bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Benefit of an On-Line Diagnostic System for the Optimization of Plasma Spray Devices and Parameters
Authors: Refke A. , Barbezat G. , Loch M. 
Published: June 2022

Abstract
The coating characteristics of plasma sprayed layers are strongly related to the spray parameters and the gun design which also determine the state of the sprayed powder particles upon impact. On-line optical measurements of particle velocity and temperature can be used for the optimization of the spray parameters as they provide information of both, characteristic of the coating as well as process stability and performance of the plasma process. With the DPV-2000 diagnostic system the correlation between particle and coating characteristics have been investigated, especially for the new Triplex technology. Differences observed in the distribution of the particle properties between the Triplex and F4 gun are due to different standard spray parameters and correlated to the inherent difference of the operation principle of both plasma guns. The typical three fold symmetry of the Triplex plasma and powder injection is observed within the particle distribution pattern which also depends on the type of powder and spray parameter used. With the help of DPV-2000 measurements it is also possible to demonstrate the excellent process stability of the Triplex gun and to define and adjust parameter windows for different applications in order to obtain the desired range of coating properties. The advantages of the DPV-2000 diagnostic should also contribute to an enhanced basic understanding of new spray processes such as the LPPS Thin Film technology. Experiments have been performed to prove the feasibility of particle diagnostics under these special spray conditions. First results are presented.
Verification of Particle Flux Imaging (PFI), an In-Situ Diagnostic Method
Authors: Zierhut J. , Pellkofer W. , Sagel A. , Haug T. , Landes K.D. 
Published: June 2022

Abstract
The innovative diagnostic system, PFI, records the radiation of the plasma jet as well as of the luminous particle flux. A desktop computer immediately converts these brightness distributions to a set of ellipses. The simple set-up of the system and the fast algorithm enables the utilization of the system in serial production. A statistical design of experiments (DOE) was applied for various process parameters to correlate the determined characteristic ellipses to the process parameters. Measurements of the process by DPV2000 and properties of the resultant coating were used to validate the established correlations. The results demonstrate the suitability of the diagnostic method PFI for quality control and quality assurance in serial production.
HVOF Process Control Using Almen and Temperature Measurement
Authors: Sauer J.P. , Sahoo P. 
Published: June 2022

Abstract
The HVOF process with reduced heat effect on the substrate and therefore minimal degradation of fatigue properties is now finding wide application in fatigue critical applications. The critical parameters for process control are residual stress in the deposit and maximum substrate temperature. Quality control tools for these parameters are deflection of Almen Strips (similar to shot peening) for simulating residual stress and the use of infared pyrometry for temperature measurement. Both of these methods are technically sensitive particularly in spraying of coupons to evaluate the effect of coating on material properties. Lessons learned will be presented and recommendations made for applications of these tools in controlling the HVOF process.
Effect of Substrate Properties on the Formation of Plasma-Sprayed Alumina Splats
Authors: Pershin V. , Pasandideh-Fard M. , Mostaghimi J. , Chandra S. 
Published: June 2022

Abstract
The effect of substrate characteristics on the formation of plasma-sprayed alumina splats was studied using both experiments and numerical simulation. Knowledge of the particle and substrate conditions is critical in understanding coating formation and in validating computational models. The size, velocity and temperature of the alumina particles prior to impact were measured using a particle in-flight diagnostic system. Experiments were performed on two substrate materials: stainless steel and glass. Substrate temperatures were varied in a range of 20-500°C and controlled with an electric heater. For each substrate material, a transition temperature was observed above which there was no fingering/splashing and the splats had a circular disk shape. A 3D computational model of free surface flows with heat transfer and solidification was used to simulate the impact of alumina particles in conditions given by the experiments. The splat shapes from numerical model were comparable to those of the experiments for hot stainless steel substrate. For a cold substrate, the numerical model did not show any fingering/splashing. In the experiments, however, we observed two types of splat shapes: intensive splashing with no central core and circular disk splat. Substrate surface contamination, not considered in the numerical model, was the probable cause of droplet splashing on the cold substrate.
Oxidation of Iron Particles During APS: Effect of the Process on Formed Oxide; Wetting of Droplets on Ceramic Substrates
Authors: Espié G. , Fauchais P. , Labbe J.C. , Vardelle A.M. , Hannoyer B. 
Published: June 2022

