bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influences on the Kinematics of the APS-Process Investigated by Means of Particle Image Velocimetry
Authors: Bach Fr.-W. , Möhwald K. , Drößler B. , Prehm J. , Rothardt T. , Copitzky T. 
Published: September 2022

Abstract
Modern thermal spray processes require wide use of diagnostics to gather an extensive process understanding. Today's diagnostic results provide the basis for future designs and advancements, particularly and increasingly on basis of computational approaches. Due to the measuring area in the square centimeter range and its quick and accurate results, the Particle Image Velocimetry (PIV) represents an enriching for thermal spray process diagnostics. Our experimental results obtained from PIV are in accordance to present theoretical and empirical derivations of some kinematic parameters of thermal spray processes. Beneath verification of well-known dominant parameters (for example powder fraction or carrier gas mass flow), this procedure enables the detection and characterization of ancillary influences on the process due to its high accuracy. By statistical analysis of our experiments, using multiple parameter variations per experiment according to the technique of "Design of Experiments" (DoE), we possibly found some hints on interactions between ancillary parameters which shall be analysed in further works carefully. In combination with detailed simulations on plasma - particle interactions and powder injection it should be possible to develop methods for thermal spray processes to minimize the particle flow expansion for an optimization of deposition rate and energy efficiency in the future.
Diagnostics at Thermal Coating Processes – Research Results of the DFG-Founded Project
Authors: Bach Fr.-W. , Henne R. , Landes K. , Lugscheider E. , Copitzky T. , Prehm J. , Droessler B. , Ernst F. , Fischer A. , Seemann K. , Streibl T. , Zimmermann S. , Bouyer E. 
Published: September 2022

Abstract
The aim of the project group consisting of four research centers and founded by the DFG (German Research Society) is to characterize the plasma spraying process by means of diagnostic methods so that, based on the requirement profile of the coating, appropriate adjusting of the process parameters can be realized. For this purpose, different, partly newly-developed diagnostic tools, like Particle Shape Imaging, Laser Doppler Anemometry, Streak Technique, Particle Image Velocimetry, Enthalpy Probe, DPV 2000 and Thermography were qualified and adjusted to each other. The new results presented in this article are limited to the areas of particle injection and substrate which are difficult to handle with diagnostic methods.
On-line Optical Diagnostics of a Rotating Internal Diameter Plasma Spray Gun Used for Coating of Cylinder Bores in Automotive Industry
Authors: Hämäläinen E. , Kriikka N. , Barbezat G. 
Published: September 2022

Abstract
Coating of cylinder bores using plasma spraying is a growing application of thermal spraying in automotive industry. The Sulzer Metco RotaPlasma manipulator provides continuous rotation of the internal diameter plasma gun and enables a cost-efficient and reliable coating of the cylinder blocks. The development towards more advanced quality control systems and closed-loop spray control systems requires an on-line measurement of the most important particle and spray parameters such as particle temperature, velocity and flux. However, the small dimensions of the plasma plume of an internal diameter spray gun together with the rotation of the gun makes the measurement difficult, if not impossible, for many traditional diagnostics equipment. In this work, SprayWatch, an imaging CCD camera based diagnostics system from Oseir Ltd. was used for measuring particle and spray parameters during the rotation of an internal diameter plasma spray gun. The results show that the SprayWatch camera system is a promising tool for both development and production monitoring of cylinder bore coating process, as well as for realising a closed-loop spray control system.
Experimental Study of Substrate Thermal Conditions at APS and HVOF
Authors: Zagorski A. , Szuecs F. , Belashchenko V. , Ivanov A. , Siegmann S. , Margadant N. 
Published: September 2022

