Academic literature on the topic 'High Velocity Air-Fuel (HVAF)'
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Journal articles on the topic "High Velocity Air-Fuel (HVAF)"
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Szymański, Krzysztof, Marek Góral, Tadeusz Kubaszek, and Paulo Cyhlar Monteiro. "Microstructure of TBC Coatings Deposited by HVAF and PS-PVD Methods." Solid State Phenomena 227 (January 2015): 373–76. http://dx.doi.org/10.4028/www.scientific.net/ssp.227.373.
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High velocity air fuel (HVAF) is one of the high velocity flame spraying process (HVFS). The HVAF method employs a combination of liquid fuel mixed in a chamber with compressed air to obtain high velocity flows. This technology can provide high deposition levels, adequate bond strength as well as high dense coating structure. The working principle of Plasma Spray – Physical Vapor Deposition (PS-PVD) is based on evaporation of the ceramic powder, which enables advanced microstructure of the deposits. In this paper, microstructure of Thermal Barrier Coating (TBC) deposited by HVAF and PS-PVD method was described.
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Hulka, Iosif, Viorel Aurel Şerban, Kari Niemi, Petri Vuoristo, and Johannes Wolf. "Comparison of Structure and Wear Properties of Fine-Structured WC-CoCr Coatings Deposited by HVOF and HVAF Spraying Processes." Solid State Phenomena 188 (May 2012): 422–27. http://dx.doi.org/10.4028/www.scientific.net/ssp.188.422.
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The aim of the work was to study the microstructure and wear properties of fine-structured HVOF and HVAF sprayed WC-10Co-4Cr coatings prepared from powder having submicron-sized tungsten carbides. The coatings were deposited by HVOF (High Velocity Oxygen Fuel) and HVAF (High Velocity Air Fuel) using propane as a fuel gas in both processes, and using oxygen or air as oxidizing gas for combustion, respectively. Nitrogen was used as carrier gas for the powder. Commercially available agglomerated and sintered cermet powder with main carbide sizes under 500 nm was used in this study. Scanning electron microscopy (SEM) and X-ray diffraction were performed in order to characterize the powder and the microstructures formed during the spraying processes. The microhardness HV0.3 of the coatings was investigated and the pin on disk test was used to determine the sliding wear behaviour. The rubber wheel abrasion test was performed in order to determine the abrasion wear resistance of the coatings.
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Myalska, Hanna, Krzysztof Szymański, and Grzegorz Moskal. "Microstructure and Selected Properties of WC-Co-Cr Coatings Deposited by High Velocity Thermal Spray Processes." Solid State Phenomena 246 (February 2016): 117–22. http://dx.doi.org/10.4028/www.scientific.net/ssp.246.117.
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Selected information about high velocity thermal spraying method were presented in this article. Three generations of thermal spraying processes based on oxygen with propane mixture, liquid fuel with oxygen and propane with air were characterized. A powder of WC-Co-Cr 86-10-4 was used for coatings deposition on a steel substrate. Four coatings were deposited by different thermal spraying systems such as Diamond Jet, JP 5000, Micro HVOF and HVAF.
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Joshi and Nylen. "Advanced Coatings by Thermal Spray Processes." Technologies 7, no. 4 (November 1, 2019): 79. http://dx.doi.org/10.3390/technologies7040079.
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Coatings are pivotal in combating problems of premature component degradation in aggressive industrial environments and constitute a strategic area for continued development. Thermal spray (TS) coatings offer distinct advantages by combining versatility, cost-effectiveness, and the ability to coat complex geometries without constraints of other in-chamber processes. Consequently, TS techniques like high-velocity oxy-fuel (HVOF) and atmospheric plasma spray (APS) are industrially well-accepted. However, they have reached limits of their capabilities while expectations from coatings progressively increase in pursuit of enhanced efficiency and productivity. Two emerging TS variants, namely high-velocity air-fuel (HVAF) and liquid feedstock thermal spraying, offer attractive pathways to realize high-performance surfaces superior to those hitherto achievable. Supersonic HVAF spraying provides highly adherent coatings with negligible porosity and its low processing temperature also ensures insignificant thermal ‘damage’ (oxidation, decarburization, etc.) to the starting material. On the other hand, liquid feedstock derived TS coatings, deposited using suspensions of fine particles (100 nm–5 µm) or solution precursors, permits the production of coatings with novel microstructures and diverse application-specific architectures. The possibility of hybrid processing, combining liquid and powder feedstock, provides further opportunities to fine tune the properties of functional surfaces. These new approaches are discussed along with some illustrative examples.
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Zha, Bai Lin, Su Lei Qiao, Ding Yuan Huang, Wei He, Zhi Hong Zha, and Xiang Bin Li. "Study of Properties of Nanostructured and Conventional WC-12Co Coatings Deposited by HVO/AF." Advanced Materials Research 709 (June 2013): 166–71. http://dx.doi.org/10.4028/www.scientific.net/amr.709.166.
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The three kinds of WC-12Co coatings were sprayed by High Velocity Oxygen/Air Fuel Spray (HVO/AF) in three different spray conditions, HVOF、HVO-AF and HVAF. The high velocity flame flow was produced by HVO/AF with the burning of kerosene and propellant which was mixed by oxygen and air at different ratio, it can be controlled from 1400°C to 2800°C.The microstructure was investigated by SEM, the phase composition was tested by XRD, and the microhardness and elastic modulus of coatings were investigated. The results indicate that the coatings with better adhesive strength and little porosity than conventional ones are dense and have a large value of elasticity and a high microhardness which is 0.4 times harder than the conventional coatings. The coatings are mainly composed of WC and Co, and there are also traces of W2C and Co6W6C. As temperature decreased, the decomposition of WC is being reduced.
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Cai, Mingwei, and Jun Shen. "Phase Transformation of High Velocity Air Fuel (HVAF)-Sprayed Al-Cu-Fe-Si Quasicrystalline Coating." Metals 10, no. 6 (June 24, 2020): 834. http://dx.doi.org/10.3390/met10060834.
