bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microstructural Formation of Vacuum Plasma Sprayed Ti-6Al-4V Alloy
Authors: Salimijazi H.R. , Coyle T.W. , Mostaghimi J. , Leblanc L. , Tsantrizos P. 
Published: September 2022

Abstract
Titanium alloys are extremely reactive in the molten state, therefore near-net shape and complex shape components cannot be produced by many techniques used for steel, aluminum and other less reactive metals. The vacuum plasma spray (VPS) process is a well-known method for coating and forming reactive metals and alloys such as titanium alloys. In this study the internal microstructure of individual splats, porosity, and mechanical properties of Ti-6Al-4V deposited by vacuum plasma spray forming (VPSF) were studied using SEM, XRD, mercury porosimetry, image analysis and mechanical testing. Results described in a companion paper show that while tensile and yield strength rise with increasing initial powders size, elongation still remains as low as 1%. The as-sprayed structure consists of α’ martensite with a small amount of residual β between the martensite colonies as well as pores between the splats. The fracture surface within the splats is indicative of ductile failure. The low cohesion between the splats results in damage accumulation at the boundaries and failure at small elongations. Post deposition heat treatments were conducted to improve the coating structure and were successful in improving the ductility to levels approaching that of traditionally processed material.
High Velocity Continuous Combustion A Review of the Technology and Performance History
Authors: Hill H.A. 
Published: September 2022

Abstract
The High Velocity Continuous Combustion (HVCC) Spray System was invented in 1993. The HVCC process uses wire as a consumable feedstock. Atomization takes place in a supersonic air jet, which is produced using a converging-diverging nozzle arrangement. The arc point is located within this supersonic air stream, which produces extremely finely atomized particles averaging 30 µm in diameter. The morphology of the HVCC produced coatings are homogeneous and consist of flat splat platelets with thin, adherent oxides. Permeation by gases and liquids through coating structures is significantly lower than that typically seen for twin wire arc spray coatings. Wear and erosion resistance of materials are significantly better than the same material applied with twin wire arc spray. The HVCC process has been successfully deployed over the past 7 years. It has been successfully used in confined space, in-situ applications, where traditional High Velocity Oxy-Fuel (HVOF) processes cannot be used for reasons of safety and practicality. These include applications in the petrochemical, paper and pulp, utility and independent power generating industries. Many other more specialized workshop and in-situ applications have also been performed with success.
Plasma Spraying of a Perovskite Suspension for SOFC Cathodes
Authors: Monterrubio-Badillo C. , Ageorges H. , Chartier T. , Coudert J.F. , Fauchais P. 
Published: September 2022

Abstract
A perovskite suspension was air plasma sprayed (APS) with a direct current (dc) plasma jet. The process conditions including the standoff distance, plasma forming gases and their ratio influence on the perovskite deposits and splats characteristics were investigated. Particularly the molten state of particles, phases obtained, morphology and composition of splats were studied. The process consists in injecting a well dispersed stable suspension of submicrometric particles. The suspension was produced by attrition milling LaMnO3 perovskite powder (mean particle size of 0.8 µm). The plasma forming gases influences drastically the obtained phases in deposits. When the plasma gas mixture contains hydrogen the heat transfer is too high and the perovskite phase is decomposed but when the plasma forming gases is Ar/He or only Ar, just a very little quantity of perovskite is found to be decomposed in the plasma jet. With Ar/He, perovskite splats are well melted, but with argon there is a high percentage of semi-melted and non-melted particles.
Study on Finishing Wear Resistant Thermally Sprayed Coatings: Influence of Feed Stock Material, Spraying Parameters and Machining Parameters
Authors: Widen J. , Szczesny D. , Jahn S. 
Published: September 2022

Abstract
HVOF-sprayed coatings have become increasingly important for many different industries. Because of this, the ability to adjust coating process parameters according to a customer’s demands becomes a necessity. Several studies have been done on various powders, spray parameters, and the resulting coating properties such as coating hardness, wear resistance, and internal stress. On the other hand few studies have been published regarding post-treatment and finishing processes. This study is intended to investigate the entire production process, from thermal spraying to the ready-to-use finished layer; the primary points of consideration were hardness, surface quality (roughness), and resulting microstructure. The scope of this study is to present initial results of cylindrical grinding as a finishing process. Several different tungsten-carbide-based coatings of various compositions and particles sizes were produced by thermal spraying under varying kerosene-oxygen flow, spray distance, and powder feed rates. Machining parameters such as speed of workpiece rotation and longitudinal feed rate were tested as well.
Sialon Coating from Sintered Mixtures of Silicon Nitride and Oxides
Authors: Seong B.G. , Hwang S.Y. , Park J.M. 
Published: September 2022

Abstract
Silicon nitride and sialons are very attractive materials for thermal spaying, but the high temperatures of spray processes lead to their decomposition instead of melting. Therefore, the use of these materials as protective coatings has been very restricted. Nevertheless, researchers have tried to provide silicon nitride-based coatings using metallic or oxide binders. Oxide binder additions to silicon nitride have been quite successful. In this paper, mixtures of silicon nitride and oxides were prepared for the thermal spraying of silicon nitride-based materials by using a detonation gun. Powders for the spraying were prepared through mixing, sintering, crushing and sieving. To get an oxide binder of low melting point, three components of oxides, Al2O3-ZrO2-TiO2, were selected; the ratio of oxides was determined to have a low melting point. When the sintering temperatures were below 1400°C, phases of the powders and coating layers were composed of α-Si3N4 and oxides and any of sialon phases were not found. By sintering at the temperatures between 1400 and 1600°C in a nitrogen gas environment, χ(chi)-sialon (Si6Al10O21N4) and β’-sialon (Si3Al3O3N5) were formed. The ratio of β’-sialon increased as the sintering temperature increased. TiO2 was transformed to a nitride, TiN. During the spraying procedure χ-sialon was decomposed to amorphous binder, but β’-sialon was not totally decomposed. Finally a coating layer composed of tetragonal-zirconia and β’-sialon was made.
Oxidation Behavior of Electroplated MCrAlY Coatings
Authors: Khan Abdus , Duda Thomas , Taylor Alan , Moore Peter , Rutter Peter , Foster John 
Published: September 2022

Abstract
High temperature oxidation behavior of MCrAlY coatings was studied at several temperatures in the range from 800 to 1100°C. In this study the MCrAlY coatings were obtained by plating using CrAlY as precursor powders in an electrolytic bath containing nickel and cobalt salt in solution. The size of the precursor CrAlY powders used was generally below 10 um. As-plated coatings consisted of a random distribution of CrAlY particles in the Ni-Co matrix. The heat-treatment of the as-plated coatings at elevated temperature resulted in the development of a gamma and beta structure. Both as-deposited and oxidized coatings were characterized by optical, scanning electron microscope and electron beam microprobe. During oxidation the coatings formed alumina scale with a negligible amount of transient nickel and chromium oxides. The spallation resistance of the oxide scale was investigated by thermal shock testing. The test consisted of a rapid cooling from 1000°C to 100°C with a two- minute dwell time at the maximum temperature. The thermal shock test was conducted in a) as–deposited and heat-treated condition and b) after preoxidation at 800°C and 1050°C, respectively. The coatings retained the alumina scale during thermal shock cycling.
HVOF Coatings of Ball-Milled Al2O3/NiCr Dispersion-Strengthened Powders
Authors: Lugscheider E. , Zwick J. , Zhang H. 
Published: September 2022

