Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Erosion-oxidation behavior of thermal sprayed Ni20Cr alloy and WC and Cr3C2 cermet coatings
Kunioshi, Clarice Terui;Correa, Olandir Vercino;Ramanathan, Lalgudi Venkataraman;
Materials Research , 2005, DOI: 10.1590/S1516-14392005000200005
Abstract: an apparatus to conduct high temperature erosion-oxidation studies up to 850 °c and with particle impact velocities up to 15 m.s-1 was designed and constructed in the corrosion laboratories of ipen. the erosion-oxidation behavior of high velocity oxy fuel (hvof) sprayed alloy and cermet coatings of ni20cr, wc 20cr7ni and cr3c2 ni20cr on a steel substrate has been studied. details of this apparatus and the erosion-oxidation behavior of these coatings are presented and discussed. the erosion-oxidation behavior of hvof coated cr3c2 25(ni20cr) was better than that of wc 20cr7ni, and the erosion-oxidation regimes have been identified for these coatings at particle impact velocity of 3.5 m.s-1, impact angle of 90° and temperatures in the range 500 to 850 °c.
Wear Resistant Thermal Sprayed Composite Coatings Based on Iron Self-Fluxing Alloy and Recycled Cermet Powders
Materials Science , 2012, DOI: 10.5755/j01.ms.18.1.1338
Abstract: Thermal spray and WC-Co based coatings are widely used in areas subjected to abrasive wear. Commercial cermet thermal spray powders for HVOF are relatively expensive. Therefore applying these powders in cost-sensitive areas like mining and agriculture are hindered. Nowadays, the use of cheap iron based self-fluxing alloy powders for thermal spray is limited. The aim of this research was to study properties of composite powders based on self-fluxing alloys and recycled cermets and to examine the properties of thermally sprayed (HVOF) coatings from composite powders based on iron self-fluxing alloy and recycled cermet powders (Cr3C2-Ni and WC-Co). To estimate the properties of recycled cermet powders, the sieving analysis, laser granulometry and morphology were conducted. For deposition of coatings High Velocity Oxy-Fuel spray was used. The structure and composition of powders and coatings were estimated by SEM and XRD methods. Abrasive wear performance of coatings was determined and compared with wear resistance of coatings from commercial powders. The wear resistance of thermal sprayed coatings from self-fluxing alloy and recycled cermet powders at abrasion is comparable with wear resistance of coatings from commercial expensive spray powders and may be an alternative in tribological applications in cost-sensitive areas. DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1338
HVOF制备的Ni60/WC-10Co4Cr涂层组织和滑动磨损性能研究  [PDF]
- , 2018,
Abstract: 为了降低超音速火焰(HVOF)喷涂金属陶瓷涂层的材料和加工成本,使其在更大范围内替代会给环境带来严重污染的电镀硬铬(EHC)涂层,本文将不同比例的Ni60与WC-10Co4Cr相混合,并采用HVOF喷涂工艺分别制备了5种金属陶瓷复合涂层.研究了这些涂层的显微组织、基本性能和滑动磨损性能,并将其与EHC涂层进行对比.结果表明:所有HVOF喷涂工艺制备的Ni60/WC-10Co4Cr涂层都很致密(孔隙率小于1%),随着WC-10Co4Cr比例的增加,Ni60/WC-10Co4Cr涂层的硬度从688.3 HV0.3增加到1 203.4 HV0.3,磨损率由2.75×10-5 mm3/N·m降低到7.29×10-7 mm3/N·m.并且,所有HVOF喷涂工艺制备的涂层和与其配对的摩擦副的磨损率以及磨擦系数均低于EHC涂层,表现出良好的抗滑动磨损性能.
In order to decrease the material and manufactural cost of the HVOF sprayed cermet coating, to replace the EHC in wider fields, five cermet composite coatings were deposited by HVOF process using the blended Ni60 and WC-10Co4Cr powders with different ratios. Microstructure, properties and sliding wear performance of the Ni60/WC-10Co4Cr coatings as well as electrolytic hard chrome (EHC) coating were investigated. The results showed that all the HVOF sprayed coatings were compact (porosities were less than 1%), their hardness increased from 688.3HV0.3 to 1203.4 HV0.3 and the wear rate decreased from 2.75×10-5 mm3/N·m to 7.29×10-7 mm3/N·m with increasing the WC-10Co4Cr ratio. The wear rates of the HVOF sprayed coatings and their counterparts as well as their frictional coefficient were lower in comparison to the EHC coating, which exhibited excellent sliding wear performance.