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Al-Cu-Fe-Si quasicrystalline coatings were prepared by high velocity air fuel spraying to study their phase transformation during the process. The feedstock powder and coating were phase characterized by scanning electron microscopy, X-ray diffractometry, differential scanning calorimetry, and transmission electron microscopy. Results show that Al3Cu2 phase, a small amount of λ-Al13Fe4 phase, quasicrystalline phase (QC), amorphous phase, and β-Al (Cu, Fe, Si) phase were present in the sprayed Al50Cu20Fe15Si15 powder. For a typical flattened powder particle, the splat periphery was surrounded by a 1 µm thick amorphous phase. The inside area of the splat was composed of the QC covered by the Al3Cu2 and Si-rich β-Al (Cu, Fe, Si) phases. Another kind of Cu- rich β-Al (Cu, Fe, Si) phase can be found close to the amorphous area with a similar composition to the original β-Al (Cu, Fe, Si) phase in the powder. Different phases were observed when the periphery and inside area of the splat were compared. This result was caused by the difference in the heating and cooling rates.
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Baiamonte, Lidia, Stefan Björklund, Antonio Mulone, Uta Klement, and Shrikant Joshi. "Carbide-laden coatings deposited using a hand-held high-velocity air-fuel (HVAF) spray gun." Surface and Coatings Technology 406 (January 2021): 126725. http://dx.doi.org/10.1016/j.surfcoat.2020.126725.
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Liu, Fuqiang, Zhiyong Li, Min Fang, and Hua Hou. "Numerical Analysis of the Activated Combustion High-Velocity Air-Fuel Spraying Process: A Three-Dimensional Simulation with Improved Gas Mixing and Combustion Mode." Materials 14, no. 3 (January 31, 2021): 657. http://dx.doi.org/10.3390/ma14030657.
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Owing to its low flame temperature and high airflow velocity, the activated combustion high-velocity air-fuel (AC-HVAF) spraying process has garnered considerable attention in recent years. Analyzing the velocity field, temperature field, and composition of AC-HVAF spray coatings plays a vital role in improving the quality of coatings. In this study, an actual spray gun is adopted as a prototype, and the radial air inlets are introduced to improve the reaction efficiency so that the chemical reaction can be completed in the combustion chamber. Furthermore, a complete three-dimensional (3D) model is established to examine the effects of radial inlets and porous ceramic sheet on the combustion and flow fields. The hexahedral cells are used to discretize the entire model for reducing the influence of false-diffusion on the calculation results. The gas flow field is simulated by the commercial Fluent software, and the results indicate that the porous ceramic sheet effectively reduces the turbulent dissipation of the airflow with a good rectification effect (the ceramic sheet ensures a consistent airflow direction). The radial inlets and the porous ceramic sheet promote the formation of vortex in the combustion chamber, increase the residence time and stroke of the gas in the combustion chamber, and improve the probability of chemical reactions. In addition, it is observed that the stability of velocity for the airflow is strongly related to the airflow density.
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SALMAN, ASMA, BRIAN GABBITAS, PENG CAO, and DELIANG ZHANG. "TRIBOLOGICAL PROPERTIES OF Ti(Al,O)/Al2O3 COMPOSITE COATING BY THERMAL SPRAYING." International Journal of Modern Physics B 23, no. 06n07 (March 20, 2009): 1407–12. http://dx.doi.org/10.1142/s0217979209061019.
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The use of thermal spray coatings provides protection to the surfaces operating in severe environments. The main goal of the current work is to investigate the possibility of using a high velocity air fuel (HVAF) thermally sprayed wear resistant Ti ( Al , O )/ Al 2 O 3 coating on tool steel (H13) which is used for making dies for aluminium high pressure die casting and dummy blocks aluminium extrusion. A feedstock of Ti ( Al , O )/ Al 2 O 3 composite powder was produced from a mixture of Al and TiO 2 powders by high energy mechanical milling, followed by a thermal reaction process. The feedstock was then thermally sprayed using a high velocity air-fuel (HVAF) technique onto H13 steel substrates to produce a composite coating. The present study describes and compares the tribological properties such as friction and sliding wear rate of the coating both at room and high temperature (700°C). The wear resistance of the coating was investigated by a tribometer using a spherical ended alumina pin as a counter body under dry and lubricating conditions. The results showed that composite coating has lower wear rate at high temperature than at room temperature without using lubricant. The composite coating was characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD). This paper reports the experimental observations and discusses the wear resistance performance of the coatings at room and high temperatures.
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Garfias Bulnes, Andrea, Vicente Albaladejo Fuentes, Irene Garcia Cano, and Sergi Dosta. "Understanding the Influence of High Velocity Thermal Spray Techniques on the Properties of Different Anti-Wear WC-Based Coatings." Coatings 10, no. 12 (November 26, 2020): 1157. http://dx.doi.org/10.3390/coatings10121157.
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This work analyzes the differences found in hard metal coatings produced by two high velocity thermal spray techniques, namely high velocity oxy-fuel (HVOF) and high velocity air-fuel (HVAF). Additionally, the effect of the metallic matrix and ceramic composition and the original carbide grain size on coating properties is compared to the most studied standard reference material sprayed by HVOF, WC-Co. For this evaluation, the physical properties of the coatings, including feedstock characteristics, porosity, thickness, roughness, hardness, and phase composition were investigated. Several characterization methods were used for this purpose: optical microscopy (OM), scanning electronic microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), and X-ray Diffraction (XRD), among others. The final performance (abrasive wear and corrosion resistance) shown by the coatings obtained by these two methodologies was also analyzed. Thus, the abrasive wear resistance was analyzed by the rubber-wheel test, while the corrosion resistance was characterized with electrochemical methods. The characterization results obtained clearly showed that the coatings exhibit different microstructures according to feedstock powder characteristics (carbide grain size and/or composition) and the thermal spray process used for its deposition. Thus, the incorporation of WB to the cermet composition led to a high hardness coating, and the complementary hardness and toughness of the WC-Co coatings justify its better abrasion resistance. The presence of Ni on the metal matrix increases the free corrosion potential of the coating to more noble region. However, the WC-Co coatings show a lower corrosion rate and hence a higher protective performance than the rest of the coatings.
Dissertations / Theses on the topic "High Velocity Air-Fuel (HVAF)"
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BERTILSSON, ERIK. "Identification of business cases for HVAFtechnology." Thesis, KTH, Industriell Management, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-154568.
