WorldWideScience

Sample records for cemented tungsten carbide

  1. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides.

    Science.gov (United States)

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-14

    In contrast to the conventional method that obtains a high fracture strength of tungsten carbide-cobalt (WC-Co) cemented carbides by reducing WC grain size to near-nano or nanoscale, a new approach has been developed to achieve ultrahigh fracture strength by strengthening the WC grains through precipitate reinforcement. The cemented carbides were prepared by liquid-state sintering the in situ synthesized WC-Co composite powders with a little excess carbon and pre-milled Cr3C2 particles having different size scales. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed.

  2. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides

    Science.gov (United States)

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-01

    In contrast to the conventional method that obtains a high fracture strength of tungsten carbide-cobalt (WC-Co) cemented carbides by reducing WC grain size to near-nano or nanoscale, a new approach has been developed to achieve ultrahigh fracture strength by strengthening the WC grains through precipitate reinforcement. The cemented carbides were prepared by liquid-state sintering the in situ synthesized WC-Co composite powders with a little excess carbon and pre-milled Cr3C2 particles having different size scales. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed.

  3. Direct Electrochemical Preparation of Cobalt, Tungsten, and Tungsten Carbide from Cemented Carbide Scrap

    Science.gov (United States)

    Xiao, Xiangjun; Xi, Xiaoli; Nie, Zuoren; Zhang, Liwen; Ma, Liwen

    2016-10-01

    A novel process of preparing cobalt, tungsten, and tungsten carbide powders from cemented carbide scrap by molten salt electrolysis has been investigated in this paper. In this experiment, WC-6Co and NaCl-KCl salt were used as sacrificial anode and electrolyte, respectively. The dissolution potential of cobalt and WC was determined by linear sweep voltammetry to be 0 and 0.6 V (vs Ag/AgCl), respectively. Furthermore, the electrochemical behavior of cobalt and tungsten ions was investigated by a variety of electrochemical techniques. Results of cyclic voltammetry (CV) and square-wave voltammetry show that the cobalt and tungsten ions existed as Co2+ and W2+ on melts, respectively. The effect of applied voltage, electrolysis current, and electrolysis times on the composition of the product was studied. Results showed that pure cobalt powder can be obtained when the electrolysis potential is lower than 0.6 V or during low current and short times. Double-cathode and two-stage electrolysis was utilized for the preparation of cobalt, tungsten carbide, and tungsten powders. Additionally, X-ray diffraction results confirm that the product collected at cathodes 1 and 2 is pure Co and WC, respectively. Pure tungsten powder was obtained after electrolysis of the second part. Scanning electron microscope results show that the diameters of tungsten, tungsten carbide, and cobalt powder are smaller than 100, 200, and 200 nm, respectively.

  4. Direct Electrochemical Preparation of Cobalt, Tungsten, and Tungsten Carbide from Cemented Carbide Scrap

    Science.gov (United States)

    Xiao, Xiangjun; Xi, Xiaoli; Nie, Zuoren; Zhang, Liwen; Ma, Liwen

    2017-02-01

    A novel process of preparing cobalt, tungsten, and tungsten carbide powders from cemented carbide scrap by molten salt electrolysis has been investigated in this paper. In this experiment, WC-6Co and NaCl-KCl salt were used as sacrificial anode and electrolyte, respectively. The dissolution potential of cobalt and WC was determined by linear sweep voltammetry to be 0 and 0.6 V ( vs Ag/AgCl), respectively. Furthermore, the electrochemical behavior of cobalt and tungsten ions was investigated by a variety of electrochemical techniques. Results of cyclic voltammetry (CV) and square-wave voltammetry show that the cobalt and tungsten ions existed as Co2+ and W2+ on melts, respectively. The effect of applied voltage, electrolysis current, and electrolysis times on the composition of the product was studied. Results showed that pure cobalt powder can be obtained when the electrolysis potential is lower than 0.6 V or during low current and short times. Double-cathode and two-stage electrolysis was utilized for the preparation of cobalt, tungsten carbide, and tungsten powders. Additionally, X-ray diffraction results confirm that the product collected at cathodes 1 and 2 is pure Co and WC, respectively. Pure tungsten powder was obtained after electrolysis of the second part. Scanning electron microscope results show that the diameters of tungsten, tungsten carbide, and cobalt powder are smaller than 100, 200, and 200 nm, respectively.

  5. Effects of laser ablation on cemented tungsten carbide surface quality

    Energy Technology Data Exchange (ETDEWEB)

    Tan, J.L.; Butler, D.L.; Sim, L.M.; Jarfors, A.E.W. [Singapore Institute of Manufacturing Technology, Singapore (Singapore)

    2010-11-15

    Although laser micromachining has been touted as being the most promising way to fabricate micro tools, there has been no proper evaluation of the effects of laser ablation on bulk material properties. The current work demonstrates the effects of laser ablation on the properties of a cemented tungsten carbide surface. Of particular interest is the resultant increase in compressive residual stresses in the ablated surface. From this study it is seen that there are no adverse effects from laser ablation of cemented tungsten carbide that would preclude its use for the fabrication of micro-tools but a finishing process may not be avoidable. (orig.)

  6. Effects of laser ablation on cemented tungsten carbide surface quality

    Science.gov (United States)

    Tan, J. L.; Butler, D. L.; Sim, L. M.; Jarfors, A. E. W.

    2010-11-01

    Although laser micromachining has been touted as being the most promising way to fabricate micro tools, there has been no proper evaluation of the effects of laser ablation on bulk material properties. The current work demonstrates the effects of laser ablation on the properties of a cemented tungsten carbide surface. Of particular interest is the resultant increase in compressive residual stresses in the ablated surface. From this study it is seen that there are no adverse effects from laser ablation of cemented tungsten carbide that would preclude its use for the fabrication of micro-tools but a finishing process may not be avoidable.

  7. Development of Bulk Nanocrystalline Cemented Tungsten Carbide for Industrial Applicaitons

    Energy Technology Data Exchange (ETDEWEB)

    Z. Zak Fang, H. Y. Sohn

    2009-03-10

    This report contains detailed information of the research program entitled "Development of Bulk Nanocrystalline Cemented Tungsten Carbide Materials for Industrial Applications". The report include the processes that were developed for producing nanosized WC/Co composite powders, and an ultrahigh pressure rapid hot consolidation process for sintering of nanosized powders. The mechanical properties of consolidated materials using the nanosized powders are also reported.

  8. Analysis of powdered tungsten carbide hard-metal precursors and cemented compact tungsten carbides using laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Novotny, K. [Laboratory of Atomic Spectrochemistry, Department of Chemistry, Faculty of Science, Masaryk University, Kotlarska 2, 611 37 Brno (Czech Republic)], E-mail: codl@sci.muni.cz; Stankova, A. [Laboratory of Atomic Spectrochemistry, Department of Chemistry, Faculty of Science, Masaryk University, Kotlarska 2, 611 37 Brno (Czech Republic); Haekkaenen, H.; Korppi-Tommola, J. [Department of Chemistry, University of Jyvaeskylae, P.O. BOX 35, FIN-40014 (Finland); Otruba, V.; Kanicky, V. [Laboratory of Atomic Spectrochemistry, Department of Chemistry, Faculty of Science, Masaryk University, Kotlarska 2, 611 37 Brno (Czech Republic)

    2007-12-15

    Laser-induced breakdown spectroscopy (LIBS) has been applied to the direct analysis of powdered tungsten carbide hard-metal precursors and cemented tungsten carbides. The aim of this work was to examine the possibility of quantitative determination of the niobium, titanium, tantalum and cobalt. The investigated samples were in the form of pellets, pressed with and without binder (powdered silver) and in the form of cemented tungsten carbides. The pellets were prepared by pressing the powdered material in a hydraulic press. Cemented tungsten carbides were embedded in resin for easier manipulation. Several lasers and detection systems were utilized. The Nd:YAG laser working at a basic wavelength of 1064 nm and fourth-harmonic frequency of 266 nm with a gated photomultiplier or ICCD detector HORIBA JY was used for the determination of niobium which was chosen as a model element. Different types of surrounding gases (air, He, Ar) were investigated for analysis. The ICCD detector DICAM PRO with Mechelle 7500 spectrometer with ArF laser (193 nm) and KrF laser (248 nm) were employed for the determination of niobium, titanium, tantalum and cobalt in samples under air atmosphere. Good calibration curves were obtained for Nb, Ti, and Ta (coefficients of determination r{sup 2} > 0.96). Acceptable calibration curves were acquired for the determination of cobalt (coefficient of determination r{sup 2} = 0.7994) but only for the cemented samples. In the case of powdered carbide precursors, the calibration for cobalt was found to be problematic.

  9. Analysis of powdered tungsten carbide hard-metal precursors and cemented compact tungsten carbides using laser-induced breakdown spectroscopy

    Science.gov (United States)

    Novotný, K.; Staňková, A.; Häkkänen, H.; Korppi-Tommola, J.; Otruba, V.; Kanický, V.

    2007-12-01

    Laser-induced breakdown spectroscopy (LIBS) has been applied to the direct analysis of powdered tungsten carbide hard-metal precursors and cemented tungsten carbides. The aim of this work was to examine the possibility of quantitative determination of the niobium, titanium, tantalum and cobalt. The investigated samples were in the form of pellets, pressed with and without binder (powdered silver) and in the form of cemented tungsten carbides. The pellets were prepared by pressing the powdered material in a hydraulic press. Cemented tungsten carbides were embedded in resin for easier manipulation. Several lasers and detection systems were utilized. The Nd:YAG laser working at a basic wavelength of 1064 nm and fourth-harmonic frequency of 266 nm with a gated photomultiplier or ICCD detector HORIBA JY was used for the determination of niobium which was chosen as a model element. Different types of surrounding gases (air, He, Ar) were investigated for analysis. The ICCD detector DICAM PRO with Mechelle 7500 spectrometer with ArF laser (193 nm) and KrF laser (248 nm) were employed for the determination of niobium, titanium, tantalum and cobalt in samples under air atmosphere. Good calibration curves were obtained for Nb, Ti, and Ta (coefficients of determination r2 > 0.96). Acceptable calibration curves were acquired for the determination of cobalt (coefficient of determination r2 = 0.7994) but only for the cemented samples. In the case of powdered carbide precursors, the calibration for cobalt was found to be problematic.

  10. Phase transformation during surface ablation of cobalt-cemented tungsten carbide with pulsed UV laser

    Energy Technology Data Exchange (ETDEWEB)

    Li, T. [Academia Sinica, Shanghai, SH (China). Shanghai Inst. of Optics and Fine Mechanics; Northwest Institute of Nuclear Technology, Xi' an (China); Lou, Q.; Dong, J.; Wei, Y. [Academia Sinica, Shanghai, SH (China). Shanghai Inst. of Optics and Fine Mechanics; Liu, J. [Northwest Institute of Nuclear Technology, Xi' an (China)

    2001-09-01

    Surface ablation of cobalt-cemented tungsten carbide hard metal has been carried out in this work using a 308 nm, 20 ns XeCl excimer laser. Surface microphotography and XRD, as well as an electron probe have been used to investigate the transformation of phase and microstructure as a function of the pulse-number of laser shots at a laser fluence of 2.5 J/cm{sup 2}. The experimental results show that the microstructure of cemented tungsten carbide is transformed from the original polygonal grains of size 3 {mu}m to interlaced large, long grains with an increase in the number of laser shots up to 300, and finally to gross grains of size 10 {mu}m with clear grain boundaries after 700 shots of laser irradiation. The crystalline structure of the irradiated area is partly transformed from the original WC to {beta}WC{sub 1-x}, then to {alpha}W{sub 2}C and CW{sub 3}, and finally to W crystal. It is suggested that the undulating 'hill-valley' morphology may be the result of selective removal of cobalt binder from the surface layer of the hard metal. The formation of non-stoichiometric tungsten carbide may result from the escape of elemental carbon due to accumulated heating of the surface by pulsed laser irradiation. (orig.)

  11. Phase transformation during surface ablation of cobalt-cemented tungsten carbide with pulsed UV laser

    Science.gov (United States)

    Li, T.; Lou, Q.; Dong, J.; Wei, Y.; Liu, J.

    Surface ablation of cobalt-cemented tungsten carbide hard metal has been carried out in this work using a 308 nm, 20 ns XeCl excimer laser. Surface microphotography and XRD, as well as an electron probe have been used to investigate the transformation of phase and microstructure as a function of the pulse-number of laser shots at a laser fluence of 2.5 J/cm2. The experimental results show that the microstructure of cemented tungsten carbide is transformed from the original polygonal grains of size 3 μm to interlaced large, long grains with an increase in the number of laser shots up to 300, and finally to gross grains of size 10 μm with clear grain boundaries after 700 shots of laser irradiation. The crystalline structure of the irradiated area is partly transformed from the original WC to βWC1-x, then to αW2C and CW3, and finally to W crystal. It is suggested that the undulating `hill-valley' morphology may be the result of selective removal of cobalt binder from the surface layer of the hard metal. The formation of non-stoichiometric tungsten carbide may result from the escape of elemental carbon due to accumulated heating of the surface by pulsed laser irradiation.

  12. Escape of carbon element in surface ablation of cobalt cemented tungsten carbide with pulsed UV laser

    Science.gov (United States)

    Li, Tiejun; Lou, Qihong; Dong, Jingxing; Wei, Yunrong; Liu, Jingru

    2001-03-01

    Surface ablation of cobalt cemented tungsten carbide hardmetal has been carried out in this work using a 308 nm, 30 ns XeCl excimer laser. The surface phase transformation on different pulse number of laser shots has been investigated by means of XRD and microphotography as well as AES at laser fluence of 2.5 J/cm 2. The experimental results showed that the phase structure of irradiated area has partly transformed from original WC to β-WC 1- x, then to α-W 2C and CW 3, and finally to W crystal. It is suggested that the formation of non-stoichiometric tungsten carbide should result from the escaping of carbon element due to accumulated heating of surface by pulsed laser irradiation.

  13. Experimental and Analytical Investigation of Cemented Tungsten Carbide Ultra-Short Pulse Laser Ablation

    Science.gov (United States)

    Urbina, J. P. Calderón; Daniel, C.; Emmelmann, C.

    Ultra-short pulse laser processing of hard materials, such as cemented tungsten carbide, requires an accurate and agile experimental and analytical investigation to obtain adequate information and setting parameters to maximize ablation rate. Therefore, this study presents a systematic approach which, first, experimentally searches for the variables with the most significant influence on the objective using a design of experiments method; and second, analyzes by means of existing ablation theory the interaction of the material and laser taking into account the Beer-Lambert law and incubation effect.Therefore, this places a basis for future analytical-experimental validation of the examined material.

  14. 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.

  15. Characterization of exposures among cemented tungsten carbide workers. Part I: Size-fractionated exposures to airborne cobalt and tungsten particles.

    Science.gov (United States)

    Stefaniak, Aleksandr B; Virji, M Abbas; Day, Gregory A

    2009-07-01

    As many as 30,000 workers in the United States of America are exposed to cemented tungsten carbides (CTC), alloys composed primarily of tungsten carbide and cobalt, which are used in cutting tools. Inhalation of cobalt-containing particles may be sufficient for the development of occupational asthma, whereas tungsten carbide particles in association with cobalt particles are associated with the development of hard metal disease (HMD) and lung cancer. Historical epidemiology and exposure studies of CTC workers often rely only on measures of total airborne cobalt mass concentration. In this study, we characterized cobalt- and tungsten-containing aerosols generated during the production of CTC with emphasis on (1) aerosol "total" mass (n=252 closed-face 37 mm cassette samples) and particle size-selective mass concentrations (n=108 eight-stage cascade impactor samples); (2) particle size distributions; and (3) comparison of exposures obtained using personal cassette and impactor samplers. Total cobalt and tungsten exposures were highest in work areas that handled powders (e.g., powder mixing) and lowest in areas that handled finished product (e.g., grinding). Inhalable, thoracic, and respirable cobalt and tungsten exposures were observed in all work areas, indicating potential for co-exposures to particles capable of getting deposited in the upper airways and alveolar region of the lung. Understanding the risk of CTC-induced adverse health effects may require two exposure regimes: one for asthma and the other for HMD and lung cancer. All sizes of cobalt-containing particles that deposit in the lung and airways have potential to cause asthma, thus a thoracic exposure metric is likely biologically appropriate. Cobalt-tungsten mixtures that deposit in the alveolar region of the lung may potentially cause HMD and lung cancer, thus a respirable exposure metric for both metals is likely biologically appropriate. By characterizing size-selective and co-exposures as well as

  16. Research on Ultrafine Tungsten Carbide-Cobalt (WC-Co) Cemented Carbide Rods of Miniature Drills for Highly Integrated Printed Circuit Board (PCB)

    Institute of Scientific and Technical Information of China (English)

    Xiaoliang SHI; Gangqin SHAO; Xinglong DUAN; Runzhang YUAN

    2005-01-01

    Nanocrystalline tungsten carbide-cobalt (WC-Co) composite powders produced through spray thermal decomposition-continuous reduction and carburization technology were used to prepare φ3.25 mm ×38 mm ultrafine tungsten carbidecobalt (WC-Co) cemented carbide rods through vacuum sintering plus sinterhip technology. The microstructure,Vickers hardness, density and Rockwell A hardness (HRA), transverse rupture strength (TRS), saturated magnetization and coercivity force were tested. The results show that the average grain size of the sintering body prepared through vacuum sintering plus sinterhip technology was 430 nm; transverse rupture strength (TRS) was 3850 MPa;Vickers hardness was 1890 and Rockwell A hardness of sintering body was 93. High strength and high hardness ultrafine WC-Co cemented carbide rods used to manufacture printed circuit board (PCB) drills were obtained.

  17. Processing of diamond enhanced cemented tungsten carbide insert for rock drilling

    Institute of Scientific and Technical Information of China (English)

    LIU Bao-chang; SUN You-hong; ZHANG Zu-pei

    2004-01-01

    This paper introduced the structure, component and sintering procedure of the Diamond/WC-Co composite insert fabricated by high pressure and high temper ature (HPHT) method as well as by hot pressing method. In HPHT method, to avoid breakage and delamination of the diamond layer, two transition layers were added between the most outer diamond layer and the WC-Co body. The transition layers compensate for differences in thermal expansion coefficient and elastic modulus of diamond layer and WC-Co substrate. Thus reduces the residual stress induced by cooling the inserts from sintering temperature to room temperature. In hot pressing method, to decrease sintering temperature so as to protect diamond, an active sintering process which achieved by adding nickel and phosphorus into the starting mixed powder is adopted. To increase the toughness of the inserts to resist breakage, proper amount of rare earth compound, LaNi5 and CeO2, are added into the original mixed powder, too. Laboratory tests indicated that both of the diamond enhanced inserts fabricated by HPHT method and by hot pressing method have relatively high hardness and impact toughness, while their wear resistance is about hundreds of times greater than that of conventional cemented tungsten carbide inserts. The results of field drilling test indicated that the diamond enhanced inserts can meet the demands of rotary percussion drilling.

  18. Modified surface morphology in surface ablation of cobalt-cemented tungsten carbide with pulsed UV laser radiation

    Science.gov (United States)

    Li, Tiejun; Lou, Qihong; Dong, Jingxing; Wei, Yunrong; Liu, Jingru

    2001-03-01

    Surface ablation of cobalt-cemented tungsten carbide hardmetal has been carried out in this work using a 308 nm, 20 ns XeCl excimer laser. The influence of ablation rate, surface roughness, surface micromorphology as well as surface phase structure on laser conditions including laser irradiance and pulse number have been investigated. The experimental results showed that the ablation rate and surface roughness were controlled by varying the number of pulses and laser irradiance. The microstructure and crystalline structure of irradiated surface layer varied greatly with different laser conditions. After 300 shots of laser irradiation at irradiance of 125 MW/cm 2, the surface micromorphology characterizing a uniform framework pattern of "hill-valleys". With the increment of laser shots at laser irradiance of 125 MW/cm 2, the microstructure of cemented tungsten carbide transformed from original polygon grains with the size of 3 μm to interlaced large and long grains after 300 shots of laser irradiation, and finally to gross grains with the size of 10 μm with clear grain boundaries after 700 shots. The crystalline structure of irradiated area has partly transformed from original WC to β-WC 1- x, then to α-W 2C and CW 3, and finally to W crystal. At proper laser irradiance and pulse number, cobalt binder has been selectively removed from the surface layer of hardmetal. It has been demonstrated that surface ablation with pulsed UV laser should be a feasible way to selectively remove cobalt binder from surface layer of cemented tungsten carbide hardmetal.

  19. Improved adhesion of diamond coating on cobalt-cemented tungsten carbide hardmetal by using pulsed-UV-laser substrate surface pretreatment

    Science.gov (United States)

    Tiejun, Li; Qihong, Lou; Jingxing, Dong; Yunrong, Wei; Jun, Zhou; Jingru, Liu; Zhiming, Zhang; Fanghong, Sun

    2002-06-01

    Pulsed-UV-laser surface ablation has been applied in substrate pretreatment in order to obtain good adhesion of diamond coating grown on cobalt-cemented tungsten carbide hardmetal. The dependence of diamond coating's adhesion on different shots of pulsed-UV-laser substrate pretreatment has been studied experimentally. The results were compared with diamond coating deposited by using traditional acid-etching substrate pretreatment. It was shown that adhesion of diamond coating grown on tungsten carbide hardmetal has been greatly improved by using pulsed-UV-laser substrate pretreatment. The corresponding laser pretreatment condition for the optimal adhesion of diamond coatings was finally obtained. It has been demonstrated that pulsed-UV-laser substrate pretreatment should be a feasible and effective method for improving adhesion of diamond coating on cobalt-cemented tungsten carbide hardmetal. It is the characteristic surface morphology produced by pulsed-UV-laser surface ablation that subsequently results in this improved adhesion of diamond coating grown on tungsten carbide hardmetal. The number of laser shots being used in substrate pretreatment has a great influence to the adhesion of diamond coating deposited on tungsten carbide hardmetal. One should always apply proper number of laser shots in pulsed-UV-laser substrate pretreatment when seeking for the optimal adhesion of diamond coating on tungsten carbide hardmetal. In this work, the corresponding number of laser shots for the optimal adhesion of diamond coating has found to be 300 laser shots.

  20. Ultrasonic ranking of toughness of tungsten carbide

    Science.gov (United States)

    Vary, A.; Hull, D. R.

    1983-01-01

    The feasibility of using ultrasonic attenuation measurements to rank tungsten carbide alloys according to their fracture toughness was demonstrated. Six samples of cobalt-cemented tungsten carbide (WC-Co) were examined. These varied in cobalt content from approximately 2 to 16 weight percent. The toughness generally increased with increasing cobalt content. Toughness was first determined by the Palmqvist and short rod fracture toughness tests. Subsequently, ultrasonic attenuation measurements were correlated with both these mechanical test methods. It is shown that there is a strong increase in ultrasonic attenuation corresponding to increased toughness of the WC-Co alloys. A correlation between attenuation and toughness exists for a wide range of ultrasonic frequencies. However, the best correlation for the WC-Co alloys occurs when the attenuation coefficient measured in the vicinity of 100 megahertz is compared with toughness as determined by the Palmqvist technique.

  1. Review on Sintering Process of WC-Co Cemented Carbide in Metal Injection Molding Technology

    Science.gov (United States)

    Prathabrao, M.; Amin, Sri Yulis M.; Ibrahim, M. H. I.

    2017-01-01

    The objective of this paper is to give an overview on sintering process of WC-Co cemented carbides in metal injection molding technology. Metal injection molding is an advanced and promising technology in producing cemented nanostructured carbides. Cemented tungsten carbide (WC-Co) hard metal is known for its high hardness and wear resistance in various applications. Moreover, areas include fine grained materials, alternative binders, and alternative sintering techniques has been discussed in this paper.

  2. Ballistic Evaluation of rolled Homogeneous Steel Armor with Tungsten Carbide and Titanium Carbide Facing.

    Science.gov (United States)

    1960-12-01

    LABORATORIES BALLISTIC EVALUATION OF ROLLED HMtOGE14EOUS STEEL ASWKR f VITH TUNGSTEN CARBIDE AND TITANIUM CARBIDE FACING (U) TECHNICAL REPORT NO. WAL...carbide steel and titanium carbide steel composite armor when attacked by cal. .40 H19B WC cores, cal. .0 AP W2 projectiles, ZOIN fragment simulating...determine the effectiveness of tungsten car- bide (WC) and titanium carbide (TIC) facing on steel armor for the defeat of steel and tungsten carbide

  3. 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. Peri

  4. Preparation and Electrocatalytic Activity of Tungsten Carbide Nanorod Arrays

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    High density tungsten carbide nanorod arrays have been prepared by magnetron sputtering (MS) using the aluminum lattice membrane (ALM) as template. Electrocatalytic properties of nitromethane electroreduction on the tungsten carbide nanorod arrays electrode were investigated by electrochemical method, and their electrocatalytic activity is approached to that of the Pt foil electrode.

  5. Microstructural Study of Titanium Carbide Coating on Cemented Carbide

    DEFF Research Database (Denmark)

    Vuorinen, S.; Horsewell, Andy

    1982-01-01

    Titanium carbide coating layers on cemented carbide substrates have been investigated by transmission electron microscopy. Microstructural variations within the typically 5µm thick chemical vapour deposited TiC coatings were found to vary with deposit thickness such that a layer structure could...... be delineated. Close to the interface further microstructural inhomogeneities were obsered, there being a clear dependence of TiC deposition mechanism on the chemical and crystallographic nature of the upper layers of the multiphase substrate....

  6. Dynamic compaction of tungsten carbide powder.

    Energy Technology Data Exchange (ETDEWEB)

    Gluth, Jeffrey Weston; Hall, Clint Allen; Vogler, Tracy John; Grady, Dennis Edward

    2005-04-01

    The shock compaction behavior of a tungsten carbide powder was investigated using a new experimental design for gas-gun experiments. This design allows the Hugoniot properties to be measured with reasonably good accuracy despite the inherent difficulties involved with distended powders. The experiments also provide the first reshock state for the compacted powder. Experiments were conducted at impact velocities of 245, 500, and 711 m/s. A steady shock wave was observed for some of the sample thicknesses, but the remainder were attenuated due to release from the back of the impactor or the edge of the sample. The shock velocity for the powder was found to be quite low, and the propagating shock waves were seen to be very dispersive. The Hugoniot density for the 711 m/s experiment was close to ambient crystal density for tungsten carbide, indicating nearly complete compaction. When compared with quasi-static compaction results for the same material, the dynamic compaction data is seen to be significantly stiffer for the regime over which they overlap. Based on these initial results, recommendations are made for improving the experimental technique and for future work to improve our understanding of powder compaction.

  7. Tribology of carbide derived carbon films synthesized on tungsten carbide

    Science.gov (United States)

    Tlustochowicz, Marcin

    Tribologically advantageous films of carbide derived carbon (CDC) have been successfully synthesized on binderless tungsten carbide manufactured using the plasma pressure compaction (P2CRTM) technology. In order to produce the CDC films, tungsten carbide samples were reacted with chlorine containing gas mixtures at temperatures ranging from 800°C to 1000°C in a sealed tube furnace. Some of the treated samples were later dechlorinated by an 800°C hydrogenation treatment. Detailed mechanical and structural characterizations of the CDC films and sliding contact surfaces were done using a series of analytical techniques and their results were correlated with the friction and wear behavior of the CDC films in various tribosystems, including CDC-steel, CDC-WC, CDC-Si3N4 and CDC-CDC. Optimum synthesis and treatment conditions were determined for use in two specific environments: moderately humid air and dry nitrogen. It was found that CDC films first synthesized at 1000°C and then hydrogen post-treated at 800°C performed best in air with friction coefficient values as low as 0.11. However, for dry nitrogen applications, no dechlorination was necessary and both hydrogenated and as-synthesized CDC films exhibited friction coefficients of approximately 0.03. A model of tribological behavior of CDC has been proposed that takes into consideration the tribo-oxidation of counterface material, the capillary forces from adsorbed water vapor, the carbon-based tribofilm formation, and the lubrication effect of both chlorine and hydrogen.

  8. Dynamic SEM wear studies of tungsten carbide cermets

    Science.gov (United States)

    Brainard, W. A.; Buckley, D. H.

    1975-01-01

    Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined. Etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the WC and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation. The wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.

  9. Effect of process parameters on induction plasma reactive deposition of tungsten carbide from tungsten metal powder

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Tungsten carbide deposit was made directly from tungsten metal powder through the reaction with methane in radio frequency induction plasma. Effect of major process parameters on the induction plasma reactive deposition of tungsten carbide was studied by optical microscopy, scanning electron microscopy, X-ray diffraction analysis, water displacement method, and microhardness test. The results show that methane flow rate, powder feed rate, particle size, reaction chamber pressure and deposition distance have significant influences on the phase composition, density, and microhardness of the deposit. Extra carbon is necessary to ensure the complete conversion of tungsten metal into the carbide.

  10. Electrocatalytic Activity of Tungsten Trioxide Micro-spheres, Tungsten Carbide Microspheres and Multi-walled Carbon Nanotube-tungsten Carbide Composites

    Institute of Scientific and Technical Information of China (English)

    LU Hongzhi; YAN Taining

    2009-01-01

    Tungsten trioxide micropheres were prepared by spray pyrolysis, and tungsten carbidemicrospheres were produced by spray pyrolysis-low temperature reduction and carbonization technology.Multi-walled carbon nanotube-tungsten carbide composites were prepared by the continuous reductionand carbonization process using multi-walled carbon nanotubes (MWCNTs) and WO_3 precursor by mo-lecular level mixing and calcination. The morphology and structure of the samples were characterized byscanning electron microscope and transmission electron microscope. Furthermore, the crystal phase was identified by X-ray diffraction. The electrocatalytic activity of the sample was analyzed by means of me-thanol oxidation. Tungsten carbide microspheres were catalytic active for methanol oxidation reaction.Nevertheless tungsten trioxide microspheres and multi-walled carbon nanotube-tungsten carbide compos-ites were not catalytic active for methanol oxidation reaction. These results indicate that tungsten carbide micropheres are promising catalyst for methanol oxidation.

  11. Dynamic SEM wear studies of tungsten carbide cermets. [friction and wear experiments

    Science.gov (United States)

    Brainard, W. A.; Buckley, D. H.

    1975-01-01

    Dynamic friction and wear experiments were conducted in a scanning electron microscope. The wear behavior of pure tungsten carbide and composite with 6 and 15 weight percent cobalt binder was examined, and etching of the binder was done to selectively determine the role of the binder in the wear process. Dynamic experiments were conducted as the tungsten carbide (WC) and bonded WC cermet surfaces were transversed by a 50 micron radiused diamond stylus. These studies show that the predominant wear process in WC is fracture initiated by plastic deformation, and the wear of the etched cermets is similar to pure WC. The presence of the cobalt binder reduces both friction and wear. The cementing action of the cobalt reduces granular separation, and promotes a dense polished layer because of its low shear strength film-forming properties. The wear debris generated from unetched surface is approximately the same composition as the bulk.

  12. Tungsten-yttria carbide coating for conveying copper

    Science.gov (United States)

    Rothman, Albert J.

    1993-01-01

    A method is provided for providing a carbided-tungsten-yttria coating on the interior surface of a copper vapor laser. The surface serves as a wick for the condensation of liquid copper to return the condensate to the interior of the laser for revolatilization.

  13. Growth stress in tungsten carbide-diamond-like carbon coatings

    NARCIS (Netherlands)

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

    2009-01-01

    Growth stress in tungsten carbide-diamond-like carbon coatings, sputter deposited in a reactive argon/acetylene plasma, has been studied as a function of the acetylene partial pressure. Stress and microstructure have been investigated by wafer curvature and transmission electron microscopy (TEM) whe

  14. Research on rare earth and iron-rich diamond-enhanced tungsten carbide composite button

    Institute of Scientific and Technical Information of China (English)

    SHI Xiaoliang; SHAO Gangqin; DUAN Longchen; YUAN Runzhang

    2004-01-01

    At the present time in china, the binder used in tungsten carbide composite button is mainly cobalt, which is very expensive. In order to solve the problems, a new type of rare earth and iron-rich diamond-enhanced tungsten carbide with high abrasive resistance and high toughness against impact, which realizes to substitute ferrum for cobalt, has been developed. The key problems in making the button are to improve the mechanical properties of matrix and increase the welding strength between the diamond and the matrix. All these problems have been solved effectively by low temperature activation hot-press sintering, doping rare earth lanthanum in matrix and high sintering pressure. The properties of the button have been determined under laboratory conditions. The test results show that its hardness is more than 90 HRA, its abrasive resistance is 39 times more than that of conventional cemented tungsten carbide, and its toughness against impact is more than 200 J. All these data show the button has very good mechanical properties.

  15. Preparation and electrocatalytic properties of tungsten carbide electrocatalysts

    Institute of Scientific and Technical Information of China (English)

    马淳安; 张文魁; 成旦红; 周邦新

    2002-01-01

    The tungsten carbide(WC) electrocatalysts with definite phase components and high specific surface area were prepared by gas-solid reduction method. The crystal structure, phase components and electrochemical properties of the as-prepared materials were characterized by XRD, BET(Brunauer Emmett and Teller Procedure) and electrochemical test techniques. It is shown that the tungsten carbide catalysts with definite phase components can be obtained by controlling the carburizing conditions including temperature, gas flowing rate and duration time. The electrocatalysts with the major phase of W2C show higher electrocatalytic activity for the hydrogen evolution reaction. The electrocatalysts with the major phase of WC are suitable to be used as the anodic electrocatalyst for hydrogen anodic oxidation, which exhibit higher hydrogen anodic oxidation electrocatalytic properties in HCl solutions.

  16. Boron carbide coating deposition on tungsten and testing of tungsten layers and coating under intense plasma load

    Energy Technology Data Exchange (ETDEWEB)

    Airapetov, A. A.; Begrambekov, L. B., E-mail: lbb@plasma.mephi.ru [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) (Russian Federation); Buzhinskiy, O. I. [State Research Center Troitsk Institute for Innovation and Fusion Research (TRINITI) (Russian Federation); Grunin, A. V.; Gordeev, A. A.; Zakharov, A. M.; Kalachev, A. M.; Sadovskiy, Ya. A.; Shigin, P. A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) (Russian Federation)

    2015-12-15

    A device intended for boron carbide coating deposition and material testing under high heat loads is presented. A boron carbide coating 5 μm thick was deposited on the tungsten substrate. These samples were subjected to thermocycling loads in the temperature range of 400–1500°C. Tungsten layers deposited on tungsten substrates were tested in similar conditions. Results of the surface analysis are presented.

  17. Boron carbide coating deposition on tungsten and testing of tungsten layers and coating under intense plasma load

    Science.gov (United States)

    Airapetov, A. A.; Begrambekov, L. B.; Buzhinskiy, O. I.; Grunin, A. V.; Gordeev, A. A.; Zakharov, A. M.; Kalachev, A. M.; Sadovskiy, Ya. A.; Shigin, P. A.

    2015-12-01

    A device intended for boron carbide coating deposition and material testing under high heat loads is presented. A boron carbide coating 5 μm thick was deposited on the tungsten substrate. These samples were subjected to thermocycling loads in the temperature range of 400-1500°C. Tungsten layers deposited on tungsten substrates were tested in similar conditions. Results of the surface analysis are presented.

  18. Effect of Plasma Boronitriding on Diamond Nucle-ation and Growth onto Cemented Carbide Substrates

    Institute of Scientific and Technical Information of China (English)

    满卫东; 汪建华; 马志斌; 王传新

    2002-01-01

    Plasma boronitriding has been successfully employed to overcome the difficulty in diamond growth on ferrous-based substrates. Commercial cobalt-sintered, tungsten-cemented carbides (WC(Co)) were pretreated by a plasma boronitriding method, diamond was then deposited by microwave-enhanced chemical vapor deposition (MPCVD). The deposited films were characterized by scanning electron microscopy and Raman spectroscopy. Continuous diamond films with a sharp characteristic Raman peak of 1334 cm-1 were grown and adhered well on the boronitrided region of the cemented carbide substrates. On the other hand, a mixture of diamond crystallites, amorphous carbon and graphitic carbon was loosely deposited on the unboronitrided region. A cobalt inert thin layer formed after plasma boronitriding pretreatment enabled the subsequent nucleation and growth of a high-quality CVD diamond.

  19. Femtosecond laser ablation of cemented carbides: properties and tribological applications

    Science.gov (United States)

    Dumitru, G.; Romano, V.; Weber, H. P.; Gerbig, Y.; Haefke, H.; Bruneau, S.; Hermann, J.; Sentis, M.

    Laser ablation with fs laser pulses was performed in air on cobalt cemented tungsten carbide by means of a Ti : sapphire laser (800 nm, 100 fs). Small and moderate fluences (2, 5, 10 J/cm2) and up to 5×104 pulses per irradiated spot were used to drill holes with aspect ratios up to 10. Cross-section cuts from laser-irradiated samples were produced and they were analysed with optical microscopy and SEM. EDX analyses were carried out on selected zones. Quasi-cylindrical holes were found for 2 J/cm2, whereas for 5 and 10 J/cm2 irregular shapes (lobes, bottoms wider than hole entrances) were found to occur after a given number of incident pulses. Layers with modified structure were evidenced at pore walls. SEM revealed a denser structure, while EDX analyses showed uniform and almost similar contents of W, C, and Co in these layers. As a direct application, patterning of coated WC-Co was carried out with 2 J/cm2 and 100 pulses per pore. The resulted surfaces were tribologically tested and these tests revealed an improved friction and wear behaviour.

  20. Feasibility study of fluxless brazing cemented carbides to steel

    Science.gov (United States)

    Tillmann, W.; Sievers, N.

    2017-03-01

    One of the most important brazing processes is the joints between cemented carbides and steel for the tool industry such as in rotary drill hammers or saw blades. Even though this technique has already been used for several decades, defects in the joint can still occur and lead to quality loss. Mostly, the joining process is facilitated by induction heating and the use of a flux to enhance the wetting of the filler alloy on the surface of the steel and cemented carbide in an ambient atmosphere. However, although the use of flux enables successful joining, it also generates voids within the joint, which reduces the strength of the connection while the chemicals within the flux are toxic and polluting. In this feasibility study, a fluxless brazing process is used to examine the joint between cemented carbides and steel for the first time. For this, ultrasound is applied during induction heating to enable the wetting between the liquid filler metal and the surfaces of the cemented carbide and steel. The ultrasound generates cavitations within the liquid filler metal, which remove the oxides from the surface. Several filler metals such as a silver based alloy Ag449, pure Zn, and an AlSi-alloy were used to reduce the brazing temperature and to lower the thermal residual stresses within the joint. As a result, every filler metal successfully wetted both materials and led to a dense connection. The ultrasound has to be applied carefully to prevent a damage of the cemented carbide. In this regard, it was observed that single grains of the cemented carbide broke out and remained in the joint. This positive result of brazing cemented carbides to steel without a flux but using ultrasound, allows future studies to focus on the shear strength of these joints as well as the behavior of the thermally induced residual stresses.

  1. Research on Diamond Enhanced Tungsten Carbide Composite Button

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    At the present, the cutters used in button bits and rock bits are mainly cobalt tungsten carbide in our country. Because of its low abrasive resistance, the bit service life and drilling efficiency was very low when the hard and extremely hard formations were being drilled. Owing to its high abrasive resistance, the diamond composite material is widely used in drilling operations. However, its toughness against impact is too low to be used in percussion drilling, only can it be used in rotary drilling. In ...

  2. Tungsten carbide laser alloying of a low alloyed steel

    Science.gov (United States)

    Cojocaru, Mihai; Taca, Mihaela

    1996-10-01

    Laser alloying is a way to change the composition of metal surfaces in order to improve their corrosion-resistance, high-temperature strength and hardness. The results of a structural and phase analysis of a tungsten carbide based surface layer prepared by laser alloying of a low carbon steel substrate are presented. Structure, phase composition and microhardness of surface alloyed layers have been investigated. The surface of the samples exhibited a thin layer with a different chemical and phase composition. An increase in alloyed surface hardness and wear-resistance was observed.

  3. Microstructures and Wear Performance of PTAW Deposited Ni-Based Coatings with Spherical Tungsten Carbide

    Directory of Open Access Journals (Sweden)

    Dewei Deng

    2015-10-01

    Full Text Available The Ni-based coatings with different content of spherical tungsten carbide were deposited by plasma transfer arc welding (PTAW method on 304 austenitic stainless steel sheets in this study. The microstructure and wear property of spherical tungsten carbide particle reinforced composite coatings were investigated by means of optical microscope, scanning electron microscope (SEM, X-ray diffraction (XRD, electron probe microanalysis (EPMA and sliding wear test. It is shown that the fraction of spherical tungsten carbides has an important influence on microstructure of Ni-based overlay. The Ni40 overlay consists of γ-Ni dendrites with interdendritic Ni-based eutectics, borides and carbides improving the wear resistance. In the case of composite coatings with different content of tungsten carbide, many new phases are observed, such as Ni2W4C and NiW. In addition, there are a large number of irregular structures in composite coatings, such as acicular structure and irregular stripe organization. The results of sliding wear test indicate that the mass loss of coatings is influenced by the content of tungsten carbide. The mass loss decreases with the increase of tungsten carbide fraction. At high load, the abrasive resistance of composite coating with 60 wt. % tungsten carbide is improved about 50-fold compared to that of Ni40 overlay.

  4. Development and characterization of nickel based tungsten carbide laser cladded coatings

    Science.gov (United States)

    Rombouts, Marleen; Persoons, Rosita; Geerinckx, Eric; Kemps, Raymond; Mertens, Myrjam; Hendrix, Willy; Chen, Hong

    Laser cladded coatings consisting of various types of tungsten carbides embedded in a NiCrBSiCFe matrix are characterized. At optimal process parameters crack-free coatings with a thickness of 0.85-1 mm, excellent bonding with the substrate, carbide concentrations up to 60 wt% and a hardness in the range of 40-55 HRC are obtained. During laser cladding the carbides have partly dissolved in the matrix as indicated by the presence of dispersed carbides in the matrix and by a carbide phase growing into the matrix along the edges of the particles. The wear coefficient during sliding contact decreases logarithmically with increasing carbide concentration.

  5. Synthesis of tungsten carbide nanocrystals and their electrochemical properties

    Institute of Scientific and Technical Information of China (English)

    Jianghua ZENG; Dingsheng YUAN; Yingliang LIU; Jingxing CHEN; Sanxiang TAN

    2009-01-01

    Tungsten carbide (WC) nanocrystals have been prepared by a solvothermal method with Mg as the reductant and WO3 and anhydrous ethanol as the precursors. The effects of time and temperature on the synthesis of WC were investigated and a probable formation mechanism was discussed. The obtained WC nanocrystals were characterized by X-ray diffraction, transmission electron microscopy, energy dispersive spec-troscopy and electrochemical methods. Hexagonal close-packed WC was successfully synthesized when the temperature was as low as 500°C. The content of carbon was more than that of W, indicating that the composition of the treated sample was C and WC only. The diameters of WC nanocrystals were ranged from 40 nm to 70 nm and the nanocrystals were dispersed on carbon films. The electrochemical measurements reveal that WC nanocrystals obviously promote Pt/C electrocatalytic ability for the oxygen reduction reaction.

  6. PIXE characterization of by-products resulting from the zinc recycling of industrial cemented carbides

    Energy Technology Data Exchange (ETDEWEB)

    Freemantle, C.S. [School of Chemical & Metallurgical Engineering and DST-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, P/Bag 3, Wits 2050 (South Africa); Pilot Tools (Pty) (Ltd), P.O. Box 27420, Benrose 2011 (South Africa); Sacks, N. [School of Chemical & Metallurgical Engineering and DST-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, P/Bag 3, Wits 2050 (South Africa); Topic, M. [iThemba LABS, National Research Foundation, P.O. Box 722, Somerset West 7129 (South Africa); Pineda-Vargas, C.A. [iThemba LABS, National Research Foundation, P.O. Box 722, Somerset West 7129 (South Africa); Faculty of Health & Wellness Sciences, CPUT, Bellville (South Africa)

    2015-11-15

    By-product materials of the widely used zinc recycling process of cemented carbides have been studied. Scanning electron microscopy and micro-PIXE techniques have identified elemental concentrations, distributions and purity of by-product materials from an industrial zinc recycling plant. Cobalt surface enrichment, lamellar microstructures of varying composition, including alternating tungsten carbide (WC) grains and globular cobalt, and regions of excess zinc contamination were found in materials with incomplete zinc penetration. Liquid Co–Zn formation occurred above 72 wt.% Zn at the furnace temperature of 930 °C, and was extracted towards the surface of poorly zinc infiltrated material, primarily by the vacuum used for zinc distillation. Surface enrichment was not observed in material that was zinc infiltrated to the sample center, which was more friable and exhibited more homogeneous porosity and elemental concentrations. The result of incomplete zinc infiltration was an enriched surface zone of up to 60 wt.% Co, compared to an original sample composition of ∼10–15 wt.% Co. The impact on resulting powders could be higher or inhomogeneous cobalt content, as well as unacceptably high zinc concentrations. PIXE has proven it can be a powerful technique for solving industrial problems in the cemented carbide cutting tool industry, by identifying trace elements and their locations (such as Zn to 0.1 wt.% accuracy), as well as the distribution of major elements within WC–Co materials.

  7. Surface roughness analysis after machining of direct laser deposited tungsten carbide

    Science.gov (United States)

    Wojciechowski, S.; Twardowski, P.; Chwalczuk, T.

    2014-03-01

    In this paper, an experimental surface roughness analysis in machining of tungsten carbide is presented. The tungsten carbide was received using direct laser deposition technology (DLD). Experiments carried out included milling of tungsten carbide samples using monolithic torus cubic boron nitride (CBN) tool and grinding with the diamond cup wheel. The effect of machining method on the generated surface topography was analysed. The 3D surface topographies were measured using optical surface profiler. The research revealed, that surface roughness generated after the machining of tungsten carbide is affected by feed per tooth (fz) value related to kinematic-geometric projection only in a minor extent. The main factor affecting machined surface roughness is the occurrence of micro grooves and protuberances on the machined surface, as well as other phenomena connected, inter alia, with the mechanism for material removal.

  8. Influence of fabricating process on microstructure and properties of spheroidal cast tungsten carbide powder

    Institute of Scientific and Technical Information of China (English)

    DAI Yu; TAN Xing-long; LI Yu-xi; YANG Jian-gao; HUANG Bai-yun

    2005-01-01

    A super-high temperature furnace was developed to fabricate spheroidal cast tungsten carbide powder with excellent flowability and fine feathery structure in a large scale. Optical microscope and scanning electron microscope were taken to characterize the morphology and microstructure of cast tungsten carbide powder. X-ray diffractometry was used to analyze the phase composition of powders involved. It is found that the carbon potential in the furnace and feeding speed play an important role on the microstructure, morphology and properties of the spheroidal cast tungsten carbide powder. As carbon potential is between 0.3% and 0.9% in the furnace, cast tungsten carbide powder with hardness over 2800(HV0.5 ), flowability over 7. 1 s/50 g and tap density over 10.3 g/cm3 is obtained.

  9. Laser deposition of Inconel 625/tungsten carbide composite coatings by powder and wire feedstock

    OpenAIRE

    Abioye, Taiwo E.

    2014-01-01

    There is an increasing global demand to extend the life span of down-hole drilling tools in order to improve operation effectiveness and efficiency of oil and gas production. Laser cladding of tungsten carbide/Ni-based alloy metal matrix composite (MMC) coatings is currently being utilised for this purpose. However, the effect of tungsten carbide dissolution on the corrosion performance of the MMC coatings has not been completely understood. In this work, a study was carried out in which lase...

  10. Preparation and investigation of ultrafine-grained tungsten carbide with high hardness and fracture toughness

    Science.gov (United States)

    Chuvil'deev, V. N.; Blagoveshchenskii, Yu. V.; Sakharov, N. V.; Boldin, M. S.; Nokhrin, A. V.; Isaeva, N. V.; Shotin, S. V.; Lopatin, Yu. G.; Smirnova, E. S.

    2015-07-01

    High-density samples of ultrafine-grained tungsten carbide with high hardness (up to 31-34 GPa) and increased fracture toughness (up to 5.2-6.4 MPa m1/2) are obtained using the technology of electropulse plasma sintering. The influence of the initial size of nanoparticles of α-WC prepared by plasmachemical synthesis on the density, structural parameters, and mechanical properties of tungsten carbide is investigated.

  11. The eta phases and mechanical properties of TIG welded joints of WC-Co cemented carbide and steel

    Institute of Scientific and Technical Information of China (English)

    赵秀娟; 杨德新; 王浩; 高泽幸治; 田头孝介; 山森英明

    2004-01-01

    The tungsten-inert-gas (TIG) arc welding experiments of cemented carbide YG30 and steel 45 were carried out using the Ni-Fe-C filling alloys. The eta phases and mechanical properties of welded joints were analyzed by means of scanning electronic microscope (SEM), transmission electronic microscope (TEM) coupled with selected diffraction, electronic probe microanalysis and bending strength methods. The experimental results show that the chemical composition of the filling alloys affects eta phase formation. When the carbon and nickel contents in filling alloys are 0.61 wt% and 55.29 wt%, respectively, no eta phases form. And the joint bending strength is the highest to 1.352GPa. But if they are 0.01wt% and 55.38wt%, the eta phases are formed at the boundaries of the cemented carbide and the weld, and the thickness of eta phase layer is about 110 micrometers. And the joint bending strength is low. Usually, these eta phases are anomalously granular, and easy to accumulate at the boundaries between cemented carbides and the weld. They are multiple M6C rich in tungsten and iron.

  12. Structure-performance relations of molybdenum- and tungsten carbide catalysts for deoxygenation

    NARCIS (Netherlands)

    Stellwagen, D.R.; Bitter, J.H.

    2015-01-01

    This work demonstrates for the first time that carbide particle size is a critical factor for the activity and stability of carbon supported tungsten- and molybdenum carbide catalysts in (hydro-)deoxygenation reactions. The stability of the catalyst was shown to increase for larger particles due to

  13. Generation and characterization of nano-tungsten carbide particles by wire explosion process

    Energy Technology Data Exchange (ETDEWEB)

    Debalina, B.; Kamaraj, M.; Murthy, B.S. [Dept. of Metallurgical and Materials Engg., IIT Madras, Chennai 600036 (India); Chakravarthi, S.R. [Dept. of Aerospace Engg, IIT Madras, Chennai 600036 (India); Sarathi, R., E-mail: rsarathi@iitm.ac.i [Dept. of Electrical Engineering, IIT Madras, Chennai 600036, Tamilnadu (India)

    2010-04-30

    The nano-tungsten carbide particles were produced by exploding tungsten conductor in different carburizing medium viz. carbon dioxide and methane atmosphere. The influence of gas pressure in explosion chamber on the size of the particles formed was analyzed. Methane gas was found to be a conducive medium to form tungsten carbide particles. Certain physico-chemical diagnostic studies such as wide angle X-ray diffraction (WAXD) and Fourier transform infra-red (FTIR) spectroscopy studies were carried out to characterize the nano-tungsten carbide powder produced by the wire explosion process. The size of the particles was measured by using transmission electron microscope (TEM) and its size distribution was analyzed by adopting log-normal distribution. Thermal conductivity of the gas plays a major role on the size of the particle formed by wire explosion process as observed in the present work.

  14. EUV nanosecond laser ablation of silicon carbide, tungsten and molybdenum

    Science.gov (United States)

    Frolov, Oleksandr; Kolacek, Karel; Schmidt, Jiri; Straus, Jaroslav; Choukourov, Andrei; Kasuya, Koichi

    2015-09-01

    In this paper we present results of study interaction of nanosecond EUV laser pulses at wavelength of 46.9 nm with silicon carbide (SiC), tungsten (W) and molybdenum (Mo). As a source of laser radiation was used discharge-plasma driver CAPEX (CAPillary EXperiment) based on high current capillary discharge in argon. The laser beam is focused with a spherical Si/Sc multilayer-coated mirror on samples. Experimental study has been performed with 1, 5, 10, 20 and 50 laser pulses ablation of SiC, W and Mo at various fluence values. Firstly, sample surface modification in the nanosecond time scale have been registered by optical microscope. And the secondly, laser beam footprints on the samples have been analyzed by atomic-force microscope (AFM). This work supported by the Czech Science Foundation under Contract GA14-29772S and by the Grant Agency of the Ministry of Education, Youth and Sports of the Czech Republic under Contract LG13029.

  15. Tungsten carbide nanoparticles as efficient cocatalysts for photocatalytic overall water splitting

    KAUST Repository

    Garcia Esparza, Angel T.

    2012-12-17

    Tungsten carbide exhibits platinum-like behavior, which makes it an interesting potential substitute for noble metals in catalytic applications. Tungsten carbide nanocrystals (≈5 nm) are directly synthesized through the reaction of tungsten precursors with mesoporous graphitic C3N 4 (mpg-C3N4) as the reactive template in a flow of inert gas at high temperatures. Systematic experiments that vary the precursor compositions and temperatures used in the synthesis selectively generate different compositions and structures for the final nanocarbide (W 2C or WC) products. Electrochemical measurements demonstrate that the WC phase with a high surface area exhibits both high activity and stability in hydrogen evolution over a wide pH range. The WC sample also shows excellent hydrogen oxidation activity, whereas its activity in oxygen reduction is poor. These tungsten carbides are successful cocatalysts for overall water splitting and give H2 and O2 in a stoichiometric ratio from H 2O decomposition when supported on a Na-doped SrTiO3 photocatalyst. Herein, we present tungsten carbide (on a small scale) as a promising and durable catalyst substitute for platinum and other scarce noble-metal catalysts in catalytic reaction systems used for renewable energy generation. Platinum replacement: The phase-controlled synthesis of tungsten carbide nanoparticles from the nanoconfinement of a mesoporous graphite C 3N4 (mpg-C3N4) reactive template is shown. The nanomaterials catalyze hydrogen evolution/oxidation reactions, but are inactive in the oxygen reduction reaction. Tungsten carbide is an effective cocatalyst for photocatalytic overall water splitting (see picture). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Durability of tungsten carbide burs for the fabrication of titanium crowns using dental CAD/CAM.

    Science.gov (United States)

    Hotta, Yasuhiro; Miyazaki, Takashi; Fujiwara, Toshihisa; Tomita, Shoko; Shinya, Akiyoshi; Sugai, Yasuhisa; Ogura, Hideo

    2004-06-01

    The purpose of this study was to evaluate the durability of tungsten carbide burs for the fabrication of titanium crowns using two dental CAD/CAM systems (DECSY, Digital Process, Japan and Cadim, Advance, Japan). A tungsten carbide bur in each system was examined and used without fracture to fabricate 51 titanium crowns. For both systems tiny chips were found on the bur blade at the 11th machining. These chips gradually enlarged as the number of machining times increased. At the first machining no significant difference in the average surface roughness was found on the crown between the two systems (1.6 microm for DECSY and 1.2 microm for Cadim). The cutting grooves became dull and the average surface roughness increased as the number of machining times increased. It is concluded that the tungsten carbide burs for both systems can be used to fabricate up to 51 titanium crowns.

  17. Microstructure and mechanical properties of WC-Ni-Al based cemented carbides developed for engineering applications

    Energy Technology Data Exchange (ETDEWEB)

    Correa, Edmilson O.; Santos, Julio N. [Universidade Federal de Itajuba, Minas Gerais (Brazil). Inst. de Engenharia Mecanica; Klein, Aloisio N. [Universidade Federal de Santa Catarina, Florianopolis (Brazil). Dept. de Engenharia de Materiais

    2011-11-15

    In this paper the influence of the Ni binder metal and Al as an additional alloying element on the microstructure and mechanical properties of WC-based cemented carbides processed by conventional powder metallurgy was studied. Microstructural examinations of the cemented carbides with 3 and 5 wt.% of Al in the binder metal indicated the presence of a very low and evenly distributed porosity as well as the presence of islands of metal binder in the microstructure. With the cemented carbide with 7 wt.% of Al in the metal binder, the presence of brittle needle-like regions was observed. The WC particles inside these regions were rounded and had a larger mean free path. Vickers hardness and flexural strength tests indicated that the cemented carbide WC-Ni - Al with addition of 5 wt.% of Al in the binder metal presented bulk hardness similar to the conventional WC-Co cemented carbides as well as superior flexure strength and fracture toughness. (orig.)

  18. Tungsten carbide encapsulated in nitrogen-doped carbon with iron/cobalt carbides electrocatalyst for oxygen reduction reaction

    Science.gov (United States)

    Zhang, Jie; Chen, Jinwei; Jiang, Yiwu; Zhou, Feilong; Wang, Gang; Wang, Ruilin

    2016-12-01

    This work presents a type of hybrid catalyst prepared through an environmental and simple method, combining a pyrolysis of transition metal precursors, a nitrogen-containing material, and a tungsten source to achieve a one-pot synthesis of N-doping carbon, tungsten carbides, and iron/cobalt carbides (Fe/Co/WC@NC). The obtained Fe/Co/WC@NC consists of uniform Fe3C and Co3C nanoparticles encapsulated in graphitized carbon with surface nitrogen doping, closely wrapped around a plate-like tungsten carbide (WC) that functions as an efficient oxygen reduction reaction (ORR) catalyst. The introduction of WC is found to promote the ORR activity of Fe/Co-based carbide electrocatalysts, which is attributed to the synergistic catalysts of WC, Fe3C, and Co3C. Results suggest that the composite exhibits comparable electrocatalytic activity, higher durability, and ability for methanol tolerance compared with commercial Pt/C for ORR in alkaline electrolyte. These advantages make Fe/Co/WC@NC a promising ORR electrocatalyst and a cost-effective alternative to Pt/C for practical application as fuel cell.

  19. MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ULTRAFINE WC/Co CEMENTED CARBIDES WITH CUBIC BORON NITRIDE AND Cr₃C₂ ADDITIONS

    Directory of Open Access Journals (Sweden)

    Genrong Zhang

    2016-03-01

    Full Text Available This study investigates the microstructure and mechanical properties of ultrafine tungsten carbide and cobalt (WC/Co cemented carbides with cubic boron nitride (CBN and chromium carbide (Cr₃C₂ fabricated by a hot pressing sintering process. This study uses samples with 8 wt% Co content and 7.5 vol% CBN content, and with different Cr₃C₂ content ranging from 0 to 0.30 wt%. Based on the experimental results, Cr₃C₂ content has a significant influence on inhibiting abnormal grain growth and decreasing grain size in cemented carbides. Near-full densification is possible when CBN-WC/Co with 0.25 wt% Cr₃C₂ is sintered at 1350°C and 20 MPa; the resulting material possesses optimal mechanical properties and density, with an acceptable Vickers hardness of 19.20 GPa, fracture toughness of 8.47 MPa.m1/2 and flexural strength of 564 MPa.u̇ Å k⃗

  20. Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding

    OpenAIRE

    Amado Paz, José Manuel; Tobar Vidal, María José; YAÑEZ CASAL, ARMANDO JOSE; Amigó Borrás, Vicente; Candel Bou, Juan Jose

    2011-01-01

    The development of hardfacing coatings has become technologically significant in many industries A common approach is the production of metal matrix composites (MMC) layers. In this work NiCr-WC MMC hardfacing layers are deposited on C25 steel by means of laser cladding. Spheroidal fused tungsten carbides is used as reinforcement phase. Three different NiCr alloys with different Cr content were tested. Optimum conditions to obtain dense, uniform carbide distribution and hardness close to nomi...

  1. Boron carbide coating deposition on tungsten substrates from atomic fluxes of boron and carbon

    Science.gov (United States)

    Sadovskiy, Y.; Begrambekov, L.; Ayrapetov, A.; Gretskaya, I.; Grunin, A.; Dyachenko, M.; Puntakov, N.

    2016-09-01

    A device used for both coating deposition and material testing is presented in the paper. By using lock chambers, sputtering targets are easily exchanged with sample holder thus allowing testing of deposited samples with high power density electron or ion beams. Boron carbide coatings were deposited on tungsten samples. Methods of increasing coating adhesion are described in the paper. 2 μm boron carbide coatings sustained 450 heating cycles from 100 to 900 C. Ion beam tests have shown satisfactory results.

  2. Development of high temperature materials for solid propellant rocket nozzle applications. [tantalum carbides-tungsten fiber composites

    Science.gov (United States)

    Manning, C. R., Jr.; Honeycutt, L., III

    1974-01-01

    Evaluation of tantalum carbide-tungsten fiber composites has been completed as far as weight percent carbon additions and weight percent additions of tungsten fiber. Extensive studies were undertaken concerning Young's Modulus and fracture strength of this material. Also, in-depth analysis of the embrittling effects of the extra carbon additions on the tungsten fibers has been completed. The complete fabrication procedure for the tantalum carbide-tungsten fiber composites with extra carbon additions is given. Microprobe and metallographic studies showed the effect of extra carbon on the tungsten fibers, and evaluation of the thermal shock parameter fracture strength/Young's Modulus is included.

  3. Calibration graphs for Ti, Ta and Nb in sintered tungsten carbide by infrared laser ablation inductively coupled plasma atomic emission spectrometry.

    Science.gov (United States)

    Kanický, V; Otruba, V; Mermet, J M

    2001-12-01

    Infrared laser ablation (IR-LA) has been studied as a sample introduction technique for the analysis of sintered cobalt-cemented tungsten carbide materials by inductively coupled plasma atomic emission spectrometry (ICP-AES). Fractionation of cobalt was observed. Linearity of calibration plots was verified at least up to 15% Ti, 8% Ta, and 3% Nb. Above 1% (m/m) Ti, Ta, and Nb, the repeatability of results was better than 3% R.S.D. The relative uncertainty at the centroid of the calibration line was in the range from +/- 3% to +/- 4% for Ti, Ta, and Nb with internal standardization by tungsten and up to +/- 5% without internal standardization. The limits of detection were 0.004% Ti, 0.001% Ta, and 0.004% Nb. Elimination of the cemented hardmetal dissolution procedure is the main advantage of this method.

  4. Growth kinetics of cubic carbide free layers in graded cemented carbides

    Science.gov (United States)

    Shi, Liu-Yong; Liu, Yi-Min; Huang, Ji-Hua; Zhang, Shou-Quan; Zhao, Xing-Ke

    2012-01-01

    In order to reveal the formation mechanism of cubic carbide free layers (CCFL), graded cemented carbides with CCFL in the surface zone were fabricated by a one-step sintering procedure in vacuum, and the analysis on microstructure and element distribution were performed by scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA), respectively. A new physical model and kinetic equation were established based on experimental results. Being different from previous models, this model suggests that nitrogen diffusion outward is only considered as an induction factor, and the diffusion of titanium through liquid phase plays a dominative role. The driving force of diffusion is expressed as the differential value between nitrogen partial pressure and nitrogen equilibrium pressure essentially. Simulation results by the kinetic equation are in good agreement with experimental values, and the effect of process parameters on the growth kinetics of CCFL can also be explained reasonably by the current model.

  5. A Hard Sell: Factors Influencing the Interwar Adoption of Tungsten Carbide Cutting Tools in Germany, Britain, and the United States.

    Science.gov (United States)

    Giffard, Hermione

    2015-10-01

    Cemented tungsten carbide cutting tools-virtually unknown to historians-came on the market in the late 1920s. Although existing literature alleges that their adoption was rapid and universal, contemporary data indicate that the rate of adoption in fact took many decades and varied greatly between the world's three leading industrialized economies of the time: Germany, England, and the United States. This article suggests that the explanation lies in differing national environments for innovation in the interwar period. It looks at many features that influence adoption by users and argues that the feature emphasized in the literature, increased cutting speed, was not the primary consideration behind adoption, but rather metal shortages. It thereby casts doubt on what measures of national productivity show. The case raises important questions about the use of production efficiency to make international comparisons and about the role of patent monopolies in introducing production innovations.

