bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Ternary Gas Mixtures on the Microstructure of Refractory Metals and Alloys Deposited by Low Pressure Plasma Spraying
Authors: Bamola R. , Sickinger A. 
Published: August 2022

Abstract
To overcome the problem of depositing dense refractory coatings, a study was undertaken on the effect of using three plasma gases simultaneously when depositing tungsten and tungsten alloys utilizing Low Pressure Plasma Spraying (LPPS). A greater degree of control of the plasma flame temperature, jet velocity, and heat transfer capability is believed to occur when using ternary gas mixtures. Samples were prepared and coated using Argon, Helium, and Hydrogen in different ratios. Variations of chamber pressures were used as an additional parameter to control and optimize the deposits. The samples were sectioned and analyzed. Microstructural features such as porosity, unmelted particles, and grain size, were characterized using optical and Scanning Electron Microscopy (SEM). Fractography was used to determine lamellar thickness and distribution. Mechanical properties were evaluated by measuring the microhardness of the different coatings in comparison to one another.
HVOF Burner System, Designed with Special Regard to Heat Management
Authors: Nassenstein K. , Josefiak L.-A. , Kill S. 
Published: August 2022

Abstract
Since the introduction of the HVOF process by J. Browning in 1982, gun design and spraying parameters have changed to achieve increasing gas resp. particle velocities. One exeption among the up-to-date HVOF systems is the GTV K2 Burner System. From the very first design study, special attention was payed to optimum heat management within the gun. This article discusses the principles of HVOF burner system, that is designed with special regard to heat management, illustrates gun behavior, and describes the results of various GTV K2 applications. The discussion covers the processing of fine powder grades, low melting materials, and oxidization sensitive materials. It is concluded that, solely in case of the K2, the injected kerosene is completely burned inside the combustion chamber.
Evaluation of Interfacial Adhesive Toughness by Simulation of Crack Propagation in Interfacial Indentation Test
Authors: Liu G. , Mouftiez A. , Robin C. , Panier S. , Lesage J. 
Published: August 2022

Abstract
One of the methods used for the evaluation of coating adherence consists of determining an apparent interfacial fracture toughness through interfacial indentation in the cross-section of the coated system. In the present paper the interfacial crack propagation in a thermal spray coated system, during interfacial indentation test, was studied by finite element method. A Vickers indenter was applied at the coating/substrate interface to perform indentation test. In order to simulate the cracking, an initial semi-circular crack lying at the interface between the substrate and the coating was considered. Since the cracks resulting from interfacial indentation test have been reported to have a semi-circular shape, the crack was forced to advance by a uniform distance normal to the crack front in the plane of interface at each step of calculation. In these conditions it was shown that the interfacial crack has a mixed fracture mode. An apparent interfacial fracture energy Jca was calculated by this method to evaluate the interfacial adhesive toughness. The model was applied to study the crack propagation at the interface between a Cr3C2-NiCr HVOF coating and a grey cast iron substrate. A reasonable agreement between the calculation results and reported experimental data was found.
Cold Spray Flow Modeling and Validation
Authors: Jodoin B. , Raletz F. , Vardelle M. 
Published: August 2022

Abstract
In Cold Gas Dynamic Spraying the nozzle is a key part that must be optimized to maximize the injected particle acceleration and improve the coating quality. In this study an axi-symmetric two-dimensional mathematical model is presented and used to predict the flow inside a commercial cold spray nozzle and the particle velocity at the nozzle exit. Comparisons between the model results and the measurements made show that the model allows predicting accurately the particle velocity in the cold spray jet even in the presence of shock waves. The study shows that the particle exit velocity depends on the type of propellant gas used and the stagnation temperature and pressure. Following this work, the design of nozzles for specific applications using this mathematical model can be considered.
Cold Spraying – Innovative Layers for New Applications
Authors: Marx S. , Paul A. , Köhler A. , Hüttl G. 
Published: August 2022

Abstract
In the last years, results of many studies have been published contributing to enhance the understanding of the fundamental mechanisms of cold spray coating generation and bonding, as well as coating characteristics. From the point of view of a job shop in thermal spraying and a user of cold spraying equipment, the procedure in development of new applications is presented. Besides the technical requirements, some general factors determining the success of industrial use of cold spraying are shown. Examples of cold sprayed coatings are described to show on one hand the possibility of a fast integration of this new technique in established coating jobs and on the other hand the exploration and use of the new possibilities of cold spraying and the development of applications, which still have not been in the focus of thermal spraying. Suggestions to further research and development activities are made on the base of practical cold spray experience.
Nozzle Exit Geometry and Lump Formation in APS
Authors: Choquet I. , Björklund S. , Johansson J. , Wigren J. 
Published: August 2022

