Journal articles: '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.

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Liu, Xuanzhen, Xiaofeng Zhao, and Fan Yang. "Room-Temperature and High-Temperature Wear Behaviors of As-Sprayed and Annealed Cr3C2-25NiCr Coatings Prepared by High Velocity Air-Fuel Spraying." Coatings 10, no. 11 (November 13, 2020): 1090. http://dx.doi.org/10.3390/coatings10111090.

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Cr3C2-25NiCr coatings were deposited on stainless steel substrates by high velocity air-fuel (HVAF) spraying. Friction and wear behaviors of as-sprayed and annealed coatings were investigated both at room-temperature (RT) and 600 °C (high-temperature, HT). The results show that annealing at 600 °C in air is effective to enhance the wear performances of the coating both at RT and HT. The enhanced wear resistance of annealed coatings is discussed from the oxide growth and the microstructural evolution of the coatings. The wear behavior of the annealed coating follows the abrasive mechanism at RT and changes to an oxidative wear at HT, in which formation of a tribo-oxide layer plays a critical role to reduce the friction coefficient and to protect the underlying coatings from abrasive damage. The findings of this work reveal the significance of oxide-scale growth and microstructural evolution on the HT wear behaviors of the Cr3C2-25NiCr coating, which provides strategies for enhancing the wear properties of such coatings for HT applications.

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Torkashvand, Kaveh, Vinod Krishna Selpol, Mohit Gupta, and Shrikant Joshi. "Influence of Test Conditions on Sliding Wear Performance of High Velocity Air Fuel-Sprayed WC–CoCr Coatings." Materials 14, no. 11 (June 4, 2021): 3074. http://dx.doi.org/10.3390/ma14113074.

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Sliding wear performance of thermal spray WC-based coatings has been widely studied. However, there is no systematic investigation on the influence of test conditions on wear behaviour of these coatings. In order to have a good understanding of the effect of test parameters on sliding wear test performance of HVAF-sprayed WC–CoCr coatings, ball-on-disc tests were conducted under varying test conditions, including different angular velocities, loads and sliding distances. Under normal load of 20 N and sliding distance of 5 km (used as ‘reference’ conditions), it was shown that, despite changes in angular velocity (from 1333 rpm up to 2400 rpm), specific wear rate values experienced no major variation. No major change was observed in specific wear rate values even upon increasing the load from 20 N to 40 N and sliding distance from 5 km to 10 km, and no significant change was noted in the prevailing wear mechanism, either. Results suggest that no dramatic changes in applicable wear regime occur over the window of test parameters investigated. Consequently, the findings of this study inspire confidence in utilizing test conditions within the above range to rank different WC-based coatings.

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Myalska, H., K. Szymański, and G. Moskal. "Microstructure And Properties Of WC-Co HVAF Coatings Obtained From Standard, Superfine And Modified By Sub-Micrometric Carbide Powders." Archives of Metallurgy and Materials 60, no. 2 (June 1, 2015): 759–66. http://dx.doi.org/10.1515/amm-2015-0203.

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Abstract In this paper, microstructure and some properties of various coatings based on WC-Co obtained by the High Velocity Air Fuel technique are discussed. Initially, two WC-Co 83-17 powders of standard and superfine size were examined as a feedstock for a coatings deposition on a steel substrate. A standard Amperit 526.074 powder and an Inframat superfine powder were applied. Then three different sub-micrometric powders, WC, Cr3C2 and TiC were applied to modify the microstructure of WC-Co (Amperit 526.074). The aim of the investigations was to compare the microstructure and basic properties of coatings deposited from different components. The influence of sub-micrometric additions on mechanical properties of basic coatings was analyzed. Microstructure characterization of powders by using SEM and characterization of their technological properties as well, are presented. For all manufactured coatings obtained by a High Velocity Air Fuel method, the microhardness, porosity, adhesion to a substrate, and fracture toughness were determined. An improvement in WC-Co coating properties, as a result of sub-micrometric carbides addition, was revealed.

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TROMPETTER, W., A. MARKWITZ, and M. HYLAND. "USE OF IBA TECHNIQUES TO CHARACTERIZE HIGH VELOCITY THERMAL SPRAY COATINGS." Modern Physics Letters B 15, no. 28n29 (December 20, 2001): 1428–36. http://dx.doi.org/10.1142/s0217984901003354.

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Spray coatings are being used in an increasingly wide range of industries to improve the abrasive, erosive and sliding wear of machine components. Over the past decade industries have moved to the application of supersonic high velocity thermal spray techniques. These coating techniques produce superior coating quality in comparison to other traditional techniques such as plasma spraying. To date the knowledge of the bonding processes and the structure of the particles within thermal spray coatings is very subjective. The aim of this research is to improve our understanding of these materials through the use of IBA techniques in conjunction with other materials analysis techniques. Samples were prepared by spraying a widely used commercial NiCr powder onto substrates using a HVAF (high velocity air fuel) thermal spraying technique. Detailed analysis of the composition and structure of the power particles revealed two distinct types of particles. The majority was NiCr particles with a significant minority of particles composing of SiO 2/ CrO 3. When the particles were investigated both as raw powder and in the sprayed coating, it was surprising to find that the composition of the coating meterial remained unchanged during the coating process despite the high velocity application.

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HAMILTON, ANURAG, ASHOK SHARMA, and UPENDER PANDEL. "SOLID PARTICLE EROSION RESISTANCE OF HVAF-SPRAYED WC-10Co-4Cr COATING ON CA6NM STEEL." Surface Review and Letters 24, Supp01 (October 31, 2017): 1850011. http://dx.doi.org/10.1142/s0218625x18500117.

