WorldWideScience

Sample records for cementite

  1. Cementite Solidification in Cast Iron

    Science.gov (United States)

    Coronado, J. J.; Sinatora, A.; Albertin, E.

    2014-06-01

    Two hypereutectic cast irons (5.01 pct Cr and 5.19 pct V) were cast and the polished surfaces of test pieces were deep-etched and analyzed via scanning electron microscopy. The results show that graphite lamellae intersect the cementite and a thin austenite film nucleates and grows on the cementite plates. For both compositions, graphite and cementite can coexist as equilibrium phases, with the former always nucleating and growing first. The eutectic carbides grow from the austenite dendrites in a direction perpendicular to the primary plates.

  2. Deformation of cementite in cold drawn pearlitic steel wire

    International Nuclear Information System (INIS)

    Nanostructural evolution of cementite lamellae in pearlitic steel wires subjected to cold drawing remains elusive, making it difficult to understand the origin of remarkable ductility in cementite. Using high-resolution transmission electron microscopy (HRTEM), the mechanisms underlying the inelastic deformation of cementite in pearlitic steel wires were examined and elucidated. Deformation of cementite in drawing should be included in two mechanisms: (1) Dislocation mechanism: deformation in low strain pearlite should rely on the movement of dislocation. Flat-crystal cementite was broken up into several different orientation cementite particles. (2) Grain rotation mechanism: the deformation mechanism should be by the rotation of cementite particles. Cementite still keeps lamellar shape, but it was divided into a multilayer structure: central nano-crystal and outermost amorphous cementite

  3. A Quantitative Investigation of Cementite Dissolution Kinetics for Continuous Heating of Hypereutectoid Steel

    Science.gov (United States)

    Lee, Seok-Jae; Clarke, Kester D.

    2015-09-01

    Cementite dissolution kinetics in austenite was investigated in a hypereutectoid steel alloy during continuous heating. The quantitative change in cementite volume fraction as a function of thermal history was determined from dilation curves by using the martensite start temperature to calculate prior austenite carbon content. Two characteristics of the cementite dissolution kinetics were found: (1) the cementite dissolution rate increased with time regardless of heating rate due to the increased surface area of cementite particles, and (2) the rate of cementite dissolution was strongly affected by heating rate. An empirical equation combining the effects of cementite volume change and heating rate is proposed to describe cementite dissolution kinetics. A continuous heating transformation diagram for hypereutectoid steels was obtained and compared with the DICTRA simulations and metallographic analyses.

  4. Specific saturation magnetization of cementite resulting from tempering of cobalt and nickel steels

    Energy Technology Data Exchange (ETDEWEB)

    Yatsura, M.M.; Kirichok, P.P.; Yatsura, O.R. (Ivano-Frankovskij Gosudarstvennyj Pedagogicheskij Inst. (Ukrainian SSR))

    1984-01-01

    Results of studying specific saturation magnetization of cementite formed in cobalt and nickel steels in the case of isothermal tempering, are presented. It is shown that tempering temperature increase or ageing duration increase bring about the increase of specific magnetization of cementite saturation of both cobalt and nickel steels. Co and Ni dissolving in cementite during steel tempering decreases its specific saturation magnetization.

  5. Evolution of cementite morphology in pearlitic steel wire during wet wire drawing

    International Nuclear Information System (INIS)

    The evolution of the cementite phase during wet wire drawing of a pearlitic steel wire has been followed as a function of strain. Particular attention has been given to a quantitative characterization of changes in the alignment and in the dimensions of the cementite phase. Scanning electron microscope observations show that cementite plates become increasingly aligned with the wire axis as the drawing strain is increased. Measurements in the transmission electron microscope show that the cementite deforms plastically during wire drawing , with the average thickness of the cementite plates decreasing from 19 nm (ε = 0) to 2 nm (ε = 3.7) in correspondence with the reduction in wire diameter. The deformation of the cementite is strongly related to plastic deformation in the ferrite, with coarse slip steps, shear bands and cracks in the cementite plates/particles observed parallel to either {110}α or {112}α slip plane traces in the ferrite.

  6. Evolution of cementite morphology in pearlitic steel wire during wet wire drawing

    DEFF Research Database (Denmark)

    Zhang, Xiaodan; Godfrey, Andrew; Hansen, Niels; Huang, Xiaoxu; Liu, Wei; Liu, Qing

    2010-01-01

    microscope observations show that cementite plates become increasingly aligned with the wire axis as the drawing strain is increased. Measurements in the transmission electron microscope show that the cementite deforms plastically during wire drawing , with the average thickness of the cementite plates......The evolution of the cementite phase during wet wire drawing of a pearlitic steel wire has been followed as a function of strain. Particular attention has been given to a quantitative characterization of changes in the alignment and in the dimensions of the cementite phase. Scanning electron...... decreasing from 19 nm (ε = 0) to 2 nm (ε = 3.7) in correspondence with the reduction in wire diameter. The deformation of the cementite is strongly related to plastic deformation in the ferrite, with coarse slip steps, shear bands and cracks in the cementite plates/particles observed parallel to either {110...

  7. Nanoscale Cementite Precipitates and Comprehensive Strengthening Mechanism of Steel

    Science.gov (United States)

    Fu, Jie; Li, Guangqiang; Mao, Xinping; Fang, Keming

    2011-12-01

    This article summarizes the state of the art of the comprehensive strengthening mechanism of steel. By using chemical phase analysis, X-ray small-angle scattering (XSAS), room temperature organic (RTO) solution electrolysis and metal embedded sections micron-nano-meter characterization method, and high-resolution transmission electron microscopy (TEM) observation, the properties of nanoscale cementite precipitates in Ti microalloyed high-strength weathering steels produced by the thin slab continuous casting and rolling process were analyzed. Except nanoscale TiC, cementite precipitates with size less than 36 nm and high volume fraction were also found in Ti microalloyed high-strength weathering steels. The volume fraction of cementite with size less than 36 nm is 4.4 times as much as that of TiC of the same size. Cementite with high volume fraction has a stronger precipitation strengthening effect than that of nanoscale TiC, which cannot be ignored. The precipitation strengthening contributions of nanoscale precipitates of different types and sizes should be calculated, respectively, according to the mechanisms of shearing and dislocation bypass, and then be added with the contributions of solid solution strengthening and grain refinement strengthening. A formula for calculating the yield strength of low-carbon steel was proposed; the calculated yield strength considering the precipitation strengthening contributions of nanoscale precipitates and the comprehensive strengthening mechanism of steels matches the experimental results well. The calculated σ s = 630 to 676 MPa, while the examined σ s = 630 to 680 MPa. The reason that "ultrafine grain strengthening can not be directly added with dislocation strengthening or precipitation strengthening" and the influence of the phase transformation on steel strength were discussed. The applications for comprehensive strengthening theory were summarized, and several scientific questions for further study were pointed out.

  8. The effect of silicon on the nanoprecipitation of cementite

    OpenAIRE

    B. Kim; Celada, Carola de; San Martín, David; Sourmail, T.; Rivera-Díaz del Castillo, P.E.J

    2013-01-01

    The current work presents a comprehensive study that aims at understanding the role of silicon on θ precipitation, as well as on the ε → θ carbide transition in tempered martensite. Cementite nucleation was modelled under paraequilibrium conditions in order to ensure the presence of silicon in the carbide, where both thermodynamic and misfit strain energies were calculated to evaluate the overall free energy change. The growth stage was investigated using in situ synchrotron radiation; three ...

  9. The effect of silicon on the nanoprecipitation of cementite

    International Nuclear Information System (INIS)

    The current work presents a comprehensive study that aims at understanding the role of silicon on θ precipitation, as well as on the ε → θ carbide transition in tempered martensite. Cementite nucleation was modelled under paraequilibrium conditions in order to ensure the presence of silicon in the carbide, where both thermodynamic and misfit strain energies were calculated to evaluate the overall free energy change. The growth stage was investigated using in situ synchrotron radiation; three alloys containing 1.4–2.3 wt.% silicon contents have been studied. Silicon appears to play a significant role in carbide growth. It was observed throughout tempering that cementite precipitation was slower in the higher silicon content alloy. Literature reports that cementite growth is accompanied by silicon partitioning, where the silicon content inside the carbide decreases as tempering progresses. Therefore it appears that the limiting factor of the growth kinetics is the rate at which silicon is rejected from the carbide; the silicon piles up at the carbide–matrix interface, acting as a barrier for further growth

  10. A Novel Observation on Cementite Formed During Intercritical Annealing of Medium Mn Steel

    Science.gov (United States)

    Luo, Haiwen; Liu, Jianhui; Dong, Han

    2016-06-01

    A medium Mn steel with the martensitic microstructure was rapidly heated at a high rate of 300 K/s to the intercritical temperature of 923 K (650 °C) and then isothermally hold for 5 minutes. Although cementite should dissolve above the Ae1 temperature due to the constraint of thermodynamics, it is surprising to find cementite particles after such intercritical annealing (IA), whose Mn contents and sizes are even up to 30 wt pct and 60 nm, respectively. Numerical simulations have been performed to reveal the mechanism responsible for this new observation. They indicate that a small nucleus of cementite in martensite could rapidly grow to the observed size before austenitization takes place during IA. Such a rapid growth is driven by the rapid partition of C from martensite into cementite. It is then concluded that the precipitation of cementite during the IA of martensitic Mn-alloyed steel appears inevitable no matter how high the heating rate is. Moreover, the growth kinetics of cementite depend on the composition and size of its neighboring martensitic phase, rather than those of cementite nucleus.

  11. Evolution of cementite morphology in pearlitic steel wire during wet wire drawing

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xiaodan [Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, 100084 (China); Godfrey, Andrew, E-mail: awgodfrey@mail.tsinghua.edu.cn [Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, 100084 (China); Hansen, Niels; Huang Xiaoxu [Center for Fundamental Research: Metal Structures in Four Dimensions, Materials Research Division, Riso National Laboratory for Sustainable Energy, DTU, DK-4000 Roskilde (Denmark); Liu Wei [Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, 100084 (China); Liu Qing [School of Materials Science and Engineering, Chongqing University, Chongqing, 400030 (China)

    2010-01-15

    The evolution of the cementite phase during wet wire drawing of a pearlitic steel wire has been followed as a function of strain. Particular attention has been given to a quantitative characterization of changes in the alignment and in the dimensions of the cementite phase. Scanning electron microscope observations show that cementite plates become increasingly aligned with the wire axis as the drawing strain is increased. Measurements in the transmission electron microscope show that the cementite deforms plastically during wire drawing , with the average thickness of the cementite plates decreasing from 19 nm ({epsilon} = 0) to 2 nm ({epsilon} = 3.7) in correspondence with the reduction in wire diameter. The deformation of the cementite is strongly related to plastic deformation in the ferrite, with coarse slip steps, shear bands and cracks in the cementite plates/particles observed parallel to either {l_brace}110{r_brace}{sub {alpha}} or {l_brace}112{r_brace}{sub {alpha}} slip plane traces in the ferrite.

  12. Experimental measurement of Young’s modulus from a single crystalline cementite

    International Nuclear Information System (INIS)

    Pure Fe–C pearlite was heat-treated and selectively etched to extract [0 0 1]- and [1 0 0]-oriented single crystalline cementite sheets. The elastic properties of the shaped cementite were measured in a simple, in situ bending test system set up inside the scanning electron microscope using a micronewton-range force sensor. The Young’s modulus experimentally measured from a single crystal sheet was lower than the value obtained from theoretical calculation

  13. An experimental and theoretical study of cementite dissolution in an Fe-Cr-C alloy

    Science.gov (United States)

    Liu, Zi-Kui; Höglund, Lars; Jönsson, Björn; Ågren, John

    1991-08-01

    The dissolution of cementite at 910 °C in an Fe-2.06Cr-3.91C (at. pct) alloy is investigated experimentally. The Cr concentration profiles in austenite and cementite are measured by means of the scanning transmission electron microscopy/energy dispersive spectrometry (STEM/EDS) technique at different dissolution times. The measurements show the Cr enrichment in the cementite during the dissolution process. The measurements suggest that the main part of the reaction for this alloy is controlled by Cr diffusion in the cementite or in the austenite matrix. This observation is in agreement with predictions of the local equilibrium hypothesis. The carbide fraction and average particle diameter are evaluated as functions of dissolution time. The Cr enrichment of the cementite results in a supersaturation and a possible decomposition of the cementite. Microstructural evidence for such a decomposition is found by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A new program package called DICTRA,[11] which is suitable for the simulation of diffusional reactions in multicomponent alloys, has been applied to the present case. The simulation is compared with the experimental data, and a good agreement between the two is found.

  14. Effect of Microstructure of Cementite on Interphase Stress State in Carbon Steel

    Institute of Scientific and Technical Information of China (English)

    CHE Lei; GOTOH Masahide; HORIMOTO Yoshiaki; HIROSE Yukio

    2007-01-01

    The experiments related to stress states of ferrite and cementite in carbon steels were carried out including in situ four-point bending and tensile test by X-ray diffraction technique. Stresses in the cementite phase can be measured by conventional X-ray diffraction instrument after a specific treatment on the specimen surface. In order to estimate the stress states in two phases, the X-ray elastic constants of two phases in single-phase state (PXEC) are determined by the experimental X-ray elastic constants of them in composite state (CXEC). The effects of volume fraction and particle size of spheroidal cementite on the interphase stress state are estimated. The experimental results are in good agreement with the theoretical relationships reported in the previous studies.

  15. Orientation Relationships between Ferrite and Cementite by Edge-to-edge Matching Principle

    Institute of Scientific and Technical Information of China (English)

    Ning Zhong; Xiaodong Wang; Zhenghong Guo; Yonghua Rong

    2011-01-01

    The crystallographic features of pearlite were investigated by experiments and edge-to-edge matching principle. Two new orientation relationships between ferrite and cementite were determinated by selected area electron diffraction and then explained by our modified edge-to-edge matching method. The consistence of the experimental results with theoretical prediction confirms the practicability of the modified edge-to-edge matching model.

  16. Calculation of the valence electron structures of alloying cementite and its biphase interface

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The valence electron structures of alloying cementite θ-(Fe, M)3C and ε-(Fe, M)3C andthose of the biphase interfaces between them and α-Fe are calculated with Yu's empirical electrontheory of solid and molecules. The calculation results accord with the actual behavior of alloys.

  17. Molecular dynamics simulation study of the effect of temperature and grain size on the deformation behavior of polycrystalline cementite

    International Nuclear Information System (INIS)

    Molecular dynamics simulations combined with quantitative atomic displacement analyses were performed to study the deformation behaviors of polycrystalline cementite (Fe3C). At low temperature and large grain size, dislocation glide acts as the preferred deformation mechanism. Due to the limited number of slip systems at low temperature, polycrystalline cementite breaks by forming voids at grain boundaries upon tensile loading. When the temperature rises or the grain size reduces, grain boundary sliding becomes the primary mechanism and plastic deformation is accommodated effectively

  18. Influence of bainite morphology on impact toughness of continuously cooled cementite free bainitic steels

    OpenAIRE

    García Caballero, Francisca; Roelofs, H; Hasler, St; Capdevila, Carlos; Chao, Jesús; Cornide, Juan

    2012-01-01

    The influence of bainite morphology on the impact toughness behaviour of continuously cooled cementite-free low carbon bainitic steels has been examined. In these steels, bainitic microstructures formed mainly by lath-like upper bainite, consisting of thin and long parallel ferrite laths, were shown to exhibit higher impact toughness values than those with a granular bainite, consisting of equiaxed ferrite structure and discrete island of marteniste/austenite (M/A) constituent....

  19. Microstructure evolution and mechanical properties of eutectoid steel with ultrafine or fine (ferrite+cementite) structure

    International Nuclear Information System (INIS)

    Eutectoid steel with the ultrafine or fine-grained ferrite (α)+cementite (θ) particles structure was formed by hot deformation of undercooled austenite at 0.1 s−1 or 5 s−1 at 650 °C using a Gleeble 1500 hot simulator and subsequent annealing. The microstructural evolution of fine (α+θ) structure was investigated by means of a scanning electronic microscope, electron backscattered diffraction and transmission electron microscope, and the mechanical properties of fine (α+θ) steel were analyzed in comparison with that of ultrafine (α+θ) steel. The results show that only dynamic transformation of undercooled austenite into proeutectoid ferrite occurs during hot deformation at 650 °C at 5 s−1. During water quenching, lamellar pearlite with small colony sizes is formed and the average size of pearlite colonies decreases with increasing the strain. By subsequent annealing at 650 °C for 30 min, the spheroidization of lamellar pearlite takes place, resulting in the formation of fine (α+θ) structure consisting of ferrite matrix with the average size of about 4.9 μm and fine cementite particles mainly within ferrite grains. In comparison with ultrafine (α+θ) steel consisting of ferrite matrix with the average size of about 1.8 μm and relatively large cementite particles mostly located at grain boundaries, the yield strength, tensile strength, uniform elongation, total elongation and work-hardening capability of fine (α+θ) steel improve markedly

  20. Mechanism of carbon influence on the transition from graphite to cementite eutectic in cast iron

    Directory of Open Access Journals (Sweden)

    E. Fraś

    2010-04-01

    Full Text Available In this work an analytical solution is used to explain mechanism of carbon influence on the transition from graphite to cementite eutectic in cast iron. It is found that this transition can be related to (1 the nucleation potential of graphite (characterized directly by the cell count, N and indirectly by nucleation coefficients Ns and b (2 the growth rate coefficient of graphite eutectic cell, (3 the temperature range, Tsc = Ts - Tc (where Ts and Tc is the equilibrium temperature of the graphite eutectic and formation temperature of the cementite eutectic respectively.and (4 the liquid volume fraction, fl after solidification of the pre-eutectic austenite. Method of estimation of Ns, b and values was presented. It has been shown that the main impact of carbon on the transition from graphite to cementite eutectic consist in increasing the eutectic cell count and growth rate of graphite eutectic cell. Analytical equations were derived to describe the absolute, CT relative chilling tendency, CTr and chill, w of cast iron.

  1. Controlled manufacturing of nanoparticles by the laser pyrolysis: Application to cementite iron carbide

    International Nuclear Information System (INIS)

    The laser pyrolysis is an attractive technique for the synthesis of different nanostructures from gas-phase precursors. The characteristics of this synthesized method are here exemplified by the production of almost pure cementite Fe3C nanomaterials, obtained by the pyrolysis of methyl methacrylate and iron pentacarbonyl (vapors). Those nanopowders exhibited core (Fe3C)-shell (MMA polymer-based) morphologies and mean particle diameters of about 8-9 nm. Preliminary magnetic measurements indicate rather high values for the saturation magnetization. By irradiating the same reactive mixture with a lower intensity radiation, the chemical content of nanopowders shifts towards mixtures of iron and maghemite/magnetite iron oxides.

  2. Mechanism of free sulfur influence on the eutectic cell count and transition from graphite to cementite eutectic in cast iron. Part II. Experimental verification

    Directory of Open Access Journals (Sweden)

    E Fraś

    2010-01-01

    Full Text Available In this work the mechanism of free sulfur influence on the transition from graphite to cementite eutectic in cast iron is experimentally verified. It has been shown that the main impact of free sulfur on the transition from graphite to cementite eutectic consist in reducing the growth rate of graphite eutectic cell.

  3. Fracture and Tensile Properties of Polyvinyl Alcohol Fiber Reinforced Cementitous Composites

    Institute of Scientific and Technical Information of China (English)

    XU Shilang; GAO Shuling

    2008-01-01

    Experiments were carried out to design polyvinyl alcohol(PVA)fiber reinforced cementitous composites(PVA-FRCCs)holding high ductility and energy consumption ability.Besides,the properties of each ingredients in composites,mixing method and technology for fresh mixture were described in detail.Then,the pseudo-strain-hardening(PSH)behavior was investigated in uniaxial tension test.As a result,them maximum ultimate tensile strain can reach 0.7 percent.On the other hand,the single edge notch(SEN)thin sheet specimens were employed to gain the normal tensile load via crack mouth opening displacement(CMOD)curves,which can show obvious PSH behavior.In addition,the curves can be divided into four zones whose fracture toughness calculation methods were discussed.The wedge splitting(WS)test method can be applied to discuss the fracture toughness.Moreover,fracture energy of SEN and WS specimens were both approximately evaluated.

  4. The crystal structure of the molybdenum cementite Mo12Fe22C10 (xi-phase)

    International Nuclear Information System (INIS)

    The crystal structure of molybdenum cementite Mo12Fe22C10 (xi-phase) has been determined by means of a single crystal x-ray diffraction study of crystal fragments. The lattice parameters were found to be: a=10.865(3), b=7.767(2), c=6.559(2) A and β=120.13(2)0, space group C2/m; Z=1. From the analysis of Patterson maps and difference Fourier analysis the atomic parameters were derived, yielding a residual of R=0.059. The crystal structure contains octahedral and triangular prismatic groups which accommodate the carbon atoms in their voids, as is usually found in interstitial compounds. The octahedral building group consists of four Mo- and two Fe-atoms, the triangular prism is built up by four Fe- and two Mo-atoms. The mode of filling of the metal polyhedra is discussed. (Author)

  5. Research of the Processes of High Temperature Influence on Cementitous Concrete

    Czech Academy of Sciences Publication Activity Database

    Bodnárová, L.; Válek, J.; Sitek, Libor; Foldyna, Josef

    2013-01-01

    Roč. 19, č. 2 (2013), s. 500-503. ISSN 1936-6612 R&D Projects: GA ČR GAP104/12/1988 Grant ostatní: GA TA ČR(CZ) TA01010948 Institutional support: RVO:68145535 Keywords : cementitous concrete * high temperature influence * physicalmechanical properties Subject RIV: JN - Civil Engineering http://www.ingentaconnect.com/content/asp/asl/2013/00000019/00000002/art00031?token=0052114d07e2a46762c6b635d3e703f252e2e3e5f7a673f7b2f267738703375686f49a0e280f5d6867

  6. Cementite Formation from Hematite-Graphite Mixture by Simultaneous Thermal-Mechanical Activation

    Science.gov (United States)

    Ashrafzadeh, Milad; Soleymani, Amir Peyman; Panjepour, Masoud; Shamanian, Morteza

    2015-04-01

    In this study, the effect of simultaneous thermal-mechanical activation (STMA) process on carbothermic reduction of hematite and also on iron carbide formation has been investigated. For this purpose, the STMA process was performed for 3 and 6 hours at 973 K (700 °C) and 1073 K (800 °C) on hematite-graphite powder mixtures (with 22 wt pct C) in argon atmosphere. The XRD patterns showed that by performing this process at 973 K (700 °C), the initial hematite reduction led to the formation of wüstite in the presence of graphite. Metallic iron phase was also formed along with wüstite phase at 1073 K (800 °C) for 3 hours, and by increasing the process time to 6 hours, in addition to the metallic iron, iron carbide was also formed. The SEM images and EDS analysis obtained at 1073 K (800 °C)were also indicative of the formation of pearlite structure along with proeutectoid cementite phase and free carbon in the form of graphite in the structure of the samples. According to the results of the image analysis, the percentage of the carbon content was more than 2.22 wt pct in this process lasting for 6 hours at 1073 K (800 °C). Also, DTA results showed that the sample hot milled for 6 hours at 1073 K (800 °C) contained more than 2.1 wt pct carbon. The mechanism of metallic iron and cementite formation from hematite was proposed. Therefore, the STMA process led to an increase in the rate of carbothermic reduction of hematite to metallic iron and reduced its starting temperature relative to the non-simultaneous application of each of the thermal and mechanical activation. Finally, this process can be brought up as a new method for the production of iron carbide from iron oxides.

  7. TEM Study of the Orientation Relationship Between Cementite and Ferrite in a Bainitic Low Carbon High Strength Low Alloy Steel

    OpenAIRE

    Illescas Fernandez, Silvia; Brown, A P; He, K.; Fernández, Javier; Guilemany Casadamon, Josep Maria

    2005-01-01

    Two different bainitic structures are observed in a steel depending on the sample heat treatment. The different types of bainitic structures exhibit different orientation relationships between cementite and the ferrite matrix. Upper bainite presents a Pitsch orientation relationship and lower bainite presents a Bagaryatski orientation relationship. Different heat treatments of low carbon HSLA steel samples have been studied using TEM in order to find the orientation relationshi...

  8. The Mössbauer spectroscopy studies of ε to cementite carbides transformation during tempering of high carbon tool steel

    Directory of Open Access Journals (Sweden)

    P. Bała

    2008-08-01

    Full Text Available Purpose: This work presents results of investigations using Mössbauer spectroscopy technique and their interpretation concerning transformation of ε to cementite carbides during tempering in relation to previously conducted dilatometric, microscopic and mechanical investigations. Investigations were performed on 120MnCrMoV8-6-4-2 steel.Design/methodology/approach: Samples taken from investigated steel were austenitized at the temperature of 900ºC and hardened in oil. Austenitizing time was 20 minutes. After that, seven of eight samples were tempered. Tempering consisted of holding the samples at 200°C for defined periods. All the times mentioned above were selected basing on IHT (Isothermal Heating Transformations diagram.Findings: The influence of the tempering time on nucleation and solubility of ε carbides, and on cementite nucleation and growth, was determined.Research limitations/implications: The analysis of phase transformations during various periods of tempering using Mössbauer spectroscopy technique made possible to reveal fine details connected with the processes.Practical implications: Optimum tempering time of tools made from the investigated steel should be in the range of 1.5-2h.Originality/value: Details descriptions of ε to cementite carbides transformation during isothermal heating from as-quenched state.

  9. Comparative study and quantification of cementite decomposition in heavily drawn pearlitic steel wires

    Energy Technology Data Exchange (ETDEWEB)

    Lamontagne, A. [University of Lyon, INSA Lyon, MATEIS–UMR CNRS 5510, Bât. St Exupéry, 3ème étage, 25 Avenue Jean Capelle, Villeurbanne Cedex 69621 (France); Massardier, V., E-mail: veronique.massardier@insa-lyon.fr [University of Lyon, INSA Lyon, MATEIS–UMR CNRS 5510, Bât. St Exupéry, 3ème étage, 25 Avenue Jean Capelle, Villeurbanne Cedex 69621 (France); Kléber, X. [University of Lyon, INSA Lyon, MATEIS–UMR CNRS 5510, Bât. St Exupéry, 3ème étage, 25 Avenue Jean Capelle, Villeurbanne Cedex 69621 (France); Sauvage, X. [University of Rouen, GPM, UMR CNRS 6634, BP 12, Avenue de l’Université, 76801 Saint-Etienne du Rouvray (France); Mari, D. [Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne, Station 3, Lausanne CH-1015 (Switzerland)

    2015-09-17

    Heavily cold-drawing was performed on a pearlitic steel wire and on an ultra-low carbon (ULC) steel wire in order to highlight and quantify the microstructural changes caused by this type of deformation. Both global techniques (thermoelectric power, electrical resistivity, internal fiction background) and local techniques (Atom Probe Tomography) were combined for this study. It was shown that two distinct stages have to be taken into account during the cold-drawing of pearlitic steels. The first stage (below a true strain of 1.5) was attributed mainly to the lamellar alignment, while the second stage (above a true strain of 1.5) was unambiguously interpreted as being due to a gradual enrichment of the carbon content of ferrite arising from the strain induced cementite decomposition. The carbon content in solid solution in ferrite was assessed as a function of the true strain. All the techniques showed that this carbon content exceeds the solubility limit of carbon in the ferrite above a true strain of 2.2. A correlation between the increase in the carbon content of ferrite and the increase in yield strength was also highlighted. Moreover, a scenario was proposed to explain the microstructural changes caused by drawing.

  10. Comparative study and quantification of cementite decomposition in heavily drawn pearlitic steel wires

    International Nuclear Information System (INIS)

    Heavily cold-drawing was performed on a pearlitic steel wire and on an ultra-low carbon (ULC) steel wire in order to highlight and quantify the microstructural changes caused by this type of deformation. Both global techniques (thermoelectric power, electrical resistivity, internal fiction background) and local techniques (Atom Probe Tomography) were combined for this study. It was shown that two distinct stages have to be taken into account during the cold-drawing of pearlitic steels. The first stage (below a true strain of 1.5) was attributed mainly to the lamellar alignment, while the second stage (above a true strain of 1.5) was unambiguously interpreted as being due to a gradual enrichment of the carbon content of ferrite arising from the strain induced cementite decomposition. The carbon content in solid solution in ferrite was assessed as a function of the true strain. All the techniques showed that this carbon content exceeds the solubility limit of carbon in the ferrite above a true strain of 2.2. A correlation between the increase in the carbon content of ferrite and the increase in yield strength was also highlighted. Moreover, a scenario was proposed to explain the microstructural changes caused by drawing

  11. The Moessbauer Spectroscopy Studies of ε to Cementite Carbides Transformation during Isothermal Heating from As-Quenched State of High Carbon Tool Steel

    International Nuclear Information System (INIS)

    This work presents results of investigations using the Moessbauer spectroscopy technique and their interpretation concerning transformation of ε to cementite carbides during tempering in relation to the previously conducted dilatometric, microscopic and mechanical investigations. Investigations were performed on 120MnCrMoV8-6-4-2 steel. The influence of the tempering time on nucleation and solubility of ε carbides, and on cementite nucleation and growth, was determined. The analysis of phase transformations during various periods of tempering using the Moessbauer spectroscopy technique made possible to reveal fine details connected with the processes. (authors)

  12. Bainite transformation of low carbon Mn-Si TRIP-assisted multiphase steels: influence of silicon content on cementite precipitation and austenite retention

    International Nuclear Information System (INIS)

    Studies dealing with TRIP-assisted multiphase steels have emphasized the crucial role of the bainite transformation of silicon-rich intercritical austenite in the achievement of a good combination of strength and ductility. The present work deals with the bainite transformation in two steels differing in their silicon content. It is shown that both carbon enrichment of residual austenite and cementite precipitation influences the kinetics of the bainite transformation. A minimum silicon content is found to be necessary in order to prevent cementite precipitation from austenite during the formation of bainitic ferrite in such a way as to allow stabilisation of austenite by carbon enrichment. (orig.)

  13. Analysis of the variation in nanohardness of pearlitic steel: Influence of the interplay between ferrite crystal orientation and cementite morphology

    Energy Technology Data Exchange (ETDEWEB)

    Debehets, Jolien, E-mail: jolien.debehets@mtm.kuleuven.be [Department of Materials Engineering, KU Leuven, University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Leuven (Belgium); Tacq, Jeroen [Department of Materials Engineering, KU Leuven, University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Leuven (Belgium); Favache, Audrey; Jacques, Pascal [Institute of Mechanics, Materials and Civil Engineering, Université catholique de Louvain, Place Sainte Barbe 2 L5.02.02, 1348 Louvain-la-Neuve (Belgium); Seo, Jin Won; Verlinden, Bert; Seefeldt, Marc [Department of Materials Engineering, KU Leuven, University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Leuven (Belgium)

    2014-10-20

    The influence of the relative orientation of the ferrite crystallite lattice and the cementite lamellae on the hardness of pearlitic steel has been investigated by a combination of nanoindentation and electron microscopy (electron back scatter diffraction (EBSD) and scanning electron microscopy (SEM)). Three pearlitic samples, each with a different interlamellar spacing, and one ferritic sample were nanoindented. Although the hardness of the ferritic sample is very similar at different spots on the sample, a large variation in hardness is obtained on each of the pearlitic samples. It has been found that this variation cannot be accounted for solely by the variation in interlamellar spacing and is related to differences in ferrite crystal orientation. As to explain the observed large variation in hardness, the ferrite crystal orientation was considered relative to the cementite lamellae orientation by calculation of the distance dislocations can glide between adjacent lamellae in the slip direction. However, no clear correlation was found for a scaling of this orientation factor with the hardness. Possible interpretations of this discrepancy are suggested.

  14. Analysis of the variation in nanohardness of pearlitic steel: Influence of the interplay between ferrite crystal orientation and cementite morphology

    International Nuclear Information System (INIS)

    The influence of the relative orientation of the ferrite crystallite lattice and the cementite lamellae on the hardness of pearlitic steel has been investigated by a combination of nanoindentation and electron microscopy (electron back scatter diffraction (EBSD) and scanning electron microscopy (SEM)). Three pearlitic samples, each with a different interlamellar spacing, and one ferritic sample were nanoindented. Although the hardness of the ferritic sample is very similar at different spots on the sample, a large variation in hardness is obtained on each of the pearlitic samples. It has been found that this variation cannot be accounted for solely by the variation in interlamellar spacing and is related to differences in ferrite crystal orientation. As to explain the observed large variation in hardness, the ferrite crystal orientation was considered relative to the cementite lamellae orientation by calculation of the distance dislocations can glide between adjacent lamellae in the slip direction. However, no clear correlation was found for a scaling of this orientation factor with the hardness. Possible interpretations of this discrepancy are suggested

  15. Simultaneous characterization of elemental segregation and cementite networks in high carbon steel products by spatially-resolved laser-induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    The reliable characterization of the level of elemental segregation and of the extent of grain-boundary cementite networks in high carbon steel products is a prerequisite for checking product quality, for the purpose of product release to customers, and to investigate the presence of defects that may have led to mechanical property failure of the product. Current methods for the characterization of segregation and cementite networks rely on two different methods of sample etching followed by visual observation, where quality scores are given based on human perception and judgment. With the continuous demand on increasing quality, some of the conventional characterization methods and their associated scoring boards have lost relevance for the precision of characterization that is required today to distinguish between a product that will perform well and one that will not. In order to move away from a qualitative, human perception based situation for the scoring of the severity of segregation and cementite networks, a new method of data evaluation based on spatially-resolved LIBS measurements was developed to provide quantitative and simultaneous characterization of both types of defects. The quantitative assessment of segregation and cementite networks is based on the acquisition of carbon concentration maps. The ability to produce rapid scanning measurements of micro and macro-scale features with adequate spatial resolution makes LIBS the measurement method of preference for this purpose. The characterization of both different defects is extracted simultaneously and from the same carbon concentration map following a series of statistical treatment and data extraction rules. LIBS results were validated against recognized methods and were applied to a significant number of routine samples. The new LIBS method offers a step change improvement in reliability for the characterization of segregation and cementite networks in steel products over the conventional methods

  16. The Moessbauer Spectroscopy Studies of Cementite Precipitations during Continuous Heating from As-Quenched State of High Carbon Cr-Mn-Mo Steel

    International Nuclear Information System (INIS)

    This work complements the knowledge concerning the kinetics of cementite precipitation during tempering. Investigations were performed on 120MnCrMoV8-6-4-2 steel. The samples of investigated steel were austenitized at the temperature of 900oC and quenched in oil. Then four of five samples were tempered. Tempering consisted of heating the samples up to chosen temperatures at the heating rate of 0.05oC/s and fast cooling after reaching desired temperature. This work presents the results of investigations performed carried out using the Moessbauer spectroscopy technique and their interpretation concerning cementite nucleation and growth during tempering. The values of hyperfine magnetic field on 57Fe atomic nuclei, determined for the third component of the Moessbauer spectrum as regards to its intensity, indicate that these are the components coming from ferromagnetic carbides. Big differences in hyperfine magnetic fields coming from Fe atoms existing in the structure of carbides, measured on samples heated up to the temperatures of 80oC and 210oC, in comparison with values for 57Fe atoms precipitated from carbides during heating up to the temperature of 350oC and 470oC, allow to state that these are the carbides of different crystal structure. The influence of hardened steel heating temperature on cementite precipitation was determined. The Moessbauer spectroscopy was applied not only for magnetic hyperfine field studies, but also to analyze the values of quadrupole splitting and isomeric shift, which resulted in significant conclusions concerning the changes in cementite precipitations morphology, chemical composition and the level of stresses being present in this research. (authors)

  17. A first-principles study of cementite (Fe3C and its alloyed counterparts: Elastic constants, elastic anisotropies, and isotropic elastic moduli

    Directory of Open Access Journals (Sweden)

    G. Ghosh

    2015-08-01

    Full Text Available A comprehensive computational study of elastic properties of cementite (Fe3C and its alloyed counterparts (M3C (M = Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Si, Ta, Ti, V, W, Zr, Cr2FeC and CrFe2C having the crystal structure of Fe3C is carried out employing electronic density-functional theory (DFT, all-electron PAW pseudopotentials and the generalized gradient approximation for the exchange-correlation energy (GGA. Specifically, as a part of our systematic study of cohesive properties of solids and in the spirit of materials genome, following properties are calculated: (i single-crystal elastic constants, Cij, of above M3Cs; (ii anisotropies of bulk, Young’s and shear moduli, and Poisson’s ratio based on calculated Cijs, demonstrating their extreme anisotropies; (iii isotropic (polycrystalline elastic moduli (bulk, shear, Young’s moduli and Poisson’s ratio of M3Cs by homogenization of calculated Cijs; and (iv acoustic Debye temperature, θD, of M3Cs based on calculated Cijs. We provide a critical appraisal of available data of polycrystalline elastic properties of alloyed cementite. Calculated single crystal properties may be incorporated in anisotropic constitutive models to develop and test microstructure-processing-property-performance links in multi-phase materials where cementite is a constituent phase.

  18. A first-principles study of cementite (Fe3C) and its alloyed counterparts: Elastic constants, elastic anisotropies, and isotropic elastic moduli

    Science.gov (United States)

    Ghosh, G.

    2015-08-01

    A comprehensive computational study of elastic properties of cementite (Fe3C) and its alloyed counterparts (M3C (M = Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Si, Ta, Ti, V, W, Zr, Cr2FeC and CrFe2C) having the crystal structure of Fe3C is carried out employing electronic density-functional theory (DFT), all-electron PAW pseudopotentials and the generalized gradient approximation for the exchange-correlation energy (GGA). Specifically, as a part of our systematic study of cohesive properties of solids and in the spirit of materials genome, following properties are calculated: (i) single-crystal elastic constants, Cij, of above M3Cs; (ii) anisotropies of bulk, Young's and shear moduli, and Poisson's ratio based on calculated Cijs, demonstrating their extreme anisotropies; (iii) isotropic (polycrystalline) elastic moduli (bulk, shear, Young's moduli and Poisson's ratio) of M3Cs by homogenization of calculated Cijs; and (iv) acoustic Debye temperature, θD, of M3Cs based on calculated Cijs. We provide a critical appraisal of available data of polycrystalline elastic properties of alloyed cementite. Calculated single crystal properties may be incorporated in anisotropic constitutive models to develop and test microstructure-processing-property-performance links in multi-phase materials where cementite is a constituent phase.

  19. A first-principles study of cementite (Fe{sub 3}C) and its alloyed counterparts: Elastic constants, elastic anisotropies, and isotropic elastic moduli

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, G., E-mail: g-ghosh@northwestern.edu [Department of Materials Science and Engineering, Robert R. McCormick School of Engineering and Applied Science, Northwestern University, 2220 Campus Drive, Evanston, IL 60208-3108 (United States)

    2015-08-15

    A comprehensive computational study of elastic properties of cementite (Fe{sub 3}C) and its alloyed counterparts (M{sub 3}C (M = Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Si, Ta, Ti, V, W, Zr, Cr{sub 2}FeC and CrFe{sub 2}C) having the crystal structure of Fe{sub 3}C is carried out employing electronic density-functional theory (DFT), all-electron PAW pseudopotentials and the generalized gradient approximation for the exchange-correlation energy (GGA). Specifically, as a part of our systematic study of cohesive properties of solids and in the spirit of materials genome, following properties are calculated: (i) single-crystal elastic constants, C{sub ij}, of above M{sub 3}Cs; (ii) anisotropies of bulk, Young’s and shear moduli, and Poisson’s ratio based on calculated C{sub ij}s, demonstrating their extreme anisotropies; (iii) isotropic (polycrystalline) elastic moduli (bulk, shear, Young’s moduli and Poisson’s ratio) of M{sub 3}Cs by homogenization of calculated C{sub ij}s; and (iv) acoustic Debye temperature, θ{sub D}, of M{sub 3}Cs based on calculated C{sub ij}s. We provide a critical appraisal of available data of polycrystalline elastic properties of alloyed cementite. Calculated single crystal properties may be incorporated in anisotropic constitutive models to develop and test microstructure-processing-property-performance links in multi-phase materials where cementite is a constituent phase.

  20. TEM study of bainitic low-carbon HSLA steel: the orientation relationships of cementite; TEM-Untersuchung eines kohlenstoffarmen bainitischen HSLA-Stahls: die Orientierungsbeziehungen von Zementit

    Energy Technology Data Exchange (ETDEWEB)

    Illescas, S.; Fernandez, J.; Guilemany, J.M. [Barcelona Univ. (Spain). Dept. de Ciencia dels Materials i Enginyeria Metallurgica; Asensio, J. [Oviedo Univ. (Spain). Dept. de Ciencia de los Materiales e Ingenieria Metalurgica

    2007-07-15

    Two different bainitic structures can be present in steel depending on the heat treatment to which the samples are subjected. The two different types of bainitic structures exhibit a different orientation relationship between the cementite and the ferrite matrix. The Pitsch orientation relationship is observed in upper bainite while the Bagaryatski orientation relationship is observed in lower bainite. Different heat treatment samples of low-carbon high strength low alloy (HSLA) steel were studied using TEM observations in order to ascertain the orientation relationship between ferrite and carbide in the different bainitic structures and to determine whether this relationship may indicate the type of bainitic structure. (orig.)

  1. REFERENCE CASES FOR USE IN THE CEMENTITOUS PARTNERSHIP PROJECT

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Kosson, D.; Garrabrants, A.

    2010-08-31

    The Cementitious Barriers Partnership Project (CBP) is a multi-disciplinary, multi-institution cross cutting collaborative effort supported by the US Department of Energy (DOE) to develop a reasonable and credible set of tools to improve understanding and prediction of the structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. The period of performance is >100 years for operating facilities and > 1000 years for waste management. The CBP has defined a set of reference cases to provide the following functions: (i) a common set of system configurations to illustrate the methods and tools developed by the CBP, (ii) a common basis for evaluating methodology for uncertainty characterization, (iii) a common set of cases to develop a complete set of parameter and changes in parameters as a function of time and changing conditions, (iv) a basis for experiments and model validation, and (v) a basis for improving conceptual models and reducing model uncertainties. These reference cases include the following two reference disposal units and a reference storage unit: (i) a cementitious low activity waste form in a reinforced concrete disposal vault, (ii) a concrete vault containing a steel high-level waste tank filled with grout (closed high-level waste tank), and (iii) a spent nuclear fuel basin during operation. Each case provides a different set of desired performance characteristics and interfaces between materials and with the environment. Examples of concretes, grout fills and a cementitious waste form are identified for the relevant reference case configurations.

  2. Morphology of the cementite in archaeological steels that have suffered fire

    International Nuclear Information System (INIS)

    We present a metallographic study of archaeological artefacts of steel, had been found in different archaeological sites, which characteristic microstructures reveal that have been affected by levels of fire. Study was performed using FEG (Field Emission Gun). In the laboratory, they are reproduced structures of steels archaeological. (Author)

  3. Research of the Processes of High Temperature Influence on Cementitous Concrete

    OpenAIRE

    Bodnárová, L.; Válek, J. (Jan); Sitek, L. (Libor); Foldyna, J.

    2013-01-01

    The paper focuses on analysis of behaviour of cement composite materials (concrete) exposed to high temperatures. Experimental work was focused on designing and verification of mix-design with higher resistance to action of high temperature. Concrete specimens were exposed to thermal load at the temperatures 200 °C, 400 °C, 600 °C and 900 °C with isothermal dwell 60 minutes. After exposition to high temperature, physicalmechanical properties were tested and compared to reference specimens, wh...

  4. Cementite-free martensitic steels: A new route to develop high strength/high toughness grades by modifying the conventional precipitation sequence during tempering

    International Nuclear Information System (INIS)

    Aluminium was added to a 0.2% C–2.5% Cr–1.4% Mo–11% Ni steel to modify the precipitation sequence during tempering treatment. The main goal was to obtain fine co-precipitation of an intermetallic phase and M2C carbides (where M is a combination of Cr, Mo and small amounts of Fe). Small angle neutron scattering, synchrotron X-ray diffraction, transmission electron microscopy and atom probe tomography were performed to characterize the nanometric precipitation. The tempering response of samples austenitized at 900 °C revealed a strong interaction between the two types of precipitation, leading to a significant modification of both the precipitation sequence of carbides and the arrangement of carbide nucleation sites compared with these sites in a single precipitation steel. Indeed, a microstructural investigation clearly showed that iron carbide precipitation was either delayed or did not occur during the tempering process, depending of the alloying elements added. Moreover, double precipitation directly influenced the mechanical resistance, as well as the toughness, leading to an ultrahigh-strength, high toughness steel.

  5. Morphology of the cementite in archaeological steels that have suffered fire; Morfologia de la cementita en aceros arqueologicos que han sufrido incendio

    Energy Technology Data Exchange (ETDEWEB)

    Criado-Martin, A. J.; Garcia, L.; Carton, M.; Criado-Portal, A. J.; Dietz, C.; Martinez, J. A.

    2013-07-01

    We present a metallographic study of archaeological artefacts of steel, had been found in different archaeological sites, which characteristic microstructures reveal that have been affected by levels of fire. Study was performed using FEG (Field Emission Gun). In the laboratory, they are reproduced structures of steels archaeological. (Author)

  6. Influence of Carbide Precipitation and Dissolution on the Microstructure of Ultra-Fine-Grained Intercritically Annealed Medium Manganese Steel

    Science.gov (United States)

    Lee, Sangwon; De Cooman, Bruno C.

    2016-04-01

    The influence of cementite precipitation and dissolution on the formation of the carbide-free, ultra-fine-grained, ferrite + austenite microstructure of medium manganese steel was analyzed. During heating to the intercritical temperature, cementite nucleates at low-angle lath martensite boundaries, austenite subsequently nucleates at ferrite/cementite boundaries, and the cementite is gradually replaced by the growing austenite grains. The intercritical austenite carbon is therefore due to cementite dissolution, rather than carbon partitioning between ferrite and austenite.

  7. Influence of Carbide Precipitation and Dissolution on the Microstructure of Ultra-Fine-Grained Intercritically Annealed Medium Manganese Steel

    Science.gov (United States)

    Lee, Sangwon; De Cooman, Bruno C.

    2016-07-01

    The influence of cementite precipitation and dissolution on the formation of the carbide-free, ultra-fine-grained, ferrite + austenite microstructure of medium manganese steel was analyzed. During heating to the intercritical temperature, cementite nucleates at low-angle lath martensite boundaries, austenite subsequently nucleates at ferrite/cementite boundaries, and the cementite is gradually replaced by the growing austenite grains. The intercritical austenite carbon is therefore due to cementite dissolution, rather than carbon partitioning between ferrite and austenite.

  8. Determination of the easy axes of small ferromagnetic precipitates in a bulk material by combined magnetic force microscopy and electron backscatter diffraction techniques

    International Nuclear Information System (INIS)

    A method to determine the magnetic easy axes of micro- and nanoscopic ferromagnetic precipitates embedded in a bulk material is proposed and applied to globular cementite (Fe3C) embedded in a ferrite matrix. The method combines magnetic force microscopy (MFM) with electron backscattered diffraction (EBSD) measurements. Magnetic domain structures in globular and in lamellar cementite precipitates in unalloyed pearlitic steels were imaged using MFM. The domain structure of the precipitates was analyzed in dependency of their size, shape and crystallographic orientation. It was found that the magnetic moments of the cementite precipitates are highly geared to their crystalline axes. The combined MFM and EBSD studies allow the conclusion that the cementite easy direction of magnetization is the long [010] axis. For fine lamellae cementite the determination of their crystallographic orientations using electron diffraction techniques is very difficult. With the previous knowledge of the behavior of the domain structure in globular cementite, the crystalline orientations of the fine lamellae cementite can be estimated by simply observing the magnetic microstructures and the topographic profiles. - Highlights: • We develop a method to determine the easy axes of nanoscopic ferromagnetic precipitates in a matrix. • We combine the magnetic force microscopy and the electron backscatter diffraction techniques. • Globular and lamellar cementite (Fe3C) precipitates are taken as examples. • MFM images revealed different orientations of the magnetic moments in cementite. • The cementite easy direction of magnetization is the long [010] axis

  9. Molecular dynamics simulation of nanoindentation on nanocomposite pearlite

    OpenAIRE

    Ghaffarian, Hadi; Taheri, Ali Karimi; Ryu, Seunghwa; Kang, Keonwook

    2016-01-01

    We carry out molecular dynamics simulations of nanoindentation to investigate the effect of cementite size and temperature on the deformation behavior of nanocomposite pearlite composed of alternating ferrite and cementite layers. We find that, instead of the coherent transmission, dislocation propagates by forming a widespread plastic deformation in cementite layer. We also show that increasing temperature enhances the distribution of plastic strain in the ferrite layer, which reduces the st...

  10. Microstructure of Hot Rolled 1.0C-1.5Cr Bearing Steel and Subsequent Spheroidization Annealing

    Science.gov (United States)

    Li, Zhen-Xing; Li, Chang-Sheng; Zhang, Jian; Li, Bin-Zhou; Pang, Xue-Dong

    2016-07-01

    The effect of final rolling temperature and cooling process on the microstructure of 1.0C-1.5Cr bearing steel was studied, and the relationship between the microstructure parameters and subsequent spheroidization annealing was analyzed. The results indicate that the increase of water-cooling rate after hot rolling and the decrease of final cooling temperature are beneficial to reducing both the pearlite interlamellar spacing and pearlite colony size. Prior austenite grain size can be reduced by decreasing the final rolling temperature and increasing the water-cooling rate. When the final rolling temperature was controlled around 1103 K (830 °C), the subsequent cooling rate was set to 10 K/s and final cooling temperature was 953 K (680 °C), the precipitation of grain boundary cementite was suppressed effectively and lots of rod-like cementite particles were observed in the microstructure. Interrupted quenching was employed to study the dissolution behavior of cementite during the austenitizing at 1073 K (800 °C). The decrease of both pearlite interlamellar spacing and pearlite colony size could facilitate the initial dissolution and fragmentation of cementite lamellae, which could shorten the spheroidization time. The fragmentation of grain boundary cementite tends to form large-size undissolved cementite particles. With the increase of austenitizing time from 20 to 300 minutes, mean diameter of undissolved cementite particles increases, indicating the cementite particle coarsening and cementite dissolution occuring simultaneously. Mean diameter of cementite particles in the final spheroidized microstructure is proportional to the mean diameter of undissolved cementite particles formed during partial austenitizing.

  11. Magnetic carbon nanostructures: microwave energy-assisted pyrolysis vs. conventional pyrolysis.

    Science.gov (United States)

    Zhu, Jiahua; Pallavkar, Sameer; Chen, Minjiao; Yerra, Narendranath; Luo, Zhiping; Colorado, Henry A; Lin, Hongfei; Haldolaarachchige, Neel; Khasanov, Airat; Ho, Thomas C; Young, David P; Wei, Suying; Guo, Zhanhu

    2013-01-11

    Magnetic carbon nanostructures from microwave assisted- and conventional-pyrolysis processes are compared. Unlike graphitized carbon shells from conventional heating, different carbon shell morphologies including nanotubes, nanoflakes and amorphous carbon were observed. Crystalline iron and cementite were observed in the magnetic core, different from a single cementite phase from the conventional process. PMID:23172110

  12. Atomic scale investigation of redistribution of alloying elements in pearlitic steel wires upon cold-drawing and annealing.

    Science.gov (United States)

    Li, Y J; Choi, P; Goto, S; Borchers, C; Raabe, D; Kirchheim, R

    2013-09-01

    A local electrode atom probe has been employed to analyze the redistribution of alloying elements including Si, Mn, and Cr in pearlitic steel wires upon cold-drawing and subsequent annealing. It has been found that the three elements undergo mechanical mixing upon cold-drawing at large strains, where Mn and Cr exhibit a nearly homogeneous distribution throughout both ferrite and cementite, whereas Si only dissolves slightly in cementite. Annealing at elevated temperatures leads to a reversion of the mechanical alloying. Si atoms mainly segregate at well-defined ferrite (sub)grain boundaries formed during annealing. Cr and Mn are strongly concentrated in cementite adjacent to the ferrite/cementite interface due to their lower diffusivities in cementite than in ferrite. PMID:23237772

  13. Atomic scale investigation of redistribution of alloying elements in pearlitic steel wires upon cold-drawing and annealing

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y.J., E-mail: y.li@mpie.de [Institut für Materialphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Max-Planck Institut für Eisenforschung, Max-Planck-Str. 1, D-40237 Düsseldorf (Germany); Choi, P. [Max-Planck Institut für Eisenforschung, Max-Planck-Str. 1, D-40237 Düsseldorf (Germany); Goto, S. [Department of Materials Science and Engineering, Faculty of Engineering and Resource Science, Akita University, Tegata Gakuencho, Akita 010-8502 (Japan); Borchers, C. [Institut für Materialphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Raabe, D., E-mail: d.raabe@mpie.de [Max-Planck Institut für Eisenforschung, Max-Planck-Str. 1, D-40237 Düsseldorf (Germany); Kirchheim, R. [Institut für Materialphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Max-Planck Institut für Eisenforschung, Max-Planck-Str. 1, D-40237 Düsseldorf (Germany)

    2013-09-15

    A local electrode atom probe has been employed to analyze the redistribution of alloying elements including Si, Mn, and Cr in pearlitic steel wires upon cold-drawing and subsequent annealing. It has been found that the three elements undergo mechanical mixing upon cold-drawing at large strains, where Mn and Cr exhibit a nearly homogeneous distribution throughout both ferrite and cementite, whereas Si only dissolves slightly in cementite. Annealing at elevated temperatures leads to a reversion of the mechanical alloying. Si atoms mainly segregate at well-defined ferrite (sub)grain boundaries formed during annealing. Cr and Mn are strongly concentrated in cementite adjacent to the ferrite/cementite interface due to their lower diffusivities in cementite than in ferrite. - Highlights: ► Mechanical alloying effect is studied on Mn, Si, and Cr in pearlite. ► Severe cold-drawing forces Mn and Cr into the ferrite. ► Si is only somewhat forced into the cementite. ► Following annealing, Si prefers to segregate at ferrite (sub)grain boundaries. ► Following annealing, Cr and Mn are strongly enriched in cementite.

  14. Thermodynamic mapping of austenite decomposition’s approach toward equilibrium in Fe–C–Mn at 700 °C

    International Nuclear Information System (INIS)

    Transformation of Fe–0.85C–11.56Mn (wt.%) at 700 °C begins by formation of grain boundary cementite in conjunction with carbon and manganese partitioning. Grain boundary cementite formation initiates regional partitioning of manganese from austenite to cementite that continues over months of cementite growth. The large disparity between manganese volume and grain boundary diffusion in austenite highlights why grain boundaries are associated with all stages of the 700 °C phase transformation in this system. Therefore, unlike carbon, manganese partitioning associated with cementite growth is localized to the immediate region near the grain boundary/cementite reaction front. The reaction path involves austenite ‘neighborhoods’, defined to have manganese chemistries and, consequently, thermodynamic properties different from the majority of the remaining matrix. The remaining matrix does partition carbon but not manganese. Along with differences between grain boundary and matrix manganese diffusivity in austenite, diffusion of carbon is up to 106 times greater than that of manganese resulting in carbon activity in austenite equilibrating at each step of cementite growth. The concept of neighborhood thermodynamics is developed for these altered austenite regions and directed toward producing a transformation pathway analysis. The concept of local equilibrium is also demonstrated not to be viable as a method for phase transformation tracking and thermodynamic mapping as the reaction moves toward equilibrium

  15. Microstructure and strengthening mechanisms in cold-drawn pearlitic steel wire

    DEFF Research Database (Denmark)

    Zhang, Xiaodan; Godfrey, Andy; Huang, Xiaoxu;

    2011-01-01

    .5. At a higher strain enhanced thinning of the cementite lamellae points to decomposition of the cementite and carbon enrichment of the ferrite lamellae. Dislocations are stored in the interior of the ferrite lamellae and their density increases to about 2×1016m−2. A high dislocation density is also...... observed at the ferrite/cementite interface. Three strengthening mechanisms have been analyzed: (i) boundary strengthening, (ii) dislocation strengthening and (iii) solid solution hardening. The individual and combined contributions, based on an assumption of linear additivity, of these mechanisms to the...

  16. Mechanism of Austenite Formation from Spheroidized Microstructure in an Intermediate Fe-0.1C-3.5Mn Steel

    Science.gov (United States)

    Lai, Qingquan; Gouné, Mohamed; Perlade, Astrid; Pardoen, Thomas; Jacques, Pascal; Bouaziz, Olivier; Bréchet, Yves

    2016-05-01

    The austenitization from a spheroidized microstructure during intercritical annealing was studied in a Fe-0.1C-3.5Mn alloy. The austenite grains preferentially nucleate and grow from intergranular cementite. The nucleation at intragranular cementite is significantly retarded or even suppressed. The DICTRA software, assuming local equilibrium conditions, was used to simulate the austenite growth kinetics at various temperatures and for analyzing the austenite growth mechanism. The results indicate that both the mode and the kinetics of austenite growth strongly depend on cementite composition. With sufficiently high cementite Mn content, the austenite growth is essentially composed of two stages, involving the partitioning growth controlled by Mn diffusion inside ferrite, followed by a stage controlled by Mn diffusion within austenite for final equilibration. The partitioning growth results in a homogeneous distribution of carbon within austenite, which is supported by NanoSIMS carbon mapping.

  17. Mechanism of Austenite Formation from Spheroidized Microstructure in an Intermediate Fe-0.1C-3.5Mn Steel

    Science.gov (United States)

    Lai, Qingquan; Gouné, Mohamed; Perlade, Astrid; Pardoen, Thomas; Jacques, Pascal; Bouaziz, Olivier; Bréchet, Yves

    2016-07-01

    The austenitization from a spheroidized microstructure during intercritical annealing was studied in a Fe-0.1C-3.5Mn alloy. The austenite grains preferentially nucleate and grow from intergranular cementite. The nucleation at intragranular cementite is significantly retarded or even suppressed. The DICTRA software, assuming local equilibrium conditions, was used to simulate the austenite growth kinetics at various temperatures and for analyzing the austenite growth mechanism. The results indicate that both the mode and the kinetics of austenite growth strongly depend on cementite composition. With sufficiently high cementite Mn content, the austenite growth is essentially composed of two stages, involving the partitioning growth controlled by Mn diffusion inside ferrite, followed by a stage controlled by Mn diffusion within austenite for final equilibration. The partitioning growth results in a homogeneous distribution of carbon within austenite, which is supported by NanoSIMS carbon mapping.

  18. CEL Working procedures for WRAP 2A formulation development test

    International Nuclear Information System (INIS)

    The WRAP 2A facility will encapsulate retrieved, stored, and newly generated contact-handled mixed low level waste (MLLW) into 55-500 gal cementitous forms. Standardized test procedures will be required to facilitate this process. Cementitous specimens will be prepared from simulated drum wastes and will be tested in the Chemical Engineering Laboratory using the laboratory operating/working procedures encorporated into this document

  19. The Effects of Fracture Origin Size on Fatigue Properties of Ductile Cast Iron with Small Chill Structures

    Science.gov (United States)

    Sameshima, Daigo; Nakamura, Takashi; Horikawa, Noritaka; Oguma, Hiroyuki; Endo, Takeshi

    Reducing the weight of a machine structure is an increasingly important consideration both for the conservation of resources during production and for the energy saving during operation. With these objectives in mind, thin-walled ductile cast iron has recently been developed. Because rapid cooling could result in brittle microstructure of cementite (chill) in this cast iron, it is necessary to investigate the effect of cementite on the fatigue properties. Therefore, fatigue tests were carried out on a ductile cast iron of block castings which contained a relatively small amount of cementite. Fracture surface observation indicated that the fracture origins were located at graphite clusters and cast shrinkage porosity, not at cementite. It appears that when the size of the cementite is smaller than that of the graphite, the cementite does not affect the fatigue properties of ductile cast iron. Not surprisingly, the fatigue lives were found to increase with decrease in the size of the fatigue fracture origin. The threshold initial stress intensity factor range ΔKini,th for fatigue failure was found to be about 3-4MPa√m, independent of microstructure.

  20. Microstructure and strengthening mechanisms in cold-drawn pearlitic steel wire

    International Nuclear Information System (INIS)

    Highlights: → Interlamellar spacing and thickness of cementite lamellae decrease in accordance with change in diameter of drawn pearlitic steel wire up to strain of 2.5. → At higher strains enhanced thinning of cementite lamellae points to decomposition of cementite and carbon enrichment of ferrite. → Dislocations are stored in ferrite lamellae and their density increases to about 2 x 1016 m-2 as determined by HRTEM. → Contributions of boundary strengthening, dislocation strengthening and solid solution hardening are estimated and by addition. Good agreement is found between estimated and measured flow stress. - Abstract: Strengthening mechanisms and strength-structure relationships have been analyzed in a cold-drawn pearlitic steel with a structural scale in the nanometer range and a flow stress of about 3.5 GPa. The wires have been drawn up to a strain of 3.7 and the structures analyzed and quantified by transmission electron microscopy and high resolution electron microscopy. The mechanical properties have been determined by tensile testing. It is found that the interlamellar spacing and the thickness of the cementite lamellae are reduced in accordance with the changes in wire diameter up to a strain of 2.5. At a higher strain enhanced thinning of the cementite lamellae points to decomposition of the cementite and carbon enrichment of the ferrite lamellae. Dislocations are stored in the interior of the ferrite lamellae and their density increases to about 2 x 1016 m-2. A high dislocation density is also observed at the ferrite/cementite interface. Three strengthening mechanisms have been analyzed: (i) boundary strengthening, (ii) dislocation strengthening and (iii) solid solution hardening. The individual and combined contributions, based on an assumption of linear additivity, of these mechanisms to the wire strength have been estimated. Good agreement has been found between the estimated and the measured flow stresses, which is followed up by a

  1. Microstructural Characterization and Mechanical Properties Analysis of Weld Metals with Two Ni Contents During Post-Weld Heat Treatments

    Science.gov (United States)

    Wu, Da-yong; Han, Xiu-lin; Tian, Hong-tao; Liao, Bo; Xiao, Fu-ren

    2015-05-01

    This study designed post-weld heat treatments, including reheating and tempering, associated with hot bending to investigate the microstructures, toughness, and hardness of two weld metals with different Ni contents (ferrite transformation temperature and increased the proportion of acicular ferrite (AF). Furthermore, a high Ni content promoted the martensite/austenite (M/A) constituent formation after reheating. The promotion of the M/A formation increased the number of cementite particles, and accelerated cementite coarsening during tempering. The large-angle grain boundary density from the AF improved the toughness despite the negative effect of cementite. The strengthening contributions were calculated, and the grain refinement was the greatest. The high Ni content decreased the effective grain size with a 2 deg tolerance angle, thus enhancing the grain refinement contribution.

  2. Revealing microstructural and mechanical characteristics of cold-drawn pearlitic steel wires undergoing simulated galvanization treatment

    International Nuclear Information System (INIS)

    Highlights: ► Annealing time on microstructure and mechanical properties of cold-drawn steel wires were studied. ► Exothermic peak in cold-drawn wire was resulting from the spheroidization of lamellar cementite. ► Spheroidization of lamellar cementite is the main effect for torsion property of wires after annealing. - Abstract: Spheroidization of lamellar cementite often occurs in cold-drawn pearlitic steel wires during galvanizing treatment, leading to the degradation of mechanical properties. Therefore, it is important to understand effects of galvanization process on microstructure and mechanical properties of cold-drawn wires. In this paper, cold-drawn steel wires were fabricated by cold drawing pearlitic steel rods from 13 mm to 6.9 mm in diameter. Thermal annealing at 450 °C was used to simulate galvanizing treatment of steel wires. Tensile strength, elongation and torsion laps of steel rods and wires with, and without, annealing treatment were determined. Microstructure was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, differential scanning calorimetry (DSC) was used to probe the spheroidization temperature of cementite. Experimental results showed that tensile strength of wires increased from 1780 MPa to 1940 MPa for annealing 10 min. Elongation of wires decreased for annealing 5 min. Tensile strength and elongation of wires were both influenced by the strain age hardening and static recovery processes. Notably, torsion laps of wires hardly changed when annealing time was less than 2.5 min, and then decreased rapidly. Its value became constant when the hold time is greater than 10 min. Lamellar cementite began to spheroidize at annealing >2.5 min, starting at the boundary of pearlitic grains, and moving inward. A broad exothermic peak was found at temperatures between 380 °C and 480 °C, resulting primarily from the spheroidization of lamellar cementite, which is responsible for the

  3. Micro- and nanostructure characterization and imaging of TWIP and unalloyed steels

    Science.gov (United States)

    Batista, L.; Rabe, U.; Hirsekorn, S.

    2012-05-01

    New design concepts for constructing light-weight and crash resistant transportation systems require the development of high strength and supra-ductile steels with enhanced energy absorption and reduced specific weight. TWIP steels combine these properties, a consequence of intensive mechanical twinning. To understand the mechanisms, related microstructures and local material properties are probed by AFAM, nanoindentation, and EBSD. The morphology of a cementite phase controls the macroscopic mechanical and magnetic properties of steels. Cementite embedded in a ferrite matrix is characterized by AFAM and MFM.

  4. Hierarchical structures in cold-drawn pearlitic steel wire

    International Nuclear Information System (INIS)

    The microstructure and crystallography of drawn pearlitic steel wires have been quantified by a number of electron microscopy techniques including scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction and nanobeam diffraction, with focus on the change in the structure and crystallography when a randomly oriented cementite structure in a patented wire during wire drawing is transformed into a lamellar structure parallel to the drawing axis. Changes in the interlamellar spacing and in the misorientation angle along and across the ferrite lamellae show significant through-diameter variations in wires drawn to large strains ⩾ 1.5. The structural evolution is hierarchical as the structural variations have their cause in a different macroscopic orientation of the cementite in the initial (patented) structure with respect to the wire axis. The through-diameter variations subdivide the lamellar structure into two distinctly different types: one (called AA) has a smaller interlamellar spacing and smaller dislocation density than the other (called ABC). During drawing, the thickness of the ferrite and cementite lamellae are reduced to 20 and 2 nm, respectively, and high-angle boundaries form in the ABC structure parallel to the cementite lamellae. The structural and crystallographic analyses suggest that boundary strengthening and dislocation strengthening are important mechanisms in the cold-drawn wire. However, differences in structural parameters between the AA and the ABC structure may affect the relative contributions of the two mechanisms to the total flow stress

  5. Thermal Stability of Nanocrystalline Structure In X37CrMoV5-l Steel

    Directory of Open Access Journals (Sweden)

    Skołek E.

    2015-04-01

    Full Text Available The aim of the study was to investigate the thermal stability of the nanostructure produced in X37CrMoV5-1 tool steel by austempering heat treatment consisted of austenitization and isothermal quenching at the range of the bainitic transformation. The nanostructure was composed of bainitic ferrite plates of nanometric thickness separated by thin layers of retained austenite. It was revealed, that the annealing at the temperature higher than temperature of austempering led to formation of cementite precipitations. At the initial stage of annealing cementite precipitations occurred in the interfaces between ferritic bainite and austenite. With increasing temperature of annealing, the volume fraction and size of cementite precipitations also increased. Simultaneously fine spherical Fe7C3 carbides appeared. At the highest annealing temperature the large, spherical Fe7C3 carbides as well as cementite precipitates inside the ferrite grains were observed. Moreover the volume fraction of bainitic ferrite and of freshly formed martensite increased in steel as a result of retained austenite transformation during cooling down to room temperature.

  6. Void nucleation in spheroidized steels during tensile deformation

    International Nuclear Information System (INIS)

    An investigation was conducted to determine the effects of various mechanical and material parameters on void formation at cementite particles in axisymmetric tensile specimens of spheroidized plain carbon steels. Desired microstructures for each of three steel types were obtained. Observations of void morphology with respect to various microstructural features were made using optical and scanning electron microscopy

  7. Metallurgical analysis of spalled work roll of hot strip mill

    International Nuclear Information System (INIS)

    In this study failure analysis of four work roll of the Hot Strip Mill is carried out. The microstructure is correlated with the chemical composition of shell and roll-life. It was concluded that for the longer service of the roll, cementite, graphite and martensite should be balanced (as per working requirement of the mill). (author)

  8. Numerical modeling of coupled heat transfer and phase transformation for solidification of the gray cast iron

    DEFF Research Database (Denmark)

    Jabbari, Masoud; Hosseinzadeh, Azin

    2013-01-01

    In the present study the numerical model in 2D is used to study the solidification bahavior of the gray cast iron. The conventional heat transfer is coupled with the proposed micro-model to predict the amount of different phases, i.e. total austenite (c) phase, graphite (G) and cementite (C), in...

  9. Structural, electronic, and magnetic properties of iron carbide Fe7C3 phases from first-principles theory

    NARCIS (Netherlands)

    Fang, C.M.; Van Huis, M.A.; Zandbergen, H.W.

    2009-01-01

    The iron carbide Fe7C3 exhibits two types of basic crystal structures, an orthorhombic (o-) form and a hexagonal (h-) one. First-principles calculations have been performed for the basic Fe7C3 forms and for the related θ-Fe3C cementite phase. Accurate total-energy calculations show that the stabilit

  10. Microstructure and strengthening mechanisms in cold-drawn pearlitic steel wire

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xiaodan, E-mail: xzha@risoe.dtu.dk [Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Tsinghua 100084 (China); Danish-Chinese Center for Nanometals, Materials Research Division, Riso National Laboratory for Sustainable Energy, Danmarks Tekniske Universitet, DK-4000 Roskilde (Denmark); Godfrey, Andy [Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Tsinghua 100084 (China); Huang Xiaoxu; Hansen, Niels [Danish-Chinese Center for Nanometals, Materials Research Division, Riso National Laboratory for Sustainable Energy, Danmarks Tekniske Universitet, DK-4000 Roskilde (Denmark); Liu Qing [School of Materials Science and Engineering, Chongqing University, Chongqing 400030 (China)

    2011-05-15

    Highlights: > Interlamellar spacing and thickness of cementite lamellae decrease in accordance with change in diameter of drawn pearlitic steel wire up to strain of 2.5. > At higher strains enhanced thinning of cementite lamellae points to decomposition of cementite and carbon enrichment of ferrite. > Dislocations are stored in ferrite lamellae and their density increases to about 2 x 10{sup 16} m{sup -2} as determined by HRTEM. > Contributions of boundary strengthening, dislocation strengthening and solid solution hardening are estimated and by addition. Good agreement is found between estimated and measured flow stress. - Abstract: Strengthening mechanisms and strength-structure relationships have been analyzed in a cold-drawn pearlitic steel with a structural scale in the nanometer range and a flow stress of about 3.5 GPa. The wires have been drawn up to a strain of 3.7 and the structures analyzed and quantified by transmission electron microscopy and high resolution electron microscopy. The mechanical properties have been determined by tensile testing. It is found that the interlamellar spacing and the thickness of the cementite lamellae are reduced in accordance with the changes in wire diameter up to a strain of 2.5. At a higher strain enhanced thinning of the cementite lamellae points to decomposition of the cementite and carbon enrichment of the ferrite lamellae. Dislocations are stored in the interior of the ferrite lamellae and their density increases to about 2 x 10{sup 16} m{sup -2}. A high dislocation density is also observed at the ferrite/cementite interface. Three strengthening mechanisms have been analyzed: (i) boundary strengthening, (ii) dislocation strengthening and (iii) solid solution hardening. The individual and combined contributions, based on an assumption of linear additivity, of these mechanisms to the wire strength have been estimated. Good agreement has been found between the estimated and the measured flow stresses, which is followed

  11. Carbide Precipitation During Tempering of a Tool Steel Subjected to Deep Cryogenic Treatment

    Science.gov (United States)

    Gavriljuk, V. G.; Sirosh, V. A.; Petrov, Yu. N.; Tyshchenko, A. I.; Theisen, W.; Kortmann, A.

    2014-05-01

    Using transmission electron microscopy, Mössbauer spectroscopy, and measurements of hardness, the carbide precipitation during tempering of steel X153CrMoV12 containing (mass pct) 1.55C, 11.90Cr, 0.70V, and 0.86Mo is studied after three treatments: quenching at RT and deep cryogenic treatment, DCT, at 77 K or 123 K (-196 °C or -150 °C). In contrast to some previous studies, no fine carbide precipitation after long-time holding at cryogenic temperatures is detected. After quenching at room temperature, RT, the transient ɛ( ɛ') carbide is precipitated between 373 K and 473 K (100 °C and 200 °C) and transformed to cementite starting from 573 K (300 °C). In case of DCT at 123 K (-150 °C), only fine cementite particles are detected after tempering at 373 K (200 °C) with their delayed coarsening at higher temperatures. Dissolution of cementite and precipitation of alloying element carbides proceed at 773 K (500 °C) after quenching at RT, although some undissolved cementite plates can also be observed. After DCT at 123 K (-150 °C), the transient ɛ( ɛ') carbide is not precipitated during tempering, which is attributed to the intensive isothermal martensitic transformation accompanied by plastic deformation. In this case, cementite is the only carbide phase precipitated in the temperature range of 573 K to 773 K (300 °C to 500 °C). If DCT is carried out at 77 K (-196 °C), the ɛ( ɛ') carbide is found after tempering at 373 K to 473 K (100 °C to 200 °C). Coarse cementite particles and the absence of alloying element carbides constitute a feature of steel subjected to DCT and tempering at 773 K (500 °C). As a result, a decreased secondary hardness is obtained in comparison with the steel quenched at RT. According to Mössbauer studies, the structure after DCT and tempering at 773 K (500 °C) is characterized by the decreased fraction of the retained austenite and clustering of alloying elements in the α solid solution. It is suggested that a competition

  12. Very high cycle fatigue behavior of SAE52100 bearing steel by ultrasonic nanocrystalline surface modification.

    Science.gov (United States)

    Cho, In Shik; He, Yinsheng; Li, Kejian; Oh, Joo Yeon; Shin, Keesam; Lee, Chang Soon; Park, In Gyu

    2014-11-01

    In this paper, the SAE52100 bearing steel contained large quantities of cementite dispersed in ferrite matrix was subjected to the ultrasonic nanocrystalline surface modification (UNSM) treatment that aims for the extension of fatigue life. The microstructure and fatigue life of the untreated and treated specimens were studied by using electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM), and a developed ultra-high cycle fatigue test (UFT). After UNSM treatment, the coarse ferrite grains (- 10 μm) were refined to nanosize (- 200 nm), therefore, nanostructured surface layers were fabricated. Meanwhile, in the deformed layer, the number density and area fraction of cementite were increased up to - 400% and - 550%, respectively, which increased with the decrease in depth from the topmost treated surface. The improvement of hardness (from 200 Hv to 280 Hv) and high cycles fatigue strength by - 10% were considered the contribution of the developed nanostructure in the UNSM treated specimen. PMID:25958512

  13. The microstructural evolution, crystallography, and thermal processing of ultrahigh carbon Fe-1.85 pct C melt-spun ribbon

    Science.gov (United States)

    Spanos, G.; Ayers, J. D.; Vold, C. L.; Locci, I. E.

    1993-01-01

    A study is presented to determine if fine microstructures could be achieved using rapid solidification to produce a fine-grained fully austenitic starting structure and then using thermal processing cycles to produce an even finer ferrite-cementite structure. The evolution, mechanisms of grain refinement, and crystallography of the resultant microstructures were examined by TEM. A thermal processing cycle consisted of quenching the ribbon in liquid nitrogen, tempering at 600 C for 10 sec, 'upquenching' to 750 C for 10 sec, and subsequently quenching again in liquid nitrogen. The heat-treatment resulted in martensite grains with sizes of about 1 micron or less in both length and thickness and cementite particles of 0.4 micron or less. It is concluded that these microstructures could be used for producing fine-grained ultrahigh carbon steels of very high strength without the brittleness associated with the formation of coarse carbide particles of the loss of strength due to graphite formation.

  14. Hierarchical structures in cold-drawn pearlitic steel wire

    DEFF Research Database (Denmark)

    Zhang, Xiaodan; Godfrey, Andrew; Hansen, Niels; Huang, Xiaoxu

    2013-01-01

    The microstructure and crystallography of drawn pearlitic steel wires have been quantified by a number of electron microscopy techniques including scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction and nanobeam diffraction, with focus on the change in...... the structure and crystallography when a randomly oriented cementite structure in a patented wire during wire drawing is transformed into a lamellar structure parallel to the drawing axis. Changes in the interlamellar spacing and in the misorientation angle along and across the ferrite lamellae show...... significant through-diameter variations in wires drawn to large strains ