 °). Different geometric shape factors (i.e., referring to an equivalent diameter, elongation factor and degree of splashing) were determined using image analysis. The spray angle had a strong effect on these geometric properties, in particular on the elongation factor of the shapes.
Sheyda Labbaf - One of the best experts on this subject based on the ideXlab platform.
-
comparative study on microstructure and corrosion behavior of nanostructured hydroxyapatite coatings deposited by high velocity oxygen fuel and flame Spraying on az61 magnesium based substrates
Applied Surface Science, 2019Co-Authors: Marzieh Mardali, Hamid R Salimijazi, F Karimzadeh, B Luthringer, C Blawert, Sheyda LabbafAbstract:Abstract Hydroxyapatite coatings are biocompatible, osteoconductive and create a corrosion resistance surface on magnesium-based implants. Thermal decomposition of HA during Thermal Spraying limits its application. To overcome the challenges associated with Thermal decomposition of HA during Thermal Spraying, high velocity oxygen fuel Spraying with a good Thermal stability for HA is proposed. In this work, the traditional flame Spraying was compared to high velocity oxy-fuel (HVOF) for HA depositions on magnesium alloy substrates. The effect of process on microstructure, morphology, corrosion behavior and cellular response of HA layers were evaluated. X-ray diffraction analysis showed that the amount of secondary phases in the HVOF deposited sample was less than that in the flame sprayed coatings. Elemental weight percentage of calcium in corroded surfaces was 21% and 34.5% for HVOF and flame sprayed coatings, respectively. Contrary to the results of the electrochemical impedance spectroscopy measurements for HVOF coating performed during the early hours of immersion in the simulated body fluid (SBF), flame sprayed coating exhibited lower corrosion rate after 5 h immersion in SBF solution.
Wuha Liu - One of the best experts on this subject based on the ideXlab platform.
-
enhancement of wear and corrosion resistance of iron based hard coatings deposited by high velocity oxygen fuel hvof Thermal Spraying
Surface & Coatings Technology, 2014Co-Authors: Wuha Liu, Fuhsheng Shieu, Weitie HsiaoAbstract:Abstract Fe-based alloy material is widely used in the corrosive environment of seawater. It is replacing expensive cobalt and nickel-based alloys. Amorphous iron-based (Fe-based) alloy coatings can be deposited on stainless steel by high-velocity oxygen fuel (HVOF) Thermal Spraying. Following Spraying, coatings were heat-treated at 500, 600, 700, 800, and 900 °C for up to three hours in a vacuum furnace. The microstructures of such coatings were analyzed herein using an optical microscope (OM) and scanning electron microscope (SEM) to monitor the morphologies of both powders and coatings of Fe-based alloy. Phase analysis was performed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The goal of this work on the modification of Fe-based alloy feedstock powder is to enhance the corrosion and wear properties of these coatings. The results of this investigation reveal that adding a cobalt material to Fe-based alloy yields coatings with enhanced corrosion and tribological characteristics.