Abstract
Nanostructured materials have a high potential to improve properties of thermal spray coatings. High-energy ball milling is an effective process to produce dispersion-strengthened powders with a homogenous nanoscale microstructure and superior mechanical properties compared to unstrengthened material. Because of the relatively low temperatures and heat flux during HVOF spraying, the microstructure of the powder particles can be maintained in the coating. In this study Al2O3- dispersion-strengthened NiCr powders were synthesised by high-energy ball milling, using optimised milling parameters. Thermal spray coatings were produced using the HVOF process. The improvement of the tribological behaviour and the potential for technical applications were evaluated. The study shows the favourable impact of mechanically alloyed MMCs on the tribological behaviour of HVOF coatings on the basis of an Al2O3-strengthened NiCr powder
Key Factors for Dense Copper Coating by HVOF Spraying
Authors: Isoyama K. , Kawakita J. , Kuroda S. , Yumoto H. 
Published: September 2022

Abstract
For thermal sprayed coatings, compactness of their constituent particles is required in many applications, e.g. to obtain impermeable anticorrosion coating in marine use. We investigated key factors to improve compactibility of deposited particles in HVOF sprayed coatings by condition measurements of spray particles. The results revealed that plastic deformability of the sprayed particles as well as their molten fraction was important to obtain the dense VHOF coatings.
Microstructure and Properties of HVOF-Sprayed TiC-Based Coatings
Authors: Berger L.-M. , Zimmermann S. , Keller H. , Schwier G. , Scholl R. , Thiele S. , Nebelung M. , Enžl R. 
Published: September 2022

Abstract
Advanced TiC-based spray powders contain molybdenum and nitrogen as alloying elements and consist of core-rim-structured (Ti,Mo)(C,N) hard phases embedded in Ni, Co or mixed Ni/Co binder phases. For the investigations of the present study, four powders with binder phase contents of 29 and 39 mass-%, corresponding to about 20 and 27 vol.-%, respectively, were prepared by agglomeration and sintering. Coating samples were sprayed using JP-5000 equipment and two spray parameter sets. During coating characterization, special emphasis was placed on the changes in chemical (carbon loss and oxygen uptake) and phase compositions during spraying and their correlation to the coating microstructures and properties. It was found that the decreases in carbon and nitrogen contents were practically independent of the spray parameters for all of the four powders, whereas the oxygen uptake was different for each of the powders. The effect of the oxygen content on different coating properties is discussed in detail. All coatings investigated in this work showed excellent properties. It is anticipated that TiC-based coatings sprayed from these types of advanced powders can complement thermal spray coating solutions based on WC and Cr3C2.
Development of HVOF Sprayed Aluminium Alloy Engine Bearings
Authors: Sturgeon A.J. , Reignier C. , Laing I. , Perrin C. 
Published: September 2022

Abstract
Aluminium-based plain bearings for gasoline internal combustion engines are traditionally manufactured by casting and rolling, followed by forming and boring. The application places severe demands on the bearing material and a combination of properties such as fatigue, seizure and wear resistance are required. These properties are achieved by using a multi-phase material comprising of a distribution of tin in an aluminium alloy matrix. HVOF has been investigated as an alternative process for bearing manufacture and as a route to producing novel bearing materials with microstructures that cannot be achieved using the conventional casting route. The work reported describes the use of different HVOF spraying systems and powder types to develop aluminium-tin based coatings for advanced bearing applications. The coatings are described in terms of microstructure characteristics. The fatigue performance of the advanced sprayed bearings is compared with conventional cast bearings.
Mechanical Properties and Microstructure of HVOF Sprayed Co and Ni Alloy Coatings
Authors: Zhang D. , Harris S.J. , McCartney D.G. 
Published: September 2022

