bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neural Networks, Design of Experiments and Other Optimization Methodologies to Quantify Parameter Dependence of Atmospheric Plasma Spraying
Authors: Guessasma S. , Montavon G. , Coddet C. 
Published: September 2022

Abstract
Off-line control of thermal spraying generally implements the quantification of the energetic, environmental, injection and geometric conditions. The interdependence of these parameters with regard to the deposit properties were studied with different statistical methodologies. The aim was to point out the large possibilities of the Artificial Neural Network methodology in the process optimization. In that way, experiments were designed considering atmospheric plasma spraying and the following operating parameters: arc current intensity, powder feed rate, carrier gas flow rate, total plasma gas flow rate, primary hydrogen content and scanning step. These parameters were related to the coating porosity level and hardness (HK). For each case, simple correlations were studied with none linear regressions, design of experiments and a Multilayer Perceptrons (MLP, with two hidden layers). Non linear correlations were compared with MLP based on the Average Sum of Absolute Error (ASAE) and other correlation factors (RSS, R2, Ra2, STD, RS and AR).
On the Study of the Thermal Fluxes Transferred during the HEATCOOL Process
Authors: Bolot R. , Deng H. , Liao H. , Coddet C. 
Published: September 2022

Abstract
A study of thermal fluxes transferred during the HEATCOOL process is proposed. The concept of this process, specially designed to enhance the residual stresses relaxation, consists in the use of a consecutive three-step procedure during the coating elaboration (heating / spraying / cooling). The present study focuses on thermal exchanges occurring during the heating step. For this, the elaborated experimental equipment incorporates a series of ten holes aligned equidistantly with 5 mm separation. A burning gas mixture (premixed acetylene and oxygen) is injected through these holes and the burning gas jets impinge and heat the substrate. The stand-off distance between the heating device and the substrate may be adjusted between 30 and 90 millimeters. Concerning thermal fluxes transferred using this experimental device, a front work piece incorporating several thermocouples was used to perform heat flux measurements. In a first step, the case of a single hole was considered. Since this method is not able to provide the thermal flux directly, the corresponding thermal fluxes were deduced using an inverse heat conduction problem method that was specially developed. Results obtained using this inverse problem method based on experimental measurements are then compared with numerical predictions obtained using a computational fluid dynamic model representing the system. For this part, the PHOENICS software was used to perform the corresponding computations.
Conjugated Gradient Method for Estimating Inversely the Flux Distribution of Cooling Jets
Authors: Liao Hanlin , Deng Hao , Coddet Christian 
Published: September 2022

Abstract
It is necessary to cool specimens during spraying in the case APS or HVOF, because process-induced heat rises the specimen temperature and leads to oxidation and spalling of coatings. A reasonable cooling just after spraying improves some properties such as microhardness, adhesion and cohesion of the coating/substrate system. In the modelling of specimen temperature and residual stress, it is necessary to know the flux distribution of the cooling jet like compressed air, CO2 liquid jet etc. Therefore, the evaluation of the flux becomes important. In order to measure and analyse the distribution of cooling flux imposed on the substrate, the theory of the inverse problem of heat conduction was applied and an experimental apparatus was designed to mesure the transient temperature. Because of its insensibility to the effect of measuring error, the conjugate gradient method, an effective method of inverse problems was chosen among several mathematical optimisation methods. The flux distributions of cooling jet can be estimated by using the measured data and a program written according to the conjugate gradient method.
In-Flight Oxidation of Metallic Particles in Plasma Spraying
Authors: Syed A.A. , Denoirjean A. , Deniorjean P. , Labbe J.C. , Fauchais P. 
Published: September 2022

