bluuebunny/crossref_metadata_2025_split huggingface dataset:
Process Modelling to Optimise the Structure of Hollow Zirconia Particles for Use in Plasma Sprayed Thermal Barrier Coatings
Authors: Klocker T. , Clyne T.W. , Dorfman M.R. 
Published: June 2022

Abstract
A numerical finite difference model has been developed to treat the transfer of heat and momentum between a gas environment and a particle injected into it. The model is based on an explicit solution scheme for the thermal field and explicit treatment of the momentum exchange. The latent heat associated with phase changes is simulated via a post-iterative heat accumulation scheme. Particle-gas heat transfer is represented by a heat transfer coefficient, which is a function of relative gas velocity. The validity of the model is confirmed via comparisons between predicted behaviour and previously-published experimental data for thermal histories and particle trajectories. Comparisons are also presented with predictions from previously-developed models. Results are then presented for the behaviour of hollow zirconia particles, with particular attention being paid to in-flight melting characteristics. It is shown that there is an optimum combination of particle size and wall thickness for the promotion of efficient melting, for a given gas flow and temperature field.
Comparative Study of Different Sealing Methods for Thick Thermal Barrier Coatings
Authors: Ahmaniemi S. , Tuominen J. , Vuoristo P. , Mäntylä T. 
Published: June 2022

Abstract
Zirconia based, 8Y2O3-ZrO2 and 22MgO-ZrO2 thick thermal barrier coatings (1000µm), were studied with different sealing methods for diesel engine applications. Aim of the sealing procedure was to improve hot corrosion resistance and mechanical properties of porous TBC coatings. The surface of the TTBCs was sealed with two different methods, phosphate based sealing treatment and laser glazing. The thickness of the densified top layer in all cases was 50-400µm. XRD analysis showed some minor phase changes and reaction products caused by phosphate based sealing treatment and some crystal orientation changes and phase changes in laser-glazed coatings. The porosity of the outer layer of the sealed coating decreased in all cases, which led to increased microhardness values. The hot corrosion resistance of TTBCs against 60Na2SO4 - 40V2O5 deposit was determined in isothermal exposure at 650°C for 200 h. Corrosion products and phase changes were studied with XRD after the test. Short-term engine test was performed for the reference coatings (8Y2O3- ZrO2 and 22MgO-ZrO2) and for the phophate sealed coatings. Engine tests were performed at the maximum load of the engine and it was aimed to evaluate the thermal cycling resistance of the sealed coatings. All the coatings passed the engine test, but some vertical cracks were detected in the phosphate sealed coatings.
Influence of a Multi-Gas Mixture on the Performance of a HPPS Plazjet System for a Thermal Barrier Coating
Authors: Dhers J. , Goubot N. , David T. , Baudoin J. , Barthelet M. , Huet J. , Ducos M. 
Published: June 2022

Abstract
The Plazjet system usually works with a binary gas mixture of nitrogen and hydrogen for the deposition of a thick TBC (NiCrAlY as a bond coat and Zirconia as a top coat). In order to improve the performances of our spraying device and ensure good quality coating, different experiments were conducted. The substitution of N2 or the classical binary mixture N2/H2 respectively by a binary N2/He, and a ternary gas composition N2/H2/He leads to an evolution of the deposition efficiency and quality coating. In order to optimise the various ratio in the gas mixture, the evolution of experimental parameters such as voltage were analysed.
Manufacture of SiC Composite Coatings by HVOF
Authors: Wielage B. , Wilden J. , Schnick T. 
Published: June 2022