WC-CoCr coatings sprayed by high velocity oxygen-fuel (HVOF) flame on AA7050 aluminum alloy: electrochemical behavior in 3.5% NaCl solution
Magnani, Marina;Suegama, Patrícia Hatsue;Recco, Abel André Candido;Guilemany, Josep Maria;Fugivara, Cecílio Sadao;Benedetti, Assis Vicente;
Materials Research , 2007, DOI: 10.1590/S1516-14392007000400010
Abstract: in the present work, the electrochemical behavior of wc-cocr coatings with 10 (w10), 15 (w15) and 20 (w20) torch passes sprayed by high velocity oxygen-fuel (hvof) flame on aa7050 aluminum alloy substrate, evaluated in 3.5% nacl solution, were compared using open-circuit potential (eoc) measurements, electrochemical impedance spectroscopy (eis) and polarization curves. the coating surfaces and their cross sections were characterized by x ray diffraction and the rockwell-c hardness test, and also by optical (om) and scanning electron microscopy (sem) before and after the corrosion tests. the electrochemical data showed that sample w10 presented higher corrosion resistance than the others in chloride solutions. in some tests, aluminum salts on the coating surface were identified by eds, indicating the corrosion of the substrate. and using aluminon, aluminum ions were detected and analyzing the surface via stereomicroscopy, hydrogen bubbles were observed, both showing that the electrolyte reached the substrate and galvanic corrosion possibly occurred. the physical characterization showed that sample w10 presented a lower number of cracks and pores, justifying its higher corrosion resistance.
Metal-Matrix Hardmetal/Cermet Reinforced Composite Powders for Thermal Spray
Materials Science , 2012, DOI: 10.5755/j01.ms.18.1.1348
Abstract: Recycling of materials is becoming increasingly important as industry response to public demands, that resources must be preserved and environment protected. To produce materials competitive in cost with primary product, secondary producers have to pursue new technologies and other innovations. For these purposes different recycling technologies for composite materials (oxidation, milling, remelting etc) are widely used. The current paper studies hardmetal/cermet powders produced by mechanical milling technology. The following composite materials were studied: Cr3C2-Ni cermets and WC-Co hardmetal. Different disintegrator milling systems for production of powders with determined size and shape were used. Chemical composition of produced powders was analysed. To estimate the properties of recycled hardmetal/cermet powders, sieving analysis, laser granulometry and angularity study were conducted. To describe the angularity of milled powders, spike parameter–quadric fit (SPQ) was used and experiments for determination of SPQ sensitivity and precision to characterize particles angularity were performed. Images used for calculating SPQ were taken by SEM processed with Omnimet Image Analyser 22. The graphs of grindability and angularity were composed. Composite powders based on Fe- and Ni-self-fluxing alloys for thermal spray (plasma and HVOF) were produced. Technological properties of powders and properties of thermal sprayed coatings from studied powders were investigated. The properties of spray powders reinforced with recycled hardmetal and cermet particles as alternatives for cost-sensitive applications were demonstrated. DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1348
Wojciech ?órawski,Otakar Bok?vka
Materials Engineering , 2012,
Abstract: The article compares the properties of plasma and HVOF thermally sprayed coatings obtained by blending the NiCrBSi and Fe2O3 powders. The deposition was performed by means of the Plancer PN-120 and the Diamond Jet guns for plasma spraying and HVOF spraying respectively. The SEM (EDS) method was employed to study the microstructure of the produced coatings. Although the blended powders differ in particle size, shape, and distribution, it is possible to obtain composite coatings with an NiCrBSi matrix containing iron oxides. Except for a different microstructure, plasma and HVOF coatings have a different phase composition, which was examined using the Bruker D-8 Advance diffractometer. Studies of the coatings wear and scuffing resistance showed that an optimal content of Fe2O3 is about 26 % for plasma sprayed coatings and 22.5 % for HVOF deposited coatings.
Friction and Wear Characteristics of Multimodal WC-12Co Coatings Deposited by HVOF

DING Zhang-xiong,CHEN Wei,WANG Qun,CAO Zheng-huang,

摩擦学学报 , 2011,
Abstract: In the present paper, two WC-12Co cermet coatings that have a multimodal structure and one WC-12Co cermet coating that has a submicron structure were deposited by high velocity oxygen fuel (HVOF) process, and the microstructure, porosity, phase structure and microhardness of the two coatings were analyzed by using scanning electron microscopy (SEM) and x-ray diffraction (XRD). The friction and wear characteristics of the two coatings were carried out on a ball-on-disc tribo-tester and the wear mechanisms of the two WC-12Co coatings were explored. Results show that the multimodal structured coating deposited by powders containing 30% nano-size WC-12Co particles had the lowest degree of decarburization during spraying and the highest microhardness. In addition, the multimodal structured coating deposited by the powders containing 50% nano-size WC-12Co particles had the lowest porosity and the highest wear resistance.