  6. Tungsten carbide promoted Pd and Pd–Co electrocatalysts for formic acid electrooxidation

    DEFF Research Database (Denmark)

    Yin, Min; Li, Qingfeng; Jensen, Jens Oluf

    2012-01-01

    Tungsten carbide (WC) promoted palladium (Pd) and palladium–cobalt (Pd–Co) nanocatalysts are prepared and characterized for formic acid electrooxidation. The WC as the dopant to carbon supports is found to enhance the CO tolerance and promote the activity of the Pd-based catalysts for formic acid...

  7. Tribological performance evaluation of tungsten carbide-based cermets and development of a fracture mechanics wear model

    Energy Technology Data Exchange (ETDEWEB)

    Bhagat, R.B. [Pennsylvania State Univ., State College, PA (United States). Applied Research Lab.; Conway, J.C. Jr. [Pennsylvania State Univ., State College, PA (United States). Applied Research Lab.; Amateau, M.F. [Pennsylvania State Univ., State College, PA (United States). Applied Research Lab.; Brezler, R.A. III [Pennsylvania State Univ., State College, PA (United States). Applied Research Lab.

    1996-12-15

    Tungsten carbide tools may exhibit sudden brittle fracture at high stresses such as are encountered in shear and slitter knives. This has limited the use of tungsten carbide tools to certain applications in spite of their high hardness and wear resistance. The objective of this investigation is to evaluate the tribological performance of selected cermets and develop a fracture mechanics wear model. Six compositions of WC-Co materials (Co ranging from 4 to 30% by weight) with or without TiC, NbC, TaC, or Mo{sub 2}C were selected for relating wear modes of these tool materials to pertinent mechanical properties such as fracture toughness and hardness. The influence of mechanical properties such as Young`s modulus, hardness, fracture toughness, modulus of rupture, and Weibull modulus on wear rates and wear modes of the selected materials is presented and discussed. The major mechanisms of wear in WC-Co materials are discussed as they apply to the development of suitable relationships between wear and mechanical properties. The wear process is by the transfer of steel from the ring to the cemented carbide block specimens, initiation of mode I cracks normal to the mating surface, propagation of mode II cracks parallel to the wear surfaces and the subsequent separation of platelets with adhered WC and Co particles through adhesive forces with the steel ring. The wear rates of the cermets do not show a consistent relationship with mode I or mode II fracture toughness, but a general trend of decreasing wear rate with hardness is seen. This suggests that the tribological performance of these cermets depends on certain specific functions of pertinent parameters including fracture toughness, hardness, applied load, coefficient of friction and microstructural characteristics. A fracture mechanics-based wear model has been developed to relate the steady state wear rate (W{sub ss}) to hardness, mode II fracture toughness, coefficient of friction, and applied load. (orig./MM)

  8. In situ diagnosis of pulsed UV laser surface ablation of tungsten carbide hardmetal by using laser-induced optical emission spectroscopy

    Science.gov (United States)

    Li, Tiejun; Lou, Qihong; Wei, Yunrong; Huang, Feng; Dong, Jingxing; Liu, Jingru

    2001-12-01

    Surface ablation of cobalt cemented tungsten carbide hardmetal with pulsed UV laser has been in situ diagnosed by using the technique of laser-induced optical emission spectroscopy. The dependence of emission intensity of cobalt lines on number of laser shots was investigated at laser fluence of 2.5 J/cm 2. As a comparison, the reliance of emission intensity of cobalt lines as a function of laser pulse number by using pure cobalt as ablation sample was also studied at the same laser condition. It was found that for surface ablation of tungsten carbide hardmetal at laser fluence of 2.5 J/cm 2, the intensities of cobalt lines fell off dramatically in the first 300 consecutive laser shots and then slowed down to a low stable level with even more shots. For surface ablation of pure cobalt at the same laser condition, the intensities of cobalt lines remained constant more or less even after 500 laser shots and then reduced very slowly with even more shots. It was concluded that selective evaporation of cobalt at this laser fluence should be responsible for the dramatic fall-off of cobalt lines with laser shots accumulation for surface ablation of tungsten carbide hardmetal. In contrast, for surface ablation of pure cobalt, the slow reduction of cobalt lines with pulse number accumulation should be due to the formation of laser-induced crater effect.

  9. Influence of binders on infrared laser ablation of powdered tungsten carbide pressed pellets in comparison with sintered tungsten carbide hardmetals studied by inductively coupled plasma atomic emission spectrometry

    Science.gov (United States)

    Holá, Markéta; Otruba, Vítězslav; Kanický, Viktor

    2006-05-01

    Laser ablation (LA) was studied as a sample introduction technique for the analysis of powdered and sintered tungsten carbides (WC/Co) by inductively coupled plasma optical emission spectrometry (ICP-OES). The possibility to work with powdered and compact materials with close chemical composition provided the opportunity to compare LA sampling of similar substances in different forms that require different preparation procedures. Powdered WC/Co precursors of sintered hardmetals were prepared for the ablation as pressed pellets with and without powdered silver as a binder, while sintered hardmetal blocks were embedded into a resin to obtain discs, which were then smoothed and polished. A Q-switched Nd:YAG laser operated at its fundamental wavelength of 1064 nm with a pulse frequency of 10 Hz and maximum pulse energy of 220 mJ was used. A single lens was used for the laser beam focusing. An ablation cell (14 cm 3) mounted on a PC-controlled XY-translator was connected to an ICP spectrometer Jobin Yvon 170 Ultrace (laterally viewed ICP, mono- and polychromator) using a 1.5-m tubing (4 mm i.d.). Ablation was performed in a circular motion (2 mm diameter). Close attention was paid to the study of the crater parametres depending on hardness, cohesion and Ag binder presence in WC/Co samples. The influence of the Co content on the depth and structure of the ablation craters of the binderless pellets was also studied. Linear calibration plots of Nb, Ta and Ti were obtained for cemented WC/Co samples, binderless and binder-containing pellets. Relative widths of uncertainty intervals about the centroids vary between ± 3% and ± 7%, and exceptionally reach a value above 10%. The lowest determinable quantities (LDQ) of Nb, Ta and Ti calculated from the calibration lines were less than 0.5% (m/m). To evaluate the possibility of quantitative elemental analysis by LA-ICP-OES, two real sintered WC/Co samples and two real samples of powdered WC/Co materials were analysed. The

  10. Influence of binders on infrared laser ablation of powdered tungsten carbide pressed pellets in comparison with sintered tungsten carbide hardmetals studied by inductively coupled plasma atomic emission spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Hola, Marketa [Research Centre for Environmental Chemistry and Ecotoxicology and Laboratory of Atomic Spectrochemistry, Faculty of Science, Masaryk University in Brno, Kotlarska 2, CZ 611 37 Brno (Czech Republic); Otruba, Vitezslav [Research Centre for Environmental Chemistry and Ecotoxicology and Laboratory of Atomic Spectrochemistry, Faculty of Science, Masaryk University in Brno, Kotlarska 2, CZ 611 37 Brno (Czech Republic); Kanicky, Viktor [Research Centre for Environmental Chemistry and Ecotoxicology and Laboratory of Atomic Spectrochemistry, Faculty of Science, Masaryk University in Brno, Kotlarska 2, CZ 611 37 Brno (Czech Republic)]. E-mail: viktork@chemi.muni.cz

    2006-05-15

    Laser ablation (LA) was studied as a sample introduction technique for the analysis of powdered and sintered tungsten carbides (WC/Co) by inductively coupled plasma optical emission spectrometry (ICP-OES). The possibility to work with powdered and compact materials with close chemical composition provided the opportunity to compare LA sampling of similar substances in different forms that require different preparation procedures. Powdered WC/Co precursors of sintered hardmetals were prepared for the ablation as pressed pellets with and without powdered silver as a binder, while sintered hardmetal blocks were embedded into a resin to obtain discs, which were then smoothed and polished. A Q-switched Nd:YAG laser operated at its fundamental wavelength of 1064 nm with a pulse frequency of 10 Hz and maximum pulse energy of 220 mJ was used. A single lens was used for the laser beam focusing. An ablation cell (14 cm{sup 3}) mounted on a PC-controlled XY-translator was connected to an ICP spectrometer Jobin Yvon 170 Ultrace (laterally viewed ICP, mono- and polychromator) using a 1.5-m tubing (4 mm i.d.). Ablation was performed in a circular motion (2 mm diameter). Close attention was paid to the study of the crater parametres depending on hardness, cohesion and Ag binder presence in WC/Co samples. The influence of the Co content on the depth and structure of the ablation craters of the binderless pellets was also studied. Linear calibration plots of Nb, Ta and Ti were obtained for cemented WC/Co samples, binderless and binder-containing pellets. Relative widths of uncertainty intervals about the centroids vary between {+-} 3% and {+-} 7%, and exceptionally reach a value above 10%. The lowest determinable quantities (LDQ) of Nb, Ta and Ti calculated from the calibration lines were less than 0.5% (m/m). To evaluate the possibility of quantitative elemental analysis by LA-ICP-OES, two real sintered WC/Co samples and two real samples of powdered WC/Co materials were analysed

  11. Tribological behaviors of graphite sliding against cemented carbide in CaCl2 solution

    Science.gov (United States)

    Guo, Fei; Tian, Yu; Liu, Ying; Wang, Yuming

    2015-12-01

    The tribological behaviors of graphite sliding against cemented carbide were investigated using a standard tribological tester Plint TE92 in a ring-on-ring contact configuration in both CaCl2 solution and deionized water. An interesting phenomenon occurred: as the CaCl2 solution concentration increased, the friction coefficient firstly decreased and was lower than that in the deionized water, and then gradually increased, exceeding the friction coefficient in the deionized water. The wear rate of the ,graphite also presented the same variation trend. According to the polarization curves of cemented carbide, contact angle measurements, Raman spectrum analysis and scanning electron microscope (SEM) images analysis, the above friction and wear behaviors of graphite sliding against cemented carbide were attributed to the graphite surface wettability and the cemented carbide surface corrosion property.

  12. Effect of SiC Nanowhisker on the Microstructure and Mechanical Properties of WC-Ni Cemented Carbide Prepared by Spark Plasma Sintering

    Directory of Open Access Journals (Sweden)

    Xiaoyong Ren

    2014-01-01

    Full Text Available Ultrafine tungsten carbide-nickel (WC-Ni cemented carbides with varied fractions of silicon carbide (SiC nanowhisker (0–3.75 wt.% were fabricated by spark plasma sintering at 1350°C under a uniaxial pressure of 50 MPa with the assistance of vanadium carbide (VC and tantalum carbide (TaC as WC grain growth inhibitors. The effects of SiC nanowhisker on the microstructure and mechanical properties of the as-prepared WC-Ni cemented carbides were investigated. X-ray diffraction analysis revealed that during spark plasma sintering (SPS Ni may react with the applied SiC nanowhisker, forming Ni2Si and graphite. Scanning electron microscopy examination indicated that, with the addition of SiC nanowhisker, the average WC grain size decreased from 400 to 350 nm. However, with the additional fractions of SiC nanowhisker, more and more Si-rich aggregates appeared. With the increase in the added fraction of SiC nanowhisker, the Vickers hardness of the samples initially increased and then decreased, reaching its maximum of about 24.9 GPa when 0.75 wt.% SiC nanowhisker was added. However, the flexural strength of the sample gradually decreased with increasing addition fraction of SiC nanowhisker.

  13. Effect of SiC nanowhisker on the microstructure and mechanical properties of WC-Ni cemented carbide prepared by spark plasma sintering.

    Science.gov (United States)

    Ren, Xiaoyong; Peng, Zhijian; Fu, Zhiqiang; Wang, Chengbiao

    2014-01-01

    Ultrafine tungsten carbide-nickel (WC-Ni) cemented carbides with varied fractions of silicon carbide (SiC) nanowhisker (0-3.75 wt.%) were fabricated by spark plasma sintering at 1350°C under a uniaxial pressure of 50 MPa with the assistance of vanadium carbide (VC) and tantalum carbide (TaC) as WC grain growth inhibitors. The effects of SiC nanowhisker on the microstructure and mechanical properties of the as-prepared WC-Ni cemented carbides were investigated. X-ray diffraction analysis revealed that during spark plasma sintering (SPS) Ni may react with the applied SiC nanowhisker, forming Ni2Si and graphite. Scanning electron microscopy examination indicated that, with the addition of SiC nanowhisker, the average WC grain size decreased from 400 to 350 nm. However, with the additional fractions of SiC nanowhisker, more and more Si-rich aggregates appeared. With the increase in the added fraction of SiC nanowhisker, the Vickers hardness of the samples initially increased and then decreased, reaching its maximum of about 24.9 GPa when 0.75 wt.% SiC nanowhisker was added. However, the flexural strength of the sample gradually decreased with increasing addition fraction of SiC nanowhisker.

  14. Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding

    Science.gov (United States)

    Amado, J. M.; Tobar, M. J.; Yáñez, A.; Amigó, V.; Candel, J. J.

    The development of hardfacing coatings has become technologically significant in many industries A common approach is the production of metal matrix composites (MMC) layers. In this work NiCr-WC MMC hardfacing layers are deposited on C25 steel by means of laser cladding. Spheroidal fused tungsten carbides is used as reinforcement phase. Three different NiCr alloys with different Cr content were tested. Optimum conditions to obtain dense, uniform carbide distribution and hardness close to nominal values were defined. The effect of Cr content respect to the microstructure, susceptibility for cracking and the wear rate of the resulting coating will also be discussed.

  15. Laser surface infiltration of tungsten-carbide in steel and aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Dahotre, N.B.; Mukherjee, K. (Michigan State Univ., East Lansing (USA))

    It has been demonstrated that surface modification in metals and alloys can be achieved by laser melting in conjunction with injection of particulate alloying elements in the heated zone. In our current experiments the authors have successfully implanted tungsten-carbide particles on the surface of several grades of carbon-steels as well as on the surface of a structural aluminum alloy. In both cases a significant increase in microhardness has been detected. Hardness profile from the interaction zone to the heat affected zone (HAZ) has been determined. The microstructural features of both the implanted zone and HAZ also have been determined. Effect of laser input energy, nature of tungsten-carbide particle size, size distribution and method of powder injection on the hardness profile have been investigated. Some preliminary examination of surface wear of such implanted material is also conducted. These results are discussed in detail.

  16. Mechanical and thermal properties of tungsten carbide – graphite nanoparticles nanocomposites

    Directory of Open Access Journals (Sweden)

    Kornaus Kamil

    2016-06-01

    Full Text Available Previous studies concerning pure tungsten carbide polycrystalline materials revealed that nanolayers of graphite located between WC grains improve its thermal properties. What is more, pressure-induced orientation of graphene nano platelets (GNP in hot pressed silicon nitride-graphene composites results in anisotropy of thermal conductivity. Aim of this study was to investigate if addition of GNP to WC will improve its thermal properties. For this purpose, tungsten carbide with 0.5–6 wt.% of GNP(12-additive underwent hot pressing. The microstructure observations performed by SEM microscopy. The anisotropy was determined via ultrasonic measurements. The following mechanical properties were evaluated: Vickers hardness, bending strength, fracture toughness KIc. The influence of GNP(12 addition on oxidation resistance and thermal conductivity was examined. It was possible to manufacture hot-pressed WC-graphene composites with oriented GNP(12 particles, however, the addition of graphene decreased both thermal and mechanical properties of the material.

  17. Dry Sliding Wear behaviour of Aluminium-Red mud- Tungsten Carbide Hybrid metal matrix composites

    Science.gov (United States)

    Devi Chinta, Neelima; Selvaraj, N.; Mahesh, V.

    2016-09-01

    Red mud is an industrial waste obtained during the processing of alumina by Bayer's process. An attempt has been made to utilize the solid waste by using it as the reinforcement material in metal matrix composites. Red mud received from NALCO has been subjected for sieve analysis and milled to 42 nanometers using high energy ball mill. Red mud is used as a reinforcement material in Pure Aluminium matrix composite at 2%, 4%, and 6% weight at 100 microns level as well as 42 nano meters along with 4%Tungsten carbide by weight. Micro and Nano structured red mud powders, Tungsten carbide powder and Aluminium is mixed in a V-Blender, compacted at a pressure of 40 bar and samples are prepared by conventional sintering with vacuum as medium. In this current work, dry sliding wear characteristics at normal and heat treatment conditions are investigated with optimal combination of Aluminium, Tungsten carbide and different weight fractions of micro and nano structured red mud powder.

  18. Numerical simulation and experiment on split tungsten carbide cylinder of high pressure apparatus.

    Science.gov (United States)

    Yang, Yunfei; Li, Mingzhe; Liu, Zhiwei; Wang, Bolong

    2015-12-01

    A new high pressure device with a split cylinder was investigated on the basis of the belt-type apparatus. The belt-type die is subjected to excessive tangential tensile stress and the tungsten carbide cylinder is easily damaged in the running process. Taking into account the operating conditions and material properties of the tungsten carbide cylinder, it is divided into 6 blocks to eliminate the tangential tensile stress. We studied two forms of the split type: radial split and tangential split. Simulation results indicate that the split cylinder has more uniform stress distribution and smaller equivalent stress compared with the belt-type cylinder. The inner wall of the tangential split cylinder is in the situation that compressive stress is distributed in the axial, radial, and tangential directions. It is similar to the condition of hydrostatic pressure, and it is the best condition for tungsten carbide materials. The experimental results also verify that the tangential split die can bear the highest chamber pressure. Therefore, the tangential split structure can increase the pressure bearing capacity significantly.

  19. Synthesis of nanosized tungsten carbide from phenol formaldehyde resin coated precursors

    Institute of Scientific and Technical Information of China (English)

    LUO Ji; GUO Zhimeng; GAO Yuxi; LIN Tao

    2008-01-01

    Nanosized tungsten carbide was synthesized from phenol formaldehyde resin (PF) coated tungsten precursors.The process has three steps in which nanosized tungsten particles were first coated with PF,then the precursors were carburized at 950℃,and finally the carburized powders were treated in flowing wet hydrogen atmosphere at 940℃ to remove the uncombined carbon.The obtained powders were characterizedusing X-ray diffraction analysis (XRD),field-emission scanning electron microscopy (FESEM),small angle X-ray scattering (SAXS),andcombustion-gas-volume method.The results indicated that single-phase WC could be synthesized using excessive PF as carburizer at a muchlower temperature compared with using mixed carbon black.After wet hydrogen treating,the mean size of the obtained WC particles was 94.5nm and the total carbon content was 6.18 wt.%.

  20. MACHINING OF NICKEL BASED ALLOYS USING DIFFERENT CEMENTED CARBIDE TOOLS

    Directory of Open Access Journals (Sweden)

    BASIM A. KHIDHIR

    2010-09-01

    Full Text Available This paper presents the results of experimental work in dry turning of nickel based alloys (Haynes – 276 using Deferent tool geometer of cemented carbide tools. The turning tests were conducted at three different cutting speeds (112, 152, 201and 269 m/min while feed rate and depth of cut were kept constant at 0.2 mm/rev and 1.5 mm, respectively. The tool holders used were SCLCR with insert CCMT-12 and CCLNR – M12-4 with insert CNGN-12. The influence of cutting speed, tool inserts type and workpiece material was investigated on the machined surface roughness. The worn parts of the cutting tools were also examined under scanning electron microscope (SEM. The results showed that cutting speed significantly affected the machined surface finish values in related with the tool insert geometry. Insert type CCMT-12 showed better surface finish for cutting speed to 201 m/min, while insert type CNGN-12 surface roughness increased dramatically with increasing of speed to a limit completely damage of insert geometer beyond 152 m/min.

  1. The Effects of Carbide Characteristics on the Performance of Tungsten Carbide-Based Composite Overlays, Deposited by Plasma-Transferred Arc Welding

    Science.gov (United States)

    Fisher, G.; Wolfe, T.; Meszaros, K.

    2013-06-01

    In Alberta, there are huge quantities of ore processed to remove bitumen from oil sands deposits. The scale of production generates very aggressive tribocorrosive conditions during the mining, extraction, and upgrading processes. It is common to apply tungsten carbide-based composite overlays to improve the reliability and extend service lives of equipment and components. The performance of the applied overlays is largely dependent on the selection of the carbide type and the wear environment. This paper will evaluate overlays containing macrocrystalline, angular eutectic, and spherical eutectic tungsten carbides and discuss the performance of the overlays with a focus on carbide properties and the interactions between the service conditions and the composite material. This discussion will demonstrate how effective selection of protective materials can improve the reliability of oil sands equipment.

  2. Investigation on the formation of tungsten carbide in tungsten-containing diamond like carbon coatings

    NARCIS (Netherlands)

    Strondl, C.; Carvalho, N.M.; Hosson, J.Th.M. De; Kolk, G.J. van der

    2003-01-01

    A series of tungsten-containing diamond-like carbon (Me-DLC) coatings have been produced by unbalanced magnetron sputtering using a Hauzer HTC-1000 production PVD system. Sputtering from WC targets has been used to form W-C:H coatings. The metal to carbon ratio has been varied to study changes in th

  3. Effect of WC/Co coherency phase boundaries on Fracture toughness of the nanocrystalline cemented carbides.

    Science.gov (United States)

    Xie, Hongxian; Song, Xiaoyan; Yin, Fuxing; Zhang, Yongguang

    2016-08-03

    The effect of coherency WC/Co phase boundaries on the fracture toughness of the nanocrystalline WC-Co cemented carbides is studied by MD simulation method. The simulation results show that the nanocrystalline WC-Co cemented carbides with coherency WC/Co phase boundaries has higher fracture toughness than that without coherency WC/Co phase boundaries. Moreover, the mechanism of why coherency WC/Co phase boundaries can improve the fracture toughness of the nanocrystalline cemented carbides is also investigated. It is found the fact that the separation energy of the coherent WC/Co phase boundary is larger than that of the incoherent WC/Co phase boundaries is the main reason for this excellent mechanical property.

  4. Effects of gradient structure on the microstructures and properties of coated cemented carbides

    Institute of Scientific and Technical Information of China (English)

    Li Chen; Enxi Wu; Fei Yin; Jia Li

    2006-01-01

    The effects of gradient structure on the microstructure and properties of coated cemented carbides were researched with optical microscopy (OM), scanning electron microscopy (SEM), strength measurements, and cutting tests. It shows that vacuum sintering of WC-Ti(C, N)-TaC-Co cemented carbides results in the formation of a surface ductile zone. The ductile zone prevents crack propagation and leads to the increase of transverse rupture strength of the substrate. The impact resistance of coated gradient inserts was obviously improved on the basis of maintaining resistance to abrasion and the forming mechanism of the gradient structure was also analyzed.

  5. Microstructure of TiC-Based Coatings on Cemented Carbide Derived by Sol-Gel Routes

    Science.gov (United States)

    Yang, Mei; Guo, Zhixing; Qi, Kaifeng; Huang, Kun; Deng, Jianxiong; Liu, Jia

    2016-12-01

    TiC-based coating is prepared by depositing TiO2 sol on cemented carbide compact and liquid phase sintering. TiC forms due to carbothermal reduction reaction of TiO2 and then reacts with WC and transforms to TiC-based solid solution. Ti content changes the WC growth mechanism and results in the multi-stepped morphology. When sintered cemented carbide is used as substrate, WC keeps the equilibrium truncated triangle prism morphology due to the relatively weak diffusion among Ti, WC, and Co.

  6. Research on Ultrafine WC-10Co Cemented Carbide with High Properties

    Institute of Scientific and Technical Information of China (English)

    SHI Xiaoliang; YANG Hua; SHAO Gangqin; DUAN Xinglong; XIONG Zhen; ZHANG Weifeng

    2006-01-01

    WC- 10Co nanocomposite powder produced by spray pyrolysis-continuous reduction and carbonization technology was used, and the vacuum sintering plus sinterhip process was adopted to prepare ultrafine WCCo cemented carbide. The microstructure, grain size, porosity, density, Rockwell A hardness ( HRA ), transverse rupture strength (TRS), saturated magnetization and coercivity force were studied. The experimental results show that average grain size of the sample prepared by vacuum sintering plus sinterhip technology was about 420 nm, transverse rupture strength was more than 3460 MPa, and Rockwell A hardness of sintered specimen was more than 92.5. Ultrafine WC- 10Co cemented carbide with high strength and high hardness is obtained.

  7. Microstructure of TiC-Based Coatings on Cemented Carbide Derived by Sol-Gel Routes

    Science.gov (United States)

    Yang, Mei; Guo, Zhixing; Qi, Kaifeng; Huang, Kun; Deng, Jianxiong; Liu, Jia

    2017-02-01

    TiC-based coating is prepared by depositing TiO2 sol on cemented carbide compact and liquid phase sintering. TiC forms due to carbothermal reduction reaction of TiO2 and then reacts with WC and transforms to TiC-based solid solution. Ti content changes the WC growth mechanism and results in the multi-stepped morphology. When sintered cemented carbide is used as substrate, WC keeps the equilibrium truncated triangle prism morphology due to the relatively weak diffusion among Ti, WC, and Co.

  8. Potential Use Of Carbide Lime Waste As An Alternative Material To Conventional Hydrated Lime Of Cement-Lime Mortars

    OpenAIRE

    Al Khaja, Waheeb A.

    1992-01-01

    The present study aimed at the possibility of using the carbide lime waste as an alternative material to the conventional lime used for cement-lime mortar. The waste is a by-product obtained in the generation of acetylene from calcium carbide. Physical and chemical properties of the wastes were studied. Two cement-lime-sand mix proportions containing carbide lime waste were compared with the same mix proportions containing conventional lime along with a control mix without lime. Specimens wer...

  9. Microfabrication of Tungsten, Molybdenum and Tungsten Carbide Rods by Laser-Assisted CVD

    OpenAIRE

    Björklund, Kajsa

    2001-01-01

    Thin films of refractory metals and carbides have been studied extensively over many years because of their wide range of application. The two major techniques used are Chemical Vapour Deposition (CVD) and Physical Vapour Deposition (PVD). These can result in the deposition of two-dimensional blanket or patterned thin films. Laser-assisted Chemical Vapour Deposition (LCVD) can provide a maskless alternative for localised deposition in two and three dimensions. This thesis describes LCVD of mi...

  10. Preparation of tungsten carbide nanoparticles by ion implantation and electrochemical etching

    Energy Technology Data Exchange (ETDEWEB)

    Kato, S. [Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Yamaki, T., E-mail: yamaki.tetsuya@jaea.go.jp [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Yamamoto, S.; Hakoda, T. [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Kawaguchi, K. [Department of Chemistry and Materials Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan); Kobayashi, T. [RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 350-0198 (Japan); Suzuki, A.; Terai, T. [Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2013-11-01

    Glassy carbon (GC) substrates were implanted with 100 keV tungsten ions at retained fluences of 4 × 10{sup 16} and 6 × 10{sup 16} ions/cm{sup 2} and surface-etched electrochemically in order to prepare tungsten-carbide (WC) nanoparticles on their topmost layers. The calculated current efficiency for the electrochemical etching was nearly the same for the two samples implanted at different fluences, suggesting the controllability of the etched depth using the consumed electric charge. The etching front reached the buried tungsten-implanted layer and increased the tungsten concentration at the surface. No oxidation of WC was observed, even under anodic potential application during electrochemical etching. The voltammogram response of the topmost nanoparticle layer was too small to be observed, probably due to the limited activity of the WC itself and the remaining low concentration. It was demonstrated that this technique could, in principle, be applied to various types of nanoparticle catalysts implanted in GC substrates.

  11. Structure and abrasive wear resistance of R6M5 steel-tungsten carbide composite coatings

    Science.gov (United States)

    Gnyusov, S. F.

    2012-09-01

    Features of the structure formation, composition, and abrasive wear resistance of R6M5 steel-tungsten carbide (R6M5-WC) composite coatings have been studied as dependent on the WC content. The introduction of ˜20 wt % WC into the hardening composition leads to an increase in the fraction of M6C carbide (in the form of eutectic inclusions with average size ˜5.9 μm at grain boundaries and dispersed ˜0.25 μm particles in the volume of grains), while a large proportion of metastable austenite (˜88 vol %) is still retained. The R6M5-WC coatings exhibit high abrasive wear resistance, which is ensured by the γ → α' martensite transformation during friction and a muiltimodal size distribution of hardening particles.

  12. Wear behaviour of laser surface hardfaced steels with tungsten carbide powder injection

    Energy Technology Data Exchange (ETDEWEB)

    Pantelis, D. (Ecole Centrale Paris, Lab. MSS/MAT, 92 - Chatenay-Malabry (France)); Michaud, H. (IRSID-UNIEUX, Coatings Service, USINOR-SACILOR Group, 42 - Firminy (France)); Freitas, M. de (Inst. Superior Tecnico, CEMUL (INIC), Lisboa (Portugal))

    1993-05-28

    The use of a laser beam for surface alloying with carbide powder injection gives thick coatings (750-800 [mu]m) without defects such as porosity and cracks. A precise correlation between the treatment parameters and the phenomena induced during the laser-material interaction is established. Optimum treatment conditions are found and applied to laser alloying of 4140 and high speed M2 tool steels with tungsten carbide injection. The laser surface treated zones, for both steels, are strongly alloyed and present a very fine microstructure with various morphologies and very high average values of the microhardness (900 HV 50 gf and 1200 HV 50 gf) compared with those of the substrates (300 HV 50 gf and 250 HV 50 gf respectively). Friction and wear tests (using a plane-ring experimental device), revealed that the laser surface coatings on both steels present wear resistances considerably higher than that of a conventional plasma-sprayed coating. (orig.)

  13. Magnetic field imaging of a tungsten carbide film by scanning nano-SQUID microscope

    Science.gov (United States)

    Shibata, Yusuke; Nomura, Shintaro; Ishiguro, Ryosuke; Kashiwaya, Hiromi; Kashiwaya, Satoshi; Nago, Yusuke; Takayanagi, Hideaki

    2016-10-01

    We present the results of magnetic field imaging by scanning nano-superconducting quantum interference device (SQUID) microscopy on a tungsten carbide (W-C) film fabricated using focused-ion-beam chemical vapor deposition. We have investigated magnetic field change by a W-C film in an external magnetic field using a scanning nano-SQUID microscope system. We have found that the reduction of the magnetic field above the W-C film was 0.9%, indicating the penetration of vortices in the W-C at an external magnetic field of 0.171 mT.

  14. Growth and tribological properties of diamond films on silicon and tungsten carbide substrates

    Science.gov (United States)

    Radhika, R.; Ramachandra Rao, M. S.

    2016-11-01

    Hot filament chemical vapor deposition technique was used to deposit microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) films on silicon (Si) and tungsten carbide (WC-6Co) substrates. Friction coefficient of larger diamond grains deposited on WC-6Co substrate shows less value approximately 0.2 while this differs marginally on films grown on Si substrate. The study claims that for a less friction coefficient, the grain size is not necessarily smaller. However, the less friction coefficient (less than 0.1 saturated value) in MCD and NCD deposited on Si is explained by the formation of graphitized tribolayer. This layer easily forms when diamond phase is thermodynamically unstable.

  15. Thin films deposited by femtosecond pulsed laser ablation of tungsten carbide

    Science.gov (United States)

    De Bonis, A.; Teghil, R.; Santagata, A.; Galasso, A.; Rau, J. V.

    2012-09-01

    Ultra-short Pulsed Laser Deposition has been applied to the production of thin films from a tungsten carbide target. The gaseous phase obtained by the laser ablation shows a very weak primary plume, in contrast with a very strong secondary one. The deposited films, investigated by Scanning Electron Microscopy, Atomic Force Microscopy, X-Ray Photoelectron Spectroscopy and X-Ray Diffraction, present a mixture of WC and other phases with lower carbon content. All films are amorphous, independently from the substrate temperature. The characteristics of the deposits have been explained in terms of thermal evaporation and cooling rate of molten particles ejected from the target.

  16. Microwave synthesis of ultrafine and nanosized powders of tungsten oxide and carbide

    Energy Technology Data Exchange (ETDEWEB)

    Nikolaenko, Irina; Kedin, Nikolay; Shveikin, Gennadii; Polyakov, Evgenii [Russian Academy of Sciences, Ekaterinburg (Russian Federation). Inst. of Solid State Chemistry

    2014-03-15

    A new method of synthesis of nanosized and ultrafine tungsten oxide and carbide powders is offered, which combines carbon carrier supported classical liquid-phase precipitation and low-temperature microwave treatment. The full range of intermediate substances obtained during thermolysis, reduction and carburization of precursors to final products is presented. It is shown that cooling of ammonium tungstate solution to 4 C and the use of carbon carrier at the precipitation stage can increase the specific surface area from 20 to 100 m{sup 2} g{sup -1}. (orig.)

  17. Solid state synthesis of tungsten carbide nanorods and nanoplatelets by a single-step pyrolysis.

    Science.gov (United States)

    Shanmugam, Sangaraju; Jacob, David S; Gedanken, Aharon

    2005-10-20

    We report a simple and efficient single-step synthesis of tungsten carbide nanorods and nanoplatelets by direct pyrolysis of a hybrid composite material of 12-tungstophosphoric acid and hexadecyltrimethylammonium bromide in a closed Swagelok cell at 1000 degrees C. The product was characterized by XRD, TGA, SEM, TEM, XPS, and CV. The diameter of the nanorods is 30-50 nm, and the length varies from 200 to 500 nm. The size of the platelets is around 55 nm. The WC exhibits an interesting structural surface with kinks, steps, and terraces which is evidenced by HRTEM studies.

  18. Effects of Rare Earth and Alkaline Earth on Spheroidizing of Eutectic Carbides in Low Tungsten White Cast Iron

    Institute of Scientific and Technical Information of China (English)

    Fu Hanguang; Zou Dening

    2004-01-01

    Tungsten Alloy White Cast Iron(TAWCI) has great brittleness and narrow application scope. The influences of Rare earth element(Ce) and alkaline earth elements ( K, Na) on the microstructures and performances of TAWCI were researched, and the idea estimating spheroidizing effect of carbides using Circular Degree (C. D) were put forward. The result shows that eutectics carbide tums into sphericity from network after modification, and carbide is refined and uniformly distributed and the C. D of eutectic carbide increases. The mechanism of carbide spheroidizing was analyzed. The impact toughness and wear resistance of TAWCI obviously improve with the rise of C. D of carbides.The service life of modified TAWCI roll is 35 % higher than that of high chromium cast iron roll, and its production cost is reduced by 25 %.

  19. Studies of the composition and reactivity of carbon species generated through laser vaporization of graphite, tantalum carbide and tungsten carbide

    Energy Technology Data Exchange (ETDEWEB)

    Ortman, B.J.

    1987-01-01

    Vapor compositions above graphite, tantalum carbide, and tungsten carbide together with the chemical reactions of C/sub 1/, C/sub 2/ and C/sub 3/ were studied by the techniques of CW laser vaporization, matrix isolation, and FTIR spectroscopy. The carbon species were scavenged by cocondensing reactive gases (N/sub 2/, H/sub 2/, O/sub 2/, CO and H/sub 2/O) with the vapors of graphitic samples in argon or nitrogen matrices. Products were identified from their infrared spectra. Photolysis and annealing studies were also conducted to detect reaction intermediates, formation of carbon clusters, and metastable C/sub 1/, C/sub 2/, and C/sub 3/ adducts with the added reactants. From these experiments, CO was shown to be potentially the most useful scavenger molecule, since it reacted with both C/sub 1/ and C/sub 2/ to form C/sub 2/O and C/sub 3/O, respectively. CO also reacted with C/sub 3/ to form an adduct, which rearranges upon photolysis to form C/sub 4/O, a previously unknown molecule. Its identity was confirmed by isotopic studies and comparison of its vibrations to those of related molecules, C/sub 3/O, C/sub 2/O, and CO.

  20. Preparation of Nano-crystalline Tungsten Carbide Thin Film by Magnetron Sputtering and Their Electrocatalytic Property for PNP Reduction

    Institute of Scientific and Technical Information of China (English)

    Hua Jun ZHENG; Jian Guo HUANG; Chun An MA

    2005-01-01

    Nano-crystalline tungsten carbide thin films were deposited on Ni substrates by magnetron sputtering using WC as target material. The crystal structure and morphology of the thin films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).Electrochemical investigations showed that the electrode of the thin film exhibited higher electrocatalytic activity in the reaction of p-nitrophenol (PNP) reduction. FT-IR analysis indicated that p-aminophenol (PAP) was synthesized after two step reduction of PNP on nano-crystalline tungsten carbide thin film electrode.

  1. Generation of pressures over 40 GPa using Kawai-type multi-anvil press with tungsten carbide anvils.

    Science.gov (United States)

    Ishii, T; Shi, L; Huang, R; Tsujino, N; Druzhbin, D; Myhill, R; Li, Y; Wang, L; Yamamoto, T; Miyajima, N; Kawazoe, T; Nishiyama, N; Higo, Y; Tange, Y; Katsura, T

    2016-02-01

    We have generated over 40 GPa pressures, namely, 43 and 44 GPa, at ambient temperature and 2000 K, respectively, using Kawai-type multi-anvil presses (KMAP) with tungsten carbide anvils for the first time. These high-pressure generations were achieved by combining the following pressure-generation techniques: (1) precisely aligned guide block systems, (2) high hardness of tungsten carbide, (3) tapering of second-stage anvil faces, (4) materials with high bulk modulus in a high-pressure cell, and (5) high heating efficiency.

  2. Thin films deposited by femtosecond pulsed laser ablation of tungsten carbide

    Energy Technology Data Exchange (ETDEWEB)

    De Bonis, A. [Dipartimento di Chimica ' A.M. Tamburro' , Universita della Basilicata, Via dell' Ateneo Lucano 10, 85100 Potenza (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali - INSTM, Via G. Giusti 9, 00121 Florence (Italy); Teghil, R., E-mail: roberto.teghil@unibas.it [Dipartimento di Chimica ' A.M. Tamburro' , Universita della Basilicata, Via dell' Ateneo Lucano 10, 85100 Potenza (Italy); Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali - INSTM, Via G. Giusti 9, 00121 Florence (Italy); Santagata, A. [Istituto Metodologie Inorganiche e Plasmi, CNR, Unita di Potenza, via S. Loja, 85050 Tito Scalo PZ (Italy); Galasso, A. [Dipartimento di Chimica ' A.M. Tamburro' , Universita della Basilicata, Via dell' Ateneo Lucano 10, 85100 Potenza (Italy); Rau, J.V. [Istituto di Struttura della Materia, CNR, Via del Fosso del Cavaliere 100, 00133 Rome (Italy)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer We have deposited amorphous tungsten carbide films by ultra-short PLD. Black-Right-Pointing-Pointer In the films different W-C phases are present. Black-Right-Pointing-Pointer The films are formed mainly by particles with nanometric size. Black-Right-Pointing-Pointer We propose that the particles are directly ejected from the target. - Abstract: Ultra-short Pulsed Laser Deposition has been applied to the production of thin films from a tungsten carbide target. The gaseous phase obtained by the laser ablation shows a very weak primary plume, in contrast with a very strong secondary one. The deposited films, investigated by Scanning Electron Microscopy, Atomic Force Microscopy, X-Ray Photoelectron Spectroscopy and X-Ray Diffraction, present a mixture of WC and other phases with lower carbon content. All films are amorphous, independently from the substrate temperature. The characteristics of the deposits have been explained in terms of thermal evaporation and cooling rate of molten particles ejected from the target.

  3. HVOF and HVAF Coatings of Agglomerated Tungsten Carbide-Cobalt Powders for Water Droplet Erosion Application

    Science.gov (United States)

    Tarasi, F.; Mahdipoor, M. S.; Dolatabadi, A.; Medraj, M.; Moreau, C.

    2016-12-01

    Water droplet erosion (WDE) is a phenomenon caused by impingement of water droplets of several hundred microns to a few millimeters diameter at velocities of hundreds of meters per second on the edges and surfaces of the parts used in such services. The solution to this problem is sought especially for the moving compressor blades in gas turbines and those operating at the low-pressure end of steam turbines. Thermal-sprayed tungsten carbide-based coatings have been the focus of many studies and are industrially accepted for a multitude of wear and erosion resistance applications. In the present work, the microstructure, phase analysis and mechanical properties (micro-hardness and fracture toughness) of WC-Co coatings are studied in relation with their influence on the WDE resistance of such coatings. The coatings are deposited by high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) processes. The agglomerated tungsten carbide-cobalt powders were in either sintered or non-sintered conditions. The WDE tests were performed using 0.4 mm water droplets at 300 m/s impact velocity. The study shows promising results for this cermet as WDE-resistant coating when the coating can reach its optimum quality using the right thermal spray process and parameters.

  4. Application of Deep Cryogenic Treatment to Uncoated Tungsten Carbide Inserts in the Turning of AISI 304 Stainless Steel

    Science.gov (United States)

    Özbek, Nursel Altan; Çİçek, Adem; Gülesİn, Mahmut; Özbek, Onur

    2016-12-01

    This study investigated the effects of deep cryogenic treatment (DCT) on the wear performance of uncoated tungsten carbide inserts. AISI 304 austenitic stainless steel, widely used in industry, was selected as the workpiece material. Cutting experiments showed that the amount of wear significantly increased with increasing cutting speed. In addition, it was found that DCT contributed to the wear resistance of the turning inserts. The treated turning inserts were less worn by 48 and 38 pct in terms of crater wear and notch wear, respectively, whereas they exhibited up to 18 pct superior wear performance in terms of flank wear. This was attributed to the precipitation of new and finer η-carbides and their homogeneous distribution in the microstructure of the tungsten carbide material after deep cryogenic treatment. Analyses via image processing, hardness measurements, and SEM observations confirmed these findings.

  5. Application of Deep Cryogenic Treatment to Uncoated Tungsten Carbide Inserts in the Turning of AISI 304 Stainless Steel

    Science.gov (United States)

    Özbek, Nursel Altan; Çİçek, Adem; Gülesİn, Mahmut; Özbek, Onur

    2016-09-01

    This study investigated the effects of deep cryogenic treatment (DCT) on the wear performance of uncoated tungsten carbide inserts. AISI 304 austenitic stainless steel, widely used in industry, was selected as the workpiece material. Cutting experiments showed that the amount of wear significantly increased with increasing cutting speed. In addition, it was found that DCT contributed to the wear resistance of the turning inserts. The treated turning inserts were less worn by 48 and 38 pct in terms of crater wear and notch wear, respectively, whereas they exhibited up to 18 pct superior wear performance in terms of flank wear. This was attributed to the precipitation of new and finer η-carbides and their homogeneous distribution in the microstructure of the tungsten carbide material after deep cryogenic treatment. Analyses via image processing, hardness measurements, and SEM observations confirmed these findings.

  6. Abnormal gradient microstructure in Cr3C2 based cemented carbide

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    With OLYMPUS PMG3 metallograph, an abnormal throe-layer gradient structure , i. e. coarsegrain zone, binder enrichment zone and normal structure zone from surface to inner, was observed in Cr3C2based cemented carbide. In the binder enrichment zone, three different shapes of anomalous coarse carbideswere observed. It is shown that the transverse rapture strength can be raised remarkably, up 20.7% from thealloy with abnormal gradient structure by removing the abnormal gradient structure. The results suggested thatthe abnormal gradient structure in the surface, especially the anomalous coarse carbides in the binder enrichment zone is the mair reason for the lower strength.

  7. R.F. magnetron sputtering of multilayered c-BN films on cemented carbide tool.

    Science.gov (United States)

    Park, Sungtae; Jeong, Sehoon; Lee, Kwangmin

    2011-02-01

    A c-BN thin film was deposited using a B4C target in a r.f. magnetron sputtering system. The c-BN layer was coated with a TiAIN adhesion layer (approximately 2 microm), boron carbide (approximately 1 microm) and BCN (10 approximately 15 nm) nano-gradient layer system. The c-BN layers with thicknesses of more than 0.5 microm were successfully deposited onto cemented carbide substrates. The high resolution XPS spectra analysis of B1s and N1s revealed that the c-BN film was mainly composed of sp3 BN bonds.

  8. Expansion into vacuum of a shocked tungsten carbide-epoxy mixture.

    Energy Technology Data Exchange (ETDEWEB)

    Reinhart, William Dodd; Thornhill, Tom Finley, III; Vogler, Tracy John; Alexander, C. Scott

    2009-03-01

    The behavior of a shocked tungsten carbide / epoxy mixture as it expands into a vacuum has been studied through a combination of experiments and simulations. X-ray radiography of the expanding material as well as the velocity measured for a stood-off witness late are used to understand the physics of the problem. The initial shock causes vaporization of the epoxy matrix, leading to a multi-phase flow situation as the epoxy expands rapidly at around 8 km/s followed by the WC particles moving around 3 km/s. There are also small amounts of WC moving at higher velocities, apparently due to jetting in the sample. These experiments provide important data about the multi-phase flow characteristics of this material.

  9. Diffusion barrier performance of pulsed laser deposited amorphous tungsten carbide films

    Science.gov (United States)

    Ghaisas, Smita

    1991-12-01

    The performance of pulsed laser deposited tungsten carbide films as diffusion barriers between a Si substrate and an Al overlayer has been investigated. Four-point probe measurement of resistance is employed to monitor the electrical stability of the Al/WC/Si metallization schemes upon thermal annealing in a vacuum for 30 min in a temperature range from 100 to 500 °C. The Glancing angle x-ray diffraction technique has been used to characterize the as-deposited as well as annealed samples. To study the metallurgical interaction between Al overlayer and the barrier film, experiments on isothermal annealings are carried out. The data obtained have been used to estimate the activation energy for the formation of the intermetallic compound WAl12. Morphological features of the annealed samples have been obtained by employing the technique of scanning electron microscopy.

  10. Pulsed laser deposition of tungsten carbide thin films on silicon (100) substrate

    Science.gov (United States)

    Suda, Y.; Nakazono, T.; Ebihara, K.; Baba, K.

    1997-01-01

    A method of synthesizing tungsten carbide (WC) thin films by a pulsed YAG laser deposition is investigated. WC thin films are deposited on silicon (100) substrates by using WC5%Co alloy targets. Glancing angle X-ray diffraction shows that the strong peaks of W 2C appear at the substrate temperature of 500°C. Beside the strong peaks of W 2C, weak peaks of WC and W 3Co 3C appear at the substrate temperature of 650°C. Auger electron spectroscopy shows that the almost stoichiometric WC films are deposited at the methane gas pressure of 1.0 Pa. Morphological features of the samples have been obtained by employing the technique of scanning electron microscopy. X-ray photoelectron spectroscopy has been used to obtain structural and compositional information about the samples.

  11. Simulation on Mechanical Properties of Tungsten Carbide Thin Films Using Monte Carlo Model

    Directory of Open Access Journals (Sweden)

    Liliam C. Agudelo-Morimitsu

    2012-12-01

    Full Text Available The aim of this paper is to study the mechanical behavior of a system composed by substrate-coating using simulation methods. The contact stresses and the elastic deformation were analyzed by applying a normal load to the surface of the system consisting of a tungsten carbide (WC thin film, which is used as a wear resistant material and a stainless steel substrate. The analysis is based on Monte Carlo simulations using the Metropolis algorithm. The phenomenon was simulated from a fcc facecentered crystalline structure, for both, the coating and the substrate, assuming that the uniaxial strain is taken in the z-axis. Results were obtained for different values of normal applied load to the surface of the coating, obtaining the Strain-stress curves. From this curve, the Young´s modulus was obtained with a value of 600 Gpa, similar to the reports.

  12. Wear and cutting performance of diamond composite material-a comparison with tungsten carbide

    Institute of Scientific and Technical Information of China (English)

    LI Xing-sheng; J. N. Boland

    2004-01-01

    A series of wear and rock cutting tests were undertaken to assess the wear and cutting performance of a thermally stable diamond composite (TSDC). The wear tests were conducted on a newly designed wear testing rig in which a rotating aluminium oxide grinding wheel is turned (also known as machined) by the testing tool element.The rock cutting tests were performed on a linear rock-cutting planer. The thrust and cutting forces acting on the tool were measured during these tests. A tungsten carbide element was also studied for comparative purposes. The wear coefficients of both materials were used to evaluate wear performance while cutting performance was assessed by tool wear and the rates of increase in forces with cutting distance.

  13. Laboratory analysis of dental sections made with commercial tungsten carbide burs coated with HFCVD diamond

    Energy Technology Data Exchange (ETDEWEB)

    Maass, F [Departamento de Fisica, Universidad de Antofagasta, Av. Angamos 601, Antofagasta (Chile); Aguilera, Y [Departamento de Ingenieria Industrial, Universidad de Antofagasta, Av. Angamos 601, Antofagasta (Chile); Avaria, J [Departamento de OdontologIa, Universidad de Antofagasta, Av. Angamos 601, Antofagasta (Chile)], E-mail: fdmaass@uantof.cl

    2008-11-01

    The objective of this study was to determine the cutting power of diamond burs obtained by the HFCVD deposition process. Diamond was deposited on the active part of each of a series of 10 commonly used Tungsten Carbide (WC) commercial burs. The quality of the section was compared with sections made by commonly used commercial burs, employing fresh human molars and a standard device [1]. Both burs and sections were analysed by using SEM and EDX techniques. The quality and tension of the deposited diamond coatings were analyzed by Raman Spectroscopy. The optimal thickness of the diamond coating which provided the best durability and finish of the sections was determined by comparative observations of results.

  14. Optimization of Tungsten Carbide Opposite Anvils Used in the In Situ High-Pressure Loading Apparatus

    Directory of Open Access Journals (Sweden)

    Zhang Ying

    2014-01-01

    Full Text Available In order to optimize the structure of anvils, finite element method is used to simulate two kinds of structures, one of which has a support ring but the other one does not. According to the simulated results, it is found that the maximum value of pressure appears at the center of culet when the bevelled angle is about 20°. Comparing the results of these two kinds of structures, we find that the efficiency of pressure transformation for the structure without support ring is larger than that for the structure with support ring. Considering the effect of von Mises stress, two kinds of tungsten carbide opposite anvils have been manufactured with bevelled angle of 10°. The experimental results for these two anvils are in good agreement with the simulation.

  15. Microstructure and Properties of Coating from Cemented Carbide on Surface of H13 Steel

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The microstructures and properties of coating from cemented carbide on the substrate of H13 by vacuum powder sintering were studied. The effect of sintering temperature on the microstructures of coating was discussed. The interface characteristics between coating and H13 steel substrate, microhardness distribution and wear resistance in the coating were analyzed. The coating from cemented carbide with thickness of 1-3 mm by vacuum powder sintering at temperature ranging from 1280 ℃ to 1300 ℃ was obtained. The experimental results indicated that the coating with microhardness of HV 1600 favorable to wear resistance is strongly bonded with the H13 steel substrate by mutual diffusion and penetration of Fe,Cr, Mo,V in substrate towards the coating and W, Co,Ni in coating towards the substrate.

  16. Influence of Combined Hard and Fine Machining on the Surface Properties of Cemented Carbides

    Directory of Open Access Journals (Sweden)

    U. Engel

    2012-09-01

    Full Text Available As a result of recent developments in cold forging cemented carbides are increasingly used as tool materials. Due to their high hardness only electrical discharge machining (EDM and grinding are suitable for tool machining. The structure of tool surface has significant influence on dominating failure mechanisms wear and fatigue. For improvement of tribological conditions the surface is polished in a finale processing step. The result of hard and fine machining is a specific combination of coarse and fine structure which is determined by processing parameters. The different surface structures lead to a particular tool behavior in forming process. This paper aims to show the influence of combined hard and fine machining on the surface properties of cemented carbides.

  17. Analysis of tungsten carbide coatings by UV laser ablation inductively coupled plasma atomic emission spectrometry

    Science.gov (United States)

    Kanicky, V.; Otruba, V.; Mermet, J.-M.

    2000-06-01

    Tungsten carbide coatings (thickness 0.1-0.2 mm) containing 8.0, 12.2, 17.2 and 22.9% Co were studied with laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES). Composition of these plasma sprayed deposits on steel disks was determined using X-ray fluorescence spectrometry and electron microprobe energy/wavelength dispersive X-ray spectrometry. The coatings were ablated by means of a Q-switched Nd:YAG laser at 266 nm (10 Hz, 10 mJ per shot) coupled to an ICP echelle-based spectrometer equipped with a segmented charge-coupled device detector. Non-linear dependences of cobalt lines intensities on the Co percentage were observed both at a single spot ablation and at a sample translation. This behaviour could be attributed to a complex phase composition of the system W-C-Co. However, employing tungsten as internal standard the linear calibration was obtained for studied analytical lines Co II 228.616 nm, Co II 230.786 nm, Co II 236.379 nm and Co II 238.892 nm.

  18. Laser cladding of tungsten carbides (Spherotene ®) hardfacing alloys for the mining and mineral industry

    Science.gov (United States)

    Amado, J. M.; Tobar, M. J.; Alvarez, J. C.; Lamas, J.; Yáñez, A.

    2009-03-01

    The abrasive nature of the mechanical processes involved in mining and mineral industry often causes significant wear to the associated equipment and derives non-negligible economic costs. One of the possible strategies to improve the wear resistance of the various components is the deposition of hardfacing layers on the bulk parts. The use of high power lasers for hardfacing (laser cladding) has attracted a great attention in the last decade as an alternative to other more standard methods (arc welding, oxy-fuel gas welding, thermal spraying). In laser cladding the hardfacing material is used in powder form. For high hardness applications Ni-, Co- or Fe-based alloys containing hard phase carbides at different ratios are commonly used. Tungsten carbides (WC) can provide coating hardness well above 1000 HV (Vickers). In this respect, commercially available WC powders normally contain spherical micro-particles consisting of crushed WC agglomerates. Some years ago, Spherotene ® powders consisting of spherical-fused monocrystaline WC particles, being extremely hard, between 1800 and 3000 HV, were patented. Very recently, mixtures of Ni-based alloy with Spherotene powders optimized for laser processing were presented (Technolase ®). These mixtures have been used in our study. Laser cladding tests with these powders were performed on low carbon steel (C25) substrates, and results in terms of microstructure and hardness will be discussed.

  19. Laser cladding of tungsten carbides (Spherotene) hardfacing alloys for the mining and mineral industry

    Energy Technology Data Exchange (ETDEWEB)

    Amado, J.M. [Departamento de Ingenieria Industrial II, Universidade da Coruna, Mendizabal s/n, Ferrol E-15403 (Spain); Tobar, M.J. [Departamento de Ingenieria Industrial II, Universidade da Coruna, Mendizabal s/n, Ferrol E-15403 (Spain)], E-mail: cote@udc.es; Alvarez, J.C.; Lamas, J.; Yanez, A. [Departamento de Ingenieria Industrial II, Universidade da Coruna, Mendizabal s/n, Ferrol E-15403 (Spain)

    2009-03-01

    The abrasive nature of the mechanical processes involved in mining and mineral industry often causes significant wear to the associated equipment and derives non-negligible economic costs. One of the possible strategies to improve the wear resistance of the various components is the deposition of hardfacing layers on the bulk parts. The use of high power lasers for hardfacing (laser cladding) has attracted a great attention in the last decade as an alternative to other more standard methods (arc welding, oxy-fuel gas welding, thermal spraying). In laser cladding the hardfacing material is used in powder form. For high hardness applications Ni-, Co- or Fe-based alloys containing hard phase carbides at different ratios are commonly used. Tungsten carbides (WC) can provide coating hardness well above 1000 HV (Vickers). In this respect, commercially available WC powders normally contain spherical micro-particles consisting of crushed WC agglomerates. Some years ago, Spherotene powders consisting of spherical-fused monocrystaline WC particles, being extremely hard, between 1800 and 3000 HV, were patented. Very recently, mixtures of Ni-based alloy with Spherotene powders optimized for laser processing were presented (Technolase). These mixtures have been used in our study. Laser cladding tests with these powders were performed on low carbon steel (C25) substrates, and results in terms of microstructure and hardness will be discussed.

  20. Statistical regression modeling and machinability study of hardened AISI 52100 steel using cemented carbide insert

    Directory of Open Access Journals (Sweden)

    Amlana Panda

    2017-01-01

    Full Text Available The present study investigates performance and feasibility of application of low cost cemented carbide insert in dry machining of AISI 52100 steel hardened to (55 ± 1 HRC which is rarely researched as far as machining of bearing steel is concerned. Machinability studies i.e. flank wear, surface roughness and morphology analysis of chip has been investigated and statistical regression modeling has been developed. The test has been conducted based on Taguchi L16 OA taking machining parameters like cutting speed, feed and depth of cut. It is observed that uncoated cemented carbide insert performs well at some selected runs (Run 1, 5 and 9 which show its feasibility for hard turning applications. The developed serrated saw tooth chip of burnt blue colour adversely affects the surface quality. Adequacy of the developed statistical regression model has been checked using ANOVA analysis (depending on F value, P value and R2 value and normal probability plot at 95% confidence level. The results of optimal parametric combinations may be adopted while turning hardened AISI 52100 steel under dry environment with uncoated cemented carbide insert.

  1. Removal of a Tungsten Carbide Ring from the Finger of a Pregnant Patient: A Case Report Involving 2 Emergency Departments and the Internet.

    Science.gov (United States)

    Moser, Alexandre; Exadaktylos, Aristomenis; Radke, Alexander

    2016-01-01

    Introduction. Destructive or nondestructive procedures may be used to remove rings from injured fingers. Because of their hardness, tungsten carbide rings present special problems. Case Presentation. The patient was a 33-year-old woman, two weeks before delivery, with a swollen and reddened ring finger. It was decided to remove a tungsten carbide ring from her ring finger. This was achieved by shattering the ring with locking pliers. The patient's ring finger recovered fully.

  2. Comparative study on discharge conditions in micro-hole electrical discharge machining of tungsten carbide (WC-Co) material

    Institute of Scientific and Technical Information of China (English)

    Hyun-Seok TAK; Chang-Seung HA; Dong-Hyun KIM; Ho-Jun LEE; Hae-June LEE; Myung-Chang KANG

    2009-01-01

    WC-Co is used widely in die and mold industries due to its unique combination of hardness, strength and wear-resistance. For machining difficult-to-cut materials, such as tungsten carbide, micro-electrical discharge machining(EDM) is one of the most effective methods for making holes because the hardness is not a dominant parameter in EDM. This paper describes the characteristics of the discharge conditions for micro-hole EDM of tungsten carbide with a WC grain size of 0.5μm and Co content of 12%. The EDM process was conducted by varying the condenser and resistance values. A R-C discharge EDM device using arc erosion for micro-hole machining was suggested. Furthermore, the characteristics of the developed micro-EDM were analyzed in terms of the electro-optical observation using an oscilloscope and field emission scanning electron microscope.

  3. Determination of emissivity coefficient of heat-resistant super alloys and cemented carbide

    Directory of Open Access Journals (Sweden)

    Kieruj Piotr

    2016-12-01

    Full Text Available This paper presents the analysis of emissivity engineering materials according to temperature. Experiment is concerned on difficult to machine materials, which may be turned with laser assisting. Cylindrical samples made of nickel-based alloys Inconel 625, Inconel 718, Waspaloy and tungsten-carbides based on cobalt matrix were analyzed. The samples’ temperature in contact method was compared to the temperature measured by non-contact pyrometers. Based on this relative, the value of the emissivity coefficient was adjusted to the right indication of pyrometers.

  4. Determination of emissivity coefficient of heat-resistant super alloys and cemented carbide

    Science.gov (United States)

    Kieruj, Piotr; Przestacki, Damian; Chwalczuk, Tadeusz

    2016-12-01

    This paper presents the analysis of emissivity engineering materials according to temperature. Experiment is concerned on difficult to machine materials, which may be turned with laser assisting. Cylindrical samples made of nickel-based alloys Inconel 625, Inconel 718, Waspaloy and tungsten-carbides based on cobalt matrix were analyzed. The samples' temperature in contact method was compared to the temperature measured by non-contact pyrometers. Based on this relative, the value of the emissivity coefficient was adjusted to the right indication of pyrometers.

  5. High Surface Area Tungsten Carbides: Synthesis, Characterization and Catalytic Activity towards the Hydrogen Evolution Reaction in Phosphoric Acid at Elevated Temperatures

    DEFF Research Database (Denmark)

    Tomás García, Antonio Luis; Li, Qingfeng; Jensen, Jens Oluf

    2014-01-01

    Tungsten carbide powders were synthesized as a potential electrocatalyst for the hydrogen evolution reaction in phosphoric acid at elevated temperatures. With ammonium metatungstate as the precursor, two synthetic routes with and without carbon templates were investigated. Through the intermediate...... nitride route and with carbon black as template, the obtained tungsten carbide samples had higher BET area. In 100% H3PO4 at temperatures up to 185°C, the carbide powders showed superior activity towards the hydrogen evolution reaction. A deviation was found in the correlation between the BET area...

  6. Catalytic acceleration of graphitisation of amorphous carbon during synthesis of tungsten carbide from tungsten and excess amorphous carbon in a solar furnace

    Energy Technology Data Exchange (ETDEWEB)

    Shohoji, N. [Inst. Nacional de Engenharia e Tecnologia Industrial, Lisbon (Portugal); Guerra Rosa, L.; Cruz Fernandes, J. [Instituto Superior Tecnico, Departamento de Engenharia de Materiais, Av. Rovisco Pais, 1049-001, Lisbon (Portugal); Martinez, D.; Rodriguez, J. [Plataforma Solar de Almeria, Centro Europeo de Ensayos de Energia Solar, Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, P.O. Box 22, 04200, Tabernas (Spain)

    1999-03-25

    Amorphous carbon is one of the allotropes of carbon possessing carbon activity a(C) higher than that of graphite (standard state with a(C) = 1). Amorphous carbon is in a metastable state but, under normal circumstances, it takes several hours to be graphitised to an extent detectable by X-ray diffraction even at temperature higher than 1500 C. In the present work, we report the accelerated graphitisation of amorphous carbon induced apparently by the catalytic action of tungsten (W) or tungsten carbide (WC) during synthesis of WC started from W and active carbon in solar furnace under controlled atmosphere (Ar or N{sub 2}). This degree of graphitisation of amorphous carbon did not proceed by the similar reaction undertaken in the traditional laboratory furnace under the comparable conditions. (orig.) 14 refs.

  7. Effects of Implant Copper Layer on Diamond Film Deposition on Cemented Carbides

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The deposition of high-quality diamond films and their adhesion on cemented carbides are strongly influenced by the catalytic effect of cobalt under typical deposition conditions.Decreasing Co content on the surface of the cemented carbide is often used for the diamond filmdeposition. But the leaching of Co from the WC-Co substrate leading to a mechanical weak surface often causes a poor adhesion. In this paper we adopted an implant copper layer preparedby vaporization to improve the mechanical properties of the Co-leached substrate. The diamondfilms were grown by microwave plasma chemical vapor deposition from CH4 :H2 gas mixture. Thecross section and the morphology of the diamond film were characterized by scanning electronmicroscopy (SEM). The non-diamond content in the film was analyzed by Raman spectroscopy.The effects of pretreatment on the concentrations of Co and Cu near the interfacial region wereexamined by energy dispersive spectrum (EDS) equipped with SEM. The adhesion of the diamondon the substrate was evaluated with a Rockwell-type hardness tester. The results indicate that thediamond films prepared with implant copper layer have a good adhesion to the cemented carbidesubstrate due to the recovery of the mechanical properties of the Co-depleted substrate after thecopper implantation and the formation of less amorphous carbon between the substrate and thediamond film.

  8. Erosion and Corrosion Behavior of Laser Cladded Stainless Steels with Tungsten Carbide

    Science.gov (United States)

    Singh, Raghuvir; Kumar, Mukesh; Kumar, Deepak; Mishra, Suman K.

    2012-11-01

    Laser cladding of tungsten carbide (WC) on stainless steels 13Cr-4Ni and AISI 304 substrates has been performed using high power diode laser. The cladded stainless steels were characterized for microstructural changes, hardness, solid particle erosion resistance and corrosion behavior. Resistance of the clad to solid particle erosion was evaluated using alumina particles according to ASTM G76 and corrosion behavior was studied by employing the anodic polarization and open circuit potential measurement in 3.5% NaCl solution and tap water. The hardness of laser cladded AISI 304 and 13Cr-4Ni stainless steel was increased up to 815 and 725Hv100 g, respectively. The erosion resistance of the modified surface was improved significantly such that the erosion rate of cladded AISI 304 (at 114 W/mm2) was observed ~0.74 mg/cm2/h as compared to ~1.16 and 0.97 mg/cm2/h for untreated AISI 304 and 13Cr-4Ni, respectively. Laser cladding of both the stainless steels, however, reduced the corrosion resistance in both NaCl and tap water.