Abstract
Air engulfment by the plasma jet in Air Plasma Spraying (APS) causes in-flight oxidation of metallic particles. This oxidation, often complex and difficult to explain by classical diffusion-controlled oxidation, is governed by several mechanisms. This paper highlights the possible in-flight oxidation mechanisms in metallic particles with a focus on convective oxidation. Two different types of austenitic stainless steel particles, Metco 41C (-106+45 µm) and Techphy (-63+50 µm) were air plasma sprayed using a dc plasma gun (PTF4 type) and were collected in an argon atmosphere. Preliminary experiments indicated that different mechanisms are likely to occur during the in-flight oxidation of particles. Mass transfer from surface to interior of particle occurred forming oxide islands in particles. The mass transfer is governed by convective movements inside liquid particles within plasma jet core due to higher plasma-particle kinematic viscosities ratio and particles Reynolds number higher than 20. The islands were composed of metastable phases consisting of mixed oxide of Fe and Cr, likely in a nonstoichiometric form of FeCr2O4. Convective movements within particles cease roughly outside of the plasma jet core and classical surface oxidation was found to be the dominating phenomenon forming the surface oxide layer. Moreover, the molten surface oxide outside the jet core is entrained to the tail of the particle if plasma conditions promote higher particle temperature, velocity and Re number.
Insights to Spraying Conditions, Microstructure and Properties and Their Statistical Correlation for Different Thermal Spraying Processes Using Complementary Characterization Methods
Authors: Margadant N. , Siegmann S. , Keller T. , Wagner W. , Kulkarni A. 
Published: September 2022

Abstract
In many empirical studies on the structure and properties of thermally sprayed coatings, a set of two predefined parameters (e.g. porosity and elastic modulus) is correlated over a narrow range of structural variation assuming a continuous correlation function. Such a data evaluation assumes the existence of physical correlation’s between material behavior and microstructure. The experimental approach, undertaken in this study, comprises a maximum range of morphologies for starting materials with nearly identical chemical compositions to reveal the influence of microstructural changes of diverse defect species on different coating properties. The large matrix of structural and physical data is statistically correlated without any preconceived assumptions concerning the mathematical functions or the physicochemical nature of the property-microstructure-correlation’s. The divergent morphologies are realized by using different coating processes such as vacuum (VPS) and atmospheric (APS) plasma spraying, water stabilized plasma spraying (WSP), wire arc (WAS)- and flame spraying (FS), including variation of process specific parameters. The microstructure is systematically analyzed along length scales starting from defects in the micrometer down to the nanometer range. The microstructure and its anisotropy is quantified by small angle neutron scattering (SANS). The phenomenological coating behavior is successively investigated starting from basic properties such as electrical and thermal conductivity, elastic constants, residual stresses up to application oriented properties such as wear resistance. Property combinations presuming high sensitivity to microstructural changes are preferentially characterized and statistically correlated.
Field Electron Emission from Surface of Plasma Sprayed and Laser Engraved AI2O3+13TiO2 and Al2O3+40TiO2 Coatings
Authors: Znamirowski Z. , Czarczynski W. , Campana F. , Janssen J.-P. , Rivenet M. , Vannier R.-N. , Pawlowski L. 
Published: September 2022

Abstract
The powders of alloys Al2O3+13wt.%TiO2 and Al2O3+40wt.% TiO2 were plasma sprayed onto aluminum rolls coated initially with Ni20Cr bond deposits. The coatings were subsequently ground, polished and submitted to laser engraving. The engraving, similar to that applied for anilox rolls manufacturing, enabled production of three different patterns with the line densities of 60, 100 and 200 1/cm and depths of about 80, 50 and 10 µm correspondingly. The patterns were engraved under angle of 60° that corresponds to a honeycomb geometry of cells. Emission current, for the electric fields up to 150 V/µm, was in the range of 10-7-10-4A for coatings containing 13 wt.% of titania and, in the range 10-11–10-9 A for that of 40 wt.% of titania. The SEM observations of engraved coating morphology was made in order to find the electron emission spots.
Effect of Particle Size and Spray Distance on the Features of Plasma Sprayed Cast Iron
Authors: Morks M.F. , Shoeib M.A. , Tsunekawa Y. , Okumiya M. 
Published: September 2022