Abstract
The main application of HVOF processes is the production of wear and/or corrosion protective coatings based on cermets (e.g. WC-Co). To reduce the weight of the sprayed volume, to increase the oxidation resistance and to reduce the costs of consumables SiC based cermets are of particular interest. The outstanding mechanical, thermal and chemical properties of SiC have made this material attractive for thermal spray applications. Thermal spraying of pure SiC is impossible, because of its decomposition at elevated temperatures. The development of suitable alloys as metallic binders enables the wetting of the SiC particles with reduced reactivity between the matrix and the hard particle during the thermal spray process. In the present work starting from the metallurgical concept of the metallic matrix to the production route from the atomization of the metallic matrices, the spray drying and sintering as well as the processability of the composites is discussed. The coatings are characterized concerning porosity and SiC content using optical and scanning electron microscopy, digital image analysis, X-ray diffraction and micro hardness testing. The wear resistance of the coatings is determined by oscillating wear test. Microstructure and performance of the SiC composite coatings are discussed with respect to technical applications.
Properties of HVOF Sprayed Multi-Scale Polymer/Silica Nanocomposite Coatings
Authors: Twardowski T.E. , Reilly M. , Knight R. 
Published: June 2022

Abstract
The high velocity oxy-fuel (HVOF) combustion spray technique has previously been shown to be an excellent solution for depositing crystalline matrix nano-reinforced polymer coatings. The use of multiple scales of reinforcement is expected to improve the load transfer from the larger reinforcing particles to the matrix through the mediation of the smaller particles. The initial step in developing multi-scale coatings is studying the effects of reinforcement size on distribution and properties. Nylon 11 coatings filled with silica particulates of 7 nm, 20 nm, 10µm and 100µm have been produced using the high velocity oxy-fuel (HVOF) combustion spray process. The physical properties and microstructure have been evaluated as a function of the reinforcement size. Nylon 11 was co-milled with the fillers to a 10% volume fraction. The filler was agglomerated at the splat boundaries in the final coating microstructures. All filled coatings had significant changes in x-ray pattern relative to pure nylon 11 coatings, indicative of both increased crystallinity and changes in crystal structure. Coatings containing the smallest reinforcements exhibited improvements of 40 % in scratch and 84 % in wear resistance above those containing the largest reinforcement particles in coatings with nominal 10 vol. % of hydrophobic silica. This increase appeared to be primarily due to filler addition and increased matrix crystallinity.
Kinetic Powder Compaction Applying the Cold Spray Process—A Study on Parameters
Authors: VIcek J. , Huber H. , Voggenreiter H. , Fischer A. , Lugscheider E. , Hallén H. , Pache G. 
Published: June 2022

Abstract
Supersonic, two-phase flow of a gas/particle mixture directed towards a substrate may enable the deposition of "cold" particles onto a "cold" substrate under certain conditions. The method is commonly known as Cold Gas Dynamic Deposition or Cold Spray. Current research shows that copper can be deposited within a wide range of parameters and velocity regimes, whereas the deposition of other materials may involve difficulties depending on the material properties and substrate characteristics. Although particle velocity is recognized as being the key factor in the deposition of particles with the cold spray process, it alone cannot describe the state of the particle prior to and during impact. A simple analysis shows that the impulse of particles with equal particle velocity and size depends significantly on its density. For common engineering metals, an interval varying by up to a factor of 5 is possible considering, for example, magnesium and molybdenum. The impact force, directly dependent on the particle's impulse, governs the pressures generated during impact. In a simplified calculation, pressure values of around 3000 MPa can be very easily determined. While the particle impulse accounts for the degree of interaction - partial or complete deformation - the particle's and the substrate's lattice structure and its capacity to deform determine the type of particle substrate interaction. Depending on these properties, the substrate, the particle or both will be deformed. Evaluating impact experiments shows distinct differences between the impacts of copper, steel and aluminum particles on aluminum and steel substrates. The paper presented may be seen as a contribution to the discussion of a theory to evaluate coating and substrate combinations prior to spraying in order to predict bonding and coating build-up or to offer guidance concerning the optimum parameter set for deposition.
Microstructure and Properties of Cold Spray Nickel
Authors: Decker M.K. , Neiser R.A. , Gilmore D. , Tran H.D. 
Published: June 2022

