WC-Co coatings deposited by the electro-thermal chemical spray method

Energy Technology Data Exchange (ETDEWEB)

Zhitomirsky, V.N. [Tel Aviv Univ. (Israel). Faculty of Engineering; Wald, S.; Rabani, L.; Zoler, D. [Propulsion Physics Division, SOREQ NRC, 81800, Yavne (Israel); Factor, M.; Roman, I. [School of Applied Sciences, The Hebrew University, 91904, Jerusalem (Israel); Cuperman, S.; Bruma, C. [School of Physics and Astronomy, Tel-Aviv University, 69978, Tel-Aviv (Israel)

2000-10-02

A novel thermal spray technology - an electro-thermal chemical spray (ETCS) for producing hard coatings is presented. The experimental coating apparatus consists of a machine gun barrel, a cartridge containing the coating material in powder form, a solid propellant, and a plasma ignition system. The plasma ignition system produces plasma in pulsed mode to ignite the solid propellant. On ignition, the drag force exerted by the combustion gases accelerates the powder particles towards the substrate. Using the ETCS technique, the process of single-shot WC-Co coating deposition on stainless steel substrate was studied. The influence of process parameters (plasma energy, mass of the solid propellant and the coated powder, distance between the gun muzzle and the substrate) on the coating structure and some of its properties were investigated. It was shown that ECTS technique effectively deposited the WC-Co coating with deposition thicknesses of 100-200 {mu}m per shot, while deposition yield of {proportional_to}70% was attained. The WC-Co coatings consisted of carbide particles distributed in amorphous matrix. The powder particle velocity was found to depend on the solid propellant mass and was weakly dependent on the plasma energy, while the particle processing temperature was strongly dependent on the plasma energy and almost independent of the solid propellant mass. Whilst increasing the solid propellant mass from 5 to 7 g, the deposition rate and yield correspondingly increased. When increasing the plasma energy, the temperature of the powder particles increased, the average carbide particle size decreased and their shape became more rounded. The deposition yield and microhardness at first increased and then achieved saturation by increasing the plasma energy. (orig.)

Pt catalysts on PANI coated WC/C nanocomposites for methanol electro-oxidation and oxygen electro-reduction in DMFC

International Nuclear Information System (INIS)

Yaldagard, Maryam; Jahanshahi, Mohsen; Seghatoleslami, Naser

2014-01-01

Highlights: • In this work nanosized WC/C were successfully coated by PANI. • Pt particles (10.56 nm) were uniformly dispersed on the surface of PANI/WC/C support. • The Pt/PANI/WC/C exhibited higher MOR activity and CO tolerance than Pt/C. • The Pt/PANI/WC/C exhibited higher activity for ORR than Pt/C in RDE experiments. • Pt/PANI/WC/C showed good stability than that of Pt/C in the presence of methanol. - Abstract: In the present study a Pt/PANI/WC/C electrocatalyst was developed to increase the methanol electro-oxidation and oxygen electro-reduction activity and stability of commercial Pt/C electrocatalyst. WC/C was coated with protonated polyaniline (PANI) in situ during the polymerization of aniline. Fourier transform infrared (FTIR) results illustrate the presence of PANI in the composite. The conductivity of PANI coated – WC/C has been compared with the conductivity of the corresponding mixtures of WC/C and Vulcan XC-72. X-ray diffraction results showed that Pt particles were dispersed on the support with mean particle size of about 10.56 nm. Transition electron microscopy images showed that the nanosized WC/C were successfully coated by PANI. Based on the electrochemical properties characterized by cyclic voltammetry, CO stripping and rotating disk electrode measurements it was found that the as prepared Pt/PANI/WC/C electrocatalyst exhibited a comparable activity for methanol oxidation reaction and oxygen reduction reaction with respect to the commercial one. A significant reduction in the potential of CO electro-oxidation peak from 0.75 V for Pt/C to 0.52 V for Pt/PANI/WC/C electrocatalyst indicates that an increase in the activity for CO electro-oxidation is achieved by replacing the carbon support by PANI coated WC/C. Chronoamerometry results also showed, in the presence of methanol the Pt/PANI/WC/C electrocatalyst still maintains a higher current density than Pt/WC/C and Pt/C

Pt catalysts on PANI coated WC/C nanocomposites for methanol electro-oxidation and oxygen electro-reduction in DMFC

Energy Technology Data Exchange (ETDEWEB)

Yaldagard, Maryam, E-mail: m_yaldagard@yahoo.com [Department of Chemical Engineering, Ferdowsi University of Mashhad, P.O. Box 91775-1111 (Iran, Islamic Republic of); Nanotechnology Research Institute, School of Chemical Engineering, Babol University of Technology (Iran, Islamic Republic of); Jahanshahi, Mohsen, E-mail: mjahan@nit.um.ac.ir [Nanotechnology Research Institute, School of Chemical Engineering, Babol University of Technology (Iran, Islamic Republic of); Seghatoleslami, Naser, E-mail: Slami@um.ac.ir [Department of Chemical Engineering, Ferdowsi University of Mashhad, P.O. Box 91775-1111 (Iran, Islamic Republic of)

2014-10-30

Highlights: • In this work nanosized WC/C were successfully coated by PANI. • Pt particles (10.56 nm) were uniformly dispersed on the surface of PANI/WC/C support. • The Pt/PANI/WC/C exhibited higher MOR activity and CO tolerance than Pt/C. • The Pt/PANI/WC/C exhibited higher activity for ORR than Pt/C in RDE experiments. • Pt/PANI/WC/C showed good stability than that of Pt/C in the presence of methanol. - Abstract: In the present study a Pt/PANI/WC/C electrocatalyst was developed to increase the methanol electro-oxidation and oxygen electro-reduction activity and stability of commercial Pt/C electrocatalyst. WC/C was coated with protonated polyaniline (PANI) in situ during the polymerization of aniline. Fourier transform infrared (FTIR) results illustrate the presence of PANI in the composite. The conductivity of PANI coated – WC/C has been compared with the conductivity of the corresponding mixtures of WC/C and Vulcan XC-72. X-ray diffraction results showed that Pt particles were dispersed on the support with mean particle size of about 10.56 nm. Transition electron microscopy images showed that the nanosized WC/C were successfully coated by PANI. Based on the electrochemical properties characterized by cyclic voltammetry, CO stripping and rotating disk electrode measurements it was found that the as prepared Pt/PANI/WC/C electrocatalyst exhibited a comparable activity for methanol oxidation reaction and oxygen reduction reaction with respect to the commercial one. A significant reduction in the potential of CO electro-oxidation peak from 0.75 V for Pt/C to 0.52 V for Pt/PANI/WC/C electrocatalyst indicates that an increase in the activity for CO electro-oxidation is achieved by replacing the carbon support by PANI coated WC/C. Chronoamerometry results also showed, in the presence of methanol the Pt/PANI/WC/C electrocatalyst still maintains a higher current density than Pt/WC/C and Pt/C.

Performance characterization of Ni60-WC coating on steel processed with supersonic laser deposition

Directory of Open Access Journals (Sweden)

Fang Luo

2015-03-01

Full Text Available Ni60-WC particles are used to improve the wear resistance of hard-facing steel due to their high hardness. An emerging technology that combines laser with cold spraying to deposit the hard-facing coatings is known as supersonic laser deposition. In this study, Ni60-WC is deposited on low-carbon steel using SLD. The microstructure and performance of the coatings are investigated through SEM, optical microscopy, EDS, XRD, microhardness and pin-on-disc wear tests. The experimental results of the coating processed with the optimal parameters are compared to those of the coating deposited using laser cladding.

Wear Evaluation of AISI 4140 Alloy Steel with WC/C Lamellar Coatings Sliding Against EN 8 Using Taguchi Method

Science.gov (United States)

Kadam, Nikhil Rajendra; Karthikeyan, Ganesarethinam

2016-10-01

The purpose of the experiments in this paper is to use the Taguchi methods to investigate the wear of WC/C coated nitrided AISI 4140 alloy steel. A study of lamellar WC/C coating which were deposited by a physical vapor deposition on nitrided AISI 4140 alloy steel. The investigation includes wear evaluation using Pin-on-disk configuration. When WC/C coated AISI 4140 alloy steel slides against EN 8 steel, it was found that carbon-rich coatings show much lower wear of the countersurface than nitrogen-rich coatings. The results were correlated with the properties determined from tribological and mechanical characterization, therefore by probably selecting the proper processing parameters the deposition of WC/C coating results in decreasing the wear rate of the substrate which shows a potential for tribological application.

DURABILITY AND TRIBOLOGICAL PROPERTIES OF THERMALLY SPRAYED WC CERMET COATING IN LUBRICATED ROLLING WITH SLIDING CONTACT

Directory of Open Access Journals (Sweden)

Mohammad Ali

2010-09-01

Full Text Available Durability and tribological properties of thermally sprayed WC-Cr-Ni cermet coating were investigated experimentally in lubricated rolling with sliding contact conditions. By means of the high energy type flame spraying (Hi-HVOF method, the coating was formed onto the axially ground and circumferentially ground roller specimens made of a thermally refined carbon steel. In the experiments, the WC cermet coated steel roller was mated with the carburized hardened steel roller without coating in line contact condition. The coated roller was mated with the smooth non-coated roller under a contact pressure of 1.0 or 1.2 GPa, and it was mated with the rough non-coated roller under a contact pressure of 0.6 or 0.8 GPa. As a result, it was found that in general, the coating on the circumferentially ground substrate shows a lower durability compared with that on the axially ground substrate and this difference appears more distinctly for the higher contact pressure for both smooth mating surface and rough mating surface. It was also found that there are significant differences in the tribological properties of WC cermet coating depending on the contact pressure. In addition, depending on the smooth or rough mating surface, remarkable differences in the tribological properties were found.

Performance and characterisation of CVD diamond coated, sintered diamond and WC-Co cutting tools for dental and micromachining applications

International Nuclear Information System (INIS)

Sein, Htet; Ahmed, Waqar; Jackson, Mark; Woodwards, Robert; Polini, Riccardo

2004-01-01

Diamond coatings are attractive for cutting processes due to their high hardness, low friction coefficient, excellent wear resistance and chemical inertness. The application of diamond coatings on cemented tungsten carbide (WC-Co) tools was the subject of much attention in recent years in order to improve cutting performance and tool life. WC-Co tools containing 6% Co and 94% WC substrate with an average grain size 1-3 μm were used in this study. In order to improve the adhesion between diamond and WC substrates, it is necessary to etch away the surface Co and prepare the surface for subsequent diamond growth. Hot filament chemical vapour deposition with a modified vertical filament arrangement has been employed for the deposition of diamond films. Diamond film quality and purity have been characterised using scanning electron microscopy and micro-Raman spectroscopy. The performance of diamond coated WC-Co bur, uncoated WC-Co bur, and diamond embedded (sintered) bur have been compared by drilling a series of holes into various materials such as human teeth, borosilicate glass and porcelain teeth. Flank wear has been used to assess the wear rates of the tools. The materials subjected to cutting processes have been examined to assess the quality of the finish. Diamond coated WC-Co microdrills and uncoated microdrills were also tested on aluminium alloys. Results show that there was a 300% improvement when the drills were coated with diamond compared to the uncoated tools

Tribological Behavior of Multilayered WC-Ti1-xAlxN Coatings Deposited by Cathodic Arc Deposition Process on High Speed Steel

International Nuclear Information System (INIS)

Kim, Jung Gu; Hwang, Woon Suk

2006-01-01

Recently, much of the current development in surface modification engineering are focused on multilayered coatings. Multilayered coatings have the potential to improve the tribological properties. Four different multilayered coatings were deposited on AISI D2 steel. The prepared samples are designed as WC-Ti 0.6 Al 0.4 N, WC-Ti 0.53 Al 0.47 N, WC-Ti 0.5 Al 0.5 N and WC-Ti 0.43 Al 0.57 N. The multilayered coatings were investigated with respect to coating surface and cross-sectional morphology, roughness, adhesion, hardness, porosity and tribological behavior. Especially, wear tests of four multilayered coatings were preformed by using a ball-on-disc configuration with a linear sliding speed of 0.017 m/sec, 5.38 N load. The tests were carried out at room temperature in air by employing AISI 52100 steel ball (H R = 66) having a diameter of 10 mm. The surface morphology, and topography of the wear scars of samples and balls have been determined by using scanning electron spectroscopy (SEM). Results have showed an improved wear resistance of the WC-Ti 1-x 6Al x N coatings with increasing of Al concentration. WC-Ti 0.43 Al 0.57 N coating with the lower surface roughness and porosity with good adhesion enhanced wear resistance

Effects of laser polishing on surface microstructure and corrosion resistance of additive manufactured CoCr alloys

Science.gov (United States)

Wang, W. J.; Yung, K. C.; Choy, H. S.; Xiao, T. Y.; Cai, Z. X.

2018-06-01

Laser polishing of 3D printed metal components has drawn great interest in view of its potential applications in the dental implant industries. In this study, corrosion resistance, surface composition and crystalline structure of CoCr alloys were investigated. The corrosion resistance, micromorphology, composition, phase transformations and crystalline structures of samples were characterized using an electrochemical analyzer, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. The results indicate that high laser powers and low object distances within a certain range can facilitate the formation of complex oxide films, which exhibits high corrosion resistance. Further, object distances have a significant influence on cooling rates during the solidification of the melt pool in laser polishing, and fast cooling generates vast amounts of vacancies and defects, which result in the crystalline phase transformation from γ to ε. Consequently, the formed oxides play an important role in corrosion resistance on the outer layer, and inner layer with γ phase also helps keep the CoCr alloys in a stable structure with high resistant to corrosion. The two process parameters in laser polishing, laser power and object distances, are demonstrated as being important for controlling the surface microstructures and corrosion resistance of the additive manufactured CoCr alloy components.

Microstructure and wear resistance of laser cladded composite coatings prepared from pre-alloyed WC-NiCrMo powder with different laser spots

Science.gov (United States)

Yao, Jianhua; Zhang, Jie; Wu, Guolong; Wang, Liang; Zhang, Qunli; Liu, Rong

2018-05-01

The distribution of WC particles in laser cladded composite coatings can significantly affect the wear resistance of the coatings under aggressive environments. In this study, pre-alloyed WC-NiCrMo powder is deposited on SS316L via laser cladding with circular spot and wide-band spot, respectively. The microstructure and WC distribution of the coatings are investigated with optical microscope (OM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). The wear behavior of the coatings is investigated under dry sliding-wear test. The experimental results show that the partially dissolved WC particles are uniformly distributed in both coatings produced with circular spot and wide-band spot, respectively, and the microstructures consist of WC and M23C6 carbides and γ-(Ni, Fe) solid solution matrix. However, due to Fe dilution, the two coatings have different microstructural characteristics, resulting in different hardness and wear resistance. The wide-band spot laser prepared coating shows better performance than the circular spot laser prepared coating.

THE STRUCTURE AND PROPERTIES OF COMPOSITE LASER CLAD COATINGS WITH Ni BASED MATRIX WITH WC PARTICLES

Directory of Open Access Journals (Sweden)

Zita Iždinská

2010-09-01

Full Text Available In this work, the influence of the processing conditions on the microstructure and abrasive wear behavior of composite laser clad coatings with Ni based matrix reinforced with 50% WC particles is analyzed. Composite powder was applied in the form of coatings onto a mild steel substrate (Fe–0.17% C by different laser powers and cladding speeds. The microstructure of the coatings was analyzed by scanning electron microscopy (SEM. Tribological properties of coatings were evaluated by pin-on-disc wear test. It appeared that the hardness of the matrix of composite coatings decreases with increasing cladding speed. However, wear resistance of composite coatings with decreasing hardness of Ni based matrix increases. Significantly enhanced wear resistance of WC composite coatings in comparison with Ni based coatings is attributed to the hard phase structures in composite coatings.

The Electro-Spark Deposited WC-Cu Coatings Modified by Laser Treatment / Powłoki WC-Cu Naniesione Elektroiskrowo I Modyfikowane Obróbką Laserową

Directory of Open Access Journals (Sweden)

Radek N.

2015-12-01

Full Text Available The main objective of the present work was to determine the influence of laser treatment on microstructure, X-ray diffraction, microhardness, surface geometric structure and roughness, corrosion resistance and tribological properties of coatings deposited on C45 carbon steel by the electro-spark deposition (ESD process. The studies were conducted using WC-Cu electrodes produced by the powder metallurgy route. The tests show that the laser-treated electro-spark deposited WC-Cu coatings are characterized by higher corrosion resistance, surface roughness and seizure resistance which come at the expense of lower microhardness. The laser treatment process causes the homogenization of the chemical composition, structure refinement and healing of microcracks and pores of the electro-spark deposited coatings. Laser treated ESD coatings can be applied in sliding friction pairs and as protective coatings.

Composite coating containing WC/12Co cermet and Fe-based metallic glass deposited by high-velocity oxygen fuel spraying

International Nuclear Information System (INIS)

Terajima, Takeshi; Takeuchi, Fumiya; Nakata, Kazuhiro; Adachi, Shinichiro; Nakashima, Koji; Igarashi, Takanori

2010-01-01

A composite coating containing WC/12Co cermet and Fe 43 Cr 16 Mo 16 C 15 B 10 metallic glass was successfully deposited onto type 304 stainless steel by high-velocity oxygen fuel (HVOF) spraying, and the microstructure and tribological properties were investigated. The microstructure of the coating was characterized by scanning electron microscopy/electron probe micro-analysis (SEM/EPMA) and X-ray diffractometry (XRD). The hardness, adhesion strength and tribological properties of the coating were tested with a Vickers hardness tester, tensile tester and reciprocating wear tester, respectively. The composite coating, in which flattened WC/12Co was embedded in amorphous Fe 43 Cr 16 Mo 16 C 15 B 10 layers, exhibited high hardness, good wear resistance and a low friction coefficient compared to the monolithic coating. The addition of 8% WC/12Co to the Fe 43 Cr 16 Mo 16 C 15 B 10 matrix increased the cross-sectional hardness from 660 to 870 HV and reduced the friction coefficient from 0.65 to 0.5. WC/12Co reinforcement plays an important role in improving the tribological properties of the Fe 43 Cr 16 Mo 16 C 15 B 10 coating.

Cyclic oxidation behavior of plasma sprayed NiCrAlY/WC-Co/cenosphere coating

Science.gov (United States)

Mathapati, Mahantayya; Ramesh M., R.; Doddamani, Mrityunjay

2018-04-01

Components working at elevated temperature like boiler tubes of coal and gas fired power generation plants, blades of gas and steam turbines etc. experience degradation owing to oxidation. Oxidation resistance of such components can be increased by developing protective coatings. In the present investigation NiCrAlY-WC-Co/Cenosphere coating is deposited on MDN 321 steel substrate using plasma spray coating. Thermo cyclic oxidation behavior of coating and substrate is studied in static air at 600 °C for 20 cycles. The thermo gravimetric technique is used to approximate the kinetics of oxidation. X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray mapping techniques are used to characterize the oxidized samples. NiCrAlY-WC-Co/Cenosphere coating exhibited lower oxidation rate in comparison to MDN 321 steel substrate. The lower oxidation rate of coating is attributed to formation of Al2O3, Cr2O3, NiO and CoWO4 oxides on the outermost surface.

Effect of helium plasma gas flow rate on the properties of WC-12 wt.%Co coatings sprayed by atmospheric plasma

Directory of Open Access Journals (Sweden)

Mihailo R. Mrdak

2014-06-01

Full Text Available The cermet coatings of WC-12wt.%Co are extensively used to improve the wear resistance of a wide range of technical components. This paper analyses the influence of the plasma gas flow of helium on the microstructure and mechanical properties of WC-12wt.%Co coatings deposited by plasma spraying at atmospheric pressure (APS. In order to obtain homogeneous and denser coatings, three different flows of He ( 8 l/min., 16 l/min. and 32 l/min were used in the research. With the application of He, coatings achieved higher values of hardness due to less degradation of the primary WC carbides. The main goal was to deposit dense and homogeneous layers of WC-12wt.%Co coatings with improved wear resistance for different applications. The test results of the microstructure of the layers were evaluated under a light microscope. The analysis of the microstructure and the mechanical properties of the deposited layers was made in accordance with the standard of Pratt-Whitney. The morphology of the powder particles and the microstructure of the best coating was examined on the SEM (scanning electron microscope. The evaluation of the mechanical properties of the layers was done by applying the HV0.3 method for microhardness testing and by applying tensile testing to test the bond strength. The research has shown that the flow of He plasma gas significantly affects the microstructure, the mechanical properties and the structure of WC-12 wt.%Co coatings.

Comparison of the microstructure and phase stability of as-cast, CAD/CAM and powder metallurgy manufactured Co-Cr dental alloys.

Science.gov (United States)

Li, Kai Chun; Prior, David J; Waddell, J Neil; Swain, Michael V

2015-12-01

The objective of this study was to identify the different microstructures produced by CC, PM and as-cast techniques for Co-Cr alloys and their phase stability following porcelain firings. Three bi-layer porcelain veneered Co-Cr specimens and one monolithic Co-Cr specimen of each alloy group [cast, powder metallurgy (PM), CAD/CAM (CC)] were manufactured and analyzed using electron backscatter diffraction (EBSD), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). Specimens were treated to incremental numbers of porcelain firings (control 0, 5, 15) with crystallographic data, grain size and chemical composition subsequently obtained and analyzed. EBSD datasets of the cast alloy indicated large grains >200 μm whereas PM and CC alloy consisted of mean arithmetic grain sizes of 29.6 μm and 19.2 μm respectively. XRD and EBSD results both indicated the highest increase in hcp content (>13vol%) for cast Co-Cr alloy after treatment with porcelain firing while PM and CC indicated .05) was observed in CC. EDS line scans indicated an increase in Cr content at the alloy surface after porcelain firing treatment for all three alloys. PM and CC produced alloy had superior fcc phase stability after porcelain firings compared to a traditional cast alloy. It is recommended that PM and CC alloys be used for porcelain-fused-to-metal restorations. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The Effects of Particle Size on the Surface Properties of an HVOF Coating of WC-Co

Energy Technology Data Exchange (ETDEWEB)

Cho, Tong Yul; Yoon, Jae Hong; Yoon, Sang Hwan; Joo, Yun Kon [Changwon National University, Changwon (Korea, Republic of); Choi, Won Ho; Son, Young Bok [Xinix Metallizing Co., Ltd, Gyungnam (Korea, Republic of)

2017-04-15

The effects of particle size on the surface properties of HVOF spray coating were studied to improve of the durability of metal components. Micro and nano sized WC-12Co powders were coated on the surface of Inconel718, and the effects of particle size on surface properties were studied. Surface hardness was reduced when the particle sizes of the powder were decreased, because the larger specific surface area of the smaller particles caused greater heat absorption and decomposition of the hard WC to less hard W{sub 2}C and graphite. Porosity was increased by decreasing the particle size, because the larger specific surface area of the smaller particles caused a greater decomposition of WC to W{sub 2}C and free carbon. The free carbon formed carbon oxide gases which created the porous surface. The friction coefficient was reduced by decreasing the particle size because the larger specific surface area of the smaller particles produced more free carbon free Co and Co oxide which acted as solid lubricants. The friction coefficient increased when the surface temperature was increased from 25 to 500 ℃, due to local cold welding. To improve the durability of metal mechanical components, WC-Co coating with the proper particle size is recommended.

Investigation on cored-eutectic structure in Ni60/WC composite coatings fabricated by wide-band laser cladding

Energy Technology Data Exchange (ETDEWEB)

Ma, Qunshuang, E-mail: maqunshuang@126.com; Li, Yajiang, E-mail: yajli@sdu.edu.cn; Wang, Juan, E-mail: jwang@sdu.edu.cn; Liu, Kun, E-mail: liu_kun@163.com

2015-10-05

Highlights: • Perfect composite coatings were fabricated using wide-band laser cladding. • Special cored-eutectic structure was synthesized in Ni60/WC composite coatings. • Cored-eutectic consists of hard carbide compounds and fine lamellar eutectic of M{sub 23}C{sub 6} carbides and γ-Ni(Fe). • Wear resistance of coating layer was significantly improved due to precipitation of M{sub 23}C{sub 6} carbides. - Abstract: Ni60 composite coatings reinforced with WC particles were fabricated on the surface of Q550 steel using LDF4000-100 fiber laser device. The wide-band laser and circular beam laser used in laser cladding were obtained by optical lens. Microstructure, elemental distribution, phase constitution and wear properties of different composite coatings were investigated. The results showed that WC particles were partly dissolved under the effect of wide-band fiber laser irradiation. A special cored-eutectic structure was synthesized due to dissolution of WC particles. According to EDS and XRD results, the inside cores were confirmed as carbides of M{sub 23}C{sub 6} enriched in Cr, W and Fe. These complex carbides were primarily separated out in the molten metal when solidification started. Eutectic structure composed of M{sub 23}C{sub 6} carbides and γ-Ni(Fe) grew around carbides when cooling. Element content of Cr and W is lower at the bottom of cladding layer. In consequence, the eutectic structure formed in this region did not have inside carbides. The coatings made by circular laser beam were composed of dendritic matrix and interdendritic eutectic carbides, lacking of block carbides. Compared to coatings made by circular laser spot, the cored-eutectic structure formed in wide-band coatings had advantages of well-distribution and tight binding with matrix. The uniform power density and energy distribution and the weak liquid convection in molten pool lead to the unique microstructure evolution in composite coatings made by wide-band laser

Nd:YOV4 laser polishing on WC-Co HVOF coating

Science.gov (United States)

Giorleo, L.; Ceretti, E.; Montesano, L.; La Vecchia, G. M.

2017-10-01

WC/Co coatings are widely applied to different types of components due to their extraordinary performance properties including high hardness and wear properties. In industrial applications High Velocity Oxy-Fuel (HVOF) technique is extensively used to deposit hard metal coatings. The main advantage of HVOF compared to other thermal spray techniques is the ability to accelerate the melted powder particles of the feedstock material at a relatively high velocity, leading to obtain good adhesion and low porosity level. However, despite the mentioned benefits, the surface finish quality of WC-Co HVOF coatings results to be poor (Ra higher than 5 µm) thus a mechanical polishing process is often needed. The main problem is that the high hardness of coating leads the polishing process expensive in terms of time and tool wear; moreover polishing becomes difficult and not always possible in case of limited accessibility of a part, micro dimensions or undercuts. Nowadays a different technique available to improve surface roughness is the laser polishing process. The polishing principle is based on focused radiation of a laser beam that melts a microscopic layer of surface material. Compared to conventional polishing process (as grinding) it ensures the possibility of avoiding tool wear, less pollution (no abrasive or liquids), no debris, less machining time and coupled with a galvo system it results to be more suitable in case of 3D complex workpieces. In this paper laser polishing process executed with a Nd:YOV4 Laser was investigated: the effect of different process parameters as initial coating morphology, laser scan speed and loop cycles were tested. Results were compared by a statistical approach in terms of average roughness along with a morphological analysis carried out by Scanning Electron Microscope (SEM) investigation coupled with EDS spectra.

Optimization of Ni-Based WC/Co/Cr Composite Coatings Produced by Multilayer Laser Cladding

Directory of Open Access Journals (Sweden)

Andrea Angelastro

2013-01-01

Full Text Available As a surface coating technique, laser cladding (LC has been developed for improving wear, corrosion, and fatigue properties of mechanical components. The main advantage of this process is the capability of introducing hard particles such as SiC, TiC, and WC as reinforcements in the metallic matrix such as Ni-based alloy, Co-based alloy, and Fe-based alloy to form ceramic-metal composite coatings, which have very high hardness and good wear resistance. In this paper, Ni-based alloy (Colmonoy 227-F and Tungsten Carbides/Cobalt/Chromium (WC/Co/Cr composite coatings were fabricated by the multilayer laser cladding technique (MLC. An optimization procedure was implemented to obtain the combination of process parameters that minimizes the porosity and produces good adhesion to a stainless steel substrate. The optimization procedure was worked out with a mathematical model that was supported by an experimental analysis, which studied the shape of the clad track generated by melting coaxially fed powders with a laser. Microstructural and microhardness analysis completed the set of test performed on the coatings.

Wear evaluation of WC inserts coated with TiN/TiAlN multinanolayers

OpenAIRE

Moreno, L. H.; Ciacedo, J. C.; Martinez, F.; Bejarano, G.; Battaille, T. S.; Prieto, P.

2010-01-01

TiN/TiAlN multilayers were deposited by radio frequency, r.f., reactive magnetron sputtering by using titanium and aluminum targets with 10 cm diameter and 99.99% purity in an argon/nitrogen atmosphere, applying a substrate temperature of 300 ºC. WC inserts were used as substrates to improve the mechanical and tribological properties of TiN/TiAlN multilayered coatings compared to other types of coatings like TiAlN monolayers and to manage greater efficiency of these coatings in different indu...

Slurry Erosion Behavior of F6NM Stainless Steel and High-Velocity Oxygen Fuel-Sprayed WC-10Co-4Cr Coating

Science.gov (United States)

Cui, S. Y.; Miao, Q.; Liang, W. P.; Huang, B. Z.; Ding, Z.; Chen, B. W.

2017-02-01

WC-10Co-4Cr coating was applied to the surface of F6NM stainless steel by high-velocity oxygen-fuel spraying. The slurry erosion behavior of the matrix and coating was examined at different rotational speeds using a self-made machine. This experiment effectively simulates real slurry erosion in an environment with high silt load. At low velocity (<6 m/s), the main failure mechanism was cavitation. Small bubbles acted as an air cushion, obstructing direct contact between sand and the matrix surface. However, at velocity above 9 m/s, abrasive wear was the dominant failure mechanism. The results indicate that WC-10Co-4Cr coating significantly improved the slurry resistance at higher velocity, because it created a thin and dense WC coating on the surface.

Stripping methods studies for HVOF WC-10Co-4Cr coating removal

Science.gov (United States)

Menini, Richard; Salah, Nihad Ben; Nciri, Rachid

2004-04-01

The use of high-velocity oxyfuel (HVOF) cermet coatings is considered to be a valuable and innovative alternative technology to replace Cr(VI) electroplating. Among others, a WC-10Co-4Cr coating is one of the best choices for landing gear components due to its excellent tribology and corrosion properties. The stripping process of such a cermet coating was studied due to its importance for the repair and overhaul of landing gear components. Stripping solutions fulfill the following criteria: keep substrate integrity; exhibit a high strip rate (SR); lead to uniform dissolution; show no galvanic corrosion; and be environmentally friendly. Three different high-strength steel substrates (4340, 300M, and Aermet100) were studied. Five different stripping solutions were selected for the electrochemical study. Only three met the targeted criteria: the meta-nitrobenzane sulfonate-sodium cyanide solution; the Rochelle salt; and a commercial nickel stripper. It was found that the process must be electrolytic, and that ultrasonic agitation is needed to enhance the overall mass transport and removal of WC particles and metallic matrix residues. When choosing the most efficient solution and conditions, the SR was found to be as high as 162 µm h-1, which is a very acceptable SR for productivity sake.

Friction and wear properties of high-velocity oxygen fuel sprayed WC-17Co coating under rotational fretting conditions

Science.gov (United States)

Luo, Jun; Cai, Zhenbing; Mo, Jiliang; Peng, Jinfang; Zhu, Minhao

2016-05-01

Rotational fretting which exist in many engineering applications has incurred enormous economic loss. Thus, accessible methods are urgently needed to alleviate or eliminate damage by rotational fretting. Surface engineering is an effective approach that is successfully adopted to enhance the ability of components to resist the fretting damage. In this paper, using a high-velocity oxygen fuel sprayed (HVOF) technique WC-17Co coating is deposited on an LZ50 steel surface to study its properties through Vickers hardness testing, scanning electric microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffractrometry (XRD). Rotational fretting wear tests are conducted under normal load varied from 10 N to 50 N, and angular displacement amplitudes vary from 0.125° to 1°. Wear scars are examined using SEM, EDX, optical microscopy (OM), and surface topography. The experimental results reveal that the WC-17Co coating adjusted the boundary between the partial slip regime (PSR) and the slip regime (SR) to the direction of smaller amplitude displacement. As a result, the coefficients of friction are consistently lower than the substrate's coefficients of friction both in the PSR and SR. The damage to the coating in the PSR is very slight. In the SR, the coating exhibits higher debris removal efficiency and load-carrying capacity. The bulge is not found for the coating due to the coating's higher hardness to restrain plastic flow. This research could provide experimental bases for promoting industrial application of WC-17Co coating in prevention of rotational fretting wear.

Influence of powder and spray parameters on erosion and corrosion properties of HVOF sprayed WC-Co-Cr coatings

Energy Technology Data Exchange (ETDEWEB)

Berget, John

1998-07-01

Thermal spraying is a generic term including various processes used to deposit coatings on surfaces. The coating material is in the form of powder or a wire and is melted or softened by means of a heat source. A gas stream accelerates the material towards a prepared surface and deposits it there to form the coating. Examples of components being maintained by application of thermal spray coatings are gate valves and ball valves for the offshore industry and turbine blades in power generations installations. Recent investigation has shown that the commonly used coating material WC-Co is not corrosion resistant. But it can be improved by the addition of Cr. The main objective of this thesis is to study the influence of spray process control variables and powder characteristics on the erosion and erosion-corrosion properties of the coatings. Spray process variables investigated include energy input, powder feed rate and spray distance. Powder characteristics studied are average size of the WC particles, relative proportions of Co and Cr in the metal phase and powder grain size distribution.

A study of Ni-based WC composite coatings by laser induction hybrid rapid cladding with elliptical spot

International Nuclear Information System (INIS)

Zhou Shengfeng; Huang Yongjun; Zeng Xiaoyan

2008-01-01

Ni-based WC composite coatings by laser induction hybrid rapid cladding (LIHRC) with elliptical spot were investigated. Results indicate that the efficiency using the elliptical spot of 6 mm x 4 mm (the major and minor axis of laser beam are 6 mm and 4 mm, respectively, the major axis is parallel to the direction of laser scanning) is higher than that using the elliptical spot of 4 mm x 6 mm (the major axis is perpendicular to the direction of laser scanning). The precipitated carbides with the blocky and bar-like shape indicate that WC particles suffer from the heat damage of 'the disintegration pattern + the growth pattern', whichever elliptical spot is used at low laser scanning speed. However, at high laser scanning speed, the blocky carbides are only formed if the elliptical spot of 6 mm x 4 mm is adopted, showing that WC particles present the heat damage of 'the disintegration pattern', whereas the fine carbides are precipitated when the elliptical spot of 4 mm x 6 mm is used, showing that WC particles take on the heat damage of 'the radiation pattern'. Especially, the efficiency of LIHRC is increased much four times higher than that of the general laser cladding and crack-free ceramic-metal coatings can be obtained

As(III) oxidation by MnO{sub 2} coated PEEK-WC nanostructured capsules

Energy Technology Data Exchange (ETDEWEB)

Criscuoli, Alessandra, E-mail: a.criscuoli@itm.cnr.it [Institute on Membrane Technology, ITM-CNR, Via P. Bucci Cubo 17/C, 87030 Rende (CS) (Italy); Majumdar, Swachchha [Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Rd., 700032 Kolkata (India); Figoli, Alberto, E-mail: a.figoli@itm.cnr.it [Institute on Membrane Technology, ITM-CNR, Via P. Bucci Cubo 17/C, 87030 Rende (CS) (Italy); Sahoo, Ganesh C. [Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Rd., 700032 Kolkata (India); Bafaro, Patrizia [Institute on Membrane Technology, ITM-CNR, Via P. Bucci Cubo 17/C, 87030 Rende (CS) (Italy); Department of Chemical Engineering and Materials, University of Calabria, Via P. Bucci Cubo 42/A, 87030 Rende (CS) (Italy); Bandyopadhyay, Sibdas [Central Glass and Ceramic Research Institute, 196, Raja S. C. Mullick Rd., 700032 Kolkata (India); Drioli, Enrico [Institute on Membrane Technology, ITM-CNR, Via P. Bucci Cubo 17/C, 87030 Rende (CS) (Italy); Department of Chemical Engineering and Materials, University of Calabria, Via P. Bucci Cubo 42/A, 87030 Rende (CS) (Italy)

2012-04-15

Highlights: Black-Right-Pointing-Pointer Successful preparation of PEEK-WC nanostructured capsules coated by MnO{sub 2}. Black-Right-Pointing-Pointer Preliminary tests of As(III) oxidation carried out in batch. Black-Right-Pointing-Pointer Complete oxidation obtained for feed concentrations of 0.1 and 0.3 ppm. - Abstract: PEEK-WC nanostructured capsules were prepared by the phase inversion technique and used as support for the coating of a manganese dioxide layer. The coating was done by a chemical treatment of the capsules followed by a thermal one. The presence of the MnO{sub 2} layer was confirmed by scanning electron microscopy (SEM), back scattering electron (BSE), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analysis. The produced capsules were, then, tested for As(III) oxidation in batch. The experiments consisted in treating 165 ml of As(III) solution with 1 g of coated capsules at fixed temperature (15 Degree-Sign C) and pH (5.7-5.8). In particular, the efficiency of the system was investigated for different As(III) concentrations (0.1, 0.3, 0.7 and 1 ppm). For feeds at lower As(III) content (0.1-0.3 ppm), tests lasted for 8 h, while prolonged runs (up to 48 h) were carried out on more concentrated solutions (0.7 and 1 ppm). The produced capsules were able to oxidize As(III) into As(V) leading to complete conversion after 3 and 4 h for feed concentrations of 0.1 and 0.3 ppm, respectively.

The analysis of the mechanical properties of F75 Co-Cr alloy for use in selective laser melting (SLM manufacturing of removable partial dentures (RPD

Directory of Open Access Journals (Sweden)

D. Jevremovic

2012-04-01

Full Text Available The presented work discusses the applicability of the selective laser melting technique (SLM in manufacture of removable partial denture (RPD frameworks with the emphasis on material properties. The paper presents initial results of a conducted test of the mechanical properties of the F75 Co-Cr dental alloy used with selective laser melting.

Thermal interaction between WC-Co coating and steel substrate in process of HVOF spraying

International Nuclear Information System (INIS)

Guilemany, J.M.; Sobolev, V.V.; Nutting, J.; Dong, Z.; Calero, J.A.

1994-01-01

The WC-Co powders can be used to produce good adhesive and wear resistant HVOF thermal spray coatings on steel and light alloys substrates. In order to understand the properties of this kind of coating, the phases which are present in the coatings and structure changes during post heat treatments have been investigated. Although the coating properties depend very much on the structure developed in the substrate-coating interfacial region it has not been yet investigated in detail. The present study is devoted to the experimental and theoretical analysis of this interfacial region. The structure characterization has been performed mainly through the use of transmission electron microscopy. To provide a theoretical investigation a realistic prediction model of the process has been developed and on its base the mathematical simulation of the substrate-coating thermal interaction has been undertaken

Characterisation of Pristine and Recoated electron beam evaporation plasma-assisted physical vapour deposition Cr-N coatings on AISI M2 steel and WC-Co substrates

International Nuclear Information System (INIS)

Avelar-Batista, J.C.; Spain, E.; Housden, J.; Fuentes, G.G.; Rebole, R.; Rodriguez, R.; Montala, F.; Carreras, L.J.; Tate, T.J.

2005-01-01

This paper is focussed on the characterisation of electron beam evaporation plasma-assisted physical vapour deposition Cr-N coatings deposited on AISI M2 steel and hardmetal (K10) substrates in two different conditions: Pristine (i.e., coated) and Recoated (i.e., stripped and recoated). Analytical methods, including X-ray diffraction (XRD), scanning electron microscopy, scratch adhesion and pin-on-disc tests were used to evaluate several coating properties. XRD analyses indicated that both Pristine and Recoated coatings consisted of a mixture of hexagonal Cr 2 N and cubic CrN, regardless of substrate type. For the M2 steel substrate, only small differences were found in terms of coating phases, microstructure, adhesion, friction and wear coefficients between Pristine and Recoated. Recoated on WC-Co (K10) exhibited a less dense microstructure and significant inferior adhesion compared to Pristine on WC-Co (K10). The wear coefficient of Recoated on WC-Co was 100 times higher than those exhibited by all other specimens. The results obtained confirm that the stripping process did not adversely affect the Cr-N properties when this coating was deposited onto M2 steel substrates, but it is clear from the unsatisfactory tribological performance of Recoated on WC-Co that the stripping process is unsuitable for hardmetal substrates

Ultra-short-period WC/SiC multilayer coatings for x-ray applications

International Nuclear Information System (INIS)

Fernández-Perea, Mónica; Pivovaroff, Mike J.; Soufli, Regina; Alameda, Jennifer; Mirkarimi, Paul; Descalle, Marie-Anne; Baker, Sherry L.; McCarville, Tom; Ziock, Klaus; Hornback, Donald; Romaine, Suzanne; Bruni, Ric; Zhong, Zhong; Honkimäki, Veijo; Ziegler, Eric; Christensen, Finn E.; Jakobsen, Anders C.

2013-01-01

Multilayer coatings enhance x-ray mirror performance at incidence angles steeper than the critical angle, allowing for improved flux, design flexibility and facilitating alignment. In an attempt to extend the use of multilayer coatings to photon energies higher than previously achieved, we have developed multilayers with ultra-short periods between 1 and 2 nm based on the material system WC/SiC. This material system was selected because it possesses very sharp and stable interfaces. In this article, we show highlights from a series of experiments performed in order to characterize the stress, microstructure and morphology of the multilayer films, as well as their reflective performance at photon energies from 8 to 384 keV

Erosion-oxidation behavior of thermal sprayed Ni20Cr alloy and WC and Cr3C2 cermet coatings

Directory of Open Access Journals (Sweden)

Clarice Terui Kunioshi

2005-06-01

Full Text Available 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.

Thin coatings for heavy industry: Advanced coatings for pipes and valves

Science.gov (United States)

Vernhes, Luc

investigation of an HVOF 80/20 Cr 3C2-NiCr coating failure in an on-off metal-seated ball valve (MSBV) used in supercritical steam lines in a power plant, along with an assessment of alternative coating solutions that are less susceptible to this failure mode. HVOF 80/20 Cr3C2-NiCr coating has been used to protect thousands of MSBVs without incident. However, in this case the valves were challenged with exposure to rapid variations in high-pressure flow and temperature, resulting in a unique situation that caused the coating to undergo cracking and cohesive failure. Carbide precipitation was found to be a major factor, resulting in coating embrittlement. Reduced coating toughness and ductility allowed thermal, mechanical, and residual stresses to initiate cracks and propagate them more easily, leading to coating failure with exposure to thermal shock. To alleviate these issues, possible coating alternatives were assessed. The third article presents the mechanical, tribological, and corrosion properties of two novel hybrid coating systems: 1) a tungsten-tungsten carbide (W-WC) top layer and a laser cladded cobalt-chromium (Co-Cr) interlayer (StelliteRTM 6 superalloy) applied to a 316 stainless steel substrate; and 2) the same W-WC top layer and an HVOF spray-and-fused Ni-W-Cr-B interlayer (ColmonoyRTM 88 superalloy) applied to an InconelRTM 718 substrate. X-ray diffraction, energy dispersive spectroscopy, and scanning electron microscopy were used to analyze the microstructure of the coating layers. Microindentation was used to measure surface hardness and the hardness profile of the coating systems. Rockwell indentation was used to assess coating adhesion according to CEN/TS 1071-8. Surface load-carrying capacity was also assessed by measuring micro- and macrohardness at high loads. Tribological properties were assessed with a linear reciprocating ball-on-flat sliding wear test, and corrosion resistance was measured by potentiodynamic polarization and electrochemical impedance

Wear Micro-Mechanisms of Composite WC-Co/Cr - NiCrFeBSiC Coatings. Part I: Dry Sliding

Directory of Open Access Journals (Sweden)

D. Kekes

2014-12-01

Full Text Available The influence of the cermet fraction in cermet/ metal composite coatings developed by High-Velocity Oxyfuel Flame (HVOF spraying on their tribological behaviour was studied. Five series of coatings, each one containing different proportion of cermet-metal components, prepared by premixing commercially available feedstocks of NiCrFeBSiC metallic and WC-Co/Cr cermet powders were deposited on AISI 304 stainless steel substrate. The microstructure of as-sprayed coatings was characterized by partial decomposition of the WC particles, lamellar morphology and micro-porosity among the solidified splats. Tribological behavior was studied under sliding friction conditions using a Si3N4 ball as counterbody and the friction coefficient and volume loss were determined as a function of the cermet fraction. Microscopic examinations of the wear tracks and relevant cross sections identified the wear mechanisms involved. Coatings containing only the metallic phase were worn out through a combination of ploughing, micro-cracking and splat exfoliation, whilst those containing only the cermet phase primarily by micro-cracking at the individual splat scale. The wear mechanisms of the composite coatings were strongly affected by their randomly stratified structure. In-depth cracks almost perpendicular to the coating/ substrate interface occurring at the wear track boundaries resulted in cermet trans-splat fracture.

Microstructures and Mechanical Properties of Co-Cr Dental Alloys Fabricated by Three CAD/CAM-Based Processing Techniques

Directory of Open Access Journals (Sweden)

Hae Ri Kim

2016-07-01

Full Text Available The microstructures and mechanical properties of cobalt-chromium (Co-Cr alloys produced by three CAD/CAM-based processing techniques were investigated in comparison with those produced by the traditional casting technique. Four groups of disc- (microstructures or dumbbell- (mechanical properties specimens made of Co-Cr alloys were prepared using casting (CS, milling (ML, selective laser melting (SLM, and milling/post-sintering (ML/PS. For each technique, the corresponding commercial alloy material was used. The microstructures of the specimens were evaluated via X-ray diffractometry, optical and scanning electron microscopy with energy-dispersive X-ray spectroscopy, and electron backscattered diffraction pattern analysis. The mechanical properties were evaluated using a tensile test according to ISO 22674 (n = 6. The microstructure of the alloys was strongly influenced by the manufacturing processes. Overall, the SLM group showed superior mechanical properties, the ML/PS group being nearly comparable. The mechanical properties of the ML group were inferior to those of the CS group. The microstructures and mechanical properties of Co-Cr alloys were greatly dependent on the manufacturing technique as well as the chemical composition. The SLM and ML/PS techniques may be considered promising alternatives to the Co-Cr alloy casting process.

Diamond-like carbon coatings enhance the hardness and resilience of bearing surfaces for use in joint arthroplasty.

Science.gov (United States)

Roy, M E; Whiteside, L A; Xu, J; Katerberg, B J

2010-04-01

The purpose of this study was to evaluate the potential of a hard diamond-like carbon (DLC) coating to enhance the hardness and resilience of a bearing surface in joint replacement. The greater hardness of a magnesium-stabilized zirconium (Mg-PSZ) substrate was expected to provide a harder coating-substrate composite microhardness than the cobalt-chromium alloy (CoCr) also used in arthroplasty. Three femoral heads of each type (CoCr, Mg-PSZ, DLC-CoCr and DLC-Mg-PSZ) were examined. Baseline (non-coated) and composite coating/substrate hardness was measured by Vickers microhardness tests, while nanoindentation tests measured the hardness and elastic modulus of the DLC coating independent of the Mg-PSZ and CoCr substrates. Non-coated Mg-PSZ heads were considerably harder than non-coated CoCr heads, while DLC coating greatly increased the microhardness of the CoCr and Mg-PSZ substrates. On the nanoscale the non-coated heads were much harder than on the microscale, with CoCr exhibiting twice as much plastic deformation as Mg-PSZ. The mechanical properties of the DLC coatings were not significantly different for both the CoCr and Mg-PSZ substrates, producing similar moduli of resilience and plastic resistance ratios. DLC coatings greatly increased hardness on both the micro and nano levels and significantly improved resilience and resistance to plastic deformation compared with non-coated heads. Because Mg-PSZ allows less plastic deformation than CoCr and provides a greater composite microhardness, DLC-Mg-PSZ will likely be more durable for use as a bearing surface in vivo. Copyright 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Effects of WC Particle Size and Co Content on the Graded Structure in Functionally Gradient WC-Co Composites

Directory of Open Access Journals (Sweden)

Yuan Yigao

2016-01-01

Full Text Available Functionally gradient WC-Co composites having a Co depleted surface zone and not comprising the h phase can be manufactured via carburizing process. During carburizing, besides carburizing process parameters, the microstructural parameters of WC-Co materials, such as WC grain size and Co content, also have significant influences on the formation of Co gradient structure. In this study, the effects of WC particle size and Co content on the gradient structure within gradient hardmetals have been studied, based on a series of carburizing experiments of WC-Co materials with different WC particle sizes and cobalt contents. The results show that both the thickness and the amplitude of the gradients within gradient WC-Co materials increase with increasing initial WC particle size and Co content of WC-Co alloys. The reason for this finding is discussed.

Annealing of Co-Cr dental alloy: effects on nanostructure and Rockwell hardness.

Science.gov (United States)

Ayyıldız, Simel; Soylu, Elif Hilal; Ide, Semra; Kılıç, Selim; Sipahi, Cumhur; Pişkin, Bulent; Gökçe, Hasan Suat

2013-11-01

The aim of the study was to evaluate the effect of annealing on the nanostructure and hardness of Co-Cr metal ceramic samples that were fabricated with a direct metal laser sintering (DMLS) technique. Five groups of Co-Cr dental alloy samples were manufactured in a rectangular form measuring 4 × 2 × 2 mm. Samples fabricated by a conventional casting technique (Group I) and prefabricated milling blanks (Group II) were examined as conventional technique groups. The DMLS samples were randomly divided into three groups as not annealed (Group III), annealed in argon atmosphere (Group IV), or annealed in oxygen atmosphere (Group V). The nanostructure was examined with the small-angle X-ray scattering method. The Rockwell hardness test was used to measure the hardness changes in each group, and the means and standard deviations were statistically analyzed by one-way ANOVA for comparison of continuous variables and Tukey's HSD test was used for post hoc analysis. P values of directly affected both the nanostructure and hardness of the Co-Cr alloy. Group III exhibited a non-homogeneous structure and increased hardness (48.16 ± 3.02 HRC) because the annealing process was incomplete and the inner stress was not relieved. Annealing in argon atmosphere of Group IV not only relieved the inner stresses but also decreased the hardness (27.40 ± 3.98 HRC). The results of fitting function presented that Group IV was the most homogeneous product as the minimum bilayer thickness was measured (7.11 Å). After the manufacturing with DMLS technique, annealing in argon atmosphere is an essential process for Co-Cr metal ceramic substructures. The dentists should be familiar with the materials that are used in clinic for prosthodontics treatments.

Validation of HVOF WC/Co Thermal Spray Coatings as a Replacement for Hard Chrome Plating on Aircraft Landing Gear

National Research Council Canada - National Science Library

Sartwell, Bruce

2004-01-01

.... This document constitutes the final report on a project to quality high-velocity oxygen-fuel (HVOF) thermal spray WC/Co coatings as a replacement for hard chrome plating on landing gear components...

Influence of Plasma Transferred Arc Process Parameters on Structure and Mechanical Properties of Wear Resistive NiCrBSi-WC/Co Coatings

Directory of Open Access Journals (Sweden)

Eitvydas GRUZDYS

2011-07-01

Full Text Available Self-fluxing NiCrBSi and related coatings received considerable interest due to their good wear as well as corrosion resistance at moderate and elevated temperatures. Hard tungsten carbide (WC particles can be included in NiCrBSi for further increase of the coating hardness and abrasive wear resistance. Flame spray technique is widely used for fabrication of NiCrBSi films. However, in such a case, subsequent remelting of the deposited coatings by flame, arc discharge or high power laser beam is necessary. In present study NiCrBSi-WC/Co coatings were formed using plasma transferred arc process. By adjusting plasma parameters, such as current, plasma gas flow, shielding gas flow, a number of coatings were formed on steel substrates. Structure of the coatings was investigated using X-ray diffractometry. Microstructure of cross-sectioned coatings was examined using scanning electron microscopy. Hardness of the coating was evaluated by means of the Vickers hardness tests. Wear tests were also performed on specimens to determine resistance to abrasive wear. Acquired results allowed estimating the influence of the deposition process parameters on structure and mechanical properties of the coatings.http://dx.doi.org/10.5755/j01.ms.17.2.482

Recent Advances in the Deposition of Diamond Coatings on Co-Cemented Tungsten Carbides

Directory of Open Access Journals (Sweden)

R. Polini

2012-01-01

Full Text Available Co-cemented tungsten carbides, namely, hard metals are largely used to manufacture high wear resistant components in several manufacturing segments. Coating hard metals with superhard materials like diamond is of utmost interest as it can further extend their useful lifespan. The deposition of diamond coatings onto WC-Co can be extremely complicated as a result of poor adhesion. This can be essentially ascribed to (i the mismatch in thermal expansion coefficients between diamond and WC-Co, at the typical high temperatures inside the chemical vapour deposition (CVD chamber, generates large residual stresses at the interface; (ii the role of surface Co inside the WC-Co matrix during diamond CVD, which promotes carbon dissolution and diffusion. The present investigation reviews the techniques by which Co-cemented tungsten carbides can be treated to make them prone to receive diamond coatings by CVD. Further, it proposes interesting ecofriendly and sustainable alternatives to further improve the diamond deposition process as well as the overall performance of the coated hard metals.

Integrated Glass Coating Manufacturing Line

Energy Technology Data Exchange (ETDEWEB)

Brophy, Brenor [Enki Technology Inc., San Jose, CA (United States)

2015-09-30

This project aims to enable US module manufacturers to coat glass with Enki’s state of the art tunable functionalized AR coatings at the lowest possible cost and highest possible performance by encapsulating Enki’s coating process in an integrated tool that facilitates effective process improvement through metrology and data analysis for greater quality and performance while reducing footprint, operating and capital costs. The Phase 1 objective was a fully designed manufacturing line, including fully specified equipment ready for issue of purchase requisitions; a detailed economic justification based on market prices at the end of Phase 1 and projected manufacturing costs and a detailed deployment plan for the equipment.

Adaptation and micro-structure of Co-Cr alloy maxillary complete denture base plates fabricated by selective laser melting technique.

Science.gov (United States)

Ye, Ye; Jiao, Ting; Zhu, Jiarui; Sun, Jian

2018-01-24

The purpose of the study was to evaluate the adaptation and micro-structure of Co-Cr alloy maxillary complete denture base plates fabricated by the selective laser melting (SLM) technique. Twenty pairs of edentulous casts were randomly and evenly divided into two groups, and manufacturing of the Co-Cr alloy maxillary complete denture base was conducted either by the SLM technique or by the conventional method. The base-cast sets were transversally sectioned into three sections at the distal canines, mesial of the first molars and the posterior palatal zone. The gap between the metal base and cast was measured in these three sections with a stereoscopic microscope, and the data were analysed using t tests. A total of five specimens of 5 mm diameter were fabricated with the Co-Cr alloy by SLM and the traditional casting technology. A scanning electron microscope (SEM) was used to evaluate the differences in microstructure between these specimens. There was no statistical difference between the three sections in all four groups (P > 0.05). At the region of the canines, the clearance value for the SLM Co-Cr alloy group was larger than that of the conventional method group (P  0.05). The SLM Co-Cr alloy has a denser microstructure behaviour and less casting defect than the cast Co-Cr alloy. The SLM technique showed initial feasibility for the manufacture of dental bases of complete dentures, but large sample studies are needed to prove its reliability in clinical applications. The mechanical properties and microstructure of the denture frameworks prepared by selective laser melting indicate that these dentures are appropriate for clinical use.

Design and simulation of thermal residual stresses of coatings on WC-Co cemented carbide cutting tool substrate

International Nuclear Information System (INIS)

Li, Anhai; Zhao, Jun; Zang, Jian; Zheng, Wei

2016-01-01

Large thermal residual stresses in coatings during the coating deposition process may easily lead to coating delamination of coated carbide tools in machining. In order to reduce the possibility of coating delamination during the tool failure process, a theoretical method was proposed and a numerical method was constructed for the coating design of WC-Co cemented carbide cutting tools. The thermal residual stresses of multi-layered coatings were analytically modeled based on equivalent parameters of coating properties, and the stress distribution of coatings are simulated by Finite element method (FEM). The theoretically calculated results and the FEM simulated results were verified and in good agreement with the experimental test results. The effects of coating thickness, tool substrate, coating type and interlayer were investigated by the proposed geometric and FEM model. Based on the evaluations of matchability of tool substrate and tool coatings, the basic principles of tool coating design were proposed. This provides theoretical basis for the selection and design of coatings of cutting tools in high-speed machining

FIB-SEM Sectioning Study of Decarburization Products in the Microstructure of HVOF-Sprayed WC-Co Coatings

Science.gov (United States)

Katranidis, Vasileios; Gu, Sai; Cox, David C.; Whiting, Mark J.; Kamnis, Spyros

2018-05-01

The thermal dissolution and decarburization of WC-based powders that occur in various spray processes are a widely studied phenomenon, and mechanisms that describe its development have been proposed. However, the exact formation mechanism of decarburization products such as metallic W is not yet established. A WC-17Co coating is sprayed intentionally at an exceedingly long spray distance to exaggerate the decarburization effects. Progressive xenon plasma ion milling of the examined surface has revealed microstructural features that would have been smeared away by conventional polishing. Serial sectioning provided insights on the three-dimensional structure of the decarburization products. Metallic W has been found to form a shell around small splats that did not deform significantly upon impact, suggesting that its crystallization occurs during the in-flight stage of the particles. W2C crystals are more prominent on WC faces that are in close proximity with splat boundaries indicating an accelerated decarburization in such sites. Porosity can be clearly categorized in imperfect intersplat contact and oxidation-generated gases via its shape.

Wear resistance of nano- and micro-crystalline diamond coatings onto WC-Co with Cr/CrN interlayers

Energy Technology Data Exchange (ETDEWEB)

Polini, Riccardo [Dipartimento di Scienze e Tecnologie Chimiche, Universita di Roma Tor Vergata, Via della Ricerca Scientifica, 1, Rome, 00133 (Italy); Barletta, Massimiliano, E-mail: barletta@ing.uniroma2.i [Dipartimento di Ingegneria Meccanica, Universita di Roma Tor Vergata, Via del Politecnico, 1, Rome, 00133 (Italy); Cristofanilli, Giacomo [Dipartimento di Scienze e Tecnologie Chimiche, Universita di Roma Tor Vergata, Via della Ricerca Scientifica, 1, Rome, 00133 (Italy)

2010-12-30

Cr/CrN bi-layers have been used recently to promote the growth of high quality Hot Filament Chemical Vapour Deposition (HFCVD) diamond coatings onto Co-cemented tungsten carbide (WC-6 wt.%Co) substrates. In the present investigation, the influence of the crystalline size of the diamond coatings on their wear endurance is looked into. Nano- (NDC) and micro-crystalline Diamond Coatings (MDC) were deposited by HFCVD onto untreated and Fluidized Bed (FB) treated Cr/CrN interlayers. NDCs, characterized by a cauliflower-like morphology, showed improved wear resistance. However, the superimposition of NDCs onto Cr/CrN interlayers micro-corrugated by FB treatment was found to be the most promising choice, leading to the formation of highly adherent and wear resistant coatings.

Sliding friction of nanocomposite WC1-x/C coatings: transfer film and its influence on tribology.

Science.gov (United States)

Liu, Y; Gubisch, M; Spiess, L; Schaefer, J A

2009-06-01

The transfer film on steel spheres formed in reciprocating sliding against nanocomposite coatings based on nanocrystalline WC1-x in amorphous carbon matrix is characterized and correlated with the tribological properties measured by a precision microtribometer. With the presence of transfer film, a coefficient of friction approximately 0.13 and a depth wear rate approximately 0.35 x 10(-10) m/N.Pass were obtained. The central zone of the transfer film covering approximately 25% of the Hertz contact area is intact while cracks and wear debris are found in the vast peripheral area. It is also heavily oxidized due to the absence of carbon, which is located at the peripherals and acts as lubricants. We propose that the oxidation of WC and adhesion of the oxides to the surface of sphere is the main mechanism for the buildup of the transfer films. With the thickening of the film, the internal stress increases. Under the shear stress, spalling and cracking of the transfer film take place. The overall tribological performance of the coatings is therefore a competing process of buildup and spalling of transfer films.

Interfacial reaction in cast WC particulate reinforced titanium metal matrix composites coating produced by laser processing

Science.gov (United States)

Liu, Dejian; Hu, Peipei; Min, Guoqing

2015-06-01

Laser injection of ceramic particle was conducted to produce particulate reinforced metal matrix composites (MMCs) coating on Ti-6Al-4V alloy. Cast WC particle (WCp) was used as injection reinforcement to avoid excessive release of carbon atoms into the melt pool. The interfaces and boundaries between WC and Ti matrix were investigated by electron microscopy study. Compared with single crystal WCp, cast WCp was an appropriate solution to control the reaction products (TiC) in the matrix and the total amount of reaction products was significantly reduced. Irregular-shape reaction layers were formed around cast WCp. The reaction layers consist of a W2C layer and a mixed layer of W and TiC. Such reaction layers are effective in load transfer under an external load.