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Swerea KIMAB has invested in a new and improved thermal spray technique, High Velocity Air-Fuel (HVAF). This has recently been introduced to the market given that the technical properties, costs and performance of the technique is still not thoroughly investigated and covered. An examination of these areas was therefore necessary to examine appropriate uses for the new technology. The investigation aimed to indicate how the new technology compares with established technologies in some areas in terms of performance and cost but also if there are any entirely new applications that the technology enables. In addition, there is also considerable uncertainty what the market for the new technology looks like today, and what it can be developed into. The market of thermal spraying is limited today. This entails that there is a great interest to investigate the preferences and equirements companies have to consider when choosing this new technology in favour of an ld one. It is also of great interest to investigate what skills and support companies’ requests in order to venture into this new technology. The aim with the work was to answer two research questions What are possible business cases for the HVAF technology from a technical as well as an economical point of view? What initiatives are necessary to get more companies and applications into the thermal spray business? The methods used for the master thesis were empirical studies, benchmarking, interviews, a survey and logical discussions. The report presents an overall knowledge bank for the most commonly used thermal spray technologies, compared with regards to characteristics and cost. As a result of the new features that the HVAF technology offers suitable application areas for the technology were identified through the work, such as high temperature corrosion protection. As a result of the survey the work also identified the general lack of knowledge about thermal spraying as the main obstacle to get more companies into using the technology.Swerea KIMAB har nyligen investerat i en förbättrad teknik för termisk sprutning, High Velocity Air-Fule (HVAF). HVAF-tekniken har nyligen introducerats på marknaden och de tekniska egenskaperna har därmedinte undersökts grundligt eller jämförts med genskaperna för befintliga termiska spruttekniker. Arbetets syfte var att belysa hur och var den nya HVAFtekniken kan konkurrera med etablerade tekniker på områden i form av prestanda och kostnad. ndersökningen syftade även till att utreda om den nya tekniken kan medföra helt nya applikationsområden. En genomgång av befintliga tekniker var till en början nödvändig för att i slutändan kunna identifiera lämpliga användningsområden för HVAF-tekniken. Det finns en stor osäkerhet kring hur marknaden för HVAF ser ut idag, och hur den kan komma att utvecklas. Själva marknaden för termisk sprutning är i dagsläget begränsad, vilket innebär att det finns ett stort intresse kring att undersöka vilka önskemål och krav företag ställer på HVAF-tekniken för att den skall kunna konkurrera på marknaden. Utöver tidigare nämda delar av arbetet syftade det även till att identifiera vilka kunskaper och vilket stöd företagen önskar vid en eventuell övergång till termisk sprutning generellt. Följande forskningsfrågor har besvarats i arbetet. Vilka nya användningsområden möjliggör HVAF-tekniken för sett ur en teknisk och ekonomisk synvinkel? Vilka initiativ är nödvändiga för att öka användandet av termisk sprutning inom industrin? Empiriska studier, benchmarking, intervjuer och en enkätundersökning var de metoder som användes för arbetet. I rapporten presenteras en övergripande kunskapsbank för de vanligaste termiska sprutteknikerna, vilken omfattar en jämförelse av egenskaper och kostnader. Lämpliga användningsområden för HVAF-tekniken har identifierades och presenteras i rapporten. exempelvis som skydd mot höga temperaturer, korrosion och abrasion. Allmän brist på kunskap om termisk sprutning har identifierats som det främsta hindret mot ökad användning av tekniken i dagsläget.
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Barth, Dominic. "Modelling and control of combustion in a high velocity air flame (HVAF) thermal spraying process." Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1266.
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Thermal spraying is a technology, which is used for coating of components and structures in order to achieve certain tribological characteristics, or for protection against corrosion, excessive temperature and wear. Within thermal spray, there are processes, which utilise combustion of liquid fuel to obtain high velocities flows providing, therefore, good adhesion of coating materials to substrates. These include High Velocity Oxygen Flame (HVOF) and High Velocity Air Flame (HVAF) process, of which the former one is widely used as it has been developed for at least two decades, while HVAF is less common. However, some studies indicate that HVAF has a number of advantages over HVOF, including the economic benefits. The thermal spray gun, based on the HVAF process, has been developed before, but the system was controlled manually. Therefore, there is a need to develop a fully automated controller of an HVAF thermal spray system. Process control of thermal spraying is highly complex as it involves simultaneous control of a number of processes, including; ignition process, combustion process, spraying material melting, as well as control and monitoring of auxiliary equipment. This paper presents the development of a control system for an HVAF thermal spray system, based on a Microchip PIC microcontroller. The designed control system was applied for controlling of thermal spraying of carbides powders, and provided a reliable ignition and stable combustion process, powder feeding and all other functions of control.
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Roy, Jean-Michel L. "Development of Cold Gas Dynamic Spray Nozzle and Comparison of Oxidation Performance of Bond Coats for Aerospace Thermal Barrier Coatings at Temperatures of 1000°C and 1100°C." Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20681.
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The purpose of this research work was to develop a nozzle capable of depositing dense CoNiCrAlY coatings via cold gas dynamic spray (CGDS) as well as compare the oxidation performance of bond coats manufactured by CGDS, high-velocity oxy-fuel (HVOF) and air plasma spray (APS) at temperatures of 1000°C and 1100°C. The work was divided in two sections, the design and manufacturing of a CGDS nozzle with an optimal profile for the deposition of CoNiCrAlY powders and the comparison of the oxidation performance of CoNiCrAlY bond coats. Throughout this work, it was shown that the quality of coatings deposited via CGDS can be increased by the use of a nozzle of optimal profile and that early formation of protective α-Al2O3 due to an oxidation temperature of 1100°C as opposed to 1000°C is beneficial to the overall oxidation performance of CoNiCrAlY coatings.
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Shrestha, Suman Kumar. "Corrosion and erosion-corrosion of High Velocity Oxy-Fuel (HVOF) sprayed NiCrSiB coatings." Thesis, University of Glasgow, 2000. http://theses.gla.ac.uk/2866/.
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Liu, Meimei. "Research and implementation of artificial neural networks models for high velocity oxygen fuel thermal spraying." Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCA003.