  9. Plasma Enhanced Chemical Vapor Deposition Nanocrystalline Tungsten Carbide Thin Film and Its Electro-catalytic Activity

    Institute of Scientific and Technical Information of China (English)

    Huajun ZHENG; Chunan MA; Jianguo HUANG; Guohua LI

    2005-01-01

    Nanocrystalline tungsten carbide thin films were fabricated on graphite substrates by plasma enhanced chemical vapor deposition (PECVD) at H2 and Ar atmosphere, using WF6 and CH4 as precursors. The crystal phase, structure and chemical components of the films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS), respectively. The results show that the film prepared at CH4/WF6concentration ratio of 20 and at 800℃ is composed of spherical particles with a diameter of 20~35 nm. Electrochemical investigations show that the electrochemical real surface area of electrode of the film is large, and the electrode of the film exhibits higher electro-catalytic activity in the reaction of methanol oxidation. The designated constant current of the film catalyst is 123.6 mA/cm2 in the mixture solution of H2SO4 and CH3OH at the concentration of 0.5 and 2.0 mol/L at 70℃, and the designated constant potential is only 0.306 V (vs SCE).

  10. The high performance of tungsten carbides/porous bamboo charcoals supported Pt catalysts for methanol electrooxidation

    Science.gov (United States)

    Ma, Chun-an; Xu, Chenbin; Shi, Meiqin; Song, Guanghui; Lang, Xiaoling

    2013-11-01

    In this paper, a kind of environmental friendly and cost-effective bamboo charcoal (BC) is used as catalyst support in DMFCs instead of carbon nanotubes (CNTs), which is toxic and expensive. After special treatments, we obtain a sponge-like three-dimensional (3D) BC, which can provide high specific surface area (1264.5 m2 g-1) and porous matrices. Then, tungsten carbide (WC) and Pt are loaded on the BCs with microwave-assisted technique and 3D structural Pt/WC/BCs electro-catalyst is finally fabricated. Subsequently, the catalyst is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In the further electrochemical investigation, it was found that Pt/WC/BCs catalyst has higher performance (2.76 mA cm-2) and better CO-tolerance for methanol oxidation compared with Pt/WC/CNTs and commercial Pt/C. Herein, we believe that the as-synthesized 3D Pt/WC/BCs catalyst has great promising application in DMFCs.

  11. Improving the Quality of Ceramic and Cemented Carbide Cutting Inserts by Diamond Grinding

    Directory of Open Access Journals (Sweden)

    Tareq Ahmad Abu Shreehah

    2005-01-01

    Full Text Available The machining of hardened steel and other difficult-to-cut materials require high quality and progressive cutting tools to meet the growing requirements for increasing productivity, improving tool life and quality of the cutting process. This study deals with an experimental investigation on the quality improvement by diamond grinding of ceramic and cemented carbide cutting inserts, comparing it with conventional batch produced types. It was found that under finish turning of hardened up to 61 HRC steel the ground cutting inserts improve the machined surface finish, reduce tool wear and breakage and subsequently extend the tool life.

  12. Thermal residual stress analysis of diamond coating on graded cemented carbides

    Institute of Scientific and Technical Information of China (English)

    HUANG Zi-qian; HE Yue-hui; CAI Hai-tao; WU Cong-hai; XIAO Yi-feng; HUANG Bai-yun

    2008-01-01

    Finite element model was developed to analyze thermal residual stress distribution of diamond coating on graded and homogeneous substrates. Graded cemented carbides were formed by carburizing pretreatment to reduce the cobalt content in the surface layer and improve adhesion of diamond coating. The numerical calculation results show that the surface compressive stress of diamond coating is 950 MPa for graded substrate and 1 250 MPa for homogenous substrate, the thermal residual stress decreases by around 24% due to diamond coating. Carburizing pretreatment is good for diamond nucleation rate, and can increase the interface strength between diamond coating and substrate.

  13. Properties of Chemically Combusted Calcium Carbide Residue and Its Influence on Cement Properties

    Directory of Open Access Journals (Sweden)

    Hongfang Sun

    2015-02-01

    Full Text Available Calcium carbide residue (CCR is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH2, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process. Thus, it is possible to use CCR as a substitute for Portland cement in concrete. In this research, we synthesized CCR and silica fume through a chemical combustion technique to produce a new reactive cementitious powder (RCP. The properties of paste and mortar in fresh and hardened states (setting time, shrinkage, and compressive strength with 5% cement replacement by RCP were evaluated. The hydration of RCP and OPC (Ordinary Portland Cement pastes was also examined through SEM (scanning electron microscope. Test results showed that in comparison to control OPC mix, the hydration products for the RCP mix took longer to formulate. The initial and final setting times were prolonged, while the drying shrinkage was significantly reduced. The compressive strength at the age of 45 days for RCP mortar mix was found to be higher than that of OPC mortar and OPC mortar with silica fume mix by 10% and 8%, respectively. Therefore, the synthesized RCP was proved to be a sustainable active cementitious powder for the strength enhanced of building materials, which will result in the diversion of significant quantities of this by-product from landfills.

  14. Modeling and Simulation of Process-Machine Interaction in Grinding of Cemented Carbide Indexable Inserts

    Directory of Open Access Journals (Sweden)

    Wei Feng

    2015-01-01

    Full Text Available Interaction of process and machine in grinding of hard and brittle materials such as cemented carbide may cause dynamic instability of the machining process resulting in machining errors and a decrease in productivity. Commonly, the process and machine tools were dealt with separately, which does not take into consideration the mutual interaction between the two subsystems and thus cannot represent the real cutting operations. This paper proposes a method of modeling and simulation to understand well the process-machine interaction in grinding process of cemented carbide indexable inserts. First, a virtual grinding wheel model is built by considering the random nature of abrasive grains and a kinematic-geometrical simulation is adopted to describe the grinding process. Then, a wheel-spindle model is simulated by means of the finite element method to represent the machine structure. The characteristic equation of the closed-loop dynamic grinding system is derived to provide a mathematic description of the process-machine interaction. Furthermore, a coupling simulation of grinding wheel-spindle deformations and grinding process force by combining both the process and machine model is developed to investigate the interaction between process and machine. This paper provides an integrated grinding model combining the machine and process models, which can be used to predict process-machine interactions in grinding process.

  15. Computer-Aided Design of Some Advanced Steels and Cemented Carbides

    Institute of Scientific and Technical Information of China (English)

    LI Lin; ZHANG Mei; HE Yan-lin; De Cooman Bruno; Wollants Patrick

    2005-01-01

    Thermodynamic and kinetic study on TRIP (transformation induced plasticity) steels, cemented carbides and mold steel for plastics were carried out in order to design modern advanced materials. With the sublattice model, equilibrium compositions of ferrite and austenite phases in TRIP steels, as well as volume fraction of austenite at inter-critical temperatures for different time were calculated. Concentration profiles of carbon, manganese, aluminum and silicon in the steels were also estimated in the lattice fixed frame of reference. The effect of Si and Mn on TRIP was discussed according to thermodynamic and kinetic analyses. In order to understand and produce the graded nanophase structure of cemented carbides, miscellaneous phases in the M-Co-C (M= Ti, Ta, Nb) systems and Co-V-C system were modeled. Solution parameters and thermodynamic properties were listed in detail. The improvement of machining behavior of prehardened mould steel for plastics was obtained by computer-aided composition design. The results showed that the matrix composition of large-section prehardened mould steel for plastic markedly influences the precipitation of non-metallic inclusion and the composition control by the aid of Thermo-Calc software package minimizes the amount of detrimental oxide inclusion. In addition, the modification of calcium was optimized in composition design.

  16. Influence of Grain Refinement on Microstructure and Mechanical Properties of Tungsten Carbide/Zirconia Nanocomposites

    Science.gov (United States)

    Nasser, Ali; Kassem, Mohamed A.; Elsayed, Ayman; Gepreel, Mohamed A.; Moniem, Ahmed A.

    2016-11-01

    WC-W2C/ZrO2 nanocomposites were synthesized by pressure-less sintering (PS) and spark plasma sintering (SPS) of tungsten carbide/yttria-stabilized tetragonal zirconia, WC/TZ-3Y. Prior to sintering, WC/TZ-3Y powders were totally ball-milled for 20 and 120 h to obtain targeted nano (N) and nano-nano (N-N) structures, indicated by transmission electron microscopy and powder x-ray diffraction (PXRD). The milled powders were processed via PS at temperatures of 1773 and 1973 K for 70 min and SPS at 1773 K for 10 min. PXRD as well as SEM-EDS indicated the formation of WC-W2C/ZrO2 composites after sintering. The mechanical properties were characterized via Vicker microhardness and nanoindentation techniques indicating enhancements for sufficiently consolidated composites with high W2C content. The effects of reducing particle sizes on phase transformation, microstructure and mechanical properties are reported. In general, the composites based on the N structure showed higher microhardness than those for N-N structure, except for the samples PS-sintered at 1773 K. For instance, after SPS at 1773 K, the N structure showed a microhardness of 18.24 GPa. Nanoindentation measurements revealed that nanoscale hardness up to 22.33 and 25.34 GPa and modulus of elasticity up to 340 and 560 GPa can be obtained for WC-W2C/ZrO2 nanocomposites synthesized by the low-cost PS at 1973 K and by SPS at 1773 K, respectively.

  17. Study on the Tribological Properties of Porous Titanium Sliding against Tungsten Carbide YG6

    Directory of Open Access Journals (Sweden)

    Zhiqiang Liu

    2017-01-01

    Full Text Available In the metal cutting process, the friction and wear behavior between the cutting tool and machined surface is the most important factor that affects the surface quality and the service life of the cutter. The irregular pore structure of porous titanium alloy has changed its mechanical properties and the processing technology. The friction and wear mechanism of the cutting tool and the machined surface is greatly different from the traditional dense metal processing because of the crumbling at the edges, tearing phenomenon and the pore agglomeration effect of chips. In this paper, the tribological characteristics and the wear mechanism of friction pair which was formed by porous titanium alloy material and hard alloy cutter were studied from cutting force, cutting speed and temperature in micro-cutting condition, and the influence of porosity on the wear rate and friction coefficient was analyzed. Results show that the main factor which influences the friction coefficient and wear rate is the porosity. The wear mechanisms of porous titanium materials were abrasive and oxidation wear while the wear mechanism of tungsten carbide YG6 was abrasive wear. The friction coefficient and wear rate of the relatively stable state are beneficial to improve the surface quality and tool life. As a result, in the micro-cutting process of porous titanium alloys, the best choice of machining parameters for different porosity materials are as follows: the load is about 8 N, the sliding speed is about 400 r/min and the temperature is about 300 °C.

  18. Influence of Grain Refinement on Microstructure and Mechanical Properties of Tungsten Carbide/Zirconia Nanocomposites

    Science.gov (United States)

    Nasser, Ali; Kassem, Mohamed A.; Elsayed, Ayman; Gepreel, Mohamed A.; Moniem, Ahmed A.

    2016-09-01

    WC-W2C/ZrO2 nanocomposites were synthesized by pressure-less sintering (PS) and spark plasma sintering (SPS) of tungsten carbide/yttria-stabilized tetragonal zirconia, WC/TZ-3Y. Prior to sintering, WC/TZ-3Y powders were totally ball-milled for 20 and 120 h to obtain targeted nano (N) and nano-nano (N-N) structures, indicated by transmission electron microscopy and powder x-ray diffraction (PXRD). The milled powders were processed via PS at temperatures of 1773 and 1973 K for 70 min and SPS at 1773 K for 10 min. PXRD as well as SEM-EDS indicated the formation of WC-W2C/ZrO2 composites after sintering. The mechanical properties were characterized via Vicker microhardness and nanoindentation techniques indicating enhancements for sufficiently consolidated composites with high W2C content. The effects of reducing particle sizes on phase transformation, microstructure and mechanical properties are reported. In general, the composites based on the N structure showed higher microhardness than those for N-N structure, except for the samples PS-sintered at 1773 K. For instance, after SPS at 1773 K, the N structure showed a microhardness of 18.24 GPa. Nanoindentation measurements revealed that nanoscale hardness up to 22.33 and 25.34 GPa and modulus of elasticity up to 340 and 560 GPa can be obtained for WC-W2C/ZrO2 nanocomposites synthesized by the low-cost PS at 1973 K and by SPS at 1773 K, respectively.

  19. Investigation of atypical molten pool dynamics in tungsten carbide-cobalt during laser deposition using in-situ thermal imaging

    Science.gov (United States)

    Xiong, Yuhong; Hofmeister, William H.; Smugeresky, John E.; Delplanque, Jean-Pierre; Schoenung, Julie M.

    2012-01-01

    An atypical "swirling" phenomenon observed during the laser deposition of tungsten carbide-cobalt cermets by laser engineered net shaping (LENS®) was studied using in-situ high-speed thermal imaging. To provide fundamental insight into this phenomenon, the thermal behavior of pure cobalt during LENS was also investigated for comparison. Several factors were considered as the possible source of the observed differences. Of those, phase difference, material emissivity, momentum transfer, and free surface disruption from the powder jets, and, to a lesser extent, Marangoni convection were identified as the relevant mechanisms.

  20. Investigation of atypical molten pool dynamics in tungsten carbide-cobalt during laser deposition using in-situ thermal imaging

    Energy Technology Data Exchange (ETDEWEB)

    Xiong Yuhong; Schoenung, Julie M. [Department of Chemical Engineering and Materials Science, University of California, Davis, California 95616 (United States); Hofmeister, William H. [Center for Laser Applications, University of Tennessee Space Institute, Tullahoma, Tennessee 37388 (United States); Smugeresky, John E. [Sandia National Laboratories, Livermore, California 94551 (United States); Delplanque, Jean-Pierre [Department of Mechanical and Aerospace Engineering, University of California, Davis, California 95616 (United States)

    2012-01-16

    An atypical ''swirling'' phenomenon observed during the laser deposition of tungsten carbide-cobalt cermets by laser engineered net shaping (LENS) was studied using in-situ high-speed thermal imaging. To provide fundamental insight into this phenomenon, the thermal behavior of pure cobalt during LENS was also investigated for comparison. Several factors were considered as the possible source of the observed differences. Of those, phase difference, material emissivity, momentum transfer, and free surface disruption from the powder jets, and, to a lesser extent, Marangoni convection were identified as the relevant mechanisms.

  1. Permanent Electron Electric Dipole Moment Search in the X^3Δ_1 Ground State of Tungsten Carbide Molecules

    Science.gov (United States)

    Lee, Jeongwon; Chen, Jinhai; Leanhardt, Aaron

    2011-06-01

    We are developing an experiment to search for the permanent electric dipole moment (EDM) of the electron using the valence electrons in the X^3Δ_1 ground state of Tungsten Carbide (WC) molecules. Currently, we are detecting the molecules by Laser Induced Fluorescence spectroscopy at ˜75cm downstream of a pulsed ablation beam source. We have a detection rate of ˜10 182W12C molecules/second in X^3Δ_1, v"=0, J"=1 state with geometric detection efficiency of 0.004. A continuous WC molecular beam is under development. Additionally, preliminary measurements of the 183W12C hyperfine structure will be presented.

  2. Size-dependent effects of tungsten carbide-cobalt particles on oxygen radical production and activation of cell signaling pathways in murine epidermal cells.

    Science.gov (United States)

    Ding, M; Kisin, E R; Zhao, J; Bowman, L; Lu, Y; Jiang, B; Leonard, S; Vallyathan, V; Castranova, V; Murray, A R; Fadeel, B; Shvedova, A A

    2009-12-15

    Hard metal or cemented carbide consists of a mixture of tungsten carbide (WC) (85%) and metallic cobalt (Co) (5-15%). WC-Co is considered to be potentially carcinogenic to humans. However, no comparison of the adverse effects of nano-sized WC-Co particles is available to date. In the present study, we compared the ability of nano- and fine-sized WC-Co particles to form free radicals and propensity to activate the transcription factors, AP-1 and NF-kappaB, along with stimulation of mitogen-activated protein kinase (MAPK) signaling pathways in a mouse epidermal cell line (JB6 P(+)). Our results demonstrated that nano-WC-Co generated a higher level of hydroxyl radicals, induced greater oxidative stress, as evidenced by a decrease of GSH levels, and caused faster JB6 P(+) cell growth/proliferation than observed after exposure of cells to fine WC-Co. In addition, nano-WC-Co activated AP-1 and NF-kappaB more efficiently in JB6(+/+) cells as compared to fine WC-Co. Experiments using AP-1-luciferase reporter transgenic mice confirmed the activation of AP-1 by nano-WC-Co. Nano- and fine-sized WC-Co particles also stimulated MAPKs, including ERKs, p38, and JNKs with significantly higher potency of nano-WC-Co. Finally, co-incubation of the JB6(+/+) cells with N-acetyl-cysteine decreased AP-1 activation and phosphorylation of ERKs, p38 kinase, and JNKs, thus suggesting that oxidative stress is involved in WC-Co-induced toxicity and AP-1 activation.

  3. Phase Analysis of Cemented Carbide WC—Co Boronised with Yttrium

    Institute of Scientific and Technical Information of China (English)

    刘寿荣; 郝建民; 等

    2002-01-01

    Phase analysis for the coated surface with B4Cand Y2O3of cemented carbide WC-20Co in vacuum-heating was carried out by high-temperature X-ray diffraction from ambient temperature to 1300℃,The results show that,the high-concentration active boron atoms are released from the boron-supply agent B4Clocated on the alloy surface and diffused into the γphase,leading to forming the three-element boron-bearing compound W2Co21B6beside forming boron-bearins compounds on the blank surface.By contrast with boronising only,the element yttrium in boronization broadens the boronising temperature range during vacuum-sistering,catalyzes the decarbonisation decomposition of B4C and promotes diffusion of active boron atoms into the bulk of WC-Co.

  4. Phase Analysis of Cemented Carbide WC-Co Boronised with Yttrium

    Institute of Scientific and Technical Information of China (English)

    刘寿荣; 郝建民; 褚连青; 宋俊亭

    2002-01-01

    Phase analysis for the coated surface with B4C and Y2O3 of cemented carbid e WC-20Co in vacuum-heating was carried out by high-temperature X-ray diffra ction from ambient temperature to 1300 ℃. The results show that, the high-conc entration active boron atoms are released from the boron-supply agent B4C loc ated on the alloy surface and diffused into the γ-phase, leading to forming th e three-element boron-bearing compound W2Co21B6 beside forming boron -bearing compounds on the blank surface. By contrast with boronising only, the element yttrium in boronization broadens the boronising temperature range during vacuum-sintering, catalyzes the decarbonisation decomposition of B4C and prom otes diffusion of active boron atoms into the bulk of WC-Co.

  5. The effect of vanadium-carbon monolayer on the adsorption of tungsten and carbon atoms on tungsten-carbide (0001 surface

    Directory of Open Access Journals (Sweden)

    Moitra A.

    2011-01-01

    Full Text Available We report a first-principles calculations to study the effect of a vanadium-carbon (VC monolayer on the adsorption process of tungsten (W and carbon (C atoms onto tungsten-carbide (WC (0001 surface. The essential configuration for the study is a supercell of hexagonal WC with a (0001 surface. When adding the VC monolayer, we employed the lowest energy configuration by examining various configurations. The total energy of the system is computed as a function of the W or C adatoms’ height from the surface. The adsorption of a W and C adatom on a clean WC (0001 surface is compared with that of a W and C adatom on a WC (0001 surface with VC monolayer. The calculations show that the adsorption energy increased for both W and C adatoms in presence of the VC monolayer. Our results provide a fundamental understanding that can explain the experimentally observed phenomena of inhibited grain growth during sintering of WC or WC-Co powders in presence of VC.

  6. PLD deposition of tungsten carbide contact for diamond photodiodes. Influence of process conditions on electronic and chemical aspects

    Science.gov (United States)

    Cappelli, E.; Bellucci, A.; Orlando, S.; Trucchi, D. M.; Mezzi, A.; Valentini, V.

    2013-08-01

    Tungsten carbide, WC, contacts behave as very reliable Schottky contacts for opto-electronic diamond devices. Diamond is characterized by superior properties in high-power, high frequency and high-temperature applications, provided that thermally stable electrode contacts will be realized. Ohmic contacts can be easily achieved by using carbide-forming metals, while is difficult to get stable Schottky contacts at elevated temperatures, due to the interface reaction and/or inter-diffusion between metals and diamond. Novel type of contacts, made of tungsten carbide, WC, seem to be the best solution, for their excellent thermal stability, high melting point, oxidation and radiation resistance and good electrical conductivity. Our research was aimed at using pulsed laser deposition for WC thin film deposition, optimizing experimental parameters, to obtain a final device characterized by excellent electronic properties, as a detector for radiation in deep UV or as X-ray dosimeter. We deposited our films by laser ablation from a target of pure WC, using different reaction conditions (i.e., substrate heating, vacuum or reactive atmosphere (CH4/Ar), RF plasma activated), to optimize both the stoichiometry of the film and its structure. Trying to obtain a material with the best electronic response, we used also two sources of laser radiation for target ablation, i.e., nano-second pulsed excimer laser ArF, and ultra-short fs Ti:Sapphire laser. The structure and chemical aspects have been evaluated by Raman and X-ray photoelectron spectroscopy (XPS), while the dosimeter photodiode response has been tested by the I-V measurements, under soft X-ray irradiation.

  7. PLD deposition of tungsten carbide contact for diamond photodiodes. Influence of process conditions on electronic and chemical aspects

    Energy Technology Data Exchange (ETDEWEB)

    Cappelli, E., E-mail: emilia.cappelli@imip.cnr.it [CNR-IMIP, Montelibretti, via Salaria Km 29.3, P.O.B. 10, 00016 Rome (Italy); Bellucci, A. [CNR-IMIP, Montelibretti, via Salaria Km 29.3, P.O.B. 10, 00016 Rome (Italy); Orlando, S. [CNR-IMIP sez. Potenza, 85050 Tito Scalo, Potenza (Italy); Trucchi, D.M. [CNR-IMIP, Montelibretti, via Salaria Km 29.3, P.O.B. 10, 00016 Rome (Italy); Mezzi, A. [CNR-ISMN, Montelibretti, via Salaria Km 29.3, P.O.B. 10, 00016 Rome (Italy); Valentini, V. [CNR-IMIP, Montelibretti, via Salaria Km 29.3, P.O.B. 10, 00016 Rome (Italy)

    2013-08-01

    Tungsten carbide, WC, contacts behave as very reliable Schottky contacts for opto-electronic diamond devices. Diamond is characterized by superior properties in high-power, high frequency and high-temperature applications, provided that thermally stable electrode contacts will be realized. Ohmic contacts can be easily achieved by using carbide-forming metals, while is difficult to get stable Schottky contacts at elevated temperatures, due to the interface reaction and/or inter-diffusion between metals and diamond. Novel type of contacts, made of tungsten carbide, WC, seem to be the best solution, for their excellent thermal stability, high melting point, oxidation and radiation resistance and good electrical conductivity. Our research was aimed at using pulsed laser deposition for WC thin film deposition, optimizing experimental parameters, to obtain a final device characterized by excellent electronic properties, as a detector for radiation in deep UV or as X-ray dosimeter. We deposited our films by laser ablation from a target of pure WC, using different reaction conditions (i.e., substrate heating, vacuum or reactive atmosphere (CH{sub 4}/Ar), RF plasma activated), to optimize both the stoichiometry of the film and its structure. Trying to obtain a material with the best electronic response, we used also two sources of laser radiation for target ablation, i.e., nano-second pulsed excimer laser ArF, and ultra-short fs Ti:Sapphire laser. The structure and chemical aspects have been evaluated by Raman and X-ray photoelectron spectroscopy (XPS), while the dosimeter photodiode response has been tested by the I–V measurements, under soft X-ray irradiation.

  8. 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.

  9. 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.

    2016-12-01

    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.

  10. Cementing Material From Rice Husk-Broken Bricks-Spent Bleaching Earth-Dried Calcium Carbide Residue

    Directory of Open Access Journals (Sweden)

    Muthengia Jackson Washira

    2012-10-01

    Full Text Available A cementious material, coded CSBR (Carbide residue Spent bleaching earth Broken bricks and Rice husks, was made from dried calcium carbide residue (DCCR and an incinerated mix of rice husks (RH, broken bricks (BB and spent bleaching earth (SBE. Another material, coded SBR (Spent bleaching earth Broken bricks and Rice husk ash, was made from mixing separately incinerated RH, SBE and ground BB in the same ash ratio as in CSBR. When CSBR was inter-ground with Ordinary Portland Cement (OPC, it showed a continued decrease in Ca(OH2 in the hydrating cement as a function of curing time and replacement levels of the cement. Up to 45 % replacement of the OPC by CSBR produced a Portland pozzolana cement (PPC material that passed the relevant Kenyan Standard. Incorporation of the CSBR in OPC reduces the resultant calcium hydroxide from hydrating Portland cement. The use of the waste materials in production of cementitious material would rid the environment of wastes and lead to production of low cost cementitious material.

  11. Study on Interface Structure and Bond Properties between Cemented Carbide and Tool Steel Blazing with amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    Bao Ming-dong; Xu Jin-fu; Xu Xue-bo; Zou Gui-sheng; Huang Geng-hua

    2004-01-01

    Cemented Carbide YG11C and Tool Steel Crl2MoV was blazed with Ni-base amorphous alloys, QG-1011,MBF-20 and MBF-75, using dynamics thermodynamics analogue testing machine Gleeble 1500D. The effects of brazing temperature, holding time and holding pressure on micro-structure and bond strength were investigated. Results showed that YG11C and Cr12MoV were all wetted well by these three Ni-base alloys, and the bond strength was as high as 220MPa,320MPa, 320MPa respectively. When the blazing temperature was at the point over the melting point 60-70℃ of Ni-base alloy, the holding time was about 2-10min, the suitable pressure was benefit for improving the brazing quality.Microanalysis showed Co in cemented carbide diffused into liquid brazing alloy and formed the Fe-Co solid .solution.

  12. Finite element analysis of thermal residual stresses at cemented carbide rock drill buttons with cobalt-gradient structure

    Institute of Scientific and Technical Information of China (English)

    HUANG Zi-qian; HE Yue-hui; CAI Hai-tao; XIAO Yi-feng; HUANG Bai-yun

    2008-01-01

    The aim of this study is to apply the concept of functionally graded materials (FGMs) to cemented carbides and to develop high-performance rock drill buttons.Cobalt-gradient structure was introduced to the surface zone of the buttons by carburizing process.Finite element method and XRD measurement were used to decide the distribution of thermal residual stress.Constitutive parameters were determined by constraint factor.Numerical results show that residual stresses of gradient buttons mainly concentrate in cobalt-gradient zone.There is compressive stress in the surface zone and tensile stress in the cobalt-rich zone.The maximum value of surface compressive stress is 180 MPa for WC-6Co cemented carbides.And the numerical results agree with the results of XRD measurement.

  13. In situ thermal imaging and three-dimensional finite element modeling of tungsten carbide-cobalt during laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Xiong Yuhong [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States); Hofmeister, William H. [Center for Laser Applications, University of Tennessee Space Institute, Tullahoma, TN 37388 (United States); Cheng Zhao [Earth Mechanics Inc., Oakland, CA 94621 (United States); Smugeresky, John E. [Sandia National Laboratories, Livermore, CA 94551 (United States); Lavernia, Enrique J. [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States); Schoenung, Julie M., E-mail: jmschoenung@ucdavis.edu [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States)

    2009-10-15

    Laser deposition is being used for the fabrication of net shapes from a broad range of materials, including tungsten carbide-cobalt (WC-Co) cermets (composites composed of a metallic phase and a hard refractory phase). During deposition, an unusual thermal condition is created for cermets, resulting in rather complex microstructures. To provide a fundamental insight into the evolution of such microstructures, we studied the thermal behavior of WC-Co cermets during laser deposition involving complementary results from in situ high-speed thermal imaging and three-dimensional finite element modeling. The former allowed for the characterization of temperature gradients and cooling rates in the vicinity of the molten pool, whereas the latter allowed for simulation of the entire sample. By combining the two methods, a more robust analysis of the thermal behavior was achieved. The model and the imaging results correlate well with each other and with the alternating sublayers observed in the microstructure.

  14. Photons transport through ultra-high molecular weight polyethylene based composite containing tungsten and boron carbide fillers

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, S.M. [National Research Center “Kurchatov Institute”, Moscow 123182 (Russian Federation); Kuznetsov, S.A. [Russian State Technological University “MATI”, Moscow 121552 (Russian Federation); Volkov, A.E.; Terekhin, P.N.; Dmitriev, S.V. [National Research Center “Kurchatov Institute”, Moscow 123182 (Russian Federation); Tcherdyntsev, V.V.; Gorshenkov, M.V. [National University of Science and Technology “MISIS”, Moscow 119049 (Russian Federation); Boykov, A.A., E-mail: kink03@gmail.com [National University of Science and Technology “MISIS”, Moscow 119049 (Russian Federation)

    2014-02-15

    Highlights: • The developed method for predicting X-ray properties of the polymer. • Higher content of the fillers results in an increase of mechanical properties. • X-ray defensive properties of the samples were investigated experimentally. -- Abstract: Polymers are a base for creating of composite materials with high mechanical and chemical properties. Using the heavy metals as filler in these composites can give them X-ray protective properties. These materials have high deactivation rates and can be used to create Personal Protective Equipment (PPE) used in aggressive environments. It was proposed a model for calculation of X-ray protection properties of the polymer-based nanocomposite materials with ultra-high molecular weight polyethylene (UHMWPE) matrix, filled with tungsten and boron carbide particles. X-ray protective properties were calculated in a wide range of filler content using the developed model. Results of calculations allow selecting most effective compounds of X-ray protective UHMWPE based composites.

  15. Role of Silicon Carbide in Phase-Evolution and Oxidation Behaviors of Pulse Electrodeposited Nickel-Tungsten Coating

    Science.gov (United States)

    Sribalaji, M.; Asiq Rahman, O. S.; Arun Kumar, P.; Suresh Babu, K.; Wasekar, Nitin P.; Sundararajan, G.; Keshri, Anup Kumar

    2017-01-01

    Silicon carbide (SiC) was reinforced in the pulse electrodeposited nickel-tungsten (Ni-W) coatings deposited on the steel substrate, and isothermal oxidation test was performed at 1273 K (1000 °C) for 24 hours. Addition of just 2 vol pct of SiC showed 26 pct increase in the relative oxidation resistance of Ni-W coating. The increased oxidation resistance was attributed to the phase evolution (SiO2, Cr2O3, CrSi2, Ni2SiO4, Cr7C3, Cr3C2, and Cr3Si), which suppressed the spallation of the oxide scale in Ni-W-2 vol pct SiC. The presence of Fe2O3 phase in the oxidized Ni-W coating was mainly responsible for the major multiple spallations at the interface and in the bulk, which resulted in the degradation of oxidation resistance.

  16. Bias-magnetron sputtering of tungsten carbide coatings on steel; Bias-Magnetron Sputtern von Wolframkarbid-Schichten auf Stahl

    Energy Technology Data Exchange (ETDEWEB)

    Gubisch, M.; Spiess, L.; Romanus, H.; Schawohl, J.; Knedlik, C. [Technische Universitaet Ilmenau, Institut fuer Werkstofftechnik/ Zentrum fuer Mikro- und Nanotechnologien (ZMN), Ilmenau (Germany)

    2004-11-01

    The influence of bias voltage between 0 V to -800 V on the properties of dc and rf magnetron sputtered tungsten carbide coatings with 1 {mu}m thickness on cold work steel 90MnCrV8 were determined. The coatings were analysed with SEM, AFM, EDX, XRD and micro hardness tester. The morphology, the chemical composition, the phase transformation and the hardness of the deposited layers were appropriated. Non-stoechiometric cubic phase of tungsten carbide WC{sub 1-x} with <100> preferred orientation formed by non reactive magnetron sputtering without ion bombardment. Chemical composition, crystallinity, preferred orientation, morphology and phases are influence by variation of bias voltage. These changes in coating properties results in significant variation of hardness between 8 GPa and 20 GPa. (Abstract Copyright [2004], Wiley Periodicals, Inc.) [German] In dieser Arbeit wird der Einfluss der Biasspannung im Bereich von 0 V bis -800 V auf die Eigenschaften von 1 {mu}m dicken DC und RF Magnetron gesputterten Wolframkarbidschichten auf niedriglegierten Kaltarbeitsstahl 90MnCrV8 untersucht. Die Schichten wurden mittels REM, EDX, AFM, Universalhaertepruefgeraet und XRD hinsichtlich der wichtigsten Schichteigenschaften wie Morphologie, Phasenausbildung, Vorzugsorientierung, Universalhaerte und chemischer Zusammensetzung charakterisiert. Ohne zusaetzlichen Ionenbeschuss bildet sich beim nichtreaktiven Magnetron Sputtern die nicht stoechiometrische kubische Phase des Wolframkarbids WC{sub 1-x} mit einer <100>-Orientierung aus. In Abhaengigkeit der Biasspannung wird die chemischen Zusammensetzung, Kristallinitaet, Vorzugsorientierung, Morphologie und die Phasenausbildung beeinflusst. Die Veraenderungen der genannten Schichteigenschaften fuehrten zu signifikanten Haerteaenderungen im Bereich von 8 GPa und 20 GPa. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

  17. Interaction of cerium and calcium-enriched phase in the preparation process of YG6 cemented carbide%铈与YG6硬质合金制备过程中富钙相的交互作用

    Institute of Scientific and Technical Information of China (English)

    何文; 谭敦强; 朱红波; 邝海; 欧阳国霞

    2016-01-01

    在硬质合金的原材料仲钨酸铵(APT)粉末中添加Ca和稀土Ce元素,探讨稀土Ce元素与硬质合金制备过程中富钙相的交互作用。材料的物相组成、显微结构及成分分别通过X射线衍射仪、扫描电子显微镜及能谱进行检测与分析。结果表明:氧化钨还原过程中会产生CaWO4和Ca4.26W10O30两种富钙相,分布在钨颗粒内部和周围,使钨颗粒的棱角钝化,碳化后富钙相转变为Ca4.26W10O30和CaC2相,富钙相可急剧降低YG6硬质合金的性能;添加适量稀土Ce可降低富钙相对钨粉的影响,钨粉颗粒的棱角变得明显,颗粒尺寸变小且分布均匀,稀土Ce与富钙相发生反应生成Ce0.9Ca0.1O1.9三元相;稀土Ce与富钙相的交互作用效果显著,与1% Ca-YG6硬质合金相比,1% Ce+1% Ca-YG6硬质合金的致密度、硬度和断裂韧性分别提高了7.8%,34.3%和67.8%。%The elements of Ca and rare earth Ce were added in APT powder. The interaction of rare earth element Ce with calcium-enriched phase was discussed during the preparation process of cemented carbide. The phase composition, microstructure and element distribution were tested by using X-ray diffractometer, scanning electron microscope and energy disperse spectroscopy, respectively. The results show that two kinds of calcium-enriched phases, CaWO4 and Ca4.26W10O30, are generated in the process of reducing tungsten oxide, which passivate tungsten particles. After carburization, calcium-enriched phases transform into the Ca4.26W10O30 and CaC2 phases. Calcium-enriched phases can sharply reduce the property of YG6 cemented carbide. Adding a moderate amount of rare earth Ce can decrease the influence of calcium-enriched phases on tungsten particles. The edges and corners of tungsten particles become more obvious, and the particle size of tungsten powders becomes smaller and uniform. During carburization process, rare earth Ce reacts with calcium-enriched phase and forms

  18. Analysis of tungsten carbide coatings by infrared laser-induced argon spark with inductively coupled plasma atomic emission spectrometry

    Science.gov (United States)

    Kanický, V.; Otruba, V.; Mermet, J.-M.

    2000-10-01

    Infrared laser ablation was studied for application to the analysis of plasma-sprayed tungsten carbide/cobalt coatings. The potential of the laser induced argon-spark (LINA-Spark™), as a sample introduction device in inductively coupled plasma atomic emission spectrometry was studied. The use of an IR laser along with defocusing led to laser-induced microplasma-based ablation. The mass ablation rate, represented by the ICP emission intensity per laser beam unit area, exhibited a flat increase in the irradiance range 2-250 GW/cm 2. A low slope (0.5) of this dependence in log-log scale gave evidence of plasma shielding. The steep increase in the measured acoustic signal when focused in front of the sample, i.e. in argon, indicated a breakdown of argon. Consequently, considerably lower ICP emissions were observed within the same range of irradiance. The cobalt/tungsten line intensity ratio in the ICP was practically constant from 1.5 up to at least 250 GW/cm 2. Acceptable precision (R.S.D.<5%) was obtained without internal standardization for irradiance between 2 and 8 GW/cm 2. Optimization of the laser pulse energy, repetition rate, beam focusing and sample displacement during interaction led to the linearization of dependences of signal vs. cobalt percentage, at least up to the highest studied value of 23% Co.

  19. A novel technique for production of nano-crystalline mono tungsten carbide single phase via mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Razavi, Mansour, E-mail: m-razavi@merc.ac.ir [Materials and Energy Research Center (MERC), P.O. Box 14155-4777, Tehran (Iran, Islamic Republic of); Rahimipour, Mohammad Reza; Yazdani-Rad, Rahim [Materials and Energy Research Center (MERC), P.O. Box 14155-4777, Tehran (Iran, Islamic Republic of)

    2011-06-09

    Highlights: > By adding WC to mixture of tungsten and carbon black unlike the system which does not contain any additive, it can lead to synthesized mono carbide tungsten. > However, the synthesize time has been reduced significantly. > Crystalline size of two systems were in nano-meter scale, this amount in system contain primary WC which was smaller than system without WC. - Abstract: Due to simultaneous synthesis of WC and W{sub 2}C phases in most of the synthesis processes and lower mechanical properties of W{sub 2}C than WC, in this work the possibility of production of nano-crystalline WC single phase as a useful refractory ceramic by means of mechanical alloying has been investigated. The raw materials containing W and C with WC were milled in a planetary ball mill. The sampling has been done in different times. As it was expected, XRD studies showed that after 75 h of milling the WC with W{sub 2}C were produced. By adding WC to the raw materials in the beginning of the process it led to the fact that after 50 h of milling WC was synthesized only without any other phases which remained stable at the higher times while milling. During broadening of XRD peaks, the size of synthesized crystalline WC was estimated in the order of nano-meter. Crystalline size and mean strain of synthesized WC in the system without additive were higher and lower than the system containing WC, respectively.

  20. Measurements of nanoparticle size distribution produced by laser ablation of tungsten and boron-carbide in N 2 ambient

    Science.gov (United States)

    Bereznai, Miklós; Heszler, Péter; Tóth, Zsolt; Wilhelmsson, Ola; Boman, Mats

    2006-04-01

    Nanoparticles (NPs) were produced by ablating tungsten and boron-carbide (B 4C) target materials in atmospheric pressure nitrogen ambient using ArF excimer laser pulses. The size distributions of the NPs formed during the ablation were monitored—within a 7-133 nm size window—by a condensation particle counter connected to a differential mobility analyzer. The laser repetition rate was varied between 1-50 Hz, and the fluence was systematically changed in the range of 0.5-15 J/cm 2, for both materials, allowing a comparative study in an extended laser parameter regime. The multishot ablation threshold ( Φth) of B 4C was determined to be ˜1.9 J/cm 2 for the laser used (ArF excimer, λ = 193 nm). Similarly to earlier studies, it was shown that the size distributions consist of mainly small nanoparticles (<˜20 nm) attributed to a non-thermal ablation mechanism below Φth. An additional broad peak appears (between 20 and 40 nm) above Φth as a consequence of the thermally induced macroscopic ablation. Chemical composition of deposited polydisperse nanoparticles was studied by X-ray photoelectron spectroscopy showing nitrogen incorporation into the boron-carbide.

  1. Comparative evaluation of particle properties, formation of reactive oxygen species and genotoxic potential of tungsten carbide based nanoparticles in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Kuehnel, Dana, E-mail: dana.kuehnel@ufz.de [Department of Bioanalytical Ecotoxicology, Helmholtz-Centre for Environmental Research Leipzig - UFZ, Permoserstr. 15, 04318 Leipzig (Germany); Scheffler, Katja [Department of Bioanalytical Ecotoxicology, Helmholtz-Centre for Environmental Research Leipzig - UFZ, Permoserstr. 15, 04318 Leipzig (Germany); Department of Cell Techniques and Applied Stem Cell Biology, University of Leipzig, Deutscher Platz 5, 04103 Leipzig (Germany); Wellner, Peggy [Department of Bioanalytical Ecotoxicology, Helmholtz-Centre for Environmental Research Leipzig - UFZ, Permoserstr. 15, 04318 Leipzig (Germany); Meissner, Tobias; Potthoff, Annegret [Fraunhofer-Institute for Ceramic Technologies and Systems (IKTS), Winterbergstr. 28, 01277 Dresden (Germany); Busch, Wibke [Department of Bioanalytical Ecotoxicology, Helmholtz-Centre for Environmental Research Leipzig - UFZ, Permoserstr. 15, 04318 Leipzig (Germany); Springer, Armin [Centre for Translational Bone, Cartilage and Soft Tissue Research, University Hospital Carl Gustav Carus, Technical University Dresden, Fetscherstrasse 74, 01307 Dresden (Germany); Schirmer, Kristin [Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Duebendorf (Switzerland); EPF Lausanne, School of Architecture, Civil and Environmental Engineering, 1015 Lausanne (Switzerland); ETH Zuerich, Institute of Biogeochemistry and Pollutant Dynamics, 8092 Zuerich (Switzerland)

    2012-08-15

    Highlights: Black-Right-Pointing-Pointer Assessment of toxic potential of tungsten carbide-based nanoparticles. Black-Right-Pointing-Pointer Evaluation of ROS and micronuclei induction of three hard metal nanomaterials. Black-Right-Pointing-Pointer Dependency of observed toxic effects on the materials physical-chemical properties. Black-Right-Pointing-Pointer Differences in several particle properties seem to modulate the biological response. - Abstract: Tungsten carbide (WC) and cobalt (Co) are constituents of hard metals and are used for the production of extremely hard tools. Previous studies have identified greater cytotoxic potential of WC-based nanoparticles if particles contained Co. The aim of this study was to investigate whether the formation of reactive oxygen species (ROS) and micronuclei would help explain the impact on cultured mammalian cells by three different tungsten-based nanoparticles (WC{sub S}, WC{sub L}, WC{sub L}-Co (S: small; L: large)). The selection of particles allowed us to study the influence of particle properties, e.g. surface area, and the presence of Co on the toxicological results. WC{sub S} and WC{sub L}/WC{sub L}-Co differed in their crystalline structure and surface area, whereas WC{sub S}/WC{sub L} and WC{sub L}-Co differed in their cobalt content. WC{sub L} and WC{sub L}-Co showed neither a genotoxic potential nor ROS induction. Contrary to that, WC{sub S} nanoparticles induced the formation of both ROS and micronuclei. CoCl{sub 2} was tested in relevant concentrations and induced no ROS formation, but increased the rate of micronuclei at concentrations exceeding those present in WC{sub L}-Co. In conclusion, ROS and micronuclei formation could not be associated with the presence of Co in the WC-based particles. The contrasting responses elicited by WC{sub S} vs. WC{sub L} appear to be due to large differences in crystalline structure.

  2. Comparison of Tungsten and Molybdenum Carbide Catalysts for the Hydrodeoxygenation of Oleic Acid

    NARCIS (Netherlands)

    Hollak, S.A.W.; Gosselink, R.J.A.; Es, van D.S.; Bitter, J.H.

    2013-01-01

    Group 6 (W, Mo) metal carbide catalysts are promising alternatives to hydrodesulfurization (NiMo, CoMo) catalysts and group 10 (Pd) type catalysts in the deoxygenation of vegetable fats/oils. Herein, we report a comparison of carbon nanofiber-supported W2C and Mo2C catalysts on activity, selectivity

  3. Alloying the X40CrMoV5-1 steel surface layer with tungsten carbide by the use of a high power diode laser

    Energy Technology Data Exchange (ETDEWEB)

    Dobrzanski, L.A. [Institute of Engineering Materials and Biomaterials, Silesian University of Technology, 44-100 Gliwice, Konarskiego St. 18A (Poland); Bonek, M. [Institute of Engineering Materials and Biomaterials, Silesian University of Technology, 44-100 Gliwice, Konarskiego St. 18A (Poland)]. E-mail: mb@zmn.mt.polsl.gliwice.pl; Hajduczek, E. [Institute of Engineering Materials and Biomaterials, Silesian University of Technology, 44-100 Gliwice, Konarskiego St. 18A (Poland); Klimpel, A. [Welding Department, Silesian University of Technology, 44-100 Gliwice, Konarskiego St. 18A (Poland)

    2005-07-15

    The paper presents the effect of alloying with tungsten carbide on properties of the X40CrMoV5-1 steel surface layer, using the high power diode laser (HPDL). Selection of laser operating conditions is discussed, as well as thickness of the alloying layer, and their influence on structure and chemical composition of the steel. Analysis of the influence of the process conditions on the thicknesses of the alloyed layer and heat-affected zone is presented.

  4. Alloying the X40CrMoV5-1 steel surface layer with tungsten carbide by the use of a high power diode laser

    Science.gov (United States)

    Dobrzański, L. A.; Bonek, M.; Hajduczek, E.; Klimpel, A.

    2005-07-01

    The paper presents the effect of alloying with tungsten carbide on properties of the X40CrMoV5-1 steel surface layer, using the high power diode laser (HPDL). Selection of laser operating conditions is discussed, as well as thickness of the alloying layer, and their influence on structure and chemical composition of the steel. Analysis of the influence of the process conditions on the thicknesses of the alloyed layer and heat-affected zone is presented.

  5. Friction of tungsten carbide-cobalt coatings obtained by means of plasma spraying

    Energy Technology Data Exchange (ETDEWEB)

    Cartier, M. (Hydromecanique et Frottement, Centre de Recherches, 42 - Andreziux-Boutheon (France)); McDonnell, L.; Cashell, E.M. (CRTC, Cork (Ireland))

    1991-11-29

    A study of the frictional properties of WC-Co-type coatings obtained by plasma spraying was carried out, the influence of the majority of the parameters involved in atmospheric spraying being analysed. This study of the correlations between the tribological behaviour and the compositionl of the coatings shows that friction is mainly determined by the method and degree of decomposition of the carbides. These in turn are linked to the effects of heat and/or oxidation, factors which can change considerably, not only as a function of the method used (plasma power, nature and flow rate of the plasma gases etc.) but also as a function of the coating process and the composition of the original powders. It has been possible to correlate the improvement in the frictional properties (resistance to seizure, reduction in the coefficient of friction) with the presence of free carbon in the coatings, associated with the carbide decomposition process. (orig.).

  6. Microstructures and dissolution of carbides occurring during the laser cladding of steel with tungsten carbide reinforced Ni- and Co-hard-alloys; Gefuegeausbildung und Karbidaufloesung beim Laserbeschichten von Stahl mit Wolframkarbid-verstaerkten Ni- und Co-Hartlegierungen

    Energy Technology Data Exchange (ETDEWEB)

    Luft, A. [Fraunhofer-Inst. fuer Werkstoffphysik und Schichttechnologie, Dresden (Germany); Techel, A. [Fraunhofer-Inst. fuer Werkstoffphysik und Schichttechnologie, Dresden (Germany); Nowotny, S. [Fraunhofer-Inst. fuer Werkstoffphysik und Schichttechnologie, Dresden (Germany); Reitzenstein, W. [Fraunhofer-Inst. fuer Werkstoffphysik und Schichttechnologie, Dresden (Germany)

    1995-05-01

    Wear resistant layers on steel were produced by laser cladding of powder mixtures consisting of a Ni- or Co-base hard alloy and coarse grained WC or fused tungsten carbide, respectively. The microstructure of the clad composite layers were investigated by metallography, SEM, EDX and image analysis. The four binder/carbide systems were found to differ strongly in the degree of partial carbide dissolution and the formation of new hard phases. (orig.) [Deutsch] Verschleissfeste Schutzschichten auf Stahl werden durch Laserbeschichten mit Pulvergemischen aus einer Ni- bzw. Co-Hartlegierung und grobkoernigem WC bzw. Wolframschmelzkarbid hergestellt. Die erzeugten Dispersionsgefuege werden mittels Metallographie, REM, EDX und Bildanalyse untersucht. Der Vergleich der vier Schichtsysteme liefert deutliche Unterschiede im Ausmass der Karbidaufloesung und der Bildung neuer Hartphasen. (orig.)

  7. Ablation of carbide materials with femtosecond pulses

    Science.gov (United States)

    Dumitru, Gabriel; Romano, Valerio; Weber, Heinz P.; Sentis, Marc; Marine, Wladimir

    2003-01-01

    The response of cemented tungsten carbide and of titanium carbonitride was investigated with respect to damage and ablation properties, under interaction with ultrashort laser pulses. These carbide materials present high microhardness and are of significant interest for tribological applications. The experiments were carried out in air with a commercial Ti:sapphire laser at energy densities on the target up to 6.5 J/cm 2. The irradiated target surfaces were analyzed with optical, SEM and AFM techniques and the damage and ablation threshold values were determined using the measured spot diameters and the calculated incident energy density distributions.

  8. Application of the laser spallation technique to the measurement of the adhesion strength of tungsten carbide coatings on superalloy substrates

    Energy Technology Data Exchange (ETDEWEB)

    Boustie, M.; Aoroux, E.; Romain, J.-P. [Ecole Nationale Superieure de Mecanique et d' Aerotechnique (ENSMA), 86 - Futuroscope (FR). Lab. de Combustion et de Detonique (LCD)

    2000-10-01

    High power pulsed lasers are used to induce shock waves in Hastelloy X targets coated with tungsten carbide of 70 {mu}m and 50 {mu}m thickness. In suitable irradiation conditions, a debonding of the substrate/coating interface due to the generation of tensile stresses is observed. Experimental results are analyzed with the use of numerical simulations yielding the stress history at interface and its dependence on laser pulse intensity up to 600 GW/cm{sup 2} with 1 ns and 3 ns durations under direct irradiation, and 23 ns with water confinement. As a consequence of shock decay during the propagation through the substrate, a strong variation of incident intensity results in a small variation of tensile stress. This allows an accurate determination of the debonding threshold which is found in the range of 1.0 to 1.3 GPa for short laser pulses (1 and 3 ns) and 0.5 to 0.6 GPa for long laser pulses (23 ns confined). (orig.)

  9. Application of the laser spallation technique to the measurement of the adhesion strength of tungsten carbide coatings on superalloy substrates

    Science.gov (United States)

    Boustie, M.; Auroux, E.; Romain, J.-P.

    2000-10-01

    High power pulsed lasers are used to induce shock waves in Hastelloy X targets coated with tungsten carbide of 70 μm and 50 μm thickness. In suitable irradiation conditions, a debonding of the substrate/coating interface due to the generation of tensile stresses is observed. Experimental results are analyzed with the use of numerical simulations yielding the stress history at interface and its dependence on laser pulse intensity up to 600 GW/cm2 with 1 ns and 3 ns durations under direct irradiation, and 23 ns with water confinement. As a consequence of shock decay during the propagation through the substrate, a strong variation of incident intensity results in a small variation of tensile stress. This allows an accurate determination of the debonding threshold which is found in the range of 1.0 to 1.3 GPa for short laser pulses (1 and 3 ns) and 0.5 to 0.6 GPa for long laser pulses (23 ns confined).

  10. Paste development and co-sintering test of zirconium carbide and tungsten in freeze-form extrusion fabrication

    Science.gov (United States)

    Li, Ang

    Ultra-high temperature ceramics are being investigated for future use in aerospace applications due to their superior thermo-mechanical properties, as well as oxidation resistance, at temperatures above 2000°C. However, their brittle properties make them susceptible to thermal shock failure. Components fabricated as functionally graded materials (FGMs) can combine the superior properties of ceramics with the toughness of an underlying refractory metal by fabricating graded composites. This paper discusses the grading of two materials through the use of a Freeze-form Extrusion Fabrication (FEF) system to build FGMs parts consisting of zirconium carbide (ZrC) and tungsten (W). Aqueous-based colloidal suspensions of ZrC and W were developed and utilized in the FEF process to fabricate test bars graded from 100%ZrC to 50%W-50%ZrC (volume percent). Following FEF processing the test bars were co-sintered at 2300°C and characterized to determine their resulting density and micro-structure. Four-point bending tests were performed to assess the strength of test bars made using the FEF process, compared to test bars prepared using conventional powder processing and isostatic pressing techniques, for five distinct ZrC-W compositions. Scanning electron microscopy (SEM) was used to verify the inner structure of composite parts built using the FEF process.

  11. Structural Evaluation and Mechanical Properties of Aluminum/Tungsten Carbide Composites Fabricated by Continual Annealing and Press Bonding (CAPB) Process

    Science.gov (United States)

    Amirkhanlou, Sajjad; Ketabchi, Mostafa; Parvin, Nader; Drummen, G. P. C.

    2014-12-01

    In the present work, a novel technique is introduced called continual annealing and press bonding (CAPB) for the manufacturing of a bulk aluminum matrix composite dispersed with 10 vol pct tungsten carbide particles (Al/WCp composite). The microstructural evolution and mechanical properties of the Al/WCp composite during various CAPB cycles were examined by scanning electron microscopy (SEM), wavelength dispersive X-ray spectroscopy (WDX), and tensile testing. The microstructure of the fabricated composite after fourteen cycles of CAPB showed homogenous distribution of the WC particles in the aluminum matrix and strong bonding between the various layers. According to WDX analysis, the manufactured Al/WCp composite did not evidence the presence of additional elements. The results indicated that the tensile strength of the composites increased with the number of CAPB cycles, and reached a maximum value of 140 MPa at the end of the fourteenth cycle, which was 1.6 times higher than the obtained value for annealed aluminum (raw material, 88 MPa). Even though the elongation of the Al/WCp composite was reduced during the initial cycles of CAPB process, it increased significantly during the final cycles. SEM observation of fracture surfaces showed that the rupture mode in the CAPB-processed Al/WCp composite was of the shear ductile rupture type.

  12. Mechanical and Tribological Properties of PVD-Coated Cemented Carbide as Evaluated by a New Multipass Scratch-Testing Method

    Directory of Open Access Journals (Sweden)

    M. Fallqvist

    2012-01-01

    Full Text Available A new test method based on multipass scratch testing has been developed for evaluating the mechanical and tribological properties of thin, hard coatings. The proposed test method uses a pin-on-disc tribometer and during testing a Rockwell C diamond stylus is used as the “pin” and loaded against the rotating coated sample. The influence of normal load on the number of cycles to coating damage is investigated and the resulting coating damage mechanisms are evaluated by posttest scanning electron microscopy. The present study presents the test method by evaluating the performance of Ti0.86Si0.14N, Ti0.34Al0.66N, and (Al0.7Cr0.32O3 coatings deposited by cathodic arc evaporation on cemented carbide inserts. The results show that the test method is quick, simple, and reproducible and can preferably be used to obtain relevant data concerning the fatigue, wear, chipping, and spalling characteristics of different coating-substrate composites. The test method can be used as a virtually nondestructive test and, for example, be used to evaluate the fatigue and wear resistance as well as the cohesive and adhesive interfacial strength of coated cemented carbide inserts prior to cutting tests.

  13. Microstructure and mechanical properties of titanium nitride coatings for cemented carbide cutting tools by pulsed high energy density plasma

    Institute of Scientific and Technical Information of China (English)

    PENG Zhijian; MIAO Hezhuo; QI Longhao; GONG Jianghong; YANG Size; LIU Chizi

    2003-01-01

    Hard, wear-resistant and well-adhesive titanium nitride coatings on cemented carbide cutting tools were prepared by the pulsed high energy density plasma technique at ambient temperature. The results of Auger spectra analysis indicated that the interface between the coating and substrate was more than 250 nm.Under optimized deposition conditions, the highest critical load measured by nanoscratch tester was more than 90 mN, which meant that the TiN film was well adhesive to the substrate; the highest nanohardness and Young's modulus according to nanoindentation tests were near to 27 and 450 GPa. The results of cutting tests evaluated by turning hardened CrWMn steel in industrial conditions indicated that the wear resistance and edge life of the cemented carbide tools were enhanced dramatically because of the deposition of titanium nitride coatings. These improvements were attributed to the three combined effects: the deposition and ion implantation of the pulsed plasma and the becoming finer of the grain sizes.

  14. FIB/FESEM experimental and analytical assessment of R-curve behavior of WC–Co cemented carbides

    Energy Technology Data Exchange (ETDEWEB)

    Tarragó, J.M., E-mail: jose.maria.tarrago@upc.edu [CIEFMA, Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain); CRnE, Centre de Recerca en Nanoenginyeria, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain); Jiménez-Piqué, E. [CIEFMA, Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain); CRnE, Centre de Recerca en Nanoenginyeria, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain); Schneider, L. [Sandvik Hyperion, Coventry CV4 0XG (United Kingdom); Casellas, D. [Fundació CTM Centre Tecnològic, 08243 Manresa (Spain); Torres, Y. [Departamento de Ingeniería y Ciencia de los Materiales y del Transporte, ETSI, Universidad de Sevilla, 41092 Sevilla (Spain); Llanes, L. [CIEFMA, Departament de Ciència dels Materials i Enginyeria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain); CRnE, Centre de Recerca en Nanoenginyeria, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain)

    2015-10-01

    Exceptional fracture toughness levels exhibited by WC–Co cemented carbides (hardmetals) are due mainly to toughening derived from plastic stretching of crack-bridging ductile enclaves. This takes place due to the development of a multiligament zone at the wake of cracks growing in a stable manner. As a result, hardmetals exhibit crack growth resistance (R-curve) behavior. In this work, the toughening mechanics and mechanisms of these materials are investigated by combining experimental and analytical approaches. Focused Ion Beam technique (FIB) and Field-Emission Scanning Electron Microscopy (FESEM) are implemented to obtain serial sectioning and imaging of crack–microstructure interaction in cracks arrested after stable extension under monotonic loading. The micrographs obtained provide experimental proof of the developing multiligament zone, including failure micromechanisms within individual bridging ligaments. Analytical assessment of the multiligament zone is then conducted on the basis of experimental information attained from FIB/FESEM images, and a model for the description of R-curve behavior of hardmetals is proposed. It was found that, due to the large stresses supported by the highly constrained and strongly bonded bridging ligaments, WC–Co cemented carbides exhibit quite steep but short R-curve behavior. Relevant strength and reliability attributes exhibited by hardmetals may then be rationalized on the basis of such toughening scenario.

  15. Microstructure and wear properties of tungsten carbide reinforced steel matrix composites

    Institute of Scientific and Technical Information of China (English)

    YOU Xian-qing; SONG Xue-feng; REN Hao; MA Jian-guo; HUANG Man-ping; ZHANG Cheng-jun

    2005-01-01

    WC(27%) reinforced steel matrix composites were produced by using an electroslag melting casting technique. The microstructure of the material was characterized using scanning electron microscopy(SEM), optical microscopy and X-ray diffraction(XRD). Energy dispersive spectroscopy(EDS) and transmission electron micro-scopy were performed to investigate the interfacial composition between WC particle and steel matrix. The results reveal that the WC particles are partially melted into the steel substrate. At the same time, a reaction layer was detected along with the periphery of WC particle, which significantly enhances the bonding strength of the interface. A slipping wear (high stress abrasion) test was utilized to understand the wear behavior of this material. Abrasive experiment displays a better wear resistance than unreinforced steel matrix when coarse WC particles are dispersed into it. The coarse particles provide greater wear-resistance than the fine particles and operatively takes on the most applied loads. Additionally, the large particles have not been peeled during the wear process for a long time, which indicates the effect of interfacial reaction on wear behavior at the ambient temperature. A double carbide (Fe, W)3C is detected in the interface zone between particles and matrices using transmission electron microscopy.

  16. Microstructural, phase evolution and corrosion properties of silicon carbide reinforced pulse electrodeposited nickel-tungsten composite coatings

    Science.gov (United States)

    Singh, Swarnima; Sribalaji, M.; Wasekar, Nitin P.; Joshi, Srikant; Sundararajan, G.; Singh, Raghuvir; Keshri, Anup Kumar

    2016-02-01

    Silicon carbide (SiC) reinforced nickel-tungsten (Ni-W) coatings were successfully fabricated on steel substrate by pulse electrodeposition method (PED) and the amount of SiC was varied as 0 g/l, 2 g/l, and 5 g/l in Ni-W coating. Effect of subsequent addition of SiC on microstructures, phases and on corrosion property of the coating was investigated. Field emission scanning electron microscopy (FE-SEM) image of the surface morphology of the coating showed the transformation from the dome like structure to turtle shell like structure. X-ray diffraction (XRD) of Ni-W-5 g/l SiC showed the disappearance of (220) plane of Ni(W), peak splitting in major peak of Ni(W) and formation of distinct peak of W(Ni) solid solution. Absence of (220) plane, peak splitting and presence of W(Ni) solid solution was explained by the high resolution transmission electron microscopy (HR-TEM) images. Tafel polarization plot was used to study the corrosion property of the coatings in 0.5 M NaCl solution. Ni-W-5 g/l SiC coating was showed higher corrosion resistance (i.e. ∼21% increase in corrosion potential, Ecorr) compared to Ni-W coating. Two simultaneous phenomena have been identified for the enhanced corrosion resistance of Ni-W-5 g/l SiC coating. (a) Presence of crystallographic texture (b) formation of continuous double barrier layer of NiWO4 and SiO2.

  17. Effect of composition of titanium in silver-copper-titanium braze alloy on dissimilar laser brazing of binder-less cubic boron nitride and tungsten carbide

    Science.gov (United States)

    Sechi, Yoshihisa; Nagatsuka, Kimiaki; Nakata, Kazuhiro

    2014-08-01

    Laser brazing with Ti as an active element in silver-copper alloy braze metal has been carried out for binder-less cubic boron nitride and tungsten carbide, using silver-copper- titanium braze alloys with titanium content that varied between 0.28 mass% and 1.68 mass%. Observations of the interface using electron probe microanalysis and scanning acoustic microscopy show that efficient interface adhesion between binder-less cubic boron nitride and the silver-copper-titanium braze alloy was achieved for the braze with a titanium content of 0. 28 mass%.

  18. Robot based deposition of WC-Co HVOF coatings on HSS cutting tools as a substitution for solid cemented carbide cutting tools

    Science.gov (United States)

    Tillmann, W.; Schaak, C.; Biermann, D.; Aßmuth, R.; Goeke, S.

    2017-03-01

    Cemented carbide (hard metal) cutting tools are the first choice to machine hard materials or to conduct high performance cutting processes. Main advantages of cemented carbide cutting tools are their high wear resistance (hardness) and good high temperature strength. In contrast, cemented carbide cutting tools are characterized by a low toughness and generate higher production costs, especially due to limited resources. Usually, cemented carbide cutting tools are produced by means of powder metallurgical processes. Compared to conventional manufacturing routes, these processes are more expensive and only a limited number of geometries can be realized. Furthermore, post-processing and preparing the cutting edges in order to achieve high performance tools is often required. In the present paper, an alternative method to substitute solid cemented carbide cutting tools is presented. Cutting tools made of conventional high speed steels (HSS) were coated with thick WC-Co (88/12) layers by means of thermal spraying (HVOF). The challenge is to obtain a dense, homogenous, and near-net-shape coating on the flanks and the cutting edge. For this purpose, different coating strategies were realized using an industrial robot. The coating properties were subsequently investigated. After this initial step, the surfaces of the cutting tools were ground and selected cutting edges were prepared by means of wet abrasive jet machining to achieve a smooth and round micro shape. Machining tests were conducted with these coated, ground and prepared cutting tools. The occurring wear phenomena were analyzed and compared to conventional HSS cutting tools. Overall, the results of the experiments proved that the coating withstands mechanical stresses during machining. In the conducted experiments, the coated cutting tools showed less wear than conventional HSS cutting tools. With respect to the initial wear resistance, additional benefits can be obtained by preparing the cutting edge by means

  19. The Effectof Underwater Explosion on the Kinetics of Alkaline Leaching of Roasted Tungsten Carbide Scraps for Recycling

    OpenAIRE

    BAIK, Seung Woo; Shibayama, Atsushi; Murata, Kenji; Fujita, Toyohisa

    2004-01-01

    Wasted tungsten scraps are important resources for recycling, however, the mechanical recycle process of tungsten has a difficulty for recycling due to its mechanical strength. Underwater explosion fracturing technique was designed for solving this problem. The kinetics for alkaline leaching of roasted tungsten alloy scraps with different size distribution prepared by two ways of crushing technique has been investigated to evaluate the effect of the underwater explosion-crushing. The merit of...

  20. On the Use of Mo/Mo2C Gradient Interlayers in Diamond Deposition onto Cemented Carbide Substrates

    Science.gov (United States)

    Gao, Jie; Hei, Hongjun; Zheng, Ke; Gao, Xueyan; Liu, Xiaoping; Tang, Bin; He, Zhiyong; Yu, Shengwang

    2016-01-01

    Molybdenum/molybdenum carbide (Mo/Mo2C) gradient interlayers were prepared via double glow plasma surface alloying (DGPSA) technique onto cemented carbide (WC-Co) substrates for diamond deposition. The morphologies, phase composition and adhesion of the interlayers were investigated, as well as their effect on the subsequent diamond deposition. The results indicated that the Mo/Mo2C gradient interlayer deposited on WC-Co substrate was composed of 4.0-μm-thick diffusion layer and 2.7-μm-thick deposition layer. The Mo concentration decreased gradually with the depth direction whereas the Co and W concentrations increased. As a result, the Co binder phase was completely restricted within the substrate by the diffusion layer. The presence of gradient diffusion layer ensured excellent adhesion of the interlayer. Subsequently, nanocrystalline diamond coatings with excellent adhesion were deposited on the interlayered substrates. Thus, the Mo/Mo2C gradient interlayers deposited via DGPSA technique were demonstrated as a novel option for depositing adherent diamond coatings on WC-Co substrates.

  1. Fatigue crack propagation resistance of cemented carbides; Resistencia a la propagacion de fisuras por fatiga en carburos cementados

    Energy Technology Data Exchange (ETDEWEB)

    Torres, Y.; Rodriguez, S.; Llanes, L.; Anglada, M.

    2001-07-01

    It is studied the fatigue crack growth behavior of two grades of WC-Co cemented carbides, both with a 10%{sub w}t of Co but with different carbide grain size, 0,8 and 2,5 {mu}m. Crack growth kinetics, measured under different load ratios, is described using an alternative form to the Paris equation. hence, it is used a model that takes into account both maximum and range of the applied stress intensity factor, k{sub m}ax and {delta}K respectively, within an equation of the form da/dN=f(K{sub m}ax, {delta}K). It is observed a significant dependence with respect to K{sub m}ax, yielding evidence of the prominence of static modes of rupture. Under these considerations, the fatigue crack growth sensitivity of the materials studied is evaluated. Finally, the damage mechanisms associated with stable and unstable fatigue crack propagation are analyzed. (Author) 11 refs.

  2. Influence of Grain Growth Inhibitors and Powder Size on the Properties of Ultrafine and Nanostructured Cemented Carbides Sintered in Hydrogen

    Directory of Open Access Journals (Sweden)

    Tamara Aleksandrov Fabijanić

    2016-08-01

    Full Text Available The influence of grain growth inhibitors and powder size on the microstructure and mechanical properties of ultrafine and nanostructured cemented carbides was researched. Three different WC powders, with an addition of different type and content of grain growth inhibitors GGIs, VC and Cr3C2 and with dBET grain sizes in the range from 95 to 150 nm were selected as starting powders. Four different mixtures with 6 and 9 wt. % Co were prepared. The consolidated samples are characterized by different microstructural and mechanical properties with respect to the characteristics of starting powders. Increased sintering temperatures led to microstructural irregularities in the form of a discontinuous WC growth, carbide agglomerates and abnormal grain growth as a consequence of coalescence via grain boundary elimination. The addition of 0.45% Cr3C2 contributed to microstructure homogeneity, reduced discontinuous and continuous grain growth, and increased Vickers hardness by approximately 70 HV and fracture toughness by approximately 0.15 MN/m3/2. The reduction of the starting powder to a real nanosize of 95 nm resulted in lower densities, and significant hardness increase, with a simultaneously small increase in fracture toughness. The consolidation of real nanopowders (dBET < 100 nm solely by conventional sintering in hydrogen without isostatic pressing is not preferred.

  3. An Experimental investigation of sea sand as an Abrasive material in vibrating chamber by using Tungsten Carbide Nozzle in Abrasive Jet machining Process.

    Directory of Open Access Journals (Sweden)

    N. S. Pawar

    2013-10-01

    Full Text Available A large number of investigation carried out in Abrasive jet machining and water jet machining process with different parameter but no detailed work have been found or carried out by using sea sand as an abrasive in AJM process by using different types of nozzles and variable parameters. The present work gives performance of sand having grain structure of 100-150 micron in the tungsten carbide nozzle. Theexperimentation in this study give characteristic of sea sand as abrasive material. The parameter like pressure, standoff distance of nozzle from work piece keeping constant and variable. It give the result of material removal rate , powder flow rate, similar to actually abrasive used like Aluminum oxide, silicon oxide etc. The R square value o.97 to 0.996 degree of polynomial equation. It is also notice that width of cut slightly increase with increase of feed rate .The taper cut slot was found to be a higher at greater stand of distance and work feed rate .Tungsten carbide is very hard. It maintain high cutting ability as abrasive strike on work piece

  4. Microstructure and abrasive wear properties of M(Cr,Fe7C3 carbides reinforced high-chromium carbon coating produced by gas tungsten arc welding (GTAW process

    Directory of Open Access Journals (Sweden)

    Soner BUYTOZ

    2010-01-01

    Full Text Available In the present study, high-chromium ferrochromium carbon hypereutectic alloy powder was coated on AISI 4340 steel by the gas tungsten arc welding (GTAW process. The coating layers were analyzed by optical microscopy, X-ray diffraction (XRD, field-emission scanning electron microscopy (FE-SEM, X-ray energy-dispersive spectroscopy (EDS. Depending on the gas tungsten arc welding pa-rameters, either hypoeutectic or hypereutectic microstructures were produced. Wear tests of the coatings were carried out on a pin-on-disc apparatus as function of contact load. Wear rates of the all coating layers were decreased as a function of the loading. The improvement of abrasive wear resistance of the coating layer could be attributed to the high hardness of the hypereutectic M7C3 carbides in the microstruc-ture. As a result, the microstructure of surface layers, hardness and abrasive wear behaviours showed different characteristics due to the gas tungsten arc welding parameters.

  5. Ti添加方式对表面无立方相层梯度硬质合金的影响%Effect of Method of Adding Ti on Functionally Graded Cemented Carbides with Cubic Carbide Free Layer

    Institute of Scientific and Technical Information of China (English)

    冯燕; 任达平; 望军

    2011-01-01

    表面无立方相层梯度硬质合金是一种非常好的涂层刀具基体材料,近年来越来越受到重视.本文主要研究了Ti添加方式对于表面无立方相层梯度硬质合金的影响.研究发现,相对于添加TiN、TiC,添加TiCN得到的表面无立方相层梯度硬质合金综合性能更好.%The functionally graded cemented carbides with cubic carbide free layer is a kind of good substrate material for coating tool. So they were paied more and more attention in recent years. This paper researched the effect of the method of adding Ti on the functionally graded cemented carbides with cubic carbide free layer. It was found that adding TiCN was better than adding TiN and TiC.

  6. Co元素对硬质合金基底金刚石涂层膜基界面结合强度的影响∗%The Influence of Co binding phase on adhesive strength of diamond coating with cemented carbide substrate

    Institute of Scientific and Technical Information of China (English)

    简小刚; 陈军

    2015-01-01

    diamond coating and the bond Mulliken population of diamond film-substrate interface. The results show that the interfacial bonding energy of WC/diamond is 6.74 J/m2 and that of WC-Co/diamond is 5.94 J/m2, which implies that the adhesive strength of WC/diamond is better than that of WC-Co/diamond. We also find that Co element can transfer the charges near the interface of WC/diamond model when the magnetic Co element exists at the WC/diamond interface. As a result, the polarity of tungsten element in tungsten carbide and the polarity of carbon element in diamond coating near the interface turn to be identical polarity, and then the charge density of tungsten in cemented carbide changes from 0.430 e/A3 to 0.201 e/A3 and the charge density of Carbon in diamond changes from −0.045 e/A3 to 0.037 e/A3, and they exclude to each other, so the distance of interface becomes larger than that from the WC/diamond model, which changes from 2.069 Åto 3.649 Å. This can explain why the existence of Co element can weaken the adhesive strength of diamond coating. Meanwhile, Mulliken population analyses show that the bond strength of WC-Co/diamond at the interface is smaller than that of WC/diamond. So this can prove that the cobalt binding phase in cemented carbide substrate can weaken the adhesive strength of diamond coating, and then we need to do some pretreatments in order to reduce the cobalt binding phase in the cemented carbide substrate before depositing diamond coating.

  7. Structure of TiBN coatings deposited onto cemented carbides and sialon tool ceramics

    OpenAIRE

    L.A. Dobrzański; M. Staszuk; J. Konieczny; W. Kwaśny; M. Pawlyta

    2009-01-01

    Purpose: The aim of this paper was investigated structure of sintered carbides WC-Co type and sialon tool ceramics with wear resistance ternary coatings TiBN type deposited by cathodes arc evaporation process (CAE-PVD).Design/methodology/approach: Observation of fracture and topography studied coatings were done by scanning electron microscope. Chemical composition was determine by energy dispersive spectrometry (EDS) method. Thin foils of substrates and coatings by transmission electron micr...

  8. Surface Layer States of Worn Uncoated and TiN-Coated WC/Co-Cemented Carbide Cutting Tools after Dry Plain Turning of Carbon Steel

    Directory of Open Access Journals (Sweden)

    Johannes Kümmel

    2013-01-01

    Full Text Available Analyzing wear mechanisms and developments of surface layers in WC/Co-cemented carbide cutting inserts is of great importance for metal-cutting manufacturing. By knowing relevant processes within the surface layers of cutting tools during machining the choice of machining parameters can be influenced to get less wear and high tool life of the cutting tool. Tool wear obviously influences tool life and surface integrity of the workpiece (residual stresses, surface quality, work hardening, etc., so the choice of optimised process parameters is of great relevance. Vapour-deposited coatings on WC/Co-cemented carbide cutting inserts are known to improve machining performance and tool life, but the mechanisms behind these improvements are not fully understood. The interaction between commercial TiN-coated and uncoated WC/Co-cemented carbide cutting inserts and a normalised SAE 1045 steel workpiece was investigated during a dry plain turning operation with constant material removal under varied machining parameters. Tool wear was assessed by light-optical microscopy, scanning electron microscopy (SEM, and EDX analysis. The state of surface layer was investigated by metallographic sectioning. Microstructural changes and material transfer due to tribological processes in the cutting zone were examined by SEM and EDX analyses.

  9. Structure and properties of selected cemented carbides and cermets covered with TiN/(Ti,Al,SiN/TiN coatings obtained by the cathodic arc evaporation process

    Directory of Open Access Journals (Sweden)

    Leszek A. Dobrzañski

    2005-06-01

    Full Text Available This study presents the results of microstructural examinations, mechanical tests and service performance tests carried out on thin TiN/(Ti,Al,SiN/TiN wear resistance coatings obtained by the CAE process on cermet and cemented carbide substrates. Microstructural examinations of the applied coatings and the substrate were made with an OPTON DSM 940 SEM and a LEICA MEF4A light microscope. Adhesion of the coatings on cemented carbides and cermets was measured using the scratch test. The cutting properties of the materials were determined from service tests in which continuous machining of C45E steel was carried out. The hardness of the substrate and the microhardness of the coatings were determined with a DUH 202 SHIMADZU ultra microhardness tester with a load of 70 mN. Roughness tests were also carried out before applying the coatings and after the PVD process. Cutting tests confirmed the advantages of the TiN/(Ti,Al,SiN/TiN type coatings obtained using the PVD method in the CAE mode on cemented carbides and cermets, as a material that undergoes very low abrasive, thermal and adhesion wear. These coatings extend tool life compared to commercially available uncoated tools with single and multi-layer coatings deposited using PVD/CVD methods.

  10. Vacuum Brazing of WC-8Co Cemented Carbides to Carbon Steel Using Pure Cu and Ag-28Cu as Filler Metal

    Science.gov (United States)

    Zhang, X. Z.; Liu, G. W.; Tao, J. N.; Shao, H. C.; Fu, H.; Pan, T. Z.; Qiao, G. J.

    2017-02-01

    The wetting and spreading behavior of commercial pure Cu and Ag-28Cu alloy on WC-8Co cemented carbide were investigated by the sessile drop technique. The contact angle of both systems obviously decreases with moderately increasing the wetting temperature. Vacuum brazing of the WC-8Co cemented carbide to SAE1045 steel using the pure Cu or Ag-28Cu as filler metal was further carried out based on the wetting results. The interfacial interactions and joint mechanical behavior involving microhardness, shear strength and fracture were analyzed and discussed. An obvious Fe-Cu-Co transition layer is detected at the WC-8Co/Cu interface, while no obvious reaction layer is observed at the whole WC-8Co/Ag-28Cu/SAE1045 brazing seam. The microhardness values of the two interlayers and the steel substrate near the two interlayers increase more or less, while those of WC-8Co cemented carbide substrates adjacent to the two interlayers decrease. The WC-8Co/SAE1045 joints using pure Cu and Ag-28Cu alloy as filler metals obtain average shear strength values of about 172 and 136 MPa, and both of the joint fractures occur in the interlayers.

  11. Vacuum Brazing of WC-8Co Cemented Carbides to Carbon Steel Using Pure Cu and Ag-28Cu as Filler Metal

    Science.gov (United States)

    Zhang, X. Z.; Liu, G. W.; Tao, J. N.; Shao, H. C.; Fu, H.; Pan, T. Z.; Qiao, G. J.

    2016-12-01

    The wetting and spreading behavior of commercial pure Cu and Ag-28Cu alloy on WC-8Co cemented carbide were investigated by the sessile drop technique. The contact angle of both systems obviously decreases with moderately increasing the wetting temperature. Vacuum brazing of the WC-8Co cemented carbide to SAE1045 steel using the pure Cu or Ag-28Cu as filler metal was further carried out based on the wetting results. The interfacial interactions and joint mechanical behavior involving microhardness, shear strength and fracture were analyzed and discussed. An obvious Fe-Cu-Co transition layer is detected at the WC-8Co/Cu interface, while no obvious reaction layer is observed at the whole WC-8Co/Ag-28Cu/SAE1045 brazing seam. The microhardness values of the two interlayers and the steel substrate near the two interlayers increase more or less, while those of WC-8Co cemented carbide substrates adjacent to the two interlayers decrease. The WC-8Co/SAE1045 joints using pure Cu and Ag-28Cu alloy as filler metals obtain average shear strength values of about 172 and 136 MPa, and both of the joint fractures occur in the interlayers.

  12. Laser-induced breakdown spectroscopy for on-line control of selective removal of cobalt binder from tungsten carbide hardmetal by pulsed UV laser surface ablation

    Science.gov (United States)

    Li, Tiejun; Lou, Qihong; Wei, Yunrong; Huang, Feng; Dong, Jingxing; Liu, Jingru

    2001-09-01

    Laser-induced breakdown spectroscopy (LIBS) was successfully used in on-line control of selective removal of cobalt from tungsten carbide hardmetal by pulsed UV laser surface ablation. The dependence of LIBS on number of laser shots was investigated at different laser fluences. The optimal laser fluence of 2.5 J/cm 2 suited for selective removal of cobalt from surface layer of hardmetal was confirmed. The result sample was also subject to different post-examinations to evaluate the feasibility of the application of LIBS in this laser ablation process. It was demonstrated that, monitoring of the emission intensity of cobalt lines could be used as a control parameter for selective removal of cobalt from surface layer of hardmetal by pulsed UV laser. The on-line implementation of the spectroscopic technique LIBS to the surface-ablation process provided important information about the optimal-ablation parameters.

  13. An Experimental Study of the Corrosion Behavior of Nickel Tungsten Carbide in Some Water-Glycol Hydraulic Fluids for Subsea Applications

    Science.gov (United States)

    Zheng, Lei; Neville, Anne; Gledhill, Andrew; Johnston, David

    2010-02-01

    Corrosion failures of components in electro-hydraulic control systems can have serious consequences for the operation of an entire subsea oil recovery system, especially in water depths more than 150 m (Fleming, Meas. Control, 2000, 33(7), p 207-213). An acceptable reason for this is that seawater ingress can have a great effect on stainless steel 316L, the most commonly used material for the failed components of the direction control valves, since chloride irons destabilize the passive film [Malik et al., Corros. Sci., 1992, 33(11), p 1809-1827; Desalination, 1994, 97(1-3), p 189-197; Al-Malahy and Hodgkiess, Desalination, 2003, 158(1-3), p 35-42]. Other materials, claimed to be seawater tolerant, are starting to be used in this system. However, problems can still exist due to the complex factors relating to the corrosion process and how the environmental parameters affect the corrosion mechanisms. In this work, the corrosion behavior of a nickel tungsten carbide cermet, one of the proposed materials, is compared with stainless steel 316L, in four different water-glycol hydraulic fluids and 50% hydraulic fluid/50% seawater solutions using an electrochemical test methodology. Systematic fluid analysis, which includes GC-MS for organic components and ICP-MS analysis for ionic content, and surface analysis of the material are carried out to assess the corrosion mechanisms. Detailed conclusions are then made to summarize the advantages and disadvantages of nickel tungsten carbide being used in this system. The effects of each factor on the corrosion rates and mechanisms are discussed.

  14. 硬质合金切削刀片优化设计%Optimum Design of Cemented Carbide Cutting Tools

    Institute of Scientific and Technical Information of China (English)

    汪志超; 谢平; 罗煜

    2011-01-01

    In order to reduce the manufacturing costs of cemented carbide cutting blades, various methods can be adopted such as adjusting the tolerance zone of the products, designing the protective straight sets for the sharp edge products with back angle bigger than 0°, and ensuring the mold's accuracy up to M level for the negative angle blades. Combined with modem high precision mold manufacturing technology and precision pressing technology, 1%~3.5% of manufacturing costs in the colligation of material, labor and machine can be saved.%为降低硬质合金切削刀片的制造成本,可以通过控制产品的公差带,为法后角大于0°的产品的锋利刃口设计保护性直台,为负角刀片设计周边尺寸可直接压制达到M级精度等级水平的模具,结合现代高精度模具制造技术和精密压制技术,在物料成本、人工费用、机器费用三方面综合达到节约硬质合金产品制造成本1%~3.5%的目的.

  15. Atom probe tomography of a Ti–Si–Al–C–N coating grown on a cemented carbide substrate

    Energy Technology Data Exchange (ETDEWEB)

    Thuvander, M.; Östberg, G. [Department of Applied Physics, Chalmers University of Technology, SE 412 96 Göteborg (Sweden); Ahlgren, M. [Sandvik Coromant, SE 126 80 Stockholm (Sweden); Falk, L.K.L., E-mail: lklfalk@chalmers.se [Department of Applied Physics, Chalmers University of Technology, SE 412 96 Göteborg (Sweden)

    2015-12-15

    The elemental distribution within a Ti–Si–Al–C–N coating grown by physical vapour deposition on a Cr-doped WC–Co cemented carbide substrate has been investigated by atom probe tomography. Special attention was paid to the coating/substrate interface region. The results indicated a diffusion of substrate binder phase elements into the Ti–N adhesion layer. The composition of this layer, and the Ti–Al–N interlayer present between the adhesion layer and the main Ti–Si–Al–C–N layer, appeared to be sub-stoichiometric. The analysis of the interlayer showed the presence of internal surfaces, possibly grain boundaries, depleted in Al. The composition of the main Ti–Al–Si–C–N layer varied periodically in the growth direction; layers enriched in Ti appeared with a periodicity of around 30 nm. Laser pulsing resulted in a good mass resolution that made it possible to distinguish between N{sup +} and Si{sup 2+} at 14 Da. - Highlights: • A Ti–Si–Al–C–N coating/WC–Co substrate interface has been analysed by APT. • The TiN adhesion layer and the Ti–Al–N interlayer appeared to be anion deficient. • Intermixing of Co and Cr from the substrate was observed in the Ti–N adhesion layer. • The Ti–Si–Al–C–N coating displayed an undulating composition in the growth direction.

  16. Microstructure and mechanical properties of (Ti,Al,Zr)N/(Ti,Al,Zr,Cr)N films on cemented carbide substrates

    Institute of Scientific and Technical Information of China (English)

    Shi-lu Zhao; Jun Zhang; Zhen Zhang; Shuang-hong Wang; Zheng-gui Zhang

    2014-01-01

    (Ti,Al,Zr)N/(Ti,Al,Zr,Cr)N bilayer films were deposited on cemented carbide (WC-8%Co) substrates by multi-arc ion plating (MAIP) using two Ti-Al-Zr alloy targets and one pure Cr target. To investigate the composition, morphology, and crystalline structure of the bilayer films, a number of complementary methods of elemental and structural analysis were used, namely, scanning electron microscopy (SEM), energy disperse X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Adhesive strength and mechanical properties of the films were evaluated by scratch testing and Vickers microindentation, respectively. It is shown that the resulting films have a TiN-type face-centered cubic (FCC) structure. The films exhibit fully dense, uniform, and columnar morphology. Furthermore, as the bias voltages vary from-50 to-200 V, the microhardness (max. Hv0.01 4100) and adhesive strength (max.>200 N) of the bilayer films are superior to those of the (Ti,Al,Zr)N and (Ti,Al,Zr,Cr)N monolayer films.

  17. Nanostructured TaxC interlayer synthesized via double glow plasma surface alloying process for diamond deposition on cemented carbide

    Science.gov (United States)

    Rong, Wolong; Hei, Hongjun; Zhong, Qiang; Shen, Yanyan; Liu, Xiaoping; Wang, Xin; Zhou, Bing; He, Zhiyong; Yu, Shengwang

    2015-12-01

    The aim in this work was to improve the adhesion of diamond coating with pre-deposition of a TaxC interlayer on cemented carbide (WC-Co) substrate by double glow plasma surface alloying technique. The following deposition of diamond coating on the interlayer was performed in a microwave plasma chemical vapor deposition (MPCVD) reactor. TaxC interlayer with an inner diffusion layer and an outer deposition layer was composed of Ta2C and TaC nanocrystalline, and it exhibited a special compact surface morphology formed of flower-shaped pits. As the gradual element distributions existed in the diffusion layer, the interlayer displayed a superior adherence to the substrate with significantly enhanced surface microhardness to the original substrate. After CVD process, the preferred orientation of TaC changed from (2 2 2) to (2 0 0) plane, and a uniform and tense diamond coating with adhesion referred to class HF 2 at least (Verein Deutscher Ingenieure 3198 norm) was obtained on the interlayered substrate. It indicated that the diffusion of Co was effectively inhibited by the formation of TaxC diffusion-deposition interlayer. The TaxC interlayer is most likely to improve the performance of diamond coatings used in cutting tools.

  18. Atom probe tomography of a Ti-Si-Al-C-N coating grown on a cemented carbide substrate.

    Science.gov (United States)

    Thuvander, M; Östberg, G; Ahlgren, M; Falk, L K L

    2015-12-01

    The elemental distribution within a Ti-Si-Al-C-N coating grown by physical vapour deposition on a Cr-doped WC-Co cemented carbide substrate has been investigated by atom probe tomography. Special attention was paid to the coating/substrate interface region. The results indicated a diffusion of substrate binder phase elements into the Ti-N adhesion layer. The composition of this layer, and the Ti-Al-N interlayer present between the adhesion layer and the main Ti-Si-Al-C-N layer, appeared to be sub-stoichiometric. The analysis of the interlayer showed the presence of internal surfaces, possibly grain boundaries, depleted in Al. The composition of the main Ti-Al-Si-C-N layer varied periodically in the growth direction; layers enriched in Ti appeared with a periodicity of around 30 nm. Laser pulsing resulted in a good mass resolution that made it possible to distinguish between N(+) and Si(2+) at 14 Da.

  19. Measurements of nanoparticle size distribution produced by laser ablation of tungsten and boron-carbide in N{sub 2} ambient

    Energy Technology Data Exchange (ETDEWEB)

    Bereznai, Miklos [Department of Optics and Quantum Electronics, University of Szeged, Dom ter 9, 6720 Szeged (Hungary) and Department of Materials Chemistry, Angstroem Laboratory, Uppsala University, PO Box 538, SE-75121 Uppsala (Sweden)]. E-mail: bereznai@physx.u-szeged.hu; Heszler, Peter [Department of Engineering Sciences, Angstroem Laboratory, Uppsala University, PO Box 534, SE-75121 Uppsala (Sweden); Research Group on Laser Physics of the Hungarian Academy of Sciences, University of Szeged, Dom ter 9, 6720 Szeged (Hungary); Toth, Zsolt [Research Group on Laser Physics of the Hungarian Academy of Sciences, University of Szeged, Dom ter 9, 6720 Szeged (Hungary); Wilhelmsson, Ola [Department of Materials Chemistry, Angstroem Laboratory, Uppsala University, PO Box 538, SE-75121 Uppsala (Sweden); Boman, Mats [Department of Materials Chemistry, Angstroem Laboratory, Uppsala University, PO Box 538, SE-75121 Uppsala (Sweden)

    2006-04-30

    Nanoparticles (NPs) were produced by ablating tungsten and boron-carbide (B{sub 4}C) target materials in atmospheric pressure nitrogen ambient using ArF excimer laser pulses. The size distributions of the NPs formed during the ablation were monitored-within a 7-133 nm size window-by a condensation particle counter connected to a differential mobility analyzer. The laser repetition rate was varied between 1-50 Hz, and the fluence was systematically changed in the range of 0.5-15 J/cm{sup 2}, for both materials, allowing a comparative study in an extended laser parameter regime. The multishot ablation threshold ({phi} {sub th}) of B{sub 4}C was determined to be {approx}1.9 J/cm{sup 2} for the laser used (ArF excimer, {lambda} = 193 nm). Similarly to earlier studies, it was shown that the size distributions consist of mainly small nanoparticles (<{approx}20 nm) attributed to a non-thermal ablation mechanism below {phi} {sub th}. An additional broad peak appears (between 20 and 40 nm) above {phi} {sub th} as a consequence of the thermally induced macroscopic ablation. Chemical composition of deposited polydisperse nanoparticles was studied by X-ray photoelectron spectroscopy showing nitrogen incorporation into the boron-carbide.

  20. Comparison of tungsten carbide and stainless steel ball bearings for grinding single maize kernels in a reciprocating grinder

    Science.gov (United States)

    Reciprocating grinders can grind single maize kernels by shaking the kernel in a vial with a ball bearing. This process results in a grind quality that is not satisfactory for many experiments. Tungesten carbide ball bearings are nearly twice as dense as steel, so we compared their grinding performa...

  1. 硬质合金孔加工刀具的技术进展%Technical Development of Cemented Carbide Cutting Tools for Hole Machining

    Institute of Scientific and Technical Information of China (English)

    王弢; 柯亚仕; 周一丹

    2011-01-01

    The types of cutting tools for hole machining commonly used in modem manufacturing techniques, carbide cutting tool materials and preparations were introduced briefly. Taking drill as an example, the influences of tool parameters design, edge grinding and cutting edge preparation technology on cutting performance were analyzed. The developing trends of cemented carbide cutting tools for hole machining were summarized.%简要介绍了现代制造技术中常用孔加工刀具的种类、硬质合金刀具的材料与制备.以钻头为例,分析了刀具参数、刃磨、刃口钝化技术对切削性能的影响,综述了硬质合金孔加工刀具技术的发展趋势.

  2. Direct solid analysis of powdered tungsten carbide hardmetal precursors by laser-induced argon spark ablation with inductively coupled plasma atomic emission spectrometry.

    Science.gov (United States)

    Holá, Markéta; Kanický, Viktor; Mermet, Jean-Michel; Otruba, Vítezslav

    2003-12-01

    The potential of the laser-induced argon spark atomizer (LINA-Spark atomizer) coupled with ICP-AES as a convenient device for direct analysis of WC/Co powdered precursors of sintered hardmetals was studied. The samples were presented for the ablation as pressed pellets prepared by mixing with powdered silver binder containing GeO2 as internal standard. The pellets were ablated with the aid of a Q-switched Nd:YAG laser (1064 nm) focused 16 mm behind the target surface with a resulting estimated power density of 5 GW cm(-2). Laser ablation ICP-AES signals were studied as a function of ablation time, and the duration of time prior to measurement (pre-ablation time) which was necessary to obtain reliable results was about 40 s. Linear calibration plots were obtained up to 10% (m/m) Ti, 9% Ta and 3.5% Nb both without internal standardization and by using germanium as an added internal standard or tungsten as a contained internal standard. The relative uncertainty at the centroid of the calibration line was in the range from +/- 6% to +/- 11% for Nb, Ta and Ti both with and without internal standardisation by Ge. A higher spread of points about the regression was observed for cobalt for which the relative uncertainty at the centroid was in the range from +/- 9% to +/- 14%. Repeatability of results was improved by the use of both Ge and W internal standards. The lowest determinable quantities calculated for calibration plots were 0.060% Co, 0.010% Nb, 0.16% Ta and 0.030% Ti with internal standardization by Ge. The LA-ICP-AES analyses of real samples led to good agreement with the results obtained by solution-based ICP determination with a relative bias not exceeding 10%. The elimination of the dissolution procedure of powdered tungsten (Nb, Ta, Ti) carbide is the principal advantage of the developed LA-ICP-AES method.

  3. Surface modification of the hard metal tungsten carbide-cobalt by boron ion implantation; Oberflaechenmodifikation des Hartmetalls Wolframkarbid-Kobalt durch Bor-Ionenimplantation

    Energy Technology Data Exchange (ETDEWEB)

    Mrotchek, I.

    2007-09-07

    In the present thesis ion beam implantation of boron is studied as method for the increasement of the hardness and for the improvement of the operational characteristics of cutting tools on the tungsten carbide-cobalt base. For the boron implantation with 40 keV energy and {approx}5.10{sup 17} ions/cm{sup 2} fluence following topics were shown: The incoerporation of boron leads to a deformation and remaining strain of the WC lattice, which possesses different stregth in the different directions of the elementary cell. The maximum of the deformation is reached at an implantation temperature of 450 C. The segregation of the new phases CoWB and Co{sub 3}W was detected at 900 C implantation temperature. At lower temperatures now new phases were found. The tribological characteristics of WC-Co are improved. Hereby the maxiaml effect was measured for implantation temperatures from 450 C to 700 C: Improvement of the microhardness by the factor 2..2.5, improvement of the wear resistance by the factor 4. The tribological effects extend to larger depths than the penetration depth of the boron implantation profile. The detected property improvements of the hard metal H3 show the possibility of a practical application of boron ion implantation in industry. The effects essential for a wer decreasement are a hardening of the carbide phase by deformation of the lattice, a hardening of the cobalt binding material and the phase boundaries because of the formation of a solid solution of the implanted boron atoms in Co and by this a blocking of the dislocation movement and the rupture spreading under load.

  4. Surface Modification of Fly Ashes with Carbide Slag and Its Effect on Compressive Strength and Autogenous Shrinkage of Blended Cement Pastes

    Institute of Scientific and Technical Information of China (English)

    HAO Chengwei; DENG Min; MO Liwu; LIU Kaiwei

    2012-01-01

    Surfaces of grade Ⅲ fly ashes were modified through mixing with carbide slag and calcining at 850 ℃ for 1 h.Mineralogical compositions and surface morphology of fly ashes before and after modification were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM),respectively.Effect of surface-modified fly ashes on compressive strength and autogenous shrinkage of blended cement pastes was investigated.Microstructures of cement pastes were examined by backscattered electron (BSE) imaging and mercury intrusion porosimetry (MIP).The experimental results showed that β-C2S was formed on the surfaces of fly ashes after modification.Hydration of β-C2S on the surface-modified fly ashes densified interface zone and enhanced bond strength between particles of fly ashes and hydrated clinkers.In addition,surface modification of fly ashes tended to decrease total porosity and 10-50 nm pores of cement pastes.Surface modification of fly ashes increased compressive strength and reduced autogenous shrinkage of cement pastes.

  5. Tungsten carbide precursors as an example for influence of a binder on the particle formation in the nanosecond laser ablation of powdered materials.

    Science.gov (United States)

    Holá, Markéta; Mikuska, Pavel; Hanzlíková, Renáta; Kaiser, Jozef; Kanický, Viktor

    2010-03-15

    A study of LA-ICP-MS analysis of pressed powdered tungsten carbide precursors was performed to show the advantages and problems of nanosecond laser ablation of matrix-unified samples. Five samples with different compositions were pressed into pellets both with silver powder as a binder serving to keep the matrix unified, and without any binder. The laser ablation was performed by nanosecond Nd:YAG laser working at 213 nm. The particle formation during ablation of both sets of pellets was studied using an optical aerosol spectrometer allowing the measurement of particle concentration in two size ranges (10-250 nm and 0.25-17 microm) and particle size distribution in the range of 0.25-17 microm. Additionally, the structure of the laser-generated particles was studied after their collection on a filter using a scanning electron microscope (SEM) and the particle chemical composition was determined by an energy dispersive X-ray spectroscope (EDS). The matrix effect was proved to be reduced using the same silver powdered binder for pellet preparation in the case of the laser ablation of powdered materials. The LA-ICP-MS signal dependence on the element content present in the material showed an improved correlation for Co, Ti, Ta and Nb of the matrix-unified samples compared to the non-matrix-unified pellets. In the case of W, the ICP-MS signal of matrix-unified pellets was influenced by the changes in the particle formation.

  6. Silica-templated synthesis of ordered mesoporous tungsten carbide/graphitic carbon composites with nanocrystalline walls and high surface areas via a temperature-programmed carburization route.

    Science.gov (United States)

    Wu, Zhangxiong; Yang, Yunxia; Gu, Dong; Li, Qiang; Feng, Dan; Chen, Zhenxia; Tu, Bo; Webley, Paul A; Zhao, Dongyuan

    2009-12-01

    Ordered mesostructured tungsten carbide and graphitic carbon composites (WC/C) with nanocrystalline walls are fabricated for the first time by a temperature-programmed carburization approach with phosphotungstic acid (PTA) as a precursor and mesoporous silica materials as hard templates. The mesostructure, crystal phase, and amount of deposited graphitic carbon can be conveniently tuned by controlling the silica template (SBA-15 or KIT-6), carburizing temperature (700-1000 degrees C), the PTA-loading amount, and the carburizing atmosphere (CH(4) or a CH(4)/H(2) mixture). A high level of deposited carbon is favorable for connecting and stabilizing the WC nanocrystallites to achieve high mesostructural regularity, as well as promoting the carburization reaction. Meanwhile, large pore sizes and high mesoporosity of the silica templates can promote WC-phase formation. These novel, ordered, mesoporous WC/C nanocomposites with high surface areas (74-169 m(2) g(-1)), large pore volumes (0.14-0.17 cm(3) g(-1)), narrow pore-size distributions (centered at about 3 nm), and very good oxidation resistance (up to 750 degrees C) have potential applications in fuel-cell catalysts and nanodevices.

  7. 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.

  8. Spark Plasma Sintering of Aluminum-Magnesium-Matrix Composites with Boron Carbide and Tungsten Nano-powder Inclusions: Modeling and Experimentation

    Science.gov (United States)

    Dvilis, E. S.; Khasanov, O. L.; Gulbin, V. N.; Petyukevich, M. S.; Khasanov, A. O.; Olevsky, E. A.

    2016-03-01

    Spark-plasma sintering (SPS) is used to fabricate fully-dense metal-matrix (Al/Mg) composites containing hard ceramic (boron carbide) and refractory metal (tungsten) inclusions. The study objectives include the modeling (and its experimental verification) of the process of the consolidation of the composites consisted of aluminum-magnesium alloy AMg6 (65 wt.%), B4C powder (15 wt.%), and W nano-powder (20 wt.%), as well as the optimization of the composite content and of the SPS conditions to achieve higher density. Discrete element modeling of the composite particles packing based on the particle size distribution functions of real powders is utilized for the determination of the powder compositions rendering maximum mixture packing densities. Two models: a power-law creep model of the high temperature deformation of powder materials, and an empirical logarithmic pressure-temperature-relative density relationship are successfully applied for the description of the densification of the aluminum-magnesium metal matrix powder composite subjected to spark-plasma sintering. The elastoplastic properties of the sintered composite samples are assessed by nanoindentation.

  9. 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.

  10. Analysis of crystallite size and microdeformation crystal lattice the tungsten carbide milling in mill high energy; Analise do tamanho do cristalito e microdeformacao da rede cristalina do carbeto de tugstenio moidos em moinho de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Silva, F.T. da; Nunes, M.A.M. [Universidade Federal do Rio Grande do Norte (PPGCEM/UFRN), Natal (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais; Oliveira, R.M.V. de; Silva, G.G. da [Instituto Federal do Rio Grande do Norte (IFRN), Natal (Brazil); Souza, C.P. de; Gomes, U.U. [Universidade Federal do Rio Grande do Norte (UFRN), Natal (Brazil)

    2010-07-01

    The tungsten carbide (WC) has wide application due to its properties like high melting point, high hardness, wear resistance, oxidation resistance and good electrical conductivity. The microstructural characteristics of the starting powders influences the final properties of the carbide. In this context, the use of nanoparticle powders is an efficient way to improve the final properties of the WC. The high energy milling stands out from other processes to obtain nanometric powders due to constant microstructural changes caused by this process. Therefore, the objective is to undertake an analysis of microstructural characteristics on the crystallite size and microdeformations of the crystal lattice using the technique of X-ray diffraction (XRD) using the Rietveld refinement. The results show an efficiency of the milling process to reduce the crystallite size, leading to a significant deformation in the crystal lattice of WC from 5h milling. (author)

  11. Measurements of Total Hemispherical Emissivity of Several Stably Oxidized Nickel-Titanium Carbide Cemented Hard Metals from 600 F to 1,600 F

    Science.gov (United States)

    Wade, William R.; Casey, F. W., Jr.

    1959-01-01

    The total hemispherical emissivity of several nickel-titanium carbide cemented hard metals have been measured over a temperature range from 600 F to l,600 F. A variety of cemented hard metals were obtained from the Kennametal Corporation. A brief discussion of the apparatus employed and the procedures used for this investigation is included. The results of the tests of specimens in the as-received and polished states indicate a nearly constant emissivity for each material tested over the temperature range considered and only slight differences in emissivity values for the different materials. Values obtained on the stably oxidized specimens range from 0.90 to 0.94 at 6000 F and o.88 to 0.92 at 1,600 F for the as-received specimens and from 0.82 to 0.89 at 600 F and 0.85 to 0.87 at 1,600 F for the polished specimens. The surface analysis of the oxidized materials as obtained by X-ray diffraction methods and metallographic techniques are presented as an aid to reproducing the surface on which these measurements were made.

  12. Research on the Microstructure and Wear Resistance of the Tungsten Carbides Reinforced Composite Coating Made From Tungsten Powder and Silicon Carbide%钨粉与碳化硅为原料制备碳化钨陶瓷涂层的组织及耐磨性研究

    Institute of Scientific and Technical Information of China (English)

    任莹; 王晓燕; 陈小凡

    2013-01-01

    As a typical boride ceramics,WC ceramics have become a researched hot point because of its high melting point,good chemi cal stability,high hardness and good resistance to abrasion.The WC granule is in-situ synthesized during the reaction of the alloy.powders employing the TIG powder surfacing.The microstructure and morphology of the tungsten carbide coating is observed and analyzed.The abrasive wear performance of the coating is also studied.%碳化钨陶瓷因具有极高的熔点、高的化学稳定性、高的硬度和优异的耐磨耐蚀性,已成为近年来金属陶瓷研究的热点之一.笔者采用钨极氩弧堆焊设备,通过原料粉末之间的高温冶金反应,在堆焊过程中原位合成碳化钨金属陶瓷涂层,对所制备的涂层试样的组织结构进行了观察分析,并且研究了涂层的耐磨料的磨损性能.

  13. In situ synthesis tungsten carbide reinforced ferrous matrix surface composites by laser cladding%激光熔覆原位合成碳化钨增强铁基表面复合材料的研究

    Institute of Scientific and Technical Information of China (English)

    陈莹莹; 李文戈; 吴培桂

    2011-01-01

    利用激光熔覆原位合成技术,在预置Ni涂层的45钢表面原位自生碳化钨陶瓷.通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、显微硬度计等分析测试手段对碳化钨陶瓷增强相的组织形貌、物相组成、化学成分及力学性能等方面进行了研究.结果表明,熔覆区内的碳化物由过饱和固溶体共晶析出;涂层与基体问的结合为冶金结合;制备的表面复合材料的硬度高于基体,改性效果极为明显.%Multiphase tungsten carbide on 45 steel was fabricated by laser cladding cooperated with combustion synthesis. The microstructure,phase composition, element distribution and mechanical properties of tungsten carbide ceramic reinforcement phase were analyzed by XRD,SEM, EDS and microhardness tester, respectively. The results show that the laser cladding region supersaturated solid solution by eutectic precipitation. The coating and the substrate is metallurgical bonding. The hardness of composite is superior to substrate. In a word, the modification effect is remarkable.

  14. Agglomeration of tungsten carbide nanoparticles in exposure medium does not prevent uptake and toxicity toward a rainbow trout gill cell line.

    Science.gov (United States)

    Kühnel, Dana; Busch, Wibke; Meissner, Tobias; Springer, Armin; Potthoff, Annegret; Richter, Volkmar; Gelinsky, Michael; Scholz, Stefan; Schirmer, Kristin

    2009-06-28

    Due to their increased production and use, engineered nanoparticles are expected to be released into the aquatic environment where particles may agglomerate. The aim of this study was to explore the role of agglomeration of nanoparticles in the uptake and expression of toxicity in the rainbow trout (Oncorhynchus mykiss) gill cell line, RTgill-W1. This cell line was chosen as model because it is known to be amenable to culture in complete as well as greatly simplified exposure media. Nano-sized tungsten carbide (WC) with or without cobalt doping (WC-Co), two materials relevant in the heavy metal industry, were applied as model particles. These particles were suspended in culture media with decreasing complexity from L15 with 10% fetal bovine serum (FBS) to L15 to L15/ex, containing only salts, galactose and pyruvate of the complete medium L15. Whereas the serum supplement in L15 retained primary nanoparticle suspensions, agglomerates were formed quickly in L15 and L15/ex. Nevertheless, scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) elemental analysis revealed an uptake of both WC and WC-Co nanoparticles into RTgill-W1 cells irrespective of the state of agglomeration of nanoparticles. The localisation seemed to be restricted to the cytoplasm, as no particles were observed in the nucleus of cells. Moreover, reduction in cell viability between 10 and 50% compared to controls were observed upon particle exposure in all media although the pattern of impact varied depending on the medium and exposure time. Short-term exposure of cells led to significant cytotoxicity at the highest nominal particle concentrations, irrespective of the particle type or exposure medium. In contrast, long-term exposures led to preferential toxicity in the simplest medium, L15/ex, and an enhanced toxicity by the cobalt-containing WC nanoparticles in all exposure media. The composition of the exposure media also influenced the toxicity of the cobalt ions, which may

  15. 钢结硬质合金的研究进展%Latest development of steel bonded cemented carbide

    Institute of Scientific and Technical Information of China (English)

    周书助; 兰登飞; 鄢玲利; 尹绍峰

    2015-01-01

    The relationship of the composition, microstructures and performance has been systematically elaborated. The main preparation technology of steel bonded carbide is summarized, and it is pointed that the powder metallurgy has been widely adopted to produce steel bonded carbide. However, due to the lower cost and better performance, electroslag melting and casting, self-propagating high temperature synthesis (SHS) and carbothermal reduction methods are full of vitality. In addition, forging and heat treatment can effectively improve the structure and performance of the alloy; Boriding, boron-sulphurizing treating process and laser cladding process can improve the surface hardness, reduce the friction coefficient and increase the service life. Finally, the development trend of steel bonded carbide is prospected.%该文较系统地阐述钢结硬质合金的成分、组织和性能之间的关系,综述钢结硬质合金的主要制备方法,指出粉末冶金法是最常用的制备方法,而电冶熔铸、自蔓延高温合成(SHS)和碳热还原法等工艺因更低的成本和更优的性能而展现出蓬勃生机.此外,锻造和热处理能够有效改善组织,提高合金性能;渗硼、硼?硫复合渗和激光熔覆等表面处理能提高合金的表面硬度,减小摩擦因数,提高使用寿命.最后,展望钢结硬质合金的发展方向.

  16. Study on diamond bit matrix materials made of tungsten carbide and steel shot%金刚石钻头胎体材料碳化钨一铸钢丸的试验研究

    Institute of Scientific and Technical Information of China (English)

    刘志义; 彭金龙; 段隆臣

    2011-01-01

    本文介绍了一种新的金刚石钻头胎体材料碳化钨-铸钢丸,这种钻头体材料的特点是钻头体表面使用铸造碳化钨材料,心部使用铸钢丸材料,从而实现钻头体表面耐磨抗冲蚀,心部高强高韧的特点.测试了这种钻头体心部材料的力学性能和表层材料的耐磨抗冲蚀能力,同时还介绍了使用含胶碳化钨粉涂抹在钻头模具表面和石墨替棒表面的方法.由于钻头体心部力学性能的提高,和传统的铸造碳化钨粉胎体金刚石钻头相比,这种方法制备的钻头体可以设计更宽更深的钻头体排屑槽,从而有利于提高钻头的钻进性能.%A new kind of diamond bit matrix material made of tungsten carbide and steel shots was introduced. The characteristics of this material are as follows: The outer bit body is of cast tungsten-carbide and the inside material is of cast steel shot, so the bit body has high wear resistance and good mechanical properties at the same time. The mechanical properties inside and the wear resistance outside of the bit were tested. At the same time a method was introduced, that is to apply a mixture of glue-included tungsten-carbide powder on the surface of the bit mold and graphite stick. The improved mechanical properties inside and good wear resistance outside made it possible to design wider and deeper junk slots. Thus the performance of bit was improved hopefully.

  17. Hydrogen evolution activity and electrochemical stability of selected transition metal carbides in concentrated phosphoric acid

    DEFF Research Database (Denmark)

    Tomás García, Antonio Luis; Jensen, Jens Oluf; Bjerrum, Niels J.

    2014-01-01

    Alternative catalysts based on carbides of Group 5 (niobium and tantalum) and 6 (chromium, molybdenum and tungsten) metals were prepared as films on the metallic substrates. The electrochemical activities of these carbide electrodes towards the hydrogen evolution reaction (HER) in concentrated......, attributable to the different electronic structures. Tungsten carbide among the studied electrode samples exhibited the highest HER activity. Upon anodic potential scans in the presence of oxygen, chromium, tantalum and tungsten carbides displayed passivation due to the formation of stable surface layers...

  18. Extraction Factor Of Tungsten Sources From Tungsten Scraps By Zinc Decomposition Process

    Directory of Open Access Journals (Sweden)

    Pee J.-H.

    2015-06-01

    Full Text Available Decomposition promoting factors and extraction process of tungsten carbide and tungstic acid powders in the zinc decomposition process of tungsten scraps which are composed mostly of tungsten carbide and cobalt were evaluated. Zinc volatility was suppressed by the enclosed graphite crucible and zinc volatilization pressure was produced in the reaction graphite crucible inside an electric furnace for ZDP (Zinc Decomposition Process. Decomposition reaction was done for 2hours at 650°, which 100% decomposed the tungsten scraps that were over 30 mm thick. Decomposed scraps were pulverized under 75μm and were composed of tungsten carbide and cobalt identified by the XRD (X-ray Diffraction. To produce the WC(Tungsten Carbide powder directly from decomposed scraps, pulverized powders were reacted with hydrochloric acid to remove the cobalt binder. Also to produce the tungstic acid, pulverized powders were reacted with aqua regia to remove the cobalt binder and oxidize the tungsten carbide. Tungsten carbide and tungstic acid powders were identified by XRD and chemical composition analysis.

  19. Progress in development of coated indexable cemented carbide inserts for machining of iron based work piece materials

    Science.gov (United States)

    Czettl, C.; Pohler, M.

    2016-03-01

    Increasing demands on material properties of iron based work piece materials, e.g. for the turbine industry, complicate the machining process and reduce the lifetime of the cutting tools. Therefore, improved tool solutions, adapted to the requirements of the desired application have to be developed. Especially, the interplay of macro- and micro geometry, substrate material, coating and post treatment processes is crucial for the durability of modern high performance tool solutions. Improved and novel analytical methods allow a detailed understanding of material properties responsible for the wear behaviour of the tools. Those support the knowledge based development of tailored cutting materials for selected applications. One important factor for such a solution is the proper choice of coating material, which can be synthesized by physical or chemical vapor deposition techniques. Within this work an overview of state-of-the-art coated carbide grades is presented and application examples are shown to demonstrate their high efficiency. Machining processes for a material range from cast iron, low carbon steels to high alloyed steels are covered.

  20. WC-Co硬质合金微观结构的参数化模型%Parametric Modeling of Microstructure of WC-Co Cemented Carbides

    Institute of Scientific and Technical Information of China (English)

    王东; 赵军; 李安海; 王泽明

    2013-01-01

    为实现WC-Co硬质合金的性能预报和微观结构的优化,提出了一种基于“随机法”构建材料二维微观结构模型的方法,该模型包含WC-Co硬质合金微观结构中WC晶粒的平均粒径、形心位置、取向角、长径和短径尺寸以及Co相体积分数等基本参数.采用C++,Matlab和Python语言汇合编程,得到可以直接导人有限元分析软件的模型.结果表明:构建的模型反映了真实的微观结构特征,实现了微观结构的参数化建模.模型的设计参数与实际参数比较吻合,证明了建模方法的可行性和模型的可靠性.%In order to realize the property prediction and microstructure optimization of WC-Co cemented carbides, a model based on "random method", which referred to the construction of two-dimensional microstructure model, was established. Some basic parameters of the microstructure of WC-Co, including average grain diameter, major axis and minor axis, centroid, orientation angle and the Co volume fraction, were considered in the model. C+ + , Matlab, Python are mixed for programming. The model can be obtained in the mixed program, which can be directly applied in the finite element software. The results show that the actual microstructure characteristics of material can be reconstructed, and the parametric model of microstructure is realized. The design parameters agree well with the actual ones, the feasibility of the method and the reliability of the model are proved.

  1. High Purity Tungsten Spherical Particle Preparation From WC-Co Spent Hard Scrap

    Directory of Open Access Journals (Sweden)

    Han Chulwoong

    2015-06-01

    Full Text Available Tungsten carbide-cobalt hard metal scrap was recycled to obtain high purity spherical tungsten powder by a combined hydrometallurgy and physical metallurgy pathway. Selective leaching of tungsten element from hard metal scrap occurs at solid / liquid interface and therefore enlargement of effective surface area is advantageous. Linear oxidation behavior of Tungsten carbide-cobalt and the oxidized scrap is friable to be pulverized by milling process. In this regard, isothermally oxidized Tungsten carbide-cobalt hard metal scrap was mechanically broken into particles and then tungsten trioxide particle was recovered by hydrometallurgical method. Recovered tungsten trioxide was reduced to tungsten particle in a hydrogen environment. After that, tungsten particle was melted and solidified to make a spherical one by RF (Ratio Frequency thermal plasma process. Well spherical tungsten micro-particle was successfully obtained from spent scrap. In addition to the morphological change, thermal plasma process showed an advantage for the purification of feedstock particle.

  2. Brazing Microstructures and Properties of 45 Steel and WC-Co Cemented Carbide%45钢与钨钴硬质合金的钎焊组织与性能

    Institute of Scientific and Technical Information of China (English)

    李玉龙; 禹业晓; 谢凤春

    2012-01-01

    In order to join the grinding bead with high-quality and high-efficiency, induction brazing of cemented carbide and the carbon steel was identified. Microstructure and Vickers hardness of the brazed joint was analyzed. Results show: (I) a good brazed joint of the cemented carbide and carbon steel can be acquired with the Cu-Zn filler metal; (ii) a -Cu and Fe-Cu-Zn ternary reaction layer were formed across the joint zone, (iii) microhardness of the cemented carbide was increased significantly due to the quenching effect of the induction heating process. After brazing, the brazed grinding head was electroplated with chromium alloy, the corrosion resistance ability was increased and the appearance was improved.%为实现中碳钢和硬质合金的高效优质钎焊,以Cu-Zn钎料对硬质合金和中碳钢进行了感应钎焊.结果表明,黄铜钎料可以使硬质合金和中碳钢形成良好的钎焊接头;分析了钎焊接头界面组织,接头区由α铜、Fe-Cu-Zn三元反应层构成;维氏硬度测试结果表明,因感应加热淬火效应,焊接后硬质合金显微硬度有显著增加;对感应钎焊的打磨头进行了电镀Cr处理,铬镀层提高了打磨头的耐蚀性和美观程度.

  3. Study on Properties of Tungsten Carbide in Nickel-based Self-lfuxing Alloy Coating in Couple Technique%两种工艺下碳化钨在镍基自熔合金涂层中的性能研究

    Institute of Scientific and Technical Information of China (English)

    王旭; 胡宇; 高峰; 马尧; 张清华; 杜倩

    2016-01-01

    In this paper, the morphologies of two mixed Nickel-base tungsten carbide coatings were studied, under the spray process of laser claddingand flame spray respectively. The decomposition and diffusion mechanism of tungsten carbide were discussed. It showed that tungsten carbide was easier to precipitate by laser cladding andη phase was found which led to the decrease of the final coating hardness.%本文研究了激光熔覆和火焰喷焊的工艺条件下,两种混合型镍基碳化钨涂层中碳化钨的组织形貌变化,分析碳化钨分解和扩散机理。结果表明:激光熔覆工艺更容易促进碳化钨溶解,并在周围析出η相,从而导致涂层硬度低于火焰喷焊工艺。

  4. Tungsten toxicity.

    Science.gov (United States)

    Witten, Mark L; Sheppard, Paul R; Witten, Brandon L

    2012-04-05

    There is emerging evidence that tungsten has toxic health effects. We summarize the recent tungsten toxicity research in this short review. Tungsten is widely used in many commercial and military applications because it has the second highest melting temperature of any element. Consequently, it is important to elucidate the potential health effects of tungsten.

  5. WC基钢结硬质合金磨损机理研究%STUDY OF WEAR MECHANISM OF THE WC STEEL-BONDED CEMENTED CARBIDE MANUFACTURED BY A NEW PROCESS

    Institute of Scientific and Technical Information of China (English)

    杜晓东; 尤显卿; 郑玉春

    2001-01-01

    The WC steel-bonded cemented carbide manufactured by a new process w as oil-quenched at 1150℃ and tempered at the low temperature 150℃ after anneal ing, and its wearability and wear mechanism were analyzed. The results show that the wear of the tested cemented carbide is caused by flaking of the hard phase, and that the development and propagation of cracks along the phase boundary between the hard phase and the substrate or the other hard phase is the reason why the h ard phase flakes.%将新工艺制造的WC钢结硬质合金退火后经1150℃油淬,150℃低温回火,分析其磨损特性和磨损机理,结果表明实验合金的磨损是由硬质相剥落造成的,裂纹沿硬质相与基体或硬质相之间的相界面萌生和扩展是硬质相剥落的原因。

  6. Tolerancia al daño inducido bajo solicitaciones de contacto cíclicas en carburos cementados WC-Co//Tolerance induced damage under cyclic contact loading of WC-Co cemented carbides

    Directory of Open Access Journals (Sweden)

    David Coureaux‐Mustelier

    2014-01-01

    Full Text Available El comportamiento mecánico de los carburos cementados WC-Co ha sido estudiado en detalle teniendo en cuenta los defectos preexistentes del material (daño intrínseco. Sin embargo, la información sobre los efectos del daño inducido en servicio (daño extrínseco en la integridad estructural de estos materiales esescasa. En este contexto, en este trabajo se evalúa la influencia del daño extrínseco en la resistencia mecánica residual de dos calidades con microestructuras diferentes. Para ello, se emplea la técnica de indentación esférica como medio para generar daño de forma controlada. Los resultados muestran que al incrementar el tamaño de grano del carburo y el contenido de cobalto, la respuesta mecánica de carburos cementados frente al contacto esférico es cada vez más cuasi-plástica, bajo la aplicación de cargas tanto monotónicas como cíclicas, y en consecuencia el material muestra una mayor tolerancia al daño.Palabras claves: carburos cementados, indentación esférica, resistencia mecánica residual, tolerancia al daño._______________________________________________________________________________AbstractThe mechanical behavior of WC-Co cemented carbides has been studied in detail taking into account the pre-existing material (intrinsic damage defects. However, information on the effects of service-induced damage (extrinsic damage on the structural integrity of these materials is limited. In this context, in thispaper the influence of extrinsic damage on the residual strength of two grades with different microstructures is evaluated. With this purpose, a spherical indentation technique is employed as a means for generating a controlled damage. The results show that by increasing the grain size of the carbide and the cobalt content, the mechanical properties of cemented carbides compared to spherical contact isincreasingly quasi-plastic, under the application of both monotonic and cyclic loads, and consequently the

  7. Development of refractory armored silicon carbide by infrared transient liquid phase processing

    Science.gov (United States)

    Hinoki, Tatsuya; Snead, Lance L.; Blue, Craig A.

    2005-12-01

    Tungsten (W) and molybdenum (Mo) were coated on silicon carbide (SiC) for use as a refractory armor using a high power plasma arc lamp at powers up to 23.5 MW/m 2 in an argon flow environment. Both tungsten powder and molybdenum powder melted and formed coating layers on silicon carbide within a few seconds. The effect of substrate pre-treatment (vapor deposition of titanium (Ti) and tungsten, and annealing) and sample heating conditions on microstructure of the coating and coating/substrate interface were investigated. The microstructure was observed by scanning electron microscopy (SEM) and optical microscopy (OM). The mechanical properties of the coated materials were evaluated by four-point flexural tests. A strong tungsten coating was successfully applied to the silicon carbide substrate. Tungsten vapor deposition and pre-heating at 5.2 MW/m 2 made for a refractory layer containing no cracks propagating into the silicon carbide substrate. The tungsten coating was formed without the thick reaction layer. For this study, small tungsten carbide grains were observed adjacent to the interface in all conditions. In addition, relatively large, widely scattered tungsten carbide grains and a eutectic structure of tungsten and silicon were observed through the thickness in the coatings formed at lower powers and longer heating times. The strength of the silicon carbide substrate was somewhat decreased as a result of the processing. Vapor deposition of tungsten prior to powder coating helped prevent this degradation. In contrast, molybdenum coating was more challenging than tungsten coating due to the larger coefficient of thermal expansion (CTE) mismatch as compared to tungsten and silicon carbide. From this work it is concluded that refractory armoring of silicon carbide by Infrared Transient Liquid Phase Processing is possible. The tungsten armored silicon carbide samples proved uniform, strong, and capable of withstanding thermal fatigue testing.

  8. 凝胶离心成形制备YG1O硬质合金管%CENTRIFUGAL GEL FORMING FOR PREPARATION OF YG10 CEMENTED CARBIDE PIPE

    Institute of Scientific and Technical Information of China (English)

    石永亮; 郭志猛; 方哲成; 曾鲜

    2012-01-01

    Centrifugal gel forming was applied to the molding of YG10 composite powders. The effect of the solids loading on the rheological behavior of YG10 composite powders slurry was investigated. The effect of the initiator amount and pressure on polymerization rate was anlysized. Moreover, the effect of the rotationl speed on the green and sintered bodies was also investigated. The results show that,the YG10 composite powders have a good dispersibility in the HEM A gel system. Using oleic acid as dispersant, the slurry with good flowability and good stability and maximum solids loading of 50vol% can be obtained. The amout of initiator is 5 mmol/L (based on the volume of the premix). In the centrifugal gel forming process,pressure can accelerate the solidification of the slurry. The green body with high density,without residue pores,the strength of 28. 3 MPa and relative density of 57% was prepared by choosing the optimum rotate speed of 4 000 r/min and using our device. YG10 cemented carbide pipe was prepared by sintering at 1 420℃ for 1 h in vacuum. It has uniform shrinkage without deformation,and the microstructure has no segregation.%将凝胶离心成形工艺应用于YG10复合粉末的坯体成形,研究了固含量对YG10复合粉末浆料的流变性的影响,分析了凝胶离心成形过程中引发剂量和压力对聚合速率的影响,并研究了离心转速对坯体和烧结体性能的影响.结果表明:以油酸作分散剂,制备稳定且流动性好的浆料最佳固含量为50%(体积分数),引发剂的加入量为5 mmol/L(相对于预混液的体积),凝胶离心成形过程中压力能够加速浆料的固化,采用自行设计的离心成型机,选择最佳转速4000 r/min,制备出的坯体密度高、无残留气孔,相对密度57%,强度28.3 MPa.坯体经真空脱胶烧结1420℃保温1h制备出YG10硬质合金管,烧结体收缩均匀无变形,组织结构完整无偏析.

  9. High-energy, high-rate consolidation of tungsten and tungsten-based composite powders

    Energy Technology Data Exchange (ETDEWEB)

    Raghunathan, S.K.; Persad, C.; Bourell, D.L.; Marcus, H.L. (Center for Materials Science and Engineering, Univ. of Texas, Austin (USA))

    1991-01-20

    Tungsten and tungsten-based heavy alloys are well known for their superior mechanical properties at elevated temperatures. However, unalloyed tungsten is difficult to consolidate owing to its very high melting temperature (3683 K). The additions of small amounts of low-melting elements such as iron, nickel, cobalt and copper, facilitate the powder processing of dense heavy alloys at moderate temperatures. Energetic high-current pulses have been used recently for powder consolidation. In this paper, the use of a homopolar generator as a power source to consolidate selected tungsten and tungsten-based alloys is examined. Various materials were consolidated including unalloyed tungsten, W-Nb, W-Ni, and tungsten heavy alloy with boron carbide. The effect of process parameters such as pressure and specific energy input on the consolidation of different alloy systems is described in terms of microstructure and property relationships. (orig.).

  10. Interaction between tungsten monocarbide and an iron-based metallic melt

    Science.gov (United States)

    Chumanov, I. V.; Anikeev, A. N.

    2015-12-01

    A technique and results of investigation of compacted tungsten carbide substrates by scanning microscopy are reported. Samples are prepared in the course of studies of the wettability of tungsten carbide substrates with the iron melt, which are performed in accordance with the sessile drop method using two different heating strategies, namely, contact and noncontact heating of metal.

  11. Depth profile analysis of various titanium based coatings on steel and tungsten carbide using laser ablation inductively coupled plasma--"time of flight" mass spectrometry.

    Science.gov (United States)

    Bleiner, D; Plotnikov, A; Vogt, C; Wetzig, K; Günther, D

    2000-01-01

    A homogenized 193 nm ArF* laser ablation system coupled to an inductively coupled plasma-"Time of Flight"-mass spectrometer (LA-ICP-TOFMS) was tested for depth profiling analysis on different single-layer Ti based coatings on steel and W carbides. Laser parameters, such as repetition rate, pulse energy and spatial resolution were tested to allow optimum depth related calibration curves. The ablation process using a laser repetition rate of 3 Hz, 120 microm crater diameter, and 100 mJ output energy, leads to linear calibration curves independent of the drill time or peak area used for calibrating the thickness of the layer. The best depth resolution obtained (without beam splitter) was 0.20 microm per laser shot. The time resolution of the ICP-TOFMS of 102 ms integration time per isotope was sufficient for the determination of the drill time of the laser through the coatings into the matrix with better than 2.6% RSD (about 7 microm coating thickness, n = 7). Variation of the volume of the ablation cell was not influencing the depth resolution, which suggests that the depth resolution is governed by the ablation process. However, the application on the Ti(N,C) based single layer shows the potential of LA-ICP-TOFMS as a complementary technique for fast depth determinations on various coatings in the low to medium microm region.

