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Sample records for carbonitrides

  1. Mechanical Performances of Carbonitriding Films on Cast Iron by Plasma Electrolytic Carbonitriding

    Institute of Scientific and Technical Information of China (English)

    PANG Hua; ZHANG Gu-Ling; WANG Xing-Quan; LV Guo-Hua; CHEN Huan; YANG Si-Ze

    2011-01-01

    The plasma electrolytic carbonitriding (PEC/N) process is applied to cast iron using an aqueous solution of acetamide and glycerin as the electrolyte. Mechanical properties of the carbonitriding layers on cast iron are investigated. After the PEC/N treatment, the microhardness and wear resistance of cast iron are improved significantly compared to the untreated substrate. When the substrate is processed at 350 V for 60s, the coating presents the highest microhardness and it is about 554.14HK0.02, and the coating with the highest hardness has the best wear resistance.%The plasma electrolytic carbonitriding (PEC/N) process is applied to cast iron using an aqueous solution of acetamide and glycerin as the electrolyte.Mechanical properties of the carbonitriding layers on cast iron are investigated.After the PEC/N treatment,the microhardness and wear resistance of cast iron are improved significantly compared to the untreated substrate.When the substrate is processed at 350 V for 60s,the coating presents the highest microhardness and it is about 554.14HK0.02,and the coating with the highest hardness has the best wear resistance.Plasma electrolytic saturation (PES) is a relatively novel surface engineering technique,which operates at room temperature and atmospheric pressure.[1-3]It includes plasma electrolytic carburizing (PEC),[4,5]plasma electrolytic nitriding (PEN)[6] and plasma electrolytic carbonitriding (PEC/N).[7-10] The relatively unrestrained size and shape,and shorter treatment time compared to vacuum-plasma processes make the PES a desirable and flexible technique for industrial use.The PES treatments on low carbon steel,[11] stainless steel[3,12] and pure iron[13] have been investigated.Researchers studied the microstructure,phase composition,corrosion resistance,microhardness and wear performance of the PES-treated samples.It was found that the diffusion of N into stainless steels can improve the corrosion resistance of stainless steels,[14] while the

  2. Facile Synthesis of Ternary Boron Carbonitride Nanotubes

    Directory of Open Access Journals (Sweden)

    Luo Lijie

    2009-01-01

    Full Text Available Abstract In this study, a novel and facile approach for the synthesis of ternary boron carbonitride (B–C–N nanotubes was reported. Growth occurred by heating simple starting materials of boron powder, zinc oxide powder, and ethanol absolute at 1150 °C under a mixture gas flow of nitrogen and hydrogen. As substrate, commercial stainless steel foil with a typical thickness of 0.05 mm played an additional role of catalyst during the growth of nanotubes. The nanotubes were characterized by SEM, TEM, EDX, and EELS. The results indicate that the synthesized B–C–N nanotubes exhibit a bamboo-like morphology and B, C, and N elements are homogeneously distributed in the nanotubes. A catalyzed vapor–liquid–solid (VLS mechanism was proposed for the growth of the nanotubes.

  3. Contribution of shot peening on carburized or carbonitrided parts

    Science.gov (United States)

    Renaud, P.; Bristiel, P.; Barrallier, L.; Desvignes, M.; Kubler, R.

    2011-01-01

    The main purpose of car manufacturers is to design parts which are light and at the same time very resistant to fatigue efforts. Surface treatments are effective means to deal with this compromise. They bring surface hardness and introduce compressive residual stresses. This experimental study focuses on the influence of shot peening on parts initially treated by carburizing or carbonitriding.

  4. Use of vacuum carbonitriding for raising the seizure resistance of gears from steel VKS-10

    Science.gov (United States)

    Lashnev, M. M.; Smirnov, A. E.; Semenov, M. Yu.

    2013-05-01

    Saturation of heat-resistant steel VKS-10 with carbon and nitrogen in a low-pressure atmosphere is studied. The possibility of increasing the fineness of the carbonitride phase and the content of retained austenite in vacuum carbonitriding is shown as compared to vacuum carburizing. Subsequent aging results in segregation of a still finer excess phase. The factors controlling vacuum carbonitriding are determined. Comparative estimation of the seizure resistance of carbonitrided layers of steel VKS-10 and carburized layers obtained on traditional heat-resistant steels is performed.

  5. Carbonitriding reactions of diatomaceous earth: phase evolution and reaction mechanisms

    Directory of Open Access Journals (Sweden)

    BRANKO MATOVIC

    2006-06-01

    Full Text Available The possibility of using diatomaceous earth as Si precursor for low temperature synthesis of non-oxide powders by carbothermal reduction-nitridation was studied. It was found that carbonitriding reactions produce phases of the Si–Al–O–N system. Already at 1300 °C, nanosized, non-oxide powders were obtained. The comparatively low reaction temperatures is attributred to the nano-porous nature of the raw material. The evolution of crystalline phases proceeded via many intermediate stages. The powders were characterized by X-ray and SEM investigations. The results showed that diatomaceous earth can be a very effective source for obtaining non-oxide powders.

  6. Effect of carbonitride precipitates on the abrasive wear behaviour of hardfacing alloy

    Science.gov (United States)

    Yang, Ke; Yu, Shengfu; Li, Yingbin; Li, Chenglin

    2008-06-01

    Hardfacing alloy of martensitic stainless steel expect higher abradability to be achieved through the addition of nitrogen being provided by the fine scale precipitation of complex carbonitride particles. Niobium and titanium as the most effective carbonitride alloying elements were added in the Fe-Cr13-Mn-N hardfacing alloy to get carbonitride precipitates. Carbonitride was systematically studied by optical microscopy, scanning electronic microscopy and energy spectrum analysis. Abrasive wear resistance of hardfacing alloy in as-welded and heat-treated conditions was tested by using the belt abrasion test apparatus where the samples slide against the abrasive belt. It is found that carbonitride particles in the hardfacing alloy are complex of Cr, Ti and Nb distributing on the grain boundary or matrix of the hardfacing alloy with different number and size in as-welded and heat-treated conditions. A large number of carbonitrides can be precipitated with very fine size (nanoscale) after heat treatment. As a result, the homogeneous distribution of very fine carbonitride particles can significantly improve the grain-abrasion wear-resisting property of the hardfacing alloy, and the mass loss is plastic deformation with minimum depth of grooving by abrasive particles and fine delamination.

  7. Microstructure and Mechanical Properties of Resistance Spot Welding Joints of Carbonitrided Low-Carbon Steels

    Science.gov (United States)

    Taweejun, Nipon; Poapongsakorn, Piyamon; Kanchanomai, Chaosuan

    2017-04-01

    Carbonitrided low-carbon steels are resistance welded in various engineering components. However, there are no reports on the microstructure and mechanical properties of their resistance spot welding (RSW) joints. Therefore, various carbonitridings were performed on the low-carbon steel sheets, and then various RSWs were applied to these carbonitrided sheets. The metallurgical and mechanical properties of the welding joint were investigated and discussed. The peak load and failure energy increased with the increases of welding current and fusion zone (FZ) size. At 11 kA welding current, the carbonitrided steel joint had the failure energy of 16 J, i.e., approximately 84 pct of untreated steel joint. FZ of carbonitrided steel joint consisted of ferrite, Widmanstatten ferrite, and untempered martensite, i.e., the solid-state transformation products, while the microstructure at the outer surfaces consisted of untempered martensite and retained austenite. The surface hardening of carbonitrided steel after RSW could be maintained, i.e., approximately 810 HV. The results can be applied to carbonitriding and RSW to achieve a good welding joint.

  8. Preparation and Characterization of Niobium Carbide and Carbonitride

    Science.gov (United States)

    Kim, Hak Soo; Bugli, Guy; Djéga-Mariadassou, Gérald

    1999-01-01

    Unsupported niobium carbide powders of NbC were prepared by carburization of commercial niobium pentoxide in flowing CH4-H2mixtures. Several routes of synthesis were investigated, leading to final carbides with specific surface areas ranging from 10 to 50 m2g-1. During direct carburization, after the first step of reduction of Nb2O5to NbO2, a long induction period which was succeeded by an acceleratory period, was observed for the reduction/carburization to NbC. In the presence of a catalyst of methane decomposition, this induction period was eliminated but the superficial carbon free contamination of the final carbide was increased. However, this contamination can be removed by a reducing treatment and CO chemisorption can be observed. The preparations through niobium oxynitride lead to face-centered cubic carbonitrides with specific surface areas ranging from 27 to 49 m2g-1. Chemical composition and cell parameter of these cabonitrides vary slightly with the synthesis conditions. After a reducing treatment, as for NbC, CO chemisorption was also observed.

  9. The reactivity of lattice carbon and nitrogen species in molybdenum (oxy)carbonitrides prepared by single-source routes

    Energy Technology Data Exchange (ETDEWEB)

    AlShalwi, M. [WestCHEM, School of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Hargreaves, J.S.J., E-mail: Justin.Hargreaves@glasgow.ac.uk [WestCHEM, School of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Liggat, J.J.; Todd, D. [WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL (United Kingdom)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Molybdenum (oxy)carbonitrides have been prepared from single source routes. Black-Right-Pointing-Pointer Nitrogen species are more reactive than carbon species within the carbonitrides. Black-Right-Pointing-Pointer The reactivity of nitrogen species is a function of carbonitride composition. -- Abstract: Molybdenum (oxy)carbonitrides of different compositions have been prepared from hexamethylenetetramine molybdate and ethylenediamine molybdate precursors and the reactivity of the lattice carbon and nitrogen species within them has been determined by temperature programmed reduction and thermal volatilisation studies. Nitrogen is found to be much more reactive than carbon and the nature of its reactivity is influenced by composition with the presence of carbon enhancing the reactivity of nitrogen. The difference in reactivity observed indicates that molybdenum carbonitrides are not suitable candidates as reagents for which the simultaneous loss of nitrogen and carbon from the lattice would be desirable.

  10. Effects of Carbo-Nitridation Process of Ti-Bearing Blast Furnace Slag on Iron Content

    Science.gov (United States)

    Shi, Z.; Zhang, X. M.; Xu, Y.

    In order to prepare corrosion-resistant refractory material, experiment chooses Ti-bearing Blast Furnace Slag as raw materials which were treated by the method of carbo-nitridation. Finally, the corrosion resistance properties of the material can be improved by this method. The carbo-nitridation process affects the iron content of the slag in the study, which have a beneficial effect on the synthesis of Ti (C. N). The results indicated that the iron content of the slag significantly increased in process of Ti (C. N) synthesis: and the iron content of slag showed an upward trend with the increase of holding time.

  11. Investigation of thin titanium carbonitride coatings deposited onto stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Timothy; Lin, Jia-Ming [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Pirolli, Laurent; Coquilleau, Laurent; Luharuka, Rajesh [Schlumberger Technology Corporation, 150 Gillingham Lane, MD-3, Sugarland, TX 77478 (United States); Teplyakov, Andrew V., E-mail: andrewt@udel.edu [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States)

    2012-11-01

    Titanium carbonitride (TiCN) coatings are commonly used in a variety of applications, from microelectronics to high-performance cutting tools. The TiCN coatings grown by chemical vapor deposition are especially attractive because this technique provides a very high degree of control during the procedure. A gas-phase deposition utilizing an organometallic precursor molecule, tetrakis-dimethylamino-titanium was used to grow thin TiCN coatings onto 4140 series steel prepared and cleaned in vacuum. A highly controlled conformal filling was achieved by the deposition performed onto a sputter-cleaned steel surface held at 600 K. The film of the overall Ti:C:N composition of 1:1:1 was produced, as demonstrated by Auger electron spectroscopy. In air, these coatings are oxidized but maintain their uniformity, as demonstrated by time-of-flight secondary ion mass spectrometry. The chemical state of the elements in the coatings was investigated by the X-ray photoelectron spectroscopy and the morphology of the films produced was investigated by atomic force microscopy. Finally, the initial mechanical testing of the films was performed by comparing Young's modulus to that of the underlying steel. - Highlights: Black-Right-Pointing-Pointer TiCN film was deposited by chemical vapor deposition onto a steel substrate. Black-Right-Pointing-Pointer The film is comprised of Ti, C, and N and is partially oxidized. Black-Right-Pointing-Pointer The depth-profiling studies confirmed that the film is uniform in thickness. Black-Right-Pointing-Pointer Microscopy investigation showed a sharp interface between the coating and substrate. Black-Right-Pointing-Pointer The topography of coated and uncoated samples is very different.

  12. Thermophysical and elastic properties of titanium carbonitrides containing molybdenum and tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Matsuda, Tetsushi, E-mail: t_matsuda@jfcc.or.jp [Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya 456-8587 (Japan); Matsubara, Hideaki [Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya 456-8587 (Japan)

    2013-06-15

    Highlights: ► (Ti,Me)(C,N) sintered bodies were prepared by hot-pressing. ► The thermophysical and elastic properties of the carbonitrides were evaluated. ► The porosities of the specimens were less than 1%. ► The Young’s modulus decreases with increasing Mo content. ► The Debye temperatures decrease with increasing Mo/W content. -- Abstract: Titanium carbonitride has good mechanical properties such as high hardness and high Young’s modulus. It is a major raw material for Ti(C,N)-based cermets, and their properties are strongly dependent on the properties of titanium carbonitrides. The thermophysical and elastic properties of the carbonitride need to be systematically investigated, so as to be used for designing cutting tools and wear-resistant tools. The thermophysical and elastic properties of (Ti,Me)(C,N) (Me = Mo. W) sintered bodies prepared by hot-pressing at 2200 °C were evaluated. The porosities of the specimens were less than 1%. The Young’s modulus decreased with increasing Mo, which seems to be the result of vacancy formation. The thermal expansion coefficient, the thermal conductivity and the Debye temperatures of (Ti,Me)(C,N) sintered bodies decreased with increasing Mo/W content.

  13. Effect of annealing temperature on hardness, thickness and phase structure of carbonitrided 304 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    El-Hossary, F.M.; Negm, N.Z.; Khalil, S.M.; Abed El-Rahman, A.M.; Raaif, M. [Sohag University, Physics Department, Faculty of Science, Sohag (Egypt); Maendl, S. [Leibniz-Institute fuer Oberflaechenmodifizierung, Leipzig (Germany)

    2010-05-15

    Carbonitriding of AISI 304 austenitic stainless steel was performed at a plasma-processing power of 450 W using inductively coupled radio frequency (rf) plasma in a gas mixture of 50% N{sub 2} and 50% C{sub 2}H{sub 2}. The rate of carbonitriding, microhardness, phase structure of the compound layer, surface microstructure and cross-section morphology were studied before and after the annealing process. At the annealing temperature up to 800 C, the microhardness values of the compound zones decrease, while the associated values of the diffused zones increase. Little change was found in the thickness of the compound and diffused zones when the carbonitrided samples were annealed up to 400 C. However, at a higher annealing temperature, the thicknesses of both zones increase. The {gamma}-Fe austenite is the main crystalline phase that can be detected by X-ray diffraction. As the annealing temperature increases up to 500 C, X-ray spectra show {alpha}-Fe and Fe{sub 5}C{sub 2} phases. Nitrogen diffuses more deeply from the near surface to the interior of the treated sample as the annealing temperature increases up to 800 C and this might explain the extent of carbonitrided thickness and the enhanced microhardness of the diffused zone. (orig.)

  14. Microstructural and compositional evolution of iron carbonitride compound layers during salt bath nitrocarburizing

    Energy Technology Data Exchange (ETDEWEB)

    Somers, M.A.J.; Colijn, P.F.; Sloof, W.G.; Mittemeijer, E.J. (Technische Hogeschool Delft (Netherlands). Lab. of Metallurgy)

    1990-01-01

    An analysis was made of iron carbonitride compound layer development during nitrocarburizing of pure iron and two iron-carbon specimens, containing 0.3 wt.-% C and 0.6 wt.-% C, respectively, in an aerated cyanate-based salt bath at 853 K. The microstructural evolution was followed by means of light- and scanning electron microscopy and X-ray diffraction analysis. Composition-depth profiles were determined as a function of nitrocarburizing time applying electron-probe microanalysis and X-ray diffraction analysis. Compound layer formation on pure iron starts with the nucleation of cementite at the surface, which is immediately followed by nucleation of {epsilon} carbonitride containing a relatively high carbon content and a relatively low nitrogen content. Thereafter, {gamma}' (carbo)nitride and finally {epsilon} nitride develop at the outer surface. In general, on continued nitrocarburizing the nitrogen content at the outer surface increases and the carbon content decreases. Accordingly, the constitution of the compound layer is determined to a large extent by the (difference between the) absorption kinetics of carbon and of nitrogen rather than by equilibrium thermodynamics. In the surface-adjacent region, the layers are highly porous, predominantly as a consequence of corrosive attack by agents of the salt bath. As compared with nitrocarburizing of pure iron, the major effect of carbon present as cementite in pearlite regions in the iron-carbon specimens appears to be promotion of the formation of {epsilon} carbonitride in the compound layer at the cost of {gamma}' (carbo)nitride. (orig.).

  15. Zirconium carbonitride pellets by internal sol gel and spark plasma sintering as inert matrix fuel material

    Science.gov (United States)

    Hedberg, Marcus; Cologna, Marco; Cambriani, Andrea; Somers, Joseph; Ekberg, Christian

    2016-10-01

    Inert matrix fuel is a fuel type where the fissile material is blended with a solid diluent material. In this work zirconium carbonitride microspheres have been produced by internal sol gel technique, followed by carbothermal reduction. Material nitride purities in the produced materials ranged from Zr(N0.45C0.55) to Zr(N0.74C0.26) as determined by X-ray diffraction and application of Vegard's law. The zirconium carbonitride microspheres have been pelletized by spark plasma sintering (SPS) and by conventional cold pressing and sintering. In all SPS experiments cohesive pellets were formed. Maximum final density reached by SPS at 1700 °C was 87% theoretical density (TD) compared to 53% TD in conventional sintering at 1700 °C. Pore sizes in all the produced pellets were in the μm scale and no density gradients could be observed by computer tomography.

  16. A facile approach to fabricate boron carbonitride microspheres via precursor pyrolysis

    Science.gov (United States)

    Zeng, Sifan; Feng, Wanlin; Luo, Heng; Tan, Yongqiang; Wang, Yu; Zhang, Haibin; Zhang, Tao; Peng, Shuming

    2017-04-01

    Bulk quantity Boron Carbonitride (BCN) microspheres were successfully synthesized via an organic precursor pyrolysis approach. The organic precursor was synthesized at 90 °C by the polymerization reaction of boron trichloride,aniline and ethylenediamine with a molar ratio of 1:1:1. All particles presented uniform spherical structure with the size of 2 μm. The products have oxidation starting temperature at 624 °C much higher than graphene (404 °C).

  17. Anti-corrosion layer prepared by plasma electrolytic carbonitriding on pure aluminum

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jie; Zhang, Yifan; Liu, Run; Wang, Bin; Hua, Ming [Key Laboratory for Beam Technology and Materials Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Xue, Wenbin, E-mail: xuewb@bnu.edu.cn [Key Laboratory for Beam Technology and Materials Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China)

    2015-08-30

    Highlights: • PEC/N can be applied to low melting point metal. • The spectroscopic characterization of plasma discharge is investigated. • Electron concentration and electron temperature are evaluated for PEC/N. • Phase composition of the carbonitrided layer is determined. • PEC/N improves the corrosion resistance of aluminum greatly. - Abstract: In this paper, plasma electrolytic carbonitriding (PEC/N) method was applied to pure aluminum for the first time. The spectroscopic characterization of plasma discharge during PEC/N process was analyzed and the electron temperature was calculated in terms of optical emission spectroscopy. The results showed the discharge plasma was in local thermal equilibrium (LTE) state. Electron concentration and electron temperature were about 6 × 10{sup 21} m{sup −3} and 4000 K, respectively. The carbonitrided layer contained Al{sub 4}C{sub 3}, AlN and Al{sub 7}C{sub 3}N{sub 3} phases. After PEC/N treatment, the corrosion resistance of pure aluminum was significantly improved, which was related to the formation of nitride phases. This work expands the application of plasma electrolysis technology on the surface modification of low melting point metal.

  18. Synthesising carbo-nitrides of some d-group transition metals using a solar furnace at PSA

    OpenAIRE

    Shohoji, Nobumitsu; Oliveira, F. A. Costa; Rosa, Luís Guerra; Fernandes, Jorge Cruz; Magalhães, Teresa; Coelho, Manuel Caldeira; Rodriguez,José; Canadas, Inmaculada; Ramos, Carlos; Martinez, Diego

    2013-01-01

    Carbo-nitride synthesis was undertaken using a solar furnace at PSA in flowing N2/Ar gas mixture under total pressure 1 atm and processing temperature T = 1600ºC for some d-group transition elements (Ti; Zr, V, Nb, Mo, W) starting from 1.5G/M (graphite/metal powder mixture with mole ratio 1.5:1) compact to ensure co-presence of free carbon with the reaction product. Clear X-ray diffraction (XRD) evidence of formation of carbo-nitride was detected for Ti (IVa group metal) showing higher N cont...

  19. Application of desirability function for optimizing the performance characteristics of carbonitrided bushes

    Directory of Open Access Journals (Sweden)

    Boby John

    2013-06-01

    Full Text Available The performance of a product is generally characterized by more than one response variable. Hence the management often faces the problem of simultaneous optimization of many response variables. This study was undertaken to simultaneously optimize the surface hardness and case depth of carbonitrided bushes. Even though lots of literature has been published on various methodologies for tackling the multi-response optimization problem, the simultaneous optimization of heat treated properties of carbonitrided bushes are not reported yet. In this research the effect of four factors and two interactions on surface hardness and case depth of carbontirded bushes were studied using design of experiments. Based on the experimental results, the expected values of the heat treated properties of the bushes were estimated for all possible combination of factors. Then the best combination which, simultaneously optimized the response variables, was arrived at using desirability function. The study showed that the optimum combination obtained through desirability function approach not only minimized the variation around the targets of surface hardness and case depth but also was superior to the ones obtained by optimizing the response variables separately. Moreover this study provides a useful and effective approach to design the production process to manufacture bushes with customer specified surface hardness and case depth targets.

  20. SURFACE HARDENING OF AUTOMOBILES AND TRACTORS PARTS BY METHOD OF LOW-TEMPERATURE CARBONITRIDING IN POWDER MEDIUM

    Directory of Open Access Journals (Sweden)

    Kostyk, V. O.

    2013-06-01

    Full Text Available Performed is strengthening of the surface layer of steel method of low-temperature carbonitriding in macrodispersed carbo - and nitrogen-bearing powder mixture. Chosen and justified the optimal technological parameters of process developed chemical-thermal processing. The diffusion coefficient of nitrogen alloyed steel 40X for the proposed treatment.

  1. Gradient nature shaping of the 20X2H4A steel structure as a carbonitriding result

    Institute of Scientific and Technical Information of China (English)

    Kozlov; E.; V.; Malinovskaya; V.; A.; Popova; N.; A.

    2005-01-01

    The study of the shaping of the gradient structure nature appearing in constructional alloy martensite 20X2H4A steel (0.2%C, 2%Cr, 4%Ni), as a result of surface saturation by carbon and nitrogen (carbonitriding) at 920℃ in industrial conditions is made in present work by methods of optical and transmission electron microscopy.……

  2. Metallic Cobalt Encapsulated in Bamboo-Like and Nitrogen-Rich Carbonitride Nanotubes for Hydrogen Evolution Reaction.

    Science.gov (United States)

    Dai, Xiaoping; Li, Zhanzhao; Ma, Yangde; Liu, Mengzhao; Du, Kangli; Su, Haixia; Zhuo, Hongying; Yu, Lei; Sun, Hui; Zhang, Xin

    2016-03-01

    Despite being technically possible, the hydrogen production by means of electrocatalytic water splitting is still practically unreachable mainly because of the lack of inexpensive and high active catalysts. Herein, a novel and facile approach by melamine polymerization, exfoliation and Co(2+)-assisted thermal annealing is developed to fabricate Co nanoparticles embedded in bamboo-like and nitrogen-rich carbonitride nanotubes (Co@NCN). The electronic interaction between the embedded Co nanoparticles and N-rich carbonitride nanotubes could strongly promote the HER performance. The optimized Co@NCN-800 exhibits outstanding HER activity with an onset potential of -89 mV (vs RHE), a large exchange current density of 62.2 μA cm(-2), and small Tafel slope of 82 mV dec(-1), as well as excellent stability (5000 cycles) in acid media, demonstrating the potential for the replacement of Pt-based catalysts. Control experiments reveal that the superior performance should be ascribed to the synergistic effects between embedded Co nanoparticles and N-rich carbonitride nanotubes, which originate from the high pyridinic N content, fast charge transfer rate from Co particles to electrodes via electronic coupling, and porous and bamboo-like carbonitride nanotubes for more active sites in HER.

  3. Gradient nature shaping of the 20X2H4A steel structure as a carbonitriding result

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ The study of the shaping of the gradient structure nature appearing in constructional alloy martensite 20X2H4A steel (0.2%C, 2%Cr, 4%Ni), as a result of surface saturation by carbon and nitrogen (carbonitriding) at 920℃ in industrial conditions is made in present work by methods of optical and transmission electron microscopy.

  4. Abrasive resistance of arc sprayed carbonitride alloying self-shielded coatings

    Science.gov (United States)

    Deng, Yu; Yu, Shengfu; Xing, Shule; Huang, Linbing; Lu, Yan

    2011-10-01

    Wear-resistant coatings were prepared on the surface of the Q235 low-carbon steel plate by HVAS with the carbonitride alloying self-shielded flux-cored wire. Detection and analysis on the microstructure and properties of the coatings were carried out by using scanning electron microscope, microhardness tester and wear tester. The forming, the wear resistance and its mechanism of the coatings were studied. The results show that the coatings have good forming, homogeneous microstructure and compact structure. The coatings have good hardness, the average microhardness value reaches 520 HV 0.1, and the highest value is up to about 560 HV 0.1. As a result, the coatings have good abrasive wear performance and adhesion strength.

  5. The structure study of boron carbonitride films obtained by use of trimethylamine borane complex

    CERN Document Server

    Kosinova, M L; Fainer, N I; Maximovski, E A; Kuznetsov, F A

    2001-01-01

    Diffraction of synchrotron radiation (SR) was used to investigate crystalline structure and phase composition of thin films (1500-5000 A) of boron carbonitride. These films were synthesized by plasma-enhanced chemical vapor deposition using nontraditional volatile single source precursor trimethylamine borane complex (CH sub 3) sub 3 N centre dot BH sub 3 and its mixture with ammonia. The effect of the gas ratio and substrate temperature on chemical and phase composition as well as the structure of the films were investigated. The XRD peculiarities of texture films and ways of increasing sensibility of measurements were considered. A possibility of the information density rise of the thin film XRD was shown due to application of different methods for recording diffraction patterns.

  6. Peculiarities and improvements of PSA solar furnace used for synthesis of refractory carbides and carbonitrides

    Energy Technology Data Exchange (ETDEWEB)

    Guerra Rosa, L.; Cruz Fernandez, J.; Amarai, P.M.; Anjinho, C.

    2001-07-01

    This paper summarises the main peculiarities found during our solar carbide and carbonitride synthesis work for Si and d-group transition elements (Ti, Zr, V, Nb, Ta, Cr, Mo, W; therefore excluding Hf in the IVB group). Comparing the reaction products obtained in the Solar furnace with those obtained in a conventional Electric Furnace, we detected several intriguing evidences apparently indicative of involvement of photochemical effects in some reactions under solar radiation. Based on the acquired experience, some improvements to be made in test set-up of the PSA solar furnace are proposed in order to enhance intelligible usage of this large-scale facility for novel materials processing. (Author) 9 refs.

  7. Leakage current mechanisms and their dependence on composition in silicon carbonitride thin films

    Science.gov (United States)

    Vijayakumar, Vishnuvardhanan; Varadarajan, Bhadri

    2015-04-01

    Electrical conduction in amorphous silicon carbonitride (a-SiCN:H) thin films deposited by plasma enhanced chemical vapor deposition (PECVD) is investigated for varying carbon to nitrogen ratios at room temperature. Films deposited with a lower carbon/nitrogen ratio showed two modes of electrical conduction; namely, Schottky emission mode below 2.3 MV cm-1 electric field and Poole-Frenkel mode from 2.3 MV cm-1 up to the breakdown field. Films with higher carbon/nitrogen ratios showed only Poole-Frenkel mode of conduction throughout the entire range of operation up to the breakdown field. The carbon rich films exhibited higher leakage currents attributed to its shallow defect energy levels leading to its higher Poole-Frenkel conductivity.

  8. The effect of C atom concentration on the electronic properties of boron carbonitride alloy nanotube in zig-zag form

    Indian Academy of Sciences (India)

    H Milani Moghaddam

    2011-06-01

    Electronic properties of single-walled boron nitride nanotube in zig-zag form are numerically investigated by replacing B atoms with C atoms. Using a tight-binding Hamiltonian, the methods based on Green’s function theory, Landauer formalism and Dyson equation, the electronic density of states and electronic conductance in boron nitride nanotube and boron carbonitride nanotube are calculated. Our calculations indicate that in a boron nitride nanotube, the localized states associated with C impurities appear as the concentration of C atoms increases. The boron carbonitride nanotube thus behaves like a semiconductor. Also, by increasing the C atom concentration, the voltage in the first step on the – characteristics decreases, whereas the corresponding current increases.

  9. Development of High Strength Steel Designed for Carbonitriding with High Nitrogen Content to Be Used for Automatic Transmission Gears

    Institute of Scientific and Technical Information of China (English)

    Youichi Watanabe

    2004-01-01

    To downsize and lighten automatic transmission components, the gears installed must be strengthened in terms of pitting endurance and/or wear resistance. The most important metallurgical factor affecting fractures is well known to be resistance to softening when steel is tempered at approximately 573 K. Carbonitriding with a high anount of nitrogen is a very effective production technique because nitrogen increases the resistance during tempering. However, structural anomalies begin to appear in the surface layer when the nitrogen content exceeds 0.6 mass% in the chromium steel generally used. To address this, we have developed new high-strength chromium steel with an optimized chemical composition that effectively inhibits anomalies even when carbonitriding with a nitrogen content of more than 0.6 mass%.We performed a drivetrain durability test on an automatic transmission component designed to have excellent contact fatigue strength and a tooth root bending impact and fatigue strength. We found that the developed steel that was carbonitrided with a content of about 0.9 mass%, and then shot peened hard, has a pitting life of roughly 4.5 times that of conventionally manufactured steel.

  10. Precipitation and Solid Solution of Titanium Carbonitride Inclusions in Hypereutectoid Tire Cord Steel

    Institute of Scientific and Technical Information of China (English)

    Chen-fan YU; Zheng-liang XUE; Wu-tao JIN

    2016-01-01

    The properties of titanium carbonitride Ti(Cx N1-x )inclusions precipitated during solidification of tire cord steels and the thermodynamic conditions for their decomposition and solid solution during billet heating were investigated using a thermodynamics method.The solid solution of Ti(Cx N1 -x )inclusions during high-temperature heating was also studied experimentally.The results revealed that:(1)the higher the content of carbon in the tire cord steel is, the greater the value of x in the Ti(Cx N1 -x )inclusions is;(2)the higher the content of carbon in the tire cord steel is,the earlier the Ti(Cx N1 -x )inclusions precipitated during the solidification process and the lower the solidification front temperature is during precipitation;(3)when an 82A steel sample was heated to 1 087 ℃,the Ti(Cx N1 -x )in-clusions possess the thermodynamic conditions of decomposition and solid solution;and (4)when 82A samples were heated to 1 1 50 and 1 250 ℃,the total number of Ti(Cx N1 -x )inclusions larger than 5 μm in diameter decreased by 55.0% and 70.3%,respectively.In addition,although smaller inclusions with diameter less than 2 μm continued to decompose when the sample was heated at 1 250 ℃ for 2 h and then cooled to 1 000 ℃ in the furnace,the number of inclusions larger than 5 μm in diameter increased.

  11. A Novel Martensitic Creep-Resistant Steel Strengthened by MX Carbonitrides with Extremely Low Coarsening Rates: Design and Characterization

    Science.gov (United States)

    Lu, Qi; Ma, Wenjie; Yan, Wei; Yang, Ke; Toda, Yoshiaki; van der Zwaag, Sybrand; Xu, Wei

    2016-09-01

    A general computational alloy design approach, based on thermodynamics and thermokinetics and coupled with a genetic algorithm optimization routine, was applied to the design of novel creep martensitic resistant steels. The optimal alloy suggested by the model has a high density of barely coarsening MX carbonitride precipitates. The model yielded precise values for the concentrations of the 10 alloying elements considered. The model alloy was produced on a 10 kg lab scale. Samples of the new alloy of one of the best commercial martensitic steels on the market P92 were subjected to a high aging temperature of 923 K (650 °C) for times up to 1000 hours. The microstructure of the new alloy in the as-produced state as well as after 1000 hours exposure has all the intended features as predicted by the model. The coarsening rate of the MX rate carbonitrides was substantially lower than that of the precipitates in the P92 steel. The very low coarsening rate explains the superior hardness at very long exposure times.