Características de los recubrimientos WC-NiCrBSiFe en función del sistema de proyección térmica  [cached]
Higuera-Hidalgo, V.,Belzunce-Varela, F. J.,Poveda-Martínez, S.
Revista de Metalurgia , 2004,
Abstract: WC-NiCrBSiFe coatings are normally used as protection against heat, corrosion and erosion actions encountered in superheater and reheater tubes in power plant boilers. This coating was thermal-spray projected using different procedures (plasma, HVOF and HFPD) onto stainless steel specimens. The microstructures, porosities, oxide contents and microhardnesses of the coatings were determined. Thermal fatigue tests under simulative power plant service conditions were conducted in an experimental combustion chamber and, finally, the adhesion between the substrate and the coating layer was evaluated by means of tensile tests.The obtained results are discussed, and special attention was paid to the specific characteristics of the different spraying procedures. El material tipo cermet WC-NiCrBSiFe se emplea como elemento protector frente al desgaste, en elementos de calderas de vapor, como son los sobrecalentadores y recalentadores de vapor, donde las condiciones de servicio tan severas (alta temperatura, erosión por cenizas volantes, etc.) acortan notablemente la vida útil de los materiales convencionales empleados. En este trabajo se ha realizado la proyección térmica de este recubrimiento por arco plasma no transferido, proyección mediante llama a elevada velocidad (HVOF) y proyección por detonación a elevada frecuencia (HFPD). Se determinaron las microestructuras, porosidades, contenidos en óxidos y microdurezas de los distintos recubrimientos obtenidos. También, se llevaron a cabo ensayos de fatiga térmica en condiciones similares a las imperantes en el interior de una caldera, mediante el empleo de un combustor experimental. Finalmente, se determinó la adherencia de las capas a los sustratos receptores, mediante ensayos de tracción. Los resultados obtenidos son discutidos en función de las características específicas de los diferentes sistemas de proyección utilizados.
Resistencia al desgaste de recubrimientos tipo cermet depositados por hvof con tratamiento térmico posterior
Revista de la Facultad de Ingeniería Universidad Central de Venezuela , 2007,
Abstract: the aim of the present work was to study the influence of chemical composition and post heat treatment on the wearresistance of cermet (ceramic - metallically) coatings deposited by the process of high velocity oxy-fuel (hvof). for such purpose, a nicrbsiwfe alloy was chosen which was mixed mechanically with wc-12%co powders to form three coatings with the following proportions: 100 % of alloy nicrbsiwfe (100nicr), 50%nicrbsi + 50 % wc-12%co (50-50) and 70 % wc-12%co + 30%nicrbsi (70-30). the feeder powders were deposited on an aisi 1020 steel substrate by using a jp-5000 gun. an oxyacetylene flame was used to perform the post heat treatment. the evaluation of the resistance to wear for these coatings was achieved by means of the test astm g65-a, b y c. the microstructure and chemical composition of the coatings as well as the wear surfaces were evaluated by means of optical microscopy (mo) and electronics microscopy (meb) coupled with an edax dx4 energy dispersive x-ray spectrometer (eds). the study showed that the resistance toabrasion wear increased with the increase of wc-co particles in the mixture wc-co-nicrbsiwfe; nevertheless, the more significant increase is due to the post heat treatment which was attributed to the precipitation hardening of the nickel′s matrix and to the better cohesion and better distribution of the second phase particles in the coating.
The corrosion resistance of HVOF sprayed coatings with intermetallic phases in aggressive environments  [PDF]
B. Formanek,J. Cizner,B. Szczucka-Lasota,R. Przeliorz
Journal of Achievements in Materials and Manufacturing Engineering , 2006,
Abstract: Purpose: The cyclic corrosion behavior of coatings with intermetallic matrix ( FeAl, NiAl and FeAl-TiAl) was investigated in aggressive gases.Design/methodology/approach: The composite coatings strengthened by a fine dispersive Al2O3 and other ceramic phases were thermally sprayed by HVOF method in Jet Kote 2 system. A kinetics test was carried out by periodic method for exposure times of up to 500 hours. Mass changes of the studied coatings during the corrosion test are presented. The surfaces of the composite coatings after the corrosion test in aggressive environments were analyzed by scanning microscopy observation.Findings: All the results confirm good heat proofness of HVOF sprayed coatings with an AlFe and AlNi intermetallics.Practical implications: Owing to the properties of intermetallic phases and HVOF sprayed coatings, they are anticipated to be applied for the protection of super heater tubes in conventional boilers or in boilers burning multicomponent waste, and combusted biomass including chlorides.Originality/value: The results show that the coatings with AlFe and AlNi intermetallic phases have very good corrosion resistance and they are the best coatings from all the coatings investigated in aggressive environments.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.