Abstract
Superior wear resistance property of cast iron coatings is strongly linked to their microstructure. Graphite formation in plasma sprayed cast iron deposit is the main reason for this distinct phenomenon owing to its self-lubricant property. Since solidification rate affects graphite formation, optimization of spray conditions such as substrate temperature, chamber pressure, particle size and spray distance are required to slow down the solidification rate. The adhesion property of cast iron coating depends strongly on the adhesive strength between the first deposited layer and the substrate. It is important to improve the adhesive strength of splats by optimization of spray parameters. In this paper, cast iron splats were sprayed on aluminum substrate by plasma spray method using high Si and Al cast iron powders in Ar atmosphere. The effect of particle size and spray distance on splat microstructure (including graphite distribution) and its adhesive strength has been investigated. A correlation between microstructure and solidification rate was also introduced. Spraying by using large particle size leads to an increase in the number fraction of disk splats and a decrease in the splat’s adhesive strength. In contrast, the number fraction of star-shaped splats and their adhesive strength increase by spraying using small particle size. Longer spray distances lead to a decrease in number fraction of disk splats and their adhesive strength. The rear-side observation of cast iron splats sprayed with different spray distances show no distinct difference.
Effect of the Chamber Pressure on the Structure of a Plasma Jet
Authors: Bolot R. , Klein D. , Coddet C. 
Published: September 2022

Abstract
The aim of the present study concerns the effect of the chamber pressure on the structure of a plasma jet. Conventional vacuum plasma spray equipments are currently designed to operate at chamber pressures higher than 10 mbar. Nevertheless, recently, the exploration of lower pressure level conditions seems to have become a new challenge. In the present study, pressure levels as low as 0.5 mbar have been achieved and tested. It is shown that a decrease in the chamber pressure provides a longer and enlarged plasma jet whose length may be longer than one meter for the lowest pressure levels considered. CFD modeling results and photographs performed under vacuum conditions are proposed for the case a standard conical nozzle. Some additional characterizations (using thermocouples and emission spectroscopy) were also conducted but the results are currently being analyzed.
Control of Particle Temperature, Velocity, and Trajectory in the Thermal Spray Process
Authors: Fincke J.R. , Swank W.D. , Bewley R.L. , Haggard D.C. , Gevelber M. , Wroblewski D. 
Published: September 2022

Abstract
The plasma-spray process features complex plasma-particle interactions that can result in process variations that limit process repeatability and coating performance. This paper reports our work on the development of real-time diagnostics and control for the plasma spray process. The strategy is to directly monitor and control those degrees of freedom of the process that are observable, controllable, and affect resulting coating properties. This includes monitoring of particle velocity and temperature as well as the shape and trajectory of the spray pattern. Diagnostics that have been developed specifically for this purpose and integrated with a closed loop process controller are described.
Sensitivity Study of Four On-Line Diagnostic Systems for Plasma Spraying
Authors: Nylén P. , Lemaitre J. , Wigren J. 
Published: September 2022

Abstract
The introduction of sensor techniques has lead to a major change in the possibility to on-line control the plasma spraying process. By the use of such techniques reproducibility of the process can be enhanced by a more precise process control of flame and particle in-flight characteristics. In this paper a comparative study of four different on-line diagnostic systems and their sensitivity is presented. The systems evaluated are: the Particle Flux Imaging (PFI) from Zierhut Messtechnik GmbH, the PlumeSpector from Tecnar Automation Ltee., the Spray and Deposit Control (SDC) from the University of Limoges/Snecma Inc. and the DifRef M from Flumesys GmbH. Tests were performed using plasma spraying of a Nickel- Aluminium alloy. A statistical design of experiments (DOE) was defined using a ± 5% variation of the five process parameters current, argon flow rate, hydrogen flow rate, powder feed rate and carrier gas flow rate. System principles, sensitivity results are given and the systems suitability for use in industrial production is discussed.
Particle Temperature and Velocity Measurements by Two-Wavelength Streak Imaging
Authors: Craig J.E. , Parker R.A. , Lee D.Y. , Wakeman T. , Heberlein J. , Guru D. 
Published: September 2022