Abstract
Electroplated nickel can be used to fabricate miniature components such as gears, linkages, and other two-dimensional mechanical structures. This process produces excellent parts, but it is slow and somewhat expensive. Because cold spray produces low oxide-content, high-density deposits at a high rate, cold spray processing might be a viable alternative to electroplated nickel components. In addition, cold gas-dynamic spray can process materials, such as stainless steel and aluminum, which can not be electroplated. The purpose of this study was to evaluate the mechanical properties of cold spray nickel in the as-sprayed and heat treated conditions, then compare them to those of bulk nickel and electroplated nickel. Characterization of freestanding structures is subjective since the final product of any thermal spray process produces a material unlike any other material formed by conventional techniques. Specifically, this investigation determines the mechanical characteristics of nickel, through metallographic imaging and tension testing. Metallographic imaging showed that as-sprayed nickel has slightly more voids than the heat-treated structures. Tension tests of the as-sprayed nickel showed little plastic behavior, while a heat treatment gives much more ductility without compromising ultimate strength.
Process Study of Thin Coating Deposition by Low Pressure Plasma Spray
Authors: Ma X.Q. , Borit F. , Guipont V. , Jeandin M. 
Published: June 2022

Abstract
In the present work thin Al2O3 coating was obtained mainly by low pressure plasma spray (LPPS). Low-porosity and low-roughness deposits resulted from the optimized spray conditions, i.e. plasma parameters, grit blasting, powder feed rate and specimen rotation speed. Results showed that LPPS processing was highly beneficial for densifying the ceramic coatings, especially when coupled to a moderate powder feed rate. Coating average surface roughness (Ra) ranged from 1.5 to 2.5 µm for a coating thickness of less than 30µm and an original substrate Ra of 1.1µm. The spray conditions were optimized particularly for a low feed rate and a high specimen rotating speed to lower surface roughness. Moreover, a specific atmosphere/temperature control device was developed (using local gas injection close to the specimen to be coated). This resulted in improving cooling efficiency, which reduced microcracking in the deposits. Mechanical pull-off adhesion test was also carried out to evaluate these low-roughness thin coatings. Adhesion was shown to be satisfactory for direct coating (i.e. without any bond coat) of a low-roughness (Ra=1.1µm) AISI 316L substrate.
Role of Some Fuel Gases on Properties of HVOF Metallic Coatings
Authors: Gourlaouen V. , Verna E. , Kho K. , Quek P.S.T. 
Published: June 2022

Abstract
HVOF spraying process is widely used to improve component life in service due to the high bond strength of the coatings, which is a result of the high particle velocity upon impact, and consequent low coating porosity. However, many parameters can affect metallic coatings properties, especially unmelted particles and oxidation level. Flame parameters, such as calorific power, combustion ratio and temperature, are of prime importance. Moreover, the fuel gas employed in this spraying process can lead to various coating properties and deposition efficiency. The aim of this work was focused on the influence of some fuel gases, namely propane, propylene (LPG) and hydrogen, on stainless steel coating characteristics. A specific domain common for those three gases was determined in order to effectively compare those gases with the same flame parameters. Flame characteristics were computed using a simple model for all the fuel gases considered. Temperature as well as calorific power were fixed. For different substrate temperatures, obtained through a special CO2 cooling nozzle system, richness was varied from 1.4 to 1.6. Microstructure investigation as well as oxide content and microhardness measurements were conducted. For the same kinetic torch parameters, thickness-per pass gave an idea of the deposition efficiency. In the range studied, deposits properties were quite similar for both LPG fuel gases. Hydrogen led to better characteristics in term of oxide content, although its deposition efficiency was a bit lower. A general law was established to link oxide content within the coatings to the flame parameters. A reasonable regression analysis was obtained for all the coatings sprayed. The combination of cooling efficiency (i.e. CO2 flow rate) and flame characteristics (i.e. interaction of the particle in flight) led to a good correlation. These correlations were further verified by spraying another metallic powder, namely Inconel 625.
Surface Modification of Plasma Sprayed Coating by Using YAG Laser Equipped With a Kaleidoscope
Authors: Chwa S.O. , Ohmori A. , Yang H. , Zhou Z. 
Published: June 2022