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Dans les procédés de projection thermique du type HVOF (High Velocity Oxygen Fuel), les propriétés du revêtement sont sensibles aux caractéristiques des particules en vol qui dépendent elles-mêmes des paramètres opératoires. En raison de la complexité des réactions chimiques et des processus thermodynamiques qui interviennent dans la formation du dépôt, l’obtention d’un modèle multi-physique complet et l'accès à une description quantitative du procédé HVOF représentent encore actuellement un défi scientifique majeur. L'étude réalisée a eu pour but de développer une méthodologie robuste reposant sur la méthodologie des réseaux de neurones artificiels (ANN), en vue de répondre à ce besoin dans le cas des revêtements NiCr-Cr3C2 élaborés par HVOF en mettant en oeuvre des paramètres opératoires variables.En premier lieu, 40 séries d’expériences de projection HVOF ont été conduites et les propriétés du revêtement obtenus ont été déterminées et analysées afin de créer les modèles ANN visés. La relation entre les paramètres opératoires, les caractéristiques des particules en vol et les propriétés du revêtement a été étudiée dans une approche initiale "intuitive", réalisée sur la base de considérations physico-chimiques classiques, ce qui a fourni une compréhension préliminaire du processus HVOF et des revêtements. Toutefois, bien que l’effet des paramètres du procédé sur ces derniers puisse être décrit qualitativement, il est impossible d’établir descorrélations quantitatives..Aussi deux modèles ANN ont été développés et mis en œuvre pour prédire les performances du revêtement (en termes de micro-dureté, porosité et taux d’usure) et traduire l’influence des paramètres opératoires (distance de projection, débit d’oxygène et débit de carburant) en faisant intervenir les variables intermédiaires (température et vitesse de particules en vol). Une procédure détaillée de création de ces deux modèles ANN est présentée, qui intègre les phénomènes physiques régissant le processus HVOF. Une série d’expériences supplémentaires a également été menées pour valider la fiabilité et estimer la précision de ces modèles ANN. Les résultats montrent que les modèles implicites ainsi développés ont des qualités prédictives satisfaisantes. La clarification des relations entre les conditions de projection, les comportements des particules en vol et les performances du revêtement est un élément clef pour assurer un contrôle optimal des revêtements déposés par HVOF. De plus, une analyse de la « valeur d’impact moyenne » (MIV) a été réalisée pour évaluer quantitativement l’influence relative de chaque entrée sur les données de sortie en vue d’affiner la prédiction.Enfin, les modèles ANN mis en forme ont été programmées et intégrés dans le système de contrôle de projection HVOF tel qu'il est mis en œuvre au laboratoire, pour parvenir un système de contrôle intelligent. À l’aide de ce système, la température et la vitesse des particules en vol peuvent être calculées à partir des paramètres opératoires et les propriétés de revêtement spécifiques peuvent être estimées. Un modèle ANN inversé a également été développé, qui prédit les paramètres opératoires optimaux à appliquer en fonction du niveau de micro-dureté visé pour le revêtement.Ce travail contribue donc à la mise au point d’un système de contrôle intelligent applicable aux procédés de projection HVOF et la démarche suivie peut en outre être étendue à d’autres techniques de projection thermique.Ainsi, sur la base d'un nombre substantiel de données, ce travail a non seulement produit une analyse de la relation entre les paramètres opératoires du procédé, le comportement des particules en vol et les propriétés du revêtement, mais a également fourni une méthode de prédiction applicable aux revêtements déposés par HVOF, au travers d'un modèle ANN optimisé. Enfin, un logiciel prototype concrétisant un tel système de contrôle intelligent adapté au procédé de projection HVOF a également été élaboréIn the high velocity oxygen fuel (HVOF) spray process, the coating properties are sensitive to the characteristics of in-flight particles, which are mainly determined by the process parameters. Due to the complex chemical and thermodynamic reactions during the deposition procedure, obtaining a comprehensive multi-physical model or analytical analysis of the HVOF process is still a challenging issue. This study proposes to develop a robust methodology via artificial neural networks (ANN) to solve this problem for the HVOF sprayed NiCr-Cr3C2 coatings under different operating parameters.First, 40 sets of HVOF spray experiments were conducted and the coating properties were tested for analysis and to build up the data set for ANN models. The relationship among the process parameters, behaviors of in-flight particles, and coating properties were investigated from an initial view, which provided a preliminary understanding of the HVOF process and sprayed coatings. Even though the effect of process parameters on the behaviors of in-flight particles and thus on the coating’ properties can be roughly summarized, it is impossible to build up direct connections among them.Second, two ANN models were developed and implemented to predict coating’s performances (in terms of microhardness, porosity and wear rate) and to analyze the influence of operating parameters (stand-off distance, oxygen flow rate, and fuel flow rate) while considering the intermediate variables (temperature and velocity of in-flight particles). A detailed procedure for creating these two ANN models is presented, which encodes the implicitly physical phenomena governing the HVOF process. A set of additional experiments was also conducted to validate the reliability and accuracy of the ANN models. The results show that the developed implicit models can satisfy the prediction requirements. Clarifying the interrelationships between the spraying conditions, behaviors of in-flight particles, and the final coating performances will provide better control of the HVOF sprayed coatings. Additionally, mean impact value (MIV) analysis was conducted to quantitatively explore the relative significance of each input on outputs for improving the effectiveness of the predictions.Lastly, the well-trained ANN models were programmed and integrated into the homemade HVOF spray control system to realize an intelligent control system. With this system, the temperature and velocity of in-flight particles can be calculated by entering process parameters, and thereafter obtaining specific coating properties. A reverse ANN model was also integrated, which calculates process parameters based on the microhardness of the coating to guide the selection of the best parameters. This integration provides a preliminary idea for the construction of an intelligent control system for HVOF spray process and can be promoted to other thermal spray technologies.Overall, based on a large data set, this work not only intuitively analyzed the relationship among process parameters, behaviors of in-flight particles, and coating’s properties, but also provided a prediction method for the HVOF spray process and HVOF sprayed coatings via the optimized and well-trained ANN model. In addition, a prototype to realize an intelligent control system for HVOF spray process has also been suggested
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Neale, James Richard Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "Experimental and numerical investigation of noise generation from the expansion of high velocity HVAC flows on board ocean going fast ferries." Awarded by:University of New South Wales. School of Mechanical and Manufacturing Engineering, 2006. http://handle.unsw.edu.au/1959.4/28371.