Abstract
Plasma spraying operations performed with high carrier gas flow rate may improve the coating properties but they can also lead to lump formation and thus coating defects. The damaged work piece must then be stripped and recoated, which implies a considerable waste in terms of coating powder, energy and time. The aim of this study was to determine the cause of the lumps, and propose process modifications for avoiding their formation while keeping the coating quality. Numerical simulations based on 3D turbulent Navier-Stokes equations in local thermal and chemical equilibrium were carried out to understand the problem and estimate the feasibility of the proposed solutions. The computational results were supplemented by experiments for validation. A first set of investigations was focused on the location and orientation of the powder port injector. It turned out that it was not possible to keep the coating quality while avoiding lump formation by simply moving the powder injector. A new geometry of the nozzle exit was then designed and successfully tested for a first application with Ni-5Al powder used in production.
Integrating a Deposition Model for Off-Line Spray Tools Programming
Authors: Trifa F.-I. , Montavon G. , Coddet C. 
Published: August 2022

Abstract
This study had for objective to build a deposit mathematical model to be interfaced with robotic simulation to predict some coating properties. The deposit model is based on a database considering the effects of the spray angle, the spray distance, the relative torch – substrate speed, the number of passes and the position of the powder injector relative to the torch trajectory. The deposit geometry, its porosity level, its hardness and its apparent Young modulus were the considered deposit geometrical and structural attributes. The processing parameters – deposit attributes relationships were analyzed and combined in a set of equations that constitute the core of the model. This set of equations was then encapsulated in the developed software to interface the deposit model with spray gun trajectories issued from robotic simulation software. Such a system permits hence to predict some deposit properties for a given set of processing parameters and for a given trajectory. This paper presents the experimental procedure leading to the determination of the deposit model, a few relationships, the procedure to define optimized simulated trajectories, and the procedure to simulate the deposit manufacturing. Then, some results are provided and discussed in relation to experimental data.
XFEM Modeling of Effective Thermal Properties and Fracture of Thermal Barrier Coatings
Authors: Michlik P. , Racek O. 
Published: August 2022

Abstract
An in-house Extended Finite Element code is employed to simulate the effect of cracks within a TBC system with a YSZ top coat and a mullite intermediate layer deposited onto a SiC substrate. Microstructural level analysis consists in decomposition of a micrograph into an image showing the crack structure and then image capturing the distribution of pores and coating materials. This later image is used to generate the adaptive Finite Element (FE) mesh while the first image defines a discontinuous enrichment of the FE approximation of the displacement field. This analysis process is versatile and takes into account the presence of the cracks within the coating so that the fracture behavior can be estimated. Stress intensity factors of selected through-thickness cracks were calculated from a domain form of the interaction integral. The concept of XFEM is also extended to thermal analysis. Again, the FE approximation is enriched in a way similar to the previous case; however the weak form is modified to enforce proper temperature changes across the crack width. The cracks are modeled as thermal insulating layers with resistance determined from the kinetic theory of gases. The effective thermal conductivity of the coating is, thereby, predicted.
Short-Pulse Laser Post Processing of PTA and Thermal Sprayed Wear and Corrosion Resistant Coatings
Authors: Wilden J. , Bergmann J.P. , Emmel A. 
Published: August 2022

Abstract
Laser post treatment is a well known procedure in order to homogenize the geometry, the microstructure and aspect of the surface of thermal sprayed coatings. Furthermore the properties of coatings, as for example corrosion resistance can be improved, as a sealing layer is induced by remelting. High power laser sources as CO2-, Nd:YAG as well as diode laser are used for this aim. They allow a very deep remelting zone in a depth-range between 0,2-2 mm. Contemporarily the hard phases as well carbides in the coating degenerate due to the very high heat input and the wear resistance of the coating decreases. Short-pulse laser are very advantageous for processing surfaces in a very narrow band (under 50 µm). Applications are nowadays developed for the surface treatment of aluminium cylinder running surfaces and of titanium implants. The short-pulse laser post processing can be a very profitable methods to improve the behaviour of coatings without damaging hard phases. Investigations on remelting of PTA- and thermal sprayed coatings with a Nd:YAG-short-puls laser and with an excimer laser are reported in this paper. Surface quality as for example roughness of PTA-coatings with tungsten carbides (NiCrBSi+60%WSC) could be improved and a slight surface sealing layer was induced. Depending on the adopted laser system, different surface roughness profiles can be reached. In further investigations the suitability of the method was proven for thermally sprayed coatings of NiCrBSi
The Coating Properties of Carbide Cermet Coatings Produced by HVOF-YAG Hybrid Spraying
Authors: Kuwashima T. , Saitoh T. , Saitoh H. , Horie H. , Ohmori A. 
Published: August 2022