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In the present investigation, WC-10Co-4Cr coating was deposited by high velocity air-fuel (HVAF) process on CA6NM hydro turbine steel. A detailed microstructural and phase compositional study was carried out on the coating. Mechanical properties of the coating were also evaluated. WC-10Co-4Cr coating showed a homogeneous, well-bonded structure with low porosity, which is mainly attributed to less decarburization of WC. Erosion resistance of the coating was evaluated by air jet erosion tester at three different impingement angles (30[Formula: see text], 60[Formula: see text] and 90[Formula: see text]) for 35 and 70[Formula: see text]m/s impact velocities. The FESEM micrographs were taken, before and after erosion tests, to determine the erosion mechanism. The test results revealed that the coating protects the substrate at 30[Formula: see text], 60[Formula: see text] and 90[Formula: see text] impingement angles. At 70[Formula: see text]m/s impact velocity, uncoated and coated steel showed higher cumulative volume loss than in the case of 35[Formula: see text]m/s impact velocity. It was observed that uncoated steel showed a ductile behavior during erosion and WC-10Co-4Cr coating showed mixed (ductile and brittle) mode of fracture during erosion.

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Lyphout, Christophe, Giovanni Bolelli, Eva Smazalova, Kazuto Sato, Junya Yamada, Šarka Houdková, Luca Lusvarghi, and Tiziano Manfredini. "Influence of hardmetal feedstock powder on the sliding wear and impact resistance of High Velocity Air-Fuel (HVAF) sprayed coatings." Wear 430-431 (July 2019): 340–54. http://dx.doi.org/10.1016/j.wear.2019.05.016.

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Xie, Xiaolong, Fucheng Yin, Xinming Wang, Xuemei Ouyang, Minghuan Li, and Jing Hu. "Corrosion Resistance to Molten Zinc of a Novel Cermet Coating Deposited by Activated Combustion High-Velocity Air Fuel (AC-HVAF)." Journal of Thermal Spray Technology 28, no. 6 (July 22, 2019): 1252–62. http://dx.doi.org/10.1007/s11666-019-00893-x.

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Ganvir, Ashish, Adwait Rajeev Jahagirdar, Antonio Mulone, Louise Örnfeldt, Stefan Björklund, Uta Klement, and Shrikant Joshi. "Novel utilization of liquid feedstock in high velocity air fuel (HVAF) spraying to deposit solid lubricant reinforced wear resistant coatings." Journal of Materials Processing Technology 295 (September 2021): 117203. http://dx.doi.org/10.1016/j.jmatprotec.2021.117203.

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Liu, Juan, Luo Ping Pan, and Jiang Cheng Yu. "Research on Cavitation and Silt Erosion Resistance of HVAF Coatings." Materials Science Forum 686 (June 2011): 618–22. http://dx.doi.org/10.4028/www.scientific.net/msf.686.618.

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Two kinds of harding coatings: WC-12Co and CrC-25NiCr were made by active combustion-high velocity air flue (AC-HVAF). By the rotating disc test rig, the systematical experiments were carried to study the wear resistance and mechanisms of coatings on different test conditions: pure water cavitation and sandy water silt erosion. On the sandy water silt erosion test condition, the wear resistance of HVAF coatings is better than that of metal matrix. However, it is reverse on the other test condition. Basing on the scanning electron microscope (SEM) analysis, the surface morphology of coating surface after wear was studied. And the influence of adhesion strength, micro-hardness and porosity ratio of HVAF coating on wear resistance was researched in detail.

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Itoh, Y., M. Saitoh, and M. Tamura. "Characteristics of MCrAlY Coatings Sprayed by High Velocity Oxygen-Fuel Spraying System." Journal of Engineering for Gas Turbines and Power 122, no. 1 (July 30, 1999): 43–49. http://dx.doi.org/10.1115/1.483173.

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High velocity oxygen-fuel (HVOF) spraying system in open air has been established for producing the coatings that are extremely clean and dense. It is thought that the HVOF sprayed MCrAlY (M is Fe, Ni and/or Co) coatings can be applied to provide resistance against oxidation and corrosion to the hot parts of gas turbines. Also, it is well known that the thicker coatings can be sprayed in comparison with any other thermal spraying systems due to improved residual stresses. However, thermal and mechanical properties of HVOF coatings have not been clarified. Especially, the characteristics of residual stress, that are the most important property from the view point of production technique, have not been made clear. In this paper, the mechanical properties of HVOF sprayed MCrAlY coatings were measured in both the case of as-sprayed and heat-treated coatings in comparison with a vacuum plasma sprayed MCrAlY coatings. It was confirmed that the mechanical properties of HVOF sprayed MCrAlY coatings could be improved by a diffusion heat treatment to equate the vacuum plasma sprayed MCrAlY coatings. Also, the residual stress characteristics were analyzed using a deflection measurement technique and a X-ray technique. The residual stress of HVOF coating was reduced by the shot-peening effect comparable to that of a plasma spray system in open air. This phenomena could be explained by the reason that the HVOF sprayed MCrAlY coating was built up by poorly melted particles. [S0742-4795(00)00701-8]

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Kiilakoski, Jarkko, Richard Trache, Stefan Björklund, Shrikant Joshi, and Petri Vuoristo. "Process Parameter Impact on Suspension-HVOF-Sprayed Cr2O3 Coatings." Journal of Thermal Spray Technology 28, no. 8 (October 31, 2019): 1933–44. http://dx.doi.org/10.1007/s11666-019-00940-7.

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Abstract Chromium oxide (Cr2O3) is commonly used as an atmospheric plasma-sprayed (APS) coating from powder feedstock in applications requiring resistance to sliding wear and corrosion, as well as amenability to texturing, e.g., in anilox rolls. Recently, high-velocity oxy-fuel spray methods involving suspension feedstock have been considered an extremely promising alternative to produce denser and more homogeneous chromium oxide coatings with lower as-sprayed surface roughness, higher hardness and potentially superior wear performance compared to conventional APS-sprayed coatings. In this study, the impact of process parameters namely auxiliary air cleaning nozzles and a transverse air curtain on suspension high-velocity oxy-fuel-sprayed Cr2O3 suspensions is presented. The produced coatings are characterized for their microstructure, mechanical properties and wear resistance by cavitation erosion. The results reveal the importance of optimized air nozzles and air curtain to achieve a vastly improved coating structure and performance.

