bluuebunny/crossref_metadata_2025_split huggingface dataset:
Droplet Flattening During Thermal Spraying at Off-Normal Angles
Authors: Sobolev V.V. , Guilemany J.M. 
Published: May 2021

Abstract
Analytical correlations between the flattening characteristics and the Reynolds number and the spraying angle are obtained. The final splat thickness is shown to decrease and the final splat radius is found to vary nonuniformly with a decrease in the spraying angle. Analytical formulae are obtained describing the pressure distribution in a flattening droplet along the droplet-substrate interface during thermal spraying at off-normal angles. The magnitudes of droplet-substrate microadhesion, deformation of the substrate surface and the coating porosity depend upon the spraying angle. The spraying angle 45° can be recommended as a reasonable limit for off-normal thermal spraying for achieving the quality coatings. The theoretical results obtained on flattening characteristics agree with those of the experimentally observed tendencies of thermal spraying at off-normal angles. The theoretical results for % relative porosity are in a reasonable agreement with experimental observations at off-normal angles between 30° and 90°.
Peening Action and Residual Stresses in HVOF Thermal Spraying of 316L Stainless Steel
Authors: Kuroda S. , Tashiro Y. , Yumoto H. , Taira S. , Fukanuma H. 
Published: May 2021

Abstract
316L stainless steel powder was sprayed by a high-pressure HVOF process. Effects of powder size and the pressure in the combustion chamber on the velocity and temperature of sprayed particles were studied by using an optical instrument firstly at the substrate position. A strong negative correlation between the particle diameter and temperature was found whereas the correlation between the diameter and the velocity was not significant. The pressure in the combustion chamber affected the velocity of sprayed particles significantly whereas the particles' temperature remained largely unchanged. In-situ curvature measurement was employed in order to sturdy the process of stress generation during HVOF spraying. From the measured curvature changes, the intensity of peening action and the resultant compressive stress by HVOF sprayed particles were found to increase with the kinetic energy of the sprayed particles. The results were further used to estimate the stress distribution within the coatings.
Analysis of Residual Stress Generated During Plasma Spraying of Glass Coatings
Authors: Bao Y. , Zhang T. , Gawne D.T. 
Published: May 2021

Abstract
An investigation has been undertaken on the analysis of residual stress in glass coatings during plasma spraying. Theoretical analysis and in-situ experimental measurements show that the residual stresses in glass coatings are particularly sensitive to the heat input from the plasma flame, since this can raise the temperature to above the glass transition temperature. Control of the spraying parameters enables the quench stress of splats to be relaxed by the end of the spraying and the only significant remaining source of stress derives from the differential contraction between the coating and substrate during cooling. The analysis also shows that a stress transition occurs during cooling and that the sign of the final residual stress depends upon the expansion coefficient of the glass. The residual stresses are shown to govern the critical coating thickness for cracking and the coating adhesion.
High Damping Capacity Iron-Chromium-Aluminium Based Coatings for Surface Vibration Control
Authors: Karimi A. , Giauque P.H. , Sagradi M. , Barbezat G. , Salito A. 
Published: May 2021

Abstract
The ability of high damping iron-chromium-aluminium alloys and coatings to absorb noise and vibrations has been investigated over a wide range of frequencies and amplitudes. The damping capacity was determined using a cantilever method based on the modal analysis technique of the flat beams and was found to be very sensitive to internal stress of specimens. Heat treatment usually enhanced the loss capability, but only an optimised annealing restored the maximum damping capacity. The influence of vibration amplitude evidenced by appearance of a maximum around ε = 10-4”, while the vibration frequency did not influence 'damping behaviour significantly. The position of the maximum damping was shifted towards lower strains with annealing time and temperature. The structure of magnetic domains was observed using the magneto-optical Kerr effect and their modification following to an applied stress or magnetic field was associated with different values of the damping capacity. Accordingly, the beneficial effect of annealing on damping capacity arises on the one hand from improved mobility of unpinned domain walls and on the other hand from growth of 90° domains considered as the principal responsible of damping. Addition of aluminium between 1-8 wt%. improved the damping values notably around 4 wt%.
Modelling of Elastic Constants of Plasma Spray Deposits with Spheroid-Shaped Voids
Authors: Leigh S.-H. , Lee G.-C. , Berndt C.C. 
Published: May 2021

