bluuebunny/crossref_metadata_2025_split huggingface dataset:
Suspension Plasma Spraying for the Preparation of Perovskite Powders and Coatings
Authors: Schiller G. , Müller M. , Gitzhofer F. 
Published: May 2021

Abstract
LaMnO3 powders and coatings have been prepared by reactive suspension plasma spraying (SPS) of MnO2 powders and LaCl3 solutions. A 40 kW inductively coupled plasma with an oxygen plasma sheath gas has been used. Water and ethanol have been tested as the liquid phase in the SPS process. High perovskite content (70-90%) has been achieved for both powders and coatings when spraying a suspension of fine MnO2 powder in a saturated ethanol solution of LaCl3 with a 1:1 molar ratio of La and Mn. Materials obtained by a 1100 °C oven treatment have been used as reference during the study. The reactor pressure was varied from 30 to 80 kPa. Low pressure was found to be necessary to suppress the formation of undesired phases in the powders and coatings obtained. A plasma post treatment of the coatings results in an increase of the perovskite content.
Arc Initiation for the Electromagnetic Powder Deposition Gun
Authors: Sledge R.L. , Bacon J.L. , Davis D.G. , Polizzi R.J. , Uglum J.R. , Zowarka R.C. 
Published: May 2021

Abstract
The Electromagnetic Powder Deposition (EPD) process converts pulsed electrical energy into kinetic and thermal energy to accelerate and heat powder material to conditions suitable for bonding. A high pressure plasma armature is electromagnetically accelerated using a railgun. A supersonic pressure wave is created when the armature accelerates through and "snowplows" the ambient gas ahead of it. The gas column is heated, compressed, and accelerated to the entrainment section of the gun, where some of the thermal and kinetic energy is transferred to an injected stream of powder material. The acceleration burst is repeated rapidly to supply the required deposition rate and to achieve steady thermal conditions. Development of a starter plasma which is reliable at ambient pressure was a major programmatic task. Generation of a low pressure linear arc required to form a planar armature during the pulsed event was investigated. Several geometries (point-to-point breakdown, rail-to-rail breakdown, and confined glow discharge) were explored using different voltage sources (dc, 60 Hz ac, 150 MHz rf, pulsed). Satisfactory operation of the confined glow discharge approach at atmospheric pressure was achieved using rf excitation. Results of testing under the various scenarios are presented and critiqued.
The Influence of Gun Parameters on Co-Injected Particles in the Spraying of Metal-Ceramic Functionally Graded Materials
Authors: Swank W.D. , Fincke J.R. , Haggard D.C. , Sampath S. , Smith W. 
Published: May 2021

Abstract
In the spraying of functionally graded coatings, the particle ensemble delivered to the substrate varies from a relatively heavy, low-melting-point metallic particle to a significantly lighter, higher-melting-point ceramic particle. The desire is to deliver to the substrate a particle ensemble which has suitable velocity and temperature for the predictable and consistent formation of coatings with mixed particle types. The key to success is a thorough understanding of the relationship between spray gun parameters and the resulting particle condition. The gun parameters examined are powder loading (injection rate), powder mixtures, and secondary plasma gas (H2). The spray characteristics measured were particle velocity, temperature, and spray pattern. The particle temperature and velocity are both significantly influenced by the flow rate of the secondary gas (gun power). The powder feed rate was found to have a small but measurable effect on both the spray pattern and the ensemble average particle temperature. It was observed that a "tight" hot particle spray pattern, unfortunately, does not necessarily minimize the number of cold unmelted particles.
Influence of the Variation of Plasma Torch Parameters on Particle Melting and Solidification
Authors: Vardelle M. , Fauchais P. , Vardelle A. , Léger A.C. 
Published: May 2021