Abstract
Although thermal spraying technique is used in many industries, it suffers from several problems. For example, the hardness of the coatings is lower than that of sintered material for the incompleted cohesiveness. An yttrium aluminum garnet (YAG) laser was used during HVOF spraying to improve the properties of the applied coating. Several carbide powders were used as thermal spray materials, and stainless steel (SUS304) was used as substrate. Coatings were sprayed by hybrid spraying method, which was combined HVOF spraying with YAG laser. The hardness of coatings sprayed by hybrid spraying was higher, and the weight loss in a blast-erosion test was smaller than that of coatings applied by HVOF spraying only. The particles deposited in the coatings obtained by hybrid spraying were very fine. Laser irradiation to the HVOF flame improve the adhesion strength between particles and the deposition of fine carbide particles in the coating. It was considered that mechanism of coating strengthening in hybrid spraying was resulted from strengthening of cohesiveness by heating effect and decreasing of porosity by flattening effect according to observation results of Ni splats sprayed by hybrid spraying method.
Plasma Torch Developments
Authors: Dzulko M. , Forster G. , Landes K.D. , Zierhut J. , Nassenstein K. 
Published: August 2022

Abstract
With the goal to improve the plasma spraying technique a considerable number of plasma gun types using different physical principles have been developed in the past. In this paper for conventional DC discharge plasma torches widely used in industry, some aspects of operation as arc fluctuations and non-symmetric plasma jets are discussed. Different construction principles with single or multiple electrodes as well as with one-piece or cascaded nozzles are compared. Finally a new torch concept is presented.
LPPS Thin Film Technology for the Application of TBC Systems
Authors: Refke A. , Hawley D. , Doesburg J. , Schmid R.K. 
Published: August 2022

Abstract
Low pressure plasma spraying (LPPS) is well established as coating process for the deposition of TBC systems for industrial gas turbines as well as aero applications under industrial standards. With the extension to LPPS Thin Film process, the operating conditions can vary in a wide range from only a few mbar up to typically 200 mbar which imposes different characteristics of the corresponding spray conditions and resulting coating properties. The flexibility of this process allows for subsequent coating of different layers for bond and top coat of a complex TBC system by using only a single TS technology. This simplifies the operational needs for industrial production and offers the potential of increased technological and economical benefits. Depending on the process conditions a broad variety of different TBC layers, multi-layer systems including bond coats & diffusion barriers, dense, porous or graded YSZ layers as well as EB-PVD like layers with columnar microstructure, can be realized using the LPPS-TF technology. Proper adjustment of spraying conditions and suited material selection allows controlling the grade of “columnarity” of the layer. Thermal cycling as well as GE erosion tests have been used to characterize and benchmark the coating quality. Transfer of such coatings onto real turbine blade has demonstrated that all substrate areas could be coated with a columnar TBC structure up to a thickness of about 250 microns. This offers the possibility either to develop coatings with optimized performance or of comparable quality at reduced production costs when compared to established vapour deposition techniques like EB-PVD. This paper presents an overview on the development of various TBC systems such as multi-layers or columnar structures by using the LPPS Thin Film technology.
Functionally Graded Coatings by HVOF-Arc Hybrid Spray Gun
Authors: Kosikowski D. , Batalov M. , Mohanty P.S. 
Published: August 2022

Abstract
Functionally graded coatings with continuous changes of microstructures and properties across the material are expected to have low residual and thermal stresses and improved bonding strength between base materials and the ceramic coatings. This paper presents a technique to produce high-performance graded coatings in which the mix of components in the coating changes continuously from the base materials out. A hybrid HVOF-Arc spray gun has been employed to create such coatings. The metallic matrix material is utilized in the form of wires that are fused by arcing process. A high velocity combustion jet carrying the ceramic particles atomizes the molten material and mixes the ceramic particles with the matrix material. The feed rate of the matrix material and the reinforcing material are controlled together giving a systematic variation of the reinforcement phase. Two material systems; WC-16%Cr3C2-Ni-5%Al and B4C-Al(5%Si) have been investigated. The in-flight particle characteristics of the process have been characterized. The resulting microstructures and process capabilities are discussed.
Injection Conditions and In-Flight Particle States in Suspension Plasma Spraying of Alumina and Zirconia Nano-Ceramics
Authors: Oberste Berghaus J. , Bouaricha S. , Legoux J.-G. , Moreau C. 
Published: August 2022

