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Sample records for carbonitrides

  1. Synthesis of transition metal carbonitrides

    Energy Technology Data Exchange (ETDEWEB)

    Munir, Zuhair A. R. (Davis, CA); Eslamloo-Grami, Maryam (Davis, CA)

    1994-01-01

    Transition metal carbonitrides (in particular, titanium carbonitride, TiC.sub.0.5 N.sub.0.5) are synthesized by a self-propagating reaction between the metal (e.g., titanium) and carbon in a nitrogen atmosphere. Complete conversion to the carbonitride phase is achieved with the addition of TiN as diluent and with a nitrogen pressure .gtoreq.0.6 MPa. Thermodynamic phase-stability calculations and experimental characterizations of quenched samples provided revealed that the mechanism of formation of the carbonitride is a two-step process. The first step involves the formation of the nonstoichiometric carbide, TiC.sub.0.5, and is followed by the formation of the product by the incorporation of nitrogen in the defect-structure carbide.

  2. Carbonitride fuel: results of researches

    International Nuclear Information System (INIS)

    Full text: The method of carbothermic conversation of uranium dioxide in a stream of nitrogen was chosen as a fundamental technology of carbonitride fuel manufacturing. The processes of producing UCN in the presence of methane and carbon oxide were investigated at carbothermic conversion of UO2 in nitrogen and nitrogen-hydrogenous atmospheres (P=0.1 MPa, T=1673-2073 K). The possibility for realization of UCN (UN) synthesis on compact UO2 samples in the presence of gas-phase transfer of carbon in in the system is demonstrated. Results are reported from reactor tests of coated particles and uranium-graphite fuel elements based on carbonitride fuel at temperatures of 1250 deg. C and 1500 deg.C to burnups if 18.5 % fima and 18.0 % fima. respectively. The specimens under test have shown high serviceability of the fuel developed (R/B) no more (3.5-6.0)·10-6). The technology of manufacturing carbonitride (nitride) fuel created in NSC KIPT and the results of its tests, including reactor tests, allow us to recommend it for using in nuclear power plants. The performance of future experiments will make it possible to realize the potential of the developed technology for producing nitride fuel base on nitrogen-15 isotope

  3. Silicon carbonitrides - a novel class of materials

    International Nuclear Information System (INIS)

    Silicon carbonitride monoliths derived from polymer powder compacts via polymer pyrolysis represent a new class of structural ceramic materials due to the complete coalescence of the powder particles during polymer decomposition and the formation of a uniform ceramic matrix free from any grain boundaries or secondary phases. The submicron pore channel system penetrating the material can be minimized in volume by infiltration of liquid polysilazane solution or by post-HIPing so that relative densities of 96 % can be reached. The monoliths are oxidation resistant up to 1600 C in air due to the formation of a highly pure silica oxidation layer and they exhibit a creep rate of 1.10-6 s-1 at 1650 C and 30 MPa load. Initially x-ray amorphous silicon carbonitride can be crystallized in nitrogen or in air to form Si3N4/SiC or Si3N4/SiC/C nanocomposites. (orig.)

  4. Silicon carbonitrides - A novel class of materials

    OpenAIRE

    SchÖnfelder, H.; Aldinger, F.; R. Riedel

    1993-01-01

    Silicon carbonitride monoliths derived from polymer powder compacts via polymer pyrolysis represent a new class of structural ceramic materials due to the complete coalescence of the powder particles during polymer decomposition and the formation of a uniform ceramic matrix free from any grain boundaries or secondary phases. The submicron pore channel system penetrating the material can be minimized in volume by infiltration of liquid polysilazane solution or by post-HIPing so that relative d...

  5. The mechanism of combustion synthesis of titanium carbonitride

    Energy Technology Data Exchange (ETDEWEB)

    Eslamloo-Grami, M.; Munir, Z.A. (Department of Mechanical, Aeronautical and Materials Engineering, University of California at Davis, Davis, California 95616-5294 (United States))

    1994-02-01

    Titanium carbonitride, TiC[sub 0.5]N[sub 0.5], is synthesized directly by a self-propagating reaction between titanium and carbon in a nitrogen atmosphere. Complete conversion to the carbonitride phase is achieved with the addition of TiN as diluent and with a nitrogen pressure [ge]0.6 MPa. Thermodynamic phase-stability calculations and experimental characterizations of quenched samples support a proposed mechanism in which the formation of the carbonitride is a two-step process. The first step involves the formation of the nonstoichiometric carbide, TiC[sub 0.5], and is followed by the formation of the product by the incorporation of nitrogen in the defect-structure carbide to form the carbonitride solid solution.

  6. 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.

  7. Laser-Induced Chemical Vapour Deposition of Silicon Carbonitride

    OpenAIRE

    Besling, W.; van der Put, P.; Schoonman, J.

    1995-01-01

    Laser-induced Chemical Vapour Deposition of silicon carbonitride coatings and powders has been investigated using hexamethyldisilazane (HMDS) and ammonia as reactants. An industrial CW CO2-laser in parallel configuration has been used to heat up the reactant gases. HMDS dissociates in the laser beam and reactive radicals are formed which increase rapidly in molecular weight by an addition mechanism. Dense polymer-like silicon carbonitride thin films and nanosized powders are formed depending ...

  8. Synthesis, sintering properties and thermal conductivity of uranium carbonitrides

    International Nuclear Information System (INIS)

    An introduction to the applications and chemistry of uranium carbonitrides is given including the potential use as a nuclear fuel. The powder synthesis of UC, UN and mixtures of UC and UN by a cyclic process is described. The correlation between the composition ratio UN/(UC+UN) in the final product and the parameters of the process is only determined qualitatively. Batch synthesis of a powder does not lead to an increase of the content of metallic impurities and oxygen. The impurity level is determined by that of the starting uranium metal and the thermal conductivity of the sintered compacts of uranium carbonitrides are determined via the measurement of the thermal diffusivity at 1100-1700 K. (Auth.)

  9. 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.

  10. An expression for solubility product of complex carbonitrides in multicomponent microalloyed austenite

    Energy Technology Data Exchange (ETDEWEB)

    Liu Xiaodong; Solberg, J.K.; Gjengedal, R. (NTH, Trondheim (Norway). Dept. of Metallurgy); Kluken, A.O. (SINTEF Metallurgy, Trondheim (Norway))

    1994-12-15

    In view of the great interest in HSLA steels with small additions of titanium, niobium and/or vanadium, the solubility products of nitrides, carbides and carbonitrides in austenite have been investigated both theoretically and experimentally by many researchers. Nordberg and Aronsson first derived the solubility product for a complex carbonitride of a single microalloying element such as niobium, on which Hudd et al made some modifications. More recently, the complex addition of microalloying elements in HSLA steels has also received more attention. Clearly, the equilibrium composition of the precipitates depends on the composition of the steel and on the temperature. Some theoretical method have been derived to give this information, but none of them deal with the solubility product of complex carbonitrides containing more than one microalloying element (e.g. niobium and titanium). In the present paper, a general solubility product expression is derived for all kinds of complex carbonitrides with multicomponent microalloying additions.

  11. Experimental study of vanadium carbide and carbonitride coatings

    Energy Technology Data Exchange (ETDEWEB)

    Chicco, B.; Summerville, E. (CSIRO Manufacturing Science and Technology, Woodville (Australia). Adelaide Lab.); Borbidge, W.E. (CSIRO Manufacturing Science and Technology, Melbourne Laboratory, Private Bag 33, Rosebank MDC, Clayton, Victoria, 3169 (Australia))

    1999-06-30

    Previous authors have established that prior nitriding or nitrocarburising will enhance the thickness of the vanadised coating formed on tool steels by the thermal diffusion (TD) process. However, whereas the single TD treatment produces a uniform surface layer of vanadium carbide, the combined treatments result in a complex vanadium carbonitride coating. Such a coating can be expected to exhibit a hardness that is lower overall and decreases away from the surface with increasing nitrogen to carbon ratio. An experimental study was undertaken to assess the relative merits of nitriding, nitrocarburising and carburising prior to TD vanadising on the steel AISI H13. The study demonstrates the specific advantages of carburising, previously untried as a pre-treatment. It produces the thickest coating (about twice as thick as that due to vanadising alone) and, perhaps more importantly, the coating is essentially vanadium carbide and exhibits a uniform high hardness across its entire span. (orig.) 30 refs.

  12. Precipitation of niobium carbonitrides in ferrite: chemical composition measurements and thermodynamic modelling

    OpenAIRE

    Perez, Michel; Courtois, E.; Acevedo, D.; T. Epicier; Maugis, Philippe

    2007-01-01

    High-resolution transmission electron microscopy and electron-energy loss spectroscopy have been used to characterize the structure and chemical composition of niobium carbonitrides in the ferrite of a Fe–Nb–C–N model alloy at different precipitation stages. Experiments seem to indicate the coexistence of two types of precipitates: pure niobium nitrides and mixed substoichiometric niobium carbonitrides. In order to understand the chemical composition of these precipitates, a thermodynamic for...

  13. Improvement of titanium alloy for biomedical applications by nitriding and carbonitriding processes under glow discharge conditions.

    Science.gov (United States)

    Czarnowska, E; Wierzchoń, T; Maranda-Niedbała, A; Karczmarewicz, E

    2000-02-01

    Although titanium alloys are used in medicine, they present low wear resistance. In this paper we present the results of studies on surface layers produced by nitriding at three different temperatures, and by carbonitriding under glow discharge conditions in order to improve wear resistance, hardness, and to modulate microstructure and chemical composition of surface layers. A cell culture model using human fibroblasts was chosen to study the effect of such treatments on the cytocompatibility of these materials. The results showed that nitrided and carbonitrided surface layers were cytocompatible. Modulation of surface microstructure by temperature in the nitriding process and chemical composition of surface layers by carbonitriding led to differences in cellular behaviour. Cell proliferation appeared to be slightly reduced from the 6th day of culture on nitrided surfaces produced at 730 degrees C and 1000 degrees C, however after 12 days of culture, the best growth was on surface layers produced at 850 degrees C. The best viability was observed on the carbonitrided layer. The orientation and shape of the cells corresponded to surface topography. Nitriding and carbonitriding under glow discharge conditions may constitute interesting techniques allowing the formation of surface layers on parts with sophisticated shapes. They may also permit modulating surface topography in a way improving the features of titanium alloys for various applications in medicine. PMID:15348050

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

    International Nuclear Information System (INIS)

    Highlights: ► Molybdenum (oxy)carbonitrides have been prepared from single source routes. ► Nitrogen species are more reactive than carbon species within the carbonitrides. ► 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.

  15. Phthalo-carbonitride: an ab initio prediction of a stable two-dimensional material

    Science.gov (United States)

    Tsetseris, Leonidas

    2016-06-01

    Using density-functional theory calculations, we identify a stable two-dimensional carbonitride polymorph which resembles the core of phthalocyanine molecules. This so-called phthalo-carbonitride is found to be the lowest-energy polymer made of tetracyanoethylene molecules. It is a two-dimensional metal in its pristine form. Functionalization of the phthalo-cores with copper or iron atoms retains the metallic character of the material, but also adds magnetization to the system. Based on these properties and the established use of phthalocyanine molecules in various applications, the growth of phthalo-carbonitride sheets can add another multi-functional building block to the research and technology of two-dimensional materials.

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

    Science.gov (United States)

    Wu, Jie; Zhang, Yifan; Liu, Run; Wang, Bin; Hua, Ming; Xue, Wenbin

    2015-08-01

    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 × 1021 m-3 and 4000 K, respectively. The carbonitrided layer contained Al4C3, AlN and Al7C3N3 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.

  17. Fundamentals of liquid phase for modern cermets and functionally graded cemented carbonitrides (FGCC)

    International Nuclear Information System (INIS)

    Metallurgical reactions and microstructure developments during sintering of modern cermets and functionally graded cemented carbonitrides (FGCC) were investigated by modern thermal and analytical methods such as mass spectrometer (MS), differential thermal analysis (DTA), differential scanning calorimeter (DSC), dilatometer (DIL), microscopy and analytical electronic microscopy with energy dispersive spectrometer (EDS). The complex phase reactions and phase equilibrium in the multi-component system Ti/Mo/W/Ta/Nb/C,N-Co/Ni were studied. The melting behaviors in the systems of TiC-WC/MoC-Ni/Co, TiC-TiN-WC-Co and TiCN-TaC-WC-Co have been established. By better understanding of the mechanisms that govern the sintering processing and metallurgical reactions, new cermets and different types of functionally graded cemented carbonitrides (FGCC) with desired microstructures and properties were developed and fabricated. (author)

  18. Study of structure and phase composition of nanocrystal silicon carbonitride films

    CERN Document Server

    Fainer, N I; Rumyantsev, Y M; Kosinova, M L; Kuznetsov, F A

    2001-01-01

    The novel ternary silicon carbonitride films were synthesised by RPECVD using hexamethyldisilazane Si sub 2 NH(CH sub 3) sub 6 as a volatile single-source precursor. Different analysis techniques such as IR, Raman spectroscopy, ellipsometry, XPS, SEM, HRTEM, and SAED were used to study their physical and chemical properties. Maximum attention has been concentrated on the application of synchrotron radiation in structure and phase investigation of thin films. On the basis of data of SEM, HRTEM and diffraction of synchrotron radiation, it was established that silicon carbonitride films represent a distribution of nanocrystals (20-90 A) in an amorphous matrix. The nanocrystalline component is a pseudo alpha-Si sub 3 N sub 4 phase faceted by high-index planes. This phase can contain carbon atoms which have insufficient influence on the modification of the alpha-Si sub 3 N sub 4 lattice parameters due to the similar atomic radius of carbon and silicon.

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

    International Nuclear Information System (INIS)

    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 × 1021 m−3 and 4000 K, respectively. The carbonitrided layer contained Al4C3, AlN and Al7C3N3 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

  20. 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.

  1. Effect of Residual Stress on Fatigue Failure of Carbonitrided Low-Carbon Steel

    Science.gov (United States)

    Kanchanomai, C.; Limtrakarn, W.

    2008-12-01

    The effect of residual stress on fatigue behavior and mechanisms of carbonitrided AISI 1015 steel under uniaxial cyclic loading has been experimentally studied. By progressive removal of thin surface layers using an electropolishing technique and subsequent residual stress measurements using an x-ray diffraction technique, the compressive residual stress at the surface was approximately 900 MPa. The stress decreased toward the center, and became stable tensile residual stress of approximately 20 MPa. The fatigue resistance of carbonitrided AISI 1015 steel was higher than that of AISI 1015 steel due to the presence of compressive residual stress in case layer. The fatigue limit of AISI 1015 steels with and without carbonitriding was 340 and 300 MPa, respectively. Subsurface cracks initiated at the case-core interface, i.e. approximately 400 μm from the surface. With increasing number of stress cycles, the subsurface cracks coalesced and propagated intergranularly through the case layer. After some incubation cycles, the subsurface cracks reached the surface of specimen, and became a main crack. During this stage, the stress increased, and caused the formation of voids in core material. Consequently, the crack propagated through the core material, interacted with voids, and caused complete fracture.

  2. Duplex treatment of 304 AISI stainless steel using rf plasma nitriding and carbonitriding

    International Nuclear Information System (INIS)

    Surface of 304 AISI austenitic stainless steel has been modified using duplex treatment technique of nitriding and carbonitriding. A thick modified nitrided layer, of approximately 20 μm, has been achieved when rf inductively coupled plasma was adjusted at 450 W for processing time of only 10 min. After performing the nitrided layer, the nitrided samples were carbonitrided using the same technique at different acetylene partial pressure ratios ranges from 10% to 70%, the balance was pure nitrogen. Different amount of nitrogen and carbon species are diffused underneath the surface through the nitrided layer during carbonitriding process and are found to be gas composition dependent. The treated samples were characterized by glow discharge optical spectroscopy, X-ray diffractometry, scanning electron microscopy and Vickers microhardness tester. The microstructure of the duplex treated layer indicates the formation of γ-Fe4N, Fe3C, CrN and nitrogen-expanded austenite (γN). The thickness of the duplex treated layer increases with increasing the acetylene partial pressure ratio. The surface microhardness of duplex treated samples has been found to be gas composition dependent and increased by 1.29 fold in comparison to the nitrided sample.

  3. Mean-square displacement of atomic complex in titanium carbonitrides TiCxNy

    International Nuclear Information System (INIS)

    Full text: The atomic mean-square displacement (MSD) is one of important characteristics of solids, and one can use it for determination of a number of other characteristics of substances. In this work the MSD of atomic complex were determined for a number of compositions of the cubic titanium carbonitrides TiCxNy using the neutron powder diffraction data. The error of MSD determination was less than 3 %. When determining intensity of diffraction maximum a correction for the thermal diffusion dispersion (TDD) was included in the neutron diffraction patterns. The contribution of TDD in the intensity of diffraction maxima was found to be less than the experiment error (no more than 1,5 %). Such small value of the TDD correction is explained by refractory of materials. The values of MSD in titanium carbonitrides for a number of compositions, determined by the neutron powder diffraction measurements, are given. It is shown, that the dependence of MSD on the concentration (C+N)/Ti has a complex character. With decrease of the total content of metalloids MSD decreases at first, reaching a minimum about concentration (C+N)/Ti≅0.80, and then increases. MSD consists of dynamic and static distortions, where the static distortions in the compounds with variable composition increase with increasing of deviation from stoichiometry. The above anomaly in the dependence of MSD on the total concentration of metalloids, apparently, point to prevalence of dynamic distortions over static ones and to complex character of concentration dependence of interatomic interactions in the titanium carbonitrides. This work was supported by the Supporting Fund for Fundamental Researches of Uzbekistan Academy of Sciences (Grant No. 6-04)

  4. Phase composition and some properties of titanium carbonitride-titanium nickelide alloys with Al2O3 nanoparticles

    Science.gov (United States)

    Ermakov, A. N.; Misharina, I. V.; Grigorov, I. G.; Pushin, V. G.; Zainulin, Yu. G.

    2009-02-01

    The phase formation in and the microstructure of titanium carbonitride-titanium nickelide alloys with aluminum oxide Al2O3 nanopowder additions are studied by X-ray diffraction, electron-microscopic, and electron-probe microanalyses. The phase interaction is characterized by the redistribution of nonmetallic elements and aluminum between refractory and binding phases with the formation of a nonstoichiometric titanium-aluminum (Ti,Al)(C,N) carbonitride and a titanium-aluminum nickelide. The number of forming phases and their compositions are controlled by the kinetic parameters of the process.

  5. Peculiarities of Production of Chromium Carbonitride Nanopowder and Its Physical-Chemical Certification

    Science.gov (United States)

    Shiryaeva, L. S.; Nozdrin, I. V.; Galevsky, G. V.

    2015-09-01

    Scientific and technological basics of plasma synthesis of chromium carbonitride have been developed, including analysis of the current production state and application of chromium carbon compounds, defining characteristics of three-jet plasma reactor, modeling- mathematical study of interaction of raw materials and plasma streams, prediction of technological parameters of plasma stream based on the modeling results, selection of optimal technological option, implementation of plasma-metallurgical technology of chromium nitride production, its physical-chemical certification and defining technical-economical production factors.

  6. Quantitative mass spectrometry of decarburization and denitridation of cemented carbonitrides during sintering

    International Nuclear Information System (INIS)

    Quantitative quadrupole mass spectrometry of (Ti,W)C-based cemented carbonitrides was carried out in order to monitor the evolution of the gas species as a function of time and temperature during vacuum sintering. Solid standards and gas mixtures as well as precise flow control were employed for calibration. Upon integration of the outgassing rates the carbon and nitrogen evolutions and mass losses during sintering of raw hardmetal powder mixtures (WC, TiC, ...) and cemented carbonitrides could be quantified. Outgassing occurs in the range of temperatures 490-1480 oC. Nitrogen outgassing of (Ti,W)(C,N) was greater than that of Ti(C,N) due to the presence of W which increases the nitrogen activity in the solid causing a higher nitrogen equilibrium pressure. TiN showed a CO (0.2 wt %) and N2 (0.5 wt %) weight loss only in the presence of the binder phase. For powder mixtures, it was observed that the amount of CO, CO2 and N2 liberated during vacuum sintering increased with the addition of cobalt in comparison with the same powders without binder phase. Nitrogen containing cermet alloys showed a greater loss of carbon than (Ti,W)C-based hardmetals. (author)

  7. Electrochemical study of lithium insertion into carbon-rich polymer-derived silicon carbonitride ceramics

    International Nuclear Information System (INIS)

    This paper presents the lithium insertion into carbon-rich polymer-derived silicon carbonitride (SiCN) ceramic synthesized by the thermal treatment of poly(diphenylsilylcarbodiimide) at three temperatures, namely 1100, 1300, and 1700 oC under 0.1 MPa Ar atmosphere. At lower synthesis temperatures, the material is X-ray amorphous, while at 1700 oC, the SiCN ceramic partially crystallizes. Anode materials prepared from these carbon-rich SiCN ceramics without any fillers and conducting additives were characterized using cyclic voltammetry and chronopotentiometric charging/discharging. We found that the studied silicon carbonitride ceramics demonstrate a promising electrochemical behavior during lithium insertion/extraction in terms of capacity and cycling stability. The sample synthesized at 1300 oC exhibits a reversible capacity of 392 mAh g-1. Our study confirms that carbon-rich SiCN phases are electrochemically active materials in terms of Li inter- and deintercalation.

  8. 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.

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

    OpenAIRE

    Kostyk, V. O.; Kostyk, K. O.; Dolzhenko, A. S.

    2013-01-01

    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.

  10. 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.

  11. Formation of titanium carbonitride film by laser treatment: Structural and transport properties

    Energy Technology Data Exchange (ETDEWEB)

    Soni, Sheetal; Pandey, A.; Gupta, Ratnesh [School of Instrumentation, Devi Ahilya University, Khandwa Road, Indore-452001 (India); Sinha, A. K., E-mail: gratnesh-ioi@yahoo.com [Indus Synchrotron Utilization Division, Raja Ramanna Center for Advanced Technology, Indore-452013 (India)

    2015-06-24

    In-plane and Out-of-plane Grazing incidence X-ray diffraction is used to characterize the preferred orientation present in the titanium carbonitride films using ADXRD beamline at INDUS 2 synchrotron radiation source. GIXRD shows the formation of mixture of FCCTiC{sub x}N{sub (1-x)} films for different values of x along with the solid solution. From the in-plane and out-of-plane XRD measurements, we have observed that a specific texture along the c-axis of Ti has been formed during the laser treatment process. Due to the diffusion of C and N into Ti, the resistance of the specimen has been decreases with respect to the resistance of pure Ti sheet. The formed phases are stable and there is no structural relaxation has been observed during annealing process.

  12. 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.

  13. Origin and dispersion strengthening of carbonitrides in a commercial hot strip micro alloyed niobium steel

    International Nuclear Information System (INIS)

    Throughout this work, a study on niobium carbonitrides formation and its hardening effect in a commercial hot strip micro alloyed 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. (Author) 28 refs

  14. Titanium carbonitride films on cemented carbide cutting tool prepared by pulsed high energy density plasma

    Science.gov (United States)

    Feng, Wenran; Liu, Chizi; Chen, Guangliang; Zhang, Guling; Gu, Weichao; Niu, Erwu; Yang, Si-Ze

    2007-03-01

    Hard films prepared by pulsed high energy density plasma (PHEDP) are characterized by high film/substrate adhesive strength, and high wear resistance. Titanium carbonitride (TiCN) films were deposited onto YG11C (ISO G20) cemented carbide cutting tool substrates by PHEDP at room temperature. XRD, XPS, SEM, AES, etc. were adopted to analyze the phases (elements) composition, microstructure and the interface of the films, respectively. The results show that, the uniform dense films are composed of grains ranging from 70 to 90 nm. According to the AES result, there is a broad transition layer between the film and the substrate, due to the ion implantation effect of the PHEDP. The transition layer is favorable for the film/substrate adhesion.

  15. Structural, elastic and thermodynamic properties of the tetragonal structure of germanium carbonitride

    Science.gov (United States)

    Xing, Mengjiang; Li, Binhua; Yu, Zhengtao; Chen, Qi

    2016-04-01

    The structural, mechanical, electronic and thermodynamic properties of the tetragonal structure germanium carbonitride (t-GeCN) were first investigated using the density function theory with the ultrasoft psedopotential scheme in the frame of the generalized gradient approximation and the local density approximation. The elastic constants have confirmed that the t-GeCN is mechanically stable and phonon spectra have confirmed that the t-GeCN is dynamically stable. The anisotropy studies show that t-GeCN exhibits a larger anisotropy in its Poisson's ratio, Young's modulus, shear modulus, sound velocities and universal elastic anisotropy index. Electronic structure study shows that t-GeCN is an indirect semiconductor with band gap of 0.628 eV. The thermodynamic properties of t-GeCN, including Debye temperature, heat capacity, Grüneisen parameter and thermal expansion coefficient are investigated utilizing the quasi-harmonic Debye model.

  16. Thermodynamic calculation of carbonitrides solubility in low-carhon steels alloyed with vanadium and aluminium

    International Nuclear Information System (INIS)

    The aim of the study is to calculate the vanadium carbonitride solubility in low-carbon steels on the basis of data on VC and VN solubility, to describe phase equilibrium in the system with regard to all phases the formation of which is possible in an austenitic region, to perform the thermodynamic calculation and to carry out an experimental investigation with the purpose of checking the permissibility of accepted simplifications. It is shown that the #betta#-Fe-V(C,N)-AlN-Al2O3 system perfectly corresponds to the case of austenitic region in low-carbon steels with vanadium and aluminium. The equations which permit to calculate phase equilibrium in this system are derived. Thermodynamic calculations are performed and comparison of their results with the data of experimental investigation of phase composition is carried out. A perfect coinsidence of calculation and experiment results is shown

  17. EELS study of niobium carbo-nitride nano-precipitates in ferrite.

    Science.gov (United States)

    Courtois, E; Epicier, T; Scott, C

    2006-01-01

    Micro-alloying steels allow higher strength to be achieved, with lower carbon contents, without a loss in toughness, weldability or formability through the generation of a fine ferrite grain size with additional strengthening being provided by the fine scale precipitation of complex carbo-nitride particles. Niobium is reported to be the most efficient micro-alloying element to achieve refinement of the final grain structure. A detailed microscopic investigation is one of the keys for understanding the first stages of the precipitation sequence, thus transmission electron microscopy (TEM) is required. Model Fe-(Nb,C) and Fe-(Nb,C,N) ferritic alloys have been studied after annealing under isothermal conditions. However the nanometre scale dimensions of the particles makes their detection, structural and chemical characterization delicate. Various imaging techniques have then been employed. Conventional TEM (CTEM) and high resolution TEM (HRTEM) were used to characterise the morphology, nature and repartition of precipitates. Volume fractions and a statistical approach to particle size distributions of precipitates have been investigated by energy filtered TEM (EFTEM) and high angle annular dark field (HAADF) imaging. Great attention was paid to the chemical analysis of precipitates; their composition has been quantified by electron energy loss spectroscopy (EELS), on the basis of calibrated 'jump-ratios' of C-K and N-K edges over the Nb-M edge, using standards of well-defined compositions. It is shown that a significant addition of nitrogen in the alloy leads to a complex precipitation sequence, with the co-existence of two populations of particles: pure nitrides and homogeneous carbo-nitrides respectively. PMID:16500107

  18. 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.

  19. Coatings on the base of nitrogen steel with carbonitride strengthening produced by the method of electron-beam surfacing

    International Nuclear Information System (INIS)

    High quality wear resistant coatings for materials working under intensive wear conditions are developed. The choice of nitrogen containing chromium-manganese steel of austenite class as a binding was caused by its strong hardening under cold plastic strain, and also by its good ductility and corrosion resistance. The use of titanium carbonitride as a hardening phase was connected with a unique combination of its high hardness and thermodynamic stability at high temperatures. It is shown that under electron-beam surfacing of composite powder coatings on the base of nitrogen chromium-manganese steel with different content of titanium carbonitride TiC0.5N0.5 the gradient cast coatings of variable chemical composition are formed. An abrasive wear resistance of the coatings is increased with the content of a hard phase increasing

  20. Synthesis and characterization of nanocrystalline hexagonal boron carbo-nitride under high temperature and high pressure

    International Nuclear Information System (INIS)

    A study of the synthesis of hexagonal boron carbo-nitride (h-BCN) compounds via a two-step high-temperature and high-pressure (HTHP) technique using melamine (C3N6H6) and boron oxide (B2O3) as raw materials is presented. An amorphous BCN precursor was prepared at 1000 K under vacuum in a resistance furnace and then single-phase h-BCN nanocrystalline was synthesized at 1600 K and 5.1 GPa in a multi-anvil apparatus. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the final products were pure h-BCN crystals with the lattice constants a 0.2510 nm and c = 0.6690 nm. The average grain size was about 150 nm. X-ray photoelectron spectroscopy (XPS) results confirmed the occurrence of bonding between C-C, C-N, C-B and N-B atoms. Raman scattering analysis suggested that there were three strong Raman bands centered at 1359, 1596 and 1617 cm-1, respectively. The band at 1617 cm-1 was considered to be consistent with the characteristic Raman peak of h-BCN

  1. Influence of radiofrequency power on compositional, structural and optical properties of amorphous silicon carbonitride films

    International Nuclear Information System (INIS)

    The silicon carbonitride (SiCN) films were deposited on n-type Si (1 0 0) and glass substrates by the radiofrequency (RF) reactive magnetron sputtering of polycrystalline silicon target under mixed reactive gases of acetylene and nitrogen. The films have been characterized by energy dispersive spectrometer (EDS), atomic force microscope (AFM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectrophotometer (UVS). The influence of RF power on the compositional, morphological, structural and optical properties of the SiCN films was investigated. The SiCN films deposited at room temperature are amorphous, and the C, Si and O compositions except N in the films are sensitive to the RF power. The surface roughness and optical band gap decrease as the RF power increases. The main bonds in the SiCN films are C-N, N-Hn, C-Hn, C-C, C≡N, Si-H and Si-C, and the intensities of the C≡N, Si-H and C-Hn bonds increase with increment of the RF power. The mechanisms of the influence of RF power on the characteristics of the films are discussed in detail.

  2. Electronic properties and microstructures of amorphous silicon carbonitrides ceramics derived from polymer precursors

    Science.gov (United States)

    Jiang, Tao

    2009-12-01

    Polymer-derived ceramics (PDCs) are a new class of high-temperature materials synthesized by thermal decomposition of polymeric precursors. These materials possess many unique features as compared with conventional ceramics synthesized by powder metallurgy based processing. For example, PDCs are neither amorphous nor crystalline. Instead, they possess nano-domain structures. Due to the direct chemical-to-ceramic processing, PDCs can be used for making components and devices with complex shapes. Thus, understanding the properties and structures of these materials are of both fundamental and practical interest. In this work, the structures and electronic behavior of polymer-derived amorphous silicon carbonitrides (SiCNs) were investigated. The materials were synthesized by pyrolysis of a commercially available liquid precursor. Ceramic materials with varied structures/properties were successfully synthesized by modifying the precursor and using different pyrolysis temperatures. The structures of the obtained materials were studied using XRD, solid state NMR, EPR, FTIR and Raman Spectroscope. The electronic behavior of the materials was investigated by measuring I-V curves, Hall effects, temperature dependent conductivity. The experiments were also performed to measure UV-Visible absorption and dielectric properties of the materials. This work leads to the following significant progresses: (i) developed quantitative technique for measuring free carbon concentration; (ii) achieved better understanding of the electronic conduction mechanisms and measured electronic structures of the materials for the first time; and (iii) demonstrated that these materials possess unusual dielectric behavior and provide qualitative explanations.

