bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlations Between In-Flight Particle Concentrations and Coating Properties in Atmospheric Plasma Spraying of Alumina
Authors: Lehtinen T. , Knuuttila J. , Vattulainen J. , Mäntylä T. , Hernberg R. 
Published: May 2021

Abstract
The plasma spraying process is controlled by various parameters that have an influence on powder particle velocities, temperatures and trajectories just before impact to the substrate. In order to fully utilize the thermal and kinetic energy of the plasma it is important to obtain information from these powder particle properties. In this work an intensified CCD camera has been used to detect in-flight particles in an atmospheric plasma spraying process. Plasma spraying was performed using fused and crushed AI2O3 powder. The powder carrier gas flow rate was varied during the spraying experiments. All the other deposition parameters were kept constant. Coatings produced using relatively new spraygun electrodes are compared with ones produced later with the same electrodes when they were worn out. The particle concentration is determined on a relative scale by the fraction of the area of a CCD camera frame covered by particle images. Further investigations necessary to clearify the relationship between the measured relative particle concentration and the true particle concentration are identified. The coatings are analyzed for wear resistance, degree of melting, deposition efficiency, hardness and porosity. The dependence of these coating properties on the relative particle concentration and the effect of electrode wear on the relative particle concentration are studied.
Influence of Shroud Gas Flow and Swirl Magnitude on Arc Jet Stability and Coating Quality in Plasma Spray
Authors: Chen H.C. , Duan Z. , Heberlein J. , Pfender E. 
Published: May 2021

Abstract
The quality of a plasma sprayed coating is influenced by the plasma jet stability; entrainment of cold air through large scale turbulence can lead to variations in particle heating and trajectories resulting in increased unmelt densities, reduced deposition efficiencies, and oxidation of metal particles. The jet instabilities are in part caused by the swirl flow of the plasma gas. With two modifications to an atmospheric pressure plasma spray torch, we have investigated the influence of reduced swirl flow on jet stability, particle trajectories, and coating quality. The modifications are (1) addition of a shroud consisting of a porous ring surrounding the anode nozzle while simultaneously injecting part of the shroud gas inside the nozzle with a swirl component in the direction opposing the plasma gas vortex, and (2) an injector ring with which part of the plasma gas is injected radially and part tangentially producing reduced vortex flow for the same plasma gas flow rate. Jet stability and particle trajectories are determined using a LaserStrobe system combined with image analysis, and coatings have been evaluated by determining porosity and unmelt density. Results indicate that deposition efficiency is most affected by reduced vortex flow, while the shroud addition reduces unmelt density and porosity.
Modeling of the Laser Engraving at Plasma Sprayed Cr2O3 Coatings on Anilox Rolls
Authors: Groc M. , Pawlowski L. , Smurov I. , Clinton G. , Pitt R. 
Published: May 2021

Abstract
This paper presents a preliminary study of mathematical modeling and numerical simulation of laser engraving process. The 1-D simulation concerned CO2 c. w. pulsed laser engraving of plasma sprayed Cr2O3 coatings as used in the manufacture of anilox rolls. The thickness of the evaporated material was calculated as a function of laser processing parameters viz. pulse length and power density. The actual thermophysical coefficients of plasma sprayed chromia were used if available and the results of calculated thickness of evaporated layer are compared with the experimentally determined depth of engraved cells to estimate unknown coefficients of liquid chromia. Finally, the experimental effect of overflow was related to the calculated thickness of liquid layer. The experimental procedure of minimization of this effect is proposed.
Crystalline Growth within Alumina and Zirconia Coatings with Coating Temperature Control during Spraying
Authors: Haddadi A. , Grimaud A. , Denoirjean A. , Nardou F. , Fauchais P. 
Published: May 2021