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This thesis details a study of strategies used to limit the flow generated noise encountered in the outlet diffusers of high velocity heating, ventilation and air conditioning (HVAC) duct systems. The underlying noise rating criterion is drawn from the specifications covering ocean going aluminium fast ferries. Although directed primarily towards the fast ferry industry the results presented herein are applicable to other niche high velocity HVAC applications. Experimental tests have been conducted to prove the viability of a high velocity HVAC duct system in meeting airflow requirements whilst maintaining acceptable passenger cabin noise levels. A 50 mm diameter circular jet of air was expanded using a primary conical diffuser with a variety of secondary outlet configurations. Noise measurements were taken across a velocity range of 15 to 60 m/s. An optimum outlet design has been experimentally identified by varying the diffuser angle, outlet duct length and the termination grill. A 4 to 5 fold reduction in required duct area was achieved with the use of a distribution velocity of 20 to 30 ms-1, without exceeding the prescribed passenger cabin noise criteria. The geometric configuration of the diffuser outlet assembly was found to have a pronounced effect on the noise spectrum radiating from the duct outlet. The development of a numerical model capable of predicting the flow induced noise generated by airflow exiting a ventilation duct is also documented. The model employs a Large Eddy Simulation (LES) CFD model to calculate the turbulent flow field through the duct diffuser section and outlet. The flow-generated noise is then calculated using a far field acoustic postprocessor based on the Ffowcs-Williams and Hawkings integral based formulation of Lighthill???s acoustic analogy. Time varying flow field variables are used to calculate the fluctuating noise sources located at the duct outlet and the resulting far field sound pressure levels. This result is then used to calculate the corresponding far field sound intensity and sound power levels. The numerical acoustic model has been verified and validated against the measured experimental results for multiple outlet diffuser configurations.
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Kutschmann, Pia, Thomas Lindner, Kristian Börner, Ulrich Reese, and Thomas Lampke. "Effect of Adjusted Gas Nitriding Parameters on Microstructure and Wear Resistance of HVOF-Sprayed AISI 316L Coatings." MDPI AG, 2019. https://monarch.qucosa.de/id/qucosa%3A34775.
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Gas nitriding is known as a convenient process to improve the wear resistance of steel components. A precipitation-free hardening by low-temperature processes is established to retain the good corrosion resistance of stainless steel. In cases of thermal spray coatings, the interstitial solvation is achieved without an additional surface activation step. The open porosity permits the penetration of the donator media and leads to a structural diffusion. An inhomogeneous diffusion enrichment occurs at the single spray particle edges within the coating’s microstructure. A decreasing diffusion depth is found with increasing surface distance. The present study investigates an adjusted process management for low-temperature gas nitriding of high velocity oxy-fuel-sprayed AISI 316L coatings. To maintain a homogeneous diffusion depth within the coating, a pressure modulation during the process is studied. Additionally, the use of cracked gas as donator is examined. The process management is designed without an additional surface activation step. Regardless of surface distance, microstructural investigations reveal a homogeneous diffusion depth by a reduced processing time. The constant hardening depth allows a reliable prediction of the coatings’ properties. An enhanced hardness and improved wear resistance is found in comparison with the as-sprayed coating condition.
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Rajagopalan, Srivatsan Vengeepuram. "Numerical analysis of a high velocity oxygen fuel (HVOF) process." Thesis, 2007. http://spectrum.library.concordia.ca/975504/1/MR34784.pdf.
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The HVOF process is used for coating protective layers on surfaces exposed to corrosion and wear. This process involves a supersonic two-phase flow of gas-solid particles. The main objective of this thesis is to explore certain key factors that influence the process efficiency such as gas-particle interactions, particle in-flight conditions, and particle loading. To study the effect of gas-particles interactions, a Lagrangian approach which tracks individual particles in the continuous gas, is used. The supersonic gas flow leaving an HVOF nozzle is over-expanded and its adjustment to the atmospheric pressure results in shock diamonds formation, while flow impingement on a substrate results in bow-shock development. Both the shocks are responsible for affecting the particle conditions. The strength and location of bow shock vary for different substrate geometries and stand-off distances. In this work, various particle sizes impinging on different substrate configurations are simulated and the particle interactions with both the shocks are presented in detail. To find the effect of particle loading on the gas phase, a dense particulate phase scenario is assumed. A fully Eulerian approach, which treats the particles as a fluid, is used to simulate the HVOF process and the two-phase flow characteristics were investigated for various particle loadings. The particulate phase was found to be dense near the nozzle centerline and dilute near the wall. In the particle-dense region, the gas phase characteristics were found to be severely affected, which significantly affects the particle velocity
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Pereira, Aaron. "Investigation of Direct Injection Fuel Sprays in High Velocity Air Flows." Thesis, 2013. http://hdl.handle.net/10012/8007.
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The study of single-plume sprays into cross-flowing air is found extensively in literature, however, with the continued development of the Spark Ignition Direct Injection (SIDI) engine, the behaviour of multi-plume sprays in cross-flowing conditions is of interest.
In the present work, the injection of a multi-plume spray into a high-velocity cross-flow is investigated; an experimental apparatus capable of providing a cross-flow with core velocities higher than 200 m/s is developed; analysis techniques are developed to characterize the cross-flow and multi-plume spray independently; the multi-plume spray is characterized as it issues into the cross-flowing air.
The round air jet used for the cross-flow was designed using the concepts put forth for the design of wind tunnel contractions. The axial and radial velocities were measured using a Particle Image Velocimetry system from LaVision Inc. and the potential core length determined for the core velocities corresponding to Mach numbers of 0.35 and 0.58. It was determined that the potential core length increases with increasing Mach number and that increased compressibility, leads to reduced mixing within the core. Furthermore, velocity profiles of the air jet show that self-similarity is preserved within the shear layer of the initial region.
The multi-plume spray was also characterized in quiescent conditions for 10 and 15 MPa injection pressures. It was found that the penetration depth and spray width increased with increasing injection pressure, but that the spray angle decreased with increasing pressure. The increase in penetration depth is consistent with the findings presented in literature, while the decrease in spray angle with increasing pressure is contrary to literature.
Next, the multi-plume spray, injected at 10 and 15 MPa, is characterized as it issues into the cross-flowing air stream at Mach numbers equal to 0.35 and 0.58. The tail length and penetration are measured and it is found that for the first, the cross-flow velocity is the primary factor with higher cross-flow velocity resulting in a longer tail length, while for the latter, the injection pressure is the major factor, with higher injection pressures resulting in higher penetrations. That being said, the injection pressure does play a small role in the tail length, with the 15 MPa injection having a slightly longer tail length than the 10 MPa injection in the Mach number 0.58 cross-flow. This is attributed to the finer atomization, which is expected from the 15 MPa injection and which leads to quicker entrainment of fuel droplets into the cross-flow.
The spray axis was predicted for each set of conditions from 0.1 ms to 1.0 ms after Start of Fuel (SOF). It was found that before 0.3 ms, the spray retains its multi-plume nature, while after 0.3 ms it behaves like a single-plume spray. Once the spray has crossed this transition point, the spray axis is temporally independent and can be predicted by the logarithmic models, similar to those used for single-plume sprays in cross-flow. The accuracy of this fit is improved upon, with the presentation of a modified correlation, which includes the momentum flux ratio inside of the logarithmic term.