Abstract
Thermal spraying technique has been widely applied for the production of ceramic protection layer on metals that used in various hostile environments. However, all sprayed coatings have defects such as connected pores and unmelted particles, which deteriorate coating properties. To improve the properties of sprayed coatings, a lot of approaches have been undertaken such as laser irradiation, seal sintering with liquid alloys and sol-gel infiltration technique. Lasers are promising technological tools due to its speedy treatment and simplicity of process control. Moreover, laser treatment technology enables not only the post-treatment but also the pre and simultaneous treatment by combining with spraying process. Generally, wide beams of as uniform as possible are preferred for use in laser surface treatment to obtain a uniform depth of melting, alloying or cladding and to cover a large area by partially overlapping of tracks. However, it is not easy to produce a uniformly treated coating by conventional laser treatment method as desired. To obtain a near-uniform beam intensity for practical laser irradiation, a kaleidoscope was installed in a conventional YAG laser. In this research, laser beam properties of YAG laser equipped with a kaleidoscope and its effect on surface modification of plasma sprayed zirconia coatings and WC-Co system coatings prepared by HVOF spraying was investigated.
Alumina Duplex Coating by Multiprocesses: Air Plasma Spraying and Plasma Enhanced Chemical Vapor Deposition
Authors: Haure T. , Denoirjean A. , Tristant P. , Hidalgo H. , Leniniven C. , Desmaison J. , Fauchais P. 
Published: June 2022

Abstract
Thick alumina coatings produced by Air Plasma Spraying have an interconnected porosity, thus the use of these coatings in oxidizing or corrosive environment is not suitable. In this paper, a study is developed in order to limit this problem on metallic substrates. It consists in using two successive techniques: APS and PECVD. Two parameters have been shown to be important: the roughness and the preheating temperature. Two types of duplex (PECVD coating as top coat or as bond coat) have been achieved on two substrates (TA6V and stainless steel 316L). The optimization of each process has shown that the substrate has to be grit blasted and preheated (360°C for PECVD and 250°C for APS). This study has revealed that a good (36 ± 5 MPa) APS coating adhesion was obtained on smooth TA6V substrates (due probably to a chemical reaction between TiO2 and alumina) while for stainless steel substrates, the Ra has to be at least 2µm to achieve 66 ± 5. When observing the first APS splats sprayed on the PECVD alumina smooth layer, they exhibited a specific appearance: low flattening degree (about 2 against 5 on metallic substrates) with most of the alumina in the splat rim or some sort of lace morphology. However, as a whole, the adhesion of the APS coating on the PECVD one was excellent: 60 + 4. An electrochemical method has shown that the PECVD layer on APS coating has reduced drastically its open porosity.
Study of Microstructure and Atomization Forming Process of Ultrasonic Arc Sprayed TiAI Alloy Coatings
Authors: Wang H. , Li P. , Guo Q. , Yang H. 
Published: June 2022

Abstract
By means of homemade ultrasonic arc spraying equipment patented, under the condition of the optimum arc spraying parameters, TiAl alloy coatings were manufactured on the aluminum alloy (LY12) matrix surface. The ultrasonic arc spraying forming process and microstructure of TiAl compounds alloy coatings were investigated by the color metallurgical microscopy, SEM, XRD, EPMA and chemical composition quantitative analysis (ICP). The results showed that TiAl compounds composite coatings can be synthesized by ultrasonic arc spraying system, the coatings possess typical lamella character, consist of TiN (or TiO), TiAl, Ti0.7.1.1 Al(N,O), Ti2.4Al(N,O), Ti2.4Al and aluminum alloy solid solution.
A Microstructural Study of HVOF and VPS Sprayed MCrAlY Coatings
Authors: Nuutinen S. , Vuoristo P. , Ahmaniemi S. , Mäntylä T. , Takeuchi J. 
Published: June 2022