  12. A simple one step organic to inorganic pyrolysis route to bulk quantity boron carbonitride/carbon nanocables

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, T.; Wang, Y.P.; Yang, J.Q. [School of Materials Science and Engineering, Harbin Institute of Technology (Weihai), Weihai 264209 (China); Huang, X.X., E-mail: swliza@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wen, G., E-mail: g.w.wen.hit@gmail.com [School of Materials Science and Engineering, Harbin Institute of Technology (Weihai), Weihai 264209 (China); School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2015-09-15

    Highlights: • Bulk quantity boron carbonitride/carbon (BCN/C) nanocables have been synthesized by a simple one step organic to inorganic pyrolysis route. • BCN/C nanocables exhibit a much better oxidation resistance than substrate carbon nanofibers. • A probable formation mechanism of the BCN/C nanocables is proposed according to the experimental results. - Abstract: Bulk quantity boron carbonitride/carbon (BCN/C) nanocables have been successfully synthesized by a simple one step organic compounds pyrolysis route at 1100 °C. The nanocables consist of nanocarbon fibers inside covered by the cylindrical BCN coatings. The characteristics of the surface morphology and the diameters of the nanocables are determined by soaking time. It is demonstrated that the elements of B, C and N are hybridly bonded in the coating. The weight loss of the nanocables is about 12% at 1200 °C which is much better than the substrate carbon nanofibers (CNFs) (more than 20% weight loss at 1200 °C). The minimum reflection coefficient below −20 dB for the products is −24.5 dB at 14.48 GHz indicating good microwave absorption properties. The results suggest that the nanocables are favorable for achieving high performance oxidization resistance and microwave absorption properties.

  13. The effect of molybdenum on niobium, titanium carbonitride precipitate evolution and grain refinement in high-temperature vacuum carburizing alloys

    Science.gov (United States)

    Enloe, Charles M.

    Existing commercial carburizing alloys can be processed at higher temperatures and shorter processing times utilizing vacuum carburizing due to the suppression of intergranular oxidation. To provide resistance to undesired grain coarsening at these elevated temperatures and associated reduction in fatigue performance, microalloyed steel variants have been developed which employ fine Ti- and Nb-carbonitrides to suppress grain growth. Grain coarsening resistance is believed to be limited by the coarsening resistance of the precipitates themselves at high temperature, so further alloy/processing developments to enhance microalloy precipitate coarsening resistance based on a greater mechanistic understanding of solute interaction with microalloy precipitates would be beneficial. Molybdenum is known to affect microalloy precipitate evolution during processing in ferrite and austenite, but a unified explanation of the role of Mo in precipitate evolution is still lacking. Accordingly, the effect of molybdenum on microalloy precipitate size and composition evolutions and the associated onset of abnormal grain growth in austenite was investigated in Mo-bearing and Mo-free, Nb,Ti-microalloyed SAE 4120 steels. Molybdenum additions of 0.30 wt pct to alloys containing Nb additions of 0.05 and 0.10 wt pct Nb delayed the onset of abnormal grain growth in hot-rolled alloys reheated and soaked at 1050 °C and 1100 °C. The coarsening rate of microalloy precipitates was also reduced in Mo-bearing alloys relative to Mo-free alloys during isothermal soaking at 1050 °C, 1100 °C, and 1150 °C. The observed microalloy precipitate coarsening rates exceeded those predicted by the Lifshitz-Slyozov-Wagner relation for volume-diffusion-controlled coarsening, which is attributed to an initial bimodal precipitate size distribution prior to reheating to elevated temperature. Heat-treatments of hot-rolled alloys (tempering and solutionizing) prior to reheating to elevated temperature in

  14. Study of bipolar pulsed plasma electrolytic carbonitriding on nanostructure of compound layer for a gamma Ti-Al alloy

    Institute of Scientific and Technical Information of China (English)

    Mahmood ALIOFKHAZRAEI; Alireza SABOUR ROUHAGHDAM; Mohsen ROOHZENDEH

    2008-01-01

    The surface hardening of a gamma Ti-Al alloy by using bipolar pulsed nanocrystalline plasma electro-lytic carbonitriding has been studied in this investigation. Coating process was performed on a triethanolamine-based electrolyte by a cooling bath. The nanostructure of the obtained compound layer was examined with the figure analysis of the scanning electron microscopy (SEM) nanographs. The effects of the process variables, i.e., fre-quency, temperature of the electrolyte, applied voltage and treatment time, have been experimentally studied. Statistical methods were used to achieve the optimum size of the nanocrystals. Finally, the contribution percentage of the effective factors of the pulsed current was revealed, and the confirmation run showed the validity of the obtained results.

  15. Titanium carbide, nitride and carbonitrides: a 13C, 14N, 15N and 47,49Ti solid-state nuclear magnetic resonance study.

    Science.gov (United States)

    MacKenzie, K J; Meinhold, R H; McGavin, D G; Ripmeester, J A; Moudrakovski, I

    1995-05-01

    The first 47,49Ti, 13C, 14N and 15N solid-state nuclear magnetic resonance (NMR) spectra of titanium carbide, nitride and a series of cubic carbonitrides have been obtained under both static and magic-angle spinning (MAS) conditions. The 15N samples were isotopically enriched by gas-solid exchange at 1000 degrees C in a closed system. The Ti spectra of the carbide and nitride are sharp, reflecting the well defined cubic symmetry of these compounds, but become considerably broadened in the carbonitride series, with the spectra being approximately the sum of TiC and TiN together with some small electric field gradient (EFG) effects. The resonance positions and widths of all the NMR spectra change as carbon is progressively replaced by nitrogen. A relationship is observed between the 13C chemical shift and the nitrogen content of the carbonitrides, suggesting a possible NMR method for estimating the composition of these compounds. Although electron paramagnetic resonance (EPR) spectra of all these compounds show typically metallic behaviour, the NMR spectra show few effects attributable to conduction electrons, probably due to the lack of s-orbital contributions to the conduction band.

  16. Plasma synthesis of titanium nitride, carbide and carbonitride nanoparticles by means of reactive anodic arc evaporation from solid titanium

    Energy Technology Data Exchange (ETDEWEB)

    Kiesler, D., E-mail: dennis.kiesler@uni-due.de; Bastuck, T.; Theissmann, R.; Kruis, F. E. [University of Duisburg-Essen, Institute of Technology for Nanostructures (NST) and Center for Nanointegration Duisburg-Essen (CENIDE) (Germany)

    2015-03-15

    Plasma methods using the direct evaporation of a transition metal are well suited for the cost-efficient production of ceramic nanoparticles. In this paper, we report on the development of a simple setup for the production of titanium-ceramics by reactive anodic arc evaporation and the characterization of the aerosol as well as the nanopowder. It is the first report on TiC{sub X}N{sub 1 − X} synthesis in a simple anodic arc plasma. By means of extensive variations of the gas composition, it is shown that the composition of the particles can be tuned from titanium nitride over a titanium carbonitride phase (TiC{sub X}N{sub 1 − X}) to titanium carbide as proven by XRD data. The composition of the plasma gas especially a very low concentration of hydrocarbons around 0.2 % of the total plasma gas is crucial to tune the composition and to avoid the formation of free carbon. Examination of the particles by HR-TEM shows that the material consists mostly of cubic single crystalline particles with mean sizes between 8 and 27 nm.

  17. Atmospheric Pressure Plasma CVD of Amorphous Hydrogenated Silicon Carbonitride (a-SiCN:H) Films Using Triethylsilane and Nitrogen

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasan Guruvenket; Steven Andrie; Mark Simon; Kyle W. Johnson; Robert A. Sailer

    2011-10-04

    Amorphous hydrogenated silicon carbonitride (a-SiCN:H) thin films are synthesized by atmospheric pressure plasma enhanced chemical vapor (AP-PECVD) deposition using the Surfx Atomflow{trademark} 250D APPJ source with triethylsilane (HSiEt{sub 3}, TES) and nitrogen as the precursor and the reactive gases, respectively. The effect of the substrate temperature (T{sub s}) on the growth characteristics and the properties of a-SiCN:H films was evaluated. The properties of the films were investigated via scanning electron microscopy (SEM), atomic force microscopy (AFM) for surface morphological analyses, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) for chemical and compositional analyses; spectroscopic ellipsometry for optical properties and thickness determination and nanoindentation to determine the mechanical properties of the a-SiCN:H films. Films deposited at low T{sub s} depict organic like features, while the films deposited at high T{sub s} depict ceramic like features. FTIR and XPS studies reveal that an increases in T{sub s} helps in the elimination of organic moieties and incorporation of nitrogen in the film. Films deposited at T{sub s} of 425 C have an index of refraction (n) of 1.84 and hardness (H) of 14.8 GPa. A decrease in the deposition rate between T{sub s} of 25 and 250 C and increase in deposition rate between T{sub s} of 250 and 425 C indicate that the growth of a-SiCN:H films at lower T{sub s} are surface reaction controlled, while at high temperatures film growth is mass-transport controlled. Based on the experimental results, a potential route for film growth is proposed.

  18. Distortion Control on Transmission Gear During Carbonitriding and Quenching%传动齿轮在碳氮共渗和淬火中的畸变控制

    Institute of Scientific and Technical Information of China (English)

    张长英

    2011-01-01

    从热处理内应力和机械加工中产生的残余应力出发,分析了造成传动齿轮在碳氮共渗和淬火过程中发生畸变的主要原因,通过优化工艺路线和淬火工艺参数,提高了传动齿轮的合格率.%Including the internal stress of heat treatment and the residual stress of machining, the main factors affecting the distortion of transmission gear during carbonitriding and quenching were analyzed. The pass rate was increases by optimizing machining arrangements and quenching process parameters.

  19. Micro Planetary Gear Medium Temperature Gas Carbonitriding%微型行星齿轮的中温气体碳氮共渗

    Institute of Scientific and Technical Information of China (English)

    杨金花; 刘忠; 吴亮

    2015-01-01

    Planetary wheel of micro planetary gear transmission using the new technology of gas carbonitriding, through trial and error, and constantly adjust the process parameters, obtained the reasonable heat treatment process route, reduces the total infiltration temperature, shortens the time of total infiltration products have obtained a higher surface hardness, wear resistance and improve the quality of products and scrap rate reduced to 5% from 15%~20%, heat energy consumption reduced by 20%~30%, and the new technology has been applied in industrial production, to achieve the service life of the request, has obtained the remarkable economic and social benefits.%对微型行星齿轮传动中的行星齿轮采用气体碳氮共渗的新工艺,通过反复试验,不断调整各工艺参数,取得了合理的热处理工艺路线,降低了共渗温度、缩短了共渗时间,产品获得了更高的耐磨性和表面硬度,提高了产品质量,废品率由15%~20%下降为5%,热处理能耗降低20%~30%,新工艺已应用于工业生产中,达到了使用寿命要求,取得了显著的经济效益和社会效益。

  20. Synthesis of complex carbonitride powders Ti{sub y}M{sub T1-y}C{sub x}N{sub 1-x} (M{sub T}: Zr, V, Ta, Hf) via a mechanically induced self-sustaining reaction

    Energy Technology Data Exchange (ETDEWEB)

    Cordoba, Jose M., E-mail: jmcordoba@icmse.csic.e [Instituto de Ciencia de Materiales de Sevilla, Centro Mixto CSIC-US, Americo Vespucio 49, 41092 Sevilla (Spain); Aviles, Miguel A.; Sayagues, Maria J.; Alcala, Maria D.; Gotor, Francisco J. [Instituto de Ciencia de Materiales de Sevilla, Centro Mixto CSIC-US, Americo Vespucio 49, 41092 Sevilla (Spain)

    2009-08-12

    The machinability of materials is a dynamic field with enormous implications in different industrial sectors because manufacturers are constantly looking for improvements that can increase the overall productivity. Manufacturers of cutting tool inserts need to develop products that can perform at higher speeds and last longer under increasingly rigorous operating conditions. It has been revealed that cermets may exhibit better properties and performances when solid solution of multiple hard compounds is added instead of a mixture of several binary ones. In this work, a mechanically induced self-sustaining reaction (MSR) is described as a suitable synthesis method to obtain a wide range of different new quaternary carbonitride systems by milling mixtures of elemental powders of transition metals and graphite in a nitrogen atmosphere. Characterization was carried out using X-ray powder diffraction, elemental analysis, energy dispersive X-ray analysis (EDX), scanning and transmission electron microscopy and electron diffraction (ED).

  1. Influence of gas environment on synthesis of silicon carbide and some carbides and carbonitrides of d-group transition metals through reaction between metal powders and amorphous carbon powders in a solar furnace at P.S.A. (plataforma solar de Almeria)

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, D.; Rodriguez, J. [Plataforma Solar de Almeria, PSA, Centro Europeo de Ensayos de Energia Solar, Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, Tabernas (Spain); Guerra Rosa, L.; Cruz Fernandes, J. [Instituto Superior Tecnico, IST, Dept. de Engenharia de Materiais, Lisboa (Portugal); Shohoji, N. [Instituto Nacional de Engenharia e Tecnologia Industrial, INETI, Instituto de Materiais e Tecnologias de Producao, Dept. de Tecnologias de Producao, Lisboa (Portugal)

    1999-03-01

    Refractory carbides and carbonitrides including silicon carbide SiC, tungsten carbide WC, titanium carbide TiC{sub x} (0.5carbonitride TiC{sub x}N{sub y} (0.5carbonitride TiC{sub x}N{sub y} formed from Ti. No special influence of atmosphere was detected on the WC formation, but conversion to SiC from Si was somewhat retarded in N{sub 2} atmosphere. In either Ar or N{sub 2} atmosphere, progress of graphitization of amorphous carbon was not detectable by X-ray diffraction analysis in the reaction with Si and Ti but graphitization of amorphous carbon appeared to be significantly accelerated in the reaction with W. (authors)

  2. Extending Horizon of Materials Processing with Solar Furnace Solar-synthesis of raw material powders (carbides and carbonitrides) and solar-sintering of ceramic powder compacts with novel prospects of introducing unstable chemical species into the reaction system

    Energy Technology Data Exchange (ETDEWEB)

    Guerra Rosa, L.; Cruz Fernandes, J.

    2002-07-01

    Solar furnace (SF) yielding high flux of concentrated solar beam has been used for our recent trial syntheses of carbides and carbonitrides of Si and d-group transition metals and, during the course of this series of preliminary work, we encountered several intriguing phenomena which cannot be interpreted in terms of available equilibrium phase relationships. These new evidences seem to indicate still unexploited potentiality of solar furnace as novel type of chemical reactor rather than mere ecological heat source replacing traditional electric furnace. Besides these raw materials powder synthesis experiments, we have been testing also potentiality of SF a reactor for sintering oxide and non-oxide ceramic powders and found that mechanical properties of the solar-sintered specimen were comparable to those of the counterpart manufactured by traditional industrial sintering process. As such, data gathered so far implicate great potentiality of SF as new type of chemical reactor. Introduction of unstable chemical species, such as non-graphitic carbon and NH{sub 3} gas with suppressed degree of dissociation, into the reaction system might further extend the range of producible materials in the SF. Thus, some review is also give concerning recent works involving usage of unstable chemical species emerging from a group of Osaka University. (Author) 35 refs.

  3. Study of carbonitriding thermochemical treatment by plasma screen in active with pressures main austenitic stainless steels AISI 409 and AISI 316L; Estudo do tratamento termoquimico de carbonitretacao por plasma em tela ativa com pressoes variaveis nos acos inoxidaveis austenitico AISI 316L e ferririco AISI 409

    Energy Technology Data Exchange (ETDEWEB)

    Melo, M.S.; Oliveira, A.M.; Leal, V.S.; Sousa, R.R.M. de; Alves Junior, C. [Centro Federal de Educacao Tecnologica do Maranhao (CEFET/MA), Sao Luis, MA (Brazil); Centro Federal de Educacao Tecnologica do Piaui (CEFET/PI), Teresina, PI (Brazil); Universidade Federal do Rio Grande do Norte (DF/UFRN), Natal, RN (Brazil). Dept. de Fisica. Labplasma

    2010-07-01

    The technique called Active Screen Plasma Nitriding (ASPN) is being used as an alternative once it offers several advantages with respect to conventional DC plasma. In this method, the plasma does not form directly in the sample's surface but on a screen, in such a way that undesired effects such as the edge effect is minimized. Stainless steels present not very satisfactory wearing characteristics. However, plasma carbonitriding has been used as to improve its resistance to wearing due to the formation of a fine surface layer with good properties. In this work, samples of stainless steel AISI 316L and AISI 409 were treated at pressures of 2.5 and 5 mbar. After the treatments they were characterized by microhardness, microscopy and Xray diffraction. Microscopy and hardness analysis showed satisfactory layers and toughness in those steels. (author)

  4. CRACK REASON ANALYSIS OF DAMAGED CARBONITRIDED PART

    Directory of Open Access Journals (Sweden)

    Karin Kocúrová

    2010-03-01

    Full Text Available The article deals with the analysis of a damaged part, which was designed for use in a mechanical clutch of a car. The crack in the part was found during the production inspection. The aim of metallographic and fractography analyses of the fracture surfaces was to discover the reasons for the crack. The reason for creating the crack was the formation of smaller cracks in the production during pressing process of the semiproduct. These cracks even grew after the following thermochemical treatment. The fracture was initiated during the straightening process of quenched part.

  5. New method for synthesis of metal carbides, nitrides and carbonitrides

    Energy Technology Data Exchange (ETDEWEB)

    Koc, R.; Folmer, J.S.; Kodambaka, S.K. [Southern Illinois Univ., Carbondale, IL (United States)] [and others

    1997-04-01

    The purpose of this work is to develop a novel synthesis method using a carbothermic reduction reaction of carbon coated precursors for producing high purity, submicron, non-agglomerated powders of metal carbide, metal nitride and metal boride systems. The authors also want to demonstrate the advantages of the process and provide information on the applicability of the process for synthesizing related advanced ceramic powders (e.g. SiC, WC, TiN, TiB{sub 2}, Si{sub 3}N{sub 4}). During the FY96 of the project, steps are taken to investigate the reaction mechanisms and phase evolution during the formation of TiC from carbon coated titania precursors and to produce submicron TiC powders with desired stoichiometries. Depending on the carbon content in the coated titania precursor, TiC powder was produced with different stoichiometries (different amount of oxygen and free carbon).

  6. Special Features of the Carbonitriding of Parts of Instrument Bearings Designed for Extreme Service Conditions

    Science.gov (United States)

    Smirnov, A. E.; Shevchenko, S. Yu.; Shchipunov, V. S.; Kunyaev, V. E.; Seval'nev, G. S.

    2016-09-01

    A study is made of complexly alloyed steel 8Kh4V9F2-Sh, which is used for fabricating parts of engineering bearings operating under extreme conditions. Vacuum processes are shown to be preferable to gas carburizing for hardening the races of precision bearings. Vacuum carburizing is shown to be an effective technique for forming quality diffusion layers.

  7. STRUCTURE FORMATION OF HYPOEUTECTOID CONSTRUCTIONS STEELS AT CARBONITRIDING WITH LOCAL INDUCTION CYCLIC HEATING

    Directory of Open Access Journals (Sweden)

    G. A. Tkachenko

    2010-01-01

    Full Text Available Improvement of mechanical characteristics of details of the soil-cultivating car. Structurization at cyclic heating of steels. The reasons of an intensification of diffusion at cyclic heating. Structure crushing, impact strength and hardness increase.

  8. Development of compound layer of iron (carbo)nitrides during nitriding of steel

    DEFF Research Database (Denmark)

    Ratajski, J.; Tacikowski, J.; Somers, Marcel A.J.

    2003-01-01

    The composition and phase constitution of a compound layer developing during gaseous nitriding was investigated at 853 K for three commercial steels (AISI 120, 4340 and 1090) and Armco iron. The compound layers were characterised by light optical microscopy, X-ray diffraction and electron probe...... microanalysis. The formation of the compound layer occurs along two distinct sequences: alpha-gamma prime-epsilon and/or alpha(theta)-epsilon2-gamma prime-epsilon1. The preferred sequence depends mainly on the chemical composition of steel and on the nitriding potential....

  9. Titanium carbonitride thick coating prepared by plasma spray synthesis and its tribological properties

    Institute of Scientific and Technical Information of China (English)

    ZHU Lin; HE JiNing; YAN DianRan; XIAO LiSong; DONG YanChun; XUE DingChuan; MENG DeLiang

    2007-01-01

    TiCN coating,owing to its superior wear-resistance,has been frequently applied in many fields. TiCN thick coating was first prepared by reactive plasma spraying. The phase composition,microstructure and tribological properties of the TiCN coating were investigated in this research. Experimental results show that the microstructure of the TiCN coating was quite dense,and there was also a little amount of titanium oxides within the coating. By XPS analysis,Ti-C and Ti-N bonds were detected in the coating. The TiCN coating exhibited superior wear-resistance. The failure mechanism was attributed to the adhesive wear,the grinding of TiCN hard-grain,as well as the coating failure by oxidation. There were more Fe,Cr,O,etc. in the failure zone,suggesting that the corrosion propagated gradually from surface to interior.

  10. Optical and electrical characteristics of plasma enhanced chemical vapor deposition boron carbonitride thin films derived from N-trimethylborazine precursor

    Energy Technology Data Exchange (ETDEWEB)

    Sulyaeva, Veronica S., E-mail: veronica@niic.nsc.ru [Department of Functional Materials Chemistry, Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Kosinova, Marina L.; Rumyantsev, Yurii M.; Kuznetsov, Fedor A. [Department of Functional Materials Chemistry, Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Kesler, Valerii G. [Laboratory of Physical Principles for Integrated Microelectronics, Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk 630090 (Russian Federation); Kirienko, Viktor V. [Laboratory of Nonequilibrium Semiconductors Systems, Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk 630090 (Russian Federation)

    2014-05-02

    Thin BC{sub x}N{sub y} films have been obtained by plasma enhanced chemical vapor deposition using N-trimethylborazine as a precursor. The films were deposited on Si(100) and fused silica substrates. The grown films were characterized by ellipsometry, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy, spectrophotometry, capacitance–voltage and current–voltage measurements. The deposition parameters, such as substrate temperature (373–973 K) and gas phase composition were varied. Low temperature BC{sub x}N{sub y} films were found to be high optical transparent layers in the range of 300–2000 nm, the transmittance as high as 93% has been achieved. BC{sub x}N{sub y} layers are dielectrics with dielectric constant k = 2.2–8.9 depending on the synthesis conditions. - Highlights: • Thin BC{sub x}N{sub y} films have been obtained by plasma enhanced chemical vapor deposition. • N-trimethylborazine was used as a precursor. • Low temperature BC{sub x}N{sub y} films were found to be high optical transparent layers (93%). • BC{sub x}N{sub y} layers are dielectrics with dielectric constant k = 2.2–8.9.

  11. The role of Ti carbonitride precipitates on fusion zone strength-toughness in submerged arc welded linepipe joints

    Energy Technology Data Exchange (ETDEWEB)

    Aucott, L., E-mail: la126@le.ac.uk [Department of Engineering, University of Leicester (United Kingdom); Wen, S.W., E-mail: shuwen.wen@tatasteel.com [Department of Engineering, University of Leicester (United Kingdom); Tata Steel, Swinden Technology Centre, Rotherham (United Kingdom); Dong, H., E-mail: hd38@le.ac.uk [Department of Engineering, University of Leicester (United Kingdom)

    2015-01-12

    The role of micro-alloying in the submerged arc welding (SAW) of high strength low alloy steel linepipe is paramount in facilitating the high strength properties of the linepipe. In this study, transmission electron microscopy analysis revealed the presence of large (0.85 µm) Ti (C,N) precipitates within the predominantly acicular ferrite SAW joint. Cross-weld Vickers hardness and Charpy impact tests revealed that the fusion zone has high hardness and low toughness properties in relation to the base metal and heat affected zone. Fractography observations made on the ductile fracture surface of the fusion zone revealed a high number of the large Ti (C,N) precipitates to be located within the microvoids – suggesting their role in nucleating microvoids. Finally, fracture micro-mechanics are used to evaluate the relationship between the coarse precipitates and reduced strength-toughness properties in the SAW weld of the API-5L grade X65 linepipe steel.

  12. 高炉内Ti(C,N)生成的热力学分析%Thermodynamic analysis of titanium carbonitride formation in blast furnace

    Institute of Scientific and Technical Information of China (English)

    李扬; 程树森; 蔡皓宇

    2013-01-01

    通过热力学计算,研究了高炉中钛氧化物的还原过程,分析了TiC、TiN在高炉风口回旋区、渣铁层及铁水中的生成和转移,并得到了Ti(C,N)在渣铁界面析出时的炉渣中TiO2的临界质量分数.利用Factsage软件计算分析了渣铁平衡时铁水中w(Ti)与w(Si)之间的相互关系,发现:w(Si)、w(Ti)及w(Si) /w(Ti)的值在炉渣成分不改变的情况下会随温度的升高而增大;炉渣碱度0.9~1.2,炉渣w(TiO2)在5.5%以下时,铁水中的w(Ti)会随碱度升高而增加;在炉缸温度一定时,炉缸中Ti(C,N)的生成依赖于渣中w(TiO2).

  13. OMCVD of molybdenum and tungsten carbonitride films from (Cp)M-(Nt-Bu){sub 2}CH{sub 3} (M = W, Mo)

    Energy Technology Data Exchange (ETDEWEB)

    Sundermeyer, J.; Radius, U. [Universitaet Wuerzburg (Germany); Stovall, W.K.; Reinhard, G. [Univ. of California, Los Angeles, CA (United States)

    1995-12-01

    Thin films were deposited on Si(100) or GaAs(100) wafers in a hot wall CVD apparatus from the volatile precursors in the range 400-580{degree}C and under a gas stream either of He or of H{sub 2}. In all cases, the films are dark and shiny in appearance. Scanning electron microscopy showed them to be tight-grained and smooth down to the sub-micron level. Powder x-ray diffraction indicated the films were largely amorphous. Annealing the molybdenum containing depositions on Si(100) at 700{degree}C under a flow of He for 3 h. brings out some sharp features characteristic of molybdenum and carbon phases. Elemental analysis was obtained by x-ray photoelectron spectroscopy. Films deposited at 400{degree}C from the tungsten precursor contained W (37-41%), C (46-48%), N(12-14%). These might be useful as protective coatings against corrosion and wear resistance.

  14. Molecular precursor derived silicon boron carbonitride/carbon nanotube and silicon oxycarbide/carbon nanotube composite nanowires for energy based applications

    Science.gov (United States)

    Bhandavat, Romil

    Molecular precursor derived ceramics (also known as polymer-derived ceramics or PDCs) are high temperature glasses that have been studied for applications involving operation at elevated temperatures. Prepared from controlled thermal degradation of liquid-phase organosilicon precursors, these ceramics offer remarkable engineering properties such as resistance to crystallization up to 1400 °C, semiconductor behavior at high temperatures and intense photoluminescence. These properties are a direct result of their covalent bonded amorphous network and free (-sp2) carbon along with mixed Si/B/C/N/O bonds, which otherwise can not be obtained through conventional ceramic processing techniques. This thesis demonstrates synthesis of a unique core/shell type nanowire structure involving either siliconboroncarbonitride (SiBCN) or siliconoxycarbide (SiOC) as the shell with carbon nanotube (CNT) acting as the core. This was made possible by liquid phase functionalization of CNT surfaces with respective polymeric precursor (e.g., home-made boron-modified polyureamethylvinylsilazane for SiBCN/CNT and commercially obtained polysiloxane for SiOC/CNT), followed by controlled pyrolysis in inert conditions. This unique architecture has several benefits such as high temperature oxidation resistance (provided by the ceramic shell), improved electrical conductivity and mechanical toughness (attributed to the CNT core) that allowed us to explore its use in energy conversion and storage devices. The first application involved use of SiBCN/CNT composite as a high temperature radiation absorbant material for laser thermal calorimeter. SiBCN/CNT spray coatings on copper substrate were exposed to high energy laser beams (continuous wave at 10.6 mum 2.5 kW CO2 laser, 10 seconds) and resulting change in its microstructure was studied ex-situ. With the aid of multiple techniques we ascertained the thermal damage resistance to be 15 kW/cm -2 with optical absorbance exceeding 97%. This represents one order of magnitude improvement over bare CNTs (1.4 kW/cm-2) coatings and two orders of magnitude over the conventional carbon paint (0.1 kW/cm -2) currently in use. The second application involved use of SiBCN/CNT and SiOC/CNT composite coatings as energy storage (anode) material in a Li-ion rechargeable battery. Anode coatings (~1mg/cm-2) prepared using SiBCN/CNT synthesized at 1100 °C exhibited high reversible (useable) capacity of 412 mAh/g -1 even after 30 cycles. Further improvement in reversible capacity was obtained for SiOC/CNT coatings with 686 mAh/g-1 at 40 cycles and approximately 99.6% cyclic efficiency. Further, post cycling imaging of dissembled cells indicated good mechanical stability of these anodes and formation of a stable passivating layer necessary for long term cycling of the cell. This improved performance was collectively attributed to the amorphous ceramic shell that offered Li storage sites and the CNT core that provided the required mechanical strength against volume changes associated with repeated Li-cycling. This novel approach for synthesis of PDC nanocomposites and its application based testing offers a starting point to carry out further research with a variety of PDC chemistries at both fundamental and applied levels.

  15. 碳氮共渗

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Characterisation and application of titanium carbonitride-based cutting tools;Composite ceramics and coatings for tribotechnical application; Crystallization of polymer-derived silicon carbonitride at 1873 K under nitrogen overpressure;1 Effect of cooling conditions on plasma-carbonitrided iron surfaces

  16. A Study of the Microstructural Basis for the Strength and Toughness Properties of As-Quenched and Quenched and Tempered High Copper HSLA-100 Steel

    Science.gov (United States)

    1991-12-01

    Incoherent FCC Copper Precipitates Decorating Dislocations and a Large Niobium Carbide or Carbonitride (arrowed) ...... ................. 49 Figure 39 TEM...shows incoherent FCC precipitates. Figure 38 also shows a niobium carbide or carbonitride that has now precipitated in the overaged condition. These...Figure 38 TEM Image Showing Incoherent FCC Copper Precipitates Decorating Dislocations and a Large Niobium Carbide or Carbonitride (arrowed) Figure 39

  17. Structural and phase transformations in 0.3C-1Cr-1Mn-1Si-Fe steel after electrolytic plasma treatment

    Science.gov (United States)

    Kozlov, Eduard; Popova, Natalya; Zhurerova, Lyaila; Nikonenko, Elena; Kalashnikov, Mark; Skakov, Mazhin

    2016-11-01

    The paper presents the transmission electron microscopy (TEM) investigations on thin foils concerning phase transitions occurred in the type 0.3C-1Cr-1Mn-1Si-Fe alloyed steel after the electrolyte plasma treatment, i.e. carbonitriding at 850°C during 5 min. TEM investigations involve two points, namely: on the specimen surface and at 50 µm distance from the surface, i.e. in transition layer. It is shown that carbonitriding results in the formation of structures the properties of which are changed at a distance from it's the specimen surface. Thus, the modified morphology of the steel matrix is represented mostly by high-temperature lamellar martensite on α-phase surface, while the intermediate layer is represented by massive martensite. After carbonitriding, the particles of the alloyed cementite and M2C0.61N0.39, M4(C,N), M7(C,N)3, M23(C,N)6 carbonitrides are observed in all layers inside α-phase crystals and at their boundaries. The concentration of carbon and nitrogen on the surface is considerably higher. The modification of quantity is observed in the distribution and the volume fraction of carbide phases with the distance from the specimen surface, while the amount of carbonitride phases significantly reduces. Also, it is shown that carbonitriding leads to a complete relaxation of the internal local stresses on the specimen surface, while in the intermediate layer plastic stresses are observed.

  18. 碳化钛粒径对碳氮化钛基金属陶瓷微观结构和力学性能的影响%EFFECT OF TITANIUM CARBIDE PARTICLE SIZE ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF TITANIUM CARBONITRIDE BASED CERMETS

    Institute of Scientific and Technical Information of China (English)

    陈文琳; 刘宁; 晁晟

    2007-01-01

    用粉末冶金真空烧结法制备了超细晶粒碳氮化钛[Ti(C,N)]基金属陶瓷.研究了原始粉末粒径对Ti(C,N)基金属陶瓷微观结构和力学性能的影响.结果表明:在化学成分相同的条件下,晶粒细化使材料的Vickers硬度和抗弯强度上升,但断裂韧性有所下降.在超细晶粒Ti(C,N)基金属陶瓷微观组织中出现了一种新型的白芯/灰壳结构和一种特殊化合物(Ni2Mo2.5W1.3)Cx.初步研究表明:由于原始粉末粒径微小,促进了扩散反应因而生成了这种芯/壳结构.芯/壳结构有利于提高材料的抗弯强度和断裂韧性.(Ni2Mo2.5W1.3)Cx有利于提高材料的Vickers硬度,但是降低了Ti(C,N)基金属陶瓷的抗弯强度和断裂韧性.