Finally, the multi-plume spray issuing into the cross-flow is characterized using PIV to measure droplet velocities. It is observed that the cross-flow momentum is imparted to the smaller droplets within the 15 MPa spray more easily than to those of the 10 MPa injection, but that the 15 MPa sprays also retain their momentum in the radial direction longer than the 10 MPa sprays. As such, the 10 MPa sprays align with the cross-flow axis faster.
Books on the topic "High Velocity Air-Fuel (HVAF)"
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Al-Abedi, G. S. A. High velocity oxy-fuel spraying (hvof) for the application of ceramic coatings. Manchester: UMIST, 1995.
Find full textBook chapters on the topic "High Velocity Air-Fuel (HVAF)"
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Fiedler, Torben, Joachim Rösler, Martin Bäker, Felix Hötte, Christoph von Sethe, Dennis Daub, Matthias Haupt, Oskar J. Haidn, Burkard Esser, and Ali Gülhan. "Mechanical Integrity of Thermal Barrier Coatings: Coating Development and Micromechanics." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 295–307. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53847-7_19.
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Abstract To protect the copper liners of liquid-fuel rocket combustion chambers, a thermal barrier coating can be applied. Previously, a new metallic coating system was developed, consisting of a NiCuCrAl bond-coat and a Rene 80 top-coat, applied with high velocity oxyfuel spray (HVOF). The coatings are tested in laser cycling experiments to develop a detailed failure model, and critical loads for coating failure were defined. In this work, a coating system is designed for a generic engine to demonstrate the benefits of TBCs in rocket engines, and the mechanical loads and possible coating failure are analysed. Finally, the coatings are tested in a hypersonic wind tunnel with surface temperatures of 1350 K and above, where no coating failure was observed. Furthermore, cyclic experiments with a subscale combustion chamber were carried out. With a diffusion heat treatment, no large-scale coating delamination was observed, but the coating cracked vertically due to large cooling-induced stresses. These cracks are inevitable in rocket engines due to the very large thermal-strain differences between hot coating and cooled substrate. It is supposed that the cracks can be tolerated in rocket-engine application.
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Tan, J. C., and M. S. J. Hashmi. "High velocity oxygen fuel (HVOF) thermal spray." In Current Advances in Mechanical Design and Production VI, 27–33. Elsevier, 1995. http://dx.doi.org/10.1016/b978-008042140-7/50004-4.
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Casteletti, L. C., A. Lombardi Neto, D. T. de Macedo, L. B. Cruvinel, and George Totten. "Stellite Superalloy Powder Deposition on 7075 Aluminum Alloy." In Encyclopedia of Aluminum and Its Alloys. Boca Raton: CRC Press, 2019. http://dx.doi.org/10.1201/9781351045636-140000303.
Full textAbstract:
Several types of powders can be deposited on metal alloys for property improvement using thermal spray processes. Aircraft grade 7075 aluminum alloy possesses good mechanical properties but poor wear and corrosion resistance. Thermal spray coatings can improve the poor wear performance of 7075 so that it is suitable for use in severe conditions by depositing a hard, wear-resisting layer over the base material. This can be done by a simple production process while maintaining the base material properties. Among the available coatings, cobalt-base superalloys, such as Stellites, provides excellent protection against corrosion and wear. However, the treatment must not deteriorate the substrate hardness. In the High Velocity Oxygen Fuel (HVOF) thermal spray process, the short resident time of the powder in the flame results in a relatively small temperature increase, which in turn results in a lower substrate temperature during the coating deposition. In the present work, HVOF thermal spray process was used to coat 7075-T3 aluminum alloy samples with Stellite 6 superalloy. This treatment resulted in layers of high hardness and improved wear performance while keeping the base material properties unchanged.
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Lucian Toma, Stefan, Radu Armand Haraga, Daniela Lucia Chicet, Viorel Paleu, and Costica Bejinariu. "Hard Alloys with High Content of WC and TiC—Deposited by Arc Spraying Process." In Welding - Modern Topics [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94605.
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Obtained by different spraying technologies: in atmospheric plasma spray, High Velocity Oxygen Fuel (HVOF) or laser cladding, the layers of hard alloys with a high content of WC and TiC find their industrial applications due to their high hardness and resistance to wear. Recognized as being a process associated with welding, the arc spraying process is a method applied industrially both in obtaining new surfaces and for reconditioning worn ones. This chapter presents the technology for obtaining ultra-hard layers based on WC and TiC - by the arc spraying process, using a classic spray device equipped with a conical nozzle system and tubular wire additional material containing ultra-hard compounds (WC, TiC). To study both the quality of deposits and the influence of thermal spray process parameters on the properties of deposits with WC and TiC content, we approached various investigative techniques, such as optical scanning microscopy (SEM), X-ray diffraction, and determination of adhesion, porosity, Vickers micro-hardness and wear resistance.
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Wood, Robert J. K., and Mandar R. Thakare. "Abrasion-Corrosion of Thermal Spray Coatings." In Materials Science and Engineering, 1265–92. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-1798-6.ch050.
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WC-based thermal-spray and High Velocity Oxy-Fuel (HVOF) coatings are extensively used in a wide range of applications ranging from downhole drilling tools to gas turbine engines. WC-based thermal spray coatings offer improved wear resistance as a result of hard phases dispersed in binder-rich regions. However, the presence of hard and soft phases within the coating can also lead to the formation of micro-galvanic couplings in aqueous environments leading to some reduction in combined wear-corrosion resistance. Furthermore, the coating also responds differently to change in mechanical loading conditions. This chapter examines the wear-corrosion performance of thermal spray coatings in a range of wear, electrochemical, and wear-corrosion tests under varying contact conditions to develop models and establish relationships between wear mechanisms, wear rates, and environmental factors such as pH and applied load.
Conference papers on the topic "High Velocity Air-Fuel (HVAF)"
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Löbel, Martin, Thomas Lindner, Thomas Mehner, Lisa-Marie Rymer, Thomas Lampke, Stefan Björklund, and Shrikant Joshi. "Microstructure and Corrosion Properties of AlCoCrFeNi High-Entropy Alloy Coatings Prepared by HVAF and HVOF." In ITSC2021, edited by F. Azarmi, X. Chen, J. Cizek, C. Cojocaru, B. Jodoin, H. Koivuluoto, Y. C. Lau, et al. ASM International, 2021. http://dx.doi.org/10.31399/asm.cp.itsc2021p0416.