Abstract
The aim of the present work is to study the microstructure of high temperature oxidation and corrosion resistant MCrAlY coatings prepared by high-velocity oxy-fuel (HVOF) spraying and to compare them to vacuum plasma sprayed (VPS) MCrAlY coatings. In this work, CoNiCrAlY, NiCoCrAlYTaReSiHf, and NiCrAlY coatings were prepared on nickel based superalloys by VPS spraying and by two types of HVOF spray process (DJ Hybrid 2600 and JP-5000). The influence of spray parameters, i.e. oxygen flow rate and spray distance, in one of the HVOF processes (DJH 2600) on coating structures and properties were studied also in more detail. The coatings sprayed with different spraying processes were studied in their as-sprayed state and after heat-treatment by optical microscope and scanning electron microscopy (SEM). The results show that selection of appropriate particle size of the spray powder has marked importance in the HVOF process; presence of fine powder particles produce oxides in the coatings and ease clogging of the nozzle in the HVOF gun. The use of appropriate size distribution of the spray powder enables preparation of HVOF MCrAlY coatings with low oxide content and dense structure. The oxide content of HVOF sprayed coatings should be kept as low as possible in order to make the post heat-treatment active in producing a dense microstructure with correct phase structure. The oxide content can be controlled e.g. by flame temperature control by means of oxygen flow rate and by appropriate spray distance selected individually for each powder. Unacceptable high oxide contents in the as-sprayed structures tend to remain unchanged after heat-treatment, whereas well-developed coating microstructure and phase structure are obtained with HVOF sprayed coatings with low oxide content. Microstructures developed in heat-treated VPS and HVOF sprayed coatings are compared.
Optimisation and Monitoring of Spray Parameters by a CCD Camera Based Imaging Thermal Spray Monitor
Authors: Vuoristo P. , Ahmaniemi S. , Nuutinen S. , Mäntylä T. , Hämäläinen E. , Arola N. , Vattulainen J. 
Published: June 2022

Abstract
On-line monitoring of two thermal spray processes by means of an imaging diagnostic technique capable of measuring several spray particle properties, such as individual and average particle temperatures, velocities and number of particles with spatial distributions, was studied by using the Spray-Watch thermal spray monitor. Aim of the work was to demonstrate the capabilities of this novel monitor in quick optimisation of certain spray gun parameters to obtain desired particle characteristics in-flight, and hence desired coating structure and properties with high deposition efficiency. Examples are given in plasma spraying of Al2O3 and HVOF spraying of NiCoCrAlY.
Capture and Evaluation of HVOF Thermal Sprayed Particles by a Gel Target
Authors: Yamada H. , Yumoto H. , Kuroda S. , Fukushima T. 
Published: June 2022

Abstract
A new method to capture and evaluate the condition of thermal sprayed particles has been developed by using an agar gel target. HVOF sprayed Hastelloy C particles were collected by a gel target placed at the substrate position, i.e., 380mm downstream from the spray nozzle exit. In the surface layer of the target, a large number of fine particles were observed, whereas in the deeper part, globular particles were trapped. The ratio of particles in the surface layer with respect to the deeper part changed by spraying parameters. Furthermore, particles in the target were separated by cutting the gel, collected after resolving the agar, and then observed by SEM. Particles collected from the target's surface layer were fine particles (under 10µm) and fragments of dendritic crystals. These collected from the deeper part were mostly unmelted particles, some of which exposed dendrites. Results obtained by other techniques such as splat observation and in-flight diagnostics are compared with these results. It was concluded that by capturing thermal sprayed particles with a gel target, it is possible to visualize and quantify the melting condition of HVOF sprayed particles.
Proposal of New Criterion for Splashing of Thermal Sprayed Particle onto Flat Substrate Surface
Authors: Fukumoto M. , Nishioka E. , Nishiyama T. 
Published: June 2022

Abstract
In the collision of a liquid droplet onto a flat surface, a splashing parameter (K=We0.5Re0.25) has been used to evaluate the flattening behavior, and a critical value of K (KC) was introduced as a criterion for splashing. In order to evaluate K of thermal sprayed particle, in-flight measurement for the velocity and temperature of the particle was conducted in this study. As a flattening pattern of the thermal sprayed particle changed significantly with a substrate temperature, the transition temperature (Tt) was also measured by changing the substrate temperature. Both K and Tt showed a tendency of monotonous decreasing with increasing the spray distance and a strong linearity was recognized in a K-Tt relationship. This straight line corresponds to a critical value for the splashing. However, as the influence of substrate temperature on the flattening is essentially independent of K, a new criterion for the splashing in the flattening of the particle was proposed in the study. That is, a splashing parameter on flattening was proposed, which considers the ratio of the flattening velocity to the impact velocity of the particle.