Abstract
The five independent elastic constants of plasma spray deposits were calculated from constitutive equations and the microstructural information (void aspect ratios and porosity) were gained from stereological analysis. The voids within the deposit were assumed to be a spheroidal shape. The structure of the deposit was considered to be transversely isotropic with respect to the spray direction, which requires five independent elastic constants of a stiffness tensor. Solid mechanics models containing spheroid-shape voids were applied to obtain the five independent elastic constants of the deposits. The calculated elastic constants were compared to the experimentally determined values.
Microstructure Study of Spinel Plasma Coatings
Authors: Lallemand G. , Fayeulle S. , Treheux D. , Esnouf C. 
Published: May 2021

Abstract
Spinel powders of different compositions were fabricated for their good properties of chemical resistance. These powders were plasma sprayed on steels and their microstructure was investigated by scanning electron microscopy (SEM), microanalysis, X-ray diffraction and transmission electron microscopy (TEM). Due to the powder fabrication process, coatings were very heterogeneous in composition, but had the spinel structure. TEM observations pointed out that splat solidification occurred with a cooling rate gradient leading to different crystallization inside a lamella. Young's moduli by the coatings were measured by the resonant frequency method and the correlation with coating microstructure was discussed.
Characterization and High Temperature Behaviour of Thermal Sprayed Coatings used in Boilers
Authors: Higuera Hidalgo V. , Carrilez Menendez A. , Belzunce Varela F.J. 
Published: May 2021

Abstract
CrNiAlTi, NiCrBSi and WC-Ni coatings have been thermal and plasma sprayed projected over a stainless steel surface in order to protect it against heat and erosion actions encountered in power plant boilers. Their microstructure, porosity and microhardness have been measured. High temperature oxidation under an atmosphere similar to service conditions in power plants and thermal fatigue tests have also been performed in our experimental combustion chamber and, finally, the adhesion between the substrate and the coating layer has been evaluated by means of tensile tests. The obtained results have been discussed paying especial attention to the microstructural materials evolution due to thermal effects and coating projection methods.
Thermophysical and Mechanical Properties of PYZ Thick Thermal Barrier Coatings
Authors: Schwingel D. , Taylor R. , Haubold T. , Wigren J. , Gualco C. , Ladru F. , Lugscheider E. , Gourlaouen N. 
Published: May 2021

Abstract
Within a Brite Euram project thick thermal barrier coatings for combustor applications were produced by plasma spraying of yttria partially stabilised zirconia (ZrO2 + 8 wt.% Y2O3). The material properties of such coatings strongly depend on their microstructure which can be altered by manipulating the parameters controlling the plasma spraying process. Covering a variation of possible microstructures, the coatings considered had a thickness of about 2 mm and were six to eight times thicker than the coatings currently in service. This investigation was concerned with an evaluation of the thermophysical and mechanical properties of these coatings and their correlation with the microstructure and the plasma spray parameters. Particular attention was paid to the influence of coating segmentation, microcracking and porosity. The experimental work included the measurement of the thermal diffusivity using the laser flash technique, thermal expansion measurements, and the determination of flexural strength and Young's modulus by means of a specially constructed four-point bend rig. Since some of the samples considered were sprayed according to a partially factorial test plan a statistical evaluation of the material data was possible yielding the correlation between process parameters and material properties.
On the Behavior of Thick and Porous Copper Deposits Under Compressive Stress
Authors: Verdy C. , Montavon G. , Coddet C. 
Published: May 2021

