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Pawel Sokolowski - One of the best experts on this subject based on the ideXlab platform.
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the microstructural studies of suspension Plasma sprayed zirconia coatings with the use of high energy Plasma Torches
Surface & Coatings Technology, 2017Co-Authors: Pawel Sokolowski, Per Nylen, Radek Musalek, Leszek łatka, Stefan Kozerski, Dagmar Dietrich, Thomas Lampke, Lech PawlowskiAbstract:Abstract The presented studies are focused on the microstructure characterization of zirconia-based coatings deposited by two types of high-energy Plasma Torches: (i) Axial III; and, (ii) hybrid version of Water-Stabilized Plasma (WSP) torch. The suspensions were formulated using solid dispersed phase of: (i) zirconia stabilized with 14 wt% of Y 2 O 3 and (ii) zirconia stabilized with 24 wt% of CeO 2 + 2.5 wt% of Y 2 O 3 and continuous phase of water with ethanol. The spray process parameters were optimized for each Plasma set-up individually. The in-flight observations (shadowgraphy) were performed to optimize the injection of the liquid feedstock into the Plasma jet. Then the coating's morphology and coating/substrate interface were characterized using conventional light microscopy and scanning electron microscopy (SEM). The results showed that through the change of deposition parameters various coatings microstructures could be obtained, in particular columnar and two-zones structures. The EDS/EDX and XRD studies showed that there was no significant change in chemical/phase composition of zirconia material before and after spraying. Electron backscatter diffraction (EBSD) method allowed to analyze the grain size in the coating microstructure as well as crystallographic orientation of individual grains. The results showed that coatings were characterized by submicrometric microstructure what corresponded to the size of powder particles used to formulate suspension. No texture was observed in the coatings microstructure. The surface topography analysis which was performed by confocal scanning laser microscopy (CSLM) and Shape From Shading (SFS) technique proved the great influence of suspension concentration on the coating structure.
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Properties of suspension Plasma sprayed zirconia coatings using different Plasma Torches
2016Co-Authors: Pawel SokolowskiAbstract:In this PhD thesis several scientific issues regarding Suspension Plasma Sprayed (SPS) zirconia coatings were studied. The coatings were analyzed mainly in terms of the application as insulating top-coat of Thermal Barrier Coatings (TBC’s). These multilayer coatings are applied onto the metallic parts of e.g. gas turbines to protect them against high temperature loads caused by the hot exhaust gases. But the initial assessment of the possibility of the use of Suspension Plasma Spraying to produce electrolyte layer in Solid Oxide Fuel Cells was done also. SOFC’s seem to be the most promising fuel cell types currently. (See Chapter 1-2 with the literature review) The first important research goal was to analyze the possibility of producing coatings being various in terms of the microstructure. The main aim was to obtain coatings characterized by very porous and irregular structure (called columnar-like) but also very dense and homogeneous coatings with typical two-zones microstructure. For this purpose two zirconia powders were used: (i) fully yttria-stabilized zirconia and (ii) ytrria-ceria-stabilized zirconia. The powders had different chemical composition, particle size and morphology. These powders were used for a suspension formulation. The other variable in the spray process was suspension concentration. The suspension with a solid content in range of 2.5 and 30 wt. % were prepared and sprayed. All suspensions were home-produced. A very important concept of this work was the use of four various, commercially-available, Plasma Torches, namely: (i) SG-100, (ii) TriplexPro-200, (iii) Axial III and (iv) WSP-H 500. The Torches were different interms of design, electric power, Plasma stabilization mode and the suspension injection angle. Due to the big differences between Plasma Torches and SPS set-ups the spray process parameters were chosen in each case individually. The last variable in theexperiment design was the topography and roughness of substrate in order to evaluate its influence on the coatings growth-up mechanisms. The substrates were prepared prior to spraying by: (i) grit-blasting, (ii) laser-treatment and by (iii) grinding. The wideii spray experiment allowed complex analysis of SPS coatings microstructure, coatings growth-up mechanisms and the development of SPS process itself. [...]
Lech Pawlowski - One of the best experts on this subject based on the ideXlab platform.
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the microstructural studies of suspension Plasma sprayed zirconia coatings with the use of high energy Plasma Torches
Surface & Coatings Technology, 2017Co-Authors: Pawel Sokolowski, Per Nylen, Radek Musalek, Leszek łatka, Stefan Kozerski, Dagmar Dietrich, Thomas Lampke, Lech PawlowskiAbstract:Abstract The presented studies are focused on the microstructure characterization of zirconia-based coatings deposited by two types of high-energy Plasma Torches: (i) Axial III; and, (ii) hybrid version of Water-Stabilized Plasma (WSP) torch. The suspensions were formulated using solid dispersed phase of: (i) zirconia stabilized with 14 wt% of Y 2 O 3 and (ii) zirconia stabilized with 24 wt% of CeO 2 + 2.5 wt% of Y 2 O 3 and continuous phase of water with ethanol. The spray process parameters were optimized for each Plasma set-up individually. The in-flight observations (shadowgraphy) were performed to optimize the injection of the liquid feedstock into the Plasma jet. Then the coating's morphology and coating/substrate interface were characterized using conventional light microscopy and scanning electron microscopy (SEM). The results showed that through the change of deposition parameters various coatings microstructures could be obtained, in particular columnar and two-zones structures. The EDS/EDX and XRD studies showed that there was no significant change in chemical/phase composition of zirconia material before and after spraying. Electron backscatter diffraction (EBSD) method allowed to analyze the grain size in the coating microstructure as well as crystallographic orientation of individual grains. The results showed that coatings were characterized by submicrometric microstructure what corresponded to the size of powder particles used to formulate suspension. No texture was observed in the coatings microstructure. The surface topography analysis which was performed by confocal scanning laser microscopy (CSLM) and Shape From Shading (SFS) technique proved the great influence of suspension concentration on the coating structure.
Jean François Coudert - One of the best experts on this subject based on the ideXlab platform.
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Electric Arc Fluctuations in DC Plasma Spray Torch
Plasma Chemistry and Plasma Processing, 2017Co-Authors: Vincent Rat, F. Mavier, Jean François CoudertAbstract:Direct current Plasma Torches for Plasma spraying applications generate electric arc instabilities. The resulting fluctuations of input electrical power hamper a proper control of heat and momentum transfers to materials for coating deposition. This paper gives an overview of major issues about arc instabilities in conventional DC Plasma Torches. Evidences of arc fluctuations and their consequences on Plasma properties and on material treatments are illustrated. Driving forces applied to the arc creating its motion are described and emphasis is put on the restrike mode that depends on the arc reattachment and the boundary layer properties around the arc column. Besides the arc root shown as a key region of instability, the Helmholtz oscillation is also described and accounts for the whole Plasma torch domain that can generate pressure fluctuations coupled with voltage ones.
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Acoustic stabilization of electric arc instabilities in nontransferred Plasma Torches
Applied Physics Letters, 2010Co-Authors: Vincent Rat, Jean François CoudertAbstract:Electric arc instabilities in dc Plasma Torches lead to nonhomogeneous treatments of nanosized solid particles or liquids injected within thermal Plasma jets. This paper shows that an additional acoustic resonator mounted on the cathode cavity allows reaching a significant damping of these instabilities, particularly the Helmholtz mode of arc oscillations. The acoustic resonator is coupled with the Helmholtz resonator of the Plasma torch limiting the amplitude of arc voltage variations. It is also highlighted that this damping is dependent on friction effects in the acoustic resonator.
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FROM TRANSFERRED ARC TO Plasma Torches
High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes), 2005Co-Authors: Jean François Coudert, Christophe Chazelas, D. Rigot, Vincent RatAbstract:International audienceThermal Plasma generated either by transferred arc or by Plasma Torches are involved in many industrial processes including, for example, cutting, welding, powder synthesis or coating elaboration by Plasma spray techniques. The common feature is that electrical energy is converted into thermal energy, which must be transferred differently following the goal of the technique. Cutting requires a high thermal flux density to the anode in order to optimize both the accuracy and the speed of cutting. On the opposite, heat transfer to the anode of a Plasma spray torch needs to be reduced, as much as possible, in order to slow down the nozzle erosion which is responsible, among other problems, of the monotonic deviation of the torche performances over a long time scale. This presentation is devoted to a general approach of the physical processes concerning an electric arc, thermally constricted and confined in the channel of a Plasma torch nozzle. Experimental results characterizing both stationnary and transient behaviour of the generated Plasma flow will be described. General tendancies observed for the shift of the torch performances and connected to the anode erosion, will be commented
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From transferred arc to Plasma Torches
High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes), 2005Co-Authors: Jean François Coudert, Christophe Chazelas, D. Rigot, Vincent RatAbstract:Thermal Plasma generated either by transferred arc or by Plasma Torches are involved in many industrial processes including, for example, cutting, welding, powder synthesis or coating elaboration by Plasma spray techniques. The common feature is that electrical energy is converted into thermal energy, which must be transferred differently following the goal of the technique. Cutting requires a high thermal flux density to the anode in order to optimize both the accuracy and the speed of cutting. On the opposite, heat transfer to the anode of a Plasma spray torch needs to be reduced, as much as possible, in order to slow down the nozzle erosion which is responsible, among other problems, of the monotonic deviation of the torche performances over a long time scale. This presentation is devoted to a general approach of the physical processes concerning an electric arc, thermally constricted and confined in the channel of a Plasma torch nozzle. Experimental results characterizing both stationnary and transient behaviour of the generated Plasma flow will be described. General tendancies observed for the shift of the torch performances and connected to the anode erosion, will be commented.