  12. TUNGSTEN BASE ALLOYS

    Science.gov (United States)

    Schell, D.H.; Sheinberg, H.

    1959-12-15

    A high-density quaternary tungsten-base alloy having high mechanical strength and good machinability composed of about 2 wt.% Ni, 3 wt.% Cu, 5 wt.% Pb, and 90wt.% W is described. This alloy can be formed by the powder metallurgy technique of hot pressing in a graphite die without causing a reaction between charge and the die and without formation of a carbide case on the final compact, thereby enabling re-use of the graphite die. The alloy is formable at hot- pressing temperatures of from about 1200 to about 1350 deg C. In addition, there is little component shrinkage, thereby eliminating the necessity of subsequent extensive surface machining.

  13. 抑制硬质合金中金属Co浸出的复合润滑剂研究%Study on composite lubricant for inhibiting cobalt leaching from cemented carbide

    Institute of Scientific and Technical Information of China (English)

    连建肖; 张秀玲; 杨桥; 贾晓鸣

    2011-01-01

    Some lubricants were made by esterification reaction of several acid lubricant additives that commonly used in industry and triethanolamine (TEA). Some solutions were prepared by mixing the reaction products and water in a certain ratio to carry on immersion tests of pure cobalt and cemented carbide tool at room temperature. The pure cobalt sheet was used as electrode to form galvanic cell with saturated calomel electrode to determine the electromotive force. According to the value of the electromotive force and combining with the amount of cobalt leaching in different solution,which was analyzed by scanning electron microscopy, the lubricant that showed good inhibiting effect on cobalt leaching was chosen. The results show that triethanolnmine oleate and boric acid-oleic acid triethanolamine can significantly inhibit cobalt leaching from cemented carbide.%选用几种工业上常用的酸类润滑添加剂与三乙醇胺进行醴化反应生成不同润滑剂,将反应产物配成一定浓度的溶液对纯钴片和硬质合金刀具在常温下做浸泡实验,用纯钴片做电极与饱和甘汞电极组成原电池测定电动势,根据电动势的大小结合电镜扫描分析判断不同润滑剂溶液使金属Co浸出的情况,优选出抑制金属Co浸出效果好的润滑剂.实验结果表明:油酸三乙醇胺和油酸硼酸三乙醇胺对Co的浸出有抑制作用.

  14. 硬质合金刀具螺旋槽缓进给磨削力研究%Research on Grinding Forces of Creep Feed Grinding Cemented Carbide Tool Helical Grooves

    Institute of Scientific and Technical Information of China (English)

    宋铁军; 周志雄; 李伟; 任莹晖

    2014-01-01

    The grinding forces of creep feed grinding cemented carbide tool helical groove were an-alyzed by grinding wheel discretization method that the grinding wheel was regarded as composion of different elementary discs.Based on the grinding forces and torques of creep feed grinding cemented carbide tool helical groove,a mathematical model of grinding force ratio was established to describe the blunting of the diamond grains.The accurate signals of the grinding forces and torques were achieved by setting up a measurement system.The grinding force ratio was analyzed based on the mathematical model and the experimental data.The results show that the grinding force ratio can be used for grinding process evaluation.%用离散化方法将砂轮看作是由一组不同直径的单位厚度薄片组成的,分析了硬质合金刀具螺旋槽缓进给成形磨削的磨削力;基于工件轴向磨削力和力矩建立了一个表征砂轮锐利程度的磨削力比数学模型。通过建立的测力系统测量了螺旋槽缓进给磨削过程中轴向磨削力和力矩,并对其信号进行了分析。在理论和实验的基础上获得了两种磨削参数下的磨削力比。研究结果表明,磨削力比可作为硬质合金刀具螺旋槽缓进给磨削过程的评价参数。

  15. Carbides composite surface layers produced by (PTA)

    Energy Technology Data Exchange (ETDEWEB)

    Tajoure, Meloud, E-mail: Tajoore2000@yahoo.com [MechanicalEng.,HIHM,Gharian (Libya); Tajouri, Ali, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com; Abuzriba, Mokhtar, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com [Materials and Metallurgical Eng., UOT, Tripoli (Libya); Akreem, Mosbah, E-mail: makreem@yahoo.com [Industrial Research Centre,Tripoli (Libya)

    2013-12-16

    The plasma transferred arc technique was applied to deposit a composite layer of nickel base with tungsten carbide in powder form on to surface of low alloy steel 18G2A type according to polish standard. Results showed that, plasma transferred arc hard facing process was successfully conducted by using Deloro alloy 22 plus tungsten carbide powders. Maximum hardness of 1489 HV and minimum dilution of 8.4 % were achieved by using an arc current of 60 A. However, when the current was further increased to 120 A and the dilution increases with current increase while the hardness decreases. Microstructure of the nickel base deposit with tungsten carbide features uniform distribution of reinforcement particles with regular grain shape half - dissolved in the matrix.

  16. PCBN tool wear mechanism in laser ultrasonically combined cutting cemented carbide%PCBN刀具激光超声复合切削硬质合金的磨损机理

    Institute of Scientific and Technical Information of China (English)

    张昌娟; 焦锋; 牛赢

    2016-01-01

    结合激光加热辅助切削和超声振动切削提出了激光超声复合切削加工工艺。采用PCBN刀具对YG10硬质合金进行普通切削、超声振动切削、激光加热辅助切削和激光超声复合切削对比试验,采用超景深显微镜观测刀具磨损量及磨损形貌,通过扫描电子显微镜(SEM)对刀具磨损区域进行能谱分析,研究激光超声复合切削条件下刀具的磨损规律、磨损形态及磨损原因。研究结果表明:与普通切削、超声振动切削及激光加热辅助切削相比,激光超声复合切削时刀具后刀面磨损量平均值分别降低57.5%、46%、41.3%,刀具使用寿命明显提高;刀具磨损形态主要表现为前刀面磨损、后刀面磨损和崩刃;激光超声复合切削硬质合金时粘接磨损、氧化磨损、相变磨损和微裂解磨损是引起PCBN刀具磨损的主要原因。%Laser ultrasonically combined cutting was proposed based on ultrasonic vibration cutting with laser heating assisted cutting. A series of experiments were conducted in conventional cutting, ultrasonic vibration cutting, laser heating assisted cutting and laser ultrasonically combined cutting YG10 cemented carbide with PCBN tools. The tool wear characteristics and tool wear mechanism were observed by using digital microscope with super depth, the energy spectrum analysis was carried out in worn areas of tools by scanning electron microscopy (SEM). The experimental results indicate that the average flank wear of PCBN tool obtained by laser ultrasonically combined cutting is reduced by almost 57.5%, 46% and 41.3% respectively when compared with that by conventional cutting, ultrasonic vibration cutting and laser heating assisted cutting, therefore the tool life is obviously lengthened. The main wear types are crater wear, flank wear and tipping for PCBN tools in cutting YG10 cemented carbide. And the adhesion, oxidation, phase transformation and micro dissociation are the

  17. 基于热电特性对YB425硬质合金刀片的使用寿命预测%Life Forecast for the YB425 Cemented Carbide Insert Basic on Thermoelectric Potential

    Institute of Scientific and Technical Information of China (English)

    陈舜青; 孟广耀

    2011-01-01

    热电特性是材料的易测量宏观物理量,而且对热电特性的测量可以不破坏材料。以YB425硬质合金刀片为研究对象,探索了刀片磨损量与其热电特性的相关关系,并且经过试验验证了YB425硬质合金刀片的热电特性与其刀片磨损量密切相关,而且基于热电特性预测硬质合金刀片的使用寿命的方法是可靠的。通过实验还建立了YB425硬质合金刀片的热电特性与其磨损量的相关关系试验公式,基于此试验公式,可以在硬质合金刀片使用前测量YB425硬质合金刀片的热电势,达到无损预测硬质合金刀片使用寿命的目的。%The thermoelectric potential is one of the major physical properties of material, and it is easy to be measured without damaging the material. In this paper, the analysis and test have been performed to explore the relationship between the wear and the thermoelectric potential of YB425 cemented carbide insert. The influence of wear on the thermoelectric potential of insert is verified by experiments. The empirical formula relating the wear and thermoelectric potential is also presented based on test data. The test results has proved that the proposed non-destructive detection method can successfully forecast the operation life of the YB425 cemented carbide insert.

  18. PYROLYTIC CARBIDE DEVELOPMENT PROGRAM

    Science.gov (United States)

    and injector design changes were made to improve the quality of the carbide produced. Niobium carbide and tantalum carbide coated nozzles are described...Additional data for pyrolytic niobium carbide and hafnium carbide is also presented. (Author)

  19. 超重力辅助燃烧合成熔渗梯度Ni-(WC-Ni)硬质合金复合材料%Fabrication of gradient WC-Ni cemented carbide materials by high-gravity-assisted combustion synthesis and infiltration

    Institute of Scientific and Technical Information of China (English)

    杨增朝; 刘光华; 徐利华; 郭世斌; 李江涛

    2013-01-01

    以超重力辅助燃烧合成熔渗工艺制备了具有梯度特征的 WC-Ni 硬质合金材料。该工艺以铝热反应为基础,施加辅助超重力场,制备出具有梯度特征的硬质合金材料。该材料具有双层梯度结构:沿重力场方向依次为Ni金属层和 WC-Ni硬质合金层。其中Ni金属层的硬度值为72HRA;硬质合金层的硬度值最高为87HRA。Ni熔体在熔渗过程中的搅动使 WC在Ni金属层出现弥散分布并导致硬质合金层 WC 的长大。熔体由底层开始向顶层逐渐凝固的特点使该梯度材料抗弯强度降低。%Gradient WC-Ni cemented carbide materials were prepared by high-gravity-assisted combustion syn-thesis and infiltration,where Ni melt was in-situ synthesized and then infiltrated into porous compacts of WC powder.The obtained materials consisted of two layers and showed a gradient feature along the high-gravity di-rection,in which the upper layer was Ni metal and the under layer was WC-Ni cemented carbide.The hardness of the Ni metal and WC-Ni cemented carbide reached 72 HRA and 87 HRA,respectively.The agitation of Ni melt during infiltration resulted in the presence of WC particles in the Ni metal and growth of WC grains in the cemented carbide layer.The WC-Ni cemented carbide materials showed a relatively low bending strength of 770 MPa,which may be connected with the down-to-up solidification kinetics.

  20. Damage and reliability of Y-TZP after cementation surface treatment.

    Science.gov (United States)

    Guess, P C; Zhang, Y; Kim, J-W; Rekow, E D; Thompson, V P

    2010-06-01

    Zirconia-based restorations are widely used in prosthetic dentistry, but their susceptibility to post-sintering cementation surface treatments remains controversial. We hypothesized that grinding (600-grit) and alumina abrasion (50 microm, 5 sec, 0.5 MPa) affect the damage modes and reliability of zirconia core material. Monolithic CAD/CAM-machined and sintered Y-TZP plates (0.5 mm thickness) were adhesively cemented to dentin-like composite substrates. Uni-axial mouth-motion cyclic contact was applied through a tungsten carbide spherical indenter (r = 3.18 mm). Results showed that zirconia core ceramic is vulnerable to lower surface radial fracture after grinding or alumina abrasion, while the as-received control chiefly fractured from load-application surface cone fracture. Significantly lower reliability of ground and alumina-abraded compared with the as-received zirconia core ceramic can be attributed to damage induced on the cementation surface. Clinical relevance concerning surface treatment protocols for zirconia framework materials prior to cementation is addressed.

  1. NAK80模具钢表面激光熔覆Ni基碳化钨合金涂层的组织和性能%Microstructure and Properties of Laser Cladding Ni-based Tungsten Carbide Alloy Coating on NAK80 Mold Steel

    Institute of Scientific and Technical Information of China (English)

    程虎; 方志刚; 赵先锐; 戴晟; 高玉新

    2011-01-01

    The Ni-based tungsten carbide alloy coating was fabricated on NAK80 mold steel by laser cladding technology. The characteristic of microstructure, micro-hardness and the formation mechanics were examined. The resuits show that the metallurgical bonding is good between the cladding coating and the steel substrate, the microstructure of laser cladding coating is composed of fir-tree crystal Cr23C6, un-melted tungsten carbide granular crystal, y-Ni solid solution and NiCr, CrB2. The micro-hardness of laser cladding coating is considerably higher than the substrate, so the wear-resisting property of mold surface is improved to some extent.%采用激光熔覆技术,在NAK80模具钢表面制备了Ni基碳化钨合金涂层.研究了激光熔覆涂层的组织结构特点及形成规律,测试分析了其显微硬度的分布特征.结果表明:涂层与基体之间呈良好冶金结合,熔覆层组织主要由树枝晶CrC、未熔碳化钨颗粒相、γ-Ni固溶体及少量分布于固溶体中的NiCr和CrB相组成;涂层的硬度远高于NAK80模具钢基体,从一定程度上改善了模具表面的耐磨性能.

  2. [Murine peritoneal neutrophil activation upon tungsten nanoparticles exposure in vivo].

    Science.gov (United States)

    Martinova, E A; Baranov, V I

    2014-01-01

    Two examples of tungsten carbide nanoparticles (d = 15 nm, 50 nm) and tungsten carbide nanoparticles with 8% cobalt (d = 50 nm) have been found to induce the neutrophil activation 3 h and 36 h after intraperitoneal administration in the doses 0.005; 0.025; 0.05; 0.25; 0.5; 1; 2.5 and 5 microgram per 1 gram body weight to FVB mice. Neutrophil activation was calculated based on the CD11b and S100 antigen expression. Effect of nanoparticles is bimodal for all tested examples.

  3. Boron carbide (B4C) coating. Deposition and testing

    Science.gov (United States)

    Azizov, E.; Barsuk, V.; Begrambekov, L.; Buzhinsky, O.; Evsin, A.; Gordeev, A.; Grunin, A.; Klimov, N.; Kurnaev, V.; Mazul, I.; Otroshchenko, V.; Putric, A.; Sadovskiy, Ya.; Shigin, P.; Vergazov, S.; Zakharov, A.

    2015-08-01

    Boron carbide was proposed as a material of in-situ protecting coating for tungsten tiles of ITER divertor. To prove this concept the project including investigation of regimes of plasma deposition of B4C coating on tungsten and tests of boron carbide layer in ITER-like is started recently. The paper contends the first results of the project. The results of B4C coating irradiation by the plasma pulses of QSPU-T plasma accelerator are presented. The new device capable of B4C film deposition on tungsten and testing of the films and materials with ITER-like heat loads and ion- and electron irradiation is described. The results of B4C coating deposition and testing of both tungsten substrate and coating are shown and discussed.

  4. Cement Conundrum

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    China aims to streamline the crowded cement industry Policymakers are looking to build a concrete wall around the cement-making industry as they seek to solidify the fluid cement market and cut excessive production.

  5. Effect of magnetic quenching on performance and structure of cemented carbides%磁场淬火处理对硬质合金组织和性能的影响

    Institute of Scientific and Technical Information of China (English)

    李荐; 郭欣; 姚建军; 周宏明; 杨俊; 江彬彬

    2012-01-01

    The effects of magnetic quenching on the performance and structure of YG6 (WC-6%Co) and YN6 (WC-6%Ni) cemented carbides were studied using powder X-ray diffraction, scanning electron microscope, optical microscope, transverse rupture strength, Vickers hardness and coervice force tests. The research conditions are: samples are held at (1 100±5) ℃ for 20-25 min, magnetic quenched for 15 min with 2 T intensity, then annealed at temperature (500±5) ℃ for 3 h. Conventional quenching treatment with YG6 (WC-6%Co) was also conducted. The results show that after magnetic quenching, Vickers hardness of YG6 increases by 3%, transverse rupture strength increases by 18%, impact toughness increases by 24%, cocrvice force increases by 25%; while transverse rupture strength of YN6 increases by 5.9%, impact toughness increases by 6.9%, and there is no significant change in Vickers hardness and coervice force of YN6. The content of α-Co in WC-Co alloy increases, solid solubility of W and C increases and the degree of the rounding of the edges and corners of carbide crystals tends to increase after magnetic quenching; and WC presenting serration feature while deflecting to ordered direction is the main reason for performance improving.%采用X线衍射(XRD)、扫描电镜(SEM)、金相(OM)、横向断裂强度、维氏硬度以及矫顽磁力测试等分析手段,研究YG6(WC-6%Co)及YN6(WC-6%Ni)合金在磁场淬火处理后的性能变化规律.研究的条件为:样品在(1 100±5)℃下保温20~25 min,在脉冲磁场强度2T下淬火15 min后再(500±5)℃回火3h;此外对YG6合金进行常规淬火比较.研究结果表明:磁场淬火可使YG6合金维氏硬度提高3%、横向断裂强度提高18%、冲击韧性提高24%、矫顽磁力提高25%;而YN6合金横向断裂强度提高5.9%,冲击韧性提高6.9%,维氏硬度和矫顽磁力无明显变化.磁场淬火使钴基硬质合金的黏结相中α-Co含量提高,W和C在黏结相中的固溶度

  6. New technologies for improving properties of the cemented carbide used in mining tools%提高钻采工具用硬质合金性能的新技术

    Institute of Scientific and Technical Information of China (English)

    张正富; 彭金辉

    2011-01-01

    The development in past two decades of main technology for improving properties of WC-Co cemented carbide used in mining tools is reviewed. These technologies focus on elevating the wear resistance and toughness, or increasing one performance but not harming another badly. Thereinto, the gradient microstructure can be used for removing the basic conflict between hardness and toughness to a certain extent. Its effect is obvious, but the technology parameters must be controlled strictly during forming the gradient microstructure. The heterogeneous microstructure, namely DC carbide, has the biggest effect on improving the toughness of alloy at the present time,and it doesn't harm the wear resistance badly at the same time. With using coarse particle WC carbonized at higher temperature, reducing cobalt content properly and controlling impurity level strictly, the heat conduction and toughness of coarse grain WC-Co alloys are increased and the thermal dilatability is decreased. So, the resistance ability to thermo-fatigue and impact is boosted remarkably for the coarse grain WC-Co alloy, and its wear resistance is not damaged obviously. In addition, the wear resistance can be enhanced greatly with adding a small quantity of diamond particles, and the toughness is not harmed obviously. Finally, the toughness and wear resistance of alloy can be improved remarkably when some element is added into the bend phase, or some second dispersing phase is precipitated in the bond phase by controlling the ingredient of alloy and technology parameters. Above-mentioned technologies are fitted for diverse applications as a result of their different effect and cost.%评述了近20年来,改善钻采工具用WC-Co硬质合金性能的主要技术方法.这些方法基本是围绕着同时提高合金的耐磨性和韧性、或者提高其中之一而不严重损害另一指标来进行的.其中,梯度硬质合金的方法能在一定程度上解决硬度与韧性的基本矛盾,效果

  7. Electro Deposition of Ni/Ni-MoS2 Self-lubricating Coating on Cemented Carbide%硬质合金表面电沉积Ni/Ni-MoS2自润滑涂层的研究

    Institute of Scientific and Technical Information of China (English)

    曹同坤; 杨岐龙; 单春生

    2012-01-01

    Ni/Ni-MoS2 self-lubricating coatings were prepared on cemented carbide by electro deposition. The effects of current density,pH value,MoS2 concentration of the plating liquid on deposition rate and MoS2 content in coatings were studied. The results indicate that the deposition rate and MoS2 content in coatings are firstly increased and then decreased with the increase of current density, pH value, MoS2 concentration of the plating liquid. The max value of deposition rate, and the max value of MoS2 content in the coatings are reached at the current of 3. 5 A/dm2 and 2 A/dm2 ,separately. The max value of deposition rate and MoS2 content in the coatings are reached at the pH value of 4. 5. The max deposition rate of 0. 812 μm/min ,and the max MoS2 content of 3. 26% are reached when the MoS2 concentration is 28 g/L.%采用电沉积方法在YT14硬质合金表面制备Ni/Ni-MoS2自润滑涂层,研究电流密度、pH值、MoS2加入量对自润滑沉积速率和涂层中MoS2含量的影响.结果表明:随着电流密度、pH值、MoS2加入量的增加,沉积速率和涂层中MoS2的含量都呈现先增加,后下降的规律;电流密度达到3.5 A/dm2时,沉积速率达到最大,电流密度为2 A/dm2时,MoS2的含量最高;在pH值约为4.5时,涂层的沉积速率和涂层中MoS2的含量达到最大值;当MoS2加入量为28g/L时,沉积速率达到最大值为0.812μm/min,涂层中MoS2的质量分数达到最大值为3.26%.

  8. 旋转超声磨削硬质合金的表面质量实验研究%Experimental Investigation on the Surface Quality in Rotary Ultrasonic Grinding of Cemented Carbide

    Institute of Scientific and Technical Information of China (English)

    赵春阳; 宫虎; 房丰洲

    2012-01-01

    In this paper, four kinds of diamond tools were used for the grinding experiments on cemented carbide YG8, with and without ultrasonic vibration. By using the white light interferometer and the microscope which has an ultra-deep observation field, surface qualities of the work-piece can be easily detected. The experimental results show that the diamond tools with big grain size, the surface roughness of the work-pieces machined with rotary ultra- sonic vibration are worse than that without rotary ultrasonic vibration; while the roughness differences between the work-pieces machined with and without rotary ultrasonic vibration are not obvious at the small grain size. Further- more, comparing with conventional diamond machining, it will be easier for rotary ultrasonic grinding to prevent the growth of cracks .%本文使用4种不同粒度型号的金刚石砂轮分别对硬质合金YG8进行了有、无旋转超声的端面磨削实验,并利用超景深显微镜和白光干涉仪观测了这两种加工方式下的工件表面质量。实验结果表明:当采用粒度号较小的金刚石砂轮时,有旋转超声的工件表面粗糙度要比无超声时的差;但对于粒度号较大的砂轮,有、无旋转超声所得到的工件表面粗糙度差异并不明显,甚至有旋转超声时的表面质量会略优于无旋转超声时的检测结果。相比于传统加工方式,旋转超声的使用可以明显减小被加工材料表面出现裂纹的几率。

  9. Effects of Carbon Content and B Class Porosity on Bending Strength of WC-8% Co Cemented Carbide%碳量及B类孔隙对WC-8%Co硬质合金抗弯强度的影响

    Institute of Scientific and Technical Information of China (English)

    闵召宇; 廖军; 时凯华; 蒋阳

    2013-01-01

    采用粉末冶金方法制备了WC-8%Co硬质合金试样,经氢气烧结后,利用钴磁测试仪、强度测试仪、电子显微镜和金相显微镜分别对试样的钴磁和抗弯强度进行测定、对试样断口和金相缺陷进行观察.研究了WC-8%Co硬质合金抗弯强度与碳量(相对磁饱和)、金相缺陷(B类孔隙)之间的关系.结果表明:将试样碳含量及孔隙度控制在一定的范围内,可以使试样抗弯强度保持在较高的水平,当试样相对磁饱和为88%~92%,B类孔隙为B00时,合金显微组织中WC晶粒较为均匀,无异常长大情况,WC-8%Co硬质合金抗弯强度可达3 286 N/mm2;同时,抗弯强度值的大小随孔隙度的增多而下降.另外,氢气烧结后经HIP处理可以有效消除WC-8%Co硬质合金中的孔隙缺陷,从而提高合金抗弯强度,经HIP处理的试样的强度比正常样的强度高出2.3%.%WC-8%Co cemented carbide specimens were prepared by powder metallurgy method. The cobalt magnetism and bending strength of the specimens were tested. The fracture surface and the defects in the microstructure were observed. Furthermore the effects of the carbon content (relative magnetic saturation) and the defects (B class pores) on the bending strength of the cemented carbide were studied. The results show that by means of controlling the carbon content and the porosity in the certain ranges, the bending strength of the WC-8%Co cemented carbide remains at a high level. When the relative magnetic saturation is in the range of 88%~92% and the metallographic B class porosity is BOO, the WC grain size of WC-8% Co is more uniform and the bending strength of the cemented carbide reaches its highest values at 3 286 N/mm2. Meanwhile, the bending strength value decreases with the increasing of porosity. In addition, HIP treatment after hydrogen sintering can effectively eliminate pore defects in the WC-8%Co cemented carbide, thus the bending strength is enhanced up to 2.3%.

  10. The effect of a weak W/SiC interface on the strength of sigma silicon carbide monofilament

    Science.gov (United States)

    Dyos; Shatwell

    1999-11-01

    Fractography studies have shown that the strength-determining flaws in silicon carbide monofilaments are generally at the core/silicon carbide interface or in the vicinity of the outside, carbon-based coating. In tungsten-cored monofilaments like DERA Sigma, the W/SiC flaws primarily determine the strength. Fracture is accompanied by brittle failure of the tungsten. The crack propagates simultaneously outwards through the silicon carbide, inwards through the tungsten and also around the W/SiC interface before being deflected into the tungsten or out through the silicon carbide. Experiments depositing boundary layers between the tungsten and silicon carbide have resulted in significantly different fracture behaviour. The tungsten fails in a ductile manner and the strength-determining flaws are located predominantly at the outside surface of the silicon carbide. This behaviour is discussed in terms of models proposed by E. Martin and W. Curtin. It is thought that the work will ultimately lead to a significantly stronger, tungsten-based monofilament.

  11. Characteristics of clad layer of mixture of stellite-6 and tungsten carbide powder by means of single-pass laser cladding%激光堆焊单道 Co 基合金与 WC 混合粉末的性能研究

    Institute of Scientific and Technical Information of China (English)

    徐国建; 刘爽; 杭争翔; 于恩洪; 李永波; 范荣博

    2014-01-01

    为了提高低碳钢表面的耐磨性能,采用 CO2激光堆焊系统,将 Co 基合金与 WC 混合粉末(WC 的质量分数为0~0.47)用单道堆焊于低碳钢表面。利用 X 射线衍射仪、能谱分析仪、扫描电子显微镜、激光显微镜、维氏硬度计和耐磨试验机对单道堆焊层的相结构、显微组织、维氏硬度、耐磨性和裂纹敏感性进行了比较分析。结果表明,这种堆焊方法的堆焊层均为亚共晶组织,且未分解 WC 弥散分散在 Co 基合金的基体上;堆焊层的维氏硬度均随 WC 含量的增加而增加。该方法具有较低的裂纹敏感性。%In order to improve the wear resistance of the clad layer,the powder mixture of stellite-6 and tungsten carbide (WC)in the range of 0 ~0.47 mass fraction of WC was deposited on mild steel plates by CO2 laser cladding system.The phase constitution,microstructure,hardness and wear resistance of the clad layer were studied with an X-ray diffractometer,energy dispersive spectroscopy,scanning electron microscope,laser microscope,Vickers hardness tester and wear tester.According to the analyzed results,the microstructure of the clad layer consists of hypoeutectic structure and undissolved tungsten carbides dispersed in the matrix of the Co-based alloy.The Vickers hardness increases with the increase of WC weight fraction.On the other hand,the crack sensitivity of the laser clad layer is low.

  12. 碳化钨纳米晶薄膜电极的制备及其对甲醇电氧化性能%Preparation of nano-crystalline tungsten carbide thin film electrode and its electrocatalytic activity for oxidation of methanol

    Institute of Scientific and Technical Information of China (English)

    郑华均; 马淳安; 黄建国

    2005-01-01

    Nano-crystalline tungsten carbide thin films were fabricated on graphite substrates by plasma enhanced chemical vapour deposition in H2 and Ar atmosphere, using WF6 and CH4 as precursors. The crystal phase, structure and chemical components of the films were characterized with X-ray diffraction(XRD), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS), respectively. The results showed that the film prepared at CH4/WF6 concentration ratio of 20, working pressure of 100Pa and temperature of 800℃ were composed of sphere particles with a diameter of 20-35nm Electrochemical investigations show that the electrochemical surface area of electrode of the film was large.The electrode of the film exhibited higher electro-catalytic activity in the reaction of methanol oxidation, and its catalytic properties were similar to those of Pt or Pt group catalysts. The constant current of the film catalyst was 123.6mA·cm-2 in the mixture solution of H2SO4 and CH3OH at the concentration of 0.5 mol·L-1 and 2.0 mol·L-1 respectively at 70℃, and its constant potential was only 0. 306V(vs. SCE).

  13. 非球面玻璃模造用碳化钨模仁磁控溅射铼-铱镀膜工艺优化%Optimization of magnetron sputtering of rhenium-iridium coating on mold core (tungsten carbide) used for aspheric glass molding

    Institute of Scientific and Technical Information of China (English)

    杜琪健

    2012-01-01

    通过钽过渡镀层与铼-铱复合镀层相结合的膜层结构,解决了非球面玻璃模造碳化钨模仁热压寿命短、沾黏等问题.通过离子源和镀膜层厚度参数的优化调整,得到了最佳镀膜工艺和参数,改善了模仁的表面品质,延长了模仁的使用寿命.镀钽膜层15 min及铼-铱膜层21 min后所得镀膜的总厚度约为270 nm,模仁热压寿命可超过3 000次.%The problems of short service life and sticking of tungsten carbide (WC) mold core used for aspheric glass molding were solved by combination of tantalum mediate coating and rhenium-indium composite coating. The parameters of ion source and coating thickness were optimized and the optimal plating conditions were obtained. The surface quality of mold core was improved and its service life greatly extended. The molding core with a coating having a total thickness of ca.270 nm obtained by successively plating Ta for 15 min and Re-Ir for 21 min can be reused for more than 3 000 times in hot embossing.

  14. 金刚石涂层硬质合金阶梯刀具的制备及钻削特性%Preparation and Drilling Characteristics of Diamond Coated Cemented Carbide Step Cutting Tool

    Institute of Scientific and Technical Information of China (English)

    向道辉; 张磊; 张玉龙; 马国峰; 周直昆; 秦强

    2016-01-01

    The diamond coating was prepared on the surface of the cemented carbide step cutting tool by using double-layered hot filament assisted chemical vapor deposition (CVD).Then the drilling characteristics and wear properties of the uncoated and coated cutting tools during drilling the composite fiber brake pad,as well as the surface qualities of the machined hole,were compared and analyzed.The results show that under the high speed drilling condition,the axial force and torque of coated cutting tool were obviously lower than those of uncoated cutting tool,showing a better drilling performance.After drilling 10 holes at the same speed and feed rate,the flank wear height of the coated cutting tool was about 0.025 mm,which was much less than the wear standard (0.2 mm), while that (0.15 mm)of uncoated cutting tool was close to the wear standard,indicating that the wear resistant of the coated cutting tool was better than that of uncoated cutting tool.The hole boundary drilled by the coated cutting tool was smooth and had no burr and tearing.The surface quality was better than that drilled by uncoated cutting tool.%采用双层热丝化学气相沉积(CVD)法在硬质合金阶梯刀具表面制备了金刚石涂层,对比分析了无涂层和涂层刀具钻削复合纤维刹车片的钻削特性和磨损性能以及加工孔的表面质量.结果表明:在高速钻削条件下,涂层刀具的轴向力和扭矩明显小于无涂层刀具的,表现出更好的钻削性能;当以相同的转速和进给量钻削出10个孔后,涂层刀具的后刀面磨损高度约为0.025 mm,远小于磨损标准(0.2 mm),无涂层刀具的后刀面磨损高度(0.15 mm)则接近磨损标准,涂层刀具的耐磨性能优于无涂层刀具的;涂层刀具钻削孔的四周圆滑,没有毛刺及撕裂现象,其表面质量好于无涂层刀具钻削孔的.

  15. Systematic studies of the nucleation and growth of ultrananocrystalline diamond films on silicon substrates coated with a tungsten layer

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Yueh-Chieh; Jiang, Gerald [Institute of Microelectronics, No.1, University Road, Tainan 701, Taiwan (China); Tu, Chia-Hao [Institute of Nanotechnology and Microsystems Engineering, No.1, University Road, Tainan 701, Taiwan (China); Department of Materials Science and Engineering, National Cheng Kung University, No.1, University Road, Tainan 701, Taiwan (China); Chang Chi [Institute of Nanotechnology and Microsystems Engineering, No.1, University Road, Tainan 701, Taiwan (China); Liu, Chuan-pu; Ting, Jyh-Ming [Department of Materials Science and Engineering, National Cheng Kung University, No.1, University Road, Tainan 701, Taiwan (China); Lee, Hsin-Li [Industrial Technology Research Institute - South, Tainan 701, Taiwan (China); Tzeng, Yonhua [Institute of Microelectronics, No.1, University Road, Tainan 701, Taiwan (China); Advanced Optoelectronics Technology Center, No.1, University Road, Tainan 701, Taiwan (China); Auciello, Orlando [Argonne National Laboratory, Materials Science Division, 9700 S. Cass Avenue, Argonne, Illinois 60439 (United States)

    2012-06-15

    We report on effects of a tungsten layer deposited on silicon surface on the effectiveness for diamond nanoparticles to be seeded for the deposition of ultrananocrystalline diamond (UNCD). Rough tungsten surface and electrostatic forces between nanodiamond seeds and the tungsten surface layer help to improve the adhesion of nanodiamond seeds on the tungsten surface. The seeding density on tungsten coated silicon thus increases. Tungsten carbide is formed by reactions of the tungsten layer with carbon containing plasma species. It provides favorable (001) crystal planes for the nucleation of (111) crystal planes by Microwave Plasma Enhanced Chemical Vapor Deposition (MPECVD) in argon diluted methane plasma and further improves the density of diamond seeds/nuclei. UNCD films grown at different gas pressures on tungsten coated silicon which is pre-seeded by nanodiamond along with heteroepitaxially nucleated diamond nuclei were characterized by Raman scattering, field emission-scanning electron microscopy, and high resolution-transmission electron microscopy.

  16. Sintering behavior of alumina-niobium carbide ceramics from polymer-filler mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Acchar, W.; Wolff, D.M.B. [Programa de Doutorado em Engenharia e Ciencia dos Materiais-UFRN, Univ. Federal do Rio Grande do Norte, Natal, RN (Brazil); S. Dantas, A.C. da [Programa de Pos-graduacao em Engenharia Mecanica-UFRN, Univ. Federal do Rio Grande do Norte - Natal, RN (Brazil)

    2003-07-01

    Studies have been developed in the literature to obtain alternative ceramic cutting tools with better properties as tungsten carbide and silicon nitride. Results have showed that the addition of titanium carbide, tungsten carbide or niobium carbide has improved the wear resistance and hardness of alumina. This work presents a study about preparation and characterization of an alumina reinforced with niobium carbide. The composite material is produced using polymer-filler mixtures. Samples with 60 wt.% polysiloxane and a mixture of 40 wt.% of niobium and alumina powder were mixed, uniaxially pressed at 200 C and sintered in flowing argon at 1200 C, 1400 C and 1600 C. The composite materials were characterized by X-ray diffraction (XRD), density measurements, fracture strength and microstructural analysis. The 60 wt% polymer+40 wt% Nb showed the presence of new crystalline phases such as NbC, Nb{sub 5}Si{sub 3} and Nb{sub 3}Si. (orig.)

  17. Cement Formation

    DEFF Research Database (Denmark)

    Telschow, Samira; Jappe Frandsen, Flemming; Theisen, Kirsten

    2012-01-01

    Cement production has been subject to several technological changes, each of which requires detailed knowledge about the high multiplicity of processes, especially the high temperature process involved in the rotary kiln. This article gives an introduction to the topic of cement, including...... an overview of cement production, selected cement properties, and clinker phase relations. An extended summary of laboratory-scale investigations on clinkerization reactions, the most important reactions in cement production, is provided. Clinker formations by solid state reactions, solid−liquid and liquid...

  18. The production of wear protection coatings reinforced with tungsten carbide by temperature-controlled welding with the CO{sub 2} laser; Herstellung wolframkarbidverstaerkter Verschleissschutzschichten durch temperaturgeregeltes Auftragschweissen mit dem CO{sub 2}-Laser

    Energy Technology Data Exchange (ETDEWEB)

    Nowotny, S.; Boddin, G.C.; Luft, A.; Techel, A. [Fraunhofer-Inst. fuer Werkstoffphysik und Schichttechnologie, Dresden (Germany); Uelze, A. [Hochschule fuer Technik und Wirtschaft Dresden (Germany)

    1995-12-31

    Protective coatings can be produced by laser coating with metal alloys reinforced by carbide, whose resistance to abrasive wear with a content of 40 to 50% by volume of hard material is comparable to sintered TC-Co hard metal. Due to the remaining ductile material behaviour and the metallurgical binding to the substrate, the coatings have high impact, fatigue and adhesion strengths. The use of process control leads to a stable coating process and to increased safety and reproduceability when working in narrow parameter areas. (orig./RHM) [Deutsch] Durch das Laserbeschichten mit karbidverstaerkten Metallegierungen koennen Schutzschichten erzeugt werden, deren Widerstand gegen Abrasivverschleiss bereits bei einem Hartstoff-Volumengehalt von 40 bis 50% gesintertem WC-Co-Hartmetall vergleichbar ist. Aufgrund des verbleibenden duktilen Werkstoffverhaltens und der metallurgischen Bindung zum Substrat verfuegen die Schichten ueber hohe Schlag-, Ermuedungs- und Haftfestigkeiten. Der Einsatz der Prozessregelung fuehrt zu einem stabilen Beschichtungsvorgang und zu einer erhoehten Sicherheit und Reproduzierbarkeit beim Arbeiten in eng begrenzten Parameterbereichen. (orig./RHM)

  19. Tungsten Alloy Outgassing Measurements

    CERN Document Server

    Rutherfoord, John P; Shaver, L

    1999-01-01

    Tungsten alloys have not seen extensive use in liquid argon calorimeters so far. Because the manufacturing process for tungsten is different from the more common metals used in liquid argon there is concern that tungsten could poison the argon thereby creating difficulties for precision calorimetry. In this paper we report measurements of outgassing from the tungsten alloy slugs proposed for use in the ATLAS FCal module and estimate limits on potential poisoning with reasonable assumptions. This estimate gives an upper limit poisoning rate of tungsten slugs.

  20. 碳化钨和Vulcan XC-72炭黑载钯催化剂对甲酸氧化的电催化性能%Electrocatalytic Performance of Tungsten Carbide and Vulcan XC-72 Carbon Supported Pd Catalyst for Formic Acid Oxidation

    Institute of Scientific and Technical Information of China (English)

    沈娟章; 季芸; 陈赵杨; 马淳安; 陆天虹

    2012-01-01

    研究了碳化钨(WC)和Vulcan XC-72炭黑(XC)作混合载体的Pd/WC-XC催化剂对甲酸氧化的电催化性能.发现Pd/WC-XC催化剂对甲酸氧化的电催化性能优于Pd/XC催化剂.而且,Pd/WC-XC催化剂的电催化性能与WC和XC的质量比有关,当质量比为3:1时,催化剂对甲酸氧化的电催化活性最好,当质量比为2:1时,催化剂对甲酸氧化的电催化稳定性性最好.%This work investigated the elecrocatalytic performance of tungsten carbide(WC) and Vulcan XC-72 carbon (XC) supported Pd(Pd/WC-XC) catalysts for formic acid oxidation.It is found that the electrocatalytic performance of the Pd/WC-XC catalysts for formic acid oxidation is better than that of the Pd/XC catalyst.Furthermore,the electrocatalytic performance of the Pd/WC-XC catalyst is related to the mass ratio of WC and XC.When the mass ratio of WC and XC is 3:1,the electrocatalytic activity of the catalyst is best.When the mass ratio of WC and XC is 2:1,the electrocatalytic stability of the catalyst is best.

  1. Structure and thermal expansion of NbC complex carbides

    Energy Technology Data Exchange (ETDEWEB)

    Khatsinskaya, I.M.; Chaporova, I.N.; Cheburaeva, R.F.; Samojlov, A.I.; Logunov, A.V.; Ignatova, I.A.; Dodonova, L.P.

    1983-11-01

    Alloying dependences of the crystal lattice parameters at indoor temperature and coefficient of thermal linear expansion within a 373-1273 K range are determined for complex NbC-base carbides by the method of mathematical experimental design. It is shown that temperature changes in the linear expansion coefficient of certain complex carbides as distinct from NbC have an anomaly (minimum) within 773-973 K caused by occurring reversible phase transformations. An increase in the coefficient of thermal linear expansion and a decrease in hardness of NbC-base tungsten-, molybdenum-, vanadium- and hafnium-alloyed carbides show a weakening of a total chemical bond in the complex carbides during alloying.

  2. Titanium Carbide-Graphite Composites

    Science.gov (United States)

    1991-11-08

    titanium carbide , titanium carbide with free graphite, titanium carbide /vanadium carbide alloy with free graphite, and titanium carbide with...from melts. The test pins were drawn across hot pressed titanium carbide wear plates with 5 newtons of normal force. The lowest friction coefficient at...22 C was 0.12 obtained with pure titanium carbide . The lowest friction coefficient at 900 C was 0.19 obtained with titanium carbide with boron and

  3. Application of diffusion barriers to the refractory fibers of tungsten, columbium, carbon and aluminum oxide

    Science.gov (United States)

    Douglas, F. C.; Paradis, E. L.; Veltri, R. D.

    1973-01-01

    A radio frequency powered ion-plating system was used to plate protective layers of refractory oxides and carbide onto high strength fiber substrates. Subsequent overplating of these combinations with nickel and titanium was made to determine the effectiveness of such barrier layers in preventing diffusion of the overcoat metal into the fibers with consequent loss of fiber strength. Four substrates, five coatings, and two metal matrix materials were employed for a total of forty material combinations. The substrates were tungsten, niobium, NASA-Hough carbon, and Tyco sapphire. The diffusion-barrier coatings were aluminum oxide, yttrium oxide, titanium carbide, tungsten carbide with 14% cobalt addition, and zirconium carbide. The metal matrix materials were IN 600 nickel and Ti 6/4 titanium. Adhesion of the coatings to all substrates was good except for the NASA-Hough carbon, where flaking off of the oxide coatings in particular was observed.

  4. Boron carbide (B{sub 4}C) coating. Deposition and testing

    Energy Technology Data Exchange (ETDEWEB)

    Azizov, E.; Barsuk, V. [Troitsk Institute for Innovation and Fusion Research (TRINITI), Moscow Region (Russian Federation); Begrambekov, L., E-mail: lbb@plasma.mephi.ru [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Buzhinsky, O. [Troitsk Institute for Innovation and Fusion Research (TRINITI), Moscow Region (Russian Federation); Evsin, A.; Gordeev, A.; Grunin, A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Klimov, N. [Troitsk Institute for Innovation and Fusion Research (TRINITI), Moscow Region (Russian Federation); Kurnaev, V. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Mazul, I. [Federal State Unitary Interprise Efremov Scientific Research Institute of Electrophysical Apparatus (NIIEFA Efremov), St-Peterburg (Russian Federation); Otroshchenko, V.; Putric, A. [Troitsk Institute for Innovation and Fusion Research (TRINITI), Moscow Region (Russian Federation); Sadovskiy, Ya.; Shigin, P.; Vergazov, S.; Zakharov, A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation)

    2015-08-15

    Boron carbide was proposed as a material of in-situ protecting coating for tungsten tiles of ITER divertor. To prove this concept the project including investigation of regimes of plasma deposition of B{sub 4}C coating on tungsten and tests of boron carbide layer in ITER-like is started recently. The paper contends the first results of the project. The results of B{sub 4}C coating irradiation by the plasma pulses of QSPU-T plasma accelerator are presented. The new device capable of B{sub 4}C film deposition on tungsten and testing of the films and materials with ITER-like heat loads and ion- and electron irradiation is described. The results of B{sub 4}C coating deposition and testing of both tungsten substrate and coating are shown and discussed.

  5. 复合电刷镀镍-钨-钴-纳米碳化硅及其性能%Electro-brush plating of nickel-tungsten-cobalt-nano silicon carbide composite coating and its properties

    Institute of Scientific and Technical Information of China (English)

    陈大川; 谢光荣; 曾鹏; 李程飞; 许小东

    2016-01-01

    A Ni-W-Co-n-SiC (nano silicon carbide) composite coating was prepared on the surface of 45 steel by electro-brush plating. The bath composition and process conditions are as follows: NiSO4·7H2O 393 g/L, Na2WO4·2H2O 23 g/L, H3BO331 g/L, citric acid 42 g/L, Na2SO46.5 g/L, CoSO4·7H2O 3 g/L, NaF 5 g/L,n-SiC 0-30 g/L, temperature 25-45 °C, pH 1.4-2.4, voltage 5-7 V, moving rate of plating pen 0.8 m/s and time 25 min. The suitable voltage for composite electro-brush plating was determined as 6 V based on the evaluation of appearance using a Ni-W-Co alloy coating as the standard. The effect ofn-SiC content in bath on the structure, microhardness and friction-wear performance of the nanocomposite coating was studied. The results showed that a crack-free Ni-W-Co-n-SiC composite coating with uniformly distributed particles can be obtained from the bath containing 15-25 g/L SiC nanoparticles. With increasingn-SiC content in bath, the crystallization degree, solid solubility of Ni, as well as microhardness and wear resistance of composite coating are increased, while the friction coefficient of the composite coating surface is changed little.%采用电刷镀工艺在45钢表面制备了Ni-W-Co-n-SiC(纳米碳化硅)复合镀层,镀液组成和工艺条件为:NiSO4·7H2O 393 g/L,Na2WO4·2H2O 23 g/L,H3BO331 g/L,柠檬酸42 g/L,Na2SO46.5 g/L,CoSO4·7H2O 3 g/L,NaF 5 g/L,n-SiC 0~30 g/L,温度25~45°C,pH 1.4~2.4,电压5~7 V,镀笔速率0.8 m/s,时间25 min.以Ni-W-Co合金镀层的外观为指标,筛选得到较适合的复合电刷镀电压为6 V.研究了镀液n-SiC含量对镀层的组织结构、显微硬度和摩擦磨损性能的影响.结果表明,镀液中n-SiC含量为15~25 g/L时,可以获得颗粒均匀分布、无微裂纹的Ni-W-Co-n-SiC复合镀层.随镀液中n-SiC含量增大,复合镀层的晶化程度、Ni固溶度和显微硬度均提高,耐磨性改善,但摩擦因数的变化不大.

  6. SURFACE MODIFICATION OF WC-Ni CEMENTED CARBIDE FOR SEALS BY HIGH-INTENSITY PULSED ION BEAM IRRADIATION%强流脉冲离子束辐照WC-Ni硬质密封材料表面改性研究

    Institute of Scientific and Technical Information of China (English)

    张锋刚; 朱小鹏; 王明阳; 雷明凯

    2011-01-01

    The WC-Ni cemented carbide, as a promising seal component material in nuclear power plant, was treated by high-intensity pulsed ion beam (HIPIB) with ion energy of 300 keV, ion current density of 300 A/cm2, I.e., at a power density of 108 W/cm2 and at a pulse duration of 70 ns up to 10 shots. The phase composition, surface morphology and element distribution in the surface of WC-Ni cemented carbide before and after HIPIB irradiation were investigated by using XRD, SEM and EPMA, and its properties were characterized by microhardness measurement and block-on-ring wear testing. It is found that the phase transformation from hexagonal WC to cubic /3-Wci_x underwent in the irradiated surface layer, and the amount of /3-Wci_x phase increased with increasing shot number. The surface remelting and selective ablation of the nickel binder phase resulted in the formation of hilly topography with numerous protrusions on the irradiated surfaces, and the dimension of protrusions expanded under repetitive irradiation. As increasing the irradiation up to 10 shots, a network of hill-valleys was finally produced on the irradiated surfaces but the surface is smoothed and densified in a micro scale. A hardened depth of 160μm was obtained, which is attributable to the strong stress wave induced during the irradiation. As a result, the wear resistance of WC-Ni cemented carbides is considerably improved by a factor of 3 along with a 38% reduction in the friction coefficient after 10-shot irradiation.%利用离子能量为300 keV,束流密度为300 A/cm2,功率密度为108 W/cm2,脉冲宽度为70 ns的强流脉冲离子束(HIPIB)对用于核主泵轴密封的WC-Ni硬质合金材料进行了表面辐照处理,辐照次数分别为1,5,10次.利用XRD,SEM和EPMA研究了HIPIB辐照前后WC-Ni硬质合金表层相组成、表面形貌和元素分布的变化,借助显微硬度计和环-块式磨损仪测试了辐照前后硬质合金表层的性能.结果表明,HIPIB辐照硬质合金表层

  7. INVESTIGATION OF AES AND XPS FOR THE ION BOMBARDED CARBON FILMS ON THE SURFACE OF TUNGSTEN ALLOY%离子束轰击钨合金表面碳膜的AES和XPS分析

    Institute of Scientific and Technical Information of China (English)

    李俊; 高剑; 张一云; 吴丽萍; 黄宁康; 赵纯培

    2000-01-01

    Tungsten alloy with special properties is a useful material in medical and weapon devices. Surface modification of ion technique is used to improve the surface hardness and wear resistance of tungsten alloy, where carbon films deposited with magnetron sputtering on the surface of tungsten alloy were bombarded by ion beam with different species AES and XPS analyses for these speciment show that tungsten carbide and tungsten nitride were formed due to N+ bombardment. Which is beneficial to the Surface hardness and wear resistance of tungsten alloy,but no carbide or no nitride as above with other ion species. Again,ion bombardness leads to mixing between the carbon and tungsten alloy hence improve the adhere of carbon film to the substrate.

  8. Tungsten-microdiamond composites for plasma facing components

    Science.gov (United States)

    Livramento, V.; Nunes, D.; Correia, J. B.; Carvalho, P. A.; Mardolcar, U.; Mateus, R.; Hanada, K.; Shohoji, N.; Fernandes, H.; Silva, C.; Alves, E.

    2011-09-01

    Tungsten is considered as one of promising candidate materials for plasma facing component in nuclear fusion reactors due to its resistance to sputtering and high melting point. High thermal conductivity is also a prerequisite for plasma facing components under the unique service environment of fusion reactor characterised by the massive heat load, especially in the divertor area. The feasibility of mechanical alloying of nanodiamond and tungsten, and the consolidation of the composite powders with Spark Plasma Sintering (SPS) was previously demonstrated. In the present research we report on the use of microdiamond instead of nanodiamond in such composites. Microdiamond is more favourable than nanodiamond in view of phonon transport performance leading to better thermal conductivity. However, there is a trade off between densification and thermal conductivity as the SPS temperature increases tungsten carbide formation from microdiamond is accelerated inevitably while the consolidation density would rise.

  9. Simple preparation of tungsten supported carbon nanoreactors for specific applications: Adsorption, catalysis and electrochemical activity

    Energy Technology Data Exchange (ETDEWEB)

    Mayani, Vishal J.; Mayani, Suranjana V.; Kim, Sang Wook, E-mail: swkim@dongguk.ac.kr

    2015-08-01

    Graphical abstract: - Highlights: • Tungsten carbon composites have shown great recognition in catalysis and electrochemistry. • W-carbon composites are prepared by template replication and W-doping on carbon cage. • Nanocomposites offer enormous assurance as adsorbent, electrode and heterogeneous catalyst. - Abstract: Porous carbon supported tungsten carbide nanoreactors, two sizes (∼25 and 170 nm), were designed using economical petroleum pitch residue followed by tungsten (W) doping. X-ray diffractions showed both carbon tungsten composites (CTC-25 and CTC-170) contained tungsten subcarbide (W{sub 2}C) and monocarbide (WC) as the major and minor crystalline phases, respectively. The present study provides a multiple perspective of carbon tungsten composites (CTCs) for methanol oxidation (as an electrode), adsorption (as an adsorbent) and degradation (as a solid catalyst) of methylene blue (MB). The operational electrodes were designed from both CTCs and used as a catalyst in an electrocatalysis process. The electrocatalysts exhibited high and stable catalytic performance (CTCE-25 > CTCE-170) in methanol electro-oxidation. The newly synthesized W-doped carbon nanoreactors were used successfully as an adsorbent for MB and a heterogeneous catalyst for MB oxidation. Ordered CTC-25 and CTC-170 exhibited dynamic MB adsorption within 15 min and complete oxidation of MB in 25–40 min. A synergetic effect between tungsten carbide and the carbon cage framework was noted.

  10. Tungsten Filament Fire

    Science.gov (United States)

    Ruiz, Michael J.; Perkins, James

    2016-01-01

    We safely remove the outer glass bulb from an incandescent lamp and burn up the tungsten filament after the glass is removed. This demonstration dramatically illustrates the necessity of a vacuum or inert gas for the environment surrounding the tungsten filament inside the bulb. Our approach has added historical importance since the incandescent…

  11. Textbook tests with tungsten

    CERN Multimedia

    Barbara Warmbein

    2010-01-01

    CERN's linear collider detector group joins forces with CALICE in building the world's first tungsten hadronic calorimeter.   Hadronic calorimeter prototype made of tungsten for the linear collider detector being equipped with CALICE scintillators. In a hall for test beam experiments at CERN, next to the CLOUD climate experiment and an irradiation facility, sits a detector prototype that is in many ways a first. It's the first ever hadronic sandwich calorimeter (HCal) prototype made of tungsten. It's the first prototype for a detector for the Compact Linear Collider Study CLIC, developed by the linear collider detector R&D group (LCD group) at CERN. And it's the first piece of hardware that results directly from the cooperation between CLIC and ILC detector study groups. Now its makers are keen to see first particle showers in their detector. The tungsten calorimeter has just moved from a workshop at CERN, where it was assembled from finely polished tungsten squares and triangles, into the ...

  12. SILICON CARBIDE FOR SEMICONDUCTORS

    Science.gov (United States)

    This state-of-the-art survey on silicon carbide for semiconductors includes a bibliography of the most important references published as of the end...of 1964. The various methods used for growing silicon carbide single crystals are reviewed, as well as their properties and devices fabricated from...them. The fact that the state of-the-art of silicon carbide semiconductors is not further advanced may be attributed to the difficulties of growing

  13. Silicon Carbide Shapes.

    Science.gov (United States)

    Free-standing silicon carbide shapes are produced by passing a properly diluted stream of a reactant gas, for example methyltrichlorosilane, into a...reaction chamber housing a thin walled, hollow graphite body heated to 1300-1500C. After the graphite body is sufficiently coated with silicon carbide , the...graphite body is fired, converting the graphite to gaseous CO2 and CO and leaving a silicon carbide shaped article remaining.

  14. Hardening of a dual-cure resin cement using QTH and LED curing units

    OpenAIRE

    Santos,Maria Jacinta Moraes Coelho; Passos, Sheila Pestana; Encarnação, Monalisa Olga Lessa da; Santos Junior,Gildo Coelho; Bottino, Marco Antonio [UNESP

    2010-01-01

    p. 110-115 OBJECTIVE: This study evaluated the surface hardness of a resin cement (RelyX ARC) photoactivated through indirect composite resin (Cristobal) disks of different thicknesses using either a light-emitting diode (LED) or quartz tungsten halogen (QTH) light source. MATERIAL AND METHODS: Eighteen resin cement specimens were prepared and divided into 6 groups according to the type of curing unit and the thickness of resin disks interposed between the cement surface and light sourc...

  15. SILICON CARBIDE DATA SHEETS

    Science.gov (United States)

    These data sheets present a compilation of a wide range of electrical, optical and energy values for alpha and beta- silicon carbide in bulk and film...spectrum. Energy data include energy bands, energy gap and energy levels for variously-doped silicon carbide , as well as effective mass tables, work

  16. Friction and metal transfer for single-crystal silicon carbide in contact with various metals in vacuum

    Science.gov (United States)

    Miyoshi, K.; Buckley, D. H.

    1978-01-01

    Sliding friction experiments were conducted with single-crystal silicon carbide in contact with transition metals (tungsten, iron, rhodium, nickel, titanium, and cobalt), copper, and aluminum. Results indicate the coefficient of friction for a silicon carbide-metal system is related to the d bond character and relative chemical activity of the metal. The more active the metal, the higher the coefficient of friction. All the metals examined transferred to the surface of silicon carbide in sliding. The chemical activity of metal to silicon and carbon and shear modulus of the metal may play important roles in metal transfer and the form of the wear debris. The less active and greater resistance to shear the metal has, with the exception of rhodium and tungsten, the less transfer to silicon carbide.

  17. Thermal Transport in Refractory Carbides.

    Science.gov (United States)

    Thermal energy transport mechanisms in titanium carbide and zirconium carbide have been studied. Several compositions of vanadium carbide alloyed...with titanium carbide were used. The electronic component of the thermal conductivity exceeded the values computed using the classical value for L in

  18. Laser irradiation of carbon-tungsten materials

    Science.gov (United States)

    Marcu, A.; Avotina, L.; Marin, A.; Lungu, C. P.; Grigorescu, C. E. A.; Demitri, N.; Ursescu, D.; Porosnicu, C.; Osiceanu, P.; Kizane, G.; Grigoriu, C.

    2014-09-01

    Carbon-tungsten layers deposited on graphite by thermionic vacuum arc (TVA) were directly irradiated with a femtosecond terawatt laser. The morphological and structural changes produced in the irradiated area by different numbers of pulses were systematically explored, both along the spots and in their depths. Although micro-Raman and Synchrotron-x-ray diffraction investigations have shown no carbide formation, they have shown the unexpected presence of embedded nano-diamonds in the areas irradiated with high fluencies. Scanning electron microscopy images show a cumulative effect of the laser pulses on the morphology through the ablation process. The micro-Raman spatial mapping signalled an increased percentage of sp3 carbon bonding in the areas irradiated with laser fluencies around the ablation threshold. In-depth x-ray photoelectron spectroscopy investigations suggested a weak cumulative effect on the percentage increase of the sp2-sp3 transitions with the number of laser pulses just for nanometric layer thicknesses.

  19. The Hone Edge of the Carbide Cemented Drill Bit and the Measurement of Hone Edge Radius%硬质合金钻头刃口钝圆及其半径的测量

    Institute of Scientific and Technical Information of China (English)

    王弢; 周一丹; 张平

    2012-01-01

    指出了硬质合金钻头刃口钝圆对切削加工的影响,说明了硬质合金钻头刃口钝圆的重要性,简要介绍了刃口钝圆的方法及常规的测量方法,提出了在Matlab中用最小二乘法拟合的数据处理方法来获得刀口钝圆半径值.与传统测量方法相比,此方法避免了常规测量方法所产生的人为的不确定因素,减少了由于测量系统的精确度引起的误差,可以准确地判断是否达到钝化参数的要求,对优化刀具结构设计、提高切削性能、增加刀具使用寿命有重要的作用和实际意义.%The influence of hone edge radius of carbide drill bit during cutting was pointed out here, and the importance of hone edge was UlustratedAnd then,the measurement of hone edge and the way to measure were introduced briefly.The hone edge radius were acquired by a new data processing method of the least squares fitting, which can avoid the artificial uncertainties,reduce the errors caused by the accuracy of the measurement system in the conventional measurement methods,and it has an important significance for optimizing cutting tool structure design, improving cutting performance, and increasing tool life.

  20. 采用溶胶-凝胶法在刀具表面制备MoS_2软涂层的研究%Investigation of the preparation of MoS_2 coating on the surface of cemented carbide by sol-gel method

    Institute of Scientific and Technical Information of China (English)

    丁志敏; 杨贺; 李宝良; 李丽

    2012-01-01

    On the basis of MoS2 soft coating on the surface of cemented carbide was successfully obtained by citric acid sol-gel method,influence of added amount of MoS2 in the coating on surface microscopic morphology and friction coefficient of MoS2 coating was studied by scanning electron microscope and friction test.The results indicated that,MoS2 coatings with high quality and good binding with the substrate on surface of cemented carbide samples can be prepared by sol-gel method of respectively adding 13,20,27g/L MoS2 into 1.6mol/L citrate solution and making one on the surface by burshing.The surface morphology of the MoS2 coating is of lamellar.The samples with MoS2 soft coating significantly reduces the friction coefficient from 0.6-0.8 of original sample to 0.15-0.25.But the adding amount of MoS2 in soft coating has no obvious difference in the friction coefficient.The fact that the soft coating could reduce the friction coefficient of samples could be attributed to the presence of the coating with MoS2,that has advantages of lower friction and great bearing capacity,and changed friction nature between the friction pairs materials becauce of the existence of coating.%在成功地采用柠檬酸溶胶-凝胶法在硬质合金试样表面制备出MoS2软涂层的基础上,采用扫描电镜形貌观察和摩擦系数测定等实验方法研究了MoS2加入量对涂层表面微观形貌及其摩擦性能的影响规律。结果表明,采用溶胶-凝胶法在1.6mol/L柠檬酸水溶液中分别添加13、20和27g/L MoS2粉末条件下,应用刷涂法均可以在硬质合金试样表面得到与基体结合牢固、表面质量较高的MoS2软涂层。所获得的MoS2软涂层的表面形貌呈片状。MoS2软涂层的存在明显地降低了硬质合金试样的摩擦系数,由硬质合金试样的0.58~0.86降低到软涂层的0.18~0.23。而具有不同MoS2加入量的软涂层间的摩擦系数相差不大。软涂层试样的摩擦系数明显低于硬质合金

  1. CEMENT SLURRIES FOR GEOTHERMAL WELLS CEMENTING

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    1994-12-01

    Full Text Available During a well cementing special place belongs to the cement slurry design. To ensure the best quality of cementing, a thorough understanding of well parameters is essential, as well as behaviour of cement slurry (especially at high temperatures and application of proven cementing techniques. Many cement jobs fail because of bad job planning. Well cementing without regarding what should be accomplished, can lead to well problems (channels in the cement, unwanted water, gas or fluid production, pipe corrosion and expensive well repairs. Cementing temperature conditions are important because bot-tomhole circulating temperatures affect slurry thickening time, arheology, set time and compressive strength development. Knowing the actual temperature which cement encounters during placement allows the selection of proper cementing materials for a specific application. Slurry design is affected by well depth, bottom hole circulating temperature and static temperature, type or drilling fluid, slurry density, pumping time, quality of mix water, fluid loss control, flow regime, settling and free water, quality of cement, dry or liquid additives, strength development, and quality of the lab cement testing and equipment. Most Portland cements and Class J cement have shown suitable performances in geot-hermal wells. Cement system designs for geothermal wells differ from those for conventional high temperature oil and gas wells in the exclusive use of silica flour instead of silica sand, and the avoidance of fly ash as an extender. In this paper, Portland cement behaviour at high temperatures is described. Cement slurry and set cement properties are also described. Published in literature, the composition of cement slurries which were tested in geothermal conditions and which obtained required compressive strength and water permeability are listed. As a case of our practice geothermal wells Velika Ciglena-1 and Velika Ciglena-la are described.

  2. Lunar cement

    Science.gov (United States)

    Agosto, William N.

    1992-01-01

    With the exception of water, the major oxide constituents of terrestrial cements are present at all nine lunar sites from which samples have been returned. However, with the exception of relatively rare cristobalite, the lunar oxides are not present as individual phases but are combined in silicates and in mixed oxides. Lime (CaO) is most abundant on the Moon in the plagioclase (CaAl2Si2O8) of highland anorthosites. It may be possible to enrich the lime content of anorthite to levels like those of Portland cement by pyrolyzing it with lunar-derived phosphate. The phosphate consumed in such a reaction can be regenerated by reacting the phosphorus product with lunar augite pyroxenes at elevated temperatures. Other possible sources of lunar phosphate and other oxides are discussed.

  3. Light transmittance of zirconia as a function of thickness and microhardness of resin cements under different thicknesses of zirconia

    OpenAIRE

    Cekic Nagas, Isil; Egilmez,Ferhan; Ergün, Gülfem; Kaya, Bekir-Murat

    2013-01-01

    Objective: The objective of this study was to compare microhardness of resin cements under different thicknesses of zirconia and the light transmittance of zirconia as a function of thickness. Study design: A total of 126 disc-shaped specimens (2 mm in height and 5 mm in diameter) were prepared from dual-cured resin cements (RelyX Unicem, Panavia F and Clearfil SA cement). Photoactivation was performed by using quartz tungsten halogen and light emitting diode light curing units under differen...

  4. Tungsten diffusion in olivine

    Science.gov (United States)

    Cherniak, D. J.; Van Orman, J. A.