  3. Amorphous structures of silicon carbonitride formed by high-dose nitrogen ion implantation into silicon carbide

    International Nuclear Information System (INIS)

    Short-range order in amorphous silicon carbonitride (a-SiCxNy) has been examined using transmission electron microscopy. Single crystals of 6H-SiC with [0 0 0 1] orientation were implanted with 180 keV nitrogen ions at ambient temperature to a fluence of 5 x 1017 N+/cm2, followed by thermally annealing at 1500 deg. C for 30 min. A fully amorphous layer was formed at the topmost layer in the as-implanted sample. A part of the amorphous phase transformed into crystalline SiC after annealing. Radial distribution functions extracted via nano-beam electron diffraction patterns clearly showed that atomistic structures of the ion-beam-induced amorphous phase are different from those of the remaining amorphous phase in the annealed sample: a-SiCxNy possesses an intermediate bond length between Si-C and Si-N, while Si-N and Si-C bonds become more pronounced in the amorphous layer of the annealed specimen

  4. Synthesis of carbo-nitride films using high-energy shock plasma deposition

    International Nuclear Information System (INIS)

    Recent investigations shows that an enhanced nitrogen content of carbo-nitride films improves wear resistance, hardness, tribological and other properties of these films. The present work reports on the properties of nitrogen rich carbon films produced by an intense gas discharge between carbon electrodes in a nitrogen atmosphere. The energy of the discharge, initial nitrogen pressure, number of discharges and geometry are varied to establish their effect on the nitrogen content and the mechanical, structural and morphological characteristics of the deposited carbon-nitride films. The structural diagnostics include optical and scanning electron microscopy, as well as Auger and Raman Spectroscopes and Rutherford Backscattering. The C-N films formed fell into two categories, differing in morphology and mechanical properties. Type I are C-N films, containing up to 35 at. % nitrogen, and which have an amorphous structure. These films are formed at relatively low plasma shock pressure and exhibit relatively low microhardness, ∼ 2 GPa. In a relatively narrow range of the plasma shock pressure and temperature the second type of C-N deposition is observed consisting of high density, closely-packed crystal-like grains growing perpendicular to the substrate surface and displaying a cauliflower-like morphology. The microhardness of these films reaches 15 GPa, as measured by the Vickers method. 14 refs., 7 figs

  5. Precipitation Behaviour of Carbonitrides in Ti-Nb-C-N Microalloyed Steels and an Engineering Application with Homogenously Precipitated Nano-particles

    Directory of Open Access Journals (Sweden)

    Yanlin WANG

    2015-11-01

    Full Text Available A thermodynamic model enabling calculation of equilibrium carbonitride composition and relative amounts as a function of steel composition and temperature has been developed previously based on the chemical equilibrium method. In the present work, actual carbonitride precipitation behaviour has been verified in the Ti-Nb-C-N microalloyed steels. The Ti microalloyed steel after refining with 0.012 % Nb exhibited highly improved tensile strength without sacrificing ductility. According to further detailed SEM and TEM analysis, the improved mechanical properties of Ti/Nb microalloyed steel could be attributed to the larger solubility of Nb and Ti, inducing fine dispersion of the carbonitrides with particle size of 2 – 10 nm in the ferrite matrix.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9622

  6. Precipitation Behaviour of Carbonitrides in Ti-Nb-C-N Microalloyed Steels and an Engineering Application with Homogenously Precipitated Nano-particles

    Directory of Open Access Journals (Sweden)

    Yanlin WANG

    2015-12-01

    Full Text Available A thermodynamic model enabling calculation of equilibrium carbonitride composition and relative amounts as a function of steel composition and temperature has been developed previously based on the chemical equilibrium method. In the present work, actual carbonitride precipitation behaviour has been verified in the Ti-Nb-C-N microalloyed steels. The Ti microalloyed steel after refining with 0.012 % Nb exhibited highly improved tensile strength without sacrificing ductility. According to further detailed SEM and TEM analysis, the improved mechanical properties of Ti/Nb microalloyed steel could be attributed to the larger solubility of Nb and Ti, inducing fine dispersion of the carbonitrides with particle size of 2 – 10 nm in the ferrite matrix.

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

    International Nuclear Information System (INIS)

    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

  8. Characterization of Boron Carbonitride (BCN Thin Films Deposited by Radiofrequency and Microwave Plasma Enhanced Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    M. A. Mannan

    2008-01-01

    Full Text Available Boron carbonitride (BCN thin films with a thickness of ~4 µ­m were synthesized on Si (100 substrate by radiofrequency and microwave plasma enhanced chemical vapor deposition using trimethylamine borane [(CH33N.BH3] as a molecular precursor. The microstructures of the films were evaluated using field emission scanning electron microscopy (FE-SEM and X-ray diffractometry (XRD. Fourier transform infrared spectroscopy (FT-IR and X-ray photoelectron spectroscopy (XPS were used to analyze the chemical bonding state and composition of the films. It has been observed that the films were adhered well to the silicon substrate even after being broken mechanically. XRD and FE-SEM results showed that the films were x-ray amorphous, rough surface with inhomogeneous microstructure. The micro hardness was measured by nano-indentation tester and was found to be approximately 2~7 GPa. FT-IR suggested the formation of the hexagonal boron carbonitride (h-BCN phase in the films. Broadening of the XPS peaks revealed that B, C and N atoms have different chemical bonds such as B-N, B-C and C-N. The impurity oxygen was detected (13~15 at.% as B-O and/or N-O.

  9. High temperature mechanical and oxidation behavior of amorphous silicon carbonitride processed via chemical nanoprecursor route

    Science.gov (United States)

    Shah, Sandeep Rameshchandra

    Polymer precursor derived ceramics have been studied since last four decades. They promise higher purity and excellent properties with lower processing temperatures in comparison to the traditional route of processing ceramics from powders. The main focus in the literature for polymer derived materials has been on the study of cross linking and pyrolysis of precursors. Relatively fewer reports are available on processing bulk components and property characterization. The polymer precursor determines the nanostructure of the resulting amorphous material and is therefore termed nanoprecursor. In the present dissertation the processing of nanoprecursor to obtain bulk ceramics is studied, with development of an innovative process to fabricate dense defect free materials. The properties of these defect free materials are characterized. Commercially available oligo-ureamethylvinylsilazane (Ceraset(TM)-SN) was used in the present dissertation. The pyrolysis at 1000°C in nitrogen or argon resulted in an amorphous ceramic with chemical composition SiC 0.86N0.82. The specimens obtained by the new process are called cast specimens. Mechanical properties such as flexural strength, hardness, Young s modulus and fracture toughness were determined. The cast specimens showed much better properties as compared to nanoprecursor derived ceramics processed by methods published in the literature. Nanoprecursor derived SiCN show excellent creep resistance at 1350°C at uniaxial stresses ranging from 25--100 MPa. Though a small deformation was measured (~2% in 7 hours), careful analysis showed that this deformation was not creep deformation. The deformation was sintering like, but resulted mainly from the reduction of the activation volume of the amorphous material. The oxidation behavior of the silicon carbonitrides was studied. The material showed passive oxidation, in air at temperature of 1350°C and exhibited parabolic kinetics. Growth rate of the oxidation scale was about a factor

  10. 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.

  11. Synthesis of Zr-Si-O-N phases by carbonitriding reaction. Characterization of crystalline phases using the Rietveld method

    Directory of Open Access Journals (Sweden)

    Mazzoni A.D.

    2001-01-01

    Full Text Available Zirconium compounds are of great interest for ceramic application due to their excellent thermal and mechanical properties. Zirconium phases of the system Zr-O-C-N were obtained using carbonitriding reactions of zircon mineral (ZrO2.SiO2, under different reaction conditions. The reaction products were studied by X-ray diffraction (XRD using the Rietveld method. Silicon was employed as internal standard. Zirconium compounds formed were m-ZrO2 (monoclinic, beta"-zirconium oxynitride and a cubic Zr(C,N,O phase whose lattice parameter a o depends on the composition. The crystallite sizes of the three zirconium phases were determined also by XRD. The minority phases present are the ones of the Si-O-N-C system. The reaction conditions employed allows to obtain reaction products with low or without silicon content.

  12. Methods for and products of processing nanostructure nitride, carbonitride and oxycarbonitride electrode power materials by utilizing sol gel technology for supercapacitor applications

    Science.gov (United States)

    Huang, Yuhong; Wei, Oiang; Chu, Chung-tse; Zheng, Haixing

    2001-01-01

    Metal nitride, carbonitride, and oxycarbonitride powder with high surface area (up to 150 m.sup.2 /g) is prepared by using sol-gel process. The metal organic precursor, alkoxides or amides, is synthesized firstly. The metal organic precursor is modified by using unhydrolyzable organic ligands or templates. A wet gel is formed then by hydrolysis and condensation process. The solvent in the wet gel is then be removed supercritically to form porous amorphous hydroxide. This porous hydroxide materials is sintered to 725.degree. C. under the ammonia flow and porous nitride powder is formed. The other way to obtain high surface area nitride, carbonitride, and oxycarbonitride powder is to pyrolyze polymerized templated metal amides aerogel in an inert atmosphere. The electrochemical capacitors are prepared by using sol-gel prepared nitride, carbonitride, and oxycarbonitride powder. Two methods are used to assemble the capacitors. Electrode is formed either by pressing the mixture of nitride powder and binder to a foil, or by depositing electrode coating onto metal current collector. The binder or coating is converted into a continuous network of electrode material after thermal treatment to provide enhanced energy and power density. Liquid electrolyte is soaked into porous electrode. The electrochemical capacitor assembly further has a porous separator layer between two electrodes/electrolyte and forming a unit cell.

  13. Amorphous and nanocrystalline titanium nitride and carbonitride materials obtained by solution phase ammonolysis of Ti(NMe2)4

    International Nuclear Information System (INIS)

    Solution phase reactions between tetrakisdimethylamidotitanium (Ti(NMe2)4) and ammonia yield precipitates with composition TiC0.5N1.1H2.3. Thermogravimetric analysis (TGA) indicates that decomposition of these precursor materials proceeds in two steps to yield rocksalt-structured TiN or Ti(C,N), depending upon the gas atmosphere. Heating to above 700 deg. C in NH3 yields nearly stoichiometric TiN. However, heating in N2 atmosphere leads to isostructural carbonitrides, approximately TiC0.2N0.8 in composition. The particle sizes of these materials range between 4-12 nm. Heating to a temperature that corresponds to the intermediate plateau in the TGA curve (450 deg. C) results in a black powder that is X-ray amorphous and is electrically conducting. The bulk chemical composition of this material is found to be TiC0.22N1.01H0.07, or Ti3(C0.17N0.78H0.05)3.96, close to Ti3(C,N)4. Previous workers have suggested that the intermediate compound was an amorphous form of Ti3N4. TEM investigation of the material indicates the presence of nanocrystalline regions x (C,N) y crystalline phases

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

    International Nuclear Information System (INIS)

    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 TiCXN1 − 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 (TiCXN1 − 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

  15. 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.

  16. Silicon carbonitride by remote microwave plasma CVD from organosilicon precursor: Growth mechanism and structure of resulting Si:C:N films

    Energy Technology Data Exchange (ETDEWEB)

    Blaszczyk-Lezak, I. [Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, PL-90-363 Lodz (Poland); Wrobel, A.M. [Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, PL-90-363 Lodz (Poland)]. E-mail: amwrobel@bilbo.cbmm.lodz.pl; Kivitorma, M.P.M. [Department of Physics, University of Turku, FIN-20014 Turku (Finland); Vayrynen, I.J. [Department of Physics, University of Turku, FIN-20014 Turku (Finland); Tracz, A. [Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, PL-90-363 Lodz (Poland)

    2007-06-30

    The remote microwave hydrogen plasma chemical vapor deposition (RP-CVD) from bis(dimethylamino)methylsilane precursor was used for the synthesis of silicon carbonitride (Si:C:N) films. The effect of thermal activation on the RP-CVD process was examined by determining the mass- and the thickness-based film growth rate and film growth yield, at different substrate temperature (T {sub S}). It was found that the mechanism of the process depends on T {sub S} and for low substrate temperature regime, 30 deg. C {<=} T {sub S} {<=} 100 deg. C, RP-CVD is limited by desorption of film-forming precursors, whereas for high substrate temperature regime, 100 deg. C < T {sub S} {<=} 400 deg. C, RP-CVD is a non-thermally activated and mass-transport limited process. The Si:C:N films were characterized by X-ray photoelectron and Fourier transform infrared spectroscopies, as well as by atomic force microscopy. The increase of T {sub S} enhances crosslinking in the film via the formation of nitridic Si-N and carbidic Si-C bonds. On the basis of the structural data a hypothetical crsosslinking reactions contributing to silicon carbonitride network formation have been proposed.

  17. Synthesis and characterization of silicon carbonitride films by plasma enhanced chemical vapor deposition (PECVD) using bis(dimethylamino)dimethylsilane (BDMADMS), as membrane for a small molecule gas separation

    Science.gov (United States)

    Kafrouni, W.; Rouessac, V.; Julbe, A.; Durand, J.

    2010-12-01

    Silicon carbonitride thin films have been deposited by plasma enhanced chemical vapor deposition (PECVD) from bis(dimethylamino)dimethylsilane (BDMADMS) as a function of X = (BDMADMS/(BDMADMS + NH 3)) between 0.1 and 1, and plasma power P (W) between 100 and 400 W. The microstructure of obtained materials has been studied by SEM, FTIR, EDS, ellipsometrie, and contact angle of water measurements. The structure of the materials is strongly depended on plasma parameters; we can pass from a material rich in carbon to a material rich in nitrogen. Single gas permeation tests have been carried out and we have obtained a helium permeance of about 10 -7 mol m -2 s -1 Pa -1 and ideal selectivity of helium over nitrogen of about 20.

  18. Study of carbonitriding thermochemical treatment by plasma screen in active with pressures main austenitic stainless steels AISI 409 and AISI 316L

    International Nuclear Information System (INIS)

    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)

  19. Atom Probe Tomography Study of Multi-microalloyed Carbide and Carbo-Nitride Precipitates and the Precipitation Sequence in Nb-Ti HSLA Steels

    Science.gov (United States)

    Kapoor, Monica; O'Malley, Ronald; Thompson, Gregory B.

    2016-05-01

    Composition analysis of carbide and carbo-nitride precipitates was performed for two Nb-Ti microalloyed steels with yield strengths of 750 and 580 MPa using an atom probe study. In the high-Ti 750 MPa steel, Ti-rich (Ti,Nb)(C,N) and Ti-rich (Ti,Nb)(C) precipitates were observed. In the high-Nb 580 MPa steel, a Ti-rich (Ti,Nb)(C,N) precipitate and (Ti,Nb)(C) clusters were noted. These (Ti,Nb)(C) clusters in the high-Nb 580 MPa steel were smaller than the (Ti,Nb)(C) precipitates in high-Ti 750 MPa steel. In general, a larger number of precipitates were found in the high-Ti 750 MPa steel. This difference in the number density of the precipitates between the two steels is attributed to the difference in Ti content. Combining the atom probe tomography results and thermodynamic calculations, the precipitation sequence in these alloys was inferred to be the following: as the temperature decreases, TiN precipitates out of the solution with successive (Ti,Nb)(C,N) layers of varying composition forming on these Ti-rich precipitates. Once N is depleted from the solution, a second set of (Ti,Nb)(C) precipitates in a similar manner in the matrix and also onto the carbo-nitride phase. This observation is consistent with previous observations in high-strength low-alloy steels containing comparable amounts of only Nb. It was noted that the amount of Nb, Nb/(Nb + Ti), in the precipitates decreased from 0.20 to 0.04 with the size of the precipitate. We believe that this is due to the Nb supersaturation in the matrix when these precipitates nucleate.

  20. Amorphous silicon carbonitride diaphragm for environmental-cell transmission electron microscope fabricated by low-energy ion beam induced chemical vapor deposition

    Science.gov (United States)

    Matsutani, Takaomi; Yamasaki, Kayo; Imaeda, Norihiro; Kawasaki, Tadahiro

    2015-12-01

    An amorphous silicon carbonitride (a-SiCN) diaphragm for an environmental-cell transmission electron microscope (E-TEM) was fabricated by low-energy ion beam induced chemical vapor deposition (LEIBICVD) with hexamethyldisilazane (HMDSN). The films were prepared by using gaseous HMDSN and N2+ ions with energies ranging from 300 to 600 eV. The diaphragms were applied to Si (1 0 0) and a Cu grid with 100-μm-diameter holes. With increasing ion energy, these diaphragms became perfectly smooth surfaces (RMS = 0.43 nm at 600 eV), as confirmed by atomic force microscopy and TEM. The diaphragms were amorphous and transparent to 200 kV electrons, and no charge-up was observed. Fourier transform infrared spectra and X-ray photoelectron spectra revealed that the elimination of organic compounds and formation of Si-N and C-N bonds can be promoted in diaphragms by increasing the ion impact energy. The resistance to electron beams and reaction gases in the E-cell was improved when the diaphragm was formed with high ion energy.

  1. Polymer-Derived Silicoboron Carbonitride Foams for CO2 Capture: From Design to Application as Scaffolds for the in Situ Growth of Metal-Organic Frameworks.

    Science.gov (United States)

    Sandra, Fabien; Depardieu, Martin; Mouline, Zineb; Vignoles, Gérard L; Iwamoto, Yuji; Miele, Philippe; Backov, Rénal; Bernard, Samuel

    2016-06-01

    A template-assisted polymer-derived ceramic route is investigated for preparing a series of silicoboron carbonitride (Si/B/C/N) foams with a hierarchical pore size distribution and tailorable interconnected porosity. A boron-modified polycarbosilazane was selected to impregnate monolithic silica and carbonaceous templates and form after pyrolysis and template removal Si/B/C/N foams. By changing the hard template nature and controlling the quantity of polymer to be impregnated, controlled micropore/macropore distributions with mesoscopic cell windows are generated. Specific surface areas from 29 to 239 m(2)  g(-1) and porosities from 51 to 77 % are achieved. These foams combine a low density with a thermal insulation and a relatively good thermostructural stability. Their particular structure allowed the in situ growth of metal-organic frameworks (MOFs) directly within the open-cell structure. MOFs offered a microporosity feature to the resulting Si/B/C/N@MOF composite foams that allowed increasing the specific surface area to provide CO2 uptake of 2.2 %. PMID:27170549

  2. Silicon carbonitride by remote microwave plasma CVD from organosilicon precursor: Physical and mechanical properties of deposited Si:C:N films

    Energy Technology Data Exchange (ETDEWEB)

    Blaszczyk-Lezak, I. [Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, PL-90-363 Lodz (Poland); Wrobel, A.M. [Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, PL-90-363 Lodz (Poland)]. E-mail: amwrobel@bilbo.cbmm.lodz.pl

    2007-07-15

    Silicon carbonitride (Si:C:N) films produced by the remote microwave hydrogen plasma chemical vapor deposition (RP-CVD) using bis(dimethylamino)methylsilane as single-source precursor and hydrogen as an upstream gas for plasma generation, were examined in terms of their physical (density) and mechanical (hardness, elastic modulus, friction coefficient, and 'plasticity index') properties. The effect of substrate temperature (varied in the range of 30-400 {sup o}C) on the properties of Si:C:N films is presented. A reasonable compositional and structural dependencies of film properties were determined using, respectively, the XPS atomic concentration ratios N/Si and C/Si, as well as the relative integrated intensities of the IR absorption bands from the Si-N and Si-C bonds (controlled by deposition temperature), evaluated in the first part of this work. In view of their good mechanical properties, Si:C:N films seem to be useful coatings for improving surface mechanics of engineering materials.

  3. First-principles density-functional study of metal-carbonitride interface adhesion: Co/TiC(001) and Co/TiN(001)

    International Nuclear Information System (INIS)

    The energetics and the electronic structure of fcc Co(001)/TiC(001) and Co(001)/TiN(001) interfaces, which are of much practical importance in the sintering of hardmetals, are investigated by means of first-principles density-functional calculations, using the plane-wave pseudopotential method. The effects of the large Co/Ti(C,N) lattice mismatch are incorporated within an approach based on a comparative analysis of a representative set of high-symmetry model interface structures. It is shown that the dominating mechanism of the Co/Ti(C,N) interface adhesion is strong covalent σ bonding between Co-3d and C(N)-2p orbitals. An extensive analysis of the electronic structure elucidates the interface-induced features of the Co-C(N) bonding and antibonding electronic states that are responsible for the enhanced strength of the interface Co-C(N) compared to bonds in bulk carbonitrides, the effect describable as metal-modified covalent bond. A detailed comparison of the energetics and relaxation effects at the Co/TiC and Co/TiN interfaces shows a weaker bonding and less pronounced relaxation effects in the Co/TiN case, which can be connected to the experimentally observed difference in the stability of those interfaces. The weaker Co/TiN adhesion is explained in terms of the relative position of the energy region of the N-2p states with respect to the Co-3d states. The calculated adhesion strength is consistent with the available data from wetting experiments with liquid Co on a TiC surface

  4. 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)

  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. Carbonitride based phosphors and light emitting devices using the same

    Science.gov (United States)

    Li, Yuanqiang; Tian, Yongchi; Romanelli, Michael Dennis

    2013-08-20

    Disclosed herein is a novel group of carbidonitride phosphors and light emitting devices which utilize these phosphors. In certain embodiments, the present invention is directed to a novel family of carbidonitride-based phosphors expressed as follows: Ca.sub.1-xAl.sub.x-xySi.sub.1-x+xyN.sub.2-x-xyC.sub.xy:A; (1) Ca.sub.1-x-zNa.sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x-xyC.sub.xy:- A; (2) M(II).sub.1-x-zM(I).sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x- -xyC.sub.xy:A; (3) M(II).sub.1-x-zM(I).sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x-xy-2w/- 3C.sub.xyO.sub.w-v/2H.sub.v:A; and (4) M(II).sub.1-x-zM(I).sub.zM(III).sub.x-xy-zSi.sub.1-x+xy+zN.sub.2-x-xy-2w/- 3-v/3C.sub.xyO.sub.wH.sub.v:A, (4a) wherein 0xy+z, and 0

  7. Carbonitridation of mechanically activated mixtures of zircon and carbon

    Energy Technology Data Exchange (ETDEWEB)

    Setoudeh, N., E-mail: nsetoudeh@mail.yu.ac.ir [Materials Engineering Department, Yasouj University, Yasouj (Iran, Islamic Republic of); Welham, N.J., E-mail: nicholas.welham@gmail.com [West Australian School of Mines, Curtin University, PO Box U1977, Perth, Western Australia (Australia)

    2014-02-15

    Highlights: • Formation temperature of ZrN and ZrC decreased to 1400 °C in the five hours milled sample. • Either ZrC or ZrN were observed in the heating of 6:1 C:Zircon samples under argon/nitrogen atmospheres. • Amount of tetragonal zirconia increased in nitrogen atmosphere. • Percentage of tetragonal zirconia increased at higher C:Zircon ratios. -- Abstract: Two different stoichiometries of zircon (ZrSiO{sub 4}) and activated carbon (C:zircon molar ratios of 3:1 and 6:1) were milled together at for 5 h and subjected to thermo-gravimetric analysis (TGA). TGA runs were performed under argon and nitrogen atmospheres. The main mass loss reaction started at around 1200 °C in all samples, but the mass loss was greater in the 6:1 C:zircon ratio samples in nitrogen. X-ray diffraction (XRD) of the residues showed the decomposition of zircon was nearly complete. Traces of ZrN along with monoclinic and tetragonal forms of zirconia were observed in the nitrogen atmosphere, however only zirconia was present after heating in argon. Heating the 6:1 C:zircon molar ratio sample for 1 h at 1400 °C in argon resulted in the formation of ZrC and SiC, in nitrogen ZrN was formed.

  8. Carbonitridation of mechanically activated mixtures of zircon and carbon

    International Nuclear Information System (INIS)

    Highlights: • Formation temperature of ZrN and ZrC decreased to 1400 °C in the five hours milled sample. • Either ZrC or ZrN were observed in the heating of 6:1 C:Zircon samples under argon/nitrogen atmospheres. • Amount of tetragonal zirconia increased in nitrogen atmosphere. • Percentage of tetragonal zirconia increased at higher C:Zircon ratios. -- Abstract: Two different stoichiometries of zircon (ZrSiO4) and activated carbon (C:zircon molar ratios of 3:1 and 6:1) were milled together at for 5 h and subjected to thermo-gravimetric analysis (TGA). TGA runs were performed under argon and nitrogen atmospheres. The main mass loss reaction started at around 1200 °C in all samples, but the mass loss was greater in the 6:1 C:zircon ratio samples in nitrogen. X-ray diffraction (XRD) of the residues showed the decomposition of zircon was nearly complete. Traces of ZrN along with monoclinic and tetragonal forms of zirconia were observed in the nitrogen atmosphere, however only zirconia was present after heating in argon. Heating the 6:1 C:zircon molar ratio sample for 1 h at 1400 °C in argon resulted in the formation of ZrC and SiC, in nitrogen ZrN was formed

  9. Thermal Contact Conductance Analysis of Nitride and Carbonitride Thin Film Coatings for Thermal Interface Material Application

    Science.gov (United States)

    Subramani, Shanmugan; Thing, Lee Yuan; Devarajan, Mutharasu

    2015-12-01

    In order to reduce and maintain the bond line thickness between substrate and LED package, solid thin film with good thermal conductivity is suggested as thermal interface material and the proposed film thickness is about less than 1 µ. The surface parameter such as roughness and hardness is a key factor which alters the contact conductance between the two matt surfaces. Consequently, filtered vacuum cathodic arc deposited nitride thin films (CrN, TiN, AlTiN, and TiCN) on copper substrate were tested for thermal interface material applications in electronic packaging. The thermal contact conductance of the prepared thin films was evaluated using surface properties such as microhardness and surface roughness. The results were verified with the theoretical model. The measured microhardness and surface roughness of CrN thin film are 17 GPa (low) and 0.768 µm (high), respectively. The measured thermal contact conductance of all thin films showed linear properties for applied pressure and very close to the values of theoretical model. High value in thermal contact conductance of about 256 W/m2 K was noticed with CrN thin film at 1100 kPa. The percentage of deviation for our measured contact conductance value from the theoretical model value was decreasing for the increased contact pressure and observed low value (7 pct) for CrN thin film at 1100 kPa. The thermal conductivity of all thin films was also calculated from the conductance model and observed high value (19.34 W/mK) with CrN thin film.

  10. 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....

  11. Carbonitride precipitation during hot direct rolling of nb-microalloyed steel

    International Nuclear Information System (INIS)

    Small ingots of Nb-microalloyed steels were cast in hot ceramic mould in order to simulate larger castings. The as- cast austenite was direct rolled in three passes from an initial thickness of 15mm to 4mm. In a series of experiments, first passes were applied in the temperature range 1200-1010 degree C, second passes between 1100-960 degree C and third passes between 1000-920 degree C. The ingots were quenched just after casting, or just before entry to or after exit from each pass to investigate changes in the precipitation of NbCN. Samples of the ingots quenched at different stages during processing were then tempered for 1 hour at 600 degree C to assess the amount of NbCN in solution at the quench temperature. As-cast austenite prior to the commencement of rolling was found to be undersaturated and Nb-based eutectic precipitates were present at high temperatures. These were stable during cooling, and supersaturation did not occur until the ingot temperature fell below 1100 degree C. Besides the eutectic precipitates, fine strain induced NbCN precipitates were present after first, second and third passes. It was found that these precipitates remove a small amount of Nb from solution. (author)

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

    Directory of Open Access Journals (Sweden)

    G. A. Tkachenko

    2016-02-01

    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.

  13. 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.

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

    International Nuclear Information System (INIS)

    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

  15. Improvement of the Surface Hardness of Stainless Steel with the TitaniumCarbonitride Ti(CN) Thin Films

    International Nuclear Information System (INIS)

    Fabrication of the Ti(CN) thin films with methods of implantation and RFsputtering for improving the surfaces hardness of stainless steel (SS) hasbeen done. Some kinds of TiC thin films which made individually by varyingof RF sputtering power from 0 up to 160 watt are implanted by the nitrogenion beams on the doses and energy ion optimum of 6.107 x 1017 ion/cm2 and100 keV, also fabrication of Ti(CN) thin films use RF sputtering method withTi target and reaction gases as argon, silene and nitrogen on the optimum ofsputtering parameter condition. The thin films yields are characterized byusing Microhardness Tester MX 170, obtained SS hardness which layered Ti(CN)as 402.5 KHN from its initial of 215.54 KHN and 371.74 KHN (layered TiC), itmeans that the SS surface hardness improve 1.867 times cumulatively. From theX-Ray Diffraction (XRD) analysis yield showed that the microstructure ofTi(CN) films on the SS substrates are dominated by characteristic cubiccrystal structure with Miller plane orientation (111) on the scattering angleof 2 θ = 44o. Morphology visualization of Ti(CN) thin films crosssection on the SS substrate is realized by Spectroscopy Electron Microscope(SEM). (author)

  16. 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.

  17. Method of production of austenitic stainless and refractory steels stabilized with titanium, with guaranteed low occurrence of nitride and carbonitride colonies

    International Nuclear Information System (INIS)

    The claim of the invention consists in steel microalloying at casting temperature in the cradle with an addition of calcium or potassium such as to achieve its final level in the steel to be 10 to 250 ppm; the ratio of the sum of calcium and potassium levels to the sulfur level should range within 0.4 and 3.0. It is advantageous to do microalloying after previous vacuum degassing of the steel in the cradle. Using the method, it is possible to achieve inexpensive and reliable increase in purity and improvement of corrosion and mechanical properties of stabilized austenitic stainless steels. (A.K.)

  18. 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.

  19. Gibbs energy of formation of cubic NbCxNy

    International Nuclear Information System (INIS)

    One calculated the activity of niobium δ-carbonitride components within 1573-1973 K temperature range. One determined the nature of activity changes of NbC and NbN along δ-phase low-nitric boundary. One determined dependence of the Gibb's free energy of formation of niobium carbonitride on its composition and temperature

  20. SiCN based Anode Materials for Lithium-Ion Batteries

    OpenAIRE

    Reinold, Lukas Mirko

    2016-01-01

    This thesis deals with the investigation of polymer-derived silicon carbonitride based anode materials for their application in lithium-ion batteries. Carbon-rich silicon carbonitrides are obtained by a pyrolysis of different organosilicon precursors, namely poly(phenylvinylsilylcarbodiimide), poly(phenylvinylsilazane), poly(diphenylsilylcarbodiimide), poly(phenylsilsesquicarbodiimide) and poly(phenylsilsesquiazane). The materials are characterized by means of Raman spectroscopy, elemental an...

  1. Direct chemical conversion of graphene to boron- and nitrogen- and carbon-containing atomic layers

    Science.gov (United States)

    Gong, Yongji; Shi, Gang; Zhang, Zhuhua; Zhou, Wu; Jung, Jeil; Gao, Weilu; Ma, Lulu; Yang, Yang; Yang, Shubin; You, Ge; Vajtai, Robert; Xu, Qianfan; MacDonald, Allan H.; Yakobson, Boris I.; Lou, Jun; Liu, Zheng; Ajayan, Pulickel M.

    2014-01-01

    Graphene and hexagonal boron nitride are typical conductor and insulator, respectively, while their hybrids hexagonal boron carbonitride are promising as a semiconductor. Here we demonstrate a direct chemical conversion reaction, which systematically converts the hexagonal carbon lattice of graphene to boron nitride, making it possible to produce uniform boron nitride and boron carbonitride structures without disrupting the structural integrity of the original graphene templates. We synthesize high-quality atomic layer films with boron-, nitrogen- and carbon-containing atomic layers with full range of compositions. Using this approach, the electrical resistance, carrier mobilities and bandgaps of these atomic layers can be tuned from conductor to semiconductor to insulator. Combining this technique with lithography, local conversion could be realized at the nanometre scale, enabling the fabrication of in-plane atomic layer structures consisting of graphene, boron nitride and boron carbonitride. This is a step towards scalable synthesis of atomically thin two-dimensional integrated circuits.

  2. 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.

  3. Study and modelling of the influence of second phase particles on the austenite grain growth in a niobium microalloyed steel; Estudio y modelizacion de la influencia de las particulas de segunda fase sobre el crecimiento de grano austenitico en un acero microaleado con niobio

    Energy Technology Data Exchange (ETDEWEB)

    San Martin, D.; Caballero, F. G.; Capdevilla, C.; Garcia-de-andres, C.

    2006-07-01

    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. (Author)

  4. Precipitates in Steels With Ti Additive Produced by CSP Process

    Institute of Scientific and Technical Information of China (English)

    LOU Yan-zhi; LIU De-lu; NI Xiao-qing

    2009-01-01

    Hot strips of low carbon steels with Ti additive [contain C 0.04%-0.07%, Si≤0. 6%, Mn≤0. 6%,Ti 0.06%-0.14% (mass percent)] produced by EAF-CSP (Electric Arc Furnaces-Compact Strip Production)process were examined by TEM, HREM and XRD. Carbonitrides with different N/C ratio were found in the samples. The varying composition of the Ti-carbonitrides resulted from the supersaturation of Ti and temperature at which the compound was formed. In the tested steel, total mass fraction of the precipitates including cementite, carbonitride and a small quantity of Fe3O4, Al2O3, Ti2 CS and AlN was about 0. 305%. XRD results showed that about a quarter of the powder extracted by electrolysis was titanium nitrides, carbonitrides and carbides. Particle arrays formed by interphase precipitation could be observed either in slabs or in hot strips. The dominant reaction mechanisms were discussed. Compared with the conventional cold charge process, small amount of Ti addition would be more effective for precipitation of fine precipitates in the steels produced by CSP process.

  5. Comparative study of the tribological behavior under hybrid lubrication of diamond-like carbon films with different adhesion interfaces

    Science.gov (United States)

    Costa, R. P. C.; Lima-Oliveira, D. A.; Marciano, F. R.; Lobo, A. O.; Corat, E. J.; Trava-Airoldi, V. J.

    2013-11-01

    This paper reports the influence of the adhesion interlayer between stainless steel and diamond-like carbon (DLC) films in two different contact conditions: in dry air and deionized water. The water was the liquid used to understand the mechanism and chemical reactions of the tribolayer formation under boundary lubrication. The effect of silicon and carbonitride adhesion interlayer was investigated on uncoated and coated DLC films. The results show that DLC/DLC pairs using carbonitride in air (30% RH) showed 60% less friction coefficient and wear less than three orders of magnitude than DLC/DLC pairs using silicon as interlayer. In deionized water, DLC/DLC pairs using carbonitride as interlayer showed 31% less friction coefficient when compared to DLC/DLC pairs with silicon. Raman related the chemical and structural changes in the DLC films during sliding in air and in the presence of water. Scratch tests showed a critical load of 14 N and 33 N in DLC films with silicon and carbonitride, respectively.