Abstract
Investigations have been carried out to study the influence of Atmospheric Plasma Spray process (APS) on the in-flight oxidation of pure iron particles. After collecting the molten droplets in-flight, XRD, SEM and Mössbauer spectroscopy are used to determine the amount and distribution of formed oxides. The results indicate that the Wüstite, Fe0.95O, is the only oxide formed during the APS. In the jet core and at the beginning of its plume, oxidation is controlled by convection within molten droplets and then for the downstream of the plasma by diffusion where the solubility of oxygen through the external oxide layer governs the growth of Wüstite. Calculations have shown that the convective movement is due to the drastic velocity difference between the plasma jet and particles. Wüstite granules can be distinguished within the particles due to the immiscibility between Fe and FeO in liquid phase. This oxide phase represents about 13 wt% of the collected particles at 100 mm stand-off distance in an Ar-H2 plasma jet (50:10 SLM) with 18 kW effective power. The amount of oxide decreases when the H2 volume percentage of the plasma, the internal diameter of the anode nozzle and the effective power increase. Sessile drop studies of molten iron on ceramic substrates are carried out to simulate the wetting of oxidized iron particles during coating formation. It is found that the oxidation state of iron particles during APS has a significant effect on the observed contact angles. A strong decrease of the contact angle is observed in the case of oxidized iron particles. In-flight oxidation of iron particles allows a better splat covering.
Splat Morphology and Graphite Formation in Plasma-Sprayed Cast Iron
Authors: Morks M.F. , Tsunekawa Y. , Okumiya M. , Shoeib M.A. 
Published: June 2022

Abstract
Fundamental aspects of a plasma sprayed cast iron coating on an aluminum alloy substrate are investigated in the present study: focusing on the effects of preheat substrate temperature (TS) and chamber pressure (PC) on the splat morphology, the adhesive strength of splats, the formation of a reaction layer and graphite. Splash-type splats appear at low TS but disk and star-shaped splats arise at high TS. Deformed substrate ridges, mainly due to the slight surface melting, are formed adjacent to the splat periphery at high TS. At low TS, pores are observed at the splat/substrate interface, which cause a decrease in the adhesion of splats. In contrast, a reaction layer composed of iron, aluminum and oxygen is ready to form at high TS. The amount of graphitized carbon increases in cast iron splats with TS. At a low PC of 26.3 kPa, disk-type splats are in the majority at a constant TS of 473 K. As PC increases, star-shaped splats appear along with disk splats. The flattening ratio of disk splats decreases with the increase of PC, because of a decrease in the kinetic energy and temperature of molten droplets. An interfacial oxide layer composed of iron, aluminum and oxygen is ready to form at high PC. The number of pores intensively increases with PC, which leads to a decrease in the adhesive strength of splats. The amount of formed graphite in cast iron splats slightly increases with PC, however, that of a rapidly solidified phase of Fe-Si-C decreases because of lowering of the solidification rate.
Splat Morphology in Spray Pattern of Plasma Spraying
Authors: Oki S. 
Published: June 2022

Abstract
New method for characterization of coating microstructures and for evaluation of coating property by means of surface morphology has been proposed. In this paper, the distribution of shape and dimensions of splat was examined using quantitative analysis of scanning electron microscope images from the surface of spray pattern as well as the surface of coating. Results obtained in this study indicate that it is necessary to analyze the spray pattern as well as the surface morphology in order to estimate the coating property by means of the distribution of splat which composes the coating. Moreover, the splats, which are in the interface between the substrate and the coating, should have the same morphology as those of the coating surface. Therefore, the analysis of the surface morphology is important even for the evaluation of coating adhesion behavior.
Microstructure Simulation of Thermally Sprayed Particles
Authors: Wilden J. , Frank H. , Müller T. 
Published: June 2022