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Abstract High-entropy alloys (HEAs) represent an innovative development approach for new alloy systems. These materials have been found to yield promising properties, such as high strength in combination with sufficient ductility as well as high wear and corrosion resistance. Especially for alloys with a body-centered cubic (bcc) structure, advantageous surface properties have been revealed. However, typical HEA systems contain high contents of expensive or scarce elements. Consequently, applying them as coatings where their use is limited to the surface represents an exciting pathway enabling economical exploitation of their superior properties. Nevertheless, processing conditions strongly influence the resulting microstructure and phase formation, which in turn has a considerable effect on the functional properties of HEAs. In the presented study, microstructural differences between high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) sprayed coatings of the alloy AlCrFeCoNi are investigated. A metastable bcc structure is formed in both coating processes. Precipitation reactions are suppressed by the rapid solidification during atomization and by the relatively low thermal input during spraying. The coating resistance to corrosive media was investigated in detail, and an improved passivation behavior was observed in the HVAF coatings.
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Varacalle, D. J., G. Irons, R. J. Lalumiere, W. D. Swank, and J. Lagerquist. "Modeling and Diagnostics of the Praxair HVAF Combustion Spray Process." In ITSC 1998, edited by Christian Coddet. ASM International, 1998. http://dx.doi.org/10.31399/asm.cp.itsc1998p0347.
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Abstract The high-velocity air-fuel process (HVAF) is an emerging technology used in the thermal spray industry. The Praxair HVAF process combines air and a liquid fuel (e.g., kerosene, diesel) to generate an energy source with extremely high gas velocities. Analytical studies were conducted to investigate gas and particle dynamics in the Praxair HVAF process for coating with WC-l2Co and stainless steel powders. The mass, momentum, and energy conservation equations were first solved, using the TORCH computer program. Typical output from the model includes temperature and velocity profiles as a function of radial and axial position. The PROCESS gas/particle computer program was then used to calculate from these temperature and velocity profiles the dynamics of particles injected into the gas plume. The primary result of the gas/particle code is a description of the injected particle temperature and velocity as a function of position in the plume. A thorough understanding of the process was obtained using this modeling technique. The results of the modeling were confirmed with process diagnostics. Particle temperature measurements for the WC-Co powder system were obtained with a two-color pyrometer; particle velocity measurements were obtained using particle imaging velocimetry. The coatings produced in the study exhibit superior quality, with high-density, high-hardness, low-oxide content, and high-bond strength.
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Korobov, S., N. V. Lezhnin, A. V. Makarov, H. L. Alwan, V. I. Shumyakov, N. N. Soboleva, M. Antonov, and M. S. Deviatiarov. "The Cavitation Resistance of WC-10Co4Cr and WC-20CrC-7Ni HVAF Coatings." In ITSC2021, edited by F. Azarmi, X. Chen, J. Cizek, C. Cojocaru, B. Jodoin, H. Koivuluoto, Y. C. Lau, et al. ASM International, 2021. http://dx.doi.org/10.31399/asm.cp.itsc2021p0722.
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Abstract Two kinds of cermet powders, WC-10Co4Cr and WC-20CrC-7Ni, were deposited on 1040 steel via high velocity air fuel (HVAF) spraying to evaluate resistance in cavitation erosion conditions with additional electrochemical effects. Coating microstructure, phase composition, and microhardness were examined along with the topography of eroded surface layers. The cavitation resistance of the WC-20CrC-7Ni coating was found to be approximately 1.3 times greater than that of the other coating, which can be attributed to its finer grain structure, lower pore density, and the presence of high Cr and Ni content in the feedstock powder which serves to strengthen the matrix.
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Matthews, S. J., and M. M. Hyland. "Statistical Optimization of HVAF Sprayed Cr3C2-NiCr Coatings for Minimizing Decarburization." In ITSC 2000, edited by Christopher C. Berndt. ASM International, 2000. http://dx.doi.org/10.31399/asm.cp.itsc2000p0543.
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Abstract High-velocity air fuel (HVAF) spraying was selected for spray trials of a Cr3C2-NiCr powder. To determine the effect of spray parameters on coating characteristics, particularly porosity and phase degradation, a statistical design of experiments was implemented. A wide range of statistical designs have been applied to the optimization of thermal spray coatings with a great deal of success. In this instance, a lack of prior knowledge and the need to assess many process-variable interactions efficiently led to the selection of a two-level full factorial design. High and low settings for each variable, including spray distance, traverse speed, and powder feedrate, were chosen based on the ranges typically used to spray similar materials. The resulting coatings were assessed for microhardness, porosity, residual stress, deposition efficiency, and phase transformation, after which several follow-up runs were conducted to explore trends brought to light by the initial factorial design.
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Hearley, J. A., J. A. Little, and A. J. Sturgeon. "Oxidation Properties of NIAI Intermetallic Coatings Prepared by High Velocity Oxy-Fuel Thermal Spraying." In ITSC 1998, edited by Christian Coddet. ASM International, 1998. http://dx.doi.org/10.31399/asm.cp.itsc1998p0089.
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Abstract A reaction-formed NiAl intermetallic compound (IMC) powder has been deposited as a coating onto low carbon steel test coupons by the High Velocity Oxy-Fuel (HVOF) process using both gaseous and liquid fuels. The microstructure of this coating has been examined using scanning electron microscopy and x-ray diffraction and was found to depend on spraying conditions. Oxidation tests on the coating in air, between the temperatures of 800°C-1200°C, revealed that an α-alumina (Al2O3) scale formed on the coating's surface. At 1200°C, a nickel spinel (NiO/NiAl2O4) and haematite (Fe2O3) phases were observed. Diffusion studies were performed to calculate an activation energy for iron ion diffusion in NiAl.
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Lopez, A. R., B. Hassan, W. L. Oberkampf, R. A. Neiser, and T. J. Roemer. "Computational Fluid Dynamics Analysis of a Wire-Feed, High-Velocity Oxygen-Fuel (HVOF) Thermal Spray Torch." In ITSC 1996, edited by C. C. Berndt. ASM International, 1996. http://dx.doi.org/10.31399/asm.cp.itsc1996p0531.