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GABBITAS, BRIAN, ASMA SALMAN, DELIANG ZHANG, and PENG CAO. "REVIEW OF RESEARCH WORK ON Ti-BASED COMPOSITE COATINGS." International Journal of Modern Physics B 23, no. 06n07 (March 20, 2009): 1707–12. http://dx.doi.org/10.1142/s0217979209061500.

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The service life of industrial components is limited predominantly by Chemical corrosion/mechanical wear. The project is concerned with the investigation of the capability of Ti ( Al , O )/ Al 2 O 3 coatings to improve the service life of tool steel (H13) used for dies in aluminium high pressure die casting. This paper gives a general review on the research work conducted at the University of Waikato on producing and evaluating the titanium/alumina based composite coatings. The powder feedstocks for making the composite coatings were produced by high energy mechanical milling of a mixture of Al and TiO 2 powders in two different molar ratios followed by a thermal reaction process. The feedstocks were then thermally sprayed using a high velocity air-fuel (HVAF) technique on H13 steel substrates to produce a Ti ( Al , O )/ Al 2 O 3 composite coatings. The performance of the coating was assessed in terms of thermal shock resistance and reaction kinetics with molten aluminium. The composite powders and coatings were characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD).

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Salman, Asma, Brian Gabbitas, and De Liang Zhang. "Titanium Based Composite Coatings Deposited by High Velocity Oxygen Fuel (HVOF) and Plasma Spraying Methods." Key Engineering Materials 551 (May 2013): 127–32. http://dx.doi.org/10.4028/www.scientific.net/kem.551.127.

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The study involves a special class of composites called interpenetrating phase composites (IPCs). The Ti(Al,O)/Al2O3 composite was produced using high energy mechanical milling of a mixture of TiO2 and Al followed by a high temperature self-propagating reaction. Characteristics of the feedstock powder were improved by treating it with an organic binder. The feedstock powder was thermally sprayed on to a substrate using high velocity oxygen fuel (HVOF) and air plasma spraying methods. The spraying methods resulted in coatings with significantly different microstructures. Compared with plasma sprayed coating, the coating produced by a HVOF spraying method showed a much finer and densely packed microstructure.

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Alwan, Hussam L., Yury S. Korobov, N. N. Soboleva, N. V. Lezhnin, A. V. Makarov, and M. S. Deviatiarov. "Study of Cavitation Erosion-Corrosion Resistance of Thermally Sprayed Ni-Based Coatings Prepared by HVAF Process." Solid State Phenomena 299 (January 2020): 893–901. http://dx.doi.org/10.4028/www.scientific.net/ssp.299.893.

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In this study, two Ni-based coating materials, namely NiCrMoNb and NiCrBSi, have been applied using High Velocity Air Fuel (HVAF) thermal spraying process. The performance of the coated surface in resistance to cavitation erosion-corrosion of both coating materials, has been evaluated using an ultrasonic vibratory method. The cumulative material loss and erosion rate curves of the two coatings have been discussed. Surface topography, microhardness, macroscopic images, and scanning electron microscope (SEM) micrographs were used to characterize the coatings before and after the cavitation test. The cavitation results showed that the NiCrMoNb coating surface has exhibited better performance than the NiCrBSi coating surface under the same test conditions. The total cumulative weight loss of the NiCrMoNb coating was about 1/3 that of the NiCrBSi coating. SEM micrographs of the eroded surfaces showed that the surface layer of the NiCrBSi coating was more damaged, compared to layer of the NiCrMoNb coating. Overall, the NiCrMoNb coating can be effectively used against the cavitation wear, due to its superior performance.

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Gao, Xing, Chang Li, Dacheng Zhang, Hexin Gao, and Xing Han. "Numerical analysis of the activated combustion high-velocity air-fuel (AC-HVAF) thermal spray process: A survey on the parameters of operation and nozzle geometry." Surface and Coatings Technology 405 (January 2021): 126588. http://dx.doi.org/10.1016/j.surfcoat.2020.126588.

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Morscher, Gregory N., Ragav P. Panakarajupally, and Leland Hoffman. "The Versatility of HVOF Burner Rig Testing for Ceramic Matrix Composite Evaluation." Journal of Composites Science 5, no. 8 (August 20, 2021): 223. http://dx.doi.org/10.3390/jcs5080223.

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Effective testing of ceramic matrix composites (CMCs) and CMC/coating systems for high temperature, high stress, high velocity and/or severe oxidation/corrosion environments is a critical need in materials/coatings evaluation for extreme environments of hot section parts in jet engine and hypersonic applications. Most current technology can evaluate two or three of the extreme conditions for a given application; however, incorporating as many of the extreme thermo-mechanical-environmental factors is highly advantageous to understand combinatorial effects. A high velocity oxygen fuel (HVOF) burner rig offers an excellent platform to evaluate many of these extreme conditions. In this work, the following three different thermo-mechanical-environmental test conditions using an HVOF rig on SiC-based CMCs are highlighted: (1) fatigue at temperature for >Mach 1 velocity and high temperature compared to typical stagnant air test environment, (2) high temperature hard particle erosion at temperature for ≤Mach 1 conditions and (3) ~Mach 5 near-hypersonic velocity conditions at very high temperature exposure.

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Singh, Hazoor, and Buta Singh Sidhu. "Erosion Characteristics of HVOF Developed Cr₃C₂-NiCr and WC-Co Coatings." Materials Science Forum 751 (March 2013): 71–79. http://dx.doi.org/10.4028/www.scientific.net/msf.751.71.

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Erosion behavior of the high velocity oxy fuel (HVOF) deposited Cr3C2-NiCr and WC-Co coatings on boiler tube steels was evaluated. The solid particle erosion study was conducted, using an air jet erosion test rig at a velocity of 26 m/s and impingement angles of 300 and 900, on uncoated as well as HVOF spray coated boiler tube steels at 250°C. The coatings are significantly harder than the substrate steel and less porous. Scanning electron microscopy (SEM) technique was used to analyze the eroded surface. Mass loss of the coatings was found higher than the boiler tube steel.

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SAKAKI, Kazuhiko, Hidenori MIYAJIMA, Masami KATO, Kazuto SATO, and Junya KITAMURA. "J043016 Effect of Spray Gun Nozzle Geometry on Mechanical Properties of WC-Cermet Coatings Prepared by High Velocity Air Fuel Spraying." Proceedings of Mechanical Engineering Congress, Japan 2013 (2013): _J043016–1—_J043016–4. http://dx.doi.org/10.1299/jsmemecj.2013._j043016-1.

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29

Kumar, Nitish, Mohit Gupta, Daniel E. Mack, Georg Mauer, and Robert Vaßen. "Columnar Thermal Barrier Coatings Produced by Different Thermal Spray Processes." Journal of Thermal Spray Technology 30, no. 6 (July 6, 2021): 1437–52. http://dx.doi.org/10.1007/s11666-021-01228-5.

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AbstractSuspension plasma spraying (SPS) and plasma spray-physical vapor deposition (PS-PVD) are the only thermal spray technologies shown to be capable of producing TBCs with columnar microstructures similar to the electron beam-physical vapor deposition (EB-PVD) process but at higher deposition rates and relatively lower costs. The objective of this study was to achieve fundamental understanding of the effect of different columnar microstructures produced by these two thermal spray processes on their insulation and lifetime performance and propose an optimized columnar microstructure. Characterization of TBCs in terms of microstructure, thermal conductivity, thermal cyclic fatigue lifetime and burner rig lifetime was performed. The results were compared with TBCs produced by the standard thermal spray technique, atmospheric plasma spraying (APS). Bondcoats deposited by the emerging high-velocity air fuel (HVAF) spraying were compared to the standard vacuum plasma-sprayed (VPS) bondcoats to investigate the influence of the bondcoat deposition process as well as topcoat–bondcoat interface topography. The results showed that the dense PS-PVD-processed TBC had the highest lifetime, although at an expense of the highest thermal conductivity. The reason for this behavior was attributed to the dense intracolumnar structure, wide intercolumnar gaps and high column density, thus improving the strain tolerance and fracture toughness.

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Alnaser, Ibrahim A., Mohammed Yunus, Rami Alfattani, and Turki Alamro. "High-Temperature Corrosion of APS- and HVOF-Coated Nickel-Based Super Alloy under Air Oxidation and Melted Salt Domains." Materials 14, no. 18 (September 7, 2021): 5119. http://dx.doi.org/10.3390/ma14185119.

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Various thermal spraying approaches, such as air/atmospheric plasma spraying (APS) and high-velocity oxy-fuel (HVOF) spraying, are widely employed by plants owing to their flexibility, low costs and the high surface quality of the manufactured product. This study focuses on the corrosion behavior of a Ni superalloy coated with powder Cr3C2-25NiCr through APS and HVOF at 950 °C under air oxidation and Na2SO4 + 0.6V2O5 molten salt environments (MSE). The results show that HVOF-deposited Ni superalloys have higher hardness and bond strength than the respective APS coating. The thermo-gravimetric probe reveals that the Ni superalloys exposed to an oxidizing air environment has a minor mass gain compared to those under the MSE domain for both non-coated and coated samples, in line with the parabola curvature rate oxidizing law. The Ni superalloys show good corrosion resistance but poor oxidation resistance in APS-deposited Ni superalloys under the MSE. HVOF-coated Ni superalloys in both environments exhibit better corrosion resistance and lower mass gain than APS-coated superalloys. The excellent coating characteristics of HVOF-coated Ni superalloys lead to their better high-temperature corrosion performance than APS.

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Prasanna, P. Akshay, P. Subramani, V. Sreenivasulu, N. Arivazhagan, M. Manikandan, and Duoli WU. "High-Temperature Corrosion Behaviour of HVOF Sprayed Cr3C2- 25NiCr Coated on Alloy X22CrMoV12-1 at 600o C." Journal of Thermal Spray and Engineering 1, no. 1 (2018): 7–12. http://dx.doi.org/10.52687/2582-1474/112.

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The present study investigates the hot corrosion behaviour of high-velocity oxy-fuel sprayed alloy X22CrMoV12-1 with Cr3C2-25NiCr coating at 600oC. The study was carried out by air and molten salt environment for both coated and uncoated substrates for 50 cycles. Thermogravimetry analysis was carried out to evaluate the hot corrosion by calculating the mass changes in each cycle. The results show that coating provides the marginally good corrosion resistance than the uncoated alloy. The formation of Fe2O3 and MoO3 phases in the uncoated substrates in both air and molten salt environments reduces the corrosion resistance at the high-temperature environment. The formation of Ni2Oand spinel oxide NiCr2O4 provided good resistance to corrosion in the coated substrates in the air and molten salt environment.

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Mohd Zulkifli, S., Muhammad Azizi Mat Yajid, Mohd Hasbullah Idris, M. Daroonparvar, and Halimaton Hamdan. "TGO Formation with NiCoCrAlYTa Bond Coat Deposition Using APS and HVOF Method." Advanced Materials Research 1125 (October 2015): 18–22. http://dx.doi.org/10.4028/www.scientific.net/amr.1125.18.

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Formation of thin and continuous layer of thermally grown oxide (TGO) in thermal barrier coating (TBC) are essential in order to avoid coating failure for high temperature applications. As-sprayed high velocity oxy-fuel (HVOF) bond coat can provide more uniform TGO layer in TBC system and much less oxide compare to air plasma spray (APS). In this paper, both APS and HVOF method are used to deposit NiCoCrAlYTa bond coat on Inconel 625 substrate followed by topcoat, YSZ deposition. Pre-oxidation process was done in normal oxygen furnace at 1000°C for 12 to 24 hours to study the characteristic of TGO formation via these two different methods. From the result obtained, it shows that HVOF method provide better TGO formation as compared to APS.

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Secosan, Ioan Florin, Ion Dragoş Uţu, Viorel Aurel Şerban, and Waltraut Brandl. "Wear Resistance of Internal WC-CoCr Coatings Produced by High Velocity Oxy-Fuel Spraying." Solid State Phenomena 188 (May 2012): 416–21. http://dx.doi.org/10.4028/www.scientific.net/ssp.188.416.