Pd enhanced WC catalyst to promote heterogeneous methane combustion

International Nuclear Information System (INIS)

Terracciano, Anthony Carmine; De Oliveira, Samuel; Siddhanti, Deepti; Blair, Richard; Vasu, Subith S.; Orlovskaya, Nina

2017-01-01

Highlights: • Pd enhanced WC catalyst particles were synthesized via mechanochemical alloying. • Catalyst was characterized by XRD, XRF, SEM, and EDS. • Catalyst was deposited on porous ZrO_2 and evaluated in heterogeneous combustion. • During combustion temperature profiles and spectral emissions were collected. - Abstract: The efficiency of combustion for low cost heat production could be greatly enhanced if an active and low cost catalyst would be used to facilitate the chemical reactions occurring during combustor operation. Within this work an experimental study of palladium (Pd) enhanced tungsten carbide (WC) catalyst, synthesized via high energy ball milling and deposited by dip coating onto a magnesia partially stabilized zirconia (MgO-ZrO_2) porous matrix of 10 ppin was evaluated in heterogeneous methane combustion. The synthesized powder was characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) analysis, as well as by X-ray Fluorescence (XRF); and the morphology of the deposited WC-Pd coating was also characterized using SEM and EDS. Performance evaluation of the heterogeneous combustor with WC-Pd coated MgO-ZrO_2 porous media was conducted at constant air flow rate and various equivalence ratios of methane/air gaseous mixtures, while monitoring axial temperature profiles within the combustion chamber using thermocouples, as well as thermal radiative and acoustic emissions from the combustor exhaust using an externally placed CCD camera and a microphone. It was found that there is a strong dependence of flame position and maximum temperature on equivalence ratio (φ) over the range of 0.47 ± 0.02 ⩽ φ ⩽ 0.75 ± 0.02. Additionally it was found that over the same equivalence ratio range, there is a characteristic 4 peak acoustic signature between 200 and 500 Hz. It was found that at higher equivalence ratios 0.51 ± 0.02 ⩽ φ ⩽ 0.75 ± 0.02 the performance of combustor

Characterization of microstructure and surface properties of hybrid coatings of WC-CoCr prepared by laser heat treatment and high velocity oxygen fuel spraying

International Nuclear Information System (INIS)

Zhang Shihong; Cho, Tong-Yul; Yoon, Jae-Hong; Fang, Wei; Song, Ki-O; Li Mingxi; Joo, Yun-Kon; Lee, Chan Gyu

2008-01-01

The microstructure and microhardness of high velocity oxygen fuel-sprayed WC-CoCr coatings were comparatively studied both before and after laser heat treatment of the coatings. Optical microscopy, scanning electron microscopy, X-ray diffraction and microhardness testing were applied to investigate the microstructure, phase composition, porosity and microhardness. The results indicate that WC is still present, and W 2 C has appeared, while neither cobalt nor σ-CrCo is detectable. Co 4 W 2 C has appeared in the high velocity oxygen fuel-sprayed coating after laser heat treatment as compared to the coating before laser treatment. The relative content of the W 2 C has not increased with laser treatment, but the laser treatment has essentially eliminated the porosity almost entirely, providing a more homogeneous and densified microstructure. The laser heat treatment has effected the formation of a denser compact coating on the substrate. After laser heat treatment, the thickness of the coating has decreased from 300 μm to 225 μm. This corresponds to an average porosity in the high velocity oxygen fuel-sprayed coating that is approximately five times greater than that in the subsequently laser heat-treated coating. The laser treatment has also resulted in an increased hardness of the coating near the surface, where the average value increased from Hv 0.2 = 1262.4 in the coating before laser heat treatment to Hv 0.2 = 1818.7 after laser heat treatment

Photofunctional Co-Cr Alloy Generating Reactive Oxygen Species for Photodynamic Applications

Directory of Open Access Journals (Sweden)

Kang-Kyun Wang

2013-01-01

Full Text Available We report the fabrication of photofunctional Co-Cr alloy plate that is prepared by a simple modification process for photodynamic application. Photoinduced functionality is provided by the photosensitizer of hematoporphyrin (Hp that initially generates reactive oxygen species (ROS such as superoxide anion radical and singlet oxygen. The photosensitizer with carboxyl group was chemically bonded to the surface of the Co-Cr alloy plate by esterification reaction. Microstructure and elemental composition of the Co-Cr alloy plate were checked with scanning electron microscopy (SEM and energy dispersive X-ray spectrometer (EDS. Fabrication of the photofunctionality of the Co-Cr alloy plate was confirmed with X-ray photoelectron spectroscopy (XPS, reflectance UV-Vis absorption, and emission spectroscopy. Reactive oxygen generation from the photofunctional Co-Cr alloy plate was confirmed by using the decomposition reaction of 1,3-diphenylisobenzofuran (DPBF. The results suggest that the immobilized photosensitizer molecules on the surface of Co-Cr alloy plate still possess their optical and functional properties including reactive oxygen generation. To open the possibility for its application as a photodynamic material to biological system, the fabricated photofunctional Co-Cr alloy is applied to the decomposition of smooth muscle cells.

Statistical Optimization of Reactive Plasma Cladding to Synthesize a WC-Reinforced Fe-Based Alloy Coating

Science.gov (United States)

Wang, Miqi; Zhou, Zehua; Wu, Lintao; Ding, Ying; Xu, Feilong; Wang, Zehua

2018-04-01

A new compound Fe-W-C powder for reactive plasma cladding was fabricated by precursor carbonization process using sucrose as a precursor. The application of quadratic general rotary unitized design was highlighted to develop a mathematical model to predict and accomplish the desired surface hardness of plasma-cladded coating. The microstructure and microhardness of the coating with optimal parameters were also investigated. According to the developed empirical model, the optimal process parameters were determined as follows: 1.4 for C/W atomic ratio, 20 wt.% for W content, 130 A for scanning current and 100 mm/min (1.67 mm/s) for scanning rate. The confidence level of the model was 99% according to the results of the F-test and lack-of-fit test. Microstructural study showed that the dendritic structure was comprised of a mechanical mixture of α-Fe and carbides, while the interdendritic structure was a eutectic of α-Fe and carbides in the composite coating with optimal parameters. WC phase generation can be confirmed from the XRD pattern. Due to good preparation parameters, the average microhardness of cladded coating can reach 1120 HV0.1, which was four times the substrate microhardness.

Study of carbide-forming element interlayers for diamond nucleation and growth on silicon and WC-Co substrates

International Nuclear Information System (INIS)

Tang, Y.; Li, Y.S.; Yang, Q.; Hirose, A.

2010-01-01

Diamond nucleation and growth on several typical carbide-forming elements (CFE) (Ti, Cr and W) coated Si and WC-Co substrates were studied. The ion beam sputtered CFE interlayers show an amorphous/nanocrystalline microstructure. The diamond formed on the CFE coated substrates shows higher nucleation density and rate and finer grain structure than on uncoated substrates. Consequently, nanocrystalline diamond thin films can be formed on the CFE coated substrates under conventional microcrystalline diamond growth conditions. Among the three tested CFE interlayers, diamond has the highest nucleation density and rate on W layer and the lowest on Ti layer. The diamond nucleation density and rate on CFE coated WC-Co are much higher than those on widely used metal nitride coated WC-Co.

INVESTIGATION THE FITTING ACCURACY OF CAST AND SLM CO-CR DENTAL BRIDGES USING CAD SOFTWARE

Directory of Open Access Journals (Sweden)

Tsanka Dikova

2017-09-01

Full Text Available The aim of the present paper is to investigate the fitting accuracy of Co-Cr dental bridges, manufactured by three technologies, with the newly developed method using CAD software. The four-part dental bridges of Co-Cr alloys were produced by conventional casting of wax models, casting with 3D printed patterns and selective laser melting. The marginal and internal fit of dental bridges was studied out by two methods – silicone replica test and CAD software. As the silicone replica test characterizes with comparatively low accuracy, a new methodology for investigating the fitting accuracy of dental bridges was developed based on the SolidWorks CAD software. The newly developed method allows the study of the marginal and internal adaptation in unlimited directions and high accuracy. Investigation the marginal fit and internal adaptation of Co-Cr four-part dental bridges by the two methods show that the technological process strongly influences the fitting accuracy of dental restorations. The fitting accuracy of the bridges, cast with 3D printed patterns, is the highest, followed by the SLM and conventionally cast bridges. The marginal fit of the three groups of bridges is in the clinically acceptable range. The internal gap values vary in different regions – it is highest on the occlusal surfaces, followed by that in the marginal and axial areas. The higher fitting accuracy of the bridges, manufactured by casting with 3D printed patterns and SLM, compared to the conventionally cast bridges is a good precondition for their successful implementation in the dental offices and laboratories.

Wear Micro-Mechanisms of Composite WC-Co/Cr - NiCrFeBSiC Coatings. Part II: Cavitation Erosion

Directory of Open Access Journals (Sweden)

D. Kekes

2014-12-01

Full Text Available Composite coatings with five different proportions of WC-Co/Cr and NiCrFeBSiC components were deposited on stainless steel by HVOF spraying. Cavitation erosion tests were performed and the material removal micro-mechanisms were identified by SEM of both the eroded areas and the specimens’ cross-sections. Waves’ propagation and deflection at the weak interfaces within the coatings resulted in local tensile stresses perpendicular to the interface direction that eventually led to material removal. Such weak interfaces are the boundaries of the carbide particles with the metal binder within the same splat, those between splats along the same layer and those between successively deposited layers.

Long-term osseointegration of 3D printed CoCr constructs with an interconnected open-pore architecture prepared by electron beam melting.

Science.gov (United States)

Shah, Furqan A; Omar, Omar; Suska, Felicia; Snis, Anders; Matic, Aleksandar; Emanuelsson, Lena; Norlindh, Birgitta; Lausmaa, Jukka; Thomsen, Peter; Palmquist, Anders

2016-05-01

an interconnected open-pore architecture were prepared by electron beam melting (EBM). After six months of submerged healing in sheep, both alloys showed similar patterns of bone formation, with densification around the implant and gradual ingrowth into the porous network. The molecular and elemental composition of the interfacial tissue was similar for both alloys. Osteocytes made direct contact with both alloys, with similar overall osteocyte density and distribution. The work attests to the potential for achieving osseointegration of EBM manufactured porous CoCr implants. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Development and kinetic analysis of cobalt gradient formation in WC-Co composites

Science.gov (United States)

Guo, Jun

2011-12-01

Functionally graded cemented tungsten carbide (FG WC-Co) is one of the main research directions in the field of WC-Co over decades. Although it has long been recognized that FG WC-Co could outperform conventional homogeneous WC-Co owing to its potentially superior combinations of mechanical properties, until recently there has been a lack of effective and economical methods to make such materials. The lack of the technology has prevented the manufacturing and industrial applications of FG WC-Co from becoming a reality. This dissertation is a comprehensive study of an innovative atmosphere heat treatment process for producing FG WC-Co with a surface cobalt compositional gradient. The process exploited a triple phase field in W-C-Co phase diagram among three phases (solid WC, solid Co, and liquid Co) and the dependence of the migration of liquid Co on temperature and carbon content. WC-Co with a graded surface cobalt composition can be achieved by controlling the diffusion of carbon transported from atmosphere during sintering or during postsintering heat treatment. The feasibility of the process was validated by the successful preparations of FG WC-Co via both carburization and decarburization process following conventional liquid phase sintering. A study of the carburization process was undertaken to further understand and quantitatively modeled this process. The effects of key processing parameters (including heat treating temperature, atmosphere, and time) and key materials variables (involving Co content, WC grain size, and addition of grain growth inhibitors) on the formation of Co gradients were examined. Moreover, a carbon-diffusion controlled kinetic model was developed for simulating the formation of the gradient during the process. The parameters involved in this model were determined by thermodynamic calculations and regression-fit of simulation results with experimental data. In summary, this research first demonstrated the principle of the approach

Physical chemistry of WC-12 %Co coatings deposited by thermal spraying at different standoff distances

Energy Technology Data Exchange (ETDEWEB)

Afzal, Muhammad; Ahmed, Furqan; Anwar, Muhammad Yousaf; Ali, Liaqat; Ajmal, Muhammad [Univ. of Engineering and Technology, Metallurgical and Materials Engineering, Lahore (Pakistan); Khan, Aamer Nusair [Institute of Industrial and Control System, Rawalpindi (Pakistan)

2015-09-15

In the present research, WC-12 %Co cermet coatings were deposited on AISI-321 stainless steel substrate using air plasma spraying. During the deposition process, the standoff distance was varied from 80 to 130 mm with 10 mm increments. Other parameters such as current, voltage, time, carrier gas flow rate and powder feed rate etc. were kept constant. The objective was to study the effects of spraying distance on the microstructure of as-sprayed coatings. The microscopic analyses revealed that the band of spraying distance ranging from 90 to 100 mm was the threshold distance for optimum results, provided that all the other spraying parameters were kept constant. In this range of threshold distance, minimum percentages of porosity and defects were observed. Further, the formation of different phases, at six spraying distances, was studied using X-ray diffraction, and the phase analysis was correlated with hardness results.

Analysis of PTA hardfacing with CoCrWC and CoCrMoSi alloys

Directory of Open Access Journals (Sweden)

Adriano Scheid

2013-12-01

Full Text Available CoCrWC alloys are widely used to protect components that operate under wear and high temperature environments. Enhanced performance has been achieved with the CoCrMoSi alloys but processing this alloy system is still a challenge due to the presence of the brittle Laves phase, particularly when welding is involved. This work evaluated Plasma Transferred Arc coatings processed with the Co-based alloy CoMoCrSi - Tribaloy T400, reinforced with Laves phase, comparing its weldability to the CoCrWC - Stellite 6, reinforced with carbides. Coatings were also analyzed regarding the response to temperature exposure at 600°C for 7 days and subsequent effect on microstructure and sliding abrasive wear. Coatings characterization was carried out by light and scanning electron microscopy, X-ray diffraction and Vickers hardness. CoCrWC coatings exhibited a Cobalt solid solution dendritic microstructure and a thin interdendritic region with eutectic carbides, while CoCrMoSi deposits exhibit a large lamellar eutectic region of Laves phase and Cobalt solid solution and a small fraction of primary Laves phase. Although phase stability was observed by X-ray diffraction, coarsening of the microstructure occurred for both alloys. CoCrMoSi showed thicker lamellar Laves phase and CoCrWC coarser eutectic carbides. Coatings stability assessed by wear tests revealed that although the wear rate of the as-deposited CoCrMoSi alloy was lower than that of CoCrWC alloy its increase after temperature exposure was more significant, 22% against 15%. Results were discussed regarding the protection of industrial components in particular, bearings in 55AlZn hot dip galvanizing components.

An update on coating/manufacturing techniques of microneedles.

Science.gov (United States)

Tarbox, Tamara N; Watts, Alan B; Cui, Zhengrong; Williams, Robert O

2017-12-29

Recently, results have been published for the first successful phase I human clinical trial investigating the use of dissolving polymeric microneedles… Even so, further clinical development represents an important hurdle that remains in the translation of microneedle technology to approved products. Specifically, the potential for accumulation of polymer within the skin upon repeated application of dissolving and coated microneedles, combined with a lack of safety data in humans, predicates a need for further clinical investigation. Polymers are an important consideration for microneedle technology-from both manufacturing and drug delivery perspectives. The use of polymers enables a tunable delivery strategy, but the scalability of conventional manufacturing techniques could arguably benefit from further optimization. Micromolding has been suggested in the literature as a commercially viable means to mass production of both dissolving and swellable microneedles. However, the reliance on master molds, which are commonly manufactured using resource intensive microelectronics industry-derived processes, imparts notable material and design limitations. Further, the inherently multi-step filling and handling processes associated with micromolding are typically batch processes, which can be challenging to scale up. Similarly, conventional microneedle coating processes often follow step-wise batch processing. Recent developments in microneedle coating and manufacturing techniques are highlighted, including micromilling, atomized spraying, inkjet printing, drawing lithography, droplet-born air blowing, electro-drawing, continuous liquid interface production, 3D printing, and polyelectrolyte multilayer coating. This review provides an analysis of papers reporting on potentially scalable production techniques for the coating and manufacturing of microneedles.

Effects of high temperature treatment on microstructure and mechanical properties of laser-clad NiCrBSi/WC coatings on titanium alloy substrate

International Nuclear Information System (INIS)

Li, Guang Jie; Li, Jun; Luo, Xing

2014-01-01

Laser-clad composite coatings on the Ti6Al4V substrate were heat-treated at 700, 800, and 900 °C for 1 h. The effects of post-heat treatment on the microstructure, microhardness, and fracture toughness of the coatings were investigated by scanning electron microscopy, X-ray diffractometry, energy dispersive spectroscopy, and optical microscopy. The wear resistance of the coatings was evaluated under dry reciprocating sliding friction at room temperature. The coatings mainly comprised some coarse gray blocky (W,Ti)C particles accompanied by the fine white WC particles, a large number of black TiC cellular/dendrites, and the matrix composed of NiTi and Ni 3 Ti; some unknown rich Ni- and Ti-rich particles with sizes ranging from 10 nm to 50 nm were precipitated and uniformly distributed in the Ni 3 Ti phase to form a thin granular layer after heat treatment at 700 °C. The granular layer spread from the edge toward the center of the Ni 3 Ti phase with increasing temperature. A large number of fine equiaxed Cr 23 C 6 particles with 0.2–0.5 μm sizes were observed around the edges of the NiTi supersaturated solid solution when the temperature was further increased to 900 °C. The microhardness and fracture toughness of the coatings were improved with increased temperature due to the dispersion-strengthening effect of the precipitates. Dominant wear mechanisms for all the coatings included abrasive and delamination wear. The post-heat treatment not only reduced wear volume and friction coefficient, but also decreased cracking susceptibility during sliding friction. Comparatively speaking, the heat-treated coating at 900 °C presented the most excellent wear resistance. - Highlights: • TiC + WC reinforced intermetallic compound matrix composite coatings were produced. • The formation mechanism of the reinforcements was analyzed. • Two precipitates were generated at elevated temperature. • Cracking susceptibility and microhardness of the coatings were improved

Effect of cobalt content on wear and corrosion behaviors of electrodeposited Ni-Co/WC nano-composite coatings.

Science.gov (United States)

Amadeh, A; Ebadpour, R

2013-02-01

Metal-ceramic composite coatings are widely used in automotive and aerospace industries as well as micro-electronic systems. Electrodeposition is an economic method for application of these coatings. In this research, nickel-cobalt coatings reinforced by nano WC particles were applied on carbon steel substrate by pulse electrodeposition from modified Watts bath containing different amounts of cobalt sulphate as an additive. Saccharin and sodium dodecyl sulphate (SDS) were also added to electroplating bath as grain refiner and surfactant, respectively. The effect of cobalt content on wear and corrosion behavior of the coatings was investigated. Wear and corrosion properties were assessed by pin-on-disk and potentiodynamic polarization methods, respectively. Phase analysis was performed by X-ray diffraction (XRD) using CuK(alpha) radiation and the worn surfaces were studied by means of Scanning Electron Microscopy (SEM). The results showed that the addition of cobalt improved the wear resistance of the coatings. In the presence of 18 g/L cobalt in electrodeposition bath, the wear rate of the coating decreased to 0.002 mg/m and the coefficient of friction reduced to 0.695 while they were 0.004 mg/m and 0.77 in the absence of cobalt, respectively. This improvement in wear properties can be attributed to the formation of hcp phase in metallic matrix. Meanwhile, the corrosion resistance of the coatings slightly reduced because cobalt is more active metal with respect to nickel.

IMPROVEMENT OF WEAR COMPONENT'S PERFORMANCE BY UTILIZING ADVANCED MATERIALS AND NEW MANUFACTURING TECHNOLOGIES: CASTCON PROCESS FOR MINING APPLICATIONS

International Nuclear Information System (INIS)

Xiaodi Huang; Richard Gertsch

2001-01-01

The fibrous monolith material was successfully consolidated in both the hot press and the hot isostatic press. Initial evaluations indicate the material will have a very high fracture toughness and be very hard. Tungsten carbide was successfully consolidated in an H13 tool steel with the incorporation of a Co-Cr layer between the WC and the steel

On the performances and wear of WC-diamond like carbon coated tools in drilling of CFRP/Titanium stacks

Science.gov (United States)

Boccarusso, L.; Durante, M.; Impero, F.; Minutolo, F. Memola Capece; Scherillo, F.; Squillace, A.

2016-10-01

The use of hybrid structures made of CFRP and titanium alloys is growing more and more in the last years in the aerospace industry due to the high strength to weight ratio. Because of their very different characteristics, the mechanical fastening represent the most effective joining technique for these materials. As a consequence, drilling process plays a key role in the assembly. The one shot drilling, i.e. the contemporary drilling of the stack of the two materials, seems to be the best option both in terms of time saving and assembly accuracy. Nevertheless, due to the considerable different machinability of fiber reinforced plastics and metallic materials, the one shot drilling is a critical process both for the holes quality and for the tools wear. This research was carried out to study the effectiveness of new generation tools in the drilling of CFRP/Titanium stacks. The tools are made of sintered grains of tungsten carbide (WC) in a binder of cobalt and coated with Diamond like carbon (DLC), and are characterized by a patented geometry; they mainly differ in parent WC grain size and binder percentage. Both the cutting forces and the wear phenomena were accurately investigated and the results were analyzed as a function of number of holes and their quality. The results show a clear increase of the cutting forces with the number of holes for all the used drilling tools. Moreover, abrasive wear phenomena that affect initially the tools coating layer were observed.

Bioactive glass coatings for orthopedic metallic implants

Energy Technology Data Exchange (ETDEWEB)

Lopez-Esteban, Sonia; Saiz, Eduardo; Fujino, Sigheru; Oku, Takeo; Suganuma, Katsuaki; Tomsia, Antoni P.

2003-06-30

The objective of this work is to develop bioactive glass coatings for metallic orthopedic implants. A new family of glasses in the SiO2-Na2O-K2O-CaO-MgO-P2O5 system has been synthesized and characterized. The glass properties (thermal expansion, softening and transformation temperatures, density and hardness) are in line with the predictions of established empirical models. The optimized firing conditions to fabricate coatings on Ti-based and Co-Cr alloys have been determined and related to the glass properties and the interfacial reactions. Excellent adhesion to alloys has been achieved through the formation of 100-200 nm thick interfacial layers (Ti5Si3 on Ti-based alloys and CrOx on Co-Cr). Finally, glass coatings, approximately 100 mu m thick, have been fabricated onto commercial Ti alloy-based dental implants.

Wear resistance and fracture mechanics of WC-Co composites

International Nuclear Information System (INIS)

Kaytbay, Saleh; El-Hadek, Medhat

2014-01-01

Manufacturing of WC-Co composites using the electroless precipitation method at different sintering temperatures of 1 100, 1 250, 1 350 and 1 500 C was successfully achieved. The chemical composition of the investigated materials was 90 wt.% WC with 10 wt.% Co, and 80 wt.% WC with 20 wt.% Co. The specific density, densification, and Vickers microhardness measurements were found to increase with increased sintering temperature for both the WC-Co compositions. The composites of tungsten carbide with 10 wt.% Co had a higher specific density and Vickers microhardness measurements than those for the composites of tungsten carbide with 20 wt.% Co. Composites with WC-10 wt.% Co had better wear resistance. The stress-strain and transverse rupture strength increased monotonically with the increase in sintering temperatures, agreeing with the material hardness and wear resistance behavior. Fractographical scanning electron microscopy analysis of the fracture surface demonstrated a rough characteristic conical shape failure in the direction of the maximum shear stress. A proposed mechanism for the formation of the conical fracture surface under compression testing is presented. (orig.)

Assessment of thermal spray coatings for wear and abrasion resistance applications

Science.gov (United States)

Karode, Ishaan Nitin

Thermal spray cermet and metallic coatings are extensively used for wear, abrasion and corrosion control in a variety of industries. The first part of the thesis focuses mainly on testing of sand erosion resistance of thermal spray coatings on carbon composites used in the manufacture of helicopter rotor blades. The test set-up employed is a sand blasting machine and is an effort to duplicate the in-flight conditions especially those encountered in hot arid conditions. The technique adopted follows the Department of Defence test method standard. Carbon Composites have excellent stiffness, strength and low weight/density. The strength to weight ratio is high. Hence, these are used in aerospace applications to a large extent. However, the biggest problem encountered with carbon composites is its low abrasion resistance as its surface is very weak. Hence, thermal spray coatings are used to improve the surface properties of CFRP. Zinc bond coats and WC-Co coatings were tested. However, high amount of thermal stresses were developed between the substrate and the coating due to large differences in the CTE's of the both, leading to high mass losses within two minutes and just 130 grams of sand sprayed on to the coatings with the sand blasting machine built; and hence the coatings with CC as a substrate could not qualify for the application. The second part of the thesis focuses on the assessment of different thermal spray coatings used for manufacture of mechanical seals in pumps and analyze the best coating material for the wear resistance application through detail quantification of material loss by block-on-ring test set-up. A machine based on Block-on-ring test set-up following ASTM G77 (Measurement of Adhesive wear resistance of thermal spray coatings) standards was built to duplicate the pump conditions. Thermally sprayed coated materials were tested in different conditions (Load, time, abrasive). WC-Co had the highest wear resistance (lower volume losses) and

Direct laser metal deposition of WC/Co/Cr powder by means of the functionally graded materials strategy

Science.gov (United States)

Angelastro, A.; Campanelli, S. L.

2017-12-01

One of the many applications of direct laser metal deposition (DLMD) is the realization of multilayer thick coatings having particular mechanical characteristics, such as high hardness. The objective of this work was to obtain a thick, very hard and wear resistant coating, containing a high percentage of tungsten carbide (WC), on an AISI 304 stainless steel substrate. In order to achieve this result, a tungsten carbide-cobalt-chrome (WC/Co/Cr) powder was processed by the DLMD method. WC/Co/Cr is a composite widely used as a wear-resistant material for cutting tools, molds, coatings and other severe applications. Because of its high hardness, poor ductility and low thermal expansion coefficient, depositing this material directly on the stainless steel substrate is very difficult. In order to overcome this problem, the strategy of functionally graded materials (FGM) was used. Colmonoy 227-F nickel alloy was chosen for this purpose in order to generate a mixture with the WC/Co/Cr powder. Four different materials were deposited, layer by layer, by mixing Colmonoy 227-F with an increasing amount of WC/Co/Cr powders, until obtaining a thick surface coating with a maximum amount of WC of 77.4 wt%. For each powder mixture, a mathematical model was applied to calculate optimal values of translation speed and overlap percentages. A metallographic examination was performed in order to detect macro- and micro-structures of the different materials. Finally, Vickers micro-hardness was measured at various locations along the transverse section to appreciate the gradual increase of the FGM hardness, starting from the substrate and culminating at the top surface of the last deposited material.

Investigation on the Tribological Behavior of Arc-Sprayed and Hammer-Peened Coatings Using Tungsten Carbide Cored Wires

Science.gov (United States)

Tillmann, W.; Hagen, L.; Schröder, P.

2017-01-01

Due to their outstanding properties, WC-W2C iron-based cermet coatings are widely used in the field of wear protection. Regarding commonly used WC-W2C reinforced coating systems, it has been reported that their tribological behavior is mainly determined by the carbide grain size fraction. Although the manufacturing route for arc-sprayed WC-W2C cermet coatings is in an advanced state, there is still a lack of knowledge concerning the performance of cored wires with tungsten carbides as filling material and their related coating properties when post-treatment processes are used such as machine hammer peening (MHP). A major objective was to characterize WC-W2C FeCMnSi coatings, deposited with different carbide grain size fractions as a filling using cored wires, with respect to their tribological behavior. Moreover, deposits derived from cored wires with a different amount of hard phases are investigated. According to this, polished MHP surfaces are compared to as-sprayed and polished samples by means of metallographic investigations. With the use of ball-on-disk and dry rubber wheel tests, dry sliding and rolling wear effects on a microscopic level are scrutinized. It has been shown that the MHP process leads to a densification of the microstructure formation. For dry sliding experiments, the MHP coatings obtain lower wear resistances, but lower coefficients of friction than the conventional coatings. In view of abrasion tests, the MHP coatings possess an improved wear resistance. Strain hardening effects at the subsurface area were revealed by the mechanical response using nanoindentation. However, the MHP process has caused a cracking of embedded carbides, which favor breakouts, leading to advanced third-body wear.

Pt-Ni/WC Alloy Nanorods Arrays as ORR Catalyst for PEM Fuel Cells

Energy Technology Data Exchange (ETDEWEB)

Begum, Mahbuba; Yurukcu, Mesut; Yurtsever, Fatma; Ergul, Busra; Kariuki, Nancy; Myers, Deborah J.; Karabacak, Tansel

2017-08-24

Polymer electrolyte membrane fuel cells (PEMFCs) among the other types of fuel cell technology are attractive power sources, especially for electric vehicle applications. While significant progress and plausible prospects of PEMFCs have been achieved, there are still some challenges related to the performance, durability, and cost that need to be overcome to make them economically viable for widespread commercialization. Our strategy is to develop thin films of high-active and stable catalyst coated on vertically aligned nanorod arrays of conductive and stable support. In this work, we fabricated tungsten carbide (WC) nanorods as support and coated them with a platinum-nickel (Pt-Ni) alloy shell denoted as Pt-Ni/WC catalysts. The Pt- Ni/WC nanorods were deposited on glassy carbon disks as well as on silicon substrates for evaluation of their electrocatalytic oxygen reduction reaction (ORR) activity and physical properties. Cyclic voltammetry experiments using rotating disk electrode were performed in perchloric acid (0.1 M HClO4) electrolyte at room temperature to characterize the ORR activity and stability of Pt-Ni/WC nanorods catalysts. Scanning electron microscopy and X-ray diffraction techniques were utilized to study the morphology and crystallographic properties, respectively.

Investigation on the parameter optimization and performance of laser cladding a gradient composite coating by a mixed powder of Co50 and Ni/WC on 20CrMnTi low carbon alloy steel

Science.gov (United States)

Shi, Yan; Li, Yunfeng; Liu, Jia; Yuan, Zhenyu

2018-02-01

In this study, a gradient composite coating was manufactured on 20CrMnTi alloy steel by laser cladding. The laser power, cladding scan velocity and powder flow rate were selected as influencing factors of the orthogonal cladding experiments. The influencing factors were optimized by the comprehensive analysis of Taguchi OA and TOPSIS method. The high significant parameters and the predicted results were confirmed by the ANOVA method. The macromorphology and microstructures are characterized by using laser microscope, SEM, XRD and microhardness tester. Comparison tests of wear resistance of gradient composite coating, 20CrMnTi cemented quenching sample and the 20CrMnTi sample were conducted on the friction-wear tester. The results show that the phases are γ-Co solid solution, Co3B, M23C6 and etc. The interlayers and wear-resisting layer also contain new hard phases as WC, W2C. The microhardness of the gradient coating was increased to 3 times as compared with that of the 20CrMnTi substrate. The wear resistance of the gradient composite coating and 20CrMnTi cemented quenching sample was enhanced to 36.4 and 15.9 times as compared with that of the 20CrMnTi.

Sampling and analysis of inactive radioactive waste tanks W-17, W-18, WC-5, WC-6, WC-8, and WC-11 through WC-14 at ORNL

Energy Technology Data Exchange (ETDEWEB)

Sears, M.B.; Giaquinto, J.M.; Griest, W.H.; Pack, R.T.; Ross, T.; Schenley, R.L.

1995-12-01

The sampling and analysis of nine inactive liquid low-level waste (LLLW) tanks at the Oak Ridge National Laboratory (ORNL) are described-tanks W-17, W-18, WC-5, WC-6, WC-8, and WC-11 through WC-14. Samples of the waste tank liquids and sludges were analyzed to determine (1) the major chemical constituents, (2) the principal radionuclides, (3) metals listed on the US Environmental Protection Agency (EPA) Contract Laboratory Program Inorganic Target Analyte List, (4) organic compounds, and (5) some physical properties. The organic chemical characterization consisted of determinations of the EPA Contract Laboratory Program Target Compound List volatile and semivolatile compounds, pesticides, and polychlorinated biphenyis (PCBs). This report provides data (1) to meet requirements under the Federal Facility Agreement (FFA) for the Oak Ridge Reservation to characterize the contents of LLLW tanks which have been removed from service and (2) to support planning for the treatment and disposal of the wastes.

Sampling and analysis of inactive radioactive waste tanks W-17, W-18, WC-5, WC-6, WC-8, and WC-11 through WC-14 at ORNL

International Nuclear Information System (INIS)

Sears, M.B.; Giaquinto, J.M.; Griest, W.H.; Pack, R.T.; Ross, T.; Schenley, R.L.

1995-12-01

The sampling and analysis of nine inactive liquid low-level waste (LLLW) tanks at the Oak Ridge National Laboratory (ORNL) are described-tanks W-17, W-18, WC-5, WC-6, WC-8, and WC-11 through WC-14. Samples of the waste tank liquids and sludges were analyzed to determine (1) the major chemical constituents, (2) the principal radionuclides, (3) metals listed on the US Environmental Protection Agency (EPA) Contract Laboratory Program Inorganic Target Analyte List, (4) organic compounds, and (5) some physical properties. The organic chemical characterization consisted of determinations of the EPA Contract Laboratory Program Target Compound List volatile and semivolatile compounds, pesticides, and polychlorinated biphenyis (PCBs). This report provides data (1) to meet requirements under the Federal Facility Agreement (FFA) for the Oak Ridge Reservation to characterize the contents of LLLW tanks which have been removed from service and (2) to support planning for the treatment and disposal of the wastes

CoCr double-layered media with NiFe and CoZrNb soft-magnetic layers (invited)

International Nuclear Information System (INIS)

Bernards, J.P.C.; Schrauwen, C.P.G.; Zieren, V.; Luitjens, S.B.

1988-01-01

The magnetic, structural, and recording properties of CoCr double-layered media are investigated. The underlayer materials NiFe (crystalline) and CoZrNb (amorphous) were combined with two different kinds of intermediate layers: Ti (crystalline) and Ge (amorphous). Applying a bias voltage during sputtering of NiFe results in a low coercivity of the NiFe layer and in a high coercivity of the CoCr layer. The structure of the NiFe layer influences the structure of the CoCr layer. A Ti layer between the NiFe and CoCr layers decreases the in-plane remanence of the CoCr layer. The coercivity of all CoZrNb layers is low, independent of the application of a bias voltage. The orientation and structure of CoCr on CoZrNb can be improved by using a Ge intermediate layer, which results in a low coercivity of the CoCr. A Ti intermediate layer increases the coercivity. Ring heads show a dependence of spike noise on the underlayer coercivity and on the applied normal force. A probe-type head shows a dependence of its output on the CoCr coercivity, which may be understood in terms of demagnetization and writing depth

WC-3015 alloy (high-temperature alloy)

International Nuclear Information System (INIS)

Anon.

1974-01-01

WC-3015 Nb alloy containing 28 to 30 Hf, 1 to 2 Zr, 13 to 16 W, 0 to 4 Ta, 0 to 5 Ti, 0.07 to 0.33 C, less than or equal to 0.02 N, less than or equal to 0.03 O, less than or equal to 0.001 H was developed for use at high temperature in oxidizing environments. Its composition can be tailored to meet specific requirements. When WC-3015 is exposed to O at elevated temperature, Hf and Nb oxidized preferentially and HfO 2 dissolves in Nb 2 O 5 to form 6HfO-Nb 2 O 5 . This complex oxide has a tight cubic lattice which resists the diffusion of O into the substrate. During 24-h exposure to air at 2400 0 F, the alloy oxidizes to a depth of approximately 0.035 in. with a surface recession of 0 to 0.004 in. Oxidation resistance of WC-3015 welds and base material can be further enhanced greatly by applying silicide coatings. WC-3015 alloy can be machined by conventional and electrical-discharge methods. It can be hot worked readily by extrusion, forging or rolling. Cold working can be used at room or elevated temperature. It can be welded by the electron-beam or Tig processes. Physical constants, typical mechanical properties at 75 to 2400 0 F, and effects of composition and heat treatment on tensile and stress-rupture properties of the alloy are tabulated

Magnetodielectric effect in CoCr2-XFeXO4

International Nuclear Information System (INIS)

Bao Huixin; Yang Sen; Ren Xiaobing

2011-01-01

Conventional multiferroics show the multiferroic behaviors below two successive transitions (a ferroelectric transition and a ferromagnetic transition). In the present study, we report the magneto-dielectric (MD) effect (both in-plane and out-of-plane) in CoCr 2-X Fe X O 4 which undergoes only a ferromagnetic transition. We found the MD effect in the pure ferromagnetic phase (T S C ) of CoCr 2 O 4 . And such MD effect is temperature dependent. The magnitude of the MD effect gradually decreases with approaching Curie temperature (T C ) and finally becomes zero at T C . With doping Fe into CoCr 2 O 4 , we found the magnitude of MD effect increases and the MD effect exists in a wider temperature region because T C increases and T S decrease with doping Fe. Our results show the coupling between the ferromagnetic and ferroelectric orders. It suggests that both the ferromagnetic and ferroelectric properties originate from the same transition.

Materials for coatings against erosion, fretting, and high-temperature oxidation

International Nuclear Information System (INIS)

Feller, H.G.; Wienstroth, U.; Balke, C.

1990-01-01

This paper investigates the applicability of Co-Cr-W alloys (CoCr29W29, CoCr29W9Y1, CoCr29W9Fe3Y1, CoCr29W9Y1Al1) as coating materials for the substrates MA 6000 and MA 754. Their properties are compared with those of Amperit 410, which is the alloy NiCo23Cr17Al12.5Y0.5. Their isothermal oxidation behaviour at temperatures up to 1000deg C is found to be better for the most part than that of the commercially available Amperit 410. Furthermore, the oxide shows distinctly better adhesion, so that better results concerning resistance to hot-gas corrosion are expected. The fretting behaviour at room temperature is characterized by very low friction factors and a strong resistance to wear. A comparable behaviour is found for resistance to erosive wear. Specimens tested for 500 hours in the pressurised beam device exhibit only minimal changes of mass in the bond MA 600/coating. Single-particle impact tests reveal that exposure of specimens to high temperatures leads to an increase in mean hardness, which is caused by a solidification of the yttrium-containing phase. (orig./MM) [de

Investigations of mussel-inspired polydopamine deposition on WC and Al{sub 2}O{sub 3} particles: The influence of particle size and material

Energy Technology Data Exchange (ETDEWEB)

Mondin, Giovanni, E-mail: giovanni.mondin@chemie.tu-dresden.de [Department of Inorganic Chemistry, Dresden University of Technology, Bergstrasse 66, 01069 Dresden (Germany); Haft, Marcel, E-mail: m.haft@ifw-dresden.de [Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Institute for Solid State Research, Helmholtzstr. 20, 01069 Dresden (Germany); Wisser, Florian M., E-mail: florian.wisser@chemie.tu-dresden.de [Department of Inorganic Chemistry, Dresden University of Technology, Bergstrasse 66, 01069 Dresden (Germany); Leifert, Annika, E-mail: annika.leifert@chemie.tu-dresden.de [Department of Inorganic Chemistry, Dresden University of Technology, Bergstrasse 66, 01069 Dresden (Germany); Mohamed-Noriega, Nasser, E-mail: nasser.mohamed-noriega@chemie.tu-dresden.de [Department of Inorganic Chemistry, Dresden University of Technology, Bergstrasse 66, 01069 Dresden (Germany); Dörfler, Susanne, E-mail: susanne.doerfler@chemie.tu-dresden.de [Department of Inorganic Chemistry, Dresden University of Technology, Bergstrasse 66, 01069 Dresden (Germany); Hampel, Silke, E-mail: s.hampel@ifw-dresden.de [Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Institute for Solid State Research, Helmholtzstr. 20, 01069 Dresden (Germany); Grothe, Julia, E-mail: stefan.kaskel@chemie.tu-dresden.de [Department of Inorganic Chemistry, Dresden University of Technology, Bergstrasse 66, 01069 Dresden (Germany); Kaskel, Stefan, E-mail: julia.grothe@chemie.tu-dresden.de [Department of Inorganic Chemistry, Dresden University of Technology, Bergstrasse 66, 01069 Dresden (Germany)

2014-12-15

Polydopamine, formed by oxidation of dopamine, is a bioinspired polymer developed for multifunctional coatings by Lee et al. in 2007 by drawing inspiration from the adhesive proteins found in mussels. Due to their high versatility and substrate-independence, polydopamine coatings are gaining considerable attention in a plethora of research fields, particularly in the coating of particles, but systematic investigations of the polydopamine coating process are lacking in the literature. In this study, we explore by TEM and thermogravimetric analysis the polydopamine coating process on alumina microparticles, tungsten carbide microparticles and tungsten carbide nanoparticles. By choosing two substrates with similar size but different material (Al{sub 2}O{sub 3} and WC), as well as two substrates of the same material but different size (WC micro- and nanoparticles) we investigate the effects of both substrate material and substrate size, in order to gain some insights into the polydopamine particle coating process. As opposed to what is generally assumed in the literature, we found that the polydopamine coating thicknesses on particles, as well as the thickness growing trend, depend on the particles size and material. In particular, after 24 h of polymerization time the polydopamine coatings reached a thickness of 65 ± 10 nm in the case of Al{sub 2}O{sub 3} microparticles, 18 ± 4 nm in the case of WC microparticles and 33 ± 6 nm in the case of WC nanoparticles. - Highlights: • The coating of different particles with polydopamine was systematically investigated. • Al{sub 2}O{sub 3} microparticles and WC microparticles and nanoparticles were investigated. • The thickness of the polydopamine coating depends on the particle size. • The thickness of the polydopamine coating depends on the particle material.

The Particle Shape of WC Governing the Fracture Mechanism of Particle Reinforced Iron Matrix Composites.

Science.gov (United States)

Li, Zulai; Wang, Pengfei; Shan, Quan; Jiang, Yehua; Wei, He; Tan, Jun

2018-06-11

In this work, tungsten carbide particles (WC p , spherical and irregular particles)-reinforced iron matrix composites were manufactured utilizing a liquid sintering technique. The mechanical properties and the fracture mechanism of WC p /iron matrix composites were investigated theoretically and experimentally. The crack schematic diagram and fracture simulation diagram of WC p /iron matrix composites were summarized, indicating that the micro-crack was initiated both from the interface for spherical and irregular WC p /iron matrix composites. However, irregular WC p had a tendency to form spherical WC p . The micro-cracks then expanded to a wide macro-crack at the interface, leading to a final failure of the composites. In comparison with the spherical WC p , the irregular WC p were prone to break due to the stress concentration resulting in being prone to generating brittle cracking. The study on the fracture mechanisms of WC p /iron matrix composites might provide a theoretical guidance for the design and engineering application of particle reinforced composites.

Potential of direct metal deposition technology for manufacturing thick functionally graded coatings and parts for reactors components

International Nuclear Information System (INIS)

Thivillon, L.; Bertrand, Ph.; Laget, B.; Smurov, I.

2009-01-01

Direct metal deposition (DMD) is an automated 3D deposition process arising from laser cladding technology with co-axial powder injection to refine or refurbish parts. Recently DMD has been extended to manufacture large-size near-net-shape components. When applied for manufacturing new parts (or their refinement), DMD can provide tailored thermal properties, high corrosion resistance, tailored tribology, multifunctional performance and cost savings due to smart material combinations. In repair (refurbishment) operations, DMD can be applied for parts with a wide variety of geometries and sizes. In contrast to the current tool repair techniques such as tungsten inert gas (TIG), metal inert gas (MIG) and plasma welding, laser cladding technology by DMD offers a well-controlled heat-treated zone due to the high energy density of the laser beam. In addition, this technology may be used for preventative maintenance and design changes/up-grading. One of the advantages of DMD is the possibility to build functionally graded coatings (from 1 mm thickness and higher) and 3D multi-material objects (for example, 100 mm-sized monolithic rectangular) in a single-step manufacturing cycle by using up to 4-channel powder feeder. Approved materials are: Fe (including stainless steel), Ni and Co alloys, (Cu,Ni 10%), WC compounds, TiC compounds. The developed coatings/parts are characterized by low porosity (<1%), fine microstructure, and their microhardness is close to the benchmark value of wrought alloys after thermal treatment (Co-based alloy Stellite, Inox 316L, stainless steel 17-4PH). The intended applications concern cooling elements with complex geometry, friction joints under high temperature and load, light-weight mechanical support structures, hermetic joints, tubes with complex geometry, and tailored inside and outside surface properties, etc

Potential of direct metal deposition technology for manufacturing thick functionally graded coatings and parts for reactors components

Science.gov (United States)

Thivillon, L.; Bertrand, Ph.; Laget, B.; Smurov, I.

2009-03-01

Direct metal deposition (DMD) is an automated 3D deposition process arising from laser cladding technology with co-axial powder injection to refine or refurbish parts. Recently DMD has been extended to manufacture large-size near-net-shape components. When applied for manufacturing new parts (or their refinement), DMD can provide tailored thermal properties, high corrosion resistance, tailored tribology, multifunctional performance and cost savings due to smart material combinations. In repair (refurbishment) operations, DMD can be applied for parts with a wide variety of geometries and sizes. In contrast to the current tool repair techniques such as tungsten inert gas (TIG), metal inert gas (MIG) and plasma welding, laser cladding technology by DMD offers a well-controlled heat-treated zone due to the high energy density of the laser beam. In addition, this technology may be used for preventative maintenance and design changes/up-grading. One of the advantages of DMD is the possibility to build functionally graded coatings (from 1 mm thickness and higher) and 3D multi-material objects (for example, 100 mm-sized monolithic rectangular) in a single-step manufacturing cycle by using up to 4-channel powder feeder. Approved materials are: Fe (including stainless steel), Ni and Co alloys, (Cu,Ni 10%), WC compounds, TiC compounds. The developed coatings/parts are characterized by low porosity (<1%), fine microstructure, and their microhardness is close to the benchmark value of wrought alloys after thermal treatment (Co-based alloy Stellite, Inox 316L, stainless steel 17-4PH). The intended applications concern cooling elements with complex geometry, friction joints under high temperature and load, light-weight mechanical support structures, hermetic joints, tubes with complex geometry, and tailored inside and outside surface properties, etc.

Potential of direct metal deposition technology for manufacturing thick functionally graded coatings and parts for reactors components

Energy Technology Data Exchange (ETDEWEB)

Thivillon, L.; Bertrand, Ph.; Laget, B. [Ecole Nationale d' Ingenieurs de Saint-Etienne (ENISE), DIPI Laboratory, 58 rue Jean Parot, 42023 Saint-Etienne cedex 2 (France); Smurov, I. [Ecole Nationale d' Ingenieurs de Saint-Etienne (ENISE), DIPI Laboratory, 58 rue Jean Parot, 42023 Saint-Etienne cedex 2 (France)], E-mail: smurov@enise.fr

2009-03-31

Direct metal deposition (DMD) is an automated 3D deposition process arising from laser cladding technology with co-axial powder injection to refine or refurbish parts. Recently DMD has been extended to manufacture large-size near-net-shape components. When applied for manufacturing new parts (or their refinement), DMD can provide tailored thermal properties, high corrosion resistance, tailored tribology, multifunctional performance and cost savings due to smart material combinations. In repair (refurbishment) operations, DMD can be applied for parts with a wide variety of geometries and sizes. In contrast to the current tool repair techniques such as tungsten inert gas (TIG), metal inert gas (MIG) and plasma welding, laser cladding technology by DMD offers a well-controlled heat-treated zone due to the high energy density of the laser beam. In addition, this technology may be used for preventative maintenance and design changes/up-grading. One of the advantages of DMD is the possibility to build functionally graded coatings (from 1 mm thickness and higher) and 3D multi-material objects (for example, 100 mm-sized monolithic rectangular) in a single-step manufacturing cycle by using up to 4-channel powder feeder. Approved materials are: Fe (including stainless steel), Ni and Co alloys, (Cu,Ni 10%), WC compounds, TiC compounds. The developed coatings/parts are characterized by low porosity (<1%), fine microstructure, and their microhardness is close to the benchmark value of wrought alloys after thermal treatment (Co-based alloy Stellite, Inox 316L, stainless steel 17-4PH). The intended applications concern cooling elements with complex geometry, friction joints under high temperature and load, light-weight mechanical support structures, hermetic joints, tubes with complex geometry, and tailored inside and outside surface properties, etc.

Mechanical characterization of cemented carbide WC-6Co (%wt) manufactured by SPS (Spark Plasma Sintering

International Nuclear Information System (INIS)

Boidi, G.; Tertuliano, A.J.; Machado, I.F.

2016-01-01

This work aimed to manufacture cemented carbide (WC-6%wtCo) obtained by SPS (Spark Plasma Sintering) process and to carry out the mechanical characterization by hardness and fracture toughness. The material was consolidated at 1100 deg C for different holding times (1 min, 5 min, 10 min), in order to evaluate the densification. A reference sample was also used to be compared to SPS. Optical and scanning electron microscopy were carried out to characterize the microstructural features of the samples and mechanical properties were obtained by hardness measurements (micro and macro) and instrumented indentation. The fracture toughness was calculated with the method of Palmqvist. Best results were found in the material sintered by SPS for 10 minutes of holding time, in which 97% of relative density and about 1600 HV_1_0 was reached. (author)

Evaluation of WC-9Co-4Cr laser surface alloyed coatings on stainless steel

CSIR Research Space (South Africa)

Obadele, A

2011-07-01

Full Text Available spectrometer (EDS), while the phase changed were observed using x-ray diffraction (XRD). The surface hardness was determined using the Vickers microhardness tester. The decomposition of WC-9Co-4Cr into W2C, C and W is as a result of low heat of formation of WC...

Effect of manufacturing process sequence on the corrosion resistance characteristics of coated metallic bipolar plates

Science.gov (United States)

Dur, Ender; Cora, Ömer Necati; Koç, Muammer

2014-01-01

Metallic bipolar plate (BPP) with high corrosion and low contact resistance, durability, strength, low cost, volume, and weight requirements is one of the critical parts of the PEMFC. This study is dedicated to understand the effect of the process sequence (manufacturing then coating vs. coating then manufacturing) on the corrosion resistance of coated metallic bipolar plates. To this goal, three different PVD coatings (titanium nitride (TiN), chromium nitride (CrN), zirconium nitride (ZrN)), with three thicknesses, (0.1, 0.5, 1 μm) were applied on BPPs made of 316L stainless steel alloy before and after two types of manufacturing (i.e., stamping or hydroforming). Corrosion test results indicated that ZrN coating exhibited the best corrosion protection while the performance of TiN coating was the lowest among the tested coatings and thicknesses. For most of the cases tested, in which coating was applied before manufacturing, occurrence of corrosion was found to be more profound than the case where coating was applied after manufacturing. Increasing the coating thickness was found to improve the corrosion resistance. It was also revealed that hydroformed BPPs performed slightly better than stamped BPPs in terms of the corrosion behavior.

Comparative investigation of smooth polycrystalline diamond films on dental burs by chemical vapor deposition

Science.gov (United States)

Sein, Htet; Ahmed, Waqar; Rego, Christopher; Jackson, Mark; Polini, Riccardo

2006-04-01

Depositions of hot filament chemical vapor-deposited diamond on cobalt-cemented tungsten carbide (WC-Co) rotary cutting dental burs are presented. Conventional dental tools made of sintered polycrystalline diamond have a number of problems associated with the heterogeneity of the crystallite, decreased cutting efficiency, and short life. A preferential (111) faceted diamond was obtained after 15 h of deposition at a growth rate of 1.1 µm/h. Diamond-coated WC-Co dental burs and conventional sintered burs are mainly used in turning, milling, and drilling operations for machining metal ceramic hard alloys such as CoCr, composite teeth, and aluminum alloy in the dental laboratory. The influence of structure, the mechanical characteristics of both diamond grains and hard alloys on the wear behavior, as well as the regimen of grinding on diamond wear are considered. Erosion wear properties are also investigated under air-sand erosion testing. After machining with excessive cutting performance, calculations can be made on flank and crater wear areas. Diamond-coated WC-Co dental burs offered significantly better erosion and wear resistance compared with uncoated WC-Co tools and sintered burs.

Polarized neutron reflectometry on Co-Cr

NARCIS (Netherlands)

van der Graaf, A.; Frederikze, H.; de Haan, P.; Rekveldt, M.Th.; Lodder, J.C.

1995-01-01

Polarized neutron reflectivity of a Co---Cr film on silicon with the easy axis of magnetization perpendicular to the plane has been measured at in-plane magnetic fields of various magnitudes. The obtained data can be well described assuming a constant atomic density and a gradual increase of the

CVD of alternated microcrystalline (MCD) and nanocrystalline (NCD) diamond films on WC-TIC-CO substrates

International Nuclear Information System (INIS)

Campos, Raonei Alves; Contin, Andre; Trava-Airoldi, Vladimir J.; Corat, Evaldo Jose; Barquete, Danilo Maciel

2010-01-01

CVD Diamond coating of WC-TiC-Co cutting tools has been an alternative to increase tool lifetime. Experiments have shown that residual stresses produced during films growth on WC-TiC-Co substrates significantly increases with increasing film thickness up to 20 μm and usually leads to film delamination. In this work alternated micro- and nanocrystalline CVD diamond films have been used to relax interface stresses and to increase diamond coatings performance. WC-TiC-Co substrates have been submitted to a boronizing thermal diffusion treatment prior to CVD diamond films growth. After reactive heat treatment samples were submitted to chemical etching in acid and alkaline solution. The diamond films deposition was performed using HFCVD reactor with different gas concentrations for microcrystalline (MCD) and nano-crystalline (NCD) films growth. As a result, we present the improvement of diamond films adherence on WC-TiC-Co, evaluated by indentation and machining tests. Samples were characterized by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) for qualitative analysis of diamond films. X-ray Diffraction (XRD) was used for phases identification after boronizing process. Diamond film compressive residual stresses were analyzed by Raman Scattering Spectroscopy (RSS). (author)

Additive manufacturing of Ti-Si-N ceramic coatings on titanium

International Nuclear Information System (INIS)

Zhang, Yanning; Sahasrabudhe, Himanshu; Bandyopadhyay, Amit

2015-01-01

Highlights: • 3D Printing or additive manufacturing of hard Ti-Si-N based ceramics coating on Ti metal substrate. • Understanding of phase transformation as a function of compositional variation. • Evaluation of influence of processing parameters and composition on wear resistance. - Abstract: In this study, Laser Engineered Net Shaping (LENS TM ) was employed towards Additive Manufacturing/3D Printing of Ti-Si-N coatings with three different Ti-Si ratios on commercially pure titanium (cp-Ti) substrate. Microstructural analysis, phase analysis using X-ray diffraction, wear resistance and hardness measurements were done on LENS™ processed 3D printed coatings. Coatings showed graded microstructures and in situ formed phases. Results showed that microstructural variations and phase changes influence coating's hardness and wear resistance directly. High hardness values were obtained from all samples’ top surface where the hardness of coatings can be ranked as 90% Ti-10% Si-N coating (2093.67 ± 144 HV 0.2 ) > 100% Ti-N coating (1846 ± 68.5 HV 0.2 ) > 75% Ti-25% Si-N coating (1375.3 ± 61.4 HV 0.2 ). However, wear resistance was more dependent on inherent Si content, and samples with higher Si content showed better wear resistance

Additive manufacturing of Ti-Si-N ceramic coatings on titanium

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yanning; Sahasrabudhe, Himanshu; Bandyopadhyay, Amit, E-mail: amitband@wsu.edu

2015-08-15

Highlights: • 3D Printing or additive manufacturing of hard Ti-Si-N based ceramics coating on Ti metal substrate. • Understanding of phase transformation as a function of compositional variation. • Evaluation of influence of processing parameters and composition on wear resistance. - Abstract: In this study, Laser Engineered Net Shaping (LENS{sup TM}) was employed towards Additive Manufacturing/3D Printing of Ti-Si-N coatings with three different Ti-Si ratios on commercially pure titanium (cp-Ti) substrate. Microstructural analysis, phase analysis using X-ray diffraction, wear resistance and hardness measurements were done on LENS™ processed 3D printed coatings. Coatings showed graded microstructures and in situ formed phases. Results showed that microstructural variations and phase changes influence coating's hardness and wear resistance directly. High hardness values were obtained from all samples’ top surface where the hardness of coatings can be ranked as 90% Ti-10% Si-N coating (2093.67 ± 144 HV{sub 0.2}) > 100% Ti-N coating (1846 ± 68.5 HV{sub 0.2}) > 75% Ti-25% Si-N coating (1375.3 ± 61.4 HV{sub 0.2}). However, wear resistance was more dependent on inherent Si content, and samples with higher Si content showed better wear resistance.

Cold compaction behavior and pressureless sinterability of ball milled WC and WC/Cu powders

Directory of Open Access Journals (Sweden)

Hashemi Seyed R.

2016-01-01

Full Text Available In this research, cold compaction behavior and pressureless sinterability of WC, WC-10%wtCu and WC-30%wtCu powders were investigated. WC and WC/Cu powders were milled in a planetary ball mill for 20h. The milled powders were cold compacted at 100, 200, 300 and 400 MPa pressures. The compressibility behavior of the powders was evaluated using the Heckel, Panelli-Ambrosio and Ge models. The results showed that the Panelli-Ambrosio was the preferred equation for description the cold compaction behavior of the milled WC and WC-30%wtCu powders. Also, the most accurate model for describing the compressibility of WC-10%wtCu powders was the Heckel equation. The cold compacts were sintered at 1400°C. It was found that by increasing the cold compaction pressure of powder compacts before sintering, the sinterability of WC-30%wtCu powder compacts was enhanced. However, the cold compaction magnitude was not affected significantly on the sinterability of WC and WC-10%wtCu powders. The microstructural investigations of the sintered samples by Scanning Electron Microscopy (SEM confirmed the presence of porosities at the interface of copper-tungsten carbide phases.

Extended solid solubility of a Co-Cr system by mechanical alloying

Energy Technology Data Exchange (ETDEWEB)

Betancourt-Cantera, J.A. [Area Academica de Ciencias de la Tierra y Materiales, UAEH Carr. Pachuca-Tulancingo Km. 4.5, Pachuca, Hidalgo 42184 (Mexico); Sanchez-De Jesus, F., E-mail: fsanchez@uaeh.edu.mx [Area Academica de Ciencias de la Tierra y Materiales, UAEH Carr. Pachuca-Tulancingo Km. 4.5, Pachuca, Hidalgo 42184 (Mexico); Torres-Villasenor, G. [Instituto de Investigaciones en Materiales-UNAM, Apdo. Postal 70-360, 04510 Mexico, DF (Mexico); Bolarin-Miro, A.M. [Area Academica de Ciencias de la Tierra y Materiales, UAEH Carr. Pachuca-Tulancingo Km. 4.5, Pachuca, Hidalgo 42184 (Mexico); Cortes-Escobedo, C.A. [Centro de Investigacion e Innovacion Tecnologica del IPN Cda. CECATI S/N, Col. Sta. Catarina, Azcapotzalco, 02250 Mexico, DF (Mexico)

2012-07-15

Highlights: Black-Right-Pointing-Pointer Solubility of the Co-Cr system is modified by means of Mechanical Alloying (MA). Black-Right-Pointing-Pointer MA induces the formation of new solid solutions of Co-Cr system in non-equilibrium. Black-Right-Pointing-Pointer MA promote the formation of metastable Co-Cr phases with greater solubility. - Abstract: Mechanical alloying, MA, has been successfully used to extend the limits of solid solubility in many commercially important metallic systems. The aim of this work is to demonstrate that MA modifies the solid solubility of the Co-Cr system. Co and Cr elemental powders were used as precursors and mixed in an adequate weight ratio to obtain Co{sub 100-x}Cr{sub x} (0 {<=} x {<=} 100, {Delta}x = 10) to study the effect of mechanical processing in the solubility of the Co-Cr system. Processing was carried out at room temperature in a shaker mixer mill using vials and balls of hardened steel as milling media with a ball:powder weight ratio of 10:1. Crystalline structure characterization of the milled powders was conducted using X-ray diffraction, and phase transformations as a function of composition were analyzed. Thermal analysis confirmed structural changes occurred in the mechanically alloyed powders. The evolution of the phase transformations with composition is reported for each composition. The results showed that after high energy ball milling for 7 h, the solid solubility between Co and Cr could be evidently extended, despite the low solid solubility at the equilibrium conditions of this system. Additionally, the micrographs of the milled powders showed that increasing composition of chromium changes the shape and size of the particles while simultaneously reducing their agglomeration; this effect is possibly attributed to the brittleness of elemental chrome.

Fracture toughness of a nanoscale WC-Co tool steel

International Nuclear Information System (INIS)

Densley, J.M.; Hirth, J.P.

1997-01-01

Tungsten carbide tool steels, comprising WC particles with 6.7--25wt% Co distributed in the interparticle regions as a quasi-continuous binder phase, can be considered as WC-Co composites. The fracture toughness of such WC-Co composites is dependent on the volume fraction, contiguity and thickness of the cobalt binder, and the size of the tungsten carbide grains. Research has shown that the ductile binder undergoes nearly all the plastic deformation during fracture, which provides the primary energy consuming process that enhances fracture resistance. Recent manufacturing developments have given rise to the production of a WC-6.7wt% Co cermet having an average WC grain size of 70 nm, with a corresponding binder mean thickness, h, of 9 nm calculated from d = h(1-V f )/V f where d = 70 nm and V f = 0.114. This composite has shown a higher wear resistance than that of conventional cermets in proportion to their hardness. Such improvement has been attributed to the difficulty in forming dislocations in the very small grains. There are also indications that the Co binder in the nanoscale cermet contains higher contents of dissolved W and C than for conventional scale cermets. Because plastic deformation is initially confined to the binder phase, it was of interest to perform mode 1 and mixed mode toughness tests on the nanoscale cermet to determine whether flow localization influenced mixed mode toughness as in bulk materials. Two generations of this cermet were provided by Rogers Tool Works. The first generation, A, had lower binder contiguity, with occasional agglomerations of WC grains. The second generation, B, was cleaner, with the cobalt binder more uniformly separating the WC grains

Marginal Accuracy and Internal Fit of 3-D Printing Laser-Sintered Co-Cr Alloy Copings.

Science.gov (United States)

Kim, Myung-Joo; Choi, Yun-Jung; Kim, Seong-Kyun; Heo, Seong-Joo; Koak, Jai-Young

2017-01-23

Laser sintered technology has been introduced for clinical use and can be utilized more widely, accompanied by the digitalization of dentistry and the development of direct oral scanning devices. This study was performed with the aim of comparing the marginal accuracy and internal fit of Co-Cr alloy copings fabricated by casting, CAD/CAM (Computer-aided design/Computer-assisted manufacture) milled, and 3-D laser sintered techniques. A total of 36 Co-Cr alloy crown-copings were fabricated from an implant abutment. The marginal and internal fit were evaluated by measuring the weight of the silicone material, the vertical marginal discrepancy using a microscope, and the internal gap in the sectioned specimens. The data were statistically analyzed by One-way ANOVA (analysis of variance), a Scheffe's test, and Pearson's correlation at the significance level of p = 0.05, using statistics software. The silicone weight was significantly low in the casting group. The 3-D laser sintered group showed the highest vertical discrepancy, and marginal-, occlusal-, and average- internal gaps ( p marginal discrepancy and the internal gap variables ( r = 0.654), except for the silicone weight. In this study, the 3-D laser sintered group achieved clinically acceptable marginal accuracy and internal fit.

Additively Manufactured Titanium and Cobalt-Chromium Implant Frameworks: Fit and Effect of Ceramic Veneering.

Science.gov (United States)

Svanborg, Per; Eliasson, Alf; Stenport, Victoria

The purpose of this study was to evaluate the fit of additively manufactured cobalt-chromium and titanium and CNC-milled titanium frameworks before and after ceramic veneering. Ten stone casts simulating an edentulous maxilla provided with six abutment analogs were produced. For each stone cast, one additively manufactured cobalt-chromium framework (AM CoCr) and one titanium framework (AM Ti) were fabricated. The fit was analyzed with a coordinate measuring machine in three dimensions (x, y, and z axes) using best-fit virtual matching of center point coordinates, before and after ceramic veneering. CNC-milled titanium frameworks (CNC Ti) and earlier results from CNC-milled cobalt-chromium frameworks (CNC CoCr) were used for comparison. All frameworks presented minor misfit before and after veneering in the horizontal plane (x- and y-axes) between 2.9 and 13.5 μm and in the vertical plane (z-axis) between 1.6 and 5.4 μm. Ceramic veneering affected the fit of all groups of frameworks. Both AM Ti and AM CoCr presented significantly smaller distortion in the vertical plane compared with the CNC-milled frameworks. Implant-supported frameworks can be produced in either Ti or CoCr using either CNC milling or additive manufacturing with a fit well within the range of 20 μm in the horizontal plane and 10 μm in the vertical plane. The fit of frameworks of both materials and production techniques are affected by the ceramic veneering procedure to a small extent.

Observation of WC grain shapes determined by carbon content during liquid phase sintering of WC-Co alloys

International Nuclear Information System (INIS)

Sona Kim; Hyoun-Ee Kim; Seok-Hee Han; Jong-Ku Park

2001-01-01

In the composite materials of WC-Co alloys, the faceted WC grains as a hard phase are dispersed in the ductile matrix of cobalt. Properties of WC-Co alloys are affected by microstructural factors such as volume fraction of WC phase, size of WC grains, and carbon content (kinds of constituent phases). Although the properties of WC-Co alloys are inevitably affected by the shape of WC grains, the shape of WC grains has not been thrown light on the properties of WC-Co alloys yet, because it has been regarded to have a uniform shape regardless of alloy compositions. It is proved that the WC grains have various shapes varying reversibly with carbon content in the sintered WC-Co compacts. This dependency of grain shape on the carbon content is attributed to asymmetric atomic structure of WC crystal. The {10 1 - 0} prismatic planes are distinguished into two groups with different surface energy according to their atomic structures. The prismatic planes of high surface energy tend to disappear in the compacts with high carbon content. In addition, these high energy prismatic planes tend to split into low energy surfaces in the large WC grains. (author)

Manufacturing issues which affect coating erosion performance in wind turbine blades

Science.gov (United States)

Cortés, E.; Sánchez, F.; Domenech, L.; Olivares, A.; Young, T. M.; O'Carroll, A.; Chinesta, F.

2017-10-01

Erosion damage, caused by repeated rain droplet impact on the leading edges of wind turbine blades, is a major cause for cost concern. Resin Infusion (RI) is used in wind energy blades where low weight and high mechanical performance materials are demanded. The surface coating plays a crucial role in the manufacturing and performance response. The Leading Edge coating is usually moulded, painted or sprayed onto the blade surface so adequate adhesion in the layers' characterization through the thickness is required for mechanical performance and durability reasons. In the current work, an investigation has been directed into the resulting rain erosion durability of the coating was undertaken through a combination of mass loss testing measurements with manufacturing processing parameter variations. The adhesion and erosion is affected by the shock wave caused by the collapsing water droplet on impact. The stress waves are transmitted to the substrate, so microestructural discontinuities in coating layers and interfaces play a key role on its degradation. Standard industrial systems are based on a multilayer system, with a high number of interfaces that tend to accelerate erosion by delamination. Analytical and numerical models are commonly used to relate lifetime prediction and to identify suitable coating and composite substrate combinations and their potential stress reduction on the interface. In this research, the input parameters for the appropriate definition of the Cohesive Zone Modelling (CZM) of the coating-substrate interface are outlined by means of Pull off testing and Peeling testing results. It allowed one to optimize manufacturing and coating process for blades into a knowledge-based guidance for leading edge coating material development. It was achieved by investigating the erosion degradation process using both numerical and laboratory techniques (Pull off, Peeling and Rain Erosion Testing in a whirling arm rain erosion test facility).

Mechanical characterization of cemented carbide WC-6Co (%wt) manufactured by SPS (Spark Plasma Sintering; Caracterizacao mecanica de metal duro WC-6Co (%massa) sinterizado via SPS (Spark Plasma Sintering)

Energy Technology Data Exchange (ETDEWEB)

Boidi, G.; Tertuliano, A.J.; Machado, I.F., E-mail: guido.boidi@usp.br [Universidade de Sao Paulo (USP), SP (Brazil). Departamento de Engenharia Mecatronica e Sistemas Mecanicos; Rodrigues, D. [BRATS- Filtros Sinterizados e Pos Metalicos, Cajamar, SP (Brazil)

2016-07-01

This work aimed to manufacture cemented carbide (WC-6%wtCo) obtained by SPS (Spark Plasma Sintering) process and to carry out the mechanical characterization by hardness and fracture toughness. The material was consolidated at 1100 deg C for different holding times (1 min, 5 min, 10 min), in order to evaluate the densification. A reference sample was also used to be compared to SPS. Optical and scanning electron microscopy were carried out to characterize the microstructural features of the samples and mechanical properties were obtained by hardness measurements (micro and macro) and instrumented indentation. The fracture toughness was calculated with the method of Palmqvist. Best results were found in the material sintered by SPS for 10 minutes of holding time, in which 97% of relative density and about 1600 HV{sub 10} was reached. (author)

Infiltration Behavior Of Mechanical Alloyed 75 wt% Cu-25 wt% WC Powders Into Porous WC Compacts

Directory of Open Access Journals (Sweden)

Şelte A.

2015-06-01

Full Text Available In this work infiltration behavior of mechanical alloyed 75 wt% Cu – 25 wt% WC powders into porous WC compacts were studied. Owing to their ductile nature, initial Cu powders were directly added to mechanical alloying batch. On the other hand initial WC powders were high energy milled prior to mechanical alloying. Contact infiltration method was selected for densification and compacts prepared from processed powders were infiltrated into porous WC bodies. After infiltration, samples were characterized via X-Ray diffraction studies and microstructural evaluation of the samples was carried out via scanning electron microscopy observations. Based on the lack of solubility between WC and Cu it was possible to keep fine WC particles in Cu melt since solution reprecipitation controlled densification is hindered. Also microstructural characterizations via scanning electron microscopy confirmed that the transport of fine WC fraction from infiltrant to porous WC skeleton can be carried out via Cu melt flow during infiltration.

Marginal Accuracy and Internal Fit of 3-D Printing Laser-Sintered Co-Cr Alloy Copings

Directory of Open Access Journals (Sweden)

Myung-Joo Kim

2017-01-01

Full Text Available Laser sintered technology has been introduced for clinical use and can be utilized more widely, accompanied by the digitalization of dentistry and the development of direct oral scanning devices. This study was performed with the aim of comparing the marginal accuracy and internal fit of Co-Cr alloy copings fabricated by casting, CAD/CAM (Computer-aided design/Computer-assisted manufacture milled, and 3-D laser sintered techniques. A total of 36 Co-Cr alloy crown-copings were fabricated from an implant abutment. The marginal and internal fit were evaluated by measuring the weight of the silicone material, the vertical marginal discrepancy using a microscope, and the internal gap in the sectioned specimens. The data were statistically analyzed by One-way ANOVA (analysis of variance, a Scheffe’s test, and Pearson’s correlation at the significance level of p = 0.05, using statistics software. The silicone weight was significantly low in the casting group. The 3-D laser sintered group showed the highest vertical discrepancy, and marginal-, occlusal-, and average- internal gaps (p < 0.05. The CAD/CAM milled group revealed a significantly high axial internal gap. There are moderate correlations between the vertical marginal discrepancy and the internal gap variables (r = 0.654, except for the silicone weight. In this study, the 3-D laser sintered group achieved clinically acceptable marginal accuracy and internal fit.

40 CFR Table 2 of Subpart Aaaaaaa... - Emission Limits for Asphalt Roofing Manufacturing (Coating) Operations

Science.gov (United States)

2010-07-01

... 40 Protection of Environment 14 2010-07-01 2010-07-01 false Emission Limits for Asphalt Roofing Manufacturing (Coating) Operations 2 Table 2 of Subpart AAAAAAA of Part 63 Protection of Environment... AAAAAAA of Part 63—Emission Limits for Asphalt Roofing Manufacturing (Coating) Operations For * * * 1...

CoCr wear particles generated from CoCr alloy metal-on-metal hip replacements, and cobalt ions stimulate apoptosis and expression of general toxicology-related genes in monocyte-like U937 cells

Energy Technology Data Exchange (ETDEWEB)

Posada, Olga M., E-mail: O.M.PosadaEstefan@leeds.ac.uk [Biomedical Engineering Department, University of Strathclyde, Wolfson Centre, Glasgow G4 0NW (United Kingdom); Gilmour, Denise [Pure and Applied Chemistry Department, University of Strathclyde, Thomas Graham Building, Glasgow G1 1XL (United Kingdom); Tate, Rothwelle J., E-mail: r.j.tate@strath.ac.uk [Strathclyde Institute for Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE (United Kingdom); Grant, M. Helen [Biomedical Engineering Department, University of Strathclyde, Wolfson Centre, Glasgow G4 0NW (United Kingdom)

2014-11-15

Cobalt-chromium (CoCr) particles in the nanometre size range and their concomitant release of Co and Cr ions into the patients' circulation are produced by wear at the articulating surfaces of metal-on-metal (MoM) implants. This process is associated with inflammation, bone loss and implant loosening and led to the withdrawal from the market of the DePuy ASR™ MoM hip replacements in 2010. Ions released from CoCr particles derived from a resurfacing implant in vitro and their subsequent cellular up-take were measured by ICP-MS. Moreover, the ability of such metal debris and Co ions to induce both apoptosis was evaluated with both FACS and immunoblotting. qRT-PCR was used to assess the effects on the expression of lymphotoxin alpha (LTA), BCL2-associated athanogene (BAG1), nitric oxide synthase 2 inducible (NOS2), FBJ murine osteosarcoma viral oncogene homolog (FOS), growth arrest and DNA-damage-inducible alpha (GADD45A). ICP-MS showed that the wear debris released significant (p < 0.05) amounts of Co and Cr ions into the culture medium, and significant (p < 0.05) cellular uptake of both ions. There was also an increase (p < 0.05) in apoptosis after a 48 h exposure to wear debris. Analysis of qRT-PCR results found significant up-regulation (p < 0.05) particularly of NOS2 and BAG1 in Co pre-treated cells which were subsequently exposed to Co ions + debris. Metal debris was more effective as an inducer of apoptosis and gene expression when cells had been pre-treated with Co ions. This suggests that if a patient receives sequential bilateral CoCr implants, the second implant may be more likely to produce adverse effects than the first one. - Highlights: • Effects of CoCr nanoparticles and Co ions on U937 cells were investigated. • Ions released from wear debris play an important role in cellular response, • Toxicity of Co ions could be related to NO metabolic processes and apoptosis. • CoCr particles were a more effective inducer of apoptosis after cell

Ultra-short-period WC/SiC multilayer coatings for x-ray applications

DEFF Research Database (Denmark)

Fernandez-Perea, M.; Pivovaroff, M. J.; Soufli, R.

2013-01-01

developed multilayers with ultra-shortperiods between 1 and 2 nm based on the material system WC/SiC. This material system was selected because it possesses very sharp and stable interfaces. In this article, we show highlights from a series of experiments performed in order to characterize the stress...

Sustainable design and manufacturing of multifunctional polymer nanocomposite coatings: A multiscale systems approach

Science.gov (United States)

Xiao, Jie

Polymer nanocomposites have a great potential to be a dominant coating material in a wide range of applications in the automotive, aerospace, ship-making, construction, and pharmaceutical industries. However, how to realize design sustainability of this type of nanostructured materials and how to ensure the true optimality of the product quality and process performance in coating manufacturing remain as a mountaintop area. The major challenges arise from the intrinsic multiscale nature of the material-process-product system and the need to manipulate the high levels of complexity and uncertainty in design and manufacturing processes. This research centers on the development of a comprehensive multiscale computational methodology and a computer-aided tool set that can facilitate multifunctional nanocoating design and application from novel function envisioning and idea refinement, to knowledge discovery and design solution derivation, and further to performance testing in industrial applications and life cycle analysis. The principal idea is to achieve exceptional system performance through concurrent characterization and optimization of materials, product and associated manufacturing processes covering a wide range of length and time scales. Multiscale modeling and simulation techniques ranging from microscopic molecular modeling to classical continuum modeling are seamlessly coupled. The tight integration of different methods and theories at individual scales allows the prediction of macroscopic coating performance from the fundamental molecular behavior. Goal-oriented design is also pursued by integrating additional methods for bio-inspired dynamic optimization and computational task management that can be implemented in a hierarchical computing architecture. Furthermore, multiscale systems methodologies are developed to achieve the best possible material application towards sustainable manufacturing. Automotive coating manufacturing, that involves paint spay and

Performance of Ti-multilayer coated tool during machining of MDN431 alloyed steel

Science.gov (United States)

Badiger, Pradeep V.; Desai, Vijay; Ramesh, M. R.

2018-04-01

Turbine forgings and other components are required to be high resistance to corrosion and oxidation because which they are highly alloyed with Ni and Cr. Midhani manufactures one of such material MDN431. It's a hard-to-machine steel with high hardness and strength. PVD coated insert provide an answer to problem with its state of art technique on the WC tool. Machinability studies is carried out on MDN431 steel using uncoated and Ti-multilayer coated WC tool insert using Taguchi optimisation technique. During the present investigation, speed (398-625rpm), feed (0.093-0.175mm/rev), and depth of cut (0.2-0.4mm) varied according to Taguchi L9 orthogonal array, subsequently cutting forces and surface roughness (Ra) were measured. Optimizations of the obtained results are done using Taguchi technique for cutting forces and surface roughness. Using Taguchi technique linear fit model regression analysis carried out for the combination of each input variable. Experimented results are compared and found the developed model is adequate which supported by proof trials. Speed, feed and depth of cut are linearly dependent on the cutting force and surface roughness for uncoated insert whereas Speed and depth of cut feed is inversely dependent in coated insert for both cutting force and surface roughness. Machined surface for coated and uncoated inserts during machining of MDN431 is studied using optical profilometer.

The influence of Co-Cr and UHMWPE particles on infection persistence : An in vivo study in mice

NARCIS (Netherlands)

Hosman, Anton H.; Bulstra, Sjoerd K.; Sjollema, Jelmer; van der Mei, Henny C.; Busscher, Henk J.; Neut, Danielle

Wear of metal-on-metal (cobaltchromium, CoCr particles) and metal-on-polyethylene (ultra-high-molecular-weight polyethylene, UHMWPE particles) bearing surfaces in hip prostheses is a major problem in orthopedics. This study aimed to compare the influence of CoCr and UHMWPE particles on the

The Tribological Performance of Hardfaced/ Thermal Sprayed Coatings for Increasing the Wear Resistance of Ventilation Mill Working Parts

Directory of Open Access Journals (Sweden)

A. Vencl

2015-09-01

Full Text Available During the coal pulverizing, the working parts of the ventilation mill are being worn by the sand particles. For this reason, the working parts are usually protected with materials resistant to wear (hardfaced/thermal sprayed coatings. The aim of this study was to evaluate the tribological performance of four different types of coatings as candidates for wear protection of the mill’s working parts. The coatings were produced by using the filler materials with the following nominal chemical composition: NiFeBSi-WC, NiCrBSiC, FeCrCTiSi, and FeCrNiCSiBMn, and by using the plasma arc welding and flame and electric arc spraying processes. The results showed that Ni-based coatings exhibited higher wear resistance than Fe-based coatings. The highest wear resistance showed coating produced by using the NiFeBSi-WC filler material and plasma transferred arc welding deposition process. The hardness was not the only characteristic that affected the wear resistance. In this context, the wear rate of NiFeBSi-WC coating was not in correlation with its hardness, in contrast to other coatings. The different wear performance of NiFeBSi-WC coating was attributed to the different type and morphological features of the reinforcing particles (WC.

Miscellaneous Coating Manufacturing: National Emission Standards for Hazardous Air Pollutants (NESHAP)

Science.gov (United States)

The national emission standards for hazardous air pollutants for miscellaneous coating manufacturing. Includes summary, rule history, compliance and implementation information, federal registry citations.

Metallurgical and interfacial characterization of PFM Co-Cr dental alloys fabricated via casting, milling or selective laser melting.

Science.gov (United States)

Al Jabbari, Y S; Koutsoukis, T; Barmpagadaki, X; Zinelis, S

2014-04-01

Bulk and interfacial characterization of porcelain fused to metal (PFM) Co-Cr dental alloys fabricated via conventional casting, milling and selective laser melting. Three groups of metallic specimens made of PFM Co-Cr dental alloys were prepared using casting (CST), milling (MIL) and selective laser sintering (SLM). The porosity of the groups was evaluated using X-ray scans. The microstructures of the specimens were evaluated via SEM examination, EDX and XRD analysis. Vickers hardness testing was utilized to measure the hardness of the specimens. Interfacial characterization was conducted on the porcelain-covered specimens from each group to test the elemental distribution with and without the application of INmetalbond. The elemental distribution of the probed elements was assessed using EDX line profile analysis. Hardness results were statistically analyzed using one-way ANOVA and Holm-Sidak's method (α=0.05). X-ray radiography revealed the presence of porosity only in the CST group. Different microstructures were identified among the groups. Together with the γ phase matrix, a second phase, believed to be the Co3Mo phase, was also observed by SEM and subsequent XRD analysis. Cr7C3 and Cr23C6 carbides were also identified via XRD analysis in the CST and MIL groups. The hardness values were 320±12 HV, 297±5 HV and 371±10 HV, and statistically significant differences were evident among the groups. The microstructure and hardness of PFM Co-Cr dental alloys are dependent on the manufacturing technique employed. Given the differences in microstructural and hardness properties among the tested groups, further differences in their clinical behavior are anticipated. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Combating Wear of ASTM A36 Steel by Surface Modification Using Thermally Sprayed Cermet Coatings

Directory of Open Access Journals (Sweden)

Vineet Shibe

2016-01-01

Full Text Available Thermal spray coatings can be applied economically on machine parts to enhance their requisite surface properties like wear, corrosion, erosion resistance, and so forth. Detonation gun (D-Gun thermal spray coatings can be applied on the surface of carbon steels to improve their wear resistance. In the present study, alloy powder cermet coatings WC-12% Co and Cr3C2-25% NiCr have been deposited on ASTM A36 steel with D-Gun thermal spray technique. Sliding wear behavior of uncoated ASTM A36 steel and D-Gun sprayed WC-12% Co and Cr3C2-25% NiCr coatings on base material is observed on a Pin-On-Disc Wear Tester. Sliding wear performance of WC-12% Co coating is found to be better than the Cr3C2-25% NiCr coating. Wear performance of both these cermet coatings is found to be better than uncoated ASTM A36 steel. Thermally sprayed WC-12% Co and Cr3C2-25% NiCr cermet coatings using D-Gun thermal spray technique is found to be very useful in improving the sliding wear resistance of ASTM A36 steel.

[The measurement of thermal expansion coefficient of Co-Cr alloy fabricated by selective laser melting].

Science.gov (United States)

Tian, Xiao-mei; Zeng, Li; Wei, Bin; Huang, Yi-feng

2015-12-01

To investigate the thermal expansion coefficient of different processing parameters upon the Co-Cr alloy prepared by selective laser melting (SLM) technique, in order to provide technical support for clinical application of SLM technology. The heating curve of self-made Co-Cr alloy was protracted from room temperature to 980°C centigrade with DIL402PC thermal analysis instrument, keeping temperature rise rate and cooling rate at 5 K/min, and then the thermal expansion coefficient of 9 groups of Co-Cr alloy was measured from 20°C centigrade to 500°C centigrade and 600°C centigrade. The 9 groups thermal expansion coefficient values of Co-Cr alloy heated from 20°C centigrade to 500°C centigrade were 13.9×10(-6)/K,13.6×10(-6)/K,13.9×10(-6)/K,13.7×10(-6)/K,13.5×10(-6)/K,13.8×10(-6)/K,13.7×10(-6)/K,13.7×10(-6)/K,and 13.9×10(-6)/K, respectively; when heated from 20°C centigrade to 600°C centigrade, they were 14.2×10(-6)/K,13.9×10(-6)/K,13.8×10(-6)/K,14.0×10(-6)/K,14.1×10(-6)/K,14.1×10(-6)/K,13.9×10(-6)/K,14.2×10(-6)/K, and 13.7×10(-6)/K, respectively. The results showed that the Co-Cr alloy has good matching with the VITA VMK 95 porcelain powder and can meet the requirement of clinic use.

On the preparation of fine V8C7-WC and V4C3-WC powders

CSIR Research Space (South Africa)

Osborne, C

1997-01-01

Full Text Available The aim of this work was to produce V8C7-WC and V4C3-WC powders with grain size between 1 and 2mu-m, as a first stage of the preparation of fine grained WC-VC-Co hardmetal. V8C7-WC powder was produced via two routes: starting from preformed V8C7...

Catalytic activity of tungsten carbide-carbon (WC@C) core-shell structured for ethanol electro-oxidation

Energy Technology Data Exchange (ETDEWEB)

Singla, Gourav, E-mail: gsinghla@gmail.com; Singh, K., E-mail: kusingh@thapar.edu; Pandey, O.P., E-mail: oppandey@thapar.edu

2017-01-15

In this study, carbon coated WC (WC@C) was synthesized through solvothermal reactions in the presence of reducing agent magnesium (Mg) by employing tungsten oxide (WO{sub 3}) as a precursor, acetone (C{sub 3}H{sub 6}O) as a carbon source. The formation of WC@C nano particles is confirmed by X-ray diffraction and Transmission electron microscopy. The thermal stability of the synthesized powder examined in air shows its stability up to 550 °C. In this method, in-situ produced outer carbon layer increase the surface area of materials which is 52.6 m{sup 2} g{sup −1} with pore volume 0.213 cm{sup 3} g{sup −1}. The Electrocatalytic activity of ethanol oxidation on a synthesized sample with and without Pt nano particles have been investigated using cyclic voltammetry (CV). The CV results show the enhancement in oxidation stability of WC@C in acidic media as well as better CO-tolerance for ethanol oxidation after the deposition of Pt nanoparticles as compared to without Pt nano particles. - Highlights: • Tungsten carbide nano powder was synthesized using acetone as carbon source. • In-situ produced outer carbon layer increase the surface area of materials. • Mesoporous WC with surface areas 52.6 m{sup 2}/g obtained. • Pt modified WC powder showed higher electrochemical stability. • Better CO-tolerance for ethanol oxidation after the deposition of Pt nanoparticles.

Exploring the potential role of tungsten carbide cobalt (WC-Co) nanoparticle internalization in observed toxicity toward lung epithelial cells in vitro.

Science.gov (United States)

Armstead, Andrea L; Arena, Christopher B; Li, Bingyun

2014-07-01

Tungsten carbide cobalt (WC-Co) has been recognized as a workplace inhalation hazard in the manufacturing, mining and drilling industries by the National Institute of Occupational Safety and Health. Exposure to WC-Co is known to cause "hard metal lung disease" but the relationship between exposure, toxicity and development of disease remain poorly understood. To better understand this relationship, the present study examined the role of WC-Co particle size and internalization on toxicity using lung epithelial cells. We demonstrated that nano- and micro-WC-Co particles exerted toxicity in a dose- and time-dependent manner and that nano-WC-Co particles caused significantly greater toxicity at lower concentrations and shorter exposure times compared to micro-WC-Co particles. WC-Co particles in the nano-size range (not micron-sized) were internalized by lung epithelial cells, which suggested that internalization may play a key role in the enhanced toxicity of nano-WC-Co particles over micro-WC-Co particles. Further exploration of the internalization process indicated that there may be multiple mechanisms involved in WC-Co internalization such as actin and microtubule based cytoskeletal rearrangements. These findings support our hypothesis that WC-Co particle internalization contributes to cellular toxicity and suggest that therapeutic treatments inhibiting particle internalization may serve as prophylactic approaches for those at risk of WC-Co particle exposure. Copyright © 2014 Elsevier Inc. All rights reserved.

Nanotoxicity: emerging concerns regarding nanomaterial safety and occupational hard metal (WC-Co) nanoparticle exposure.

Science.gov (United States)

Armstead, Andrea L; Li, Bingyun

As the number of commercial and consumer products containing engineered nanomaterials (ENMs) continually rises, the increased use and production of these ENMs presents an important toxicological concern. Although ENMs offer a number of advantages over traditional materials, their extremely small size and associated characteristics may also greatly enhance their toxic potentials. ENM exposure can occur in various consumer and industrial settings through inhalation, ingestion, or dermal routes. Although the importance of accurate ENM characterization, effective dosage metrics, and selection of appropriate cell or animal-based models are universally agreed upon as important factors in ENM research, at present, there is no "standardized" approach used to assess ENM toxicity in the research community. Of particular interest is occupational exposure to tungsten carbide cobalt (WC-Co) "dusts," composed of nano- and micro-sized particles, in hard metal manufacturing facilities and mining and drilling industries. Inhalation of WC-Co dust is known to cause "hard metal lung disease" and an increased risk of lung cancer; however, the mechanisms underlying WC-Co toxicity, the inflammatory disease state and progression to cancer are poorly understood. Herein, a discussion of ENM toxicity is followed by a review of the known literature regarding the effects of WC-Co particle exposure. The risk of WC-Co exposure in occupational settings and the updates of in vitro and in vivo studies of both micro- and nano-WC-Co particles are discussed.

Polycrystalline Diamond Coating of Additively Manufactured Titanium for Biomedical Applications.

Science.gov (United States)

Rifai, Aaqil; Tran, Nhiem; Lau, Desmond W; Elbourne, Aaron; Zhan, Hualin; Stacey, Alastair D; Mayes, Edwin L H; Sarker, Avik; Ivanova, Elena P; Crawford, Russell J; Tran, Phong A; Gibson, Brant C; Greentree, Andrew D; Pirogova, Elena; Fox, Kate

2018-03-14

Additive manufacturing using selective laser melted titanium (SLM-Ti) is used to create bespoke items across many diverse fields such as medicine, defense, and aerospace. Despite great progress in orthopedic implant applications, such as for "just in time" implants, significant challenges remain with regards to material osseointegration and the susceptibility to bacterial colonization on the implant. Here, we show that polycrystalline diamond coatings on these titanium samples can enhance biological scaffold interaction improving medical implant applicability. The highly conformable coating exhibited excellent bonding to the substrate. Relative to uncoated SLM-Ti, the diamond coated samples showed enhanced mammalian cell growth, enriched apatite deposition, and reduced microbial S. aureus activity. These results open new opportunities for novel coatings on SLM-Ti devices in general and especially show promise for improved biomedical implants.

SiC interlayer by laser-cladding on WC-Co substrates for CVD diamond deposition

Energy Technology Data Exchange (ETDEWEB)

Contin, Andre; Fraga, Mariana Amorim; Vieira, Jose; Trava-Airoldi, Vladimir Jesus; Corat, Evaldo Jose, E-mail: andrecontin@yahoo.com.br [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil); Campos, Raonei Alves [Universidade Federal do Sul e Sudeste do Para (UNIFESSPA), Belem, PA (Brazil); Vasconcelos, Getulio [Instituto de Estudos Avancados (IEA), Sao Jose dos Campos, SP (Brazil)

2016-07-01

Full text: Despite their huge industrial potential and commercial interest, the direct diamond coating on cemented carbide (WC-Co) is limited, mainly because of the catalytic effect of Cobalt (Co) and the high difference in thermal expansion coefficient [1]. This results in poor adherence between diamond and WC-Co. In addition, the low diamond film adhesion to the cemented carbide useless for machining applications. Removal of Co binder from the substrate surface by superficial etching is one of the techniques used to improve the adhesion between diamond and WC-Co. For the present study, diamond films were deposited on WC-Co substrates with an intermediate barrier to block the Co diffusion to the surface substrate. The laser cladding process produced the SiC barrier, in which a powder layer is melted by a laser irradiation to create the coating on the substrate. The use of laser cladding is the novel method for an intermediate barrier for cemented carbides. The advantages of laser cladding include a faster processing speed, precision, versatility. We reported the application of pretreatment method called ESND (Electrostatic self-assembly seeding of nanocrystalline diamond). The nucleation density was around 10{sup 11}part/cm{sup 2}. Diamond films were grown by Hot Filament Chemical Vapor Deposition. Characterization of samples included Field Emission Gun-Scanning Electron Microscopy (FEG-SEM), Energy Dispersive X-ray (EDX), X-ray diffraction (XRD) and Raman Scattering Spectroscopy. Results showed that laser irradiation formed stable Co compounds in the interfacial barrier. It is because nucleation and good quality of diamond film since the cobalt are no longer free to migrate to the surface during the CVD diamond deposition. Reference: [1] Y. X. Cui, B. Shen, F. H. Sun. Diamond deposition on WC–Co substrate with amorphous SiC interlayer, Surface Engineering, 30, (2014) 237-243. (author)

Novel diamond-coated tools for dental drilling applications.

Science.gov (United States)

Jackson, M J; Sein, H; Ahmed, W; Woodwards, R

2007-01-01

The application of diamond coatings on cemented tungsten carbide (WC-Co) tools has been the subject of much attention in recent years in order to improve cutting performance and tool life in orthodontic applications. WC-Co tools containing 6% Co metal and 94% WC substrate with an average grain size of 1 - 3 microm were used in this study. In order to improve the adhesion between diamond and WC substrates it is necessary to etch cobalt from the surface and prepare it for subsequent diamond growth. Alternatively, a titanium nitride (TiN) interlayer can be used prior to diamond deposition. Hot filament chemical vapour deposition (HFCVD) with a modified vertical filament arrangement has been employed for the deposition of diamond films to TiN and etched WC substrates. Diamond film quality and purity has been characterized using scanning electron microscopy (SEM) and micro Raman spectroscopy. The performances of diamond-coated WC-Co tools, uncoated WC-Co tools, and diamond embedded (sintered) tools have been compared by drilling a series of holes into various materials such as human tooth, borosilicate glass, and acrylic tooth materials. Flank wear has been used to assess the wear rates of the tools when machining biomedical materials such as those described above. It is shown that using an interlayer such as TiN prior to diamond deposition provides the best surface preparation for producing dental tools.

[Research progress in CoCr metal-ceramic alloy fabricated by selective laser melting].

Science.gov (United States)

Yan, X; Lin, H

2018-02-09

Cobalt-chromium alloys have been applied to dental porcelain fused to metal (PFM) restorations over the past decades owing to their excellent corrosion resistance, good biocompatibility and low price. The production of CoCr metal-ceramic restorations has always been based on traditional lost-wax casting techniques. However, in recent years, selective laser melting (SLM) is becoming more and more highly valued by dental laboratories and dental practitioners due to its individuation, precision and efficiency. This paper mainly reviews the recent researches on the production process of copings, microstructure, mechanical property, metal-ceramic bond strength, fit of copings, corrosion resistance and biocompatibility of SLM CoCr metal-ceramic alloy.

Manufacturing and coating of optical components for the EnMAP hyperspectral imager

Science.gov (United States)

Schürmann, M.; Gäbler, D.; Schlegel, R.; Schwinde, S.; Peschel, T.; Damm, C.; Jende, R.; Kinast, J.; Müller, S.; Beier, M.; Risse, S.; Sang, B.; Glier, M.; Bittner, H.; Erhard, M.

2016-07-01

The optical system of the hyperspectral imager of the Environmental Mapping and Analysis Program (EnMAP) consists of a three-mirror anastigmat (TMA) and two independent spectrometers working in the VNIR and SWIR spectral range, respectively. The VNIR spectrometer includes a spherical NiP coated Al6061 mirror that has been ultra-precisely diamond turned and finally coated with protected silver as well as four curved fused silica (FS) and flint glass (SF6) prisms, respectively, each with broadband antireflection (AR) coating, while the backs of the two outer prisms are coated with a high-reflective coating. For AR coating, plasma ion assisted deposition (PIAD) has been used; the high-reflective enhanced Ag-coating on the backside has been deposited by magnetron sputtering. The SWIR spectrometer contains four plane and spherical gold-coated mirrors, respectively, and two curved FS prisms with a broadband antireflection coating. Details about the ultra-precise manufacturing of metal mirrors and prisms as well as their coating are presented in this work.

Exploring the potential role of tungsten carbide cobalt (WC-Co) nanoparticle internalization in observed toxicity toward lung epithelial cells in vitro

Energy Technology Data Exchange (ETDEWEB)

Armstead, Andrea L. [Biomaterials, Bioengineering and Nanotechnology Laboratory, Department of Orthopaedics, School of Medicine, West Virginia University, Morgantown, WV 26506 (United States); Pharmaceutical and Pharmacological Sciences Graduate Program, School of Pharmacy, West Virginia University, Morgantown, WV 26506 (United States); Arena, Christopher B. [Biomaterials, Bioengineering and Nanotechnology Laboratory, Department of Orthopaedics, School of Medicine, West Virginia University, Morgantown, WV 26506 (United States); E.J. Van Liere Research Program, School of Medicine, West Virginia University, Morgantown, WV 26506 (United States); Li, Bingyun, E-mail: bili@hsc.wvu.edu [Biomaterials, Bioengineering and Nanotechnology Laboratory, Department of Orthopaedics, School of Medicine, West Virginia University, Morgantown, WV 26506 (United States); Pharmaceutical and Pharmacological Sciences Graduate Program, School of Pharmacy, West Virginia University, Morgantown, WV 26506 (United States); E.J. Van Liere Research Program, School of Medicine, West Virginia University, Morgantown, WV 26506 (United States); Mary Babb Randolph Cancer Center, Morgantown, WV 26506 (United States)

2014-07-01

Tungsten carbide cobalt (WC-Co) has been recognized as a workplace inhalation hazard in the manufacturing, mining and drilling industries by the National Institute of Occupational Safety and Health. Exposure to WC-Co is known to cause “hard metal lung disease” but the relationship between exposure, toxicity and development of disease remain poorly understood. To better understand this relationship, the present study examined the role of WC-Co particle size and internalization on toxicity using lung epithelial cells. We demonstrated that nano- and micro-WC-Co particles exerted toxicity in a dose- and time-dependent manner and that nano-WC-Co particles caused significantly greater toxicity at lower concentrations and shorter exposure times compared to micro-WC-Co particles. WC-Co particles in the nano-size range (not micron-sized) were internalized by lung epithelial cells, which suggested that internalization may play a key role in the enhanced toxicity of nano-WC-Co particles over micro-WC-Co particles. Further exploration of the internalization process indicated that there may be multiple mechanisms involved in WC-Co internalization such as actin and microtubule based cytoskeletal rearrangements. These findings support our hypothesis that WC-Co particle internalization contributes to cellular toxicity and suggest that therapeutic treatments inhibiting particle internalization may serve as prophylactic approaches for those at risk of WC-Co particle exposure. - Highlights: • Hard metal (WC-Co) particle toxicity was established in lung epithelial cells. • Nano-WC-Co particles caused greater toxicity than micro-WC-Co particles. • Nano- and micro-WC-Co particles were capable of inducing cellular apoptosis. • Nano-WC-Co particles were internalized by lung epithelial cells. • WC-Co particle internalization was mediated by actin dynamics.

Exploring the potential role of tungsten carbide cobalt (WC-Co) nanoparticle internalization in observed toxicity toward lung epithelial cells in vitro

International Nuclear Information System (INIS)

Armstead, Andrea L.; Arena, Christopher B.; Li, Bingyun

2014-01-01

Tungsten carbide cobalt (WC-Co) has been recognized as a workplace inhalation hazard in the manufacturing, mining and drilling industries by the National Institute of Occupational Safety and Health. Exposure to WC-Co is known to cause “hard metal lung disease” but the relationship between exposure, toxicity and development of disease remain poorly understood. To better understand this relationship, the present study examined the role of WC-Co particle size and internalization on toxicity using lung epithelial cells. We demonstrated that nano- and micro-WC-Co particles exerted toxicity in a dose- and time-dependent manner and that nano-WC-Co particles caused significantly greater toxicity at lower concentrations and shorter exposure times compared to micro-WC-Co particles. WC-Co particles in the nano-size range (not micron-sized) were internalized by lung epithelial cells, which suggested that internalization may play a key role in the enhanced toxicity of nano-WC-Co particles over micro-WC-Co particles. Further exploration of the internalization process indicated that there may be multiple mechanisms involved in WC-Co internalization such as actin and microtubule based cytoskeletal rearrangements. These findings support our hypothesis that WC-Co particle internalization contributes to cellular toxicity and suggest that therapeutic treatments inhibiting particle internalization may serve as prophylactic approaches for those at risk of WC-Co particle exposure. - Highlights: • Hard metal (WC-Co) particle toxicity was established in lung epithelial cells. • Nano-WC-Co particles caused greater toxicity than micro-WC-Co particles. • Nano- and micro-WC-Co particles were capable of inducing cellular apoptosis. • Nano-WC-Co particles were internalized by lung epithelial cells. • WC-Co particle internalization was mediated by actin dynamics

Completion report for the isolation and remediation of inactive liquid low-level radioactive waste tanks WC-5, WC-6, WC-8, WC-19, 3002-A, 7560, and 7562 at Oak Ridge National Laboratory Oak Ridge, Tennessee

International Nuclear Information System (INIS)

1997-12-01

The Federal Facility Agreement (FFA) between the U.S. Environmental Protection Agency (EPA), Tennessee Department of Environment and Conservation (TDEC), and U.S. Department of Energy (DOE) requires that all liquid low-level waste tanks at Oak Ridge National Laboratory removed from service, designated in the FFA as Category D, be remediated in accordance with Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) requirements. A human health risk screening assessment was conducted for inactive Tanks WC-5, WC-6, WC-8, WC-19, 3002-A, 7560, and 7562 as part of an evaluation to determine the method of remediation necessary to safely and permanently isolate and remediate the tanks. Risk screening assessment results indicated that the health risks associated with these tanks were within or below the EPA range of concern of 1 x 10 -4 to 1 x 10 -6 . On the basis of these results and with regulators concurrence, it was determined that either no action or in-place stabilization of the tanks would satisfy risk-based remediation goals. Therefore, decisions were made and approved by DOE to remediate these tanks in-place as maintenance actions rather than actions under the CERCLA process. Letters documenting these decisions were approved by DOE and subsequently submitted to TDEC and EPA, who concurred with the maintenance actions. Tanks WC-5, WC-6, WC-8, WC-19, 3002-A, 7560, and 7562 were isolated from associated piping, electrical systems, and instrumentation and were grouted in-place. Tank 7562 was originally isolated from associated piping and instrumentation and left in-place empty for future remedial consideration. Upon further consideration, the decision was made by DOE, with concurrence by the regulators, to complete the maintenance action of Tank 7562 by grouting it in-place in March 1997

Mechanical Properties and Wear Behavior of AA5182/WC Nanocomposite Fabricated by Friction Stir Welding at Different Tool Traverse Speeds

Science.gov (United States)

Paidar, Moslem; Asgari, Ali; Ojo, Olatunji Oladimeji; Saberi, Abbas

2018-03-01

Grain growth inhibition at the heat-affected zone, improved weld strength and superior tribological properties of welds are desirable attributes of modern manufacturing. With the focused on these attributes, tungsten carbide (WC) nanoparticles were employed as reinforcements for the friction stir welding of 5-mm-thick AA5182 aluminum alloy by varying tool traverse speeds. The microstructure, microhardness, ultimate tensile strength, fracture and wear behavior of the resultant WC-reinforced welds were investigated, while unreinforced AA5182 welds were employed as controls for the study. The result shows that the addition of WC nanoparticles causes substantial grain refinement within the weld nugget. A decrease in traverse speed caused additional particle fragmentation, improved hardness value and enhanced weld strength in the reinforced welds. Improved wear rate and friction coefficient of welds were attained at a reduced traverse speed of 100 mm/min in the WC-reinforced welds. This improvement is attributed to the effects of reduced grain size/grain fragmentation and homogeneous dispersion of WC nanoparticles within the WC-reinforced weld nugget.

Development of coatings for ultrasonic additive manufacturing sonotrode using laser direct metal deposition process

Energy Technology Data Exchange (ETDEWEB)

Niyanth S, Niyanth [ORNL; Dehoff, Ryan R [ORNL; Jordan, Brian H [ORNL; Babu, Sudarsanam Suresh [ORNL

2016-10-01

ORNL partnered with Fabrisonic, LLC to develop galling resistant hard facing coatings on sonotrodes used to fabricate 3D printed materials using ultrasonic additive manufacturing. The development and deployment of a coated sonotrode is expected to push the existing state of the art to facilitate the solidstate additive manufacturing of hard steels and titanium alloys. To this effect a structurally amorphous stainless steel material and cobalt chrome material were deposited on the sonotrode material. Both the deposits showed good adhesion to the substrate. The coatings made using the structurally amorphous steel materials showed cracking during the initial trials and cracking was eliminated by deposition on a preheated substrate. Both the coatings show hardness in excess of 600 HVN. Thus the phase 1 of this project has been used to identify suitable materials to use to coat the sonotrode. Despite the fact that successful deposits were obtained, the coatings need to be evaluated by performing detailed galling tests at various temperatures. In addition field tests are also necessary to test the stability of these coatings in a high cycle ultrasonic vibration mode. If awarded, phase 2 of the project would be used to optimize the composition of the deposit material to maximize galling resistance. The industrial partner would then use the coated sonotrode to fabricate builds made of austenitic stainless steel to test the viability of using a coated sonotrode.

Selective Laser Melting Technique of Co-Cr Dental Alloys: A Review of Structure and Properties and Comparative Analysis with Other Available Techniques.

Science.gov (United States)

Koutsoukis, Theodoros; Zinelis, Spiros; Eliades, George; Al-Wazzan, Khalid; Rifaiy, Mohammed Al; Al Jabbari, Youssef S

2015-06-01

The aim of this study was to review the effect of selective laser melting (SLM) procedure on the properties of dental structures made of Co-Cr alloys and to evaluate its quality and compare it to those produced by conventional casting and milling fabrication techniques. A computerized database search using PubMed and Scopus was conducted for peer-reviewed scientific research studies regarding the use of SLM in Co-Cr dental alloys with no restrictions for publication years. The search engines provided hundreds of results, and only 48 scientific research papers, case studies, or literature reviews were considered relevant for this review. The innovative manufacturing concept of SLM offers many advantages compared with casting and milling fabrication techniques. SLM provides different microstructure from casting and milling with minimal internal porosity and internal fitting, marginal adaptation, and comparable bond strength to porcelain. Mechanical and electrochemical properties of SLM structures are enhanced compared to cast, while clinical longevity of single-metal ceramic crowns is comparable to Au-Pt dental alloy. The SLM technique provides dental prosthetic restorations more quickly and less expensively without compromising their quality compared with restorations prepared by casting and milling techniques. The current SLM devices provide metallic restorations made of Co-Cr alloys for removable and fixed partial dentures without compromising the alloy or restoration properties at a fraction of the time and cost, showing great potential to replace the aforementioned fabrication techniques in the long term; however, further clinical studies are essential to increase the acceptance of this technology by the worldwide dental community. © 2015 by the American College of Prosthodontists.

Stress in tungsten carbide-diamond like carbon multilayer coatings

NARCIS (Netherlands)

Pujada, B.R.; Tichelaar, F.D.; Janssen, G.C.A.M.

2007-01-01

Tungsten carbide-diamond like carbon (WC-DLC) multilayer coatings have been prepared by sputter deposition from a tungsten-carbide target and periodic switching on and off of the reactive acetylene gas flow. The stress in the resulting WC-DLC multilayers has been studied by substrate curvature.

Hard chrome-coated and fullerene-doped metal surfaces in orthopedic bearings

OpenAIRE

Sonntag, Robert; Feige, Katja; Santos, Claudia Beatriz dos; Kretzer, Jan Philippe

2017-01-01

Metal-on-metal bearings for total hip replacements have been introduced as an alternative to polyethylene in young and more active patients. These have, however, been shown to be prone to implant malpositioning and have been limited by some specific design features. In that context, coatings present an option to increase wear resistance by keeping the high fracture strength of the metal substrate. A custom-made electroplating setup was designed for the coating of CoCr substrates using (a) an ...

Contribution to the quantum study of neutral tungsten carbide WC and ionized (WC"q"+, q=1 and 2)

International Nuclear Information System (INIS)

Sabor, Said

2015-01-01

Metal carbides and oxides are more interesting in catalytic and industrial domains. Tungsten carbide WC has been detected as serious substituent of platinum Pt catalytic. The ultimate goal of this thesis is theoretical studies of electronic structure, stability and the bound nature on WC, WO and its cations. Our preliminary research were motivated by the available spectroscopic data on W, W"+, W"2"+, WC and WC"2"+. We used the methodology (CASSCF/MRCI/MRCI+Q/aug-cc-pV5Z(-PP)) implemented on MOLPRO package to perform quantum calculations with high accuracy taking into account the correlation and relativistic effects with a specific treatment of spin orbit coupling for some low lying excited electronic states of WC"n"+, (n=0, 1 et 2). Our results are shown in good agreement with those available in the literature. Furthermore, in this work for the first time we demonstrated that a carbide dication (WC"2"+) is thermodynamically stable. (author) [fr

Comparison of the bond strength of ceramics to Co-Cr alloys made by casting and selective laser melting.

Science.gov (United States)

Lawaf, Shirin; Nasermostofi, Shahbaz; Afradeh, Mahtasadat; Azizi, Arash

2017-02-01

Considering the importance of metal-ceramic bond, the present study aimed to compare the bond strength of ceramics to cobalt-chrome (Co-Cr) alloys made by casting and selective laser melting (SLM). In this in-vitro experimental study, two sample groups were prepared, with one group comprising of 10 Co-Cr metal frameworks fabricated by SLM method and the other of 10 Co-Cr metal frameworks fabricated by lost wax cast method with the dimensions of 0.5 × 3 × 25 mm (following ISO standard 9693). Porcelain with the thickness of 1.1 mm was applied on a 3 × 8-mm central rectangular area of each sample. Afterwards, bond strengths of the samples were assessed with a Universal Testing Machine. Statistical analysis was performed with Kolmogorov-Smirnov test and T-test. Bond strength in the conventionally cast group equaled 74.94 ± 16.06 MPa, while in SLM group, it equaled 69.02 ± 5.77 MPa. The difference was not statistically significant ( P ≤ .05). The results indicated that the bond strengths between ceramic and Co-Cr alloys made by casting and SLM methods were not statistically different.

Study on single step solid state synthesis of WC@C nanocomposite and electrochemical stability of synthesized WC@C & Pt/WC@C for alcohol oxidation (methanol/ethanol)

Energy Technology Data Exchange (ETDEWEB)

Singla, Gourav, E-mail: gsinghla@gmail.com; Singh, K., E-mail: kusingh@thapar.edu; Pandey, O.P., E-mail: oppandey@thapar.edu

2016-04-25

WC@C nano composite was prepared by a single step solid–state reaction through in situ reduction and carburization of WO{sub 3} in the presence of Mg and activated charcoal. The XRD results and thermodynamics analysis showed that the optimization of reaction temperature facilitates the reduction as well as carburization of tungsten oxide(s) at different reaction temperature. Thermogravimetric analysis of the product was done to assess the thermal stability in air. The Raman spectroscopy was used to find out the nature (amorphous/graphitic) of carbon in the obtained phase. The N{sub 2} adsorption–desorption measurement showed a narrow pore size distribution from 3 to 4 nm with BET surface area of up to 522.5 m{sup 2}/g. TEM/HRTEM images confirmed formation of the WC nano particles with spherical morphology. Electrochemical stability of pure and platinized carbide sample (Pt/WC) has been investigated using cyclic voltammetry in acidic media for alcohol (methanol and ethanol) oxidation. - Highlights: • Tungsten carbide nano powder was synthesized using charcoal as carbon source. • Formation of WC occurs through the formation of lower tungsten oxide. • CO{sub 2}/CO ratio effect the formation of WC. • Mesoporous tungsten carbide with surface areas 522.5 m{sup 2}/g obtained by using charcoal. • Pt modified WC powder showed higher electrochemical stability.

Review of Thermal Spray Coating Applications in the Steel Industry: Part 2—Zinc Pot Hardware in the Continuous Galvanizing Line

Science.gov (United States)

Matthews, S.; James, B.

2010-12-01

This two-part article series reviews the application of thermal spray coating technology in the production of steel and steel sheet products. Part 2 of this article series is dedicated to coating solutions in the continuous galvanizing line. The corrosion mechanisms of Fe- and Co-based bulk materials are briefly reviewed as a basis for the development of thermal spray coating solutions. WC-Co thermal spray coatings are commonly applied to low Al-content galvanizing hardware due to their superior corrosion resistance compared to Fe and Co alloys. The effect of phase degradation, carbon content, and WC grain size are discussed. At high Al concentrations, the properties of WC-Co coatings degrade significantly, leading to the application of oxide-based coatings and corrosion-resistant boride containing coatings. The latest results of testing are summarized, highlighting the critical coating parameters.

Mechanical Performance of Cold-Sprayed A357 Aluminum Alloy Coatings for Repair and Additive Manufacturing

Science.gov (United States)

Petráčková, K.; Kondás, J.; Guagliano, M.

2017-12-01

Cold-sprayed coatings made of A357 aluminum alloy, a casting alloy widely used in aerospace, underwent set of standard tests as well as newly developed fatigue test to gain an information about potential of cold spray for repair and additive manufacturing of loaded parts. With optimal spray parameters, coating deposition on substrate with smooth surface resulted in relatively good bonding, which can be further improved by application of grit blasting on substrate's surface. However, no enhancement of adhesion was obtained for shot-peened surface. Process temperature, which was set either to 450 or 550 °C, was shown to have an effect on adhesion and cohesion strength, but it does not influence residual stress in the coating. To assess cold spray perspectives for additive manufacturing, flat tensile specimens were machined from coating and tested in as-sprayed and heat-treated (solution treatment and aging) condition. Tensile properties of the coating after the treatment correspond to properties of the cast A357-T61 aluminum alloy. Finally, fatigue specimen was proposed to test overall performance of the coating and coating's fatigue limit is compared to the results obtained on cast A357-T61 aluminum alloy.

Photoelastic analysis of mandibular full-arch implant-supported fixed dentures made with different bar materials and manufacturing techniques.

Science.gov (United States)

Zaparolli, Danilo; Peixoto, Raniel Fernandes; Pupim, Denise; Macedo, Ana Paula; Toniollo, Marcelo Bighetti; Mattos, Maria da Glória Chiarello de

2017-12-01

To compare the stress distribution of mandibular full dentures supported with implants according to the bar materials and manufacturing techniques using a qualitative photoelastic analysis. An acrylic master model simulating the mandibular arch was fabricated with four Morse taper implant analogs of 4.5×6mm. Four different bars were manufactured according to different material and techniques: fiber-reinforced resin (G1, Trinia, CAD/CAM), commercially pure titanium (G2, cpTi, CAD/CAM), cobalt‑chromium (G3, Co-Cr, CAD/CAM) and cobalt‑chromium (G4, Co-Cr, conventional cast). Standard clinical and laboratory procedures were used by an experienced dental technician to fabricate 4 mandibular implant-supported dentures. The photoelastic model was created based on the acrylic master model. A load simulation (150N) was performed in total occlusion against the antagonist. Dentures with fiber-reinforced resin bar (G1) exhibited better stress distribution. Dentures with machined Co-Cr bar (G3) exhibited the worst standard of stress distribution, with an overload on the distal part of the posteriors implants, followed by dentures with cast Co-Cr bar (G4) and machined cpTi bar (G2). The fiber-reinforced resin bar exhibited an adequate stress distribution and can serve as a viable alternative for oral rehabilitation with mandibular full dentures supported with implants. Moreover, the use of the G1 group offered advantages including reduced weight and less possible overload to the implants components, leading to the preservation of the support structure. Copyright © 2017 Elsevier B.V. All rights reserved.

Ternary ceramic thermal spraying powder and method of manufacturing thermal sprayed coating using said powder

Energy Technology Data Exchange (ETDEWEB)

Vogli, Evelina; Sherman, Andrew J.; Glasgow, Curtis P.

2018-02-06

The invention describes a method for producing ternary and binary ceramic powders and their thermal spraying capable of manufacturing thermal sprayed coatings with superior properties. Powder contain at least 30% by weight ternary ceramic, at least 20% by weight binary molybdenum borides, at least one of the binary borides of Cr, Fe, Ni, W and Co and a maximum of 10% by weight of nano and submicro-sized boron nitride. The primary crystal phase of the manufactured thermal sprayed coatings from these powders is a ternary ceramic, while the secondary phases are binary ceramics. The coatings have extremely high resistance against corrosion of molten metal, extremely thermal shock resistance and superior tribological properties at low and at high temperatures.

Isothermal and dynamic oxidation behaviour of Mo-W doped carbon-based coating

Science.gov (United States)

Mandal, Paranjayee; Ehiasarian, Arutiun P.; Hovsepian, Papken Eh.

2015-10-01

The oxidation behaviour of Mo-W doped carbon-based coating (Mo-W-C) is investigated in elevated temperature (400-1000 °C). Strong metallurgical bond between Mo-W-C coating and substrate prevents any sort of delamination during heat-treatment. Isothermal oxidation tests show initial growth of metal oxides at 500 °C, however graphitic nature of the as-deposited coating is preserved. The oxidation progresses with further rise in temperature and the substrate is eventually exposed at 700 °C. The performance of Mo-W-C coating is compared with a state-of-the-art DLC(Cr/Cr-WC/W:C-H/a:C-H) coating, which shows preliminary oxidation at 400 °C and local delamination of the coating at 500 °C leading to substrate exposure. The graphitisation starts at 400 °C and the diamond-like structure is completely converted into the graphite-like structure at 500 °C. Dynamic oxidation behaviour of both the coatings is investigated using Thermo-gravimetric analysis carried out with a slow heating rate of 1 °C/min from ambient temperature to 1000 °C. Mo-W-C coating resists oxidation up to ˜800 °C whereas delamination of DLC(Cr/Cr-WC/W:C-H/a:C-H) coating is observed beyond ˜380 °C. In summary, Mo-W-C coating provides improved oxidation resistance at elevated temperature compared to DLC(Cr/Cr-WC/W:C-H/a:C-H) coating.

Interactions between tungsten carbide (WC) particulates and metal matrix in WC-reinforced composites

International Nuclear Information System (INIS)

Lou, D.; Hellman, J.; Luhulima, D.; Liimatainen, J.; Lindroos, V.K.

2003-01-01

A variety of experimental techniques have been used to investigate the interactions between tungsten carbide (WC-Co 88/12) particulates and the matrix in some new wear resistant cobalt-based superalloy and steel matrix composites produced by hot isostatic pressing. The results show that the chemical composition of the matrix has a strong influence on the interface reaction between WC and matrix and the structural stability of the WC particulates in the composite. Some characteristics of the interaction between matrix and reinforcement are explained by the calculation of diffusion kinetics. The three-body abrasion wear resistance of the composites has been examined based on the ASTM G65-91 standard procedure. The wear behavior of the best composites of this study shows great potential for wear protection applications

Development of nanostructured PVD coatings for total knee replacement joints using HIPIMS

Science.gov (United States)

Sugumaran, Arunprabhu A.

The aim of this study was to develop thin film coatings for total knee replacement joints using high power impulse magnetron sputtering (HIPIMS). An industrial size four cathode magnetron sputtering system equipped with direct current (DC) and HIPIMS power supplies was used for this purpose. Initially, Plasma diagnostics were carried out using optical emission spectroscopy (OES) while sputtering Ti target in Ar + N2 atmosphere by utilizing various HIP IMS/conventional DCMS (henceforth UBM) source combinations by varying the process parameters such as coil current and N2 flow. Then, single layer titanium nitride (TiN) coating was deposited by varying the degree of HIPIMS utilisation and the process parameters such as bias voltage and coil current to thoroughly understand the effect of degree of HIPIMS utilisation on the microstructure, residual stress, texture, mechanical, tribological and corrosion properties of such coatings. The degree of HIPIMS utilisation was altered by increasing the number of HIPIMS targets used for the deposition. Four different source combinations were used for this purpose, as follows: 4 cathodes in conventional DCMS mode to deposit pure UBM coating, 1 HIPIMS + 3UBM and 2HIPIMS + 2UBM cathodes to deposit combined HIPIMS/UBM coatings and 2HIPIMS cathodes to deposit pure HIPIMS coatings. TiN/NbN, TiCN/NbCN and CrN/NbN multilayer coatings were deposited on CoCr alloy test buttons along with other (HSS, SS and Si) substrates since our intended application is on total knee replacement joints made of CoCr alloy. The knowledge gained by investigating the TiN (Ar + N[2]) plasma and the properties of TiN was used to determine the process parameters for depositing the multilayer coatings. X- ray diffraction (XRD) technique was used for calculating the texture, residual stress and bilayer thickness of the coatings. Nanoindentation method was used to determine the nano hardness of the coatings. The adhesion strength of the coatings was estimated by

Diamond-like carbon coatings enhance scratch resistance of bearing surfaces for use in joint arthroplasty: hard substrates outperform soft.

Science.gov (United States)

Roy, Marcel E; Whiteside, Leo A; Katerberg, Brian J

2009-05-01

The purpose of this study was to test the hypotheses that diamond-like carbon (DLC) coatings will enhance the scratch resistance of a bearing surface in joint arthroplasty, and that a hard ceramic substrate will further enhance scratch resistance by reducing plastic deformation. We tested these hypotheses by applying a hard DLC coating to medical-grade cobalt chromium alloy (CoCr) and magnesia-stabilized zirconia (Mg-PSZ) femoral heads and performing scratch tests to determine the loads required to cause cohesive and adhesive fracture of the coating. Scratch tracks of DLC-coated and noncoated heads were then scanned by optical profilometry to determine scratch depth, width, and pile-up (raised edges), as measures of susceptibility to scratching. DLC-coated CoCr specimens exhibited cohesive coating fracture as wedge spallation at an average load of 9.74 N, whereas DLC-coated Mg-PSZ exhibited cohesive fracture as arc-tensile cracks and chipping at a significantly higher average load of 41.3 N (p coating fracture, DLC-CoCr delaminated at an average load of 35.2 N, whereas DLC-Mg-PSZ fractured by recovery spallation at a significantly higher average load of 46.8 N (p DLC-CoCr and DLC-Mg-PSZ specimens exhibited significantly shallower scratches and less pile-up than did uncoated specimens (p DLC-Mg-PSZ better resisted plastic deformation, requiring significantly higher loads for cohesive and adhesive coating fracture. These findings supported both of our hypotheses. (c) 2008 Wiley Periodicals, Inc.

Magnetic phase diagram of Co(Cr1-xA lx) 2O4 (x = 0.0-1.0)

Science.gov (United States)

Padam, R.; Sarkar, T.; Mathieu, R.; Thota, S.; Pal, D.

2017-08-01

We report the role of Al substitution in the magnetic properties of spinel CoCr2O4 by means of temperature dependent dc and ac magnetization and heat capacity measurements. Various compositions (0.0 ≤ x ≤ 1.0) of polycrystalline Co(Cr1-xAlx)2O4 samples have been prepared by sol-gel processing and their crystal structure was investigated by X-ray diffraction which was found to crystallize in the normal cubic spinel structure. For x ≤ 0.1, the system exhibits multiple magnetic orderings (long range ferrimagnetic ordering TC, spin-spiral ordering TS, and lock-in transition TL), similar to that of the parent compound, CoCr2O4. However, all the compositions between x = 0.1 and 0.5 exhibit long range ferrimagnetic ordering below TC and also a short range order at low temperature. Spin-glass like ordering was noticed between x = 0.6 and 0.8 due to the diluted B-site occupancy, whereas the end compound CoAl2O4 (x = 1.0) shows antiferromagnetic behavior. On the basis of these results, we propose a magnetic phase diagram for the Co(Cr1-xAlx)2O4 series as a function of the Al content (x) and measuring temperature (T).

Corrosion resistance assessment of Co-Cr alloy frameworks fabricated by CAD/CAM milling, laser sintering, and casting methods.

Science.gov (United States)

Tuna, Süleyman Hakan; Özçiçek Pekmez, Nuran; Kürkçüoğlu, Işin

2015-11-01

The effects of fabrication methods on the corrosion resistance of frameworks produced with Co-Cr alloys are not clear. The purpose of this in vitro study was to evaluate the electrochemical corrosion resistance of Co-Cr alloy specimens that were fabricated by conventional casting, milling, and laser sintering. The specimens fabricated with 3 different methods were investigated by potentiodynamic tests and electrochemical impedance spectroscopy in an artificial saliva. Ions released into the artificial saliva were estimated with inductively coupled plasma-mass spectrometry, and the results were statistically analyzed. The specimen surfaces were investigated with scanning electron microscopy before and after the tests. In terms of corrosion current and Rct properties, statistically significant differences were found both among the means of the methods and among the means of the material groups (Pcorrosion than those produced by milling and laser sintering. The corrosion resistance of a Co-Cr alloy specimens fabricated by milling or laser sintering was greater than that of the conventionally cast alloy specimens. The Co-Cr specimens produced by the same method also differed from one another in terms of corrosion resistance. These differences may be related to the variations in the alloy compositions. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

A Comparison of Afghanistan, Yuma, Az, and Manufactured Sands Melted on EB-PVD Thermal Barrier Coatings

Science.gov (United States)

2014-09-18

mentoring me through the field of geology . His vast knowledge in this field and close “First Cousins” motivate me to broaden my knowledge within the...Blade sand sample BC – Bond Coat Button A – TBC Button made by Manufacturer A Button B – TBC Button made by Manufacturer B Ca – Calcium CMAS... Calcium , Magnesium, Aluminum, Silicate CTIO – Coating Technology Integration Office Cr – Chromium CTE – Coefficient of Thermal Expansion DoD

Metal modified tungsten carbide (WC) for catalytic and electrocatalytic applications

Science.gov (United States)

Mellinger, Zachary J.

One of the major challenges in the commercialization of proton exchange membrane fuel cells (PEMFC) is the cost, and low CO tolerance of the anode electrocatalyst material. The anode typically requires a high loading of precious metal electrocatalyst (Pt or Pt--Ru) to obtain a useful amount of electrical energy from the electrooxidation of methanol (CH3OH) or ethanol (C2H5OH). The complete electro--oxidation of methanol or ethanol on these catalysts produces strongly adsorbed CO on the surface, which reduces the activity of the Pt or Pt--Ru catalysts. Another major disadvantage of these electrocatalyst components is the scarcity and consequently high price of both Pt and Ru. Tungsten monocarbide (WC) has shown similar catalytic properties to Pt, leading to the utilization of WC and metal modified WC as replacements to Pt and Pt--Ru. In this thesis we investigated WC and Pt--modified WC as a potentially more CO--tolerant electrocatalysts as compared to pure Pt. These catalysts would reduce or remove the high loading of Pt used industrially. The binding energy of CO, estimated using temperature programmed desorption, is weaker on WC and Pt/WC than on Pt, suggesting that it should be easier to oxidize CO on WC and Pt/WC. This hypothesis was verified using cyclic voltammetry to compare the electro--oxidation of CO on WC, Pt/WC, and Pt supported on carbon substrates, which showed a lower voltage for the onset of oxidation of CO on WC and Pt/WC than on Pt. After observing these improved properties on the Pt/WC catalysts, we decided to expand our studies to investigate Pd--modified WC as Pd is less expensive than Pt and has shown more ideal properties for alcohol electrocatalysis in alkaline media. Pd/WC showed a lower binding energy of CO than both its parent metal Pd as well as Pt. Then, density functional theory (DFT) calculations were performed to determine how the presence of Pd affected the bonding of methanol and ethanol on the WC surface. The DFT studies showed

Nanotoxicity: emerging concerns regarding nanomaterial safety and occupational hard metal (WC-Co nanoparticle exposure

Directory of Open Access Journals (Sweden)

Armstead AL

2016-12-01

Full Text Available Andrea L Armstead,1,2 Bingyun Li1–3 1Department of Orthopaedics, School of Medicine, 2School of Pharmacy, West Virginia University, 3Mary Babb Randolph Cancer Center, Morgantown, WV, USA Abstract: As the number of commercial and consumer products containing engineered nanomaterials (ENMs continually rises, the increased use and production of these ENMs presents an important toxicological concern. Although ENMs offer a number of advantages over traditional materials, their extremely small size and associated characteristics may also greatly enhance their toxic potentials. ENM exposure can occur in various consumer and industrial settings through inhalation, ingestion, or dermal routes. Although the importance of accurate ENM characterization, effective dosage metrics, and selection of appropriate cell or animal-based models are universally agreed upon as important factors in ENM research, at present, there is no “standardized” approach used to assess ENM toxicity in the research community. Of particular interest is occupational exposure to tungsten carbide cobalt (WC-Co “dusts,” composed of nano- and micro-sized particles, in hard metal manufacturing facilities and mining and drilling industries. Inhalation of WC-Co dust is known to cause “hard metal lung disease” and an increased risk of lung cancer; however, the mechanisms underlying WC-Co toxicity, the inflammatory disease state and progression to cancer are poorly understood. Herein, a discussion of ENM toxicity is followed by a review of the known literature regarding the effects of WC-Co particle exposure. The risk of WC-Co exposure in occupational settings and the updates of in vitro and in vivo studies of both micro- and nano-WC-Co particles are discussed. Keywords: engineered nanomaterial, occupational exposure, lung disease, cancer, toxicity, particle

Biološka razgradnja i mehaničko ponašanje sinteriranih kompakata od Co-Cr legure u prahu dopiranih sa ZrO2 rabljenih u stomatologiji

OpenAIRE

Băilă, Diana-Irinel; Mocioiu, Oana-Cătălina; Truşcă, Roxana; Surdu, Adrian; Zaharia, Cătălin; Bunea, Mihaela

2016-01-01

Direct Metal Laser Sintering je postupak moderne tehnologije s primjenom u različitim industrijama, uključujući medicinsku industriju. Namjena ovog istraživanja bila je dobiti sinterirane kompakte Co-Cr praha dopiranog sa ZrO2 u cilju poboljšanja biološke aktivnosti implantata te ponašanja in vitro nakon uranjanja u simuliranu biološku tekućinu (SBF) tijekom 21 dana. Co-Cr prašak (ST2724G) rabljen je za izradu jednog referentnog uzorka Co-Cr i 4 kompakta Co-Cr dopirana sa ZrO2 u sljedećim pos...

Sampling and analysis of the inactive waste tanks TH-2, WC-1, and WC-15

International Nuclear Information System (INIS)

Autrey, J.W.; Keller, J.M.; Griest, W.H.; Botts, J.L.; Schenley, R.L.; Sipe, M.A.

1992-02-01

Thirty-eight inactive liquid low-level radioactive waste tanks are currently managed by the Environmental Restoration Program of Oak Ridge National Laboratory. The contents of these tanks are to be characterized in preparation for future corrective actions and remediation activities as part of compliance with the pending Federal Facility Agreement for the Oak Ridge Reservation. Twenty-nine of these tanks were sampled and analyzed in 1989. Three of the tanks (TH-2, WC-1, and WC-15) were not accessible from the surface and thus were not sampled until 1990. This report presents the sampling and analytical results of that campaign. All three tanks in this report had negligible regulatory organic compounds in the samples that were collected. There were no US Environmental Protection Agency (EPA) Target Compound List (TCL) constituents for volatile organics detected in any of the aqueous samples. The only semivolatile organics detected were 2-chlorophenol (52 μg/L) in tank TH-2 and dichloroethane (14--15 μg/L) and diethyl either (15--17 μg/L) in tank WC-15. A thin oil layer was discovered floating on top of the aqueous contents in tank WC-15. The analysis of the oil layer detected no volatile organics and showed only one EPA TCL constituent, di-n-butylphthalate, at 1900 μg/L. Low levels of Resource Conservation and Recovery Act (RCRA) metals were observed in the samples from tank TH-2, but only the mercury level exceeded the RCRA limit. Samples from tank WC-1 had elevated levels of the RCRA metals barium, chromium, and lead. There were also finely suspended particles in one of the samples from tank WC-1, which was filtered and analyzed separately. This solid fines have levels of transuranium elements 238 Pu and 241 Am high enough to classified as transuranic waste

Porous niobium coatings fabricated with selective laser melting on titanium substrates: Preparation, characterization, and cell behavior.

Science.gov (United States)

Zhang, Sheng; Cheng, Xian; Yao, Yao; Wei, Yehui; Han, Changjun; Shi, Yusheng; Wei, Qingsong; Zhang, Zhen

2015-08-01

Nb, an expensive and refractory element with good wear resistance and biocompatibility, is gaining more attention as a new metallic biomaterial. However, the high price of the raw material, as well as the high manufacturing costs because of Nb's strong oxygen affinity and high melting point have limited the widespread use of Nb and its compounds. To overcome these disadvantages, porous Nb coatings of various thicknesses were fabricated on Ti substrate via selective laser melting (SLM), which is a 3D printing technique that uses computer-controlled high-power laser to melt the metal. The morphology and microstructure of the porous Nb coatings, which had pores ranging from 15 to 50 μm in size, were characterized with scanning electron microscopy (SEM). The average hardness of the coating, which was measured with the linear intercept method, was 392±37 HV. In vitro tests of the porous Nb coating which was monitored with SEM, immunofluorescence, and CCK-8 counts of cells, exhibited excellent cell morphology, attachment, and growth. The simulated body fluid test also proved the bioactivity of the Nb coating. Therefore, these new porous Nb coatings could potentially be used for enhanced early biological fixation to bone tissue. In addition, this study has shown that SLM technique could be used to fabricate coatings with individually tailored shapes and/or porosities from group IVB and VB biomedical metals and their alloys on stainless steel, Co-Cr, and other traditional biomedical materials without wasting raw materials. Copyright © 2015 Elsevier B.V. All rights reserved.

Manufacturing PDMS micro lens array using spin coating under a multiphase system

International Nuclear Information System (INIS)

Sun, Rongrong; Yang, Hanry; Rock, D Mitchell; Danaei, Roozbeh; Panat, Rahul; Kessler, Michael R; Li, Lei

2017-01-01

The development of micro lens arrays has garnered much interest due to increased demand of miniaturized systems. Traditional methods for manufacturing micro lens arrays have several shortcomings. For example, they require expensive facilities and long lead time, and traditional lens materials (i.e. glass) are typically heavy, costly and difficult to manufacture. In this paper, we explore a method for manufacturing a polydimethylsiloxane (PDMS) micro lens array using a simple spin coating technique. The micro lens array, formed under an interfacial tension dominated system, and the influence of material properties and process parameters on the fabricated lens shape are examined. The lenses fabricated using this method show comparable optical properties—including surface finish and image quality—with a reduced cost and manufacturing lead time. (paper)

BARRIERS TO THE USE OF RADIATION-CURABLE ADHESIVES IN THE COATED AND LAMINATED SUBSTRATE MANUFACTURING INDUSTRY

Science.gov (United States)

The paper gives results of an investigation of barriers to the use of radiation-cured technology in the coated and laminated substrate manufacturing industry. t presents information gathered from radiation-curable coating and equipment suppliers as well as technical publications....

[Application of occupational hazard risk index model in occupational health risk assessment in a decorative coating manufacturing enterprises].

Science.gov (United States)

He, P L; Zhao, C X; Dong, Q Y; Hao, S B; Xu, P; Zhang, J; Li, J G

2018-01-20

Objective: To evaluate the occupational health risk of decorative coating manufacturing enterprises and to explore the applicability of occupational hazard risk index model in the health risk assessment, so as to provide basis for the health management of enterprises. Methods: A decorative coating manufacturing enterprise in Hebei Province was chosen as research object, following the types of occupational hazards and contact patterns, the occupational hazard risk index model was used to evaluate occupational health risk factors of occupational hazards in the key positions of the decorative coating manufacturing enterprise, and measured with workplace test results and occupational health examination. Results: The positions of oily painters, water-borne painters, filling workers and packers who contacted noise were moderate harm. And positions of color workers who contacted chromic acid salts, oily painters who contacted butyl acetate were mild harm. Other positions were harmless. The abnormal rate of contacting noise in physical examination results was 6.25%, and the abnormality was not checked by other risk factors. Conclusion: The occupational hazard risk index model can be used in the occupational health risk assessment of decorative coating manufacturing enterprises, and noise was the key harzard among occupational harzards in this enterprise.

Evaluación de las transformaciones estructurales en recubrimientos de WC10Ni depositados por laser cladding sobre acero para herramienta EN 12379

Directory of Open Access Journals (Sweden)

Candel, J. J.

2011-08-01

Full Text Available Carbide metal matrix composite materials are known for a high resistance to all types of wear. It is due to a beneficial combination of properties given by hard phase particles included in a tough matrix. Different kinds of those materials have been employed in the development of new high properties cutting tools. Laser cladding (LC technique allows obtaining an accurate defect-free coating with a low thermal affectation of the component. But in the case of WC cermet coatings due to its high laser absorption and the different mechanical and thermal properties between substrate and coating can appear a wide range of different defects as cracks, pores, massive carbide dilution and lacks of adherence. The aim of the present work is to study the metallurgical transformations during LC process of WC cermet coating on cold work tool steel substrate (EN 12379. Also it has been related process parameters with defects generation. Microstructure and composition of the coating and the heat affected zone have been analysed. Microhardness evolution profile has been obtained. Results show that although process parameters control reduce the generation of defects, in the deposition of overlapped layers appear different metallurgical transformations related with massive WC decomposition and the diffusion of alloying elements from substrate to the coating.

Los materiales compuestos de matriz metálica reforzados con carburos, son conocidos por su elevada resistencia a todos los tipos de desgaste, debido a la combinación de las partículas duras en una matriz metálica tenaz. Diferentes tipos de estos materiales, se han empleado en el desarrollo de nuevas herramientas de corte de altas prestaciones. La técnica de láser cladding (LC, permite obtener recubrimientos libres de defectos sobre zonas muy concretas, con un aporte de calor muy localizado. Pero en el caso de carburos de wolframio (WC, debido a la enorme absorción de energía y la

Morphology Analysis and Process Research on Novel Metal Fused-coating Additive Manufacturing

Science.gov (United States)

Wang, Xin; Wei, Zheng ying; Du, Jun; Ren, Chuan qi; Zhang, Shan; Zhang, Zhitong; Bai, Hao

2017-12-01

Existing metal additive manufacturing equipment has high capital costs and slow throughput printing. In this paper, a new metal fused-coating additive manufacturing (MFCAM) was proposed. Experiments of single-track formation were conducted using MFCAM to validate the feasibility. The low melting alloy was selected as the forming material. Then, the effect of process parameters such as the flow rate, deposition velocity and initial distance on the forming morphology. There is a strong coupling effect between the single track forming morphology. Through the analysis of influencing factors to improve the forming quality of specimens. The experimental results show that the twice as forming efficiency as the metal droplet deposition. Additionally, the forming morphology and quality were analyzed by confocal laser scanning microscope and X-ray. The results show that the metal fused-coating process can achieve good surface morphology and without internal tissue defect.

Structural analysis of sputtered (W-C)1-xMx (M≡Fe,Co) films with 0≤x≤0.20

International Nuclear Information System (INIS)

Cavaleiro, A.; Trindade, B.; Vieira, M.T.

1993-01-01

Structural characterization of (W-C) 1-x M x (M≡Fe,Co) films with 0≤x≤0.20 was carried out using electron probe microanalysis (EPMA), X-ray diffraction (XRD) and transmission electron microscopy-electron diffraction (TEM-ED). The results showed that the structure of these films depends on the percentage of iron and cobalt and becomes amorphous with increasing content of these elements. The microstructure of the crystalline coatings was found to be composed of small grains of β-WC 1-x with a high number of defects. A strong β-WC 1-x [311] texture was observed for iron and cobalt contents around 5.5 at.%. The films richer in iron and cobalt showed typical amorphous XRD and ED patterns, exhibiting two broad peaks and two wide diffuse rings respectively. Moreover, bright-field analysis revealed fairly contrasted images, the structure of these films being difficult to resolve. (orig.)

The influence of metallic ions from CoCr28Mo6 on the osteogenic differentiation and cytokine release of human osteoblasts

Directory of Open Access Journals (Sweden)

Jonitz-Heincke A

2015-09-01

Full Text Available Inflammatory reactions associated with osteolysis and implant loosening can be the result of generated CoCr particles and the simultaneous release of ions, which are the consequence of wear at the articulating surfaces of metallic implants. By now, there is little knowledge about the influence of CoCr ions on the viability of human osteoblasts (hOB.

Effect of surfactant concentration in the electrolyte on the tribological properties of nickel-tungsten carbide composite coatings produced by pulse electro co-deposition

Science.gov (United States)

Kartal, Muhammet; Uysal, Mehmet; Gul, Harun; Alp, Ahmet; Akbulut, Hatem

2015-11-01

A nickel plating bath containing WC particles was used to obtain hard and wear-resistant particle reinforced Ni/WC MMCs on steel surfaces for anti-wear applications. Copper substrates were used for electro co-deposition of Ni matrix/WC with the particle size of <1 μm tungsten carbide reinforcements. The influence of surfactant (sodium dodecyl sulfate, SDS) concentration on particle distribution, microhardness and wear resistance of composite coatings has been studied. The nickel films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of the surfactant on the zeta potential, co-deposition and distribution of WC particles in the nickel matrix, as well as the tribological properties of composite coatings were also investigated. The tribological behaviors of the electrodeposited WC composite coatings sliding against M50 steel ball (Ø 10 mm) were examined on a CSM Instrument. All friction and wear tests were performed without lubrication at room temperature and in the ambient air (relative humidity 55-65%).

Effects of repeated firing on the marginal accuracy of Co-Cr copings fabricated by selective laser melting.

Science.gov (United States)

Zeng, Li; Zhang, Yong; Liu, Zheng; Wei, Bin

2015-02-01

Selective laser melting (SLM) is a technique used to fabricate Co-Cr dental restorations; however, because marginal accuracy is important for the long-term success of restorations, the marginal accuracy of SLM after repeated firings must be considered. The purpose of this study was to evaluate the marginal accuracy of dental Co-Cr alloy copings fabricated by SLM and to investigate the effects of repeated firing on the marginal fit of these copings. SLM-fabricated and cast Co-Cr alloy copings (n=15) were prepared for a zirconia die. The marginal gap widths of each group were evaluated with a silicone replica technique after the first, third, fifth, and seventh firing cycle. The thickness of the reference point was measured with a stereomicroscope with ×100 magnification. Analysis of variance was used to evaluate the effect of repeated firing on the marginal accuracy of the 2 alloys. The Student t test was used to compare the marginal gap widths of the SLM-fabricated and cast Co-Cr alloy copings after repeated firing (α=.05). The marginal gap width values between the 2 groups at all firing periods were statistically significant (P.05). The SLM copings demonstrated superior marginal accuracy at all firings. Repeated firing had no significant influence on the marginal accuracy of both copings, and the marginal fit of both copings after repeated firing was within a clinically acceptable range. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

FY 2000 report on the results of the regional consortium R and D project - Regional new technology creation R and D. First year report. Functional molds with highly polished diamond coatings; 2000 nendo chiiki consortium kenkyu kaihatsu jigyo - chiiki shingijutsu soshutsu kenkyu kaihatsu. Kyomen diamond maku wo yusuru kokino kanagata (shonendo) seika hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-03-01

The development was proceeded with of the technology to form the uniform diamond coating on mold with the complicated shape and also to highly polish it by a new chemical polishing method. The new chemical polishing method is a method using TiAlX intermetallic compounds as grindstone. Reaction with each other of Ti and C by frictional heat expedites diamond polishing. 1) development of the controlling technology of diamond coating interface; 2) development of the 3-D diamond polishing system; 3) demonstrative test on diamond coating; 4) study of a possibility of the commercialization. 1) was divided into the development of the controlling technology of diamond coating interface and the survey of super-hard alloys suitable for diamond coating formation. In the latter, it was found out that the highly Co containing particular WC super-hard alloys were bad in adhesiveness to diamond coating. Therefore, studies were made on the manufacturing of super-hard alloys which use coarse WC only near the surface and does not have much Co and on the use of SiC excellent in adhesiveness both to super-hard alloys and diamond for intermediate layer. (NEDO)

Atomic diffusion induced degradation in bimetallic layer coated cemented tungsten carbide

International Nuclear Information System (INIS)

Peng, Zirong; Rohwerder, Michael; Choi, Pyuck-Pa; Gault, Baptiste; Meiners, Thorsten; Friedrichs, Marcel; Kreilkamp, Holger; Klocke, Fritz; Raabe, Dierk

2017-01-01

Highlights: • We study the temporal degradation of PtIr/Cr/WC and PtIr/Ni/WC systems. • Short cut diffusion, segregation, oxidation and interdiffusion reactions occurred. • Outward diffusion of Cr (Ni) via PtIr grain boundaries triggered the degradation. • The microstructure of the PtIr layer controlled the systems stability. • We propose an atomic diffusion induced degradation mechanism. - Abstract: We investigated the temporal degradation of glass moulding dies, made of cemented tungsten carbide coated with PtIr on an adhesive Cr or Ni interlayer, by electron microscopy and atom probe tomography. During the exposure treatments at 630 °C under an oxygen partial pressure of 1.12 × 10"−"2"3 bar, Cr (Ni) was found to diffuse outwards via grain boundaries in the PtIr, altering the surface morphology. Upon dissolution of the interlayer, the WC substrate also started degrading. Extensive interdiffusion processes involving PtIr, Cr (Ni) and WC took place, leading to the formation of intermetallic phases and voids, deteriorating the adhesion of the coating.

In-Service Evaluation of HVOF Coated Main Landing Gear on Navy P-3 Aircraft

Science.gov (United States)

Devereaux, jon L.; Forrest, Clint

2008-01-01

Due to the environmental and health concerns with Electroplated Hard Chrome (EHC), the Hard Chrome Alternatives Team (HCAT) has been working to provide an alternative wear coating for EHC. The US Navy selected Tungsten-Carbide Cobalt (WC- 17Co) High Velocity Oxy-Fuel (HVOF) thermal spray coating for this purpose and completed service evaluations on select aircraft components to support the HCAT charter in identifying an alternative wear coating for chrome plating. Other benefits of WC-Co thermal spray coatings over EHC are enhanced corrosion resistance, improved durability, and exceptional wear properties. As part of the HCAT charter and to evaluate HVOF coatings on operational Navy components, the P-3 aircraft was selected for a service evaluation to determine the coating durability as compared to chrome plating. In April 1999, a VP-30 P-3 aircraft was outfitted with a right-hand Main Landing Gear (MLG) shock strut coated with WCCo HYOF thermal spray applied to the piston barrel and four axle journals. The HVOF coating on the piston barrel and axle journals was applied by Southwest United Industries, Inc. This HVOF coated strut assembly has since completed 6,378 landings. Teardown analysis .for this WC-Co HVOF coated MLG asset is significant in assessing the durability of this wear coating in service relative to EHC and to substantiate Life Cycle Cost (LCC) data to support a retrograde transition from EHC to HVOF thermal spray coatings. Findings from this teardown analysis may also benefit future transitions to HVOF thermal spray coatings by identifying enhancements to finishing techniques, mating bearing and liner material improvements, improved seal materials, and improvements in HVOF coating selection.

Effect of surfactant concentration in the electrolyte on the tribological properties of nickel-tungsten carbide composite coatings produced by pulse electro co-deposition

Energy Technology Data Exchange (ETDEWEB)

Kartal, Muhammet, E-mail: kartal@sakarya.edu.tr [Sakarya University, Engineering Faculty, Metallurgical & Materials Engineering Department, Esentepe Campus, 54187 Sakarya (Turkey); Uysal, Mehmet [Sakarya University, Engineering Faculty, Metallurgical & Materials Engineering Department, Esentepe Campus, 54187 Sakarya (Turkey); Gul, Harun [Duzce University, Gumusova Vocational School, 81850 Duzce (Turkey); Alp, Ahmet; Akbulut, Hatem [Sakarya University, Engineering Faculty, Metallurgical & Materials Engineering Department, Esentepe Campus, 54187 Sakarya (Turkey)

2015-11-01

Highlights: • Effect of surfactant concentration on the co-deposited WC was investigated. • In the Ni matrix significantly high hardness was achieved by WC co-deposition. • Optimum surfactant resulted in obtaining superior wear resistance in the Ni. • Friction coefficient was decreased by WC co-deposition in the Ni matrix. - Abstract: A nickel plating bath containing WC particles was used to obtain hard and wear-resistant particle reinforced Ni/WC MMCs on steel surfaces for anti-wear applications. Copper substrates were used for electro co-deposition of Ni matrix/WC with the particle size of <1 μm tungsten carbide reinforcements. The influence of surfactant (sodium dodecyl sulfate, SDS) concentration on particle distribution, microhardness and wear resistance of composite coatings has been studied. The nickel films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of the surfactant on the zeta potential, co-deposition and distribution of WC particles in the nickel matrix, as well as the tribological properties of composite coatings were also investigated. The tribological behaviors of the electrodeposited WC composite coatings sliding against M50 steel ball (Ø 10 mm) were examined on a CSM Instrument. All friction and wear tests were performed without lubrication at room temperature and in the ambient air (relative humidity 55–65%).

Microstructural Characteristics and Tribological Behavior of HVOF-Sprayed Novel Fe-Based Alloy Coatings

Directory of Open Access Journals (Sweden)

Andrea Milanti

2014-01-01

Full Text Available Thermally-sprayed Fe-based coatings have shown their potential for use in wear applications due to their good tribological properties. In addition, these kinds of coatings have other advantages, e.g., cost efficiency and positive environmental aspects. In this study, the microstructural details and tribological performances of Fe-based coatings (Fe-Cr-Ni-B-C and Fe-Cr-Ni-B-Mo-C manufactured by High Velocity Oxygen Fuel (HVOF thermal spray process are evaluated. Traditional Ni-based (Ni-Cr-Fe-Si-B-C and hard-metal (WC-CoCr coatings were chosen as references. Microstructural investigation (field-emission scanning electron microscope FESEM and X-Ray diffractometry XRD reveals a high density and low oxide content for HVOF Fe-based coatings. Particle melting and rapid solidification resulted in a metastable austenitic phase with precipitates of mixed carbides and borides of chromium and iron which lead to remarkably high nanohardness. Tribological performances were evaluated by means of the ball on-disk dry sliding wear test, the rubber-wheel dry particle abrasion test, and the cavitation erosion wear test. A higher wear resistance validates Fe-based coatings as a future alternative to the more expensive and less environmentally friendly Ni-based alloys.

Direct laser sintered WC-10Co/Cu nanocomposites

Science.gov (United States)

Gu, Dongdong; Shen, Yifu

2008-04-01

In the present work, the direct metal laser sintering (DMLS) process was used to prepare the WC-Co/Cu nanocomposites in bulk form. The WC reinforcing nanoparticles were added in the form of WC-10 wt.% Co composite powder. The microstructural features and mechanical properties of the laser-sintered sample were characterized by X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDX), and nanoindentation tester. It showed that the original nanometric nature of the WC reinforcing particulates was well retained without appreciable grain growth after laser processing. A homogeneous distribution of the WC reinforcing nanoparticles with a coherent particulate/matrix interfacial bonding was obtained in the laser-sintered structure. The 94.3% dense nanocomposites have a dynamic nanohardness of 3.47 GPa and a reduced elastic modulus of 613.42 GPa.

Direct laser sintered WC-10Co/Cu nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Gu Dongdong [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016 (China)], E-mail: dongdonggu@nuaa.edu.cn; Shen Yifu [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016 (China)

2008-04-30

In the present work, the direct metal laser sintering (DMLS) process was used to prepare the WC-Co/Cu nanocomposites in bulk form. The WC reinforcing nanoparticles were added in the form of WC-10 wt.% Co composite powder. The microstructural features and mechanical properties of the laser-sintered sample were characterized by X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDX), and nanoindentation tester. It showed that the original nanometric nature of the WC reinforcing particulates was well retained without appreciable grain growth after laser processing. A homogeneous distribution of the WC reinforcing nanoparticles with a coherent particulate/matrix interfacial bonding was obtained in the laser-sintered structure. The 94.3% dense nanocomposites have a dynamic nanohardness of 3.47 GPa and a reduced elastic modulus of 613.42 GPa.

Direct laser sintered WC-10Co/Cu nanocomposites

International Nuclear Information System (INIS)

Gu Dongdong; Shen Yifu

2008-01-01

In the present work, the direct metal laser sintering (DMLS) process was used to prepare the WC-Co/Cu nanocomposites in bulk form. The WC reinforcing nanoparticles were added in the form of WC-10 wt.% Co composite powder. The microstructural features and mechanical properties of the laser-sintered sample were characterized by X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDX), and nanoindentation tester. It showed that the original nanometric nature of the WC reinforcing particulates was well retained without appreciable grain growth after laser processing. A homogeneous distribution of the WC reinforcing nanoparticles with a coherent particulate/matrix interfacial bonding was obtained in the laser-sintered structure. The 94.3% dense nanocomposites have a dynamic nanohardness of 3.47 GPa and a reduced elastic modulus of 613.42 GPa

Grinding of WC-Co hard-metals

NARCIS (Netherlands)

Hegeman, J.B.J.W.; Hosson, de J.Th.M.; With, de G.

2001-01-01

Morphol. of ground surface of WC-Co cermets with 10 and 20% Co was studied. A deformed and detached surface layer was found on top of the specimens after surface grinding with a diamond wheel. Etching the surface layer revealed WC grains in the subsurface of the machined specimens. Most of these

Coat and hair color: hair cortisol and serotonin levels in lactating Holstein cows under heat stress conditions.

Science.gov (United States)

Ghassemi Nejad, Jalil; Kim, Byong-Wan; Lee, Bae-Hun; Sung, Kyung-Il

2017-01-01

The deleterious effects of heat stress on animal health are being increasingly recognized. This study aimed to determine hair cortisol (HC) and serotonin levels in lactating Holstein cows under heat stress conditions with different coat and hair-cut color. Forty-five multiparous lactating Holstein cows (days in milk = 130 ± 47, body weight = 753 ± 85 kg) were divided to two main groups of over 80% black coat color (BC) and over 85% white coat color (WC) visually observed based on registry certificates and subdividing to black hair sample (BH) and white hair samples (WH) in 2 × 2 factorial arrangements. Hair samples were taken from the forehead of the individuals. Higher HC levels were observed in BC than WC cows (P  0.05). Serotonin levels showed no difference between BC and WC (P > 0.05). Interaction between coat color and hair color was not significant (P > 0.05). The cortisol levels in hair are not affected by pigmentation. However, pigmentation within the coat alters cortisol levels. In conclusion, white coat color retains less cortisol than the black coat. Therefore, white coats are preferable for dairy cows under heat stress conditions. © 2016 Japanese Society of Animal Science.

Manufacturing technologies for nanocomposite ceramic structural materials and coatings

Energy Technology Data Exchange (ETDEWEB)

Gadow, R. [Universitaet Stuttgart, Institut fuer Fertigungstechnik keramischer Bauteile, D-70569 Stuttgart, Allmandring 7b (Germany)], E-mail: rainer.gadow@ifkb.uni-stuttgart.de; Kern, F.; Killinger, A. [Universitaet Stuttgart, Institut fuer Fertigungstechnik keramischer Bauteile, D-70569 Stuttgart, Allmandring 7b (Germany)

2008-02-25

The new material class of ceramic nanocomposites, containing at least one phase in nanometric dimension, has achieved special interest in previous years. While earlier research was focused on materials science and microstructural details in laboratory scale the subject of developing suitable manufacturing technologies in technical scale is the challenge for the manufacturing engineer. The same high-performance features which make the nanocomposite materials so interesting in their properties are absolutely detrimental if it comes to production of these materials. Extreme hardness, toughness and abrasion resistance make the state of the art cutting-and-machining operations extremely cost intensive so that, from a manufacturing point of view, true near-net-shape manufacturing is mandatory to accomplish reasonable cost targets. Ceramic feedstocks with both, high solid content to reduce shrinkage and warping and stable processing conditions are required to accomplish this aim of near-net-shape processing. Stable and reproducible processing conditions, e.g. favourable rheological properties for injection moulding are essentials for the manufacturing engineer. These prerequisites of ceramic production technologies cannot be reached with pure nanopowders in the 10-20 nm range but materials with a micro-nano architecture can fulfill these requirements, using a mixture of a submicron-sized matrix in the 100-200 nm range and smaller nanosized additives in <20% content which contribute the desired functionality. By using these micro-nanocomposites near-net-shape ceramic forming technologies such as injection moulding, gel casting and slip casting have been developed which lead to high-performance materials at affordable production cost. Advanced surface technologies include nanoceramic coatings made by thermokinetic deposition processes. Modern ceramic processing, i.e. spray drying leads to fine granulated nanopowders with appropriate flowability for subsequent APS plasma or

Experimental investigation of surface quality in ultrasonic machining of WC-Co composites through Taguchi method

Directory of Open Access Journals (Sweden)

B. S. Pabla

2016-08-01

Full Text Available In manufacturing industries, the demand of WC-Co composite is flourishing because of the distinctive characteristics it offers such as: toughness (with hardness, good dimensional stability, higher mechanical strength etc. However, the difficulties in its machining restrict the application and competitiveness of this material. The current article has been targeted at evaluation of the effect of process conditions (varying power rating, cobalt content, tool material, part thickness, tool geometry, and size of abrasive particle on surface roughness in ultrasonic drilling of WC-Co composite. Results showed that abrasive grit size is most influential factor. From the microstructure analysis, the mode of material deformation has been observed and the parameters, i.e. work material properties, grit size, and power rating was revealed as the most crucial for the deformation mode.

Residual stress and crack initiation in laser clad composite layer with Co-based alloy and WC + NiCr

International Nuclear Information System (INIS)

Lee, Changmin; Park, Hyungkwon; Yoo, Jaehong; Lee, Changhee; Woo, WanChuck; Park, Sunhong

2015-01-01

Highlights: • Major problem, clad cracking in laser cladding process, was researched. • Residual stress measurements were performed quantitatively by neutron diffraction method along the surface of specimens. • Relationship between the residual stress and crack initiation was showed clearly. • Ceramic particle effect in the metal matrix was showed from the results of residual stress measurements. • Initiation sites of generating clad cracks were specifically studied in MMC coatings. - Abstract: Although laser cladding process has been widely used to improve the wear and corrosion resistance, there are unwanted cracking issues during and/or after laser cladding. This study investigates the tendency of Co-based WC + NiCr composite layers to cracking during the laser cladding process. Residual stress distributions of the specimen are measured using neutron diffraction and elucidate the correlation between the residual stress and the cracking in three types of cylindrical specimens; (i) no cladding substrate only, (ii) cladding with 100% stellite#6, and (iii) cladding with 55% stellite#6 and 45% technolase40s. The microstructure of the clad layer was composed of Co-based dendrite and brittle eutectic phases at the dendritic boundaries. And WC particles were distributed on the matrix forming intermediate composition region by partial melting of the surface of particles. The overlaid specimen exhibited tensile residual stress, which was accumulated through the beads due to contraction of the coating layer generated by rapid solidification, while the non-clad specimen showed compressive. Also, the specimen overlaid with 55 wt% stellite#6 and 45 wt% technolase40s showed a tensile stress higher than the specimen overlaid with 100% stellite#6 possibly, due to the difference between thermal expansion coefficients of the matrix and WC particles. Such tensile stresses can be potential driving force to provide an easy crack path ways for large brittle fractures

Residual stress and crack initiation in laser clad composite layer with Co-based alloy and WC + NiCr

Energy Technology Data Exchange (ETDEWEB)

Lee, Changmin; Park, Hyungkwon; Yoo, Jaehong [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Lee, Changhee, E-mail: chlee@hanyang.ac.kr [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Woo, WanChuck [Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Park, Sunhong [Research Institute of Industrial Science & Technology, Hyo-ja-dong, Po-Hang, Kyoung-buk, San 32 (Korea, Republic of)

2015-08-01

Highlights: • Major problem, clad cracking in laser cladding process, was researched. • Residual stress measurements were performed quantitatively by neutron diffraction method along the surface of specimens. • Relationship between the residual stress and crack initiation was showed clearly. • Ceramic particle effect in the metal matrix was showed from the results of residual stress measurements. • Initiation sites of generating clad cracks were specifically studied in MMC coatings. - Abstract: Although laser cladding process has been widely used to improve the wear and corrosion resistance, there are unwanted cracking issues during and/or after laser cladding. This study investigates the tendency of Co-based WC + NiCr composite layers to cracking during the laser cladding process. Residual stress distributions of the specimen are measured using neutron diffraction and elucidate the correlation between the residual stress and the cracking in three types of cylindrical specimens; (i) no cladding substrate only, (ii) cladding with 100% stellite#6, and (iii) cladding with 55% stellite#6 and 45% technolase40s. The microstructure of the clad layer was composed of Co-based dendrite and brittle eutectic phases at the dendritic boundaries. And WC particles were distributed on the matrix forming intermediate composition region by partial melting of the surface of particles. The overlaid specimen exhibited tensile residual stress, which was accumulated through the beads due to contraction of the coating layer generated by rapid solidification, while the non-clad specimen showed compressive. Also, the specimen overlaid with 55 wt% stellite#6 and 45 wt% technolase40s showed a tensile stress higher than the specimen overlaid with 100% stellite#6 possibly, due to the difference between thermal expansion coefficients of the matrix and WC particles. Such tensile stresses can be potential driving force to provide an easy crack path ways for large brittle fractures

Evaluation of metal-ceramic bond characteristics of three dental Co-Cr alloys prepared with different fabrication techniques.

Science.gov (United States)

Wang, Hongmei; Feng, Qing; Li, Ning; Xu, Sheng

2016-12-01

Limited information is available regarding the metal-ceramic bond strength of dental Co-Cr alloys fabricated by casting (CAST), computer numerical control (CNC) milling, and selective laser melting (SLM). The purpose of this in vitro study was to evaluate the metal-ceramic bond characteristics of 3 dental Co-Cr alloys fabricated by casting, computer numerical control milling, and selective laser melting techniques using the 3-point bend test (International Organization for Standardization [ISO] standard 9693). Forty-five specimens (25×3×0.5 mm) made of dental Co-Cr alloys were prepared by CAST, CNC milling, and SLM techniques. The morphology of the oxidation surface of metal specimens was evaluated by scanning electron microscopy (SEM). After porcelain application, the interfacial characterization was evaluated by SEM equipped with energy-dispersive spectrometry (EDS) analysis, and the metal-ceramic bond strength was assessed with the 3-point bend test. Failure type and elemental composition on the debonding interface were assessed by SEM/EDS. The bond strength was statistically analyzed by 1-way ANOVA and Tukey honest significant difference test (α=.05). The oxidation surfaces of the CAST, CNC, and SLM groups were different. They were porous in the CAST group but compact and irregular in the CNC and SLM groups. The metal-ceramic interfaces of the SLM and CNC groups showed excellent combination compared with those of the CAST group. The bond strength was 37.7 ±6.5 MPa for CAST, 43.3 ±9.2 MPa for CNC, and 46.8 ±5.1 MPa for the SLM group. Statistically significant differences were found among the 3 groups tested (P=.028). The debonding surfaces of all specimens exhibited cohesive failure mode. The oxidation surface morphologies and thicknesses of dental Co-Cr alloys are dependent on the different fabrication techniques used. The bond strength of all 3 groups exceed the minimum acceptable value of 25 MPa recommended by ISO 9693; hence, dental Co-Cr alloy

Tough-coated hard powders for hardmetals of novel properties

International Nuclear Information System (INIS)

Toth, R.E.; Smid, I.; Kladler, G.; Korb, G.; Sherman, A.; Ettmayer, P.

2001-01-01

The properties and performance of conventional materials and composites are constrained by solubility limits, diffusion coefficients, and compatibility of physical and chemical constituent properties in their phase equilibria. To escape these limits, ingenious ways of combining strength, toughness, and wear resistance by way of various coatings and laminations have been devised. These coated tools are systematically discarded after only about 10 % of their wear tolerance has been used. Tough-coated hard powders (TCHP), patented by EnDurAloy (USA), are hard refractory particles CVD coated with nanolayers of WC and Co. Consolidation of TCHP creates an engineered homogeneous cellular structure whose interconnected tough WC-Co 'shells' each contain a wear-resistant core (e.g., TiN). In TCHP's, the coating is throughout the tool, not only on the surface, combining the strength, heat resistance, and toughness of cemented carbides with the chemical and abrasion wear resistance of harder materials. As wear progresses, new wear-resistant material continuously replaces the working surfaces and edges of the tool until its geometry reaches its maximum limits. TCHP tools are then reusable many times. Specific coating and consolidation processes, characterization of compacts, and test comparisons with conventional materials are discussed. (author)

Operation of microstrip gas chambers manufactured on glass coated with high resistivity diamond-like layers

CERN Document Server

Boimska, B; Dominik, Wojciech; Hoch, M; Million, Gilbert; Ropelewski, Leszek; Sauli, Fabio; Sharma, A

1997-01-01

We describe recent observations and measurements realized with micro-strip gas chambers (MSGCs) manufactured on boro-silicate glass coated with a thin layer of diamond-like carbon (DLC) having a surface resistivity around 4.10$^{16}\\Omega/\\Box$. The role of the back-pla electrode configuration and potential in the detector performance has been studied. Even for this very high resistivity of the coatings, MSGCs operate differently from those manufactured on bare boro-silicate glass; the charge gain increases with the radiation flux for counting rates above 103 Hz/mm2, reaching a value 60% higher for 105 Hz/mm2. This behavior does not depend on the presence and potential of the back plane electrode; however, both maximum gain and rate capability are influenced by the drift field. From this study, compared with measurements realized previously with other detectors, we deduce that for stable high rate operation of MSGCs the resistivity of the coating should not exceed ~10$^{15}\\Omega/\\Box$.

Electrochemical properties of mixed WC and Pt-black powders

Directory of Open Access Journals (Sweden)

MAJA D. OBRADOVIC

2008-12-01

Full Text Available The electrochemical characteristics of a mixture of Pt-black and WC powders and its catalytic activity for methanol and formic acid oxidation were investigated in acid solution. XRD and AFM measurements revealed that the WC powder employed for the investigation was a single-phase material consisting of crystallites/spherical particles of average size of about 50 nm, which were agglomerated into much larger particles. Cyclic voltammetry showed that the WC underwent electrochemical oxidation, producing tungstate species. In the case of the mixed Pt + WC powders, the tungstate species were deposited on the Pt as a thin film of hydrous tungsten oxide. Enhanced hydrogen intercalation in the hydrous tungsten oxide was observed and it was proposed to be promoted in mixed powders by the presence of hydrogen adatoms on bare Pt sites. The determination of Pt surface area in the Pt + WC layer by stripping of underpotentially deposited Cu revealed that the entire Pt surface was accessible for underpotential deposition of Cu. Investigation of the electrochemical oxidation of methanol and formic acid on Pt + WC and pure Pt layers did not indicate electrocatalytic promotion due to the presence of WC.

The erosion performance of cold spray deposited metal matrix composite coatings with subsequent friction stir processing

Energy Technology Data Exchange (ETDEWEB)

Peat, Tom, E-mail: tompeat12@gmail.com [Department of Mechanical & Aerospace Engineering, University of Strathclyde, James Weir Building, 75 Montrose Street, Glasgow G1 1XJ (United Kingdom); Galloway, Alexander; Toumpis, Athanasios [Department of Mechanical & Aerospace Engineering, University of Strathclyde, James Weir Building, 75 Montrose Street, Glasgow G1 1XJ (United Kingdom); McNutt, Philip [TWI Ltd., Granta Park, Cambridge CB21 6AL (United Kingdom); Iqbal, Naveed [TWI Technology Centre, Wallis Way, Catcliff, Rotherham, S60 5TZ (United Kingdom)

2017-02-28

Highlights: • WC-CoCr, Cr{sub 3}C{sub 2}-NiCr and Al{sub 2}O{sub 3} coatings were cold spray deposited on AA5083 and friction stir processed. • The SprayStirred WC-CoCr demonstrated a hardness increase of 100% over the cold sprayed coating. • As-deposited and SprayStirred coatings were examined under slurry erosion test conditions. • Mass and volume loss was measured following 20-min exposure to the slurry. • The WC-CoCr and Al2O3 demonstrated a reduction in volume loss of approx. 40% over the cold sprayed coating. - Abstract: This study forms an initial investigation into the development of SprayStir, an innovative processing technique for generating erosion resistant surface layers on a chosen substrate material. Tungsten carbide – cobalt chromium, chromium carbide – nickel chromium and aluminium oxide coatings were successfully cold spray deposited on AA5083 grade aluminium. In order to improve the deposition efficiency of the cold spray process, coatings were co-deposited with powdered AA5083 using a twin powder feed system that resulted in thick (>300 μm) composite coatings. The deposited coatings were subsequently friction stir processed to embed the particles in the substrate in order to generate a metal matrix composite (MMC) surface layer. The primary aim of this investigation was to examine the erosion performance of the SprayStirred surfaces and demonstrate the benefits of this novel process as a surface engineering technique. Volumetric analysis of the SprayStirred surfaces highlighted a drop of approx. 40% in the level of material loss when compared with the cold spray deposited coating prior to friction stir processing. Micro-hardness testing revealed that in the case of WC-CoCr reinforced coating, the hardness of the SprayStirred material exhibits an increase of approx. 540% over the unaltered substrate and 120% over the as-deposited composite coating. Microstructural examination demonstrated that the increase in the hardness of the

Characterization of hard coatings produced by laser cladding using laser-induced breakdown spectroscopy technique

Energy Technology Data Exchange (ETDEWEB)

Varela, J.A.; Amado, J.M.; Tobar, M.J.; Mateo, M.P.; Yañez, A.; Nicolas, G., E-mail: gines@udc.es

2015-05-01

Highlights: • Chemical mapping and profiling by laser-induced breakdown spectroscopy (LIBS) of coatings produced by laser cladding. • Production of laser clads using tungsten carbide (WC) and nickel based matrix (NiCrBSi) powders. • Calibration by LIBS of hardfacing alloys with different WC concentrations. - Abstract: Protective coatings with a high abrasive wear resistance can be obtained from powders by laser cladding technique, in order to extend the service life of some industrial components. In this work, laser clad layers of self-fluxing NiCrBSi alloy powder mixed with WC powder have been produced on stainless steel substrates of austenitic type (AISI 304) in a first step and then chemically characterized by laser-induced breakdown spectroscopy (LIBS) technique. With the suitable laser processing parameters (mainly output power, beam scan speed and flow rate) and powders mixture proportions between WC ceramics and NiCrBSi alloys, dense pore free layers have been obtained on single tracks and on large areas with overlapped tracks. The results achieved by LIBS technique and applied for the first time to the analysis of laser clads provided the chemical composition of the tungsten carbides in metal alloy matrix. Different measurement modes (multiple point analyses, depth profiles and chemical maps) have been employed, demonstrating the usefulness of LIBS technique for the characterization of laser clads based on hardfacing alloys. The behavior of hardness can be explained by LIBS maps which evidenced the partial dilution of some WC spheres in the coating.

Additive manufactured Ti6Al4V scaffolds with the RF- magnetron sputter deposited hydroxyapatite coating

International Nuclear Information System (INIS)

Chudinova, E; Surmeneva, M; Surmenev, R; Koptioug, A; Scoglund, P

2016-01-01

Present paper reports on the results of surface modification of the additively manufactured porous Ti6Al4V scaffolds. Radio frequency (RF) magnetron sputtering was used to modify the surface of the alloy via deposition of the biocompatible hydroxyapatite (HA) coating. The surface morphology, chemical and phase composition of the HA-coated alloy were studied. It was revealed that RF magnetron sputtering allows preparing a homogeneous HA coating onto the entire surface of scaffolds. (paper)

Porosity and wear resistance of flame sprayed tungsten carbide coatings

Science.gov (United States)

Winarto, Winarto; Sofyan, Nofrijon; Rooscote, Didi

2017-06-01

Thermal-sprayed coatings offer practical and economical solutions for corrosion and wear protection of components or tools. To improve the coating properties, heat treatment such as preheat is applied. The selection of coating and substrate materials is a key factor in improving the quality of the coating morphology after the heat treatment. This paper presents the experimental results regarding the effect of preheat temperatures, i.e. 200°C, 300°C and 400°C, on porosity and wear resistance of tungsten carbide (WC) coating sprayed by flame thermal coating. The powders and coatings morphology were analyzed by a Field Emission Scanning Electron Microscope equipped with Energy Dispersive Spectrometry (FE-SEM/EDS), whereas the phase identification was performed by X-Ray diffraction technique (XRD). In order to evaluate the quality of the flame spray obtained coatings, the porosity, micro-hardness and wear rate of the specimens was determined. The results showed that WC coating gives a higher surface hardness from 1391 HVN up to 1541 HVN compared to that of the non-coating. Moreover, the wear rate increased from 0.072 mm3/min. to 0.082 mm3/min. when preheat temperature was increased. Preheat on H13 steel substrate can reduce the percentage of porosity level from 10.24 % to 3.94% on the thermal spray coatings.

[Emission characteristics and safety evaluation of volatile organic compounds in manufacturing processes of automotive coatings].

Science.gov (United States)

Zeng, Pei-Yuan; Li, Jian-Jun; Liao, Dong-Qi; Tu, Xiang; Xu, Mei-Ying; Sun, Guo-Ping

2013-12-01

Emission characteristics of volatile organic compounds (VOCs) were investigated in an automotive coating manufacturing enterprise. Air samples were taken from eight different manufacturing areas in three workshops, and the species of VOCs and their concentrations were measured by gas chromatography-mass spectrometry (GC-MS). Safety evaluation was also conducted by comparing the concentration of VOCs with the permissible concentration-short term exposure limit (PC-STEL) regulated by the Ministry of Health. The results showed that fifteen VOCs were detected in the indoor air of the automotive coatings workshop, including benzene, toluene, ethylbenzene, xylene, ethyl acetate, butyl acetate, methyl isobutyl ketone, propylene glycol monomethyl ether acetate, trimethylbenzene and ethylene glycol monobutyl ether, Their concentrations widely ranged from 0.51 to 593.14 mg x m(-3). The concentrations of TVOCs were significantly different among different manufacturing processes. Even in the same manufacturing process, the concentrations of each component measured at different times were also greatly different. The predominant VOCs of indoor air in the workshop were identified to be ethylbenzene and butyl acetate. The concentrations of most VOCs exceeded the occupational exposure limits, so the corresponding control measures should be taken to protect the health of the workers.

Microstructural and Mechanical Study of Inconel 625 – Tungsten Carbide Composite Coatings Obtained by Powder Laser Cladding

Directory of Open Access Journals (Sweden)

Huebner J.

2017-06-01

Full Text Available This study focuses on the investigation of fine (~0.54 μm tungsten carbide particles effect on structural and mechanical properties of laser cladded Inconel 625-WC composite. Three powder mixtures with different Inconel 625 – WC weight ratio (10, 20 and 30 weight % of WC were prepared. Coatings were made using following process parameters: laser beam diameter ø ≈ 500 μm, powder feeder rotation speed – 7 m/min, scanning velocity – 10 m/min, laser power – 220 W changed to 320 W, distance between tracks – 1 mm changed to 0.8 mm. Microstructure and hardness were investigated. Coatings produced by laser cladding were crack and pore free, chemically and structurally homogenous. High cooling rate during cladding process resulted in fine microstructure of material. Hardness improved with addition of WC from 396.3 ±10.5 HV for pure Inconel 625, to 469.9 ±24.9 HV for 30 weight % of WC. Tungsten carbide dissolved in Inconel 625 which allowed formation of intergranular eutectic that contains TCP phases.

Functionalization of CoCr surfaces with cell adhesive peptides to promote HUVECs adhesion and proliferation

Energy Technology Data Exchange (ETDEWEB)

Castellanos, Maria Isabel, E-mail: maria.isabel.castellanos@upc.edu [Biomaterials, Biomechanics and Tissue Engineering Group, Department of Materials Science and Metallurgical Engineering, Technical University of Catalonia (UPC), ETSEIB, 08028 Barcelona (Spain); Centre for Research in Nanoengineering (CRNE), UPC, 08028 Barcelona (Spain); Mas-Moruno, Carlos, E-mail: carles.mas.moruno@upc.edu [Biomaterials, Biomechanics and Tissue Engineering Group, Department of Materials Science and Metallurgical Engineering, Technical University of Catalonia (UPC), ETSEIB, 08028 Barcelona (Spain); Centre for Research in Nanoengineering (CRNE), UPC, 08028 Barcelona (Spain); Grau, Anna, E-mail: agraugar@gmail.com [Biomaterials, Biomechanics and Tissue Engineering Group, Department of Materials Science and Metallurgical Engineering, Technical University of Catalonia (UPC), ETSEIB, 08028 Barcelona (Spain); Centre for Research in Nanoengineering (CRNE), UPC, 08028 Barcelona (Spain); Serra-Picamal, Xavier, E-mail: xserrapicamal@gmail.com [Institute for Bioengineering of Catalonia (IBEC), 08028 Barcelona (Spain); University of Barcelona and CIBER-BBN, 08036 Barcelona (Spain); Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona (Spain); Trepat, Xavier, E-mail: xtrepat@ub.edu [Institute for Bioengineering of Catalonia (IBEC), 08028 Barcelona (Spain); University of Barcelona and CIBER-BBN, 08036 Barcelona (Spain); Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona (Spain); Albericio, Fernando, E-mail: fernando.albericio@irbbarcelona.org [Department of Chemistry, University of Barcelona, CIBER-BBN, 08028 Barcelona (Spain); Joner, Michael, E-mail: michaeljoner@me.com [Department of Cardiology, Deutsches Herzzentrum München, 80636 Munich (Germany); CVPath Institute, Gaithersburg, MD 20878 (United States); and others

2017-01-30

Highlights: • We immobilized peptides on CoCr alloy through physisorption and covalent bonding. • Surface activation is an essential step prior to silanization to enhance peptide attachment. • Biofunctionalized surface characteristics were discussed. • RGDS, YIGSR and combination peptides display an improved HUVECs adhesion and proliferation. - Abstract: Biomimetic surface modification with peptides that have specific cell-binding moieties is a promising approach to improve endothelialization of metal-based stents. In this study, we functionalized CoCr surfaces with RGDS, REDV, YIGSR peptides and their combinations to promote endothelial cells (ECs) adhesion and proliferation. An extensive characterization of the functionalized surfaces was performed by XPS analysis, surface charge and quartz crystal microbalance with dissipation monitoring (QCM-D), which demonstrated the successful immobilization of the peptides to the surface. Cell studies demonstrated that the covalent functionalization of CoCr surfaces with an equimolar combination of RGDS and YIGSR represents the most powerful strategy to enhance the early stages of ECs adhesion and proliferation, indicating a positive synergistic effect between the two peptide motifs. Although these peptide sequences slightly increased smooth muscle cells (SMCs) adhesion, these values were ten times lower than those observed for ECs. The combination of RGDS with the REDV sequence did not show synergistic effects in promoting the adhesion or proliferation of ECs. The strategy presented in this study holds great potential to overcome clinical limitations of current metal stents by enhancing their capacity to support surface endothelialization.

Structural and magnetic properties of [001] CoCr2O4 thin films

NARCIS (Netherlands)

Guzman, Roger; Heuver, Jeroen; Matzen, Sylvia; Magen, Cesar; Noheda, Beatriz

2017-01-01

The spinel CoCr2O4 (CCO) is one of the few bulk multiferroics with net magnetic moment. However, studies on the properties of CCO thin films are scarce. Here, we investigate the interplay between microstructure and magnetism of a series of CCO epitaxial thin films by means of x-ray diffraction,

Modelizacion de la formación de recubrimientos de WC-Co por proyección HVOF sobre sustratos de cobre

Directory of Open Access Journals (Sweden)

Sobolev, V. V.

1997-10-01

Full Text Available Present paper deals with the mathematical simulation of the heat transfer between a WC-Co coating and a copper substrate during HVOF spraying. This modelling includes the investigation of temperature variation, coating solidification, melting and subsequent solidification in the substrate interfacial region and specific features of the substrate-coating thermal interaction. The results obtained are used for modelling of the development of the coating structure and adhesion during HVOF spraying of the WC-Co powder on a copper substrate. Two types of substrate were considered: smooth (polished and rough. Variations of solidification times, solidification velocity, thermal gradient and cooling velocity in the coating and substrate interfacial region are studied. Development of the amorphous and crystalline structures in the coating and of the crystalline structure in the substrate interfacial region is discussed. Behaviour of the crystal size and intercrystalline distance with respect to the thermal spray parameters and morphology of the substrate surface is analyzed. Optimal conditions for the formation of fine and dense crystalline structure are determined. Structural changes in the solid state of the substrate occurring because of heating and rapid cooling are considered. Mechanical and thermal mechanisms of development of the substrate-coating adhesion are discussed. Results obtained agree well with experimental data.