Abstract
A large expansion of the applicability of thermally sprayed coatings will be achieved, if there is success in tailoring the coatings structure. This is particularly necessary for functional coatings with special electrochemical or electromechanical properties. The coating structure is determined by the solidification of the sprayed particles on the substrate respectively the earlier deposited particles. In addition to the particle parameters - particle size, velocity, degree of melting and temperature of the melt, the substrate surface conditions - roughness, temperature, activity - influence the spreading and subsequently the solidification of the particles and the formation of the coating. Theoretical parameter studies show the particular influence of the above mentioned parameters on the coatings microstructure. The influence of the remelting of deposited particles caused by the following particles is regarded. The amount of remelted volume depends on the particle feed rate, particle size distribution, heat content and substrate temperature. By controlling these parameters even directionally solidified coatings can be produced. The calculations are in good agreement with the experiments.
Computer Simulation of Shrouding on the Profile of a Plasma Jet
Authors: Zhang T. , Liu B. , Bao Y. , Gawne D.T. 
Published: June 2022

Abstract
Jets produced in conventional atmospheric plasma spraying are inevitably heterogeneous due to the mechanics of a rapid gas flow entering a stagnant environment. The resulting high air content together with considerable velocity and temperature variations will adversely affect the quality of coatings. This paper applies a CFD code to simulate the effect of a solid shield and a gas shroud on the characteristics of a plasma jet. The computational results show that the geometry and gas flow rates of the shrouding systems have an important influence on the quality of the plasma flow. The work shows that shrouding can substantially reduce the entrained air content and the temperature and velocity gradients in the jet. The model is applied to predict the optimum shrouding conditions for plasma spraying.
Calculated and Measured Oxygen Contents in the Gas Flow of a Shrouded Thermal Spray Process
Authors: Jamais S. , Creaven M. , Rinaldi C. 
Published: June 2022

Abstract
Shrouding a thermal spray process to reduce the oxidation of particle stream is not a new concept. Nevertheless the actual use of this idea is not very widely used in practice, due to some problems arising. In this paper the results of the study performed to optimize two shrouding devices for thermal spray are presented. Gas flows inside the device and in between its outlet and the target were modeled by Computational Fluid Dynamics both for an arc-wire and a plasma system. To validate the modeling methodology measurements were performed of the oxygen content using a gas sampling probe and a paramagnetic O2 analyzer. A good agreement between calculated and measured O2 values was obtained. Modeling results in different conditions could suggest the best shroud configuration and shielding gas flows necessary to reduce the oxygen content around the particle stream at very low values. Coatings with very low defect contents can now be produced.
Modeling of the Natural Gas HVOF Process
Authors: Bolot R. , Planche M.P. , Coddet C. 
Published: June 2022

Abstract
A supersonic external flow and high particle velocities, which lead to low porosity coatings, characterize the High Velocity Oxygen Fuel (HVOF) process. A numerical study of this process is proposed in the present work. In a first step, the PHOENICS CFD code is used for the computation of the flow inside a CDS gun and within the supersonic external jet: a two-dimensional axisymmetric geometry is used. The combustion model assumes chemical equilibrium whereas the turbulence effect is taken into account using the Chen-Kim k-ε model, which is appropriate for the computation of round jets. In a second step, an in-house code is used in order to simulate the flow/particles interactions. Finally, numerical results obtained on in-flight particle characteristics are compared with measurements obtained with the DPV2000 system.
Computer Simulation and Control of Plasma Spraying Processes
Authors: Kundas S. , Ilyushenko A. 
Published: June 2022

Abstract
Integrated technological complex for computer simulation, experimental study and practical realization of plasma spraying processes was created. Main features of development are possibility of simulation of all plasma spraying stages (moving and heating particles in plasma jet, coating structure formation, heat transfer and strained-stress state of coating-substrate system) separately and in the mode of end-to-end; data base with material and gas properties; possibility of experimental measurement of main plasma spraying parameters and entering them in the computer in the real time mode; graphic visualization of simulation and experimental measurement results; computer control of plasma spaying equipment; fabrication of initial lots of products according to developed technology. Complex is designed on the base of VPS «Plasmatechnik» equipment. Experimental measurement of particle temperature, velocity and coating temperature were conducted with original optoelectronics system. All technological and measurement equipment are connected with computer with special interfaces and working under computer control.
3-D Modeling of Gas Flow and Particle Spray Jet in Plasma Spraying
Authors: Mariaux G. , Baudry C. , Vardelle A.M. 
Published: June 2022

Abstract
This paper presents a numerical simulation of the plasma spraying of alumina particles using a three-dimensional commercial fluid dynamics code ESTET 3.4 . The objective of this study is to investigate the effect of (i) turbulence model and turbulence radial profiles at the torch exit on plasma flow and particle behavior, (ii) particle injection conditions on particle trajectories and heating and (iii) plasma jet fluctuations on temperature and velocity flow fields. The comparison of predictions with experimental measurements of gas and particle velocity and temperature, makes it possible to determine the influential parameters and set them to pertinent values.
Mathematical Modeling of Deformation and Solidification of Molten Droplet on a Flat Substrate in a Plasma Spray Process
Authors: Ilyuschenko A. , Lakubenya A. , Gromyko G. , Zayats G. 
Published: June 2022

Abstract
In the present paper mathematical model of the deformation behavior of a liquid spherical particle upon its impingement onto a solid surface, including flattening and simultaneous solidification is developed. Particle-substrate interactions are investigated for typical thermal spray process. Numerical simulation for the complete Navier-Stokes equations is based on the finite-difference method on rectangular mesh in cylindrical coordinates. The energy equation is solved for both particle and substrate regions using the adjoint conditions for the temperature. In this paper main attention is paid to investigation of the temperature in contact of the particle with substrate. In connection with the oxide films effect on the surface substrate taking onto account thermal resistance of oxide is simulated. Heat transfer process in particle and substrate has been modeled by 2-D problem of heat conduction with influencing hydrodynamic processes into molten particle. Particle solidification and the movement of the solidification front have been described by means of one-dimensional Stefan problem. Numerical results for the heat transfer process and the effect of some important processing parameters such as particle diameter, viscosity, oxide films and temperature of plasma on the flattening and solidification of a single liquid particle have been discussed. Numerical algorithms were realized in the form of applied programs complex.
Microstructural Evaluation of Plasma Sprayed Coatings Using Fractal Characterization
Authors: Bianchi L. , Llorca-lsern N. , Bertran G. 
Published: June 2022

Abstract
Depending on working parameters, plasma spraying process allows to achieve original metallic and/or ceramic coating microstructures varying from quite dense to high porosity materials. Combined to the versatility of the process in terms of coating shaping, this leads to an extended field of applications. For instance, porous coatings are required for stress accommodation or filtering applications due to their high specific area, whereas dense coatings are needed for the electrolyte in S.O.F.C technology. Past works have shown that porosity is not a convenient parameter to describe completely coating microstructure and that the main difficulty is to find a unique parameter capable to describe the microcrack network and pores distribution. In this paper we propose a fractal approach of coating microstructure based on confocal microscopy of fluorescent impregnated coatings. Fractal dimensions as well as porosity data are given and analyzed for various plasma-spayed coating microstructures. This work is a contribution to characterize plasma-sprayed coatings. Coatings properties are related to the microstructure which depends on the spraying process.
Influence of Coating Thickness on Fatigue Properties of Sprayed Co-Based Self-Fluxing Alloy with Fusing Treatment
Authors: Oh J. , Shimizu M. , Komotori J. 
Published: June 2022