  19. HARDENING OF THE ELECTRODESIEGED IRON CHEMICAL HEAT TREATMENT

    Directory of Open Access Journals (Sweden)

    V. I. Serebrovskii

    2015-01-01

    Full Text Available Summary. Currently in the repair and manufacture at the stage of recovery of steel parts, widely used special coatings formed by electrolytic effects on ferrous ions. This technique offers high performance, ease of implementation, low cost of technological equipment and materials used, as well as easy automation of the process. However, this method has several disadvantages: low fatigue strength of reconditioned parts, insufficiently strong grip of the iron coating to the substrate, particularly in alloy steels, insufficient wear resistance. For the purpose of increasing durability and wear resistance of parts, restored through electrochemical action, it is proposed to use chemical-heat treatment, consisting in the application of carbonitriding. Investigated the efficacy of different modes of carbonitriding in the highly carburizing paste-and their influence on the structure and properties of iron plating. It is established that the nitrocarburizing both low and high temperatures repeatedly (6-7.5 times increases the microhardness of the coatings. The highest hardness is obtained by low-temperature carbonitriding with direct quenching in water. Conducting the carbonitriding process at low temperatures (650 °C, significantly increases the hardness of the iron coatings, increasing the limit of its fluidity, a and also greatly increases its endurance limit. Nitrocarburized fatigue strength of samples with iron precipitation on the surface, as shown by our studies, not only higher strength of the same samples without carbonitriding (more than 2 times, but higher than the fatigue strength of the base metal without coatings. Raising the temperature of the carbonitriding did not increase the hardness of electrolytic iron. Developed a rational technology of hardening of steel parts, re-chain iron fortification. Selected optimum conditions for carbonitriding hardening restored iron fortification, with the purpose of increasing durability of machine

  20. Thermodynamic Research on Precipitates in Low Carbon Nb-Microalloyed Steels Produced by Compact Strip Production

    Institute of Scientific and Technical Information of China (English)

    Song XIANG; Guoquan LIU; Yang LI; Changrong LI; Andong WANG

    2007-01-01

    Microalloying element Nb in low carbon steels produced by compact strip production (CSP) process plays an important role in inhibiting recrystallization, decreasing the transformation temperature and grain refinement.With decreasing the rolling temperature, dislocations can be pinned by carbonitrides and the strength is increased. Based on the two sublattice model, with metal atom sublattice and interstitial atom sublattice,a thermodynamic model for carbonitride was established to calculate the equilibrium between matrix and carbonitride. In the steel produced by CSP, the calculation results showed that the starting temperature of precipitation of Ti and Nb are 1340℃ and 1040℃, respectively. In the range of 890-950℃, Nb rapidly precipitated. And the maximum of the atomic fraction of Nb in carbonitride was about 0.68. The morphologies and energy spectrum of the precipitates showed that (NbTi) (CN) precipitated near the dislocations. The experiment results show that Nb rapidly precipitated when the temperature was lower than 970℃, and the atomic fraction of Nb in carbonitride was about 60%-80%. The calculation results are in agreement with the experiment data. Therefore the thermodynamic model can be a useful assistant tool in the research on the precipitates in the low carbon steels produced by CSP.

  1. STRENGTHENING MECHANISMS IN Nb-Ti-V MICROALLOYED STEEL

    Directory of Open Access Journals (Sweden)

    Vinícius Lopes Vieira Martins

    2014-10-01

    Full Text Available Yield strength of Nb-Ti-V microalloyed steel has been investigated as a function of its microstructure obtained after industrial rolling on a hot strip mill. Optical (OM and transmission electron microscopy (TEM were used to reveal the ferrite grain structure, fine carbonitride precipitation and dislocation substructures. It was found that the effects of solid solution and grain size hardening were not sufficient to justify the results of tensile testing. Additional strengthening was attributed to carbonitride precipitation in austenite, interphase precipitation during transformation, and the formation of dislocations. All contributions of these microstructural features on mechanical property were estimated from empirical models available from literature. A global effect of both austenite and interphase carbonitride precipitation hardening was proposed. It was verified that yield strength calculated from cumulative effect of different strengthening mechanisms has presented good fitting with experimental tensile test.

  2. Niobium carbide precipitation in microalloyed steel

    Energy Technology Data Exchange (ETDEWEB)

    Klinkenberg, C.; Hulka, K. [Niobium Products Co. GmbH, Duesseldorf (Germany); Bleck, W. [Inst. for Ferrous Metallurgy, RWTH Aachen Univ., Aachen (Germany)

    2004-11-01

    The precipitation of niobium carbo-nitrides in the austenite phase, interphase and ferrite phase of microalloyed steel was assessed by a critical literature review and a round table discussion. This work analyses the contribution of niobium carbide precipitates formed in ferrite in the precipitation hardening of commercially hot rolled strip. Thermodynamics and kinetics of niobium carbo-nitride precipitation as well as the effect of deformation and temperature on the precipitation kinetics are discussed in various examples to determine the amount of niobium in solid solution that will be available for precipitation hardening after thermomechanical rolling in the austenite phase and successive phase transformation. (orig.)

  3. 碳氮共渗

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    [篇名 ] A study on friction and wear behaviour of carburized, carbonitrided and borided AISI 1020 and 5115 steels, [篇名 ] Alloy Carburization at Temperatures of 1,200 - 2,100 F(650-1,150 ℃), [篇名] Amorphous silicon carbonitride fibers drawn from alkoxide modified ceraser, [ 篇名 ] Bearings with incrcased reliability, [篇名 ] Bright outlook for hard coatings, [ 篇名 ] Carbonitridc coating by low-temperature diffusion process, [ 篇名 ] Carbonitridc nanomaterials, thin films, and solids.

  4. JPRS Report, Science & Technology, USSR: Materials Science

    Science.gov (United States)

    2007-11-02

    of an anodic oxide film of Ti02 with very low electron conductivity preventing reactions liberating oxygen on the surface of the" specimens. The...for 15 minutes. The oxidation of specimens with a titanium carbonitride Impurity began at approximately 380°C, resulting in the formation of Ti02

  5. Computation-Based Analysis of the Methods of Hardening of Gears from Heat-Resistant Steels

    Science.gov (United States)

    Semenov, M. Yu.; Gavrilin, I. N.; Ryzhova, M. Yu.

    2014-05-01

    A mathematical model is developed for estimating the contact fatigue of gears subjected to various kinds of thermochemical treatment. The model includes design of the contact stress state and of the loading capacity of the diffusion layer. The ranges of application of vacuum carburizing, vacuum carbonitriding, and ion nitriding for hardening gears with various geometrical parameters are determined.

  6. Interagency Coordinating Committee on Structural Ceramics FY 1992

    Science.gov (United States)

    2007-11-02

    production of biobased composites. Investigation of the effects of magnetic fields applied during polymerization and processing of plastics on...source. Comparison of experimental results with predictions from elastic- plastic finite element modeling of stress distributions. Number in... PLASTIC BEHAVIOR AND PROPERTIES OF TITANIUM CARBIDE AND TITANIUM CARBONITRIDE MONOLITHIC AND COMPOSITE MATERIALS D. C. Halverson (916) 823-0238

  7. A New Type of Submerged-Arc Flux-Cored Wire Used for Hardfacing Continuous Casting Rolls%A New Type of Submerged-Arc Flux-Cored Wire Used for Hardfacing Continuous Casting Rolls

    Institute of Scientific and Technical Information of China (English)

    YANG Ke; ZHANG Zhi-xi; HU Wang-qin; BAO Ye-feng; JIANG Yong-feng

    2011-01-01

    It is expected that the welding hardfacing of continuous casting rolls has better welding performance and higher wear resistance. A new type of submerged-arc hardfacing flux-cored wire has been developed through nitrogen replacing part of carbon and addition of the nitrogen-fixing elements of niobium and titanium. And microstructure, degree of hardness and high-temperature wear resistance of its deposited metal samples were also investigated. It is found that the microstructure is martensite, residual austenite and carbonitride precipitates. As a result, the hardfacing metal with homogeneous distribution of very fine carbonitride particles had high hardness and excellent wear-re- sisting property during high-temperature wear, which could significantly extend the service life of continuous casting rolls.

  8. Ab initio study of the electronic structure andelastic properties of Al5C3N

    Institute of Scientific and Technical Information of China (English)

    Xu Xue-Wen; Hu Long; Yu Xiao; Lu Zun-Ming; Fan Ying; Li Yang-xian; Tang Cheng-Chun

    2011-01-01

    We investigate the electronic structure,chemical bonding and elastic properties of the hexagonal aluminum carbonitride,Al5C3N,by ab initio calculations.Al5C3N is a semiconductor with a narrow indirect gap of 0.81 eV.The valence bands below the Fermi level (EF) originate from the hybridized Al p-C p and Al p-N p states.The calculated bulk and Young's moduli are 201 GPa and 292 GPa,which are slightly lower than those of Ti3SiC2.The values of the bulk-to-shear-modulus and bulk-modulus-to-c44 are 1.73 and 1.97,respectively,which axe higher than those of Ti2AlCand Ti2AlN,indicating that Al5C3N is a ductile ceramic.

  9. End Uses Mechanical Properties Settled By The Modified Sintering Conditions Of The Metal Injection Molding Process

    Science.gov (United States)

    Marray, Tarek; Jaccquet, Philippe; Moinard-Checot, Delphine; Fabre, Agnès; Barrallier, Laurent

    2011-01-01

    Most common mechanical applications require parts with specific properties as hard faced features. It is well known that treating parts under suitable atmospheres may improve hardness and strength yield of steels. Heat treatment process and more particularly thermo-chemical diffusion processes (such as carburizing or its variation: carbonitriding) can be performed to reach the industrial hardness profile requirements. In this work, a low-alloyed steel feedstock based on water soluble binder system is submitted to the MIM process steps (including injection molding, debinding and sintering). As-sintered parts are then treated under a low pressure carbonitriding treatment. This contribution focuses on preliminary results such as microstructural analyses and mechanical properties which are established at each stage of the process to determine and monitor changes.

  10. Study creep in 4340 steels with different microstructure and plasma carbon nitridation processing; Estudo de fluencia em acos 4340 com diferentes microestruturas e tratamento de carbonitretacao a plasma

    Energy Technology Data Exchange (ETDEWEB)

    Abdalla, A.J., E-mail: abdalla@ieav.cta.b [Departamento de Ciencia e Tecnologia Aeroespacial (IEAv/DCTA), Sao Jose dos Campos, SP (Brazil). Inst. de Estudos Avancados; Carrer, I.R.; Barboza, M.J.R.; Baggio-Scheid, V.H. [Universidade de Sao Paulo (EEL/USP), Lorena, SP (Brazil). Escola de Engenharia; Moura Neto, C.; Reis, D.A.P. [Departamento de Ciencia e Tecnologia Aeroespacial (ITA/DCTA), Sao Jose dos Campos, SP (Brazil). Inst. Tecnologico de Aeronautica

    2010-07-01

    From the AISI 4340 bars specimens were made-for-test of creep, they were subjected to different heat treatments for the formation of multiphase microstructures. After this initial treatment, a lot of the specimens were tested in creep. One second batch of specimens was treated with a plasma carbonitriding, and later, were also tested. The carbonitriding layer and microstructure were characterized with X-ray analysis, laser confocal microscopy and hardness testing. Tests showed that the hardness in the steel was reduced due to thermochemical treatment at 500 deg C. We observed variation in creep behavior due to different microstructures formed. After the plasma treatment, there was a considerable reduction in the rate of creep and an increase in the time required for fracture. (author)

  11. 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 ...

  12. STRENGTHENING MECHANISMS IN Nb-Ti-V MICROALLOYED STEEL

    OpenAIRE

    Vinícius Lopes Vieira Martins; Felipe Pereira Vasconcelos; Juno Gallego

    2014-01-01

    Yield strength of Nb-Ti-V microalloyed steel has been investigated as a function of its microstructure obtained after industrial rolling on a hot strip mill. Optical (OM) and transmission electron microscopy (TEM) were used to reveal the ferrite grain structure, fine carbonitride precipitation and dislocation substructures. It was found that the effects of solid solution and grain size hardening were not sufficient to justify the results of tensile testing. Additional strengthening w...

  13. Zircon Carburation Studies as Intermediate Stage in the Zirconium Fabrication; Estudios encaminados a la carburacion del circon como etapa intermedia en la obtencion de circonio

    Energy Technology Data Exchange (ETDEWEB)

    Almagro Huertas, V.; Saenz de Tejada Gonzalez, L.; Lopez Rodriguez, M.

    1963-07-01

    Zirconium carbide and carbonitride mixtures were obtained by Kroll's method.Reaction products have been identified by micrography and X-ray diffraction analysis. The optimum graphite content in the initial charge for the carburation reaction has been studied. zirconium, silicon and carbon content in the final product has been controlled as a function of current in the furnace and reaction time.Further chlorination of the final product was performed successfully. (Author) 16 refs.

  14. Elaboration de céramiques poreuses ordonnées à base de carbure de silicium

    OpenAIRE

    Majoulet, Olivier

    2012-01-01

    SiC based non-oxide type ceramics have been largely studied due to high thermostructural properties.In particular, Silicoboron carbonitrides (SiBCN) display high mechanic reliability and stay stableuntil temperature such as 2200 °C due to a low atomic mobility in their structure. The developpementof the Polymer Derived Ceramics (PDCs) route played a major role in the production of technicalceramics with controlled properties. Through the thermolysis of preceramic polymers, a large rangeof cer...

  15. Application of active powders at fluidised bed heat treatment technologies

    OpenAIRE

    Babul, T.; Kucharieva, N.

    2014-01-01

    The paper describes the principles and conditions of carrying out of a new type of fluidised bed thermochemical treatment in chemically active powders with different ways of fluidisation. These new fluidised bed thermochemical treatments in chemically active powders are primarily for the formation of surface diffusion layers on parts made of constructional and tool steel. This method can be used for sherardising, alitising, carbonitriding, nitrocarburising, carburising or boronising. Chara...

  16. Electronic properties of cubic TaC{sub x}N{sub 1-x}: A comparative study using self-consistent cluster and ab initio band-structure calculations and X-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lavrentyev, A.A.; Gabrelian, B.V.; Vorzhev, V.B.; Nikiforov, I.Ya. [Department of Physics, Don State Technical University, Gagarin Sq. 1, Rostov-on-Don (Russian Federation); Khyzhun, O.Yu. [Frantsevych Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Krzhyzhanivsky Street, UA-03142 Kyiv (Ukraine)], E-mail: khyzhun@ipms.kiev.ua

    2009-03-20

    To investigate the influence of substitution of carbon atoms for nitrogen atoms in the cubic TaC{sub x}N{sub 1-x} carbonitrides, total and partial densities of states were calculated for TaC, TaC{sub 0.5}N{sub 0.5} and TaN compounds (NaCl structure) using the self-consistent cluster (with the FEFF8 code) and ab initio band-structure augmented plane wave + local orbitals (APW + LO) methods. In the present work a rather good agreement of the theoretical FEFF8 and APW + LO data for electronic properties of the TaC{sub x}N{sub 1-x} system under consideration was obtained. The results indicate that a strong hybridization of the Ta 5d- and C(N) 2p-like states is characteristic for the valence band of the TaC{sub x}N{sub 1-x} carbonitrides. When going from TaC to TaN through the TaC{sub 0.5}N{sub 0.5} carbonitride, the main maxima of curves representing total and partial Ta 5d densities of states shift in the direction opposite to the position of the Fermi level. In the above sequence of compounds, an increase of occupation of the near-Fermi sub-band formed by contributions of Ta 5d(t{sub 2g}) states has been detected. The theoretical FEFF8 and APW + LO results for the electronic structure of the TaC{sub x}N{sub 1-x} carbonitrides were found to be in excellent agreement with the experimental data derived in the present work employing X-ray photoelectron, emission and absorption spectroscopy methods for cubic TaC{sub 0.98}, TaC{sub 0.52}N{sub 0.49} and TaN{sub 0.97} compounds.

  17. Splitting phenomenon in martensitic transformation of X12CrMoWVNbN10-1-1 steel

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Xingang; Han, Lizhan; Gu, Jianfeng [Shanghai Jiao Tong Univ. (China). Shanghai Key Laboratory of Materials Laser Processing and Modification

    2015-06-15

    The splitting phenomenon was detected in martensitic transformation of X12CrMoWVNbN10-1-1 steel using high resolution dilatometry under certain conditions. In-situ observation of austenite grain growth was carried out. Direct experimental results indicated that this splitting is not connected with the concentration gradient in the austenite resulting from the dissolution of carbonitrides during heating, but instead may be caused by the occurrence of abnormal grain growth.

  18. Cathodic cage nitriding of AISI 409 ferritic stainless steel with the addition of CH4

    Directory of Open Access Journals (Sweden)

    Rômulo Ribeiro Magalhães de Sousa

    2012-04-01

    Full Text Available AISI 409 ferritic stainless steel samples were nitrided using the cathodic cage plasma nitriding technique (CCPN, with the addition of methane to reduce chromium precipitation, increase hardness and wear resistance and reduce the presence of nitrides when compared to plasma carbonitriding. Microhardness profiles and X-Ray analysis confirm the formation of a very hard layer containing mainly ε-Fe3N and expanded ferrite phases.

  19. РАЗРАБОТКА И ОСВОЕНИЕ ТЕХНОЛОГИИ ПРОИЗВОДСТВА РУЛОННОГО ПРОКАТА КЛАССОВ ПРОЧНОСТИ Х60-Х70 ТОЛЩИНОЙ БОЛЕЕ 12 ММ ДЛЯ ИЗГОТОВЛЕНИЯ ТРУБ

    OpenAIRE

    Салганик, Виктор; Денисов, Сергей

    2008-01-01

    The controlled rolling technology is developed for niobium steel bars with strength of X60-X70 and more than 12 mm thick. It is suggested to use microalloyed steels with carbonitride elements with carbon content less than 0. 2 %, manganese 1. 2-1. 8, silicium 0. 15-0. 60 %. The efficient regimes of controlled rolling process with speeded bars cooling and different chemical content are established due to the mathematical modeling. Finally, a concrete chemical composition is chosen taking into ...

  20. Precipitate phases in normalized and tempered ferritic/martensitic steel P92

    Science.gov (United States)

    Shen, Yinzhong; Liu, Huan; Shang, Zhongxia; Xu, Zhiqiang

    2015-10-01

    Ferritic/martensitic steel P92 is a promising candidate for cladding and duct applications in Sodium-Cooled Fast Reactor. The precipitate phases of the P92 steel normalized at 1323 K (1050 °C) for 30 min and tempered at 1038 K (765 °C) for 1 h have been investigated using transmission electron microscopes. Four types of phases consisting of M23C6, MX, M2X and sigma-FeCr were identified in the steel. MX phases consist of Nb-rich M(C,N) carbonitride, Nb-rich MC carbide, V-rich M(C,N) carbonitride, V-rich MC carbide, V-rich MN nitride, and complex MC carbides with Nb-rich MC core and V-rich MC wings. M2X phases consist of Cr-rich M2(C,N) carbonitride, Cr-rich M2C carbide and M2N nitride. Sigma-FeCr has a simple tetragonal lattice and a typical chemical formula of Fe0.45Cr0.45W0.1. M23C6 and MX are the dominant phases, while the sigma-FeCr has the lowest content. The formation of sigma-FeCr and M2X phases in the steel is also discussed.

  1. Nano- and Macro-wear of Bio-carbo-nitrided AISI 8620 Steel Surfaces

    Science.gov (United States)

    Arthur, Emmanuel Kwesi; Ampaw, Edward; Zebaze Kana, M. G.; Adetunji, A. R.; Olusunle, S. O. O.; Adewoye, O. O.; Soboyejo, W. O.

    2015-12-01

    This paper presents the results of an experimental study of nano- and macro-scale wear in a carbo-nitrided AISI 8620 steel. Carbo-nitriding is carried out using a novel method that involves the use of dried, cyanide-containing cassava leaves, as sources of carbon and nitrogen. These are used in a pack cementation that is used to diffuse carbon and nitrogen into case layers at intermediate temperatures [673.15 K, 723.15 K, 773.15 K, and 823.15 K (400 °C, 450 °C, 500 °C, and 550 °C)]. Nano- and macro-scale wear properties are studied in the case-hardened surfaces, using a combination of nano-scratch and pin-on-disk experiments. The measured wear volumes (at both nano- and macro-length scales) are shown to increase with decreasing pack cyaniding temperature. The nano- and macro-wear resistances are also shown to be enhanced by the in situ diffusion of carbon and nitrogen from cyanide-containing bio-processed waste. The underlying wear mechanisms are also elucidated via atomic force microscopy and scanning electron microscopy observations of the wear tracks. The implications of the results are discussed for the design of hardened carbo-nitrided steel surfaces with improved wear resistance.

  2. Advanced WC-Co cermet composites with reinforcement of TiCN prepared by extended thermal plasma route

    Energy Technology Data Exchange (ETDEWEB)

    Mondal, B. [Centre for Advanced Materials Processing, Central Mechanical Engineering Research Institute, Mahatma Gandhi Avenue, Durgapur 713 209, West Bengal (India)], E-mail: bnmondal@rediffmail.com; Das, P.K. [Central Glass and Ceramic Research Institute, Kolkata (India); Singh, S.K. [Institute of Minerals and Materials Technology (IIMT), Bhubeneswar (India)

    2008-12-20

    The synthesis of titanium carbonitride (TiCN) powders by thermal plasma using extended arc thermal plasma reactor and the effect of TiCN reinforcement for the development of advanced WC-Co cermets has been studied with respect to hardness and fracture toughness. These classes of materials are being investigated for future application in wear-resistant seals, cutting tools, etc. Metallurgical reactions and microstructural developments during sintering of cermets and functionally graded cemented carbonitrides are being investigated by analytical methods such as differential thermal analysis/thermo-gravimetric analysis, X-ray diffraction and analytical Scanning electron microscopy with energy dispersive X-ray spectroscopy. By an in-depth understanding of the complex phase reactions and the mechanisms that govern the sintering process and metallurgical reactions, new cermets and different types of functionally graded cemented carbonitrides with desired microstructures and properties have been attempted to develop. The significant improvement of micro-hardness was observed with optimal concentration of TiCN reinforcement addition in WC-Co system without sacrificing much fracture toughness value of the composite cermets.

  3. 微合金钢中钛钼复合析出的第一性原理研究%Study on First Principle of Complex Precipitation of Titanium and Molybdenum in Micro-alloyed Steel

    Institute of Scientific and Technical Information of China (English)

    赵冬伟; 曹建春; 周晓龙; 彭谦之

    2012-01-01

    The formation energy of complex carbonitrides of titanium and molybdenum, which may precipitate in low alloyed steel, was computed using materials studiq-CASTEP module. The calculated results indicate that the effect of molybdenum on the formation energy of (Ti1-xMox)C presents a parasol trend. The formation energy of (Ti1-x Mox)C first decreases and then increases with increasing molybdenum content, and the maximum appears when Ti/Mo is 1. The formation energy of titanium carbide is lower than that of molybdenum carbide. Molybdenum can reduce the formation energy of (Ti1-x Mox)(CyN1-y) and the impact becomes sluggish as molybdenum content increasing. The formation energy of nitrogen-rich carbonitrides is lower than that of carbon-rich carbonitrides.%利用Materials Studio中CASTEP模块对钢中出现的钛钼复合析出相的形成能进行计算.结果表明,Mo含量对碳化钛钼形成能的影响趋势呈抛物线状,以Ti/Mo值等于1为界,随着Mo含量的增加,碳化钛钼的形成能先降低后升高;TiC的形成能比MoC的低,Mo会降低碳氮化钛钼的形成能,且降低幅度随钼含量增加逐渐减小;富氮的碳氮化钛钼比富碳的碳氮化钛钼具有更低的形成能.

  4. 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.

  5. Phase Evolution during the Sintering of Submicron Ti(C,N)-Based Cermets

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The submicron powder mixtures of TiC-TiN-WC-Mo-C-Ni sintered at 1400℃ or below in vacuum were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. The results showed that Mo2C formed at 800℃ or below. Both WC and Mo2C disappeared at 1200℃, and TiN disappeared at 1250℃. In addition, the variations of lattice constants of the titanium carbonitride and nickel binder phase with sintering temperature were experimentally obtained, and the reason was analyzed.

  6. Residual Stress Induced by Nitriding and Nitrocarburizing

    DEFF Research Database (Denmark)

    Somers, Marcel A.J.

    2005-01-01

    The present chapter is devoted to the various mechanisms involved in the buildup and relief of residual stress in nitrided and nitrocarburized cases. The work presented is an overview of model studies on iron and iron-based alloys. Subdivision is made between the compound (or white) layer......, developing at the surfce and consisting of iron-based (carbo)nitrides, and the diffusion zone underneath, consisting of iron and alloying element nitrides dispersed in af ferritic matrix. Microstructural features are related directly to the origins of stress buildup and stres relief....

  7. Influence Of Heat Treatment On Duplex Stainless Steel To Study The Material Properties

    Directory of Open Access Journals (Sweden)

    Jithin M

    2015-02-01

    Full Text Available Abstract The various heat treatment processes are annealing normalizing hardening tempering spheroidising surface hardening flame and induction hardening nitriding cyaniding carbonitriding carburizing etc Heat treatment on duplex stainless steel is to improve ductility toughness strength hardness and to relieve internal stress developed in the material. Here basically the experiment of hardness test impact test wear test and compression is done to get idea about heat treated duplex stainless steel which has extensive uses in all industries and scientific research and development fields.

  8. Advanced Surface Technology

    DEFF Research Database (Denmark)

    Møller, Per; Nielsen, Lars Pleht

    This new significant book on advanced modern surface technology in all its variations, is aimed at both teaching at engineering schools and practical application in industry. The work covers all the significant aspects of modern surface technology and also describes how new advanced techniques make......, nitriding, carbonitriding, and many other lesser-known thermochemical processes used for solving technological problems. The book is richly illustrated with pictures and figures showing how the technology creates new innovative solutions for industry and how surfaces are becoming integral to the function...

  9. New Possibilities of Shaping the Surface Properties in Austempered Ductile Iron Castings

    Directory of Open Access Journals (Sweden)

    D. Myszka

    2013-01-01

    Full Text Available The paper presents recent developments concerning the formation of surface layer in austempered ductile iron castings. It was found thatthe traditional methods used to change the properties of the surface layer, i.e. the effect of protective atmosphere during austenitising or shot peening, are not fully satisfactory to meet the demands of commercial applications. Therefore, new ways to shape the surface layer and the surface properties of austempered ductile iron castings are searched for, to mention only detonation spraying, carbonitriding, CVD methods, etc.

  10. The analysis of strength properties of ceramic preforms for infiltration process

    OpenAIRE

    P. Putyra; P. Kurtyka; L. Jaworska; M. Podsiadło; B Smuk

    2008-01-01

    Purpose: The goal of this work is the optimization of sintering process of the ceramic preforms based on Si3N4 and Al2O3-Ti(C,N) materials. The influence of pore forming additives on porosity, microstructures and compressive strength are investigated. The aim of this study is to obtain the nitrides and carbides base preforms material for the infiltration process of molten aluminium alloys.Design/methodology/approach: The method of obtaining the silicon nitride and oxide-carbonitride porous pr...

  11. Nitriding and Nitrocarburizing; Current Status and Future Challenges

    DEFF Research Database (Denmark)

    Somers, Marcel A. J.

    in a compound layer consisting of iron (carbo-)nitrides and a diffusion zone, consisting of a dispersion of alloying element nitrides in ferrite. The compound layer provides beneficial tribological and corrosion performance, while the diffusion zone is responsible for improved fatigue performance. Furthermore......, aspects of low temperature surface hardening of stainless steels in a gaseous environment will be addressed. Here, the developed case consists of expanded austenite and/or expanded martensite, which essentially is a super saturated solid solution of nitrogen/carbon in austenite/martensite. The current...

  12. Oxygen adsorption and dissociation during the oxidation of monolayer Ti2C

    KAUST Repository

    Gan, Liyong

    2013-08-20

    Exfoliated two-dimensional early transition metal carbides and carbonitrides are usually not terminated by metal atoms but saturated by O, OH, and/or F, thus making it difficult to understand the surface structure evolution and the induced electronic modifications. To fill this gap, density functional theory and molecular dynamics simulations are performed to capture the initial stage of the oxidation process of Ti2C, a prototypical example from the recently fabricated class of two-dimensional carbides and carbonitrides. It is shown that the unsaturated Ti 3d orbitals of the pristine Ti2C surface interact strongly with the approaching O2 molecules, resulting in barrierless O2 dissociation. The diffusion of the dissociated O atoms is also found to be very facile. Molecular dynamics simulations suggest that both dissociation and diffusion are enhanced as the O2 coverage increases to 0.25 monolayer. For a coverage of less than 0.11 monolayer, the adsorbates lead to a minor modification of the electronic properties of Ti2C, while the modification is remarkable at 0.25 monolayer. The formed Ti2CO2 after O saturation is an indirect narrow gap semiconductor (0.33 eV) with high intrinsic carrier concentration at room temperature and high thermodynamic stability at intermediate temperature (e.g., 550 °C).

  13. Effects of combined silicon and molybdenum alloying on the size and evolution of microalloy precipitates in HSLA steels containing niobium and titanium

    Energy Technology Data Exchange (ETDEWEB)

    Pavlina, Erik J., E-mail: e.pavlina@deakin.edu.au [Deakin University, Institute for Frontier Materials, 75 Pigdons Road, Waurn Ponds, Victoria (Australia); Van Tyne, C.J.; Speer, J.G. [Colorado School of Mines, Advanced Steel Processing and Products Research Center, 1500 Illinois Street, Golden, CO (United States)

    2015-04-15

    The effects of combined silicon and molybdenum alloying additions on microalloy precipitate formation in austenite after single- and double-step deformations below the austenite no-recrystallization temperature were examined in high-strength low-alloy (HSLA) steels microalloyed with titanium and niobium. The precipitation sequence in austenite was evaluated following an interrupted thermomechanical processing simulation using transmission electron microscopy. Large (~ 105 nm), cuboidal titanium-rich nitride precipitates showed no evolution in size during reheating and simulated thermomechanical processing. The average size and size distribution of these precipitates were also not affected by the combined silicon and molybdenum additions or by deformation. Relatively fine (< 20 nm), irregular-shaped niobium-rich carbonitride precipitates formed in austenite during isothermal holding at 1173 K. Based upon analysis that incorporated precipitate growth and coarsening models, the combined silicon and molybdenum additions were considered to increase the diffusivity of niobium in austenite by over 30% and result in coarser precipitates at 1173 K compared to the lower alloyed steel. Deformation decreased the size of the niobium-rich carbonitride precipitates that formed in austenite. - Highlights: • We examine combined Si and Mo additions on microalloy precipitation in austenite. • Precipitate size tends to decrease with increasing deformation steps. • Combined Si and Mo alloying additions increase the diffusivity of Nb in austenite.

  14. Neodymium-rich precipitate phases in a high-chromium ferritic/martensitic steel

    Science.gov (United States)

    Shen, Yinzhong; Zhou, Xiaoling; Shang, Zhongxia

    2016-05-01

    Neodymium being considered as nitride forming element has been used in a design of advanced ferritic/martensitic (FM) steels for fossil fired power plants at service temperatures of 630 °C to 650 °C to effectively improve the creep strength of the steels. To fully understand the characteristics of neodymium precipitates in high-Cr FM steels, precipitate phases in an 11Cr FM steel with 0.03 wt% addition of Nd have been investigated by transmission electron microscopy. Three neodymium phases with a face-centered cubic crystal structure and different composition were observed in the steel. They consisted of neodymium carbonitride with an average lattice parameter of 1.0836 nm, Nd-rich carbonitride mainly containing Mn, and Nd-rich MN nitride mainly containing Mn and Co. Other three Nd-rich and Nd-containing phases, which appear to be Nd-Co-Cr/Nd-rich intermetallic compounds and Cr-Fe-rich nitride containing Nd, were also detected in the steel. Nd-relevant precipitates were found to be minor phases compared with M23C6 and Nb/V/Ta-rich MX phases in the steel. The content of Nd in other precipitate phases was very low. Most of added Nd is considered to be present as solid solution in the matrix of the steel.

  15. Influence of non-metallic second phases on fatigue behaviour of high strength steel components; Efecto de segundas fases no metalicas sobre el comportamiento a fatiga de componentes de acero con elevadas solicitaciones

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, L.; Elvira, R.; Garcia de Andoin, A.; Pizarro, R.; Bertrand, C.

    2005-07-01

    To assess the real effect of the inclusion type on fatigue life of ultra clean high strength steels mechanical components made of 100Cr6 steel were fatigue tested and fracture surfaces analysed to determine the origin of fatigue cracks.Two heats proceedings from different steelmaking routes were taken for the tests. The material were forged into ring shape components which were fatigue tested under compression-compression loads. Failures were analysed by SFEM (Scanning field Emission Microscopy), proving that most of failures at high loads were originated by manganese sulphides of small size (10-70 micros), while less than 40% of all fatigue cracks due to inclusions were caused by titanium carbonitrides and hard oxides. It has been demonstrated that once number and size of hard inclusions have been reduced, the hazardous effect of oxides and carbonitrides on the fatigue life decreases also. However, softer inclusions as manganese sulphides, currently considered as less hazardous, play a more relevant role as direct cause of fatigue failure and they should be taken into account in a deeper way in order to balance both machinability and fatigue life requirements in high strength steel components. (Author) 11 refs.