  6. X-ray determination of the thickness of thin films of TiC, TiN, Ti(N,C)

    International Nuclear Information System (INIS)

    A possible application of X-ray diffraction methods in studying thin wear-resistant films of titanium carbides, nitrides and carbonitrides, deposited on hard metal substrates is dealt with. Special emphasis is put on the texture elimination when measuring the layer thickness. The results are compared with those of the metallographic method. (author). 3 figs., 4 tabs., 11 refs

  7. Selected Topics on Mass Transport in Gas-solid Interactions

    DEFF Research Database (Denmark)

    Somers, Marcel A.J.

    2004-01-01

    -controlled dissolution of carbon in an austenite matrix, nucleation of nitrides at an iron surface, the competition between surface reaction and solid state diffusion during iron-nitride layer growth and the evolution of the morphology of a carbonitride layer during nitrocarburizing. The work presented focuses on the...

  8. Survey of post-irradiation examinations made of mixed carbide fuels

    International Nuclear Information System (INIS)

    Post-irradiation examinations on mixed carbide, nitride and carbonitride fuels irradiated in fast flux reactors Rapsodie and DFR were carried out during the seventies and early eighties. In this report, emphasis was put on the fission gas release, cladding carburization and head-end gaseous oxidation process of these fuels, in particular, of mixed carbides. (author). 8 refs, 16 figs, 3 tabs

  9. The aging by precipitation of Nb (C,N) in extra low carbon content steel

    International Nuclear Information System (INIS)

    Carbonitride precipitation has been studied in a high-niobium acicular - ferrite - type steel. Interphase precipitation occurred only in those samples in which high transformation temperatures led to distinctly polygonal-ferrite microestructures. In this latter case, precipitation occurred during a subsequent aging treatment, with a strong tendency for heterogeneous nucleation on dislocations. (Author)

  10. Microalloyed V-Nb-Ti and V steels Pt. 2 - precipitation behaviour during processing of structural beams

    Energy Technology Data Exchange (ETDEWEB)

    Tanniru, M.; Shanmugam, S.; Misra, R.D.K.; Panda, D.; Jansto, S.

    2005-02-15

    A comparative evaluation of the precipitation behaviour in V-Nb-Ti and V steels using transmission electron microscopy was undertaken to study the effective cumulative role of the microalloying additions. While the mechanical properties were similar, there were significant differences in the precipitation behaviour of the two steels. The microstructure of the V-Nb-Ti and V steels consisted predominantly of polygonal ferrite and fine pearlite; in addition, the former contained a small amount of bainite. The V-Nb-Ti steel exhibited significantly greater precipitation of carbonitrides compared with the V steel. In the V-Nb-Ti steel the carbonitrides precipitated as compounds (triplex and duplex type) of Ti, Nb, and V, while in the V steel they were V(C,N). They were characterised by cuboid (45-70 nm), spherical/irregular (20-45 nm), and fine/needleshaped (10-20 nm) morphology. The carbonitride precipitates grew as multimicroalloying compounds, depending on the processing conditions, as the number of microalloying elements increased. Coarse carbonitrides tended to precipitate preferentially along the grain boundaries, whereas fine carbides were dispersed in the matrix. The stoichiometric ratio of triplex carbonitrides in the V-Nb-Ti steel was Ti{sub 0.55}Nb{sub 0.35}V{sub 0.10}, while those of duplex type were Ti{sub 0.95}V{sub 0.05}, Nb{sub 0.70}V{sub 0.30}, and Ti{sub 0.73}Nb{sub 0.27}. Three microalloying elements (Ti, Nb, V) formed a coherent M{sub 4}C{sub 3} type of carbide in the V-Nb-Ti steel and exhibited short range order with the ferrite matrix, displayed by the diffraction pattern as a 'chemically sensitive' or 'superlattice' reflection. However, Nb formed the finest carbides (< 2 nm) and exhibited a ring form of selected area diffraction pattern. The carbonitrides that precipitated in the ferrite followed Baker-Nutting orientation relationships, and their partitioning was not observed in the pearlite or bainitic ferrite. The bainite

  11. Processing and properties of carbon containing silicon nitride ceramics derived from the pyrolysis of polyhydridochlorosilazanes

    International Nuclear Information System (INIS)

    The pyrolysis reactions of a polyhydridochlorosilazane and ESCA-investigations of the produced amorphous silicon carbonitride powders are reported. The as produced powder crystallizes to β-Si3N4 and β-SiC in the presence of a glassy phase containing Y2O3 and Al2O3. During pressureless sintering of the silicon carbonitride powder dense Si3N4/SiC-composits can be obtained. The microstructure of gas pressure sintered samples (10 MPa, 1900 C) shows elongated Si3N4 grains and equiaxial SiC particles. The crack path reveals the formation of elastic bridges resulting in a relatively high fracture toughness of about 10 MPa.m1/2. (orig.)

  12. Tempering behavior of a semi-high speed steel containing nitrogen

    International Nuclear Information System (INIS)

    The decomposition behavior of martensite and precipitation characteristics of carbonitrides during the tempering process of a low-alloy high-speed steel (semi-HSS) containing nitrogen were investigated by means of transmission electron microscopy, scanning electron microscopy, energy dispersive spectrometry and electron energy loss spectroscopy. The results shown the secondary hardening effect is reinforced with addition of nitrogen and the secondary hardening temperature range has expanded. The stability of retained austenite is also studied. When tempered in the temperature range of 425-525 deg. C, large quantities of fine-scale V-rich nitride precipitations distribute in the matrix homogeneously. A complex carbonitride phase can form when tempered at 550 deg. C

  13. Influence of second phase particles on the deformation of. alpha. -Fe at cryogenic temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Yue, S.; Bratina, W.J. (Univ. of Toronto (Canada))

    The deformation of fine grained polygonal ferrite (HSLA) steels was shown to be sensitive to variations in second phase particle characteristics. In particular a steel which contained a dispersion of fine niobium carbonitrides exhibited virtually no elongation to fracture at 77K, whereas a steel containing both fine niobium carbonitrides and coarser Fe{sub 3}C type particles exhibited considerable Luders strain and strain to fracture at 77K. It was observed that for the first steel, necking coincided with the nucleation of a Luders band whereas in the second steel, the nucleated Luders band propagated along the entire gauge length even at 77K. Luders band propagation and the delay of the onset of necking are connected by work hardening which, in turn, is governed by microstructural parameters such as grain size and second phase particles and it is these that result in this contrasting deformation behavior at 77K.

  14. In vitro hemocompatibility on thin ceramic and hydrogel films deposited on polymer substrate performed in arterial flow conditions.

    Science.gov (United States)

    Major, Roman; Trembecka-Wójciga, Klaudia; Kot, Marcin; Lackner, Juergen M; Wilczek, Piotr; Major, Boguslaw

    2016-04-01

    Hydrogel coatings were stabilized by titanium carbonitride a-C:H:Ti:N buffer layers deposited directly onto the polyurethane (PU) substrate beneath a final hydrogel coating. Coatings of a-C:H:Ti:N were deposited using a hybrid method of pulsed laser deposition (PLD) and magnetron sputtering (MS) under high vacuum conditions. The influence of the buffer a-C:H:Ti:N layer on the hydrogel coating was analysed by means of a multi-scale microstructure study. Mechanical tests were performed at an indentation load of 5mN using Berkovich indenter geometry. Haemocompatible analyses were performed in vitro using a blood flow simulator. The blood-material interaction was analysed under dynamic conditions. The coating fabrication procedure improved the coating stability due to the deposition of the amorphous titanium carbonitride buffer layer. PMID:26838818

  15. Determination of the coefficient of reflection of metastable argon atoms from the discharge tube wall

    International Nuclear Information System (INIS)

    Radial profiles of the density of metastable atoms Ar(3P2) in the positive column of a dc glow discharge in argon were measured. Gas-discharge glass tubes with clean inner surfaces and surfaces covered with a carbonitride or carbon film were utilized. The parameters of the discharge plasma under experimental conditions were calculated in the framework of a one-dimensional (along the tube radius) discharge model. The coefficient K of reflection of Ar(3P2) atoms from the tube wall was estimated by comparing the measured and calculated density profiles. It is found that, for a clean tube wall, the coefficient of reflection is K = 0.4 ± 0.2, whereas for a wall covered with a carbonitride or carbon film, it is K < 0.2

  16. 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.

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

    OpenAIRE

    Rômulo Ribeiro Magalhães de Sousa; Francisco Odolberto de Araújo; José Alzamir Pereira da Costa; Antonio Maia de Oliveira; Mineia Sampaio Melo; Clodomiro Alves Junior

    2012-01-01

    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.

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

    OpenAIRE

    William de Melo Silva; José Rubens Gonçalves Carneiro; Vladimir Jesus Trava-Airoldi

    2013-01-01

    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 ...

  19. Nitriding and Nitrocarburizing; Current Status and Future Challenges

    DEFF Research Database (Denmark)

    Somers, Marcel A. J.

    This contribution addresses the current understanding of gaseous nitriding and nitrocarburizing. Aspects of thermodynamics, kinetics and microstructure development in iron and heat treatable steel will be explained. In these materials the nitrided/ nitrocarburized case can be subdivided 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...

  20. Deposition of chromium nitrides, oxy-nitrides and titanium carbides on steel substrates by DC magnetron sputtering

    International Nuclear Information System (INIS)

    The present paper deals with the deposition of chromium and titanium nitrides, oxynitrides, carbides and carbonitrides onto low carbon steel by reactive magnetron sputtering. The films were obtained by using different reactive gases (02, N2, CH4,). The process advancement and the corresponding film composition variations were investigated as a function of the specific reactivity of each gas. In addition, the cathode poisoning phenomena were studied. (author). 4 refs., 6 figs

  1. Population analysis solution to hardness enhancement in TiCxN1-x

    International Nuclear Information System (INIS)

    We investigated the hardness enhancement in titanium carbonitrides (TiCxN1-x) by the population analysis method based on first-principles calculations. Populations for bonds Ti---C and Ti---N in TiCxN1-x (0.25xN1-x has been calculated based on the obtained overlap populations. The calculated results are in good agreement with the available experimental data.

  2. Zircon Carburation Studies as Intermediate Stage in the Zirconium Fabrication

    International Nuclear Information System (INIS)

    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

  3. Refractory wear resistant powder materials for metallurgy

    International Nuclear Information System (INIS)

    Powder materials on the basis of high-alloy nickel alloys containing up to 50 % (in mass) of Co, Cr, Mo, W, Ti, Nb, Al and up to 10 % refractory thermally stable compounds (oxides, carbides, nitrides, carbonitrides) have been developed. They feature a high strength, corrosion- and wear resistance at 800-1000 deg C, a satisfactory ductility at room and working temperatures, a decreased tendency towards crack formation, they are workable by cutting. 4 refs., 4 figs

  4. Nitriding and Nitrocarburizing; Current Status and Future Challenges

    OpenAIRE

    Somers, Marcel A.J.

    2013-01-01

    This contribution addresses the current understanding of gaseous nitriding and nitrocarburizing. Aspects of thermodynamics, kinetics and microstructure development in iron and heat treatable steel will be explained. In these materials the nitrided/ nitrocarburized case can be subdivided 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 corrosi...

  5. 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.

  6. N-type emitters passivation through antireflective phosphorus doped a-SiCxNy:H(n) stacks

    OpenAIRE

    Orpella García, Alberto; Blanqué, Servane; Roiati, V.; Martín García, Isidro; Voz Sánchez, Cristóbal; Puigdollers i González, Joaquim; Alcubilla González, Ramón

    2009-01-01

    This paper studies the passivation of industrially textured deep silicon emitters using amorphous silicon carbonitride layers in stack configuration, deposited by plasma enhanced chemical vapor deposition. With this technique, emitter saturation current density can be decreased to values around 250 fA middot cm-2. As a consequence, open circuit voltages can be increased 25 mV achieving values around 640 mV.

  7. Image-based Cohesive Element Modelling of Low Temperature Crack Propagation in Alloy 82 Weld Metal

    OpenAIRE

    Klimaytys G, Jivkov AP, Engelberg DL

    2014-01-01

    Exposure of Alloy 82 welds to hydrogen containing, de-oxygenated aqueous environments at temperatures below 150°C can result in embrittlement, manifested by a significant reduction of its resistance to cracking. The embrittlement is brought about by nano-scale niobium and titanium rich carbonitrides at grain boundaries which act as hydrogen traps. The presence of stresses may then result in low temperature crack propagation (LTCP).The work reported in this paper provides a better understandi...

  8. Optical and EPR study of a-SiC.sub.x./sub.N.sub.y./sub. films obtained by magnetron sputtering

    Czech Academy of Sciences Publication Activity Database

    Savchenko, Dariia; Kulikovsky, V.; Vorlíček, Vladimír; Lančok, Ján; Kalabukhova, E.

    Lille: European Materials Research Society, 2014 - (Lippert, T.). G.XI. 5 [E- MRS 2014 Spring Meeting. 26.05.2014-30.05.2014, Lille] R&D Projects: GA MŠk(CZ) LM2011029; GA ČR GP13-06697P Grant ostatní: SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : silicon carbonitride films * carbon dangling bonds * EPR * interface defects Subject RIV: BM - Solid Matter Physics ; Magnetism

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

    OpenAIRE

    Jithin M; Anees Abdul Hameed; Ben Jose; Anush Jacob

    2015-01-01

    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 ...

  10. Complex influence of carbon, niobium and vanadium on the mechanical properties of the structural steel S355N

    OpenAIRE

    Рябікіна, Марина Анатоліівна; Ставровська, В. Є.

    2015-01-01

    The role of microalloying additions of V, Nb, Ti manifested mainly as a result of their influence on the formation of substitution solid solution; dispersion, shape and distribution of the carbides (carbonitrides); the structure of boundaries and the fine structure of the grains; reducing the negative impact of harmful impurities. It is important to precise knowledge of the required number of microalloying elements in the steel. The objective of the present article is to review the role of Nb...

  11. Fabrication of ordered porous silicon carbide-based ceramics

    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...

  12. Optical and magnetic resonance study of a-SiC.sub.x./sub.N.sub.y./sub. films obtained by magnetron sputtering

    Czech Academy of Sciences Publication Activity Database

    Savchenko, Dariia; Kulikovsky, V.; Vorlíček, Vladimír; Lančok, Ján; Kiselov, V.; Kalabukhova, E.

    2014-01-01

    Roč. 251, č. 6 (2014), s. 1178-1185. ISSN 0370-1972 R&D Projects: GA ČR GP13-06697P; GA MŠk(CZ) LM2011029 Grant ostatní: SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : dangling bonds * electron paramagnetic resonance * Raman spectroscopy * silicon carbonitride * thin films Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.489, year: 2014

  13. Investigation on Cutting Tool Performance of α-Si3N4 - β SiAlON Ceramics

    OpenAIRE

    Çalışkan, Fatih; Tatlı, Zafer; Kılıç, Serkan; Sönmez, Hakkı

    2014-01-01

    One of the ceramic products is ceramic cutting edges and these are used as cutting tools for fabrication of metal products (ferrous and non ferrous metals) at very high speeds. These cutting tools can mainly be classified silicon nitride, alumina, mixed-ceramics, titanium carbonitride, cubic boron nitride and hard ceramic particle reinforced metals. Ceramic cutting tools offer a high productivity because of their superior hardness, fracture toughness and resistance of elevated temperature whi...

  14. High-strength low-alloy (HSLA) steels: Visokotrdna malolegirana (HSLA) konstrukcijska jekla:

    OpenAIRE

    Skobir Balantič, Danijela Anica

    2011-01-01

    Micro-alloyed, high-strength, low-alloy (HSLA) steels are important structural materials and contain small amounts of alloying elements, such as niobium, titanium, vanadium, and aluminium, which enhance the strength through the formation of stable carbides, nitrides or carbonitrides and have an effect on the hardenability. Such steels contain less than 0.1 % of the alloying additions, used individually or in combination. Yield strength increments of two or three times that of plain carbon-man...

  15. New approach for modelling strain induced precipitation of Nb(C,N) in HSLA steels during multipass hot deformation in austenite

    OpenAIRE

    Nagarajan, V.; Palmiere, E.J.; Sellars, C.M.

    2009-01-01

    A new model for strain induced precipitation of Nb(C,N) is developed from the existing model for single pass hot deformation. This new model can be extended to multipass deformation to explain the microstructural evolution during the hot deformation of Nb supersaturated high strength low alloy (HSLA) steels. The key feature of this model is the microband geometry employed, which leads to determination of the local solute concentration at microbands, and hence the potential for carbonitride pr...

  16. 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.

  17. Contribution to the study of the (U,Pu)C,N system

    International Nuclear Information System (INIS)

    The reactions of UC, PuC, (U,Pu)C, UC2 and U(C1-xOx) with nitrogen at moderate temperatures (room temperature to 400 C) are described. The influence of the uptake of nitrogen by the powders necessary to sinter the carbides upon the nature of the final product has been investigated; it has been shown that the sintered carbides are hyper-stoichiometric. The reactions of carbon with UN, PuN and (U,Pu)N has also been studied. Under vacuum, carbon reacts on the nitrides at temperatures as low as 1100 C; nitrogen is replaced by carbon and the final product is a carbonitride. The reaction is: MN + x C → MN1-xCx + x/2N2. The reaction is limited and the carbonitrides have a fixed composition in presence of M2C3 or MC2; hence it is impossible to produce pure MC using the reaction. The ternary diagram U-C-N, Pu-C-N and (U,Pu)C-N have been drawn. They show clearly that it is possible to obtain single phase carbonitrides in a wide domain of compositions. (author)

  18. 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.

  19. Evaluation of Cermet Fuels Test Data

    International Nuclear Information System (INIS)

    Test results characterizing ceramic-metallic (cermet) fuels are available from fuel development programs conducted for the ANP project, the 710 reactor program and the Argonne National Laboratory (ANL) nuclear rocket program. There is some overlap in the materials candidates tested in these programs. Test conditions were however significantly different due to wide variation in intended applications of these high temperature cermet fuels. This paper provides an overview of these development efforts, define (where possible) the damage mechanisms thought to be responsible for fuel operating limitations, and identify the fundamental physical mechanisms thought to be responsible. In more recent years, a new form of cermet fuels based on uranium-zirconium carbonitride (U,Zr)CN was developed and tested by the Innovative Nuclear Space Power and Propulsion Institute, University of Florida, and the Scientific Research Associates 'LUTCH' of Russia. The most significant outcome of the joint INSPILUTCH program was the establishment of the high temperature characteristics of the uranium-zirconium carbonitride, (U,Zr)CN and its long term compatibility with the metallic matrix. The improved features of uranium-zirconium carbonitride include chemical compatibility with tungsten matrix and stability at temperatures as high as 3300 K, high uranium density, and high thermal conductivity. The paper also presents a brief summary of the (U,Zr)CN base cermet fuel test results. (authors)

  20. The effect of tempering on mechanical properties of 50Mn18Cr4WN retaining ring material

    International Nuclear Information System (INIS)

    50Mn18Cr4WN is a retaining ring steel. It is strengthened by solution heat treatment and cold working. The process produces high macro residual stress. The retaining ring must be tempered for stress-relief. When the ring is sleeved, it is heated too. If the retaining ring is tempered, are the mechanical properties of the retaining ring damaged? The problem is described in the article. The tempering of testing pieces was carried out at several temperatures: 350degC, 400degC, 450degC, 500degC and 650degC. The tempering time was 3h. The yield point, tensile strength, elongation and reduction of area were determined by means of the tensile test. In the results, for temperatures between 350degC and 450degC, the yield point, tensile strength, elongation and reduction of area did not change notably. A stress corrosion cracking test was also carried out in a 3%Ni4NO3, 36%Ca(NO3)2 aqueous solution. K1scc values after tempering at 450degC and without tempering were measured. The results showed that the K1scc after tempering at 450degC decreased notably. Micrographs show that carbo-nitride precipitated. The precipitated carbo-nitride particles increased in size at the grain boundaries. The precipitated carbonitride particles increased in number at slip lines. It is clear that the precipitated particles lead to the increase of micro-cells and the micro-cells aggravated the stress corrosion cracking process. (orig.)

  1. Atom probe field ion microscopy characterizations of VVER steels

    International Nuclear Information System (INIS)

    An atom probe field ion microscopy (APFIM) characterization of Soviet types 15Kh2MFA Cr-Mo-V (VVER 440) and 15Kh2NMFA Ni-Cr-Mo-V (VVER 1000) pressure vessel steels has been performed. Field ion microscopy has revealed that the lath boundaries in unirradiated VVER 440 and VVER 1000 steels are decorated with a thin film of brightly-imaging molybdenum carbonitride precipitates and some coarser vanadium carbides. Atom probe analysis has revealed significant enrichments of phosphorous at the lath boundaries

  2. 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.

  3. INFLUENCE OF THERMAL DIFFUSION CARBONITRATION AND STRUCTURE OF DIFFUSION COATINGS ON MECHANICAL PROPERTIES OF P6M5 TOOL STEEL

    Directory of Open Access Journals (Sweden)

    N. G. Kouhareva

    2014-12-01

    Full Text Available The paper investigates micro-structure, distribution of chemical elements in diffusion carbonitride coatings on P6M5 steel that have been obtained in powder cyanoless media at temperature 450–550 °C, distribution of micro-hardness and also results of the experiments on wear resistance executed at loads of 50 and 400 MPa.Influence of  machining temperature on  dimension and shape of  hardening phases is shown in the paper. The paper also considers influence of these characteristics on mechanical properties of carbonitrated P6M5 steel.

  4. Thermodynamic investigations of transition metal systems containing coabon and nitrogen

    OpenAIRE

    Teng, Lidong

    2004-01-01

    In view of the important applications of carbides and carbo-nitrides of transition metals in the heat-resistant and hard materials industries, the thermodynamic activities of Cr and Mn in the Cr-C, Fe-Cr-C, Mn-Ni-C and Mn-Ni-C-N systems have been studied in the present work by the use of the galvanic cell technique. CaF2single crystals were used as the solid electrolyte. The phase relationships in selected regions of the systems in question were investigated by the use of the equilibration te...

  5. MOCVD of Cr-based coatings using Cr(NEt2)4 as single source precursor

    International Nuclear Information System (INIS)

    Chromium carbo-nitride coatings with low nitrogen contents have been deposited by low pressure MOCVD using Cr(NEt2)4 as single source precursor. Depositions were carried out in the temperature range 300-520 deg C either under high vacuum without carrier gas or using a partial pressure of nitrogen or hydrogen as carrier gas. All the films are X-ray amorphous and they exhibit a uniform and specular surface morphology with a metallic shiny aspect. The major volatile by-products were analyzed and a decomposition mechanism is proposed. Preliminary properties of these films are also reported. (author). 13 refs., 1 fig., 1 tab

  6. Strengthening mechanisms in a pipeline microalloyed steel with a complex microstructure

    International Nuclear Information System (INIS)

    The microstructure of a commercial pipeline microalloyed steel has been characterized by optical and electron microscopy considering the particularity of the thermomechanical processing without accelerated cooling. The microstructure was a mixture of polygonal ferrite (PF) and granular bainite (GB). The well-known structure–property relationship for PF microalloyed steels is used in structures where high misorientation boundaries in the acicular ferrite are significant. In order to quantify the contributions of the precipitation strengthening as well as the dislocation hardening, representative carbonitride particles and dislocation densities were determined in sample areas by transmission electron microscopy

  7. Strengthening mechanisms in a pipeline microalloyed steel with a complex microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Morales, E.V., E-mail: evalen@uclv.edu.cu [Department of Physics, Central University of Las Villas, CP 54830 Santa Clara, VC (Cuba); Materials Engineering Department/DEMa, Pontifical Catholic University of Rio de Janeiro/PUC-Rio, Rua Marques de S. Vicente 225, Gávea, Rio de Janeiro, RJ CEP 222541-900 (Brazil); Silva, R.A.; Bott, I.S.; Paciornik, S. [Materials Engineering Department/DEMa, Pontifical Catholic University of Rio de Janeiro/PUC-Rio, Rua Marques de S. Vicente 225, Gávea, Rio de Janeiro, RJ CEP 222541-900 (Brazil)

    2013-11-15

    The microstructure of a commercial pipeline microalloyed steel has been characterized by optical and electron microscopy considering the particularity of the thermomechanical processing without accelerated cooling. The microstructure was a mixture of polygonal ferrite (PF) and granular bainite (GB). The well-known structure–property relationship for PF microalloyed steels is used in structures where high misorientation boundaries in the acicular ferrite are significant. In order to quantify the contributions of the precipitation strengthening as well as the dislocation hardening, representative carbonitride particles and dislocation densities were determined in sample areas by transmission electron microscopy.

  8. 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.

  9. Niobium in rail steels

    International Nuclear Information System (INIS)

    The strengthening capacity of niobium in high carbon steels is governed by the carbon content, soaking conditions prior to rolling and the finish rolling temperature. Yield and tensile strengths may be increased by up to 70-100 MPa (10-15 k.s.i.) in C-Mn-Cr rails with niobium additions of about 0.03 percent. The strengthening mechanism appears to be precipitation hardening of niobium carbonitride in the pro-eutectoid ferrite and ferrite lamellae in pearlite. In addition, ductility improvements may be effected through the austenite grain refining action of niobium in hot rolling leading to a reduction in pearlite colony size

  10. Wear Behavior of Austempered Ductile Iron with Nanosized Additives

    OpenAIRE

    J. Kaleicheva

    2014-01-01

    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 isotherma...

  11. Wireless passive polymer-derived SiCN ceramic sensor with integrated resonator/antenna

    Science.gov (United States)

    Li, Yan; Yu, Yuxi; San, Haisheng; Wang, Yansong; An, Linan

    2013-10-01

    This paper presents a passive wireless polymer-derived silicon carbonitride (SiCN) ceramic sensor based on cavity radio frequency resonator together with integrated slot antenna. The effect of the cavity sensor dimensions on the Q-factor and resonant frequency is investigated by numerical simulation. A sensor with optimal dimensions is designed and fabricated. It is demonstrated that the sensor signal can be wirelessly detected at distances up to 20 mm. Given the high-temperature stability of the SiCN, the sensor is very promising for high-temperature wireless sensing applications.

  12. Application of phase equilibria and chemical thermodynamics to the preparation, farbiration, and performance of advanced fast reactor fuel materials

    International Nuclear Information System (INIS)

    Described are some phase equilibria and chemical thermodynamics of systems relevant to the production and operation of the so-called ''advanced'' fast breeder reactor fuels. The systems discussed include UPu carbides, nitrides, oxycarbides and carbonitrides. Some examples of the application of these phase equilibria to the preparation, fabrication and behaviour of the materials in temperature gradients appropriate to reactor conditions are presented. Finally, aspects of the complex four and five component, U-C-O-N and U-Pu-C-O-N systems are discussed, a detailed knowledge of which is required for an analysis of advanced fuel behaviour

  13. Recrystallization and texture in a ferritic stainless steel: An EBSD study

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, C.W. [Department of Metals and Materials Engineering, University of British Columbia, Vancouver BC V6T 1Z4 (Canada); Robaut, F.; Maniguet, L. [CMTC-INPG, St. Martin d' Heres (France); Mithieux, J.D.; Schmitt, J.H. [CRI R and D Groupe Arcelor, Isbergues (France); Brechet, Y. [LTPCM-INPG, St. Martin d' Heres (France)

    2003-08-01

    The recrystallization behavior of laboratory-processed AISI409 ferritic stainless steel sheet has been studied with a focus on texture inhomogeneity and ''sluggish'' recrystallization kinetics, mainly using EBSD in the scanning electron microscope. Pronounced texture gradients were observed in some grain orientations and correlated to the deformation-induced substructure. The strong pinning of some boundaries has been linked not only to textural effects, but also to the precipitation of fine titanium carbonitrides. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  14. Spire Project: Work Package 2 (WP2): Metallurgy before irradiation: Deliverable 4: European Commission-5th Framework program Spire-Contract N FIS5-1999-00223

    International Nuclear Information System (INIS)

    9Crimo (EM-10) and 9Crimonbv (T-91) Steels have been investigated by microstructural characterisation and mechanical properties optical microscopy, sem, tem in thin foils, EDS-TEM analysis in carbon extraction replicas and XRD analysis in phase extraction residues have been carried out in both materials. Quantitative analysis were undertaken to determine the width of the martensite laths/sub grains and the size and distribution of the carbide and carbonitride precipitates, tensile test, impact test with standard and miniature specimens, fracture toughness and small punch test were performed on the EM-10 Steel, and creep test on the T-91 Steel. (Author)

  15. Influencia del acabado superficial sobre el comportamiento tribológico de capas nitrocarburadas en acero X40CrMoV5 1

    OpenAIRE

    Miguel, V.; Calatayud, A.; Coello, J.; Martínez, A.; Caminero, A.

    2005-01-01

    In this work the surface roughness behaviour in the forming of gaseous nitrocarburized layers has been analyzed. Ra values from 0.02 to 1.50 μm. has been considered. Obtained results prove a minor influence on layer thickness. A little increase of Ra has been observed. The abrasive wear resistance of nitrocarburized specimens was researched. The carbonitride ε is the only constituent in the about 6 μm thickness layers that have been carried out in this work. The tests revealed a minor wear re...

  16. 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...

  17. Mechanical properties of a microalloyed steel with hig niobium content

    International Nuclear Information System (INIS)

    A higher-than-usual niobium content is being considered as a possible alternative to heavy low-temperature controlled rolling which is usually required in order to develop high strenght and toughness in microalloyed steel. In the present study, the effect of 0.24% Nb dissolved in austenite on the strenght and toughness of polygonal ferrite has been investigated. The niobium addition reduced the ferrite grain size but at the same time led to the deterioration of impact properties without raising yield strenght. Electron microscope observations suggested that the decrease in toughless was caused by intercrystalline fracture due to preferential carbonitride precipitation at austenite grain boundaries. (Author)

  18. Centreline formation of Nb(C, N eutectic in structural steel

    Directory of Open Access Journals (Sweden)

    J. Bernetič

    2010-01-01

    Full Text Available The reduction of area in the through thickness direction is an essential mechanical property of thick steel heavy plates. By a routine control, a very small through thickness reduction of area was found for tensile specimen of a 90 mm plate. Careful investigations of the fracture and section of specimens cut from the as solidified continuously cast 250mmthick slab showed that the cause was the presence of coarse particles of niobium carbonitride as constituent of the quasi eutectic Fe-Nb(C, N that form because of the centerline segregation of niobium.

  19. Centreline formation of Nb(C, N) eutectic in structural steel

    OpenAIRE

    J. Bernetič; Bradaškja, B.; G. Kosec; Bricelj, E.; B. Kosec; F. Vodopivec; Kosec, L.

    2010-01-01

    The reduction of area in the through thickness direction is an essential mechanical property of thick steel heavy plates. By a routine control, a very small through thickness reduction of area was found for tensile specimen of a 90 mm plate. Careful investigations of the fracture and section of specimens cut from the as solidified continuously cast 250mmthick slab showed that the cause was the presence of coarse particles of niobium carbonitride as constituent of the quasi eutectic Fe-Nb(C, N...

  20. Particularities of structure formation of multilayer nitrogen-bearing coating produced by electron beam surfacing of thin-walled articles

    International Nuclear Information System (INIS)

    A structural study is made into a steel Kh20AG20 base composite material 6 mm thick produced by electron beam weld-surfacing on a carbon steel substrate 3 mm thick. Certain regularities in structure formation of nitrogen-bearing coatings are revealed depending on the temperature in an electron beam affected zone. It is shown that the structure of a multilayer coating is nonuniform and varies with depth smoothly. The phase composition constitutes a ferritic-austenitic matrix with chromium carbide and carbonitride inclusions

  1. Structural forms of cubic BC2N

    International Nuclear Information System (INIS)

    Superhard cubic boron-carbonitrides (c-BC2N) are studied with the use of the ab initio pseudopotential density functional method. The total energy, lattice constant, bulk and shear moduli, and electronic band structures as well as the electron density of states are calculated for all the possible c-BC2N structures in an eight-atom zinc-blende-structured cubic unit cell. The results obtained provide a plausible explanation for recent experimental observations as well as a possible path to synthesis of the materials

  2. Boundary and sub-boundary hardening in tempered martensitic 9Cr steel during long-term creep at 650 C

    Energy Technology Data Exchange (ETDEWEB)

    Abe, Fujio [National Institute for Materials Science, Sengen, Tsukuba (Japan)

    2010-07-01

    The boundary and 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 boundary and sub-boundary hardening. This improves long-term creep strength of base metal. The enhancement of boundary and sub-boundary hardening is significantly reduced in fine-grained region of Ac{sub 3} HAZ simulated specimens of conventional steel P92. In NIMS 9Cr 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. Newly alloy-designed 9Cr steel with 160 ppm boron and 85 ppm nitrogen exhibits much higher creep rupture strength of base metal than P92 and also no Tpe-IV fracture in welded joints at 650 C. (orig.)

  3. 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.

  4. Thermodynamic stability of in situ W–ZrC and W–Zr(CN) composites

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jae-Hee [Korea Aerospace Research Institute, Daejeon 305-806 (Korea, Republic of); Zhe, Gao [Saint-Gobain Research Shanghai Co., Ltd, Wenjing-road, Minhang-district, Shanghai 200245 (China); Lim, Jaehyuk [Samsung Electronics, Yongin 446-811 (Korea, Republic of); Park, Choongkwon [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Kang, Shinhoo, E-mail: shinkang@snu.ac.kr [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of)

    2015-10-25

    Powders of W–ZrC and W–Zr(CN) were carbothermally synthesized in situ from milled mixtures of graphite, WO{sub 3} and ZrO{sub 2}. The thermal stability of Zr(CN) in a W matrix was simulated and compared with that of ZrC in W in terms of free energy change and carbide coarsening. Carbon and nitrogen had high mutual affinity in Zr(CN) of B1 crystal structure, which led their activity curves to exhibit strong negative deviation from ideal mixing behavior. Zr(CN) was more stable than ZrC up to 2075 K; however, a microstructural study showed that it became less stable than ZrC at around 1975 K. This result is attributed to the decreasing thermodynamic stability of ZrN with increasing temperature. Other transition metal carbonitrides containing group 4–6 elements are expected to show similar coarsening behaviors at high temperatures. - Highlights: • The Zr(CN) phase formed due to the high affinity between C and N in ZrC. • A complete reversal of the slope is found in the formation energy curves. • The growth of the carbonitride is due to the nitrogen, reducing the stability. • Solid solutions containing group 4 elements would show similar growth behavior.

  5. Zr N and Zr O2 production by zirconium carbon nitridation (Zr Si O4)

    International Nuclear Information System (INIS)

    Structural ceramics based on nitrides, oxynitrides like, Zr N-Si3 N4 and Zr O2 Si2 O N2 have good thermal and mechanical properties, with curves in technological applications. Many obtention methods are propose, but carbonitriding reactions (carbon reduction and simultaneous nitriding) of zircon (Zr O2 Si O2) may be interest because a low cost raw material is used. In this work the carbonitriding of zircon and the principal reaction conditions: carbon quantity, N2 flow, temperature and reaction time are studied. The phases formed were followed using XRD and the weight loss of the samples. The final products were: Zr N with low content of Si C and/or Si3 N4 or the monoclinic form of Zr O2. The products be obtained can be predicted according to the reaction conditions employed. During the reaction Si O(g) loss is observed and silica can be completely eliminated if reaction conditions are adjusted. (author)

  6. Influence of non-metallic second phases on fatigue behaviour of high strength steel components

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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

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

    KAUST Repository

    Gan, Li-Yong

    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).

  9. 9%Cr heat resistant steels: Alloy design, microstructure evolution and creep response at 650 deg. C

    International Nuclear Information System (INIS)

    Highlights: → 9Cr alloys with varying Ti and C contents were designed, produced and crept at 650 deg. C. → Sub-grain and precipitate distribution and evolution investigated by STEM-HAADF. → Correlations between microstructure evolution and mechanical properties were studied. → Coarsening of sub-grain size was larger for Ti-containing 9Cr alloys. → 9Cr alloy with low C and no Ti showed the highest creep strength of all studied alloys. - Abstract: In this work 9%Cr alloys were designed supported by computational thermodynamic methods. Two sets of alloys were produced: 9%Cr alloys with 0.1%C and 0.05%C and 9%Cr alloys containing ∼0.03% Ti with 0.1%C and 0.05%C (always wt%). Microstructure investigations showed good agreement with the predicted phases of the thermodynamic modeling. The volume fraction of precipitated M23C6 carbides is directly related to the carbon content of the alloys. For Ti-containing alloys the precipitation of nano-sized Ti-rich MX carbonitrides was observed. The microstructure evolution (sub-grain and particle size) during creep at 650 deg. C/100 MPa was investigated by STEM-HAADF. The sub-grain size evolution and the coarsening of precipitates (MX carbonitrides, M23C6 and Laves phase) were more pronounced for Ti-containing alloys. 9Cr alloys without Ti and with low carbon content presented the highest creep strength of all investigated alloys.

  10. 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.

  11. Investigations of Li-containing SiCN(O) ceramics via 7Li MAS NMR.

    Science.gov (United States)

    Gumann, Sina; Nestle, Nikolaus; Liebau-Kunzmann, Verena; Riedel, Ralf

    2007-04-01

    Lithium-containing silicon (oxy)carbonitride ceramics (SiCN(O):Li) were synthesized via precursor-to-ceramic-transformation of Li-containing (poly)silazanes. The precursors were obtained by lithiation of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane with n-butyllithium and by reaction of a commercial poly(organosilazane) VL20 with metallic lithium. The annealing treatment was carried out at temperatures between 200 and 1400 degrees C in argon (DeltaT=200 degrees C) and yielded Li-containing silicon (oxy)carbonitride. X-ray powder diffraction revealed that the resulting SiCN(O):Li ceramics were basically amorphous up to temperatures of 1000 degrees C and formed LiSi(2)N(3), graphite and silicon carbide as crystalline phases at higher temperatures. (7)Li MAS NMR spectroscopy was carried out to investigate the structure of the Li-containing phases and to study the reaction path of metallic Li with polysilazane. Based on the NMR spectra, there is almost no difference found in the chemical shift of the SiCN(O):Li ceramics obtained at different temperatures. Accordingly, Li is assigned to be mainly coordinated to N and O present as contaminant element. Relaxation time measurements showed that the most mobile Li(+) species seems to be present in the product obtained in the pyrolysis temperature range between 600 and 1000 degrees C. PMID:17418540

  12. 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.)

  13. Structure and mechanical properties of corrosion-resistant high-nitrogen 04Kh22AG15N8M2F and 05Kh19AG10N7MFB steels after hot deformation

    Science.gov (United States)

    Blinov, E. V.; Khadyev, M. S.

    2012-03-01

    The structure and mechanical properties of corrosion-resistant high-nitrogen austenitic 04Kh22AG15N8M2F and 05Kh19AG10N7MFB steels are studied after hot rolling at 950 and 1100°C. The following specific features of the structure of hot-rolled 04Kh22AG15N8M2F steel are revealed: the presence of coarse grain-boundary precipitates of the molybdenum-rich σ phase and its nonuniform distribution over the volume of austenite grains. The 05Kh19AG10N7MFB steel hot rolled at 950°C contains ultrafine carbonitrides particles and has the best combination of a high strength and a sufficient elasticity and impact toughness. The structures of the hot-rolled steels have no ferrite, martensite, and traces of recrystallized austenite grains.

  14. 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)

  15. Design of martensitic/ferritic heat-resistant steels for application at 650 deg. C with supporting thermodynamic modelling

    Energy Technology Data Exchange (ETDEWEB)

    Knezevic, V.; Balun, J. [Max-Planck-Institut fuer Eisenforschung GmbH, 40074 Duesseldorf (Germany); Sauthoff, G. [Max-Planck-Institut fuer Eisenforschung GmbH, 40074 Duesseldorf (Germany)], E-mail: g.sauthoff@mpie.de; Inden, G.; Schneider, A. [Max-Planck-Institut fuer Eisenforschung GmbH, 40074 Duesseldorf (Germany)

    2008-03-25

    In view of developing novel heat-resisting steels for applications in conventional power plants with service temperatures of 650 deg. C, a series of martensitic/ferritic model steels with 12 wt.%Cr were studied to achieve an increased creep resistance through additional alloying with various elements for controlled precipitation of M{sub 23}C{sub 6} carbides, MX carbonitrides and intermetallic Laves phase. The alloy design relied on thermodynamic simulation calculations using Thermo-Calc and DICTRA. The mechanical testing concentrated on creep at 650 deg. C for up to 8000 h. The alloy optimization resulted in creep rupture strengths above those of the martensitic/ferritic P92 steel. The work was part of a cooperative project within the German MARCKO program.

  16. Design of martensitic/ferritic heat-resistant steels for application at 650 deg. C with supporting thermodynamic modelling

    International Nuclear Information System (INIS)

    In view of developing novel heat-resisting steels for applications in conventional power plants with service temperatures of 650 deg. C, a series of martensitic/ferritic model steels with 12 wt.%Cr were studied to achieve an increased creep resistance through additional alloying with various elements for controlled precipitation of M23C6 carbides, MX carbonitrides and intermetallic Laves phase. The alloy design relied on thermodynamic simulation calculations using Thermo-Calc and DICTRA. The mechanical testing concentrated on creep at 650 deg. C for up to 8000 h. The alloy optimization resulted in creep rupture strengths above those of the martensitic/ferritic P92 steel. The work was part of a cooperative project within the German MARCKO program

  17. The effect of nitrogen on the coarsening rate of precipitate phases in iron-based alloys with chromium and vanadium. Experimental and theoretical investigations

    Energy Technology Data Exchange (ETDEWEB)

    Lindwall, Greta; Frisk, Karin [Swerea KIMAB AB, Kista (Sweden). Virtual Lab.

    2013-05-15

    A comparison of the coarsening of nitrogen-rich vanadium precipitates and the coarsening of carbon-rich vanadium precipitates is presented. The precipitate phases are studied experimentally, via fabrication of model alloys, and theoretically, via simulations utilizing the DICTRA software. The experimental investigations indicate that the nitrogen-rich precipitates exhibit a slower coarsening behaviour than the carbon-rich precipitates. Analysis using thermodynamic and kinetic modelling shows that this can be explained by the higher thermodynamic stability of the nitrogen-rich precipitate compared to the carbon-rich precipitate. The calculated coarsening rates are compared with the measured rates, and found to be in satisfactory agreement using reasonable values for the interfacial energies. The investigations are motivated by the fine precipitate size distribution of nitrides and carbonitrides characteristic for high nitrogen alloyed tool steels produced by means of powder metallurgy. (orig.)

  18. 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.

  19. On thermal lattice dilatation of some transition metal compounds

    International Nuclear Information System (INIS)

    The report deals with the thermal lattice dilatation of cubic transition metal compounds. The thermal dilatation is determined through the variation of the lattice constants. The measurements are carried out 'in situ' by use of a high-temperature X-ray diffractometer chamber. The evaluation relates to both the linear thermal expansion coefficient α and, for some compounds, the specific heat at constant volume Csub(V) and the Grueneisen constant γ. In general a higher thermal dilatation is observed for nitrides than for carbides with the compounds formed by the transition metals belonging to the IVA and VA groups. The influence exerted by vacancies and by the oxygen dissolved in the lattice on the thermal dilatation of carbonitrides of zirconium, hafnium and tantalum is explained by the more pronounced anharmonic character of atomic vibrations in the crystal lattice. (orig.)

  20. 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.

  1. Phase Transformation Behavior of Porous TiNi Alloys Produced by Powder Metallurgy Using Magnesium as a Space Holder

    Science.gov (United States)

    Aydoğmuş, Tarik; Bor, Elif Tarhan; Bor, Şakir

    2011-09-01

    Porous TiNi alloys with porosities in the range of 51 to 73 pct were prepared successfully applying a new powder metallurgy fabrication route in which magnesium was used as a space holder, resulting in either single austenite phase or a mixture of austenite and martensite phases dictated by the composition of the starting powders, but entirely free from secondary brittle intermetallics, oxides, nitrides, and carbonitrides. Since transformation temperatures are very sensitive to composition, deformation, and oxidation, for the first time, transformation temperatures of porous TiNi alloys were investigated using chemically homogeneous specimens in as-sintered and aged conditions eliminating secondary phase, contamination, and deformation effects. It was found that the porosity content of the foams has no influence on the phase transformation temperatures both in as-sintered and aged conditions, while deformation, oxidation, and aging treatment are severely influential.

  2. Application of electrochemical plasma techniques in surface engineering of iron based structural materials

    International Nuclear Information System (INIS)

    The surface of austenitic stainless steels 304L and 316L was modified by various complex surface treatments: - plasma electrolytic carbo-nitriding by means of Plasma electrolytic saturation (PES); the saturation of cathodic surfaces with C, N was performed using suitable electrolytes (aqueous solutions of inorganic acids, appropriate salts containing the desired elements and certain organic compounds); -electrodeposition of Al from ChCl based Ionic Liquid. The coatings obtained in various experimental conditions have been investigated by means of electron spectroscopy, scanning electron microscopy, energy dispersion x-ray spectrometry, electrochemical techniques, and the properties of the thin films have been correlated with the microstructure and the composition of the surface layers which are strongly dependents of the different regimes of diffusion treatments. The preliminary results on Electrochemical Plasma Technology (EPT) treatments demonstrate that we can select the processing parameters for essential improvement of corrosion behaviour in some aggressive medium and high values of microhardness. (authors)

  3. 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

    International Nuclear Information System (INIS)

    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.

  4. Effects of Electric Discharge Plasma Treatment on the Thermal Conductivity of Polymer-Metal Nitride/Carbide Composites

    Science.gov (United States)

    Parali, Levent; Kurbanov, Mirza A.; Bayramov, Azad A.; Tatardar, Farida N.; Sultanakhmedova, Ramazanova I.; Xanlar, Huseynova Gulnara

    2015-11-01

    High-density polymer composites with semiconductor or dielectric fillers such as aluminum nitride (AIN), aluminum oxide (Al2O3), titanium carbide (TiC), titanium nitride (TiN), boron nitride (BN), silicon nitride (Si3N4), and titanium carbonitride (TiCN) were prepared by the hot pressing method. Each powder phase of the composites was exposed to an electric discharge plasma process before composite formation. The effects of the electric discharge plasma process and the filler content (volume fraction) on the thermal conductivity, volt-ampere characteristics, thermally stimulated depolarization current, as well as electrical and mechanical strength were investigated. The results of the study indicate that, with increasing filler volume fraction, the thermal conductivity of the samples also increased. Furthermore, the thermal conductivity, and electrophysical and mechanical properties of the high-density polyethylene + 70% BN composite modified using the electric discharge plasma showed improvement when compared with that without electric discharge plasma treatment.

  5. Effects of methane in the deposition of superconducting niobium nitride thin films at ambient substrate temperature

    International Nuclear Information System (INIS)

    Thin films of the niobium-carbon-nitrogen system have been prepared at ambient substrate temperature by rf diode reactive sputtering in an argon-nitrogen atmosphere with controlled amounts of methane added to the sputter gas. Superconducting transition temperatures ranged from approximately 11 to 15.85 0K. Auger and x-ray diffraction analysis indicate that all films were of the single phase B1 structure with a small amount of ν-phase hexagonal structure in the very low carbon containing films. A correlation of the superconducting properties, room temperature sheet resistance, preferred crystallite orientation, and film composition was observed. The results of this investigation show that high T/sub c/ niobium nitride/niobium carbonitride thin films can be prepared at ambient substrate temperatures with the proper amount of nitrogen and methane partial pressures during film deposition. These films have potential application for the fabrication of high T/sub c/ Josephson tunnel junctions

  6. Sintering by SPS of ultrafine TiCxN1-x powders obtained using mechanically induced self sustaining reaction

    International Nuclear Information System (INIS)

    In this work high purity and nanometer character titanium carbonitride TiCxN1-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.

  7. 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.

  8. 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.

  9. Methods for manufacturing porous nuclear fuel elements for high-temperature gas-cooled nuclear reactors

    Science.gov (United States)

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

    2010-02-23

    Methods for manufacturing porous nuclear fuel elements for use in advanced high temperature gas-cooled nuclear reactors (HTGR's). 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, a thin coating of nuclear fuel may be deposited inside of a highly porous skeletal structure made, for example, of reticulated vitreous carbon foam.

  10. Evaluation of End Mill Coatings

    Energy Technology Data Exchange (ETDEWEB)

    L. J. Lazarus; R. L. Hester,

    2005-08-01

    Milling tests were run on families of High Speed Steel (HSS) end mills to determine their lives while machining 304 Stainless Steel. The end mills tested were made from M7, M42 and T15-CPM High Speed Steels. The end mills were also evaluated with no coatings as well as with Titanium Nitride (TiN) and Titanium Carbo-Nitride (TiCN) coatings to determine which combination of HSS and coating provided the highest increase in end mill life while increasing the cost of the tool the least. We found end mill made from M42 gave us the largest increase in tool life with the least increase in cost. The results of this study will be used by Cutting Tool Engineering in determining which end mill descriptions will be dropped from our tool catalog.

  11. A strain-based computational design of creep-resistant steels

    International Nuclear Information System (INIS)

    This work reports on a study into the design of creep-resistant precipitation-hardened austenitic steels using an integrated thermodynamics-based model in combination with a genetic algorithm optimization routine. The key optimization parameter is the secondary stage creep strain at the intended service temperature and time, taking into account the coarsening rate of MX carbonitrides and its effect on the threshold stress for secondary creep. The creep stress to reach a maximal allowed creep strain (taken as 1%) at a given combination of service temperature and time is formulated and maximized. The model was found to predict the behaviour of commercial austenitic creep-resistant steels accurately. By means of the alloy optimization scheme, three new steel compositions are presented, yielding optimal creep strength for various intended service times (10, 103, 105 h). According to the evaluation parameter employed, the newly defined compositions will outperform existing precipitate-strengthened austenitic creep-resistant steels

  12. 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.

  13. Method of nitriding refractory metal articles

    Science.gov (United States)

    Tiegs, Terry N.; Holcombe, Cressie E.; Dykes, Norman L.; Omatete, Ogbemi O.; Young, Albert C.

    1994-01-01

    A method of nitriding a refractory-nitride forming metal or metalloid articles and composite articles. A consolidated metal or metalloid article or composite is placed inside a microwave oven and nitrogen containing gas is introduced into the microwave oven. The metal or metalloid article or composite 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 or composite is maintained at that temperature for a period of time sufficient to convert the article of metal or metalloid or composite to an article or composite 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.

  14. 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.

  15. High temperature properties of TiCN-Mo2C-Co cermets studied by mechanical spectroscopy

    International Nuclear Information System (INIS)

    Low frequency internal friction measurements were performed on TiC0.7N0.3-Mo2C-Co cermets in an inverted torsion-pendulum working with forced oscillations. A thermally activated high temperature background and three thermally activated peaks were observed in the internal friction spectra. Two peaks, which are stable during thermal treatments, appear (at 1 Hz) at about 1050 K and 1200 K respectively. The third peak, appearing at about 950 K, is only observed during the first heating of the as-received samples. In order to locate the relaxation phenomena, similar measurements were performed on carbide-carbonitride skeletons, in which the metallic binder phase was chemically removed. Complementary microstructural characterizations, performed by conventional TEM, allow one to identify the physical mechanisms responsible for the IF peaks and background. (orig.)

  16. Study of corrosion behavior for nitrocarburized sintered Astaloy CrM + C

    International Nuclear Information System (INIS)

    Salt bath nitriding/nitrocarburizing is a surface treatment developed to improve tribological and corrosion properties of ferrous materials. In this research, sintered Astaloy CrM + 0.3% C samples were nitrocarburized at 580 deg. C for 1, 1.5, 2 and 2.5 h. The microstructure and phase composition of the surface layer was investigated by optical and scanning microscopy and X-ray diffraction. Corrosion behavior of samples was evaluated using both potentiodynamic polarization technique and electrochemical impedance spectroscopy in 3.5% sodium chloride solution. XRD analyses indicate that the surface layer in nitrocarburized samples is mainly composed of ε-iron carbonitride (Fe2-3(CN)). The results reveal that salt bath nitrocarburizing for at least 2 h can improve significantly corrosion resistance of sintered Astaloy CrM + C.

  17. 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%.

  18. Enhancement of strength properties of hot rolled 10KHSND steel

    International Nuclear Information System (INIS)

    To find out the reasons of low hot rolling yield for 10KhSND steel sheets in mechanical properties, titanium effect in the range of 0.008-0.03% concentrations is studied. It is established that the titanium content in a solid solution is conserved within 0.003-0.005%, the rest of titanium is bound to carbonitrides Ti(C, N). It is shown that alloys with 0.025-0.03% titanium content possess the increased values of ultimate and yield strength the necessary level of impact strength and good wealdability. The good steel yield, when the titanium content is sustained at the given level, increases from 40 to 85%

  19. Studying factors responsible for increasing ductility of the ferritic steel 08Kh18T1 in the course of repeated hot rolling

    International Nuclear Information System (INIS)

    Two possible reasons for embrittlement of ferritic steel 08Kh18T1 after high temperature (T ≥ 1100 deg C) rolling are considered: an α-phase grain growth and precipitation of titanium carbonitride fine crystal spreading along subboundaries under conditions of dynamic polygonization. Repeat rolling at more low temperatures ranging from 800 to 1000 deg C results in formation of other substructure that is of lath subgrain type. In the case of high deformation degree the accumulation of distortions over a large face of subcrystals results in stratification in a plane perpendicular to a fracture surface, and in so doing it changes the stressed state on main crack propagation so that the thickness (radius) of plastic zone increases and the temperature of ductile-brittle transition decreases

  20. Influence of carbon and nitrogen on corrosion resistance of high purity Fe-50mass% Cr alloys

    International Nuclear Information System (INIS)

    High purity Fe-50mass%Cr alloys containing (C+N) in the range of 30 to 500 mass ppm were prepared and their corrosion resistance was investigated. Pitting potential in a 3.5mass%NaCl solution at 343K rose with reducing (C+N) content. Alloys containing (C+N) at less than 100 mass ppm did not sustain pitting corrosion. However, alloys containing 500 mass ppm (C+N) corroded severely in 6%FeCl3+1/20N HCl solutions. Heat treatment at 923K was recognized as influencing corrosion resistance due to precipitation of carbonitrides only in the case of the alloy containing 500 mass ppm (C+N). (orig.)

  1. Synthesis and Characteristics of Ultra-Fine Superconducting Powders in the Nb-N, Nb-N-C, Nb-Ti-N-C systems

    International Nuclear Information System (INIS)

    The single phase powders of NbN, NbN1-yCy, Nb1-xTixN1-yCy with a mean particle size of 10-70nm were prepared in the nitrogen plasma flow of a microwave discharge at a hydrogen reduction of NbF5 only, or in a mixture with C5H12, or with the addition of TiCl4. It was established that the critical magnetic field of ultra-fine niobium-titanium carbonitride powders is about three times higher as compared with bulk samples of the same composition. The critical magnetic field ran up to 55T for ultra-fine powders with the optimal composition Nb0.8Ti0.2N0.8C0.2. This material may be interesting for the technical superconductivity in the helium temperature range

  2. 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.

  3. The effect of tempering temperature on the features of phase transformations in the ferritic–martensitic steel EK-181

    Energy Technology Data Exchange (ETDEWEB)

    Polekhina, N.A. [Institute of Strength Physics and Materials Science SB RAS, 2/1 Akademichesky av., Tomsk 634055 (Russian Federation); Litovchenko, I.Yu.; Tyumentsev, A.N. [Institute of Strength Physics and Materials Science SB RAS, 2/1 Akademichesky av., Tomsk 634055 (Russian Federation); Tomsk State University, 36 Lenin av., Tomsk 634050 (Russian Federation); V.D. Kuznetsov Siberian Physical-Technical Institute at Tomsk State University, 1 Novosobornaya Sq., Tomsk 634050 (Russian Federation); Astafurova, E.G. [Institute of Strength Physics and Materials Science SB RAS, 2/1 Akademichesky av., Tomsk 634055 (Russian Federation); Chernov, V.M.; Leontyeva-Smirnova, M.V. [JSC “A.A. Bochvar High-Technology Research Institute of Inorganic Materials”, 5 Rogov st., Moscow 123060 (Russian Federation)

    2014-12-15

    Using the methods of dilatometry and differential scanning calorimetry, critical points of phase transformations in the low-activation ferritic–martensitic steel EK-181 (RUSFER-EK-181) are identified. The characteristic temperature intervals of precipitation of carbide phases are revealed. It is shown that particles of the metastable carbide M{sub 3}C are formed within the temperature range (500–600) °C. Formation of the stable phases M{sub 23}S{sub 6} and V(CN) begins at the temperatures higher than T = 650 °S. An important feature of microstructure after tempering at T = 720 °S is high density of nanoparticles (⩽10 nm) of vanadium carbonitride V(CN)

  4. Nanosized Si3N4/SiC-powders by polysilazane/polycarbosilane-pyrolysis

    International Nuclear Information System (INIS)

    The preparation of the nanosized powders has been realized by gasphase-pyrolysis of volatile precursor compounds at temperatures between 600 and 1200 C. Silicon carbonitride powders have been created from polysilazanes, which have been synthesized by ammonolysis of alkylchlorosilanes. Silicon carbide powders have been prepared from 1,1,3,3-tetramethyl-1,3-disilacyclobutane, gained by the dechlorination- and coupling reaction of chloromethyldimethylchlorosilane with magnesium. The ball-like powder particles have a diameter between 100 and 500 nm and a surface of 10 to 50 m2/g. They are X-ray amorphous and can be crystallized upper 1400 C to α-Si3N4 and β-SiC respectively. (orig.)

  5. Specific detection of proteins using Nanomechanical resonators

    DEFF Research Database (Denmark)

    Fischer, Lee MacKenzie; Wright, V.A.; Guthy, C.; Yang, N.; McDermott, M.T.; Buriak, J.M.; Evoy, S.

    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...

  6. Microstructure and properties of dual-phase steels containing fine precipitates

    Energy Technology Data Exchange (ETDEWEB)

    Gau, J.S.; Koo, J.Y.; Nakagawa, A.; Thomas, G.

    1981-07-01

    Very fine particles (carbides or carbonitrides) of the order of 20 A were extensively examined in the ferrite regions of dual-phase steels subjected to intercritical annealing followed by fast quenching to room temperature. These particles are probably formed during quenching after intercritical annealing. The driving force for the precipitation reaction may arise from the supersaturation of carbon (or nitrogen) in the ferrite phase. These precipitates in certain alloy compositions cause a deviation from the generally observed two phase mixture rule in that the strength of the dual-phase steels having a higher volume fraction of martensite is lower than that having a lower volume fraction of martensite. Thus, the influence of such precipitates must be considered in the structure-property relations of dual-phase steels when fast quenching is employed after intercritical annealing.

  7. Fabrication of nano-scaled polymer-derived SiAlCN ceramic components using focused ion beam

    International Nuclear Information System (INIS)

    Fully dense polymer-derived amorphous silicoaluminum carbonitride (SiAlCN) ceramics were synthesized from polysilazane as preceramic precursors followed by a thermal decomposition process. The nanofabrication of amorphous SiAlCN ceramics was implemented with a focused ion beam (FIB). FIB conditions such as the milling rate, the beam current, and the number of passes were considered. It was found that nanopatterns with a feature size of less than 100 nm could be fabricated onto polymer-derived ceramics (PDCs) precisely and quickly. Specific nanostructures of thin walls, nozzle, and gear have been fabricated as demonstrations, indicating that the FIB technique was a promising method to realize nanostructures on PDCs, especially for microelectromechanical system and micro/nano-sensor applications. (paper)

  8. Synthesis and high temperature stability of amorphous Si(B)CN-MWCNT composite nanowires

    Science.gov (United States)

    Bhandavat, Romil; Singh, Gurpreet

    2012-02-01

    We demonstrate synthesis of a hybrid nanowire structure consisting of an amorphous polymer-derived silicon boron-carbonitride (Si-B-C-N) shell with a multiwalled carbon nanotube core. This was achieved through a novel process involving preparation of a boron-modified liquid polymeric precursor through a reaction of trimethyl borate and polyureasilazane under atmospheric conditions; followed by conversion of polymer to glass-ceramic on carbon nanotube surfaces through controlled heating. Chemical structure of the polymer was studied by liquid-NMR while evolution of various ceramic phases was studied by Raman spectroscopy, solid-NMR, Fourier transform infrared and X-ray photoelectron spectroscopy. Electron microscopy and X-ray diffraction confirms presence of amorphous Si(B)CN coating on individual nanotubes for all specimen processed below 1400 degree C. Thermogravimetric analysis, followed by TEM revealed high temperature stability of the carbon nanotube core in flowing air up to 1300 degree C.

  9. Fabrication of nano-scaled polymer-derived SiAlCN ceramic components using focused ion beam

    Science.gov (United States)

    Tian, Ye; Shao, Gang; Wang, Xingwei; An, Linan

    2013-09-01

    Fully dense polymer-derived amorphous silicoaluminum carbonitride (SiAlCN) ceramics were synthesized from polysilazane as preceramic precursors followed by a thermal decomposition process. The nanofabrication of amorphous SiAlCN ceramics was implemented with a focused ion beam (FIB). FIB conditions such as the milling rate, the beam current, and the number of passes were considered. It was found that nanopatterns with a feature size of less than 100 nm could be fabricated onto polymer-derived ceramics (PDCs) precisely and quickly. Specific nanostructures of thin walls, nozzle, and gear have been fabricated as demonstrations, indicating that the FIB technique was a promising method to realize nanostructures on PDCs, especially for microelectromechanical system and micro/nano-sensor applications.

  10. 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

    2016-08-19

    MXenes, carbides, nitrides and carbonitrides of early transition metals are the new members of two dimensional materials family given with a formula of [Formula: see text] 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. PMID:27377143

  11. 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.

  12. Solubility of niobium in austenite in the presence of Nb(C,N)

    International Nuclear Information System (INIS)

    It was developed some equations to calculate the solubility of niobium in austenite in the presence of NbC sub(0.87) or NbN. These equations were applied to steels with carbon, nitrogen and niobium content varying from 10-3 to 1 wt %, and for 800-13000C temperature range. The results obtained were compared with experimental data from literature, and showed a good agreement. Using those equations, it was developed an algorithm to calculate the solubility of niobium in austenite in the presence of niobium carbonitride (NbC sub(x) N sub(y)). The results obtained by this method were compared with experimental data, and also showed a good agreement. (Author)

  13. Correlation of Fractographic Features with Mechanical Properties in Systematically Varied Microstructures of Cu-Strengthened High-Strength Low-Alloy Steel

    Science.gov (United States)

    Das, Arpan; Das, Swapan Kumar; Tarafder, Soumitra

    2009-12-01

    Fracture is often the culmination of continued deformation. Therefore, it is probable that a fracture surface may contain an imprint of the deformation processes that were operative. In this study, the deformation behavior of copper-strengthened high-strength low-alloy (HSLA) 100 steel has been investigated. Systematic variation of the microstructure has been introduced in the steel through various aging treatments. Due to aging, the coherency, size, shape, and distribution of the copper precipitates were changed, while those of inclusions, carbides, and carbonitrides were kept unaltered. Two-dimensional dimple morphologies, quantified from tensile fracture surfaces, have been correlated to the nature of the variation of the deformation parameters with aging treatment.

  14. The development of nano-modified Ti(C,N) cermets.

    Science.gov (United States)

    Rong, Chunlan; Chen, Wenling; Zhang, Xiaobo; Liu, Ning

    2007-01-01

    The unique combination of mechanical properties such as excellent wear resistance and good chemical stability at elevated temperature helps titanium carbonitride based (Ti (C, N)-based) cermets to play an important roles in metal cutting operations. Nowadays, cermets cutting tools are widely used for semi-finishing and finishing works on steel and cast iron. However, their brittleness is still an unavoidable limitation for their utilization. With the development of nano-technology, nano-modified cermets have received more attention due to the high toughening enhancements. In this review, the development of nano-modified Ti(C,N) cermets is discussed including the fabrication, microstructure, mechanical properties, cutting performance and the practical applications in different fields. Many patents having important effect on the development of cermets were noticed, too. PMID:19076029

  15. 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.

  16. Properties of Cr(C,N) hard coatings deposited in Ar-C2H2-N2 plasma

    International Nuclear Information System (INIS)

    Several chromium carbonitride (Cr-(C,N)) coatings were prepared with different C:N ratios by varying the N2 and C2H2 flow. Chromium nitride (Cr-N) and chromium carbide (Cr-C) coatings were also prepared for comparison. The coatings were deposited in two different ion-plating systems: by reactive evaporation in BAI730M (Balzers) apparatus at high temperature (450 deg. C) and by reactive sputtering in plasma-beam Sputron (Balzers) apparatus at low temperature (200 deg. C). Among mechanical properties microhardness, adhesion (measured by scratch test) and surface roughness were evaluated. Oxidation of the coatings was carried out by heating the samples at temperatures of 750-900 deg. C in an oxygen atmosphere. Crystal structure and microstructure were studied by XRD, TEM and SEM. Chemical State of the elements was observed by XPS. The concentration and depth profiles of the samples oxidized at various temperatures were measured by AES, EDX and GDOES

  17. Features of mass transfer and structure forming for coatings based on titanium borides in the process of thermal reactional electric spark strengthening

    International Nuclear Information System (INIS)

    The regularities of mass transfer and structure formation in the process of thermal reaction electric spark hardening (TRESH) of titanium boride base coatings are investigated. For coatings deposition of titanium alloy VT3-1 and stainless steel 12Kh18N9T substrates aluminium-, copper- and steel sheathed Ti+B, Ti+B+diamond, and TiB2-Ti electrodes are used. It is revealed that coatings wear resistance and TRESH efficiency are determined by the electrode sheath. The highest microhardness of the coatings is obtained with the use of the electrode of TiB2Ti composition. The best wear resistance is observed in coatings with a diamond content up to 40 vol.%. Partial graphitization of diamond results in the formation of composite coatings hardened with carbide and carbonitride phases

  18. Quality control of chemical heat treatment by the fractography method

    International Nuclear Information System (INIS)

    A fractographic investigation is carried out of fracture of a nitrided layer of 38KhMYuA steel and of cemented and cyanided layers of 12KhM3A steel. It is established that a fracture of the nitrided layer consists of three zones of crystalline facets: 1) a surface zone of fine crystalline facets located in a single plane and having the appearance of a white band (Σ-phase zone); 2) zone of acicular facets whose presence is due to the break-down of the carbonitride phase; 3) zone of large facets of boundary breakdown. The fractures of cemented and cyanided samples consist of multiple fine facets of multi-face shapes. It has been found that the depth and the microstructure of a diffusion layer in steel after chemothermal processing can be most rapidly and objectively evaluated by the fractographic method

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

    International Nuclear Information System (INIS)

    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 M2N 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 Cr2(C, N) caused by the compositions change like Cr supply to MX carbonitride is more essential.

  20. First-principles study of elastic and stability properties of ZrC-ZrN and ZrC-TiC alloys

    International Nuclear Information System (INIS)

    Ab initio calculations of the elastic constants for several cubic ordered structures of zirconium carbonitride (ZrCxN1-x) and zirconium-titanium carbide (ZrxTi1-xC) alloys were carried out. The calculations of total and formation energies, bulk modulus and elastic constants as functions of composition were performed with an ab initio pseudo-potential method. The predicted equilibrium lattice parameters are slightly higher than those found experimentally (on average by 0.2-0.4%). The predicted formation energies indicate that the ZrCxN1-x alloys are stable even at 0 K in the whole concentration range, while the homogeneous ZrxTi1-xC alloys can be stabilized only at high temperatures. Spinodal decomposition of the latter alloys into cubic domains takes place over a wide range of compositions and temperatures. For the carbonitrides, the shear modulus G, the Young's modulus E and the Poisson ratio σ reach an extremum for carbon-rich alloys, and this is attributed to a maximum value of the shear modulus C44 that corresponds to a valence-electron concentration in the range of 8.2-8.3. This extremal behavior finds its origin in the response of the band structure of ZrCxN1-x alloys for 0≤x≤1, caused by the monoclinic strain that determines this shear modulus. In contrast, the other shear modulus 1/2(C11-C12) does not exhibit any extremum over the whole composition range. These results are in contrast with those for Zr-Ti carbides for which the elastic properties gradually increase from ZrC to TiC.

  1. Effect of nitrogen microalloying on structure and properties of quenched martensitic steels

    International Nuclear Information System (INIS)

    Highlights: ► High temperature thermomechanical treatment with various hot rolling schemes is effective for realization of the high-strength state of structural martensitic steels after low-temperature tempering. ► Hot deformation by radial-shear rolling results in higher plasticity at the same strength level in comparison with longitudinal rolling. ► Radial-shear rolling allows obtaining polygonized substructure, peculiar “twisted” grain structure and texture favorable for strength and plasticity in an axial direction. ► The UTS level of the studied nitrogen-containing steels is 300–500 MPa higher than this for nitrogen-free analogs. -- Abstract: Structure, phase transformation features and the strengthening of nitrogen-microalloyed structural C(0.2–0.5)CrNiMoNV steels from alloying and high-temperature thermomechanical treatment (HTMT) by various hot deformation routes have been investigated using X-ray diffraction analysis, optical microscopy, hardness measurements and tensile testing. The nitrogen alloying retards recrystallization processes during hot deformation widens ε-carbonitride region and allows more effective thermomechanical treatment application for realization of high-strength state after low temperature tempering of quenched martensitic steels. Heat and thermomechanical treatment regimes providing increase of deformation and fracture resistance after quenching and tempering were determined. A complete dissolution of special carbonitrides during HTMT and following low-temperature tempering provide high strength level (by 300–500 MPa higher than for nitrogen-free analogs) combined with sufficient ductility and fracture toughness. HTMT comprising hot deformation by the radial-shear rolling with the same strain and deformation temperature as under longitudinal rolling, allows obtaining polygonized substructure, peculiar “twisted” in a definite direction grain structure and texture favorable for strength and plasticity

  2. Microstructure and properties of 13Cr5Ni1Mo0.025Nb0.09V0.06N super martensitic stainless steel

    International Nuclear Information System (INIS)

    Highlights: ► Characterization of the microstructures of a commercial martenistic stainless steel. ► Excess N content causes the occurrence of coarse carbo-nitride and Cr2N. ► Correlation of microstructures with mechanical and corrosion properties. ► The poor pitting resistance is due to Cr rich precipitates. - Abstract: The morphological microstructure, the density and dispersion of high angle boundaries, morphology and micro chemical composition of precipitates and the volume fraction of retained austenite of a commercial super martensitic stainless steel (SMSS) normalized and tempered at various temperatures were characterized by optical microscope, scanning electron microscope (SEM), electron backscattered diffraction (EBSD), transmission electron microscope (TEM) and X-ray diffraction (XRD) in the light of equilibrium phase diagram of the alloy calculated using Thermo-Calc software. The mechanical properties and pitting corrosion resistance were determined to correlate with microstructures. Two kinds of morphology of precipitate were observed in tempered commercial super martensitic stainless. Besides the globular Nb and V rich carbo-nitride precipitates, rod-like Cr rich nitrides were formed due to excess N content. While high density of high angle boundaries and precipitates contribute to strength properties, the dislocation softening of the matrix and retained austenite from tempering restore the ductility and impact toughness properties. The poor resistance to pitting corrosion is attributed to the occurrence of Cr rich precipitates. It is demonstrated that by lowering the nitrogen content and adding niobium, the Cr rich precipitates can be suppressed and the mechanical properties and resistance to pitting corrosion can be significantly improved.

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

    International Nuclear Information System (INIS)

    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

  4. 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.)

  5. Microstructure, mechanical properties, deformation, and fracture of V-4Ti-4Cr alloys

    International Nuclear Information System (INIS)

    Full text of publication follows: The effect of the mode of thermomechanical treatment (TMT) on the microstructure, mechanical properties, mechanisms of plastic deformation, and fracture of V-4Ti-4Cr alloys has been studied. For these alloys, the TMT modes that provide a volumetrically uniform distribution of superfine particles of oxy-carbonitride phases, a substantial growth of their density, and an increase in recrystallization temperature have been substantiated. Interrelations have been found between the microstructure of the alloys and the features of their mechanical behavior, such as the level of strength and plasticity, discontinuous yielding, and an abnormal temperature dependence of strength. It has been shown that these phenomena are underlined by the high thermodynamic instability of the V-4Ti-4Cr alloys after TMT which is due to the presence of supersaturated solid solutions of titanium with interstitial elements, local inhomogeneities in composition, and superfine particles of oxy-carbonitride phases. The great variety of thermally activated obstacles that appear during TMT and mechanical tests at elevated temperatures are responsible for the significantly extended range of the anomalous temperature dependence of yield strength and the conservation of high values of strength up to T ≅850 deg. C. The phenomenon of strain localization has been revealed whose temperature range coincides with the range of discontinuous yielding. The conclusion has been made that this phenomenon can be a direct reason for the discontinuous yielding that testifies to local mechanical instabilities in strain localization bands. Analysis of possible mechanisms and important features of the structural and stream instabilities of plastic flow in these bands has been performed. The TMT modes have been substantiated that provide high thermal stability of the microstructure and a significant increase in short-time strength of the V-4Ti-4Cr alloys over a wide temperature range

  6. Performance Evaluation of Advanced Ferritic/Martensitic Steels for a SFR Fuel Cladding

    International Nuclear Information System (INIS)

    High-chromium(9-12 wt.%) ferritic/martensitic steels are currently being considered as candidate materials for cladding and duct applications in a Gen-IV SFR (sodium-cooled fast reactor) nuclear system because of their higher thermal conductivities and lower expansion coefficients as well as excellent irradiation resistance to void swelling when compared to austenite stainless steels. Since the operation condition in the design of Gen-IV SFR would be envisioned to be harsh from the viewpoints of temperature (≥600 .deg. C) and irradiation dose (≥200 dpa), the primary emphasis is on the fuel cladding materials, i.e. high-Cr ferritic/martensitic steels. The ferritic/martensitic steels for the fuel cladding are commonly used in a 'normalized and tempered' condition. This heat treatment involves a solutionizing treatment (austenitizing) that produces austenite and dissolves the M23C6 carbides and MX carbonitrides, followed by an air cooling that transforms the austenite to martensite. Precipitation sequence during a long-term creep exposure is strongly influenced by the distribution of those in the as heat treated condition of the steels. Their creep strength has been improved by their martensitic lath structure, the precipitation strengthening effects of M23C6 carbides and MX carbonitrides and the solid solution strengthening effects of Mo and W in the matrix. Especially, the precipitation strengthening effect of MX is important because its coarsening rate is small and a fine particle size is maintained for a long-term creep exposure. Z-phase formation from MX-type precipitates has been proposed as a degradation mechanism for a long-term creep regime. The ferritic/martensitic steels should need to improve their performance to be utilized in the high burn-up fuel cladding. For this purpose, KAERI has been developing advanced ferritic/martensitic steels since 2007. This study includes some performance evaluation results of the mechanical and microstructural

  7. Contribution to the study of the (U,Pu)C,N system; Contribution a l'etude du systeme (U,Pu)C,N

    Energy Technology Data Exchange (ETDEWEB)

    Lorenzelli, R. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1968-07-01

    The reactions of UC, PuC, (U,Pu)C, UC{sub 2} and U(C{sub 1-x}O{sub x}) with nitrogen at moderate temperatures (room temperature to 400 C) are described. The influence of the uptake of nitrogen by the powders necessary to sinter the carbides upon the nature of the final product has been investigated; it has been shown that the sintered carbides are hyper-stoichiometric. The reactions of carbon with UN, PuN and (U,Pu)N has also been studied. Under vacuum, carbon reacts on the nitrides at temperatures as low as 1100 C; nitrogen is replaced by carbon and the final product is a carbonitride. The reaction is: MN + x C {yields} MN{sub 1-x}C{sub x} + x/2N{sub 2}. The reaction is limited and the carbonitrides have a fixed composition in presence of M{sub 2}C{sub 3} or MC{sub 2}; hence it is impossible to produce pure MC using the reaction. The ternary diagram U-C-N, Pu-C-N and (U,Pu)C-N have been drawn. They show clearly that it is possible to obtain single phase carbonitrides in a wide domain of compositions. (author) [French] On decrit les reactions avec l'azote de UC, PuC,(U,Pu)C,UC{sub 2} et U(C{sub 1-x}O{sub x}), par action directe de l'azote a temperature moderee (de l'ambiante a 450 C). On a etudie l'influence de la contamination par l'azote des poudres de carbures necessaires au frittage sur la nature des produits frittes; on a montre que les carbures frittes obtenus sont hyperstoechiometriques. On a etudie parallelement les reactions du carbone avec UN, PuN et (U,Pu)N. Sous vide le carbone reagit sur les nitrures des 1100 C: le carbone se substitue a l'azote; l'azote libere est elimine et le produit final est un carbonitrure. La reaction s'ecrit: MN + x C {yields} MN{sub 1-x}C{sub x} + x/2N{sub 2}. La reaction est limitee et les carbonitrures obtenus ont une composition limite fixe en presence des carbures superieurs M{sub 2}C{sub 3} et MC{sub 2}; il est donc impossible d'obtenir MC pur par cette reaction. Les diagrammes

  8. Preparation and sintering of Zr(C,N,O) phases

    International Nuclear Information System (INIS)

    The Zr(C,O,N) compounds form a great mono-phase zone belonging to the pseudoternary ZrO-ZrN-ZrC system.Theses phases have cubic crystalline structure with ao parameter depending on the C, O2 and N2 content.These phases have many potential applications in the manufacture of ceramic pieces utilizable as electronic conductors.The Zr (C,O,N) phases can be obtained from ZrO2 by carbonitriding reactions: that is carbothermal reduction and simultaneous nitriding.In this work a series of experiences of carbonitriding of zirconia under different conditions (temperatures between 1400 and 1600degC, times of 120 min, carbon content between 20 and 40%) in order to obtain suitable powders to be sintered.The XRD analysis shows the Zr(C,O,N) as the main products and β -ZrON as the only secondary product in proportions depending on the obtaining conditions.The variables employed were the C content and the reaction temperature.The Zr(C,O,N) content varies between 40 and 90% and tends to increase with the temperature and the carbon content whereas the β -ZrON phase varies between the 40 and 10 % decreasing its proportion with temperature and the carbon content.The oxidation resistance of these phases was studied by DTA-TG tests in air.Results show complete oxidation reaction at ∼500degC in air.The sintering of these materials was made on disks obtained by pressing of powders of Zr(C,N,O) contents higher than 90%.Sintering was performed in nitrogen atmosphere and temperatures between 1450 and 1620degC.Disks were characterized by pycnometry and Hg volumeter.The densities obtained were between 5 and 6,6g/cm3 with a tendency to increase with the Zr(C,N,O) phase content, the temperature and the sintering time.Sintered disks were characterized by dilatometry in N2

  9. Precipitation in V bearing microalloyed steel containing low concentrations of Ti and Nb

    Energy Technology Data Exchange (ETDEWEB)

    Shanmugam, S.; Tanniru, M.; Misra, R.D.K.; Panda, D.; Jansto, S.

    2005-08-15

    The paper describes the precipitation behaviour in a thermomechanically processed V bearing microalloyed steel containing small additions of Ti and Nb (0.007-0.008 wt-%) using analytical transmission electron microscopy. An intriguing aspect is the significant precipitation of titanium and niobium at these low concentrations, contributing to strength. A high density of multimicroalloyed precipitates of (V, Nb, Ti)(C, N) are observed instead of simple TiN, TiC, and NbC precipitates. They are characterised as cuboidal (45-70 nm), spherical (20-45 nm), irregular (20-45 nm), and fine (10-20 nm). Estimation of solubility products of carbides and nitrides of V, Nb, and Ti implies that the precipitation of titanium occurs primarily in austenite. Interphase precipitation of niobium occurs during austenite to ferrite transformation, while complete precipitation of vanadium takes place in the austenite-ferrite region close to completion of transformation. Substoichiometric concentrations of Ti and Nb, the presence of nitrogen, and the mutual extensive solubility of microalloying carbonitrides explains the formation of core shell (triplex/duplex) precipitates with highly stable nitrides ((Ti, Nb, V)N) in the core and carbides ((Ti, Nb, V)C) in the shell. The qualitative stochiometric ratios of triplex and duplex carbonitrides were Ti{sub 0.}5{sub 3}Nb{sub 0.35}V{sub 0.12} and Ti{sub 0.6}V{sub 0.4}, Nb{sub 0.51}V{sub 0.49} and Ti{sub 0}.{sub 64}Nb{sub 0.36}. Extensive precipitation of fine carbides on dislocation substructures, and sub-boundaries occurred. They were generally characterised as vanadium carbide precipitates with ordered cubic L1{sub 2} structure and exhibited a Baker-Nutting orientation relationship with the ferrite matrix. M{sub 4}C{sub 3} types of carbides were also observed similar to the steel, having high concentrations of Ti and Nb. (author)

  10. 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

  11. Effect of cobalt on microstructure and creep deformation behaviour of tempered martensitic 9% Cr steel for USC power

    Energy Technology Data Exchange (ETDEWEB)

    Helis, L.; Toda, Y.; Abe, F. [NIMS, Tsukuba (Japan). Structural Metals Center; Hara, T. [NIMS, Tsukuba (Japan). Advanced Nano Characterization Center; Miyazaki, H. [NIMS, Tokyo (Japan). Materials Data Sheet Station

    2008-07-01

    Four ingots with chemical composition 9Cr-3W-0/5Co-0.2V-0.05Nb-0.08C-0.05N, varying in the amount of Co addition were studied. Creep tests were conducted at temperature of 923K. Steels with 3% and 5% Co showed creep resistance superior to those with 1% and 0% Co at stresses above 140MPa. On the other hand 5% Co steel showed a significant deterioration in long term creep properties at 80MPa. Calculation by Thermo-Calc. suggested and observation of microstructure before the creep test confirmed the presence of about 6% and 0.4% of delta-ferrite in Co free and 1% Co steel, respectively. ICP mass spectrometry measurement showed that the amount of precipitation in steels after heat treatment increased with increase in Co addition, especially significant gap was found between 1% and 3% Co steels. Distribution of precipitation was studied by SEM and TEM. Particles of M{sub 23}C{sub 6} and MX carbonitrides preferentially precipitated around prior austenitic grain boundaries. Density of precipitation around these boundaries was found to depend on prior austenitic grain size, which is affected by the presence of anti o-ferrite and precipitation at normalizing temperature. Particles of Laves phase precipitated in the microstructure during the creep tests at 923K at all stresses. Its precipitation at the early stage was also enhanced by the addition of Co. It is known that creep properties of steels with fine grain deteriorate faster than those with coarse grains, due to the faster recovering during the keep at high temperatures. Combination of larger prior austenitic grains and higher precipitation contributes to the prolonged life of steels with higher amount of Co after testing at 923K and 160MPa. Deterioration in long term creep strength of steels with high amount of Co can be attributed to the precipitation Cr(V,Nb)N particles known as Z-phase, which is associated with dissolution of MX carbonitrides. (orig.)

  12. Relation among rolling parameters, microstructures and mechanical properties in an acicular ferrite pipeline steel

    International Nuclear Information System (INIS)

    The correlation among thermo-mechanical controlled processing (TMCP) parameters, microstructures and mechanical properties of an acicular ferrite (AF) pipeline steel was investigated in this study. The steel was hot rolled by four different kinds of TMCP to obtain different AF microstructures, and the corresponding mechanical properties were analyzed. Electron backscatter diffraction (EBSD) analysis was conducted to determine the effective grain size (EGS) in the steel. It was found that the EGS in the steel reduced obviously with decrease of the finish rolling temperature (FRT), but little changed with the cooling rate (CR) and the simulated coiling temperature (SCT). Additionally, the fraction of low angle grain boundaries (LAGBs) increased with increasing CR in the experimental range. It was shown that yield strength of the steel was enhanced by the increased CR and SCT, and reduced FRT, which were corresponding with the increases of LAGB fraction and precipitated carbonitrides as well as the decrease of EGS, respectively. Charpy impact results showed that the low temperature toughness of the steel with FRT about 40 oC above Ar3 tended to be the best, which was in good accordance with the highest fraction of high angle grain boundaries (HAGBs), but seemed not to be related with the EGS.

  13. 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.

  14. Effects of nickel and cobalt addition on creep strength and microstructure of the precipitation-strengthened 15Cr ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Shibuya, Masachika; Toda, Yoshiaki; Sawada, Kota; Kushima, Hideaki; Kimura, Kazuhiro [National Inst. for Materials Science, Tsukuba, Ibaraki (Japan)

    2010-07-01

    Creep strength of 15Cr ferritic steel with ferrite matrix was increased by precipitation strengthening of intermetallic compounds. It was higher than those of 9-12Cr ferritic steels with a tempered martensitic microstructure strengthened by carbide and carbonitride. Addition of nickel was confirmed to improve Charpy impact toughness of the 15Cr steels, however, creep strength was slightly reduced by the addition of nickel. Microstructure of the 15Cr steel changes from ferrite single phase to dual phases of ferrite and martensite with the addition of nickel which is an austenite stabilizing element. The 15Cr steels investigated in the previous study, contain 3mass% of cobalt which is also an austenite stabilizing element, therefore, the influence of nickel and cobalt combination on mechanical properties and microstructure of the 15Cr-1Mo-6W-V-Nb steel is investigated in this study. Creep strength, Charpy impact toughness and microstructure of the steel were strongly influenced by the composition of nickel and cobalt. Design guideline of the 15Cr steel is discussed with respect to a role of microstructure and combination of nickel and cobalt addition. (orig.)

  15. Effect of microalloying elements and hot deformation on microstructure of direct-quenched steel plates

    International Nuclear Information System (INIS)

    The effects of microalloys (Nb, V, Ti and Nb-Ti) and hot deformation on microstructure were investigated in direct-quenched HSLA steels. Nb and Ti were shown to improve both strength and toughness of the steels, while V showed little effectiveness in improving the strength of the steels. Quantitative analysis showed that dissolved NB and Ti in austenite increased the hardenability of austenite, so that they refined the ferrite grain size and increased the fraction of bainite in the steels. On the other hand, dissolved V was much less effective in increasing;the hardenability of austenite. It was found that an addition of 0.03%Nb decreases the strength of Ti bearing steels reheated to a low temperature. Combined additions of microalloying elements decreases the solubility of carbonitrides and reduces the amount of dissolved microalloying elements in austenite during reheating through the formation of complex precipitates. Controlled rolling below 950 C had a considerable effect on improving the toughness of Nb bearing direct-quenched steels. Deformation of more than 50% in the un-recrystallized austenite region significantly refined the bainite microstructure, while deformation of less than 30% was less effective. It was shown that the increase in toughness due to the heavy deformation of un-recrystallized austenite resulted from the decrease in the length of lathlike ferrite and the decrease in the packet size of bainite

  16. Wear resistance behavior between gaseous carburising followed by salt bat nitriding and gaseous nitrocarburising of microalloyed steels

    International Nuclear Information System (INIS)

    Full text.The effect of salt bath nitriding and nitrocarburising on the microstructure, and the microhardness and the wear resistance of microalloyed steels was investigated. The wear tests were carried out on the specimens nitrocarburised in the ambient atmosphere and the results are compared with those of the nitrided specimens. Nitrocarburising and nitriding process have been carried out respectively at 1203 degreK for 5h in CH4/ NH3 atmosphere and 853 degreK for 7h. The heat treatment applied after the nitrocarburising process and which consists to an quenching and tempering induces in the near surface, one composed structure of martensite and the very fine precipitation of nitrides and carbonitrides. However, this structural state improves the microhardness profile and the wear resistance. It was found that the weight loss of nitrocarburised samples is more less pronounced than that the nitrided samples. The microstructures of the nitrided and nitrocarburised cases and worn surface topographies were observed by optical microscope and scanning electron microscope (SEM. The phases structures formed since the near surface to the substrat were determined by x-ray diffraction (XRD) using Cu Kα radiation

  17. Evolution of Minor Phases in a 9PctCr Steel: Effect of Tempering Temperature and Relation with Hydrogen Trapping

    Science.gov (United States)

    Hurtado-Noreña, Carolina; Danón, Claudio Ariel; Luppo, María Inés; Bruzzoni, Pablo

    2015-09-01

    The evolution of minor phases in ASTM A335 P91 steel has been studied on specimens submitted to different thermal treatments including a tempering step. Particular emphasis has been put on the tempering temperature range 573 K to 873 K (300 °C to 600 °C), which has not been yet intensively studied. The techniques used in this investigation were X-ray diffraction with synchrotron light, scanning electron microscopy with field emission gun and transmission electron microscopy. In the low tempering temperature range [573 K to 673 K (300 °C to 400 °C)], retained austenite, Fe3C and MX precipitates are observed. In the high tempering temperature range [773 K to 1053 K (500 °C to 780 °C)], M23C6-type carbides, MX-type carbonitrides and M2X precipitates are observed. The effect of the microstructure on hydrogen trapping is analyzed. The distorted matrix around the M2X and MX particles provides the most important trap sites in the P91 steel.

  18. Calorimetric Investigation of Thermal Stability of 304H Cu (Fe-17.7Cr-9.3Ni-2.95Cu-0.91Mn-0.58Nb-0.24Si-0.1C-0.12N-Wt Pct) Austenitic Stainless Steel

    Science.gov (United States)

    Tripathy, Haraprasanna; Subramanian, Raju; Hajra, Raj Narayan; Rai, Arun Kumar; Rengachari, Mythili; Saibaba, Saroja; Jayakumar, Tammana

    2016-05-01

    The sequence of phase instabilities that take place in a Fe-17.7Cr-9.3Ni-0.58Nb-2.95Cu-0.12N (wt pct) austenitic stainless steel (304H Cu grade) as a function of temperature has been investigated using dynamic calorimetry. The results obtained from this investigation are supplemented by Thermocalc-based equilibrium and Scheil-Gulliver nonequilibrium solidification simulation. The following phase transformation sequence is found upon slow cooling from liquid: L → L + γ → L + γ + MX → γ + MX + δ → γ +MX + M23C6 → γ + MX + M23C6 + Cu. Under slow cooling, the solidification follows austenite + ferrite (AF) mode, which is in accordance with Thermocalc prediction and Scheil-Gulliver simulation. However, higher cooling rates result in skeletal δ-ferrite formation, due to increased segregation tendency of Nb and Cr to segregate to interdendritic liquid. The solidification mode is found to depend on combined Nb + Cu content. Experimental estimates of enthalpy change associated with melting and secondary phase precipitation are also obtained. In addition a semi-quantitative study on the dissolution kinetics of M23C6 type carbides has also been investigated. The standard solution treatment at 1413 K (1140 °C) is found to be adequate to dissolve both Cu and M23C6 into γ-austenite; but the complete dissolution of MX type carbonitrides occurs near the melting region.

  19. Laves-phase in the China Low Activation Martensitic steel after long-term creep exposure

    International Nuclear Information System (INIS)

    Highlights: • The crept specimen was divided into three regions according to stress levels. • The creep stress could enhance the microstructure recovery. • Laves phase showed different features along the length of crept specimen. • The density of Laves phase was high, while its size was small near the neck region. • The creep stress enhanced the formation of Laves phase during creep. - Abstract: Creep test at 600 °C under 130 MPa for the China Low Activation Martensitic (CLAM) steel was performed up to 7913 h in this study. According to the stress level, the crept specimen was divided into three regions in order to investigate the influence of stress on Laves-phase formation. In addition to the expected M23C6 carbide and MX carbonitride, the amount and the size of Laves phase in these three regions on the crept specimen were characterized by transmission electron microscopy. Laves phase could be found in all the regions and the creep stress could promote the formation of Laves phase

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

    International Nuclear Information System (INIS)

    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 M23C6 and small spherical MC. The two lower-chromium steels contained blocky M7C3 and small needle-shaped carbonitrides in addition to M23C6. 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

  1. 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.

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

    International Nuclear Information System (INIS)

    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

  3. Microanalytical characterization of a powder metallurgical ledeburitic tool steel by transmission electron microscopy

    International Nuclear Information System (INIS)

    The microanalytical investigation of a new powder metallurgic tool steel was performed with an analytical transmission electron microscope. The chemical composition of the matrix and the precipitates were determined with the help of X-ray spectrometry (EDX) and electron energy loss spectrometry (EELS). The crystallographic parameters of the precipitates were determined by means of convergent beam electron diffraction (CBED). Two different types of precipitates could be prooved: small spherical precipitates with grain sizes of 0.3-1μm of type MX and larger precipitates with grain sizes of 1-4μm of type M7X3. The EDX and EELS microanalyses for the carbide MX resulted in a composition of 56.5 at.%V, 8.5 at.%Cr, 30 at.%C and 5 at.%N. For the carbide M7X3 the composition was 11at.%V, 32at.%Cr, 29at.%Fe and 28 at.%C. The lattice constant of the cubic vanadium carbonitride was determined as 0.4122 nm. The lattice constants of the hexagonal M7X3 are a0 = 0.69 nm and c0 = 0.47 nm. (Author)

  4. A review of mechanical behaviour and stress effects in hard superconductors

    International Nuclear Information System (INIS)

    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 Nb-Ti and Nb-Zr exhibit good strength and extensive ductility at room temperature. Mechanical tests on these alloys at 4.2 K revealed serrated stress-strain curves, non-linear elastic effects, and reduced ductility. The non-linear behaviour is probably due to twinning and de-twinning or a reversible stress-induced martensitic transformation. The brittle A-15 compound superconductors, such as Nb3Sn and V3Ga, exhibit unusual elastic properties and structural instabilities at cryogenic temperatures. Multifilamentary composites consisting of superconducting filaments in a normal metal matrix are normally used for superconducting devices. The mechanical properties of alloy and compound composites, tapes, as well as composites of niobium carbonitride chemically vapour deposited on high strength carbon fibres are presented. Hysteretic stress-strain behaviour in the metal matrix composites produces significant heat generation, an effect which may lead to degradation in performance of high field magnets. Measurements of the critical current density, Jsub(c), under stress in a magnetic field are reported. Modest stress-reversible degradation in Jsub(c) is observed in Nb-Ti composites while more serious degradation is found in Nb3Sn samples. The importance of mechanical behaviour on device performance is discussed. (author)

  5. Solid solution cermet: (Ti,Nb)(CN)-Ni cermet.

    Science.gov (United States)

    Kwon, Hanjung; Jung, Sun-A

    2014-11-01

    Solid solution powders without W, (Ti,Nb)(CN) powders with a B1 structure (NaCl like), were synthesized by high energy milling and carbothermal reduction in nitrogen. The range of molar ratios of Ti/Nb for forming complete (Ti,Nb)(CN) phase was broader than that of Ti/W for the (Ti,W)(CN) phase because carbide or carbonitride of Nb had a B1 crystal structure identical to Ti(CN) while WC had a hexagonal crystal structure. The results revealed that the hardness of (Ti,Nb)(CN)-Ni cermets was higher than that of (Ti,W)(CN)-Ni cermets. The lower density of the (Ti,Nb)(CN) powder contributed to the higher hardness compared to (Ti,W)(CN) because the volumetric ratio of (Ti,Nb)(CN) in the (Ti,Nb)(CN)-Ni cermets was higher than that of (Ti,Nb)(CN) in the (Ti,W)(CN)-Ni cermets at the same weight ratio of Ni. Additionally, it was assumed that intrinsic the properties of (Ti,Nb)(CN) could also be the cause for the high hardness of the (Ti,Nb)(CN)-Ni cermets. PMID:25958611

  6. Metallurgical investigation of the base material and weldments of the 9% chromium X 10 CrMoVNb 9 1

    International Nuclear Information System (INIS)

    In the as-supplied condition, the steel X 10CrMoVNb 91 exhibits martensitic microstructure containing chromium carbide particles (M23C6) 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 M23 C6 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 Ac1 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)

  7. 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).

  8. Characterisation of Laves phase precipitation and its correlation to creep rupture strength of ferritic steels

    International Nuclear Information System (INIS)

    The Laves phase precipitation process was characterised by means of field emission scanning electron microscopy to demonstrate its effect on creep rupture strength of steels with a fully ferritic matrix. To eliminate the effects of carbide and carbonitride precipitations so that the creep rupture data can be analysed exclusively in relation to the Laves phase precipitation process, an alloy Fe–9Cr–3Co–3W (wt.%) without C and N additions was used for the study. Creep rupture strengths were measured and volume fraction and particle size of Laves phase precipitates in the ruptured specimens were analysed. It was found that the creep rupture strength started to collapse (or decrease more rapidly) long before the Laves phase precipitation reached equilibrium fraction. This was related to the onset of the coarsening of Laves phase particles, which precipitated only on grain boundaries and hence contributed little to precipitation strengthening. Creep deformation had no effect either on the precipitation kinetics or on the growth kinetics of Laves phase particles. - Highlights: • Laves phase precipitation at 650 °C was characterised for Fe–9Cr–3W–3Co alloy. • Laves phase precipitated predominantly on grain boundaries. • Creep deformation had no effect on Laves phase precipitation and growth kinetics. • Creep strength started to collapse long before Laves phase precipitation is ended. • Collapse of creep strength was attributed to the coarsening of Laves phase particles

  9. Microstructure and cutting performance of Ti(C, N)-based cermets heat-treated in nitrogen

    Institute of Scientific and Technical Information of China (English)

    LIU Wenjun; XIONG Weihao; ZHENG Yong; SHI Zengmin; YE Jiajian

    2007-01-01

    Ti(C, N)-based cermets were treated using hot isostatic pressing (HIP) at 1423 K in nitrogen. The microstructures compared with the as-sintered cermets were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray analysis, and electron microprobe analysis. It was found that high nitrogen activity in the surface zone resulted in the formation of gradient structure. Approximately 20-μm-deep, nitrogen-rich and titanium-rich hard surface zone was introduced by the beat treatment. The nitrogen activity was the driving force that caused the transportation of the atoms through the binder, titanium towards the surface, and tungsten and molybdenum inwards. In the surface zone, the particle size became fine, the inner rim disappeared, and the volume fraction of the outer rim and the binder phase considerably reduced. Small grains of TiN, WC, Mo2C, and nitrogen-rich carbonitride phases formed in the surface zone during the heat treatment, improving the tribological property of the heat-treated cermet.