Abstract
Systematic measurements of heat fluxes into the substrate under the conditions of APS and HVOF have been performed with the use of a specially designed calorimeter. Results of measurements are presented in terms of the heat absorbed by a 150 mm diameter disk related to the electrical input power (EIP) and/or to the plasma/gas enthalpy. Depending on the process conditions heat flux into the substrate could reach as much as 20 per cent of the torch input power. Influences of gas composition, torch power and standoff distance on the heat transfer efficiency as well as the radial distributions of heat fluxes have been studied in detail and compared for three types of guns. Data obtained from the measurements of the radial distribution of heat fluxes in the plasma plume allowed estimating effective plasma jet diameter and the heat flux density, respectively. Rates of jet expansion differ significantly between the F4 and PlazJet plasma torches. Direct measurements of the substrate temperatures with the use of thermal paints have been performed and temperature patterns were compared with the results of 3D heat transfer modeling. Experimental values of heat fluxes were used in the calculations. Comparison showed that the experimental data on heat transfer efficiency could be used for accurate predictions of the substrate thermal conditions during thermal spraying.
DC Plasma Diagnostics for Improvement of Plasma Spraying Process under Soft Vacuum Conditions
Authors: Rat V. , Bouyer E. , Henne R.H. , Mayr W. 
Published: September 2022

Abstract
The vacuum plasma spraying process has to be optimized for each task in order to obtain the required mechanical and electrical properties for the desired coatings. This paper deals with the characterization of plasma and powder spray jets at deposition conditions for Solid Oxide Fuel Cells layers. First, DC plasma jets under soft vacuum conditions are characterized by using an enthalpy probe system and a Schlieren optic installation. The influence of the inner contour of the plasma spray torch anode on the temperature and velocity profiles as well on the shape of the plasma jets are investigated. Second, Laser Doppler Anemometry (LDA) measurements were performed for (8 mol %) yttria stabilized zirconia (YSZ) powder (-20+5 µm) spray jets for two chamber pressures, different argon carrier gas flow rates and injection modes. The results show that a M3 Laval nozzle and a F4V nozzle with conical inner profile allow to obtain a larger plasma volume and a more uniform plasma than with a standard F4 anode nozzle resulting in a better treatment of solid particles in the plasma. LDA measurements, using a M3 anode nozzle, show that the penetration and the acceleration of particles in the core of the plasma jet have their optimum at 10 kPa with an inclined injection with respect to the plasma jet axis for a 3.75 slpm carrier gas flow rate.
Examination of the Dry Ice Removal Process for Thermal Sprayed Coatings by Particle Image Velocimetry
Authors: Redeker C.F. , Bach Fr.-W. , Copitzky T. 
Published: September 2022

Abstract
The life time of some thermal sprayed coatings is limited. Flaking or partial removal of the coating reduces its protective effect. To allow further use of the component the coating has to be reworked before the part gets heavily damaged. The damaged coating must be removed with minimum impact on the surface of the component. Many removal methods as chemical, electrochemical or waterjet techniques have to be used with great care to prevent damaging of the substrate or are environmentally hazardous. An alternative technique which removes the coating selective with minimum impact on the substrate is the use of dry ice. Pellets of solid carbon dioxide are accelerated by means of compressed air. During the impact the carbon dioxide sublimates at a temperature of –78°C. The sublimation generates a large expansion (~600 times) of the carbon dioxide. The coating is strongly cooled while the shock wave of the sublimation destroys the cohesion. To support this process and to enlarge the thermal stresses in the coating a laser can be used. In this contribution the pellet velocity is measured and compared for three different dry ice jet devices by particle image velocimetry. Analysed parameters which are supposed to have an influence to the particle velocity are the mass flow of the compressed air, nozzle geometry and the working principles of the devices. The pellet velocity and the resulting kinetic energy are important process parameter. The results are used to optimise the laser assisted dry ice jet process.
Highly Porous Deposits of Cr2O3 Prepared by Plasma Co-spraying of Cr2O3 and Al
Authors: Neufuss K. , Kolman B. , Ctibor P. , Chráska P. , Laakso J. , Ahmaniemi S. , Vuoristo P. , Mäntylä T. 
Published: September 2022

Abstract
By modification of parameters in plasma spraying it is possible to alter porosity of the deposits only in a relatively small range. Industrial applications may require to adjust the porosity in wider range, to double or triple the original value in some cases. Such changes can be achieved only by special procedures. One of them is plasma spraying of ceramic/metal deposit followed by removal of the metal within the coating. The material removal is performed by dissolving, by leaching or by its extraction with an appropriate process. The paper describes preparation of very porous Cr2O3 coatings by this method from a composite Cr2O3/Al deposit. The initial porosity of approximately 13% (total porosity) was increased to 37% or 51% respectively by changing the initial volume of aluminum in the ceramic/metal plasma-sprayed composite. The discussion is complemented by observation of the resulting coating structure and detailed characterizations of the pore structure and porosity.
Interconnected Porosity of Plasma Sprayed Alumina Coatings: Evaluation and Modification
Authors: Haure T. , Denoirjean A. , Tristant P. , Desmaison J. , Fauchais P. , Maître A. 
Published: September 2022

Abstract
For electrical or thermal insulation, the porosity of an air plasma sprayed (APS) coating is an important property to control. Moreover in aggressive environment the interconnected porosity is responsible for the substrate corrosion. To solve, at least partially, this problem, deposition by mutitechniques (APS and a PECVD) was used to close interconnected and opened porosities. In this study, titanium alloy (TA6V) substrates were coated by alumina using either one or both deposition processes. Electrochemical characterization technique was used to evaluate the open porosity in alumina coatings. It consists of evaluating the polarization resistance of the reference sample surface (uncoated substrate) and to compare it to coated ones. After different tests for selecting the electrolyte solution, the influences of different parameters (thickness and relative position) of each deposition process on coating porosity were examined.
Evaluation of the Photodecomposition Efficiency of the Nanostructured TiO2 Sol Precursor Plasma Coatings
Authors: Choi Hanshin , Han Changmin , Lee Changhee , Kim Hyungjun 
Published: September 2022

Abstract
Two kind of the feedstock materials were used to produce the atmospheric plasma sprayed coatings. One is the spraying dried powder and the other is the nano-particle dispersed sol precursor. Coating properties were evaluated by the XRD, Raman spectroscopy, SEM and TEM. Also, the photodecomposition efficiency was examined by measuring the decomposition rate of the MB(methylene blue) in a water-cooled solution during the UV radiation and compared to the decomposition efficiency of the optimum coating produced using spraying dried particle. Both the anatase phase fraction and the photodecomposition rate of the coating using the sol precursor were higher than that of the optimum coating using the spraying dried powder.
Microstructure and Electrical Properties of RF and DC Plasma-Sprayed TiO2 Coatings
Authors: Branland N. , Meillot E. , Fauchais P. , Vardelle A. , Gitzhofer F. , Boulos M. 
Published: September 2022

Abstract
Relationships between the electrical properties of thermally sprayed titania coatings and their microstructure have been investigated. As far as possible, a broad range of microstructures was produced by using various processes of plasma spraying with different powder size ranges and variations of the plasma operating parameters. The two spraying processes consisted of DC plasma spraying and RF plasma spraying. Physical properties of plasma-sprayed coatings are generally influenced by their microstructure. But the electrical properties of plasma-sprayed titania coatings are known to be strongly influenced by their stoichiometry. It is the reason why coatings with identical stoichiometry were compared. It was found that electrical resistivity was directly linked to the quality of the contact between the splats and their density through the titania plasma-sprayed coatings.
Influence of Plasma Spray Parameters on Microstructural Characteristics of TiO2 Deposits
Authors: Berger - Keller N. , Bertrand G. , Coddet C. , Meunier C. 
Published: September 2022

Abstract
Titanium dioxide (TiO2) has emerged as an excellent photocatalyst material for environmental purification about two decades ago. In order to avoid the use of TiO2 powder, which requires later separation from the treated liquid, few researchers reported on ways of fixing TiO2. In these cases, many difficulties must be overcome such as maintaining the photoactive anatase phase as well as the mechanical stability and avoiding the mass transfer limitations. Thermal spraying seems to be an appropriate process to provide ceramic coatings exhibiting such characteristics. The present work assesses the influence of several spray parameters on the morphology of deposits, dominated by two void systems – interlamellar pores and interlamellar cracks – and on their crystalline structures. TiO2 was atmospherically plasma sprayed by systematically varying the process conditions including torch power, plasma gas mixture Ar/H2 and Ar/He, and cooling device. An analytical procedure based on XRD patterns was established for the determination of the relative amounts of anatase and rutile in the coatings. An Ar/He mixture as compared to an Ar/H2 one seems to enhance the formation of anatase from 38vol% to 44vol%. In both cases, a reduction of the plasma power increases the amount of anatase. Several methods of porosity determination were performed: image analysis, Archimedean porosimetry and calculation from phases, mass and thickness. Generally, the results indicate a total porosity varying between 15 and 25% depending on the spraying conditions.
Structure and Properties of Plasma Sprayed Wollastonite Coatings
Authors: Liu Xuanyong , Zeng Yi , Ding Chuanxian 
Published: September 2022