Abstract
Pure copper thick deposits were vacuum plasma sprayed in such a way that several porosity levels were obtained. Mechanical compressive tests permitted to assess the mechanical behavior of these materials and to study the associated pore microstructural changes. A linear porosity level decrease was observed during the first stages of the compressive squeezing, until the stress reached a specific value corresponding to a transition between pore contraction and copper splats deformation. Stereological measurements showed that the pore squeezing was isotropic.
High Corrosion Resistant Iron-Based Amorphous Coatings Obtained by Thermal Spraying
Authors: Otsubo F. , Era H. , Kishitake K. , Matsumoto H. 
Published: May 2021

Abstract
Fe-Cr(-Mo) alloy coatings were thermal sprayed by different processes of LPPS, HVOF and HPS. The as-sprayed coating by LPPS is perfectly amorphous and coatings by other processes contain partly crystalline phases. The amorphous phases crystallize at 773 K or more and shows a high hardness of about 1000 to 1400 DPN just after crystallization. The anodic polarization curves of the coatings shift from active to passive state in 1N H2SO4 and 1N HCl solutions. The coatings obtained by LPPS indicate the lowest active and passive current densities and possess the best corrosion resistance. The corrosion resistance of the coatings obtained by other processes are better than a SUS316L stainless steel coating. The LPPS coating of Fe-Cr-C-P alloy is not attacked on immersion test in 6% FeCl3·6H2O solution containing 0.05N HCl at the corrosion potential, while large pit corrosion is developed in a SUS316L stainless steel sheet.
Compressive Behaviour of Plasma Sprayed High-Alloy Steels
Authors: Volenik K. , Novak V. , Dubsky J. , Chraska P. , Neufuss K. 
Published: May 2021

Abstract
The mechanical properties of plasma sprayed metals and alloys are important in most applications. It a posttreatment by forming of plasma deposited coatings is required, their response to compressive loading is decisive. This paper is concerned with the compressive behaviour of two high-alloy steels sprayed by a water stabilized plasma gun. Martensitic (13.2 % Cr) and austenitic (19.6 % Cr, 11.6 % Ni) steels were plasma sprayed onto plain steel substrates. Small cube-shaped test samples were cut out of thick coatings by an electrospark technique. Compressive load was applied along axes parallel and perpendicular to the substrate and coating surfaces. In addition, comparative samples of bulk steels produced by conventional metallurgy were tested. The compressive behaviour of the as-sprayed martensitic steel was anisotropic at room temperature, i.e. dependent on the orientation of the compression axis. As a result of compression, the splat shapes changed in a manner depending on the orientation of the compression axis. The room temperature compression tests showed that the yield stress of this steel was decreased and the anisotropy was reduced by annealing after plasma spraying. At room temperature, the anisotropy of the as-sprayed austenitic steel and the effect of annealing were less pronounced in comparison with the martensitic steel. Very low values of the yield stress were observed in both steels compressed at the annealing temperature. In spite of the presence of oxide films enveloping each splat, the coatings were prone to considerable plastic deformation, in particular if compressed along the axis perpendicular to the surface.
Comprehensive Methods for Studying Microinhomogeneity in Thermal Spray Coatings with Amorphous-Crystalline Structure
Authors: Grigorenko G. , Borisova A. 
Published: May 2021

Abstract
An integrated approach was developed for investigation of thermal spray coatings with the amorphous-crystalline structure. The new approach combines methods of metallography, differential thermal and X-ray phase analysis, scanning electron microscopy and X-ray microanalysis. This makes it possible to reveal structural, phase and chemical heterogeneity, determine the degree of amorphization of coatings, temperature and heat of crystallization of the amorphous phase during heating. The new integrated approach was used to study amorphous-crystalline coatings of the Ni-P, Fe-Ni-B and Fe-B systems produced by thermal spraying.
Effect of WC-Co Addition on the Adhesion of HVOF Ni-Based Coatings
Authors: Li C.J. , Li H. 
Published: May 2021