  10. Characterisation of Laves phase precipitation and its correlation to creep rupture strength of ferritic steels

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, S.; Yang, M.; Song, X.L.; Tang, S.; Xiang, Z.D., E-mail: zhidongxiang@hotmail.com

    2014-12-15

    The Laves phase precipitation process was characterised by means of field emission scanning electron microscopy to demonstrate its effect on creep rupture strength of steels with a fully ferritic matrix. To eliminate the effects of carbide and carbonitride precipitations so that the creep rupture data can be analysed exclusively in relation to the Laves phase precipitation process, an alloy Fe–9Cr–3Co–3W (wt.%) without C and N additions was used for the study. Creep rupture strengths were measured and volume fraction and particle size of Laves phase precipitates in the ruptured specimens were analysed. It was found that the creep rupture strength started to collapse (or decrease more rapidly) long before the Laves phase precipitation reached equilibrium fraction. This was related to the onset of the coarsening of Laves phase particles, which precipitated only on grain boundaries and hence contributed little to precipitation strengthening. Creep deformation had no effect either on the precipitation kinetics or on the growth kinetics of Laves phase particles. - Highlights: • Laves phase precipitation at 650 °C was characterised for Fe–9Cr–3W–3Co alloy. • Laves phase precipitated predominantly on grain boundaries. • Creep deformation had no effect on Laves phase precipitation and growth kinetics. • Creep strength started to collapse long before Laves phase precipitation is ended. • Collapse of creep strength was attributed to the coarsening of Laves phase particles.

  11. High-temperature oxidation of EhP648-VI alloy

    International Nuclear Information System (INIS)

    Investigations were carried out in 1000-1200 deg C temperature range on 20x15x(2.45-01) mm sheets of EhP 648-VI alloy melted of pure-charge materials. Oxidation kinetics was studied by thermogravimetric method in continuous heating. It is shown that oxidation of EhP648-VI alloy in 1000-1200 deg C temperature range includes chromium diffusion in oxide crystal lattice, opposing oxygen diffusion along the grain boundaries and oxide microcracks, and chromium, tungsten, molybdenum oxide evaporation. Scale on EhP648-VI alloy, consisting basically of α-Cr2O3, is subjected to a compression stress resulting in crack formation. It's protective properties are due to cracks and a thin surface layer of NiCr2O4 spinel. Chromium, tungsten and molybdenum diffusion from the base to scale proceeds along the alloy grain boundaries and volume, couses changes in alloy chemical composition and structure depletion of chromium, tungsten and molybdenum, and filling the grain boundary vacancies with α-Cr or σ-phase particles, that are substituted for (Ti, Nb) (C, N) carbonitride particles by increase of temperature and oxidation time

  12. The Cause of Premature Tensile Fracture of Gas-Nitrocarburized Steel

    Science.gov (United States)

    Hwang, Jaeyoon; Han, Jeongho; Lee, Young-Kook

    2016-08-01

    The objective of the present study was to investigate the mechanism of premature tensile fracture of the gas-nitrocarburized steel. For this purpose, tempered martensitic steel specimens were nitrocarburized at 853 K (580 °C) for maximum 3.5 hours, and tensile-strained at room temperature. The prolongation of nitrocarburizing time caused the high strength, the short elongation, and the heavy serrations at the yield point elongation range of the tensile flow curve. The serrations were generated by vertical cracking at the specimen surface, which started at the bottom of the gauge portion, and were propagated to the top of the gauge portion with increasing tensile strain up to the yield point elongation. The vertical cracks were triggered at the porous compound layer when the local deformation occurred by the propagation of the Lüders band from the bottom to the top of the gauge portion. The cracks readily passed through the diffusion layer with an assistance of ɛ-carbonitride particles, which formed at the boundaries of tempered martensite during nitrocarburizing, resulting in brittle fracture at the diffusion layer and finally in premature failure of the gas-nitrocarburized specimens.

  13. 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. PMID:22160745

  14. Comportamiento de la descarga luminiscente anormal dependiendo de la atmósfera gaseosa en un sistema apto para tratamiento de materiales

    Directory of Open Access Journals (Sweden)

    Armando Sarmiento-Santos

    2013-01-01

    Full Text Available The generation of the DC glow discharge can be in stationary state or with flow of gas atmosphere, where the gas is between two electrodes. Applying a voltage between the electrodes above a certain threshold value or disruption value that depends on the type of gas, the geometric characteristics of the system, and atmosphere pressure, it is possible the generation and maintenance of gaseous discharge. The type of discharge may be classified according to the potential difference applied between the electrodes and the corresponding electrical current flowing through the system, being the abnormal glow discharge of particular interest. Reactive species generated in the glow discharge are used to generate physical and chemical interactions on a surface, which can be exploited for surface treatment and synthesis of materials such as nitriding, carbonitriding and polymerization, but also has great potential for application as a thermal source. The present work describes the set up of a furnace for materials treatment which works by the impact of active species from the negative column of low pressure glow discharge, using direct current. In this setup, the temperature is controlled as a function of gas pressure, type and gas proportions of the mixture in which the discharge is generated (Ar, N2 , H2 , aire, Ar/N2 , N2 /H2 , y Ar/H2 .

  15. 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.

  16. Synthesis of nanostructured multiphase Ti(C,N)/a-C films by a plasma focus device

    International Nuclear Information System (INIS)

    Nanostructured multiphase Ti(C,N)/a-C films were deposited using a 3.3 kJ pulsed plasma focus device onto silicon (1 0 0) substrates at room temperature. The plasma focus device, fitted with solid titanium anode instead of usual hollow copper anode, was operated with nitrogen and Ar/CH4 as the filling gas. Films were deposited with different number of shots, at 80 mm from top of the anode and at zero angular position with respect to anode axis. X-ray diffraction results show the diffraction peaks related to different compounds such as TiC2, TiN, Ti2CN, Ti and TiC0.62 confirming the deposition of multiphase titanium carbo-nitride composite films on silicon. X-ray photoelectron spectroscopy confirms the formation of Ti-C, C-N, Ti-N, Ti-O and C-C bonds in the films. Scanning electron microscopy reveals that the nanostructure grains are agglomerates of smaller nanoparticles about 10-20 nm in size. Raman studies verify the formation of multiphase Ti(C,N) and also of amorphous graphite in the films. The maximum microhardness value of the composite film is 14.8 ± 1.3 GPa for 30 shots.

  17. Use of AWCC in evaluation of unknown fissile materials

    International Nuclear Information System (INIS)

    An important technological problem in the sphere of non-proliferation and safeguards is nondestructive analysis (NDA) methodology for qualitative and quantitative characterization of nuclear materials. Additionally, NDA tends to be labor and time intensive. Two NDA techniques used at KIPT included Gamma Spectroscopy (for qualitative analysis) and Neutron activation (for quantitative analysis). Gamma Spectroscopy was used to confirm the presence of radionuclides within the samples, whereas an Active Well Coincidence Counter (AWCC) in the active mode was used to quantitatively determine the 235U content in particular types of fissile materials at KIPT. This paper describes the usage of the AWCC at NSG KIPT for characterizing nuclear materials for IAEA safeguards. It was also an opportunity to estimate fissile materials of unknown composition. The equipment used was a model JCC-51 AWCC using a shift register model JSR-12 from Canberra and two neutron sources [AN-HP (241ArnLi)]. A Compaq Presario computer using Windows version of NCC (Los Alamos software) was used to operate the AWCC. Materials studied in this project included highly enriched nuclear material in the form of powder, compacts (tablets, microspheres, rods), salt and scrap. The chemical composition of nuclear material included uranium metal, uranium dioxide, uranium nitride, uranium carbonitride, thorium dioxide, and mixtures of these compounds. Scrap consisted of uranium and impurities of hydrocarbons, carbon, silicon, tungsten, etc

  18. 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.

  19. The Cause of Premature Tensile Fracture of Gas-Nitrocarburized Steel

    Science.gov (United States)

    Hwang, Jaeyoon; Han, Jeongho; Lee, Young-Kook

    2016-05-01

    The objective of the present study was to investigate the mechanism of premature tensile fracture of the gas-nitrocarburized steel. For this purpose, tempered martensitic steel specimens were nitrocarburized at 853 K (580 °C) for maximum 3.5 hours, and tensile-strained at room temperature. The prolongation of nitrocarburizing time caused the high strength, the short elongation, and the heavy serrations at the yield point elongation range of the tensile flow curve. The serrations were generated by vertical cracking at the specimen surface, which started at the bottom of the gauge portion, and were propagated to the top of the gauge portion with increasing tensile strain up to the yield point elongation. The vertical cracks were triggered at the porous compound layer when the local deformation occurred by the propagation of the Lüders band from the bottom to the top of the gauge portion. The cracks readily passed through the diffusion layer with an assistance of ɛ-carbonitride particles, which formed at the boundaries of tempered martensite during nitrocarburizing, resulting in brittle fracture at the diffusion layer and finally in premature failure of the gas-nitrocarburized specimens.

  20. Spark plasma sintering of TiyNb1−yCxN1−x monolithic ceramics obtained by mechanically induced self-sustaining reaction

    International Nuclear Information System (INIS)

    Nanometer-sized titanium–niobium carbonitride powders (TiyNb1−yCxN1−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 °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 (TiyNb1−yCxN1−x) with good mechanical properties and excellent wear resistance. The optimum values of nanomechanical properties were found for the Ti0.3Nb0.7C0.5N0.5 ceramic composition, which exhibited a high hardness over 26.0 GPa and Young's modulus around 400 GPa.

  1. 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.

  2. The effect of nitrogen and vanadium on hardenability of medium carbon 0.4 %C and 1.8 %Cr steel

    Directory of Open Access Journals (Sweden)

    R. Staoeko

    2008-10-01

    Full Text Available Purpose: To investigate the effect of V and N on hardenability of steel containing 0.4 % C and 1.8 % Cr.Design/methodology/approach: Four laboratory melts with different N and V contents were used. Hardenability of steel was investigated using standard Jominy test and Grossmann analytical method. The effect of calculated undissolved carbonitride V(C,N content on austenite grain size was investigated.Findings: Nitrogen addition without microalloying elements increased the austenite grain size. Very high hardenability was obtained in steel containing 0.004 %N and 0.08 %V at 870oC. Addition of 0.08 %V at elevated nitrogen content significantly decreased the grain size and at 870oC increased the hardenability of steel.Practical implications: Investigated steel showed very high hardenability with ideal critical diameter DiJ approximately 200 mm, at appropriate austenitizing temperature. Higher nitrogen content in steel with vanadium addition retards austenite grain growth in broad austenitizing temperature range.Originality/value: Results of investigations provide valuable information on the effect of vanadium and nitrogen content on the hardenability of quenched and tempered steel with 1.8 % Cr. Thermodynamic calculations enable to select the optimum austenitizing temperature range.

  3. 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.

  4. 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.

  5. Formation of Si-C-N ceramics from melamine-carbosilazane single source precursors

    International Nuclear Information System (INIS)

    A series of melamine-carbosilazane pre-ceramic macromolecules (Mel-CSZs) were prepared by the condensation of melamine with different organochlorosilanes (RxSiCl4-x where R is CH3/C6H5 and x is 1, 2 or 3) using pyridine as a solvent under nitrogen atmosphere. These melamine-based carbosilazane macromolecules (Mel-CSZs) were characterized by infrared spectroscopy (FT-IR), mass spectrometry (MS), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The backbone of the resulting Mel-CSZs consists of melamine and carbosilazane building blocks. Pyrolysis of these Mel-CSZs at 600 deg. C under nitrogen and vacuum afforded the corresponding silicon-based nonoxide carbonitride ceramics (Si-C-N). The microstructure and textural morphology of the resulting fine ceramic materials were examined using FT-IR, powder X-ray diffraction (XRD), and scanning electron microscopy (SEM). - Graphical abstract: Pyrolysis of the prepared melamine-organosilane macromolecules afforded Si-C-N ceramics with different textural morphology

  6. X-Ray diffraction characteristics of Ti /SUB 1-x/ Nb /SUB x/ C /SUB o.5/ N /SUB 0.5/ solid solutions

    International Nuclear Information System (INIS)

    A study of the influence of production factors (temperature and length of synthesis, method of addition of the components, repeated refinement and homogenization) on the parameters of the structure of phases of variable composition was made. The solid solutions were synthesized from titanium and niobium carbide and nitride powders, and the carbonitride of the composition Ti /SUB 0.77/ Nb /SUB 0.23/ C /SUB 0.5/ N /SUB 0.5/ , by the carbothermal method. X-ray diffraction was taken by a DRON-3 diffractometer controlled by an SM-1 computer. The lattice parameter, the characteristics of the fine crystal structure and the residual macrostresses were determined. It was concluded that the nature of the original components does not influence the character of the concentration relationship of the microstructural parameters, a change in which occurs only under the influence of synethesis temperature and is accompanied by effects of diffusion perfection of the structure of the phases of variable composition

  7. Liquid phase interaction in TiC0,5N0,5-TiNi-Mo and TiC0,5N0,5-TiNi-Ti-Mo

    International Nuclear Information System (INIS)

    Using the methods of X ray diffraction analysis, electron microscopy and X ray spectrum microanalysis a study was made into specific features of phase and structure formation in alloys TiC0,5N0,5-TiNi-Mo and TiC0,5N0,5-TiNi-Mo in the presence of a liquid phase at temperatures of 1380-1600 deg C. It is revealed that the physical and chemical processes taking place during the liquid-phase sintering result in the formation of a three-phase alloy consisting of nonstoichiometric titanium carbonitride TiC0.5-xN0.5-x, a molybdenum base solid solution of titanium, nickel and carbon Mo(Ti, Ni, C) and one of two intermetallic compounds, either TiNi or Ni3Ti. Metallic element concentration in individual phase constituents of the alloy is determined by means of X ray spectrum microanalysis

  8. Oxygen sensors increasing role to improve high temperature industrial processes

    International Nuclear Information System (INIS)

    Zirconium Dioxide (ZrO/sub 2/) Oxygen sensors have benefited from design improvements in recent months which increase reliability and use in high temperature applications such as metal treating, refractory and ceramics processes and conservation of fuel during combustion. Zirconia as an In-Situ Oxygen Sensor is capable of meeting extreme conditions of ''temperature'', ''time'' and ''atmosphere''. A small solid cylinder of zirconia has been fused successfully to an Alumina tube. The adaptation of metal alloy tube as a conductor, creates a unique approach to improve performance and the service life of Oxygen Sensors in heat treating metals. A Microprocessor Controller has been utilized to provide direct readout in % weight Carbon from .1 to 1.5%, or in % oxygen for oxygen rich atmospheres. The microprocessor is capable of solving the complex Nernst equation; EMF=.0215 x T x 1n o/sub 1//O/sub 2/. The controller will adjust automatically to hold a constant setpoint, regardless of process temperature change. Atmosphere control systems, using a Zirconia In-Situ Oxygen Sensor, are finding use in Carbonitriding, Carbon restoration, neutral hardening, Endothermic gas generator control, ceramic and refractory processing in kilns and control of combustion burners

  9. Effect of vanadium and titanium modification on the microstructure and mechanical properties of a microalloyed HSLA steel

    International Nuclear Information System (INIS)

    DMR-249A is a low carbon microalloyed high-strength low-alloy (HSLA) steel. While DMR-249A plates of thickness less than 18 mm meet the specified room temperature yield strength (390 MPa) and Charpy impact toughness (78J at -60 deg. C) in the as-rolled condition, thicker plates require water quenching and tempering. Elimination of the quenching and tempering treatment can result in significant cost and energy savings besides offering increased productivity. Therefore, in the present work, modifications to the base DMR-249A steel composition have been investigated with the objective of producing thicker gage plates (24 mm) capable of meeting the specified properties in the normalized condition. Plates from three modified compositions i.e., containing 0.015 wt.% titanium and 0.06, 0.09 and 0.12 wt.% vanadium respectively and one composition with 0.10 wt.% vanadium, and without any titanium were investigated over a range of normalizing temperatures (875-1000 deg. C). In all cases, only the steel without titanium met the specified properties in the normalized condition. Microstructural investigations using scanning and transmission electron microscopy, as well as support evidence from calculations performed using ThermoCalc software, suggest that this is due to the presence of nanoscale vanadium rich carbonitride particles distributed throughout the matrix. These particles were absent in the titanium-containing steel at a similar vanadium level.

  10. Nano-scale materials

    Energy Technology Data Exchange (ETDEWEB)

    Barrera, J.; Smith, D.C.; Devlin, D.J.

    1998-12-31

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Highly selective, alumina-supported molybdenum carbonitrides were prepared by solution impregnation using the metal amide Mo{sub 2}(N(CH{sub 3}){sub 2}){sub 6} as a molecular precursor. On the basis of relative weight percents, these materials demonstrate a 5- to 8-fold increase in catalytic activity over similar materials prepared by traditional solid-state approaches. The catalytic activities of these materials are very dependent upon the type of alumina support used. Impregnation of Mo{sub m}C{sub x}N{sub y} into preformed alumina pellets resulted in a material that specifically isomerized n-heptane into equal amounts of 2- and 3-methylhexanes, as well as iso-butane. No evidence of aromatic products was observed at operating temperatures below 420{degrees}C. The product selectivity of the isomers was 56% at a n-heptane conversion efficiency of 57%. Impregnating Mo{sub m}C{sub x}N{sub y} into an alumina powder resulted in an extremely selective aromatized and dehydrogenated material. The products from this material consist only of aromatics and n-heptenes with less than 2% isomerization or cracking products.

  11. Study on the cutting of self-fluxing alloy of Ni-Cr-WC systems. Ni-Cr-WC kei jiyo gokin yosha himaku no sessaku kako ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Inui, Y.; Hayami, T.; Kubohori, T.; Ikuta, T. (Kinki University, Osaka (Japan). Faculty of Science and Technology)

    1991-03-31

    In this paper, to investigate the cutting of sprayed self-fluxing alloy films of Ni-Cr-WC system containing 35 and 50%WC-Co composite grains in the Ni-Cr matrix, cutting tests by the lathe turning method were performed using CBN tools containing either oxide or carbonitride systems as a binder. Self-fluxing alloy films with about 2mm thichness, which were sprayed on the surface of a cylindrical substrate made of low carbon steel, were used as cutting materials. The wear was increased rapidly at the early stage of cutting, but this was changed to the gradual increasing level after about 30 seconds of cutting. The tool was subject to the abrasive action in cutting, and was fractured when CBN content was low. The CBN tool containing oxide system was found most suitable for cutting of these alloys. The variation in resistance to cutting was observed at the early stage, but this was disappeared after 90 seconds. The roughness of the cutting surface was decreased with cutting time. 8 refs., 10 figs., 2 tabs.

  12. Investigation of the isothermal precipitation behaviour of nickel-base alloys using electrochemical phase extraction

    International Nuclear Information System (INIS)

    Electrochemical phase extraction methods have been developed empirically for the selective separation of the precipitates in metallic materials. A detailed description of the process has been undertaken to allow optimization for various nickel-base alloys. For this part of the investigation, 16 model alloys were prepared as test electrodes and the electrolyte composition was varied over a wide range. The results enabled a series of effects to be explained on the basis of electrochemical data. The large number of test parameters limited the scope of the preliminary experiments and the range of model alloys used. In the nickel-base alloys, titanium carbo-nitride and primary M6C precipitates were identified. During isothermal ageing, M23C6 (except in Alloy KSN), Ni3Al (in INCONEL 617), Laves phases (in Hastelloy X and INCONEL 617), M12C (in HASTELLOY X and INCONEL 617) and α-tungsten (in the tungsten-containing alloys) were precipitated. The precipitation behaviour changed in the alloys investigated from intracrystalline to intercrystalline with increasing ageing temperature. The intracrystalline secondary precipitations affect the microhardness, structure and the solid-solution lattice. (orig.)

  13. Effect of carbon and niobium on the microstructure and impact toughness of a high silicon 12% Cr ferritic/martensitic heat resistant steel

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Zhongfei [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Wang, Pei, E-mail: pwang@imr.ac.cn [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Li, Dianzhong [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Zhang, Yutuo [Shenyang Ligong University, 6 Nanping Road, Shenyang 110159 (China); Li, Yiyi [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)

    2014-10-20

    In order to guide the design of 9–12% Cr ferritic/martensitic (F/M) heat resistant steels appropriate for use in accelerator-driven system, the impact toughness and behavior of precipitation of a 12% Cr F/M heat resistant steel containing high C and Si concentrations have been investigated. Particular focus has been given to the interaction of carbon and carbonitride-forming element. Because of the presence of primary NbC and a large amount of M{sub 23}C{sub 6}, the impact toughness of the investigated steel was much lower than that of the commercial 9–12% Cr F/M heat resistant steels. The primary NbC crystallizes directly from liquid metal when the Nb concentration is higher than a critical value. The critical value of Nb decreases with increase in the carbon concentration. In addition, the higher content and faster precipitation kinetics of M{sub 23}C{sub 6} in the investigated steel during the tempering heat treatment also lowers the impact toughness.

  14. 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.)

  15. The influence of the pyrolysis temperature on the electrochemical behavior of carbon-rich SiCN polymer-derived ceramics as anode materials in lithium-ion batteries

    Science.gov (United States)

    Reinold, Lukas Mirko; Yamada, Yuto; Graczyk-Zajac, Magdalena; Munakata, Hirokazu; Kanamura, Kiyoshi; Riedel, Ralf

    2015-05-01

    Within this study we report on the impact of the pyrolysis temperature on the structural and electrochemical properties of the poly(phenylvinylsilylcarbodiimide) derived silicon carbonitride (SiCN) ceramic. Materials pyrolysed at 800 °C and 1300 °C, SiCN 800 and SiCN 1300, are found amorphous. Raman spectroscopy measurements indicate the increase in ordering of the free carbon phase with increasing pyrolysis temperature which leads to lower capacity recovered by SiCN 1300. Significant hysteresis is found for materials pyrolysed at 800 °C during electrochemical lithium insertion/extraction. This feature is attributed to much higher hydrogen content in SiCN 800 sample. An aging of SiCN 800 reflected by a change of elemental composition upon contact to air and a strong film formation are attenuated at a higher pyrolysis temperature. Single particle microelectrode investigation on SiCN 800 and SiCN 1300 clarify different electrochemical behavior of the materials. Much lower charge transfer resistance of SiCN 1300 in comparison to SiCN 800 explains better high currents electrochemical performance. Lithium ions diffusion coefficient Dmin ranges from 3.2 10-9 cm2s-1 to 6.4 10-11 cm2s-1 and is independent on the potential.

  16. The negative effect of Zr addition on the high temperature strength in alumina-forming austenitic stainless steels

    International Nuclear Information System (INIS)

    The effect of a Zr addition on the precipitation behavior and mechanical properties in Nb-containing alumina-forming austenitic (AFA) stainless steels was investigated using tensile tests, scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM) analysis. The TEM observation showed that a Zr addition led to the formation of a (Nb,Zr)(C,N) complex particle, which coarsened the Nb-rich carbonitride. Tensile tests were performed at an elevated temperature (700 °C), and both the tensile and yield strengths decreased with a Zr addition. This unexpected result of a Zr addition was due to the reduction of the precipitation strengthening by particle coarsening. - Highlights: • The effect of Zr on high temperature strength in AFA steel containing Nb was studied. • Both the tensile and yield strengths of an AFA steel decreased with Zr-addition. • This is due to the reduction of precipitation strengthening by particle coarsening. • Nb(C,N) and (Nb,Zr)(C,N) particles were precipitated in an AFA and Zr-added AFA steel. • The size of (Nb,Zr)(C,N) particle is much bigger than that of Nb(C,N) particle

  17. Welding stainless steels for structures operating at liquid helium temperature

    International Nuclear Information System (INIS)

    Superconducting magnets for fusion energy reactors require massive monolithic stainless steel weldments which must operate at extremely low temperatures under stresses approaching 100 ksi (700 MPa). A three-year study was conducted to determine the feasibility of producing heavy-section welds having usable levels of strength and toughness at 4.20K for fabrication of these structures in Type 304LN plate. Seven welding processes were evaluated. Test weldments in full-thickness plate were made under severe restraint to simulate that of actual structures. Type 316L filler metal was used for most welds. Welds deposited under some conditions and which solidify as primary austenite have exhibited intergranular embrittlement at 4.20K. This is believed to be associated with grain boundary metal carbides or carbonitrides precipitated during reheating of already deposited beads by subsequent passes. Weld deposits which solidify as primary delta ferrite appear immune. Through use of fully austenitic filler metals of low nitrogen content under controlled shielded metal arc welding conditions, and through use of filler metals solidifying as primary delta ferrite where only minimum residuals remain to room temperature, welds of Type 316L composition have been made with 4.2K yield strength matching that of Type 304LN plate and acceptable levels of soundness, ductility and toughness

  18. Texture recrystallization formation in 08Kh18T1

    International Nuclear Information System (INIS)

    Effect of heat treatment of semi-finished hot-rolled products before cold rolling and the strain degree on texture formation and the value of a plastic anisotropy coefficient in a cold-rolled sheet of the 08Kh18T1 steel after recrystallization has been investigated. The cold-rolled sheet of the ferritic stainless 08Kh18T1 steel after recrystallization at 950 deg C during 3 min is shown to have texture components like low-carbon steels: (111)(110), (111)(112), (112)(110), (100)(110) and axial component with axis (111). The quantative ratio of ideal oreientations in the steel depends on the degree of cold metal strain and to a larger extent on the structural state of semi-finished rolled products before cold rolling. Titanium addition in a stainless steel with 18% Cr affects formation, being favourable for texture sheet stamping with predominance of grain orientation with plane (111) only then, when titanium binds carbon and nitrogen in heat stable and disperse carbonitrides, which be in a cold-rolled sheet before recrystallization semi-finished hot-rolled products is to be subjected to stabilizing heat treatment before rolling. Increase in metal of orientations with plane (111) affects favourably increase of the plastic anisotropy coefficient of sheet rolling

  19. Structure of MoCN films deposited by cathodic arc evaporation

    International Nuclear Information System (INIS)

    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 C2H2 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

  20. 渗碳工艺在汽车车身齿轮中的应用%Application of Carburizing Technology in Automotive Gear

    Institute of Scientific and Technical Information of China (English)

    覃莉莉

    2013-01-01

    The practical application of the heat treatment process of carburizing and carbonitriding in automotive gear was experimentally researched.The results show that the process combined with gear hookers can realize the purpose to easily control microstructure and simple operating,and obtain a certain number of surface residual austenite and carbide mixture,enhance the strength and excellent plasticity,ductility of automotive gear,so it also increases the anti-fatigue life.The process is used in practical production to shorten manufacturing cycle,save production cost,improve economic benefits.%实验研究了渗碳及碳氮共渗热处理工艺在汽车齿轮生产中的实用效果.结果表明,该工艺结合齿轮挂具技术,不仅可以实现组织易控、操作简单的目的,还可以获得一定数量的表层残余奥氏体和碳化物的混合物,提高车用齿轮的强度,得到优良的材料塑形和韧性,从而提高了车用齿轮的抗疲劳寿命;该技术应用到实际生产中,缩短制造周期,节约生产成本,提高工厂的经济效益.

  1. Effect of vanadium and titanium modification on the microstructure and mechanical properties of a microalloyed HSLA steel

    Energy Technology Data Exchange (ETDEWEB)

    Show, B.K., E-mail: bijay_show@rediffmail.com [Defence Metallurgical Research Laboratory, Kanchanbagh P.O., Hyderabad 500058, Andhra Pradesh (India); Veerababu, R., E-mail: veeru_met@yahoo.com [Defence Metallurgical Research Laboratory, Kanchanbagh P.O., Hyderabad 500058, Andhra Pradesh (India); Balamuralikrishnan, R., E-mail: bmk_pgh@yahoo.com [Defence Metallurgical Research Laboratory, Kanchanbagh P.O., Hyderabad 500058, Andhra Pradesh (India); Malakondaiah, G., E-mail: director@dmrl.drdo.in [Defence Metallurgical Research Laboratory, Kanchanbagh P.O., Hyderabad 500058, Andhra Pradesh (India)

    2010-03-15

    DMR-249A is a low carbon microalloyed high-strength low-alloy (HSLA) steel. While DMR-249A plates of thickness less than 18 mm meet the specified room temperature yield strength (390 MPa) and Charpy impact toughness (78J at -60 deg. C) in the as-rolled condition, thicker plates require water quenching and tempering. Elimination of the quenching and tempering treatment can result in significant cost and energy savings besides offering increased productivity. Therefore, in the present work, modifications to the base DMR-249A steel composition have been investigated with the objective of producing thicker gage plates (24 mm) capable of meeting the specified properties in the normalized condition. Plates from three modified compositions i.e., containing 0.015 wt.% titanium and 0.06, 0.09 and 0.12 wt.% vanadium respectively and one composition with 0.10 wt.% vanadium, and without any titanium were investigated over a range of normalizing temperatures (875-1000 deg. C). In all cases, only the steel without titanium met the specified properties in the normalized condition. Microstructural investigations using scanning and transmission electron microscopy, as well as support evidence from calculations performed using ThermoCalc software, suggest that this is due to the presence of nanoscale vanadium rich carbonitride particles distributed throughout the matrix. These particles were absent in the titanium-containing steel at a similar vanadium level.

  2. Multi analysis of the effect of grain size on the dynamic behavior of microalloyed steels

    Energy Technology Data Exchange (ETDEWEB)

    Zurek, Anna K [Los Alamos National Laboratory; Muszka, K [AGH; Majta, J [AGH; Wielgus, M [AGH

    2009-01-01

    This study presents some aspects of multiscale analysis and modeling of variously structured materials behavior in quasi-static and dynamic loading conditions. The investigation was performed for two different materials of common application: high strength microalloyed steel (HSLA, X65), and as a reference more ductile material, Ti-IF steel. The MaxStrain technique and one pass hot rolling processes were used to produce ultrafine-grained and coarse-grained materials. The efficiency and inhomogeneity of microstructure refinement were examined because of their important role in work hardening and the initiation and growth of fracture under tensile stresses. It is shown that the combination of microstructures characterized by their different features contributes to the dynamic behavior and final properties of the product. In particular, the role of solute segregation at grain boundaries as well as precipitation of carbonitrides in coarse and ultrafine-grained structures is assessed. The predicted mechanical response of ultrafine-grained structures, using modified KHL model is in reasonable agreement with the experiments. This is a result of proper representation of the role of dislocation structure and the grain boundary and their multiscale effects included in this model.

  3. Structure and Properties of Thermomechanically-processedHSLA Steels for Naval Applications

    Directory of Open Access Journals (Sweden)

    A. Ghosh

    2007-07-01

    Full Text Available Four high-strength low-alloy (HSLA steels with varying chemical compositions were forgedin two different temperature ranges followed by cooling in various media. Microstructures andmechanical properties of the steels were evaluated. The microstructures obtained in water–quenchedlow-carbon HSLA steels were lath martensite packet within the pancaked grains. On air or sandcooling predominantly bainitic ferrite or granular bainite structure forms. The strength propertiesof these steels decreased with decrease in cooling rate and is accompanied by an increase inelongation and impact toughness values. The ductile-to-brittle transition temperature of HSLA-100grade steel was found to be – 40 oC. The impact fracture surface of air cooled HSLA-100 steel showedductile failure with formation of dimples at 20 oC and at – 20 oC. The fracture mode changed to brittlefailure with formation of cleavage and river pattern at – 40 oC and at – 60 oC. The microstructuresof the ultra-low carbon HSLA steel show lath ferrite or granular ferrite in water-quenched condition.With slower cooling rate, the volume fraction of lath ferrite decreased with an increase in formationof polygonal ferrite. The maximum strength value obtained in air-cooled condition is achieved dueto precipitation of fine microalloying carbides and carbonitrides. Slower cooling rate increases thevolume fraction of polygonal ferrite which increases the toughness value.

  4. A comprehensive study on the microstructure of high strength low alloy pipeline welds

    Energy Technology Data Exchange (ETDEWEB)

    Beidokhti, B., E-mail: beidokhti@um.ac.ir [Department of Materials Science and Metallurgical Engineering, Engineering Faculty, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Kokabi, A.H.; Dolati, A. [Department of Material Science and Engineering, Sharif University of Technology, Azadi Ave., Tehran (Iran, Islamic Republic of)

    2014-06-01

    Highlights: • The effect of alloying elements on the microstructure of HSLA welds was investigated. • The microstructure of welds has been studied carefully using optical microscopy, scanning and transition electron microscopy. • Type and shape of main inclusions was determined. - Abstract: The microstructural characteristic of HSLA welds containing different amounts of titanium were evaluated carefully. It was observed that the microstructure of welds consisted of ferrite with mixed morphologies, and small amounts of pearlite and martensite–austenite micro-constituents. Because of insufficient time for diffusion of carbon, formation of pearlite lamellae could not be completed in the weld region. Martensite was formed from carbon enrichment of austenite during nucleation and growth of acicular ferrite and bainitic ferrite. While coarse manganese sulfide particles had weak interface strength with matrix and formed some micro-fissures; increasing titanium amount of welds dispersed different modified morphologies of inclusions in the microstructure. Several types of precipitates including spherical, cubical, fine and irregular titanium carbonitride were found in the microstructure and they were favorite sites for nucleation of acicular ferrite. The size of cubical/spherical and fine precipitates was measured between 70–100 and 10–20 nm, respectively. Low energy interface of inclusion/matrix and the depletion of carbon in austenite were proposed as the nucleation mechanisms of acicular ferrite from nano-sized inclusions.