  16. APFIM characterization of a high phosphorus Russian RPV weld

    Science.gov (United States)

    Miller, M. K.; Russell, K. F.

    1996-03-01

    A microstructural characterization of a high phosphorus (0.035 wt% P) weld from the pressure vessel of a Russian VVER nuclear reactor has been performed. The microstructure of these steels consists of intragranular and intergranular vanadium carbonitride precipitates of average composition 51.3 ± 0.9 at% V, 18.8 ± 0.7 at% C, 22.1 ± 0.7 at% N, 4.9 ± 0.4 at% Cr, 2.4 ± 0.3 at% Mo, 0.36 ± 0.05 at% Fe, 0.07 ± 0.05 at% B and 0.03 ± 0.03 at% P. The lath and grain boundaries were also coated with a thin film of molybdenum carbonitride precipitates. The phosphorus coverage at the boundaries in the unirradiated material was ˜ 13% of a monolayer in agreement with predictions from the McLean model of equilibrium segregation. After neutron irradiation to a fluence of 1.15 × 10 20 n cm -2, the phosphorus coverage had increased significantly to up to ˜ 60% of a monolayer. This result indicates that neutron irradiation significantly enhanced the phosphorus segregation process. Phosphorus and copper clusters were also observed in the matrix of the neutron-irradiated material.

  17. Estudio y modelización de la influencia de las partículas de segunda fase sobre el crecimiento de grano austenítico en un acero microaleado con niobio

    Directory of Open Access Journals (Sweden)

    San Martín, D.

    2006-04-01

    Full Text Available The austenite grain growth occurred during continuous heating in a niobium microalloyed steel has been investigated in this work. The effect of temperature and heating rate on the grain size is studied. The free grain coarsening temperature is determined as a function of the heating rate. It is found that unpinning by precipitates occurs around 40-70K below the temperature of complete dissolution of carbonitrides. Furthermore, a new model has been proposed to describe the austenite grain coarsening under the influence of niobium carbonitrides during continuous heating at different rates.

    En este trabajo se ha estudiado el crecimiento de grano austenítico producido durante el calentamiento continuo de un acero CMnNb. Se ha analizado la influencia de la velocidad de calentamiento sobre dicho proceso y se ha calculado la temperatura de crecimiento libre del grano austenítico, a la cual desaparece la influencia del pinzamiento provocado por los precipitados de carbonitruro de niobio. Finalmente, se propone un modelo del proceso de crecimiento de grano austenítico bajo pinzamiento que permite predecir el tamaño de grano austenítico (TGA que se alcanza en el acero a una determinada temperatura por calentamiento continuo a velocidad conocida.

  18. Microstructure and Properties of Low Temperature Composite Chromized Layer on H13 Tool Steel

    Institute of Scientific and Technical Information of China (English)

    Cuilan WU; Chengping LUO; Ganfeng ZOU

    2005-01-01

    Low temperature composite chromizing is a process composed of a plain ion-carbonitriding or ion-nitriding at 550~580℃, followed by a low-temperature chromizing in a salt-bath of 590℃. The microstructure and properties of the low temperature composite chromized layer on H13 tool steel were investigated using metallography,X-ray diffraction, microanalysis, hardness and wear tests. It was found that this low temperature process was thermodynamically and kinetically possible, and the composite chromized layer on H13 steel, with a thickness of 3~6μm,consisted of three sub-layers (bands), viz. the outer Cr-rich one, the intermediate (black) one, and the inner, original white layer. After chromizing, the former diffusion layer was thickened. The results of X-ray diffraction showed that the composite chromized layer contained such nitrides and carbides of chromium as CrN, Cr2N, (Cr, Fe)23C6, and (Cr, Fe)7C3, as well as plain α-(Fe, Cr). A high surface microhardness of 1450~1550 HV0.025, which is much higher than that obtained by the conventional ion carbonitriding and ion nitriding, was obtained. In addition, an excellent wear resistance was gained on the composite chromized layer.

  19. Plasmachemical Synthesis of Nanopowders in the System Ti(O,C,N for Material Structure Modification

    Directory of Open Access Journals (Sweden)

    Michael Filkov

    2016-01-01

    Full Text Available Refractory nanoparticles are finding broad application in manufacturing of materials with enhanced physical properties. Production of carbide, nitride, and carbonitride nanopowders in high volumes is possible in the multijet plasmachemical reactor, where temperature and velocity distributions in reaction zone can be controlled by plasma jet collision angle and mixing chamber geometry. A chemical reactor with three Direct Current (DC arc plasma jets intersecting at one point was applied for titanium carbonitride synthesis from titanium dioxide, propane-butane mixture, and nitrogen. The influence of process operational parameters on the product chemical and phase composition was investigated. Mixing conditions in the plasma jet collision zone, particles residence time, and temperatures were evaluated with the help of Computational Fluid Dynamics (CFD simulations. The synthesized nanoparticles have predominantly cubic shape and dimensions in the range 10–200 nm. Phase compositions were represented by oxycarbonitride phases. The amount of free (not chemically bonded carbon in the product varied in the range 3–12% mass, depending on synthesis conditions.

  20. Boundary and sub-boundary hardening in high-Cr ferritic steels during long-term creep at 650 C

    Energy Technology Data Exchange (ETDEWEB)

    Abe, F. [National Institute for Materials Science (NIMS) (Japan)

    2008-07-01

    The sub-boundary hardening is shown to be the most important strengthening mechanism in creep of the 9% Cr steel base metal and welded joints. The addition of boron reduces the coarsening rate of M{sub 23}C{sub 6} carbides along boundaries near prior austenite grain boundaries during creep, enhancing the sub-boundary hardening. This improves long-term creep strength. The enhancement of boundary and subboundary hardening by fine distribution of precipitates along boundaries is significantly reduced in fine-grained region of Ac{sub 3} HAZ simulated specimens of conventional steels P92 and P122. In NIMS 9% Cr boron steel welded joints, the grain size and distribution of carbonitrides are substantially the same between the HAZ and base metal, where fine carbonitrides are distributed along the lath and block boundaries as well as along prior austenite grain boundaries. This is essential for the suppression of Type IV fracture in NIMS 9% Cr boron steel welded joints. (orig.)

  1. Evolution of Ti-Based Nonmetallic Inclusions During Solution Treatment of Maraging 250 Steel: Thermodynamic Calculations and Experimental Verification

    Science.gov (United States)

    Shmulevitsh, Mati; Pinkas, Malki; Weizman, Amir; Frage, Nachum

    2011-06-01

    The evolution of Ti-based nonmetallic inclusions in Maraging 250 steel, namely Ti(CxN1-x) and Ti4C2S2, was investigated experimentally. Their stability in austenite also was analyzed by a thermodynamic analysis of the Fe-Ni-Ti-C-N-S system. It was established that the total concentration of the inclusions decreases from 0.024 pct to 0.008 pct after treatment at 1453 K (1180 °C) for 3 hours. The Ti4C2S2 inclusions completely dissolve in austenite at 1523 K (1250 °C) during 1 hour of treatment. The composition of the carbonitride inclusions is shifted toward higher TiN contents when they dissolve in austenite. Nitrogen-enriched titanium carbonitride inclusions are stable in austenite and their fraction may be reduced only by controlling nitrogen content in the steel. The experimental observations are in good agreement with the results of the thermodynamic analysis.

  2. Nitrogen Contents on Tribological Properties of Magnetron Sputtered SiCN Coatings

    Institute of Scientific and Technical Information of China (English)

    TIETUN SUN; Y.Q. FU; J. WEI; H. J. DU

    2004-01-01

    Silicon carbonitride (SiCN) coatings were deposited on silicon and tungsten carbide substrates by co-sputtering silicon and carbon in argon and nitrogen mixture atmosphere using magnetron-sputtering system. The effect of the N2concentration, RF substrate bias voltage and target current on film deposition rate, roughness, adhesion, mechanical and tribological properties of coatings were investigated. The deposition rate was found to increase with the increasing nitrogen concentration. X-ray photoelectron spectroscopy analysis showed that high nitrogen concentration in the nitrogen-argon gas mixture enhanced the incorporation of C and N but reduced the incorporation of Si. SiCN coatings have good tribological properties at a N2 concentration of approximately 60%.

  3. Cation intercalation and high volumetric capacitance of two-dimensional titanium carbide.

    Science.gov (United States)

    Lukatskaya, Maria R; Mashtalir, Olha; Ren, Chang E; Dall'Agnese, Yohan; Rozier, Patrick; Taberna, Pierre Louis; Naguib, Michael; Simon, Patrice; Barsoum, Michel W; Gogotsi, Yury

    2013-09-27

    The intercalation of ions into layered compounds has long been exploited in energy storage devices such as batteries and electrochemical capacitors. However, few host materials are known for ions much larger than lithium. We demonstrate the spontaneous intercalation of cations from aqueous salt solutions between two-dimensional (2D) Ti3C2 MXene layers. MXenes combine 2D conductive carbide layers with a hydrophilic, primarily hydroxyl-terminated surface. A variety of cations, including Na(+), K(+), NH4(+), Mg(2+), and Al(3+), can also be intercalated electrochemically, offering capacitance in excess of 300 farads per cubic centimeter (much higher than that of porous carbons). This study provides a basis for exploring a large family of 2D carbides and carbonitrides in electrochemical energy storage applications using single- and multivalent ions.

  4. Investigation of the chemical interaction in the TiC-Si3N4 system

    Directory of Open Access Journals (Sweden)

    Izhevskyi V.A.

    1999-01-01

    Full Text Available Chemical interaction in the TiCSi3N4 system was investigated. Thermodynamic calculations and kinetic analysis were carried out for a number of powder mixtures with various TiC:Si3N4 molar ratios in the temperature range 1300-1750 °C. Stability regions of the TiC-Si3N4 composites were defined. It was shown that the main reaction products are silicon carbide and titanium carbonitride. The overall chemical interaction is described in terms of chemical reaction between titanium carbide and silicon nitride, and the diffusion of carbon and nitrogen through the coherent reaction products layer after completion of the initial direct interaction of the components.

  5. Effect of Heat Treatment on the Microstructure and Hardness of 17Cr-0.17N-0.43C-1.7 Mo Martensitic Stainless Steel

    Science.gov (United States)

    Krishna, S. Chenna; Gangwar, Narendra Kumar; Jha, Abhay K.; Pant, Bhanu; George, Koshy M.

    2015-04-01

    The microstructure and hardness of a nitrogen-containing martensitic stainless steel were investigated as a function of heat treatment using optical microscopy, electron microscopy, amount of retained austenite, and hardness measurement. The steel was subjected to three heat treatments: hardening, cryo treatment, and tempering. The hardness of the steel in different heat-treated conditions ranged within 446-620 HV. The constituents of microstructure in hardened condition were lath martensite, retained austenite, M23C6, M7C3, MC carbides, and M(C,N) carbonitrides. Upon tempering at 500 °C, two new phases have precipitated: fine spherical Mo2C carbides and needle-shaped Cr2N particles.

  6. XPS, XRD and laser Raman analysis of surface modified of 6150 steel substrates for the deposition of thick and adherent diamond-like carbon coatings

    Energy Technology Data Exchange (ETDEWEB)

    Silva, William de Melo; Carneiro, Jose Rubens Goncalves, E-mail: williammelosilva@gmail.com [Pontificia Universidade Catolica de Minas Gerais (PUC-MG), Belo Horizonte (Brazil). Dept. de Engenharia Mecanica; Trava-Airoldi, Vladimir Jesus [Associate Laboratory of Sensors and Materials, National Institute for Space Research, Sao Jose dos Campos, SP (Brazil)

    2013-11-01

    Although the 6150 steel has an excellent fatigue and impact resistance, it is unsuitable to operate it when the corrosion is a limited factor. We propose here a sequence of steel pre-treatment by carburizing, carbonitriding and nitriding in order to improve the poor adhesion between Diamond Like-Carbon coatings on steel. This sequence is our attempt to reduce the difference between the coefficients of thermal expansion of steel and DLC through the graded interface. This work demonstrates the quantitative analysis of the molecules present at surface using X-ray photoelectron spectroscopy. The crystallographic structures are investigated by X-ray diffraction which shows the formation of carbides and nitride phases. Raman spectroscopy reveals the carburizing surface characteristics where DLC coating is nucleated and grown at the substrate. At the end of the analysis it is possible to verify which molecules and phases are formed on the steel surface interface after each step of pre-treatment. (author)

  7. Specific detection of proteins using Nanomechanical resonators

    DEFF Research Database (Denmark)

    Fischer, Lee MacKenzie; Wright, V.A.; Guthy, C.;

    2008-01-01

    of probes onto their surfaces in order to enable the specificity of the detection. Such nanoresonator-based specific detection of proteins is here reported using streptavidin as target system, and immobilized biotin as probe. Nanomechanical resonators resistant to stiction were first realized from silicon...... carbonitride using a novel fabrication method. Vapor-phase deposition of mercaptopropyl trimethoxysilane was performed, and an added mass of 2.22 +/- 0.07 fg/mu m(2) was measured. This linker molecule was used to attach biotin onto the devices, enabling the specific detection of streptavidin. A mass of 3.6 fg....../mu m(2) was attributed to the added streptavidin, corresponding to one molecule per 27 nm(2). The specificity of this recognition was confirmed by exposing the devices to a solution of streptavidin that was already saturated with biotin. An additional negative control was also performed by also...

  8. Microstructural and weldability evaluation of 310TaN

    Energy Technology Data Exchange (ETDEWEB)

    Lundin, C.D.; Qiao, C.Y.P. [Univ. of Tennessee, Knoxville, TN (United States); Swindeman, R.W. [Oak Ridge National Lab., TN (United States)

    1996-08-01

    Excellent weldability and good microstructural stability of 310TaN, in terms of the formation and growth of secondary phases at elevated temperature, was revealed in this investigation. The interganular stress corrosion resistance of 310TaN is superior to modified 800H and 310HCbN evaluated previously due to the fact that TaC, TaN and Ta(C,N) particles are more stable compared to Nb-rich or Ti-rich carbides, nitrides and carbonitrides presented in the other advanced alloys. Using resistance spot welding technique for which extremely fast cooling is a characteristic, it was found that a very minor amount of gain boundary liquation takes place during welding thermal cycling. The limited grain boundary liquation is of the eutectic type i.e., a low tendency to weld HAZ hot cracking.

  9. Method of nitriding, carburizing, or oxidizing refractory metal articles using microwaves

    Science.gov (United States)

    Holcombe, Cressie E.; Dykes, Norman L.; Tiegs, Terry N.

    1992-01-01

    A method of nitriding an article of refractory-nitride-forming metal or metalloids. A consolidated metal or metalloid article is placed inside a microwave oven and nitrogen containing gas is introduced into the microwave oven. The metal or metalloid article is heated to a temperature sufficient to react the metal or metalloid with the nitrogen by applying a microwave energy within the microwave oven. The metal or metalloid article is maintained at that temperature for a period of time sufficient to convert the article of metal or metalloid to an article of refractory nitride. in addition, a method of applying a coating, such as a coating of an oxide, a carbide, or a carbo-nitride, to an article of metal or metalloid by microwave heating.

  10. XPS, XRD and laser raman analysis of surface modified of 6150 steel substrates for the deposition of thick and adherent diamond-like carbon coatings

    Directory of Open Access Journals (Sweden)

    William de Melo Silva

    2013-06-01

    Full Text Available Although the 6150 steel has an excellent fatigue and impact resistance, it is unsuitable to operate it when the corrosion is a limited factor. We propose here a sequence of steel pre-treatment by carburizing, carbonitriding and nitriding in order to improve the poor adhesion between Diamond Like-Carbon coatings on steel. This sequence is our attempt to reduce the difference between the coefficients of thermal expansion of steel and DLC through the graded interface. This work demonstrates the quantitative analysis of the molecules present at surface using X-ray photoelectron spectroscopy. The crystallographic structures are investigated by X-ray diffraction which shows the formation of carbides and nitride phases. Raman spectroscopy reveals the carburizing surface characteristics where DLC coating is nucleated and grown at the substrate. At the end of the analysis it is possible to verify which molecules and phases are formed on the steel surface interface after each step of pre-treatment.

  11. Evolution of dislocation density, size of subgrains and MX-type precipitates in a P91 steel during creep and during thermal ageing at 600 deg. C for more than 100,000 h

    Energy Technology Data Exchange (ETDEWEB)

    Panait, Clara Gabriela, E-mail: clara.panait@ensmp.fr [MINES ParisTech, Centre des Materiaux, CNRS UMR 7633, BP 87 91003 Evry Cedex (France); Vallourec Research Aulnoye, Route de Leval, B.P. 20149, 59620 Aulnoye-Aymeries (France); Zielinska-Lipiec, Anna; Koziel, Tomasz; Czyrska-Filemonowicz, Aleksandra [AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Krakow (Poland); Gourgues-Lorenzon, Anne-Francoise [MINES ParisTech, Centre des Materiaux, CNRS UMR 7633, BP 87 91003 Evry Cedex (France); Bendick, Walter [Salzgitter Mannesmann Forschung GmbH, Ehinger Strasse 200, D-47259 Duisburg (Germany)

    2010-06-25

    There are rather few quantitative data on the microstructure of the 9-12%Cr heat resistant steels after long-term creep. This paper presents results of the quantitative measurement of the size of MX precipitates, subgrain size and dislocation density in a P91 steel that had been creep tested for 113,431 h at 600 deg. C. The same measurements were conducted in the same P91 steel in the as received conditions. Transmission electron microscopy investigations were conducted using thin foils and revealed a decrease in dislocation density and an increase in subgrain size after creep exposure. MX carbonitrides are very stable during thermal and creep exposure of P91 steel at 600 deg. C up to 113,431 h. Electron backscatter diffraction (EBSD) investigations also revealed a significant change in the substructure of the steel after creep exposure.

  12. Effect of carbon on interstitial ordering and magnetic properties of ε-Fe2(N,C)1-z

    DEFF Research Database (Denmark)

    Brink, Bastian; Ståhl, Kenny; Christiansen, Thomas Lundin;

    2017-01-01

    Hexagonal ε-iron nitride and ε-iron carbonitride phases are formed on nitriding and nitrocarburizing ofiron and steel surfaces and can exist in broad compositional ranges. Long-range nitrogen ordering andmagnetic properties for ε-iron nitrides and their dependence on composition have been the focus...... samplemagnetometry. Neutron diffraction patterns showed 001 and 301 superstructure reflections, confirminga previously proposed structural model in space group P31m (compared to P6322 for the pure nitrides).On partial substitution of nitrogen by carbon in ε-iron nitride the Curie temperature......, the saturationmagnetization and the hyperfine fields of the iron atoms are increased, while isomer shifts are decreased.The effects on the a and c lattice parameters indicate a change in interstitial ordering, which is related tomore favorable interactions between a nitrogen and carbon atom than among nitrogen atoms...

  13. Effect of zirconium addition on the austenite grain coarsening behavior and mechanical properties of 900 Mpa low carbon bainite steel

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The ultra-free bainitic microstructure of a 900 MPa low carbon bainitic Cu-Ni-Mo-B steel was obtained by a newly developed relaxation precipitation control (RPC) phase transformation processing.In a pan-cake like prior-anstenite grain,the microstructure consisted of lath bainite,a little of abnormal granular bainite,and acicular ferrite.The effect of zirconium carbonitrides on the austenite grain coarsening behavior was studied by transmission electron microscopy (TEM).The results show that,the lath is narrower with increasing cooling rate.The ratio of all kinds of bainitic microstructure is proper with the intermediate cooling rate;and Zr-containing precipitates distribute uniformly,which restrains austenite grain growing in heat-affected welding zone.

  14. Nitrocarburizing treatments using flowing afterglow processes

    Science.gov (United States)

    Jaoul, C.; Belmonte, T.; Czerwiec, T.; David, N.

    2006-09-01

    Nitrocarburizing of pure iron samples is achieved at 853 K and is easily controlled by introducing C 3H 8 in the afterglow of a flowing microwave Ar-N 2-H 2 plasma. The carbon uptake in the solid is actually possible with methane but strongly limited. The use of propane enhances the carbon flux and the ɛ/α configuration is synthesized for the first time by this kind of process. For this stack, diffusion paths in the ternary system determined from chemical analyses by secondary neutral mass spectrometry reproduce satisfactorily X-ray diffraction results which only reveal, as optical micrographs, ɛ and α phases. Propane offers an accurate control of the nitrocarburizing conditions. As an example, a modulation of N and C contents in iron could be achieved to create new carbonitride multilayers.

  15. Nitrocarburizing treatments using flowing afterglow processes

    Energy Technology Data Exchange (ETDEWEB)

    Jaoul, C. [Laboratoire de Science et Genie des Surfaces (UMR CNRS 7570), Ecole des Mines, Parc de Saurupt, 54042 Nancy Cedex (France); Belmonte, T. [Laboratoire de Science et Genie des Surfaces (UMR CNRS 7570), Ecole des Mines, Parc de Saurupt, 54042 Nancy Cedex (France)]. E-mail: Thierry.Belmonte@mines.inpl-nancy.fr; Czerwiec, T. [Laboratoire de Science et Genie des Surfaces (UMR CNRS 7570), Ecole des Mines, Parc de Saurupt, 54042 Nancy Cedex (France); David, N. [Laboratoire de Chimie du Solide Mineral, Universite Henri Poincare Nancy-I, Vandoeuvre-Les-Nancy (France)

    2006-09-30

    Nitrocarburizing of pure iron samples is achieved at 853 K and is easily controlled by introducing C{sub 3}H{sub 8} in the afterglow of a flowing microwave Ar-N{sub 2}-H{sub 2} plasma. The carbon uptake in the solid is actually possible with methane but strongly limited. The use of propane enhances the carbon flux and the {epsilon}/{alpha} configuration is synthesized for the first time by this kind of process. For this stack, diffusion paths in the ternary system determined from chemical analyses by secondary neutral mass spectrometry reproduce satisfactorily X-ray diffraction results which only reveal, as optical micrographs, {epsilon} and {alpha} phases. Propane offers an accurate control of the nitrocarburizing conditions. As an example, a modulation of N and C contents in iron could be achieved to create new carbonitride multilayers.

  16. Properties of amorphous SiBNC-ceramic fibres

    Energy Technology Data Exchange (ETDEWEB)

    Baldus, H.-P. [Bayer AG, Leverkusen (Germany); Passing, G. [Bayer AG, Leverkusen (Germany); Scholz, H. [Fraunhofer-Institut fuer Silicatforschung (ISC), Wuerzburg (Germany); Sporn, D. [Fraunhofer-Institut fuer Silicatforschung (ISC), Wuerzburg (Germany); Jansen, M. [Bonn Univ. (Germany). Inst. fuer Anorganische Chemie; Goering, J. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Koeln (Germany). Inst. fuer Werkstoff-Forschung

    1997-06-01

    A new amorphous ceramic material consisting of Si, N, C, and B can be synthesized by pyrolysis of a preceramic polyborosilazane (PBS-Me) made of the ``single source`` precursor Cl{sub 3}Si-NH-BCl{sub 2} (TADB). Novel ceramic fibers consisting of borosilicon carbonitride (SiBN{sub 3}C) can be synthesized from this polymer by using a simple melt spinning process, followed by an intermediate curing step and successive pyrolysis of the obtained infusible green fibers. In the present paper we report on the preparation of the ceramic fibres, as well as their thermal stability, and their mechanical behaviour, including high temperature creep data. The reported mechanical data will be correlated to the microstructure of the fibers. (orig.)

  17. Sintering by SPS of ultrafine TiC{sub x}N{sub 1}-x powders obtained using mechanically induced self sustaining reaction.; Sinterizacion por SPS de polvos ultrafinos de TiC{sub x}N{sub 1}-x obtenidos mediante reacciones de autopropagacion inducidas mecanicamente

    Energy Technology Data Exchange (ETDEWEB)

    Borrell, A.; Fernandez, A.; Torrecillas, R.; Cordoba, J. M.; Aviles, M. A.; Gotor, F. J.

    2010-07-01

    In this work high purity and nanometer character titanium carbonitride TiC{sub x}N{sub 1}-x powders were obtained by mechanically induced self sustaining reaction (MSR) in a high-energy planetary ball mill, from a mixture of titanium with graphite or carbon nano fiber (CNFs) in a nitrogen atmosphere. A promising method for developing these materials is the coupling of the MSR with SPS sintering technique. The product is sintered at 1400 degree centigrade and 1700 degree centigrade, obtaining a completely dense monolithic ceramic (>99% t.d). In this work, the influence of SPS treatment and carbon precursor on material microstructures was studied and the main mechanical properties of the end material were evaluated. (Author) 21 refs.

  18. Thermal analysis study of polymer-to-ceramic conversion of organosilicon precursors

    Directory of Open Access Journals (Sweden)

    Galusek D.

    2008-01-01

    Full Text Available The organosilicon precursors attract significant attention as substances, which upon heating in inert or reactive atmosphere convert directly to oxide or non-oxide ceramics, like nitrides, carbides, carbonitrides, boroncarbonitrides, oxycarbides, alons, etc. In characterisation, and in study of conversion of these polymers to ceramics thermal analysis plays an important role. The degree of cross-linking of the polymer vital for achievement of high ceramic yield is estimated with the use of thermal mechanical analysis (TMA. Decomposition of polymers and their conversion to ceramics is studied by the combination of differential thermal analysis (DTA, differential scanning calorimetry (DSC thermogravimetry(TG, and mass spectrometry (MS. The use of these methods in study of the polymer-to-ceramic conversion is illustrated by case studies of a commercially available poly(allylcarbosilane as the precursor of SiC, and a poly(hydridomethylsilazane as the precursor of SiCN.

  19. Porous nuclear fuel element for high-temperature gas-cooled nuclear reactors

    Science.gov (United States)

    Youchison, Dennis L.; Williams, Brian E.; Benander, Robert E.

    2011-03-01

    Porous nuclear fuel elements for use in advanced high temperature gas-cooled nuclear reactors (HTGR's), and to processes for fabricating them. Advanced uranium bi-carbide, uranium tri-carbide and uranium carbonitride nuclear fuels can be used. These fuels have high melting temperatures, high thermal conductivity, and high resistance to erosion by hot hydrogen gas. Tri-carbide fuels, such as (U,Zr,Nb)C, can be fabricated using chemical vapor infiltration (CVI) to simultaneously deposit each of the three separate carbides, e.g., UC, ZrC, and NbC in a single CVI step. By using CVI, the nuclear fuel may be deposited inside of a highly porous skeletal structure made of, for example, reticulated vitreous carbon foam.

  20. Porous nuclear fuel element with internal skeleton for high-temperature gas-cooled nuclear reactors

    Science.gov (United States)

    Youchison, Dennis L.; Williams, Brian E.; Benander, Robert E.

    2013-09-03

    Porous nuclear fuel elements for use in advanced high temperature gas-cooled nuclear reactors (HTGR's), and to processes for fabricating them. Advanced uranium bi-carbide, uranium tri-carbide and uranium carbonitride nuclear fuels can be used. These fuels have high melting temperatures, high thermal conductivity, and high resistance to erosion by hot hydrogen gas. Tri-carbide fuels, such as (U,Zr,Nb)C, can be fabricated using chemical vapor infiltration (CVI) to simultaneously deposit each of the three separate carbides, e.g., UC, ZrC, and NbC in a single CVI step. By using CVI, the nuclear fuel may be deposited inside of a highly porous skeletal structure made of, for example, reticulated vitreous carbon foam.

  1. 镀合金

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    [ 篇名 ] Influence of WC addition an microstructures of laser-melted Ni-based alloy coating, [ 篇名 ] Microstructure and dry sliding wear behavior of laser clad Ni-based alloy coating with the addition of SiC, [ 篇名 ] Preparation of Advanced Lithium Secondary Batteries with Tin-Iron Alloy Plating Anodes and Their Charge-Discharge Behaviors, [篇名] SnAg-alloy coating for connectors and soldering applications, [篇名] Structure and properties of wear-resistant titanium carbonitride-based coatings, [篇名] The analysis of the deposition mechanism of Zn/Ni alloy plating using an EQCM, [ 篇名 ]The effect of heat treatment on wear resistance of parts having hard-alloy coating.

  2. New Developments in Thermo-Chemical Diffusion Processes

    Institute of Scientific and Technical Information of China (English)

    Bernd Edenhofer

    2004-01-01

    Thermo-chemical diffusion processes like carburising, nitriding and boronizing play an important part in modern manufacturing technologies. They exist in many varieties depending on the type of diffusing element used and the respective process procedure. The most important industrial heat treatment process is case-hardening, which consists of thermochemical diffusion process carburising or its variation carbonitriding, followed by a subsequent quench. The latest developments of using different gaseous carburising agents and increasing the carburising temperature are one main area of this paper. The other area is the evolvement of nitriding and especially the ferritic nitrocarburising process by improved process control and newly developed process variations using carbon, nitrogen and oxygen as diffusing elements in various process steps. Also boronizing and special thermo-chemical processes for stainless steels are discussed.

  3. Vibrational and mechanical properties of single layer MXene structures: a first-principles investigation

    Science.gov (United States)

    Yorulmaz, Uğur; Özden, Ayberk; Perkgöz, Nihan K.; Ay, Feridun; Sevik, Cem

    2016-08-01

    MXenes, carbides, nitrides and carbonitrides of early transition metals are the new members of two dimensional materials family given with a formula of {{{M}}}n+1 X n . Recent advances in chemical exfoliation and CVD growth of these crystals together with their promising performance in electrochemical energy storage systems have triggered the interest in these two dimensional structures. In this work, we employ first principles calculations for n = 1 structures of Sc, Ti, Zr, Mo and Hf pristine MXenes and their fully surface terminated forms with F and O. We systematically investigated the dynamical and mechanical stability of both pristine and fully terminated MXene structures to determine the possible MXene candidates for experimental realization. In conjunction with an extensive stability analysis, we report Raman and infrared active mode frequencies for the first time, providing indispensable information for the experimental elaboration of MXene field. After determining dynamically stable MXenes, we provide their phonon dispersion relations, electronic and mechanical properties.

  4. Effect of V and V-N Microalloying on Deformation-Induced Ferrite Transformation in Low Carbon Steels

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Deformation-induced ferrite transformation (DIFT) has been proved to be an effective approach to refine ferrite grains. This paper shows that the ferrite grains can further be refined through combination of DIFT and V or VN microalloying. Vanadium dissolved in γ matrix restrains DIFT. During deformation, vanadium carbonitrides rapidly precipitate due to strain-induced precipitation, which causes decrease in vanadium dissolved in matrix and indirectly accelerates DIFT. Under heavy deformation, deformation induced ferrite (DIF) grains in V microalloyed steel were finer than those in V free steel. The more V added to steel, the finer DIF grains obtained. Moreover, the addition of N to V microalloyed steels can remarkably accelerate precipitation of V,and then promote DIFT. However, DIF grains in V-N microalloyed steel easily coarsen.

  5. Nitrogen Contents on Tribological Properties of Magnetron Sputtered SiCN Coatings

    Institute of Scientific and Technical Information of China (English)

    TIETUNSUN; Y.Q.FU; J.WEI; H.J.DU

    2004-01-01

    Silicon carbonitride (SiCN) coatings were deposited on silicon and tungsten carbide substrates by co-sputtering silicon and carbon in argon and nitrogen mixture atmosphere using magnetron-sputtering system. The effect of the N2 concentration, RF substrate bias voltage and target current on film deposition rate, roughness, adhesion, mechanical and tribological properties of coatings were investigated. The deposition rate was found to increase with the increasing nitrogen concentration. X-ray photoelectron spectroscopy analysis showed that high nitrogen concentration in the nitrogen-argon gas mixture enhanced the incorporation of C and N but reduced the incorporation of Si. SiCN coatings have good tribological properties at a N2 concentration of approximately 60%.

  6. Corrosion properties of S-phase layers formed on medical grade austenitic stainless steel.

    Science.gov (United States)

    Buhagiar, Joseph; Dong, Hanshan

    2012-02-01

    The corrosion properties of S-phase surface layers formed in AISI 316LVM (ASTM F138) and High-N (ASTM F1586) medical grade austenitic stainless steels by plasma surface alloying with nitrogen (at 430°C), carbon (at 500°C) and both carbon and nitrogen (at 430°C) has been investigated. The corrosion behaviour of the S-phase layers in Ringer's solutions was evaluated using potentiodynamic and immersion corrosion tests. The corrosion damage was evaluated using microscopy, hardness testing, inductive coupled plasma mass spectroscopy and X-ray diffraction. The experimental results have demonstrated that low-temperature nitriding, carburising and carbonitriding can improve the localised corrosion resistance of both industrial and medical grade austenitic stainless steels as long as the threshold sensitisation temperature is not reached. Carburising at 500°C has proved to be the best hardening treatment with the least effect on the corrosion resistance of the parent alloy.

  7. Production and Machining of Thin Wall Gray and Ductile Cast Iron

    Energy Technology Data Exchange (ETDEWEB)

    Fleischman, E.H. (INEEL POC); Li, H.; Griffin, R.; Bates, C.E.; Eleftheriou, E.