Abstract
A study of the flattening and cooling of particles plasma-sprayed on a substrate is presented. The characteristic parameters of the splats are linked to the parameters of the impacting particles by using an experimental device consisting of a phase Doppler particle analyzer and a high-speed pyrometer. However, during the long experiments required to get reliable correlations, it was observed that variations in plasma spray operating conditions may alter the particles behavior in the plasma jet. Therefore, a simple and easy-to-use system was developed to control in real time the spray jet. In this paper, the effect of carrier gas flow rate, arc current and powder mass flow rate is investigated. The results on zirconia and alumina powders show the capability of the technique to sense the particle spray position and width.
Robot Trajectory Generation and Coating Temperature Prediction of Plasma Sprayed Coatings
Authors: Nylén P. , Edberg M. 
Published: May 2021

Abstract
This paper presents a simulation method in which robot trajectories can be optimised to produce an even coating thickness and how they can be used to predict transient coating temperatures on complex geometries. The coating thickness was simulated by the use of a commercial Offline programming (OLP) system. A robot trajectory was calculated, maintaining a constant spraying distance and normal orientation to the surface. The trajectory was optimised to give a uniform coating thickness while also handling non collision requirements. The plasma was represented as an ideal gas with temperature dependent thermodynamic and transport properties. The governing equations were solved by a developed finite difference elliptic code using a simplified turbulence model. The particles were modelled by a stochastic discrete particle model. The robot trajectory together with the heat transfer model were then used to calculate transient coating and substrate temperatures by the use of the finite element method (FEM). The model predictions were tentatively compared with experimental measurements and reasonable correlations were obtained.
Plasma Processing of Functionally Graded Materials Part II: Deposit Formation
Authors: Jewett T.J. , Smith W.C. , Herman H. , Margolies J. , Sampath S. 
Published: May 2021

Abstract
Two sets of plasma spray processing conditions were utilized in the investigation of graded layers, consisting of NiCrAlY and PSZ. Following the optimization of the plasma spray parameters and particle characteristics, the deposition efficiencies (DEs) of various powder species was examined. Selection of the best suited powders for coating production were selected based on the DE results. The base DEs were corrected by conducting the analyses using pre-deposited substrates as targets. Individual mixed coating layers were prepared and their compositions confirmed by image analysis. The effects of standoff distance and substrate temperature were also seen to have an effect on the DE and thus the coating formation. It is suggested that two-feeder, single injector plasma processing may not be the optimal method for the formation of FGMs.
Simultaneous Independent Measurement of Splat Diameter and Cooling Time during Impact on a Substrate of Plasma Sprayed Molybdenum Particles
Authors: Gougeon P. , Moreau C. 
Published: May 2021

Abstract
In thermal spray processes, the coating structure is the result of flattening and cooling of molten droplets on the substrate. The study of the cooling time and evolution of the splat size during impact is then of the highest importance to understand the influence of the spray parameters and substrate characteristics on the coating structure. Measurement of particle temperature during impact requires the use of a high-speed 2-color pyrometer to collect the thermal emission of the particle during flattening. Simultaneous measurement of the splat size with this pyrometer is difficult since the size of the particle can change as it cools down. To measure the splat size independently, a new measurement technique has been developed. In this technique the splat size is measured from the attenuation of the radiation of a laser beam illuminating the particle during impact. Results are presented for plasma sprayed molybdenum particles impacting on a glass substrate at room temperature. It is shown that the molybdenum splat reaches its maximum extent about 2 microseconds after the impact. In this work, we show that this increase of the splat surface is followed by a phase during which the splat size decreases significantly during 2 to 3 microseconds.
Phase Composition of Plasma-Sprayed Yttria Stabilized Zirconia
Authors: Ilavsky J. , Stalick J.K. 
Published: May 2021

Abstract
The phase composition of plasma sprayed (8wt%) YSZ was studied using neutron and X-ray scattering. Comparison shows that neutron scattering is superior for analysis of the phase composition as well as for the analysis of the yttria content of the tetragonal phase. The presence of large amounts of the cubic phase are probably often neglected in standard XRD analysis due to scattering-related limitations and the inherent difficulty of the analysis. The importance of this fact needs to be addressed in future studies. The amount of monoclinic, tetragonal, and cubic phases was determined for as-sprayed deposits and for samples annealed at various temperatures. The as-sprayed deposit was composed of metastable phases, and the phase composition on annealing did not change significantly until 1400 °C for one hour. This indicates the relative stability of the phase composition. The influence of the spray distance is not clear, but the resultant phase composition may be related to the deposition temperature.
Structural Characterization of Chromium Carbide-Nickel Chromium Coatings Obtained by HVOF-Spraying
Authors: Guilemany J.M. , Calero J.A. 
Published: May 2021

Abstract
Chromium carbide-nickel chromium coatings produced by HVOF spraying are widely used for high temperature wear and erosion resistant applications. Examination of the literature shows that whilst the mechanical properties of these coatings have been widely investigated, there has been little research into the physical processes occurring during HVOF spraying of this system, such as carbide dissolution, liquid-metallic phase oxidation, decarburisation and rapid solidification. The purpose of the present work has been to perform a systematic characterisation of the chromium carbide-nickel chromium system in both the initial powder and as-sprayed states with a variety of spraying conditions using optical, scanning and transmission electron microscopy, electron microprobe and X-ray diffraction. The presence of amorphous and nanocrystalline phases has been demonstrated. The nanocrystalline structures tend to be Ni rich, with the amorphous phases rich in Cr. Carbides of the form Cr3C2 were found to be dissolved slightly during spraying, increasing the Cr and C contents of the liquid metallic phase. There was no evidence of chromium carbide oxidation.
Fatigue Life in Bending and Coatings Residual Stress in Tungsten Carbide Thermal Spray Coatings
Authors: McGrann R.T.R. , Shadley J.R. , Rybicki E.F. , Graving D.J. , Badger B.E. , Somerville D.A. , Emery W.A. 
Published: May 2021

Abstract
Tungsten caibide (WC) thermal spray coatings are being used for wear protection on selected components of aircraft. Tungsten carbide coatings are being used on aircraft flap tracks and fan and compressor blade mid-span dampers. However, a larger use of tungsten carbide coatings is being considered for other commercial aircraft applications where it would be used as a replacement for chrome plating. For instance, WC coatings are currently being tested on aircraft landing gear parts. One factor that affects the suitability of WC coatings for these applications is the fatigue life of the coated part. Coatings, whether chrome plating or thermal spray coating, can reduce the fatigue life of the part compared to an uncoated part. This study compares the fatigue life of uncoated 6061 aluminum specimens to the fatigue life of WC thermal sprayed coated 6061 aluminum specimens. The relation between the residual stress level in the coating and the fatigue life of the specimens is also investigated. Fatigue tests were run on cantilever flat beam specimens that were coated on one side. Specimens were cycled in bending so that the coatings experienced tensile fatigue stresses. Residual stress levels for each type of coating were determined using the Modified Layer Removal Method on specimens processed along with the cantilever flat beam specimens. Test results show that the fatigue life of the WC coated specimens is directly related to the level of compressive residual stress in the coating.
Effect of Powder Types on Mechanical Properties of D-Gun Coatings
Authors: Kim M.C. , Kim S.B. , Hong J.W. 
Published: May 2021

Abstract
Mechanical properties of WC-Co D-Gun coatings produced from various powders were determined by using a four-point bend test equipped with a special device for strain measurements. The MOR(Modulus of Rupture), elastic modulus, fracture strain and toughness were measured from stress-strain curves using the four-point bend tests. The fracture strength values were increased in the order of clad, sintered, agglomerated(no densification), blended and cast & crushed powder coatings. The Co content blended with WC-Co cermet powders significantly increased fracture strain values and decreased elastic modulus values. It was found that the type of powder more significantly influenced the mechanical properties of D-Gun coatings than the composition of powders. The toughness of thermal spray coatings was increased by using WC-Co powders (high MOR) blended with self-fluxing alloy powders (high fracture strain).
Analysis of Different Mechanisms of Coating-Substrate Adhesion in Thermal Spraying
Authors: Sobolev V.V. , Guilemany J.M. , Nutting J. 
Published: May 2021