En el presente trabajo se ha investigado la simulación matemática de la transferencia de calor entre un recubrimiento de WC-Co y un sustrato de cobre durante la proyección HVOF. Este modelo incluye el estudio de la variación de termperatura, solidificación del recubrimiento, la fusión y posterior solidificación en la región interfacial del sustrato, y caracerísticas especiales de la interacción térmica sustrato- recubrimiento. Los resultados obtenidos han sido utilizados en la modelización del desarrollo de la

Theoretical studies on the electronic and optoelectronic properties of [A.2AP(w)/A*.2AP(WC)/C.2AP(w)/C*.2AP(WC)/C.A(w)/C*.A(WC)]-Au8 mismatch nucleobase complexes

Science.gov (United States)

Srivastava, Ruby

2018-01-01

The electronic and optoelectronic properties of [A.2AP(w)/A*.2AP(WC)/C.2AP(w)/C*.2AP(WC)/C.A(w)/ C*.A(WC)]-Au8 metal-mismatch nucleobase complexes are investigated by means of density functional theory and time-dependent methods. We selected these mispairs as 2-aminopurine (2AP) produces incorporation errors when binding with cytosine (C) into the wobble (w) C.2AP(w) mispair, and is tautomerised into Watson-Crick (WC)-like base mispair C*.2AP(WC) and less effectively produces A.2AP(w)/A*.2AP(WC) mispairs. The vertical ionisation potential, vertical electron affinity, hardness and electrophilicity index of these complexes have also been discussed. The modifications of energy levels and charge density distributions of the frontier orbitals are also analysed. The absorption spectra of these complexes lie in the visible region, which suggests their application in fluorescent-bio imaging. The mechanism of cooperativity effect is studied by molecular orbital potential (MEP), atoms-in-molecules (AIM) and natural bond orbital analyses. Most metalated pairs have smaller HOMO-LUMO band gaps than the isolated mismatch nucleobases which suggest interesting consequences for electron transfer through DNA duplexes.

Hydrophilic Polymer Embolism: Implications for Manufacturing, Regulation, and Postmarket Surveillance of Coated Intravascular Medical Devices.

Science.gov (United States)

Mehta, Rashi I; Mehta, Rupal I

2018-03-19

Hydrophilic polymers are ubiquitously applied as surface coatings on catheters and intravascular medical technologies. Recent clinical literature has heightened awareness on the complication of hydrophilic polymer embolism, the phenomenon wherein polymer coating layers separate from catheter and device surfaces, and may be affiliated with a range of unanticipated adverse reactions. Significant system barriers have limited and delayed reporting on this iatrogenic complication, the full effects of which remain underrecognized by healthcare providers and manufacturers of various branded devices. In 2015, the United States Food and Drug Administration acknowledged rising clinical concerns and stated that the agency would work with stakeholders to further evaluate gaps that exist in current national and international device standards for coated intravascular medical technologies. The present article reviews current knowledge on this complication as well as factors that played a role in delaying detection and dissemination of information and new knowledge once hazards and clinical risks were identified. Furthermore, organ-specific effects and adverse reaction patterns are summarized, along with implications for device manufacturing, safety assurance, and regulation. Qualitative and quantitative particulate testing are needed to optimize coated intravascular device technologies. Moreover, general enhanced processes for medical device surveillance are required for timely adverse event management and to ensure patient safety.

HFCVD Diamond-Coated Mechanical Seals

Directory of Open Access Journals (Sweden)

Raul Simões

2018-05-01

Full Text Available A mechanical seal promotes the connection between systems or mechanisms, preventing the escape of fluids to the exterior. Nonetheless, due to extreme working conditions, premature failure can occur. Diamond, due to its excellent properties, is heralded as an excellent choice to cover the surface of these devices and extend their lifetime. Therefore, the main objective of this work was to deposit diamond films over mechanical seals and test the coated seals on a water pump, under real working conditions. The coatings were created by hot filament chemical vapor deposition (HFCVD and two consecutive layers of micro- and nanocrystalline diamond were deposited. One of the main difficulties is the attainment of a good adhesion between the diamond films and the mechanical seal material (WC-Co. Nucleation, deposition conditions, and pre-treatments were studied to enhance the coating. Superficial wear or delamination of the film was investigated using SEM and Raman characterization techniques, in order to draw conclusions about the feasibility of these coatings in the WC-Co mechanical seals with the purpose of increasing their performance and life time. The results obtained gave a good indication about the feasibility of this process and the deposition conditions used, with the mechanical seals showing no wear and no film delamination after a real work environment test.

Two feasible approaches to enhance the wear behaviors of NiCrBSi coating in atmosphere and aqueous environments

Science.gov (United States)

Ye, Yuwei; Wang, Chunting; Zheng, Wenru; Xiong, Wei; Wang, Yongxin; Li, Xiaogang

2017-09-01

NiCrBSi coating was deposited successfully on the surface of 316 stainless steel substrate by means of plasma spraying. The microstructures and mechanical property were analyzed by scanning electron microscopy, x-ray diffraction, and a Vickers hardness tester. The wear performances of the coatings sliding against the GCr15 ball under ambient air and water conditions were investigated, and two feasible approaches (tungsten carbide (WC)-doping and heat treatment) were used to improve the tribological performance. Results showed that the hardness of the NiCrBSi coating increased by 12.5% and 28.5% and the porosity decreased by 26.1% and 47.8%, respectively, after WC-doping and heat treatment. During dry friction, the friction coefficient and wear rate of the NiCrBSi coating were about 0.47 and 1.4  ×  10-5 mm3 N-1 m-1, respectively. These values were higher than those obtained on other coatings. In water conditions, all coatings showed a lower friction and wear rate than that in ambient air, which was as a result of the lubrication effect of water. Significantly, with WC-doping and heat treatment, the friction coefficients of both coatings were about 18.5% and 36.7%, respectively, lower than that of the NiCrBSi coating. Furthermore, the wear rates of both coatings were about 20% and 70%, respectively, lower than that of the NiCrBSi coating.

Influence of R.F. sputter parameters on the magnetic orientation of Co-Cr layers

NARCIS (Netherlands)

Lodder, J.C.; Wielinga, T.

1984-01-01

Co-Cr layers for the perpendicular recording mode were deposited by means of RF-sputtering. The most important sputter parameters, i.e. the RF sputter high voltage VRF, the argon pressure Par and the substrate holder temperature Tsh, gave an optimum value for perpendicular orientation of the

SAE 1045 steel/WC-Co/Ni-Cu-Ni/SAE 1045 steel joints prepared by dynamic diffusion bonding: Microelectrochemical studies in 0.6 M NaCl solution

International Nuclear Information System (INIS)

Andreatta, Francesco; Matesanz, Laura; Akita, Adriano H.; Paussa, Luca; Fedrizzi, Lorenzo; Fugivara, Cecilio S.; Gomez de Salazar, Jose M.; Benedetti, Assis V.

2009-01-01

Corrosion of SAE 1045 steel/WC-Co/Ni-Cu-Ni/SAE 1045 steel interfaces was investigated in 0.6 M NaCl solution using an electrochemical microcell, which enables local electrochemical characterization at the micrometer scale. Two pieces of steel, one with a WC-Co coating covered with Ni (12 μm) and Cu (5 μm) layers, and the other with a Ni (15 μm) layer, were welded by dynamic diffusion bonding. A WC-Co coating was applied to the steel by the high velocity oxygen-fuel process, and Ni-Cu and Ni layers by electroplating. Polarization curves were recorded using an electrochemical microcell. Different regions of welded samples were investigated, including steel, cermet coating, and steel/cermet and steel/Ni-Cu-Ni/cermet interfaces. Optical and electronic microscopes were employed to study the corroded regions. Potentiodynamic polarization curves obtained using the microcell revealed that the base metal was more susceptible to corrosion than the cermet. In addition, cermet steel/cermet and steel/Ni-Cu-Ni/cermet joints exhibited different breakdown potentials. Steel was strongly corroded in the regions adjacent to the interfaces, while the cermet was less corroded. Iron oxides/hydroxides and chloride salts were the main corrosion products of steel. After removal of the superficial layer of corrosion products, iron oxides were mainly observed. Chloride ions were detected mainly on a copper-enriched layer placed between two Ni-enriched layers.

Resource recovery of WC-Co cermet using hydrothermal oxidation technique

International Nuclear Information System (INIS)

Gao Ningfeng; Inagaki, F.; Sasai, R.; Itoh, H.; Watari, K.

2005-01-01

WC-Co cermet is widely used in industrial applications such as cutting tools, dies, wear parts and so on. It is of great importance to establish the recycling process for the precious metal resources contained in WC-Co cermet, because all these metals used in Japan are imported. In this paper we reported a hydrothermal oxidation technique using nitric acid for the reclamation of WC and Co. The WC-Co cermet specimens with various WC particle sizes and Co contents were hydrothermally treated in HNO 3 aqueous solutions at temperatures of 110-200 C for durations of 6-240 h. The Co was preferentially leached out into the acidic solution, while the WC was oxidized to insoluble WO 3 hydrate which was subsequently separated by filtration. The hydrothermal treatment parameters such as solvent concentrations, treatment temperatures, holding time were optimized in respect to different kinds of WC-Co cermets. A hydrothermal oxidation treatment in 3M HNO 3 aqueous solution at 150 C for 24 h was capable of fully disintegrating the cermet chip composed of coarse WC grains of 1-5 μm in size with 20 wt% of Co as binder. While the more oxidation resistant specimen composed of fine WC grains of 0.5-1.0 μm in size with 13 wt% of Co, was completely disintegrated by a treatment in 7 M HNO 3 aqueous solution at 170 C for 24 h. The filtered solid residues were composed of fine WO 3 .0.33H 2 O powder and a small amount of WO 3 . The recovered WO 3 .0.33H 2 O powder can be easily returned to the industrial process for the synthesis of WC powder so that the overall recycling cost can be possibly lowered. (orig.)

Atomic layer deposition synthesis and evaluation of core–shell Pt-WC electrocatalysts

International Nuclear Information System (INIS)

Hsu, Irene J.; Chen, Jingguang G.; Jiang, Xiaoqiang; Willis, Brian G.

2015-01-01

Pt-WC core shell particles were produced using atomic layer deposition (ALD) to deposit Pt layers onto WC particle substrates. A range of Pt depositions were used to determine the growth mechanism for the Pt-WC powder system. TEM imaging and Cu stripping voltammetry found that Pt ALD growth on WC powder substrates was similar to that on WC thin films. However, excess free carbon was found to affect Pt ALD by blocking adsorption sites on WC. The Pt-WC samples were evaluated for the oxygen reduction reaction using a rotating disk electrode to obtain quantitative activity information. The mass and specific activities for the 30 and 50 ALD cycle samples were found to be comparable to a 10 wt. % Pt/C catalyst. However, higher overpotentials and lower limiting currents were observed with ALD Pt-WC compared to Pt/C catalysts, indicating that the oxygen reduction mechanism is not as efficient on Pt-WC as on bulk Pt. Additionally, these Pt-WC catalysts were used to demonstrate hydrogen evolution reaction activity and were found to perform as well as bulk Pt catalyst but with a fraction of the Pt loading, in agreement with the previous work on Pt-WC thin film catalysts

Microstructural study of tungsten influence on Co-Cr alloys

International Nuclear Information System (INIS)

Karaali, A.; Mirouh, K.; Hamamda, S.; Guiraldenq, P.

2005-01-01

Alloying elements, such as W, Mo, Mn,..., are of a great importance in the preoxidation of dental alloys and, consequently, on the ceramic/metal bond quality. This study deals with the effect of tungsten addition on the microstructural state of Co-Cr dental alloys, before the ceramisation process. These materials were prepared by unidirectional solidification. Their characterization has been carried out, using transmission electron microscopy (TEM) and X-ray diffraction. It shows that the addition of tungsten up to 8 wt.% induces structural transformations, which are believed to be linked to the added amount of tungsten

Carbon-coated tungsten and molybdenum carbides for electrode of electrochemical capacitor

International Nuclear Information System (INIS)

Morishita, Takahiro; Soneda, Yasushi; Hatori, Hiroaki; Inagaki, Michio

2007-01-01

New electrode materials for electrochemical capacitor, tungsten carbide WC and molybdenum carbide Mo 2 C coated by porous carbon, were prepared through a simple heat treatment of the mixture of K 2 WO 4 and K 2 MoO 4 , respectively, with hydroxy propyl cellulose. Carbide changed to hydroxide during the 1st charge-discharge cycle in H 2 SO 4 aqueous electrolyte, which showed redox reaction in further charge-discharge cycles, in addition to electric double layers of the carbon formed on its surface. The carbon-coated carbide gave a high capacitance in 1 mol L -1 H 2 SO 4 electrolyte, as about 350 F cm -3 for carbon-coated WC and 550-750 F cm -3 for carbon-coated Mo 2 C. Coating of carbon inhibits the growth of carbide particles during their formation, of which the small particle size make possible to complete transformation to hydroxides during the 1st charge-discharge cycle, and also disturbs the agglomeration of tungsten and molybdenum hydroxides during charge-discharge cycles, as well as porous carbon coated act as electrode material for electric double layers of electrolyte ions

The Modeling of Nitrogen Mass Transport in CoCr Alloys

Directory of Open Access Journals (Sweden)

Petraitienė Akvilė

2016-12-01

Full Text Available The kinetics of plasma nitriding of CoCr alloy below temperatures of nitrides formation and mechanisms of nitrogen penetration are analyzed by proposed kinetic modeling in this article. Proposed nitrogen diffusion model is based on the trapping – detrapping (TD model and developed taking into account the effect of the concentration dependent diffusivity of nitrogen, nitrogen adsorption on the surface of alloy and surface swelling process. The model indicates the influence of chromium atoms to nitrogen atoms diffusivity. The model consists of time and depth dependent diffusion, which is described by a partial differential equation, and it is solved by using Crank – Nicolson finite difference method. By fitting of experimental nitrogen depth profiles, it is shown that nitrogen diffusion coefficient varies with nitrogen concentration according to Einstein-Smoluchowski relation. Nitrogen depth profiles in plasma nitrided medical grade CoCr alloy (ISO 5831 – 12 at T = 400 °C for 1, 4 and 20 hours calculated on the basis of this model are in good agreement with experimental nitrogen profiles. Furthermore, the swelling process is showed and analyzed, derived the dependency of swelling rate on nitriding duration – the swelling rate is inversely proportional to the square root of nitriding duration. The obtained diffusion coefficient value and the swelling process rates satisfy the experimental data form Ref. The derived model explains physical processes during plasma nitriding and allows obtaining nitrogen depth profiles for any requisite nitriding duration.

The Nature of Bonding in WC and WN

Institute of Scientific and Technical Information of China (English)

无

2001-01-01

The nature of bonding in the title compounds has been studied by using CASSCF and FOCl techniques. The ground states of WC and WN are found to be 3Δ and 4∑- state arising primarily from:...1σ2σ21π41δ13σ1 and ...1σ2σ21π41δ23σ1 configuration respectively. WC shows a strong character of covalent bond while WN have obvious character of ionic bond and the dissociation energy of WN is larger than that of WC (6.15 and 5.41 eV respective).

Investigations on the corrosion resistance of metallic bipolar plates (BPP) in proton exchange membrane fuel cells (PEMFC) - understanding the effects of material, coating and manufacturing

Science.gov (United States)

Dur, Ender

Polymer Electrolyte Membrane Fuel Cell (PEMFC) systems are promising technology for contributing to meet the deficiency of world`s clean and sustainable energy requirements in the near future. Metallic bipolar plate (BPP) as one of the most significant components of PEMFC device accounts for the largest part of the fuel cell`s stack. Corrosion for metallic bipolar plates is a critical issue, which influences the performance and durability of PEMFC. Corrosion causes adverse impacts on the PEMFC`s performance jeopardizing commercialization. This research is aimed at determining the corrosion resistance of metallic BPPs, particularly stainless steels, used in PEMFC from different aspects. Material selection, coating selection, manufacturing process development and cost considerations need to be addressed in terms of the corrosion behavior to justify the use of stainless steels as a BPP material in PEMFC and to make them commercially feasible in industrial applications. In this study, Ti, Ni, SS304, SS316L, and SS 430 blanks, and BPPs comprised of SS304 and SS316L were examined in terms of the corrosion behavior. SS316L plates were coated to investigate the effect of coatings on the corrosion resistance performance. Stamping and hydroforming as manufacturing processes, and three different coatings (TiN, CrN, ZrN) applied via the Physical Vapor Deposition (PVD) method in three different thicknesses were selected to observe the effects of manufacturing processes, coating types and coating thicknesses on the corrosion resistance of BPP, respectively. Uncoated-coated blank and formed BPP were subjected to two different corrosion tests: potentiostatic and potentiodynamic. Some of the substantial results: 1- Manufacturing processes have an adverse impact on the corrosion resistance. 2- Hydroformed plates have slightly higher corrosion resistance than stamped samples. 3- BPPs with higher channel size showed better corrosion resistance. 4- Since none of the uncoated samples

Tribological coating of titanium alloys by laser processing

Science.gov (United States)

Pang, Wang

Titanium-based alloys have been used for aerospace materials for many years. Recently, these alloys are now being increasingly considered for automotive, industrial and consumer applications. Their excellent creep resistance, corrosion resistance and relative higher specific strength ratio are attractive for many applications. However, the main obstacle for the wide adoption of Ti alloys in various industries is their poor tribological properties. In slide wear, Ti deforms and adhesive wear readily occurs. Their poor tribological properties are mainly due to low hardness and absolute values of tensile and shear strength. Different surface modification techniques have been studied in order to improve the tribological characteristics of Ti alloys, i.e. PVD, nitrding, carburizing, boriding, plating etc. Coatings produced by these techniques have their own limitations such as thermal distortion and grain growth. A different approach is to introduce hard particles in the Ti alloy matrix to form a MMC coating, which has tailor-made hardness and wear resistance properties. Laser cladding or laser alloying techniques facilitate the fabrication of surface MMC on Ti alloys without thermal distortion to the substrate. In this project, the fabrication of hard and wear resistant layers of metal matrix composite on titanium alloys substrate by laser surface alloying was investigated. Powder mixtures of Mo and WC were used to form the MMC layer. By optimizing the processing parameters and pre-placed powder mixture compositions, surface MMC of different properties have been successfully fabricated on CP-Ti and Ti6A14V respectively. The structure and characteristics of the MMC surface were investigated by metallography, SEM, XRD, and E-DAX. It was found that the hardness of the laser alloyed Mo/WC MMC surface was 300% higher than that of the CP-Ti substrate Excellent metallurgical bonding with the MMC layer of the substrate has been achieved. The relative kinetic frictional tests

Reactive Sintering of Bimodal WC-Co Hardmetals

Directory of Open Access Journals (Sweden)

Marek Tarraste

2015-09-01

Full Text Available Bimodal WC-Co hardmetals were produced using novel technology - reactive sintering. Milled and activated tungsten and graphite powders were mixed with commercial coarse grained WC-Co powder and then sintered. The microstructure of produced materials was free of defects and consisted of evenly distributed coarse and fine tungsten carbide grains in cobalt binder. The microstructure, hardness and fracture toughness of reactive sintered bimodal WC-Co hardmetals is exhibited. Developed bimodal hardmetal has perspective for demanding wear applications for its increased combined hardness and toughness. Compared to coarse material there is only slight decrease in fracture toughness (K1c is 14.7 for coarse grained and 14.4 for bimodal, hardness is increased from 1290 to 1350 HV units.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7511

Corrosion behaviour and surface analysis of a Co-Cr and two Ni-Cr dental alloys before and after simulated porcelain firing.

Science.gov (United States)

Qiu, Jing; Yu, Wei-Qiang; Zhang, Fu-Qiang; Smales, Roger J; Zhang, Yi-Lin; Lu, Chun-Hui

2011-02-01

This study evaluated the corrosion behaviour and surface properties of a commercial cobalt-chromium (Co-Cr) alloy and two nickel-chromium (Ni-Cr) alloys [beryllium (Be)-free and Be-containing] before and after a simulated porcelain-firing process. Before porcelain firing, the microstructure, surface composition and hardness, electrochemical corrosion properties, and metal-ion release of as-cast alloy specimens were examined. After firing, similar alloy specimens were examined for the same properties. In both as-cast and fired conditions, the Co-Cr alloy (Wirobond C) showed significantly more resistance to corrosion than the two Ni-Cr alloys. After firing, the corrosion rate of the Be-free Ni-Cr alloy (Stellite N9) increased significantly, which corresponded to a reduction in the levels of Cr, molybdenum (Mo), and Ni in the surface oxides and to a reduction in the thickness of the surface oxide film. The corrosion properties of the Co-Cr alloy and the Be-containing Ni-Cr alloy (ChangPing) were not significantly affected by the firing process. Porcelain firing also changed the microstructure and microhardness values of the alloys, and there were increases in the release of Co and Ni ions, especially for Ni from the Be-free Ni-Cr alloy. Thus, the corrosion rate of the Be-free Ni-Cr alloy increased significantly after porcelain firing, whereas the firing process had little effect on the corrosion susceptibility of the Co-Cr alloy and the Be-containing Ni-Cr alloy. © 2011 Eur J Oral Sci.

Micromechanics of fracture in WC-Co hardmetals

International Nuclear Information System (INIS)

Dusza, J.; Parilak, L.

1986-01-01

A study has been made in WC-Co cemented carbides with grain sizes of 2.1 - 3.6 μm and 13 - 32 vol% Co, of the relationship between the fracture toughness and microstructural parameters and micromechanisms of fracture. Regression analyses have been used to derive empirical relationships between fracture toughness, and the binder spacing, the contiguity and the relative proportions of fracture in the binder phase and between contiguous WC grains

Infrared processed Cu composites reinforced with WC particles

International Nuclear Information System (INIS)

Deshpande, P.K.; Li, J.H.; Lin, R.Y.

2006-01-01

Copper matrix composites with WC particle reinforcements have been prepared with an innovative infrared infiltration technique. The volume content of the reinforcement particles in the composite is about 53%. The relative composite density of as high as 99.9% has been obtained with this process. The electric conductivity of composites prepared in this study as determined by a four-point probe method, is similar to commercially available Cu/W composites containing 52 vol% tungsten. Microhardness, microstructure and wear resistance of the composites were also determined. The microstructure of Cu/WC composite reveals excellent wetting between the two constituent phases, WC and copper. The microhardness values of all completely infiltrated Cu/WC composites were in the range of 360-370 HV which is significantly higher than the microhardness of pure copper, 65 HV. Wear resistance of the composites was determined with a pin on disk wear test technique. The wear test results show that composites prepared in this study performed much better than those commercially available Cu/W composites by more than two-fold against silicon carbide abrasive disks

Overview of PVD wear resistant coatings

International Nuclear Information System (INIS)

Teeter, F.J.

1999-01-01

The combined functionality of wear-resistant and low-friction multilayer coatings has widened application possibilities for a new generation of coated tools. For the first time tool wear mechanisms are comprehensively addressed both at the cutting edge and contact areas away from the edge where chip evacuation is facilitated. Since its recent market introduction a combined TiA1N and WC/C PVD coating has been proven to increase cutting performance in various metal cutting operations, notably drilling and tapping of steels and aluminum alloys. Significant improvements have been obtained under dry as well as with coolant conditions. The results of laboratory metal cutting tests and field trials to date will be described. Correlations between chip formation / wear mechanisms and coating properties are given to explain the effectiveness of this coating. (author)

Hot isostatic pressing of nanosized WC-Co hardmetals

International Nuclear Information System (INIS)

Azcona, I.; Ordonez, A.; Sanchez, J.M.; Castro, F.; Dominguez, L.

2001-01-01

A new technique based on hot isostatic pressing (HIP) has been developed to produce dense nanosized WC-Co hardmetals without the addition of grain growth inhibitors. The glass encapsulation process is the key for the effective application of isostatic pressure at temperatures well below those usually required for reaching the closed porosity state in the WC-Co system. Fully dense WC-Co samples with cobalt contents ranging from 10 to 12 wt. % have been obtained by this technique at temperatures between 1000 o C and 1200 o C with 150 MPa of applied isostatic pressure for 30 minutes. The role of isostatic pressure on the activation of densification mechanisms is discussed. (author)

Laser cladding of wear resistant metal matrix composite coatings

International Nuclear Information System (INIS)

Yakovlev, A.; Bertrand, Ph.; Smurov, I.

2004-01-01

A number of coatings with wear-resistant properties as well as with a low friction coefficient are produced by laser cladding. The structure of these coatings is determined by required performance and realized as metal matrix composite (MMC), where solid lubricant serves as a ductile matrix (e.g. CuSn), reinforced by appropriate ceramic phase (e.g. WC/Co). One of the engineered coating with functionally graded material (FGM) structure has a dry friction coefficient 0.12. Coatings were produced by coaxial injection of powder blend into the zone of laser beam action. Metallographic and tribological examinations were carried out confirming the advanced performance of engineered coatings

Feasibility of using Big Area Additive Manufacturing to Directly Manufacture Boat Molds

Energy Technology Data Exchange (ETDEWEB)

Post, Brian K. [ORNL; Chesser, Phillip C. [ORNL; Lind, Randall F. [ORNL; Sallas, Matthew R. [ORNL; Love, Lonnie J. [ORNL

2018-01-01

The goal of this project was to explore the feasibility of using Big Area Additive Manufacturing (BAAM) to directly manufacture a boat mold without the need for coatings. All prior tooling projects with BAAM required the use to thick coatings to overcome the surface finish limitations of the BAAM process. While the BAAM process significantly lowers the cost of building the mold, the high cost element rapidly became the coatings (cost of the material, labor on coating, and finishing). As an example, the time and cost to manufacture the molds for the Wind Turbine project with TPI Composites Inc. and the molds for the submarine project with Carderock Naval Warfare Systems was a fraction of the time and cost of the coatings. For this project, a catamaran boat hull mold was designed, manufactured, and assembled with an additional 0.15” thickness of material on all mold surfaces. After printing, the mold was immediately machined and assembled. Alliance MG, LLC (AMG), the industry partner of this project, experimented with mold release agents on the carbon-fiber reinforced acrylonitrile butadiene styrene (CF ABS) to verify that the material can be directly used as a mold (rather than needing a coating). In addition, for large molds (such as the wind turbine mold with TPI Composites Inc.), the mold only provided the target surface. A steel subframe had to be manufactured to provide structural integrity. If successful, this will significantly reduce the time and cost necessary for manufacturing large resin infusion molds using the BAAM process.

Nanocomposite tribological coatings with "chameleon" surface adaptation

Science.gov (United States)

Voevodin, A. A.; Fitz, T. A.; Hu, J. J.; Zabinski, J. S.

2002-07-01

Nanocomposite tribological coatings were designed to respond to changing environmental conditions by self-adjustment of their surface properties to maintain good tribological performance in any environment. These smart coatings have been dubbed "chameleon" because, analogous to a chameleon changing its skin color to avoid predators, the coating changes its "skin" chemistry and structure to avoid wear. The concept was originally developed using WC, diamondlike carbon, and WS2 material combination for adaptation to a humid/dry environment cycling. In order to address temperature variation, nanocomposite coatings made of yttria-stabilized zirconia (YSZ) in a gold matrix were developed with encapsulated nanosized reservoirs of MoS2 and diamondlike carbon (DLC). Coatings were produced using a combination of laser ablation and magnetron sputtering. They were characterized by x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, x-ray energy dispersive spectroscopy, and micro-Raman spectroscopy. Results were correlated with mechanical and tribological characterization. Coating hardness was evaluated using nanoindentation, while coating adhesion and toughness were estimated using scratch and Vickers indentation tests. Friction and wear endurance measurements of YSZ/Au/MoS2/DLC coatings against steel and Si3N4 balls were performed at room temperature in controlled humidity air, dry nitrogen, and vacuum environments, as well as at 500 degC in air. Depending on the environment, coating friction surface changed its chemistry and structure between (i) graphitic carbon for sliding in humid air [coating friction coefficients (c.o.f. 0.10-0.15)], (ii) hexagonal MoS2 for sliding in dry N2 and vacuum (c.o.f. 0.02-0.05), and (iii) metallic Au for sliding in air at 500 degC (c.o.f. 0.10-0.20). The unique coating skin adaptation realized with YSZ/Au/MoS2/DLC and WC/DLC/WS composites proves a universal applicability of the chameleon design concept

Nanocomposite tribological coatings with 'chameleon' surface adaptation

International Nuclear Information System (INIS)

Voevodin, A.A.; Fitz, T.A.; Hu, J.J.; Zabinski, J.S.

2002-01-01

Nanocomposite tribological coatings were designed to respond to changing environmental conditions by self-adjustment of their surface properties to maintain good tribological performance in any environment. These smart coatings have been dubbed 'chameleon' because, analogous to a chameleon changing its skin color to avoid predators, the coating changes its 'skin' chemistry and structure to avoid wear. The concept was originally developed using WC, diamondlike carbon, and WS 2 material combination for adaptation to a humid/dry environment cycling. In order to address temperature variation, nanocomposite coatings made of yttria-stabilized zirconia (YSZ) in a gold matrix were developed with encapsulated nanosized reservoirs of MoS 2 and diamondlike carbon (DLC). Coatings were produced using a combination of laser ablation and magnetron sputtering. They were characterized by x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, x-ray energy dispersive spectroscopy, and micro-Raman spectroscopy. Results were correlated with mechanical and tribological characterization. Coating hardness was evaluated using nanoindentation, while coating adhesion and toughness were estimated using scratch and Vickers indentation tests. Friction and wear endurance measurements of YSZ/Au/MoS 2 /DLC coatings against steel and Si 3 N 4 balls were performed at room temperature in controlled humidity air, dry nitrogen, and vacuum environments, as well as at 500 deg. C in air. Depending on the environment, coating friction surface changed its chemistry and structure between (i) graphitic carbon for sliding in humid air [coating friction coefficients (c.o.f. 0.10-0.15)], (ii) hexagonal MoS 2 for sliding in dry N 2 and vacuum (c.o.f. 0.02-0.05), and (iii) metallic Au for sliding in air at 500 deg. C (c.o.f. 0.10-0.20). The unique coating skin adaptation realized with YSZ/Au/MoS 2 /DLC and WC/DLC/WS composites proves a universal applicability of the chameleon design

Ceramic Defects in Metal-Ceramic Fixed Dental Prostheses Made from Co-Cr and Au-Pt Alloys: A Retrospective Study.

Science.gov (United States)

Mikeli, Aikaterini; Boening, Klaus W; Lißke, Benjamin

2015-01-01

Ceramic defects in porcelain-fused-to-metal (PFM) restorations may depend on framework alloy type. This study assessed ceramic defects on cobalt-chromium- (Co-Cr-) and gold-platinum- (Au-Pt-) based PFM restorations. In this study, 147 Co-Cr-based and 168 Au-Pt-based PFM restorations inserted between 1998 and 2010 (139 patients) were examined for ceramic defects. Detected defects were assigned to three groups according to clinical defect relevance. Ceramic defect rates (Co-Cr-based: 12.9%; Au-Pt-based: 7.2%) revealed no significant difference but a strong statistical trend (U test, P = .082). Most defects were of little clinical relevance. Co-Cr PFM restorations may be at higher risk for ceramic defects compared to Au-Pt-based restorations.

Tribological behavior of W-DLC coated rubber seals

NARCIS (Netherlands)

Pei, Y.T.; Bui, X.L.; Zhou, X.B.; Hosson, J.Th.M. De

2008-01-01

Tungsten-containing diamond-like carbon (W-DLC) coatings have been deposited on FKM (fluorocarbon) and HNBR (hydrogenated nitrile butadiene) rubbers via unbalanced magnetron reactive sputtering from a WC target in a C2H2/Ar plasma. The surface morphology and fracture cross sections of uncoated and

Phase size distribution in WC/Co hardmetal

International Nuclear Information System (INIS)

Roebuck, B.; Bennett, E.G.

1986-01-01

A high-resolution field emission scanning electron microscope was used to perform accurate quantitative metallography on a variety of WC/Co hardmetals. Particular attention was paid to obtaining the mean size and size distribution of the cobalt phase by linear analysis. Cobalt regions are frequently submicron and difficult to resolve adequately by conventional methods. The WC linear intercept distributions, and contiguity were also measured at the same time. The results were used to examine the validity of theoretic derivations of cobalt intercept size

Simulation of microstructure evolution in fused-coating additive manufacturing based on phase field approach

Directory of Open Access Journals (Sweden)

Ru-wei Geng

2017-11-01

Full Text Available The mechanical properties of metal components are determined by the solidification behaviour and microstructure. A quantitative phase field model is used to investigate the microstructure evolution of fused-coating additive manufacturing, by which to improve the quality of deposition. During the fused-coating process, the molten metal in a crucible flows out of a nozzle and then reaches the substrate. The solidification happens at the moment when the molten metal comes into contact with substrate moving in three-dimensional space. The macroscopic heat transfer model of fused-coating is established to get the temperature field considered as the initial temperature boundary conditions in the phase field model. The numerical and experimental results show that the morphology of grains varies with different solidification environments. Columnar grains are observed during the early period at the bottom of fused-coating layer and the equiaxed grains appear subsequently ahead of the columnar grains. Columnar dendrites phase field simulations about the grains morphology and solute distribution are conducted considering the solidification environments. The simulation results are in good agreement with experimental results.

Erosion protection of carbon-epoxy composites by plasma-sprayed coatings

International Nuclear Information System (INIS)

Alonso, F.; Fagoaga, I.; Oregui, P.

1991-01-01

This paper deals with the production of plasma-sprayed erosion-resistant coatings on carbon-fibre - epoxy composites, and the study of their erosion behaviour. The heat sensitivity of the composite substrate requires a specific spraying procedure in order to avoid its degradation. In addition, several bonding layers were studied to allow spraying of the protective coatings. Two different functional coatings were sprayed onto an aluminium-glass bonding layer, a WC-12Co cermet and an Al 2 O 3 ceramic oxide. The microstructure and properties of these coatings were studied and their erosion behaviour determined experimentally in an erosion-testing device. (orig.)

Effects of sintering temperature on the microstructural evolution and wear behavior of WCp reinforced Ni-based coatings

Science.gov (United States)

Chen, Chuan-hui; Bai, Yang; Ye, Xu-chu

2014-12-01

This article focuses on the microstructural evolution and wear behavior of 50wt%WC reinforced Ni-based composites prepared onto 304 stainless steel substrates by vacuum sintering at different sintering temperatures. The microstructure and chemical composition of the coatings were investigated by X-ray diffraction (XRD), differential thermal analysis (DTA), scanning and transmission electron microscopy (SEM and TEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The wear resistance of the coatings was tested by thrust washer testing. The mechanisms of the decomposition, dissolution, and precipitation of primary carbides, and their influences on the wear resistance have been discussed. The results indicate that the coating sintered at 1175°C is composed of fine WC particles, coarse M6C (M=Ni, Fe, Co, etc.) carbides, and discrete borides dispersed in solid solution. Upon increasing the sintering temperature to 1225°C, the microstructure reveals few incompletely dissolved WC particles trapped in larger M6C, Cr-rich lamellar M23C6, and M3C2 in the austenite matrix. M23C6 and M3C2 precipitates are formed in both the γ/M6C grain boundary and the matrix. These large-sized and lamellar brittle phases tend to weaken the wear resistance of the composite coatings. The wear behavior is controlled simultaneously by both abrasive wear and adhesive wear. Among them, abrasive wear plays a major role in the wear process of the coating sintered at 1175°C, while the effect of adhesive wear is predominant in the coating sintered at 1225°C.

Insulator coated magnetic nanoparticulate composites with reduced core loss and method of manufacture thereof

Science.gov (United States)

Zhang, Yide (Inventor); Wang, Shihe (Inventor); Xiao, Danny (Inventor)

2004-01-01

A series of bulk-size magnetic/insulating nanostructured composite soft magnetic materials with significantly reduced core loss and its manufacturing technology. This insulator coated magnetic nanostructured composite is comprises a magnetic constituent, which contains one or more magnetic components, and an insulating constituent. The magnetic constituent is nanometer scale particles (1-100 nm) coated by a thin-layered insulating phase (continuous phase). While the intergrain interaction between the immediate neighboring magnetic nanoparticles separated by the insulating phase (or coupled nanoparticles) provide the desired soft magnetic properties, the insulating material provides the much demanded high resistivity which significantly reduces the eddy current loss. The resulting material is a high performance magnetic nanostructured composite with reduced core loss.

Characterisation of WC-12Co thermal spray powders and HPHVOF wear resistant coatings

CSIR Research Space (South Africa)

Lovelock, HDL

1998-01-01

Full Text Available were selected for the deposition of thermal spray coatings using the JP 5000 high pressure high velocity oxyfuel (HPHVOF) system. Dry sand rubber wheel abrasion tests were performed on the coatings in order to determine the effect of powder...

Hard Chrome-Coated and Fullerene-Doped Metal Surfaces in Orthopedic Bearings.

Science.gov (United States)

Sonntag, Robert; Feige, Katja; Dos Santos, Claudia Beatriz; Kretzer, Jan Philippe

2017-12-20

Metal-on-metal bearings for total hip replacements have been introduced as an alternative to polyethylene in young and more active patients. These have, however, been shown to be prone to implant malpositioning and have been limited by some specific design features. In that context, coatings present an option to increase wear resistance by keeping the high fracture strength of the metal substrate. A custom-made electroplating setup was designed for the coating of CoCr substrates using (a) an industrial standard chromium electrolyte; (b) a custom-made hexavalent chromium (Cr 6+ ) electrolyte with a reduced chromium trioxide (CrO₃) content, both without solid additives and (c) with the addition of fullerene (C 60 ) nanoparticles; and (d) a trivalent chromium (Cr 3+ ) electrolyte with C 60 addition. All coatings showed an increase in microhardness compared with the metal substrate. Trivalent coatings were thinner (10 µm) than the hexavalent coatings (23-40 µm) and resulted in increased roughness and crack density. Wear was found to be reduced for the hexavalent chromium coatings by 70-84% compared with the CoCr-CoCr reference bearing while the trivalent chromium coating even increased wear by more than 300%. The addition of fullerenes to the electrolyte did not show any further tribological effect.

Hard Chrome-Coated and Fullerene-Doped Metal Surfaces in Orthopedic Bearings

Directory of Open Access Journals (Sweden)

Robert Sonntag

2017-12-01

Full Text Available Metal-on-metal bearings for total hip replacements have been introduced as an alternative to polyethylene in young and more active patients. These have, however, been shown to be prone to implant malpositioning and have been limited by some specific design features. In that context, coatings present an option to increase wear resistance by keeping the high fracture strength of the metal substrate. A custom-made electroplating setup was designed for the coating of CoCr substrates using (a an industrial standard chromium electrolyte; (b a custom-made hexavalent chromium (Cr6+ electrolyte with a reduced chromium trioxide (CrO3 content, both without solid additives and (c with the addition of fullerene (C60 nanoparticles; and (d a trivalent chromium (Cr3+ electrolyte with C60 addition. All coatings showed an increase in microhardness compared with the metal substrate. Trivalent coatings were thinner (10 µm than the hexavalent coatings (23–40 µm and resulted in increased roughness and crack density. Wear was found to be reduced for the hexavalent chromium coatings by 70–84% compared with the CoCr–CoCr reference bearing while the trivalent chromium coating even increased wear by more than 300%. The addition of fullerenes to the electrolyte did not show any further tribological effect.

Optimization of Cvd Diamond Coating Type on Micro Drills in Pcb Machining

Science.gov (United States)

Lei, X. L.; He, Y.; Sun, F. H.

2016-12-01

The demand for better tools for machining printed circuit boards (PCBs) is increasing due to the extensive usage of these boards in digital electronic products. This paper is aimed at optimizing coating type on micro drills in order to extend their lifetime in PCB machining. First, the tribotests involving micro crystalline diamond (MCD), nano crystalline diamond (NCD) and bare tungsten carbide (WC-Co) against PCBs show that NCD-PCB tribopair exhibits the lowest friction coefficient (0.35) due to the unique nano structure and low surface roughness of NCD films. Thereafter, the dry machining performance of the MCD- and NCD-coated micro drills on PCBs is systematically studied, using diamond-like coating (DLC) and TiAlN-coated micro drills as comparison. The experiments show that the working lives of these micro drills can be ranked as: NCD>TiAlN>DLC>MCD>bare WC-Co. The superior cutting performance of NCD-coated micro drills in terms of the lowest flank wear growth rate, no tool degradation (e.g. chipping, tool tipping) appearance, the best hole quality as well as the lowest feed force may come from the excellent wear resistance, lower friction coefficient against PCB as well as the high adhesive strength on the underneath substrate of NCD films.

Comparison and evaluation of marginal and internal gaps in cobalt-chromium alloy copings fabricated using subtractive and additive manufacturing.

Science.gov (United States)

Kim, Dong-Yeon; Kim, Ji-Hwan; Kim, Hae-Young; Kim, Woong-Chul

2018-01-01

To evaluate the marginal and internal gaps of cobalt-chromium (Co-Cr) alloy copings fabricated using subtractive and additive manufacturing. A study model of an abutment tooth 46 was prepared by a 2-step silicone impression with dental stone. Fifteen stereolithography files for Co-Cr alloy copings were compiled using a model scanner and dental CAD software. Using the lost wax (LW), wax block (WB), soft metal block (SMB), microstereolithography (μ-SLA), and selected laser melting (SLM) techniques, 15 Co-Cr alloy copings were fabricated per group. The marginal and internal gaps of these Co-Cr alloy copings were measured using a digital microscope (160×), and the data obtained were analyzed using the non-parametric Kruskal-Wallis H-test and post-hoc Mann-Whitney U-test with Bonferroni correction. The mean values of the marginal, axial wall, and occlusal gaps were 91.8, 83.4, and 163μm in the LW group; 94.2, 77.5, and 122μm in the WB group; 60.0, 79.4, and 90.8μm in the SMB group; 154, 72.4, and 258μm in the μ-SLA group; and 239, 73.6, and 384μm in the SLM group, respectively. The differences in the marginal and occlusal gaps between the 5 groups were statistically significant (P<.05). The marginal gaps of the LW, WB, and SMB groups were within the clinically acceptable limit, but further improvements in the μ-SLA and SLM approaches may be required prior to clinical implementation. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Development and evaluation of two PVD-coated β-titanium orthodontic archwires for fluoride-induced corrosion protection.

Science.gov (United States)

Krishnan, Vinod; Krishnan, Anand; Remya, R; Ravikumar, K K; Nair, S Asha; Shibli, S M A; Varma, H K; Sukumaran, K; Kumar, K Jyothindra

2011-04-01

The present research was aimed at developing surface coatings on β titanium orthodontic archwires capable of protection against fluoride-induced corrosion. Cathodic arc physical vapor deposition PVD (CA-PVD) and magnetron sputtering were utilized to deposit thin films of titanium aluminium nitride (TiAlN) and tungsten carbide/carbon (WC/C) coatings on β titanium orthodontic archwires. Uncoated and coated specimens were immersed in a high fluoride ion concentration mouth rinse, following a specially designed cycle simulating daily use. All specimens thus obtained were subjected to critical evaluation of parameters such as electrochemical corrosion behaviour, surface analysis, mechanical testing, microstructure, element release, and toxicology. The results confirm previous research that β titanium archwires undergo a degradation process when in contact with fluoride mouth rinses. The study confirmed the superior nature of the TiAlN coating, evident as many fewer changes in properties after fluoride treatment when compared with the WC/C coating. Thus, coating with TiAlN is recommended in order to reduce the corrosive effects of fluorides on β titanium orthodontic archwires. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

[Comparison of clinical effects of Co-Cr alloy cast post-core and everStick fiber post in restoration of labially or lingually inclined maxillary central incisor].

Science.gov (United States)

Qian, Yu-Mei; Zhong, Qun; Chen, Shuang

2017-02-01

To compare the clinical effect of Co-Cr alloy cast post-core and everStick fiber post in restoration of maxillary central incisor with labial or lingual inclination, and provide theoretical basis for clinical application. Ninety-seven labially or lingually inclined maxillary central incisors were treated in our hospital from March 2012 to March 2014. The patients were randomly divided into group A (n=49) and group B (n=48), and received post -core and crown restoration. Patients in group A underwent Co-Cr alloy cast post and core restoration and patients in group B underwent everStick fiber post and core restoration. After two-year of follow-up, root fracture, post break, crown or post dislodgment and gingival marginal discoloration were recorded and analyzed using SPSS 19.0 software package. Chi-square test showed that the success rate of restoration was significantly different between 2 groups (P<0.05). The incidence of root fracture and gingival marginal discoloration of Co-Cr alloy cast post-core was higher than that of everStick fiber post, but there was no significant difference in the incidence of post break, crown or post dislodgment. EverStick fiber post is better than Co-Cr alloy cast post and core to prevent root fracture and gingival marginal discoloration. Its fracture pattern is repairable and favorable for preserving tooth.

Cavitation Erosion in Hydraulic Turbine Components and Mitigation by Coatings: Current Status and Future Needs

Science.gov (United States)

Singh, Raghuvir; Tiwari, S. K.; Mishra, Suman K.

2012-07-01

Cavitation erosion is a frequently observed phenomenon in underwater engineering materials and is the primary reason for component failure. The damage due to cavitation erosion is not yet fully understood, as it is influenced by several parameters, such as hydrodynamics, component design, environment, and material chemistry. This article gives an overview of the current state of understanding of cavitation erosion of materials used in hydroturbines, coatings and coating methodologies for combating cavitation erosion, and methods to characterize cavitation erosion. No single material property fully characterizes the resistance to cavitation erosion. The combination of ultimate resilience, hardness, and toughness rather may be useful to estimate the cavitation erosion resistance of material. Improved hydrodynamic design and appropriate surface engineering practices reduce damage due to cavitation erosion. The coatings suggested for combating the cavitation erosion encompasses carbides (WC Cr2C3, Cr3C2, 20CrC-80WC), cermets of different compositions (e.g., 56W2C/Ni/Cr, 41WC/Ni/Cr/Co), intermetallic composites, intermetallic matrix composites with TiC reinforcement, composite nitrides such as TiAlN and elastomers. A few of them have also been used commercially. Thermal spraying, arc plasma spraying, and high velocity oxy-fuel (HVOF) processes have been used commercially to apply the coatings. Boronizing, laser surface hardening and cladding, chemical vapor deposition, physical vapor deposition, and plasma nitriding have been tried for surface treatments at laboratory levels and have shown promise to be used on actual components.

Structure and friction properties of cermet and oxide explosion coatings

International Nuclear Information System (INIS)

RGrigorov, A.I.; Semenov, A.P.; Fed'ko, Yu.P.; Shtejn, L.M.

1977-01-01

Conditions have been specified for spraying explosion coatings of cermets over Kh18N10T stainless steel and an aluminum alloy. A mixture of WC and CO powders served as a material for spraying. The method of micro-X-ray spectrum analysis has been used to study the structure of the transition zone between the coating and the substrate and to establish the mechanism responsible for the formation of a cermet layer

Metal-ceramic bond strength of Co-Cr alloy fabricated by selective laser melting.

Science.gov (United States)

Xiang, Nan; Xin, Xian-Zhen; Chen, Jie; Wei, Bin

2012-06-01

This study was to evaluated the metal-ceramic bond strength of a Co-Cr dental alloy prepared using a selective laser melting (SLM) technique. Two groups comprised of twenty Co-Cr metal bars each were prepared using either a SLM or traditional lost-wax casting method. Ten bars from each group were moulded into standard ISO 9693:1999 dimensions of 25 mm × 3 mm × 0.5 mm with 1.1 mm of porcelain fused onto an 8 mm × 3 mm rectangular area in the centre of each bar. Metal-ceramic bonding was assessed using a three-point bending test. Fracture mode analysis and area fraction of adherence porcelain (AFAP) were determined by measuring Si content of specimens by SEM/EDS. Student's t-test within the groups demonstrated no significant difference for the mean bond strength between the SLM and traditional cast sample groups. While SEM/EDS analysis indicated a mixed fracture mode on the debonding interface of both the SLM and the cast groups, the SLM group showed significantly more porcelain adherence than the control group (p<0.05). The SLM metal-ceramic system exhibited a bonding strength that exceeds the requirement of ISO 9691:1999(E) and it even showed a better behaviour in porcelain adherence test comparable to traditional cast methods. Copyright © 2012 Elsevier Ltd. All rights reserved.

Allergic contact dermatitis from resin hardeners during the manufacture of thermosetting coating paints.

Science.gov (United States)

Foulds, I S; Koh, D

1992-02-01

5 production operators from 2 factories manufacturing thermosetting coating paint developed work-related skin disorders within 12 months of the introduction of a new powdered paint product. All 5 workers were found to have allergic contact dermatitis from 2 epoxy resin hardeners, both of which were commercial preparations of triglycidyl isocyanurate (TGIC). 2 of the workers had concomitant sensitization to epoxy resin in the standard series and several of the epoxy resin preparations at the workplace. TGIC has been reported as a contact sensitizer both in persons producing the chemical and among end-users of TGIC-containing products. These 5 reported cases document allergic contact dermatitis from commercial TGIC among exposed workers during an intermediate process of powdered paint manufacture. The possibility of substituting this epoxy resin hardener with less sensitizing alternatives should be explored.

Estudio por emisión acústica del comportamiento a flexión de recubrimientos WC-Co obtenidos por plasma atmosférico

Directory of Open Access Journals (Sweden)

Segovia, F.

2007-12-01

Full Text Available Plasma sprayed cermet coatings WC-Co are used in a wide range of industrial applications, mainly due to their wear resistance even in corrosive environments. The objective of this work is to analyze mechanical response of hard metal coatings by means of three- and four-points bend tests applying acoustic emission technique to determine failure critical strength. It has been observed the effect of supported charge level in structural damage by means of optical microscopy and scanning electron microscopy. Acoustic emission has allowed us to relate damage level to stresses level and then to understand coatings failure mechanism.

Los recubrimientos de cermet WC-Co proyectados por plasma se utilizan en un amplio rango de aplicaciones industriales, principalmente por su resistencia al desgaste, incluso en medio corrosivo. El objetivo de este trabajo es analizar la respuesta mecánica de los recubrimientos de metal duro mediante ensayos de flexión a 3 y 4 puntos aplicando el método de emisión acústica para determinar las tensiones críticas de fallo. Se ha observado el efecto del nivel de carga soportado en el dañado estructural mediante microscopia óptica y electrónica de barrido. La emisión acústica ha permitido relacionar el grado de dañado con el nivel de tensiones y, así, entender el mecanismo de fallo de los recubrimientos.

Lightning Tests on the WC-130 Research Aircraft.

Science.gov (United States)

1982-12-01

in the WC-136 tests at various times.) E- Feild Fiber Optic Test Article Sensor Transmitter (Typ)WiePr Indtuced Voltag Sensor"" *Fiber I"=Current optic...well-characterized. 5.1 Skin Current Measurements Skin current vectors were measured at five fuselage locations on the left side of the WC-130 at a...MGL-S7) which were mounted so that they sampled two orthogonal components of the skin current vector . The measured responses were then inte- grated

Comportamiento a desgaste de recubrimientos de WC proyectados por plasma a partir de polvos micro y nanoestructurados

Directory of Open Access Journals (Sweden)

Salvador, M. D.

2008-06-01

Full Text Available The aim of the present work is the study of wear behaviour of different WC coatings deposited on stainless steel substrate by means of atmospheric plasma spraying (APS. Two types of WC commercial powders, with different metal binder (12% Cobalt and 10% Nickel have been deposited in order to analyse the influence of the metal matrix and thickness of the coating in tribological properties.The microstructure of the depositions was characterized using scanning electron microscopy (SEM and X-ray diffraction analysis (XRD. On the other hand, tribology characterization of the coatings was made by pin-on-disk wear tests against alumina (2400HV and silicon nitride (1600HV ceramic balls, without lubrication. Wear rates and friction coefficient evolution have been calculated. Finally, wear tracks and wear debris have been analysed with the help of SEM.The results of each pair of tested materials show different mechanisms of wear related to the nature of the ball that has been used, obtaining higher wear rates with silicone nitride ball..In a second phase of the study, in order to examine the influence of the initial particle size on the wear properties of the coatings, cobalt based coatings have been analysed with different initial particle size (micrometric and nanometric particles.Results show that nanostructured coatings have higher wear resistance than microstrutured ones for high loads. However for low loads, behaviour is similar in spite of the microstructural differences appreciated.

El objetivo de este trabajo es estudiar el comportamiento a desgaste de distintos recubrimientos de WC sobre acero inoxidable mediante proyección por plasma atmosférico. Se proyectan dos tipos de polvos comerciales con base cobalto (12 % y níquel (10 %, con el objeto de analizar la influencia de la matriz e incluso del espesor del recubrimiento. Los recubrimientos obtenidos se caracterizan microestructuralmente por microscopía electrónica de barrido y

An Investigation into the Use of Manufactured Sand as a 100% Replacement for Fine Aggregate in Concrete

Directory of Open Access Journals (Sweden)

Martins Pilegis

2016-06-01

Full Text Available Manufactured sand differs from natural sea and river dredged sand in its physical and mineralogical properties. These can be both beneficial and detrimental to the fresh and hardened properties of concrete. This paper presents the results of a laboratory study in which manufactured sand produced in an industry sized crushing plant was characterised with respect to its physical and mineralogical properties. The influence of these characteristics on concrete workability and strength, when manufactured sand completely replaced natural sand in concrete, was investigated and modelled using artificial neural networks (ANN. The results show that the manufactured sand concrete made in this study generally requires a higher water/cement (w/c ratio for workability equal to that of natural sand concrete due to the higher angularity of the manufactured sand particles. Water reducing admixtures can be used to compensate for this if the manufactured sand does not contain clay particles. At the same w/c ratio, the compressive and flexural strength of manufactured sand concrete exceeds that of natural sand concrete. ANN proved a valuable and reliable method of predicting concrete strength and workability based on the properties of the fine aggregate (FA and the concrete mix composition.

An Investigation into the Use of Manufactured Sand as a 100% Replacement for Fine Aggregate in Concrete.

Science.gov (United States)

Pilegis, Martins; Gardner, Diane; Lark, Robert

2016-06-02

Manufactured sand differs from natural sea and river dredged sand in its physical and mineralogical properties. These can be both beneficial and detrimental to the fresh and hardened properties of concrete. This paper presents the results of a laboratory study in which manufactured sand produced in an industry sized crushing plant was characterised with respect to its physical and mineralogical properties. The influence of these characteristics on concrete workability and strength, when manufactured sand completely replaced natural sand in concrete, was investigated and modelled using artificial neural networks (ANN). The results show that the manufactured sand concrete made in this study generally requires a higher water/cement (w/c) ratio for workability equal to that of natural sand concrete due to the higher angularity of the manufactured sand particles. Water reducing admixtures can be used to compensate for this if the manufactured sand does not contain clay particles. At the same w/c ratio, the compressive and flexural strength of manufactured sand concrete exceeds that of natural sand concrete. ANN proved a valuable and reliable method of predicting concrete strength and workability based on the properties of the fine aggregate (FA) and the concrete mix composition.

Pulsed Laser Deposition Processing of Improved Titanium Nitride Coatings for Implant Applications

Science.gov (United States)

Haywood, Talisha M.

Recently surface coating technology has attracted considerable attention of researchers to develop novel coatings with enhanced functional properties such as hardness, biocompatibility, wear and corrosion resistance for medical devices and surgical tools. The materials currently being used for surgical implants include predominantly stainless steel (316L), cobalt chromium (Co-Cr), titanium and its alloys. Some of the limitations of these implants include improper mechanical properties, corrosion resistance, cytotoxicity and bonding with bone. One of the ways to improve the performance and biocompatibility of these implants is to coat their surfaces with biocompatible materials. Among the various coating materials, titanium nitride (TiN) shows excellent mechanical properties, corrosion resistance and low cytotoxicity. In the present work, a systematic study of pulsed laser ablation processing of TiN coatings was conducted. TiN thin film coatings were grown on commercially pure titanium (Ti) and stainless steel (316L) substrates at different substrate temperatures and different nitrogen partial pressures using the pulsed laser deposition (PLD) technique. Microstructural, surface, mechanical, chemical, corrosion and biological analysis techniques were applied to characterize the TiN thin film coatings. The PLD processed TiN thin film coatings showed improvements in mechanical strength, corrosion resistance and biocompatibility when compared to the bare substrates. The enhanced performance properties of the TiN thin film coatings were a result of the changing and varying of the deposition parameters.

Stellar C III Emissions as a New Classification Parameter for (WC) Central Stars

Science.gov (United States)

Feibelman, W. A.

1999-01-01

We report detection of stellar C III lambda 1909 emission in International Ultraviolet Explorer (IUE) echelle spectra of early-type [WC] planetary nebula central stars (CSPNs). Additionally, stellar C III emission at lambda 2297 is observed in early- and late-type [WC) CSPNS. Inclusion of these C III features for abundance determinations may resolve a conflict of underabundance of C/O for early type [WC2] - [WC4] CSPNS. A linear dependence on stellar C III lambda 2297 equivalent widths can be used to indicate a new classification of type [WCUV] central stars.

Magnetically anisotropic additive for scalable manufacturing of polymer nanocomposite: iron-coated carbon nanotubes

International Nuclear Information System (INIS)

Yamamoto, Namiko; Manohara, Harish; Platzman, Ellen

2016-01-01

Novel nanoparticles additives for polymer nanocomposites were prepared by coating carbon nanotubes (CNTs) with ferromagnetic iron (Fe) layers, so that their micro-structures can be bulk-controlled by external magnetic field application. Application of magnetic fields is a promising, scalable method to deliver bulk amount of nanocomposites while maintaining organized nanoparticle assembly throughout the uncured polymer matrix. In this work, Fe layers (∼18 nm thick) were deposited on CNTs (∼38 nm diameter and ∼50 μm length) to form thin films with high aspect ratio, resulting in a dominance of shape anisotropy and thus high coercivity of ∼50–100 Oe. The Fe-coated CNTs were suspended in water and applied with a weak magnetic field of ∼75 G, and yet preliminary magnetic assembly was confirmed. Our results demonstrate that the fabricated Fe-coated CNTs are magnetically anisotropic and effectively respond to magnetic fields that are ∼10 3 times smaller than other existing work (∼10 5 G). We anticipate this work will pave the way for effective property enhancement and bulk application of CNT–polymer nanocomposites, through controlled micro-structure and scalable manufacturing. (paper)

Wear Resistant Thermal Sprayed Composite Coatings Based on Iron Self-Fluxing Alloy and Recycled Cermet Powders

Directory of Open Access Journals (Sweden)

Heikki SARJAS

2012-03-01

Full Text Available 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

A comparative study of tribological behavior of plasma and D-gun sprayed coatings under different wear modes

International Nuclear Information System (INIS)

Sundararajan, G.; Rao, D.S.; Prasad, K.U.M.; Joshi, S.V.

1998-01-01

In recent years, thermal sprayed protective coatings have gained widespread acceptance for a variety of industrial applications. A vast majority of these applications involve the use of thermal sprayed coatings to combat wear. While plasma spraying is the most versatile variant of all the thermal spray processes, the detonation gun (D-gun) coatings have been a novelty until recently because of their proprietary nature. The present study is aimed at comparing the tribological behavior of coatings deposited using the two above techniques by focusing on some popular coating materials that are widely adopted for wear resistant applications, namely, WC-12% Co, Al 2 O 3 , and Cr 3 C 2 -NiCr. To enable a comprehensive comparison of the above indicated thermal spray techniques as well as coating materials, the deposited coatings were extensively characterized employing microstructural evaluation, microhardness measurements, and XRD analysis for phase constitution. The behavior of these coatings under different wear modes was also evaluated by determining their tribological performance when subjected to solid particle erosion tests, rubber wheel sand abrasion tests, and pin-on-disk sliding wear tests. Among all the coating materials studied, D-gun sprayed WC-12% Co, in general, yields the best performance under different modes of wear, whereas plasma sprayed Al 2 O 3 shows least wear resistance to every wear mode

Microstructure and tribological behavior of tungsten-containing diamondlike carbon coated rubbers

NARCIS (Netherlands)

Pei, Y.T.; Bui, X.L.; Zhou, Xiao; Hosson, J.Th.M. De

2008-01-01

Tungsten-containing diamondlike carbon (W-DLC) coatings have been deposited on FKM (fluorocarbon), ACM (acrylate), and HNBR (hydrogenated nitrile butadiene) rubbers via unbalanced magnetron reactive sputtering from a WC target in C2H2/Ar plasma. The surface morphology and, fracture cross sections of

Vanadium carbide coatings: deposition process and properties

International Nuclear Information System (INIS)

Borisova, A.; Borisov, Y.; Shavlovsky, E.; Mits, I.; Castermans, L.; Jongbloed, R.

2001-01-01

Vanadium carbide coatings on carbon and alloyed steels were produced by the method of diffusion saturation from the borax melt. Thickness of the vanadium carbide layer was 5-15 μm, depending upon the steel grade and diffusion saturation parameters. Microhardness was 20000-28000 MPa and wear resistance of the coatings under conditions of end face friction without lubrication against a mating body of WC-2Co was 15-20 times as high as that of boride coatings. Vanadium carbide coatings can operate in air at a temperature of up to 400 o C. They improve fatigue strength of carbon steels and decrease the rate of corrosion in sea and fresh water and in acid solutions. The use of vanadium carbide coatings for hardening of various types of tools, including cutting tools, allows their service life to be extended by a factor of 3 to 30. (author)

Phase composition and microstructure of WC-Co alloys obtained by selective laser melting

Science.gov (United States)

Khmyrov, Roman S.; Shevchukov, Alexandr P.; Gusarov, Andrey V.; Tarasova, Tatyana V.