Abstract
A two-wavelength particle imaging sensor has been developed to measure temperature and velocity of individual particles in most thermal spray devices. The sensor provides continuous updates to particle condition profiles, histograms and correlation’s. The software locates particle streaks, determines the intensity ratio and dimensions of each streak, and calculates the particle temperature and velocity. Many forms of advanced materials processing technologies, such as thermal spray, spray-forming and atomization have considerable need of process control sensor technology. These measurements provide the basis for application of the sensor to many of these processes. Particle temperature and velocity measurements of plasma-sprayed ceramic powder were obtained using the sensor. The average temperature varied from 2800 K to 3000 K as the current to the plasma was increased from 700 amps to 900 amps. The average velocity varied from 85 m/s to 99 m/s over the same range. These results compare favorably with similar measurements, reported in the literature. With its full-stream field of view, the vision-based particle sensor can be applied to control strategies for the purpose of providing stable particle temperatures and velocities over long duration plasma spray processes.
Simple Self-Selective Method of Velocity Measurement for Particles in Spray Coating
Authors: Lebedev M. , Akedo J. 
Published: September 2022

Abstract
A simple, low-cost technique for measuring the velocity of particles for spray coating methods is presented. The accuracy of measurement is determined by the precision of the only quantity of geometrical size of the deposited layer. Self-selection of the particles with parameters suitable for deposition occurs. For typical deposition conditions, a velocity of 650 m/s was detected. This technique allows in situ velocity monitoring during process.
Real-Time Control for Plasma Spray: Production Issues and Distribution Implications
Authors: Gevelber M. , Cui C. , Vattiat B. , Wroblewski D. , Fincke J.R. , Swank W.D. 
Published: September 2022

Abstract
This paper investigates the advantages that an advanced control system can provide for plasma spray deposition in terms of variation reduction and greater ability to engineer coating structure. We report our work on implementing a feedback control system that automatically adjusts system inputs to maintain the desired particle states in spite of process variations. The limitations and performance capabilities of both feed forward and real-time control are evaluated. Important system characteristics needed to develop such controllers are discussed including dominant nonlinearalities, dynamics, cross-coupling, distributions, and sensor issues. Performance is evaluated in terms of engineering coating structure and production objectives.
Integration of a Feedback Controller into a Standard In-Flight Particle Sensor
Authors: Blain J. , Pouliot L. , Nadeau F. , Bisson J.-F. , Vaudreuil G. , Moreau C. 
Published: September 2022

Abstract
This paper first presents some typical results that illustrate the need for closed-loop stabilization of plasma spraying processes. A strategy to identify the most efficient control actuators is then explained, followed by a description of a robust operator closed-loop feedback method. This method can be directly implemented on current commercial sensors and applied to older spraying equipment than cannot easily be interfaced to modern computers. The method is also capable of implementing tight computer-controlled closed-loop feedback on more modern equipment. A discussion of minimum sensor requirements is also given.
Modern Gas Supply Systems for Thermal Spraying
Authors: Park Dave , Krömmer W. , Heinrich P. 
Published: September 2022

Abstract
Industrial gas product supply has a dramatic influence on the quality, consistency, and performance of thermal spray coatings and their application equipment. The various thermal spray processes test the limits of common gas supply modes in the areas of safety, pressure, purity, storage, and recovery. Selection criteria for the gas and supply mode, using the latest methods, are discussed for plasma, HVOF and cold spray techniques.
How to Improve the Reliability and Reproducibility of Plasma Sprayed Coatings
Authors: Fauchais P. , Vardelle M. 
Published: September 2022