Abstract
Self-fluxing nickel based materials are widely used as hard coating materials. HVOF process is promising to produce dense coating with high adhesion. In present study the effects of HVOF spray conditions, and WC-Co addition into self-fluxing nickel based material (NiCrBSi) and the introduction of HVOF WC-Co bond coat on the adhesion of HVOF NiCrBSi coatings are investigated. With regarding to NiCrBSi material, the spray conditions are optimized by orthogonal regression experimental design method with adhesive strength. The adhesive strength is estimated by tensile test. The results show that the adhesive strength of the NiCrBSi coating sprayed at the optimized conditions reaches to about 40MPa. It is found that the addition of WC-Co material through mechanical blending can improve the adhesion of HVOF NiCrBSi coating. The adhesive strength is increased with the increase in WC-Co content in the composite powder. The introduction of HVOF WC-Co bond coat between NiCrBSi coating and substrate can improve the adhesive strength. The multiply enhancing effect on the adhesive strength of HVOF nickel based coating is recognized by applying HVOF WC-Co bond coat to NiCrBSi-WC-Co composite coating.
Microstructure Development During Plasma Spraying of Molybdenum Part 2: Coating Microstructure and Properties
Authors: Jiang X.Y. , Sampath S. , Vardelle A. , Vardelle M. , Fauchais P. 
Published: May 2021

Abstract
This is part II of the two part paper based on international collaboration between the University of Limoges, France and the State University of New York, Stony Brook, USA, aimed at fundamental understanding the relationship between processing condition and microstructure development and properties of thermally sprayed materials. In this study, the effects of deposition temperature on the microstructure and properties development of molybdenum coating was investigated. It is found that with the increase of steel substrate temperature, the molybdenum splat morphology changes from fragmented to more contiguous disk-like shape. The splats on molybdenum substrate show predominantly disk shape. With the increase in deposition temperature, the coating exhibits better lamellar structure with less interlayer pores and debris. The fracture characteristics changes gradually from interlamellar to trans-lamellar and, thermal conductivity is enhanced. Higher deposition temperature improves dramatically the adhesion and bonding of the splats, therefore the physical and mechanical properties of coatings.
Physico-Chemical Aspects of Plasma Spray Coatings
Authors: Klinskaya N. , Jilyaev V. , Pankratov A. 
Published: May 2021

Abstract
The results of an investigation into compound, structure and some properties of composite plasma coatings based on stellite with an addition of titanium nitride are presented. It is shown that the coating formed in a gas-air plasma is characterized by better wear resistance and resistance to scaling. The results of industrial test lend support to wide use of such coatings in machine parts and units that work under the simultaneous influence of impact, abrasive wear and high temperature.
In-Flight Particle Concentration and Velocity Measurements in Thermal Spraying Using a Non-Intensified CCD Camera
Authors: Vattulainen J. , Lehtinen T. , Hernberg R. , Knuuttila J. , Mantyla T. 
Published: May 2021

Abstract
Plasma spraying is a complicated process involving many partly interdependent parameters, which are in industrial spray environments difficult to optimise without laborious and time consuming experiments. In this work a non-intensified CCD camera without any external illumination is used for in-flight particle visualisation. Particle visualisation is based purely on the spontaneous light emitted by the hot particles. The motivation for this work is to outline the possibilities to develope a CCD based, low cost and rugged in-situ measurement system suitable also for industrial use. The measurement method has been tested with Plasmatechnik A3000S plasma spraying equipment using fused and crushed Al2O3 powder. Using digital image processing techniques relative particle concentrations and particle velocities have been calculated from the acquired images. These results have been correlated with wear resistance and deposition efficiency of the coatings produced with different powder feed rate and powder port adjustments. Coatings were also produced using both new and worn electrodes. The benefits and limitations of the method are discussed and the measurement results are compared against measurements made using laser sheet illumination, which can give information concerning also the colder and/or smaller particles not visible for the passive CCD system.
Plasma Spraying Using Ar-He-H2 Gas Mixtures
Authors: Janisson S. , Vardelle A. , Coudert J.F. , Pateyron B. , Fauchais P. , Meillot E. 
Published: May 2021