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Abstract The fluid and particle dynamics of a High-Velocity Oxygen-Fuel Thermal Spray torch are analyzed using computational and experimental techniques. Three-dimensional Computational Fluid Dynamics (CFD) results are presented for a curved aircap used for coating interior surfaces such as engine cylinder bores. The device analyzed is similar to the Metco Diamond Jet Rotating Wire (DJRW) torch. The feed gases are injected through an axisymmetric nozzle into the curved aircap. Premixed propylene and oxygen are introduced from an annulus in the nozzle, while cooling air is injected between the nozzle and the interior wall of the aircap. The combustion process is modeled using a single-step finite- rate chemistry model with a total of 9 gas species which includes dissociation of combustion products. A continually-fed steel wire passes through the center of the nozzle and melting occurs at a conical tip near the exit of the aircap. Wire melting is simulated computationally by injecting liquid steel particles into the flow field near the tip of the wire. Experimental particle velocity measurements during wire feed were also taken using a Laser Two-Focus (L2F) velocimeter system. Flow fields inside and outside the aircap are presented and particle velocity predictions are compared with experimental measurements outside of the aircap.
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Varga, M., L. Janka, M. Rodríguez Ripoll, L. M. Berger, S. Thiele, V. Matikainen, P. Vuoristo, L. Janka, and H. Ben Hamouda. "High Temperature Sliding of TiC Based Hardmetal Coatings Against TWIP Steel." In ITSC2021, edited by F. Azarmi, X. Chen, J. Cizek, C. Cojocaru, B. Jodoin, H. Koivuluoto, Y. C. Lau, et al. ASM International, 2021. http://dx.doi.org/10.31399/asm.cp.itsc2021p0278.
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Abstract Manufacturing of steel components is often done at high temperatures (HT) posing a serious challenge to components such as forming tools. Thermal spray coatings provide a cost-effective solution for surface protection under HT, corrosive environments and severe wear conditions. Thermally sprayed coatings based on cubic hard materials such as TiC and TiCN can provide an alternative to widely used Cr3C2-NiCr. While the latter possess a superb oxidation resistance and wear resistance at HT, they are prone to degradation in the presence of Mn, an element commonly alloyed in many modern steel grades such as TWIP (twinning-induced plasticity steel). In this study, a (Ti,Mo)(C,N)-29% Ni hardmetal feedstock powder was prepared by agglomeration and sintering. Coatings were deposited using a high velocity air-fuel (HVAF) spray process. The coating was benchmarked against a standard Cr3C2-NiCr coating obtained with the same spray process. Our work comprises analyses of the feedstock powder along with the resulting coating microstructure after deposition and heat treatment. Further, the HT sliding behavior against TWIP steel using a HT pin-on-disc tribometer at 700°C was investigated. The results showed a clear benefit of the TiCN-based coating, with almost no wear detected, while the Cr3C2-coating showed a significant wear loss. Based on these results, the TiCN-based coating is regarded as potential solution for prospective forming applications of modern high Mn steels, such as TWIP.
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Saad, Idris, and Saiful Bari. "Effect by Guide Vane Swirl and Tumble Device to Improve the Air-Fuel Mixing of Diesel Engine Running With Higher Viscous Fuels." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-62297.
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The purpose of this study was to investigate the effect guide vane swirl and tumble device (GVSTD) on the in-cylinder airflow particularly to generate turbulent kinetic energy (TKE) and velocity inside the combustion chamber and around fuel injected region. High velocity and TKE would accelerate the evaporation, diffusion and mixing processes of CI engines, particularly when alternative fuels of higher viscosity and density (known as HVF — higher viscous fuel) are used. A verified simulation base model was prepared by the SolidWorks software and analysed using ANSYS software to study the reference data of the resulting in-cylinder airflow characteristics. Then GVSTD models were developed and imposed on the intake runner of the base model. The parametric optimization technique was used to find the optimum number of vanes for the GVSTD model. This was done by preparing 10 GVSTD models with the vane number varied from 3 to 12. The models were then tested on the base model individually. Generally, GVSTD improve in-cylinder TKE and velocity. Additionally, this research found that GVSTD with 3 vanes resulted in an improved TKE and velocity of about 6.3% and 10.4% respectively when compared to the base model. Therefore, it may be said that the use of GVSTD can increase the chances to improve the performance of a CI engine and reduce the emission when run on HVF.
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Fiala, Petr, and Karel Hajmrle. "Cobalt Based Antifretting Coatings." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-23547.
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Some cobalt based coatings have excellent antifretting properties when rubbed against titanium alloy hardware. The coatings are presently used in the gas turbine industry for specific antifretting applications. Their superior performance compared to the current art CuNiIn coatings has been demonstrated. This paper discusses the influence of coating structure on its mechanical properties and antifretting performance. The coating structure can be greatly modified by changing the coating application method (HVOF or plasma spraying). HVOF (High Velocity Oxygen-Fuel) and plasma spray equipment together with TriplexPro™ 200 gun configured to spray HVOF and plasma type coatings were used. The resulting coating properties can be tailored to specific application requirements encountered in aircraft engines and other industrial applications.
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Russo, Dario, Andrea Scrivani, Gabriele Rizzi, Alessandro Lanzi, and Carlo Giolli. "eXclean®: A New Surface Preparation of Turbine Components for Deposition of MCrAlY Coatings With Super Clean Interface." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50685.
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The most commonly used structural materials for blades and other high temperature components of gas turbines are nickel base superalloys. A TBC protection coating system consists of a top coat of yttria partially stabilized zirconia and an underlying bond coat, usually MCrAlY (where M stands for Ni, Co or a combination of both). MCrAlYs are normally deposited by the thermal spray processes: air plasma spray (APS), vacuum plasma spray (VPS/LPPS) or high velocity oxygen fuel (HVOF). The adhesion between the bond coat and the substrate, and therefore of the whole thermal barrier system, strongly depends upon the surface roughness. A high level of roughness generally denotes better adhesion, especially with the HVOF thermal spray process where it is a necessity. Generally the roughness is reached by means of grit blasting with an abrasive media; this results in a certain level of surface contamination due to the entrapment of abrasive particles. The aim of this work was to set up a new surface preparation process in order to obtain a completely clean surface with a suitable roughness, which can be coated afterwards with HVOF or VPS/LPPS thermal spray technology. The tests carried out by this process on turbine blades, coated with a HVOF system, led to obtaining a coating/base material interface without any contamination caused by the surface preparation.