Abstract
Wollastonite coating deposited on Ti-6Al-4V substrate was prepared using atmospheric plasma spraying technology. Scan electron microscopy, transmission electron microscopy and X-ray diffraction were used to investigate the microstructure, surface morphology and phase compositions of coatings. Simulated body fluid tests were carried out to evaluate the bioactivity of the coating. Osteoblasts culturing test was used to examine the cytocompatibility of wollastonite coatings. The tensile bonding strength of the coating was measured with ASTM C-633 methods. The results obtained indicated that the plasma sprayed wollastonite coating had a rough surface and lamellar structure including some pores and microcracks. The primary crystalline phase of the coating was triclinic wollastonite. Glassy phase with nanocrystals was also found in the coating. The bonding strength of wollastonite coating reaches to about 39 MPa. This was explained in term of that the thermal expansion coefficient of wollastonite coatings is close to the Ti-6Al-4V substrate. The apatite layer was formed on the surface of plasma sprayed wollastonite coating soaked in SBF solution, which indicates wollastonite coating had a good bioactivity. Osteoblasts survive and proliferate on the surface of wollastonite coating, which indicates plasma sprayed wollastonite coatings possess excellent cytocompatibility.
Microcrystallographic Study of Plasma Sprayed Alumina Deposit by Transmission Electron Microscopy
Authors: Zahari Nur Ismarrubie , Sugano M. , Satake T. , Ohmori A. 
Published: September 2022

Abstract
To clarify the formation micromechanism of plasma spray deposits, internal microstructures have been examined by transmission electron microscopy on the thin films prepared from different depths of the plasma sprayed Al2O3 deposits. Microstructures in the top layer have consisted of both the coarse grains of 1 µm and the fine ones of 0.2 µm in average diameter. Point defects were contained mostly in γ phase grains. In the mid-layer, columnar structures often developed in parallel or in radial directions which adjoined with γ phase grains. From the SAD analyses, columnar grains were identified as α phase and lay in a twin crystal orientation relationship to each other between the joined grains. The bottom layer was composed of a mixture of the coarse grains of 0.2 µm and the fine ones of 0.02 µmin average grain diameter. It was found that the spray deposit was composed of different microstructures in crystallization, depending on depth to the thickness direction of the spray deposit.
The Use of Acoustic Emission Techniques for Characterizing Failure Mechanisms of Thermal Barrier Coatings Under Thermal Cycling Conditions
Authors: Robin Philippe C. , Gitzhofer François , Boulos Maher I. 
Published: September 2022

Abstract
Thermal barrier coatings are mainly used to protect underlying alloys from heat and chemical aggressions, especially in jet turbines and diesel engines. The challenge in TBCs’ applications is to use them to protect the upper moving turbine’s blades where their surface temperature can reach 1200°C. The limiting effect is the reliability of these coatings. The work described in this paper is a continuation of our earlier research work, which is focused on the use of Acoustic Emission Technique to assess the long-term behavior of thermal barrier coatings under thermal cycling conditions. Emphasis is placed in this presentation on the comparison of different signal processing techniques and the evaluation of their potential usefulness for the prediction of the coating behavior and failure modes. The work is carried out in parallel with a finite element modeling study of the thermal and stress distribution in the coating, which provides a valuable insight in the coating stress distribution prior to failure.
Analysis of Pore Connectivity Modification and Structure Densification of Y-PSZ Coatings After In Situ Laser Remelting Implementing Electrochemical Test
Authors: Antou G. , Hlawka F. , Cornet A. , Montavon G. , Coddet C. , Staerck J. , Fréneaux O. 
Published: September 2022