2018-03-01

Phase composition and microstructure of initial WC, BK8 (powder alloy 92 wt.% WC-8 wt.% Co), Co powders, ball-milled powders with four different compositions (1) 25 wt.% WC-75 wt.% Co, (2) 30 wt.% BK8-70 wt.% Co, (3) 50 wt.% WC-50 wt.% Co, (4) 94 wt.% WC-6 wt.% Co, and bulk alloys obtained by selective laser melting (SLM) from as-milled powders in as-melted state and after heat treatment were investigated by scanning electron microscopy and X-ray diffraction analysis. Initial and ball-milled powders consist of WC, hexagonal α-Co and face-centered cubic β-Co. The SLM leads to the formation of major new phases W3Co3C, W4Co2C and face-centered cubic β-Co-based solid solution. During the heat treatment, there occurs partial decomposition of the face-centered cubic β-Co-based solid solution with the formation of W2C and hexagonal α-Co solid solution. The microstructure of obtained bulk samples, in general, corresponds to the observed phase composition.

Development of process technologies for improvement of electroless nickel coatings properties

International Nuclear Information System (INIS)

Barba-Pingarrón, A; Trujillo-Barragán, M; Hernandez-Gallegos, M A; Valdez-Navarro, R; Bolarín-Miró, A; Jesús, F Sánchez – de; Vargas-Mendoza, L; Molera-Sola, P

2013-01-01

This paper describes research and technology developments that enable to improve nickel electroless coating properties. This work deals with: (a) different methods in order to achieve Ni-P-Mo coatings. (b) Other development is related with coatings with addition of hard particles such as SiC, WC or Al 2 O 3 ,(c) Electroless nickel deposits on PBT and austempered ductile iron (ADI). (d) In addition, nickel coatings were deposited on powder metallic pieces and finally, electroless nickel coatings, in conjunction with layers from thermal spray process were formed. Characterization of all coatings by means of optical microscopy, scanning electron microscopy, micro-hardness, wear and corrosion tests were carried out. Results indicate positive increment in both mechanical and electrochemical properties which enhance field applications in Mexican industry.

Comparative Assessment of Copper-Coated Kapton: Analysis of Microclad from Several Manufacturing Lots

Energy Technology Data Exchange (ETDEWEB)

Martz, Joseph Christopher [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Spearing, Dane Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Labouriau, Andrea [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Judge, Elizabeth [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kelly, Daniel [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dirmyer, Matthew R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Milenski, Helen Marie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Patterson, Brian M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sandoval, Cynthia Wathen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Usov, Igor Olegovich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Beaux, Miles Frank II [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Henderson, Kevin C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Torres, Joseph Angelo [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Edwards, Stephanie Lynn [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vodnik, Douglas R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Keller, Jennie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mccabe, Rodney James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Livescu, Veronica [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Cowan, Joseph Sarno [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Aragonez, Robert J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tokash, Justin Charles [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lawrence, Samantha Kay [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Leon Brito, Neliza [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-04-03

Microclad is a composite material consisting of a thin copper coating applied on a single side over a Kapton substrate. Kapton is the commercial designator for polyimide supplied by DuPont. Microclad is a key material in detonator manufacture and function. Detonators which utilize Microclad function when a large current applied through a thin bridge etched into the copper produces a plasma, accelerating a Kapton flyer into an explosive (PETN) pellet. The geometry and properties of the Microclad are a critical element of this process.

Characterization of hard coatings produced by laser cladding using laser-induced breakdown spectroscopy technique

Science.gov (United States)

Varela, J. A.; Amado, J. M.; Tobar, M. J.; Mateo, M. P.; Yañez, A.; Nicolas, G.

2015-05-01

Protective coatings with a high abrasive wear resistance can be obtained from powders by laser cladding technique, in order to extend the service life of some industrial components. In this work, laser clad layers of self-fluxing NiCrBSi alloy powder mixed with WC powder have been produced on stainless steel substrates of austenitic type (AISI 304) in a first step and then chemically characterized by laser-induced breakdown spectroscopy (LIBS) technique. With the suitable laser processing parameters (mainly output power, beam scan speed and flow rate) and powders mixture proportions between WC ceramics and NiCrBSi alloys, dense pore free layers have been obtained on single tracks and on large areas with overlapped tracks. The results achieved by LIBS technique and applied for the first time to the analysis of laser clads provided the chemical composition of the tungsten carbides in metal alloy matrix. Different measurement modes (multiple point analyses, depth profiles and chemical maps) have been employed, demonstrating the usefulness of LIBS technique for the characterization of laser clads based on hardfacing alloys. The behavior of hardness can be explained by LIBS maps which evidenced the partial dilution of some WC spheres in the coating.

Hot corrosion of Co-Cr, Co-Cr-Al, and Ni-Cr alloys in the temperature range of 700-750 deg C

Science.gov (United States)

Chiang, K. T.; Meier, G. H.

1980-01-01

The effect of SO3 pressure in the gas phase on the Na2SO4 induced hot corrosion of Co-Cr, Ni-Cr, and Co-Cr-Al alloys was studied in the temperature range 700 to 750 C. The degradation of the Co-Cr and Ni-Cr alloys was found to be associated with the formation of liquid mixed sulfates (CoSO4-Na2SO4 or NiSO4-Na2SO4) which provided a selective dissolution of the Co or Ni and a subsequent sulfidation oxidation mode of attack which prevented the maintenance of a protective Cr2O3 film. A clear mechanism was not developed for the degradation of Co-Cr-Al alloys. A pitting corrosion morphology was induced by a number of different mechanisms.

Dodecahedral W@WC Composite as Efficient Catalyst for Hydrogen Evolution and Nitrobenzene Reduction Reactions.

Science.gov (United States)

Chen, Zhao-Yang; Duan, Long-Fa; Sheng, Tian; Lin, Xiao; Chen, Ya-Feng; Chu, You-Qun; Sun, Shi-Gang; Lin, Wen-Feng

2017-06-21

Core-shell composites with strong phase-phase contact could provide an incentive for catalytic activity. A simple, yet efficient, H 2 O-mediated method has been developed to synthesize a mesoscopic core-shell W@WC architecture with a dodecahedral microstructure, via a one-pot reaction. The H 2 O plays an important role in the resistance of carbon diffusion, resulting in the formation of the W core and W-terminated WC shell. Density functional theory (DFT) calculations reveal that adding W as core reduced the oxygen adsorption energy and provided the W-terminated WC surface. The W@WC exhibits significant electrocatalytic activities toward hydrogen evolution and nitrobenzene electroreduction reactions, which are comparable to those found for commercial Pt/C, and substantially higher than those found for meso- and nano-WC materials. The experimental results were explained by DFT calculations based on the energy profiles in the hydrogen evolution reactions over WC, W@WC, and Pt model surfaces. The W@WC also shows a high thermal stability and thus may serve as a promising more economical alternative to Pt catalysts in these important energy conversion and environmental protection applications. The current approach can also be extended or adapted to various metals and carbides, allowing for the design and fabrication of a wide range of catalytic and other multifunctional composites.

Electrochemical corrosion of cermet coatings in artificial marine water

International Nuclear Information System (INIS)

Cabot, P.L.; Fernandez, J.; Guilemany, J.M.

1998-01-01

The electrochemical corrosion of different WC+12Co coatings sprayed on 34CrMo4 (UNS-G41350) steel by the high velocity oxygen fuel technique has been studied by corrosion potential and impedance measurements considering previous SEM observations and EDX microanalysis. The experiments were conducted in artificial marine water at 20 C and the impedance spectra were obtained at the corresponding corrosion potentials for the substrate, coating and substrate-coating systems. The impedance diagrams indicated that the electrochemical corrosion of the steel-coating systems is controlled by oxygen diffusion through a porous film of corrosion products, as in the case of the shot-blasted steel. In contrast, the corrosion of the coating appeared to be controlled by diffusion of oxygen through the electrolyte. The impedance diagrams obtained for the steel-coating systems depended on the porosities of the cermet coatings, thus being an useful procedure to characterize metals coated by cermets. (orig.)

Liquid Phase Sintering of (Ti,Zr)C with WC-Co.

Science.gov (United States)

Ma, Taoran; Borrajo-Pelaez, Rafael; Hedström, Peter; Blomqvist, Andreas; Borgh, Ida; Norgren, Susanne; Odqvist, Joakim

2017-01-11

(Ti,Zr)C powder was sintered with WC-Co following an industrial process, including an isotherm at 1410 °C. A series of interrupted sintering trials was performed with the aim of studying the sintering behavior and the microstructural evolution during both solid-state and liquid-state sintering. Reference samples, using the same elemental compositions but with the starting components TiC and ZrC instead of (Ti,Zr)C, were also sintered. The microstructure was investigated using scanning electron microscopy and energy dispersive X-ray spectroscopy. It is found that the (Ti,Zr)C phase decomposes into Ti-rich and Zr-rich nano-scale lamellae before the liquid-state of the sintering initiates. The final microstructure consists of the binder and WC as well as two different γ phases, rich in either Ti (γ₁) or Zr (γ₂). The γ₂ phase grains have a core-shell structure with a (Ti,Zr)C core following the full sintering cycle. The major differences observed in (Ti,Zr)C with respect to the reference samples after the full sintering cycle were the referred core-shell structure and the carbide grain sizes; additionally, the microstructural evolution during sintering differs. The grain size of carbides (WC, γ₁, and γ₂) is about 10% smaller in WC-(Ti,Zr)C-Co than WC-TiC-ZrC-Co. The shrinkage behavior and hardness of both composites are reported and discussed.

Liquid Phase Sintering of (Ti,ZrC with WC-Co

Directory of Open Access Journals (Sweden)

Taoran Ma

2017-01-01

Full Text Available (Ti,ZrC powder was sintered with WC-Co following an industrial process, including an isotherm at 1410 °C. A series of interrupted sintering trials was performed with the aim of studying the sintering behavior and the microstructural evolution during both solid-state and liquid-state sintering. Reference samples, using the same elemental compositions but with the starting components TiC and ZrC instead of (Ti,ZrC, were also sintered. The microstructure was investigated using scanning electron microscopy and energy dispersive X-ray spectroscopy. It is found that the (Ti,ZrC phase decomposes into Ti-rich and Zr-rich nano-scale lamellae before the liquid-state of the sintering initiates. The final microstructure consists of the binder and WC as well as two different γ phases, rich in either Ti (γ1 or Zr (γ2. The γ2 phase grains have a core-shell structure with a (Ti,ZrC core following the full sintering cycle. The major differences observed in (Ti,ZrC with respect to the reference samples after the full sintering cycle were the referred core-shell structure and the carbide grain sizes; additionally, the microstructural evolution during sintering differs. The grain size of carbides (WC, γ1, and γ2 is about 10% smaller in WC-(Ti,ZrC-Co than WC-TiC-ZrC-Co. The shrinkage behavior and hardness of both composites are reported and discussed.

Method of manufacturing a graphite coated fuel can

International Nuclear Information System (INIS)

Saito, Koichi; Uchida, Shunsuke.

1984-01-01

Purpose: To improve the close bondability and homogeneity of a graphite coating formed at the inner surface of a fuel can. Method: A coating containing graphite dispersed in a volatile organic solvent is used and a graphite coating is formed to the inner surface of a fuel can by way of a plunger method. After applying graphite coating, an inert gas is caused to flow at a certain flow rate to the inside of the fuel can horizontally rotaged so that gassification and evaporation of the volatile organic solvent contained in the graphite coating may be promoted. Since drying of the graphite coating coated to the inner surface of the fuel can thus be controlled, a graphite coating with satisfactory close bondability and homogeneity can be formed. (Kawakami, Y.)

Influence of WC addition on the microstructure and mechanical properties of NbC-Co cermets

International Nuclear Information System (INIS)

Huang, S.G.; Li, L.; Van der Biest, O.; Vleugels, J.

2007-01-01

NbC-24.5 wt.% Co cermets with up to 30 wt.% WC were obtained by solid state hot pressing at 1300 o C under a pressure of 45 MPa for 10 min and pressureless liquid phase sintering at 1360 o C for 60 min. The effect of WC addition on the microstructure and mechanical properties of NbC-Co based cermets was investigated. The hot pressed cermets exhibited interconnected and irregular niobium carbide (NbC) or (Nb,W)C grains, whereas the shape of the NbC grains changed from faceted with rounded corners to spherical, as the WC content increased in the pressureless sintered cermets. The undissolved WC increased with increasing WC addition. A clear core/rim structure was observed in the hot pressed cermets with 10-30 wt.% WC additions, whereas this structure was gradually eliminated when pressureless sintering. The hardness remains nearly constant whereas the fracture toughness slightly increases with increasing WC addition. The dissolution of WC in the Co binder and NbC grains, as well as the formation of a solid solution (Nb,W)C phase were supported by thermodynamic calculations

Evaluation of marginal/internal fit of chrome-cobalt crowns: Direct laser metal sintering versus computer-aided design and computer-aided manufacturing.

Science.gov (United States)

Gunsoy, S; Ulusoy, M

2016-01-01

The purpose of this study was to evaluate the internal and marginal fit of chrome cobalt (Co-Cr) crowns were fabricated with laser sintering, computer-aided design (CAD) and computer-aided manufacturing, and conventional methods. Polyamide master and working models were designed and fabricated. The models were initially designed with a software application for three-dimensional (3D) CAD (Maya, Autodesk Inc.). All models were fabricated models were produced by a 3D printer (EOSINT P380 SLS, EOS). 128 1-unit Co-Cr fixed dental prostheses were fabricated with four different techniques: Conventional lost wax method, milled wax with lost-wax method (MWLW), direct laser metal sintering (DLMS), and milled Co-Cr (MCo-Cr). The cement film thickness of the marginal and internal gaps was measured by an observer using a stereomicroscope after taking digital photos in ×24. Best fit rates according to mean and standard deviations of all measurements was in DLMS both in premolar (65.84) and molar (58.38) models in μm. A significant difference was found DLMS and the rest of fabrication techniques (P 0.05). DMLS was best fitting fabrication techniques for single crown based on the results.The best fit was found in marginal; the larger gap was found in occlusal.All groups were within the clinically acceptable misfit range.

Development and characterization of laser clad high temperature self-lubricating wear resistant composite coatings on Ti–6Al–4V alloy

International Nuclear Information System (INIS)

Liu, Xiu-Bo; Meng, Xiang-Jun; Liu, Hai-Qing; Shi, Gao-Lian; Wu, Shao-Hua; Sun, Cheng-Feng; Wang, Ming-Di; Qi, Long-Hao

2014-01-01

Highlights: • A novel high temperature self-lubricating anti-wear composite coating was fabricated. • Reinforced carbides as well as self-lubricating sulfides were in situ synthesized. • Microhardness of the Ti–6Al–4V substrate was significantly improved. • Friction coefficient and wear rate of the composite coating were greatly reduced. - Abstract: To enhance the wear resistance and friction-reducing capability of titanium alloy, a process of laser cladding γ-NiCrAlTi/TiC + TiWC 2 /CrS + Ti 2 CS coatings on Ti–6Al–4V alloy substrate with preplaced NiCr/Cr 3 C 2 –WS 2 mixed powders was studied. A novel coating without cracks and few pores was obtained in a proper laser processing. The composition and microstructure of the fabricated coating were examined by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) techniques, and tribological properties were evaluated using a ball-on-disc tribometer under dry sliding wear test conditions at 20 °C (room-temperature), 300 °C, 600 °C, respectively. The results show that the coating has unique microstructure consisting of α-Ti, TiC, TiWC 2 , γ-NiCrAlTi, Ti 2 CS and CrS phases. Average microhardness of the composite coating is 1005 HV 0.2 , which is about 3-factor higher than that of Ti–6Al–4V substrate (360 HV 0.2 ). The friction coefficient and wear rate of the coating are greatly decreased due to the combined effects of the dominating anti-wear capabilities of reinforced TiC and TiWC 2 carbides and the CrS and Ti 2 CS sulfides which have excellent self-lubricating property

Characterizing the Effects of Micro Electrical Discharge Machining Parameters on Material Removal Rate during Micro EDM Drilling of Tungsten Carbide (WC-Co)

Science.gov (United States)

Hourmand, Mehdi; Sarhan, Ahmed A. D.; Sayuti, Mohd

2017-10-01

Micro-dies, molds and miniaturized products can be manufactured using micro EDM process. In this research, EDM machine and on-machine fabricated CuW micro-electrode were utilized to produce the micro holes in WC-16%Co. The effects of voltage, current, pulse ON time, pulse OFF time, capacitor and rotating speed on Material removal rate (MRR) during micro EDM drilling of WC-16% Co was analyzed using fractional factorial design method. ANOVA analysis shows that increasing current, rotating speed, capacitor and decreasing voltage and pulse ON time lead to the amplify in MRR. It was found that out of all the factors, current and capacitor had the most significant effect on MRR, while the effect of capacitor was more than current. Eventually, it can be concluded that micro holes can be produced using EDM machine.

Structure and hardness of a hard metal alloy prepared with a WC powder synthesized at low temperature

Energy Technology Data Exchange (ETDEWEB)

Costa, F.A. da [Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil)], E-mail: francineac@yahoo.com; Medeiros, F.F.P. de [Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil); Silva, A.G.P. da [Laboratorio de Materiais Avancados, UENF, 28015-620 Campos de Goytacazes, RJ (Brazil); Gomes, U.U. [Departamento de Fisica Teorica e Experimental, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil); Filgueira, M. [Laboratorio de Materiais Avancados, UENF, 28015-620 Campos de Goytacazes, RJ (Brazil); Souza, C.P. de [Laboratorio de Termodinamica e Reatores, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil)

2008-06-25

The structure and hardness of a WC-10 wt% Co alloy prepared with an experimental WC powder are compared with those of another alloy of the same composition produced under the same conditions and prepared with a commercial WC powder. The experimental WC powder was synthesized by a gas-solid reaction between APT and methane at low temperature and the commercial WC powder was conventionally produced by a solid-solid reaction between tungsten and carbon black. WC-10 wt% Co alloys with the two powders were prepared under the same conditions of milling and sintering. The structure of the sample prepared with the experimental WC powder is homogeneous and coarse grained. The structure of the sample prepared with the commercial powder is heterogeneous. Furthermore the size and shape of the WC grains are significantly different.

Flexural strength of pure Ti, Ni-Cr and Co-Cr alloys submitted to Nd:YAG laser or TIG welding.

Science.gov (United States)

Rocha, Rick; Pinheiro, Antônio Luiz Barbosa; Villaverde, Antonio Balbin

2006-01-01

Welding of metals and alloys is important to Dentistry for fabrication of dental prostheses. Several methods of soldering metals and alloys are currently used. The purpose of this study was to assess, using the flexural strength testing, the efficacy of two processes Nd:YAG laser and TIG (tungsten inert gas) for welding of pure Ti, Co-Cr and Ni-Cr alloys. Sixty cylindrical specimens were prepared (20 of each material), bisected and welded using different techniques. Four groups were formed (n=15). I: Nd:YAG laser welding; II- Nd:YAG laser welding using a filling material; III- TIG welding and IV (control): no welding (intact specimens). The specimens were tested in flexural strength and the results were analyzed statistically by one-way ANOVA. There was significant differences (pTIG and laser welding and also between laser alone and laser plus filling material. In conclusion, TIG welding yielded higher flexural strength means than Nd:YAG laser welding for the tested Ti, Co-Cr and Ni-Cr alloys.

Gene number determination and genetic polymorphism of the gamma delta T cell co-receptor WC1 genes

Directory of Open Access Journals (Sweden)

Chen Chuang

2012-10-01

Full Text Available Abstract Background WC1 co-receptors belong to the scavenger receptor cysteine-rich (SRCR superfamily and are encoded by a multi-gene family. Expression of particular WC1 genes defines functional subpopulations of WC1+ γδ T cells. We have previously identified partial or complete genomic sequences for thirteen different WC1 genes through annotation of the bovine genome Btau_3.1 build. We also identified two WC1 cDNA sequences from other cattle that did not correspond to sequences in the Btau_3.1 build. Their absence in the Btau_3.1 build may have reflected gaps in the genome assembly or polymorphisms among animals. Since the response of γδ T cells to bacterial challenge is determined by WC1 gene expression, it was critical to understand whether individual cattle or breeds differ in the number of WC1 genes or display polymorphisms. Results Real-time quantitative PCR using DNA from the animal whose genome was sequenced (“Dominette” and sixteen other animals representing ten breeds of cattle, showed that the number of genes coding for WC1 co-receptors is thirteen. The complete coding sequences of those thirteen WC1 genes is presented, including the correction of an error in the WC1-2 gene due to mis-assembly in the Btau_3.1 build. All other cDNA sequences were found to agree with the previous annotation of complete or partial WC1 genes. PCR amplification and sequencing of the most variable N-terminal SRCR domain (domain 1 which has the SRCR “a” pattern of each of the thirteen WC1 genes showed that the sequences are highly conserved among individuals and breeds. Of 160 sequences of domain 1 from three breeds of cattle, no additional sequences beyond the thirteen described WC1 genes were found. Analysis of the complete WC1 cDNA sequences indicated that the thirteen WC1 genes code for three distinct WC1 molecular forms. Conclusion The bovine WC1 multi-gene family is composed of thirteen genes coding for three structural forms whose

An evaluation of the electric arc spray and (HPPS) processes for the manufacturing of high power plasma spraying MCrAIY coatings

Science.gov (United States)

Sacriste, D.; Goubot, N.; Dhers, J.; Ducos, M.; Vardelle, A.

2001-06-01

The high power plasma torch (PlazJet) can be used to spray refractory ceramics with high spray rates and deposition efficiency. It can provide dense and hard coating with high bond strengths. When manufacturing thermal barrier coatings, the PlazJet gun is well adapted to spraying the ceramic top coat but not the MCrAIY materials that are used as bond coat. Arc spraying can compete with plasma spraying for metallic coatings since cored wires can be used to spray alloys and composites. In addition, the high production rate of arc spraying enables a significant decrease in coating cost. This paper discusses the performances of the PlazJet gun, and a twin-wire are spray system, and compares the properties and cost of MCrAIY coatings made with these two processes. For arc spraying, the use of air or nitrogen as atomizing gas is also investigated.

Metal-ceramic bond strength between a feldspathic porcelain and a Co-Cr alloy fabricated with Direct Metal Laser Sintering technique.

Science.gov (United States)

Dimitriadis, Konstantinos; Spyropoulos, Konstantinos; Papadopoulos, Triantafillos

2018-02-01

The aim of the present study was to record the metal-ceramic bond strength of a feldspathic dental porcelain and a Co-Cr alloy, using the Direct Metal Laser Sintering technique (DMLS) for the fabrication of metal substrates. Ten metal substrates were fabricated with powder of a dental Co-Cr alloy using DMLS technique (test group) in dimensions according to ISO 9693. Another ten substrates were fabricated with a casing dental Co-Cr alloy using classic casting technique (control group) for comparison. Another three substrates were fabricated using each technique to record the Modulus of Elasticity ( E ) of the used alloys. All substrates were examined to record external and internal porosity. Feldspathic porcelain was applied on the substrates. Specimens were tested using the three-point bending test. The failure mode was determined using optical and scanning electron microscopy. The statistical analysis was performed using t-test. Substrates prepared using DMLS technique did not show internal porosity as compared to those produced using the casting technique. The E of control and test group was 222 ± 5.13 GPa and 227 ± 3 GPa, respectively. The bond strength was 51.87 ± 7.50 MPa for test group and 54.60 ± 6.20 MPa for control group. No statistically significant differences between the two groups were recorded. The mode of failure was mainly cohesive for all specimens. Specimens produced by the DMLS technique cover the lowest acceptable metal-ceramic bond strength of 25 MPa specified in ISO 9693 and present satisfactory bond strength for clinical use.

Características de los recubrimientos WC-NiCrBSiFe en función del sistema de proyección térmica

Directory of Open Access Journals (Sweden)

Higuera-Hidalgo, V.

2004-10-01

Full Text Available 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.

Some aspects of finite element modelling of ultrasonically aided micro-EDM of CoCr alloys

Directory of Open Access Journals (Sweden)

Ghiculescu Daniel

2017-01-01

Full Text Available The paper deals with finite element modelling of micromachining CoCr alloys by ultrasonically aided electrical discharge machining. This hybrid machining process has two components: a thermal one due to EDM, and a mechanical one to ultrasonic assistance. Both components were modelled using Thermal and Structural Mechanics time dependent modules of Comsol Multiphysics. The results were compared with the experimental data obtained in our laboratories, proving a good agreement and offering some solutions for machining optimization.

WC1 is a hybrid γδ TCR coreceptor and pattern recognition receptor for pathogenic bacteria.

Science.gov (United States)

Hsu, Haoting; Chen, Chuang; Nenninger, Ariel; Holz, Lauren; Baldwin, Cynthia L; Telfer, Janice C

2015-03-01

WC1 proteins are uniquely expressed on γδ T cells and belong to the scavenger receptor cysteine-rich (SRCR) superfamily. While present in variable, and sometimes high, numbers in the genomes of mammals and birds, in cattle there are 13 distinct genes (WC1-1 to WC1-13). All bovine WC1 proteins can serve as coreceptors for the TCR in a tyrosine phosphorylation dependent manner, and some are required for the γδ T cell response to Leptospira. We hypothesized that individual WC1 receptors encode Ag specificity via coligation of bacteria with the γδ TCR. SRCR domain binding was directly correlated with γδ T cell response, as WC1-3 SRCR domains from Leptospira-responsive cells, but not WC1-4 SRCR domains from Leptospira-nonresponsive cells, bound to multiple serovars of two Leptospira species, L. borgpetersenii, and L. interrogans. Three to five of eleven WC1-3 SRCR domains, but none of the eleven WC1-4 SRCR domains, interacted with Leptospira spp. and Borrelia burgdorferi, but not with Escherichia coli or Staphylococcus aureus. Mutational analysis indicated that the active site for bacterial binding in one of the SRCR domains is composed of amino acids in three discontinuous regions. Recombinant WC1 SRCR domains with the ability to bind leptospires inhibited Leptospira growth. Our data suggest that WC1 gene arrays play a multifaceted role in the γδ T cell response to bacteria, including acting as hybrid pattern recognition receptors and TCR coreceptors, and they may function as antimicrobials. Copyright © 2015 by The American Association of Immunologists, Inc.

Ring head recording on perpendicular media: Output spectra for CoCr and CoCr/NiFe media

Science.gov (United States)

Stubbs, D. P.; Whisler, J. W.; Moe, C. D.; Skorjanec, J.

1985-04-01

The recording density response for sputtered CoCr (thickness=0.5 μm) and CoCr/NiFe (t=0.25 μm/0.5 μm) as well as evaporated CoNi (t=0.12 μm) and Co surface-doped iron oxide particulate media has been measured by reading and writing with Mn-Zn ferrite heads (gap length=0.375 μm, track width=37 μm) in contact with the media. Measurements to 200 kfc/i (thousand flux changes per inch) show a gap null around 115 kfc/i. The data have been normalized by dividing out the head sensitivity to obtain the value of spacing plus transition width (d+a) for the various media. For the CoCr media this value varied from 0.075-0.088 μm; for CoNi, 0.100 μm, and for the particulate medium, 0.163 μm. In addition, testing with a larger gapped Mn-Zn ferrite head (g=2.43 μm) shows that the head fields are distorted by the soft magnetic underlayer in dual layer CoCr/NiFe samples when the gap length is large compared to the distance to the underlayer.

Small-sized and contacting Pt-WC nanostructures on graphene as highly efficient anode catalysts for direct methanol fuel cells.

Science.gov (United States)

Wang, Ruihong; Xie, Ying; Shi, Keying; Wang, Jianqiang; Tian, Chungui; Shen, Peikang; Fu, Honggang

2012-06-11

The synergistic effect between Pt and WC is beneficial for methanol electro-oxidation, and makes Pt-WC catalyst a promising anode candidate for the direct methanol fuel cell. This paper reports on the design and synthesis of small-sized and contacting Pt-WC nanostructures on graphene that bring the synergistic effect into full play. Firstly, DFT calculations show the existence of a strong covalent interaction between WC and graphene, which suggests great potential for anchoring WC on graphene with formation of small-sized, well-dispersed WC particles. The calculations also reveal that, when Pt attaches to the pre-existing WC/graphene hybrid, Pt particles preferentially grow on WC rather than graphene. Our experiments confirmed that highly disperse WC nanoparticles (ca. 5 nm) can indeed be anchored on graphene. Also, Pt particles 2-3 nm in size are well dispersed on WC/graphene hybrid and preferentially grow on WC grains, forming contacting Pt-WC nanostructures. These results are consistent with the theoretical findings. X-ray absorption fine structure spectroscopy further confirms the intimate contact between Pt and WC, and demonstrates that the presence of WC can facilitate the crystallinity of Pt particles. This new Pt-WC/graphene catalyst exhibits a high catalytic efficiency toward methanol oxidation, with a mass activity 1.98 and 4.52 times those of commercial PtRu/C and Pt/C catalysts, respectively. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of lipopolysaccharides on the corrosion behavior of Ni-Cr and Co-Cr alloys.

Science.gov (United States)

Yu, Weiqiang; Qian, Chao; Weng, Weimin; Zhang, Songmei

2016-08-01

Lipopolysaccharides (LPS) are constituents of gingival crevicular fluid and may affect the base metal alloys used in metal ceramic crowns. The role of LPS in base metal alloys is currently unknown. The purpose of this in vitro study was to evaluate the effects of gram-negative bacterial LPS on the electrochemical behavior of Ni-Cr and Co-Cr alloys. Alloy specimens were divided into 4 groups according to Escherichia coli LPS concentration (0, 0.15, 15, and 150 μg/mL) in acidic saliva (pH 5). Open circuit potential (OCP) and potentiodynamic polarization behavior were examined using a computer-controlled potentiostat. Metal ions released from the 2 alloys were measured by immersion in LPS-free solution and 150 μg/mL LPS solution and analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). Data were evaluated using 1-way ANOVA (α=.05). Compared with control groups, medium LPS concentration (15 μg/mL) accelerated Ni-Cr alloy corrosion (Palloy corrosion (Pcorrosion current density, and polarization resistance parameters. After immersion in high LPS concentrations (150 μg/mL), a slight increase in Ni ion release (P >.05) was observed for the Ni-Cr alloy, while a more significant Co ion release (Palloy. LPS negatively affected the electrochemical behavior of both the Ni-Cr and Co-Cr alloys. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Influence of the Manufacturing Process on Defects in the Galvanized Coating of High Carbon Steel Wires

Directory of Open Access Journals (Sweden)

Marcello Gelfi

2017-03-01

Full Text Available This study is a detailed failure analysis of galvanized high carbon steel wires, which developed coating cracks during the torsion test performed as a quality control at the end of the manufacturing process. Careful visual inspections showed that the cracks are already present in the coating before the torsion test. In order to explain the origin of these cracks, systematic metallographic investigations were performed by means of optical and scanning electron microscope on both the wires and the rods that have been cold drawn to produce the wire. The chemical composition of the galvanized coatings was evaluated by means of energy dispersive spectroscopy. Micro bidimensional X-ray diffraction experiments were also performed to measure the residual stresses in the galvanized coating. The results showed that the failure is related to two main factors: the relatively high content of silicon in the steel and the unsuitable cooling rate of the rods at the exit from the galvanizing bath. The mechanism proposed to explain the origin of the defects was supported by Finite Elements Methods simulations and verified with in-plant tests. The proper countermeasures were then applied and the problem successfully solved.

Influence of the Manufacturing Process on Defects in the Galvanized Coating of High Carbon Steel Wires.

Science.gov (United States)

Gelfi, Marcello; Solazzi, Luigi; Poli, Sandro

2017-03-06

This study is a detailed failure analysis of galvanized high carbon steel wires, which developed coating cracks during the torsion test performed as a quality control at the end of the manufacturing process. Careful visual inspections showed that the cracks are already present in the coating before the torsion test. In order to explain the origin of these cracks, systematic metallographic investigations were performed by means of optical and scanning electron microscope on both the wires and the rods that have been cold drawn to produce the wire. The chemical composition of the galvanized coatings was evaluated by means of energy dispersive spectroscopy. Micro bidimensional X-ray diffraction experiments were also performed to measure the residual stresses in the galvanized coating. The results showed that the failure is related to two main factors: the relatively high content of silicon in the steel and the unsuitable cooling rate of the rods at the exit from the galvanizing bath. The mechanism proposed to explain the origin of the defects was supported by Finite Elements Methods simulations and verified with in-plant tests. The proper countermeasures were then applied and the problem successfully solved.

Combating Wear of ASTM A36 Steel by Surface Modification Using Thermally Sprayed Cermet Coatings

OpenAIRE

Shibe, Vineet; Chawla, Vikas

2016-01-01

Thermal spray coatings can be applied economically on machine parts to enhance their requisite surface properties like wear, corrosion, erosion resistance, and so forth. Detonation gun (D-Gun) thermal spray coatings can be applied on the surface of carbon steels to improve their wear resistance. In the present study, alloy powder cermet coatings WC-12% Co and Cr3C2-25% NiCr have been deposited on ASTM A36 steel with D-Gun thermal spray technique. Sliding wear behavior of uncoated ASTM A36 ste...

Pixelated coatings and advanced IR coatings

Science.gov (United States)

Pradal, Fabien; Portier, Benjamin; Oussalah, Meihdi; Leplan, Hervé

2017-09-01

Reosc developed pixelated infrared coatings on detector. Reosc manufactured thick pixelated multilayer stacks on IR-focal plane arrays for bi-spectral imaging systems, demonstrating high filter performance, low crosstalk, and no deterioration of the device sensitivities. More recently, a 5-pixel filter matrix was designed and fabricated. Recent developments in pixelated coatings, shows that high performance infrared filters can be coated directly on detector for multispectral imaging. Next generation space instrument can benefit from this technology to reduce their weight and consumptions.

Micro-texturing into DLC/diamond coated molds and dies via high density oxygen plasma etching

Directory of Open Access Journals (Sweden)

Yunata Ersyzario Edo

2015-01-01

Full Text Available Diamond-Like Carbon (DLC and Chemical Vapor Deposition (CVD-diamond films have been widely utilized not only as a hard protective coating for molds and dies but also as a functional substrate for bio-MEMS/NEMS. Micro-texturing into these hard coated molds and dies provides a productive tool to duplicate the original mother micro-patterns onto various work materials and to construct any tailored micro-textures for sensors and actuators. In the present paper, the high density oxygen plasma etching method is utilized to make micro-line and micro-groove patterns onto the DLC and diamond coatings. Our developing oxygen plasma etching system is introduced together with characterization on the plasma state during etching. In this quantitative plasma diagnosis, both the population of activated species and the electron and ion densities are identified through the emissive light spectroscopy and the Langmuir probe method. In addition, the on-line monitoring of the plasmas helps to describe the etching process. DLC coated WC (Co specimen is first employed to describe the etching mechanism by the present method. Chemical Vapor Deposition (CVD diamond coated WC (Co is also employed to demonstrate the reliable capacity of the present high density oxygen plasma etching. This oxygen plasma etching performance is discussed by comparison of the etching rates.

Erosion resistance of FeAl-TiB2 and FeAl-WC at room and elevated temperatures

International Nuclear Information System (INIS)

Alman, D.E.; Tylczak, J.H.; Hawk, J.A.

2000-01-01

The resistance of FeAl-40%TiB 2 and FeAl-80%WC cermets to solid particle erosion at 25, 180, 500 and 700 C was evaluated and compared to the behavior of WC-6%Co (Co-90%WC) cemented carbides. Even though the WC-Co contained a higher volume fraction of the hard phase, the erosion rates of the FeAl-cermets were similar in magnitude to the erosion rates of the WC-Co. However, the erosion rates of the FeAl-cermets either were constant (FeAl-TiB 2 ) or decreased (FeAl-WC) with increasing test temperature; whereas, the erosion rates of the WC-Co cemented carbides increased with increasing test temperature. This indicated that once the microstructures of the FeAl-cermets are optimized for wear resistance, these materials might make promising candidates for high-temperature wear applications

Microstructural examination by TEM of WC/Co composites prepared by conventional and Microwave processes

International Nuclear Information System (INIS)

Agrawal, D.; Cheng, J.; Papworth, A.J.; Jain, H.; Williams, D.B.

2001-01-01

Recently, significant developments and advances have taken place in the field of microwave processing of ceramics, composites and metals. Microwave sintering technology of WC/Co based hard metal parts has been now developed for commercial products. Microwave processed WC/Co parts reportedly have exhibited superior performance over standard parts. Additionally, the microwave process requires only one tenth of the total cycle time employed in a conventional process. Laboratory corrosion and impact resistance tests have proved that microwave processed WC/Co parts are several times more resistant than the conventional parts of the same composition. The scanning transmission electron microscopic (STEM) examination conducted an conventionally and microwave sintered WC/Co samples exhibited remarkable difference in the chemistry of cobalt binder phase. It is understood that the superior mechanical properties of microwave sintered part are due to the pure cobalt phase present at the grain boundary of WC grains, while the conventionally sintered part showed there was substantial inter-alloying of Co with tungsten. (author)

Physical properties and microstructure of Ti(CN)-based cermets with different WC particle size

International Nuclear Information System (INIS)

Deng, Ying; Deng, Ling; Xiong, Xiang; Ye, J.W.; Li, P.P.

2014-01-01

Ti(CN)-based cermets with different WC particle sizes from 0.2 to 4 μm were prepared at 1450 °C with 2 MPa Air pressure. The microstructure of cermets was investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), Transmission electron microscope (TEM). The results showed that all the cermets with different WC particle sizes have a typical “core–rim” structure. With the increase of WC powder sizes, the frequency and portion of Ti(C 0.7 N 0.3 ) cores and rim are somewhat decreased while the portion of white core is increased, due to the relative dissolution rate decreasing. In addition, the fracture mode of Ti(C,N) based cermets is a mixture of trans-granular (primary) and inter-granular (subordinate) fracture. The TRS (about 1850 MPa) of the cermets fluctuate slightly with the WC particle sizes from 0.2 to 1.0 μm, but decrease evidently with WC particle sizes up to 2 μm

Interacción térmica recubrimiento-sustrato en la proyección a alta velocidad (HVOF de partículas (polvo de WC-Co

Directory of Open Access Journals (Sweden)

Sobolev, V. V.

1995-06-01

Full Text Available The mathematical simulation of the thermal interaction between a 34CrMo4 (UNS-G41350 steel substrate and a coating formed by the droplets of WC-12 % Co powder particles during HVOF spraying is undertaken. Analysis of the heat transfer processes permitted the investigation of the temperature evolution, coating solidification, substrate fusion and solidification, particular features of the thermal interactions between the substrate and the coating as well as between the successive coating layers. The analysis has also permitted to estimate the optimal conditions of the substrate and the coating structure formation. The obtained results were used in subsequent articles to predict the structure parameters, which agree with the experimental data.

Se utiliza la simulación matemática para establecer la interacción térmica entre un substrato y un recubrimiento obtenido mediante proyección térmica de alta velocidad, HVOF. El substrato es un acero 34CrMo4(UNS-G41350 y el recubrimiento está formado por la solidificación de gotas semifundidas de partículas de polvo de WC-12 % Co. El análisis del proceso de transferencia de calor permite la investigación de la evolución de la temperatura, la solidificación del recubrimiento, la fusión y posterior solidificación del substrato, las características peculiares de la interacción térmica entre el substrato y la primera capa de recubrimiento, así como con las diferentes capas sucesivas, y la estimación de las condiciones óptimas para la formación de la estructura del substrato y del recubrimiento. Los resultados obtenidos se han utilizado en posteriores artículos para predecir parámetros estructurales que están, por su parte, en concordancia con los datos experimentales.

Abrasive wear of WC-NiMoCrFeCo thermally sprayed coatings in dependence on different types of abrasive sands

Czech Academy of Sciences Publication Activity Database

Kašparová, M.; Zahálka, F.; Houdková, Š.; Ctibor, Pavel

2010-01-01

Roč. 48, č. 1 (2010), s. 75-85 ISSN 0023-432X R&D Projects: GA AV ČR 1QS200430560 Institutional research plan: CEZ:AV0Z20430508 Keywords : WC-Hastelloy * abrasive wear * Al2O3 sand * SiO2 sand * braun size * abrasive efficiency Subject RIV: JG - Metallurgy Impact factor: 0.471, year: 2010 http://kovmat.sav.sk/abstract.php?rr=48&cc=1&ss=73

Performance Analysis Review of Thorium TRISO Coated Particles during Manufacture, Irradiation and Accident Condition Heating Tests

International Nuclear Information System (INIS)

2015-03-01

Thorium, in combination with high enriched uranium, was used in all early high temperature reactors (HTRs). Initially, the fuel was contained in a kernel of coated particles. However, particle quality was low in the 1960s and early 1970s. Modern, high quality, tristructural isotropic (TRISO) fuel particles with thorium oxide and uranium dioxide (UO 2 ) had been manufactured since 1978 and were successfully demonstrated in irradiation and accident tests. In 1980, HTR fuels changed to low enriched uranium UO 2 TRISO fuels. The wide ranging development and demonstration programme was successful, and it established a worldwide standard that is still valid today. During the process, results of the thorium work with high quality TRISO fuel particles had not been fully evaluated or documented. This publication collects and presents the information and demonstrates the performance of thorium TRISO fuels.This publication is an outcome of the technical contract awarded under the IAEA Coordinated Research Project on Near Term and Promising Long Term Options for Deployment of Thorium Based Nuclear Energy, initiated in 2012. It is based on the compilation and analysis of available results on thorium TRISO coated particle performance in manufacturing and during irradiation and accident condition heating tests

Manufacturing of 380/220 V 63 A power supply panel on UO2 kernel coating unit

International Nuclear Information System (INIS)

Triyono; Mudjiman, Supardjono; Hidayat, Nur

2013-01-01

The panel 380/220 Volts voltage source current 63 Amperes relay AC output on UO 2 kernel coating unit has been manufactured. The activities include: installation and function panel test. The electrical installation of load includes : 220 Volts temperature monitor/controller, 220 Volts scraber pump, 220 Volts vacuum pump, 220 Volts solenoid valve gas and 380 Volts induction furnace. The component of installation includes: 380 Volts earth leakage circuit breaker, 380 Volts relay AC, 220 Volts magnetic circuit breaker, 100/5 Amperes current transformator ratio, voltmeter, ampermeter and push button normally open-close and temperature monitor/control in the box size 70x50x20 cm. The testing of voltage source has been unload and full load to determine the performance of the tool. The result of manufacture and function test voltage source 380/220 Volts at the UO 2 kernel coating unit showed that: the voltage source can work without load and full load safely. The load includes: voltage 380-382 Volts current 4-4,1 Amperes of induction furnace, voltage 223 Volts current 0,5 Amperes of vacuum pump, voltage 223 Volts current 4 Amperes of scraber pump, voltage 223 Volts current 0,3 Amperes of solenoid valve gas and 222 Volts current 0,03 Amperes temperature monitor/control. (author)

Latest Developments in PVD Coatings for Tooling

Directory of Open Access Journals (Sweden)

Gabriela Strnad

2010-06-01

Full Text Available The paper presents the recent developments in the field of PVD coating for manufacturing tools. A review of monoblock, multilayer, nanocomposite, DLC and oxinitride coatings is discussed, with the emphasis on coatings which enables the manufacturers to implement high productivity processes such as high speed cutting and dry speed machining.

Microstructure and mechanical properties of TiB2–TiC–WC composite ceramic tool materials

International Nuclear Information System (INIS)

Song, Jinpeng; Huang, Chuanzhen; Zou, Bin; Liu, Hanlian; Wang, Jun

2012-01-01

Highlights: ►Effect of sintering parameters on TiB 2 –TiC–WC composites has been investigated. ► Ni element was dispersed in the interface between WC and matrix grains. ► The fracture mode changed from intergranular fracture to transgranular fracture. ► The microstructure and mechanical properties of the composite were improved. -- Abstract: TiB 2 –TiC–WC composites with Ni as a sintering aid were fabricated by a hot-press technique at 1700 °C and 1650 °C for 1 h, respectively. The microstructure and mechanical properties were investigated. The composites were analyzed by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). The matrix phases consisted of TiB 2 and TiC. No severe chemical reactions happened between the additive and matrix. The microstructure consisted of the fine WC grains and uniform matrix grains. When the proper WC content added to TiB 2 –TiC composites, the growth of matrix grains was inhibited and the mechanical properties of the composites were improved. The interface energy was strengthened by Ni that dispersed in the interfaces among WC grains and matrix grains, which made the fracture mode change from intergranular fracture to transgranular fracture. The transgranular fracture and the pulling out of WC grains played a predominant role in the propagating of cracks when WC content was 20 wt.% in TiB 2 –TiC–WC composites. The optimal mechanical properties of TiB 2 –TiC–20 wt.%WC composite were 955.71 MPa of flexural strength, 7.5 MPa m 1/2 of fracture toughness and 23.5 GPa of Vickers hardness.

Structural and Mechanical Properties of the ZrC/Ni-Nanodiamond Coating Synthesized by the PVD and Electroplating Processes for the Cutting Knifes

Science.gov (United States)

Chayeuski, V.; Zhylinski, V.; Cernashejus, O.; Visniakov, N.; Mikalauskas, G.

2018-04-01

In this work, combined gradient ZrC/Ni-nanodiamond ultradispersed diamonds (UDD) coatings were synthesized on the surface of knife blades made of hard alloy WC-2 wt.% Co by electroplating and cathode arc evaporation PVD techniques to increase the durability period of a wood-cutting milling tool. The microstructure, phase and elemental composition, microhardness, and adhesion strength of the coatings were investigated. Ni-UDD layer is not mixed with the ZrC coating and hard alloy substrate. Cobalt is present in Ni-UDD layer after deposition of ZrC. The ZrC/Ni-nanodiamond coating consists of separate phases of zirconium carbide (ZrC), α-Ni, and Ni-UDD. The maximum value of microhardness of the Ni-nanodiamond coating is 5.9 GPa. The microhardness value of the ZrC/Ni-nanodiamond coatings is 25 ± 6 GPa, which corresponds to the microhardness of the hard alloy substrate and ZrC coating. The obtained high values of the critical loads on the scratch track of the ZrC/Ni-nanodiamond coating in 24 N prove a sufficiently high value of the adhesion strength of the bottom Ni-UDD layer with WC-Co substrate. Pilot testing of ZrC/Ni-nanodiamond-coated cutting tools proved their increasing durability period to be 1.5-1.6 times higher than that of bare tools, when milling laminated chipboard.

PREPARATION OF WC-Co POWDER BY DIRECT REDUCTION AND CARBONIZATION

Institute of Scientific and Technical Information of China (English)

Zhonglai Yi; Gangqin Shao; Xinglong Duan; Peng Sun; Xiaoliang Shi; Zhen Xiong; Jingkun Guo

2005-01-01

A new approach to produce superfine WC-Co powder by direct reduction and carbonization is proposed.Water-soluble salts containing W and Co were used as raw materials. Tungsten and cobalt oxide powder (CoWO4/WO3)was first formed by a spray-pyrolysis technique, which was then mixed with carbon black and converted to WC-Co composite powder at 950℃ for 4 h in N2 atmosphere. The resulting powder has a particle size of 100-300 nm.

Analysis of Capillary Coating Die Flow in an Optical Fiber Coating Applicator

OpenAIRE

Kyoungjin Kim

2011-01-01

Viscous heating becomes significant in the high speed resin coating process of glass fibers for optical fiber manufacturing. This study focuses on the coating resin flows inside the capillary coating die of optical fiber coating applicator and they are numerically simulated to examine the effects of viscous heating and subsequent temperature increase in coating resin. Resin flows are driven by fast moving glass fiber and the pressurization at the coating die inlet, while ...

High quality ceramic coatings sprayed by high efficiency hypersonic plasma spraying gun

International Nuclear Information System (INIS)

Zhu Sheng; Xu Binshi; Yao JiuKun

2005-01-01

This paper introduced the structure of the high efficiency hypersonic plasma spraying gun and the effects of hypersonic plasma jet on the sprayed particles. The optimised spraying process parameters for several ceramic powders such as Al 2 O 3 , Cr 2 O 3 , ZrO 2 , Cr 3 C 2 and Co-WC were listed. The properties and microstructure of the sprayed ceramic coatings were investigated. Nano Al 2 O 3 -TiO 2 ceramic coating sprayed by using the high efficiency hypersonic plasma spraying was also studied. Compared with the conventional air plasma spraying, high efficiency hypersonic plasma spraying improves greatly the ceramic coatings quality but at low cost. (orig.)

Retention Load Values of Telescopic Crowns Made of Y-TZP and CoCr with Y-TZP Secondary Crowns: Impact of Different Taper Angles

Directory of Open Access Journals (Sweden)

Susanne Merk

2016-05-01

Full Text Available This study aimed to examine and compare the retention load values (RL of different telescopic crown assemblies (Y-TZP and CoCr primary crowns with electroformed and Y-TZP secondary crowns each with three different taper angles (0°, 1° and 2°. Thirty Y-TZP primary crowns with electroformed gold copings (Z/G group and Y-TZP secondary crowns (Z/Z group and 30 CoCr primary crowns with electroformed gold copings (C/G group and Y-TZP secondary crowns (C/Z group, each with taper angles of 0°, 1° and 2°, were fabricated, respectively. With the exception of the electroformed gold copings, all specimens were Computer-Aided-Design/Computer-Aided-Manufacturing (CAD/CAM-milled, then sintered and afterwards manually adapted. In order to stabilize the gold copings, they were fixed in a tertiary structure. The secondary crowns were constructed with a hook, which ensured self-alignment with an upper chain. Afterwards, 20 pull-off test cycles were performed in a universal testing machine under artificial saliva and after weighing the secondary crowns with a 5 kg object for 20 s. Data were analyzed by one-way and two-way Analysis of Variance (ANOVA. C/Z with 1° showed higher (p = 0.009 RL than 0° and 2° tapers. C/G at 1° also showed higher (p = 0.001 RL than at tapers of 0° and 2°. Z/G and C/G at 0° showed lower RL than Z/Z and C/Z (p < 0.001. Primary crowns had no impact on the 0° group. Z/G showed lower RL as compared to C/Z within the 1° group (p = 0.007 and Z/Z in the 2° group (p = 0.006. The primary crown material had no influence on RL. Electroformed copings showed lower RL. Further investigations for 1° as well as for the long-term performance after thermomechanical aging are necessary.

Electrical insulation and conduction coating for fusion experimental devices

International Nuclear Information System (INIS)

Onozuka, Masanori; Tsujimura, Seiji; Toyoda, Masahiko; Inoue, Masahiko; Abe, Tetsuya; Murakami, Yoshio

1996-01-01

The development of electrical insulation and conduction coating methods that can be applied to large components of fusion experimental devices has been investigated. A thermal spraying method is used to coat the insulation or conduction materials on the structural components because of its applicability for large surfaces. The insulation material chosen was Al 2 O 3 , while Cr 3 C 2 -NiCr and WC-NiCr were chosen as conduction materials. These materials were coated on stainless steel substrates to examine the basic characteristics of the coated layers, such as their adhesive strength to the substrate, thermal shock resistance, electrical resistance, dielectric breakdown voltage, and thermal conductivity. It was found that they have sufficient electrical insulation and conduction properties, respectively. In addition, the sliding tests of the coated layers showed adequate frictional properties. The spraying method was tested on a 100- x 1000-mm surface and found to be applicable for large surfaces of experimental fusion devices. 9 refs., 6 figs., 15 tabs

The effect of ion irradiation and elevated temperature on the microstructure and the properties of C/W/C/B multilayer coating

Energy Technology Data Exchange (ETDEWEB)

Vlcak, Petr, E-mail: petr.vlcak@fs.cvut.cz

2016-03-01

Graphical abstract: - Highlights: • C/W/C/B multilayer PVD coating was treated by 45 keV nitrogen ion irradiation. • The effect of ion irradiation and elevated temperature on microstructure was analyzed. • Formation of new compounds and degradation of carbon fraction were observed. • The causes of the observed changes in surface properties were discussed. - Abstract: C/W/C/B multi-layer PVD coating with a layer period of 10 nm and 500 nm in thickness was irradiated with 45 keV N ions at fluence of 1 × 10{sup 17} cm{sup −2}. Ion irradiation was performed at room temperature or at an elevated temperature of 500 °C. The microstructure was investigated by X-ray diffraction, by X-ray photoelectron spectroscopy, and by Raman spectroscopy. The results showed that implanted N ions bond both with W atoms and with C atoms. N ion irradiation induced the formation of WC and WC{sub 1−x} phases. The energetic ions transformed the C bonds in defect sp{sup 2} and defect sp{sup 3} hybridizations, resulting in graphitization of the carbon fraction in the multilayer coating. Ion irradiation reduced the cohesive strength of the monolayers, reduced hardness of the C/W/C/B coating, increased its surface roughness and increased its friction coefficient. An elevated temperature during ion irradiation caused a better arrangement of the WC phase and further graphitization of the carbon fraction, in comparison with a coating treated by ion irradiation at room temperature. There is discussion of the causes of the observed changes in surface properties.

Surface analysis of WC--Co composite materials (2) Quantitative Auger electron spectrometry

International Nuclear Information System (INIS)

Tongson, L.L.; Biggers, J.V.; Dayton, G.O.; Bind, J.M.; Knox, B.E.

1978-01-01

The unique sensitivity of Auger electron spectrometry (AES) to combined carbon has been exploited in measuring the surface compositions of hot-pressed, conventionally sintered and mixed powders of WC--Co composite materials. AES sensitivity factors for tungsten and carbon (in WC) relative to cobalt were determined. The concentrations of the major elements in hot-pressed samples measured with AES using the relative sensitivity method were compared to those obtained independently by electron microprobe (EMP) and x-ray fluorescence (XRF) techniques. Corollary studies using ion scattering spectrometry (ISS) showed the absence of (1) matrix effects in the AES measurements, (2) preferential sputtering during ion bombardment, and (3) deposition of the easier-to-sputter component (cobalt) onto WC

Benzotriazole (BTA), A Promising Corrosion Inhibitor for WC-Co Hardmetal

Energy Technology Data Exchange (ETDEWEB)

Schnyder, B.; Stoessel-Sittig, C.; Koetz, R.; Hochstrasser-Kurz, S. [ETH Zuerich (Switzerland); Virtanen, S. [ETH Zuerich (Switzerland); Jaeggi, Ch. [University of Bern (Switzerland); Eichenberger, N. [University of Bern (Switzerland); Szoecs, E. [University of Bern (Switzerland); Siegenthaler, H. [University of Bern (Switzerland); Ziegler, P. [AGIE SA (Switzerland); Beltrami, I. [AGIE SA (Switzerland)

2004-03-01

Wire Electro-Discharge Machining (W-EDM) of tungsten carbide with Co-binder may lead to corrosion and discolouration at the surface. The corrosion behaviour of WC-Co based hardmetal was investigated in different aqueous solutions (acidic, neutral, and alkaline solutions). At open-circuit potential WC-Co based hardmetals show rather high dissolution rates in all types of electrolyte. An efficient corrosion inhibitor (benzotriazole, C{sub 6}H{sub 5}N{sub 3}) could be found for a borate buffer solution, pH = 8.4. (author)

Production and Characterization of WC-Reinforced Co-Based Superalloy Matrix Composites

Science.gov (United States)

Özgün, Özgür; Dinler, İlyas

2018-05-01

Cobalt-based superalloy matrix composite materials were produced through the powder metallurgy technique using element powders at high purity and nano-sized wolfram carbide (WC) reinforcement in this study. An alloy that had the same chemical composition as the Stellite 6 alloy but not containing carbon was selected as the matrix alloy. The powder mixtures obtained as a result of mixing WC reinforcing member and element powders at the determined ratio were shaped by applying 300 MPa of pressure. The green components were sintered under argon atmosphere at 1240 °C for 120 minutes. The densities of the sintered components were determined by the Archimedes' principle. Microstructural characterization was performed via X-ray diffraction analysis, scanning electron microscope examinations, and energy-dispersive spectrometry. Hardness measurements and tensile tests were performed for determining mechanical characteristics. The relative density values of the sintered components increased by increasing the WC reinforcement ratio and they could almost reach the theoretical density. It was determined from the microstructural examinations that the composite materials consisted of fine and equiaxed grains and coarse carbides demonstrating a homogeneous dispersion along the microstructure at the grain boundaries. As it was the case in the density values, the hardness and strength values of the composites increased by increasing the WC ratio.

Fracture toughness measurements of WC-based hard metals

International Nuclear Information System (INIS)

Prakash, L.; Albert, B.

1983-01-01

The fracture toughness of WC-based cemented carbides was determined by different methods. The values obtained are dependent on the procedure of measurement. Each method thoughness of hard metals mutually. (orig.) [de

Lotus Dust Mitigation Coating and Molecular Adsorber Coating

Science.gov (United States)

O'Connor, Kenneth M.; Abraham, Nithin S.

2015-01-01

NASA Goddard Space Flight Center has developed two unique coating formulations that will keep surfaces clean and sanitary and contain contaminants.The Lotus Dust Mitigation Coating, modeled after the self-cleaning, water-repellant lotus leaf, disallows buildup of dust, dirt, water, and more on surfaces. This coating, has been successfully tested on painted, aluminum, glass, silica, and some composite surfaces, could aid in keeping medical assets clean.The Molecular Adsorber Coating is a zeolite-based, sprayable molecular adsorber coating, designed to prevent outgassing in materials in vacuums. The coating works well to adsorb volatiles and contaminates in manufacturing and processing, such as in pharmaceutical production. The addition of a biocide would also aid in controlling bacteria levels.

Soft phonon modes driven huge difference on lattice thermal conductivity between topological semimetal WC and WN

Science.gov (United States)

Guo, San-Dong; Chen, Peng

2018-04-01

Topological semimetals are currently attracting increasing interest due to their potential applications in topological qubits and low-power electronics, which are closely related to their thermal transport properties. Recently, the triply degenerate nodal points near the Fermi level of WC are observed by using angle-resolved photoemission spectroscopy. In this work, by solving the Boltzmann transport equation based on first-principles calculations, we systematically investigate the phonon transport properties of topological semimetals WC and WN. The predicted room-temperature lattice thermal conductivities of WC (WN) along the a and c directions are 1140.64 (7.47) W m-1 K-1 and 1214.69 (5.39) W m-1 K-1. Considering the similar crystal structure of WC and WN, it is quite interesting to find that the thermal conductivity of WC is more than two orders of magnitude higher than that of WN. It is found that, different from WN, the large acoustic-optical (a-o) gap prohibits the acoustic+acoustic → optical (aao) scattering, which gives rise to very long phonon lifetimes, leading to ultrahigh lattice thermal conductivity in WC. For WN, the lack of an a-o gap is due to soft phonon modes in optical branches, which can provide more scattering channels for aao scattering, producing very short phonon lifetimes. Further deep insight can be attained from their different electronic structures. Distinctly different from that in WC, the density of states of WN at the Fermi level becomes very sharp, which leads to destabilization of WN, producing soft phonon modes. It is found that the small shear modulus G and C44 limit the stability of WN, compared with WC. Our studies provide valuable information for phonon transports in WC and WN, and motivate further experimental studies to study their lattice thermal conductivities.

Erosion Testing of Coatings for V-22 Aircraft Applications

Directory of Open Access Journals (Sweden)

G. Y. Richardson

2003-01-01

Full Text Available High-velocity (183 m/sec sand erosion tests in a wind tunnel were conducted to evaluate developmental coatings from three separate companies under funding by the Navy's phase I small business innovative research program. The purpose of the coatings was to address a particular problem the V-22 tilt-rotor aircraft (Osprey was having with regard to ingestion of sand particles by a titanium impeller that was associated with the aircraft's environmental control system. The three coatings that were deposited on titanium substrates and erosion-tested included (1 SixCy/DLC multilayers deposited by chemical vapor deposition (CVD; (2 WC/TaC/TiC processed by electrospark deposition; and (3 polymer ceramic mixtures applied by means of an aqueous synthesis. The erosion test results are presented; they provided the basis for assessing the suitability of some of these coatings for the intended application.

Optical thin films and coatings from materials to applications

CERN Document Server

Flory, Francois

2013-01-01

Optical coatings, including mirrors, anti-reflection coatings, beam splitters, and filters, are an integral part of most modern optical systems. This book provides an overview of thin film materials, the properties, design and manufacture of optical coatings and their use across a variety of application areas.$bOptical coatings, including mirrors, anti-reflection coatings, beam splitters, and filters, are an integral part of most modern optical systems. Optical thin films and coatings provides an overview of thin film materials, the properties, design and manufacture of optical coatings and their use across a variety of application areas. Part one explores the design and manufacture of optical coatings. Part two highlights unconventional features of optical thin films including scattering properties of random structures in thin films, optical properties of thin film materials at short wavelengths, thermal properties and colour effects. Part three focusses on novel materials for optical thin films and coatings...