Abstract
Fatigue strength and fracture mechanism of a medium carbon steel having carbon content of 0.35%C with gas flame thermally sprayed Co-based alloy coatings were investigated by rotating bending tests. After fusing treatment, machining was done to make three kinds of specimens having 0.3mm, 0.5mm and 1.0mm in coating thickness. The fatigue strength of all coated specimens was much higher than that of the substrate and that of the grit blasted ones. Especially, it was found that the fatigue strength of the specimens with 1.0mm coating was remarkably higher compared to those with 0.3mm and 0.5mm coatings. That is, fatigue characteristics depend on coating thickness, and fatigue strength increases with the increase of coating thickness. The result showed that at lower stress levels, the fatigue cracks were initiated only inside the substrate of 0.3mm and 0.5mm coated specimens (Internal failure in the substrate). At higher stress levels the fatigue cracks were initiated at the coating layer, originated from the porosity located in coating layer of all coated specimens (Coated layer failure). But no fracture mode transition was noticed for the case of 1.0mm coated specimen. The cause of the fracture mode transition depending on the coating thickness was discussed on the basis of the results from calculation of the stress at the location where the fatigue fracture was initiated.
The Influence of the Process Parameters on the Properties of Detonation Sprayed WC-12Co Coatings
Authors: Sivakumar G. , Ramakrishna L. , Jain V. , Srinivasarao D. , Sundararajan G. , Reddy G.M. 
Published: June 2022

Abstract
In recent years, the thermal spray technique has emerged as the most useful method for developing a wide variety of coatings which enhance the performance and durability of engineering components exposed to diverse forms of wear. Among the thermal spray techniques, detonation spray coating (DSC) has retained its position as one of the best available techniques for obtaining dense, wear-resistant coatings. Notwithstanding the advantages of the DSC technology over other thermal spray variants, the understanding of the fundamental aspects of this technology is still extremely limited. In view of the above, a major programme has been undertaken in this laboratory to assess the parametric impact of the key DSC process variables (oxy-fuel ratio, spray distance, powder feed rate and shot frequency) on the mechanism of coating formation and the properties of the resulting coating. As a part of the above exercise, the key DSC process variables have been varied systematically employing a statistical design and the properties of the WC-12Co coatings so obtained have been evaluated. The results of such a study are presented in this paper. In particular, it has been demonstrated that useful conclusions regarding the influence of process parameters on the properties of the WC-12Co coating cannot be reached unless the scatter in the experimentally measured coating property data is also simultaneously taken into account.
Wear Resistance of HVOF-Sprayed Carbide Coatings
Authors: Rodríguez M.A. , Klisans J. , Bavaresco L. , Scagni A. , Arenas F. 
Published: June 2022

Abstract
The cermet materials have been developed to protect surfaces against wear and corrosion. In cutting tools technology as well as chromium replacement, WC coatings have been used to improve life and performance at higher temperatures. This work compares the abrasion and adhesion resistance of a WC-Co mixed in a x:y relation with a NiCrBSiW alloy deposited by High Velocity Oxy-Fuel (HVOF) process using a JP-5000 gun in two conditions: as sprayed and thermally treated. Abrasion and adhesion tests were performed according to ASTM G-65 and ASTM C-633 respectively. The microstructure and composition of the coatings, failure and worn surface were evaluated using Optical (OM) and Scanning Electron Microscopy (SEM) as well as X-Ray energy Dispersive Spectroscopy (EDX) and X-Ray diffraction (XRD). Vickers microhardness under a 500g load has been averaged from 8 indentations per sample. The results showed that the coatings studied presented a similar microhardness as well as good abrasion resistance. The best behavior of the post-heated coating could be attributed to a lower porosity, better distributions and effective cohesion between hard phases. Partial recrystallization of the amorphous phase produced during the thermal spray process into sub-carbides could be related to the improvement in abrasion resistance of the post-treated coating.