  5. Effect of carbon and niobium on the microstructure and impact toughness of a high silicon 12% Cr ferritic/martensitic heat resistant steel

    International Nuclear Information System (INIS)

    In order to guide the design of 9–12% Cr ferritic/martensitic (F/M) heat resistant steels appropriate for use in accelerator-driven system, the impact toughness and behavior of precipitation of a 12% Cr F/M heat resistant steel containing high C and Si concentrations have been investigated. Particular focus has been given to the interaction of carbon and carbonitride-forming element. Because of the presence of primary NbC and a large amount of M23C6, the impact toughness of the investigated steel was much lower than that of the commercial 9–12% Cr F/M heat resistant steels. The primary NbC crystallizes directly from liquid metal when the Nb concentration is higher than a critical value. The critical value of Nb decreases with increase in the carbon concentration. In addition, the higher content and faster precipitation kinetics of M23C6 in the investigated steel during the tempering heat treatment also lowers the impact toughness

  6. Electron microscopy an indispensable tool for knowledge based design and development of nuclear materials

    International Nuclear Information System (INIS)

    Development of materials for core components such as clad and wrapper for the Indian sodium cooled fast reactors and the plasma facing components in the ITER program has been a continuous indigenous effort involving a close collaboration between the designer, materials researcher and industry. In recent times there has been an intensive effort to design and develop new radiation resistant and high temperature materials which include the advanced austenitic and ferritic steels. An elaborate TEM investigation of the 20% Cold Worked SS316 austenitic stainless steel wrapper exposed to different damage levels from the Fast Breeder Test Reactor at Kalpakkam provided an in depth understanding on the mechanism of evolution of radiation induced phase changes and voids. The identification of η and G phases with unique microchemistry at 40 and 83 dpa respectively and the consequent depletion of beneficial elements Ni and Si from the matrix, resulted in precipitate associated voids and a high degree of volumetric swelling. This knowledge provided the impetus to develop alloy D9 and its variants with higher Ni, Ti and optimum amounts of Si and P where precipitation of fine stable Ti carbides/carbonitrides and phosphides imparts superior strength while the matrix precipitate interfaces act as defect sinks to control void swelling

  7. Spray forming and mechanical properties of a new type powder metallurgy superalloy

    Science.gov (United States)

    Jia, Chong-Lin; Ge, Chang-Chun; Xia, Min; Gu, Tian-Fu

    2015-11-01

    The deposited billet of a new type powder metallurgy (PM) superalloy FGH4095M for use in turbine disk manufacturing has been fabricated using spray forming technology. The metallurgical quality of the deposited billet was analyzed in terms of density, texture, and grain size. Comparative research was done on the microstructure and mechanical properties between the flat disk preform prepared with hot isostatic pressing (HIP) and the same alloy forgings prepared with HIP followed by isothermal forging (IF). The results show that the density of the spray-formed and nitrogen-atomized deposit billet is above 99% of the theoretical density, indicating a compact structure. The grains are uniform and fine. The billet has weak texture with a random distribution in the spray deposition direction and perpendicular to the direction of deposition. A part of atomizing nitrogen exists in the preform in the form of carbonitride. Nitrogen-induced microporosity causes the density reduction of the preform. Compared with the process of HIP+IF, the superalloy FGH4095M after HIP has better mechanical properties at both room temperature and high temperature. The sizes of the γ‧ phase are finer in microstructure of the preform after HIP in comparison with the forgings after HIP+IF. This work shows that SF+HIP is a viable processing route for FGH4095M as a turbine-disk material. Project supported by the National Natural Science Foundation of China (Grant Nos. 50974016 and 50071014).

  8. Synthesis and properties of new reinforcing agents and superconducting filaments

    International Nuclear Information System (INIS)

    Work on high-strength reinforcing agents is briefly reviewed and new areas of need noted. Three new reinforcing agents including high-modulus boron nitride (BN) fibers, aluminum diboride (AlB2) flakes, and boron carbide (B4C) fibers are described which satisfy many of these needs. Preparation of a high-modulus BN fiber which combines good dielectric properties, high thermal stability, and good strength is described. Recent work on synthesis and properties of single-crystal flakes of AlB2 is considered, with emphasis on their unique planar reinforcing characteristics and resistance to mechanical shock. Progress on improving the strength of B4C fiber is described along with efforts to develop a high-temperature composite for use at 12000C. Problems and goals for superconducting filaments are summarized. A program to develop a continuous multifilament yarn of niobium carbonitride (NbCN) is discussed. The NbCN filaments display a high T/sub c/, acceptable mechanical properties, and inherent stability to flux jumps. 3 tables, 3 figures

  9. 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.

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

    International Nuclear Information System (INIS)

    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 micro constituents 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 s 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. (Author)

  11. 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.

  12. The corrosion behavior of Cr-(C,N) PVD hard coatings deposited on various substrates

    International Nuclear Information System (INIS)

    A comparison was made between the electrochemical corrosion behavior of chromium carbonitride (Cr-(C,N)) and chromium nitride (Cr-N) coatings produced by evaporation in a thermionic-arc ion-plating apparatus at 450 deg. C. These coatings were deposited on substrates in the form of discs of mild-steel (CK 45) and stainless-steel (SS 304). Potentiodynamic polarization tests, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) were the techniques used to characterize the corrosion behavior. The potentiodynamic tests revealed the current density versus potential for the coated and uncoated substrates and the difference in their corrosion potentials (Ecorr). In all cases the Ecorr shifted to a more positive potential after the coatings were applied. The electrochemical impedance spectroscopy measurements as a function of immersion time were carried out in a 0.5 M NaCl solution at the Ecorr. The corrosion properties, lower current density, and higher polarization resistance were found to be two to six times better than the uncoated substrate for the Cr-(C,N) coatings and two orders of magnitude better for the Cr-N coatings

  13. Efecto de segundas fases no metálicas sobre el comportamiento a fatiga de componentes de acero con elevadas solicitaciones

    Directory of Open Access Journals (Sweden)

    González, L.

    2005-02-01

    Full Text Available To assess the real effect of the inclusion type on fatigue life of ultra clean high strength steels mechanical components made of l00Cr6 steel were fatigue tested and fracture surfaces analysed to determine the origin of fatigue cracks. Two heats proceeding 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 microns, 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. Keywords Fatigue. Non-metallic inclusions. MnS. Bearing steel. 100Cr6

    Con objeto de evaluar la influencia de las inclusiones sobre la vida a fatiga, se ha realizado un estudio sobre componentes de acero de rodamientos 100Cr6 determinando, en cada caso, las causas del fallo por fatiga. El material, procedente de dos coladas fabricadas con distinto proceso, se forjó en caliente para obtener componentes finales en forma de anillo que, posteriormente, se ensayaron a fatiga de compresión-compresión. Tras analizar los fallos mediante microscopía electrónica SFEM (Scanning Field Emission Microscopy, se comprobó que la mayoría de los fallos, a altas cargas, fueron debidos a la presencia de MnS de pequeño tamaño (10-70 μm, mientras que nitruros y

  14. 9-12% Cr heat resistant steels. Alloy design, TEM characterisation of microstructure evolution and creep response at 650 C

    International Nuclear Information System (INIS)

    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 M23C6 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 M23C6 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 evolution and creep response was

  15. 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

  16. Synthesis of pre-ceramics carbides nano-powders for future nuclear industry: applications of laser pyrolysis and inductively coupled plasma processes

    International Nuclear Information System (INIS)

    Nano-structured carbides ceramics are envisaged for next generation nuclear reactors. Compared to classical materials, nano-structured ceramics appear as potentially interesting because the reduction of the grain size which compose them at a nano-metric scale allows to improve their thermomechanical properties and could induce them a better irradiation resistance on account of the strong density of the grain boundaries they contain. To elaborate such materials, it is required to synthesize nano-metric powders in significant quantities and with a controlled stoichiometry. Laser pyrolysis and inductively coupled plasma techniques, developed respectively at the CEA and at EMPA, can be used. In laser pyrolysis, the precursors used can be gaseous or liquid. They decompose in absorbing the energy of a CO2 laser beam and form thus a vapor sur-saturated in species which nucleate to induce the growth of nano-particles. The interaction zone with the laser being very short, the time available for this growth is limited too; the final size of the synthesized particles can thus be controlled. The only difficulty is to find a precursor absorbing the wave length emitted by the laser. For the inductively coupled plasma technique, the decomposition of precursors is obtained in introducing a thermal plasma generated by a radiofrequency inductor. The temperature reached in the core of the plasma is ∼ 10000 C; with such a temperature, it is possible to decompose all type of gaseous or liquid precursor, but solid micrometric powders too. The control of the growth of nanoparticles is assured by the presence of a quench ring injecting a cold gas perpendicularly to the plasma which cools suddenly the gaseous phase. The compounds studied more particularly here was silicon carbide (SiC), zirconium carbide (ZrC) and titanium carbonitride (TiCxNy). (O.M.)

  17. 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.

  18. Nanostructured component fabrication by electron beam-physical vapor deposition

    Science.gov (United States)

    Singh, Jogender; Wolfe, Douglas E.

    2005-08-01

    Fabrication of cost-effective, nano-grained net-shaped components has brought considerable interest to Department of Defense, National Aeronautics and Space Administration, and Department of Energy. The objective of this paper is to demonstrate the versatility of electron beam-physical vapor deposition (EB-PVD) technology in engineering new nanostructured materials with controlled microstructure and microchemistry in the form of coatings and net-shaped components for many applications including the space, turbine, optical, biomedical, and auto industries. Coatings are often applied on components to extent their performance and life under severe environmental conditions including thermal, corrosion, wear, and oxidation. Performance and properties of the coatings depend upon their composition, microstructure, and deposition condition. Simultaneous co-evaporation of multiple ingots of different compositions in the high energy EB-PVD chamber has brought considerable interest in the architecture of functional graded coatings, nano-laminated coatings, and design of new structural materials that could not be produced economically by conventional methods. In addition, high evaporation and condensate rates allowed fabricating precision net-shaped components with nanograined microstructure for various applications. Using EB-PVD, nano-grained rhenium (Re) coatings and net-shaped components with tailored microstructure and properties were fabricated in the form of tubes, plates, and Re-coated spherical graphite cores. This paper will also present the results of various metallic and ceramic coatings including chromium, titanium carbide (TiC), titanium diboride (TiB2), hafnium nitride (HfN), titanium-boron-carbonitride (TiBCN), and partially yttria stabilized zirconia (YSZ) TBC coatings deposited by EB-PVD for various applications.

  19. Effect of welding thermal cycles on the structure and properties of simulated heat-affected zone areas in X10CrMoVNb9-1 (T91) steel at a state after 100,000 h of operation

    International Nuclear Information System (INIS)

    The article presents results of structural tests (light, scanning electron and scanning transmission electron microscopy) of X10CrMoVNb9-1 (T91) creep-resisting steel after approximately 100,000 h of operation. It was ascertained that the parent metal of T91 steel is characterized by the microstructure of tempered martensite with M23C6 carbide precipitates and few dispersive precipitates of MX-type niobium and vanadium carbonitrides. The most inconvenient change in T91 steel precipitate morphology due to long-term operation is the appearance of the Laves Fe2Mo phase which along with M23C6 carbide particles forms elongated blocks and conglomerates on grain boundaries. The article also presents results of tests related to the effect of simulated welding thermal cycles on selected properties of X10CrMoVNb9-1 (T91) grade steel at a state after approximately 100,000 h of operation. The tests involved the determination of the chemical composition of the steel tested as well as impact tests, hardness measurements and microscopic metallographic examination (based on light microscopy) of simulated heat-affected zone (HAZ) areas for a cooling time (t8/5) restricted within a range between 3 s and 120 s, with and without heat treatment. The tests revealed that, among other results, hardness values of simulated HAZ areas in X10CrMoVNb9-1 (T91) steel do not guarantee cold crack safety of the steel at the state without additional heat treatment. It was also observed that simulated welding thermal cycles of cooling times t8/5=3, 12, 60 and 120 s do not significantly affect the toughness and hardness of simulated HAZ areas of the steel tested

  20. 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. PMID:26909865

  1. Enhanced Sintering of TiNi Shape Memory Foams under Mg Vapor Atmosphere

    Science.gov (United States)

    Aydoğmuş, Tarik; Bor, Şakir

    2012-12-01

    TiNi alloy foams are promising candidates for biomaterials to be used as artificial orthopedic implant materials for bone replacement applications in biomedical sector. However, certain problems exist in their processing routes, such as formation of unwanted secondary intermetallic phases leading to brittleness and deterioration of shape memory and superelasticity characteristics; and the contamination during processing resulting in oxides and carbonitrides which affect mechanical properties negatively. Moreover, the eutectic reaction present in Ti-Ni binary system at 1391 K (1118 °C) prevents employment of higher sintering temperatures (and higher mechanical properties) even when equiatomic prealloyed powders are used because of Ni enrichment of TiNi matrix as a result of oxidation. It is essential to prevent oxidation of TiNi powders during processing for high-temperature (>1391 K i.e., 1118 °C) sintering practices. In the current study, magnesium powders were used as space holder material to produce TiNi foams with the porosities in the range of 40 to 65 pct. It has been found that magnesium prevents secondary phase formation and contamination. It also prevents liquid phase formation while enabling employment of higher sintering temperatures by two-step sintering processing: holding the sample at 1373 K (1100 °C) for 30 minutes, and subsequently sintering at temperatures higher than the eutectic temperature, 1391 K (1118 °C). By this procedure, magnesium may allow sintering up to temperatures close to the melting point of TiNi. TiNi foams produced with porosities in the range of 40 to 55 pct were found to be acceptable as implant materials in the light of their favorable mechanical properties.

  2. Enhancement of bioactivity of pulsed magnetron sputtered TiCxNy with bioactive glass (BAG) incorporated polycaprolactone (PCL) composite scaffold

    International Nuclear Information System (INIS)

    Titanium carbonitride (TiCxNy) 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 TiCxNy/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 TiCxNy 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

  3. Effects of heat treatment processes on microstructure and creep properties of a high nitrogen 15Cr-15Ni austenitic heat resistant stainless steel

    International Nuclear Information System (INIS)

    Highlights: → CTMT induced elongated clusters of fine (Nb,Cr,Fe)(C,N) particles. → Hot rolling in MTMT induced evenly distributed fine (Nb,Cr,Fe)(C,N). → Number and distribution of Cu precipitates not affected by hot rolling. → Distribution homogeneity of fine (Nb,Cr,Fe)(C,N) promotes creep strength increase. → Finer grain size structure promotes lower creep ductility. - Abstract: Conventional thermo-mechanical treatment (CTMT) and modified thermo-mechanical treatment (MTMT) process were applied for manufacturing a high nitrogen niobium-stabilized 15Cr-15Ni austenitic alloy. CTMT process consists of 5 h of solution treatment at 1270 deg. C followed by water quenching and subsequent aging at 820 deg. C for 50 h. MTMT process differs from CTMT process in hot plastic deformation performed immediately after the solution treatment at 1270 deg. C and longer aging time. Microstructure and creep properties of the steel obtained by both processing routes were investigated. Creep rupture tests at 750 deg. C showed double increase in rupture time brought about by MTMT process. Examination of crept microstructure by transmission electron microscopy revealed that the improved creep properties in MTMT process were mainly due to improved distribution uniformity of fine nano-sized carbonitride precipitates in the austenitic matrix and that MTMT process has no effects on the number density and distribution of copper precipitates present in the steel. However, the creep ductility in MTMT process drastically reduced comparing to CTMT process. The higher density of grain boundaries due to finer grain recrystallized microstructures and the formation of higher volume fraction of coarser M23C6 precipitates at the boundaries are believed to be the main reason for the lower creep ductility in MTMT process.

  4. 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.

  5. 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. PMID:25460405

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

    International Nuclear Information System (INIS)

    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

  7. Physical and chemical characterization of surfaces of nitrogen implanted steels

    International Nuclear Information System (INIS)

    The studied steels are of industrial type (42CD4, 100C6, Z200C13). Very often, the low carbon steel XCO6 has been used as a reference material. The aim of the research is to understand and to explain the mechanisms of wear resistance to improvement. A good characterization of the implanted layer is thus necessary. It implies to establish the distribution profiles of the implanted ions to identify the chemical and structural state of the phases created during implantation as a function of various implantation parameters (dose, temperature). Temperature is the particularly parameter. Its influence is put in evidence both during implantation and during annealings under vacuum. Nitrogen distribution profiles are performed thanks to the non destructive 15N(p,αγ)12C nuclear reaction. The chemical state of the Fe-N phases formed by implantation is determined using first Electron Conversion Moessbauer Spectroscopy and secondly, as a complement, using grazing angle X ray diffraction. The detected compounds are ε-nitrides, ε-carbonitrides, (N) - martensite and α-Fe16N2 whose evolution is carefully followed versus temperature. The diffraction technique reveals a texture of the implanted layer. This preferentiel orientation is found to be temperature dependent but dose independent. The carbon presence at the surface is studied as a function of implantation conditions (vacuum, temperature, dose). Carbon profiling is obtained using α backscattering (12C(α,α') reaction at 5,7 MeV). Thus is achieved a complete characterization of the implanted zone whose evolution as a function of implantation parameters (especially temperature) is correlated with tribological results

  8. 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.

  9. Influence of the initial metallurgical state and the austenizing conditions on the distribution of austenitc grain size of the martensitic-ferritic steel T91(9%Cr-1%Mo-V-Nb)

    International Nuclear Information System (INIS)

    It is a known fact that the austenizing conditions (speed of heating to the austenite temperature and austenizing time) as well as the initial metallurgical state of the material strongly influence the distribution of austenitic grain size in steels. This distribution will be one of the parameters that will control the behavior of the material in a later transformation from the austenite -by continuous cooling or in the isothermal case - and this behavior will determine the product's final mechanical properties. Based on the published literature, we have studied the influence of the initial metallurgical state and the speed of heating to austenite on the distribution of austenitic grain size for a certain austenizing temperature and time for a martensitic-iron ASTM A213 grade T91 steel. Two-stage thermal cycles were designed for this, that is, tempering for a variable period of time at the industrial tempering temperature (780oC) followed by the austenizing (1050oC, 30 minutes) 'in situ'. We have analyzed the following as a whole: 1) the role of the stabilizing elements (Nb, V) that eventually control the anchoring of the austenitic grain boundary by carbide or carbonitride precipitation. Therefore, we have tried to vary the fraction of these elements present in solid solution by annealing before austenizing. 2) the role of the speed of heating to austenite. In this case, we have considered two different values (1 and 30oC/s), previously reported as inferior and superior, respectively, to the speed of 'critical' heat needed to produce a distribution of heterogeneous austenitic grain size when the metallurgical state before the austenizing is quenched and tempered. Preliminary results suggest that a annealing stage after tempering in the plant and prior to eventual austenizing significantly reduces the influence of the heating to austenite speed in the development of a heterogeneous structure of austenitic grains (CW)

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

    International Nuclear Information System (INIS)

    Highlights: ► Processing of Fe-based cermets by pressureless sintering and spark plasma sintering. ► Influence of carbon content on the sintering mechanism and hardness. ► The cermet phase diagram was calculated and permits to explain the microstructure. ► SPS provides ferritic matrix and different carbide distribution than CPS samples. ► 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. Plasma-arc reactor for production possibility of powdered nano-size materials

    International Nuclear Information System (INIS)

    Nano-size materials of various chemical compositions find increasing application in life nowadays due to some of their unique properties. Plasma technologies are widely used in the production of a range of powdered nano-size materials (metals, alloys, oxides, nitrides, carbides, borides, carbonitrides, etc.), that have relatively high melting temperatures. Until recently, the so-called RF-plasma generated in induction plasma torches was most frequently applied. The subject of this paper is the developments of a new type of plasma-arc reactor, operated with transferred arc system for production of disperse nano-size materials. The new characteristics of the PLASMALAB reactor are the method of feeding the charge, plasma arc control and anode design. The disperse charge is fed by a charge feeding system operating on gravity principle through a hollow cathode of an arc plasma torch situated along the axis of a water-cooled wall vertical tubular reactor. The powdered material is brought into the zone of a plasma space generated by the DC rotating transferred plasma arc. The arc is subjected to Auto-Electro-Magnetic Rotation (AEMR) by an inductor serially connected to the anode circuit. The anode is in the form of a water-cooled copper ring. It is mounted concentrically within the cylindrical reactor, with its lower part electrically insulated from it. The electric parameters of the arc in the reactor and the quantity of processed charge are maintained at a level permitting generation of a volumetric plasma discharge. This mode enables one to attain high mean mass temperature while the processed disperse material flows along the reactor axis through the plasma zone where the main physico-chemical processes take place. The product obtained leaves the reactor through the annular anode, from where it enters a cooling chamber for fixing the produced nano-structure. Experiments for AlN synthesis from aluminium power and nitrogen were carried out using the plasma reactor

  12. Corrosion of vanadium and V 3Ti 1Si in flowing lithium

    International Nuclear Information System (INIS)

    A pumped Li loop fabricated from a titanium stabilized Type 316 steel was designed and constructed. At temperatures of about 823 K, experiments over a duration of more than 7500 h were performed. A magnetic trap had to be incorporated just before the flowmeter to avoid the precipitation of magnetic particles. Therefore it was possible to investigate the influence of the magnetic trap on the corrosion behaviour of V in flowing Li. The results are as follows: - The corrosion rate of V is about 14 μm/year and independent of the nitrogen content of Li. The corrosion rate of V 3Ti 1Si depends on the N concentration of Li. At about 30 wppm N in Li a vanadium-titanium-nitride is formed at the surface of the specimens. Hence, a low rate of 4 μm/year can be stated. - Both materials pick-up more N than C from Li, pure vanadium double as much nitrogen as the alloy V 3Ti 1Si. - N diffuses into the bulk of both materials, whilst C is bound near the surface. The hardening at the surface is due to the up-take of N. - The vanadium-carbonitride-, respectively the vanadium-titanium-nitride-layers have a strong influence on the weight loss and the up-take of non-metals. - The magnetic trap reduces the weight loss of vanadium in a significant way. The positive influence of the magnetic trap is supposed to be due to the reduction of the nitrogen content of Li. - The corrosion rates of the alloy V 3Ti 1Si show, that the dissolution due to V loss does not affect the lifetime of the alloy. The comparison with steels and nickle-base-alloys demonstrates the advantages of this material. Nevertheless, the purification of the Li and the control of its nonmetal-levels is indispensable. (orig./HP)

  13. 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.

  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. Calculation and experimental investigation of multi-component ceramic systems

    International Nuclear Information System (INIS)

    This work shows a way to combine thermodynamic calculations and experiments in order to get useful information on the constitution of metal/non-metal systems. Many data from literature are critically evaluated and used as a basis for experiments and calculations. The following multi-component systems are treated: 1. Multi-component systems of 'ceramic' materials with partially metallic bonding (carbides, nitrides, oxides, borides, carbonitrides, borocarbides, oxinitrides of the 4-8th transition group metals) 2. multi-component systems of non-metallic materials with dominant covalent bonding (SiC, Si3N4, SiB6, BN, Al4C3, Be2C) 3. multi-component systems of non-metallic materials with dominant heteropolar bonding (Al2O3, TiO2, BeO, SiO2, ZrO2). The interactions between 1. and 2., 2. and 3., 1. and 3. are also considered. The latest commercially available programmes for the calculation of thermodynamical equilibria and phase diagrams are evaluated and compared considering their facilities and limits. New phase diagrams are presented for many presently unknown multi-component systems; partly known systems are completed on the basis of selected thermodynamic data. The calculations are verified by experimental investigations (metallurgical and powder technology methods). Altogether 690 systems are evaluated, 126 are calculated for the first time and 52 systems are experimentally verified. New data for 60 ternary phases are elaborated by estimating the data limits for the Gibbs energy values. A synthesis of critical evaluation of literature, calculations and experiments leads to new important information about equilibria and reaction behaviour in multi-component systems. This information is necessary to develop new stable and metastable materials. (orig./MM)

  16. Effect of welding thermal cycles on the structure and properties of simulated heat-affected zone areas in X10CrMoVNb9-1 (T91) steel at a state after 100,000 h of operation

    Energy Technology Data Exchange (ETDEWEB)

    Łomozik, Mirosław, E-mail: miroslaw.lomozik@is.gliwice.pl [Instytut Spawalnictwa, Testing of Materials Weldability and Welded Constructions Department, 44-100 Gliwice, Bł. Czesława 16-18 (Poland); Hernas, Adam, E-mail: adam.hernas@polsl.pl [Silesian University of Technology, Faculty of Materials Engineering and Metallurgy, 40-019 Katowice, Krasińskiego 8 str. (Poland); Zeman, Marian L., E-mail: marian.zeman@is.gliwice.pl [Instytut Spawalnictwa, Testing of Materials Weldability and Welded Constructions Department, 44-100 Gliwice, Bł. Czesława 16-18 (Poland)

    2015-06-18

    The article presents results of structural tests (light, scanning electron and scanning transmission electron microscopy) of X10CrMoVNb9-1 (T91) creep-resisting steel after approximately 100,000 h of operation. It was ascertained that the parent metal of T91 steel is characterized by the microstructure of tempered martensite with M{sub 23}C{sub 6} carbide precipitates and few dispersive precipitates of MX-type niobium and vanadium carbonitrides. The most inconvenient change in T91 steel precipitate morphology due to long-term operation is the appearance of the Laves Fe{sub 2}Mo phase which along with M{sub 23}C{sub 6} carbide particles forms elongated blocks and conglomerates on grain boundaries. The article also presents results of tests related to the effect of simulated welding thermal cycles on selected properties of X10CrMoVNb9-1 (T91) grade steel at a state after approximately 100,000 h of operation. The tests involved the determination of the chemical composition of the steel tested as well as impact tests, hardness measurements and microscopic metallographic examination (based on light microscopy) of simulated heat-affected zone (HAZ) areas for a cooling time (t{sub 8/5}) restricted within a range between 3 s and 120 s, with and without heat treatment. The tests revealed that, among other results, hardness values of simulated HAZ areas in X10CrMoVNb9-1 (T91) steel do not guarantee cold crack safety of the steel at the state without additional heat treatment. It was also observed that simulated welding thermal cycles of cooling times t{sub 8/5}=3, 12, 60 and 120 s do not significantly affect the toughness and hardness of simulated HAZ areas of the steel tested.

  17. Influencia del acabado superficial sobre el comportamiento tribológico de capas nitrocarburadas en acero X40CrMoV5 1

    Directory of Open Access Journals (Sweden)

    Miguel, V.

    2005-12-01

    Full Text Available In this work the surface roughness behaviour in the forming of gaseous nitrocarburized layers has been analyzed. Ra values from 0.02 to 1.50 μm. has been considered. Obtained results prove a minor influence on layer thickness. A little increase of Ra has been observed. The abrasive wear resistance of nitrocarburized specimens was researched. The carbonitride ε is the only constituent in the about 6 μm thickness layers that have been carried out in this work. The tests revealed a minor wear resistance of the external part in the layers. This way, the external zone is less effective to wear phenomena than the internal. The specimens with small roughness parameters values show a higher poor wear resistance zone.

    En este trabajo se estudia la influencia que el acabado superficial del acero X40CrMoV5 1 tiene sobre la capa blanca o de combinación formada en el proceso de la nitrocarburación gaseosa. Se consideran acabados superficiales en el rango de 0,02 a 1,50 μm para Ra. Los resultados obtenidos indican que la rugosidad aumenta en todos los casos, aunque tiene poca influencia sobre el espesor de capa formada. También se ha investigado el comportamiento frente al desgaste abrasivo de las capas obtenidas que están constituidas en su totalidad por nitrocarburo ε y son de un espesor aproximado de 6 μm. Se ha encontrado un comportamiento diferenciado frente al desgaste de la zona externa de la capa frente a la zona subsuperficial. Los resultados revelan que la capa externa de la capa de combinación es poco efectiva frente al desgaste en relación con la capa subsuperficial. La zona de peor comportamiento es mayor para las probetas con acabados superficiales más finos.

  18. Effect of simulated thermal cycles on the microstructure of the heat-affected zone in HSLA-80 and HSLA-100 steel plates

    Science.gov (United States)

    Shome, M.; Gupta, O. P.; Mohanty, O. N.

    2004-03-01

    The influence of weld thermal simulation on the transformation kinetics and heat-affected zone (HAZ) microstructure of two high-strength low-alloy (HSLA) steels, HSLA-80 and HSLA-100, has been investigated. Heat inputs of 10 kJ/cm (fast cooling) and 40 kJ/cm (slow cooling) were used to generate single-pass thermal cycles with peak temperatures in the range of 750 °C to 1400 °C. The prior-austenite grain size is found to grow rapidly beyond 1100 °C in both the steels, primarily with the dissolution of niobium carbonitride (Nb(CN)) precipitates. Dilatation studies on HSLA-80 steel indicate transformation start temperatures (T s ) of 550 °C to 560 °C while cooling from a peak temperature (T p ) of 1000 °C. Transmission electron microscopy studies show here the presence of accicular ferrite in the HAZ. The T s value is lowered to 470 °C and below when cooled from a peak temperature of 1200 °C and beyond, with almost complete transformation to lath martensite. In HSLA-100 steel, the T s value for accicular ferrite is found to be 470 °C to 490 °C when cooled from a peak temperature of 1000 °C, but is lowered below 450 °C when cooled from 1200 °C and beyond, with correspondingly higher austenite grain sizes. The transformation kinetics appears to be relatively faster in the fine-grained austenite than in the coarse-grained austenite, where the niobium is in complete solid solution. A mixed microstructure consisting of accicular ferrite and lath martensite is observed for practically all HAZ treatments. The coarse-grained HAZ (CGHAZ) of HSLA-80 steel shows a higher volume fraction of lath martensite in the final microstructure and is harder than the CGHAZ of HSLA-100 steel.