Microstructure Characterization of WCCo-Mo Based Coatings Produced Using High Velocity Oxygen Fuel

Directory of Open Access Journals (Sweden)

Serkan Islak

2015-12-01

Full Text Available The present study has been carried out in order to investigate the microstructural properties of WCCo-Mo composite coatings deposited onto a SAE 4140 steel substrate by high velocity oxygen fuel (HVOF thermal spray. For this purpose, the Mo quantity added to the WCCo was changed as 10, 20, 30 and 40 wt. % percents. The coatings are compared in terms of their phase composition, microstructure and hardness. Phase compound and microstructure of coating layers were examined using X-ray diffractometer (XRD and scanning electron microscope (SEM. XRD results showed that WCCo-Mo composite coatings were mainly composed of WC, W2C, Co3W3C, Mo2C, MoO2, Mo and Co phases. The average hardness of the coatings increased with increasing Mo content.

The influence of aggregates type on W/C ratio on the strength and other properties of concrete

Science.gov (United States)

Malaiskiene, J.; Skripkiunas, G.; Vaiciene, M.; Karpova, E.

2017-10-01

The influence of different types of aggregates and W/C ratio on concrete properties is analysed. In order to achieve this aim, lightweight (with expanded clay aggregate) and normal concrete (with gravel aggregate) mixtures are prepared with different W/C ratios. Different W/C ratios are selected by reducing the amount of cement when the amount of water is constant. The following properties of concrete have been determined: density, compressive strength and water absorption. Additionally, the statistical data analysis is performed and influence of aggregate type and W/C ratio on concrete properties is determined. The empirical equations indicating dependence between concrete strength and W/C and strength of aggregate are obtained for normal concrete and light-weight concrete.

Transfer coating by electron initiated polymerization

International Nuclear Information System (INIS)

Nablo, S.V.

1985-01-01

The high speed and depth of cure possible with electron initiated monomer/oligomer coating systems provide many new opportunities for approaches to product finishing. Moreover, the use of transfer or cast coating using films or metallic surfaces offers the ability to precisely control the surface topology of liquid film surfaces during polymerization. Transfer coating such as with textiles has been a commercial process for many years and the synergistic addition of EB technology permits the manufacture of unusual new products. One of these, the casting paper used in the manufacture of vinyl and urethane fabrics, is the first EB application to use a drum surface for pattern replication in the coating. In this case the coated paper is cured against, and then released from, an engraved drum surface. Recent developments in the use of plastic films for transfer have been applied to the manufacture of transfer metallized and coated paper and paperboard products for packaging. Details of these and related processes will be presented as well as a discussion of the typical product areas using this high speed transfer technology. (author)

Contribution to the study of atmospheric projection and under partial vacuum of tungsten carbide particles with cobalt or nickel binder. Application to fretting coatings on steel

International Nuclear Information System (INIS)

Vinayo, Maria-Elena

1985-01-01

This research thesis addresses the plasma spraying (atmospheric, under controlled atmosphere, and under reduced pressure) of tungsten carbides with a metallic binder (WC/Co, WC/Ni; W 2 C/Co). This work comprised an optimisation of the spraying process under reduced pressure, the study of the influence of the powder production process on the physicochemical and micro-structural characteristics as well as on coating fretting properties, and a correlation between spraying parameters in a controlled atmosphere (power and pressure) and coating physico-chemical and micro-structural properties. Results show a high decarburization-oxidation of tungsten carbides during atmospheric spraying, as well as an important evaporation of cobalt. Under reduced pressure, high losses of carbides are noticed. These both phenomena strongly depend on the powder production process. Fretting results highlight remarkable performance of coatings obtained by atmospheric spraying [fr

Wear behaviour of plasma-sprayed AlSi/B4C composite coatings

International Nuclear Information System (INIS)

Sarikaya, Ozkan; Anik, Selahaddin; Celik, Erdal; Okumus, S. Cem; Aslanlar, Salim

2007-01-01

This paper describes the wear behaviour of AlSi/B 4 C composite coatings with 0-25 wt% B 4 C particles for diesel engine motors. These coatings were successfully fabricated on AlSi substrates using an atmospheric plasma spray technique. The produced samples were characterized by means of an optical microscope, scanning electron microscope and microhardness tester. The obtained results pointed out that an increase of B 4 C particles in AlSi coatings was caused on the rising of the microhardness values and the decrease of the thermal expansion coefficient of the coatings. The friction and wear experiments were performed under dry conditions using a ball-on-dics configuration against WC/Co counter material for different loads. It was concluded that wear resistance of the coatings produced using B 4 C powders is greatly improved compared with the substrate material. The highest wear resistance of the coatings were also determined in the 20% B 4 C coating

Search for the optimally suited cantilever type for high-frequency MFM

International Nuclear Information System (INIS)

Koblischka, M R; Wei, J D; Kirsch, M; Lessel, M; Pfeifer, R; Brust, M; Hartmann, U; Richter, C; Sulzbach, T

2007-01-01

To optimize the performance of the high-frequency MFM (HF-MFM) technique [1-4], we performed a search for the best suited cantilever type and magnetic material coating. Using a HF-MFM setup with hard disk writer poles as test samples, we carried out HF-MFM imaging at frequencies up to 2 GHz. For HF-MFM, it is an essential ingredient that the tip material can follow the fast switching of the high-frequency fields. In this contribution, we investigated 6 different types of cantilevers (i) the 'standard' MFM tip (Nanoworld Pointprobe) with 30 nm CoCr coating, (ii) a 'SSS' (Nanoworld SuperSharpSilicon TM ) cantilever with a 10 nm CoCr coating, (iii) a (Ni, Zn)-ferrite coated pointprobe tip (iv) a Ba 3 Co 2 Fe 23 O 41 (BCFO) coated pointprobe tip, (v) a low-coercivity NiCo alloy coated tip, and (vi) a permalloy-coated tip

A theoretical understanding on the CO-tolerance mechanism of the WC(0001) supported Pt monolayer: Some improvement strategies

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xilin [College of Physics and Materials Science, Henan Normal University, Xinxiang, 453007 (China); Lu, Zhansheng [College of Physics and Materials Science, Henan Normal University, Xinxiang, 453007 (China); Collaborative Innovation Center of Nano Functional Materials and Applications, Henan Province (China); Yang, Zongxian, E-mail: yzx@henannu.edu.cn [College of Physics and Materials Science, Henan Normal University, Xinxiang, 453007 (China); Collaborative Innovation Center of Nano Functional Materials and Applications, Henan Province (China)

2016-12-15

Highlights: • The mechanism of CO tolerance and oxidation on Pt{sub ML}/WC(0001) is clarified. • The high tolerance of Pt{sub ML}/WC(0001) to CO originate from the weak adsorption. • The minimum energy path and the rate-determining step are identified. • The activity of Pt{sub ML}/WC(0001) to CO oxidation is comparable to that of Pt(111). • Some probable strategies are proposed to improve the activity of Pt{sub ML}/WC(0001). - Abstract: The deposition of platinum on the tungsten carbide (Pt/WC) have been achieved and proved with high stability, activity and CO-tolerance toward some reactions in experiments. Although a lot of experimental efforts have been focused on understanding the activity, stability and CO-tolerance of Pt/WC, the relevant theoretical works related to the CO-tolerance mechanism are still scarce. In current study, the adsorption and oxidation of CO on the Pt monolayer supported on WC(0001) surface (Pt{sub ML}/WC(0001)) are investigated using density functional theory calculations. It is found that the oxidation of CO on Pt{sub ML}/WC(0001) proceeds preferably along the Langmuir-Hinshelwood mechanism. The energy barrier of 1.06 eV for the rate-determining step of OOCO formation is almost equal to that (1.05 eV) for CO oxidation by atomic O on Pt(111), while the adsorption energy of 1.59 eV for CO on Pt{sub ML}/WC(0001) is smaller than that on Pt(111) (1.85 eV), indicating that the high resistance to CO poisoning of Pt{sub ML}/WC(0001) may originate from the weak interaction between them. To further improve the CO tolerance, some probable strategies are proposed based on the relevant kinetics results. The current results are helpful to understanding the origin of the highly resistant to CO poisoning of Pt{sub ML}/WC(0001) and rationally designing catalysts to improve the CO oxidation activity.

Computational manufacturing as a bridge between design and production.

Science.gov (United States)

Tikhonravov, Alexander V; Trubetskov, Michael K

2005-11-10

Computational manufacturing of optical coatings is a research area that can be placed between theoretical designing and practical manufacturing in the same way that computational physics can be placed between theoretical and experimental physics. Investigations in this area have been performed for more than 30 years under the name of computer simulation of manufacturing and monitoring processes. Our goal is to attract attention to the increasing importance of computational manufacturing at the current state of the art in the design and manufacture of optical coatings and to demonstrate possible applications of this research tool.

Laser and electron-beam powder-bed additive manufacturing of metallic implants: A review on processes, materials and designs.

Science.gov (United States)

Sing, Swee Leong; An, Jia; Yeong, Wai Yee; Wiria, Florencia Edith

2016-03-01

Additive manufacturing (AM), also commonly known as 3D printing, allows the direct fabrication of functional parts with complex shapes from digital models. In this review, the current progress of two AM processes suitable for metallic orthopaedic implant applications, namely selective laser melting (SLM) and electron beam melting (EBM) are presented. Several critical design factors such as the need for data acquisition for patient-specific design, design dependent porosity for osteo-inductive implants, surface topology of the implants and design for reduction of stress-shielding in implants are discussed. Additive manufactured biomaterials such as 316L stainless steel, titanium-6aluminium-4vanadium (Ti6Al4V) and cobalt-chromium (CoCr) are highlighted. Limitations and future potential of such technologies are also explored. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Mechanical properties of hot-pressed Al-4.5 wt. % Cu/WC composite

Directory of Open Access Journals (Sweden)

Samaneh Bernoosi

2014-12-01

Full Text Available In this study, the elemental powders of aluminum and copper were initially subjected to mechanical alloying using an attrition ball mill under argon atmosphere to produce an Al-4.5 wt% Cu powder alloy. The WC nanoparticles were then added to the powder alloy and milled in a planetary ball mill to explore the role of the WC nanoparticles on the mechanical properties of the fabricated composite powder. The experimental results revealed that a solid solution of Al-Cu could be formed after MA and a good dispersion of the WC nanoparticles in the aluminum matrix was obtained as characterized using X-ray diffraction and scanning electron microscopy, respectively. The results of hardness and compression tests of the hot pressed composites indicated that the MA followed by the hot-press processes was successful to fabricate an alloy and a metal matrix composite with considerable mechanical properties. However, a decreasing trend in the hardness and strength of the composites with the WC contents of more than 5wt% was observed. The maximum values of 260 HV and 575 MPa were obtained for a composite containing 5 wt% of nano ceramic particles.

Characterization of boride-based powders and detonation gun sprayed cermet coatings

International Nuclear Information System (INIS)

Keraenen, J.; Stenberg, T.; Maentylae, T.

1995-01-01

Detonation gun sprayed (DGS) cermet coatings containing complex ternary transition metal boride as hard particles dispersed in a stainless steel or nickel based superalloy matrix have been characterized. Microstructure of the coatings, as well as powders, were studied with optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and analytical transmission electron microscopy (AEM). X-ray microanalysis of the coatings were carried out using energy dispersive X-ray spectrometer (EDS) attached to the SEM and AEM. Moreover, abrasion wear resistance of the coatings was evaluated with a rubber wheel abrasion test equipment. The general microstructure of studied coatings appeared to be heterogeneous in the terms of the distribution, size and crystallographic nature of the phases. Nonetheless, very low porosities were obtained and in the coatings the oxide phase as well as the unmelted particles and the formation of oxide phase were avoided by optimization of DGS parameters. So far the abrasive wear resistance of boride-based cermet coatings is not so good as that of the WC-12Co coatings

Compression deformation of WC: atomistic description of hard ceramic material

Science.gov (United States)

Feng, Qing; Song, Xiaoyan; Liu, Xuemei; Liang, Shuhua; Wang, Haibin; Nie, Zuoren

2017-11-01

The deformation characteristics of WC, as a typical hard ceramic material, were studied on the nanoscale using atomistic simulations for both the single-crystal and polycrystalline forms under uniaxial compression. In particular, the effects of crystallographic orientation, grain boundary coordination and grain size on the origin of deformation were investigated. The deformation behavior of the single-crystal and polycrystalline WC both depend strongly on the orientation towards the loading direction. The grain boundaries play a significant role in the deformation coordination and the potential high fracture toughness of the nanocrystalline WC. In contrast to conventional knowledge of ceramics, maximum strength was obtained at a critical grain size corresponding to the turning point from a Hall-Petch to an inverse Hall-Petch relationship. For this the mechanism of the combined effect of dislocation motion within grains and the coordination of stress concentration at the grain boundaries were proposed. The present work has moved forward our understanding of plastic deformability and the possibility of achieving a high strength of nanocrystalline ceramic materials.

Binder extrusion of sliding wear of WC-Co alloys

International Nuclear Information System (INIS)

Larsen-Basse, J.

1985-01-01

It has previously been proposed that preferential removal of the cobalt binder is an important mechanism in the abrasive wear of cemented carbides in the WC-Co family. It is here demonstrated that binder extrusion occurs also in metal-to-metal sliding wear contacts. The wear scar generated by sliding a hardened steel ball repeatedly over a polished WC-Co surface was studied by SEM. The extruded cobalt fragments accumulate by surface defects, such as cracks caused by the sliding loaded ball, and gradual microfragmentation of the carbide grains follows. The energy required to extrude the cobalt and cause the gradual change in surface layer microstructure is provided by the frictional forces

Single layer and multilayer wear resistant coatings of (Ti,Al)N: a review

International Nuclear Information System (INIS)

PalDey, S.; Deevi, S.C.

2003-01-01

We review the status of (Ti,Al)N based coatings obtained by various physical vapor deposition (PVD) techniques and compare their properties. PVD techniques based on sputtering and cathodic arc methods are widely used to deposit wear resistant (Ti,Al)N coatings. These techniques were further modified to improve the metal ionization rate and to eliminate macrodroplets from plasma streams. We summarize manufacture of target/cathode, substrate materials for deposition of coatings, deposition parameters, and the effect of deposition parameters on the physical and mechanical properties of (Ti,Al)N coatings. It is shown that (Ti,Al)N coatings by PVD enhance the wear, thermal, and oxidation resistance of a wide variety of tool materials. We discuss the wear resistant properties of (Ti,Al)N for various machining applications as compared with coatings such as TiN, Ti(C,N) and (Ti,Zr)N. High hardness (∼28-32 GPa), relatively low residual stress (∼5 GPa), superior oxidation resistance, high hot hardness, and low thermal conductivity make (Ti,Al)N coatings most desirable in dry machining and machining of abrasive alloys at high speeds. Multicomponent coatings based on different metallic and nonmetallic elements combine the benefit of individual components leading to a further refinement of coating properties. Alloying additions such as Cr and Y drastically improve the oxidation resistance, Zr and V improve the wear resistance, whereas, Si increases the hardness and resistance to chemical reactivity of the film. Addition of boron improves the abrasive wear behavior of Ti-Al based coatings due to the formation of TiB 2 and BN phases depending on the deposition conditions. Hafnium based nitrides and carbides have potential for resistance to flank and crater wear. The presence of a large number of interfaces between individual layers of a multilayered structure results in a drastic increase in hardness and strength. (Ti,Al)N multilayer super lattice coatings with lattice

Parametric Study of Slurry-Erosion of Hydroturbine Steels with and without Detonation Gun Spray Coatings using Taguchi Technique

Science.gov (United States)

Grewal, Harpreet Singh; Bhandari, Sanjeev; Singh, Harpreet

2012-09-01

WC-Co-Cr coatings were deposited on some hydroturbine 13Cr4Ni and 16Cr5Ni steels by the detonation-gun spray process. An in-depth characterization of the as-sprayed coating was done using X-ray diffraction (XRD) and scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDS) techniques. Microhardness and porosity measurements were also made. The coating was found to have a typical splat-like morphology with some indications of unmelted carbide particles. The XRD results showed the presence of WC as the primary phase along with W2C and Co6W6C as secondary phases. Furthermore, the slurry erosion behavior of the coatings was investigated to ascertain the usefulness of the coatings to reduce the slurry erosion of the steels. The effect of four operating factors viz. the velocity, impact angle, concentration, and particle size on the slurry erosion of coated and bare steels has been studied using a high-speed jet-type test rig. The sand used as an erodent was collected from a power plant to replicate the actual turbine conditions. It has been observed that the given cermet coating can enhance the erosion resistance of the steel. Velocity was found to be the most significant factor affecting the erosion behavior of the coating, whereas it was the erodent particle size in the case of uncoated steel. As evidenced from the SEM images, the platelet mechanism of erosion seemed to be the prominent one, causing the removal of material from the surface of the steel, whereas for the coating, the formation and interlinking of cracks resulted in the removal of material.

Metallography and quality of dies made from WC-Co cemented carbides; Metallographie und Qualitaetskontrolle von WC-Co-Hartmetallmatrizen

Energy Technology Data Exchange (ETDEWEB)

Forejt, M. [Inst. of Technology, Faculty of Mechanical Engineering, Technical Univ., Brno (Czech Republic); Krejcova, J. [Inst. of Technology, Faculty of Mechanical Engineering, Technical Univ., Brno (Czech Republic); Smutna, J. [Inst. of Physics of Materials, ASCR, Brno (Czech Republic); Krejci, J. [Inst. of Physics of Materials, ASCR, Brno (Czech Republic)

1995-05-01

As opposite to cutting tools made from cemented carbides, forming tools (dies) seem to be on the periphery of the interest, although specific loading conditions (increased temperature, relatively high strain rate, high pressure and cyclic loading) impose different requirements on the material. The present paper contains results of light and SEM metallography of WC + Co cemented carbide dies used for screw nuts production. Two problems were pursued viz. final preparation of the surface of operative cavity after drilling and defects that appear when recycled cemented carbides are used for die production. (orig.) [Deutsch] Im Gegensatz zu Hartmetall-Schneidwerkzeugen scheinen Formwerkzeuge (Matrizen) nur am Rande des Interesses zu liegen, obwohl hier die spezifischen Beanspruchungsbedingungen (hoehere Temperaturen, relativ hohe Dehnrate, hoher Druck und zyklische Belastung) zu besonderen Anforderungen an den Werkstoff fuehren. Es werden die Ergebnisse der lichtmikroskopischen und REM-Untersuchungen an WC-Co-Hartmetallmatrizen fuer die Mutternherstellung beschrieben. Zwei Themen werden behandelt, und zwar die Endbearbeitung der Formhohlraum-Oberflaeche nach dem Bohren und die Fehler, die durch die Verwendung von Hartmetallschrott fuer die Matrizenherstellung auftreten koennen. (orig.)

Domain structures and temperature-dependent spin reorientation transitions in c-axis oriented Co-Cr thin films

International Nuclear Information System (INIS)

Kusinski, Greg J.; Krishnan, Kannan M.; Thomas, Gareth; Nelson, E. C.

2000-01-01

Highly c-axis oriented Co 95 Cr 5 films with perpendicular anisotropy were grown epitaxially on Si (111), using an Ag seed layer, by physical vapor deposition. Films were characterized by x-ray diffraction, transmission electron microscopy (TEM), selected area electron diffraction, and Lorentz microscopy in a TEM. The following epitaxial relationship was confirmed: (111) Si (parallel sign)(111) Ag (parallel sign)(0001) CoCr ;[2(bar sign)20] Si (parallel sign)[2(bar sign)20] Ag (parallel sign)[1(bar sign)100] CoCr . Magnetic domain structures of these films were observed as a function of thickness; t, in the range, 200 Aa c ≅300 Aa, the magnetization was found to be effectively in-plane of the film, and above t c a regular, stripe-like domain pattern with a significant, alternating in sign, perpendicular component was observed. The spin reorientation transitions of the stripe domains to the in-plane magnetization were studied dynamically by observing the domains as a function of temperature by in situ heating up to 350 degree sign C. The critical transition thickness, t c , which is a function of K u and magnetostatic energy, was found to increase with increasing temperature. The stripe-domain period, L observed at room temperature was found to increase gradually with thickness; L=90 nm at t=300 Aa, and L=110 nm at t=700 Aa. (c) 2000 American Institute of Physics

Synthesis and Multi Scale Tribological Behavior of WC-Co/Nanodiamond Nanocomposites.

Science.gov (United States)

Nieto, Andy; Jiang, Lin; Kim, Jaekang; Kim, Dae-Eun; Schoenung, Julie M

2017-08-01

Nanodiamonds (ND) present a unique combination of desirable mechanical, functional, and chemical characteristics that are ideally suited for reinforcing and enhancing the wear resistance of carbide based materials. Tungsten carbide cobalt (WC-Co) matrix nanocomposites reinforced with varying amounts of ND (2 - 10 vol.%) were synthesized here by spark plasma sintering. The rapid thermal consolidation route enabled attainment of dense samples with a significant retention of the metastable diamond phase. NDs affected the microstructural evolution, chemistry, and mechanical properties of WC-Co. Macroscale reciprocating pin-on-disk tests were conducted to assess wear behavior under conditions relevant to service environments, e.g., high cycles and high contact pressure. Microscale tribological properties were assessed using microscratch tests in order to investigate the intrinsic effects of ND on the localized mechanical and tribological response of WC-Co-ND composites. The incorporation of 10 vol.% ND enhanced wear resistance at both the micro- and macroscale, by 28% and 35%, respectively.

The Synthesis of Nanostructured WC-Based Hardmetals Using Mechanical Alloying and Their Direct Consolidation

Directory of Open Access Journals (Sweden)

N. Al-Aqeeli

2014-01-01

Full Text Available Tungsten carbide- (WC- based hardmetals or cemented carbides represent an important class of materials used in a wide range of industrial applications which primarily include cutting/drilling tools and wear resistant components. The introduction and processing of nanostructured WC-based cemented carbides and their subsequent consolidation to produce dense components have been the subject of several investigations. One of the attractive means of producing this class of materials is by mechanical alloying technique. However, one of the challenging issues in obtaining the right end-product is the possible loss of the nanocrystallite sizes due to the undesirable grain growth during powder sintering step. Many research groups have engaged in multiple projects aiming at exploring the right path of consolidating the nanostructured WC-based powders without substantially loosing the attained nanostructure. The present paper highlights some key issues related to powder synthesis and sintering of WC-based nanostructured materials using mechanical alloying. The path of directly consolidating the powders using nonconventional consolidation techniques will be addressed and some light will be shed on the advantageous use of such techniques. Cobalt-bonded hardmetals will be principally covered in this work along with an additional exposure of the use of other binders in the WC-based hardmetals.

Genotoxicity of tungsten carbide-cobalt (WC-Co) nanoparticles in vitro: mechanisms-of-action studies.

Science.gov (United States)

Moche, Hélène; Chevalier, Dany; Vezin, Hervé; Claude, Nancy; Lorge, Elisabeth; Nesslany, Fabrice

2015-02-01

We showed previously that tungsten carbide-cobalt (WC-Co) nanoparticles (NP) can be used as a nanoparticulate positive control in some in vitro mammalian genotoxicity assays. Here, we investigate the mechanisms of action involved in WC-Co NP genotoxicity in L5178Y mouse lymphoma cells and primary human lymphocytes, in vitro. Data from the micronucleus assay coupled with centromere staining and from the chromosome-aberration assay show the involvement of both clastogenic and aneugenic events. Experiments with the formamidopyrimidine DNA glycosylase (FPG)-modified comet assay showed a slight (non-significant) increase in FPG-sensitive sites in the L5178Y mouse lymphoma cells but not in the human lymphocytes. Electron paramagnetic resonance spin-trapping results showed the presence of hydroxyl radicals (•OH) in WC-Co NP suspensions, with or without cells, but with time-dependent production in the presence of cells. However, a significant difference in •OH production was observed between human lymphocytes from two different donors. Using H2O2, we showed that WC-Co NP can participate in Fenton-like reactions. Thus, •OH might be produced either via intrinsic generation by WC-Co NP or through a Fenton-like reaction in the presence of cells. Copyright © 2015 Elsevier B.V. All rights reserved.

Failure mechanism of coated biomaterials under high impact-sliding contact stresses

Science.gov (United States)

Chen, Ying

This study uses a newly developed testing method--- inclined cyclic impact-sliding test to investigate the failure behaviors of different types of biomaterials, (SS316L, Ti6Al4V and CoCr) coated by different coatings (TiN, DLC and PEO), under extremely high dynamic contact stress conditions. This test method can simulate the combined impact and sliding/rolling loading conditions, which is very practical in many aspects of commercial usages. During the tests, fatigue cracking, chipping, peeling and material transferring were observed in damaged area. This research is mainly focused on the failure behaviors of load-bearing materials which cyclic impacting and sliding are always involved. This purpose was accomplished in the three stages: First, impact-sliding test was carried out on TiN coated unhardened M2. It was found that soft substrate can cause early failure of coating due to the considerable plastic deformation in the substrate. In this case, stronger substrate is required to support coating better when tested under high contact stresses. Second, PEO coated Ti-6Al-4V was tested under pure sliding and impact-sliding wear conditions. PEO coating was found not strong enough to afford the high contact pressure under cyclic impact-sliding wear test due to its porous surface structure. However, the wear performance of PEO coating was enhanced due to the sub-stoichiometric oxide. To sum up, for load-bearing biomedical implants involved in high impacting movement, PEO coating may not be a promising surface protection. Third, the dense, smooth PVD/CVD bio-inert coatings were reconsidered. DLC and TiN coatings, combined by different substrates together with different interface materials were tested under the cyclic impact-sliding test using a set of proper loading. The results show that to choose a proper combination of coating, interface and substrate based on their mechanical properties is of great importance under the test condition. Hard substrates provide support

Transfer coating by electron initiated polymerization

International Nuclear Information System (INIS)

Nablo, S.V.

1984-01-01

The high speed and depth of cure possible with electron initiated monomer/oligomer coating systems provide many new opportunities for approaches to product finishing. Moreover, the use of transfer or cast coating using films or metallic surfaces offers the ability to precisely control the surface topology of liquid film surfaces during polymerization. Transfer coating such as with textiles has been a commercial process for many years and the synergistic addition of EB technology permits the manufacture of unusual new products. One of these, the casting paper used in the manufacture of vinyl and urethane fabrics, is the first EB application to use a drum surface for pattern replication in the coating. In this case the coated paper is cured against, and then released from, an engraved drum surface. Recent developments in the use of plastic films for transfer have been applied to the manufacture of transfer metallized and coated paper and paperboard products for packaging. Details of these and related processes are presented as well as a discussion of the typical product areas (e.g. photographic papers, release papers, magnetic media) using this high speed transfer technology

Microstructure and hardness of WC-Co particle reinforced iron matrix surface composite

Directory of Open Access Journals (Sweden)

Zhang Peng

2013-11-01

Full Text Available In this study, a high Cr cast iron surface composite material reinforced with WC-Co particles 2-6 mm in size was prepared using a pressureless sand mold infiltration casting technique. The composition, microstructure and hardness were determined by means of energy dispersive spectrometry (EDS, electron probe microanalysis (EPMA, scanning electron microscope (SEM and Rockwell hardness measurements. It is determined that the obtained composite layer is about 15 mm thick with a WC-Co particle volumetric fraction of ~38%. During solidification, interface reaction takes place between WC-Co particles and high chromium cast iron. Melting and dissolving of prefabricated particles are also found, suggesting that local Co melting and diffusion play an important role in promoting interface metallurgical bonding. The composite layer is composed of ferrite and a series of carbides, such as (Cr, W, Fe23C6, WC, W2C, M6C and M12C. The inhomogeneous hardness in the obtained composite material shows a gradient decrease from the particle reinforced metal matrix composite layer to the matrix layer. The maximum hardness of 86.3 HRA (69.5 HRC is obtained on the particle reinforced surface, strongly indicating that the composite can be used as wear resistant material.

Electrical insulation and conduction coating for fusion experimental devices

Energy Technology Data Exchange (ETDEWEB)

Onozuka, Masanori; Tsujimura, Seiji; Toyoda, Masahiko; Inoue, Masahiko [Mitsubishi Heavy Industries, Ltd., Yokohama (Japan); Abe, Tetsuya; Murakami, Yoshio [Japan Atomic Energy Research Inst., Naka (Japan)

1996-01-01

The development of electrical insulation and conduction coating methods that can be applied to large components of fusion experimental devices has been investigated. A thermal spraying method is used to coat the insulation or conduction materials on the structural components because of its applicability for large surfaces. The insulation material chosen was Al{sub 2}O{sub 3}, while Cr{sub 3}C{sub 2}-NiCr and WC-NiCr were chosen as conduction materials. These materials were coated on stainless steel substrates to examine the basic characteristics of the coated layers, such as their adhesive strength to the substrate, thermal shock resistance, electrical resistance, dielectric breakdown voltage, and thermal conductivity. It was found that they have sufficient electrical insulation and conduction properties, respectively. In addition, the sliding tests of the coated layers showed adequate frictional properties. The spraying method was tested on a 100- x 1000-mm surface and found to be applicable for large surfaces of experimental fusion devices. 9 refs., 6 figs., 15 tabs.

Metrology for Fuel Cell Manufacturing

Energy Technology Data Exchange (ETDEWEB)

Stocker, Michael [National Inst. of Standards and Technology, Gaithersburg, MD (United States); Stanfield, Eric [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

2015-02-04

The project was divided into three subprojects. The first subproject is Fuel Cell Manufacturing Variability and Its Impact on Performance. The objective was to determine if flow field channel dimensional variability has an impact on fuel cell performance. The second subproject is Non-contact Sensor Evaluation for Bipolar Plate Manufacturing Process Control and Smart Assembly of Fuel Cell Stacks. The objective was to enable cost reduction in the manufacture of fuel cell plates by providing a rapid non-contact measurement system for in-line process control. The third subproject is Optical Scatterfield Metrology for Online Catalyst Coating Inspection of PEM Soft Goods. The objective was to evaluate the suitability of Optical Scatterfield Microscopy as a viable measurement tool for in situ process control of catalyst coatings.

Hydrogen effects in anodic grinding of WC-Co sintered alloy

International Nuclear Information System (INIS)

Lunarska, E.; Zaborski, St.

2001-01-01

The effects of anodic polarization applied in grinding of sintered WC C o alloy on properties of surface layer, quality of ground surface and efficiency of the treatment were studied. The nonmonotonical change of the surface roughness, the energy consumption and the wear of tool was stated at increasing anodic polarization. The optimum values of above parameters were achieved at application of anodic polarization at which the Co selective dissolution and hydrogen ingress into the ground metal. affecting the internal friction spectra were stated. The assistance of hydrogen induced deterioration and Co selective dissolution in the surface layer in the anodic grinding of WC-Co alloy has been discussed. (author)

Negative and anomalous T-dependent magnetization trend in CoCr2O4 nanoparticles

Science.gov (United States)

Kamran, M.; Nadeem, K.; Mumtaz, M.

2017-10-01

We studied the temperature dependent magnetic properties of cobalt chromite (CoCr2O4) nanoparticles. X-ray diffraction revealed the cubic spinel structure of the nanoparticles and average crystallite size was about 42 nm. Raman and Fourier transform infrared spectroscopy confirmed the formation of single phase spinel structure. ZFC/FC curves revealed a paramagnetic (PM) to ferromagnetic (FiM) transition at TC = 100 K with conical spiral state at TS = 27 K and lock-in state at TL = 13 K. Negative magnetization is observed in the ZFC curve under 50 Oe applied field, which gets suppressed upon the application of higher field. The TC was shifted towards higher temperature with the application of higher field, while TS and TL remain unaffected. M-H loops showed FiM behavior below 100 K and nearly PM at TC = 100 K. Below 75 K, an abnormal decrease in MS is observed down to 5 K, which may be due to presence of stiffed/strong conical spin spiral and lock in states at low temperatures. Modified Kneller's law showed a good fit for temperature dependent Hc at higher temperature and deviated at low temperature (disordered surface spins. Nanoparticles showed slow spin relaxation in both ZFC and FC protocols at 5 K, which signifies the presence of spin-glass like behavior at low temperatures. Both curves were fitted with stretched exponential law and the value of β lies in the spin-glass regime. In summary, CoCr2O4 nanoparticles showed anomalous decrease of MS with decreasing temperature, negative magnetization at low field and rather stiffed/strong conical spin spiral and lock-in states in combination with spin-glass behavior at the low temperatures.

Machinability of Al-SiC metal matrix composites using WC, PCD and MCD inserts

Energy Technology Data Exchange (ETDEWEB)

Beristain, J.; Gonzalo, O.; Sanda, A.

2014-04-01

The aim of this work is the study of the machinability of aluminium-silicon carbide Metal Matrix Composites (MMC) in turning operations. The cutting tools used were hard metal (WC) with and without coating, different grades and geometries of Poly-Crystalline Diamond (PCD) and Mono-Crystalline Diamond (MCD). The work piece material was AMC225xe, composed of aluminium-copper alloy AA 2124 and 25% wt of SiC, being the size of the SiC particles around 3 {mu}m. Experiments were conducted at various cutting speeds and cutting parameters in facing finishing operations, measuring the surface roughness, cutting forces and tool wear. The worn surface of the cutting tool was examined by Scanning Electron Microscope (SEM). It was observed that the Built Up Edge (BUE) and stuck material is higher in the MCD tools than in the PCD tools. The BUE acts as a protective layer against abrasive wear of the tool. (Author)

Laser-Based Additive Manufacturing of Zirconium

Directory of Open Access Journals (Sweden)

Himanshu Sahasrabudhe

2018-03-01

Full Text Available Additive manufacturing of zirconium is attempted using commercial Laser Engineered Net Shaping (LENSTM technique. A LENSTM-based approach towards processing coatings and bulk parts of zirconium, a reactive metal, aims to minimize the inconvenience of traditional metallurgical practices of handling and processing zirconium-based parts that are particularly suited to small volumes and one-of-a-kind parts. This is a single-step manufacturing approach for obtaining near net shape fabrication of components. In the current research, Zr metal powder was processed in the form of coating on Ti6Al4V alloy substrate. Scanning electron microscopy (SEM and energy dispersive spectroscopy (EDS as well as phase analysis via X-ray diffraction (XRD were studied on these coatings. In addition to coatings, bulk parts were also fabricated using LENS™ from Zr metal powders, and measured part accuracy.

Smart Nanocomposite Coatings with Chameleon Surface Adaptation in Tribological Applications

Science.gov (United States)

Voevodin, A. A.; Zabinski, J. S.

Smart nanocomposite tribological coatings were designed to respond to changing environmental conditions by self-adjustment of their surface properties to maintain good tribological performance in any environment. These coatings have been dubbed "chameleon" because of their ability to change their surface chemistry and structure to avoid wear. The first "chameleon" coatings were made of WC, WS2, and DLC; these coatings provided superior mechanical toughness and performance in dry/humid environmental cycling. In order to address temperature variation, the second generation of "chameleon" coatings were made of yttria stabilized zirconia (YSZ) in a gold matrix with encapsulated nano-sized reservoirs of MoS2 and DLC. High temperature lubrication with low melting point glassy ceramic phases was also explored. All coatings were produced using a combination of laser ablation and magnetron sputtering. They were thoroughly characterized by various analytical, mechanical, and tribological methods. Coating toughness was remarkably enhanced by activation of a grain boundary sliding mechanism. Friction and wear endurance measurements were performed in controlled humidity air, dry nitrogen, and vacuum environments, as well as at 500-600 °C in air. Unique friction and wear performance in environmental cycling was demonstrated.

Measuring c-quark polarization in W+c samples at ATLAS and CMS

CERN Document Server

Kats, Yevgeny

2016-01-01

The process $pp \\to W^-c$ produces polarized charm quarks. The polarization is expected to be partly retained in $\\Lambda_c$ baryons when those form in the $c$-quark hadronization. We argue that it will likely be possible for ATLAS and CMS to measure the $\\Lambda_c$ polarization in the $W$+$c$ samples in Run 2 of the LHC. This can become the first measurement ever of a longitudinal polarization of charm quarks. Its results will provide a unique input to the understanding of polarization transfer in fragmentation. They will also allow applying the same measurement technique to other (e.g., new physics) samples of charm quarks in which the polarization is a priori unknown. The proposed analysis is similar to the ATLAS and CMS measurements of the $W$+$c$ cross section in the 7 TeV run that used reconstructed $D$-meson decays for charm tagging.

CANDU fuel : design/manufacturing interaction

International Nuclear Information System (INIS)

Graham, N.A.

1999-01-01

The design of CANDU fuel has been the product of intense cooperation among fuel designers and fuel manufacturers. The developments of some of the novel processes in fuel manufacture are outlined. These include the brazed-split-spacer design, the resistance welded endcap and CANLUB coatings. (author)

Spatial transport of atomic coherence in electromagnetically induced absorption with a paraffin-coated Rb vapor cell.

Science.gov (United States)

Lee, Yoon-Seok; Moon, Han Seb

2014-06-30

We report the spatial transport of spontaneously transferred atomic coherence (STAC) in electromagnetically induced absorption (EIA), which resulted from moving atoms with the STAC of the 5S(1/2) (F = 2)-5P(3/2) (F' = 3) transition of (87)Rb in a paraffin-coated vapor cell. In our experiment, two channels were spatially separate; the writing channel (WC) generated STAC in the EIA configuration, and the reading channel (RC) retrieved the optical field from the spatially transported STAC. Transported between the spatially separated positions, the fast light pulse of EIA in the WC and the delayed light pulse in the RC were observed. When the laser direction of the RC was counter-propagated in the direction of the WC, we observed direction reversal of the transported light pulse in the EIA medium. Furthermore, the delay time, the magnitude, and the width of the spatially transported light pulse were investigated with respect to the distance between the two channels.

Physico-chemical profiles of the wobble ↔ Watson-Crick G*·2AP(w) ↔ G·2AP(WC) and A·2AP(w) ↔ A*·2AP(WC) tautomerisations: a QM/QTAIM comprehensive survey.

Science.gov (United States)

Brovarets', Ol'ha O; Voiteshenko, Ivan S; Hovorun, Dmytro M

2017-12-20

This study is intended to clarify in detail the tautomeric transformations of the wobble (w) G*·2AP(w) and A·2AP(w) nucleobase mispairs involving 2-aminopurine (2AP) into the Watson-Crick (WC) G·2AP(WC) and A*·2AP(WC) base mispairs (asterisks denote mutagenic tautomers of the DNA bases), respectively, by quantum-mechanical methods and Bader's Quantum Theory of Atoms in Molecules. Our previously reported methodology has been used, which allows the evolution of the physico-chemical parameters to be tracked along the entire internal reaction coordinate (IRC), not exclusively in the stationary states of these reactions. These biologically important G*·2AP(w) ↔ G·2AP(WC) and A·2AP(w) ↔ A*·2AP(WC) w ↔ WC tautomerisations, which are involved in mutagenic tautomerically-conformational pathways, determine the origin of the transitions and transversions induced by 2AP. In addition, it is established that they proceed through planar, highly stable, zwitterionic transition states and they exhibit similar physico-chemical profiles and stages of sequential intrapair proton transfer, followed by spatial rearrangement of the nucleobases relative to each other within the base pairs. These w ↔ WC tautomerisations occur non-dissociatively and are accompanied by a significant alteration in geometry (from wobble to Watson-Crick and vice versa) and redistribution of the specific intermolecular interactions, which can be divided into 10 patterns including AHB H-bonds and loosened A-H-B covalent bridges along the IRC of tautomerisation. Based on the redistribution of the geometrical and electron-topological parameters of the intrapair hydrogen bonds, exactly 9 key points have been allocated to characterize the evolution of these reactions.

Mechanical intermixing of components in (CoMoNi)-based systems and the formation of (CoMoNi)/WC nanocomposite layers on Ti sheets under ball collisions

Science.gov (United States)

Romankov, S.; Park, Y. C.; Shchetinin, I. V.

2017-11-01

Cobalt (Co), molybdenum (Mo), and nickel (Ni) components were simultaneously introduced onto titanium (Ti) surfaces from a composed target using ball collisions. Tungsten carbide (WC) balls were selected for processing as the source of a cemented carbide reinforcement phase. During processing, ball collisions continuously introduced components from the target and the grinding media onto the Ti surface and induced mechanical intermixing of the elements, resulting in formation of a complex nanocomposite structure onto the Ti surface. The as-fabricated microstructure consisted of uniformly dispersed WC particles embedded within an integrated metallic matrix composed of an amorphous phase with nanocrystalline grains. The phase composition of the alloyed layers, atomic reactions, and the matrix grain sizes depended on the combination of components introduced onto the Ti surface during milling. The as-fabricated layer exhibited a very high hardness compared to industrial metallic alloys and tool steel materials. This approach could be used for the manufacture of both cemented carbides and amorphous matrix composite layers.

Tribological behavior of Al-WC nano-composites fabricated by ultrasonic cavitation assisted stir-cast method

Science.gov (United States)

Pal, Arpan; Poria, Suswagata; Sutradhar, Goutam; Sahoo, Prasanta

2018-03-01

In the present study, the effects of WC nano-particles content on the microstructure, hardness, wear, and friction behavior of aluminum matrix composites are investigated. Al-WC nano composites with varying wt% of WC (0, 1, 1.5, and 2) are fabricated using ultrasonic cavitation assisted stir-cast method. The microstructure of the nano-composite samples is analyzed using optical microscopy and scanning electron microscopy. Elemental composition is determined by energy dispersive x-ray analysis. Vicker’s microhardness test is performed in different locations on the composite sample surface with a load of 50 gf and 10s dwell time. Wear and friction of the composites under dry sliding is studied using a pin-on-disk tribotester for varying normal load (10–40 N) and sliding speed (0.1–0.4 m/s). Uniform distribution of nano-WC is observed over composite surface without noticeable clustering. Reinforcement of nano-WC particles improves wear resistance and frictional behavior of the composite. Hardness is seen to increase with increase in wt% of nano-particles. Wear behavior of composites depends on formation of layers over the surface mixed with oxidized debris and counter-face particles. Wear mechanism changes from adhesion to abrasion with increase in wt% of hard nano particles.

A multilayer innovative solution to improve the adhesion of nanocrystalline diamond coatings

Energy Technology Data Exchange (ETDEWEB)

Poulon-Quintin, A., E-mail: poulon@icmcb-bordeaux.cnrs.fr [CNRS, ICMCB, UPR 9048, F-33600 Pessac (France); Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France); Faure, C.; Teulé-Gay, L.; Manaud, J.P. [CNRS, ICMCB, UPR 9048, F-33600 Pessac (France); Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac (France)

2015-03-15

Highlights: • Improvement of the NCD adhesion on WC-12%Co substrates for tooling applications using a multi-interlayer additional system. • Reduction of the graphite layer thickness and continuity at the interface with the diamond. • Transmission electron microscopy study for a better understanding of the diffusion phenomena occurring at the interfaces. - Abstract: Nano-crystalline diamond (NCD) films grown under negative biased substrates by chemical vapor deposition (CVD) are widely used as surface overlay coating onto cermet WC-Co cutting tools to get better performances. To improve the diamond adhesion to the cermet substrate, suitable multi-layer systems have been added. They are composed of a cobalt diffusion barrier close to the substrate (single and sequenced nitrides layers) coated with a nucleation extra layer to improve the nucleus density of diamond during CVD processing. For all systems, before and after diamond deposition, transmission electron microscopy (TEM) has been performed for a better understanding of the diffusion phenomena occurring at the interfaces and to evaluate the presence of graphitic species at the interface with the diamond. Innovative multilayer system dedicated to the regulation of cobalt diffusion coated with a bilayer system optimized for the carbon diffusion control, is shown as an efficient solution to significantly reduce the graphite layer formation at the interface with the diamond down to 10 nm thick and to increase the adhesion of NCD diamond layer as scratch-tests confirm.

Stress analysis of thermal sprayed coatings using a semi-destructive hole-drilling strain gauge method

International Nuclear Information System (INIS)

Dolhof, V.; Musil, J.; Cepera, M.; Zeman, J.

1995-01-01

Residual stress is an important parameter in coating technology since it often relates to the maximum coating thickness which can be deposited without spallation, and this applies to coatings produced by different thermal spray and thin film technologies. Indeed, the mechanisms by which residual stress is built up or locked into a coating depends markedly on the deposition process and coating structure (growth structure, phase composition) in the same way too. Methods for determining residual stresses in materials include both destructive and non-destructive methods. This contribution describes semi-destructive hole-drilling strain gauge method modified for measurement of residual stresses in thermal sprayed coatings. This method of stress analysis was used for determination of stress levels in thermal sprayed WC-17% Co coatings onto 13% Cr steel substrates. Results show that deposition conditions and final coating structure influence directly the residual stress level in the coatings. It is proved that semi-destructive hole-tube drilling measurement is effective reproducible method of coating stress analysis and good solution for optimization of deposition process

Solid lubricant behavior of MoS2 and WSe2-based nanocomposite coatings

Science.gov (United States)

Domínguez-Meister, Santiago; Rojas, Teresa Cristina; Brizuela, Marta; Sánchez-López, Juan Carlos

2017-12-01

Tribological coatings made of MoS2 and WSe2 phases and their corresponding combinations with tungsten carbide (WC) were prepared by non-reactive magnetron sputtering of individual targets of similar composition. A comparative tribological analysis of these multiphase coatings was done in both ambient air (30-40% relative humidity, RH) and dry nitrogen (RHgoverns the tribological behavior for each type of environment. This allowed conclusions to be made about the influence of the coating microstructure and composition on the tribological response. The best performance obtained with a WSex film (specific wear rate of 2 × 10-8 mm3 N-1m-1 and a friction coefficient of 0.03-0.05) was compared with that of the well-established MoS2 lubricant material.

Development of electrical insulation and conduction coating for fusion experimental devices

Energy Technology Data Exchange (ETDEWEB)

Onozuka, M. [Mitsubishi Heavy Industries Ltd., Yokohama (Japan); Tsujimura, S. [Mitsubishi Heavy Industries Ltd., Yokohama (Japan); Toyoda, M. [Mitsubishi Heavy Industries Ltd., Yokohama (Japan); Inoue, M. [Mitsubishi Heavy Industries Ltd., Yokohama (Japan); Abe, T. [Japan Atomic Energy Research Inst., Naka (Japan); Murakami, Y. [Japan Atomic Energy Research Inst., Naka (Japan)

1995-12-31

Development of electrical insulation and conduction methods that can be applied for large components have been investigated for future large fusion experimental devices. A thermal spraying method is employed to coat the insulation or conduction materials on the structural components. Al{sub 2}O{sub 3} has been selected as an insulation material, while Cr{sub 3}C{sub 2}-NiCr and WC-NiCr have been chosen as conduction materials. These materials were coated on stainless steel base plates to examine the basic characteristics of the coated layers, such as their adhesive strength to the base plate and electrical resistance. It was found that they have sufficient electrical insulation and conduction properties, respectively. In addition, the sliding tests of the coated layers showed sufficient frictional properties. The applicability of the spraying method was examined on a 100mm x 1000mm surface and found to be applicable for large surfaces in fusion experimental devices. (orig.).

Development of electrical insulation and conduction coating for fusion experimental devices

International Nuclear Information System (INIS)

Onozuka, M.; Tsujimura, S.; Toyoda, M.; Inoue, M.; Abe, T.; Murakami, Y.

1995-01-01

Development of electrical insulation and conduction methods that can be applied for large components have been investigated for future large fusion experimental devices. A thermal spraying method is employed to coat the insulation or conduction materials on the structural components. Al 2 O 3 has been selected as an insulation material, while Cr 3 C 2 -NiCr and WC-NiCr have been chosen as conduction materials. These materials were coated on stainless steel base plates to examine the basic characteristics of the coated layers, such as their adhesive strength to the base plate and electrical resistance. It was found that they have sufficient electrical insulation and conduction properties, respectively. In addition, the sliding tests of the coated layers showed sufficient frictional properties. The applicability of the spraying method was examined on a 100mm x 1000mm surface and found to be applicable for large surfaces in fusion experimental devices. (orig.)

Concrete manufactured with crushed asphalt as partial replacement of natural aggregates

Directory of Open Access Journals (Sweden)

L. Coppola

2016-09-01

Full Text Available The paper focuses on the reuse of crushed asphalt (GA as a partial replacement (up to 20% of natural aggregates for concrete manufacture. Addition of GA aggregates produced a positive effect on workability loss. The GA mixes, however, showed a significant tendency to bleed and segregate at the highest replacement percentage applied. GA led to a decrease of compressive strength in concrete (with respect to that of the reference concrete up to 50% due to the weakness of the cement paste / recycled aggregate interface. To compensate for this negative effect, a reduction of w/c for the GA concretes was necessary. A decrease of w/c allowed the GA concretes to show drying shrinkage values substantially similar to those of reference concrete with the same cement factor. The experimental results confirmed the possibility of partial substitution (max. 15% of natural aggregates with crushed asphalt for making concrete.

An alternative approach to estimate the W/C ratio of hardened concrete using image analysis

NARCIS (Netherlands)

Valcke, S.; Nijland, T.G.; Larbi, J.A.

2009-01-01

The water cement (w/c) ratio is a typical quality parameter for concrete. The NT Build 361 Nordtest method is a standard for estimating the w/c ratio in hardened concrete and is based on the relationship between the ilc ratio and the capillary porosity in the cement paste. The latter can be

Evaluation of Advanced Polymers for Additive Manufacturing

Energy Technology Data Exchange (ETDEWEB)

Rios, Orlando [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Carter, William G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kutchko, Cindy [PPG Industries, Pittsburgh, PA (United States); Fenn, David [PPG Industries, Pittsburgh, PA (United States); Olson, Kurt [PPG Industries, Pittsburgh, PA (United States)

2017-09-08

The goal of this Manufacturing Demonstration Facility (MDF) technical collaboration project between Oak Ridge National Laboratory (ORNL) and PPG Industries, Inc. (PPG) was to evaluate the feasibility of using conventional coatings chemistry and technology to build up material layer-by-layer. The PPG-ORNL study successfully demonstrated that polymeric coatings formulations may overcome many limitations of common thermoplastics used in additive manufacturing (AM), allow lightweight nozzle design for material deposition, and increase build rate. The materials effort focused on layer-by-layer deposition of coatings with each layer fusing together. The combination of materials and deposition results in an additively manufactured build that has sufficient mechanical properties to bear the load of additional layers, yet is capable of bonding across the z-layers to improve build direction strength. The formulation properties were tuned to enable a novel, high-throughput deposition method that is highly scalable, compatible with high loading of reinforcing fillers, and inherently low-cost.

Abrasive Wear Resistance of the Iron- and WC-based Hardfaced Coatings Evaluated with Scratch Test Method

Directory of Open Access Journals (Sweden)

A. Vencl

2013-06-01

Full Text Available Abrasive wear is one of the most common types of wear, which makesabrasive wear resistance very important in many industries. Thehard facing is considered as useful and economical way to improve theperformance of components submitted to severe abrasive wear conditions, with wide range of applicable filler materials. The abrasive wear resistance of the three different hardfaced coatings (two iron‐based and one WC‐based, which were intended to be used for reparation of the impact plates of the ventilation mill, was investigated and compared. Abrasive wear tests were carried‐out by using the scratch tester under the dry conditions. Three normal loads of 10, 50 and 100 N and the constant sliding speed of 4 mm/s were used. Scratch test was chosen as a relatively easy and quick test method. Wear mechanism analysis showed significant influence of the hardfaced coatings structure, which, along with hardness, has determined coatings abrasive wear resistance.

COBRA-WC: a version of COBRA for single-phase multiassembly thermal hydraulic transient analysis

International Nuclear Information System (INIS)

George, T.L.; Basehore, K.L.; Wheeler, C.L.; Prather, W.A.; Masterson, R.E.

1980-07-01

The objective of this report is to provide the user of the COBRA-WC (Whole Core) code a basic understanding of the code operation and capabilities. Included in this manual are the equations solved and the assumptions made in their derivations, a general description of the code capabilities, an explanation of the numerical algorithms used to solve the equations, and input instructions for using the code. Also, the auxiliary programs GEOM and SPECSET are described and input instructions for each are given. Input for COBRA-WC sample problems and the corresponding output are given in the appendices. The COBRA-WC code has been developed from the COBRA-IV-I code to analyze liquid Metal Fast Breeder Reactor (LMFBR) assembly transients. It was specifically developed to analyze a core flow coastdown to natural circulation cooling

Investigation of aperiodic W/C multi-layer mirror for X-ray optics

International Nuclear Information System (INIS)

Wang Zhanshan; Cheng Xinbin; Zhu Jingtao; Huang Qiushi; Zhang Zhong; Chen Lingyan

2011-01-01

Design, fabrication and characterization of aperiodic tungsten/carbon (W/C) multi-layer mirror were studied. W/C multi-layer was designed as a broad-angle reflective supermirror for Cu-Kα line (λ = 0.154 nm) in the grazing incident angular range (0.9-1.1 deg.) using simulated annealing algorithm. To deposit the W/C depth-graded multi-layer mirror accurately, we introduce an effective layer growth rate as a function of layer thickness. This method greatly improves the reflectivity curve compared to the conventional multi-layer mirror prepared with constant growth rate. The deposited multi-layer mirror exhibits an average reflectivity of 19% over the grazing incident angle range of 0.88-1.08 deg. which mainly coincides with the designed value. Furthermore, the physical mechanisms were discussed and the re-sputtering process of light-atom layers is accounted for the modification of layer thicknesses which leads to the effective growth rates. Using this calibration method, the aperiodic multi-layer mirrors can be better fabricated for X-ray optics.

Oxidation Behavior of FeCrAl -coated Zirconium Cladding prepared by Laser Coating

Energy Technology Data Exchange (ETDEWEB)

Kim, Il-Hyun; Kim, Hyun-Gil; Choi, Byung-Kwan; Park, Jeong-Yong; Koo, Yang-Hyun; Kim, Jin-Seon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-05-15

From the recent research trends, the ATF cladding concepts for enhanced accident tolerance are divided as follows: Mo-Zr cladding to increase the high temperature strength, cladding coating to increase the high temperature oxidation resistance, FeCrAl alloy and SiC/SiCf material to increase the oxidation resistance and strength at high temperature. To commercialize the ATF cladding concepts, various factors are considered, such as safety under normal and accident conditions, economy for the fuel cycle, and developing development challenges, and schedule. From the proposed concepts, it is known that the cladding coating, FeCrAl alloy, and Zr-Mo claddings are considered as a near/mid-term application, whereas the SiC material is considered as a long-term application. Among them, the benefit of cladding coating on Zr-based alloys is the fuel cycle economy regarding the manufacturing, neutron cross section, and high tritium permeation characteristics. However, the challenge of cladding coating on Zr-based alloys is the lower oxidation resistance and mechanical strength at high-temperature than other concepts. Another important point is the adhesion property between the Zr-based alloy and coating materials. A laser coating method supplied with FeCrAl powders was developed to decrease the high-temperature oxidation rate in a steam environment through a systematic study for various coating parameters, and a FeCrAl-coated Zircaloy-4 cladding tube of 100 mm in length to the axial direction can be successfully manufactured.

Failure modes observed on worn surfaces of W-C-Co sputtered coatings

International Nuclear Information System (INIS)

Ramalho, A.; Cavaleiro, A.; Miranda, A.S.; Vieira, M.T.

1993-01-01

During scratch testing, the indenter gives rise to a distribution of stresses similar to that observed in tribocontacts. In this work, r.f.-sputtered W-C-Co coatings deposited from sintered WC + Co (6, 10 and 15 wt.% Co) at various substrate biases were scratched and tested tribologically and the morphology of the damaged surfaces was analysed. The cobalt content of the coatings is the main factor determining their tribological characteristics. The failure modes observed on the worn pin-on-disc tested surfaces are explained and compared with those obtained by scratch testing. In spite of it not being possible to establish quantitative results for the wear resistance of W-C-Co coatings from scratch testing, an estimation can be performed based on the observation of the failure modes in the scratch track. Thus scratch testing can be used to predict the tribological behaviour of coated surfaces. This possibility can reduce the number and cost of tribological tests. (orig.)

Nondestructive testing technology for measurement coatings thickness on material

International Nuclear Information System (INIS)

Yang Mingtai; Wu Lunqiang; Zhang Lianping

2008-01-01

The principle, applicability range, advantage and disadvantage of electromagnetic, eddy current method, β backscatter method and XRF methods for nondestructive testing coating thickness of material have been reviewed. The relevant apparatus and manufacturers have been summarized. And the application and developmental direction of manufacturers for nondestructive testing coatings thickness has been foreshowed. (authors)

Critical Damage Analysis of WC-Co Tip of Conical Pick due to Coal Excavation in Mines

Directory of Open Access Journals (Sweden)

Saurabh Dewangan

2015-01-01

Full Text Available WC-Co based tools are widely used in the field of coal and rock excavation because of their unique combination of strength, hardness, and resistance to abrasive wear. Conical pick is one of the coal cutting tools. The tip of the pick is made of WC-Co material. As coal and rock are heterogeneous elements, they pose various constraints during excavation. As a result the tools wear out during the process. Other parameters like cutting techniques, tool orientation, and environmental conditions also affect the tool significantly. The wearing phenomenon greatly reduces the service life of the tools and thereby cuts down the production rate. To prevent such wearing process, it is important to investigate the different wear mechanisms in WC-Co. Simultaneously, there has to be an ongoing endeavour for the development of better quality WC-Co. This paper focuses on different wear mechanisms in a conical pick which has been used in a continuous miner machine for coal cutting. The worn out surface has been observed by using FE-SEM (field emission scanning electron microscopy and EDS (energy dispersive X-ray spectroscopy. The mechanisms, namely, coal/rock intermixing, cracking and crushing of WC grains, and adhesion of rock particles, have been predominantly investigated in this study. A little indication of corrosive decay in the WC grain has also been reported. The EDS has detected material concentration in a selected area or point of the worn-out surface. The spectrograph confirms the presence of coal/rock materials. Elements such as W, C, Ca, K, O, and Co have been mainly found in different concentrations at different positions.

Room-Temperature Deformation and Martensitic Transformation of Two Co-Cr-Based Alloys

Science.gov (United States)

Cai, S.; Schaffer, J. E.; Huang, D.; Gao, J.; Ren, Y.

2018-05-01

Deformation of two Co-Cr alloys was studied by in situ synchrotron X-ray diffraction. Both alloys show stress-induced martensite transformation, which is affected by phase stabilities and transformation strains. Crystal structure of WC in Co-20Cr-15W-10Ni is identified. Compared with other phases present, it is elastically isotropic, exhibits high strength, and can elastically withstand strains exceeding 1 pct. Texture change during phase transformation is explained based on the crystal orientation relationship between γ- and ɛ-phases.

Manufacturing and testing of fuel cans with barrier coating for LWR type reactors in USA and Japan

International Nuclear Information System (INIS)

Gorskij, V.V.

1988-01-01

Papers on manufacturing methods for fuel cans of zircalloy with barrier coating of zirconium prepared by pressing an internal tube into external one as well as by pressing of two-layer tubes with further rolling are reviewed. Heat treatment based on creation of the assigned gradient of temperature over tube wall cross section in order to change the structure of a thin layer of the outside surfce when conserving the initial structure of the rest cross section is developed to increase corrosion resistance. Eddy current and ultrasound methods for control of quality and thickness of the barrier layer of zirconium are used

Overview of PAT process analysers applicable in monitoring of film coating unit operations for manufacturing of solid oral dosage forms.

Science.gov (United States)

Korasa, Klemen; Vrečer, Franc

2018-01-01

Over the last two decades, regulatory agencies have demanded better understanding of pharmaceutical products and processes by implementing new technological approaches, such as process analytical technology (PAT). Process analysers present a key PAT tool, which enables effective process monitoring, and thus improved process control of medicinal product manufacturing. Process analysers applicable in pharmaceutical coating unit operations are comprehensibly described in the present article. The review is focused on monitoring of solid oral dosage forms during film coating in two most commonly used coating systems, i.e. pan and fluid bed coaters. Brief theoretical background and critical overview of process analysers used for real-time or near real-time (in-, on-, at- line) monitoring of critical quality attributes of film coated dosage forms are presented. Besides well recognized spectroscopic methods (NIR and Raman spectroscopy), other techniques, which have made a significant breakthrough in recent years, are discussed (terahertz pulsed imaging (TPI), chord length distribution (CLD) analysis, and image analysis). Last part of the review is dedicated to novel techniques with high potential to become valuable PAT tools in the future (optical coherence tomography (OCT), acoustic emission (AE), microwave resonance (MR), and laser induced breakdown spectroscopy (LIBS)). Copyright © 2017 Elsevier B.V. All rights reserved.