    2014-03-01

    Diffusion of tungsten has been characterized in synthetic forsterite and natural olivine (Fo90) under dry conditions. The source of diffusant was a mixture of magnesium tungstate and olivine powders. Experiments were prepared by sealing the source material and polished olivine under vacuum in silica glass ampoules with solid buffers to buffer at NNO or IW. Prepared capsules were annealed in 1 atm furnaces for times ranging from 45 min to several weeks, at temperatures from 1050 to 1450 °C. Tungsten distributions in the olivine were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for W diffusion in forsterite: D=1.0×10-8exp(-365±28 kJ mol/RT) m s Diffusivities for the synthetic forsterite and natural Fe-bearing olivine are similar, and tungsten diffusion in olivine shows little dependence on crystallographic orientation or oxygen fugacity. The slow diffusivities measured for W in olivine indicate that Hf-W ages in olivine-metal systems will close to diffusive exchange at higher temperatures than other chronometers commonly used in cosmochronology, and that tungsten isotopic signatures will be less likely to be reset by subsequent thermal events.

  5. Gas tungsten arc welder

    Science.gov (United States)

    Christiansen, D.W.; Brown, W.F.

    A welder for automated closure of fuel pins by a gas tungsten arc process in which a rotating length of cladding is positioned adjacent a welding electrode in a sealed enclosure. An independently movable axial grinder is provided in the enclosure for refurbishing the used electrode between welds.

  6. OPAL Silicon Tungsten Luminometer

    CERN Multimedia

    OPAL was one of the four experiments installed at the LEP particle accelerator from 1989 - 2000. The Silicon Tungsten Luminometer was part of OPAL's calorimeter which was used to measure the energy of particles. Most particles end their journey in calorimeters. These detectors measure the energy deposited when particles are slowed down and stopped.

  7. Indication of worn WC/C surface locations of a dry-running twin-screw rotor by the oxygen incorporation in tungsten-related Raman modes

    Science.gov (United States)

    Debus, J.; Schindler, J. J.; Waldkirch, P.; Goeke, S.; Brümmer, A.; Biermann, D.; Bayer, M.

    2016-10-01

    By comparing the worn and untouched locations of a tungsten-carbide/carbon surface of a dry-running twin-screw rotor, we demonstrate that tungsten-oxide Raman modes become observable only at worn locations and the integral intensity of the Raman line at 680 cm-1, which is related to the incipient oxidation of the tungsten-carbide stretching mode, is enhanced. Its frequency and width moreover change significantly, thus indicating the mechanical distortion of the bonding that has been occurred during the wearing process. The shape of the tungsten-oxide Raman lines, resembling the Voigt function, hints at a surface morphology that is a characteristic for an amorphous solid environment. Our Raman scattering results may be exploited to characterize the degree of wear of coated surfaces and to identify signatures of a tribological layer.

  8. Gas-phase photofragmentation of tris(methyl vinyl ketone) tungsten(0) and the relationship to laser-assisted CVD of tungsten oxide thin films.

    Science.gov (United States)

    Bitner, Theodore W; Zink, Jeffrey I

    2002-02-25

    The gas-phase laser-induced photofragmentation of tris(methyl vinyl ketone) tungsten(0) is studied, and the photoproducts are identified by time-of-flight mass spectroscopy. The initially populated excited electronic state of the complex is attributed to metal-to-ligand charge transfer by analysis of the electronic and preresonance Raman spectra. The major metal-containing photofragmentation products are W(+) and WO(+); smaller amounts of WC(+) and W(C(2)H(2))(+) are also observed. Intramolecular ligand coupling occurs, and dimeric products and their fragments are identified. Reaction pathways that explain the observed products are proposed. Thin films on silicon substrates are produced by laser-assisted chemical vapor deposition. The films consist of polycrystalline tungsten oxide with less than 10% tungsten carbide and are characterized by X-ray diffraction, SEM, and Auger electron spectroscopy. Relationships between the composition of the gas-phase photofragments and that of the solid films are discussed.

  9. Titanium Carbide: Nanotechnology, Properties, Application

    OpenAIRE

    Galevsky, G. V.; Rudneva, V. V.; Garbuzova, A. K.; Valuev, Denis Viktorovich

    2015-01-01

    The paper develops scientific and technological bases for fabrication of titanium carbide which is a nanocomponent of composite materials. The authors determine optimum technology specifications and the main titanium carbide properties: fineness of titaniferous raw materials, carbide-forming agent quantity, set temperature of plasma flow, tempering temperature, titanium carbide yield, productivity, specific surface, size and shape of particles. The paper includes equations to describe how the...

  10. Synthesis of Mo and W carbide and nitride nanoparticles via a simple "urea glass" route.

    Science.gov (United States)

    Giordano, Cristina; Erpen, Christian; Yao, Weitang; Antonietti, Markus

    2008-12-01

    A simple, inexpensive, and versatile route for the synthesis of metal nitrides and carbides (such as Mo2N, Mo2C, W2N and WC) nanoparticles was set up. For the first time, metal carbides were obtained using urea as carbon-source. MoCl5 and WCl4 are in a first step contacted with alcohols and an appropriate amount of urea to form a polymer-like, glassy phase, which acts as the starting product for further conversions. Just by heating this phase it was possible to prepare either molybdenum and tungsten nitrides or carbides simply by changing the metal precursor/urea molar ratio. In this procedure, urea plays a double role as a nitrogen/carbon source and stabilizing agent (necessary for the nanoparticle dispersion). Molybdenum and tungsten nitride and carbides synthesized are almost pure and highly crystalline. Sizes estimated by WAXS range around 20 and 4 nm in diameter for Mo and W nitrides or carbides, respectively. The specific surface area was found between 10 and 80 m2/g, depending on the metal and the initial ratio of metal precursor to urea.

  11. GRANULATION TRIALS OF WASTE THE DUST SILICON CARBIDE FOR UTILIZATION IN METALLURGY

    Directory of Open Access Journals (Sweden)

    Gabriel Borowski

    2016-09-01

    Full Text Available The article presents the results of laboratory granulation tests of dust silicon carbide and the results of research on the selection of the binder and the properties of the granules obtained. The research material was a waste of the silicon carbide powder with a high fragmentation, mixed with a cement or an organic modified starch specimen. Six tests were performed in a disc granulator with 100 cm in diameter. In each series of trial specified: the type and share of the binder, the diameter of the granules, tenderness, type of structure and mechanical properties. Good granules of silicon carbide obtained with the addition of cement binder with 4% of the mass fraction and at least 24 hours of seasoning. The binder should be added twice by powdering, first in a stirred granulator, and again after manufacture. It was found that the resulting granules may be used as a replacement of ferrosilicon in the process of steelmaking.

  12. Relation between Modulus of Elasticity and Compressive Strength of Ultrahigh-Strength Mortar with Mixed Silicon Carbide as Fine Aggregate

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Ultrahigh-strength mortar mixed surface-oxidized silicon carbide as a fine aggregate was prepared by means of press-casting followed by curing in an autoclave. The relation between modulus of elasticity up to 111 GPa and compressive strength up to 360 MPa of mortar mixed silicon carbide was discussed and it was revealed that the contributions of the aggregate hardness and of the interfacial strength between the aggregate and the cement paste on the elasticity of mortar were imporant.

  13. Titanium Carbide: Nanotechnology, Properties, Application

    Science.gov (United States)

    Galevsky, G. V.; Rudneva, V. V.; Garbuzova, A. K.; Valuev, D. V.

    2015-09-01

    The paper develops scientific and technological bases for fabrication of titanium carbide which is a nanocomponent of composite materials. The authors determine optimum technology specifications and the main titanium carbide properties: fineness of titaniferous raw materials, carbide-forming agent quantity, set temperature of plasma flow, tempering temperature, titanium carbide yield, productivity, specific surface, size and shape of particles. The paper includes equations to describe how the major specifications of the fabrication technique influence the content of titanium carbide and free carbon in the end product.

  14. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2002-07-30

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, a comparison study of the three cement systems examined the effect that cement drillout has on the three cement systems. Testing to determine the effect of pressure cycling on the shear bond properties of the cement systems was also conducted. This report discusses testing that was performed to analyze the alkali-silica reactivity of ULHS in cement slurries.

  15. Silicon carbide reinforced silicon carbide composite

    Science.gov (United States)

    Lau, Sai-Kwing (Inventor); Calandra, Salvatore J. (Inventor); Ohnsorg, Roger W. (Inventor)

    2001-01-01

    This invention relates to a process comprising the steps of: a) providing a fiber preform comprising a non-oxide ceramic fiber with at least one coating, the coating comprising a coating element selected from the group consisting of carbon, nitrogen, aluminum and titanium, and the fiber having a degradation temperature of between 1400.degree. C. and 1450.degree. C., b) impregnating the preform with a slurry comprising silicon carbide particles and between 0.1 wt % and 3 wt % added carbon c) providing a cover mix comprising: i) an alloy comprising a metallic infiltrant and the coating element, and ii) a resin, d) placing the cover mix on at least a portion of the surface of the porous silicon carbide body, e) heating the cover mix to a temperature between 1410.degree. C. and 1450.degree. C. to melt the alloy, and f) infiltrating the fiber preform with the melted alloy for a time period of between 15 minutes and 240 minutes, to produce a ceramic fiber reinforced ceramic composite.

  16. Mineral resource of the month: tungsten

    Science.gov (United States)

    Shedd, Kim B.

    2012-01-01

    The article offers information on tungsten. It says that tungsten is a metal found in chemical compounds such as in the scheelite and ore minerals wolframite. It states that tungsten has the highest melting point and it forms a compound as hard as diamond when combined with carbon. It states that tungsten can be used as a substitute for lead in fishing weights, ammunition, and hunting shot. Moreover, China started to export tungsten materials and products instead of tungsten raw materials.

  17. Characterization of Silicon Carbide.

    Science.gov (United States)

    The various electrical and structural measurement techniques for silicon carbide are described. The electrical measurements include conductivity, resistivity, carrier concentration, mobility, doping energy levels, and lifetime. The structural measurements include polytype determination and crystalline perfection. Both bulk and epitaxial films are included.

  18. Composition Comprising Silicon Carbide

    Science.gov (United States)

    Mehregany, Mehran (Inventor); Zorman, Christian A. (Inventor); Fu, Xiao-An (Inventor); Dunning, Jeremy L. (Inventor)

    2012-01-01

    A method of depositing a ceramic film, particularly a silicon carbide film, on a substrate is disclosed in which the residual stress, residual stress gradient, and resistivity are controlled. Also disclosed are substrates having a deposited film with these controlled properties and devices, particularly MEMS and NEMS devices, having substrates with films having these properties.

  19. Development of Tungsten Based Composites

    Science.gov (United States)

    1992-02-01

    W-3.0% Ni-1.6% Fe and a zirconium foil (2 mils ) laminate. In addition, a GTE tungsten alloy (tungsten blended with 8% nickel and 2% iron) was...vescide.Wolframbleche sollten des- direction. i.e. the longitudinal direction. qu’elles sont lonaitudinales ou transver- ’AIM 1btakeristalliso tion noch 1 Stunde

  20. Cobalt exposure in a carbide tip grinding process.

    Science.gov (United States)

    Stebbins, A I; Horstman, S W; Daniell, W E; Atallah, R

    1992-03-01

    Reports relating hard metal disease or nonspecific respiratory symptoms to tungsten or cobalt exposure have been published in the past 20 yr. This report discusses a work site investigation of a small company, employing approximately 50 workers, producing carbide tip saw blades for the woodworking industry. Cobalt exposure was characterized by ambient air monitoring (area and personnel), particle size determination, and biological monitoring. Area sampling for cadmium, cobalt, and tungsten indicated low ambient air levels in all manufacturing areas except the grinding department, which had cobalt air levels approaching the threshold limit value of 0.05 mg/m3. Area airborne cobalt exposure levels measured over six shifts in the grinding department ranged from 0.017 to 0.12 mg/m3 for the total collection method and 0.002 to 0.028 mg/m3 for the method collecting respirable particles. Cobalt content in the total and respirable fractions was similar. Urine monitoring indicated production workers have elevated cobalt levels, and the grinders' levels were higher than other production workers. The grinding coolant was found to have elevated cobalt concentrations. A survey of coolants from nine carbide grinding shops indicated the elevated cobalt concentrations may be common.

  1. Preparation of tungsten oxide

    Science.gov (United States)

    Bulian, Christopher J.; Dye, Robert C.; Son, Steven F.; Jorgensen, Betty S.; Perry, W. Lee

    2009-09-22

    Tungsten trioxide hydrate (WO.sub.3.H.sub.2O) was prepared from a precursor solution of ammonium paratungstate in concentrated aqueous hydrochloric acid. The precursor solution was rapidly added to water, resulting in the crash precipitation of a yellow white powder identified as WO.sub.3.H.sub.2O nanosized platelets by x-ray diffraction and scanning electron microscopy. Annealing of the powder at 200.degree. C. provided cubic phase WO.sub.3 nanopowder, and at 400.degree. C. provided WO.sub.3 nanopowder as a mixture of monoclinic and orthorhombic phases.

  2. Evaluation of adhesive and compressive strength of glass ionomer cements.

    Science.gov (United States)

    Ramashanker; Singh, Raghuwar D; Chand, Pooran; Jurel, Sunit Km; Tripathi, Shuchi

    2011-12-01

    The aim of the study was to assess, compare and evaluate the adhesive strength and compressive strength of different brands of glass ionomer cements to a ceramometal alloy. (A) Glass ionomer cements: GC Fuji II (GC Corporation, Tokyo), Chem Flex (Dentsply DeTrey, Germany), Glass ionomer FX (Shofu-11, Japan), MR dental (MR dental suppliers Pvt Ltd, England). (B) Ceramometal alloy (Ni-Cr: Wiron 99; Bego, Bremen, Germany). (C) Cold cure acrylic resin. (E) Temperature cum humidity control chamber. (F) Instron Universal Testing Machine. Four different types of Glass ionomer cements were used in the study. From each type of the Glass ionomer cements, 15 specimens for each were made to evaluate the compressive strength and adhesive strength, respectively. The 15 specimens were further divided into three subgroups of five specimens. For compressive strength, specimens were tested at 2, 4 and 12 h by using Instron Universal Testing Machine. To evaluate the adhesive strength, specimens were surface treated with diamond bur, silicone carbide bur and sandblasting and tested under Instron Universal Testing Machine. It was concluded from the study that the compressive strength as well as the adhesive bond strength of MR dental glass ionomer cement with a ceramometal alloy was found to be maximum compare to other glass ionomer cements. Sandblasting surface treatment of ceramometal alloy was found to be comparatively more effective for adhesive bond strength between alloy and glass ionomer cement.

  3. 49 CFR 173.338 - Tungsten hexafluoride.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Tungsten hexafluoride. 173.338 Section 173.338... SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.338 Tungsten hexafluoride. (a) Tungsten... expansion test, must be condemned if removed from tungsten hexafluoride service. [ 74 FR 16143, Apr. 9,...

  4. Asphalt cement poisoning

    Science.gov (United States)

    ... petroleum material that hardens when it cools. Asphalt cement poisoning occurs when someone swallows asphalt. If hot ... found in: Road paving materials Roofing materials Tile cements Asphalt may also be used for other purposes.

  5. Chemical Analysis Methods for Silicon Carbide

    Institute of Scientific and Technical Information of China (English)

    Shen Keyin

    2006-01-01

    @@ 1 General and Scope This Standard specifies the determination method of silicon dioxide, free silicon, free carbon, total carbon, silicon carbide, ferric sesquioxide in silicon carbide abrasive material.

  6. Deposition and Coating Properties on CVD Tungsten

    Institute of Scientific and Technical Information of China (English)

    DU Ji-hong; LI Zheng-xiang; LIU Gao-jian; ZHOU Hui-Huang; CHUN liang

    2004-01-01

    Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.

  7. Fabrication of a tantalum-clad tungsten target for LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, A.T., E-mail: atnelson@lanl.gov [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); O' Toole, J.A.; Valicenti, R.A. [Accelerator Operations and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Maloy, S.A. [Civilian Nuclear Program Office, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2012-12-15

    Development of a solid state bonding technique suitable to clad tungsten targets with tantalum was completed to improve operation of the Los Alamos Neutron Science Centers spallation target. Significant deterioration of conventional bare tungsten targets has historically resulted in transfer of tungsten into the cooling system through corrosion resulting in increased radioactivity outside the target and reduction of delivered neutron flux. The fabrication method chosen to join the tantalum cladding to the tungsten was hot isostatic pressing (HIP) given the geometry constraints of a cylindrical assembly and previous success demonstrated at KENS. Nominal HIP parameters of 1500 Degree-Sign C, 200 MPa, and 3 h were selected based upon previous work. Development of the process included significant surface engineering controls and characterization given tantalums propensity for oxide and carbide formation at high temperatures. In addition to rigorous acid cleaning implemented at each step of the fabrication process, a three layer tantalum foil gettering system was devised such that any free oxygen and carbon impurities contained in the argon gas within the HIP vessel was mitigated to the extent possible before coming into contact with the tantalum cladding. The result of the numerous controls and refined techniques was negligible coarsening of the native Ta{sub 2}O{sub 5} surface oxide, no measureable oxygen diffusion into the tantalum bulk, and no detectable carburization despite use of argon containing up to 5 ppm oxygen and up to 40 ppm total CO, CO{sub 2}, or organic contaminants. Post bond characterization of the interface revealed continuous bonding with a few microns of species interdiffusion.

  8. Fabrication of a tantalum-clad tungsten target for LANSCE

    Science.gov (United States)

    Nelson, A. T.; O'Toole, J. A.; Valicenti, R. A.; Maloy, S. A.

    2012-12-01

    Development of a solid state bonding technique suitable to clad tungsten targets with tantalum was completed to improve operation of the Los Alamos Neutron Science Centers spallation target. Significant deterioration of conventional bare tungsten targets has historically resulted in transfer of tungsten into the cooling system through corrosion resulting in increased radioactivity outside the target and reduction of delivered neutron flux. The fabrication method chosen to join the tantalum cladding to the tungsten was hot isostatic pressing (HIP) given the geometry constraints of a cylindrical assembly and previous success demonstrated at KENS. Nominal HIP parameters of 1500 °C, 200 MPa, and 3 h were selected based upon previous work. Development of the process included significant surface engineering controls and characterization given tantalums propensity for oxide and carbide formation at high temperatures. In addition to rigorous acid cleaning implemented at each step of the fabrication process, a three layer tantalum foil gettering system was devised such that any free oxygen and carbon impurities contained in the argon gas within the HIP vessel was mitigated to the extent possible before coming into contact with the tantalum cladding. The result of the numerous controls and refined techniques was negligible coarsening of the native Ta2O5 surface oxide, no measureable oxygen diffusion into the tantalum bulk, and no detectable carburization despite use of argon containing up to 5 ppm oxygen and up to 40 ppm total CO, CO2, or organic contaminants. Post bond characterization of the interface revealed continuous bonding with a few microns of species interdiffusion.

  9. RECOVERY OF URANIUM FROM TUNGSTEN

    Science.gov (United States)

    Newnam, K.

    1959-02-01

    A method is presented for the rccovery of uranium which has adhered to tungsten parts in electromagnetic isotope separation apparatus. Such a tungsten article is dissolved electrolytically in 20% NaOH by using the tungsten article as the anode. The resulting solution, containing soluble sodium lungstate and an insoluble slime, is then filtered. The slime residue is ignited successively with sodium nitrate and sodium pyrosulfate and leashed, and the resulting filtrates are combined with the original filtrate. Uranium is then recovered from the combined flltrates by diuranate precipitation.

  10. Microstructure of alumina-matrix composites reinforced with nanometric titanium and titanium carbide dispersions

    OpenAIRE

    Elizabeth Refugio-García; David Hernández-Silva; Eduardo Terrés-Rojas; José Amparo Rodríguez-García; Enrique Rocha-Rangel

    2012-01-01

    The synthesis of alumina (Al2O3)-composites having different amount of very fine titanium and titanium carbide reinforcement-particles has been explored. Two experimental steps have been set for the synthesis; the first step consisted of the pressureless-sintering of Al2O3-titanium powders which were thoroughly mixed under high energy ball-milling and through the second step it was induced the formation of titanium carbide during different times at 500 ºC by the cementation packing process. S...

  11. Tungsten resources of Brazil

    Science.gov (United States)

    White, Max Gregg

    1974-01-01

    Brazilian tungsten production, 85 percent of which is exported, comes almost entirely from scheelite-bearing tactites in northeast Brazil, and has reached an annual rate of about 2,000 metric tons (2,200 short tons) of scheelite concentrate with 70 percent WO3. Scheelite ore reserves, located principally in the State of Rio Grande do Norte, are estimated to be as high as 8,300,000 tons (9,100,000 short tons) containing 0.7 percent WO3. Minor deposits (or those about which only minimal information is available) of wolframite, with which some cassiterite is associated, are located in Sao Paulo, Santa Catarina, and Rio Grande do Sul. Both the scheelite and the wolframite deposits are considered . to be late Precambrian A (620 to 900 m.y.) or early Cambrian in age.

  12. Synthesis and characterization of transition metal carbides and their catalytic applications

    Science.gov (United States)

    Wan, Cheng

    Transition metal (both monometallic and bimetallic) carbides have been synthesized by an amine-metal oxide composite (AMOC) method. The composite reduces the diffusion distances among each element and allows the formation of carbides to take place as low as 610°C, which is significantly lower than traditional carbide synthesis methods (above 1500°C). Additionally, amines act not only as carbon sources and reducing agents, but also morphological templates which helps to make uniform transition metal carbide (TMC) nanocrystals with various shapes. Beyond morphology control, AMOC method can also help to synthesize multiple phases of monometallic carbides, which includes four phases of molybdenum carbides (alpha-MoC1-x, beta-Mo2C, eta-MoC, and gamma-MoC), two phases of tungsten carbides (W2C and WC), and three phases of chromium carbides (Cr3C2-x, Cr7C3, and Cr3C2). Molybdenum carbide has been proposed as a possible alternative to platinum for catalyzing the hydrogen evolution reaction (HER). Previous studies were limited to only one phase, which is beta-Mo2C with an Fe 2N structure. Here, four molybdenum carbide materials including gamma-MoC with a WC type structure which was stabilized for the first time as a phase pure nanomaterial. Moreover, a wide range of magnetic iron-doped molybdenum carbide (Mo2-xFexC) nanomaterials were also synthesized, which exhibits a better HER activity to non-doped beta-Mo2C. A group of (CrxFe1-x)7C3 (0.2< x<1) solid solutions have also been synthesized for the first time as nanomaterials via AMOC method, which demonstrate excellent catalytic activities for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Other carbides/nitrides made from AMOCs include WN1-x, Fe3C, Fe3-xN, Fe3Mo3C, N 2Mo3C, Ni3Mo3C, Ni6Mo 6C, and Mo0.5W0.5C.

  13. Tungsten chemical vapor deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Hirano, Kiichi; Takeda, Nobuo.

    1993-07-13

    A tungsten chemical vapor deposition method is described, comprising: a first step of selectively growing a first thin tungsten film of a predetermined thickness in a desired region on the surface of a silicon substrate by reduction of a WF[sub 6] gas introduced into an atmosphere of a predetermined temperature containing said silicon substrate; and a second step of selectively growing a second tungsten film of a predetermined thickness on said first thin tungsten film by reduction of said WF[sub 6] with a silane gas further introduced into said atmosphere, wherein the surface state of said substrate is monitored by a pyrometer and the switching from said first step to said second step is performed when the emissivity of infrared light from the substrate surfaces reaches a predetermined value.

  14. Silicon carbide sewing thread

    Science.gov (United States)

    Sawko, Paul M. (Inventor)

    1995-01-01

    Composite flexible multilayer insulation systems (MLI) were evaluated for thermal performance and compared with currently used fibrous silica (baseline) insulation system. The systems described are multilayer insulations consisting of alternating layers of metal foil and scrim ceramic cloth or vacuum metallized polymeric films quilted together using ceramic thread. A silicon carbide thread for use in the quilting and the method of making it are also described. These systems provide lightweight thermal insulation for a variety of uses, particularly on the surface of aerospace vehicles subject to very high temperatures during flight.

  15. ENTIRELY AQUEOUS SOLUTION-GEL ROUTE FOR THE PREPARATION OF ZIRCONIUM CARBIDE, HAFNIUM CARBIDE AND THEIR TERNARY CARBIDE POWDERS

    Directory of Open Access Journals (Sweden)

    Zhang Changrui

    2016-07-01

    Full Text Available An entirely aqueous solution-gel route has been developed for the synthesis of zirconium carbide, hafnium carbide and their ternary carbide powders. Zirconium oxychloride (ZrOCl₂.8H₂O, malic acid (MA and ethylene glycol (EG were dissolved in water to form the aqueous zirconium carbide precursor. Afterwards, this aqueous precursor was gelled and transformed into zirconium carbide at a relatively low temperature (1200 °C for achieving an intimate mixing of the intermediate products. Hafnium and the ternary carbide powders were also synthesized via the same aqueous route. All the zirconium, hafnium and ternary carbide powders exhibited a particle size of ∼100 nm.

  16. Methods of producing continuous boron carbide fibers

    Energy Technology Data Exchange (ETDEWEB)

    Garnier, John E.; Griffith, George W.

    2015-12-01

    Methods of producing continuous boron carbide fibers. The method comprises reacting a continuous carbon fiber material and a boron oxide gas within a temperature range of from approximately 1400.degree. C. to approximately 2200.degree. C. Continuous boron carbide fibers, continuous fibers comprising boron carbide, and articles including at least a boron carbide coating are also disclosed.

  17. China’s Tungsten Resources Supply and Demand Situation

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    <正>China’s production of tungsten products mainly includes tungsten ore concentrates and a series of intermediate tungsten products such as ferro-tungsten, tungstic acid, sodium tungstate, calcium tungstate, tungsten trioxide, tungsten blue oxide, ammonium paratungstate, ammonium metatungstate, tungsten powder etc. During the period between 1949-1997, China produced 1.85 million tons of tungsten ore concentrates, in which 873,000 tons were exported with US$3.1 billion in value.

  18. Low-chromium reduced-activation chromium-tungsten steels

    Energy Technology Data Exchange (ETDEWEB)

    Klueh, R.L.; Alexander, D.J.; Maziasz, P.J. [Oak Ridge National Lab., TN (United States)

    1996-10-01

    Bainitic microstructures formed during continuous cooling can differ from classical upper and lower bainite formed during isothermal transformation. Two types of non-classical bainite were observed depending on the cooling rate: carbide-free acicular bainite at rapid cooling rates and granular bainite at slower cooling rates. The Charpy impact toughness of the acicular ferrite was found to be considerably better than for the granular bainite. It was postulated that alloying to improve the hardenability of the steel would promote the formation of acicular bainite, just as increasing the cooling rate does. To test this, chromium and tungsten were added to the 2 1/4Cr-2W and 2 1/4Cr-2WV steel compositions to increase their hardenability, and the microstructures and mechanical properties were examined.

  19. Further development of the tungsten-fibre reinforced tungsten composite

    Energy Technology Data Exchange (ETDEWEB)

    Gietl, Hanns; Hoeschen, Till; Riesch, Johann [Max-Planck-Institut fuer Plasmaphysik, 85748 Garching (Germany); Aumann, Martin; Coenen, Jan [Forschungszentrum Juelich, IEK4, 52425 Juelich (Germany); Huber, Philipp [Lehrstuhl fuer Textilmaschinenbau und Institut fuer Textiltechnik (ITA), 52062 Aachen (Germany); Neu, Rudolf [Max-Planck-Institut fuer Plasmaphysik, 85748 Garching (Germany); Technische Universitaet Muenchen, 85748 Garching (Germany)

    2016-07-01

    For the use in a fusion device tungsten has a unique property combination. The brittleness below the ductile-to-brittle transition temperature and the embrittlement during operation e.g. by overheating, neutron irradiation are the main drawbacks for the use of pure tungsten. Tungsten fibre-reinforced tungsten composites utilize extrinsic mechanisms to improve the toughness. After proofing that this idea works in principle the next step is the conceptual proof for the applicability in fusion reactors. This will be done by producing mock-ups and testing them in cyclic high heat load tests. For this step all constituents of the composite, which are fibre, matrix and interface, and all process steps need to be investigated. Tungsten fibres are investigated by means of tension tests to find the optimum diameter and pretreatment. New interface concepts are investigated to meet the requirements in a fusion reactor, e.g. high thermal conductivity, low activation. In addition weaving processes are evaluated for their use in the fibre preform production. This development is accompanied by an extensive investigation of the materials properties e.g. single fibre tension tests.

  20. Effect of tempering after cryogenic treatment of tungsten carbide–cobalt bounded inserts

    Indian Academy of Sciences (India)

    Nirmal S Kalsi; Rakesh Sehgal; Vishal S Sharma

    2014-04-01

    Cryogenic treatment is a recent advancement in the field of machining to improve the properties of cutting tool materials. Tungsten carbide is the most commonly used cutting tool material in the industry and the technique can also be extended to it. Although the importance of tempering after cryogenic treatment has been discussed by many researchers, very little information is available in published literature about the effect of multi-tempering after cryogenic treatment. In this study, an attempt has been made to understand effect of the number of post-tempering cycles during cryogenic treatment on tungsten carbide–cobalt inserts. Metallurgical investigations have been performed to observe the effect of such post-tempering on the inserts by analysing microhardness and microstructural changes. The crystal structure and morphology were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction analysis. Metallurgical investigations revealed a significant improvement in tungsten carbide inserts having three tempering cycles, after cryogenic treatment, with marginal differences for two cycles of tempered inserts, established by the study of wear behaviour in turning.

  1. A new class of electrocatalysts for hydrogen production from water electrolysis: metal monolayers supported on low-cost transition metal carbides.

    Science.gov (United States)

    Esposito, Daniel V; Hunt, Sean T; Kimmel, Yannick C; Chen, Jingguang G

    2012-02-15

    This work explores the opportunity to substantially reduce the cost of hydrogen evolution reaction (HER) catalysts by supporting monolayer (ML) amounts of precious metals on transition metal carbide substrates. The metal component includes platinum (Pt), palladium (Pd), and gold (Au); the low-cost carbide substrate includes tungsten carbides (WC and W(2)C) and molybdenum carbide (Mo(2)C). As a platform for these studies, single-phase carbide thin films with well-characterized surfaces have been synthesized, allowing for a direct comparison of the intrinsic HER activity of bare and Pt-modified carbide surfaces. It is found that WC and W(2)C are both excellent cathode support materials for ML Pt, exhibiting HER activities that are comparable to bulk Pt while displaying stable HER activity during chronopotentiometric HER measurements. The findings of excellent stability and HER activity of the ML Pt-WC and Pt-W(2)C surfaces may be explained by the similar bulk electronic properties of tungsten carbides to Pt, as is supported by density functional theory calculations. These results are further extended to other metal overlayers (Pd and Au) and supports (Mo(2)C), which demonstrate that the metal ML-supported transition metal carbide surfaces exhibit HER activity that is consistent with the well-known volcano relationship between activity and hydrogen binding energy. This work highlights the potential of using carbide materials to reduce the costs of hydrogen production from water electrolysis by serving as stable, low-cost supports for ML amounts of precious metals.

  2. Technology of Iron Carbide Synthesis

    Institute of Scientific and Technical Information of China (English)

    M.Bahgat

    2006-01-01

    Iron carbides are very promising metallurgical products and can be used for steelmaking process, where it plays as an alternative raw material with significant economic advantages. Also it has many other applications,e.g. catalysts, magnets, sensors. The present review investigates the different properties and uses of the iron carbides. The commercial production and the different varieties for the iron carbides synthesis (gaseous carburization, mechanochemical synthesis, laser pyrolysis, plasma pyrolysis, chemical vapor deposition and ion implantation) were reviewed. Also the effect of different factors on the carburization process like gas composition, raw material, temperature, reaction time, catalyst presence and sulfur addition was indicated.

  3. Fivefold twinned boron carbide nanowires.

    Science.gov (United States)

    Fu, Xin; Jiang, Jun; Liu, Chao; Yuan, Jun

    2009-09-01

    Chemical composition and crystal structure of fivefold twinned boron carbide nanowires have been determined by electron energy-loss spectroscopy and electron diffraction. The fivefold cyclic twinning relationship is confirmed by systematic axial rotation electron diffraction. Detailed chemical analysis reveals a carbon-rich boron carbide phase. Such boron carbide nanowires are potentially interesting because of their intrinsic hardness and high temperature thermoelectric property. Together with other boron-rich compounds, they may form a set of multiply twinned nanowire systems where the misfit strain could be continuously tuned to influence their mechanical properties.

  4. Effect of filler size on wear resistance of resin cement.

    Science.gov (United States)

    Shinkai, K; Suzuki, S; Katoh, Y

    2001-11-01

    The purpose of this study was to evaluate the effect of filler size on the wear of resin cements. Materials tested included four experimental dual-cure resin cements (Kuraray) consisting of different-sized filler particles. A rectangular box cavity was prepared on the flattened occlusal surface of extracted human molars. Ceramic inlays for the cavities were fabricated using the Cerec 2 system. The Cerec inlays were cemented with the respective cements and adhesive systems according to the manufacturer's directions. The restored surface was finished by wet-grinding with an 800-grit silicon carbide paper. Six specimens were prepared for each resin cement. Half of the specimens were subjected to a three-body wear test for 200,000 cycles, and the others were subjected to a toothbrush abrasion test for 30,000 cycles. The worn surface of each restoration was scanned by a profilometer (Surfcom 475 A) at eight different points for each restoration. The wear value was determined by measuring the vertical gap depth on the profilometric tracings. The data were statistically analyzed by one-way analysis of variance (ANOVA) and Scheffe's test. The results showed that, with increase of filler size, the wear value decreased in the toothbrush test and increased in the three-body wear test. The cement with 0.04-microm filler exhibited the lowest wear value among the materials in the three-body wear test, and the same wear value as the cement with 0.97-microm filler in the toothbrush test. Based upon the results of this study, it is concluded that the wear of resin cements was affected by the filler size as well as the mode of wear test.

  5. Microstructure of alumina-matrix composites reinforced with nanometric titanium and titanium carbide dispersions

    Directory of Open Access Journals (Sweden)

    Elizabeth Refugio-García

    2012-12-01

    Full Text Available The synthesis of alumina (Al2O3-composites having different amount of very fine titanium and titanium carbide reinforcement-particles has been explored. Two experimental steps have been set for the synthesis; the first step consisted of the pressureless-sintering of Al2O3-titanium powders which were thoroughly mixed under high energy ball-milling and through the second step it was induced the formation of titanium carbide during different times at 500 ºC by the cementation packing process. SEM and EDS analysis of the microstructures obtained in both sintered and cemented bodies were performed in order to know the effect of the activated carbon used as cementing agent on the titanium for each studied composite. It was observed that a titanium carbide layer growth from the surface into the bulk and reaches different depth as the titanium content in the composites increases. On the other hand, the use of ductile titanium notably enhanced density level and fracture toughness of the composites.

  6. Thermal reaction of SiC films with tungsten and tungsten-rhenium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Roger, J.; Le Petitcorps, Y. [Univ Bordeaux 1, Lab Composites Thermostruct, CNRS-SAFRAN-CEA-UB1, UMR 5801, F-33600 Pessac, (France); Roger, J.; Audubert, F. [CEA Cadarache, DEN/DEC/SPUA/LTEC, F-13108 St Paul Les Durance, (France)

    2008-07-01

    Solid-state reactions between SiC films and W-xRe (x = 0, 5 and 25 at%) substrates on thermal annealing between 1673 K and 1873 K for various durations have been investigated. SiC coatings were deposited on metallic wires by hot filament chemical vapour deposition (HFCVD) from a gas mixture of tetramethyl-silane (TMS) and hydrogen at 1373 K under normal pressure. The interface zones were characterized using scanning electron and optical microscopies, X-ray diffraction and electron microprobe microanalysis. All analyses reveal that SiC reacts with substrates. Various metal silicides and carbides were formed in layered reaction and the presence of these phases was confirmed by electron probe microanalysis. The effects of rhenium on the reactivity were established by the determination of growth kinetics deducted from the thicknesses of reaction zones as a function of annealing time. It has been found that an increase in the diffusion kinetics and activation energy with the quantity of rhenium in the tungsten wire. (authors)

  7. The tungsten metallome of Pyrococcus furiosus

    NARCIS (Netherlands)

    Sevcenco, A.M.; Pinkse, M.; Bol, E.; Krijgen, G.; Wolterbeek, H.; Verhaert, P.D.E.M.; Hagedoorn, P.L.; Hagen, W.R.

    2009-01-01

    The tungsten metallome of the hyperthermophilic archaeon Pyrococcus furiosus has been investigated using electroanalytical metal analysis and native–native 2D-PAGE with the radioactive tungsten isotope W-187 (t1/2 = 23.9 h). P. furiosus cells have an intracellular tungsten concentration of 29 mM, of

  8. The tungsten metallome of Pyrococcus furiosus

    NARCIS (Netherlands)

    Sevcenco, A.M.; Pinkse, M.W.H.; Bol, E.; Krijger, G.C.; Wolterbeek, H.T.; Verhaert, P.; Hagedoorn, P.L.; Hagen, W.R.

    2009-01-01

    The tungsten metallome of the hyperthermophilic archaeon Pyrococcus furiosus has been investigated using electroanalytical metal analysis and native-native 2D-PAGE with the radioactive tungsten isotope W-187 (t(1/2) = 23.9 h). P. furiosus cells have an intracellular tungsten concentration of 29 mu M

  9. Tungsten:Balance between Demand and Supply

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    <正>In 2011,the tungsten market remained basically consistent with macro economic trends. In the first half of 2011, under the backdrop of upward economic situation,tungsten export and domestic consumption grew significantly and tungsten enterprises achieved remarkable economic benefits. However, as European debt crisis deepened in the second half of 2011, the global economic growth slowed down and

  10. Tungsten:Value Regression Is Inevitable Trend

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    <正>China boasts rich reserve of tungsten resources,which accounts for about 65% of proved global tungsten mineral resource reserve,ranking top in the world.Judging from global production in the past five years,China’s tungsten production also far outstrips those of other countries,about

  11. Growth inhibition by tungsten in the sulfur-oxidizing bacterium Acidithiobacillus thiooxidans.

    Science.gov (United States)

    Negishi, Atsunori; Muraoka, Tadashi; Maeda, Terunobu; Takeuchi, Fumiaki; Kanao, Tadayoshi; Kamimura, Kazuo; Sugio, Tsuyoshi

    2005-11-01

    Growth of five strains of sulfur-oxidizing bacteria Acidithiobacillus thiooxidans, including strain NB1-3, was inhibited completely by 50 microM of sodium tungstate (Na(2)WO(4)). When the cells of NB1-3 were incubated in 0.1 M beta-alanine-SO(4)(2-) buffer (pH 3.0) with 100 microM Na(2)WO(4) for 1 h, the amount of tungsten bound to the cells was 33 microg/mg protein. Approximately 10 times more tungsten was bound to the cells at pH 3.0 than at pH 7.0. The tungsten binding to NB1-3 cells was inhibited by oxyanions such as sodium molybdenum and ammonium vanadate. The activities of enzymes involved in elemental sulfur oxidation of NB1-3 cells such as sulfur oxidase, sulfur dioxygenase, and sulfite oxidase were strongly inhibited by Na(2)WO(4). These results indicate that tungsten binds to NB1-3 cells and inhibits the sulfur oxidation enzyme system of the cells, and as a result, inhibits cell growth. When portland cement bars supplemented with 0.075% metal nickel and with 0.075% metal nickel and 0.075% calcium tungstate were exposed to the atmosphere of a sewage treatment plant containing 28 ppm of H(2)S for 2 years, the weight loss of the portland cement bar with metal nickel and calcium tungstate was much lower than the cement bar containing 0.075% metal nickel.

  12. Method of synthesizing tungsten nanoparticles

    Science.gov (United States)

    Thoma, Steven G; Anderson, Travis M

    2013-02-12

    A method to synthesize tungsten nanoparticles has been developed that enables synthesis of nanometer-scale, monodisperse particles that can be stabilized only by tetrahydrofuran. The method can be used at room temperature, is scalable, and the product concentrated by standard means. Since no additives or stabilizing surfactants are required, this method is particularly well suited for producing tungsten nanoparticles for dispersion in polymers. If complete dispersion is achieved due to the size of the nanoparticles, then the optical properties of the polymer can be largely maintained.

  13. Assessment of Tungsten Content on Tertiary Creep Deformation Behavior of Reduced Activation Ferritic-Martensitic Steel

    Science.gov (United States)

    Vanaja, J.; Laha, Kinkar

    2015-10-01

    Tertiary creep deformation behavior of reduced activation ferritic-martensitic (RAFM) steels having different tungsten contents has been assessed. Creep tests were carried out at 823 K (550 °C) over a stress range of 180 to 260 MPa on three heats of the RAFM steel (9Cr-W-0.06Ta-0.22V) with tungsten content of 1, 1.4, and 2.0 wt pct. With creep exposure, the steels exhibited minimum in creep rate followed by progressive increase in creep rate until fracture. The minimum creep rate decreased, rupture life increased, and the onset of tertiary stage of creep deformation delayed with the increase in tungsten content. The tertiary creep behavior has been assessed based on the relationship, , considering minimum creep rate () instead of steady-state creep rate. The increase in tungsten content was found to decrease the rate of acceleration of tertiary parameter ` p.' The relationships between (1) tertiary parameter `p' with minimum creep rate and time spent in tertiary creep deformation and (2) the final creep rate with minimum creep rate revealed that the same first-order reaction rate theory prevailed in the minimum creep rate as well as throughout the tertiary creep deformation behavior of the steel. A master tertiary creep curve of the steels has been developed. Scanning electron microscopic investigation revealed enhanced coarsening resistance of carbides in the steel on creep exposure with increase in tungsten content. The decrease in tertiary parameter ` p' with tungsten content with the consequent decrease in minimum creep rate and increase in rupture life has been attributed to the enhanced microstructural stability of the steel.

  14. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2002-01-23

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems: foamed and sodium silicate slurries. Comparison studies of the three cement systems examined several properties: tensile strength, Young's modulus, water permeability, and shear bond. Testing was also done to determine the effect that temperature cycling has on the shear bond properties of the cement systems. In addition, analysis was carried out to examine alkali silica reactivity of slurries containing ULHS. Data is also presented from a study investigating the effects of mixing and pump circulation on breakage of ULHS. Information is also presented about the field application of ULHS in cementing a 7-in. intermediate casing in south Texas.

  15. Influence of tungsten and titanium on the structure of chromium cast iron

    Directory of Open Access Journals (Sweden)

    D. Kopyciński

    2012-01-01

    Full Text Available The paper analyses the as-cast state structure of chromium cast iron designed for operation under harsh impact-abrasive conditions. In the process of chromium iron castings manufacture, very strong influence on the structure of this material have the parameters of the technological process. Among others, adding to the Fe-Cr-C alloy the alloying elements like tungsten and titanium leads to the formation of additional carbides in the structure of this cast iron, which may favourably affect the casting properties, including the resistance to abrasive wear.

  16. Studies of silicon carbide and silicon carbide nitride thin films

    Science.gov (United States)

    Alizadeh, Zhila

    Silicon carbide semiconductor technology is continuing to advance rapidly. The excellent physical and electronic properties of silicon carbide recently take itself to be the main focused power device material for high temperature, high power, and high frequency electronic devices because of its large band gap, high thermal conductivity, and high electron saturation drift velocity. SiC is more stable than Si because of its high melting point and mechanical strength. Also the understanding of the structure and properties of semiconducting thin film alloys is one of the fundamental steps toward their successful application in technologies requiring materials with tunable energy gaps, such as solar cells, flat panel displays, optical memories and anti-reflecting coatings. Silicon carbide and silicon nitrides are promising materials for novel semiconductor applications because of their band gaps. In addition, they are "hard" materials in the sense of having high elastic constants and large cohesive energies and are generally resistant to harsh environment, including radiation. In this research, thin films of silicon carbide and silicon carbide nitride were deposited in a r.f magnetron sputtering system using a SiC target. A detailed analysis of the surface chemistry of the deposited films was performed using x-ray photoelectron spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy whereas structure and morphology was studied atomic force microscopy (AFM), and nonoindentation.

  17. Process Of Bonding Copper And Tungsten

    Science.gov (United States)

    Slattery, Kevin T.; Driemeyer, Daniel E.

    1999-11-23

    Process for bonding a copper substrate to a tungsten substrate by providing a thin metallic adhesion promoting film bonded to a tungsten substrate and a functionally graded material (FGM) interlayer bonding the thin metallic adhesion promoting film to the copper substrate. The FGM interlayer is formed by thermal plasma spraying mixtures of copper powder and tungsten powder in a varied blending ratio such that the blending ratio of the copper powder and the tungsten powder that is fed to a plasma torch is intermittently adjusted to provide progressively higher copper content/tungsten content, by volume, ratio values in the interlayer in a lineal direction extending from the tungsten substrate towards the copper substrate. The resulting copper to tungsten joint well accommodates the difference in the coefficient of thermal expansion of the materials.

  18. Vacuum Gas Tungsten Arc Welding

    Science.gov (United States)

    Weeks, J. L.; Todd, D. T.; Wooten, J. R.

    1997-01-01

    A two-year program investigated vacuum gas tungsten arc welding (VGTAW) as a method to modify or improve the weldability of normally difficult-to-weld materials. After a vacuum chamber and GTAW power supply were modified, several difficult-to-weld materials were studied and key parameters developed. Finally, Incoloy 903 weld overlays were produced without microfissures.

  19. Mineral of the month: tungsten

    Science.gov (United States)

    Shedd, Kim B.

    2006-01-01

    Tungsten has the highest melting point of all metals, one of the highest densities and, when combined with carbon, is almost as hard as diamond. These and other properties make it useful in a wide variety of important commercial, industrial and military applications.

  20. Tungsten biochemistry of Pyrococcus furiosus

    NARCIS (Netherlands)

    Bevers, L.E.

    2008-01-01

    Tungsten is the heaviest element that exhibits biological activity (atomic number 74), when it is present in an enzyme. It is taken up by cells in the form of tungstate, and it is subsequently processed into an organic cofactor referred to as tungstopterin, which is found as active center in several

  1. Thermal response of nanostructured tungsten

    NARCIS (Netherlands)

    Kajita, Shin; De Temmerman, G.; Morgan, Thomas; van Eden, Stein; de Kruif, Thijs; Ohno, Noriyasu

    2014-01-01

    The thermal response of nanostructured tungsten, which was fabricated in the linear divertor simulator NAGDIS-II, was investigated using pulsed plasma in the MAGNUM-PSI device and by using high powered laser pulses. The temperature evolution in response to the pulses was measured with an infrared fa

  2. Experimental investigation on material migration phenomena in micro-EDM of reaction-bonded silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Liew, Pay Jun [Department of Mechanical Systems and Design, Tohoku University, Aramaki Aoba 6-6-01, Aoba-ku, Sendai, 980-8579 (Japan); Manufacturing Process Department, Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100, Durian Tunggal, Melaka (Malaysia); Yan, Jiwang, E-mail: yan@mech.keio.ac.jp [Department of Mechanical Engineering, Faculty of Science and Technology, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama, 223-8522 (Japan); Kuriyagawa, Tsunemoto [Department of Mechanical Systems and Design, Tohoku University, Aramaki Aoba 6-6-01, Aoba-ku, Sendai, 980-8579 (Japan)

    2013-07-01

    Material migration between tool electrode and workpiece material in micro electrical discharge machining of reaction-bonded silicon carbide was experimentally investigated. The microstructural changes of workpiece and tungsten tool electrode were examined using scanning electron microscopy, cross sectional transmission electron microscopy and energy dispersive X-ray under various voltage, capacitance and carbon nanofibre concentration in the dielectric fluid. Results show that tungsten is deposited intensively inside the discharge-induced craters on the RB-SiC surface as amorphous structure forming micro particles, and on flat surface region as a thin interdiffusion layer of poly-crystalline structure. Deposition of carbon element on tool electrode was detected, indicating possible material migration to the tool electrode from workpiece material, carbon nanofibres and dielectric oil. Material deposition rate was found to be strongly affected by workpiece surface roughness, voltage and capacitance of the electrical discharge circuit. Carbon nanofibre addition in the dielectric at a suitable concentration significantly reduced the material deposition rate.

  3. Laser melting of uranium carbides

    Science.gov (United States)

    Utton, C. A.; De Bruycker, F.; Boboridis, K.; Jardin, R.; Noel, H.; Guéneau, C.; Manara, D.

    2009-03-01

    In the context of the material research aimed at supporting the development of nuclear plants of the fourth Generation, renewed interest has recently arisen in carbide fuels. A profound understanding of the behaviour of nuclear materials in extreme conditions is of prime importance for the analysis of the operation limits of nuclear fuels, and prediction of possible nuclear reactor accidents. In this context, the main goal of the present paper is to demonstrate the feasibility of laser induced melting experiments on stoichiometric uranium carbides; UC, UC1.5 and UC2. Measurements were performed, at temperatures around 3000 K, under a few bars of inert gas in order to minimise vaporisation and oxidation effects, which may occur at these temperatures. Moreover, a recently developed investigation method has been employed, based on in situ analysis of the sample surface reflectivity evolution during melting. Current results, 2781 K for the melting point of UC, 2665 K for the solidus and 2681 K for the liquidus of U2C3, 2754 K for the solidus and 2770 K for the liquidus of UC2, are in fair agreement with early publications where the melting behaviour of uranium carbides was investigated by traditional furnace melting methods. Further information has been obtained in the current research about the non-congruent (solidus-liquidus) melting of certain carbides, which suggest that a solidus-liquidus scheme is followed by higher ratio carbides, possibly even for UC2.

  4. High Strength Carbide-Based Fibrous Monolith Materials for Solid Rocket Nozzles

    Science.gov (United States)

    2008-02-19

    3950°C and 3928°C, respectively. Compared to refractory metal candidates such as Rhenium (W) and Tungsten (W), these carbides offer significant...45HfC-10VC at 1538 W/cm² in the LHMEL Facility laser Sample gone within ~3 seconds, ablated and blew away; carbon foam backing remained intact for...Response of 45TaC-45HfC-10VC at 1529 W/cm² in the LHMEL Facility laser Sample gone within 6 seconds, ablated and blew away; carbon foam backing

  5. Tympanoplasty with ionomeric cement

    DEFF Research Database (Denmark)

    Kjeldsen, A D; Grøntved, A M

    2000-01-01

    with isolated erosion of the long incus process have been treated with a new surgical technique in which the ossicular chain was rebuilt with ionomeric cement. The results in hearing performance (mean pure-tone average (PTA) 0.5, 1 and 2 kHz) were evaluated pre- and post-surgery, and compared to those...... of > 10 dB, in 4 there was a slight improvement and in 2 a decline. The difference was not statistically significant. Hearing improvement using ionomeric cement in type II tympanoplasty was satisfactory. Reconstruction of the ossicular chain with ionomeric cement is recommended, as the procedure is easy...

  6. Cement and concrete

    Science.gov (United States)

    Corley, Gene; Haskin, Larry A.

    1992-01-01

    To produce lunar cement, high-temperature processing will be required. It may be possible to make calcium-rich silicate and aluminate for cement by solar heating of lunar pyroxene and feldspar, or chemical treatment may be required to enrich the calcium and aluminum in lunar soil. The effects of magnesium and ferrous iron present in the starting materials and products would need to be evaluated. So would the problems of grinding to produce cement, mixing, forming in vacuo and low gravity, and minimizing water loss.

  7. Ablation study of tungsten-based nuclear thermal rocket fuel

    Science.gov (United States)

    Smith, Tabitha Elizabeth Rose

    The research described in this thesis has been performed in order to support the materials research and development efforts of NASA Marshall Space Flight Center (MSFC), of Tungsten-based Nuclear Thermal Rocket (NTR) fuel. The NTR was developed to a point of flight readiness nearly six decades ago and has been undergoing gradual modification and upgrading since then. Due to the simplicity in design of the NTR, and also in the modernization of the materials fabrication processes of nuclear fuel since the 1960's, the fuel of the NTR has been upgraded continuously. Tungsten-based fuel is of great interest to the NTR community, seeking to determine its advantages over the Carbide-based fuel of the previous NTR programs. The materials development and fabrication process contains failure testing, which is currently being conducted at MSFC in the form of heating the material externally and internally to replicate operation within the nuclear reactor of the NTR, such as with hot gas and RF coils. In order to expand on these efforts, experiments and computational studies of Tungsten and a Tungsten Zirconium Oxide sample provided by NASA have been conducted for this dissertation within a plasma arc-jet, meant to induce ablation on the material. Mathematical analysis was also conducted, for purposes of verifying experiments and making predictions. The computational method utilizes Anisimov's kinetic method of plasma ablation, including a thermal conduction parameter from the Chapman Enskog expansion of the Maxwell Boltzmann equations, and has been modified to include a tangential velocity component. Experimental data matches that of the computational data, in which plasma ablation at an angle shows nearly half the ablation of plasma ablation at no angle. Fuel failure analysis of two NASA samples post-testing was conducted, and suggestions have been made for future materials fabrication processes. These studies, including the computational kinetic model at an angle and the

  8. POZZOLAN AND CEMENTS WITH POZZOLAN

    OpenAIRE

    Hasan KAPLAN; Hanifi BİNİCİ

    1995-01-01

    Cement, one of the basic material of construction engineering, has an important place in view of strength and cost of structures. Cement consumption is increasing parallel to development of building construction sector. For cement producers, minimal cost is desired by using new and economical material sources. On the other hand, the controllers and contractors need cheaper, safer and higher strength materials. From this respect cement industry tends to use cement with pozzolan. In Türkiye, ce...

  9. Standard Test Method for Abrasive Wear Resistance of Cemented

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2005-01-01

    1.1 This test method covers the determination of abrasive wear resistance of cemented carbides. 1.2 The values stated in inch-pound units are to be regarded as the standard. The SI equivalents of inch-pound units are in parentheses and may be approximate. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  10. Thermal conductivity of boron carbides

    Science.gov (United States)

    Wood, C.; Emin, D.; Gray, P. E.

    1985-01-01

    Knowledge of the thermal conductivity of boron carbide is necessary to evaluate its potential for high-temperature thermoelectric energy conversion applications. Measurements have been conducted of the thermal diffusivity of hot-pressed boron carbide BxC samples as a function of composition (x in the range from 4 to 9), temperature (300-1700 K), and temperature cycling. These data, in concert with density and specific-heat data, yield the thermal conductivities of these materials. The results are discussed in terms of a structural model that has been previously advanced to explain the electronic transport data. Some novel mechanisms for thermal conduction are briefly discussed.

  11. Laser cleaning of tungsten ribbon

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Aniruddha, E-mail: nontee65@rediffmail.com [Advanced Fuel Fabrication Facility, Bhabha Atomic Research Centre, Tarapur, Maharashtra, 401504 (India); Sonar, V.R.; Das, D.K.; Bhatt, R.B.; Behere, P.G.; Afzal, Mohd.; Kumar, Arun [Advanced Fuel Fabrication Facility, Bhabha Atomic Research Centre, Tarapur, Maharashtra, 401504 (India); Nilaya, J.P.; Biswas, D.J. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, 400085 (India)

    2014-07-01

    Removal of a thin oxide layer from a tungsten ribbon was achieved using the fundamental, second and third harmonic radiation from a Q- switched Nd-YAG laser. It was found that beyond the threshold, oxide removal was achieved at all wavelengths for a wide range of fluence values. The removal mechanism of the oxide layer was found to be critically dependent on both wavelength and fluence of the incident radiation and has been identified as ejection or sublimation. The un-cleaned and cleaned surfaces were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS) and atomic force microscopy (AFM). Laser cleaned tungsten ribbons were used in a thermal ionization mass spectrometer (TIMS) to determine isotopic composition of Neodymium atoms.

  12. Synthesis of nanosized tungsten powder

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Nanosized tungsten powder was synthesized by means of different methods and under different conditions with nanosized WO3 powder. The powder and the intermediate products were characterized using XRD, SEM, TEM, BET (Brunauer Emmett Teller Procedure) and SAXS (X-ray diffracto-spectrometer/Kratky small angle scattering goniometer). The results show that nanosized WO3 can be completely reduced to WO2 at 600℃ after 40 min, and WO2 can be reduced to W at 700℃ after 90 min, moreover, the mean size of W particles is less than 40 nm. Furthermore, the process of WO3→WO2→W excelled that of WO3→W in getting stable nanosized tungsten powder with less grain size.

  13. Does speciation matter for tungsten ecotoxicology?

    Science.gov (United States)

    Strigul, Nikolay

    2010-09-01

    Tungsten is a widely used transition metal that has not been thoroughly investigated with regards to its ecotoxicological effects. Tungsten anions polymerize in environmental systems as well as under physiological conditions in living organisms. These polymerization/condensation reactions result in the development of several types of stable polyoxoanions. Certain chemical properties (in particular redox and acidic properties) differentiate these polyanions from monotungstates. However, our current state of knowledge on tungsten toxicology, biological and environmental effects is based entirely on experiments where monotungstates were used and assumed by the authors to be the form of tungsten that was present and that produced the observed effect. Recent discoveries indicate that tungsten speciation may be important to ecotoxicology. New results obtained by different research groups demonstrate that polytungstates develop and persist in environmental systems, and that polyoxotungstates are much more toxic than monotungstates. This paper reviews the available toxicological information from the standpoint of tungsten speciation and identifies knowledge gaps and pertinent future research directions.

  14. Experimental Study of Stabilized Soil Utilizing Circulating Fluidized Bed Combustion Desulfurization Ash with Carbide Slag and Desulfurization Gypsum

    Directory of Open Access Journals (Sweden)

    Dezhi Shao

    2015-01-01

    Full Text Available This paper discusses the feasibility of preparing soil stabilizer which is circulating fluidized bed combustion ash-based, supplemented with carbide slag and desulfurization gypsum, composed entirely of complete industrial wastes. The results show that CFBC ash has better pozzolanic activity than fly ash. When stabilizer total content is 10% and the ratio of CFBC ash : carbide slag : desulfurization gypsum is 7.2 : 1.8 : 1, compressive strength of stabilized soil can reach the maximum of 2.12 MPa at the age of 28 d of curing. Stabilizer can meet the strength requirements of cement-soil mixing pile composite foundation and cement-soil mixing pile waterproof curtain.

  15. Fine grain tungsten produced with nanoscale powder

    Institute of Scientific and Technical Information of China (English)

    Tao Lin; Fang Zhao; Liying Zhang; Chengyi Wu; Zhimeng Guo

    2005-01-01

    Nanoscale tungsten powder was prepared by reducing nanoscale tungsten trioxide in hydrogen to WO2.90 and further to W powder. After compacted with a rubber die, the nanoscale tungsten powder was sintered in a high-temperature dilatometer to investigate its shrinkage process. The results show that the compact of the nanoscale tungsten powder starts to shrink at 1050℃ and ends at 1500℃. The shrinkage rate reaches the maximum value at 1210℃. The relative density of sintered samples is 96.4%, and its grain size is about 5.8 μm.

  16. 40 CFR 421.100 - Applicability: Description of the primary tungsten subcategory.

    Science.gov (United States)

    2010-07-01

    ... primary tungsten subcategory. 421.100 Section 421.100 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Primary Tungsten Subcategory § 421.100 Applicability: Description of the primary tungsten... tungsten at primary tungsten facilities....

  17. Kinetics and Mechanisms of Creep in Sintered Alpha Silicon Carbide and Niobium Carbide.

    Science.gov (United States)

    1985-09-18

    CARBIDE AND NIOBIUM CARBIDE Supported by 30 F (DMR-812-0804) and ARO (MIPR’s 43-48, 127-83, 141-84) U August, 1985 NCSU .LET tow A CL School of Engineering...SILICON CARBIDE AND NIOBIUM CARBIDE Supported by NSF (DMR-812-0804) and ARO (MIPR’s 43-48, 127-83, 141-84) August, 1985 L. U. 1’ ’’ b b MASTER COPY - FOR...and Mechanisms of Creep in Sintered May 1, 1982-June 15, 1985 Alpha Silicon Carbide and Niobium Carbide 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(*) 11

  18. Development and Application of a Theory of Plastic Deformation of Cemented Alloys

    Science.gov (United States)

    1961-03-23

    found widespread applications in the carbide tool industry, in bearings, and in some structural parts . In spite of -’.:e high strengths of alloys such...thermal stresses do play a part in the behavior of such cemented alloys, but there has been no simple correlation between these stresses and mechanical...using transverse rupture bars. Mont of the room-temperature measurements were performed on a 1Hounsfield Tensometer using a three-point loading device

  19. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2001-10-23

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses tasks performed in the fourth quarter as well as the other three quarters of the past year. The subjects that were covered in previous reports and that are also discussed in this report include: Analysis of field laboratory data of active cement applications from three oil-well service companies; Preliminary findings from a literature review focusing on problems associated with ultra-lightweight cements; Summary of pertinent information from Russian ultra-lightweight cement literature review; and Comparison of compressive strengths of ULHS systems using ultrasonic and crush methods Results reported from the fourth quarter include laboratory testing of ULHS systems along with other lightweight cement systems--foamed and sodium silicate slurries. These comparison studies were completed for two different densities (10.0 and 11.5 lb/gal) and three different field application scenarios. Additional testing included the mechanical properties of ULHS systems and other lightweight systems. Studies were also performed to examine the effect that circulation by centrifugal pump during mixing has on breakage of ULHS.

  20. Some features of sintering of tungsten powders

    Directory of Open Access Journals (Sweden)

    Andreiev Igor Viktorovich

    2016-01-01

    Full Text Available A method of activating the sintering process for tungsten powders using a closed reaction space and hydrogen, steam-saturated water was observed. This sintering process is allowed to activate super coarse-grained (1000μm tungsten powder sat relatively low temperatures (1000-1200°C.

  1. Structures and transitions in tungsten grain boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Frolov, T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Zhu, Q. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Marian, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Rudd, R. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-02-07

    The objective of this study is to develop a computational methodology to predict structure, energies of tungsten grain boundaries as a function of misorientation and inclination. The energies and the mobilities are the necessary input for thermomechanical model of recrystallization of tungsten for magnetic fusion applications being developed by the Marian Group at UCLA.

  2. Thermo-Mechanical Characterization of Silicon Carbide-Silicon Carbide Composites at Elevated Temperatures Using a Unique Combustion Facility

    Science.gov (United States)

    2009-09-10

    F THERMO-MECHANICAL CHARACTERIZATION OF SILICON CARBIDE - SILICON CARBIDE COMPOSITES AT ELEVATED...MECHANICAL CTERIZATION OF SILICON CARBIDE -SILIC BIDE COMPOSITES AT LEVATED TEMPER S USING A UNIQUE COMBUSTION FACILITY DISSERTATI N Ted T. Kim...THERMO-MECHANICAL CHARACTERIZATION OF SILICON CARBIDE - SILICON CARBIDE COMPOSITES AT ELEVATED TEMPERATURES USING A UNIQUE COMBUSTION FACILITY

  3. PART II. HYDRATED CEMENTS

    Directory of Open Access Journals (Sweden)

    Milan Drabik

    2014-09-01

    Full Text Available Essential focus of the study has been to acquire thermoanalytical events, incl. enthalpies of decompositions - ΔH, of technological materials based on two types of Portland cements. The values of thermoanalytical events and also ΔH of probes of technological compositions, if related with the data of a choice of minerals of calcium-silicate-sulfate-aluminate hydrates, served as a valued input for the assessment of phases present and phase changes due to the topical hydraulic processes. The results indicate mainly the effects of "standard humidity" or "wet storage" of the entire hydration/hydraulic treatment, but also the presence of cement residues alongside calcium-silicate-sulfate-aluminate hydrates (during the tested period of treatment. "A diluting" effect of unhydrated cement residues upon the values of decomposition enthalpies in the studied multiphase system is postulated and discussed

  4. Tribological properties of sputtered tungsten and tungsten nitride thin films

    Institute of Scientific and Technical Information of China (English)

    Wong; K.M.; ShenY.G.; Wong; P.L.

    2001-01-01

    The surface roughness, hardness and tribological properties of tungsten (W) and tung-sten nitride (WNx) thin films prepared by dc magnetron sputtering and reactive magnetron sputter-ing in Ar-N2 gas mixtures have been studied using atomic force microscopy (AFM), nanoindenta-tion measurements and ball-on-disc wear testing. A pronounced surface roughness was observedonly for films under compressive strains. The surface was flat under tension but rough under com-pression. Similar hardness with value about 20 GPa were observed in the W and WNx (x=0.3)films. This is thought to be due to the fact the grains are restricted to a very small size in the coat-ings. The higher coefficients of friction (0.4 for W and 0.9 for WN0.3) suggest that WN0.3 is not theoptimum phase. Finally, discussions are made with tribological test results.

  5. Seed growth of tungsten diselenide nanotubes from tungsten oxides.

    Science.gov (United States)

    Kim, Hyun; Yun, Seok Joon; Park, Jin Cheol; Park, Min Ho; Park, Ji-Hoon; Kim, Ki Kang; Lee, Young Hee

    2015-05-13

    We report growth of tungsten diselenide (WSe2) nanotubes by chemical vapor deposition with a two-zone furnace. WO3 nanowires were first grown by annealing tungsten thin films under argon ambient. WSe2 nanotubes were then grown at the tips of WO3 nanowires through selenization via two steps: (i) formation of tubular WSe2 structures on the outside of WO3 nanowires, resulting in core (WO3)-shell (WSe2) and (ii) growth of WSe2 nanotubes at the tips of WO3 nanowires. The observed seed growth is markedly different from existing substitutional growth of WSe2 nanotubes, where oxygen atoms are replaced by selenium atoms in WO3 nanowires to form WSe2 nanotubes. Another advantage of our growth is that WSe2 film was grown by simply supplying hydrogen gas, where the native oxides were reduced to thin film instead of forming oxide nanowires. Our findings will contribute to engineer other transition metal dichacogenide growth such as MoS2, WS2, and MoSe2.

  6. Structural and electrical properties in tungsten/tungsten oxide multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Cacucci, Arnaud [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 9 Avenue Alain Savary, BP47870, F-21078 DIJON Cedex (France); Potin, Valérie, E-mail: valerie.potin@u-bourgogne.fr [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 9 Avenue Alain Savary, BP47870, F-21078 DIJON Cedex (France); Imhoff, Luc [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 9 Avenue Alain Savary, BP47870, F-21078 DIJON Cedex (France); Martin, Nicolas [Institut FEMTO-ST, UMR 6174 CNRS, Université de Franche-Comté, ENSMM, UTBM, 32 Avenue de l' observatoire, F-25044, BESANCON Cedex (France)

    2014-02-28

    Tungsten and tungsten oxide periodic nanometric multilayers have been deposited by DC reactive sputtering using the reactive gas pulsing process. Different pulsing periods have been used for each deposition to produce metal-oxide periodic alternations ranging from 3.3 to 71.5 nm. The morphology, crystallinity and chemical composition of these films have been investigated by transmission electron microscopy and energy-dispersive X-ray spectroscopy techniques. The produced multilayers exhibited an amorphous structure and the composition stability of WO{sub 3} sub-layers has been pointed out. Moreover, electrical properties have also been studied by the van der Pauw technique. It revealed a clear stability of resistivity versus temperature for almost all samples and an influence of the multilayered structure on the resistivity behavior. - Highlights: • W/WO{sub 3} multilayers with nanometric periods are produced by gas pulsing. • Multilayers are mainly amorphous and the oxide sub-layers composed of WO{sub 3}. • Crystallized inclusions of β-W and β-W{sub 3}O phases in metallic sub-layers • Metallic-like behavior with low temperature coefficient of resistance.

  7. [Calcium carbide of different crystal formation synthesized by calcium carbide residue].

    Science.gov (United States)

    Lu, Zhong-yuan; Kang, Ming; Jiang, Cai-rong; Tu, Ming-jing

    2006-04-01

    To recycle calcium carbide residue effectively, calcium carbide of different crystal form, including global aragonite, calcite and acicular calcium carbide was synthesized. Both the influence of pretreatment in the purity of calcium carbide, and the influence of temperatures of carbonization reaction, release velocity of carbon dioxide in the apparition of calcium carbide of different crystal form were studied with DTA-TG and SEM. The result shows that calcium carbide residue can take place chemistry reaction with ammonia chlorinate straight. Under the condition that pH was above 7, the purity of calcium carbide was above 97%, and the whiteness was above 98. Once provided the different temperatures of carbonization reaction and the proper release velocity of carbon dioxide, global aragonite, calcite and acicular calcium carbide were obtained.

  8. The mechanical effect of the existing cement mantle on the in-cement femoral revision.

    LENUS (Irish Health Repository)

    Keeling, Parnell

    2012-08-01

    Cement-in-cement revision hip arthroplasty is an increasingly popular technique to replace a loose femoral stem which retains much of the original cement mantle. However, some concern exists regarding the retention of the existing fatigued and aged cement in such cement-in-cement revisions. This study investigates whether leaving an existing fatigued and aged cement mantle degrades the mechanical performance of a cement-in-cement revision construct.

  9. Cement Mason's Curriculum. Instructional Units.

    Science.gov (United States)

    Hendirx, Laborn J.; Patton, Bob

    To assist cement mason instructors in providing comprehensive instruction to their students, this curriculum guide treats both the skills and information necessary for cement masons in commercial and industrial construction. Ten sections are included, as follow: related information, covering orientation, safety, the history of cement, and applying…

  10. Reducing cement's CO2 footprint

    Science.gov (United States)

    van Oss, Hendrik G.

    2011-01-01

    The manufacturing process for Portland cement causes high levels of greenhouse gas emissions. However, environmental impacts can be reduced by using more energy-efficient kilns and replacing fossil energy with alternative fuels. Although carbon capture and new cements with less CO2 emission are still in the experimental phase, all these innovations can help develop a cleaner cement industry.

  11. Deuterium retention in TiC and TaC doped tungsten at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Zibrov, M., E-mail: mzibrov@gmail.com [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe shosse 31, 115409 Moscow (Russian Federation); Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, D-85748 Garching (Germany); Mayer, M.; Gao, L.; Elgeti, S. [Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, D-85748 Garching (Germany); Kurishita, H. [International Research Centre for Nuclear Materials Science, IMR, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Gasparyan, Yu.; Pisarev, A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe shosse 31, 115409 Moscow (Russian Federation)

    2015-08-15

    Samples made of tungsten doped either with titanium carbide (W–1.1TiC) or tantalum carbide (W–3.3TaC) were either exposed to D{sub 2} gas at a pressure of 100 kPa at 800–963 K or irradiated by 38 eV/D ions at 800 K. The deuterium (D) inventory in the samples was examined by nuclear reaction analysis and thermal desorption spectroscopy. The D bulk concentration and total retention in W–3.3TaC were comparable in all cases to that in pure polycrystalline W. The D bulk concentration in W–1.1TiC was more than one order of magnitude higher than that in pure W after exposure to D{sub 2} gas, and was also several times higher than that in W–1.1TiC after irradiation at 800 K. It is suggested that D trapping inside the carbide precipitates in W–1.1TiC becomes essential at high temperatures.

  12. Sputtered tungsten-based ternary and quaternary layers for nanocrystalline diamond deposition.

    Science.gov (United States)

    Walock, Michael J; Rahil, Issam; Zou, Yujiao; Imhoff, Luc; Catledge, Shane A; Nouveau, Corinne; Stanishevsky, Andrei V

    2012-06-01

    Many of today's demanding applications require thin-film coatings with high hardness, toughness, and thermal stability. In many cases, coating thickness in the range 2-20 microm and low surface roughness are required. Diamond films meet many of the stated requirements, but their crystalline nature leads to a high surface roughness. Nanocrystalline diamond offers a smoother surface, but significant surface modification of the substrate is necessary for successful nanocrystalline diamond deposition and adhesion. A hybrid hard and tough material may be required for either the desired applications, or as a basis for nanocrystalline diamond film growth. One possibility is a composite system based on carbides or nitrides. Many binary carbides and nitrides offer one or more mentioned properties. By combining these binary compounds in a ternary or quaternary nanocrystalline system, we can tailor the material for a desired combination of properties. Here, we describe the results on the structural and mechanical properties of the coating systems composed of tungsten-chromium-carbide and/or nitride. These WC-Cr-(N) coatings are deposited using magnetron sputtering. The growth of adherent nanocrystalline diamond films by microwave plasma chemical vapor deposition has been demonstrated on these coatings. The WC-Cr-(N) and WC-Cr-(N)-NCD coatings are characterized with atomic force microscopy and SEM, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and nanoindentation.

  13. Cementing a wellbore using cementing material encapsulated in a shell

    Energy Technology Data Exchange (ETDEWEB)

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Floyd, III, William C.; Spadaccini, Christopher M.; Vericella, John J.; Cowan, Kenneth Michael

    2017-03-14

    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  14. Cementing a wellbore using cementing material encapsulated in a shell

    Science.gov (United States)

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Spadaccini, Christopher M.; Cowan, Kenneth Michael

    2016-08-16

    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  15. Technology Roadmaps: Cement

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2009-07-01

    To support its roadmap work focusing on key technologies for emissions reductions, the International Energy Agency (IEA) also investigated one particular industry: cement. Cement production includes technologies that are both specific to this industry and those that are shared with other industries (e.g., grinding, fuel preparation, combustion, crushing, transport). An industry specific roadmap provides an effective mechanism to bring together several technology options. It outlines the potential for technological advancement for emissions reductions in one industry, as well as potential cross-industry collaboration.

  16. Cement og politik

    DEFF Research Database (Denmark)

    Lund, Joachim

    2012-01-01

    as well as in the public sphere. Most of the extensive job creating measures he carried out as a minister for public works necessarily involved the use of great amounts of cement – the primary produce of F.L. Smidth & Co. Gunnar Larsen thus became an easy target for Communist propaganda, picturing him...... of the Soviet Union (including an F.L. Smidth & Co. cement plant in former Estonia). He spent the last 15 months of the occupation in Sweden and was arrested after having returned to Copenhagen in May, 1945. Although a Copenhagen city court prison sentence for economic collaboration was reversed, he had...

  17. Conduction mechanism in boron carbide

    Science.gov (United States)

    Wood, C.; Emin, D.

    1984-01-01

    Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

  18. Investigation of Infiltrated and Sintered Titanium Carbide

    Science.gov (United States)

    1952-04-01

    taneive investigations in this field during the ’time preceding this contract, and concentrated their effort® On titanium carbide as the’ refractospy...component • The Basic work of this investigation consisted of? X, KpälfiCÄVtloh and refinement of cOmätrcial grades of titanium carbide hj...facilitate a comparison between the different methods» an investigation was then carried out with composite bodies* consisting of titanium carbide asd

  19. Advanced microstructure of boron carbide.

    Science.gov (United States)

    Werheit, Helmut; Shalamberidze, Sulkhan

    2012-09-26

    The rhombohedral elementary cell of the complex boron carbide structure is composed of B(12) or B(11)C icosahedra and CBC, CBB or B□B (□, vacancy) linear arrangements, whose shares vary depending on the actual chemical compound. The evaluation of the IR phonon spectra of isotopically pure boron carbide yields the quantitative concentrations of these components within the homogeneity range. The structure formula of B(4.3)C at the carbon-rich limit of the homogeneity range is (B(11)C) (CBC)(0.91) (B□B)(0.09) (□, vacancy); and the actual structure formula of B(13)C(2) is (B(12))(0.5)(B(11)C)(0.5)(CBC)(0.65)(CBB)(0.16) (B□B)(0.19), and deviates fundamentally from (B(12))CBC, predicted by theory to be the energetically most favourable structure of boron carbide. In reality, it is the most distorted structure in the homogeneity range. The spectra of (nat)B(x)C make it evident that boron isotopes are not randomly distributed in the structure. However, doping with 2% silicon brings about a random distribution.

  20. Shock-wave strength properties of boron carbide and silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Grady, D.E.

    1994-02-01

    Time-resolved velocity interferometry measurements have been made on boron carbide and silicon carbide ceramics to assess dynamic equation-of-state and strength properties of these materials. Hugoniot pecursor characteristics, and post-yield shock and release wave properties, indicated markedly different dynamic strength and flow behavior for the two carbides.

  1. Development of tungsten fibre-reinforced tungsten composites towards their use in DEMO—potassium doped tungsten wire

    Science.gov (United States)

    Riesch, J.; Han, Y.; Almanstötter, J.; Coenen, J. W.; Höschen, T.; Jasper, B.; Zhao, P.; Linsmeier, Ch; Neu, R.

    2016-02-01

    For the next step fusion reactor the use of tungsten is inevitable to suppress erosion and allow operation at elevated temperature and high heat loads. Tungsten fibre-reinforced composites overcome the intrinsic brittleness of tungsten and its susceptibility to operation embrittlement and thus allow its use as a structural as well as an armour material. That this concept works in principle has been shown in recent years. In this contribution we present a development approach towards its use in a future fusion reactor. A multilayer approach is needed addressing all composite constituents and manufacturing steps. A huge potential lies in the optimization of the tungsten wire used as fibre. We discuss this aspect and present studies on potassium doped tungsten wire in detail. This wire, utilized in the illumination industry, could be a replacement for the so far used pure tungsten wire due to its superior high temperature properties. In tensile tests the wire showed high strength and ductility up to an annealing temperature of 2200 K. The results show that the use of doped tungsten wire could increase the allowed fabrication temperature and the overall working temperature of the composite itself.

  2. Influence of storage times on bond strength of resin cements to root canal

    Directory of Open Access Journals (Sweden)

    Matheus Coêlho Bandéca

    2010-03-01

    Full Text Available The resin cements are responsible to retention of the indirect materials decreasing marginal leakage, increasing failure resistance compared with conventional cementation. The cementation within root canal is very hard due unfavorable conditions regarding the application of adhesive techniques caused by inadequate access. Therefore, considering the possibility to decrease steps of cementation, this study was performed to evaluate the bond strength of self-adhesive resin cement (RelyX TM U100, 3M ESPE and resin cement combined with self-ecthing adhesive system (Panavia® F 2.0, Kuraray light-cured with Quartz Tungsten Halogen (QTH following storage at 37 °C immediately after light-curing, 24 and 48 hours and 7 days. The root canals were prepared to receive the glass fiber post in the depth of 10 mm, irrigated with 17% EDTA and NaOCl, rinsed with distilled water and dried using paper points. The roots were perpendicularly sectioned into approximately 1 mm thick sections, obtaining ninety-six slices (n = 12. The slices were trimmed using a cylindrical diamond bur in the proximal surfaces until it touched the post and attached into a device, which were mounted on a strength tester (Bisco and loaded in tension at a speed of 0.5 mm/min until failure occurred at specimens. The analysis of variance (ANOVA and Tukey's post-hoc tests showed significant statistical differences (P .05. The resin cements 24 and 48 hours after light-curing were statistically similar among themselves (P > .05. The both resin cement showed similar bond strength into root canal on different storage times. The highest bond strength values of the resin cements were showed 7 days after curing.

  3. Fracture behaviour of polycrystalline tungsten

    Science.gov (United States)

    Gaganidze, Ermile; Rupp, Daniel; Aktaa, Jarir

    2014-03-01

    Fracture behaviour of round blank polycrystalline tungsten was studied by means of three point bending Fracture-Mechanical (FM) tests at temperatures between RT and 1000 °C and under high vacuum. To study the influence of the anisotropic microstructure on the fracture toughness (FT) and ductile-to-brittle transition (DBT) the specimens were extracted in three different, i.e. longitudinal, radial and circumferential orientations. The FM tests yielded distinctive fracture behaviour for each specimen orientation. The crack propagation was predominantly intergranular for longitudinal orientation up to 600 °C, whereas transgranular cleavage was observed at low test temperatures for radial and circumferentially oriented specimens. At intermediate test temperatures the change of the fracture mode took place for radial and circumferential orientations. Above 800 °C all three specimen types showed large ductile deformation without noticeable crack advancement. For longitudinal specimens the influence of the loading rate on the FT and DBT was studied in the loading rate range between 0.06 and 18 MPa m1/2/s. Though an increase of the FT was observed for the lowest loading rate, no resolvable dependence of the DBT on the loading rate was found partly due to loss of FT validity. A Master Curve approach is proposed to describe FT vs. test temperature data on polycrystalline tungsten. Fracture safe design space was identified by analysis compiled FT data.

  4. Methods for producing silicon carbide fibers

    Energy Technology Data Exchange (ETDEWEB)

    Garnier, John E.; Griffith, George W.

    2016-03-01

    Methods of producing silicon carbide fibers. The method comprises reacting a continuous carbon fiber material and a silicon-containing gas in a reaction chamber at a temperature ranging from approximately 1500.degree. C. to approximately 2000.degree. C. A partial pressure of oxygen in the reaction chamber is maintained at less than approximately 1.01.times.10.sup.2 Pascal to produce continuous alpha silicon carbide fibers. Continuous alpha silicon carbide fibers and articles formed from the continuous alpha silicon carbide fibers are also disclosed.

  5. Silicon carbide fibers and articles including same

    Energy Technology Data Exchange (ETDEWEB)

    Garnier, John E; Griffith, George W

    2015-01-27

    Methods of producing silicon carbide fibers. The method comprises reacting a continuous carbon fiber material and a silicon-containing gas in a reaction chamber at a temperature ranging from approximately 1500.degree. C. to approximately 2000.degree. C. A partial pressure of oxygen in the reaction chamber is maintained at less than approximately 1.01.times.10.sup.2 Pascal to produce continuous alpha silicon carbide fibers. Continuous alpha silicon carbide fibers and articles formed from the continuous alpha silicon carbide fibers are also disclosed.

  6. Effects of heat treatment on mechanical properties and microstructure of tungsten fi ber reinforced grey cast iron matrix composites

    Directory of Open Access Journals (Sweden)

    Peng jianHong

    2009-11-01

    Full Text Available In this study, grey cast iron matrix composites reinforced by different volume fractions of tungsten fibers (Vr = 0.95 %, 1.90 %, 2.85 %, 3.80 % were investigated in as-cast and under the heat treatment temperatures of 1,000℃ and 1,100℃. The microstructure and mechanical properties of the composites were analyzed and tested by means of SEM, micro-hardness tester and three-point bend testing. The results show that with increasing of the volume fraction of tungsten fibers, the composites reinforced by the tungsten fiber have higher fl exural strength and modulus than that of cast iron without reinforcement, and the fl exural strength increases with the increasing of heat treatment temperatures. Due to diffusion reaction between matrix and reinforcing phases, the process of heat treatment, the number of graphite fl akes in the matrix seemingly becomes lower; and some hard carbide particles are formed around the residual tungsten fi bers. Not only does the hardness of both matrix and reinforcement change tremendously, but also the region of reinforcement is also extended from the original 0.11 mm to 0.19 mm in radius.

  7. Osteotransductive bone cements.

    Science.gov (United States)

    Driessens, F C; Planell, J A; Boltong, M G; Khairoun, I; Ginebra, M P

    1998-01-01

    Calcium phosphate bone cements (CPBCs) are osteotransductive, i.e. after implantation in bone they are transformed into new bone tissue. Furthermore, due to the fact that they are mouldable, their osteointegration is immediate. Their chemistry has been established previously. Some CPBCs contain amorphous calcium phosphate (ACP) and set by a sol-gel transition. The others are crystalline and can give as the reaction product dicalcium phosphate dihydrate (DCPD), calcium-deficient hydroxyapatite (CDHA), carbonated apatite (CA) or hydroxyapatite (HA). Mixed-type gypsum-DCPD cements are also described. In vivo rates of osteotransduction vary as follows: gypsum-DCPD > DCPD > CDHA approximately CA > HA. The osteotransduction of CDHA-type cements may be increased by adding dicalcium phosphate anhydrous (DCP) and/or CaCO3 to the cement powder. CPBCs can be used for healing of bone defects, bone augmentation and bone reconstruction. Incorporation of drugs like antibiotics and bone morphogenetic protein is envisaged. Load-bearing applications are allowed for CHDA-type, CA-type and HA-type CPBCs as they have a higher compressive strength than human trabecular bone (10 MPa).

  8. Deuterium blistering in tungsten and tungsten vanadium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Arshad, Kameel; Yuan, Yue; Cheng, Long; Wang, Jun [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Zhou, Zhang-Jian [School of Materials Science and Engineering, University of Science and Technology Beijing (USTB), Beijing 100083 (China); De Temmerman, Gregory [FOM Institute for Plasma Physics, Edisonbaan 14, 3439 MN, Nieuwegein (Netherlands); ITER Organization, Route de Vinon-sur-Verdon, CS90 046, 13067 St Paul Lez Durance Cedex (France); Lu, Guang-Hong, E-mail: lgh@buaa.edu.cn [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China)

    2016-06-15

    In order to evaluate D blistering behavior in W based plasma facing materials, rolled W and different grades of W-V targets were exposed to high flux of 1.2 × 10{sup 24} m{sup −2} s{sup −1}, low energy (38 eV) D plasma at two different surface temperatures. The blistering behavior was investigated by means of scanning electron microscopy, accompanied by electron back-scattering diffraction. Highest numbers of blisters were observed on the surface of rolled tungsten. The addition of V precursor to W suppressed D blister formation. In the case of W-V alloys, comparatively submicron V-containing materials have shown high tendency but small size blisters formation than micron V-containing samples. A high density of blisters was observed near the (111) plane on the surface of both V-containing alloys. Nano-sized blisters were also observed on V enriched surface.

  9. Visible light photoinactivation of bacteria by tungsten oxide nanostructures formed on a tungsten foil

    Energy Technology Data Exchange (ETDEWEB)

    Ghasempour, Fariba [Plasma Physics Research Centre, Science and Research Branch, Islamic Azad University, P.O. Box 147789-3855, Tehran (Iran, Islamic Republic of); Azimirad, Rouhollah [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Amini, Abbas [School of Computing, Engineering and Mathematics, University of Western Sydney, Kingswood, NSW 2751 (Australia); Akhavan, Omid, E-mail: oakhavan@sharif.edu [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588-89694, Tehran (Iran, Islamic Republic of)

    2015-05-30

    Highlights: • Synthesis of tungsten oxide nano/micro-structures on W foils using KOH as a catalyst. • Strong antibacterial activity of tungsten oxide nanorods under visible light irradiation. • Decrease in photoinactivation of bacteria on tungsten oxide nano/micro-rods doped by potassium. - Abstract: Antibacterial activity of tungsten oxide nanorods/microrods were studied against Escherichia coli bacteria under visible light irradiation and in dark. A two-step annealing process at temperatures up to 390 °C and 400–800 °C was applied to synthesize the tungsten oxide nanorods/microrods on tungsten foils using KOH as a catalyst. Annealing the foils at 400 °C in the presence of catalyst resulted in formation of tungsten oxide nanorods (with diameters of 50–90 nm and crystalline phase of WO{sub 3}) on surface of tungsten foils. By increasing the annealing temperature up to 800 °C, tungsten oxide microrods with K{sub 2}W{sub 6}O{sub 19} crystalline phase were formed on the foils. The WO{sub 3} nanorods showed a strong antibacterial property under visible light irradiation, corresponding to >92% bacterial inactivation within 24 h irradiation at room temperature, while the K{sub 2}W{sub 6}O{sub 19} microrods formed at 800 °C could inactivate only ∼45% of the bacteria at the same conditions.

  10. Surface science and electrochemical studies of metal-modified carbides for fuel cells and hydrogen production

    Science.gov (United States)

    Kelly, Thomas Glenn

    Carbides of the early transition metals have emerged as low-cost catalysts that are active for a wide range of reactions. The surface chemistry of carbides can be altered by modifying the surface with small amounts of admetals. These metal-modified carbides can be effective replacements for Pt-based bimetallic systems, which suffer from the drawbacks of high cost and low thermal stability. In this dissertation, metal-modified carbides were studied for reactions with applications to renewable energy technologies. It is demonstrated that metal-modified carbides possess high activity for alcohol reforming and electrochemical hydrogen production. First, the surface chemistry of carbides towards alcohol decomposition is studied using density functional theory (DFT) and surface science experiments. The Vienna Ab initio Simulation Package (VASP) was used to calculate the binding energies of alcohols and decomposition intermediates on metal-modified carbides. The calculated binding energies were then correlated to reforming activity determined experimentally using temperature programmed desorption (TPD). In the case of methanol decomposition, it was found that tungsten monocarbide (WC) selectively cleaved the C-O bond to produce methane. Upon modifying the surface with a single layer of metal such as Ni, Pt, or Rh, the selectivity shifted towards scission of the C-H bonds while leaving the C-O bond intact, producing carbon monoxide (CO) and H2. High resolution energy loss spectroscopy (HREELS) was used to examine the bond breaking sequence as a function of temperature. From HREELS, it was shown that the surfaces followed an activity trend of Rh > Ni > Pt. The Au-modified WC surface possessed too low of a methanol binding energy, and molecular desorption of methanol was the most favorable pathway on this surface. Next, the ability of Rh-modified WC to break the C-C bond of C2 and C3 alcohols was demonstrated. HREELS showed that ethanol decomposed through an acetaldehyde

  11. Mineral resource of the month: hydraulic cement

    Science.gov (United States)

    van Oss, Hendrik G.

    2012-01-01

    Hydraulic cements are the binders in concrete and most mortars and stuccos. Concrete, particularly the reinforced variety, is the most versatile of all construction materials, and most of the hydraulic cement produced worldwide is portland cement or similar cements that have portland cement as a basis, such as blended cements and masonry cements. Cement typically makes up less than 15 percent of the concrete mix; most of the rest is aggregates. Not counting the weight of reinforcing media, 1 ton of cement will typically yield about 8 tons of concrete.

  12. Dielectronic recombination of tungsten ions

    Science.gov (United States)

    Li, Bowen; O'Sullivan, Gerry; Dong, Chenzhong; Chen, Ximeng

    2016-08-01

    Ab initio calculations of dielectronic recombination rate coefficients of Ne-, Pd- and Ag-like tungsten have been performed. Energy levels, radiative transition probabilities and autoionization rates were calculated using the Flexible Atomic Code. The contributions from different channels to the total rate coefficients are discussed. The present calculated rate coefficients are compared with other calculations where available. Excellent agreement has been found for Ne-like W while a large discrepancy was found for Pd-like W, which implies that more ab initio calculations and experimental measurements are badly needed. Further calculations demonstrated that the influence of configuration interaction is small while nonresonant radiative stabilizing (NRS) contribution to doubly excited non-autoionizing states are vital. The data obtained are expected to be useful for modeling plasmas for fusion applications, especially for the ITER community, which makes experimental verification even more essential.

  13. Ligand sphere conversions in terminal carbide complexes

    DEFF Research Database (Denmark)

    Morsing, Thorbjørn Juul; Reinholdt, Anders; Sauer, Stephan P. A.

    2016-01-01

    Metathesis is introduced as a preparative route to terminal carbide complexes. The chloride ligands of the terminal carbide complex [RuC(Cl)2(PCy3)2] (RuC) can be exchanged, paving the way for a systematic variation of the ligand sphere. A series of substituted complexes, including the first exam...

  14. Boron carbide whiskers produced by vapor deposition

    Science.gov (United States)

    1965-01-01

    Boron carbide whiskers have an excellent combination of properties for use as a reinforcement material. They are produced by vaporizing boron carbide powder and condensing the vapors on a substrate. Certain catalysts promote the growth rate and size of the whiskers.

  15. Titanium Carbide Bipolar Plate for Electrochemical Devices

    Energy Technology Data Exchange (ETDEWEB)

    LaConti, Anthony B.; Griffith, Arthur E.; Cropley, Cecelia C.; Kosek, John A.

    1998-05-08

    Titanium carbide comprises a corrosion resistant, electrically conductive, non-porous bipolar plate for use in an electrochemical device. The process involves blending titanium carbide powder with a suitable binder material, and molding the mixture, at an elevated temperature and pressure.

  16. Hydroxide catalysis bonding of silicon carbide

    NARCIS (Netherlands)

    Veggel, A.A. van; Ende, D.A. van den; Bogenstahl, J.; Rowan, S.; Cunningham, W.; Gubbels, G.H.M.; Nijmeijer, H.

    2008-01-01

    For bonding silicon carbide optics, which require extreme stability, hydroxide catalysis bonding is considered [Rowan, S., Hough, J. and Elliffe, E., Silicon carbide bonding. UK Patent 040 7953.9, 2004. Please contact Mr. D. Whiteford for further information: D.Whiteford@admin.gla.ac.uk]. This techn

  17. Cement from magnesium substituted hydroxyapatite.

    Science.gov (United States)

    Lilley, K J; Gbureck, U; Knowles, J C; Farrar, D F; Barralet, J E

    2005-05-01

    Brushite cement may be used as a bone graft material and is more soluble than apatite in physiological conditions. Consequently it is considerably more resorbable in vivo than apatite forming cements. Brushite cement formation has previously been reported by our group following the mixture of nanocrystalline hydroxyapatite and phosphoric acid. In this study, brushite cement was formed from the reaction of nanocrystalline magnesium-substituted hydroxyapatite with phosphoric acid in an attempt to produce a magnesium substituted brushite cement. The presence of magnesium was shown to have a strong effect on cement composition and strength. Additionally the presence of magnesium in brushite cement was found to reduce the extent of brushite hydrolysis resulting in the formation of HA. By incorporating magnesium ions in the apatite reactant structure the concentration of magnesium ions in the liquid phase of the cement was controlled by the dissolution rate of the apatite. This approach may be used to supply other ions to cement systems during setting as a means to manipulate the clinical performance and characteristics of brushite cements.

  18. POZZOLAN AND CEMENTS WITH POZZOLAN

    Directory of Open Access Journals (Sweden)

    Hasan KAPLAN

    1995-02-01

    Full Text Available Cement, one of the basic material of construction engineering, has an important place in view of strength and cost of structures. Cement consumption is increasing parallel to development of building construction sector. For cement producers, minimal cost is desired by using new and economical material sources. On the other hand, the controllers and contractors need cheaper, safer and higher strength materials. From this respect cement industry tends to use cement with pozzolan. In Türkiye, cement with pozzolan is produced by adding the pozzolan, which has a large reservoir in the country, in cement in sertain amount. However this type of cement is consumed in the construction sector, sortage of scientific investigation and speculative news on the subject.are worried the users and producers. In this paper, prior to an experimental study on the cements having pozzolan additive, historical development of pozzolan, reservoir of Turkiye, and comparison with portland cement is carried out. Advantages and disadvantages of pozzolan are also discussed in some points.

  19. Process for making silicon carbide reinforced silicon carbide composite

    Science.gov (United States)

    Lau, Sai-Kwing (Inventor); Calandra, Salavatore J. (Inventor); Ohnsorg, Roger W. (Inventor)

    1998-01-01

    A process comprising the steps of: a) providing a fiber preform comprising a non-oxide ceramic fiber with at least one coating, the coating comprising a coating element selected from the group consisting of carbon, nitrogen, aluminum and titanium, and the fiber having a degradation temperature of between 1400.degree. C. and 1450.degree. C., b) impregnating the preform with a slurry comprising silicon carbide particles and between 0.1 wt % and 3 wt % added carbon c) providing a cover mix comprising: i) an alloy comprising a metallic infiltrant and the coating element, and ii) a resin, d) placing the cover mix on at least a portion of the surface of the porous silicon carbide body, e) heating the cover mix to a temperature between 1410.degree. C. and 1450.degree. C. to melt the alloy, and f) infiltrating the fiber preform with the melted alloy for a time period of between 15 minutes and 240 minutes, to produce a ceramic fiber reinforced ceramic composite.

  20. SINTERED REFRACTORY TUNGSTEN ALLOYS. Gesinterte hochschmelzende wolframlegierungen

    Energy Technology Data Exchange (ETDEWEB)

    Kieffer, R.; Sedlatschek, K.; Braun, H.

    1971-12-15

    Dependence of the melting point of the refractory metals on their positions in the periodic system - alloys of tungsten with other refractory metals - sintering of the alloys - processing of the alloys - technological properties.

  1. Characterization of a Cobalt-Tungsten Interconnect

    DEFF Research Database (Denmark)

    Harthøj, Anders; Holt, Tobias; Caspersen, Michael

    2012-01-01

    A ferritic steel interconnect for a solid oxide fuel cell must be coated in order to prevent chromium evaporation from the steel substrate. The Technical University of Denmark and Topsoe Fuel Cell have developed an interconnect coating based on a cobalt-tungsten alloy. The purpose of the coating...... is to act both as a diffusion barrier for chromium and provide better protection against high temperature oxidation than a pure cobalt coating. This work presents a characterization of a cobalt-tungsten alloy coating electrodeposited on the ferritic steel Crofer 22 H which subsequently was oxidized in air...... of oxidation time. The coating had completely oxidized during the 300 h oxidation time. GDOES measurements showed that the tungsten was located in an inner zone in the coating/substrate interface. The outer layer of the coating did not contain any tungsten after oxidation but consisted mainly of cobalt...

  2. Thermal stability of warm-rolled tungsten

    DEFF Research Database (Denmark)

    Alfonso Lopez, Angel

    Pure tungsten is considered as armor material for the most critical parts of fusion reactors (thedivertor and the blanket first wall), mainly due to its high melting point (3422 °C). This is becauseboth the divertor and the first wall have to withstand high temperatures during service which...... and recrystallization occur in tungsten, and quantifying the kinetics and microstructuralaspects of these restoration processes. Two warm-rolled tungsten plates are annealed attemperatures between 1100 °C and 1350 °C, under vacuum conditions or argon atmosphere. Theeffects of annealing on the microstructure...... on these activation energies) to lower annealingtemperatures allows predicting the lifespan of these tungsten plates under fusion reactor conditions.A much longer lifetime at normal operating temperatures was found for the plate W67 (e.g. at least1 million years at 800 °C) as compared to the plate W90 (e.g 71 years...

  3. 纳米碳化钽对SPS烧结钨显微结构的影响%Effect of Nano-TaC on Microstructure of Sintered Tungsten by SPS

    Institute of Scientific and Technical Information of China (English)

    张苹苹; 沈卫平; 周亚南; 马明亮; 张庆玲; 王青云

    2012-01-01

    Dispersion strengthened tungsten with nano-tantalum carbide (TaC) was prepared by Spark Plasma Sintering (SPS) process at 1700 ℃ for 1 min. The results show that the grain size of tungsten will be larger if the particle size of tungsten powder is larger. When the particle size of tungsten powder is 3 μm, the grain size of tungsten is 22.19 μm. And then, with the increase of TaC content, the grain size of tungsten will be finer. When the particle size of tungsten powder is 200 nm and the content of TaC is 4%, the grain size of sintered tungsten is about 5.91 μm. It also can be seen that TaC is spherical, it exists at grain boundaries of the sintered tungsten. Some transgranular fracture can be seen in fracture surface of pure tungsten by SPS, but it is mainly intergranular fracture in fracture surface of dispersion strengthened tungsten with nano-tantalum carbide.%通过放电等离子体烧结(SPS)方法在1700℃下制备纳米碳化钽(TaC)弥散强化钨块,研究钨粉原始粉末粒度大小和添加碳化钽的量对烧结钨块微观组织的影响.结果表明:不同粒度钨粉(30 nm、200 nm和3μm)制备的钨块,烧结后的粒径随原始粉末粒度的增大而增大,3 μm钨粉烧结后的晶粒平均直径为22.19μm;同一种粒度钨粉(如200 nm)中分别添加质量分数为0%,1%,2%和4%的碳化钽,烧结后钨晶粒的平均直径随碳化钽添加量的增加而减小,加入量为4%时晶粒平均直径为5.91 μm.通过SEM分析可以看出,碳化钽在烧结钨中是以球形状态存在的.从断口可以看出,纯钨烧结体为穿晶断裂,加入碳化钽的钨烧结体为晶间断裂.

  4. US cement industry

    Energy Technology Data Exchange (ETDEWEB)

    Nisbet, M.A.

    1997-12-31

    This paper describes the cement and concrete industry, and provides data on energy use and carbon dioxide emissions. The potential impact of an energy tax on the industry is briefly assessed. Opportunities identified for reducing carbon dioxide emissions include improved energy efficiency, alternative fuels, and alternative materials. The key factor in determining CO{sub 2} emissions is the level of domestic production. The projected improvement in energy efficiency and the relatively slow growth in domestic shipments indicate that CO{sub 2} emissions in 2000 should be about 5% above the 1990 target. However, due to the cyclical nature of cement demand, emissions will probably be above target levels during peak demand and below target levels during demand troughs. 7 figs., 2 tabs.

  5. Ultrafast laser-triggered emission from hafnium carbide tips

    Science.gov (United States)

    Kealhofer, Catherine; Foreman, Seth M.; Gerlich, Stefan; Kasevich, Mark A.

    2012-07-01

    Electron emission from hafnium carbide (HfC) field emission tips induced by a sub-10-fs, 150-MHz repetition rate Ti:sapphire laser is studied. Two-photon emission is observed at low power with a moderate electric bias field applied to the tips. As the bias field and/or laser power is increased, the average current becomes dominated by thermally enhanced field emission due to laser heating: both the low thermal conductivity of HfC and the laser's high repetition rate can lead to a temperature rise of several hundred Kelvin at the tip apex. The contribution of current from a thermal transient at times shorter than the electron-phonon coupling time is considered in the context of the two-temperature model (TTM). Under the conditions of this experiment, the integrated current from the thermal transient is shown to be negligible in comparison with the two-photon emission. A finite element model of the laser heating and thermal conduction supports these conclusions and is also used to compare the nature of thermal effects in HfC, tungsten, and gold tips.

  6. Processes and applications of silicon carbide nanocomposite fibers

    Energy Technology Data Exchange (ETDEWEB)

    Shin, D G; Cho, K Y; Riu, D H [Nanomaterials Team, Korea Institute of Ceramic Engineering and Technology, 233-5 Gasan-dong, Guemcheon-gu, Seoul 153-801 (Korea, Republic of); Jin, E J, E-mail: dhriu15@seoultech.ac.kr [Battelle-Korea Laborotary, Korea University, Anamdong, Seongbuk-gu, Seoul (Korea, Republic of)

    2011-10-29

    Various types of SiC such as nanowires, thin films, foam, and continuous fibers have been developed since the early 1980s, and their applications have been expanded into several new applications, such as for gas-fueled radiation heater, diesel particulate filter (DPF), ceramic fiber separators and catalyst/catalyst supports include for the military, aerospace, automobile and electronics industries. For these new applications, high specific surface area is demanded and it has been tried by reducing the diameter of SiC fiber. Furthermore, functional nanocomposites show potentials in various harsh environmental applications. In this study, silicon carbide fiber was prepared through electrospinning of the polycarbosilane (PCS) with optimum molecular weight distribution which was synthesized by new method adopting solid acid catalyst such as ZSM-5 and {gamma}-Al{sub 2}O{sub 3}. Functional elements such as aluminum, titanium, tungsten and palladium easily doped in the precursor fiber and remained in the SiC fiber after pyrolysis. The uniform SiC fibers were produced at the condition of spinning voltage over 20 kV from the PCS solution as the concentration of 1.3 g/ml in DMF/Toluene (3:7) and pyrolysis at 1200deg. C. Pyrolyzed products were processed into several interesting applications such as thermal batteries, hydrogen sensors and gas filters.

  7. Processes and applications of silicon carbide nanocomposite fibers

    Science.gov (United States)

    Shin, D. G.; Cho, K. Y.; Jin, E. J.; Riu, D. H.

    2011-10-01

    Various types of SiC such as nanowires, thin films, foam, and continuous fibers have been developed since the early 1980s, and their applications have been expanded into several new applications, such as for gas-fueled radiation heater, diesel particulate filter (DPF), ceramic fiber separators and catalyst/catalyst supports include for the military, aerospace, automobile and electronics industries. For these new applications, high specific surface area is demanded and it has been tried by reducing the diameter of SiC fiber. Furthermore, functional nanocomposites show potentials in various harsh environmental applications. In this study, silicon carbide fiber was prepared through electrospinning of the polycarbosilane (PCS) with optimum molecular weight distribution which was synthesized by new method adopting solid acid catalyst such as ZSM-5 and γ-Al2O3. Functional elements such as aluminum, titanium, tungsten and palladium easily doped in the precursor fiber and remained in the SiC fiber after pyrolysis. The uniform SiC fibers were produced at the condition of spinning voltage over 20 kV from the PCS solution as the concentration of 1.3 g/ml in DMF/Toluene (3:7) and pyrolysis at 1200°C. Pyrolyzed products were processed into several interesting applications such as thermal batteries, hydrogen sensors and gas filters.

  8. Research on Laser Cladded Nickel Based Nanometer Tungsten Carbide Composite Coating

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guang-jun; DAI Jian-qiang; WANG Hui-ping; YAN Min-jie; XI Wen-long; ZOU Chang-gu; GE Da-fang

    2004-01-01

    CO2 laser is adopted on the surface of austenitic stainless steel (1Cr18Ni9) to clad nickel based nanometer WC/Co composite coating. SEM, EDAX, XRD, AFM and Scratch Testers are adopted to conduct analysis and research on the microstructure, composition, phase and bonding strength of the coating. Results indicate that the microstructure of coating is metallurgically bonded with stainless steel base, eliminating porosities and cracks. The coating has a considerable quantity of nanometer particles visible with a granularity ≤ 100nm under a nanoscope atomic microscope. The bonding strength of the laser cladded coating is remarkably improved respectively compared with conventional hot-sprayed coating and spray welding. The nanometer effect of nanometer WC/Co introduced into the coating plays an important role in the laser cladding processes.

  9. Research on Laser Cladded Nickel Based Nanometer Tungsten Carbide Composite Coating

    Institute of Scientific and Technical Information of China (English)

    ZHANGGuang-jun; DAIJian-qiang; WANGHui-ping; YANMin-jie; XIWen-long; ZOUChang-gu; GEDa-fang

    2004-01-01

    CO2 laser is adopted on the surface of austenitic stainless steel (1Cr18Ni9) to clad nickel based nanometer WC/Co composite coating. SEM, EDAX, XRD, AFM and Scratch Testers are adopted to conduct analysis and research on the microstructure, composition, phase and bonding strength of the coating. Results indicate that the microstructure of coating is metallurgically bonded with stainless steel base, eliminating porosities and cracks. The coating has a considerable quantity of nanometer particles visible with a granularity ≤100nm under a nanoscope atomic microscope. The bonding strength of the laser cladded coating is remarkably improved respectively compared with conventional hot-sprayed coating and spray welding. The nanometer effect of nanometer WC/Co introduced into the coating plays an important role in the laser cladding processes.

  10. Inelastic deformation and failure of tungsten carbide under ballistic-loading conditions

    NARCIS (Netherlands)

    Hazell, P.J.; Appleby-Thomas, G.J.; Herlaar, K.; Painter, J.

    2010-01-01

    High-speed photography has been used to investigate the dynamic behaviour of similar grades of WC-Co hardmetals during ballistic impacts with velocities in the range of 28-484. m/s. Key features of the failure of similar grades of WC-Co materials during complimentary impacts have been observed and d

  11. First-principles calculations of structural stability and mechanical properties of tungsten carbide under high pressure

    Science.gov (United States)

    Li, Xinting; Zhang, Xinyu; Qin, Jiaqian; Zhang, Suhong; Ning, Jinliang; Jing, Ran; Ma, Mingzhen; Liu, Riping

    2014-11-01

    The structural stability and mechanical properties of WC in WC-, MoC- and NaCl-type structures under high pressure are investigated systematically by first-principles calculations. The calculated equilibrium lattice constants at zero pressure agree well with available experimental and theoretical results. The formation enthalpy indicates that the most stable WC is in WC-type, then MoC-type finally NaCl-type. By the elastic stability criteria, it is predicted that the three structures are all mechanically stable. The elastic constants Cij, bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν of the three structures are studied in the pressure range from 0 to 100 GPa. Furthermore, by analyzing the B/G ratio, the brittle/ductile behavior under high pressure is assessed. Moreover, the elastic anisotropy of the three structures up to 100 GPa is also discussed in detail.

  12. Wheel efficiency in the diamond-spark erosion grinding of tungsten carbides

    Science.gov (United States)

    Uzunjan, M. D.; Krasnoscek, J. S.

    1982-11-01

    Diamond-spark erosion grinding on metallic bond is a highly productive process used in working difficult materials. It is of considerable interest to investigate the efficiency of diamond wheels in the grinding of hard alloys while supplying impulse energy to the cutting zone. The efficiency of 150 x 10 x 3 ACK cup wheels made with ACB diamonds on MB1 bond as evaluated experimentally by the multifactor method using the following optimized parameters: removal rate Q (cu mm/min), specific diamond consumption q (mg/g) and a specific grinding cost C (kopecks/cu cm). A TI5K6 hard alloy sample 60 sq mm in cross section was ground using a 3B642 grinder with a 3% soda solution as coolant. The cutting zone was supplied with electrical impulse energy from an SGI 40-440 generator. The mean current ranged from 4 to 10 amps, the impulse frequency was 88 kHz, the degree of porosity was 2, the anode was the diamond wheel and the cathode was the treated material.

  13. Fabrication and Radiocharacterization of Boron Carbide and Tungsten Incorporated Rubber Shields

    OpenAIRE

    Marzieh Salimi; Eskandar Asadi Amirabadi; Nima Ghal-Eh; Zahra Soltani; Gholam Reza Etaati

    2013-01-01

    Radioactive ray safeguard is a physical impediment which is placed between radioactive source and the protected object in order to decrease the amount of rays' radiation in the protected area. Different materials such as lead, iron, graphite, water, poly ethylene, concrete, or rubber can be used for protection against nuclear radiations. In safeguard's common designing, two types of Gama and Neutron radiations are usually considered. The weakening amount of Gama radiations is proportional to ...

  14. Influence of powder granulometry on the sintering of binderless tungsten carbide

    Energy Technology Data Exchange (ETDEWEB)

    Arenas, F.; Cabezas, M. [Univ. Inst. of Tech., Caracas (Venezuela). Dept. of Materials Technology; Montoya, E.; Lira, J. [Simon Bolivar Univ., Caracas (Venezuela). Dept. of Materials Science

    2002-07-01

    In the production of uniaxially pressed components, the powder size, distribution and pressure used are key factors to obtain a high quality product. Several models have been reported to correlate the packing and sintered densities as a function of the compaction pressure but, most of them for spherical-like and wide particle size distributions. In this work, a series of submicron average particle size (0.8, 0.4 and 0.2 {mu}m) commercial WC powder mixes are evaluated for pressures in the range 200-350 MPa. The cobalt binderless samples were vacuum solid state sintered at 1400 C for 1 h. The results indicated that both green and sintered densification (Dr) increased with pressure (p) and that the bimodal and trimodal mixtures studied follow a mathematical expression of the type: Ln(1/(1-Dr)) = 0.428 x 10{sup -2} p + 0.576 for the green relative density in the whole pressure range evaluated. (orig.)

  15. Tungsten carbide modified high surface area carbon as fuel cell catalyst support

    Science.gov (United States)

    Shao, Minhua; Merzougui, Belabbes; Shoemaker, Krista; Stolar, Laura; Protsailo, Lesia; Mellinger, Zachary J.; Hsu, Irene J.; Chen, Jingguang G.

    Phase pure WC nanoparticles were synthesized on high surface area carbon black (800 m 2 g -1) by a temperature programmed reaction (TPR) method. The particle size of WC can be controlled under 30 nm with a relatively high coverage on the carbon surface. The electrochemical testing results demonstrated that the corrosion resistance of carbon black was improved by 2-fold with a surface modification by phase pure WC particles. However, the WC itself showed some dissolution under potential cycling. Based on the X-ray diffraction (XRD) and inductively coupled plasma (ICP) analysis, most of the WC on the surface was lost or transformed to oxides after 5000 potential cycles in the potential range of 0.65-1.2 V. The Pt catalyst supported on WC/C showed a slightly better ORR activity than that of Pt/C, with the Pt activity loss rate for Pt/WC/C being slightly slower compared to that of Pt/C. The performance and decay rate of Pt/WC/C were also evaluated in a fuel cell.

  16. Tungsten carbide coatings with different binders prepared by low power plasma spray system

    Institute of Scientific and Technical Information of China (English)

    GAO Yang; M.F.Morks; FU Ying-qing

    2004-01-01

    Thermal spraying of cermet coatings is widely used for protection of machining parts against wear and corrosion. These coatings consist of WC particles in metal binders such as Co, Cr and Ni. Three kinds of WC powders with different metal binders (Co, NiCr and CoCr) were sprayed by low power plasma spray system on Al-Si-Cu alloy substrate. Fundamental aspects of sprayed cermet coatings, including (i) the effects of binder type on the coating structure, (ii) the hardness and (iii) the microstructure, were investigated. All cermet coatings have the same phase structure such as WC and W2 C. However, the intensities of these phases are different in each coating, mainly due to the difference in solidification rate in each case. Moreover, the hardness measurements are found to be different in each coating. The results show that, binder type has a significant effect on the physical and mechanical properties of the sprayed coatings.

  17. Tungsten-zirconium carbide-rhenium alloys with extraordinary thermal stability

    Energy Technology Data Exchange (ETDEWEB)

    Yang, X.D. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xie, Z.M.; Miao, S. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); Liu, R.; Jiang, W.B. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Zhang, T., E-mail: zhangtao@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Wang, X.P., E-mail: xpwang@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Fang, Q.F. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); Liu, C.S., E-mail: csliu@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Luo, G.N. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Liu, X. [Southwest Institute of Plasma Physics, Chengdu (China)

    2016-05-15

    The low recrystallization temperature (1200 °C) of pure W is a serious limitation for application as facing plasma materials in fusion reactor. In this paper, W-0.5wt.%ZrC-1wt.%Re (WZR) alloy with recrystallization temperature up to 1800 °C was prepared by mechanical milling and spark plasma sintering. The grain size of WZR alloy is about 2.6 μm, smaller than that of pure W (4.4 μm), which keeps unchanged until the annealing temperature increases to 1800 °C. Tensile tests indicate that the WZR alloys exhibit excellent comprehensive properties: the ductile to brittle transition temperature of WZR is in the range from 400 °C to 500 °C, about 200 °C lower than that of pure W prepared by the same process; the total elongation (TE) of WZR at 600 °C is above 30%, which is about 2 times that of pure W (at 700 °C). Meanwhile its tensile strength keeps ∼450 MPa before and after 1800 °C annealing as well as its TE increases after annealing. WZR alloy exhibits higher hardness (489HV) than that of pure W (453HV) at room temperature. Microstructure analysis indicates that the strengthening of nano-sized ZrC particles dispersion and Re solid solution improve tensile properties and thermal stability of WZR alloy.

  18. Advances in Glass Ionomer Cements

    OpenAIRE

    KAYA, Dt. Tuğba; TİRALİ, Yard. Doç. Dr. Resmiye Ebru

    2013-01-01

    In recent years there have been a number of innovations and developments with respect to glass ionomer cements and their applications in clinical dentistry. This article considers some of the recent outstanding studies regarding the field of glass ionomer cement applications, adhesion and setting mechanisms, types, advantage and disadvantages among themselves and also to enhance the physical and antibacterial properties under the title of 'Advances in Glass Ionomer Cements'. As their biologic...

  19. Cement penetration after patella venting.

    Science.gov (United States)

    Jones, Christopher W; Lam, Li-On; Butler, Adam; Wood, David J; Walsh, William R

    2009-01-01

    There is a high rate of patellofemoral complications following total knee arthroplasty. Optimization of the cement-bone interface by venting and suction of the tibial plateau has been shown to improve cement penetration. Our study was designed to investigate if venting the patella prior to cementing improved cement penetration. Ten paired cadaver patellae were allocated prior to resurfacing to be vented or non-vented. Bone mineral density (BMD) was measured by DEXA scanning. In vented specimens, a 1.6 mm Kirschner wire was used to breach the anterior cortex at the center. Specimens were resurfaced with standard Profix instrumentation and Versabond bone cement (Smith and Nephew PLC, UK). Cement penetration was assessed from Faxitron and sectioned images by a digital image software package (ImageJ V1.38, NIH, USA). Wilcoxon rank sum test was used to assess the difference in cement penetration between groups. The relationship between BMD and cement penetration was analyzed by Pearson correlation coefficient. There was a strong negative correlation between peak BMD and cement penetration when analyzed independent of experimental grouping (r(2)=-0.812, p=0.004). Wilcoxon rank sum testing demonstrated no significant difference (rank sum statistic W=27, p=0.579) in cement penetration between vented (10.53%+/-4.66; mean+/-std dev) and non-vented patellae (11.51%+/-6.23; mean+/-std dev). Venting the patella using a Kirschner wire does not have a significant effect on the amount of cement penetration achieved in vitro using Profix instrumentation and Versabond cement.

  20. Precipitating Mechanism of Carbide in Cold-Welding Surfacing Metals

    Institute of Scientific and Technical Information of China (English)

    Yuanbin ZHANG; Dengyi REN

    2004-01-01

    Carbides in a series of cold-welding weld metals were studied by means of SEM, TEM and EPMA, and the forming mechanism of carbide was proposed according to their distribution and morphology. Due to their different carbide-forming tendency, Nb and Ti could combine with C to form particulate carbide in liquid weld metal and depleted the carbon content in matrix, while V induced the carbide precipitated along grain boundary. But too much Nb or Ti alone resulted in coarse carbide and poor strengthened matrix. When suitable amount of Nb, Ti and V coexisted in weld metal, both uniformly distributed particulate carbide and well strengthened matrix could be achieved. It was proposed that the carbide nucleated on the oxide which dispersed in liquid weld metal, and then grew into multi-layer complex carbide particles by epitaxial growth. At different sites, carbide particles may present as different morphologies.

  1. Hydrothermal synthesis of xonotlite from carbide slag

    Institute of Scientific and Technical Information of China (English)

    Jianxin Cao; Fei Liu; Qian Lin; Yu Zhang

    2008-01-01

    Carbide slag was used as the calcareous materials for the first time to prepare xonotlite via dynamic hydrothermal synthesis.The effects of influential factors including different calcination temperatures,pretreatment methods of the carbide slag and process param-eters of hydrothermal synthesis on the microstructure and morphology of xonotlite were explored using XRD and SEM techniques.The results indicate that the carbide slag after proper calcination could be used to prepare pure xonotlite;and different calcination tern-peratures have little effect on the crystallinity of synthesized xonotlitc,but have great impact on the morphology of secondary particles.The different pretreatment methods of the carbide slag pose great impact on the crystallinity and morphology of secondary particles of xonotlite.Xonotlite was also synthesized from pure CaO under the salne experimental conditions as that prepared from calcined carbide slag for comparison.Little amount of impurities in carbide slag has no effect on the mechanism of hydrothermal synthesizing xonotlite from carbide slag.

  2. Atomically Thin Heterostructures Based on Single-Layer Tungsten Diselenide and Graphene

    KAUST Repository

    Lin, Yu-Chuan

    2014-11-10

    Heterogeneous engineering of two-dimensional layered materials, including metallic graphene and semiconducting transition metal dichalcogenides, presents an exciting opportunity to produce highly tunable electronic and optoelectronic systems. In order to engineer pristine layers and their interfaces, epitaxial growth of such heterostructures is required. We report the direct growth of crystalline, monolayer tungsten diselenide (WSe2) on epitaxial graphene (EG) grown from silicon carbide. Raman spectroscopy, photoluminescence, and scanning tunneling microscopy confirm high-quality WSe2 monolayers, whereas transmission electron microscopy shows an atomically sharp interface, and low energy electron diffraction confirms near perfect orientation between WSe2 and EG. Vertical transport measurements across the WSe2/EG heterostructure provides evidence that an additional barrier to carrier transport beyond the expected WSe2/EG band offset exists due to the interlayer gap, which is supported by theoretical local density of states (LDOS) calculations using self-consistent density functional theory (DFT) and nonequilibrium Green\\'s function (NEGF).

  3. Formation of nanoscale titanium carbides in ferrite: an atomic study

    Science.gov (United States)

    Lv, Yanan; Hodgson, Peter; Kong, Lingxue; Gao, Weimin

    2016-03-01

    The formation and evolution of nanoscale titanium carbide in ferrite during the early isothermal annealing process were investigated via molecular dynamics simulation. The atomic interactions of titanium and carbon atoms during the initial formation process explained the atoms aggregation and carbides formation. It was found that the aggregation and dissociation of titanium carbide occurred simultaneously, and the composition of carbide clusters varied in a wide range. A mechanism for the formation of titanium carbide clusters in ferrite was disclosed.

  4. Thermal Shock-resistant Cement

    Energy Technology Data Exchange (ETDEWEB)

    Sugama T.; Pyatina, T.; Gill, S.

    2012-02-01

    We studied the effectiveness of sodium silicate-activated Class F fly ash in improving the thermal shock resistance and in extending the onset of hydration of Secar #80 refractory cement. When the dry mix cement, consisting of Secar #80, Class F fly ash, and sodium silicate, came in contact with water, NaOH derived from the dissolution of sodium silicate preferentially reacted with Class F fly ash, rather than the #80, to dissociate silicate anions from Class F fly ash. Then, these dissociated silicate ions delayed significantly the hydration of #80 possessing a rapid setting behavior. We undertook a multiple heating -water cooling quenching-cycle test to evaluate the cement’s resistance to thermal shock. In one cycle, we heated the 200 and #61616;C-autoclaved cement at 500 and #61616;C for 24 hours, and then the heated cement was rapidly immersed in water at 25 and #61616;C. This cycle was repeated five times. The phase composition of the autoclaved #80/Class F fly ash blend cements comprised four crystalline hydration products, boehmite, katoite, hydrogrossular, and hydroxysodalite, responsible for strengthening cement. After a test of 5-cycle heat-water quenching, we observed three crystalline phase-transformations in this autoclaved cement: boehmite and #61614; and #61543;-Al2O3, katoite and #61614; calcite, and hydroxysodalite and #61614; carbonated sodalite. Among those, the hydroxysodalite and #61614; carbonated sodalite transformation not only played a pivotal role in densifying the cementitious structure and in sustaining the original compressive strength developed after autoclaving, but also offered an improved resistance of the #80 cement to thermal shock. In contrast, autoclaved Class G well cement with and without Class F fly ash and quartz flour failed this cycle test, generating multiple cracks in the cement. The major reason for such impairment was the hydration of lime derived from the dehydroxylation of portlandite formed in the autoclaved

  5. Phosphate based oil well cements

    Science.gov (United States)

    Natarajan, Ramkumar

    The main application of the cement in an oil well is to stabilize the steel casing in the borehole and protect it from corrosion. The cement is pumped through the borehole and is pushed upwards through the annulus between the casing and the formation. The cement will be exposed to temperature and pressure gradients of the borehole. Modified Portland cement that is being used presently has several shortcomings for borehole sealant. The setting of the Portland cement in permafrost regions is poor because the water in it will freeze even before the cement sets and because of high porosity and calcium oxide, a major ingredient it gets easily affected by the down hole gases such as carbon dioxide. The concept of phosphate bonded cements was born out of considerable work at Argonne National Laboratory (ANL) on their use in stabilization of radioactive and hazardous wastes. Novel cements were synthesized by an acid base reaction between a metal oxide and acid phosphate solution. The major objective of this research is to develop phosphate based oil well cements. We have used thermodynamics along with solution chemistry principles to select calcined magnesium oxide as candidate metal oxide for temperatures up to 200°F (93.3°C) and alumina for temperatures greater than 200°F (93.3°C). Solution chemistry helped us in selecting mono potassium phosphate as the acid component for temperatures less than 200°F (93.3°C) and phosphoric acid solution greater than 200°F (93.3°C). These phosphate cements have performance superior to common Portland well cements in providing suitable thickening time, better mechanical and physical properties.

  6. Characterization of Nanometric-Sized Carbides Formed During Tempering of Carbide-Steel Cermets

    OpenAIRE

    Matus K.; Pawlyta M.; Matula G.; Gołombek K.

    2016-01-01

    The aim of this article of this paper is to present issues related to characterization of nanometric-sized carbides, nitrides and/or carbonitrides formed during tempering of carbide-steel cermets. Closer examination of those materials is important because of hardness growth of carbide-steel cermet after tempering. The results obtained during research show that the upswing of hardness is significantly higher than for high-speed steels. Another interesting fact is the displacement of secondary ...

  7. Influence of Eta-Phase on Wear Behavior of WC-Co Carbides

    Directory of Open Access Journals (Sweden)

    A. Formisano

    2016-01-01

    Full Text Available Cemented carbides, also known as Widia, are hard metals produced by sintering process and widely used in mechanical machining. They show high cutting capacity and good wear resistance; consequently, they result to be excellent materials for manufacturing cutting tools and sandblast nozzles. In this work, the wear resistance of WC-Co carbides containing Eta-phase, a secondary phase present in the hard metals when a carbon content deficiency occurs, is analyzed. Different mixtures of carbide are prepared and sintered, with different weight percentages of carbon, in order to form Eta-phase and then analyze how the carbon content influences the wear resistance of the material. This characterization is carried out by abrasive wear tests. The test parameters are chosen considering the working conditions of sandblast nozzles. Additional information is gathered through microscopic observations and the evaluation of hardness and microhardness of the different mixtures. The analyses highlight that there is a limit of carbon content below which bad sintering occurs. Considering the mixtures without these sintering problems, they show a wear resistance depending on the size and distribution of the Eta-phase; moreover, the one with high carbon content deficiency shows the best performance.

  8. Ductile-Phase-Toughened Tungsten for Plasma-Facing Materials

    Science.gov (United States)

    Cunningham, Kevin Hawkins

    A variety of processing approaches were employed to fabricate ductile-phase-toughened (DPT) tungsten (W) composites. Mechanical testing and analytical modeling were used to guide composite development. This work provides a basis for further development of W composites to be used in structural divertor components of future fusion reactors. W wire was tested in tension, showing significant ductility and strength. Coatings of copper (Cu) or tungsten carbide (WC) were applied to the W wire via electrodeposition and carburization, respectively. Composites were fabricated using spark plasma sintering (SPS) to consolidate W powders together with each type of coated W wire. DPT behavior, e.g. crack arrest and crack bridging, was not observed in three-point bend testing of the sintered composites. A laminate was fabricated by hot pressing W and Cu foils together with W wires, and subsequently tested in tension. This laminate was bonded via hot pressing to thick W plate as a reinforcing layer, and the composite was tested in three-point bending. Crack arrest was observed along with some fiber pullout, but significant transverse cracking in the W plate confounded further fracture toughness analysis. The fracture toughness of thin W plate was measured in three-point bending. W plates were brazed with Cu foils to form a laminate. Crack arrest and crack bridging were observed in three-point bend tests of the laminate, and fracture resistance curves were successfully calculated for this DPT composite. An analytical model of crack bridging was developed using the basis described by Chao in previous work by the group. The model uses the specimen geometry, matrix properties, and the stress-displacement function of a ductile reinforcement ("bridging law") to calculate the fracture resistance curve (R-curve) and load-displacement curve (P-D curve) for any test specimen geometry. The code was also implemented to estimate the bridging law of an arbitrary composite using R-curve data

  9. Carbothermal synthesis of silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Janney, M.A.; Wei, G.C.; Kennedy, C.R.; Harris, L.A.

    1985-05-01

    Silicon carbide powders were synthesized from various silica and carbon sources by a carbothermal reduction process at temperatures between 1500 and 1600/sup 0/C. The silica sources were fumed silica, methyltrimethoxysilane, and microcrystalline quartz. The carbon sources were petroleum pitch, phenolic resin, sucrose, and carbon black. Submicron SiC powders were synthesized. Their morphologies included equiaxed loosely-bound agglomerates, equiaxed hard-shell agglomerates, and whiskers. Morphology changed with the furnace atmosphere (argon, nitrogen, or nitrogen-4% hydrogen). The best sintering was observed in SiC derived from the fumed-silica-pitch and fumed-silica-sucrose precursors. The poorest sintering was observed in SiC derived from microcrystalline quartz and carbon black. 11 refs., 16 figs., 10 tabs.