  19. Structure and mechanical properties of PVD coatings for tool materials

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2010-09-01

    Full Text Available Purpose: The goal of this work is to investigate and compare the properties of (Ti,AlN, Ti(C,N and (Ti,Al,SiN coatings, deposited on cemented carbide and cermet substrates.Design/methodology/approach: Coatings deposition were carried out using the PVD method by the cathodic arc evaporation (CAE process. Investigations of surfaces and structures of the deposited coatings were carried out with use of SEM and TEM methods. Roughness parameter measurements, adhesion evaluation of the coatings on the investigated inserts, the Vickers microhardness measurements and detailed cutting tests were carried out to compare the properties of the investigated materials.Findings: The results of the investigations carried out confirm the advantages of PVD coatings deposited onto both: cemented carbides and cermets, especially in case of (Ti,AlN and (Ti,Al,SiN coatings. Coatings deposited onto the investigated substrates are characterised by good adhesion, high microhardness, taking effect in very high increasing of wear resistance.Practical implications: Deposition of hard, thin, multicomponent coatings on materials surface by PVD method features one of the most intensely developed directions of improvement of the working properties of materials. Employment of introduced combinations of substrates and coatings make it possible to transit of machining of semi-products from roughing to semi-finishing or finishing in one setting.Originality/value: Coatings based on (Ti,AlN, (Ti,Al,SiN as well as Ti(C,N were developed to provide better performance over titanium nitride since the incorporation of aluminum or carbon in TiN increased hardness, decreased coefficient of friction of the coatings. Tools with such coatings reveal a significant life extension in service compared to the uncoated tools or coated with simple coatings based on monolayers of nitrides or carbonitrides, improvement of the tribological contact conditions in the tool-chip-machined material contact zone

  20. Chemistry of Two-Dimensional Transition Metal Carbides (MXenes)

    Science.gov (United States)

    Mashtalir, Olha

    With consumer trends pushing toward smaller, faster, more flexible, multitasking devices, researchers striving to meet these needs have targeted two-dimensional (2D) materials---and graphene in particular---as holding the most promise for use in advanced applications. But in 2011, a significant interest has been triggered by a newly discovered family of novel 2D materials---layered transitional metal carbides and carbonitrides, named MXenes. Those compounds were of general formula Mn+1 XnTx, where M stands for metal atom, X is C and/or N, n = 1, 2 or 3, and Tx represents surface groups. Being initially suggested as a material for electrical energy storage systems, MXenes' properties and their potential applications have not been explored. This work is the first complete study of MXenes' chemistry that sheds light on the chemical composition, structure and properties of these novel materials and possible routes of its modification. The research was focused on 2D titanium carbide, Ti3C2Tx, chosen as the representative of the MXene family. The kinetic study of Ti 3C2Tx synthesis discovered the main synthesis parameters, viz. temperature, time and particle size, that affect the etching process and define the quality of final product. MXenes were found to be able to spontaneously accommodate various ions and small organic molecules between the layers leading to preopening of the structure. A major challenge of large scale production of delaminated, atomically thin 2D MXene layers was solved with two delamination techniques involving dimethyl sulfoxide and isopropyl amine pre-intercalation followed by sonication in water. Ti3C2Tx was also found to possess adsorptive and photocatalytic properties, revealing its potential for environmental applications. It also showed limited stability in water and in the presence of oxygen, providing important practical information on proper handling and storage of MXene materials. Completion of this work allowed the performance of energy

  1. Non-metallic inclusions in high manganese austenitic alloys

    Directory of Open Access Journals (Sweden)

    A. Grajcar

    2011-07-01

    Full Text Available Purpose: The aim of the paper is to identify the type, fraction and chemical composition of non-metallic inclusions modified by rare-earth elements in an advanced group of high-manganese austenitic C-Mn-Si-Al-type steels with Nb and Ti microadditions.Design/methodology/approach: The heats of 3 high-Mn steels of a various content of Si, Al and Ti were melted in a vacuum induction furnace and a modification of non-metallic inclusions was carried out by the mischmetal in the amount of 0.87 g or 1.74 g per 1 kg of steel. Evaluation of the metallurgical purity of steels with non-metallic inclusions was done basing on determination their fraction, type, size and morphology. Stereological parameters of the inclusions were assessed by the use of automatic image analyzer cooperating with light microscope. EDS method was used to assess the chemical composition of non-metallic inclusions.Findings: It was found that the steels are characterized by high metallurgical purity connected to low concentrations of phosphorus and gases at a slightly higher sulphur content, introduced to a melt together with electrolytic manganese. The steels contain fine sulfide inclusions with a mean size from 21 to 25 µm2 in a majority and their fraction equals from 0.047 to 0.09%, depending on sulphur content. MnS, carbonitrides of the (Ti,Nb(C,N type and complex carbosulfides containing Mn, Ti and Nb were identified in steels. The beneficial influence in decreasing a fraction of non-metallic inclusions and their susceptibility to elongate in a rolling direction has a higher addition of mischmetal and titanium microaddition. A modification of the chemical composition of non-metallic inclusions by Ce, La and Nd proceeds in an external zone of inclusions.Research limitations/implications: Further investigations relating the type and morphology of non-metallic inclusions to mechanical properties of sheets at various sections according to the rolling direction are needed

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

    Directory of Open Access Journals (Sweden)

    P. Putyra

    2008-10-01

    Full Text Available 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 preform for the infitration process is the free sintering process. The preforms were produced by the mixing of ceramic powders with organic binders, drying and sintering.Porosity, density were measured for the materials. Microstructure observation was carried out using scanning microscope. The compressive strength of Si3N4 and Al2O3-Ti(C,N porous preforms were investigated.Findings: For sintered porous Si3N4 preforms, influence of the porous forming additives on material porosity is observed. Compressive strengths of Si3N4 were in the range of 2.9-4.8 MPa. The highest value of the compressive strength was obtained for Al2O3-Ti(C,N preform with 8 wt.% of tylose and 25 wt.% of glykol.For these materials compressive strength were in the range of 13.2 up to 14.3 MPa. In spite of lower value of the compressive strength for Si3N4 preforms, this material exhibits high shock thermal resistance.Practical implications: Pressureless infiltration of molten metals into ceramics is the most cost-effective approach to liquid-metal processing of MMCs. Metal matrix composites are applied widely in aircraft production technologies and defence technology.Originality/value: Infiltration of molten metals into porous ceramic preforms is the only technique suitable for the fabrication of high volume fraction of ceramic materials in MMCs. Infiltration process generates thermal stresses in the ceramics preforms. The thermal shock resistance of Al2O3 is lower than Si3N4 or Al2O3-Ti

  3. Nitride and carbide preforms for infiltration process

    Directory of Open Access Journals (Sweden)

    A. Twardowska

    2007-11-01

    Full Text Available Purpose: Infiltration of molten metals into porous ceramic preforms is the only technique suitable for the fabrication of high volume fraction of ceramic materials in MMCs. The most popular material for porous preforms is Al2O3 because of its low cost. Infiltration process generates thermal stresses in the Al2O3 preforms. The thermal shock resistance of Al2O3 is lower than for Si3N4 or Al2O3/TiC+TiN materials. The aim of this study is to obtain the nitride and carbide 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 preform for the infiltration process is the free sintering process. Some of selected properties of this material are presented. The preforms were produced by the mixing of ceramic powders with organic binders, followed by forming, drying and firing. Ceramic preforms of 65% porosity were produced. Microscopic investigations revealed good joints between the ceramic particles.Findings: The material consist of the base component (90 wt.% of α-Si3N4, 5 wt.% of Al2O3, 5 wt.% of Y2O3, which were mixed with 40 wt.% of polyethylene glycol 6000 (mixed in Turbula porosity is 25.7 %. The higher value of porosity 66.6% was obtained for material with 20 wt.% tylose. The grain size of Si3N4 and method of the mixtures preparing (mixing with or without milling have the significant influence on compacts’ porosity. For 68 wt.% Al2O3, 2 wt.% ZrO2 and 30 wt.% Ti(C,N with addition of glycol 6000, the value of porosity is 67%. α-Si3N4 material produced shows strong bonding with aluminium and AlSi11 aluminium alloy.Practical implications: Pressureless infiltration of molten metals into ceramics is the most cost-effective approach to liquid-metal processing of MMCs. Metal matrix composites are applied widely in aircraft production technologies and defence technology.Originality/value: Compared to widely used alumina

  4. Multilayer, hybrid PVD coatings on Ti6Al4V titanium alloy

    Directory of Open Access Journals (Sweden)

    W. Pawlak

    2009-12-01

    Full Text Available Purpose: The main purpose of this paper was to develop hybrid PVD technology of deposition wear resistant, multilayer coatings onto diffusion-hardened Ti6Al4V titanium alloy. Titanium and its alloys are desirable materials in modern constructions and vehicles. They have a high specific strength and very good corrosion resistance and biocompatibility. On the other hand, they have a low load-bearing capacity and poor tribological properties, as, for example, high friction coefficient, low resistance to adhesive and abrasive wear and tendency to galling. Development of multiplex coatings depositions techniques is vital for expanding of areas of titanium alloys usage.Design/methodology/approach: In the present work a new approach to coatings deposition onto diffusion hardened in glow discharge plasma (in Ar+O2 atmosphere Ti6Al4V titanium alloy was proposed by means of a hybrid PVD method including three coatings deposition methods: Reactive Magnetron Sputtering (RMS, Filtered Cathodic Arc Evaporation (FCAE and Pulsed Cathodic Arc Deposition (PCAD. The main aim of the work was to develop multilayer coatings combined of sublayers of titanium or chromium carbonitrides or of pure, hard carbon ones.Findings: It was concluded from the results of investigations that not every proposed multilayer structure ensure good frictional properties of Ti6Al4V alloy even when the coating posses very high hardness. The lowest value of wear and friction coefficient was determined for multilayer coating with (TiC/Cx3 structure.Research limitations/implications: Further research is necessary for a better understanding of the mechanisms of friction and wear as well as the origin of superhardness of particular multilayers.Practical implications: Multilayer coatings deposited by means of the hybrid PVD technique can be used for low friction and wear protection of titanium alloys.Originality/value: Originality value of this paper consists in use in one process of three

  5. Use of AWCC in evaluation of unknown fissile materials

    International Nuclear Information System (INIS)

    An important technological problem in the sphere of non-proliferation and safeguards is nondestructive analysis (NDA) methodology for qualitative and quantitative characterization of nuclear materials. Additionally, NDA tends to be labor and time intensive. Two NDA techniques used at KIPT included Gamma Spectroscopy (for qualitative analysis) and Neutron activation (for quantitative analysis). Gamma Spectroscopy was used to confirm the presence of radionuclides within the samples, whereas an Active Well Coincidence Counter (AWCC) in the active mode was used to quantitatively determine the 235U content in particular types of fissile materials at KIPT. This paper describes the usage of the AWCC at NSC KIPT for characterizing nuclear materials for IAEA safeguards. It was also an opportunity to estimate fissile materials of unknown composition. The equipment used was a model JCC-51 AWCC using a shift register model JSR-12 from Canberra and two neutron sources [AN-HP (241AmLi)]. A Compaq Presario computer using Windows version of NCC (Los Alamos software) was used to operate the AWCC. Materials studied in this project included highly enriched nuclear material in the form of powder, compacts (tablets, microspheres, rods), salt and scrap. The chemical composition of nuclear material included uranium metal, uranium dioxide, uranium nitride, uranium carbonitride, thorium dioxide, and mixtures of these compounds. New standards were used to recalibrate the AWCC using material obtained at KIPT with documented compositional values more similar to the materials to be measured, and in similar containers as well. During this study, the AWCC calibration curves were obtained for uranium metal and uranium dioxide with different enrichments up to 90 % for 235U. A broad spectrum of other fissile materials of unknown composition with differing enrichments has also been studied, and the items' isotopic and quantitative compositions have also been determined. Using the new calibration

  6. Effect of V and Nb on the Microstructure and Creep Property of High Chromium (12%Cr) Ferritic Steel%V和Nb对12%Cr铁索体钢微观组织和蠕变特性的影响

    Institute of Scientific and Technical Information of China (English)

    沈喜训; 刘俊亮; 徐洲

    2012-01-01

    The effect of trace amounts of vanadium and niobium on the microstructure and the distribution and morphology of precipitates of 12%Cr ferritic heat resistant steel was studied by the optical microscopy (OM) and the transmission electron microscopy (TEM) equipped with energy dispersive X-ray spectroscopy (EDS). The testing results illuminated that the ferrite steel with V and Nb holds a narrow martensite lath structure. It is also found that the M23C6-type carbides combined with the MX-type carbonitrides, have fine small particle size and precipitate along all sorts of boundaries and in the δ-ferrite phase in the manner of acicular or clubbed shape while the M23C6-type carbides singly precipitated present a rectangle or ellipse shape with a relative larger particle size. The above optimized structure and the dispersed strengthening from MX-type carbinitrides itself restrain the recovery and recrystallization of tempered martensite structure, and thus improve the creep-resistant of ferrite steel.%利用光学显微镜和透射电子显微镜以及光电子能谱分析方法,研究了元素V和Nb对12%Cr铁素体耐热钢的微观组织和析出相的形态和分布的影响.结果表明:添加V和Nb的铁素体钢具有更窄的马氏体板条组织;附于MX型碳氮化物生长的M23C6碳化物呈细小的针状或短棒状析出,而单独析出的M23 C6尺寸较大,呈椭圆形.这些组织上的优化和MX型碳氮化物的弥散析出有效抑制了回火马氏体组织的回复和再结晶,提高了铁素体钢的蠕变抗力.

  7. The effects of small titanium additions on the mechanical properties and the microstructures of controlled rolled niobium-bearing HSLA plate steels

    Energy Technology Data Exchange (ETDEWEB)

    He Kejian (Univ. of Strathclyde, Glasgow (United Kingdom)); Baker, T.N. (Univ. of Strathclyde, Glasgow (United Kingdom))

    1993-09-15

    Effects of small Ti additions (0.010, 0.022%) on mechanical properties and microstructures of Nb-bearing HSLA plate steels under two different rolling schedules were investigated. For comparison, a Ti-free steel was controlled rolled to 814 C. A side effect of the Ti additions was observed on strength of Nb-bearing steels. The lower yield stress values and hardness levels for all Ti-Nb steels were reduced both in as-rolled and normalized conditions, depending on Ti/N ratio and details of thermomechanical process. However, the Ti-Nb steels with a lower finish rolling temperature (FRT), 800 C, showed better toughness than the Ti-free control steel. For Ti-Nb steels, toughness was improved significantly by lowering the FRT from 940 to 800 C, owing mainly to considerable refinement of ferrite grain sizes and fewer fine carbides available for dispersion hardening. No advantages were observed for over-stoichiometric Ti addition (Ti/N=4.4). The steel with under-stoichiometric Ti addition (Ti/N = 2) and a lower FRT (800 C) showed best overall mechanical and toughness properties among all processed Ti-Nb steels. Precipitation of Nb nitrides and carbides in the Nb steels was changed by Ti additions which led to formation of complex Ti-Nb nitrides and carbonitrides, i.e. Ti-rich plates and cuboids. Moreover, these plates and cuboids acted as nucleating cores on which pure carbides formed, i.e. Nb carbide in 0.01%Ti steels whereas Nb-rich Ti-Nb carbide in 0.022%Ti steels. In as-rolled samples, no Al was found in the complex particles or as individual AlN while in the normalized condition, fine AlN precipitates were detected frequently with understoichiometric titanium addition (0.01%Ti), whereas formation of AlN was suppressed by the over-stoichiometric Ti addition (in 0.022%Ti). The Ti/N ratio, therefore, has a strong influence on type of precipitation and size.

  8. Characterization of precipitates in the weld HAZ for a range of offshore steels

    Energy Technology Data Exchange (ETDEWEB)

    Weatherly. G.C.; Yin. Z.M.; Wolosiuk, M.

    1989-01-01

    A detailed study was made of the dissolution, precipitation and compositional changes associated with microalloying elements (Nb, V, Ti) in a series of HSLA steels. Both welds and Gleeble simulated samples were studied and compared at two heat inputs, 3 and 6 kJ/mm, for 4 steels, BS4360 and LT60, which are Nb and Nb-V grades, and 350 WT CAB and 350 WT STRAND, which are Nb-V-Ti containing steels. The behaviour of the Nb and Nb-V grades was dictated by the dissolution behaviour of the coarse Nb-rich particles found in the base plate of both steels. The Gleeble samples of the BS4360 steel showed nearly complete dissolution of the particles. The LT60 steel contained a coarser size distribution of Nb carbo-nitrides, and this resulted in a greater fraction of particles surviving the weld cycles in LT60 than BS4360. Reprecipitation effects were observed in the LT60 welds at the higher input but not in the Gleeble simulated samples. The Ti-Nb bearing steels showed more complex behaviour than the Nb, V-containing steels because the particle composition was dependent on the history of the steel and the particular thermal cycle. Mean Ti/Nb content of the particles increased after Gleeble thermal cycling and as the fusion line was approached, attributed to the Nb caps loss and formation of Ti-rich skins. In the Gleeble samples all the fine spheroidal particles dissolved after the thermal cycles, but reprecipitation effects were observed in the welds. The transformation products produced on cooling the Gleeble samples were studied by electron microscopy techniques. The formation of ferrite or bainite structures and the appearance of MA or carbides in the inter-ferrite regions was shown to be related to the C content and cooling rate of the weld. The MA phase was favoured at low C levels and faster cooling rates for a given steel. 9 refs., 29 figs., 3 tabs.

  9. 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

  10. Single-source-precursor synthesis of dense SiC/HfC(x)N(1-x)-based ultrahigh-temperature ceramic nanocomposites.

    Science.gov (United States)

    Wen, Qingbo; Xu, Yeping; Xu, Binbin; Fasel, Claudia; Guillon, Olivier; Buntkowsky, Gerd; Yu, Zhaoju; Riedel, Ralf; Ionescu, Emanuel

    2014-11-21

    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/HfC(x)N(1-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/HfC(x)N(1-x)-based nanocomposites using the spark plasma sintering (SPS) technique. The results showed that dense monolithic SiC/HfC(x)N(1-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). PMID:25278173

  11. The fuel to clad heat transfer coefficient in advanced MX-type fuel pins

    International Nuclear Information System (INIS)

    Advanced fuels (mixed carbides, nitrides and carbonitrides) are characterised by a high thermal conductivity compared to that of oxide fuels (5 times greater) and their behaviour under irradiation (amount of swelling, fracture behaviour, restructuring) is far more sensitive to the design parameters and to the operating temperature than that of oxide fuels. The use of advanced fuels is therefore conditioned by the possibility of mastering the above phenomena, and the full exploitation of their favorable neutron characteristics depends upon a good understanding of the mutual relationships of the various parameters, which eventually affect the mechanical stability of the pin. By far the most important parameter is the radial temperature profile which controls the swelling of the fuel and the build-up of stress fields within the pin. Since the rate of fission gas swelling of these fuels is relatively large, a sufficient amount of free space has to be provided within the pin. This space originally appears as fabrication porosity and as fuel-to-clad clearance. Due to the large initial gap width and to the high fuel thermal conductivity, the range of the fuel operating temperatures is mainly determined by the fuel-to-clad heat transfer coefficient h, whose correct determination becomes one of the central points in modelling. During the many years of modelling activity in the field of oxide fuels, several theoretical models have been developed to calculate h, and a large amount of experimental data has been produced for the empirical adjustment of the parameters involved, so that the situation may be regarded as rather satisfactory. The analysis lead to the following conclusions. A quantitative comparison of experimental h-values with existing models for h requires rather sophisticated instrumented irradiation capsules, which permit the measurement of mechanical data (concerning fuel and clad) together with heat rating and temperatures. More and better well

  12. Characterization of the corrosion behavior of an austenitic stainless steel for biomedical applications coated with Ti N, Ti CN And DLC PVD coatings; Caracterizacao do comportamento frente a corrosao de um aco inoxidavel austenitico para aplicacoes biomedicas com revestimentos PVD de TiN, TiCN e DLC

    Energy Technology Data Exchange (ETDEWEB)

    Antunes, Renato Altobelli

    2006-07-01

    Metallic biomaterials must present a combination of properties such as corrosion resistance, biocompatibility and mechanical resistance. Austenitic stainless steels, especially AISI 316L combine these properties with the easy of fabrication at low cost. However, they are prone to corrosion in physiological solutions. Furthermore, their corrosion products may lead to infectious ou allergenic reactions in the tissues around the implant device. In the present work, coatings produced by physical vapour deposition (PVD) methods have been applied on the surface of a 316L stainless steel to increase its corrosion resistance and biocompatibility. Three thin films were tested: titanium nitride (TiN), titanium carbonitride (TiCN) and diamond-like carbon (DLC). These materials present high hardness, wear resistance and intrinsic biocompatibility that are key features when considering biomedical applications. The characterization of the electrochemical behavior of the stainless steel coated with the three different films showed that the presence of surface defects are deleterious to the corrosion resistance of the substrate. These defects were observed using scanning electron microscopy. The evolution of the electrochemical behavior of the coated steel was explained through a mechanism based on the experimental results obtained using electrochemical impedance spectroscopy. Two different passivation treatments were carried out on the stainless steel surface, either in sulfuric or nitric acid solutions, to increase its corrosion resistance. The results suggested que these treatments were not efficient, but may be modified to improve its performance. The electronic properties of the passive films of the non-passivated and passivated stainless steel were studied using the Mott-Schottky approach. The films presented a duplex character. Below the flat band potential the behavior is typical of a highly doped type-p semiconductor. Above the flat band potential is typical of a highly

  13. El Ensayo de Punzonado en Caliente Aplicado a un Acero Microaleado con Niobio Application of the Bradawling Test to Low Carbon Niobium Microalloyed Steel

    Directory of Open Access Journals (Sweden)

    E. Hurtado

    2005-01-01

    Full Text Available Se caracterizó mecánica y microestructuralmente la deformación plástica isotérmica en probetas cilíndricas de acero microaleado con niobio, sometidas a pruebas de punzonado a alta temperatura. Las temperaturas de ensayo fueron de 840°C, 900°C y 960°C con velocidades de avance del punzón de 1.3 mm/min, 4.5 mm/min y 13 mm/min, hasta una profundidad de 8 mm. Se observó una mayor resistencia del material a 960°C que a 900°C y 840°C, lo cual está relacionado con la precipitación dinámica de carbonitruros en el interior del grano y la inhibición de la recristalización de la austenita. El ensayo es sensible tanto a la precipitación como a la recristalización. Se muestra que el método usado es un ensayo con un estado de esfuerzos triaxial generado intencionalmente, de alta simetría y geometría simple, por lo que puede ser complementario a ensayos de torsión y tensión uniaxial en caliente.The mechanical and microstructural characteristics of isothermal plastic deformation were determined on cylindrical samples of niobium microalloyed steel tested at high temperatures. Test temperatures were 840°C, 900°C and 960°C at crosshead speeds of 1.3 mm/min, 4.5 mm/min and 13 mm/min to a penetration depth of 8 mm. Greater resistance of the material was observed at 960°C than at 900°C and 840°C. This was related to the intergranular precipitation of niobium carbonitrides and austenite recrystallization inhibition. The bradawling test is sensitive to both recrystallization and precipitation. It is shown that the method used is a triaxial stress state test, highly symmetrical with a simple geometry, and therefore may be used as a test complementary to heated uniaxial torsion and compression testing .

  14. 回火对微合金管线钢疲劳裂纹扩展行为的影响%Effects of tempering treatment on fatigue crack propagation behavior of microalloyed pipeline steels

    Institute of Scientific and Technical Information of China (English)

    李红英; 宾杰; 林武; 魏冬冬; 李阳华; 曹俊

    2011-01-01

    采用MTS858电液伺服万能试验机、扫描电镜及透射电镜研究回火对一种高强度微合金管线钢疲劳裂纹扩展行为的影响.研究结果表明:回火可提高微合金管线钢疲劳裂纹扩展的门槛值,降低疲劳裂纹扩展速率,但对裂纹扩展稳态区的扩展速率影响不大;回火使碳氮化物沉淀析出、晶间马氏体/奥氏体(M/A)组元由岛状转变为点状及细条状,形成马氏体薄膜结构,阻碍变形和裂纹在材料中扩展,增加裂纹的偏折程度;在控轧控冷终冷温度进行2~4 h回火热处理,可以提高微合金管线钢强韧性和抗疲劳裂纹扩展能力.%The effects of different tempering treatments on fatigue crack propagation behavior of a high strength microalloyed pipeline steel were investigated by MTS858 material testing system, scanning electron microscopy and transmission electron microscopy. The results show that tempering treatments can improve the fatigue crack propagation threshold and reduce the fatigue crack growth rate of microalloyed pipeline steels, but with little effects on the intermediate region of stable crack propagation. Tempering treatment can promote the precipitation of microalloyed carbonitrides and transform the martensite/austenite (M/A) components at the grain boundary from islands to spots and strips, and the M/A components can be further changed to thin-film martensite as tempering time increases, and all these structures can inhibit the propagation and increase the deflection of fatigue crack. The strength, toughness and fatigue crack propagation resistance of microalloyed pipeline steels can be promoted by 2-4 h tempering at the final cooling temperature of thertno-mechanical control process.

  15. Characterization of the corrosion behavior of an austenitic stainless steel for biomedical applications coated with Ti N, Ti CN And DLC PVD coatings

    International Nuclear Information System (INIS)

    Metallic biomaterials must present a combination of properties such as corrosion resistance, biocompatibility and mechanical resistance. Austenitic stainless steels, especially AISI 316L combine these properties with the easy of fabrication at low cost. However, they are prone to corrosion in physiological solutions. Furthermore, their corrosion products may lead to infectious ou allergenic reactions in the tissues around the implant device. In the present work, coatings produced by physical vapour deposition (PVD) methods have been applied on the surface of a 316L stainless steel to increase its corrosion resistance and biocompatibility. Three thin films were tested: titanium nitride (TiN), titanium carbonitride (TiCN) and diamond-like carbon (DLC). These materials present high hardness, wear resistance and intrinsic biocompatibility that are key features when considering biomedical applications. The characterization of the electrochemical behavior of the stainless steel coated with the three different films showed that the presence of surface defects are deleterious to the corrosion resistance of the substrate. These defects were observed using scanning electron microscopy. The evolution of the electrochemical behavior of the coated steel was explained through a mechanism based on the experimental results obtained using electrochemical impedance spectroscopy. Two different passivation treatments were carried out on the stainless steel surface, either in sulfuric or nitric acid solutions, to increase its corrosion resistance. The results suggested que these treatments were not efficient, but may be modified to improve its performance. The electronic properties of the passive films of the non-passivated and passivated stainless steel were studied using the Mott-Schottky approach. The films presented a duplex character. Below the flat band potential the behavior is typical of a highly doped type-p semiconductor. Above the flat band potential is typical of a highly

  16. 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.)

  17. 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

  18. Fuel development for reactors of new generation in Ukraine

    International Nuclear Information System (INIS)

    elements development with fuel on a basis: Metal: uranium, alloys of uranium; Ceramic: uranium dioxide, thorium dioxide, uranium carbonitride, uranium oxycarbide, mixed oxide of uranium and thorium. The special attention is given to discussion of the basic technological schemes of reception of the fuel microspheres, coated particles and spherical fuel elements for HTGR. Features of reception carbongraphite materials and products by the methods of volumetric gas-phase condensation of porous preparations by pyrocarbon are considered. Results of investigations of the basic fuel elements characteristics and their components, materials and products with pyrocarbon binding, including in conditions of reactor irradiations are discussed. The review concerning the experience of the development the fuel elements with fuel based on metal uranium is given. In NSC KIPT constructions and manufacturing techniques of components for active zones of new perspective directions of atomic engineering are created and proved, also was laid the foundation for the base design and technological decisions for the fourth generation nuclear reactors

  19. 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.

  20. 几种碳源对碳热还原氮化法制备Ti(C,N)粉末的影响%Influence of several carbon source on Ti(C,N)powders prepared by carbothermal reduction and nitridation method

    Institute of Scientific and Technical Information of China (English)

    余鹏飞; 叶金文; 刘颖; 何旭; 王杰; 杨嘉

    2011-01-01

    以纳米TiO2和不同碳源为原料,采用碳热还原氮化法,制备了Ti(C,N)粉末.通过X射线衍射分析、热分析、扫描电镜、化学成分分析等手段研究了TiO2碳热还原氮化过程的反应机理和不同碳源对制备碳氮化钛粉末的影响.结果表明,在TiO2碳热还原氮化过程中,前期主要为TiO2/C固-固反应,后期CO参与的气-固反应变为主要反应;当碳黑为碳源时,比之活性碳和石墨,反应最为完全,而且粉末产物粒度较为细小均匀;同时随着碳黑比表面积的增大,碳氮比随之降低,游离碳和氧含量随之减小;当以比表面积为600m2/g的碳黑为碳源时,配碳量为28.8%的混合物在加热到1700℃,保温3h,氮气流量为1000mL/min的条件下,得到了游离碳含量<0.2%、氧含量<0.5%,总碳为11.42%的碳氮化钛粉末.%Ti(C,N)powders can be prepared by carbothermal reduction and nitridation method with the nanometer TiO2 and different carbon source as starting materials. X-ray diffractometer,TG/DSC thermal analyzer, SEM and chemical analysis are applied to investigate the reaction mechanism on carbothermal reduction-nitridation of TiO2 and the effects of different cardon source on preparation of titanium carbonitride powders. The results show that,in the reaction process,the predominant reaction mechanism is TiO2/C solid-solid reaction in the beginning and subsequent the gas-solid reaction in which CO participates. The reaction of mixtures with carbon black as the carbon source is more complete than those with active carbon and graphite, and the former is finer than the latter two in the grains of reaction products. At the same time,with the specific surface area of carbon black increasing,the carbon/nitrogen ratio declines, and the free carbon content and oxygen content decrease.Moreover,if the mixtures with carbon black specific surface of 600m2/g as the carbon source and a carbon content of 28. 8% were isothermal treated for 3h at 1700℃ in an

  1. 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

  2. The research of the ceramic fuel pins, irradiated in the technological channels of the ATS of IVG.1 reactor

    International Nuclear Information System (INIS)

    the fuel pins behavior in the case of the increase of the number of the reactor start-ups from 4 to the reserve 40 and duration of the tests from ∼700 s to reverse 5000 s is made. It is shown that their strength can reduce under the influence of the oxy-nitration, erosion, evaporating, corrosion under the pressure and tiredness of the vibrational load down to hazardous low level. That's why the first principal decision of the problem of increasing the serviceability of the ceramic fuel pins in the nitrogen - cooled channels is to change the carbide fuel pins to the carbonitride ones. The second decision of the problem is to remove the curling of the bundles of the fuel pins in the heating sections. In that case the favourable situation is created, in which the maximal depth of the fuel pins oxy-nitration will be of the principal value, and this value, according to the design estimations, is not to exceed 30 μm by the end of the full-resource tests. Taking into account this fact, the conclusion of the possibility to use the rod carbide fuel pins in the nitrogen cooled reactor without changing their material composition is made

  3. Phase transitions in multicomponent interstitial alloys on the base of titanium and vanadium carbides

    International Nuclear Information System (INIS)

    ordered phase with cubic structure is found. Existence of cubic and trigonal ordered phases in Ti0.98Mo0.02C0.6, Ti1-xVxC0.6 and Ti0.8V0.2C0.62 is determined; it is related to preferred distribution of carbon over octahedral interstitial positions and to distortion of metal sublattice, accordingly. The ordered phases in Ti0.87Ta0.13C0.71, Ti0.8Ta0.1Nb0.1C0.7 and Ti0.85Nb0.15C0.71 are absent because the replacement of a part of titanium atoms by tantalum and niobium decreases the upper concentration limit of existence of carbon atoms ordering in titanium carbide. In Ti1-xTaxC0.6 and Ti1-xNbxC0.6 short-range order is found and the dependence of character of Ti-Ta interaction on carbon content is established in carbides Ti1-xTaxCy, at decreasing it from C/Ti=1 up to C/Ti=0.6 the short range parameter changes approaching to that of Ti1-xTax. The existence regions of orthorhombic and hexagonal ordered phases, characteristics of order - order phase transition in VC0.47, VC0.33N0.12 and VC0.36O0.06N0.07 are determined. Nucleation of orthorhombic phase in vanadium subcarbide and subcarbonitride occurs by the heterogeneous mechanism, and phase transformation occurs through nucleation of bidimensional domains. By low-temperature (from 300 K to 12 K) neutron diffraction study of structures of titanium carbide, carbonitride and complex carbide a new low-temperature phase is found in the temperature interval of 12 K- 40 K, due to nonstoichiometry and power non equivalence of positions. In TiC0.67 correlation between structure and thermal capacity is determined at low temperatures (from 100 K to 30 K), consisting in decreasing of a thermal capacity at ordering in comparison with disordered state that is connected by changing of spectrum of an electronic subsystem. Regular researches of thermal capacity of nonstoichiometric titanium carbonitrides, oxycarbonitrides and complex carbides are carried out at low temperatures. In titanium carbide decrease in degree of long-range order is

  4. The development of high strength corrosion resistant precipitation hardening cast steels

    Science.gov (United States)

    Abrahams, Rachel A.

    delta-ferrite free in the as-cast condition. In this material, proper quench processing to eliminate excessive retained austenite was found to be most influential in terms of high strengths. It was also found that cooling below 0°C provided the best combination of strength and toughness, with the specific strength of the material exceeding that of cast Ti-6Al-4V material. Fractography studies suggest that titanium carbonitride and titanium carbon-nitride-sulfide inclusions limit the toughness of cast materials due to long exposures to ideal growth conditions during initial cooling. OIM studies also suggest that the retained austenite in properly processed 11-11PH alloy takes on an interlath structure, which likely contributes to toughness of the alloy, even at high-strength, peak aged conditions. Yield strengths approaching 235 ksi (1620 MPa) were achieved during initial heat treatment trials. It is expected that further improvements in properties can be achieved with continued improvement of processing for this new cast alloy system.

  5. Functionalized carbon nanostructures for hydrogen catalysis

    Science.gov (United States)

    Hu, Lung-Hao

    Sodium borohydride, NaBH4, is widely used as a source of pure hydrogen. Hydrogen is of interest because it is a source of clean energy. It can be converted directly into electrical energy by means of fuel cells. One of the objectives of this thesis was to develop a new catalytic process to (i) enhance the rate of hydrogen generation, and (ii) to achieve hydrogen generation equal to 100% of the theoretically expected value. The catalyst investigated in this research is constructed by starting from single wall carbon nanotubes (SWNT). This material has a very high specific surface area and good conductivity. The SWNT were formed into a paper by a special filtration process. Polysilazane, a polymeric precursor (Ceraset(TM)-SN from KiON Corp., Wiesbaden, Germany) was diluted by acetone and then layered onto SWNT paper. The Ceraset coated SWNT was then pyrolyzed at 1100°C for three hours to form a silicon carbonitride (SiCN), polymer derived ceramic (PDC), layer on the surface of SWNT filtered paper. This functionalized SiCN carbon nanotube paper (SiCN/CNT) was used as the substrate for catalyst dispersions. The catalyst consisted of transition metals, Pt/Pd/Ru. Suspension solutions of Pt, Pd and Ru were impregnated onto the SiCN/CNT paper with the expectation of creating a monolayer of these transition metals on surface of the SiCN/CNT substrate. It is likely that an interaction could occur between the transition metals and the silicon atoms present in the SiCN layer on the surface of the carbon nanotubes. It is known that transition metals and silicon react to form silicides, suggesting the formation of a strong Si-transition metal bond. Therefore, it is possible that this bond could provide good wetting of metal atoms on SiCN functionalized carbon nanotube substrate. In the limit a monolayer of the transition metals may be achieved, which would correspond to a near zero dihedral angle between the substrate and the cluster of transition metals. In such a scenario a

  6. 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.