Abstract
In this paper the influence on the coating generation of substrate preheating during spraying, relative movements torch to substrate and cooling conditions is systematically studied for partially stabilized zirconia and alumina coatings. Beads and coatings are sprayed with Ar-H2 dc plasma jets in air. The obtained structure, resulting hardness and adhesion/cohesion for each spraying condition is discussed.
Plasma Sprayed Zirconia: Relationships Between Particle Parameters, Splat Formation and Deposit Generation-Part I: Impact and Solidification
Authors: Léger A.C. , Vardelle M. , Vardelle A. , Fauchais P. , Sampath S. , Berndt C.C. , Herman H. 
Published: May 2021

Abstract
Joint research work between the University of Limoges and the State University of New York, Stony Brook, has been carried out on the impact and solidification of plasma sprayed zirconia particles. A measurement device, consisting of a phase doppler particle analyser and a pyrometer, was used to correlate the characteristic parameters of splats to those of the substrate and to the size, velocity and temperature of the impacting particles.
Droplet Impact and Solidification in a Thermal Spray Process: Droplet-Substrate Interactions
Authors: Pasandideh-Fard M. , Mostaghimi J. 
Published: May 2021

Abstract
Experiments have shown that the mechanical properties of plasma-sprayed coatings depend to a large extent on the details of the spraying process, in particular, they are strongly dependent on the details of the solidification and deformation history of the individual droplets which are in turn highly affected by the substrate conditions such as its temperature, material, and surface thermal contact resistance. In this study, droplet-substrate interactions are investigated through a complete numerical solution of droplet impact and solidification for a typical thermal spray process. The energy equation is numerically solved for both droplet and substrate regions; the solution is based on the Enthalpy Method for the liquid and solidified parts of the droplet, and the conduction heat transfer in the substrate. The numerical solution for the complete Navier-Stokes equations is based on the modified SOLA-VOF method using rectangular mesh in axisymmetric geometry. The developed model is suited for investigating droplet impact and simultaneous solidification permitting any desired condition at the substrate. The splat shape, the solidification front, and the temperature profile in the entire droplet and substrate regions are obtained at any desired time elapsed after the impact. Through these results, the nucleation and growth of solidification and droplet-substrate interactions are extensively studied.
Mathematical Modeling of Flattening Process on Rough Surfaces in Thermal Spray
Authors: Fukanuma H. 
Published: May 2021

Abstract
Thermal spray layers are formed on rough surfaces; however, the flattening process on rough surfaces has not yet been clarified. A mathematical flattening model which takes into account the roughness of the substrate or previously coated layers is proposed in this paper. As a result of surface roughness, the flattening degree and the flattening time decrease with increasing surface roughness in this model. In addition, the characterization of surface roughness is introduced for the flattening model. Several calculated cases of the flattening model are shown.
Splat Solidification of Tin Droplets
Authors: Bhola R. , Chandra S. 
Published: May 2021

Abstract
An experimental study was done of the impact and solidification of tin droplets falling on a stainless steel surface. The surface temperature was varied from 25°C to 240°C. Measurements were made of droplet diameters and contact angles during droplet spread. At a surface temperature of 240°C there was no solidification, and a simple model of liquid droplet impact successfully predicted the extent of droplet spread. Droplets impacting on surfaces at 25°C and 150°C solidified before spreading was complete.
Tensile Bond Strength Variance of Thermally Sprayed Coatings with Respect to Adhesive Type
Authors: Evans K.A. 
Published: May 2021

Abstract
A Round Robin study involving 19 coating suppliers and independent laboratories was conducted on tensile testing of thermally sprayed coatings to determine the accuracy and consistency of the tensile data among the participating labs and within a lab. One coating system (NiCrAl) and two adhesive types (film vs. liquid epoxy) were used. The results showed the average tensile strengths for the coating system using the liquid epoxy systems (EC2086/EC2214) were consistently higher than the average values which resulted using the film epoxy system (FMIOOO). However, less scatter in the results was observed when the FMIOOO film epoxy was used.
Minimization of the Residual Bending of Plates with Sprayed Coatings
Authors: Kroupa F. , Neufuss K. , Lauschmann H. , Materna A. , Oliva V. 
Published: May 2021