    2000-11-03

    The University of Alabama at Birmingham, in cooperation with the American Foundry Society, companies across North America, with support from the U.S. Department of Energy, is conducting a project to develop an understanding of the factors that control the machinability of cast gray and ductile iron. Differences of as much as 500% have been found in machinability have been observed at the same strength. The most machinable irons were those with a high cell counts and few carbonitride inclusions. Additions of tin and copper can be added to both gray and ductile iron to stabilize the pearlite, but excessive additions (above those required to produce the desired pearlite content) degrade the machinability.

  8. Radial crushing strength, microhardness and microstructure of molybdenum alloyed sintered steels

    Energy Technology Data Exchange (ETDEWEB)

    Candela, N.; Plaza, R.; Gordo, E.; Torralba, J.M. [Dept. de Ciencia de Materiales e Ing. Metalurgica, Univ. Carlos III de Madrid, Leganes (Spain); Rosso, M. [Materials Science and Chemical Eng. Dept., Politecnico di Torino (Italy)

    2001-07-01

    Prealloyed iron based powders with different Mo - Cu - Ni - C contents were uniaxially compacted at 700 MPa and sintered at 1120 C in nitrogen - hydrogen atmosphere. After sintering, all materials were thermochemically treated by plasma, gas and salt bath nitriding. The treatment's conditions were: plasma carbonitriding treatment at T=580 C in 76% N{sub 2}-19%H{sub 2}-5%CH{sub 4} atmosphere, gas nitriding treatment at T=750 C in 50% ENDO-50% NH{sub 3} atmosphere, salt bath nitriding treatment at T= 570 C during 2 h. with salt type Ternifer. Materials were evaluated through the study of radial crushing strength and a complete microstructural study was carried out using optical and scanning electron microscopy (SEM). Finally the fracture surface was analysed through SEM. (orig.)

  9. Effect of Microstructure on Low Temperature Cracking Behavior of EN82H Welds

    Energy Technology Data Exchange (ETDEWEB)

    W. J. Mills; C. M. Brown; M. G. Burke

    2001-04-30

    As-fabricated EN82H welds are susceptible to low temperature embrittlements in 54 degree C hydrogenated water. Values of J[sub]IC in water are typically 90% to 98% lower than those in air due to a fracture mechanism transition from microvoid coalescence to hydrogen-included intergranular fracture. Environmental J[sub]IC testing demonstrated that a high temperature (1093 degree C) anneal and furnace-cool alleviates the material's susceptibility to hydrogen-induced intergranular cracking. To identify metallurgical and compositional features that are responsible for the material's environment-sensitive behavior, detailed characterization of the microstructure and grain boundary chemistry for the as-fabricated and as-annealed materials was performed. Results from light optical microscopy, analytical electron microscopy, electron probe microanalysis, Auger electron spectroscopy and mechanical property characterization are used to provide insight into the observed low temperature embrittlement phenomenon. The key microstructural feature responsible for low temperature cracking in as-fabricated welds appears to be fine niobium and titanium-rich carbonitrides that cover most grain boundaries. These precipitates are effective hydrogen traps that promote hydrogen-induced intergranular cracking. Dissolution the fine carbonitrides during the 1093 degree C anneal reduces grain boundary trapping sites, which accounts for the improved fracture resistance displayed by the annealed weld. The role of strength level in promoting low temperature embrittlement is evaluated by cold-rolling the annealed weld to increase its yield strength from 280 to 640 MPa. The annealed and cold-rolled weld exhibits high toughness in 54 degree C water and shows no evidence of hydrogen-induced intergranular cracking, thereby demonstrating that strength is not a primary cause of low temperature embrittlement.

  10. Microstructural evolution of ASTM P91 after 100,000 hours exposure at 550 C and 600 C

    Energy Technology Data Exchange (ETDEWEB)

    Cipolla, L.; Venditti, D.; Di Gianfrancesco, A. [Centro Sviluppo Materiali SpA, Rome (Italy); Caminada, S. [TenarisDalmine, Dalmine (Italy); Danielsen, H.K. [Technical Univ. of Denmark, Lyngby (Denmark)

    2010-07-01

    ASTM A335 P91 samples were investigated after creep testing at 550 C and 600 C for over 10{sup 5} h. X-Ray Diffraction, Scanning and Transmission Electron Microscopy were adopted to assess the microstructural evolution of the material in terms of precipitation changes during high temperature exposure. Mean equivalent diameters and average chemical compositions of MX and M{sub 23}C{sub 6} precipitates and Laves phases were assessed through the analysis of a large number of particles. Their growth and coarsening kinetics were determined at 600 C on many samples with increasing exposure times up to 100,000 hours. Also the presence of modified Z-phase, Cr(V, Nb)N, was investigated. The high microstructural stability of Grade 91 is related to the presence of fine and distributed MX carbonitrides, always present even after very long term temperature exposure. The mean size of MX carbonitrides remains almost constant and stays below 45 nm after 10{sup 5} h at 600 C. Although MX particles exhibit a Cr enrichment with increasing ageing times, indicating that they are absorbing Cr atoms from the surrounding matrix, their transformation into Z-phase is still at a very preliminary stage: only a few hybrid MX/Z particles and a few Z-phase precipitates were identified in the most aged sample after 10{sup 5} at 600 C. Coarsening of M{sub 23}C{sub 6} occurs during thermal exposure, but their average equivalent diameter, initially of 140 nm in the as-treated material, remains below 200 nm after 10{sup 5} h at 600 C. Laves particles form at grain boundaries after a relatively short time and soon become the largest precipitates. (orig.)

  11. Influence of the carbon content on the phase composition and mechanical properties of P92-type steel

    Science.gov (United States)

    Dudko, V. A.; Fedoseeva, A. E.; Belyakov, A. N.; Kaibyshev, R. O.

    2015-11-01

    The deformation behavior and the microstructure evolution under the creep of 10Kh9V2MFBR steel (Russian analog of the P92 steel) (in wt %, Fe-8.9% Cr-0.05% Si-0.2% Mn-1.9% W-0.5% Mo-0.25% V-0.07Nb-0.08% N-0.01% B) with the standard (0.1%) and lowered (0.018%) carbon contents have been investigated. After the heat treatment, which included normalizing at 1050°C and tempering at 720-750°C, carbides M 23 C 6 and carbonitrides M(C,N) are formed in the 10Kh9V2MFBR steel, while in the 02Kh9V2MFBR steel (modified P92 steel), carbides M 23 C 6, nitrides M 2N, and carbonitrides M(C,N) as well as δ-ferrite (23%) were found. The measurements of hardness and tensile tests at room and elevated temper-atures did not reveal substantial distinctions in the short-term mechanical properties of both steels. The hardness of steels after tempering was 220 HB. At the same time, the creep characteristics of the steels were found to be different. A decrease in the carbon content leads to an increase in the long-term creep strength and creep limit at 650°C for short-term tests with time-to-fracture shorter than 103 h. The time to fracture of steels with various carbon contents is almost the same in long-term creep tests. Factor responsible for such effect of carbon on the creep strength are discussed.

  12. Improved Creep Behavior of a High Nitrogen Nb-Stabilized 15Cr-15Ni Austenitic Stainless Steel Strengthened by Multiple Nanoprecipitates

    Science.gov (United States)

    Ha, Vu The; Jung, Woo Sang; Suh, Jin Yoo

    2011-11-01

    Austenitic stainless steels are expected to be a major material for boiler tubes and steam turbines in future ultra-supercritical (USC) fossil power plants. It is of great interest to maximize the creep strength of the materials without increasing the cost. Precipitation strengthening was found to be the best and cheapest way for increasing the creep strength of such steels. This study is concerned with improving creep properties of a high nitrogen Nb-stabilized 15Cr-15Ni austenitic alloy through introducing a high number of nanosized particles into the austenitic matrix. The addition of around 4 wt pct Mn and 0.236 wt pct N into the 15Cr-15Ni-0.46Si-0.7Nb-1.25Mo-3Cu-Al-B-C matrix in combination with a special multicycled aging-quenching heat treatment resulted in the fine dispersion of abundant quantities of thermally stable (Nb,Cr,Fe)(C,N) precipitates with sizes of 10 to 20 nm. Apart from the carbonitrides, it was found that a high number of coherent copper precipitates with size 40 to 60 nm exist in the microstructure. Results of creep tests at 973 K and 1023 K (700 °C and 750 °C) showed that the creep properties of the investigated steel are superior compared to that of the commercial NF709 alloy. The improved creep properties are attributed to the improved morphology and thermal stability of the carbonitrides as well as to the presence of the coherent copper precipitates inside the austenitic matrix.

  13. Effect of precipitates on long-term creep deformation properties of P92 and P122 type advanced ferritic steels for USC power plants

    Energy Technology Data Exchange (ETDEWEB)

    Yoshizawa, M., E-mail: yoshizaw-mtr@sumitomometals.co.jp [Corporate Research and Development Laboratories, Sumitomo Metal Industries, Ltd., 1-8 Fuso-cho, Amagasaki, Hyogo 660-0891 (Japan); Igarashi, M.; Moriguchi, K. [Corporate Research and Development Laboratories, Sumitomo Metal Industries, Ltd., 1-8 Fuso-cho, Amagasaki, Hyogo 660-0891 (Japan); Iseda, A. [Tubular Products Technology Department, Sumitomo Metal Industries, Ltd., 1-8-11 Harumi, Chuo-ku, Tokyo 104-6111 (Japan); Armaki, Hassan Ghassemi; Maruyama, K. [Graduate School of Environmental Studies, Tohoku University, 6-6-02 Aobayama, Sendai 980-8579 (Japan)

    2009-06-15

    Long-term creep rupture strengths and the microstructural stability of ASME P92 and P122 pipes have been studied using creep testing at the temperatures from 550 to 700 deg. C and detailed scanning transmission electron microscopy. Creep rupture strength of P92 is found to be more stable than that of P122 at temperatures over 600 deg. C, which is mainly due to the difference in their Cr content. P122 type model steel with reduced Cr content, 9%Cr, has been prepared to explore the effect of Cr on the stability of MX and formation of Z-phase during creep deformation. MX in 9%Cr steel is found to be stable even after prolonged exposure at 650 deg. C, while Cr and Fe concentration to MX without marked coarsening has been observed in 10.5%Cr steel after aging for 10,000 h at 650 deg. C. This seems to lead to the transition of MX carbonitride into the Z-phase after aging for 23,000 h, which requires ordering in a M{sub 2}N lattice to achieve a tetragonal Z-phase to be stable. Creep deformation behavior in the transient creep region of the steels is almost same up to about 7000 h, while in the acceleration creep region the creep rate of 10.5%Cr steel becomes much faster than that of 9%Cr steel, resulting in shorter rupture life. It is obvious that the creep rupture strength degradation starts prior to the formation of Z-phase in 10.5%Cr steel. It is thus concluded that Z-phase is not a necessary factor for degradation of creep rupture strength but the instability of the fine precipitates such as Cr{sub 2}(C, N) caused by the compositions change like Cr supply to MX carbonitride is more essential.

  14. Synthesis of two-dimensional materials by selective extraction.

    Science.gov (United States)

    Naguib, Michael; Gogotsi, Yury

    2015-01-20

    CONSPECTUS: Two-dimensional (2D) materials have attracted much attention in the past decade. They offer high specific surface area, as well as electronic structure and properties that differ from their bulk counterparts due to the low dimensionality. Graphene is the best known and the most studied 2D material, but metal oxides and hydroxides (including clays), dichalcogenides, boron nitride (BN), and other materials that are one or several atoms thick are receiving increasing attention. They may deliver a combination of properties that cannot be provided by other materials. The most common synthesis approach in general is by reacting different elements or compounds to form a new compound. However, this approach does not necessarily work well for low-dimensional structures, since it favors formation of energetically preferred 3D (bulk) solids. Many 2D materials are produced by exfoliation of van der Waals solids, such as graphite or MoS2, breaking large particles into 2D layers. However, these approaches are not universal; for example, 2D transition metal carbides cannot be produced by any of them. An alternative but less studied way of material synthesis is the selective extraction process, which is based on the difference in reactivity and stability between the different components (elements or structural units) of the original material. It can be achieved using thermal, chemical, or electrochemical processes. Many 2D materials have been synthesized using selective extraction, such as graphene from SiC, transition metal oxides (TMO) from layered 3D salts, and transition metal carbides or carbonitrides (MXenes) from MAX phases. Selective extraction synthesis is critically important when the bonds between the building blocks of the material are too strong (e.g., in carbides) to be broken mechanically in order to form nanostructures. Unlike extractive metallurgy, where the extracted metal is the goal of the process, selective extraction of one or more elements from

  15. Carbon effect in the sintered highspeed steels matrix composites – HSSMC

    Directory of Open Access Journals (Sweden)

    G. Matula

    2012-11-01

    Full Text Available Goal: The goal of this monograph is development of the tool materials being the outcome of the concept of merging the surface engineering as the domain of knowledge with technology which is the powder metallurgy. The result are the fabricated materials with the gradient, high-speed steels matrix composites (HSSMC surface layers on steel substrate, combining the mutually exclusive mechanical properties like the high surface hardness and ductility of a tool.Project/methodology/approach: Modern powder forming technologies were used for fabrication of the developed tool materials, e.g., powder injection moulding, pressureless forming, and classic compacting. Sintering was carried out in the vacuum or protective atmosphere conditions, which makes direct material hardening possible from the sintering temperature. Testing of mechanical properties encompassed hardness testing, bending strength testing, and determining the abrasion wear resistance. Detailed structural examinations were carried out to determine the effect of temperature and atmosphere during sintering on type and size of the carbide- and carbonitride precipitations. Moreover, retained austenite portion was determined after hardening and tempering.Achievements: The original achievement is development of the method of the polymer-powder slurry moulding for fabrication of coatings which, because of the binding agent degradation and sintering, form the homogeneous or gradient HSSMC surface layers on the steel substrate - completed or fabricated in the same technological process. Tool materials fabricated with this method are characteristic of high ductility of the steel core and high hardness of the surface layer.Limitations of research/applications: The assumption of the powder injection moulding technique is forming of the small elements with complex shapes and, therefore, this technology is not designed for fabrication of tools with the big overall dimensions. In case of the pressureless

  16. Carbothermic synthesis of 820 μm uranium nitride kernels: Literature review, thermodynamics, analysis, and related experiments

    Energy Technology Data Exchange (ETDEWEB)

    Lindemer, T.B. [Harbach Engineering and Solutions, Dayton, OH 45458 (United States); Voit, S.L.; Silva, C.M.; Besmann, T.M. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6223 (United States); Hunt, R.D., E-mail: huntrd@ornl.gov [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6223 (United States)

    2014-05-01

    The US Department of Energy is developing a new nuclear fuel that would be less susceptible to ruptures during a loss-of-coolant accident. The fuel would consist of tristructural isotropic coated particles with uranium nitride (UN) kernels with diameters near 825 μm. This effort explores factors involved in the conversion of uranium oxide–carbon microspheres into UN kernels. An analysis of previous studies with sufficient experimental details is provided. Thermodynamic calculations were made to predict pressures of carbon monoxide and other relevant gases for several reactions that can be involved in the conversion of uranium oxides and carbides into UN. Uranium oxide–carbon microspheres were heated in a microbalance with an attached mass spectrometer to determine details of calcining and carbothermic conversion in argon, nitrogen, and vacuum. A model was derived from experiments on the vacuum conversion to uranium oxide–carbide kernels. UN-containing kernels were fabricated using this vacuum conversion as part of the overall process. Carbonitride kernels of ∼89% of theoretical density were produced along with several observations concerning the different stages of the process.

  17. Facile synthesis, microstructure and photophysical properties of core-shell nanostructured (SiCN)/BN nanocomposites

    Science.gov (United States)

    Zhang, Qian; Jia, Dechang; Yang, Zhihua; Cai, Delong; Laine, Richard M.; Li, Qian; Zhou, Yu

    2017-01-01

    Increasing structural complexity at nanoscale can permit superior control over photophysical properties in the precursor-derived semiconductors. We demonstrate here the synthesis of silicon carbonitride (SiCN)/boron nitride (BN) nanocomposites via a polymer precursor route wherein the cobalt polyamine complexes used as the catalyst, exhibiting novel composite structures and photophysical properties. High Resolution Transmission Electron Microscopy (HRTEM) analysis shows that the diameters of SiCN-BN core-shell nanocomposites and BN shells are 50‒400 nm and 5‒25 nm, respectively. BN nanosheets (BNNSs) are also observed with an average sheet size of 5‒15 nm. The photophysical properties of these nanocomposites are characterized using the UV-Vis and photoluminescence (PL) analyses. The as-produced composites have emission behavior including an emission lifetime of 2.5 ns (±20 ps) longer observed in BN doped SiCN than that seen for SiC nanoparticles. Our results suggest that the SiCN/BN nanocomposites act as semiconductor displaying superior width photoluminescence at wavelengths spanning the visible to near-infrared (NIR) spectral range (400‒700 nm), owing to the heterojunction of the interface between the SiC(N) nanowire core and the BN nanosheet shell.

  18. Reduction of Intergranular Cracking Susceptibility by Precipitation Control in 2.25Cr Heat-Resistant Steels

    Science.gov (United States)

    Sung, Hyun Je; Heo, Nam Hoe; Kim, Sung-Joon

    2017-03-01

    This research is performed to decrease reheat cracking susceptibility in the T/P23 heat-resistant steels (2.25Cr1.5WVNbTi), in other words, to reduce phosphorus and sulfur segregation concentration at the prior austenite grain boundary/carbide interfaces (GCIs) and the carbide-free prior austenite grain boundaries (carbide-free PAGBs) causing intergranular cracking. The increase of bulk vanadium content reduces the amount of M23C6 carbides consuming carbon atoms which can repulse phosphorus and sulfur from interfaces, but promotes the precipitation reaction of V-rich MX carbo-nitrides. Such a precipitation reaction results in the lower segregation concentration of phosphorus or no sulfur at the GCIs and the carbide-free PAGBs. This is because the carbon atoms remaining after precipitation reaction segregates to the interfaces and repels phosphorus and sulfur. Also, tungsten segregation can increase the cohesive grain boundary strength as one of the grain boundary strengtheners. Consequently, the lower segregation concentration of the impurities and the segregation of tungsten atoms lower the intergranular cracking susceptibility.

  19. Characterization of Nanometric-Sized Carbides Formed During Tempering of Carbide-Steel Cermets

    Directory of Open Access Journals (Sweden)

    Matus K.

    2016-06-01

    Full Text Available 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 hardness effect observed for this material to a higher tempering temperature range. Determined influence of the atmosphere in the sintering process on precipitations formed during tempering of carbide-steel cermets. So far examination of carbidesteel cermet produced by powder injection moulding was carried out mainly in the scanning electron microscope. A proper description of nanosized particles is both important and difficult as achievements of nanoscience and nanotechnology confirm the significant influence of nanocrystalline particles on material properties even if its mass fraction is undetectable by standard methods. The following research studies have been carried out using transmission electron microscopy, mainly selected area electron diffraction and energy dispersive spectroscopy. The obtained results and computer simulations comparison were made.

  20. Transparent Conductive Two-Dimensional Titanium Carbide Epitaxial Thin Films.

    Science.gov (United States)

    Halim, Joseph; Lukatskaya, Maria R; Cook, Kevin M; Lu, Jun; Smith, Cole R; Näslund, Lars-Åke; May, Steven J; Hultman, Lars; Gogotsi, Yury; Eklund, Per; Barsoum, Michel W

    2014-04-08

    Since the discovery of graphene, the quest for two-dimensional (2D) materials has intensified greatly. Recently, a new family of 2D transition metal carbides and carbonitrides (MXenes) was discovered that is both conducting and hydrophilic, an uncommon combination. To date MXenes have been produced as powders, flakes, and colloidal solutions. Herein, we report on the fabrication of ∼1 × 1 cm(2) Ti3C2 films by selective etching of Al, from sputter-deposited epitaxial Ti3AlC2 films, in aqueous HF or NH4HF2. Films that were about 19 nm thick, etched with NH4HF2, transmit ∼90% of the light in the visible-to-infrared range and exhibit metallic conductivity down to ∼100 K. Below 100 K, the films' resistivity increases with decreasing temperature and they exhibit negative magnetoresistance-both observations consistent with a weak localization phenomenon characteristic of many 2D defective solids. This advance opens the door for the use of MXenes in electronic, photonic, and sensing applications.

  1. Mechanical behavior and stress effects in hard superconductors: a review

    Energy Technology Data Exchange (ETDEWEB)

    Koch, C. C.; Easton, D. S.

    1977-11-01

    The mechanical properties of type II superconducting materials are reviewed as well as the effect of stress on the superconducting properties of these materials. The bcc alloys niobium-titanium and niobium-zirconium exhibit good strength and extensive ductility at room temperature. Mechanical tests on these alloys at 4.2/sup 0/K revealed serrated stress-strain curves, nonlinear elastic effects and reduced ductility. The nonlinear behavior is probably due to twinning and detwinning or a reversible stress-induced martensitic transformation. The brittle A-15 compound superconductors, such as Nb/sub 3/Sn and V/sub 3/Ga, exhibit unusual elastic properties and structural instabilities at cryogenic temperatures. Multifilamentary composites consisting of superconducting filaments in a normal metal matrix are generally used for superconducting devices. The mechanical properties of alloy and compound composites, tapes, as well as composites of niobium carbonitride chemically vapor deposited on high strength carbon fibers are presented. Hysteretic stress-strain behavior in the metal matrix composites produces significant heat generation, an effect which may lead to degradation in the performance of high field magnets. Measurements of the critical current density, J/sub c/, under stress in a magnetic field are reported. Modest stress-reversible degradation in J/sub c/ was observed in niobium-titanium composites, while more serious degradation was found in Nb/sub 3/Sn samples. The importance of mechanical behavior to device performance is discussed.

  2. Microstructure and Mechanical Properties of V-Nb Microalloyed Ultrafine-Grained Dual-Phase Steels Processed Through Severe Cold Rolling and Intercritical Annealing

    Science.gov (United States)

    Papa Rao, M.; Subramanya Sarma, V.; Sankaran, S.

    2017-03-01

    Ultrafine-grained (UFG) dual-phase (DP) steel was produced by severe cold rolling (true strain of 2.4) and intercritical annealing of a low carbon V-Nb microalloyed steel in a temperature range of 1003 K to 1033 K (730 °C to 760 °C) for 2 minutes, and water quenching. The microstructure of UFG DP steels consisted of polygonal ferrite matrix with homogeneously distributed martensite islands (both of size produced through intercritical annealing at 1013 K (740 °C) has good combination of strength (1295 MPa) and ductility (uniform elongation, 13 pct). The nanoscale V- and Nb-based carbides/carbonitrides and spheroidized cementite particles have played a crucial role in achieving UFG DP microstructure and in improving the strength and work hardening. Analysis of work hardening behavior of the UFG DP steels through modified Crussard-Jaoul analysis showed a continuously varying work hardening rate response which could be approximated by 2 or 3 linear regimes. The transmission electron microscopy analysis on post tensile-tested samples indicated that these regimes are possibly related to the work hardening of ferrite, lath, and twin martensite, respectively.

  3. Femtosecond ablation of ultrahard materials

    Science.gov (United States)

    Dumitru, G.; Romano, V.; Weber, H. P.; Sentis, M.; Marine, W.

    Several ultrahard materials and coatings of definite interest for tribological applications were tested with respect to their response when irradiated with fs laser pulses. Results on cemented tungsten carbide and on titanium carbonitride are reported for the first time and compared with outcomes of investigations on diamond and titanium nitride. The experiments were carried out in air, in a regime of 5-8 J/cm2 fluences, using the beam of a commercial Ti:sapphire laser. The changes induced in the surface morphology were analysed with a Nomarski optical microscope, and with SEM and AFM techniques. From the experimental data and from the calculated incident energy density distributions, the damage and ablation threshold values were determined. As expected, the diamond showed the highest threshold, while the cemented tungsten carbide exhibited typical values for metallic surfaces. The ablation rates determined (under the above-mentioned experimental conditions) were in the range 0.1-0.2 μm per pulse for all the materials investigated.

  4. Static Recrystallization Kinetics and Crystallographic Texture of Nb-Stabilized Ferritic Stainless Steel Based on Orientation Imaging Microscopy

    Science.gov (United States)

    Malta, Paula Oliveira; Alves, Davi Silva; Ferreira, Aline Oliveira Vasconcelos; Moutinho, Iane Dutra; Dias, Carolina Arriel Pedroso; Santos, Dagoberto Brandão

    2017-01-01

    In the present study, Nb-stabilized ferritic stainless steel was prepared with annealing (430-A) and without annealing (430-NA) annealing, and the microstructure of the resulting samples was examined. The steel was then subjected to cold rolling and isothermal annealing in order to analyze its recrystallization kinetics and texture evolution. Microstructural characterization was performed by scanning and transmission electron microscopies. Recrystallization kinetics were evaluated by measuring the microhardness of the samples, and analyzing their kernel average misorientation and grain orientation spread via electron backscatter diffraction. The Avrami exponent data revealed that one-dimensional grain growth occurred owing to the migration of high-angle grain boundaries. The mean activation energies for recrystallization for 430-NA and 430-A was found to be 365 and 419 kJ mol-1, respectively. The recrystallization texture was influenced by oriented nucleation and selected growth mechanisms, as well as by the Nb carbonitride distribution and grain boundary energy. The recrystallized and growing grains with the {554} orientation showed a dimensional advantage over the other recrystallized components. The coincident site lattice boundaries were attributed to the progression of recrystallization since the CSL numeric fraction increased as the temperature increased. The {554} component was associated with the ∑19a boundary, which exerted a significant control on the selective growth during the recrystallization.

  5. Metallurgical investigation of the base material and weldments of the 9% chromium X 10 CrMoVNb 9 1. Metallkundliche Untersuchungen am Grundwerkstoff und an Schweissverbindungen des 9%-Chromstahles X 10 CrMoVNb 9 1

    Energy Technology Data Exchange (ETDEWEB)

    Bruehl, F.; Weber, H. (Mannesmann Anlagenbau AG, Duesseldorf (Germany, F.R.)); Cerjak, H. (Technische Univ., Graz (Austria). Inst. fuer Werkstoffkunde, Festigkeitslehre und Materialpruefung); Schwaab, P. (Mannesmann-Forschungsinstitut GmbH, Duisburg (Germany, F.R.))

    1991-01-01

    In the as-supplied condition, the steel X 10CrMoVNb 91 exhibits martensitic microstructure containing chromium carbide particles (M{sub 23}C{sub 6}) on the martensite lath boundaries and fine precipitates of coherent and non-coherent Nb-V carbonitrides of the type MX in the grain interior. If the material is subjected to creep testing the precipitation of Laves phase and additional precipitation of M{sub 23} C{sub 6} and MX takes place in the microstructure and overaging of coherent MX takes place in the microstructure and overaging of coherent MX phase begins. Recovery and recrystallization processes occur more quickly. The creep-rupture behaviour of the material can be assumed to be predominantly governed by the MX precipitate, while the concentrations of vanadium, niobium, carbon and nitrogen in the precipitate play a major role on the effectiveness of the precipitate. In weldments, the creep damage initiates, as a rule, at the edge of the HAZ adjacent to the unaffected base material. The short-time heating of these zones to tempertures just above A{sub c1} temperature results in the formation of austenite with very low carbon content, because the carbides hardly go into solution at this temperature. During cooling this austenite transforms to martensite, which is very soft. Moreover, this martensite recrystallizes almost completely when conventionally tempered at about 750deg C. (orig./MM).

  6. Cyclic deformation behaviour of austenitic steels at ambient and elevated temperatures

    Indian Academy of Sciences (India)

    Th Nebel; D Eifler

    2003-02-01

    The aim of the present investigation is to characterise cyclic deformation behaviour and plasticity-induced martensite formation of metastable austenitic stainless steels at ambient and elevated temperatures, taking into account the influence of the alloying elements titanium and niobium. Titanium and niobium are ferrite-stabilising elements which influence the ferrite crystallisation. Furthermore, They form carbides and/or carbonitrides and thus limit the austenite-stabilising effect of carbon and nitrogen. Several specimen batches of titanium and niobium alloyed austenite and of a pure Cr-Ni-steel for comparison were tested under stress and total strain control at a frequency of 5 Hz and triangular load-time waveforms. Stress-strain-hysteresis and temperature measurements were used at ambient temperature to characterise cyclic deformation behaviour. Plasticity-induced martensite content was detected with non-destructive magnetic measuring techniques. The experiments yield characteristic cyclic deformation curves and corresponding magnetic signals according to the actual fatigue state and the amount of martensite. Fatigue behaviour of X6CrNiTi1810 (AISI 321), X10CrNiCb189 (AISI 348) and X5CrNi1810 (AISI 304) is characterised by cyclic hardening and softening effects which are strongly influenced by specific loading conditions. Martensite formation varies with the composition, loading conditions, temperature and number of cycles.

  7. Studies on plutonium-zirconium co-precipitation and carbothermal reduction in the internal gelation process for nitride fuel preparation

    Science.gov (United States)

    Hedberg, Marcus; Ekberg, Christian

    2016-10-01

    Sol-gel based techniques are one way to lower the handling of highly radioactive powders when producing transuranium-containing fuel. In this work inert matrix (Zr0.6,Pu0.4)N fuel has been produced by internal gelation followed by carbothermal reduction. No co-gelation was observed during internal gelation and a two phase material could be detected by scanning electron microscopy in the nitrided microspheres. Sintering has been performed in both Ar and N2. X-ray diffraction revealed that sintering in N2 produced a solid solution, while sintering in Ar did not. The final metal composition in the microspheres was determined by ICP-MS to be about 41% Pu and 59% Zr. Vegard's law was applied to estimate the nitride purity in the solid solution pellet to be Zr0.6Pu0.4N0.87C0.13 making the final material more of a carbonitride than a pure nitride.

  8. X-ray photoelectron spectroscopy of select multi-layered transition metal carbides (MXenes)

    Science.gov (United States)

    Halim, Joseph; Cook, Kevin M.; Naguib, Michael; Eklund, Per; Gogotsi, Yury; Rosen, Johanna; Barsoum, Michel W.

    2016-01-01

    In this work, a detailed high resolution X-ray photoelectron spectroscopy (XPS) analysis is presented for select MXenes-a recently discovered family of two-dimensional (2D) carbides and carbonitrides. Given their 2D nature, understanding their surface chemistry is paramount. Herein we identify and quantify the surface groups present before, and after, sputter-cleaning as well as freshly prepared vs. aged multi-layered cold pressed discs. The nominal compositions of the MXenes studied here are Ti3C2Tx, Ti2CTx, Ti3CNTx, Nb2CTx and Nb4C3Tx, where T represents surface groups that this work attempts to quantify. In all the cases, the presence of three surface terminations, sbnd O, sbnd OH and sbnd F, in addition to OH-terminations relatively strongly bonded to H2O molecules, was confirmed. From XPS peak fits, it was possible to establish the average sum of the negative charges of the terminations for the aforementioned MXenes. Based on this work, it is now possible to quantify the nature of the surface terminations. This information can, in turn, be used to better design and tailor these novel 2D materials for various applications.

  9. RJJ-75-9TG井式气体渗碳炉工艺渗碳软件的应用%RJJ-75-9TG pit gas carburizing furnace carburizing process software applications

    Institute of Scientific and Technical Information of China (English)

    王海成

    2014-01-01

    选用北京培特公司技术开发的HT8002AC 井式炉渗碳/碳氮共渗工艺过程计算机控制系统,技术改进2台RJJ-75-9TG 井式气体渗碳炉的渗碳控制系统,实现计算机对整个工艺渗碳全过程的模拟控制,并时刻跟踪和修正现场设备参数的动态变化。提升了渗碳件的产品质量,确保汉德公司两到三年之内的自制件,能够达到国际出口标准。%Selection of Beijing tissue culture technology development company HT8002AC pit furnace carburizing / carbonitriding process computer control systems, technical improvements 2 RJJ-75-9TG pit gas carburizing carburizing furnace control system, the entire computer analog control the whole process of carburizing process and time tracking and dynamic correction field device parameters. Improve product quality carburizing, ensuring homemade pieces Hande within two to three years to reach the international export standards.

  10. Dynamic Recrystallization Behaviour of Nb-Ti Microalloyed Steels

    Institute of Scientific and Technical Information of China (English)

    MA Liqiang; LIU Zhenyu; JIAO Sihai; YUAN Xiangqian; WU Di

    2008-01-01

    The dynamic recrystallization(DRX)behavior of Nb-Ti microalloyed steels was investigated by isothermal single compression tests in the temperature range of 900-1 150 ℃ at constant strain rates of 0.1-5 S-1.DRX was retarded effectively at low temperature due to the onset of dynamic precipitation of Nb and Ti carbonitrides,resulting in higher values of the peak strain.An expression was developed for the activation energy of deformation as a function of the contents of Nb and Ti in solution as well as other alloying elements.A BeW value of corrective factor was determined and applied to quantify the retardation produced by increase in the amount of Nb and Ti dissolved at the reheating temperature.The ratio of critical strain to peak strain decreases with increasing equivalent Nb content.In addition,the effects of Ti content and deformation conditions on DRX kinetics and steady state grain size were determined.Finally,the kinetics of dynamic precipitation was determined and effect of dynamic precipitation on the onset of DRX was clarified based on the comparison between precipitate pinning force and recrystallization driving force.

  11. A Model to Simulate Titanium Behavior in the Iron Blast Furnace Hearth

    Science.gov (United States)

    Guo, Bao-Yu; Zulli, Paul; Maldonado, Daniel; Yu, Ai-Bing

    2010-08-01

    The erosion of hearth refractory is a major limitation to the campaign life of a blast furnace. Titanium from titania addition in the burden or tuyere injection can react with carbon and nitrogen in molten pig iron to form titanium carbonitride, giving the so-called titanium-rich scaffold or buildup on the hearth surface, to protect the hearth from subsequent erosion. In the current article, a mathematical model based on computational fluid dynamics is proposed to simulate the behavior of solid particles in the liquid iron. The model considers the fluid/solid particle flow through a packed bed, conjugated heat transfer, species transport, and thermodynamic of key chemical reactions. A region of high solid concentration is predicted at the hearth bottom surface. Regions of solid formation and dissolution can be identified, which depend on the local temperature and chemical equilibrium. The sensitivity to the key model parameters for the solid phase is analyzed. The model provides an insight into the fundamental mechanism of solid particle formation, and it may form a basic model for subsequent development to study the formation of titanium scaffold in the blast furnace hearth.

  12. SiC-Si[sub 3]N[sub 4] composite coatings produced by plasma-enhanced chemical vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gerretsen, J. (Centre for Technical Ceramics, Netherlands Organization for Applied Scientific Research, Eindhoven (Netherlands)); Kirchner, G. (Centre for Technical Ceramics, Netherlands Organization for Applied Scientific Research, Eindhoven (Netherlands)); Kelly, T. (Irish Science and Technology Agency, Dublin (Ireland)); Mernagh, V. (Irish Science and Technology Agency, Dublin (Ireland)); Koekoek, R. (Tempress, Hoogeveen (Netherlands)); McDonnell, L. (Tekscan Ltd., Cork (Ireland))

    1993-10-08

    Silicon carbonitride coatings have been produced by plasma-enhanced chemical vapour deposition (CVD) on AISI 440C steel in a hot-wall reactor at 250 C from a mixture of SiH[sub 4], N[sub 2]-NH[sub 3] and C[sub 2]H[sub 4], and analysed by electron probe microanalysis and Rutherford backscattering spectroscopy-elastic recoil detection. Coatings with different ratios of silicon carbide to silicon nitride and silicon suband superstoichiometries have been deposited. Stoichiometric coatings show a maximum in their mechanical properties. Depending on the SiC-to-Si[sub 3]N[sub 4] ratio, the Knoop hardness values vary between 1500 and 2800 HK[sub 0.025]. Internal stress is low at a level of 100-300 MPa. The pinhole density is less than 2 cm[sup -2]. The fracture toughness as determined from indention tests is 4 MPa m[sup 1/2]. Linear polarization testing results show excellent protection of the substrate material against chemically aggressive media as compared with conventional CVD. (orig.)

  13. Long-term creep testing and microstructure evaluation of P91 steel weld joints

    Energy Technology Data Exchange (ETDEWEB)

    Jandova, D.; Kasl, J.; Kanta, V. [SKODA VYZKUM s.r.o., Plzen (Czech Republic)

    2007-06-15

    Trial weld joints were made from wrought and cast modified 9Cr-lMo-V steel using GTAW and SMAW methods. Creep testing was carried out at temperature range from 525 deg C to 625 deg C and stresses from 50 to 240 MPa. Time to rupture of welds made from tube segments and cast plates reached almost 30 000 hours and 20 000 hours respectively. Creep strength was evaluated according the Larson-Miller parametric equation and microstructure was investigated using both light and electron microscopy. Creep rupture strength of both weld joints tested at temperatures below 600 deg C falls into the {+-}20% scatter band of the creep rupture strength of the parent material. At 600 deg C and 625 deg C the creep strength dropped by 27% and 30% for the plate weld and the tube weld respectively. All ruptures occurred in fine grain and intercritically reheated heat affected zones either in the parent material or in the weld metal. Observation of thin foils prepared from selected regions of the weld joints revealed differences in precipitation processes and the structure recovery causing decrease of dislocation density in some regions. Fine ferritic grains with low density of fine carbonitride precipitate occurred in critical localities. Soft grains were deformed and cavities at grain boundaries initiated the crack propagation. (orig.)

  14. Reduction of Intergranular Cracking Susceptibility by Precipitation Control in 2.25Cr Heat-Resistant Steels

    Science.gov (United States)

    Sung, Hyun Je; Heo, Nam Hoe; Kim, Sung-Joon

    2017-01-01

    This research is performed to decrease reheat cracking susceptibility in the T/P23 heat-resistant steels (2.25Cr1.5WVNbTi), in other words, to reduce phosphorus and sulfur segregation concentration at the prior austenite grain boundary/carbide interfaces (GCIs) and the carbide-free prior austenite grain boundaries (carbide-free PAGBs) causing intergranular cracking. The increase of bulk vanadium content reduces the amount of M23C6 carbides consuming carbon atoms which can repulse phosphorus and sulfur from interfaces, but promotes the precipitation reaction of V-rich MX carbo-nitrides. Such a precipitation reaction results in the lower segregation concentration of phosphorus or no sulfur at the GCIs and the carbide-free PAGBs. This is because the carbon atoms remaining after precipitation reaction segregates to the interfaces and repels phosphorus and sulfur. Also, tungsten segregation can increase the cohesive grain boundary strength as one of the grain boundary strengtheners. Consequently, the lower segregation concentration of the impurities and the segregation of tungsten atoms lower the intergranular cracking susceptibility.

  15. 2D metal carbides and nitrides (MXenes) for energy storage

    Science.gov (United States)

    Anasori, Babak; Lukatskaya, Maria R.; Gogotsi, Yury

    2017-01-01

    The family of 2D transition metal carbides, carbonitrides and nitrides (collectively referred to as MXenes) has expanded rapidly since the discovery of Ti3C2 in 2011. The materials reported so far always have surface terminations, such as hydroxyl, oxygen or fluorine, which impart hydrophilicity to their surfaces. About 20 different MXenes have been synthesized, and the structures and properties of dozens more have been theoretically predicted. The availability of solid solutions, the control of surface terminations and a recent discovery of multi-transition-metal layered MXenes offer the potential for synthesis of many new structures. The versatile chemistry of MXenes allows the tuning of properties for applications including energy storage, electromagnetic interference shielding, reinforcement for composites, water purification, gas- and biosensors, lubrication, and photo-, electro- and chemical catalysis. Attractive electronic, optical, plasmonic and thermoelectric properties have also been shown. In this Review, we present the synthesis, structure and properties of MXenes, as well as their energy storage and related applications, and an outlook for future research.

  16. TEM investigations of fine niobium precipitates in HSLA steel

    Energy Technology Data Exchange (ETDEWEB)

    Beres, M.; Weirich, T.E.; Mayer, J. [Gemeinschaftslabor fuer Elektronenmikroskopie (GFE), RWTH Aachen, Aachen (Germany); Hulka, K. [Niobium Products Co. GmbH, Duesseldorf (Germany)

    2004-11-01

    Commercially produced 0.03% C, 0.08% Nb, 0.01% Ti high strength low alloyed (HSLA) steel in the form of 20 mm thick plates was investigated. The steel was thermomechanically processed and the mechanical properties of the steel were evaluated by tensile testing. Using analytical and high resolution transmission electron microscopy the distribution, morphology, composition, crystal structure and particle size of niobium and titanium carbonitrides were observed and identified in these steels. The distribution of the precipitates was found to be nearly random, with occasional occurrence of precipitation free zones. Complex agglomerates with a cubic TiN seed crystal overgrown by a cubic NbC particle were the most commonly observed precipitates. Further TEM analysis in the accelerated cooled and tempered specimens in 1/4 plate thickness did not reveal any evidence that additional precipitation in the ferrite occurred. Precipitation in ferrite was only detected after subsequent cold deformation and tempering of the same samples. By a combination of EFTEM, STEM, HRTEM in addition to EDX spectroscopy, a large population of strain induced NbC precipitates with fcc crystal structure ranging in size down to 2 nm were identified in the ferrite matrix. (orig.)

  17. Wear Behavior of Austempered Ductile Iron with Nanosized Additives

    Directory of Open Access Journals (Sweden)

    J. Kaleicheva

    2014-03-01

    Full Text Available The microstructure and properties of austempered ductile iron (ADI strengthened with nanosized addtives of titanium nitride + titanium carbonitride (TiN + TiCN, titanium nitride TiN and cubic boron nitride cBN are investigated. The TiN, TiCN and cBN, nanosized particles are coated by electroless nickel coating EFTTOM-NICKEL prior to the edition to the melt. The spheroidal graphite iron samples are undergoing an austempering, including heating at 900 оС for an hour, after that isothermal retention at 280 оС, 2 h and 380 оС, 2h. The metallographic analysis by optical metallographic microscope GX41 OLIMPUS and hardness measurements by Vickers Method are performed. The structure of the austempered ductile iron consists of lower bainite and upper bainite.Experimental investigation of the wear by fixed abrasive are also carried out. The influence of the nanosized additives on the microstructure, mechanical and tribological properties of the austempered ductile irons (ADI is studied.

  18. Microstructural characterization of 5-9% chromium reduced-activation steels

    Energy Technology Data Exchange (ETDEWEB)

    Jayaram, R. [Univ. of Pittsburgh, PA (United States); Klueh, R.L. [Oak Ridge National Lab., TN (United States)

    1997-08-01

    The microstructures of a 9Cr-2W-0.25-0.1C (9Cr-2WV), a 9Cr-2W-0.25V-0.07Ta-0.1C (9Cr-2WVTa), a 7Cr-2W-0.25V-0.07Ta-0.1C (7Cr-2WVTa), and a 5Cr-2W-0.25V-0.07Ta-0.1C (5Cr-2WVTa) steel (all compositions are in weight percent) have been characterized by Analytical Electron Microscopy (AEM) and Atom Probe Field Ion Microscopy (APFIM). The matrix in all four reduced-activation steels was 100% martensite. In the two 9Cr steels, the stable precipitates were blocky M{sub 23}C{sub 6} and small spherical MC. The two lower-chromium steels contained blocky M{sub 7}C{sub 3} and small needle-shaped carbonitrides in addition to M{sub 23}C{sub 6}. AEM and APFIM analysis revealed that in the steels containing tantalum, the majority of the tantalum was in solid solution. The experimental observations were in good agreement with phases and compositions predicted by phase equilibria calculations.

  19. Present situation in research on nitrogen alloying hardfacing alloy%氮合金化耐磨堆焊的研究现状

    Institute of Scientific and Technical Information of China (English)

    刘跃; 张国赏; 魏世忠

    2012-01-01

    The change of nitrogen content of welding process, the precipitated behavior, morphology and the role of carbonitride of surfacing layer were summarized. Strengthening mechanism of nitrogen alloying hardfacing alloy was also discussed. The hardness of high temperature wear-resistance, tarnish resistance and tensile strength of the nitrogen alloying hardfacing alloy were analyzed. Nitrogen alloying hardfacing alloy had a good application prospect, and were becoming one of the most important aspects in current researches.%概述氮合金化堆焊材料在焊接过程中氮含量变化,堆焊层中碳氮化物的析出行为、形态及作用,介绍了氮合金堆焊层强化机理,分析了氮对堆焊层的硬度、高温耐磨性、耐蚀性、抗拉强度等性能的影响.指出氮合金化堆焊合金是当前研究的重要方向之一,氮合金化堆焊材料具有广阔的发展前景.

  20. An investigation on microstructure and mechanical propertiesof a Nb-microalloyed nano/ultrafine grained 201 austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Samaei Baghbadorani, H., E-mail: h.samaeibaghbadorani@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Kermanpur, A. [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Najafizadeh, A. [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Fould Institute of Technology, Fouldshare 84916-63763 (Iran, Islamic Republic of); Behjati, P.; Rezaee, A.; Moallemi, M. [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of)

    2015-06-11

    The present study was aimed to investigate the mechanical properties of a nano/ultrafine grained Nb-containing 201 austenitic stainless steel. For this purpose, 90% cold rolled sheets with fully martensitic microstructure were isothermally annealed at 900 °C for different times of 1 to 1800 s, leading to the reversion of strain- induced α′-martensite to austenite and significant grain refinement. Ferritescopy, X-ray diffractometery and optical/electron microscopy techniques along with hardness measurements and tensile tests were used to study the evolution in microstructure and mechanical properties in the course of annealing. It was found that heavy cold-rolling promoted formation of Nb-rich carbonitrides which effectively retarded the growth of fine reverted austenite grains. The obtained results showed that the complete transformation of martensite to austenite took about 60 s with the corresponding austenite grain size of about 90 nm. This sample had an ultrahigh yield strength of 1170 MPa, which was almost four times higher than that of the raw material and outstanding elongation of 37%. Further, the true stress–strain curves of the reversion annealed samples revealed two distinct uniform elongation stages (stage I and stage II), whereas, the onset of stage II was concurrent with pronounced strain hardening. This was related to the sharp increase in the formation of α′-martensite upon tensile straining.

  1. APFIM characterization of 15Kh2MFA Cr-Mo-V and 15Kh2NMFA Ni-Cr-Mo-V type steels

    Science.gov (United States)

    Miller, M. K.; Jayaram, R.; Othen, P. J.; Brauer, G.

    1994-03-01

    A microstructural characterization of 15Kh2MFA Cr-Mo-V and 15Kh2NMFA Ni-Cr-Mo-V type steels that are used in the pressure vessels of Russian VVER 440 and VVER 1000 nuclear reactors, respectively, has been performed with the use of the techniques of atom-probe field-ion microscopy (APFIM) and transmission electron microscopy. The microstructure of these materials was found to be tempered martensite and bainite. A high number density of coarse (≈ 50 to ≈ 500 nm) blocky M 7C 3 carbides and some inclusions were observed. In addition to these coarse carbides, some finer (≈ 10 nm diameter) approximately spherical MC carbides were also observed in the VVER 440 steel. Field-ion microscopy has revealed that the lath boundaries in both unirradiated VVER 440 and VVER 1000 reactor steels are decorated with an ultrathin semicontinuous film of molybdenum-carbonitride precipitates. Atom-probe analysis has revealed a high enrichment of phosphorus at the lath boundaries.

  2. Structure of MoCN films deposited by cathodic arc evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Gilewicz, A., E-mail: adam.gilewicz@tu.koszalin.pl [Koszalin University of Technology, Faculty of Technology and Education, Sniadeckich 2, 75-453 Koszalin (Poland); Jedrzejewski, R.; Kochmanska, A.E. [West Pomeranian University of Technology Szczecin, Faculty of Mechanical Engineering and Mechatronics, 19 Piastów Ave., 70-313 Szczecin (Poland); Warcholinski, B. [Koszalin University of Technology, Faculty of Technology and Education, Sniadeckich 2, 75-453 Koszalin (Poland)

    2015-02-27

    Molybdenum carbonitride (MoCN) coatings were deposited onto HS6-5-2 steel substrate using pure Mo targets in mixed acetylene and nitrogen atmosphere by cathodic arc evaporation. The structural properties of MoCN coatings with different carbon contents (as an effect of the C{sub 2}H{sub 2} flow rate) were investigated systematically. Phase and chemical composition evolution of the coatings were characterized both by the glancing angle of X-ray diffraction (XRD) and wavelength dispersive spectrometry, respectively. These analyses have been supplemented by estimates of grain sizes and stress in the coatings. The XRD results show that the increase in acetylene flow rate causes the formation of molybdenum carbide (MoC) hexagonal phase in the coatings, a reduction of grain size and an increase in internal stress. - Highlights: • MoN and MoCN coatings were deposited by cathodic arc evaporation in nitrogen atmosphere. • MoCN coatings were formed using different acetylene flow rates. • Phase composition evolution was observed. • Crystallite size and stress were calculated.

  3. PERFORMANCE IMPROVEMENT OF CREEP-RESISTANT FERRITIC STEEL WELDMENTS THROUGH THERMO-MECHANICAL TREATMENT AND ALLOY DESIGN

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Yukinori [ORNL; Babu, Prof. Sudarsanam Suresh [University of Tennessee, Knoxville (UTK); Shassere, Benjamin [ORNL; Yu, Xinghua [ORNL

    2016-01-01

    Two different approaches have been proposed for improvement of cross-weld creep properties of the high temperature ferrous structural materials for fossil-fired energy applications. The traditional creep strength-enhanced ferritic (CSEF) steel weldments suffer from Type IV failures which occur at the fine-grained heat affected zone (FGHAZ). In order to minimize the premature failure at FGHAZ in the existing CSEF steels, such as modified 9Cr-1Mo ferritic-martensitic steels (Grade 91), a thermo-mechanical treatment consisting of aus-forging/rolling and subsequent aus-aging is proposed which promotes the formation of stable MX carbonitrides prior to martensitic transformation. Such MX remains undissolved during welding process, even in FGHAZ, which successfully improves the cross-weld creep properties. Another approach is to develop a new fully ferrtic, creep-resistant FeCrAl alloy which is essentially free from Type IV failure issues. Fe-30Cr-3Al base alloys with minor alloying additions were developed which achieved a combination of good oxidation/corrosion resistance and improved tensile and creep performance comparable or superior to Grade 92 steel.

  4. Modeling of point defects and rare gas incorporation in uranium mono-carbide

    Science.gov (United States)

    Chartier, A.; Van Brutzel, L.

    2007-02-01

    An embedded atom method (EAM) potential has been established for uranium mono-carbide. This EAM potential was fitted on structural properties of metallic uranium and uranium mono-carbide. The formation energies of point defects, as well as activation energies for self migration, have been evaluated in order to cross-check the suitability of the potential. Assuming that the carbon vacancies are the main defects in uranium mono-carbide compounds, the migration paths and energies are consistent with experimental data selected by Catlow[C.R.A. Catlow, J. Nucl. Mater. 60 (1976) 151]. The insertion and migration energies for He, Kr and Xe have also been evaluated with available inter-atomic potentials [H.H. Andersen, P. Sigmund, Nucl. Instr. and Meth. B 38 (1965) 238]. Results show that the most stable defect configuration for rare gases is within uranium vacancies. The migration energy of an interstitial Xe is 0.5 eV, in agreement with the experimental value of 0.5 eV [Hj. Matzke, Science of advanced LMFBR fuels, Solid State Physics, Chemistry and Technology of Carbides, Nitrides and Carbonitrides of Uranium and Plutonium, North-Holland, 1986].

  5. Precipitation behavior and martensite lath coarsening during tempering of T/P92 ferritic heat-resistant steel

    Institute of Scientific and Technical Information of China (English)

    Lin-qing Xu; Dan-tian Zhang; Yong-chang Liu; Bao-qun Ning; Zhi-xia Qiao; Ze-sheng Yan; Hui-jun Li

    2014-01-01

    Tempering is an important process for T/P92 ferritic heat-resistant steel from the viewpoint of microstructure control, as it facili-tates the formation of final tempered martensite under serving conditions. In this study, we have gained deeper insights on the mechanism underlying the microstructural evolution during tempering treatment, including the precipitation of carbides and the coarsening of martensite laths, as systematically analyzed by optical microscopy, transmission electron microscopy, and high-resolution transmission electron mi-croscopy. The chemical composition of the precipitates was analyzed using energy dispersive X-ray spectroscopy. Results indicate the for-mation of M3C (cementite) precipitates under normalized conditions. However, they tend to dissolve within a short time of tempering, owing to their low thermal stability. This phenomenon was substantiated by X-ray diffraction analysis. Besides, we could observe the precipitation of fine carbonitrides (MX) along the dislocations. The mechanism of carbon diffusion controlled growth of M23C6 can be expressed by the Zener’s equation. The movement of Y-junctions was determined to be the fundamental mechanism underlying the martensite lath coarsening process. Vickers hardness was estimated to determine their mechanical properties. Based on the comprehensive analysis of both the micro-structural evolution and hardness variation, the process of tempering can be separated into three steps.

  6. Corrosion resistance appraisal of TiN, TiCN and TiAlN coatings deposited by CAE-PVD method on WC-Co cutting tools exposed to artificial sea water

    Science.gov (United States)

    Matei, A. A.; Pencea, I.; Branzei, M.; Trancă, D. E.; Ţepeş, G.; Sfăt, C. E.; Ciovica (Coman), E.; Gherghilescu, A. I.; Stanciu, G. A.

    2015-12-01

    A new advanced sintered composite cutting tool has been developed based on tungsten carbide matrix ligated with cobalt (WC-Co) additivated with tantalum carbide (TaC), titanium carbide (TiC) and niobium carbide (NbC) as grain growth inhibitors. Titanium nitride (TiN), titanium carbonitride (TiCN) and titanium aluminium nitride (TiAlN) coatings were deposited on these tools by CAE-PVD technique to find out the best solution to improve the corrosion resistance of this tool in marine environment. The electrochemical behaviours of the specimens in 3.5% NaCl water solution were estimated by potentiodynamic polarization measurements i.e. the open circuit potential (Eoc), corrosion potential (Ecorr) and corrosion current density (icorr). Wide angle X-ray diffraction (WAXD), optical microscopy (OM) and atomic force microscopy (AFM) investigations have been carried on tested and untested specimens to substantiate the corrosion resistance of the tested specimens. Based on the open circuit potential (Eoc) and corrosion potential (Ecorr) results, the tested specimens were ranked as TiN, TiAlN, TiCN and WC-Co while on corrosion current density (icorr) and protective efficiency (P) values they have been ranked as TiN, TiAlN, WC-Co and TiCN. The WAXD, MO and AFM results unambiguously show that the corrosion resistance depends on the nature and morphology of the coating.

  7. Plastic behavior of medium carbon vanadium microalloyed steel at temperatures near g « a transformation

    Directory of Open Access Journals (Sweden)

    Lourenço N.J.

    2001-01-01

    Full Text Available Dilatometric techniques were used to build the continuous cooling transformation (CCT diagram for a medium carbon microalloyed steel; the microstructure and hardness were determined at different cooling rates. The mechanical behavior of the steel in the austenite field and at temperatures approaching austenite to ferrite transformation was measured by means of hot torsion tests under isothermal and continuous cooling conditions. The no recrystallization temperatures, Tnr, and start of phase transformation, Ar3, were determined under continuous cooling condition using mean flow stress vs. inverse of absolute temperature diagrams. Interruption of static recrystallization within the interpass time in the austenite field indicated that the start of vanadium carbonitride precipitation occurred under 860 °C. Austenite transformation was found to start at around 710 °C, a temperature similar to that measured by dilatometry, suggesting that interphase precipitation delays the transformation of deformed austenite. Pearlite was observed at temperatures ranging from 650 °C to 600 °C, with the flow curves taking on a particular shape, i.e., stress rose sharply as strain was increased, reaching peak stress at low deformation, around 0.2, followed by an extensive softening region after peak stress.

  8. Tribological performance evaluation of coated steels with TiNbCN subjected to tribo-chemical wear in Ringers solution

    Energy Technology Data Exchange (ETDEWEB)

    Caballero G, J.; Aperador, W. [Universidad Militar Nueva Granada, Volta Research Group, 101-80 Bogota (Colombia); Caicedo, J. C., E-mail: g.ing.materiales@gmail.com [Universidad del Valle, Tribology Polymers, Powder Metallurgy and Processing of Solid Recycled Research Group, Cali (Colombia)

    2016-11-01

    With the aim of generating solutions against the deterioration of the joint prostheses, it was studied the tribo-corrosive behavior of titanium niobium carbonitride (TiNbCN) deposited on stainless steel AISI 316 LVM using the technique of magnetron sputtering physical vapor deposition. The tests were performed in a balanced saline solution (Ringers solution) which represents the characteristics of the body fluids, using an equipment where the micro-abrasive wear is generated by the contact of micro particles in the system; the micro-abrasion-corrosion mechanism is described by means of the incorporation of an electrochemical cell consisting of three electrodes. Both the substrate and the coating, were subjected to micro-abrasive wear simultaneously with the electrochemical tests of Tafel polarization curves and electrochemical impedance spectroscopy (EIS); subsequently of the tests, the specimens were analyzed by optical microscopy and scanning electron microscopy characterizing the surface morphology. It was observed that the coating presents an increase in its corrosion and wear resistance with the presence of a simulated biological fluid. The samples were characterized via X-ray diffraction. (Author)

  9. Spark plasma sintering of Ti{sub y}Nb{sub 1-y}C{sub x}N{sub 1-x} monolithic ceramics obtained by mechanically induced self-sustaining reaction

    Energy Technology Data Exchange (ETDEWEB)

    Borrell, Amparo, E-mail: aborrell@upvnet.upv.es [Instituto de Tecnologia de Materiales (ITM), Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN) (Consejo Superior de Investigaciones Cientificas - Universidad de Oviedo - Principado de Asturias), Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Salvador, Maria Dolores [Instituto de Tecnologia de Materiales (ITM), Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Garcia-Rocha, Victoria [ITMA Materials Technology, Parque Tecnologico de Asturias, 33428 Llanera (Asturias) (Spain); Fernandez, Adolfo [Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN) (Consejo Superior de Investigaciones Cientificas - Universidad de Oviedo - Principado de Asturias), Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); ITMA Materials Technology, Parque Tecnologico de Asturias, 33428 Llanera (Asturias) (Spain); Chicardi, Ernesto; Gotor, Francisco J. [Instituto de Ciencia de Materiales de Sevilla (CSIC-US), Calle Americo Vespucio 49, 41092 Sevilla (Spain)

    2012-05-01

    Nanometer-sized titanium-niobium carbonitride powders (Ti{sub y}Nb{sub 1-y}C{sub x}N{sub 1-x}) with different Ti/Nb atomic ratios were obtained by a mechanically induced self-sustaining reaction, and sintered by spark plasma sintering technique at 1500 Degree-Sign C for 1 min in a vacuum atmosphere. Mechanical properties such as hardness and Young's modulus were determined by nanoindentation technique and friction and wear coefficients assessed by ball-on-disk testing using alumina ball in dry sliding conditions. The fracture surface and wear tracks of samples were examined by scanning electron microscopy. Results showed that it is possible to obtain dense monolithic ceramics from the solid solution (Ti{sub y}Nb{sub 1-y}C{sub x}N{sub 1-x}) with good mechanical properties and excellent wear resistance. The optimum values of nanomechanical properties were found for the Ti{sub 0.3}Nb{sub 0.7}C{sub 0.5}N{sub 0.5} ceramic composition, which exhibited a high hardness over 26.0 GPa and Young's modulus around 400 GPa.

  10. Static Recrystallization Kinetics and Crystallographic Texture of Nb-Stabilized Ferritic Stainless Steel Based on Orientation Imaging Microscopy

    Science.gov (United States)

    Malta, Paula Oliveira; Alves, Davi Silva; Ferreira, Aline Oliveira Vasconcelos; Moutinho, Iane Dutra; Dias, Carolina Arriel Pedroso; Santos, Dagoberto Brandão

    2017-03-01

    In the present study, Nb-stabilized ferritic stainless steel was prepared with annealing (430-A) and without annealing (430-NA) annealing, and the microstructure of the resulting samples was examined. The steel was then subjected to cold rolling and isothermal annealing in order to analyze its recrystallization kinetics and texture evolution. Microstructural characterization was performed by scanning and transmission electron microscopies. Recrystallization kinetics were evaluated by measuring the microhardness of the samples, and analyzing their kernel average misorientation and grain orientation spread via electron backscatter diffraction. The Avrami exponent data revealed that one-dimensional grain growth occurred owing to the migration of high-angle grain boundaries. The mean activation energies for recrystallization for 430-NA and 430-A was found to be 365 and 419 kJ mol-1, respectively. The recrystallization texture was influenced by oriented nucleation and selected growth mechanisms, as well as by the Nb carbonitride distribution and grain boundary energy. The recrystallized and growing grains with the {554} orientation showed a dimensional advantage over the other recrystallized components. The coincident site lattice boundaries were attributed to the progression of recrystallization since the CSL numeric fraction increased as the temperature increased. The {554} component was associated with the ∑19a boundary, which exerted a significant control on the selective growth during the recrystallization.

  11. Effect of vacuum oxy-nitrocarburizing on the microstructure of tool steels: an experimental and modeling study

    Directory of Open Access Journals (Sweden)

    Nikolova Maria

    2017-01-01

    Full Text Available The thermochemical treatments of tool steels improve the performance of the components with respect to surface hardness, wear and tribological performance as well as corrosion resistance. Compared to the conventional gas ferritic nitrocarburizing process, the original vacuum oxy-nitrocarburizing is a time-, cost-effective and environmentally-friendly gas process. Because of the oxidizing nature of the gas atmosphere, there is no need to perform subsequent post-oxidation.In this study, a vacuum oxynitrocarburizing process was carried out onto four tool steels (AISI H10, H11, H21 and D2 at 570 °C, after hardening and single tempering. The structural analysis of the compound and diffusion layers was performed by optical and electron microscopy, X-ray diffraction and glow discharge optical emission spectrometry (GDOES methods. A largely monophase ε- layer is formed with a carbon accumulation at the substrate adjacent area. The overlaying oxides adjacent to the ε-carbonitride phase contained Fe3O4 (magnetite as a main constituent. A thermodynamic modelling approach was also performed to understand and optimize the process. The “Equilib module” of FactSage software which uses Gibbs energy minimization method, was used to estimate the possible products during vacuum oxynitrocarburising process.

  12. Interface description using computational methods and tribological characteristic of Ti N/Ti C films prepared by reactive pulse arc evaporation technique

    Energy Technology Data Exchange (ETDEWEB)

    Devia N, D. M. [Universidad Nacional de Colombia, Sede Manizales, Campus La Nubia, Manizales, Caldas (Colombia); Gonzalez C, J. M.; Ruden M, A., E-mail: dmdevian@utp.edu.co [Universidad del Valle, Edificio 349, espacio 1003, Ciudad Universitaria Melendez, Cali (Colombia)

    2013-10-01

    The Ti N/Ti C bilayers have been deposited by Plasma Assisted Physical Vapor Deposition Technique - Reactive Pulsed Arc. The coatings were analyzed by X-ray photoelectron spectroscopy (XP S) and X-ray diffraction (XRD). From the signal treatment of the narrow XP S spectra and the XRD diffraction patterns, the formation of Ti N (titanium nitride), Ti C (titanium carbide) and Ti CN (titanium carbonitride) was confirmed, with fm-3m spatial group, corresponding to the Fcc phase of the synthesized compounds. The multilayer was simulated using Density Functional Theory (DFT) by the Unrestricted Hartree Fock method. Charge distributions and electron total density were obtained; finding bond formation at the interphase, electrical neutrality and system stability. Anomalies in the corners of the structures due to edge effect, simulation ideality and the no internal tension inclusion, intrinsic to the growing, are observed. The ball on disc tribometer was used to measure the friction and wear coefficient to verify the interface formation. (Author)

  13. High sensitivity and high resolution element 3D analysis by a combined SIMS–SPM instrument

    Directory of Open Access Journals (Sweden)

    Yves Fleming

    2015-04-01

    Full Text Available Using the recently developed SIMS–SPM prototype, secondary ion mass spectrometry (SIMS data was combined with topographical data from the scanning probe microscopy (SPM module for five test structures in order to obtain accurate chemical 3D maps: a polystyrene/polyvinylpyrrolidone (PS/PVP polymer blend, a nickel-based super-alloy, a titanium carbonitride-based cermet, a reticle test structure and Mg(OH2 nanoclusters incorporated inside a polymer matrix. The examples illustrate the potential of this combined approach to track and eliminate artefacts related to inhomogeneities of the sputter rates (caused by samples containing various materials, different phases or having a non-flat surface and inhomogeneities of the secondary ion extraction efficiencies due to local field distortions (caused by topography with high aspect ratios. In this respect, this paper presents the measured relative sputter rates between PVP and PS as well as in between the different phases of the TiCN cermet.

  14. Microscopical characterization of {alpha}{double_prime}Fe{sub 16}N{sub 2} obtained by plasma assisted processes

    Energy Technology Data Exchange (ETDEWEB)

    Hinojosa, G.; Oseguera, J.; Salas, O.; Schabes-Retchkiman, P.S. [ITESM-CEM, Mexico City (Mexico)

    1996-01-01

    Nitriding of iron and carbon steels enhances their mechanical and tribological properties. The origin of the improvement arises from the formation of a nitride compound surface layer, and a diffusion zone f nitrogen interstitially dissolved in ferrite. The top layers may be composed of {var_epsilon} and {gamma}{prime} (carbo)nitrides. The solubility of nitrogen in the {alpha}-Fe (ferrite) decreases with temperature. If a nitrided piece is slowly cooled, precipitation of the metastable nitride {alpha}{double_prime} in the ferritic matrix usually precedes the formation of the more stable phase {gamma}{prime}. However, when the piece is quenched, formation of nitrogen tetragonal martensite {alpha}{prime} is observed instead. After a tempering process, this martensite leads to the precipitation of the {alpha}{double_prime} phase coherent with the ferrite. Further aging or aging of the {alpha}{double_prime} obtained from slow cooling leads to the stable precipitate {gamma}{prime}. These transformations are accompanied of hardness changes. The aim of this work is to present the optical microscopy, HREM and TEM characterization of the {alpha}{double_prime} precipitate, obtained in plasma-nitrided iron, and relate the hardness profile after aging with the transformation of this precipitate.

  15. Structure and mechanical properties of the 03Kh14GNF steel after deformation and annealing

    Science.gov (United States)

    Shaburov, D. V.; Valitov, V. G.; Mirzaev, D. A.; Yakovleva, I. L.; Kirpichnikov, M. S.; Vetoshkina, T. Yu.

    2009-04-01

    It has been shown that the annealing of cold-worked 03Kh14GNF steel is accompanied by several strengthening and softening processes that take place in different temperature intervals. Therefore, the temperature dependence of its hardness has a complicated form; i.e., it contains several maxima and minima. The following processes should be noted: recovery and recrystallization of δ ferrite, precipitation of M 2(CN) carbonitrides and M 23C6 carbides from the α martensite, their dissolution in the γ phase, the formation of austenite with different stability, polygonization of the α martensite, etc. Tempering for 30 h can produce the level of mechanical properties required according to technical specifications for two processing regimes. These regimes are the annealing at 680°C and at 600°C, but in the second case the high plasticity is probably caused by the formation of a highly stable austenite that is retained down to room temperature. However, the degree of plasticity of this γ phase at room and lower temperatures is unknown. After annealing at 660°C, the steel does not achieve the level of ultimate strength of 480 N/mm2, which is required by the technical specifications. However, since the relative elongation of 35% exceeds the required magnitude, the required level of mechanical properties can apparently be produced by a decrease in the duration of annealing to 20-25 h.

  16. Behaviour of Z phase in 9–12%Cr steels

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson; Hald, John

    2006-01-01

    –12%), Z phase precipitates much faster than in 9%Cr steels. Precipitation of Z phase is associated with dissolution of MX carbonitrides, and causes a breakdown in long term creep strength in 9–12%Cr steels. High Cr steels show creep instabilities accompanied with Z phase precipitation, whereas low Cr...... steels show good long term creep stability. A niobium free CrVN variant of the modified Z phase was observed for the first time during the course of this work. The solution temperature of the Cr(V,Nb)N and CrVN modified Z phases was found to be close to 800uC for 11–12%Cr steels, much lower than the 1200......The literature on the behaviour of modified Z phase Cr(V,Nb)N in creep resistant martensitic 9–12%Cr steels is briefly reviewed. Ten different 9–12%Cr steels were investigated after prolonged exposure at 600–660uC; the modified Z phase was found in all of them. In steels with high Cr content (11...

  17. A thermodynamic model of the Z-phase Cr(V, Nb)N

    DEFF Research Database (Denmark)

    Danielsen, Hilmar Kjartansson; Hald, John

    2007-01-01

    Precipitation of large Z-phase particles, Cr(V, Nb)N, replacing fine MX carbonitrides, Nb(C, N) or V(N, C), has recently been identified as a major cause for premature breakdown in long-term creep strength of a number of new 9%–12% Cr martensitic steels, especially the high Cr variants......-phase is a crucial factor for the long-term creep stability of these steels. Driving force calculations with the model allow estimates of the influence of the individual alloying elements on the rate of Z-phase precipitation, and can thus contribute useful information for alloy design to delay and retard Z....... A thermodynamic model of the Z-phase has been developed based on the regular solution model. The model predicts Z-phase to be stable and to fully replace the MX particles in most of the new 9%–12% Cr steels, which is in good agreement with experimental observations. The rate of precipitation of Z...

  18. B4CN3 and B3CN4 monolayers as the promising candidates for metal-free spintronic materials

    Science.gov (United States)

    Pan, Hongzhe; Sun, Yuanyuan; Zheng, Yongping; Tang, Nujiang; Du, Youwei

    2016-09-01

    The search for candidates of spintronic materials, especially among the two-dimensional (2D) materials, has attracted tremendous attentions over the past decades. By using a particle swarm optimization structure searching method combined with density functional calculations, two kinds of boron carbonitride monolayer structures (B4CN3 and B3CN4) are proposed and confirmed to be dynamically and kinetically stable. Intriguingly, we demonstrate that the magnetic ground states of the two B x C y N z systems are ferromagnetic ordering with a high Curie temperature of respectively 337 K for B4CN3 and 309 K for B3CN4. Furthermore, based on their respective band structures, the B4CN3 is found to be a bipolar magnetic semiconductor (BMS), while the B3CN4 is identified to be a type of spin gapless semiconductor (SGS), both of which are potential spintronic materials. In particular, carrier doping in the B4CN3 can induce a transition from BMS to half-metal, and its spin polarization direction is switchable depending on the doped carrier type. The BMS property of B4CN3 is very robust under an external strain or even a strong electric field. By contrast, as a SGS, the electronic structure of B3CN4 is relatively sensitive to external influences. Our findings successfully disclose two promising materials toward 2D metal-free spintronic applications.

  19. Precipitates in electrical steels

    Energy Technology Data Exchange (ETDEWEB)

    Jenkins, Keith [Development and Market Research, Cogent Power Limited, Corporation Road, Newport, South Wales NP19 OXT (United Kingdom)], E-mail: keith.jenkins@cogent-power.com; Lindenmo, Magnus [Development and Market Research, Cogent Power Limited, Corporation Road, Newport, South Wales NP19 OXT (United Kingdom)

    2008-10-15

    Precipitates heavily influence the magnetic properties of electrical steels, either as a key controlled requirement as part of the manufacturing process or as an unwanted harmful residual in the final product. In this current work copper-manganese sulphides precipitates are the primary inhibitor species in the conventional grain-oriented (CGO) steels examined and grain boundary pinning is effective at a mean precipitate size of 30-70 nm. The growth of CuMnS has been studied and the results show that a precipitate size above {approx}100 nm allows the onset of secondary recrystallisation in the heating conditions applied. The effect of precipitates on the magnetic properties of both grain-oriented and non-oriented steels in their final product form is then examined. Examples of grain-oriented material still containing large numbers of precipitates clearly show the detrimental effects with increases in total power loss of 40% or more. Loss deterioration by about 20% is also seen in samples of high silicon non-oriented material in which titanium carbo-nitride precipitates have been observed. In this case the precipitates are believed to have formed during cooling after final annealing. Finally a grain-oriented steel with a large number of very small precipitates, which do not seem to have any harmful effect on the magnetic properties, is demonstrated.

  20. New Insights into Understanding Irreversible and Reversible Lithium Storage within SiOC and SiCN Ceramics

    Directory of Open Access Journals (Sweden)

    Magdalena Graczyk-Zajac

    2015-02-01

    Full Text Available Within this work we define structural properties of the silicon carbonitride (SiCN and silicon oxycarbide (SiOC ceramics which determine the reversible and irreversible lithium storage capacities, long cycling stability and define the major differences in the lithium storage in SiCN and SiOC. For both ceramics, we correlate the first cycle lithiation or delithiation capacity and cycling stability with the amount of SiCN/SiOC matrix or free carbon phase, respectively. The first cycle lithiation and delithiation capacities of SiOC materials do not depend on the amount of free carbon, while for SiCN the capacity increases with the amount of carbon to reach a threshold value at ~50% of carbon phase. Replacing oxygen with nitrogen renders the mixed bond Si-tetrahedra unable to sequester lithium. Lithium is more attracted by oxygen in the SiOC network due to the more ionic character of Si-O bonds. This brings about very high initial lithiation capacities, even at low carbon content. If oxygen is replaced by nitrogen, the ceramic network becomes less attractive for lithium ions due to the more covalent character of Si-N bonds and lower electron density on the nitrogen atom. This explains the significant difference in electrochemical behavior which is observed for carbon-poor SiCN and SiOC materials.

  1. 9-12% Cr heat resistant steels. Alloy design, TEM characterisation of microstructure evolution and creep response at 650 C

    Energy Technology Data Exchange (ETDEWEB)

    Rojas Jara, David

    2011-03-21

    This work was carried out aiming to design and characterise 9-12% Cr steels with tailormade microstructures for applications in fossil fuel fired power plants. The investigations concentrated in the design and characterisation of heat resistant steels for applications in high oxidising atmospheres (12% Cr) and 9% Cr alloys for components such as rotors (P91). ThermoCalc calculations showed to be a reliable tool for alloy development. The modeling also provided valuable information for the adjustment of the processing parameters (austenisation and tempering temperatures). Two 12% Cr heat resistant steels with a fine dispersion of nano precipitates were designed and produced supported by thermodynamic modeling (ThermoCalc). A detailed characterisation of the microstructure evolution at different creep times (100 MPa / 650 C / 8000 h) was carried out by scanning transmission electron microscopy (STEM). The results of the microstructure analysis were correlated with the mechanical properties in order to investigate the influence of different precipitates (especially M{sub 23}C{sub 6} carbides) on the creep strength of the alloys. Precipitation of Laves phase and Z-phase was observed after several hundred hours creep time. Very few Z-phase of the type Cr(V,Ta)N nucleating from existing (V,Ta)(C,N) was observed. Both alloys show growth and coarsening of Laves phase, meanwhile the MX carbonitrides present a very slow growth and coarsening rate. Alloys containing Laves phase, MX and M{sub 23}C{sub 6} precipitates show best creep properties. The influence of hot-deformation and tempering temperature on the microstructure evolution on one of the designed 12% Cr alloys was studied during short-term creep at 80-250 MPa and 650 C. Quantitative determination of dislocation density and sub-grain size in the initial microstructure and after creep was investigated by STEM combined with the high-angle annular dark-field detector (HAADF). A correlation between microstructure

  2. Effects of niobium additions on the structure, depth, and austenite grain size of the case of carburized 0.07% C steels

    Science.gov (United States)

    Islam, M. A.; Bepari, M. M. A.

    1996-10-01

    Carbon (0.07%) steel samples containing about 0.04% Nb singly and in combination with nitrogen were carburized in a natural Titas gas atmosphere at a temperature of 1223 K (950 °C) and a pressure of about 0.10 MPa for 1/2 to 4 h, followed by slow cooling in the furnace. Their microstructures were studied by optical microscopy. The austenite grain size of the case and the case depths were determined on baseline samples of low-carbon steels and also on niobium and (Nb + N) microalloyed steel samples. It was found that, when compared to the baseline steel, niobium alone or in combination with nitrogen decreased the thickness of cementite network near the surface of the carburized case of the steels. However, niobium in combination with nitrogen was more effective than niobium in reducing the thickness of cementite network. Niobium with or without nitrogen inhibited the formation of Widmanstätten cementite plates at grain boundaries and within the grains near the surface in the hypereutectoid zone of the case. It was also revealed that, when compared to the baseline steel, niobium decreased the case depth of the carburized steels, but that niobium with nitrogen is more effective than niobium alone in reducing the case depth. Niobium as niobium carbide (NbC) and niobium in the presence of nitrogen as niobium carbonitride, [Nb(C,N)] particles refined the austenite grain size of the carburized case, but Nb(C,N) was more effective than NbC in inhibiting austenite grain growth.

  3. A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

    Science.gov (United States)

    Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han; Maloy, Stuart A.

    2017-02-01

    The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This study aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide a comparative assessment of their high-temperature structural performance. The KJQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at a significantly lower strength region. It appeared that at high temperatures ≥600 °C the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. Irradiation studies have revealed, however, that the NFAs have much stronger radiation resistance than tempered martensitic steels, such as lower radiation-induced swelling, finer helium bubble formation, lower irradiation creep rate and reduced low temperature embrittlement.

  4. Biotribological behavior of Ag-ZrCxN1-x coatings against UHMWPE for joint prostheses devices.

    Science.gov (United States)

    Calderon V, S; Sánchez-López, J C; Cavaleiro, A; Carvalho, S

    2015-01-01

    This study aims to evaluate the structural, mechanical and tribological properties of zirconium carbonitrides (ZrCxN1-x) coatings with embedded silver nanoparticles, produced with the intention of achieving a material with enhanced multi-functional properties, including mechanical strength, corrosion resistance, tribological performance and antibacterial behavior suitable for their use in joint prostheses. The coatings were deposited by direct current (DC) reactive magnetron sputtering onto 316 L stainless steel, changing the silver content from 0 to 20 at% by modifying the current density applied to the targets. Different nitrogen and acetylene gas fluxes were used as reactive gases. The coatings revealed different mixtures of crystalline ZrCxN1-x, silver nanoparticles and amorphous carbon phases. The hardness of the films was found to be mainly controlled by the ratio between the hard (ZrCxN1-x) and soft (Ag and amorphous carbon) phases in the films, fluctuating between 7.4 and 20.4 GPa. The coefficient of friction, measured against ultra-high molecular weight polyethylene (UHMWPE) in Hank's balanced salt solution with 10 gL(-1) albumin, is governed by the surface roughness and hardness. The UHMWPE wear rates were in the same order of magnitude (between 1.4 and 2.0 × 10(-6)mm(3)N(-1)m(-1)), justified by the effect of the protective layer of albumin formed during the tests. The small differences were due to the hydrophobic/hydrophilic character of the surface, as well as to the silver content.

  5. 热浸渗铝X70管线钢扩渗工艺研究%Research on Hot Diffusion Aluminizing Process of X70 Pipe Line Steel

    Institute of Scientific and Technical Information of China (English)

    黄敦伟; 胡爱萍; 张宏伟; 孔德军

    2013-01-01

    The relationship between hot diffusion aluminizing temperature,infiltration time and thickness of aluminized coating of X70 pipe line steel was researched by quadratic orthogonal regression testing method.The regression equation of the alloying layer thickness was established.The optimum process for hot diffusion aluminizing treatment was gotten.The surface and interface morphologies of X70 pipeline steel after the aluminizing treatment were observed,and Fe and Al content change by the carbonitride layer were analyzed.The element diffusion mechanism of hot dipping alumetizing process was discussed.The results show that alloying layer thickness is increased with the rising of insulation temperture and the extending of diffusion time.The ideal inoulation temperature is 950 ℃ and time is insulation 6 h.%采用二次正交回归试验方法,研究了X70管线钢热扩渗铝保温温度、扩渗时间与渗铝层厚度的关系,建立了渗层回归方程,得到X70管线钢最优的热扩渗铝工艺参数.观察了X70管线钢热浸渗铝处理后的表面、界面微观形貌,分析了Fe和Al的含量沿渗层的变化情况,并对热浸渗铝过程中的元素扩散机理进行了探讨.结果表明:渗铝层厚度随保温温度的升高和扩渗时间的延长而增大,适宜的保温温度为950℃,扩渗时间为6h.

  6. Analysis on Formation of Cracks in High Nb and Ti Content Billet and Control Measures%高Nb、Ti含量钢坯开裂原因分析及控制措施

    Institute of Scientific and Technical Information of China (English)

    梁文; 吴润; 陈吉清; 裴海; 张鹏武; 刘志勇; 韩荣东

    2013-01-01

    采用酸洗、金相检测、能谱分析等方法,对高Nb、Ti含量钢坯在轧钢过程中的开裂原因进行研究,结果表明:大量析出的碳氮化物引起的内部微裂纹是造成高Nb、Ti含量钢开裂的直接原因.高温热塑性试验证实,高Nb、Ti含量钢在660 ~910℃下存在脆性温度区间.通过成分控制、稳定拉速、降低二冷段冷却速率以及稳定结晶器液面,可基本消除高Nb、Ti含量钢轧钢开裂现象.%The causes of cracks in high Nb and Ti content billet in the process of steel rolling was investigated by pickling,metallography detection and energy spectrum analysis.The results show that the direct reason for crack forming is the inner microcracks caused by large amount of carbonitride separated out in the process.It is proved in the thermoplasticity test that there is a brittleness temperature range at 660 ~910 ℃ for the steel.The cracks can be avoided through controlling chemical compositions,stabilizing the casting speed and liquid level in the mold,and reducing the cooling rate in the secondary cooling.

  7. Origen y endurecimiento por dispersión de carbonitruros en un acero comercial microaleado al niobio y laminado en caliente

    Directory of Open Access Journals (Sweden)

    Valencia, E.

    1998-12-01

    Full Text Available Throughout this work, a study on niobium carbonitrides formation and its hardening effect in a commercial hot strip microalloyed steel is presented. Optic and electron micrographs were obtained while mechanical tests and indirect models allow to predict samples yield strength, taking into account the steel composition and its structural characteristics. The results showed an extended precipitation on austenite boundary cells during the last thermomechanical processing stages, which probably achieved a considerable contribution to the hardening by dispersion in the material studied. Otherwise, no evidence of precipitation in ferrite by means of transmission electron microscopy (TEM was observed. A poor interphase precipitation was detected in about 10 per cent of the total observed zones with no appreciated contribution to the steel hardness.

    Se presenta un estudio sobre el origen de los carbonitruros de niobio y su efecto en el endurecimiento de un acero comercial microaleado y laminado en caliente. Para tal fin se utilizaron micrografías ópticas y electrónicas; así como también ensayos mecánicos y modelos indirectos que permitieron predecir el límite elástico teniendo en cuenta la composición del acero y sus características estructurales. Los resultados mostraron una extensa precipitación en la austenita durante las últimas fases del proceso de laminación siendo ésta responsable del principal aporte al endurecimiento por dispersión en el material investigado. No hubo evidencias de precipitación en la ferrita por observaciones al microscopio electrónico de transmisión y sólo una escasa precipitación interfásica fue detectada en un 10 % de las zonas observadas sin una apreciable contribución al endurecimiento del acero.

  8. A comparative assessment of the fracture toughness behavior of ferritic-martensitic steels and nanostructured ferritic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Byun, Thak Sang; Hoelzer, David T.; Kim, Jeoung Han; Maloy, Stuart A.

    2017-02-01

    The Fe-Cr alloys with ultrafine microstructures are primary candidate materials for advanced nuclear reactor components because of their excellent high temperature strength and high resistance to radiation-induced damage such as embrittlement and swelling. Mainly two types of Fe-Cr alloys have been developed for the high temperature reactor applications: the quenched and tempered ferritic-martensitic (FM) steels hardened primarily by ultrafine laths and carbonitrides and the powder metallurgy-based nanostructured ferritic alloys (NFAs) by nanograin structure and nanoclusters. This study aims at elucidating the differences and similarities in the temperature and strength dependences of fracture toughness in the Fe-Cr alloys to provide a comparative assessment of their high-temperature structural performance. The KJQ versus yield stress plots confirmed that the fracture toughness was inversely proportional to yield strength. It was found, however, that the toughness data for some NFAs were outside the band of the integrated dataset at given strength level, which indicates either a significant improvement or deterioration in mechanical properties due to fundamental changes in deformation and fracture mechanisms. When compared to the behavior of NFAs, the FM steels have shown much less strength dependence and formed narrow fracture toughness data bands at significantly lower strength region. It appeared that at high temperatures ≥ 600 ºC the NFAs cannot retain the nanostructure advantage of high strength and high toughness either by high-temperature embrittlement or by excessive loss of strength. It is reviewed, however, that the NFAs has much stronger radiation resistance at high temperatures, such as lower radiation-induced swelling, finer helium bubble formation and lower irradiation creep rate.

  9. Characterization of TiN, TiC and Ti(C,N) in titanium-alloyed ferritic chromium steels focusing on the significance of different particle morphologies

    Energy Technology Data Exchange (ETDEWEB)

    Michelic, S.K., E-mail: susanne.michelic@unileoben.ac.at [Chair of Ferrous Metallurgy, Montanuniversitaet Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria); Loder, D. [Chair of Ferrous Metallurgy, Montanuniversitaet Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria); Reip, T.; Ardehali Barani, A. [Outokumpu Nirosta GmbH, Essener Straße 244, 44793 Bochum (Germany); Bernhard, C. [Chair of Ferrous Metallurgy, Montanuniversitaet Leoben, Franz-Josef-Straße 18, 8700 Leoben (Austria)

    2015-02-15

    Titanium-alloyed ferritic chromium steels are a competitive option to classical austenitic stainless steels owing to their similar corrosion resistance. The addition of titanium significantly influences their final steel cleanliness. The present contribution focuses on the detailed metallographic characterization of titanium nitrides, titanium carbides and titanium carbonitrides with regard to their size, morphology and composition. The methods used are manual and automated Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy as well as optical microscopy. Additional thermodynamic calculations are performed to explain the precipitation procedure of the analyzed titanium nitrides. The analyses showed that homogeneous nucleation is decisive at an early process stage after the addition of titanium. Heterogeneous nucleation gets crucial with ongoing process time and essentially influences the final inclusion size of titanium nitrides. A detailed investigation of the nuclei for heterogeneous nucleation with automated Scanning Electron Microscopy proved to be difficult due to their small size. Manual Scanning Electron Microscopy and optical microscopy have to be applied. Furthermore, it was found that during solidification an additional layer around an existing titanium nitride can be formed which changes the final inclusion morphology significantly. These layers are also characterized in detail. Based on these different inclusion morphologies, in combination with thermodynamic results, tendencies regarding the formation and modification time of titanium containing inclusions in ferritic chromium steels are derived. - Graphical abstract: Display Omitted - Highlights: • The formation and modification of TiN in the steel 1.4520 was examined. • Heterogeneous nucleation essentially influences the final steel cleanliness. • In most cases heterogeneous nuclei in TiN inclusions are magnesium based. • Particle morphology provides important information

  10. Microstructural development and mechanical properties of iron based cermets processed by pressureless and spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Alvaredo, P. [Department of Materials Science and Engineering, IQMAAB, University Carlos III Madrid, Avda. de la Universidad, 30, 28911 Leganes (Spain); Gordo, E., E-mail: elena.gordo@uc3m.es [Department of Materials Science and Engineering, IQMAAB, University Carlos III Madrid, Avda. de la Universidad, 30, 28911 Leganes (Spain); Van der Biest, O.; Vanmeensel, K. [Katholieke Universiteit Leuven, Kasteelpark Arenberg, 44 3001 Heverlee (Belgium)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Processing of Fe-based cermets by pressureless sintering and spark plasma sintering. Black-Right-Pointing-Pointer Influence of carbon content on the sintering mechanism and hardness. Black-Right-Pointing-Pointer The cermet phase diagram was calculated and permits to explain the microstructure. Black-Right-Pointing-Pointer SPS provides ferritic matrix and different carbide distribution than CPS samples. Black-Right-Pointing-Pointer Pressureless sintered samples contain retained austenite at room temperature. - Abstract: Iron-based cermets are an interesting class of metal-ceramic composites in which properties and the factors influencing them are to be explored. In this work the metal matrix contains Cr, W, Mo and V as alloying elements, and the hard phase is constituted by 50 vol% of titanium carbonitride (TiCN) particles. The work studies the influence of the C content and the processing method on the sinterability, microstructure and hardness of the developed cermet materials. For that purpose, cermet samples with different C content in the matrix (0 wt%, 0.25 wt%, 0.5 wt%, 1.0 wt%) were prepared by conventional pressureless sintering (CPS) and, in order to achieve finer microstructures and to reduce the sintering time, by spark plasma sintering (SPS). The density and hardness (HV30) of the processed materials was evaluated, while their phase composition and microstructure was characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The equilibrium phase diagram of the composite material was calculated by ThermoCalc software in order to elucidate the influence of the carbon content on the obtained phases and developed microstructures.

  11. Antibacterial Activity of Ti₃C₂Tx MXene.

    Science.gov (United States)

    Rasool, Kashif; Helal, Mohamed; Ali, Adnan; Ren, Chang E; Gogotsi, Yury; Mahmoud, Khaled A

    2016-03-22

    MXenes are a family of atomically thin, two-dimensional (2D) transition metal carbides and carbonitrides with many attractive properties. Two-dimensional Ti3C2Tx (MXene) has been recently explored for applications in water desalination/purification membranes. A major success indicator for any water treatment membrane is the resistance to biofouling. To validate this and to understand better the health and environmental impacts of the new 2D carbides, we investigated the antibacterial properties of single- and few-layer Ti3C2Tx MXene flakes in colloidal solution. The antibacterial properties of Ti3C2Tx were tested against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) by using bacterial growth curves based on optical densities (OD) and colonies growth on agar nutritive plates. Ti3C2Tx shows a higher antibacterial efficiency toward both Gram-negative E. coli and Gram-positive B. subtilis compared with graphene oxide (GO), which has been widely reported as an antibacterial agent. Concentration dependent antibacterial activity was observed and more than 98% bacterial cell viability loss was found at 200 μg/mL Ti3C2Tx for both bacterial cells within 4 h of exposure, as confirmed by colony forming unit (CFU) and regrowth curve. Antibacterial mechanism investigation by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) coupled with lactate dehydrogenase (LDH) release assay indicated the damage to the cell membrane, which resulted in release of cytoplasmic materials from the bacterial cells. Reactive oxygen species (ROS) dependent and independent stress induction by Ti3C2Tx was investigated in two separate abiotic assays. MXenes are expected to be resistant to biofouling and offer bactericidal properties.

  12. The effects of laser surface modification on the microstructure and properties of gas-nitrided 42CrMo4 steel

    Science.gov (United States)

    Kulka, M.; Panfil, D.; Michalski, J.; Wach, P.

    2016-08-01

    Gas nitriding, together with gas carburizing and gas carbonitriding, was the most commonly used thermochemical treatment, resulting in many advantageous properties: high hardness, enhanced corrosion resistance, considerably improved wear resistance and fatigue strength. However, an unfavorable increase in the thickness of compound layer (ε+γ‧) close to the surface was observed after conventional gas nitriding. This was the reason for undesirable embrittlement and flaking. Therefore, a controlled gas nitriding was developed, reducing the thickness of compound layer. In this study, laser modification with or without re-melting was carried out after the controlled gas nitriding in order to change microstructure and to improve wear resistance. The effects of laser beam power on the dimensions of simple laser tracks were analyzed. It enabled to control the obtained microstructure and to select the laser processing parameters during producing the multiple tracks. Such a treatment was necessary to investigate wear resistance. Laser re-melting resulted in dissolving the majority of nitrides as well as in producing the martensitic structure in re-melted and heat-affected zones. This treatment required argon shielding in order to protect the surface against uncontrolled oxidation. Laser heat treatment without re-melting caused a modification of ε nitrides which became less porous and more compact. Simultaneously, it provided heat-affected zone with the partially martensitic structure of increased hardness below compound zone. Argon shielding was not necessary in this case because of the resistance of nitrides to oxidation during rapid heating and cooling. All the laser-modified layers, irrespective if the nitrided layer was re-melted or not, were characterized by the improved wear resistance compared to the typical gas-nitrided layer.

  13. The manufacture, confectioning and application testing of SiC and Si{sub 3}N{sub 4}/SiC fibres. Final report; Herstellung, Konfektionierung und anwendungstechnische Pruefung von SiC- sowie Si{sub 3}N{sub 4}/SiC-Fasern. Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Roesch, L.; Geisberger, G.; Kalchauer, W.

    1991-12-31

    The aim of the research project was the laboratory development of processes for the manufacture of ceramic fibres based on silicon carbide and silicon carbo-nitride, which can be used as components in high temperature materials in the temperature range of 900 to 1300 C. These fibres with a diameter of about 10 to 15 micrometres, should have a tensile strength of 1.8-2.5 GPa and an elastic modulus of at least 200 GPa. Starting from different methyl chlor-disilanes, polysilane, polysilazane and polysilan/siloxane copolymers are produced by suitable chemical reactions. These polymer resins are to be examined for their melting spinning properties and modified if necessary. The spun polymer multi-filament bundles should be made unmeltable by suitable processes and converted by pyrolysis under inert gas into ceramic fibres. After this, mechanical tests (for tensile strength, elastic modulus, temperature resistance) must be carried out on these fibres. (orig./MM) [Deutsch] Ziel des Forschungsvorhabens war die labormaessige Entwicklung von Verfahren zur Herstellung von keramischen Fasern auf der Basis von Siliciumcarbid und Siliciumcarbonitrid, welche als Bestandteile in Hochtemperaturwerkstoffen im Temperaturbereich von 900 bis 1300 C eingesetzt werden koennen. Diese Fasern sollten bei einem Durchmesser von etwa 10 bis 15 Mikrometern eine Zugfestigkeit von 1,8-2,5 GPa und ein E-Modul von mindestens 200 GPa aufweisen. Ausgehend von verschiedenen Methylchlordisilanen sollten durch entsprechende chemische Reaktionen Polysilane, Polysilazane und Polysilan/siloxan-Copolymere hergestellt werden. Diese Polymerharze waren auf ihre Schmelzspinnfaehigkeit hin zu untersuchen und ggf. entsprechend zu modifizieren. Die versponnenen Polymermultifilament-Buendel sollten durch geeignete Verfahren unschmelzbar gemacht werden und durch Pyrolyse unter Inertgas in keramische Fasern umgewandelt werden. Anschliessend waren an diesen Faeden mechanische Untersuchungen (Zugfestigkeit, E

  14. Microhardness study of Ti(C, N films deposited on stainless steel 316 by the hallow cathode discharge gun

    Directory of Open Access Journals (Sweden)

    A.J. Novinrooz

    2005-12-01

    Full Text Available Purpose: The micro hardness properties of Titanium Carbonitride composite coated on SS-316 substrates were studied to achieve a desired harden surfaces.Design/methodology/approach: Hollow Cathode Discharge gun (HCD–gun was employed for deposition of the Ti(C, N on SS-316. The evaporated and ionized metal (Ti was coated as an under layer with 0.5 ampere beam current and 100 volt bias voltage. The reactant nitrogen and methane gasses were fed through inlet in to the chamber containing Ti element to form Ti (C, N matrix with an optimized ratio.Findings: In this work, Glow Discharge Optical emission Spectroscopy (GDOS used for compositional analysis of the content elements. On the bases of this operation it was revealed the existence of Ti, C, N elements, X-ray diffraction (XRD technique was utilized to investigate films crystalline structure. The investigation showed that samples with different stoichiometry have a fcc structure with (111 plan of reflection. The atomic ratio of carbon and nitrogen were measured using energy dispersive X-ray (EDX analysis. The optimized value was funned to be TiC0.87 N0.13. The atomic force microscopy (AFM and scanning electron microscopy (SEM were employed to study the films microstructure. A hardness of 3250 HV was obtained in the carbon content C/C+ N atomic ratio of 9 to 1 using a Vickers microhardness tester.Research limitations/implications: As the study was carried out on a limited surfaces, we shall endeavor further attempt on large area deposition.Practical implications: The tools coated in titanium accompanied by nitride and carbide has shown significant improvement. Good compatibility of Ti (C, N compound makes these composite suitable in various technical and industrial applications.Originality/value: It may be remarked that, the hardness obtained in this work is very encouraging and therefore, it is convenient to regard this as a privileged step taken in tool manufacturing aspect.

  15. Studies on Nb Microalloying of 13Cr Super Martensitic Stainless Steel

    Science.gov (United States)

    Ma, Xiaoping; Wang, Lijun; Subramanian, Sundaresa V.; Liu, Chunming

    2012-12-01

    The effect of Nb microalloying on microstructure, mechanical properties, and pitting corrosion properties of quenched and tempered 13 pct Cr-5 pct Ni-0.02 pct C martensitic stainless steels with different Mo and N contents was investigated. The microstructure, density, and dispersion of high-angle boundaries, nanoscale precipitates, and amount of retained austenite were characterized by using electron backscattered diffraction, transmission electron microscopy, and X-ray diffraction to correlate with properties. The results show that the combined effects of lowering nitrogen content in 13 pct Cr-5 pct Ni-1~2 pct Mo-0.02 pct C steels to 0.01 wt pct, and adding 0.1 pct Nb are to decrease the amount of Cr-rich precipitates, as Nb preferentially combines with residual carbon and nitrogen to form carbonitrides, suppressing the formation of Cr2N and Cr23C6. Austenite grain refinement can be achieved by Nb microalloying through proper heat treatment. If the nitrogen content is kept high, then Cr-rich precipitates would occur irrespective of microalloying addition. The NbN would also occur at high temperature, which will act as substrate for nucleation of coarse precipitates during subsequent tempering, impairing the toughness of the steel. It was shown that the addition of Nb to low interstitial super martensitic stainless steel retards the formation of reversed austenite and results in the formation of nanoscale precipitates (5 to 15 nm), which contribute to a significant increase in strength. More importantly, the pitting corrosion resistance was found to increase with Nb addition. This is attributed to suppression of Cr-rich precipitates, which can cause local depletion of Cr in the matrix and the initiation of pitting corrosion.