Abstract
A high velocity oxy-fuel spraying system using liquid fuel (HVOLF) has produced Stellite 6 (CoCrWC) and NiCoCrAlY coatings from gas atomised powders of both alloys. Comparative coatings were prepared by weld 0verlay (Stellite 6) and vacuum plasma spraying (VPS) of NiCoCrAlY. The original powders and coatings were characterised by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The presence or absence of cored dendritic microstructures in etched surfaces was used to interpret the degree of melting which took place during spraying, i.e. &gt;80% in VPS and &lt;20% in HVOLF. Low levels of oxide were formed in HVOLF coatings due to the reduced level of thermal transfer during the short heating cycle involved in spraying. For the same reason less melting occurred which permitted sufficient plastic deformation of the solid fraction to occur, reducing voidage between particles and then allowing the liquid fraction to weld them together. This pattern of short cycle heating with both NiCoCrAlY and Stellite 6 particles influenced second phase formation. In NiCoCrAlY coatings the β (Co Ni Al) phase remained as relatively coarse precipitates in the as - sprayed condition whilst in Stellite 6 little carbide eutectic formed. HVOLF spraying can produce coatings with different hardness values when compared with VPS coatings and weld overlays. This may widen the range of coating applications as well as reduce costs.
Experimental Correlation between Flattening Degree and Reynolds Number of Spray Particles
Authors: Li C.-J. , Liao H.-L. , Gougeon P. , Montavon G. , Coddet C. 
Published: September 2022

Abstract
The particle parameters including particle size, velocity and temperature influence significantly splat formation process in thermal spraying. The flattening degree of subsequent splat determines the coating structure and properties. Both theoretical analysis and simulation of splatting process indicate that the flattening degree depends on Reynolds number (Re) of spray particles. The experimental correlations suggest that the theoretical models overestimate the flattening degree. In the present study, with careful control of particle size and measurement of particle velocity and temperature, the relationship between the flattening degree and particle Reynolds number is examined experimentally. Copper powders of small size range are used to ensure valid of mean particle size. Plasma spraying is carried out under different conditions to change particle velocity and temperature. The particle velocity and temperature are measured using DPV- 2000. Splats were deposited on preheated polished stainless substrate surface. The diameter of individual splat was measured. The flattening degree was estimated using average diameter of splats and spray particles for individual spray condition. Using the exponential formula of Re with a power of 0.2, it was found that experimental correlation yielded a coefficient about half of that given by Madjeski’s model.
Evaluation of Sn and Al2O3 Splats by Fractal Geometry
Authors: Hikari R. , Amada S. , Uematsu S. 
Published: September 2022

Abstract
The quality of thermal sprayed coatings greatly depends on the individual flattened splats. Generally they are characterized by two main factors, flattening ratio and splat profile. The flattening ratio is specified straightforward, but it is difficult what factor should be selected from the various properties for the splat profiles. Fractal geometry is introduced to the profile evaluation of the splats which are formed by the free-fall metal droplets and by the alumina coatings using plasma spraying method. The fractal dimension of each splat was measured by SIA (Slit Island Analysis) technique which measures the ratio of area to contour length of the island appeared on the horizontally sliced plane of the splat. The obtained fractal dimension was related to with Re and We numbers in a bi-linear form, which is the same characteristics as the unevenness ratio obtained previously. It was concluded that fractal dimension is an effective measure to evaluate the splat profile.
Effect of Reynolds Number of Molten Spray Particles on Splat Formation in Plasma Spraying
Authors: Li C.-J. , Liao H.-L. , Gougeon P. , Montavon G. , Coddet C. 
Published: September 2022

Abstract
A thermal spray coating is formed through successive impact, flattening, rapid cooling and solidification processes of a stream of spray droplets. Splashing may occur during droplet flattening process. Recent studies suggested that splashing can be suppressed when a molten droplet impacts on a preheated flat substrate. In this study, the splatting behavior in plasma spray is examined using molten spray droplets of different Reynolds number. Splats are deposited on preheated flat stainless steel surface. The morphology of splats is examined using optical microscopy and scanning electron microscopy. To adjust Reynolds number of spray droplets, copper droplets are produced using both Ar-H2 and Ar-He-H2 plasma jets under different operating conditions. As a result, the Reynolds number of spray droplets have been varied from about 18,000 to 90,000. It has been found that Reynolds number will influence splashing phenomena during splatting and consequent splat morphology. At low Reynolds number, splats present a regular disc morphology. However, when Reynolds number was increased up to about 5x104, the severe splashing around periphery of splat droplet was clearly observed despite the preheating of substrate. Based on the morphology of splats, a model for the spreading of molten droplet is proposed to explain the effect of Reynolds number on the flattening behavior of molten spray droplet.
Influence of Substrate Temperature on Formation of Micrometric Splats Obtained by Plasma Spraying Liquid Suspension
Authors: Fazilleau J. , Delbos C. , Violier M. , Coudert J-F. , Fauchais P. , Bianchi L. , Wittmann-Ténèze K. 
Published: September 2022