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Arc root behavior in Plasma spray torch
IEEE Transactions on Plasma Science, 2005Co-Authors: Christophe Chazelas, Jean François Coudert, Pierre FauchaisAbstract:Plasma Torches are involved in many industrial processes, but Plasma jet instabilities reduce the reproducibility and the efficiency of processes in which they are involved. In this current work, a setup has been developed to visualize the arc attachment at the anode. It allows to simulate the effect of cold boundary layer on the arc attachment in conditions similar to those encountered in direct current (dc) Plasma spray Torches
Vincent Rat - One of the best experts on this subject based on the ideXlab platform.
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Control of the Arc Motion in DC Plasma Spray Torch with a Cascaded Anode
Journal of Thermal Spray Technology, 2019Co-Authors: Rodion Zhukovskii, Christophe Chazelas, Armelle Vardelle, Vincent RatAbstract:Two common concerns in DC Plasma Torches are stability of Plasma jet and anode erosion. The challenge is how to get a stable Plasma jet with minimal anode erosion. This study tackles this question by using either a swirling gas injection or an external axial magnetic field applied to the Oerlikon SinplexPro™ Plasma torch. A 3-D, time-dependent MHD model of the Plasma torch operation was used to predict the value of the external magnetic field and its effect on the heat flux to the anode and Plasma jet stability. The special feature of the model is to couple the gas phase and electrodes that makes it possible to follow the anode temperature evolution. For specific operation conditions (anode of Ø9 mm, 500 A, Ar 60 NLPM), the model predicted that the maximal value of the azimuthal self-magnetic field inducted by the arc current was 0.055 T; it also showed that an external magnetic field of 0.05 to 0.1 T could make it possible to limit the anode erosion without noticeably disturbing the Plasma jet issuing from the Plasma torch. We expect this approach to help to better understand the arc behavior in commercial Plasma Torches and control anode erosion.
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Electric Arc Fluctuations in DC Plasma Spray Torch
Plasma Chemistry and Plasma Processing, 2017Co-Authors: Vincent Rat, F. Mavier, Jean François CoudertAbstract:Direct current Plasma Torches for Plasma spraying applications generate electric arc instabilities. The resulting fluctuations of input electrical power hamper a proper control of heat and momentum transfers to materials for coating deposition. This paper gives an overview of major issues about arc instabilities in conventional DC Plasma Torches. Evidences of arc fluctuations and their consequences on Plasma properties and on material treatments are illustrated. Driving forces applied to the arc creating its motion are described and emphasis is put on the restrike mode that depends on the arc reattachment and the boundary layer properties around the arc column. Besides the arc root shown as a key region of instability, the Helmholtz oscillation is also described and accounts for the whole Plasma torch domain that can generate pressure fluctuations coupled with voltage ones.
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Acoustic stabilization of electric arc instabilities in nontransferred Plasma Torches
Applied Physics Letters, 2010Co-Authors: Vincent Rat, Jean François CoudertAbstract:Electric arc instabilities in dc Plasma Torches lead to nonhomogeneous treatments of nanosized solid particles or liquids injected within thermal Plasma jets. This paper shows that an additional acoustic resonator mounted on the cathode cavity allows reaching a significant damping of these instabilities, particularly the Helmholtz mode of arc oscillations. The acoustic resonator is coupled with the Helmholtz resonator of the Plasma torch limiting the amplitude of arc voltage variations. It is also highlighted that this damping is dependent on friction effects in the acoustic resonator.