  16. Enhancement of bioactivity of pulsed magnetron sputtered TiC{sub x}N{sub y} with bioactive glass (BAG) incorporated polycaprolactone (PCL) composite scaffold

    Energy Technology Data Exchange (ETDEWEB)

    Anusha Thampi, V.V.; Subramanian, B., E-mail: subramanianb3@gmail.com

    2015-11-15

    Titanium carbonitride (TiC{sub x}N{sub y}) thin films were fabricated on SS 316 L by pulsed reactive DC magnetron sputtering using titanium and graphite targets. The sputtered film was characterized microstructurally by X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The XRD pattern revealed that the film was preferentially oriented along (200) axis with a grain size of 20 nm. A globular morphology was observed from electron micrograph while Energy dispersive X-ray spectroscopy (EDS) showed the compositional purity of the film. To improve the bioactivity, bioactive glass (BAG) nanopowders of size 60 nm, synthesized by sol–gel method, was incorporated into a polycaprolactone (PCL) scaffold (BAG-PCL), which was applied over TiC{sub x}N{sub y}/SS (BAG-PCL/TiCN/SS). In-vitro bioactivity studies of BAG-PCL showed the apatite formation, which was confirmed from fourier transform infrared (FTIR) spectrum and SEM. In-vitro corrosion studies in simulated body fluid (SBF) solution showed that the coated specimen had a higher charge transfer resistance than stainless steel (SS) bare. The enhancement of bioactivity was monitored by hemocompatibility and cytocompatibility, where an improved cell attachment and lower thrombus formation was observed for the coatings with BAG-PCL. - Highlights: • Fabrication of TiC{sub x}N{sub y} thin films on SS 316 L (TiCN/SS) by reactive pulsed DC magnetron sputtering. • Synthesis of BAG nanopowders (45S5) by sol–gel method. • Incorporation of BAG nanopowders into PCL matrix to form polymer composite scaffold. • BAG-PCL scaffold was coated on TiCN/SS to enhance the bioactivity.

  17. Electrochemical insertion of lithium into polymer derived silicon oxycarbide and oxycarbonitride ceramics

    Science.gov (United States)

    Ahn, Dongjoon

    There has recently been great interest in lithium storage at the anode of Li-ion rechargeable battery in order to replace the carbon-based anode. Over the last two decades, carbon-based anode, especially graphite, was utilized as anode in lithium ion batteries because of its cyclic stability and coulombic efficiency. However, low capacity and the thermal runaway resulted from the solid electrolyte interface (SEI) formation on the graphite anode during charging and discharging cycles. This inhibited the further development of lithium ion batteries for Plug-in Hybrid Electrical Vehicle (PHEV) or Electrical Vehicle (EV) which demand both high energy and high power density. The goal of this research was to develop the anode material, Silicon Oxycarbide (SixOyCz) and Silicon Carbonitride (SixCyNz), from Polymer Derived Ceramics (PDCs) for lithium-ion batteries application and to understand the thermodynamics and kinetics of intercalation mechanism in the host material. This includes as three main categories: (1) Characterization of PDCs, (2) measurement of electrochemical phenomena of PDCs anode in half-cell which used lithium foil as anode, (3) analysis of the lithium intercalation mechanism and diffusion coefficient in PDCs. In this thesis, the first objective was to synthesize possible anode materials and construct the proper battery structure to experiment its intercalation and deintercalation behaviors. Also, various experiments such as cyclic stability, capacity retention and C-rate capability were performed in order to estimate the feasibility of PDCs as new anode materials for the next generation. The second objective was to determine the reversible and irreversible capacity from different fraction of Si, C, O and N composition. Based on this analysis, the mixed bond sites in SixOyCz had higher reversible and irreversible capacity than the free carbon sites. The third objective was to examine the hysteretic response of lithium intercalation to SiCO. According to

  18. 模具表面化学热处理工艺的透析%Analysis of"Password"for Chemical Heat Treatment Process of Mold Surface

    Institute of Scientific and Technical Information of China (English)

    洪桂香

    2015-01-01

    化学热处理就是利用化学反应和物理冶金相结合的方法,改变金属材料表面的化学成分和组织结构,从而使材料表面获得某种性能的工艺过程。化学热处理能有效地提高模具表面的抗氧化性等性能。几乎所有的化学热处理工艺均可用于模具钢的表面处理。根据模具表面的化学热处理目的及基本组成,介绍了模具表面的化学热处理的方法、作用及其工艺过程,研究了模具表面的离子渗氮化学热处理,分析了模具表面的渗碳或碳氮共渗化学热处理,提出了模具表面离子渗硼、渗金属的化学热处理。%Chemical heat treatment is the process of combining of chemical reaction with physical metallurgy, so as to change chemical composition and structure on the surface of the metal material, and so a certain performance of the material surface can be obtained. Chemical heat treatment can effectively improve the mold surface properties, such as oxidation resistance. Almost all the chemical heat treatment process can be used for the surface treatment of steels. According to the purpose and procedure of chemical heat treatment on the surface of the mould, the methods, effect and process of the chemical heat treatment on the surface of the mold were described;the ion nitriding into mould surface was studied;the way of carbonitriding into the surface of the mold was analyzed and the measures for ion boronizing, surface alloying were put forward.

  19. Design of heat treatments for 9-12%Cr steels to optimise creep resistance for power plant applications

    Energy Technology Data Exchange (ETDEWEB)

    Morris, P.F.; Sachadel, U.A.; Clarke, P.D. [Tata Steel Europe, Rotherham (United Kingdom). Swinden Technology Centre; CRD and T, IJmuiden (Netherlands)

    2010-07-01

    Optimisation of the creep rupture properties of Steel 92 (9%Cr, 0.5%Mo, 2%W) by modification of heat treatment and C:N ratio has been studied. It was shown that a higher austenization temperature and double tempering at lower temperature can significantly extend creep life of the standard composition. The increase in austenization temperature from 1060 C and double tempering at 660 C/3h instead of single tempering at 780 C/2h resulted in the increase of stress rupture life from 1,734 to 6,179h at 650 C/110MPa. Even greater improvement in creep life was achieved by the combination of the modified heat treatment and decreased C:N ratio. In this case the creep life was extended to 10,255 h at 650 C/110MPa. A further increase in austenitization temperature to 1200 C for the decreased C:N ratio variant extended the rupture life to 17,118h. Initial results indicate that this modified heat treatment schedule does not result in notch brittle behaviour and most of the improvement in creep strength remains after a simulated post weld heat treatment at 740 C. The stress rupture programme is continuing and at 600 C test durations are approaching 60,000h. To explain the effect on rupture life thermodynamic calculations, microscopic investigations and a literature study were performed. Electron metallography investigations revealed that the lower tempering temperature resulted in a finer distribution of nano-size particles. Calculations show that increasing the austenitization temperature gave more dissolved B, N, C, Nb and V. The lower C:N ratio resulted in a higher atomic fraction of N in nano-size particles on subsequent tempering. Dissolved B should stabilize M{sub 23}M{sub 6} and dissolved N, C, Nv, and V should allow precipitation of a higher volume fraction of nano-size carbo-nitrides during tempering. Literature data suggest that lower tempering temperatures could also change their type from MX to M{sub 2}X. (orig.)

  20. Austenite grain growth behavior of a 82B high carbon steel%82B高碳钢奥氏体晶粒长大行为

    Institute of Scientific and Technical Information of China (English)

    金桂香; 王福明; 李克非; 付军; 李长荣

    2013-01-01

    利用直线截点法计算各试样的奥氏体平均晶粒尺寸,得出82B高碳钢的奥氏体粗化温度为950℃,通过Thermo-calc热力学计算和能谱分析可知,晶粒粗化的主要原因是950℃时V、Ti、Nb碳氮化物数量的大大减少,即析出相粒子钉扎作用的减弱和消除.随着加热温度的升高和保温时间的延长,82B高碳钢奥氏体晶粒尺寸增大,其生长模型的公式为D=6.82×104t0079 exp(-8.04×104/RT).当加热温度为1000℃,保温时间为60~90 min时,82B原奥氏体晶粒尺寸小于67μm,晶粒细小均匀,且微合金元素V充分溶解在奥氏体中.%The austenite grain coarsening temperature of 82B high carbon steel is 950℃ by measuring average grain size with linear cut point method.The results of EDS analysis and thermodynamic calculation based on Thermo-calc show that the main reason of grain coarsening is that the quantity of carbonitrides of elements V,Ti and Nb is decreased heavily for the steel heating at 950 ℃,which means the pinning effect of the precipitated phase particles is weakened or eliminated.The average austenite grain size increases with the increasing of the heating temperature and the holding time,which can be described by the austenite grain growth model D =6.82 × 104t0079exp(-8.04 × 104/RT).When the heating temperature is 1000 ℃ and the holding time is between 60 min and 90 min,the austenite grain size of 82B steel is uniform and smaller than 67 μm,and the micro-alloying element V is dissolved into austenite adequately.

  1. Determination of the non-recrystallization temperature (TNR) in multiple microalloyed steels

    Science.gov (United States)

    Homsher, Caryn Nicole

    Rolling mill metallurgists must be able to easily and accurately determine critical temperatures such as the non-recrystallization temperature (T NR) to properly plan rolling schedules for desired properties. Microalloyed steels have small additions of alloying elements such as V, Ti, and Nb, to improve mechanical properties through grain size control and precipitation strengthening. The value of TNR is based on both alloying elements and deformation parameters. To easily predict TNR, equations have been developed and utilized in the literature and industry. However, each equation has certain limitations which constrain its applicability. This study was completed using ten laboratory grade low-carbon microalloyed steels designed to meet the API X-70 specification with varying amounts of V, Nb, and Ti. Double-hit deformation tests were conducted on a Gleeble® 3500 system in the standard pocket-jaw configuration at the Colorado School of Mines to determine experimental values of TNR. Double-hit deformation tests involve cylindrical specimens in an axisymmetric compression test. The test method requires six steps: 1) reheat to ensure most precipitates dissolve back into solution, 2) cool to deformation temperature, 3) compress with given strain and strain rate, 4) hold for interpass time, 5) deform specimen again holding everything else constant, and 6) measure the percent recrystallized or percent fractional softening. The TNR is the temperature where fractional softening is equal to 20 %. Niobium plays the largest role in influencing TNR. Complex niobium-vanadium-carbonitride precipitates are believed to play a significant role increasing TNR in the Hi-V alloy The experimental values of TNR were compared with predicted values of TNR from four equations in the literature. The Bai 2011 equation was the most reliable of the existing empirical formulas considered, while the commonly used Boratto equation was not accurate in predicting the TNR for the alloys in this

  2. Mechanical properties and microstructure of long term thermal aged WWER 440 RPV steel

    Science.gov (United States)

    Kolluri, M.; Kryukov, A.; Magielsen, A. J.; Hähner, P.; Petrosyan, V.; Sevikyan, G.; Szaraz, Z.

    2017-04-01

    The integrity assessment of the Reactor Pressure Vessel (RPV) is essential for the safe and Long Term Operation (LTO) of a Nuclear Power Plant (NPP). Hardening and embrittlement of RPV caused by neutron irradiation and thermal ageing are main reasons for mechanical properties degradation during the operation of an NPP. The thermal ageing-induced degradation of RPV steels becomes more significant with extended operational lives of NPPs. Consequently, the evaluation of thermal ageing effects is important for the structural integrity assessments required for the lifetime extension of NPPs. As a part of NRG's research programme on Structural Materials for safe-LTO of Light Water Reactor (LWR) RPVs, WWER-440 surveillance specimens, which have been thermal aged for 27 years (∼200,000 h) at 290 °C in a surveillance channel of Armenian-NPP, are investigated. Results from the mechanical and microstructural examination of these thermal aged specimens are presented in this article. The results indicate the absence of significant long term thermal ageing effect of 15Cr2MoV-A steel. No age hardening was detected in aged tensile specimens compared with the as-received condition. There is no difference between the impact properties of as-received and thermal aged weld metals. The upper shelf energy of the aged steel remains the same as for the as-received material at a rather high level of about 120 J. The T41 value did not change and was found to be about 10 °C. The microstructure of thermal aged weld, consisting carbides, carbonitrides and manganese-silicon inclusions, did not change significantly compared to as-received state. Grain-boundary segregation of phosphorus in long term aged weld is not significant either which has been confirmed by the absence of intergranular fracture increase in the weld. Negligible hardening and embrittlement observed after such long term thermal ageing is attributed to the optimum chemical composition of 15Cr2MoV-A for high thermal stability.

  3. Effect of Nb on the precipitated phases of MX in switch K2 spring steel%Nb对转K2弹簧钢中MX析出相的影响

    Institute of Scientific and Technical Information of China (English)

    吴华林; 王福明; 李长荣; 张博

    2011-01-01

    采用Thermo-Calc热力学软件,对转K2弹簧钢在400~1600℃存在的平衡析出相及Nb、V在奥氏体相中的固溶规律进行了计算,探讨了各合金元素含量对析出相析出规律的影响,并利用碳萃取复型与透射电镜(TEM)分析了Nb含量对析出相的影响.结果表明:转K2弹簧钢中平衡析出相主要为MX、M7C3、M3C2和AlN;Nb能显著提高MX相的稳定性.TEM分析表明,析出相尺寸变化范围为几纳米到100纳米以上,形态多呈近似球形或圆片状;随Nb含量增加,从低温铁素体中析出的细小颗粒所占比例显著增大,未溶解碳氮化物比%Equilibrium precipitated phases in switch K2 spring steel in the temperature range of 400 to 1600℃ and the solubilities of Nb and V in austenite were calculated by using the thermodynamic software Thermo-Calc to investigate the effect of alloying element content on the equilibrium precipitated phases.Then,the effect of Nb content on the precipitated phases was analyzed by carbon extraction replica and transmission electron microscopy(TEM).It is shown that the main equilibrium precipitated phases in switch K2 spring steel are MX,M7C3,M3C2 and AlN,and the stability of MX phase can be significantly improved by adding Nb.TEM results reveal that the precipitated phases are spherical or disc-shaped,and their sizes range from several nanometers to more than 100nm.With the content of Nb increasing,the proportion of fine particles which precipitated from low-temperature phase ferrite increases dramatically,and the proportion of undissolved carbonitride also increases,overall the average particles size is refined.The large precipitates are Nb-rich carbides,while the small ones are V-rich carbides,which is in accordance with the results of thermodynamic calculations.

  4. Single-source-precursor synthesis of dense SiC/HfCxN1-x-based ultrahigh-temperature ceramic nanocomposites

    Science.gov (United States)

    Wen, Qingbo; Xu, Yeping; Xu, Binbin; Fasel, Claudia; GuillonPresent Address: Forschungszentrum Jülich, Institut Für Energie-Und Klimaforschung 1: Werkstoffsynthese Und Herstellungsverfahren, Wilhelm-Johnen-Straße, D.-52425 Jülich., Olivier; Buntkowsky, Gerd; Yu, Zhaoju; Riedel, Ralf; Ionescu, Emanuel

    2014-10-01

    A novel single-source precursor was synthesized by the reaction of an allyl hydrido polycarbosilane (SMP10) and tetrakis(dimethylamido)hafnium(iv) (TDMAH) for the purpose of preparing dense monolithic SiC/HfCxN1-x-based ultrahigh temperature ceramic nanocomposites. The materials obtained at different stages of the synthesis process were characterized via Fourier transform infrared (FT-IR) as well as nuclear magnetic resonance (NMR) spectroscopy. The polymer-to-ceramic transformation was investigated by means of MAS NMR and FT-IR spectroscopy as well as thermogravimetric analysis (TGA) coupled with in situ mass spectrometry. Moreover, the microstructural evolution of the synthesized SiHfCN-based ceramics annealed at different temperatures ranging from 1300 °C to 1800 °C was characterized by elemental analysis, X-ray diffraction, Raman spectroscopy and transmission electron microscopy (TEM). Based on its high temperature behavior, the amorphous SiHfCN-based ceramic powder was used to prepare monolithic SiC/HfCxN1-x-based nanocomposites using the spark plasma sintering (SPS) technique. The results showed that dense monolithic SiC/HfCxN1-x-based nanocomposites with low open porosity (0.74 vol%) can be prepared successfully from single-source precursors. The average grain size of both HfC0.83N0.17 and SiC phases was found to be less than 100 nm after SPS processing owing to a unique microstructure: HfC0.83N0.17 grains were embedded homogeneously in a β-SiC matrix and encapsulated by in situ formed carbon layers which acted as a diffusion barrier to suppress grain growth. The segregated Hf-carbonitride grains significantly influenced the electrical conductivity of the SPS processed monolithic samples. While Hf-free polymer-derived SiC showed an electrical conductivity of ca. 1.8 S cm-1, the electrical conductivity of the Hf-containing material was analyzed to be ca. 136.2 S cm-1.A novel single-source precursor was synthesized by the reaction of an allyl hydrido

  5. Fenómenos de envejecimiento y oxidación a altas temperaturas en tres aceros inoxidables altamente aleados

    Directory of Open Access Journals (Sweden)

    Botella, J.

    1999-02-01

    Full Text Available The oxidation kinetics in air up to 50 h at 1,373 and 1,473 K of three refractory stainless steels (25Cr20Ni, 21Cr11Ni(1, 21Cr11Ni(2 are studied. At 1,373 K, the best results are those of 25Cr20Ni followed by those of 21Cr11Ni(1, with 0,036 % lanthanides, and the worst behaviour is that of 21Cr11Ni(2, with 0,010 % lanthanides. A 2 h oxidation treatment at 1,323 K in air produces oxidation layers from 1 to 3 μm in thickness for the three materials. Scanning electron microscopy and energy dispersive microanalysis (SEM-EDX and X-ray diffraction (XRD characterisation of the oxidation layers give the same characteristics for the three steels: Mn Cr2O4 spinel type in the outer part, Cr2O3 in the inner one, with a SiO2 barrier in the oxide-metal interface and a large amount of internal and intergranular precipitates (also Si02 in 21Cr11Ni materials. After ageing tests, at 1,073 K for 400 h, about 10 vol. % of the σ-phase is present in the 25Cr20Ni (AISI 310 S material, while no a-phase is present in the 21Cr11Ni materials perhaps due to the high nitrogen content. The application of field emission SEM with EDX allows the analysis of σ-phase and carbides, nitrides and carbonitrides present. The steel 25Cr20Ni only forms, in addition to the σ-phase, M23C6 type carbides, while the steel 21Cr11Ni(1 forms these carbides and M15N nitrides (M8N in the surface and the steel 21Cr11Ni(2 forms mainly carbonitrides M6(CN. The relatively higher nitrogen level in the 21Cr11Ni(1 alloy could explain the different behaviour of both 21Cr11Ni steels.

    Se parte de tres aceros inoxidables austeníticos refractarios (25Cr20Ni, 21Cr11Ni(1, 21Cr11Ni(2 y se estudian las cinéticas de oxidación al aire, hasta 50 h a 1.373 y 1.473 K. El mejor comportamiento a 1

  6. Application of silage ramie byproducts for Pleurotus eryngii cultivation%青贮苎麻副产物栽培刺芹侧耳技术研究

    Institute of Scientific and Technical Information of China (English)

    谢纯良; 严理; 朱作华; 李智敏; 胡镇修; 彭源德

    2013-01-01

    针对食用菌培养基质严重短缺和苎麻副产物直接晾晒干燥成本高、体积大、不便于长途运输等问题,进行青贮苎麻副产物栽培刺芹侧耳试验.通过测定不同营养条件下刺芹侧耳的菌丝生长速率和生物学效率,确定了青贮苎麻副产物培养基栽培刺芹侧耳的适宜配方,并对产品品质进行了检测.结果表明:培养基pH为5.5,培养基中含苎麻副产物50%和水分67.5%,并添加1%碳酸钙和1%白糖时栽培刺芹侧耳的效果较好,生物学效率达70%以上;与常规棉籽壳培养基相比,青贮苎麻副产物培养基栽培产品的蛋白质含量提高了30%,总糖和脂肪含量分别降低了24%和33%.%Faced by issues in the mushroom cultivation,such as substrates shortage,high cost and large volume in direct air-dry or inconvenient long-distance transportation,silage ramie byproducts were tested for Pleurotus eryngii cultivation in this study.The effects of moisture,pH,calcium salts,sugars,additives,and carbonitride on the Pleurotus eryngii growth were measured from mycelial growth rate and biological efficiency.The optimal medium conditions of the silage ramie byproducts and mushroom residues for eryngii cultivation as well as the product quality were also determined.The results showed that the when the cultivation medium contained 50% silage ramie byproducts,35% nitrogen source,67.5% moisture content,1% calcium carbonate and 1% sucrose with a 5.5 pH value,the biological efficiency of Pleurotus eryngii could reach up to 70% above; Compared with the cotton seed hulls medium cultivation,the protein content of the Pleurotus eryngii was increased by 30% and the total sugar and fat were reduced by 24% and 33%,respectively.This study demonstrated that the silage ramie byproduct should be a good raw material for Pleurotus eryngii cultivation.

  7. DLC涂层改善气门挺柱摩擦学性能的试验研究%Experimental Study on Effects of DLC Coating on Improvement of Tappet Tribology Characteristics

    Institute of Scientific and Technical Information of China (English)

    李伟军; 李周裕; 王媛慧

    2015-01-01

    为探求DLC涂层对气门挺柱摩擦学性能的影响,制备了三种不同表面处理的气门挺柱,搭建了配气机构试验台架,对比分析了不同顶面处理方法的气门挺柱在不同转速和缸盖温度下的摩擦功耗;测试了试验前后气门挺柱和凸轮的表面形态,研究了DLC涂层表面特性及其耐磨损特性。试验结果表明,DLC涂层能够减小气门挺柱表面粗糙度,含Si的DLC涂层表面粗糙度极小;气门挺柱与凸轮之间的摩擦力矩随着凸轮轴转速上升逐渐减小,随着缸盖温度上升逐渐增大;相对于传统碳氮共渗气门挺柱,DLC涂层能有效减小摩擦损失,含Si的DLC涂层能减小高达20%的摩擦损失;无涂层气门挺柱和不含Si的DLC涂层气门挺柱的耐磨性较差,含Si的DLC涂层具有极好的耐磨性。%In order to analyze the effects of DLC coating on tribology characteristics of valve tap-pet,tappets with three different kinds of surface treatment were prepared and valvetrain mechanism test bench was built.Then friction loss of valve tappets with different valve tappet top surface treat-ment was tested under different oil temperature.Surface profiles of valve tappets and cams were test-ed before and after the experiments to study the surface characteristic and anti-wear ability of DLC coating.The results show that DLC coating can reduce surface roughness of tappet and DLC coating with Si has extremely small roughness.Friction torque between tappet and cam decreases as the rota-tion speed of camshaft gets bigger and increases when the oil temperature is higher.DLC coating can effectively improve friction loss.Compared with traditional tappet with carbonitriding,DLC coating with Si can cut down friction loss by as large as 20%.Tappets with no coating and with coating with-out Si have bad anti-wear ability,while DLC coating with Si has prefect wear resistance ability.

  8. Z-phase in 9-12% Cr steels

    Energy Technology Data Exchange (ETDEWEB)

    Danielsen, Hilmar; Hald, John [Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Manufacturing Engineering and Management

    2004-04-01

    Precipitation of the complex nitride Z-phase Cr(Nb,V)N has recently been identified as a major cause for premature breakdown in creep strength of a number of new 9-12%Cr martensitic steels. These steels are primarily used in steam pipes and steam turbines of thermal power plants. Z-phase precipitation cancels out the beneficial effects of MX carbo-nitrides rich in V and Nb, which form the backbone of the creep strength of 9-12%Cr steels. Very little is known about the stability of Z-phase, and there are currently no means of predicting its occurrence. The development of a thermodynamic model based on the Thermo-Calc software could provide means to predict in which steels the Z-phase will appear. Ultimately this could form the basis for development of new high strength 9-12%Cr martensitic steels that would be immune to Z-phase precipitation. This could hopefully increase service parameters of future power plants and thus raise efficiency. A literature survey of the Z-phase was made in order to gather all available information for a thermodynamic model, mainly chemical composition and solution temperature of the Z-phase as a function of steel composition are of importance. The survey did not give a complete overview of the Z-phase, so heat treatment experiments and metallographic investigations were carried out to fill the identified gaps. As the model neared completion it became clear that it predicted the Z-phase to be stable in basically all 9-12%Cr steels, that contain its constituents. This also applied to steels like the X20CrMoV121 (12CrMoV), which has been in service for decades and has shown no signs of a breakdown in strength. Close inspection of this steel after very long service exposure showed the Z-phase to be present in a new version (CrVN), albeit in much smaller quantities compared with the newer steels. This effectively makes Z-phase precipitation a kinetic problem, and if its precipitation is sufficiently slow it will not affect the stability of a

  9. Microstructure of spray-formed superalloy FGH4095%氮气喷射成形FGH4095的组织特征

    Institute of Scientific and Technical Information of China (English)

    张宇; 葛昌纯; 沈卫平; 邱成杰

    2012-01-01

    以氮气为雾化气体采用喷射成形工艺制备了FGH4095高温合金沉积坯,记录了沉积过程坯体表面温度曲线,并采用定量金相法、排水法测试了坯体致密度,观察了坯体晶粒及γ′相的形貌.结果表明采用氮气作为雾化介质进行喷射成型喷射沉积坯基体致密度可达99%以上,但也存在着较大的(1—2μm)的气孔,经热等静压和近等温锻后宏观气孔闭合,氮以尺寸不超过1μm的碳氮化物形式存在.喷射沉积坯以等轴晶组织为主,坯体内部平均晶粒尺寸约为20-40μm,近表面区域晶粒较细,约为13μm;一次γ′相多数呈尺寸约0-3—0.5μm不规则块状形貌.喷射成形坯组织结构的形成与喷射成形过程的降温过程有密切关系.%Spray-forming technology can produce billets with similar microstructure and higher productivity compared with the P/M pro- cess. The nickel based superalloy FGH4095 billet was produced by spray-forming with nitrogen as atomization gas. The pressure of the atomization gas and the temperature of the deposit zone were recorded. The compactness of the deposit was characterized by quantitative metallography and Archimedes method. The grain structure of γ substrate and the size and morphology of γ′ phase were observed. Results show that the density of the deposit produced by nitrogen spray forming reaches about 99% and little amount of pores with diameters about 1--2 μm could be detected in the deposit matrix. While, pores could be enclosed by HIP and near iso-thermal forging process; Nitrogen was existed as carbonitride with diameters less than 1 μm. The average grain size of the equiaxed grains in the interior of the deposit is about 20-40 μm, while the grains near the surface of the deposit are finer with average grain size about 13μm; the primary γ′ phase which has diameters about 0.3-0.5 μm possesses irregular block feature. The microstructure of the spray

  10. Development of Advanced Wear and Corrosion Resistant Systems Through Laser Surface Alloying and Materials Simulations

    Energy Technology Data Exchange (ETDEWEB)

    R. P. Martukanitz and S. Babu

    2007-05-03

    precipitation of titanium carbonitrides during laser surface alloying provided there was sufficient amount of dissolved titanium, carbon, and nitrogen in the liquid steel. This was confirmed experimentally by using a powder mixture of 431-martensitic steel, titanium carbide powder, and nitrogen shielding, during laser deposition to produce deposits exhibiting relatively high hardness (average surface hardness of 724 HV). The same approach was extended to direct diode laser processing and similar microstructures were attained. The above analysis was extended to develop an in-situ precipitation of Ti(CN) during laser deposition. The Ti addition was achieving by mixing the 431 martensitic steel powders with ferro-titanium. The dissolution of nitrogen was achieved by using 100% nitrogen shielding gas, which was indicated by thermodynamic analysis. Demonstrations were also conducted utilizing the tools developed during the program and resulted in several viable composite coating systems being identified. This included the use of TiC and ferro-titanium in martensitic-grade stainless steel matrix material with and without the use of active N2 shielding gas, WC hard particles in a martensitic-grade stainless steel matrix material, WC and BN in a nickel-based matrix material, and WC in highly alloyed iron-based matrix. Although these demonstrations indicated the potential of forming composite coatings, in certain instances, the intended industrial applications involved unique requirements, such as coating of internal surfaces, which hindered the full development of the improved coating technology. However, it is believed that the addition of common hard particles, such as WC or TiC, to matrix material representing martensitic grades of stainless steel offer opportunities for improved performance at relatively low material cost.

  11. Microstructural analysis as the indicator for suitability of weld repairing of the heat resistant Cr - Ni steel

    Directory of Open Access Journals (Sweden)

    Odanović, Z.

    2010-08-01

    Full Text Available Metallurgical evaluation was performed on a fractured column tube of the reformer furnace in an ammonia plant. The tubes were manufactured from centrifugally cast heat resistant steel HK 40. Optical and scanning electron microscope (SEM were used for microstructural and fracture analysis. For composition determination of the microconstituents energy dispersive X ray spectroscopy (EDS was used. To evaluate mechanical properties, hardness and microhardness measurements were performed. Investigations based on the microstructural features with the idea to indicate suitability of weld repair of the column were performed in this study. It was observed that the crack initiation, caused by oxidation/corrosion and thermal stresses induced by temperature gradient, appeared in the inner side of the tube wall and propagation occurred along grain boundaries. The results clearly showed the presence of an irregular microstructure which contributed to crack propagation through the tube wall. An occurrence of precipitated needle-shaped carbides/carbonitrides and brittle σ phase was also identified in the microstructure. Results of the microstructural and fracture analysis clearly indicate that reformer furnace columns made of heat resistant steel HK 40 were unsuitable for weld repair.

    La evaluación metalúrgica se realizó en un tubo de columna con fracturas, que es parte del horno reformador en una planta de amoníaco. Estos tubos son fundidos centrífugamente y fabricados en acero resistente al calor, de tipo HK- 40. Para el análisis microestructural de la fractura se ha utilizado microscopía óptica y electrónica de barrido (SEM. La composición de los micro-constituyentes se determinó por espectrometría de rayos X de energía dispersiva (EDS. Las propiedades mecánicas se evaluaron mediante mediciones de microdureza Vickers. Las investigaciones en este estudio se han llevado a cabo con el fin de demostrar la idoneidad de reparación por

  12. Synthesis of IV-VI Transition Metal Carbide and Nitride Nanoparticles Using a Reactive Mesoporous Template for Electrochemical Hydrogen Evolution Reaction

    KAUST Repository

    Alhajri, Nawal Saad

    2016-01-01

    content rather than nitride. In addition, the reactivity of the transition metals of group IV-VI with the reactive template was investigated under a flow of N2 at different temperatures in the range of 1023 to 1573 K while keeping the weight ratio constant at 1:1. The results show that Ti, V, Nb, Ta, and Cr reacted with mpg-C3N4 at 1023 K to form nitride phase with face centered cubic structure. The nitride phase destabilized at higher temperature ≥1223 K through the reaction with the remaining carbon residue originated from the decomposition of the template to form carbonitride and carbide phases. Whereas, Mo and W produce a hexagonal structure of carbide irrespective of the applying reaction temperature. The tendency to form transition metal nitrides and carbides at 1023 K was strongly driven by the free energy of formation. The observed trend indicates that the free energy of formation of nitride is relatively lower for group IV and V transition metals, whereas the carbide phase is thermodynamically more favorable for group VI, in particular for Mo and W. The thermal stability of nitride decreases at high temperature due to the evolution of nitrogen gas. The electrocatalytic activities of the produced nanoparticles were tested for hydrogen evolution reaction in acid media and the results demonstrated that molybdenum carbide nanoparticles exhibited the highest HER current with over potential of 100 mV vs. RHE, among the samples prepared in this study. This result is attributed to the sufficiently small particle size (8 nm on average) and accordingly high surface area (308 m2 g-1). Also, the graphitized carbon layer with a thickness of 1 nm on its surface formed by this synthesis provides excellent electron pathway to the catalyst which will improve the rate of electron transfer reaction.

  13. Microstructural analysis of weld cracking in 718 Plus superalloy

    Science.gov (United States)

    Vishwakarma, Krutika

    chemistries. The main discernible difference was the formation of gamma' as the main strengthening precipitate in 718 Plus alloys in the as received and 950°C solution heat treated condition. The other phases present in the pre-weld microstructure were Nb rich MC type carbides, Ti rich carbonitrides and grain boundary delta phase. Solution heat treated plates of all the three alloys were welded with a sharp focus electron beam with the welding parameters of 44 kV voltage, 79 mA current and 152 cm/min speed. The microsegregation pattern of 718 Plus during solidification of the fusion zone indicated that while Fe, Co, W and Cr segregated to the core of the gamma dendrites, Nb, Ti and Al were extensively rejected into the interdendritic liquid. Electron diffraction and x-ray microanalysis using transmission electron microscopy (TEM) of the fusion zone showed that the major secondary phases that formed from the interdendritic liquid were gamma/MC type carbide eutectic and gamma/Laves eutectic constituents. Heat affected Zone (HAZ) microfissuring due to liquation was observed in all the alloys with resolidified products on the liquated and resolidified grain boundaries. Grain boundary liquation and segregation of minor alloying elements was considered to he the primary reason for liquation of HAZ grain boundaries which caused cracking. Evidence of constitutional liquation of Nb rich MC type carbides in 718 Plus was found in the region adjacent to the fusion zone and also on the cracked grain boundaries. The resolidified products along the microfissures consisted of gamma + Laves and gamma + MC type carbide eutectics. Complete and partial healing of microfissuring by backfilling was also observed. Segregation of B was detected by SIMS on the grain boundaries of both the 718 Plus alloys, with higher concentration of Bon HC 49 grain boundaries. Also, for the first time, P was detected by SIMS on the cracked grain boundaries on both the alloys, which confirmed that grain boundary