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Thermal spray coatings, and in particular those applied by HVOF process, are being used in a diverse range of engineering applications to extend component life by retarding wear and corrosion degradation [1]. Coatings performance is strongly dependent on microstructure [2]. The mechanical properties are a complex function of carbide size, shape and distribution, matrix hardness and toughness and the presence of various reaction products. This paper is focused on the wear resistance of WC-based coatings containing 10 mass% Co and 4 mass% Cr as the metallic binder, involving a heat-treated steel rings as substrate, a hot rolled product of structural steel in accordance with DIN EN 10113-2 for steel construction, detaining a tensile strength about 520-680 N/mm2. A feedstock powder of WC-CoCr 86 10 4 agglomerated/sintered was used for coatings production. It has good properties, such as: high resistance against oxidation and corrosion (due to the metallic component), good wear resistance (due to the ceramic component) and with a hardness in range of 1000-1300HV. The coatings have been produced by HVOF spraying of four different WC-CoCr grain size of powder particles, such as:sample 1 (-45+22µm), sample2 (-22+5µm), sample 3 (-10+2µm) and sample 4 (-2+0.5µm), using an ID CoolFlow mono gun developed especially for internal surfaces. This type of gun is a HP HVOF system for high pressure, but cold internal HVOF spraying. The morphology and the structure of the sprayed coatings were investigated by means of scanning electron microscopy (SEM/EDS) and the qualitative and quantitative phase composition of those coatings were determined applying the x-ray diffraction technique (XRD). In order to determine the sliding wear resistance of the coated samples, it was used the pin on ring test method under dry condition, with and without compressed air. This method consists into a stationary ball loaded against a ring sample in relative motion. The sliding wear rate of the tested samples was calculated from the volume of material lost during the test. The investigated samples were examined by means of stereo and light microscopy before and after exposure to wear tests. Based on the obtained results it was demonstrated that the coatings obtained from -10+2µm powder particles exhibit an optimal wear behavior when exposed to severe conditions.

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Kaur, Manpreet, Harpreet Singh, and Satya Prakash. "X-Ray Diffraction Study of High Velocity Oxy-Fuel (HVOF) Sprayed Cr₃C₂-NiCr Coating." Advanced Materials Research 620 (December 2012): 186–92. http://dx.doi.org/10.4028/www.scientific.net/amr.620.186.

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Among the various characterization techniques, X-ray diffraction (XRD) analysis is a key method which reveals various phases and protective oxides formed on the surfaces of exposed specimens. This paper discusses the XRD study of two boiler steels, namely ASTMSAE213-T22 and SAE-347H with and without High Velocity Oxy-fuel (HVOF) spray Cr3C2-NiCr coating, which were exposed to air, molten salt [Na2SO4-82%Fe2(SO4)3], and actual boiler environments. XRD analysis has been discussed and the results obtained from the analysis are shown. The performance of the steels was found to improve after the deposition of the coating, which may be attributed to the formation of protective phases.

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Malinina, Marina, Tina Sammi, and Michael M. Gasik. "Corrosion Resistance of Homogeneous and FGM Coatings." Materials Science Forum 492-493 (August 2005): 305–10. http://dx.doi.org/10.4028/www.scientific.net/msf.492-493.305.

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Homogeneous and FGM environmental barrier coatings (EBC) made of alumina – NiCr on the steel substrates by high-velocity oxygen fuel (HVOF) spraying technique were studied. At room temperature, these coatings were characterized by DC polarization measurements and by electrochemical impedance spectroscopy (EIS) after various exposure times in highly aggressive basic solutions. At high temperatures (400-750°C) corrosion resistance was tested in respect to sulfide – sulfate – chloride – carbonate melts in air, which simulates environments in incinerators, kraft recovery boilers and turbines. After testing, the samples were examined by SEM and EDS and their corrosion resistance was compared.

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36

Zafer, Yunus Emre, Sneha Goel, Ashish Ganvir, Anton Jansson, and Shrikant Joshi. "Encapsulation of Electron Beam Melting Produced Alloy 718 to Reduce Surface Connected Defects by Hot Isostatic Pressing." Materials 13, no. 5 (March 9, 2020): 1226. http://dx.doi.org/10.3390/ma13051226.

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Defects in electron beam melting (EBM) manufactured Alloy 718 are inevitable to some extent, and are of concern as they can degrade mechanical properties of the material. Therefore, EBM-manufactured Alloy 718 is typically subjected to post-treatment to improve the properties of the as-built material. Although hot isostatic pressing (HIPing) is usually employed to close the defects, it is widely known that HIPing cannot close open-to-surface defects. Therefore, in this work, a hypothesis is formulated that if the surface of the EBM-manufactured specimen is suitably coated to encapsulate the EBM-manufactured specimen, then HIPing can be effective in healing such surface-connected defects. The EBM-manufactured Alloy 718 specimens were coated by high-velocity air fuel (HVAF) spraying using Alloy 718 powder prior to HIPing to evaluate the above approach. X-ray computed tomography (XCT) analysis of the defects in the same coated sample before and after HIPing showed that some of the defects connected to the EBM specimen surface were effectively encapsulated by the coating, as they were closed after HIPing. However, some of these surface-connected defects were retained. The reason for such remnant defects is attributed to the presence of interconnected pathways between the ambient and the original as-built surface of the EBM specimen, as the specimens were not coated on all sides. These pathways were also exaggerated by the high surface roughness of the EBM material and could have provided an additional path for argon infiltration, apart from the uncoated sides, thereby hindering complete densification of the specimen during HIPing.

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Ma, Ning, Zhen Xiong Cheng, Huan Tao Wu, and Fu Xing Ye. "HVOF Spraying Process Optimization for the Deposition of Submicron Structural WC-12Co Coatings." Advanced Materials Research 785-786 (September 2013): 839–43. http://dx.doi.org/10.4028/www.scientific.net/amr.785-786.839.