Abstract
The theory of residual stresses and of residual bending of plates with relatively thick sprayed coatings is summarized and some methods to minimize the bending are proposed. The particular case of an aluminium alloy substrate with a relatively thick plasma sprayed ceramic coating, with a large difference of thermal expansion coefficients, is discussed.
Supersonic Induction Plasma Spraying of Dense YSZ Electrolyte Membranes
Authors: Mailhot K. , Gitzhofer F. , Boulos M.I. 
Published: May 2021

Abstract
In this paper, RF induction plasma deposition of Yttria Stabilized Zirconia (YSZ) is studied with the objective of producing dense solid electrolyte membranes for Solid Oxide Fuel Cells (SOFC). Different RF induction plasma torch configurations were tested. The results show that high density layers could be obtained using a supersonic Laval nozzle attachment on a standard torch. Coating with apparent porosity of less than 1% could be obtained using this technique at relatively high deposition rates. Optical or electron microscopic examination of the deposit coupled with image analysis show, however, that porosity measurements using these techniques can suffer from relatively large discrepancies depending on equipment setting. A discussion is presented of the validity of this porosity measurement technique.
Slurry Erosion of Arc-Sprayed Metal and Composite Coatings
Authors: Arsenault B. , Legoux J.-G. , Hawthorne H. 
Published: May 2021

Abstract
Two grades of stainless steel, 316 and 440-C, in the form of solid wire, and two cored wires, Duocor and 95-MXC, were used. Coatings were made using the Miller BP-400 and TAFA 9000 systems. Slurry jet erosion tests were conducted using a 10 %w/w alumina particle/water slurry. Two alumina particle sizes, 320 and 80 grit (nominal grain diameters 35 μm and 200 μm, respectively) were used at impinging angles of 90° and 20°. The nominal impact velocity of the slurry was 15 m/s and the nozzle-specimen distance 100 mm. The volume loss of material under various slurry erosion conditions was related to the coating properties and microstructure. Results indicate that the wear behavior of arc sprayed materials is dependent on the erodent particle size; for large erodent particle size, the relative erosion is almost independent of the impinging angle, while for the smaller particle size the angle effect is the dominant factor. This behavior can be related to the lamella structure and the relative toughness of the different phases of the coatings.
Low Friction Cobalt-Based Coatings for Titanium Alloys
Authors: Hajmrie K. , Chilkowich A.P. 
Published: May 2021

Abstract
Protective coatings adapted for titanium alloys which come into frictional contact with one another are described. Among the many coatings investigated, the best ones are cobalt based. The coatings are sprayed only on one of the rubbing surfaces. During rubbing, a small part of the coating transfers to the unprotected titanium alloy surface. The rubbing pair is thus essentially composed of two cobalt alloy-based surfaces. This leads to low coefficient of friction and little or no damage to the rubbing surfaces. The coatings find particular application in the protection from adhesive and fretting wear, galling and seizure of gas turbine and jet engine parts or the like made from titanium alloys.
Tailored Solutions for Off-Shore Applications by Plazjet Sprayed Coatings
Authors: Ladru F. , Lugscheider E. , Jungklaus H. , Herbst C. , Kvernes I. 
Published: May 2021

Abstract
For very large structures and parts in critical environments, a materials solution often cannot be found by using one material. The specific desired properties for those structures, like stiffness, ductility, high temperature stability, corrosion resistance, etc. are difficult to fulfill with only one material. In this case a solution may be found by using coatings and design their specific properties to replenish each other by their combination. The Thermal Spraying processes offer the necessary flexibility of producing thin to thick, ductile, soft to hard coatings while due to the wide range of process temperatures it is possible to process a wide range of materials, both as coating and structure. In this paper the some recent and important developments in Thermal Spraying to produce coatings for technical demanding structures will be described. These developments consist of High Power Plasma Spraying, powder- and process control development. To ensure process consistency during long spraying times and to apply reproducible coating quality a suitable process control is of great importance and the development of temperature control by Pyrometry and Thermography will be presented. The example will be drawn according to the application of a coating on a ball valve for off-shore and ship diesel engine parts (piston and valve).
The Effect of Tungsten Contamination from the Spray Gun on the Performance of a Thermal Barrier Coating
Authors: Wigren J. , Pejryd L. , Karlsson H. 
Published: May 2021