Abstract
This paper presents what is our actual knowledge in the development of the on-line control of the plasma spray process. First the influence of the different parameters on coating properties is recalled. The dependence of particle parameters at impact on macroscopic parameters such as the gas composition, its enthalpy, the injection conditions… is discussed together with the possible actions to compensate for the voltage drop due to electrodes erosion. The transient aspect of the plasma jet due to the arc root fluctuations and their consequence on particle parameters is also presented. Then the different sensors able to work in booths harsh environment are described. The way they are used, informations they provide, the possibility they give to monitor the spray parameters for a good working area is discussed. At last what would really be necessary for a real on-line control is presented and it is concluded that we are still far to achieve this objective.
The Influence of Spray Parameters on Ni20Cr Coating Properties Using On-line Optimization Process
Authors: Guilemany J.M. , Nin J. , Miguel J.R. , Navarro J. , Gaona M. 
Published: September 2022

Abstract
Thermal and kinetic history of particles inside the jet plume of atmospheric plasma spray (APS) provide the particles with a certain velocity and temperature prior to the impact onto the substrate. Adjusting these velocity and temperature allows to control final coating's properties. The properties of the obtained coatings mostly depend on particle's conditions prior to the impingement. A set of experiments were done in order to optimize an atmospheric plasma process by means of an online monitoring system. The study is done by changing some spraying parameters that certainly affect the velocity and the temperature of the in-flight particles. Plasma gas flow rates and spraying distance were the parameters changed in this work, whereas all the other spraying conditions were kept constant. On-line monitoring system Spray-Watch (Oseir Ltd.) was used to achieve the parameters optimization by the measurement of velocity, temperature and spatial distribution of the Ni20Cr inflight particles. The study of the coated samples includes microstructure characterization by means of Optical Microscopy (OM), Scanning Electron Microscopy (SEMEDS) and X-ray diffraction to study the effect of the spraying parameters in phase composition. Roughness measurements and mechanical properties are also included.
On-Line Monitoring Assisted Spray Process Optimization of Thermal Barrier Coatings
Authors: Tricoire A. , Legros E. , Vardelle A. , Ahmaniemi S. , Vuoristo P. , Mäntylä T. 
Published: September 2022

Abstract
The objective of this study is to increase the deposition rate in the plasma-spray manufacturing of thermal barrier coatings without altering the quality of the coatings. The experimental part involves the measurement of in-flight particle characteristics and analysis of coatings properties when varying the hydrogen content of the plasma-forming gas, the torch nozzle diameter and the powder feed rate. The experimental results of particle measurements are discussed in the light of the gas flow fields projected by a 3-D model of the plasma spray process.
Influence of Secondary Hydrogen on the Microstructure of Plasma-Sprayed Yttria-Stabilized Zirconia Coatings
Authors: Bisson J.F. , Moreau C. , Dorfman M. , Dambra C. , Mallon J. 
Published: September 2022

Abstract
The influence of secondary hydrogen and current on the deposition efficiency (DE) and microstructure properties of yttria-stabilized zirconia (YSZ) coatings was evaluated. In order to better understand the influence of the spray process on coating consistency, an YSZ powder, -125+44 µm, was sprayed with nitrogen/hydrogen parameters and a 9MB gun. DE and coating porosity produced using two different spray gun conditions yielding the same input power were compared. Amperage was allowed to vary between 500 A and 560 A and hydrogen was adjusted in order to maintain constant power, while nitrogen flow was kept at a fixed level. Several power conditions, ranging from 32 to 39 kW, were tested. Different injection geometries, i.e., radial with and without a backward component, were also compared. The latter was found to produce higher in-flight temperatures due to a longer residence time of the powder particles in the hotter portion of the plasma. Porosity was based on cross-sectional photomicrographs. In-flight particle temperature and velocity measurements were also carried out with the DPV-2000 for each condition. Test results showed that DE and coating density could vary significantly when a different hydrogen flow rate was used in order to maintain constant input power. On the other hand, DE was found to correlate very well with the temperature of the in-flight particles. Therefore, to obtain more consistent and reproducible DE and microstructures, it is preferable to maintain constant the in-flight particle temperature instead of keeping the input power constant by adjusting the secondary hydrogen flow rate for obtaining more consistent and reproducible DE and microstructures.