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The submicron structural WC-12Co coatings were deposited by a high-velocity oxy-fuel (HVOF) system from agglomerated WC-12Co powders with carbide grain size of 0.7~0.9μm in this study. Effects of HVOF spraying parameters on the microstructure and properties of submicron structural WC-12Co coatings were examined. The results showed that both the fuel flow rate and spraying distance influenced significantly the microhardness and porosity of coatings, and cooling condition also had a few effect on the porosity of coatings. Through a series of experiments, the spraying parameters for the WC-12Co coatings preparation were optimized as follows: propane gas pressure was 0.65 MPa, propane flow rate of 16.7 L/min, oxygen pressure of 0.7 MPa, oxygen flow rate of 100 L/min, spraying distance of 270 mm and with compressed air cooling. The porosity of WC-12Co coating sprayed at the optimum parameters was lower than 1%, and its microhardness was HV0.11141±67.

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Hu, Wenjie, Sergii Markovych, Kun Tan, Oleksandr Shorinov, and Tingting Cao. "SURFACE REPAIR OF AIRCRAFT TITANIUM ALLOY PARTS BY COLD SPRAYING TECHNOLOGY." Aerospace technic and technology, no. 3 (June 26, 2020): 30–42. http://dx.doi.org/10.32620/aktt.2020.3.04.

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Titanium alloys have the advantages of high specific strength, good corrosion resistance, high heat resistance, and low density, which is the main structural material of aerospace system components, including compressor blade, cartridge receiver, blisk, engine nacelle, thermal baffle and so on. At present, about three-quarters of titanium and titanium alloys in the world are used in the aerospace industry, including A350 for 14%, F18 for 15 %, B787 for 15 %, SU-57 for 18 %, J-20 for 20 %, FC-31 fighters for 25 %, F35 for about 27 %, and F22 up to 41 %, etc, so it has the reputation of "space metal". However, its low wear resistance limits the further development of titanium alloy. Besides, its high manufacturing cost, if only require the occasion of surface performance can reduce the use of the substrate, and then reduced the cost. Therefore, the study of aircraft titanium alloy is of great significance, the protection of titanium alloy includes alloying technology and coating technology. Alloying technology mainly adds other elements on its basis to improve the performance, while the most popular method is coating technology, the present, there are many coating technologies, include high-velocity oxy-fuel (HVOF), HVAF, cold spraying, laser cladding, laser micro-fusion in-situ synthesized technology, micro-arc oxidation, laser melt injection (LMI), supersonic laser deposition (SLD) and supersonic plasma spray technology, surface repair titanium alloy parts by cold spraying technology are good ways to solve those problems. Because of its low process temperature, no oxidation, only plastic deformation, and repair efficiency are high, the protective coating has high bonding strength and good impact toughness. In this paper, the types and applications of aircraft titanium alloys were reviewed, the latest research results of surface repair of titanium alloys parts by cold spraying technology were reviewed, technological parameters of the cold gas dynamic spraying technology was analyzed, including powder size of particles, morphologies, critical velocity, particle compression rate, substrate preheating effects on the particle/substrate adhesion, etc.

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39

Porcayo-Calderón, J., O. Sotelo-Mazón, M. Casales-Diaz, J. A. Ascencio-Gutierrez, V. M. Salinas-Bravo, and L. Martinez-Gomez. "Electrochemical Study of Ni20Cr Coatings Applied by HVOF Process in ZnCl2-KCl at High Temperatures." Journal of Analytical Methods in Chemistry 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/503618.

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Corrosion behavior of Ni20Cr coatings deposited by HVOF (high velocity oxygen-fuel) process was evaluated in ZnCl2-KCl (1 : 1 mole ratio) molten salts. Electrochemical techniques employed were potentiodynamic polarization curves, open circuit potential, and linear polarization resistance (LPR) measurements. Experimental conditions included static air and temperatures of 350, 400, and 450°C. 304-type SS was evaluated in the same conditions as the Ni20Cr coatings and it was used as a reference material to assess the coatings corrosion resistance. Coatings were evaluated as-deposited and with a grinded surface finished condition. Results showed that Ni20Cr coatings have a better corrosion performance than 304-type SS. Analysis showed that Ni content of the coatings improved its corrosion resistance, and the low corrosion resistance of 304 stainless steel was attributed to the low stability of Fe and Cr and their oxides in the corrosive media used.

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Mahalingam, Savisha, Abreeza Manap, Salmi Mohd Yunus, and Nurfanizan Afandi. "Thermal Stability of Rare Earth-PYSZ Thermal Barrier Coating with High-Resolution Transmission Electron Microscopy." Coatings 10, no. 12 (December 10, 2020): 1206. http://dx.doi.org/10.3390/coatings10121206.

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Durability of a thermal barrier coating (TBC) depends strongly on the type of mixed oxide in the thermally grown oxide (TGO) of a TBC. This study aims on discovering the effect of thermal stability in the TGO area containing mixed oxides. Two different bondcoats were studied using high-resolution transmission electron microscopy: high-velocity oxygen fuel (HVOF) and air-plasma spray (APS), under isothermal and thermal cyclic tests at 1400 °C. The HVOF bondcoats were intact until 1079 cycles. In comparison, APS failed at the early stage of thermal cycling at 10 cycles. The phase transformation of topcoat from tetragonal to the undesired monoclinic was observed, leading to TBC failure. The results showed that the presence of transient aluminas found in HVOF bondcoat helps in the slow growth of α-Al2O3. In contrast, the APS bondcoat does not contain transient aluminas and transforms quickly to α-Al2O3 along with spinel and other oxides. This fast growth of mixed oxides causes stress at the interface (topcoat and TGO) and severely affects the TBC durability leading to early failure. Therefore, the mixed oxide with transient aluminas slows down the quick transformation into alpha-aluminas, which provides high thermal stability for a high TBC durability.

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Rana, Nidhi, R. Jayaganthan, and Satya Prakash. "Microstructural Features and Oxidation Behaviour of NiCrAlY Coatings Obtained by HVOF Process." Advanced Materials Research 585 (November 2012): 507–11. http://dx.doi.org/10.4028/www.scientific.net/amr.585.507.

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NiCrAlY coating system has been widely used for the advanced gas turbines to provide protection against high temperature oxidation and corrosion. Various methods have been used to develop these superalloy coatings. In present investigation, NiCrAlY superalloy coatings have been deposited on the superalloy substrate (Superni76) using commercially available NiCrAlY powder and High Velocity Oxide Fuel (HVOF) process. These coatings have been characterised in terms of their microhardness, porosity, microstructure features and surface roughness. The coatings have been oxidized cyclically (1hour heating and 20minutes cooling) in air at 900οC. The weight change curves have been plotted and the parabolic rate constant has been evaluated. The oxides formed after oxidation has been studied by using various techniques like optical microscopy, FESEM/EDAX and XRD. It has been observed Al¬2O3, NiCr2O4 and Cr2O3 formed upon oxidation of the coatings provide protection to the substrate alloy.

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Hamilton, Anurag, Ashok Sharma, and Upender Pandel. "Effect of Impingement Angle on Erosion Resistance of HVOF Sprayed WC-10Co-4Cr Coating on CA6NM Steel." Key Engineering Materials 751 (August 2017): 79–83. http://dx.doi.org/10.4028/www.scientific.net/kem.751.79.

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In the present investigation, WC–10Co–4Cr coating was deposited by high velocity oxy-fuel (HVOF) process on CA6NM hydro turbine steel to improve its erosion resistance. The coating was characterized in term of crossectional microstructure, phase, microhardness and fracture toughness using a field emission scanning electron microscope (FESEM), X-ray diffractometer and microhardness tester respectively. Solid particle erosion resistance of the substrate and coating were evaluated by air jet erosion tester at two different impingement angles (30° and 90°). Coating microstructure has shown a homogeneous and well-bonded laminar morphology. The microhardness of the coating was observed more than three times higher than CA6NM substrate. This resulted in significant improvement in erosion resistance of coated CA6NM steel at both impingement angles.

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Lu, Zhe, Guanlin Lyu, Abhilash Gulhane, Hyeon-Myeong Park, Jun Seong Kim, Yeon-Gil Jung, and Jing Zhang. "Experimental and Modeling Studies of Bond Coat Species Effect on Microstructure Evolution in EB-PVD Thermal Barrier Coatings in Cyclic Thermal Environments." Coatings 9, no. 10 (September 28, 2019): 626. http://dx.doi.org/10.3390/coatings9100626.

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In this work, the effects of bond coat species on the thermal barrier coating (TBC) microstructure are investigated under thermal cyclic conditions. The TBC samples are prepared by electron beam-physical vapor deposition with two species of bond coats prepared by either air-plasma spray (APS) or high-velocity oxygen fuel (HVOF) methods. The TBC samples are evaluated in a variety of thermal cyclic conditions, including flame thermal fatigue (FTF), cyclic furnace thermal fatigue (CFTF), and thermal shock (TS) tests. In FTF test, the interface microstructures of TBC samples show a sound condition without any delamination or cracking. In CFTF and TS tests, the TBCs with the HVOF bond coat demonstrate better thermal durability than that by APS. In parallel with the experiments, a finite element (FE) model is developed. Using a transient thermal analysis, the high-temperature creep-fatigue behavior of the TBC samples is simulated similar to the conditions used in CFTF test. The FE simulation predicts a lower equivalent stress at the interface between the top coat and bond coat in bond coat prepared using HVOF compared with APS, suggesting a longer cyclic life of the coating with the HVOF bond coat, which is consistent with the experimental observation.

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Zheng, Jiahui, Deming Yang, and Yang Gao. "Effect of Vacuum Heat Treatment on the High-Temperature Oxidation Resistance of NiCrAlY Coating." Coatings 10, no. 11 (November 13, 2020): 1089. http://dx.doi.org/10.3390/coatings10111089.

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NiCrAlY coatings were prepared using high-velocity oxygen fuel spraying (HVOF), and the coatings were removed from the substrate to achieve a uniform shape. Vacuum heat treatment (VHT) of the as-sprayed coatings was conducted at different temperatures (1000, 1100, and 1200 °C), and the specimens were subjected to isothermal oxidation exposure testing in air at 1100 °C for up to 21 h. The results show that the high temperature oxidation resistance of the coating increased gradually with the increase in VHT temperature, and the coating of VHT1200 had higher oxidation resistance. The high temperature oxidation resistance of the coating was related to the microstructure transformation of the coating. In VHT coatings, β-NiAl became a dispersed irregular block morphology. The γ’-Ni3Al in VHT1000 presented a granular morphology. However, in VHT1100 and VHT1200, γ’-Ni3Al became a lamellar morphology. This transformation of microstructure promotes the form of exclusive α-Al2O3 scale. With the increase in VHT temperature, the content of yttrium on coatings’ surface was increased and the pores were gradually eliminated. The concentration of yttrium on coatings’ surface prevented the formation of θ-Al2O3 and low porosity was beneficial in improving the internal oxidation of the coating.

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VALLEJO, N. DIAZ, O. SANCHEZ, J. C. CAICEDO, W. APERADOR, and G. ZAMBRANO. "HOT CORROSION OF YTTRIUM STABILIZED ZIRCONIA COATINGS DEPOSITED BY AIR PLASMA SPRAY ON A NICKEL-BASED SUPERALLOY." Surface Review and Letters 24, no. 06 (November 24, 2016): 1750084. http://dx.doi.org/10.1142/s0218625x17500846.