Abstract
A new thermal spray process is under development in order to produce thin coatings (thickness lower than 50 µm), with a fine microstructure (grain size smaller than 1 µm). It consists in injecting in a Direct Current (D.C.) plasma jet a suspension containing submicronic particles of the material to be deposited. To study the interaction between the plasma jet and the suspension, a system based on a pendulum allows the collection of particles at different distances from the injection point. In this paper the effect of substrate temperature upon the formation of micrometric zirconia splats was studied, glass and stainless steel were used as substrate materials.
Partially Melted Particle and Its Splat Morphology
Authors: Zhang H. , Xiong H.B. , Zheng L.L. , Vaidya A. , Li L. 
Published: September 2022

Abstract
The melting behavior of in-flight particle and its impact on splat morphology are studied. A group parameter, “melting index”, has been derived to correlate the melting status of inflight particles with particle size, velocity, and temperature which can be measured experimentally. Numerical simulations have been used to determine the unknown parameters in the melting index. The effect of particle size on its melting behavior has been investigated.
Synthesis of BCN Coatings in Thermal Plasma Jets
Authors: Wank A. , Wielage B. 
Published: September 2022

Abstract
The system B-C-N contains the hardest known materials like diamond, cubic boron nitride and boron carbide, which also show excellent chemical resistance. The oxidation resistance is shifted to higher temperatures in comparison to pure diamond. But pure BCN coatings cannot be produced by conventional thermal spray processes, as the materials lack both a liquid phase and sufficient ductility to permit deposition. Conventional VPS equipment is successfully applied in Thermal Plasmajet CVD processes for high deposition rate synthesis of diamond coatings. The feasibility of SiCN or boron carbide synthesis by this method has also been proven. The use of liquid precursors results in outstanding deposition rates and improved operational safety. Methylized borazine is applied for synthesis of BCN coatings in thermal plasma jets. The use of single source precursors is advantageous with concern to the homogeneity of the coating forming species stoichiometry. For long-term storage cooling is necessary, but also under ambient conditions the precursor shows sufficient stability. Plasma gun nozzles with different diameter and design are applied and evaluated with concern to the resulting coating properties. Deposition rates of up to 1,500 µm/h have been achieved with homogeneous coating thickness and morphology on areas with 50 mm diameter. No porosity is detected in SEM investigations on cross sections and fracture surfaces show a fine columnar coating morphology. XRD investigations point at an amorphous structure. Only for very high substrate temperatures the formation of crystalline boron carbide B8C and h-BN or graphite phases is detected. Oxygen contamination results in boric acid formation and therefore has to be avoided carefully. During coating deposition on mild steel substrates the formation of boride and nitride reaction zones is observed. VPS sprayed nickel or molybdenum interlayers permit to inhibit the evolution of reaction zones. Thereby BCN coatings with thicknesses of up to 10 µm are deposited without local delamination. Space resolved emission spectroscopic analyses are carried out in order to detect coating forming and intermediate species. As Thermal Plasmajet CVD is a pure gas phase deposition process, the control of the space resolved emission permits easy process control.
Research on Fluid Properties of Low Energy, High Efficiency and Non-transferred Arc Plasma Jet
Authors: Yan Zhijun , An Liantong , Gao Yang , Huang XiaoOu 
Published: September 2022

Abstract
A mathematical model was used to describe the fluid flow, electromagnetic and heat flow of the plasma jet in the non-transferred model. A computer program has been developed to simulate the fluid properties of the low energy and high efficiency plasma jet. The numerical results approximate the measurements by using the enthalpy probe.