Abstract
In dc plasma spray guns, the properties of the plasma forming gas largely control the characteristics of the plasma jet and the momentum and heat of the particles injected into the flow. This paper examines the effect of Ar-He-H2 mixtures on the dynamic and static behavior of plasma jets expressed in terms of arc voltage and gas velocity. Correlations between these parameters and operating variables (arc current, gas flow rate, volume composition) were established from a dimensional analysis and supported by the calculation of the thermodynamic and transport properties of the gas mixtures used in the study.
Oxidation Control in Atmospheric Plasma Spraying: Comparison Between Ar/H2/He and Ar/H2 Mixtures
Authors: Denoirjean A. , Lagnoux O. , Fauchais P. , Sember V. 
Published: May 2021

Abstract
Plasma spraying of metals and metallic alloys performed in controlled atmosphere or soft vacuum results in coatings with a low oxidation level and excellent thermomechanical properties. Unfortunately, the spraying cost is drastically increased by one or two orders of magnitude compared to air plasma spraying (APS). Thus the minimisation of oxidation during APS is a key issue for the development of such coatings. Oxygen concentrations sucked into plasma jets have been measured by an enthalpy probe linked to a mass spectrometer. This technique allows to determine simultaneously plasma composition, temperature and velocity distributions within the plasma plume. Results have been compared to those obtained with a two-dimensional turbulent flow model. The obtained results have shown that surrounding air entrainment is reduced when using adequate Ar/H2/He mixtures which viscosity is higher than that of Ar/H, mixtures, limiting the turbulence in the jet fringes and pumping of the surrounding atmosphere.
Influence of Injector Geometry on Particle Trajectories: Analysis of Particle Dynamics in the Injector and Plasma Jet
Authors: Vardelle M. , Vardelle A. , Dussoubs B. , Fauchais P. , Roemer T.J. , Neiser R.A. , Smith M.F. 
Published: May 2021

Abstract
The conditions of particle injection into the side of plasma jets play an important role in determining the microstructure and properties of sprayed deposits. However, few investigations have been carried out on this topic. The current work presents the results of an experimental and computational study of the influence of injector geometry and gas mass flow rate on particle dynamics at injector exit and in the plasma jet. Two injector geometries were tested: a straight tube and a curved tube with various radii of curvature. Zirconia powders with different particle size range and morphology were used. A possible size segregation effect in the injector was analyzed from the space distribution of particles collected on a stick tape. The spray pattern in the plasma jet was monitored from the thermal radiation emitted by particles. An analysis of the particle behavior in the injector and mixing of the carrier-gas flow with the plasma jet was carried out using a 3-D computational fluids dynamics code.
Absolute Coating Porosity Measurement Using Image Analysis
Authors: Mailhot K. , Gitzhofer F. , Boulos M.I. 
Published: May 2021

Abstract
This paper describes the procedure that has been developed for absolute porosity measurement using Image Analysis (IA). Because of the crumbly nature of the composite substrate, it was not possible to proceed with standard method. The IA conducted on Optical Microscopy did not show enough contrast between pores and other features to be automated. The IA conducted on Scanning Electron Microscopy (SEM) with back scattered electron imaging gives enough contrast for automatic threshold determination. The SEM magnification is a parameter to be considered because it filters the information. Three frames at 500X magnification are enough for measuring the porosity of homogeneous supersonic induction plasma sprayed 18 mm samples (thickness 50-100 µm). The established calibration almost shows a 1 to 1 ratio for the image analysis as measured porosity versus the Archimedean porosity. Application of this absolute porosity determination by IA can be found in the Functionally Graded Materials (FGM) which composition is not constant over the layer thickness.
The Place of Thermal Spraying in Industry Today and the Prospects for the Future
Authors: Huchin J.P. 
Published: May 2021

Abstract
In 1913, in the dawning years of the 20th century, Doctor Schoop published a process for "depositing metal under an air flow" in the Scientific American, opening new horizons to surface treatment techniques. Therefore, surface treatments were taken into account right from the design stage by engineers, and their performances became input for devising objects right from the time they were conceived. There is a constant acceleration in the means employed, ever greater system automatisation and a continuous broadening in the applications