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FROM TRANSFERRED ARC TO Plasma Torches
High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes), 2005Co-Authors: Jean François Coudert, Christophe Chazelas, D. Rigot, Vincent RatAbstract:International audienceThermal Plasma generated either by transferred arc or by Plasma Torches are involved in many industrial processes including, for example, cutting, welding, powder synthesis or coating elaboration by Plasma spray techniques. The common feature is that electrical energy is converted into thermal energy, which must be transferred differently following the goal of the technique. Cutting requires a high thermal flux density to the anode in order to optimize both the accuracy and the speed of cutting. On the opposite, heat transfer to the anode of a Plasma spray torch needs to be reduced, as much as possible, in order to slow down the nozzle erosion which is responsible, among other problems, of the monotonic deviation of the torche performances over a long time scale. This presentation is devoted to a general approach of the physical processes concerning an electric arc, thermally constricted and confined in the channel of a Plasma torch nozzle. Experimental results characterizing both stationnary and transient behaviour of the generated Plasma flow will be described. General tendancies observed for the shift of the torch performances and connected to the anode erosion, will be commented
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From transferred arc to Plasma Torches
High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes), 2005Co-Authors: Jean François Coudert, Christophe Chazelas, D. Rigot, Vincent RatAbstract:Thermal Plasma generated either by transferred arc or by Plasma Torches are involved in many industrial processes including, for example, cutting, welding, powder synthesis or coating elaboration by Plasma spray techniques. The common feature is that electrical energy is converted into thermal energy, which must be transferred differently following the goal of the technique. Cutting requires a high thermal flux density to the anode in order to optimize both the accuracy and the speed of cutting. On the opposite, heat transfer to the anode of a Plasma spray torch needs to be reduced, as much as possible, in order to slow down the nozzle erosion which is responsible, among other problems, of the monotonic deviation of the torche performances over a long time scale. This presentation is devoted to a general approach of the physical processes concerning an electric arc, thermally constricted and confined in the channel of a Plasma torch nozzle. Experimental results characterizing both stationnary and transient behaviour of the generated Plasma flow will be described. General tendancies observed for the shift of the torch performances and connected to the anode erosion, will be commented.
Roberto Nunes Szente - One of the best experts on this subject based on the ideXlab platform.
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An improvement on the modelling of non-transferred Plasma Torches
Journal of Physics D: Applied Physics, 1999Co-Authors: R C Bianchini, R C Favalli, Marcos De Mattos Pimenta, Roberto Nunes SzenteAbstract:In the modelling of non-transferred Plasma Torches, the electrical potential is normally used in the same way as in the simulation of transferred Plasma Torches. This approach results in physically questionable current density profiles. A modification is proposed in the manner that the electrical potential is used in the simulation of non-transferred Plasma Torches. The new model provides in physically acceptable results. A comparison of the results obtained from the two models (the previously used and the presently proposed), shows differences of up to 50% in the velocity and 20% in the temperature were found. Tests were performed with the new model showing the possibility of using it for a broad range of parameters.
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PHYSICAL AND MATHEMATICAL MODELING OF NON TRANSFERRED Plasma Torches
Brazilian Journal of Physics, 1998Co-Authors: R C Favalli, Roberto Nunes SzenteAbstract:The main objective of this work is to obtain temperature and velocity profiles of the Plasma jet, including the electric arc region, generated by non transferred Plasma Torches. The profiles are obtained from a numerical solution of the conservation equations wich were used to describe the Plasma flow. This modelling approach will help the development and optimization of Plasma Torches, saving time and reducing costs of an alternative empirical development; it could also give some insight on the phenomena occuring inside the torch. Fluid mechanics models for laminar and turbulent flows were adopted to simulate the Plasma inside and outside the torch. Patankar's control volume method was chosen to solve the resulting coupled differential equations. The method is very stable and requires less computational time than higher order methods, although it can be less accurate for some applications. A computer code was developed to simulate the jet flow of a Plasma torch. The results obtained from this program compared very well with published ones, corroborating the assumptionsn of the present model and the numerical method. Temperature and velocity profiles for a Plasma torch with dimentions and operating conditions similar to the ones used in indusrtial applications of spraying were generated and analyzed. The Plasma torch simulated had an eletric arc of 100A, Plasma gas flow rate of 20 l / min, cross section of 5.2 mm and anode length of 13mm.