Abstract
The morphologies of Y-PSZ coatings remelted after (i.e., post-treated) or simultaneously (i.e., in situ) with their deposition were observed by optical and scanning electron microscopy in order to study the behavior of the coatings during laser irradiation. A change in the microstructure, from lamellar to dendritic, was observed in both cases. Moreover, cracks and delaminations are less emphasized for the coatings treated during deposition than for those treated after deposition. Finally, the pore connectivity was evaluated implementing an electrochemical test. Results clearly indicate that the coatings obtained by in situ laser remelting are significantly more impervious than as-sprayed coatings.
A Raman Study on Plasma-Sprayed Thermal Barrier Coatings During Thermal Cycling
Authors: Niccolai F. , Bardi U. , Muniz Miranda M. , Giannozzi M. 
Published: September 2022

Abstract
Yttria Partially Stabilized Zirconia (YPSZ) coatings are used as Thermal Barrier Coatings (TBCs) because of their capability to improve gas turbine performance by allowing higher turbine inlet temperature and reduced cooling air flow. Usually, YPSZ layers are applied by plasma spray on Ni-based superalloys pre-coated with a bond coat layer of MCrAlY, where M is Co, Ni, or both. In this work we used Raman spectroscopy to study the performance of TBCs during thermal cycling at two different temperature (1273K and 1373K). Raman scattering is capable of detecting monoclinic zirconia and to analyze residual stresses of the coatings with an higher sensitivity than traditional X-ray diffraction measurements. Raman spectra were analyzed by deconvolution methods in order to study the evolution of the relative intensities and position of different bands. We found that the position of the 635 cm-1 band shifts to higher values of wave number during thermal cycling and by comparing this data with those reported in literature, it is possible to retrieve the value of residual stresses in zirconia coating. We also observed a relation between the intensities of the bands at 602 cm-1 and 635 cm-1 band and the number of thermal cycles performed.
Functionally Graded HVOF Sprayed NiCr-Al2O3 Coatings for Demanding Applications
Authors: Turunen E. , Varis T. , Ruusuvuori K. , Gustafsson T.E. , Hannula S.-P. , Gasik M. , Antila E. 
Published: September 2022

Abstract
Functionally graded (FG) coatings were manufactured by High Velocity Oxy-Fuel (HVOF) thermal spraying and tested aiming for the high temperature applications. Single layers were manufactured and their elastic modulus measured by using Impulse Excitation Technique (IET). Obtained data was used for modeling of optimal gradient structure. Dual feeding hose for HVOF gun was developed. Calibration procedure for the concurrent use of two powder feeders was performed. NiCr-Al2O3 coatings with coating thickness of 600 µm and 1000 µm were manufactured and tested. Promising results were obtained from high temperature corrosion tests.
The Effect of a High Thermal Gradient on Sintering and Stiffening in the Top Coat of a Thermal Barrier Coating (TBC) System
Authors: Tsipas S.A. , Golosnoy I.O. , Clyne T.W. 
Published: September 2022

Abstract
Superalloy substrates coated with plasma sprayed CoNiCrAlY bond coats and yttria-stabilized zirconia top coats have been subjected to a high heat flux in a controlled atmosphere chamber. The sintering exhibited by the top coat under these conditions has been studied and compared with the behavior observed during isothermal heating, both when attached to the substrate and when detached. Sintering has been characterized by (a) microstructural examinations, (b) dilatometry, in both in-plane and through-thickness directions, and (c) stiffness measurements, using both cantilever bending and nanoindentation. A numerical heat flow model has been used to explore the stress state under isothermal and thermal gradient conditions. Sintering proceeds faster at higher temperature, but is retarded by the presence of tensile stresses (from differential thermal expansion between coating and substrate) within the top coat. Sintering occurs preferentially near the free surface of the top coat under gradient conditions, not only because of the higher temperature, but also because the in-plane stress is more compressive in that region.