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In this research, the electrochemical impedance spectroscopy (EIS) and Tafel analysis were utilized to study the hot corrosion performance at 700[Formula: see text]C of air plasma-sprayed (APS) yttria-stabilized zirconia (YSZ) coatings with a NiCrAlY bond coat grown by high velocity oxygen fuel spraying (HVOF), deposited on an INCONEL 625 substrate, in contact with corrosive solids salts as vanadium pentoxide V2O5 and sodium sulfate Na2SO4. The EIS data were interpreted based on proposed equivalent electrical circuits using a suitable fitting procedure performed with Echem AnalystTM Software. Phase transformations and microstructural development were examined using X-ray diffraction (XRD), with Rietveld refinement for quantitative phase analysis, scanning electron microscopy (SEM) was used to determinate the coating morphology and corrosion products. The XRD analysis indicated that the reaction between sodium vanadate (NaVO[Formula: see text] and yttrium oxide (Y2O[Formula: see text] produces yttrium vanadate (YVO[Formula: see text] and leads to the transformation from tetragonal to monoclinic zirconia phase.

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Piola, Richard, Andrew S. M. Ang, Matthew Leigh, and Scott A. Wade. "A comparison of the antifouling performance of air plasma spray (APS) ceramic and high velocity oxygen fuel (HVOF) coatings for use in marine hydraulic applications." Biofouling 34, no. 5 (May 18, 2018): 479–91. http://dx.doi.org/10.1080/08927014.2018.1465052.

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47

Myoung, Sang-Won, Zhe Lu, Yeon-Gil Jung, Byung-Koog Jang, Young-Soo Yoo, Seong-Moon Seo, Baig-Gyu Choi, and Chang-Yong Jo. "Effect of Plasma Pretreatment on Thermal Durability of Thermal Barrier Coatings in Cyclic Thermal Exposure." Advances in Materials Science and Engineering 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/593891.

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Plasma pretreatment on the top and bond coats was performed and its influence on the thermal durability of thermal barrier coating (TBC) system was investigated through cyclic thermal exposure. Two types of bond coat were prepared by different methods, namely, air plasma spray (APS) and high-velocity oxy-fuel (HVOF), and two kinds of feedstock powder were employed for preparing the top coat in APS process. The better thermal durability was achieved in the vertically cracked TBC with the surface modified bond coat or with the bond coat prepared by APS process. The hardness and fracture toughness values of TBCs increased because of densification of the top coat during cyclic thermal exposure, and the bond coat prepared by HVOF process showed higher values than that by APS process. The TBCs with the surface modified bond coat were more efficient in improving adhesive strength than those without plasma pretreatment on the bond coat. The relationship between microstructure evolution and thermomechanical characteristics of TBCs with plasma pretreatment was discussed in cyclic thermal exposure.

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Wang, Hai Qiang, Takeshi Osaki, Yukiko Nakahara, and Shi Jie Zhu. "Residual Stress in Oxide on NiCrAlY Coating Evaluated by Photoluminescence Spectroscope." Materials Science Forum 750 (March 2013): 27–30. http://dx.doi.org/10.4028/www.scientific.net/msf.750.27.

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The purpose of this study was to understand the effects of thermal exposure temperature on residual stress in thermal grown oxide (TGO) on NiCrAlY coating. The residual stresses in the TGO layer were measured by photo-stimulated luminescence spectrum. High velocity oxygen fuel sprayed (HVOF) method was used to fabricate NiCrAlY coating material. The thermal exposure tests were conducted in air at 900°C, 1000°C, 1100°C for up to 1000 hours using an electric furnace. It was shown that the thickness of the TGO increases with an increase in thermal exposure time with a parabolic curve. The residual stress in the TGO layer increases in thermal exposure time up to 75 hours, and then, the residual stress in the TGO layer decreases slowly. The effects of surface roughness on the residual stress in the TGO were discussed based on experimental results and analysis.

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Jung, Jine Sung, Keun Bong Yoo, Eui Hyun Kim, Chae Hong Jeon, and Do Hyang Kim. "The Thermal Cyclic Behavior of the VPS and HVOF-Sprayed MCrAlY Coatings." Key Engineering Materials 326-328 (December 2006): 1141–44. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.1141.

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Rotating components used in the hot sections of land-based gas turbine are exposed to severe environment of several ten thousands operating hours above 1100. To protect such components against high temperature oxidation an intermediate bond coat is applied, typical of a MCrAlY-type metal alloy. Various processing methods have been studied for bond coat deposition. This study is concerned with the cyclic oxidation behavior of CoNiCrAlY coatings. Coatings were deposited by a vacuum plasma spray and high-velocity oxygen fuel method on a nickel-based superalloy (GTD-111). Cyclic thermal oxidation test condition is at 1100 in ambient air for various periods of time. Tests were used to evaluate the oxidation resistance of the spray-coated specimens. The microstructure and morphology of as-sprayed and of tested specimens were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The oxide phases formed on the coating surface are NiO, CoCr2O4, and Al2O3. The nickel oxide of them was to be dominant with increasing cycles. The differences in microstructure and phase composition in the interface with coating layer are reported. The influence of coating process methods on coating characteristics and degradation mechanisms is discussed. The HVOF coating with the splats was more resistant on the high temperature oxidation than the VPS coating.

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Feng, Zheng Qu, Lu Wang, Wei Ze Wang, Kai Di Cheng, and Cheng Zhou Chen. "Failure Analysis of the outside Coating on the Furnace Roller." Applied Mechanics and Materials 853 (September 2016): 431–35. http://dx.doi.org/10.4028/www.scientific.net/amm.853.431.

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Abstract:

A failure case of the outside coating on the furnace roller is presented in this study. The coating consists of WC-Co, which is deposited on 45 steel by High Velocity Oxygen Fuel (HVOF) spraying. The spalling of coatings has been found in the middle of the roller. Rust was also observed on the coatings of the roller. The failure analysis of the coating was performed in terms of composition analysis, and microstructure observation etc. In addition, the effects of different sandblasting post-treatments were compared. And the effect of substrate material is investigated on the corrosion of coatings. It was concluded that the sandblasting particles remained on the substrate surface have effects on the failure of the coating. The peeling-off coating on the roller is also related with the formation of iron oxides. Less sand can be remained on the substrate surface when air purging and brushing is used after the sand-blasting compared with air purging or non-treatment is applied. The stainless steel shows more excellent corrosion resistance than the low carbon steel when they are used as substrate for WC-Co coatings.

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Journal articles on the topic 'High Velocity Air-Fuel (HVAF)'

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