Abstract
Plasma spraying of ceramic nano-powders suspended in a liquid carrier medium is an emerging technology, which allows the formation of thinner coatings with microstructures more refined than conventional plasma spraying. An external injection system, where the suspension enters the plasma jet radially, is installed on a F4-Sulzer Metco dc torch for the production of nanostructured Al2O3 and ZrO2 coatings. The effect of injection parameters, such as initial droplet diameter, droplet velocity and suspension flow rate is studied. The suspension droplets are continuously generated through an exchangeable micron-sized nozzle with a superimposed pulse of variable ultrasonic frequency. The heat transfer from the plasma to the liquid feed is optimized at high droplet velocity, moderate counter-current injection angle and flow rates not exceeding a threshold value, which depends on the plasma enthalpy and the latent heat of the suspension medium. A significant effect of initial droplet size (220 – 500 µm) or solid concentration (5 – 15 %) is not observed. In-flight particle states are measured for different plasma conditions, and are related to the resulting microstructures by SEM and XRD. High particle temperatures give rise to a refinement in crystallite size, while the particle velocities govern the deposition efficiencies and porosity levels. The results show that the particles follow closely the gas flow in the free stream, as well as in the stagnation boundary layer close to the substrate by virtue of their limited inertia. The prominent difference in microstructure between highly porous alumina and very dense zirconia coatings is explained in terms of particle impact velocities, which are simulated for typical operating conditions as a function of particle size and free-stream gas velocity.
Comparative Study of the Properties of WC-Co Nanostructured and Bimodal Coatings, Sprayed by High Velocity Oxy-Fuel (HVOF)
Authors: Guilemany J.M. , Dosta S. , Nin J. , Miguel J.R. 
Published: August 2022

Abstract
Over the last years, the grain size reduction to the nanometric scale has experienced an increasing interest because of its enhanced properties. This study is based on WC-Co cermet materials, which have a great application in the wear resistance materials field. In the Thermal Spray Center (CPT) of the University of Barcelona, two coatings using nanostructured and bimodal WC-Co cermet powders have been obtained by means of High Velocity Oxygen-Fuel (HVOF) technique. Both were sprayed under the same spraying parameters. Structural characterization for both feedstock materials and coatings have been performed using XRD, SEM and TEM. The friction wear resistance of the coatings has been studied by Ball-on-Disk test (ASTM G99-90), and the abrasive wear resistance has been quantified by Rubber-Wheel test (ASTM G65-91). Finally, the corrosion resistance has been studied by electrochemical techniques and a salt fog spray test. The nanostructured coating shows more hardness, but the bimodal coating shows better abrasive and friction wear resistance. Both coatings shows good corrosion resistance, better than the conventional coatings of WC-Co. The bimodal powder have the added advantage of being not as expensive as the nanostructured powder, and even providing better properties.
Formation of Nanoscale Composite Coatings via HVOF and Wire-Arc Spraying
Authors: Branagan D.J. , Marshall M.C. , Meacham B.E. 
Published: August 2022

Abstract
In the materials world, there are two distinct usages of the term nanotechnology; Particulate Materials Nanotechnology (PMN) and Bulk Materials Nanotechnology (BMN). Both approaches have been used in attempts to produce nanoscale coatings with characteristic length scales from 10 to 100 nm. While particulate strategies are widespread, a different approach is presented which focuses on producing coatings through a solid / solid state transformation which results in the refinement of the microstructural scale (i.e. phase / grain size) down to the nanoscale regime. The essential features of BMN are the 2-d grain and phase boundary defects and achieving this nanoscale regime is key to enhancing bulk properties. This paper will attempt to clarify the terminology, definitions, and usages of the term nanoscale to clear up misconceptions and clearly show the salient features allowing for the production of nanoscale microstructures on an industrial scale. A clear demonstration of this achievement will be presented with a case study on the formation of amorphous / nanocomposite coatings while processing in air using off the shelf thermal spray technology using conventionally sized feedstock. Examples of nanostructured HVOF and wire-arc as-sprayed and heat treated coatings with average phase sizes of 50 nm and 80 nm respectively will be presented using detailed TEM micrographs.
Study of Ni/Al2O3 Deposition on Metallic Surface using RF Plasma Process
Authors: Oukacine L. , Gitzhofer F. , Abatzoglou N. , Gravelle D.V. 
Published: August 2022

Abstract
This work is aimed at acquiring knowledge on successive deposition of alumina and nickel coatings on a metallic substrate using an RF plasma torch. The composition and morphology of various Ni/Al2O3 steam reforming catalysts, prepared by plasma spraying of precursor nickel suspensions, are studied in this work. As Ni/γ-Al2O3 is a well known reforming catalyst it was decided to study the deposition of a particular catalytic formulation on a metallic substrate. The purpose of this study was to find the means of building 2D monolithic catalysts by plasma deposition. Since 2D monolithic catalysts are non-porous, their specific areas available for hosting the catalytic reactions are low. Thus, It is essential to have very good dispersion of the active catalytic sites. Such dispersion is only possible only if the deposit can take place at the nanometer scale. The suspension plasma spraying is assessed for its ability to produce such structures. This method permits the formation of nanocrystalline structures within a few seconds. The main difficulty is the control of the various spraying parameters in order to obtain satisfactory deposition. The Ni/γ-Al2O3 catalysts so obtained are characterized by scanning electron microscopy, field electron microscopy and X-Ray diffraction.