  10. Thermal Expansion of Hafnium Carbide

    Science.gov (United States)

    Grisaffe, Salvatore J.

    1960-01-01

    Since hafnium carbide (HfC) has a melting point of 7029 deg. F, it may have many high-temperature applications. A literature search uncovered very little information about the properties of HfC, and so a program was initiated at the Lewis Research Center to determine some of the physical properties of this material. This note presents the results of the thermal expansion investigation. The thermal-expansion measurements were made with a Gaertner dilatation interferometer calibrated to an accuracy of +/- 1 deg. F. This device indicates expansion by the movement of fringes produced by the cancellation and reinforcement of fixed wave-length light rays which are reflected from the surfaces of two parallel quartz glass disks. The test specimens which separate these disks are three small cones, each approximately 0.20 in. high.

  11. Electroanalytical determination of tungsten and molybdenum in proteins.

    Science.gov (United States)

    Hagedoorn, P L; van't Slot, P; van Leeuwen, H P; Hagen, W R

    2001-10-01

    Recent crystal structure determinations accelerated the progress in the biochemistry of tungsten-containing enzymes. In order to characterize these enzymes, a sensitive determination of this metal in protein-containing samples is necessary. An electroanalytical tungsten determination has successfully been adapted to determine the tungsten and molybdenum content in enzymes. The tungsten and molybdenum content can be measured simultaneously from 1 to 10 microg of purified protein with little or no sample handling. More crude protein samples require precipitation of interfering surface active material with 10% perchloric acid. This method affords the isolation of novel molybdenum- and tungsten-containing proteins via molybdenum and tungsten monitoring of column fractions, without using radioactive isotopes. A screening of soluble proteins from Pyrococcus furiosus for tungsten, using anion-exchange column chromatography to separate the proteins, has been performed. The three known tungsten-containing enzymes from P. furiosus were recovered with this screening.

  12. Scandia doped tungsten matrix for impregnated cathode

    Institute of Scientific and Technical Information of China (English)

    WANG Jinshu; WANG Yanchun; LIU Wei; LI Hongyi; ZHOU Meiling

    2008-01-01

    As a matrix for Sc-type impregnated cathode,scandia doped tungsten with a uniform ldistribution of SC2O3 was obtained by powder metallurgy combined with the liquid-solid doping method.The microstructure and composition of the powder and the anti-ion bombardment behavior of scandium in the matrix were studied by means of SEM,EDS,XRD,and in-situ AES methods.Tungsten powder covered with scandium oxide,an ideal scandium oxide-doped tungsten powder for the preparation of Sc-type impregnated cathode,was obtained using the liquid-solid doping method.Compared with the matrix prepared with the mechanically mixed powder of tungsten and scandium oxide,SC2O3-W matrix prepared with this kind of powder had smaller grain size and uniform distribution of scandium.Sc on the surface of Sc2O3 doped tungsten mauix had good high temperature stability and good anti-ion bombardment capability.

  13. Stabilization of boron carbide via silicon doping.

    Science.gov (United States)

    Proctor, J E; Bhakhri, V; Hao, R; Prior, T J; Scheler, T; Gregoryanz, E; Chhowalla, M; Giulani, F

    2015-01-14

    Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping.

  14. Calcium carbide poisoning via food in childhood.

    Science.gov (United States)

    Per, Hüseyin; Kurtoğlu, Selim; Yağmur, Fatih; Gümüş, Hakan; Kumandaş, Sefer; Poyrazoğlu, M Hakan

    2007-02-01

    The fast ripening of fruits means they may contain various harmful properties. A commonly used agent in the ripening process is calcium carbide, a material most commonly used for welding purposes. Calcium carbide treatment of food is extremely hazardous because it contains traces of arsenic and phosphorous. Once dissolved in water, the carbide produces acetylene gas. Acetylene gas may affect the neurological system by inducing prolonged hypoxia. The findings are headache, dizziness, mood disturbances, sleepiness, mental confusion, memory loss, cerebral edema and seizures. We report the case of a previously healthy 5 year-old girl with no chronic disease history who was transferred to our Emergency Department with an 8-h history of coma and delirium. A careful history from her father revealed that the patient ate unripe dates treated with calcium carbide.

  15. The Newly Released Export Quota for Tungsten Products

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    <正>China’s Ministry of Commerce recently announced the second lot of export quota for tungsten products in 2005. Based on the new quota, the second lot for Ammonium Paratung-state (APT) and Ammonium Metatungstate (AMT) will be 1,232 tons. The second lot for tungsten trioxide and blue tungsten oxide will be 1,480 tons and the second lot for tungsten powder and its products will be 428 tons.

  16. Process for the recovery of tungsten in a pure form from tungsten-containing materials

    Energy Technology Data Exchange (ETDEWEB)

    Fruchter, M.; Moscovici, A.

    1986-12-16

    A process is described for the recovery of tungsten from tungsten-containing materials which comprises the steps of (i) admixing the tungsten-containing material with a melt at a temperature of between 680/sup 0/C and 750/sup 0/C. The melt consists of a salt selected from the group consisting of sodium nitrate, sodium nitrite and mixtures thereof in a substantially stoichiometrical amount to the tungsten constituent of the tungsten-containing material. This is done to disintegrate the tungsten-containing material and to form sodium tungstate, cooling the melt, and leaching the cooled melt with water to obtain an aqueous solution of sodium tungstate; (ii) admixing a solution of calcium chloride with the aqueous solution of sodium tungstate at a temperature of between 40/sup 0/C and 95/sup 0/C to form a calcium tungstate precipitate and separating the calcium tungstate; (iii) admixing the calcium tungstate with a preheated concentrated hydrochloric acid solution to form a tungstic acid precipitate and a CaCl/sub 2/ solution having a concentration of between 80 g/l and 180 g/l free HCl and separating the tungstic acid precipitate and obtaining tungstic acid which is substantially free of calcium ions, and (iv) calcining the tungstic acid to convert it to tungstic oxide and reducing the tungstic oxide to form metallic tungsten.

  17. Selective etching of silicon carbide films

    Science.gov (United States)

    Gao, Di; Howe, Roger T.; Maboudian, Roya

    2006-12-19

    A method of etching silicon carbide using a nonmetallic mask layer. The method includes providing a silicon carbide substrate; forming a non-metallic mask layer by applying a layer of material on the substrate; patterning the mask layer to expose underlying areas of the substrate; and etching the underlying areas of the substrate with a plasma at a first rate, while etching the mask layer at a rate lower than the first rate.

  18. Cemented total hip arthroplasty with Boneloc bone cement.

    Science.gov (United States)

    Markel, D C; Hoard, D B; Porretta, C A

    2001-01-01

    Boneloc cement (WK-345, Biomet Inc, Warsaw, Ind) attempted to improve cement characteristics by reducing exotherm during polymerization, lowering residual monomer and solubility, raising molecular weight, and lowering airborne monomer and aromatic amines. To study the efficacy of this cement, a selected group of 20 patients were prospectively enrolled and followed up after hip arthroplasty. All components were cemented. During the enrollment period, approximately 70 other hip arthroplasties were performed. Clinical evaluation was based on the Harris hip score. Radiographic evaluation was based on assessment of position of the components, subsidence, and/or presence of radiolucencies. Patients had follow-up for an average of 42 months (11 to 58 months); 1 was lost to follow-up. Of these, 7 (35%) had failure at last follow-up. Despite its initial promise, Boneloc cement had an unacceptably high failure rate over a relatively short follow-up period and is not recommended for use. Despite the longevity and odor toxicity problems with conventional bone cement, new cement technologies must be approached with caution.

  19. Magnesium oxychloride cement concrete

    Indian Academy of Sciences (India)

    A K Misra; Renu Mathur

    2007-06-01

    The scope of magnesium oxychloride (MOC) cement in concrete works has been evaluated. MOC cement concrete compositions of varying strengths having good placing and finishing characteristics were prepared and investigated for their compressive and flexural strengths, -values, abrasion resistance etc. The durability of MOC concrete compositions against extreme environmental conditions viz. heating–cooling, freezing–thawing, wetting–drying and penetration and deposition of salts etc were investigated. The results reveal that MOC concrete has high compressive strength associated with high flexural strength and the ratio of compressive to flexural strength varies between 6 and 8. The elastic moduli of the compositions studied are found to be 23–85 GPa and the abrasion losses between 0.11 and 0.20%. While alternate heating–cooling cycles have no adverse effect on MOC concrete, it can be made durable against freezing–thawing and the excessive exposure to water and salt attack by replacing 10% magnesium chloride solution by magnesium sulphate solution of the same concentration.

  20. Process optimization for diffusion bonding of tungsten with EUROFER97 using a vanadium interlayer

    Science.gov (United States)

    Basuki, Widodo Widjaja; Aktaa, Jarir

    2015-04-01

    Solid-state diffusion bonding is a selected joining technology to bond divertor components consisting of tungsten and EUROFER97 for application in fusion power plants. Due to the large mismatch in their coefficient of thermal expansions, which leads to serious thermally induced residual stresses after bonding, a thin vanadium plate is introduced as an interlayer. However, the diffusion of carbon originated from EUROFER97 in the vanadium interlayer during the bonding process can form a vanadium carbide layer, which has detrimental influences on the mechanical properties of the joint. For optimal bonding results, the thickness of this layer and the residual stresses has to be decreased sufficiently without a significant reduction of material transport especially at the vanadium/tungsten interface, which can be achieved by varying the diffusion bonding temperature and duration. The investigation results show that at a sufficiently low bonding temperature of 700 °C and a bonding duration of 4 h, the joint reaches a reasonable high ductility and toughness especially at elevated test temperature of 550 °C with elongation to fracture of 20% and mean absorbed Charpy impact energy of 2 J (using miniaturized Charpy impact specimens). The strength of the bonded materials is about 332 MPa at RT and 291 MPa at 550 °C. Furthermore, a low bonding temperature of 700 °C can also help to avoid the grain coarsening and the alteration of the grain structure especially of the EUROFER97 close to the bond interface.

  1. Combustion synthesis of novel boron carbide

    Science.gov (United States)

    Harini, R. Saai; Manikandan, E.; Anthonysamy, S.; Chandramouli, V.; Eswaramoorthy, D.

    2013-02-01

    The solid-state boron carbide is one of the hardest materials known, ranking third behind diamond and cubic boron nitride. Boron carbide (BxCx) enriched in the 10B isotope is used as a control rod material in the nuclear industry due to its high neutron absorption cross section and other favorable physico-chemical properties. Conventional methods of preparation of boron carbide are energy intensive processes accompanied by huge loss of boron. Attempts were made at IGCAR Kalpakkam to develop energy efficient and cost effective methods to prepare boron carbide. The products of the gel combustion and microwave synthesis experiments were characterized for phase purity by XRD. The carbide formation was ascertained using finger-print spectroscopy of FTIR. Samples of pyrolized/microwave heated powder were characterized for surface morphology using SEM. The present work shows the recent advances in understanding of structural and chemical variations in boron carbide and their influence on morphology, optical and vibrational property results discussed in details.

  2. Dilatometric analysis on shrinkage behavior during non-isothermal sintering of nanocrystalline tungsten mechanically alloyed with molybdenum

    Energy Technology Data Exchange (ETDEWEB)

    Srivastav, Ajeet K., E-mail: ajeetshri@gmail.com [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Murty, B.S. [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036 (India)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Alloying with Mo reduces the WC contamination during milling. Black-Right-Pointing-Pointer Kirkendall effect assisted enhanced diffusion influences the densification of W-Mo alloys Black-Right-Pointing-Pointer Densification kinetics improved with Mo alloying in nanocrystalline tungsten. Black-Right-Pointing-Pointer Densification starts with Mo diffusion and later W and Mo both diffuse along the grain boundaries. - Abstract: The paper attempts to study the shrinkage behavior of nanocrystalline tungsten mechanically alloyed with molybdenum (5, 10, 15 and 20 wt.%). The dilatometric analysis was performed by Setsys Evolution TMA (ambient to 1600 Degree-Sign C) using constant heating rate (CHR) method. The significant improvement in shrinkage with alloying of molybdenum is attributed to reduced grain size, lowered tungsten carbide contamination and enhanced diffusion kinetics. The initial stage sintering kinetics of W-20Mo alloy has been investigated. The densification starts with Mo diffusion (calculated activation energy = 128 kJ/mol) and proceeds with the diffusion of both along the grain boundaries (calculated activation energy = 307 {+-} 1 kJ/mol).

  3. 40 CFR 721.10168 - Cesium tungsten oxide.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Cesium tungsten oxide. 721.10168... Substances § 721.10168 Cesium tungsten oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cesium tungsten oxide (PMN P-08-275; CAS No....

  4. Study of tungsten based positron moderators

    Energy Technology Data Exchange (ETDEWEB)

    Lucio, O.G. de; Pérez, M.; Mendoza, U.; Morales, J.G.; Cruz, J.C. [Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, 01000 México DF (Mexico); DuBois, R.D. [Missouri University of Science and Technology, Rolla, MO 65409 (United States)

    2015-07-01

    Positrons and how they interact with matter has a growing interest in many fields. Most of their uses require the production of slow positron beams with a well-defined energy, but since these particles are usually generated by means of a radioactive source, they are fast and with a broad distribution of energies. For this reason it is necessary to moderate them to lower energies via inelastic collisions. Then, they can be accelerated to the desired energies. This requires the use of a moderator. Tungsten is one of the most commonly used moderator materials because of its reasonable efficiency and relatively low cost. In this work we present different methods of producing transmission tungsten-based moderators, with particular interest in a combination of tungsten thin foils and grids. We also show results about the characterization of these moderators by ion beam analysis and microscopy techniques along with their relative moderation efficiencies.

  5. Element 74, the Wolfram Versus Tungsten Controversy

    Energy Technology Data Exchange (ETDEWEB)

    Holden,N.E.

    2008-08-11

    Two and a quarter centuries ago, a heavy mineral ore was found which was thought to contain a new chemical element called heavy stone (or tungsten in Swedish). A few years later, the metal was separated from its oxide and the new element (Z=74) was called wolfram. Over the years since that time, both the names wolfram and tungsten were attached to this element in various countries. Sixty years ago, IUPAC chose wolfram as the official name for the element. A few years later, under pressure from the press in the USA, the alternative name tungsten was also allowed by IUPAC. Now the original, official name 'wolfram' has been deleted by IUPAC as one of the two alternate names for the element. The history of this controversy is described here.

  6. Grout cement. ; Grout cement to fill ground/grout cement to fill cracks. Chunyuyo cement. ; Jiban chunyuyo cement /hibiware chunyuyo cement

    Energy Technology Data Exchange (ETDEWEB)

    Okaue, H. (Nittetsu Cement Co. Ltd., Hokkaido (Japan))

    1991-09-01

    Ground grout cement is grouted into the ground under high pressure in high water ratio (100 to 1000%) in the form of milk differing from concrete in terms of the water-cement ratio. The grouted milk is governed by characteristics of the cement the milk itself possesses, resulting in variable grouting modes, which are divided in fracture grouting, permeation grouting and boundary grouting. Their applications include cutting off of water in dams, ground reinforcement, prevention of water gushing in tunnel excavation, natural ground reinforcement, improvement of sandy soil and prevention of its collapse, and stabilization of ground for urban civil engineering works such as subway, water supply and sewerage constructions. Grout cement to fill cracks in concrete structures is so grouted into cracks that the slurry fills up contiguous cracks to a certain level and goes upward while pushing out air or water existing in the cracks. The slurry filled into the cracks solidifies and hardens while being absorbed into the concrete, and finally integrates with the concrete. The grout cement is used to rework such concrete structures as dams, tunnels, and bridge bases. 6 figs., 4 tabs.

  7. 21 CFR 888.4200 - Cement dispenser.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027)...

  8. Metamagnetism of η-carbide-type transition-metal carbides and nitrides

    Science.gov (United States)

    Waki, T.; Terazawa, S.; Umemoto, Y.; Tabata, Y.; Sato, K.; Kondo, A.; Kindo, K.; Nakamura, H.

    2011-09-01

    η-carbide-type transition-metal compounds include the frustrated stella quadran-gula lattice. Due to characteristics of the lattice, we expect subtle transitions between frustrated and non-frustrated states. Here, we report metamagnetic transitions newly found in η-carbide-type compounds Fe3W3C, Fe6W6C and Co6W6C.

  9. Cements containing by-product gypsum

    Energy Technology Data Exchange (ETDEWEB)

    Bensted, J. [University of Greenwich, London (United Kingdom). School of Biological and Chemical Sciences

    1995-12-31

    Chemical by-product gypsum can readily replace natural gypsum in Portland cements and in blended cements like Portland pfa cement and Portland blast furnace cement without technical detriment in many instances. Indeed, sometimes the technical performance of the cement can be enhanced. The hydration chemistry is often changed, in that where there is at least some retardation of setting, more AFT phase (ettringite) is formed during early hydration at the expense of calcium silicate hydrates. By-product gypsum can also replace natural gypsum in speciality products like calcium aluminate cement-Portland cement mixes for producing quick setting cements and in calcium sulphoaluminate-type expansive cements. However, by-products gypsum have proved to be less successful for utilization in API Classes of oilwell cements, because of the greater difficulty in obtaining batch-to-batch consistency in properties like thickening time and slurry rheology. 11 refs., 3 figs., 5 tabs.

  10. Thermal cycling and high power density hydrogen ion beam irradiation of tungsten layers on tungsten substrate

    Science.gov (United States)

    Airapetov, A. A.; Begrambekov, L. B.; Gretskaya, I. Yu; Grunin, A. V.; Dyachenko, M. Yu; Puntakov, N. A.; Sadovskiy, Ya A.

    2016-09-01

    Tungsten layers with iron impurity were deposited on tungsten substrates modeling re-deposited layers in a fusion device. The samples were tested by thermocycling and hydrogen ion beam tests. Thermocycling revealed globule formation on the surface. The size of the globules depended on iron impurity content in the coating deposited. Pore formation was observed which in some cases lead to exfoliation of the coatings. Hydrogen ion irradiation lead to formation of blisters on the coating and finally its exfoliation.

  11. Aluminum-tungsten fiber composites with cylindrical geometry and controlled architecture of tungsten reinforcement

    OpenAIRE

    Lucchese, Carl Joesph

    2010-01-01

    A aluminum matrix-W rod/wire structural material in support of DARPA initiative BAA 08-23 was developed and its density and mechanical strength ascertained, both being part of the DARPA matrices. Aluminum tubes and four 90 degree cross-ply tungsten fiber layers were arranged such that under extreme static pressure conditions the aluminum would viscoplastically flow into the tungsten arrangement to create a metal matrix composite. It was found that a cold isostatic process induced "Brazilian" ...

  12. Silicon Carbide From a Carbon Nodule in the Canyon Diablo Meteorite

    Science.gov (United States)

    Leung, I. S.; Winston, R.

    2011-12-01

    The Canyon Diablo Meteorite fell in the Arizona desert 50,000 years ago, giving rise to the well-preserved Meteor Crater. Irons of various sizes were scattered around the crater rim and on the surrounding plains. We studied a rusty specimen containing a carbon nodule. We dug out small blocks of sooty carbon by means of a sharp tungsten carbide tip. These carbon materials contain traces of silicon carbide (SiC) and diamond/lonsdaleite. We report here our findigs of two groups of SiC grains. (1) Relatively large crystals, about 80-90 microns in size. Their colors are in shades of blue, green and neutral. One of the grains are composed of a cluster of 3 crystals of the 3C polytype, whereas, 7 other individual crystals are of hexagonal structure. All crystals in this group have dark, rounded resorption rims. (2) Small crystals, about 30-50 microns in size. They are pale blue in color, and they lack dark-colored rims. These two distinct groups probably have different modes of origin. The large crystals seem to be early-formed, but had been reheated or partially melted, as indicated by the bead-like rims. The complexities displayed by these SiC crystals might have resulted from a long residence time in the meteorite while it was still in space. Their origin might be akin to that of SiC occurring in carbonaceous chondrites and interplanetary dust particles.

  13. ITER tungsten divertor design development and qualification program

    Energy Technology Data Exchange (ETDEWEB)

    Hirai, T., E-mail: takeshi.hirai@iter.org [ITER Organization, Route de Vinon sur Verdon, F-13115 Saint Paul lez Durance (France); Escourbiac, F.; Carpentier-Chouchana, S.; Fedosov, A.; Ferrand, L.; Jokinen, T.; Komarov, V.; Kukushkin, A.; Merola, M.; Mitteau, R.; Pitts, R.A.; Shu, W.; Sugihara, M. [ITER Organization, Route de Vinon sur Verdon, F-13115 Saint Paul lez Durance (France); Riccardi, B. [F4E, c/ Josep Pla, n.2, Torres Diagonal Litoral, Edificio B3, E-08019 Barcelona (Spain); Suzuki, S. [JAEA, Fusion Research and Development Directorate JAEA, 801-1 Mukouyama, Naka, Ibaragi 311-0193 (Japan); Villari, R. [Associazione EURATOM-ENEA sulla Fusione, Via Enrico Fermi 45, I-00044 Frascati, Rome (Italy)

    2013-10-15

    Highlights: • Detailed design development plan for the ITER tungsten divertor. • Latest status of the ITER tungsten divertor design. • Brief overview of qualification program for the ITER tungsten divertor and status of R and D activity. -- Abstract: In November 2011, the ITER Council has endorsed the recommendation that a period of up to 2 years be set to develop a full-tungsten divertor design and accelerate technology qualification in view of a possible decision to start operation with a divertor having a full-tungsten plasma-facing surface. To ensure a solid foundation for such a decision, a full tungsten divertor design, together with a demonstration of the necessary high performance tungsten monoblock technology should be completed within the required timescale. The status of both the design and technology R and D activity is summarized in this paper.

  14. A Study of Scandia Doped Tungsten Nano-Powders

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Scandia and rhenium doped tungsten powders were prepared by solid-liquid doping combined with two-step reduction method. The particle size of doped tungsten and distribution of scandia and rhenium were studied by SEM, EDS, XRD and granularity analysis. Experimental results showed that scandia distributed evenly on the surface of tungsten particles. Addition of scandia and rhenium decreased the particle size of doped tungsten, and the more the content of scandia and rhenium, the smaller the doped tungsten particles. Tungsten powders doped with 3% Sc2O3 and 3% Re (mass fraction) had an average size of about 80 nm in diameter. The mechanism of the decrease in the tungsten particle size was discussed.

  15. Visible light photoinactivation of bacteria by tungsten oxide nanostructures formed on a tungsten foil

    Science.gov (United States)

    Ghasempour, Fariba; Azimirad, Rouhollah; Amini, Abbas; Akhavan, Omid

    2015-05-01

    Antibacterial activity of tungsten oxide nanorods/microrods were studied against Escherichia coli bacteria under visible light irradiation and in dark. A two-step annealing process at temperatures up to 390 °C and 400-800 °C was applied to synthesize the tungsten oxide nanorods/microrods on tungsten foils using KOH as a catalyst. Annealing the foils at 400 °C in the presence of catalyst resulted in formation of tungsten oxide nanorods (with diameters of 50-90 nm and crystalline phase of WO3) on surface of tungsten foils. By increasing the annealing temperature up to 800 °C, tungsten oxide microrods with K2W6O19 crystalline phase were formed on the foils. The WO3 nanorods showed a strong antibacterial property under visible light irradiation, corresponding to >92% bacterial inactivation within 24 h irradiation at room temperature, while the K2W6O19 microrods formed at 800 °C could inactivate only ∼45% of the bacteria at the same conditions.

  16. Electrospark doping of steel with tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Denisova, Yulia, E-mail: yukolubaeva@mail.ru; Shugurov, Vladimir, E-mail: shugurov@opee.hcei.tsc.ru [Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, 634055, Russia, Tomsk, 2/3 Akademicheskiy Ave (Russian Federation); Petrikova, Elizaveta, E-mail: elizmarkova@yahoo.com [Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, 634055, Russia, Tomsk, 2/3 Akademicheskiy Ave (Russian Federation); National Research Tomsk State University, 36 Lenin Str. Tomsk, 634050 (Russian Federation); Seksenalina, Malika, E-mail: sportmiss@bk.ru [National Research Tomsk Polytechnic University, 30 Lenin Str. Tomsk, 634050 (Russian Federation); Ivanova, Olga, E-mail: ivaov@mail.ru; Ikonnikova, Irina, E-mail: irinaikonnikova@yandex.ru [Tomsk State University of Architecture and Building, 2 Solyanaya Sq. Tomsk, 634003 (Russian Federation); Kunitsyna, Tatyana, E-mail: kma11061990@mail.ru; Vlasov, Victor, E-mail: rector@tsuab.ru [National Research Tomsk Polytechnic University, 30 Lenin Str. Tomsk, 634050 (Russian Federation); Tomsk State University of Architecture and Building, 2 Solyanaya Sq. Tomsk, 634003 (Russian Federation); Klopotov, Anatoliy, E-mail: klopotovaa@tsuab.ru [National Research Tomsk State University, 36 Lenin Str. Tomsk, 634050 (Russian Federation); Tomsk State University of Architecture and Building, 2 Solyanaya Sq. Tomsk, 634003 (Russian Federation); Ivanov, Yuriy, E-mail: yufi55@mail.ru [Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences, 634055, Russia, Tomsk, 2/3 Akademicheskiy Ave (Russian Federation); National Research Tomsk State University, 36 Lenin Str. Tomsk, 634050 (Russian Federation); National Research Tomsk Polytechnic University, 30 Lenin Str. Tomsk, 634050 (Russian Federation)

    2016-01-15

    The paper is devoted to the numerical modeling of thermal processes and the analysis of the structure and properties of the surface layer of carbon steel subjected to electrospark doping with tungsten. The problem of finding the temperature field in the system film (tungsten) / substrate (iron) is reduced to the solution of the heat conductivity equation. A one-dimensional case of heating and cooling of a plate with the thickness d has been considered. Calculations of temperature fields formed in the system film / substrate synthesized using methods of electrospark doping have been carried out as a part of one-dimensional approximation. Calculations have been performed to select the mode of the subsequent treatment of the system film / substrate with a high-intensity pulsed electron beam. Authors revealed the conditions of irradiation allowing implementing processes of steel doping with tungsten. A thermodynamic analysis of phase transformations taking place during doping of iron with tungsten in equilibrium conditions has been performed. The studies have been carried out on the surface layer of the substrate modified using the method of electrospark doping. The results showed the formation in the surface layer of a structure with a highly developed relief and increased strength properties.

  17. Gas tungsten arc welder with electrode grinder

    Science.gov (United States)

    Christiansen, David W.; Brown, William F.

    1984-01-01

    A welder for automated closure of fuel pins by a gas tungsten arc process in which a rotating length of cladding is positioned adjacent a welding electrode in a sealed enclosure. An independently movable axial grinder is provided in the enclosure for refurbishing the used electrode between welds.

  18. Proton Induced Effects on Tungsten Powder

    CERN Multimedia

    2012-01-01

    In the HRMT-10 experiment, that took place in HiRadMat facility of CERN/SPS, the effects of a high-power incident proton beam on a tungsten powder target were investigated. In this video, 2.64E11 protons @ 440 GeV are impinging on the target.

  19. Proton Induced Effects on Tungsten Powder

    CERN Multimedia

    HiRadMat facility of CERN/SPS

    2012-01-01

    In the HRMT-10 experiment, that took place in HiRadMat facility of CERN/SPS, the effects of a high-power incident proton beam on a tungsten powder target were investigated. In this video, 1.7E11 protons @ 440 GeV are impinging on the target.

  20. Proton Induced Effects on Tungsten Powder

    CERN Multimedia

    2012-01-01

    In the HRMT-10 experiment, that took place in HiRadMat facility of CERN/SPS, the effects of a high-power incident proton beam on a tungsten powder target were investigated. In this video, 1.85E11 protons @ 440 GeV are impinging on the target.

  1. Proton Induced Effects on Tungsten Powder

    CERN Multimedia

    2012-01-01

    In the HRMT-10 experiment, that took place in HiRadMat facility of CERN/SPS, the effects of a high-power incident proton beam on a tungsten powder target were investigated. In this video, 2E11 protons @ 440 GeV are impinging on the target.

  2. Proton Induced Effects on Tungsten Powder

    CERN Multimedia

    2012-01-01

    In the HRMT-10 experiment, that took place in HiRadMat facility of CERN/SPS, the effects of a high-power incident proton beam on a tungsten powder target were investigated. In this video, 1.3E11 protons @ 440 GeV are impinging on the target.

  3. Titanium tungsten coatings for bioelectrochemical applications

    DEFF Research Database (Denmark)

    Wierzbicki, Rafal; Amato, Letizia; Łopacińska, J.

    2011-01-01

    This paper presents an assessment of titanium tungsten (TiW) coatings and their applicability as components of biosensing systems. The focus is put on using TiW as an electromechanical interface layer between carbon nanotube (CNT) forests and silicon nanograss (SiNG) cell scaffolds. Cytotoxicity...

  4. OPAL Example Segment of Silicon Tungsten Luminometer

    CERN Multimedia

    OPAL was one of the four experiments installed at the LEP particle accelerator from 1989 - 2000. The Silicon Tungsten Luminometer was part of OPAL's calorimeter which was used to measure the energy of particles. Most particles end their journey in calorimeters. These detectors measure the energy deposited when particles are slowed down and stopped.

  5. Alternative Fuels in Cement Production

    DEFF Research Database (Denmark)

    Larsen, Morten Boberg

    for the most significant alternative fuel energy contributors in the German cement industry. Solid alternative fuels are typically high in volatile content and they may differ significantly in physical and chemical properties compared to traditional solid fossil fuels. From the process point of view......The substitution of alternative for fossil fuels in cement production has increased significantly in the last decade. Of these new alternative fuels, solid state fuels presently account for the largest part, and in particular, meat and bone meal, plastics and tyre derived fuels (TDF) accounted......, considering a modern kiln system for cement production, the use of alternative fuels mainly influences 1) kiln process stability (may accelerate build up of blockages preventing gas and/or solids flow), 2) cement clinker quality, 3) emissions, and 4) decreased production capacity. Kiln process stability...

  6. Magnesium substitution in brushite cements.

    Science.gov (United States)

    Alkhraisat, Mohammad Hamdan; Cabrejos-Azama, Jatsue; Rodríguez, Carmen Rueda; Jerez, Luis Blanco; Cabarcos, Enrique López

    2013-01-01

    The use of magnesium-doped ceramics has been described to modify brushite cements and improve their biological behavior. However, few studies have analyzed the efficiency of this approach to induce magnesium substitution in brushite crystals. Mg-doped ceramics composed of Mg-substituted β-TCP, stanfieldite and/or farringtonite were reacted with primary monocalcium phosphate (MCP) in the presence of water. The cement setting reaction has resulted in the formation of brushite and newberyite within the cement matrix. Interestingly, the combination of SAED and EDX analyses of single crystal has indicated the occurrence of magnesium substitution within brushite crystals. Moreover, the effect of magnesium ions on the structure, and mechanical and setting properties of the new cements was characterized as well as the release of Ca(2+) and Mg(2+) ions. Further research would enhance the efficiency of the system to incorporate larger amounts of magnesium ions within brushite crystals.

  7. Computer simulations for thorium doped tungsten crystals

    Energy Technology Data Exchange (ETDEWEB)

    Eberhard, Bernd

    2009-07-17

    Tungsten has the highest melting point among all metals in the periodic table of elements. Furthermore, its equilibrium vapor pressure is by far the lowest at the temperature given. Thoria, ThO{sub 2}, as a particle dopant, results in a high temperature creep resistant material. Moreover, thorium covered tungsten surfaces show a drastically reduced electronic work function. This results in a tremendous reduction of tip temperatures of cathodes in discharge lamps, and, therefore, in dramatically reduced tungsten vapor pressures. Thorium sublimates at temperatures below those of a typical operating cathode. For proper operation, a diffusional flow of thorium atoms towards the surface has to be maintained. This atomic flux responds very sensitively on the local microstructure, as grain boundaries as well as dislocation cores offer ''short circuit paths'' for thorium atoms. In this work, we address some open issues of thoriated tungsten. A molecular dynamics scheme (MD) is used to derive static as well as dynamic material properties which have their common origin in the atomistic behavior of tungsten and thorium atoms. The interatomic interactions between thorium and tungsten atoms are described within the embedded atom model (EAM). So far, in literature no W-Th interaction potentials on this basis are described. As there is no alloying system known between thorium and tungsten, we have determined material data for the fitting of these potentials using ab-initio methods. This is accomplished using the full potential augmented plane wave method (FLAPW), to get hypothetical, i.e. not occurring in nature, ''alloy'' data of W-Th. In order to circumvent the limitations of classical (NVE) MD schemes, we eventually couple our model systems to external heat baths or volume reservoirs (NVT, NPT). For the NPT ensemble, we implemented a generalization of the variable cell method in combination with the Langevin piston, which results in a

  8. Mirror Surface Grinding of Steel Bonded Carbides

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The steel bonded carbide, a composite material, is very difficult to be machined to a fine finish mirror surface. In this paper, an electrolytic in-process dressing (ELID) grinding with metallic bond super-hard abrasive wheel was developed for grinding steel bonded carbide GT35. Factors affecting ELID grinding performance were analyzed by an atomic force microscope (AFM). Based on the analysis of AFM topography of the fine ground mirror surface of the steel bonded carbide, a schematic diagram of the mechanism of micro-removal of the ground surface was described. The AFM topography also shows that the hard brittle carbide particles, on the surface of steel bonded carbide, were machined out by ductile cutting. Since the grinding cracks in the ground surface are due to temperature gradient, temperature distribution in the grinding area was analyzed by finite element method (FEM). Experimental results indicate that a good mirror surface with Ra<0.02pm can be obtained by the developed ELID grinding system.

  9. Development of an Extreme High Temperature n-type Ohmic Contact to Silicon Carbide

    Science.gov (United States)

    Evans, Laura J.; Okojie, Robert S.; Lukco, Dorothy

    2011-01-01

    We report on the initial demonstration of a tungsten-nickel (75:25 at. %) ohmic contact to silicon carbide (SiC) that performed for up to fifteen hours of heat treatment in argon at 1000 C. The transfer length method (TLM) test structure was used to evaluate the contacts. Samples showed consistent ohmic behavior with specific contact resistance values averaging 5 x 10-4 -cm2. The development of this contact metallization should allow silicon carbide devices to operate more reliably at the present maximum operating temperature of 600 C while potentially extending operations to 1000 C. Introduction Silicon Carbide (SiC) is widely recognized as one of the materials of choice for high temperature, harsh environment sensors and electronics due to its ability to survive and continue normal operation in such environments [1]. Sensors and electronics in SiC have been developed that are capable of operating at temperatures of 600 oC. However operating these devices at the upper reliability temperature threshold increases the potential for early degradation. Therefore, it is important to raise the reliability temperature ceiling higher, which would assure increased device reliability when operated at nominal temperature. There are also instances that require devices to operate and survive for prolonged periods of time above 600 oC [2, 3]. This is specifically needed in the area of hypersonic flight where robust sensors are needed to monitor vehicle performance at temperature greater than 1000 C, as well as for use in the thermomechanical characterization of high temperature materials (e.g. ceramic matrix composites). While SiC alone can withstand these temperatures, a major challenge is to develop reliable electrical contacts to the device itself in order to facilitate signal extraction

  10. Portland cement-blast furnace slag blends in oilwell cementing applications

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, D.T.; DiLullo, G.; Hibbeler, J. [and others

    1995-12-31

    Recent investigations of blast furnace slag cementing technologies. have been expanded to include Portland cement/blast furnace slag blends. Mixtures of Portland cement and blast furnace slag, while having a long history of use in the construction industry, have not been used extensively in oilwell cementing applications. Test results indicate that blending blast furnace slag with Portland cement produces a high quality well cementing material. Presented are the design guidelines and laboratory test data relative to mixtures of blast furnace slag and Portland cements. Case histories delineating the use of blast furnace slag - Portland cement blends infield applications are also included.

  11. Microstructure and properties of liquid-phase sintered tungsten heavy alloys by using ultra-fine tungsten powders

    Institute of Scientific and Technical Information of China (English)

    于洋; 王尔德

    2004-01-01

    The microstructure and properties of liquid-phase sintered 93W-4.9Ni-2.1Fe tungsten heavy alloys using ultra-fine tungsten powders (medium particle size of 700 nm) and original tungsten powders (medium particle size of 3 μm) were investigated respectively. Commercial tungsten powders (original tungsten powders) were mechanically milled in a high-energy attritor mill for 35 h. Ultra-fine tungsten powders and commercial Ni, Fe powders were consolidated into green compacts by using CIP method and liquid-phase sintering at 1 465 ℃ for 30 min in the dissociated ammonia atmosphere. Liquid-phase sintered tungsten heavy alloys using ultra-fine tungsten powders exhibit full densification (above 99% in relative density) and higher strength and elongation compared with conventional liquidphase sintered alloys using original tungsten powders due to lower sintering temperature at 1 465 ℃ and short sintering time. The mechanical properties of sintered tungsten heavy alloy are found to be mainly dependent on the particles size of raw tungsten powders and liquid-phase sintering temperature.

  12. Calcium Orthophosphate Cements and Concretes

    Directory of Open Access Journals (Sweden)

    Sergey V. Dorozhkin

    2009-03-01

    Full Text Available In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are a bioactive and biodegradable grafting material in the form of a powder and a liquid. Both phases form after mixing a viscous paste that after being implanted, sets and hardens within the body as either a non-stoichiometric calcium deficient hydroxyapatite (CDHA or brushite, sometimes blended with unreacted particles and other phases. As both CDHA and brushite are remarkably biocompartible and bioresorbable (therefore, in vivo they can be replaced with newly forming bone, calcium orthophosphate cements represent a good correction technique for non-weight-bearing bone fractures or defects and appear to be very promising materials for bone grafting applications. Besides, these cements possess an excellent osteoconductivity, molding capabilities and easy manipulation. Furthermore, reinforced cement formulations are available, which in a certain sense might be described as calcium orthophosphate concretes. The concepts established by calcium orthophosphate cement pioneers in the early 1980s were used as a platform to initiate a new generation of bone substitute materials for commercialization. Since then, advances have been made in the composition, performance and manufacturing; several beneficial formulations have already been introduced as a result. Many other compositions are in experimental stages. In this review, an insight into calcium orthophosphate cements and concretes, as excellent biomaterials suitable for both dental and bone grafting application, has been provided.

  13. Chemical Modification Methods of Nanoparticles of Silicon Carbide Surface

    OpenAIRE

    Anton S. Yegorov; Vitaly S. Ivanov; Alexey V. Antipov; Alyona I. Wozniak; Kseniia V. Tcarkova.

    2015-01-01

    silicon carbide exhibits exceptional properties: high durability, high thermal conductivity, good heat resistance, low thermal expansion factor and chemical inactivity. Reinforcement with silicon carbide nanoparticles increases polymer’s tensile strength and thermal stability.Chemical methods of modification of the silicon carbide surface by means of variety of reagents from ordinary molecules to macromolecular polymers are reviewed in the review.The structure of silicon carbide surface layer...

  14. The Influence of Feed Rate on Surface Roughness of TIC–WC Carbide And Al2O3 Ceramics SAWN-OFF with Inner Edge of Diamond Disc

    Directory of Open Access Journals (Sweden)

    Raimundas Mikolaitis

    2011-02-01

    Full Text Available The paper presents results of measurements of surface roughness of titanium-tungsten carbide (T14K8 and aluminium oxide (Al2O3 ceramics surfaces sawn-off with inner edge of diamond disc. The cutting process was performed by cutting machine “АЛМАЗ-4” with 60/40 grain size disc. The dependence of average roughness Ra of the sawn-off surface on feed speed of the workpiece was established.Article in Lithuanian

  15. Silicon Carbide Solar Cells Investigated

    Science.gov (United States)

    Bailey, Sheila G.; Raffaelle, Ryne P.

    2001-01-01

    The semiconductor silicon carbide (SiC) has long been known for its outstanding resistance to harsh environments (e.g., thermal stability, radiation resistance, and dielectric strength). However, the ability to produce device-quality material is severely limited by the inherent crystalline defects associated with this material and their associated electronic effects. Much progress has been made recently in the understanding and control of these defects and in the improved processing of this material. Because of this work, it may be possible to produce SiC-based solar cells for environments with high temperatures, light intensities, and radiation, such as those experienced by solar probes. Electronics and sensors based on SiC can operate in hostile environments where conventional silicon-based electronics (limited to 350 C) cannot function. Development of this material will enable large performance enhancements and size reductions for a wide variety of systems--such as high-frequency devices, high-power devices, microwave switching devices, and high-temperature electronics. These applications would supply more energy-efficient public electric power distribution and electric vehicles, more powerful microwave electronics for radar and communications, and better sensors and controls for cleaner-burning, more fuel-efficient jet aircraft and automobile engines. The 6H-SiC polytype is a promising wide-bandgap (Eg = 3.0 eV) semiconductor for photovoltaic applications in harsh solar environments that involve high-temperature and high-radiation conditions. The advantages of this material for this application lie in its extremely large breakdown field strength, high thermal conductivity, good electron saturation drift velocity, and stable electrical performance at temperatures as high as 600 C. This behavior makes it an attractive photovoltaic solar cell material for devices that can operate within three solar radii of the Sun.

  16. Low pH Cements

    Energy Technology Data Exchange (ETDEWEB)

    Savage, David; Benbow, Steven [Quintessa Ltd., Henley-on-Thames (United Kingdom)

    2007-05-15

    The development of low-pH cements for use in geological repositories for radioactive waste stems from concerns over the potential for deleterious effects upon the host rock and other EBS materials (notably bentonite) under the hyperalkaline conditions (pH > 12) of cement pore fluids. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non-pozzolanic silica flour. SKB and Posiva have ruled out the use of blast furnace slag and fly-ash and are focusing on silica fume as a blending agent. Currently, no preferred composition has been identified by these agencies. SKB and Posiva have defined a pH limit {<=} 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio {<=} 0.8. Although there are potential implications for the performance of the spent fuel and cladding due to the presence of hyperalkaline fluids from cement, the principal focus for safety assessment lies with the behaviour of bentonite. There are a number of potential constraints on the interaction of hyperalkaline cement pore fluids with bentonite, including mass balance, thermodynamic issues, mass transport, and kinetics, but none of these is likely to be limiting if conventional OPC cements are employed in repository construction. Nevertheless: Low-pH cements may supply approximately 50 % less hydroxyl ions than conventional OPC for a given volume of cement, but mass balance constraints are complicated by the uncertainty concerning the type of secondary minerals produced during cement-bentonite interaction. The change of aqueous

  17. Low pH Cements

    Energy Technology Data Exchange (ETDEWEB)

    Savage, David; Benbow, Steven [Quintessa Ltd., Henley-on-Thames (United Kingdom)

    2007-05-15

    The development of low-pH cements for use in geological repositories for radioactive waste stems from concerns over the potential for deleterious effects upon the host rock and other EBS materials (notably bentonite) under the hyperalkaline conditions (pH > 12) of cement pore fluids. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non-pozzolanic silica flour. SKB and Posiva have ruled out the use of blast furnace slag and fly-ash and are focusing on silica fume as a blending agent. Currently, no preferred composition has been identified by these agencies. SKB and Posiva have defined a pH limit {<=} 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio {<=} 0.8. Although there are potential implications for the performance of the spent fuel and cladding due to the presence of hyperalkaline fluids from cement, the principal focus for safety assessment lies with the behaviour of bentonite. There are a number of potential constraints on the interaction of hyperalkaline cement pore fluids with bentonite, including mass balance, thermodynamic issues, mass transport, and kinetics, but none of these is likely to be limiting if conventional OPC cements are employed in repository construction. Nevertheless: Low-pH cements may supply approximately 50 % less hydroxyl ions than conventional OPC for a given volume of cement, but mass balance constraints are complicated by the uncertainty concerning the type of secondary minerals produced during cement-bentonite interaction. The change of aqueous

  18. Fabrication of thorium bearing carbide fuels

    Science.gov (United States)

    Gutierrez, Rueben L.; Herbst, Richard J.; Johnson, Karl W. R.

    1981-01-01

    Thorium-uranium carbide and thorium-plutonium carbide fuel pellets have been fabricated by the carbothermic reduction process. Temperatures of 1750.degree. C. and 2000.degree. C. were used during the reduction cycle. Sintering temperatures of 1800.degree. C. and 2000.degree. C. were used to prepare fuel pellet densities of 87% and >94% of theoretical, respectively. The process allows the fabrication of kilogram quantities of fuel with good reproducibility of chemicals and phase composition. Methods employing liquid techniques that form carbide microspheres or alloying-techniques which form alloys of thorium-uranium or thorium-plutonium suffer from limitation on the quantities processed of because of criticality concerns and lack of precise control of process conditions, respectively.

  19. Titanium carbide nanocrystals in circumstellar environments.

    Science.gov (United States)

    von Helden, G; Tielens, A G; van Heijnsbergen, D; Duncan, M A; Hony, S; Waters, L B; Meijer, G

    2000-04-14

    Meteorites contain micrometer-sized graphite grains with embedded titanium carbide grains. Although isotopic analysis identifies asymptotic giant branch stars as the birth sites of these grains, there is no direct observational identification of these grains in astronomical sources. We report that infrared wavelength spectra of gas-phase titanium carbide nanocrystals derived in the laboratory show a prominent feature at a wavelength of 20.1 micrometers, which compares well to a similar feature in observed spectra of postasymptotic giant branch stars. It is concluded that titanium carbide forms during a short (approximately 100 years) phase of catastrophic mass loss (>0.001 solar masses per year) in dying, low-mass stars.

  20. Ionisation Potentials of Metal Carbide Clusters

    Science.gov (United States)

    Dryza, Viktoras; Addicoat, M.; Gascooke, Jason; Buntine, Mark; Metha, Gregory

    2006-03-01

    Photo-Ionisation Efficiency (PIE) experiments have been performed on gas phase niobium and tantalum carbide clusters to determine their ionisation potentials (IPs). For TanCm (n = 3-4, m = 0-4) clusters an oscillatory behaviour is observed such that clusters with an odd number of carbon atoms have higher IPs and clusters with an even number of carbons have lower IPs. Excellent agreement is found with relative IPs calculated using density functional theory for the lowest energy structures, which are consistent with the development of a 2x2x2 face-centred nanocrystal. For the niobium carbide clusters we observe the species Nb4C5 and Nb4C6. Initial calculations suggest that these clusters contain carbon-carbon bonding. Interestingly, the stoichiometry for Nb4C6 is half that of a metcar, M8C12. Preliminary data will also be shown on bimetallic-carbide clusters.

  1. Mechanical Properties of Crystalline Silicon Carbide Nanowires.

    Science.gov (United States)

    Zhang, Huan; Ding, Weiqiang; Aidun, Daryush K

    2015-02-01

    In this paper, the mechanical properties of crystalline silicon carbide nanowires, synthesized with a catalyst-free chemical vapor deposition method, were characterized with nanoscale tensile testing and mechanical resonance testing methods inside a scanning electron microscope. Tensile testing of individual silicon carbide nanowire was performed to determine the tensile properties of the material including the tensile strength, failure strain and Young's modulus. The silicon carbide nanowires were also excited to mechanical resonance in the scanning electron microscope vacuum chamber using mechanical excitation and electrical excitation methods, and the corresponding resonance frequencies were used to determine the Young's modulus of the material according to the simple beam theory. The Young's modulus values from tensile tests were in good agreement with the ones obtained from the mechanical resonance tests.

  2. Silicon carbide, an emerging high temperature semiconductor

    Science.gov (United States)

    Matus, Lawrence G.; Powell, J. Anthony

    1991-01-01

    In recent years, the aerospace propulsion and space power communities have expressed a growing need for electronic devices that are capable of sustained high temperature operation. Applications for high temperature electronic devices include development instrumentation within engines, engine control, and condition monitoring systems, and power conditioning and control systems for space platforms and satellites. Other earth-based applications include deep-well drilling instrumentation, nuclear reactor instrumentation and control, and automotive sensors. To meet the needs of these applications, the High Temperature Electronics Program at the Lewis Research Center is developing silicon carbide (SiC) as a high temperature semiconductor material. Research is focussed on developing the crystal growth, characterization, and device fabrication technologies necessary to produce a family of silicon carbide electronic devices and integrated sensors. The progress made in developing silicon carbide is presented, and the challenges that lie ahead are discussed.

  3. 40 CFR 421.310 - Applicability: Description of the secondary tungsten and cobalt subcategory.

    Science.gov (United States)

    2010-07-01

    ... the production of tungsten or cobalt at secondary tungsten and cobalt facilities processing tungsten... secondary tungsten and cobalt subcategory. 421.310 Section 421.310 Protection of Environment ENVIRONMENTAL... CATEGORY Secondary Tungsten and Cobalt Subcategory § 421.310 Applicability: Description of the...

  4. 21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device...: Polymethylmethacrylate (PMMA) Bone Cement.”...

  5. Ultrarapid microwave synthesis of superconducting refractory carbides

    Energy Technology Data Exchange (ETDEWEB)

    Vallance, Simon R. [Department of Chemical and Environmental Engineering, University of Nottingham (United Kingdom); School of Chemistry, University Nottingham (United Kingdom); Round, David M. [School of Chemistry, University Nottingham (United Kingdom); Ritter, Clemens [Institut Laue-Langevin, Grenoble (France); Cussen, Edmund J. [WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow (United Kingdom); Kingman, Sam [Department of Chemical and Environmental Engineering, University of Nottingham (United Kingdom); Gregory, Duncan H. [WestCHEM, Department of Chemistry, University of Glasgow (United Kingdom)

    2009-11-26

    Nb{sub 1-x}Ta{sub x}C Carbides can be synthesized by high power MW methods in less than 30 s. In situ and ex situ techniques probing changes in temperature and dielectric properties with time demonstrate that the reactions self-terminate as the loss tangent of the materials decreases. The resulting carbides are carbon deficient and superconducting; T{sub c} correlates linearly to unit cell volume, reaching a maximum at NbC. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  6. Silicon carbide microsystems for harsh environments

    CERN Document Server

    Wijesundara, Muthu B J

    2011-01-01

    Silicon Carbide Microsystems for Harsh Environments reviews state-of-the-art Silicon Carbide (SiC) technologies that, when combined, create microsystems capable of surviving in harsh environments, technological readiness of the system components, key issues when integrating these components into systems, and other hurdles in harsh environment operation. The authors use the SiC technology platform suite the model platform for developing harsh environment microsystems and then detail the current status of the specific individual technologies (electronics, MEMS, packaging). Additionally, methods

  7. Cementation of Loose Sand Particles based on Bio-cement

    Institute of Scientific and Technical Information of China (English)

    RONG Hui; QIAN Chunxiang

    2014-01-01

    Loose sand particles could be cemented to sandstone by bio-cement (microbial induced magnesium carbonate). The bio-sandstone was firstly prepared, and then the compressive strength and the porosity of the sandstone cemented by microbial induced magnesium carbonate were tested to characterize the cementation effectiveness. In addition, the formed mineral composition and the microstructure of bio-sandstone were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The experimental results show that the feasibility of binding loose sand particles using microbial induced magnesium carbonate precipitation is available and the acquired compressive strength of bio-sandstone can be excellent at certain ages. Moreover, the compressive strength and the porosity could be improved with the increase of microbial induced magnesium carbonate content. XRD results indicate that the morphology of magnesium carbonate induced by microbe appears as needles and SEM results show that the cementation of loose sand particles to sandstone mainly relies on the microbial induced formation of magnesium carbonate precipitation around individual particles and at particle-particle contacts.

  8. Production of carbide-free thin ductile iron castings

    Institute of Scientific and Technical Information of China (English)

    M. Ashraf Sheikh

    2008-01-01

    The fast cooling rate of thin ductile iron castings requires special consideration to produce carbide-free castings. Extraor-dinary care was taken to select the charge to produce castings of 100-mm long round bars with 16-ram diameter. The castings show the presence of carbides in the bars. Seven melts were made with different temperatures and with different compositions to get rid of carbides. After chemical analyses, it was found that the extra purity of the charge with less than 0.008wt% sulfur in the castings was the cause of carbides. To remove the carbides fi'om the castings, sulfur should be added to the charge.

  9. Ultra-rapid processing of refractory carbides; 20 s synthesis of molybdenum carbide, Mo2C.

    Science.gov (United States)

    Vallance, Simon R; Kingman, Sam; Gregory, Duncan H

    2007-02-21

    The microwave synthesis of molybdenum carbide, Mo(2)C, from carbon and either molybdenum metal or the trioxide has been achieved on unprecedented timescales; Ex- and in-situ characterisation reveals key information as to how the reaction proceeds.

  10. Effect of different light curing methods on mechanical and physical properties of resin-cements polymerized through ceramic discs

    Directory of Open Access Journals (Sweden)

    Isil Cekic-nagas

    2011-08-01

    Full Text Available OBJECTIVE: The aim of this study was to compare the polimerization ability of three different light-curing units (quartz tungsten halogen, light-emitting diodes and plasma arc and their exposure modes (high-intensity and soft-start by determination of microhardness, water sorption and solubility, and diametral tensile strength of 5 dual-curing resin cements. Material and methods: A total of 720 disc-shaped samples (1 mm height and 5 mm diameter were prepared from different dual-curing resin cements (Duolink, Nexus, Bifix-QM, Panavia F and RelyX Unicem. Photoactivation was performed by using quartz tungsten halogen (high-power and soft-up modes, light-emitting diode (standard and exponential modes and plasma arc (normal and ramp-curing modes curing units through ceramic discs. Then the samples (n=8/per group were stored dry in the dark at 37°C for 24 h. The Vickers hardness test was performed on the resin cement layer with a microhardness tester (Shimadzu HMV. For sorption and solubility tests; the samples were stored in a desiccator at 37°C and weighed to a constant mass. The samples were weighed both before and after being immersed in deionized water for different periods of time (24 h and 7 days and being desiccated. The diametral tensile strength of the samples was tested in a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically by nonparametric Kruskal Wallis and Mann-Whitney U tests at 5% significance level. RESULTS: Resin cement and light-curing unit had significant effects (p0.05 were obtained with different modes of LCUs. Conclusion: The study indicates that polymerization of resin cements with different light-curing units may result in various polymer structures, and consequently different mechanical and physical properties.

  11. Joining of silicon carbide using interlayer with matching coefficient of thermal expansion

    Energy Technology Data Exchange (ETDEWEB)

    Perham, T. [Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering]|[Lawrence Berkeley National Lab., CA (United States)

    1996-11-01

    The primary objective of this study is to develop a technique for joining a commercially available Silicon Carbide that gives good room temperature strength and the potential for good high temperature strength. One secondary objective is that the joining technique be adaptable to SiC{sub f}/SiC composites and/or Nickel based superalloys, and another secondary objective is that the materials provide good neutron irradiation resistance and low activation for potential application inside nuclear fusion reactors. The joining techniques studied here are: (1) reaction bonding with Al-Si/Si/SiC/C; (2) reaction/infiltration with calcium aluminum silicate; (3) ion exchange mechanism to form calcium hexaluminate (a refractory cement); and (4) oxide frit brazing with cordierite.

  12. Femtosecond fiber laser additive manufacturing of tungsten

    Science.gov (United States)

    Bai, Shuang; Liu, Jian; Yang, Pei; Zhai, Meiyu; Huang, Huan; Yang, Lih-Mei

    2016-04-01

    Additive manufacturing (AM) is promising to produce complex shaped components, including metals and alloys, to meet requirements from different industries such as aerospace, defense and biomedicines. Current laser AM uses CW lasers and very few publications have been reported for using pulsed lasers (esp. ultrafast lasers). In this paper, additive manufacturing of Tungsten materials is investigated by using femtosecond (fs) fiber lasers. Various processing conditions are studied, which leads to desired characteristics in terms of morphology, porosity, hardness, microstructural and mechanical properties of the processed components. Fully dense Tungsten part with refined grain and increased hardness was obtained and compared with parts made with different pulse widths and CW laser. The results are evidenced that the fs laser based AM provides more dimensions to modify mechanical properties with controlled heating, rapid melting and cooling rates compared with a CW or long pulsed laser. This can greatly benefit to the make of complicated structures and materials that could not be achieved before.

  13. Synthesis and electrical characterization of tungsten oxide nanowires

    Institute of Scientific and Technical Information of China (English)

    Huang Rui; Zhu Jing; Yu Rong

    2009-01-01

    Tungsten oxide nanowires of diameters ranging from 7 to 200 nm are prepared on a tungsten rod substrate by using the chemical vapour deposition (CVD) method with vapour-solid (VS) mechanism. Tin powders are used to control oxygen concentration in the furnace, thereby assisting the growth of the tungsten oxide nanowires. The grown tungsten oxide nanowires are determined to be of crystalline W18O49. Ⅰ-Ⅴ curves are measured by an in situ transmission electron microscope (TEM) to investigate the electrical properties of the nanowires. All of the Ⅰ-Ⅴ curves observed are symmetric, which reveals that the tungsten oxide nanowires are semiconducting. Quantitative analyses of the experimental I V curves by using a metal-semiconductor-metal (MSM) model give some intrinsic parameters of the tungsten oxide nanowires, such as the carrier concentration, the carrier mobility and the conductivity.

  14. Induction plasma spheroidization of tungsten and molybdenum powders

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The melting, evaporation and oxidation behaviors as well as the solidification phenomena of tungsten and molybdenum in induction plasma were studied. Scanning electron microscopy was used to examine the morphology and the cross section of plasma-processed powders. X-ray diffraction was used to analyze the oxides formed on the particle surface of these two metals. The influence of spray chamber pressure on the spheroidization and oxidation phenomena was discussed. The results show that fewer Mo particles than W particles are spheroidized at the same powder feed rate under the same plasma spray condition although molybdenum has a lower melting point. A small fraction of tungsten is evaporized and condensed either on the surface of tungsten particles nearby or on the wall of spray chamber. Tungsten oxides were found in tungsten powder processed under soft vacuum condition. Extremely large grains form inside some spheroidized particles of tungsten powder.

  15. Epitaxial growth of tungsten nanoparticles on alumina and spinel surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Suarez, T; Lopez-Esteban, S; Pecharroman, C; Esteban-Cubillo, A; Moya, J S [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), C/ Sor Juana Ines de la Cruz 3, 28049, Cantoblanco, Madrid (Spain); Diaz, L A; Torrecillas, R [Nanomaterials and Nanotechnology Research Center (CINN), Consejo Superior de Investigaciones CientIficas (CSIC), C/ Francisco Pintado Fe 26, 33011, Oviedo, Asturias (Spain); Gremillard, L [Universite de Lyon, INSA-Lyon, MATEIS, UMR CNRS 5510, 20 avenue Albert Einstein, Villeurbanne F-69621 (France)], E-mail: jsmoya@icmm.csic.es

    2008-05-28

    Isolated tungsten nanoparticles ({alpha}-W and {beta}-W phase) were synthesized and epitaxially grown on alumina and spinel particle surfaces with an average tungsten size of {<=}20 nm for a low tungsten content (of {<=}1.5 vol%). Using tungsten (VI) ethoxide alcoholic solutions, tungsten trioxide hydrated precursors were attached to a ceramic grains surface as a nanoparticle coating. High-resolution transmission electron microscopy (HRTEM) micrographs showed epitaxial interfaces between alumina, spinel and metallic tungsten. This epitaxial growth is assumed to be due to the effect of water vapour on the sublimation of ortho-tungstic acid during the reduction process in a hydrogen atmosphere. The planes involved in the epitaxy were found to be (22-bar 0){sub Al2O3} parallel (121){sub W} and (311){sub MgAl2O4} parallel (110){sub W}.

  16. Seating load parameters impact on dental ceramic reinforcement conferred by cementation with resin-cements.

    LENUS (Irish Health Repository)

    Addison, Owen

    2010-09-01

    Cementation of all-ceramic restorations with resin-cements has been demonstrated to reduce the incidence of fracture in service. The aim was to investigate the influence of loading force and loading duration applied during cementation on the reinforcement conferred by a resin-cement on a leucite reinforced glass-ceramic.

  17. 76 FR 76760 - Gray Portland Cement and Cement Clinker From Japan

    Science.gov (United States)

    2011-12-08

    ... Portland Cement and Cement Clinker From Japan Determination On the basis of the record \\1\\ developed in the... antidumping duty order on gray Portland cement and cement clinker from Japan would be likely to lead to... the Commission are contained in USITC Publication 4281 (December 2011), entitled Gray Portland...

  18. An ex-situ and in-situ evaluation of carbides as potential electrocatalysts

    Science.gov (United States)

    Weigert, Erich

    One of the most prominent challenges facing the commercialization of the direct methanol fuel cell (DMFC) is the high cost of its electrocatalyst components, particularly the anode. The anode typically requires a high loading of precious metal electrocatalyst (Pt-Ru) to obtain a useful amount of electrical energy from the electrooxidation of methanol (CH3OH). The complete electrooxidation of methanol on these catalysts produces strongly adsorbed CO on the surface, which reduces the activity of Pt. The presence of Ru in these electrocatalysts assists with the decomposition of H2O to more efficiently remove the poisoning CO species as CO2(g). The primary disadvantage of these electrocatalyst components is the scarcity and consequently high price of both Pt and Ru. A series of surface science studies ultrahigh vacuum (UHV) have identified molybdenum and tungsten carbide materials as potential alternative DMFC anode electrocatalysts. Both of these materials demonstrated activity towards the decomposition of methanol and water molecules. The purpose of this research was to extend these investigations by the synthesis and characterization of more realistic carbide materials. This was accomplished by a combination of surface science and electrochemical experiments. The electrochemical studies were performed both in-situ and ex-situ in order to better address the "materials gap" and "pressure gap" that often separate findings in UHV studies from results in more realistic environments. Thin film surfaces of molybdenum carbide could be produced on various carbon substrates in a vacuum system by physical vapor deposition (PVD). When modified with low coverages of Pt, MoC phase molybdenum carbides were found to be more active towards the electrooxidation of hydrogen in an acidic electrolyte than Ptmodified carbon substrates in cyclic voltammetry (CV) studies. These surfaces demonstrated a limited range of electrochemical stability in this acid solution. Mo2C surfaces have

  19. Antibacterial potential of contemporary dental luting cements.

    Science.gov (United States)

    Daugela, Povilas; Oziunas, Rimantas; Zekonis, Gediminas

    2008-01-01

    The aims of this investigation were to evaluate the antibacterial activities of different types of dental luting cements and to compare antibacterial action during and after setting. Agar diffusion testing was used to evaluate the antibacterial properties of seven types of dental luting cements (glass ionomer cements (GICs), resin modified GICs, resin composite, zinc oxide eugenol, zinc oxide non-eugenol, zinc phosphate, zinc polycarboxylate cements) on Streptococcus mutans bacteria. Instantly mixed zinc phosphate cements showed the strongest antibacterial activity in contrast to the non-eugenol, eugenol and resin cements that did not show any antibacterial effects. Non-hardened glass ionomer, resin modified and zinc polycarboxylate cements exhibited moderate antibacterial action. Hardened cements showed weaker antibacterial activities, than those ones applied right after mixing.

  20. Freezing resistance of high iron phoasphoaluminate cement

    Science.gov (United States)

    Zhang, S. X.; Lu, L. C.; Wang, S. D.; Zhao, P. Q.; Gong, C. C.

    2017-03-01

    The influence of freeze-thaw cycle on the mechanical properties of high iron phoasphoaluminate cement was investigated in the present study. The visual examination was conducted to evaluate the surface damage. The deterioration considering the weight loss, modulus loss of relative dynamic elastic and strength loss of mortar were also investigated. The morphology of hydration products were analysed by SEM. Compared with ordinary Portland cement and sulphoaluminate cement, the frost resistance of high iron phosphoraluminate cement is better. Hydration products of high iron phoasphoaluminate cement contain sheet crystals, and a lot of gel form a dense three-dimensional network structure, which results in a lower porosity. Different from ordinary Portland cement, the hydration product of high iron phoasphoaluminate cement does not contain Ca(OH)2, and low alkalinity reduces its osmotic pressure. The lower porosity and osmotic pressure are the two main reasons which causes in the higher frost resistance of high iron phoasphoaluminate cement.