Abstract
Different mechanisms of development of the substrate-coating adhesion during thermal spraying are considered. One of the most important is mechanical interlocking formed chiefly due to roughness of the substrate surface, high pressures developed upon the droplet impact and solidification of the lower part of the splat. Possible deformation of the substrate surface and rebounding of the impinging droplets are considered. Thermal mechanisms involving partial or complete melting and subsequent solidification in the substrate interfacial region is shown to be effective in creation of the adhesive bonds. The role of the diffusion processes and the influence of the splat morphology on adhesion is discussed. Mechanisms of splashing of droplets impinging onto the substrate surface during thermal spraying and their influence on the coating-substrate adhesion are considered. Roughness of the substrate surface is shown to be critically important to obtain good adhesion. Transition temperature is shown to exist which determines the splat morphology on the smooth surface of the substrate. With a "cold" substrate when its initial temperature is less than the transition temperature the splashing occurs. When the substrate initial temperature exceeds the transition one a regular splat is formed. The theoretical results agree well with the observed behaviour of the thermal spray coatings and in the case of the thermal mechanisms of adhesion these results are in a good agreement with the experimental data.
Measurement of Stress Development during HVOF Thermal Spray
Authors: Kuroda S. , Tashiro Y. , Yumoto H. , Taira S. , Fukanuma H. 
Published: May 2021

Abstract
Direct and quantitative observation of the stress generation during HVOF spray is carried out by measuring the curvature of substrates in-situ during spraying. A high pressure HVOF gun is used to spray SUS316L, Hastelloy C and WC-12%Co powder onto SUS316L substrates. The observed curvature data indicate that there are 3 regimes of stress evolution during the HVOF spray: (1) generation of compressive stress on the substrate surface at the beginning of spraying, (2) stress buildup in the coating during spraying, and (3) superposition of stress due to the mismatch in the thermal expansivity between the coating and the substrate as the specimen cools down to the room temperature after fabrication. Compressive stress ranging from 70 to 400 MPa is observed in the second regime during the HVOF spray; the value depending on the powder materials and spray conditions. Microstructural observation reveals that a significant portion of the coatings consists of poorly molten particles. Beneath the coatings formed by the HVOF process, a thin layer of increased hardness exists within the substrate.
Thermal Residual Stresses in Functionally Gradient Coatings
Authors: Andritschky M. , Teixeira V. , Stöver D. 
Published: May 2021

Abstract
The present contribution concerns with a numerical modelling of the residual stress distribution within a multilayered coating system which consists of a functionally gradient material (FGM). The structure of the graded system is made of a ceramic layer and a metallic layer, where between them there is an interlayer which is a graded composite made of the metal and ceramic. The composition changes gradually from 0% ceramic to 100% ceramic. This graded interlayer was modelled as a serie of perfectly bonded finite thin layers, each having slightly different material properties. We analyse the FGM design in respect to thermal stress optimization (e.g. reduction the interfacial stresses). The case of a bilayer, thick ceramic coating on a metallic substrate and a graded thermal barrier coating (TBC) is considered. The effects on thermal residual stress gradients of the compositional profiles and graded interlayer thickness were studied. This FGM stress model enable us to calculate the thermal strain and stress distributions, which gives a contribute to a better understanding of the failure of a graded coating system and is, therefore, a potential tool for FGM stress optimization to improve the thermo-mechanical stability of multilayer graded structures such as high temperature ceramic coatings for use in thermal barrier applications.
Oxidation in HVOF-Sprayed Steel
Authors: Smith M.F. , Dykhuizen R.C. , Neiser R.A. 
Published: May 2021

Abstract
It is widely held that most of the oxidation in thermally sprayed coatings occurs on the surface of the droplet after it has flattened. The evidence in this paper suggests that, for the conditions studied here, oxidation of the top surface of flattened droplets is not the dominant oxidation mechanism. In this study, a mild steel wire (AISI 1025) was sprayed using a high-velocity oxy-fuel (HVOF) torch onto copper and aluminum substrates. Ion milling and Auger spectroscopy were used to examine the distribution of oxides within individual splats. Conventional metallographic analysis was also used to study oxide distributions within coatings that were sprayed under the same conditions. An analytical model for oxidation of the exposed surface of a splat is presented. Based on literature data, the model assumes that diffusion of iron through a solid FeO layer is the rate limiting factor in forming the oxide on the top surface of a splat. An FeO layer only a few thousandths of a micron thick is predicted to form on the splat surface as it cools. However, the experimental evidence shows that the oxide layers are typically 100x thicker than the predicted value. These thick, oxide layers are not always observed on the top surface of a splat. Indeed, in some instances the oxide layer is on the bottom, and the metal is on the top. The observed oxide distributions are more consistently explained if most of the oxide formed before the droplets impact the substrate.
Sprayability and Properties of TiC-Ni Based Powders in the Detonation Gun and HVOF Processes
Authors: Vuoristo P. , Mäntylä T. , Berger L.-M. , Nebelung M. 
Published: May 2021

Abstract
Agglomerated and sintered TiC-Ni based powders were sprayed by detonation gun spray (DGS) and high-velocity oxy-fuel (HVOF) spray processes. Influence of the binder content (20 and 27 vol.-%) and some alloying elements, such as Mo, Co and N on the coating properties were investigated. The coating structures and properties were investigated by optical microscopy, hardness measurements, X-ray diffraction analysis and by rubber-wheel abrasion wear test. It was found that alloying the hard phase with Mo and N leads to an improvement of the coating properties. Alloying of the binder phase with Co did not affect the coating properties. Porosity in the powder granules was found to beneficial in order to melt more efficiently the particles in the DGS process and especially in the HVOF process. HVOF spraying of powders with the higher binder content of 27 vol.-% was found to be advantageous for the preparation of coatings with dense microstructures and good wear resistances.
The Structure and Properties of Two Fe-Cr-B-Based Coatings Sprayed Using HVOF
Authors: Dent A.H. , Horlock A.J. , McCartney D.G. , Harris S.J. 
Published: May 2021

Abstract
Two boron-rich Fe/Cr based gas atomised powders (Armacor M and Armacor C) have been thermally sprayed using the HVOF process and the resultant deposits subsequently characterised, using X-ray diffraction, scanning electron microscopy (SEM), plan view transmission electron microscopy (TEM), and microhardness measurements. The wear and corrosion characteristics of the two alloy coatings have also been investigated by three body abrasive wear (utilising cross-sectional TEM to examine the worn surfaces) and potentiodynamic corrosion testing respectively. Results from microstructural analysis of the as-sprayed deposits revealed the presence of small chromium-iron boride precipitates within a predominantly amorphous matrix in the Fe-based Armacor M coating. The Fe-Cr-based Armacor C coating, however, consisted mainly of regions of nano- and microcrystalline material interspersed with chromium boride precipitation. Iron-chromium oxides have been observed within both of the alloy coatings studied. Both of these alloys exhibit good abrasive wear resistance when compared with other metallic based HVOF sprayed coatings. Both Armacor M and Armacor C also exhibit extensive passivation on exposure to an acidic solution. The wear and corrosion test results are related to the microstructural observations.
The Use of Metallographic Standards in Calibration of the Polishing Process
Authors: Sauer J.P. 
Published: May 2021

Abstract
The metallographic process for evaluating thermally sprayed coatings is sometimes viewed as a variable process in the scope of coating evaluation. There is always a question as to whether the failure of a coating is polishing related or an actual change in the spray production process. The use of metallographic standards similar to hardness calibration can be implemented to provide assurance of a repeatable metallographic polishing. Development and use of the standards will be discussed and examples given of the standards principle.
ISO 14000 Environmental Management System: A New Challenge for Coating Shops
Authors: Ebert K. , Roelleke S. , Verpoort C.M. 
Published: May 2021

Abstract
Coating shops are under increasing pressure by stringent legislation to demonstrate sound environmental performance. This paper describes how one can combine the environmental requirements according to ISO 14000 with existing Quality Management Systems according to ISO 9000. The Environmental Management System requires that a company establishes and maintains an environmental policy with a strong commitment to continual improvement and prevention of pollution. The company has to establish environmental targets with a timeframe by which they are to be achieved. In this paper, some practical aspects of prevention of pollution by using new processes, practices and materials will be described. Some important aspects like recycling of waste from dust collectors or sand blasting units will be discussed.