Anticorrosive coatings: a review

DEFF Research Database (Denmark)

Sørensen, Per Aggerholm; Kiil, Søren; Dam-Johansen, Kim

2009-01-01

of volatile organic compounds (VOCs) have caused significant changes in the anticorrosive coating industry. The requirement for new VOC-compliant coating technologies means that coating manufacturers can no longer rely on the extensive track record of their time-served products to convince consumers...... of their suitability for use. An important aspect in the development of new VOC-compliant, high-performance anticorrosive coating systems is a thorough knowledge of the components in anticorrosive coatings, their interactions, their advantages and limitations, as well as a detailed knowledge on the failure modes......, and inhibitive coatings are outlined. In the past decades, several alternatives to organic solvent-borne coatings have reached the commercial market. This review also presents some of these technologies and discusses some of their advantages and limitations. Finally, some of the mechanisms leading to degradation...

Regularities of structure formation on different stages of WC-Co hard alloys fabrication

Energy Technology Data Exchange (ETDEWEB)

Chernyavskij, K S

1987-03-01

Some regularities of structural transformations in powder products of the hard alloys fabrication have been formulated on the basis of results of the author works and other native and foreign reseachers. New data confirming the influene of technological prehistory of carbide powder on the mechanism of its particle grinding as well as the influence of the structural-energy state of WC powder on the course of the WC-Co alloy structure formation processes are given. Some possibilities for the application in practice of the regularities studied are considered.

Anisotropic atomic packing model for abnormal grain growth mechanism of WC-25 wt.% Co alloy

International Nuclear Information System (INIS)

Ryoo, H.S.; Hwang, S.K.

1998-01-01

During liquid phase sintering, cemented carbide particles grow into either faceted or non-faceted grain shapes depending on ally system. In case of WC-Co alloy, prism-shape faceted grains with (0001) planes and {1 bar 100} planes on each face are observed, and furthermore an abnormal grain growth has been reported to occur. When abnormal grain growth occurs in WC crystals, dimension ratio, R, of the length of the side of the triangular prism face to the height of the prism is higher than 4 whereas that for normal grains is approximately 2. Abnormal grain growth in this alloy is accelerated by the fineness of starting powders and by high sintering temperature. To account for the mechanism of the abnormal grain growth, there are two proposed models which drew much research attention: nucleation and subsequent carburization and transformation of η (W 3 Co 3 C) phase into WC, and coalescence of coarse WC grains through dissolution and re-precipitation. Park et al. proposed a two-dimensional nucleation theory to explain the abnormal grain growth of faceted grains. There are questions, however, on the role of η phase on abnormal grain growth. The mechanism of coalescence of spherical grains as proposed by Kingery is also unsuitable for faceted grains. So far theories on abnormal grain growth do not provide a satisfactory explanation on the change of R value during the growth process. In the present work a new mechanism of nucleation and growth of faceted WC grains is proposed on the ground of anisotropic packing sequence of each atom

Prediction of crack paths in WC-Co alloys

International Nuclear Information System (INIS)

Spiegler, R.; Fischmeister, H.F.

1992-01-01

This paper reports on a crack propagating through the WC-o microstructure which has to choose between paths along the binder/carbide interface and paths across binder regions. The latter paths are selected when the crack enters a binder region at a large angle from the nearest carbide interface, while the interface paths are preferred by cracks entering at a small angle. A critical angle can be defined for the switch from one type of crack path to the other. Empirical data for the area fractions of the two crack paths in widely different WC-Co alloys can be accounted for by a single critical angle, var-phi c = 25 degrees. Finite element analysis of the stress field in a region of binder enclosed between carbide grains shows that the preferred site for the growth of stress-induced microvoids will move from the carbide grain flanks to the interior of the binder region when the entry angle of the crack exceeds 24 degrees. Thus the observation of a critical angle deciding the crack path is verified by the stress field analysis and given a physical explanation in terms of the most likely site for microvoid formation

Titanium diboride coatings and their interaction with the substrates

International Nuclear Information System (INIS)

Pierson, H.O.; Randich, E.

1978-01-01

An experimental investigation of the chemical vapor deposition (CVD) of titanium diboride (TiB 2 ) on metallic substrates, using the hydrogen reduction of TiCl 4 and BCl 3 at 1 atmosphere and at temperatures between 850 0 C and 1050 0 C is described. To be coated, the substrate had to meet the following requirements: (1) ability to withstand the deposition temperature without detrimental transformation, (2) chemical inertness to the by-products of the reaction (mostly HCl), (3) reasonable matching of its thermal expansion with that of TiB 2 . The latter requirement may be partially circumvented by using a ductile intermediate coating such as Cu or Ni. Substrates meeting these requirements were W, Ta, Ni, WC, TiC, Kovar and some high chrome steels. Coatings on these substrates were examined by metallographic techniques, scanning electron microscope, x-ray diffraction and electron microprobe. The structures and the degree of interdiffusion were determined. In most cases, intermediate borides of the type M 3 B and M 2 B were formed. The hardness of the coatings was 3330 +- 310 kg/mm 2 (VHN 50 ). Coatings of TiB 2 have already been used successfully on letdown valves in a bench scale coal liquefaction reactor at Sandia Laboratories

Comparative studies on mechanical properties of WC-Co composites sintered by SPS and conventional techniques

Directory of Open Access Journals (Sweden)

Pristinskiy Yuri

2017-01-01

Full Text Available Spark plasma sintering (SPS is an extremely fast solidification technique for compounds that are difficult to sinter within the material group metals, ceramics, or composites thereof, SPS uses a uniaxial pressure and a very rapid heating cycle to consolidate these materials. With SPS the main benefit is the ability to control the WC grain size due to the short sintering times at high temperature. Additionally, its allows to avoid negative reactions between WC and cobalt and to minimize the formation of undesirable phases in sintered composites. The WC-6wt.% Co cermet prepared by SPS processing achieves the enhanced mechanical properties with the hardness of 18.3 GPa and the fracture toughness of 15.5 MPa·m1/2 in comparison to standard reference tungsten carbide/cobalt material.

Performance characterization of metallic substrates coated by HVOF WC–Co

International Nuclear Information System (INIS)

Venter, Andrew M.; Oladijo, O. Philip; Luzin, Vladimir; Cornish, Lesley A.; Sacks, Natasha

2013-01-01

Integral to the performance of high-velocity oxygen-fuel (HVOF) coatings is the thermo-mechanical interaction associated with the thermal misfit, or differences in thermal expansion coefficients (CTEs), between coating and substrate. This investigation reports results on the microstructures, chemical phase content, coating–substrate misfit residual stress, and wear resistance. For this purpose a systematic characterization of WC–Co sprayed coatings on a number of substrates covering a range of CTE values were pursued for both the as-coated and heat-treated conditions. The neutron diffraction technique in conjunction with sub-millimeter sized gauge volumes enabled depth-resolved studies of the stress in the coatings and substrates by paying special attention to the determination of the stress contribution attributed by the final spray process. In the as-coated condition the stress values in the coatings were compressive for CTEs larger than that of WC–Co and tensile for CTE lower than WC–Co. Wear resistance increased for increased compressive stress and macrohardness. In the heat-treated condition, this trend became enhanced due to increased compressive stress in the coatings. - Highlights: • Four different substrate systems coated with HVOF WC-Co has been investigated. • Each substrate set encompassed the grit-blast surface and as-coated conditions, as well as their heat-treated counterparts. • Microstructural, macrohardness, wear performance and depth-resolved residual stress characterised. • Successful application of neutron strain scanning to investigating the combined systems, coatings and substrates. • Link observed between macrohardness, residual stress and wear performance

Thermal response of plasma sprayed tungsten coating to high heat flux

International Nuclear Information System (INIS)

Liu, X.; Yang, L.; Tamura, S.; Tokunaga, K.; Yoshida, N.; Noda, N.; Xu, Z.

2004-01-01

In order to investigate the thermal response of tungsten coating on carbon and copper substrates by vacuum plasma spray (VPS) or inert gas plasma spray (IPS), annealing and cyclic heat load experiments of these coatings were conducted. It is indicated that the multi-layered tungsten and rhenium interface of VPS-W/CFC failed to act as a diffusion barrier at elevated temperature and tungsten carbides were developed after 1 h incubation time when annealing temperature was higher than 1600 deg. C. IPS-W/Cu and W/C without an intermediate bonding layer were failed by the detachment of the tungsten coating at 900 and 1200 deg. C annealing for several hours, respectively. Cyclic heat load of electron beam with 35 MW/m 2 and 3-s pulse duration indicated that IPS-W/Cu samples failed with local detachment of the tungsten coating within 200 cycles and IPS-W/C showed local cracks by 300 cycles, but VPS-W/CFC withstood 1000 cycles without visible damages. However, crack creation and propagation in VPS-W/CFC were also observed under higher heat load

Exploiting Additive Manufacturing Infill in Topology Optimization for Improved Buckling Load

DEFF Research Database (Denmark)

Clausen, Anders; Aage, Niels; Sigmund, Ole

2016-01-01

Additive manufacturing (AM) permits the fabrication of functionally optimized components with high geometrical complexity. The opportunity of using porous infill as an integrated part of the manufacturing process is an example of a unique AM feature. Automated design methods are still incapable...... the standard and coating approaches to topology optimization for the MBB beam benchmark case. The optimized structures are additively manufactured using a filamentary technique. This experimental study validates the numerical model used in the coating approach. Depending on the properties of the infill...

Tablet coating by injection molding technology - Optimization of coating formulation attributes and coating process parameters.

Science.gov (United States)

Desai, Parind M; Puri, Vibha; Brancazio, David; Halkude, Bhakti S; Hartman, Jeremy E; Wahane, Aniket V; Martinez, Alexander R; Jensen, Keith D; Harinath, Eranda; Braatz, Richard D; Chun, Jung-Hoon; Trout, Bernhardt L

2018-01-01

We developed and evaluated a solvent-free injection molding (IM) coating technology that could be suitable for continuous manufacturing via incorporation with IM tableting. Coating formulations (coating polymers and plasticizers) were prepared using hot-melt extrusion and screened via stress-strain analysis employing a universal testing machine. Selected coating formulations were studied for their melt flow characteristics. Tablets were coated using a vertical injection molding unit. Process parameters like softening temperature, injection pressure, and cooling temperature played a very important role in IM coating processing. IM coating employing polyethylene oxide (PEO) based formulations required sufficient room humidity (>30% RH) to avoid immediate cracks, whereas other formulations were insensitive to the room humidity. Tested formulations based on Eudrajit E PO and Kollicoat IR had unsuitable mechanical properties. Three coating formulations based on hydroxypropyl pea starch, PEO 1,000,000 and Opadry had favorable mechanical (35% elongation, >95×10 4 J/m 3 toughness) and melt flow (>0.4g/min) characteristics, that rendered acceptable IM coats. These three formulations increased the dissolution time by 10, 15 and 35min, respectively (75% drug release), compared to the uncoated tablets (15min). Coated tablets stored in several environmental conditions remained stable to cracking for the evaluated 8-week time period. Copyright © 2017 Elsevier B.V. All rights reserved.

PCB extraction from ORNL tank WC-14 using a unique solvent

International Nuclear Information System (INIS)

Bloom, G.A.; Lucero, A.J.; Koran, L.J.; Turner, E.N.

1995-09-01

This report summarizes the development work of the Engineering Development Section of the Chemical Technology Division at Oak Ridge National Laboratory (ORNL) for an organic extraction method for removing polychlorinated biphenyls (PCBs) from tank WC-14. Tank WC-14 is part of the ORNL liquid low-level radioactive tank waste system and does not meet new secondary containment and leak detection regulations. These regulations require the tank to be taken out of service, and remediated before tank removal. To remediate the tank, the PCBs must be removed; the tank contents can then be transferred to the Melton Valley Storage Tanks before final disposal. The solvent being used for the PCB extraction experiments is triethylamine, an aliphatic amine that is soluble in water below 60 degrees F but insoluble in water above 90 degrees F. This property will allow the extraction to be carried out under fully miscible conditions within the tank; then, after tank conditions have been changed, the solvent will not be miscible with water and phase separation will occur. Phase separation between sludge, water, and solvent will allow solvent (loaded with PCBs) to be removed from the tank for disposal. After removing the PCBs from the sludge and removing the sludge from the tank, administrative control of the tank can be transferred to ORNL's Environmental Restoration Program, where priorities will be set for tank removal. Experiments with WC-14 sludge show that greater than 90% extraction efficiencies can be achieved with one extraction stage and that PCB concentration in the sludge can be reduced to below 2 ppm in three extractions. It is anticipated that three extractions will be necessary to reduce the PCB concentration to below 2 ppm during field applications. The experiments conducted with tank WC-14 sludge transferred less than 0.03% of the original alpha contamination and less than 0.002% of the original beta contamination

Coating and Characterization of Mock and Explosive Materials

Directory of Open Access Journals (Sweden)

Emily M. Hunt

2012-01-01

Full Text Available This project develops a method of manufacturing plastic-bonded explosives by using use precision control of agglomeration and coating of energetic powders. The energetic material coating process entails suspending either wet or dry energetic powders in a stream of inert gas and contacting the energetic powder with atomized droplets of a lacquer composed of binder and organic solvent. By using a high-velocity air stream to pneumatically convey the energetic powders and droplets of lacquer, the energetic powders are efficiently wetted while agglomerate drying begins almost immediately. The result is an energetic powder uniformly coated with binder, that is, a PBX, with a high bulk density suitable for pressing. Experiments have been conducted using mock explosive materials to examine coating effectiveness and density. Energetic materials are now being coated and will be tested both mechanically and thermally. This allows for a comprehensive comparison of the morphology and reactivity of the newly coated materials to previously manufactured materials.

Modification of WC-Co Hard Metal by Ion Implantation with Ti+, AI+, N+, C+ and B+

International Nuclear Information System (INIS)

Rassoul, El.M.A.; Saleh, Z.A.; Waheed, A.F.; Abdel- Samad, S.M.; EI- Awadi, G.A.

2010-01-01

WC/Co hard metal was implanted by Ti + , AI + , N + , C + , and B + ions at a dose of 5x 10 17 ions/cm 2 at different energies ranging from 50 keV to 200 keV. The implanted layers were investigated by means of nano indentation, calotte measurements, SEM, X-ray diffraction XRD, tribometer and EDX. The maximum implanted zone was about 0.13 μm. The hardness of WC-Co was increased by a factor of 140% after its implantation by Ti, AI, and N and increased by a factor of 170 % after implantation by Ti + , AI + , C + , N + and B + ions as compared to the original value. Also friction coefficient of WC/Co was improved after ion implantation.

Multilayered and composite PVD-CVD coatings in cemented carbides manufacture

International Nuclear Information System (INIS)

Glushkov, V.N.; Anikeev, A.I.; Anikin, V.N.; Vereshchaka, A.S.

2001-01-01

Carbide cutting tools with wear-resistant coatings deposited by CVD process are widely employed in mechanical engineering to ensure a substantially longer service life of tool systems. However, the relatively high temperature and long time of the process make the substrate decarburise and, as a result, the bend strength and performance characteristics of a tool decrease. The present study suggests the problem of deteriorated strength of CVD-coated carbide tools be solved by the development of a technology that combines arc-PVD and CVD processes to deposit multilayered coatings of titanium and aluminium compounds. (author)

AlSiTiN and AlSiCrN multilayer coatings: Effects of structure and surface composition on tribological behavior under dry and lubricated conditions

International Nuclear Information System (INIS)

Faga, Maria Giulia; Gautier, Giovanna; Cartasegna, Federico; Priarone, Paolo C.; Settineri, Luca

2016-01-01

Graphical abstract: - Highlights: • The demand for high performance nanostructured coatings has been increasing. • AlSiTiN and AlSiCrN nanocomposite coatings were deposited by PVD technique. • Coatings were analyzed in terms of structure, hardness and adhesion. • Tribological properties under dry and lubricated conditions were studied. • The effects of surface and bulk properties on friction evolution were assessed. - Abstract: Nanocomposite coatings have been widely studied over the last years because of their high potential in several applications. The increased interest for these coatings prompted the authors to study the tribological properties of two nanocomposites under dry and lubricated conditions (applying typical MQL media), in order to assess the influence of the surface and bulk properties on friction evolution. To this purpose, multilayer and nanocomposite AlSiTiN and AlSiCrN coatings were deposited onto tungsten carbide-cobalt (WC-Co) samples. Uncoated WC-Co materials were used as reference. Coatings were analyzed in terms of hardness and adhesion. The structure of the samples was assessed by X-ray diffraction (XRD), while the surface composition was studied by XPS analysis. Friction tests were carried out under both dry and lubricated conditions using an inox ball as counterpart. Both coatings showed high hardness and good adhesion to the substrate. As far as the friction properties are concerned, in dry conditions the surface properties affect the sliding contact at the early beginning, while bulk structure and tribolayer formation determine the main behavior. Only AlSiTiN coating shows a low and stable coefficient of friction (COF) under dry condition, while the use of MQL media results in a rapid stabilization of the COF for all the materials.

CVD coating of alumina film of CW-[Beta]t-Co cemented carbide by using hydrogen sulphide contained atmosphere. Ryuka suiso wo fukumu CVD fun'iki wo mochiite no WC-[Beta]t-Co choko gokinjo eno Al2O3 hifuku

Energy Technology Data Exchange (ETDEWEB)

Ueki, M.; Kodama, H. (Toshiba Tungaloy Co. Ltd., Kawasaki (Japan)); Suzuki, H. (Chiba Institute of Technology, Chiba (Japan). Faculty of Engineering)

1994-06-15

For the purpose of forming Al2O3, a hard material, of uniform thickness on an ultrahard alloy as base material, addition of H2S gas to the reaction gas was investigated. WC-9 mass% [beta]t-7 mass%Co ([beta]t is a solid solution of 22%Ti, 33%TaC and 45%WC) as base body was covered with TiC, TiN, and Al2O3 successively. At the time of CVD coating of Al2O3, H2S of 0-0.84 vol% was added to the reaction gas (H2 gas containing 2.3%AlCl3 and 2.8%CO2). As the results, the following information was obtained: Thickness (A) of Al2O3 in the edge section and that (B) in the fiat section respectively increase with the addition of H2S of up to 0.3% while A/B decreases in this range of H2S concentration and levels off above 0.3%. And the growth rate of Al2O3 increases with addition of H2S. This fact may be attributed to the reason that H2S is a catalyst of forming H2O in the reaction gas. A possible reason of decrease of A/B is that the S content in Al2O3 is larger in the edge section than in the flat section. The addition of H2S transforms the Al2O3 film to coarse columnar crystals and tends to lower the strength of the film and weaken its contact to the ground. 5 refs., 5 figs.

Atomic composition of WC/ and Zr/O-terminated diamond Schottky interfaces close to ideality

Energy Technology Data Exchange (ETDEWEB)

Piñero, J.C., E-mail: josecarlos.pinero@uca.es [Dpto. Ciencias de los Materiales, Universidad de Cádiz, Puerto Real, Cádiz,11510 (Spain); Araújo, D. [Dpto. Ciencias de los Materiales, Universidad de Cádiz, Puerto Real, Cádiz,11510 (Spain); Fiori, A. [National Institute for Materials Science, Tsukuba, Ibaraki (Japan); Traoré, A. [Institut Néel, CNRS-UJF, av. des Martyrs, Grenoble,38042 France (France); Villar, M.P. [Dpto. Ciencias de los Materiales, Universidad de Cádiz, Puerto Real, Cádiz,11510 (Spain); Eon, D.; Muret, P.; Pernot, J. [Institut Néel, CNRS-UJF, av. des Martyrs, Grenoble,38042 France (France); Teraji, T. [National Institute for Materials Science, Tsukuba, Ibaraki (Japan)

2017-02-15

Highlights: • Metal/O-terminated diamond interfaces are analyzed by a variety of TEM techniques. • Thermal treatment is shown to modify structural and chemical interface properties. • Electrical behavior vs annealing is shown to be related with interface modification. • Interfaces are characterized with atomic resolution to probe inhomogeneities. • Oxide formation and modification is demonstrated in both Schottky diodes. - Abstract: Electrical and nano-structural properties of Zr and WC-based Schottky power diodes are compared and used for investigating oxide-related effects at the diamond/metal interface. Differences in Schottky barrier heights and ideality factors of both structures are shown to be related with the modification of the oxygen-terminated diamond/metal interface configuration. Oxide formation, oxide thickness variations and interfacial oxygen redistribution, associated with thermal treatment are demonstrated. Ideality factors close to ideality (n{sub WC} = 1.02 and n{sub Zr} = 1.16) are obtained after thermal treatment and are shown to be related with the relative oxygen content at the surface (OCR{sub WC} = 3.03 and OCR{sub Zr} = 1.5). Indeed, thermal treatment at higher temperatures is shown to promote an escape of oxygen for the case of the WC diode, while it generates a sharper accumulation of oxygen at the metal/diamond interface for the case of Zr diode. Therefore, the metal-oxygen affinity is shown to be a key parameter to improve diamond-based Schottky diodes.

Fundamentals of grinding : surface conditions of ground WC-Co systems

NARCIS (Netherlands)

Hegeman, JBJW; De Hosson, JTM; Shulepov, SY; Lousberg, N; de With, G; Brebbia, CA; Kenny, JM

1999-01-01

This paper concentrates on the fundamentals of grinding of inorganic materials. A statistical grinding model was developed based on the topography of the grinding wheel. The results of the model are compared with the results of grinding experiments on WC-Co hardmetals. The calculated profiles and

Innovative manufacturing and materials for low cost lithium ion batteries

Energy Technology Data Exchange (ETDEWEB)

Carlson, Steven [Optodot Corporation, Woburn, MA (United States)

2015-12-29

This project demonstrated entirely new manufacturing process options for lithium ion batteries with major potential for improved cost and performance. These new manufacturing approaches are based on the use of the new electrode-coated separators instead of the conventional electrode-coated metal current collector foils. The key enabler to making these electrode-coated separators is a new and unique all-ceramic separator with no conventional porous plastic separator present. A simple, low cost, and high speed manufacturing process of a single coating of a ceramic pigment and polymer binder onto a re-usable release film, followed by a subsequent delamination of the all-ceramic separator and any layers coated over it, such as electrodes and metal current collectors, was utilized. A suitable all-ceramic separator was developed that demonstrated the following required features needed for making electrode-coated separators: (1) no pores greater than 100 nanometer (nm) in diameter to prevent any penetration of the electrode pigments into the separator; (2) no shrinkage of the separator when heated to the high oven heats needed for drying of the electrode layer; and (3) no significant compression of the separator layer by the high pressure calendering step needed to densify the electrodes by about 30%. In addition, this nanoporous all-ceramic separator can be very thin at 8 microns thick for increased energy density, while providing all of the performance features provided by the current ceramic-coated plastic separators used in vehicle batteries: improved safety, longer cycle life, and stability to operate at voltages up to 5.0 V in order to obtain even more energy density. The thin all-ceramic separator provides a cost savings of at least 50% for the separator component and by itself meets the overall goal of this project to reduce the cell inactive component cost by at least 20%. The all-ceramic separator also enables further cost savings by its excellent heat stability

Titanium Carbides Coatings for Wear Resistant Biomedical Devices: Manufacturing and Modeling

International Nuclear Information System (INIS)

Contro, R.; Vena, P.; Gastaldi, D.; Masante, S.; Cavallotti, P. L.; Nobili, L.; Bestetti, M.

2008-01-01

Deposition of Titanium Carbide coatings on Ti6Al4V substrate, through the reactive magnetron sputtering technique is here presented. The mechanical characterization of the coatings has been carried out through a set of indentation tests at different maximum applied loads. The elastic stiffness as well as the hardness of the coating-substrate system indicate that these coatings are suitable candidates for wear resistance applications in the orthopaedic field. Numerical simulation of the indentation tests allowed the identification of the constitutive parameters of the titanium carbide. Good agreement was achieved between experimental and numerical results

Mickey Leland Energy Fellowship Report: Development of Advanced Window Coatings

Energy Technology Data Exchange (ETDEWEB)

Bolton, Ladena A.; Alvine, Kyle J.; Schemer-Kohrn, Alan L.

2014-08-05

Advanced fenestration technologies for light and thermal management in building applications are of great recent research interest for improvements in energy efficiency. Of these technologies, there is specific interest in advanced window coating technologies that have tailored control over the visible and infrared (IR) scattering into a room for both static and dynamic applications. Recently, PNNL has investigated novel subwavelength nanostructured coatings for both daylighting, and IR thermal management applications. Such coatings rese still in the early stages and additional research is needed in terms of scalable manufacturing. This project investigates aspects of a potential new methodology for low-cost scalable manufacture of said subwavelength coatings.

Fabrication of hard cermets by in-situ synthesis and infiltration of metal melts into WC powder compacts

Directory of Open Access Journals (Sweden)

Guanghua Liu

2017-12-01

Full Text Available Hard carbide cermets are prepared by in-situ synthesis and infiltration of metal melts into WC powder compacts. Ni–W and Ni–W–Cr metal melts are in-situ synthesized from thermite reactions and infiltrated into WC powder compacts under high-gravity. During the infiltration, W in the metal melts reacts with WC to form W2C, and more W2C and W are observed at the upper parts of the cermets than the lower parts. The cermets show a maximum hardness of 15.4 GPa, which is higher than most commercial cemented carbides, although they are not fully dense and have a porosity of 15–20%.

Additive Manufacturing of Wind Turbine Molds

Energy Technology Data Exchange (ETDEWEB)

Post, Brian [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Richardson, Bradley [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lloyd, Peter [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Love, Lonnie [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Nolet, Stephen [TPI Composites, Scottsdale, AZ (United States); Hannan, James [TPI Composites, Scottsdale, AZ (United States)

2017-07-01

The objective of this project was to explore the utility of Big Area Additive Manufacturing (BAAM) for low cost manufacturing of wind turbine molds. Engineers at Oak Ridge National Laboratory (ORNL) and TPI Composites (TPI) collaborated to design and manufacture a printed mold that can be used for resin infusion of wind turbine components. Specific focus was on required material properties (operating temperatures and pressures, coefficient of thermal expansion (CTE), thermal conductivity), surface finish (accuracy and coatings) and system integration (integrated vacuum ports, and heating element). The project began with a simple proof of principle components, targeting surface coatings and material properties for printing a small section (approximately 4’ x 4’ x 2’) of a mold. Next, the second phase scaled up and integrated with the objective of capturing all of the necessary components (integrated heating to accelerate cure time, and vacuum, sealing) for resin infusion on a mold of significant size (8’ x 20’ x 6’).

WC1+ γδ T cells from cattle naturally infected with Mycobacterium avium subsp. paratuberculosis respond differentially to stimulation with PPD-J.

Science.gov (United States)

Albarrak, S M; Waters, W R; Stabel, J R; Hostetter, J M

2017-08-01

A role for γδ T cells in protection against mycobacterial infections including Johne's disease (JD) has been suggested. In neonatal calves where the risk to infection with Mycobacterium avium subsp. paratuberculosis (MAP) is high, the majority of circulating CD3 + lymphocytes are γδ TCR + . Bovine γδ T cells are divided into two major subsets based on the surface expression of workshop cluster 1 (WC1). The WC1 + subset, the predominant subset in periphery, is further divided into WC1.1 + and WC1.2 + subpopulations. The ability of γδ T cells to produce IFN-γ prior to CD4 + αβ T cell activation could be crucial to the outcome of MAP infection. In the current study, cattle were naturally infected with MAP and were classified as either in the subclinical or clinical stage of infection. Compared to the control non-infected group, γδ T cell frequency in circulating lymphocytes was significantly lower in the clinical group. The observed decline in frequency was restricted to the WC1.2 + subset, and was not associated with preferential migration to infection sites (distal-ileum). γδ T cells proliferated significantly in recall responses to stimulation with purified protein derivative from MAP (PPD-J) only in subclinically infected cattle. These responses were a heterogeneous mixture of WC1.1 and WC1.2 subsets. Proliferation and IFN-γ production by the WC1.1 + γδ T cell subset was significantly higher in the subclinical group compared to the control and clinical groups. Our data indicates differences in MAP-specific ex-vivo responses of peripheral WC1 + γδ T cells of cattle with the subclinical or clinical form of JD. Copyright © 2017 Elsevier B.V. All rights reserved.

Protective Coatings

Science.gov (United States)

1980-01-01

General Magnaplate Corporation's pharmaceutical machine is used in the industry for high speed pressing of pills and capsules. Machine is automatic system for molding glycerine suppositories. These machines are typical of many types of drug production and packaging equipment whose metal parts are treated with space spinoff coatings that promote general machine efficiency and contribute to compliance with stringent federal sanitation codes for pharmaceutical manufacture. Collectively known as "synergistic" coatings, these dry lubricants are bonded to a variety of metals to form an extremely hard slippery surface with long lasting self lubrication. The coatings offer multiple advantages; they cannot chip, peel or be rubbed off. They protect machine parts from corrosion and wear longer, lowering maintenance cost and reduce undesired heat caused by power-robbing friction.

Laser pulse heating of steel mixing with WC particles in a irradiated region

Science.gov (United States)

Shuja, S. Z.; Yilbas, B. S.; Ali, H.; Karatas, C.

2016-12-01

Laser pulse heating of steel mixing with tungsten carbide (WC) particles is carried out. Temperature field in the irradiated region is simulated in line with the experimental conditions. In the analysis, a laser pulse parameter is introduced, which defines the laser pulse intensity distribution at the irradiated surface. The influence of the laser parameter on the melt pool size and the maximum temperature increase in the irradiated region is examined. Surface temperature predictions are compared with the experimental data. In addition, the distribution of WC particles and their re-locations in the treated layer, due to combination of the natural convection and Marangoni currents, are predicted. The findings are compared to the experimental data. It is found that surface temperature predictions agree well with the experimental data. The dislocated WC particles form a streamlining in the near region of the melt pool wall, which agree with the experimental findings. The Gaussian distribution of the laser pulse intensity results in the maximum peak temperature and the maximum flow velocity inside the melt pool. In this case, the melt pool depth becomes the largest as compared to those corresponding to other laser pulse intensity distributions at the irradiated surface.

A study of TiN-coated metal-on-polymer bearing materials for hip prosthesis

Science.gov (United States)

Lee, Sung Bai; Choi, Jin Young; Park, Won Woong; Jeon, Jun Hong; Won, Sung Ok; Byun, Ji Young; Lim, Sang Ho; Han, Seung Hee

2010-08-01

The TiN-coated metal-on-polymer hip prosthetic pair has the potential to reduce wear debris of UHMWPE (ultra-high molecular weight polyethylene) and to prevent metallic-ion-induced cytotoxicity. However, high quality and adherent film is a key to the clinical success of hip prostheses. In this study, titanium nitride (TiN) films were deposited on stainless steel using plasma immersion ion implantation & deposition (PIII&D) technique to create high-quality film and an adherent interface. The chemical state and composition were analyzed by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and energy dispersive spectroscopy (EDS). The mechanical properties of the films were characterized using a micro-hardness tester and a pin-on-disk wear tester, and an x-ray diffractometer (XRD) was used for a crystallographic analysis. The PIII&D-treated TiN films showed a stoichiometric and (200) preferred orientation and micro-hardness up to 150 % higher than untreated film. A TiN-coated specimen using the PIII&D process also showed less UHMWPE wear compared to untreated specimens. The volumetric wear rate of UHMWPE could be reduced by as much as 42 % compared to when Co-Cr alloy was used. The results of this study show that advanced TiN-coating via the PIII&D process is a viable means of reducing UHMWPE wear in the metal-on-polymer bearing couple.

MEDICAL MANUFACTURING INNOVATIONS

Directory of Open Access Journals (Sweden)

Cosma Sorin Cosmin

2015-02-01

Full Text Available The purpose of these studies was to improve the design and manufacturing process by selective laser melting, of new medical implants. After manufacturing process, the implants were measured, microscopically and mechanical analyzed. Implants manufactured by AM can be an attractive option for surface coatings to improve the osseointegration process. The main advantages of customized implants made by AM process are: the precise adaptation to the region of implantation, better cosmesis, reduced surgical times and better performance over their generic counterparts. These medical manufacturing changes the way that the surgeons are planning surgeries and engineers are designing custom implant. AM process has eliminated the constraints of shape, size, internal structure and mechanical properties making it possible for fabrication of implants that conform to the physical and mechanical requirements of implantation according to CT images. This article will review some custom implants fabricated in DME using biocompatible titanium.

Applicability of near-infrared spectroscopy in the monitoring of film coating and curing process of the prolonged release coated pellets.

Science.gov (United States)

Korasa, Klemen; Hudovornik, Grega; Vrečer, Franc

2016-10-10

Although process analytical technology (PAT) guidance has been introduced to the pharmaceutical industry just a decade ago, this innovative approach has already become an important part of efficient pharmaceutical development, manufacturing, and quality assurance. PAT tools are especially important in technologically complex operations which require strict control of critical process parameters and have significant effect on final product quality. Manufacturing of prolonged release film coated pellets is definitely one of such processes. The aim of the present work was to study the applicability of the at-line near-infrared spectroscopy (NIR) approach in the monitoring of pellet film coating and curing steps. Film coated pellets were manufactured by coating the active ingredient containing pellets with film coating based on polymethacrylate polymers (Eudragit® RS/RL). The NIR proved as a useful tool for the monitoring of the curing process since it was able to determine the extent of the curing and hence predict drug release rate by using partial least square (PLS) model. However, such approach also showed a number of limitations, such as low reliability and high susceptibility to pellet moisture content, and was thus not able to predict drug release from pellets with high moisture content. On the other hand, the at-line NIR was capable to predict the thickness of Eudragit® RS/RL film coating in a wide range (up to 40μm) with good accuracy even in the pellets with high moisture content. To sum up, high applicability of the at-line NIR in the monitoring of the prolonged release pellets production was demonstrated in the present study. The present findings may contribute to more efficient and reliable PAT solutions in the manufacturing of prolonged release dosage forms. Copyright © 2016 Elsevier B.V. All rights reserved.

Application of in-plane x-ray diffraction technique for residual stress measurement of TiN film/WC-Co alloy

International Nuclear Information System (INIS)

Takago, Shigeki; Yasui, Haruyuki; Awazu, Kaoru; Sasaki, Toshihiko; Hirose, Yukio; Sakurai, Kenji

2006-01-01

An in-plane X-ray diffraction technique was used to measure the residual stress of a CVD (chemical vapor deposition) TiN-coated WC-Co alloy. We could obtain the diffraction pattern from a thin film layer, eliminating that of the substrate. In the case of a conventional X-ray diffractometer, the X-ray penetration depth is about few μm. However, for a grazing incidence beam it is only 0.2μm. Depth profiles of residual stress in TiN film layer were evaluated by the present method and the conventional sin 2 ψ technique. We concluded that the in-plane diffraction technique enables us to determine the residual stress in a DVD-TiN film having an oriented texture. It was found that the residual tensile stress generated a mismatch of the coefficient of thermal expansion between the film and the substrate. (author)

Application of in-plane x-ray diffraction technique for residual stress measurement of TiN film/WC-Co alloy

Energy Technology Data Exchange (ETDEWEB)

Takago, Shigeki; Yasui, Haruyuki; Awazu, Kaoru [Industrial Research Inst. of Ishikawa, Kanazawa, Ishikawa (Japan); Sasaki, Toshihiko; Hirose, Yukio [Kanazawa Univ., Dept. of Materials Science and Engineering, Kanazawa, Ishikawa (Japan); Sakurai, Kenji [National Inst. for Materials Science, Tsukuba, Ibaraki (Japan)

2006-06-15

An in-plane X-ray diffraction technique was used to measure the residual stress of a CVD (chemical vapor deposition) TiN-coated WC-Co alloy. We could obtain the diffraction pattern from a thin film layer, eliminating that of the substrate. In the case of a conventional X-ray diffractometer, the X-ray penetration depth is about few {mu}m. However, for a grazing incidence beam it is only 0.2{mu}m. Depth profiles of residual stress in TiN film layer were evaluated by the present method and the conventional sin{sup 2}{psi} technique. We concluded that the in-plane diffraction technique enables us to determine the residual stress in a DVD-TiN film having an oriented texture. It was found that the residual tensile stress generated a mismatch of the coefficient of thermal expansion between the film and the substrate. (author)

The effect of solvents and hydrophilic additive on stable coating and controllable sirolimus release system for drug-eluting stent.

Science.gov (United States)

Kim, Seong Min; Park, Sung-Bin; Bedair, Tarek M; Kim, Man-Ho; Park, Bang Ju; Joung, Yoon Ki; Han, Dong Keun

2017-09-01

Various drug-eluting stents (DESs) have been developed to prevent restenosis after stent implantation. However, DES still needs to improve the drug-in-polymer coating stability and control of drug release for effective clinical treatment. In this study, the cobalt-chromium (CoCr) alloy surface was coated with biodegradable poly(D,L-lactide) (PDLLA) and sirolimus (SRL) mixed with hydrophilic Pluronic F127 additive by using ultrasonic spray coating system in order to achieve a stable coating surface and control SRL release. The degradation of PDLLA/SRL coating was studied under physiological solution. It was found that adding F127 reduced the degradation of PDLLA and improved the coating stability during 60days. The effects of organic solvent such as chloroform and tetrahydrofuran (THF) on the coating uniformity were also examined. It was revealed that THF produced a very smooth and uniform coating compared to chloroform. The patterns of in vitro drug release according to the type of organic solvent and hydrophilic additive proposed the possibility of controllable drug release design in DES. It was found that using F127 the drug release was sustained regardless of the organic solvent used. In addition, THF was able to get faster and controlled release profile when compared to chloroform. The structure of SRL molecules in different organic solvents was investigated using ultra-small angle neutron scattering. Furthermore, the structure of SRL is concentration-dependent in chloroform with tight nature under high concentration, but concentration-independent in THF. These results strongly demonstrated that coating stability and drug release patterns can be changed by physicochemical properties of various parameters such as organic solvents, additive, and coating strategy. Copyright © 2017 Elsevier B.V. All rights reserved.

Development of corrosion and wear resistant coatings by an improved HVOF spraying process

Energy Technology Data Exchange (ETDEWEB)

Ishikawa, Y.; Kawakita, J.; Kuroda, S. [National Inst. for Materials Science, Tsukuba (Japan)

2005-07-01

We have developed an improved HVOF spray process called ''Gas-shrouded HVOF'' (GS-HVOF) over the past several years. By using an extension nozzle at the exit of a commercial HVOF spray gun, GS-HVOF is capable of controlling the oxidation of sprayed materials during flight as well as achieving higher velocity of sprayed particles. These features result in extremely dense and clean microstructure of the sprayed coatings. The process has been successfully applied to corrosion resistant alloys such as SUS316L, Hastelloy C, and alloy 625 as well as cermets such as WC-Cr{sub 3}C{sub 2}-Ni. The spray process, coatings microstructure and property evaluation will be discussed with potential industrial applications in the near future. (orig.)

An Experimental Study on Slurry Erosion Resistance of Single and Multilayered Deposits of Ni-WC Produced by Laser-Based Powder Deposition Process

Science.gov (United States)

Balu, Prabu; Hamid, Syed; Kovacevic, Radovan

2013-11-01

Single and multilayered deposits containing different mass fractions of tungsten carbide (WC) in nickel (Ni)-matrix (NT-20, NT-60, NT-80) are deposited on a AISI 4140 steel substrate using a laser-based powder deposition process. The transverse cross section of the coupons reveals that the higher the mass fraction of WC in Ni-matrix leads to a more uniform distribution through Ni-matrix. The slurry erosion resistance of the fabricated coupons is tested at three different impingement angles using an abrasive water jet cutting machine, which is quantified based on the erosion rate. The top layer of a multilayered deposit (i.e., NT-60 in a two-layer NT-60 over NT-20 deposit) exhibits better erosion resistance at all three tested impingement angles when compared to a single-layer (NT-60) deposit. A definite increase in the erosion resistance is noted with an addition of nano-size WC particles. The relationship between the different mass fractions of reinforcement (WC) in the deposited composite material (Ni-WC) and their corresponding matrix (Ni) hardness on the erosion rate is studied. The eroded surface is analyzed in the light of a three-dimensional (3-D) profilometer and a scanning electron microscope (SEM). The results show that a volume fraction of approximately 62% of WC with a Ni-matrix hardness of 540 HV resulting in the gouging out of WC from the Ni-matrix by the action of slurry. It is concluded that the slurry erosion resistance of the AISI 4140 steel can be significantly enhanced by introducing single and multilayered deposits of Ni-WC composite material fabricated by the laser-based powder deposition process.

Precision Optical Coatings for Large Space Telescope Mirrors

Science.gov (United States)

Sheikh, David

This proposal “Precision Optical Coatings for Large Space Telescope Mirrors” addresses the need to develop and advance the state-of-the-art in optical coating technology. NASA is considering large monolithic mirrors 1 to 8-meters in diameter for future telescopes such as HabEx and LUVOIR. Improved large area coating processes are needed to meet the future requirements of large astronomical mirrors. In this project, we will demonstrate a broadband reflective coating process for achieving high reflectivity from 90-nm to 2500-nm over a 2.3-meter diameter coating area. The coating process is scalable to larger mirrors, 6+ meters in diameter. We will use a battery-driven coating process to make an aluminum reflector, and a motion-controlled coating technology for depositing protective layers. We will advance the state-of-the-art for coating technology and manufacturing infrastructure, to meet the reflectance and wavefront requirements of both HabEx and LUVOIR. Specifically, we will combine the broadband reflective coating designs and processes developed at GSFC and JPL with large area manufacturing technologies developed at ZeCoat Corporation. Our primary objectives are to: Demonstrate an aluminum coating process to create uniform coatings over large areas with near-theoretical aluminum reflectance Demonstrate a motion-controlled coating process to apply very precise 2-nm to 5- nm thick protective/interference layers to large areas, Demonstrate a broadband coating system (90-nm to 2500-nm) over a 2.3-meter coating area and test it against the current coating specifications for LUVOIR/HabEx. We will perform simulated space-environment testing, and we expect to advance the TRL from 3 to >5 in 3-years.

WC Nanocrystals Grown on Vertically Aligned Carbon Nanotubes: An Efficient and Stable Electrocatalyst for Hydrogen Evolution Reaction.

Science.gov (United States)

Fan, Xiujun; Zhou, Haiqing; Guo, Xia

2015-05-26

Single nanocrystalline tungsten carbide (WC) was first synthesized on the tips of vertically aligned carbon nanotubes (VA-CNTs) with a hot filament chemical vapor deposition (HF-CVD) method through the directly reaction of tungsten metal with carbon source. The VA-CNTs with preservation of vertical structure integrity and alignment play an important role to support the nanocrystalline WC growth. With the high crystallinity, small size, and uniform distribution of WC particles on the carbon support, the formed WC-CNTs material exhibited an excellent catalytic activity for hydrogen evolution reaction (HER), giving a η10 (the overpotential for driving a current of 10 mA cm(-2)) of 145 mV, onset potential of 15 mV, exchange current density@ 300 mV of 117.6 mV and Tafel slope values of 72 mV dec(-1) in acid solution, and η10 of 137 mV, onset potential of 16 mV, exchange current density@ 300 mV of 33.1 mV and Tafel slope values of 106 mV dec(-1) in alkaline media, respectively. Electrochemical stability test further confirms the long-term operation of the catalyst in both acidic and alkaline media.

Synthesis and Deposition of TiC-Fe Coatings by Oxygen-acetylene Flame Spraying

Institute of Scientific and Technical Information of China (English)

无

2003-01-01

A simpler and more convenient method for producing wear-resistant, TiC-reinforced coatings were investigated in this study. It consists of the simultaneous synthesis and deposition of TiC-Fe materials by oxyacetylene flame spraying.Solid reagents bound together to form a single particle are injected into the flame stream where an in-situ reaction occurs. The reaction products are propelled onto a substrate to form a coating. Microstructural analyses reveal that TiC and Fe are the dominant phases in the coatings. The reaction between Ti and C happens step by step along with the reactive spray powder flight, and TiC-Fe materials were mainly synthesized where the spray distance is 125～170 mm. The TiC-Fe coatings are composed of alternate TiC-rich and TiC-poor lamellae with different microhardness of 11.9～13.7 and 3.0～6.0 Gpa, respectively. Submicron and round TiC particles are dispersed within a ductile metal matrix. The peculiar microstructure is thought to be responsible for its good wear resistance, which is better nearly five times than WC-reinforced cermet coatings obtained by traditional oxyacetylene flame spray.

Abnormal growth of faceted (WC) grains in a (Co) liquid matrix

International Nuclear Information System (INIS)

Park, Y.J.; Yoon, D.Y.

1996-01-01

If the grains dispersed in a liquid matrix are spherical, their surface atomic structure is expected to be rough (diffuse), and their coarsening has been observed to be controlled by diffusion in the matrix. They do not, furthermore, undergo abnormal growth. On the other hand, in some compound material systems, the grains in liquid matrices are faceted and often show abnormal coarsening behavior. Their faceted surface planes are expected to be singular (atomically flat) and therefore grow by a defect-assisted process and two-dimensional (2-D) nucleation. Contrary to the usual coarsening theories, their growth velocity is not linearly dependent on the driving force arising from the grain size difference. If the growth of the faceted grains occurs by 2-D nucleation, the rate is expected to increase abruptly at a critical supersaturation, as has been observed in crystal growth in melts and solutions. It is proposed that this growth mechanism leads to the abnormal grain coarsening. The 2-D nucleation theory predicts that there is a threshold initial grain size for the abnormal grain growth (AGG), and the propensity for AGG will increase with the heat-treatment temperature. The AGG behavior will also vary with the defects in the grains. These predictions are qualitatively confirmed in the sintered WC-Co alloy prepared from fine (0.85-microm) and coarse (5.48-microm) WC powders and their mixtures. The observed dependence of the AGG behavior on the sintering temperature and the milling of the WC powder is also qualitatively consistent with the predicted behavior

Metal matrix coated fiber composites and the methods of manufacturing such composites

Science.gov (United States)

Weeks, J.K. Jr.; Gensse, C.

1993-09-14

A fiber coating which allows ceramic or metal fibers to be wetted by molten metals is disclosed. The coating inhibits degradation of the physical properties caused by chemical reaction between the fiber and the coating itself or between the fiber and the metal matrix. The fiber coating preferably includes at least a wetting layer, and in some applications, a wetting layer and a barrier layer between the fiber and the wetting layer. The wetting layer promotes fiber wetting by the metal matrix. The barrier layer inhibits fiber degradation. The fiber coating permits the fibers to be infiltrated with the metal matrix resulting in composites having unique properties not obtainable in pure materials. 8 figures.

In-situ investigation of stress conditions during expansion of bare metal stents and PLLA-coated stents using the XRD sin(2)ψ-technique.

Science.gov (United States)

Kowalski, Wolfgang; Dammer, Markus; Bakczewitz, Frank; Schmitz, Klaus-Peter; Grabow, Niels; Kessler, Olaf

2015-09-01

Drug eluting stents (DES) consist of platform, coating and drug. The platform often is a balloon-expandable bare metal stent made of the CoCr alloy L-605 or stainless steel 316 L. The function of the coating, typically a permanent polymer, is to hold and release the drug, which should improve therapeutic outcome. Before implantation, DES are compressed (crimped) to allow implantation in the human body. During implantation, DES are expanded by balloon inflation. Crimping, as well as expansion, causes high stresses and high strains locally in the DES struts, as well as in the polymer coating. These stresses and strains are important design criteria of DES. Usually, they are calculated numerically by finite element analysis (FEA), but experimental results for validation are hardly available. In this work, the X-ray diffraction (XRD) sin(2)ψ-technique is applied to in-situ determination of stress conditions of bare metal L-605 stents, and Poly-(L-lactide) (PLLA) coated stents. This provides a realistic characterization of the near-surface stress state and a validation option of the numerical FEA. XRD-results from terminal stent struts of the bare metal stent show an increasing compressive load stress in tangential direction with increasing stent expansion. These findings correlate with numerical FEA results. The PLLA-coating also bears increasing compressive load stress during expansion. Copyright © 2015 Elsevier Ltd. All rights reserved.

Tuning of magnetic transition temperatures in nanoparticles of CoCr2O4 multiferroic by B-site mixing

International Nuclear Information System (INIS)

Kumar, D.; Mohanty, P.; Singh, V.P.; Galivarapu, Jagadish K.; Banerjee, A.; Ganesan, V.; Rath, Chandana

2014-01-01

Highlights: • Pure CoCr 2−x Fe x O 4 (x = 0.1 and 0.2) nanoparticles of 16–20 and 6–10 nm show enhancement of T c from 100 to 110 K and T s from 18 K to 36 K with increasing Fe. • The theoretical variation of reciprocal susceptibility with temperature in paramagnetic region using the function χ −1 = T/C + 1/χ 0 – b/(T − θ) is fitted with the experimental data. • The difference in ferrimagnetic Curie point, θ f and paramagnetic Curie point, θ p is 30 K and 7 K respectively for sample x = 0.1 and 0.2 indicating a sharp ferri- to para-magnetic transition in the former one. - Abstract: Pure CoCr 2−x Fe x O 4 nanoparticles synthesized through conventional coprecipitation technique show particle size distribution in the range of 16–20 and 6–10 nm for x = 0.1 and 0.2 respectively. Magnetic and specific heat measurements show an enhancement of paramagnetic to collinear ferrimagnetic transition temperature, T c from 100 to 110 K and to a short range non-collinear spiral ordering, T s from 18 to 36 K with increasing x from 0.1 to 0.2 respectively. In addition, a strong disagreement between the paramagnetic moment obtained from the fitting of χ −1 = T/C + 1/χ 0 – b/(T − θ) and ferrimagnetic moment measured from the M vs. H loop at 10 K corroborates the nonsaturation behavior of magnetization at 50–100 kOe field and an order of magnitude higher coercivity (H c ). The enhancement of T c and T s with increasing Fe concentration is attributed to an intrinsic change in non-collinear to collinear spin structure and strong J A–B interaction

Dry coating of solid dosage forms: an overview of processes and applications.

Science.gov (United States)

Foppoli, Anastasia Anna; Maroni, Alessandra; Cerea, Matteo; Zema, Lucia; Gazzaniga, Andrea

2017-12-01

Dry coating techniques enable manufacturing of coated solid dosage forms with no, or very limited, use of solvents. As a result, major drawbacks associated with both organic solvents and aqueous coating systems can be overcome, such as toxicological, environmental, and safety-related issues on the one hand as well as costly drying phases and impaired product stability on the other. The considerable advantages related to solventless coating has been prompting a strong research interest in this field of pharmaceutics. In the article, processes and applications relevant to techniques intended for dry coating are analyzed and reviewed. Based on the physical state of the coat-forming agents, liquid- and solid-based techniques are distinguished. The former include hot-melt coating and coating by photocuring, while the latter encompass press coating and powder coating. Moreover, solventless techniques, such as injection molding and three-dimensional printing by fused deposition modeling, which are not purposely conceived for coating, are also discussed in that they would open new perspectives in the manufacturing of coated-like dosage forms.

Characterization of coatings and the low cycle fatigue behaviour of 316L

International Nuclear Information System (INIS)

Groot, P.; Horsten, M.G.; Tjoa, G.L.

1993-03-01

In the framework of the European Fusion Technology Programme ECN participates in a NET task PSM-8 'Coatings and Surface Effects on Stainless Steel 316L'. High emissivity coatings were developed for enhanced heat transfer from graphite tiles to a Stainless Steel First Wall. Four candidate materials, Cr 2 O 3 , Black Cr, Al 2 O 3 /TiO 2 and TiC were tested as candidate high emissivity coatings. These coatings were manufactured by atmospheric and vacuum plasma spraying technique and the Black Chromium coatings were manufactured by a galvanic coating technique. The tests included total emissivity measurements and Low Cycle Fatigue (LCF) experiments. The total emissivity of two TiC coatings at 525 K appeared to be 0.62 and 0.64. The total emissivity of the TiC and 5 wt% TiO 2 /Al 2 O 3 coating was about 0.7. (orig.)

Preciscavanje otpadnih voda u postupcima prerade i flegmatizacije eksploziva / Refining of waste waters in processes of manufacturing and coating of high explosives

Directory of Open Access Journals (Sweden)

Mirjana Anđelković-Lukić

2002-03-01

Full Text Available U radu su prikazani tehnološki postupci prerade (flegmatizacije eksploziva pri kojima dolazi do zagađenja okoline otpadnim vodama. Prikazani su neki od načina prerade otpadnih voda pre nego što se ispuste u javne vodotokove. / The paper deals with production processes of manufacturing and coating Ugh explosives which pollute environment with waste waters. Some methods of refining waste waters before letting them into open water current are presented.

Investigation of Plasma Spray Coatings as an Alternative to Hard Chrome Plating on Internal Surfaces

Science.gov (United States)

2006-09-14

obtain a full curve, with runout defined as 107 cycles. Maximum stresses were 220ksi, which is just below yield, and above the maximum that would be...4.7. Abrasive wear 4.7.1. Test methods Abrasive wear was measured using the ASTM G-65 method of a rubber wheel with dry sand rubbing against the...coated with WC self fluxing material (NI-988) and used to test different finishing methods. Silicon carbide, aluminum oxide and diamond grinding wheels

Effect of resin coating and occlusal loading on microleakage of Class II computer-aided design/computer-aided manufacturing fabricated ceramic restorations: a confocal microscopic study.

Science.gov (United States)

Kitayama, Shuzo; Nasser, Nasser A; Pilecki, Peter; Wilson, Ron F; Nikaido, Toru; Tagami, Junji; Watson, Timothy F; Foxton, Richard M

2011-05-01

To evaluate the effect of resin coating and occlusal loading on microleakage of class II computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic restorations. Molars were prepared for an mesio-occlusal-distal (MOD) inlay and were divided into two groups: non-coated (controls); and resin-coated, in which the cavity was coated with a combination of a dentin bonding system (Clearfil Protect Bond) and a flowable resin composite (Clearfil Majesty Flow). Ceramic inlays were fabricated using the CAD/CAM technique (CEREC 3) and cemented with resin cement (Clearfil Esthetic Cement). After 24 h of water storage, the restored teeth in each group were divided into two subgroups: unloaded or loaded with an axial force of 80 N at a rate of 2.5 cycles/s for 250,000 cycles while stored in water. After immersion in 0.25% Rhodamine B solution, the teeth were sectioned bucco-lingually at the mesial and distal boxes. Tandem scanning confocal microscopy (TSM) was used for evaluation of microleakage. The locations of the measurements were assigned to the cavity walls and floor. Loading did not have a significant effect on microleakage in either the resin-coated or non-coated group. Resin coating significantly reduced microleakage regardless of loading. The cavity floor exhibited greater microleakage compared to the cavity wall. TSM observation also revealed that microleakage at the enamel surface was minimal regardless of resin coating. In contrast, non-coated dentin showed extensive leakage, whereas resin-coated dentin showed decreased leakage. Resin coating with a combination of a dentin-bonding system and a flowable resin composite may be indicated prior to impression-taking when restoring teeth with CAD/CAM ceramic inlays in order to reduce microleakage at the tooth-resin interface.

Topology Optimization for Additive Manufacturing

DEFF Research Database (Denmark)

Clausen, Anders

This PhD thesis deals with the combination of topology optimization and additive man-ufacturing (AM, also known as 3D-printing). In addition to my own works, the thesis contains a broader review and assessment of the literature within the field. The thesis first presents a classification...... of the various AM technologies, a review of relevant manufacturing materials, the properties of these materials in the additively manufactured part, as well as manufacturing constraints with a potential for design optimization. Subsequently, specific topology optimization formulations relevant for the most im...... for scalable manufacturing. In relation to interface problems it is shown how a flexible void area may be included into a standard minimum compliance problem by employing an additional design variable field and a sensitivity filter. Furthermore, it is shown how the design of coated structures may be modeled...

Influence of Aggregate Coated with Modified Sulfur on the Properties of Cement Concrete

Directory of Open Access Journals (Sweden)

Swoo-Heon Lee

2014-06-01

Full Text Available This paper proposes the mixing design of concrete having modified sulfur-coated aggregate (MSCA to enhance the durability of Portland cement concrete. The mechanical properties and durability of the proposed MSCA concrete were evaluated experimentally. Melting-modified sulfur was mixed with aggregate in order to coat the aggregate surface at a speed of 20 rpm for 120 s. The MSCA with modified sulfur corresponding to 5% of the cement weight did not significantly affect the flexural strength in a prism concrete beam specimen, regardless of the water-cement ratio (W/C. However, a dosage of more than 7.5% decreased the flexural strength. On the other hand, the MSCA considerably improved the resistance to the sulfuric acid and the freezing-thawing, regardless of the sulfur dosage in the MSCA. The coating modified sulfur of 5% dosage consequently led to good results for the mechanical properties and durability of MSCA concrete.

Tribological performance of an H-DLC coating prepared by PECVD

Science.gov (United States)

Solis, J.; Zhao, H.; Wang, C.; Verduzco, J. A.; Bueno, A. S.; Neville, A.

2016-10-01

Carbon-based coatings are of wide interest due to their application in machine elements subjected to continuous contact where fluid lubricant films are not permitted. This paper describes the tribological performance under dry conditions of duplex layered H-DLC coating sequentially deposited by microwave excited plasma enhanced chemical vapour deposition on AISI 52100 steel. The architecture of the coating comprised Cr, WC, and DLC (a-C:H) with a total thickness of 2.8 μm and compressive residual stress very close to 1 GPa. Surface hardness was approximately 22 GPa and its reduced elastic modulus around 180 GPa. Scratch tests indicated a well adhered coating achieving a critical load of 80 N. The effect of normal load on the friction and wear behaviours were investigated with steel pins sliding against the actual coating under dry conditions at room temperature (20 ± 2 °C) and 35-50% RH. The results show that coefficient of friction of the coating decreased from 0.21 to 0.13 values with the increase in the applied loads (10-50 N). Specific wear rates of the surface coating also decrease with the increase in the same range of applied loads. Maximum and minimum values were 14 × 10-8 and 5.5 × 10-8 mm-3/N m, respectively. Through Raman spectroscopy and electron microscopy it was confirmed the carbon-carbon contact, due to the tribolayer formation on the wear scars of the coating and pin. In order to further corroborate the experimental observations regarding the graphitisation behaviour, the existing mathematical relationships to determine the graphitisation temperature of the coating/steel contact as well as the flash temperature were used.

Stress distribution in Co-Cr implant frameworks after laser or TIG welding.

Science.gov (United States)

de Castro, Gabriela Cassaro; de Araújo, Cleudmar Amaral; Mesquita, Marcelo Ferraz; Consani, Rafael Leonardo Xediek; Nóbilo, Mauro Antônio de Arruda

2013-01-01

Lack of passivity has been associated with biomechanical problems in implant-supported prosthesis. The aim of this study was to evaluate the passivity of three techniques to fabricate an implant framework from a Co-Cr alloy by photoelasticity. The model was obtained from a steel die simulating an edentulous mandible with 4 external hexagon analog implants with a standard platform. On this model, five frameworks were fabricated for each group: a monoblock framework (control), laser and TIG welding frameworks. The photoelastic model was made from a flexible epoxy resin. On the photoelastic analysis, the frameworks were bolted onto the model for the verification of maximum shear stress at 34 selected points around the implants and 5 points in the middle of the model. The stresses were compared all over the photoelastic model, between the right, left, and center regions and between the cervical and apical regions. The values were subjected to two-way ANOVA, and Tukey's test (α=0.05). There was no significant difference among the groups and studied areas (p>0.05). It was concluded that the stresses generated around the implants were similar for all techniques.

"Diamond" over-coated Microstrip Gas Chambers for high rate operation

CERN Document Server

Barr, A J; Bouclier, Roger; Capéans-Garrido, M; Dominik, Wojciech; Hoch, M; Manzin, G; Million, Gilbert; Ropelewski, Leszek; Sauli, Fabio; Sharma, A

1997-01-01

We describe the recent developments on the diamond-like carbon (DLC) over-coated Microstrip Gas Chambers made on drawn glass substrates. MSGC surface coating with thin DLC layer of stable and controlled resistivity was proposed to overcome the limitation of detector operation due to surface charging-up under avalanches. This brings also advantages for the detector manufacturing technology. The thin layer, deposited on top of a manufactured MSGC (over-coating), demonstrates excellent mechanical properties and very good stability. We report on recent measurements with DLC over-coated MSGCs of various surface resistivities (ranging from 1013W/r to 1016W/r) on D-263 and AF45 glass substrates. Over-coated MSGCs exhibit good rate capability for the resistivity of the surface around 1015W/r. Stable operation up to 50 mC/cm of accumulated charge from avalanches has been demonstrated.