Abstract
A traditional plasma spray gun consists of an anode and a cathode. During spraying small particles of anode material of either copper or tungsten, depending on the brand of the gun, will be worn off and deposited in the coating. The size and frequency of the particles from a copper anode has generally a dramatic appearance (in the beginning or at the end of its life) whereas a tungsten nozzle normally behaves more randomly during its life. Tungsten particles can therefore be expected anywhere in a plasma sprayed coating. Unfortunately the material properties of tungsten is not very compatible with a thermal barrier coating of partially stabilized zirconia and it is shown that a contamination will cause a catastrophic failure, if located in, for a thermal barrier, a critical region. The behavior of tungsten at elevated temperatures is investigated and clearly show the detrimental effect of tungsten on the life and performance of a thermal barrier coating.
Microstructure Control of Zirconia Thermal Barrier Coatings by Using YAG Laser Combined Plasma Spraying Technique
Authors: Zhou Z. , Eguch N. , Ohmori A. 
Published: May 2021

Abstract
As an ideal zirconia thermal barrier coating, the coating microstructure with the strong bonding among coating particles and with certain amount porosities in the coating without connected porosity is desirable. However, it is difficult for usual plasma-spraying to create a zirconia coating with these characters. In order to obtain an excellent zirconia coating with these characters, we prepared zirconia coating on steel substrate under coated with NiCrAlY alloys by means of a hybrid spraying (that is, YAG laser combined plasma spraying) and studied the effect of this hybrid spraying process and plasma and laser conditions on the microstructure of coating, and further compared the microstructure of the coating in this hybrid spraying with that in post-laser irradiation of as-sprayed zirconia coating. It is known that the microstructure with densification is formed by the post-laser irradiation of as-sprayed coating and that microcracks are newly produced in the process of rapid cooling. However, by using this newly-developed hybrid spraying, the microstructure with partial densification in the coating without connected porosities was formed and cracks which is generally produced in the post-laser irradiation treatment were inhibited completely. In addition, this hybrid spraying can be done without the post-treatment of coating. Furthermore, the coating properties, such as hardness and wear resistance associated with bonding state among the coating particles in the zirconia coating created by this hybrid spraying were improved.
Deposition of Nickel-Aluminum Bronze Powder by Cold Gas-Dynamic Spray Method on 2618 AI for Developing Wear Resistant Coatings
Authors: Bhagat R.B. , Amateau M.F. , Papyrin A. , Conway J.C. , Stutzman B. , Jones B. 
Published: May 2021

Abstract
In an emerging thermal spray process a coating is formed by exposing a metallic or dielectric substrate to a high-velocity jet of solid-phase particles, which have been accelerated by a supersonic gas jet at a temperature much lower than the melting or softening temperature of the particle material. This is known as "Cold Gas-Dynamic Spray" (CGDS) method. Using this method, 2618 Al substrates were coated with nickel-aluminum bronze powders (~100 and ~400 mesh) in an effort to obtain improved wear resistance. The coatings have been examined for their microstructure, hardness, and bond strength. Triple lug shear tests performed on coated panels provided quantitative measurement of the coating/substrate interfacial shear strength. The steady state wear rates were determined using the pin-on-rotating ring test at a pressure of 690 kPa and a sliding velocity of 9 m/s. The wear resistance of the nickel-aluminum bronze coatings is discussed in conjunction with scanning electron microscopy (SEM) examination of the wear tracks and metallography of the polished transverse cross-sections. Though the coatings are not completely free from porosity, they exhibit high interfacial shear strength and wear resistance due to the low-temperature, ballistic impingement of the powders in the cold gas-dynamic spray method. The ~400 mesh powder coating shows higher interfacial shear strength and wear resistance in comparison with the ~100 mesh powder coating.
Arc Voltage Fluctuations as an Indication of Spray Torch Anode Condition
Authors: Duan Z. , Beall L. , Planche M.P. , Heberlein J. , Pfender E. , Stachowicz M. 
Published: May 2021

Abstract
Arc voltage fluctuations of a plasma spray torch are primarily an indication of the movement of the arc attachment inside the anode nozzle. These fluctuation have been shown to influence the deposition process. In order to detect changes in the operating conditions which affect coating quality, a method has been developed for on-line analysis of these fluctuations. Voltage fluctuation have been recorded together with light emission fluctuations and with acoustic emissions from the plasma jet and analyzed on-line using a workstation operating with the LabView environment. Anodes with different wear characteristics have been examined in this study. A clear correlation has been found between the changes in the dominant frequencies of all three signals and the conditions of the torch anode and the coating properties. Appearance of a group of frequency peaks in the 2 to 5 kHz range indicates a more unstable plasma jet and is correlated with anode erosion and increased coating porosity. The results of this study provide us with a convenient method to detect coating deterioration due to anode erosion.
Monitoring of Nozzle Wear during Plasma Spray
Authors: Xi J. , Krishnappa G. , Moreau C. 
Published: May 2021

Abstract
Presented in this paper are the results of preliminary experiments carried out for monitoring of plasma nozzle wear. The experiment system consists of two microphones, one accelerometer and voltage measurement. In the experiment, three nozzles were tested, new, used and worn. The test results show clearly the difference in acoustic characteristics with wear in the nozzle. Some observations obtained from the experiment include: 1) the microphone mounted at 45° may be the best choice for nozzle wear monitoring; 2) voltage signal could be used with the 45° microphone as an indicator for severe nozzle wear; 3) vibration signal is not as sensitive to nozzle wear as 45° microphone and voltage signal; and 4) the 90° microphone is insensitive to nozzle wear.
New Developments in the Plasma Transferred Arc Process
Authors: DuMola R.J. , Heath G.R. 
Published: May 2021

Abstract
The plasma transferred arc process continues to be the coating method of choice for the application of cobalt base alloys onto valve and valve trim. Although new applications have been developed over the years, the process remains largely associated with the application of high performance, highly alloyed powders for relatively small parts or small areas of large parts. The use of the plasma transferred arc process for large volume application has been limited by the robustness and performance characteristics of the equipment and the use of cobalt. A new plasma transferred arc system (power source, torch and process controller) has been developed which allows the application of powder metal alloys at deposition rates of up to 40 pounds per hour. In addition, there has been a development of new non-cobalt powder alloys with excellent mixed corrosion and wear resistance properties. These capabilities have rendered the process technically and economically viable for large and demanding applications in the mining, power utility and steel industries. The new PTA system and the recent developments in powder alloys will be discussed. Reference will be made to specific applications in target industries.
The Ultimate Spray Booth
Authors: Pejryd L. , Wigren J. , Hanner N. 
Published: May 2021

Abstract
Reproducibility is a current challenge for the thermal spray industry. Reproducibility associated problems represent a large cost every year not only in terms of rejections and rework, but also in costs for destructive testing and decreased production flow. Thermal spray coatings are moving in the direction of being considered only as a "band aid" to becoming a design element. One of the prerequisites for such a development is an increase in reproducibility for thermal spray coatings. The purpose of this paper is to outline a vision aiming in the direction of a future "ultimate spray booth", where thermal spraying is as reproducible and reliable as machining, grinding or other production processes. A way to increase reproducibility and reliability in the future spray shop involves utilising major parts of IT - technology. This also includes active co-operation design-production in the pre-spray process. This paper will deal with areas such as: operation drawings and lists through multimedia techniques, education programs for operators and designers through multimedia techniques, CAD/CAM, Off-line programming and simulation, On-line diagnostics of flame (particle diagnostics) and coating (temperature & Acoustic emission measurements), on-line Statistical Process Control and Knowledge Based System techniques.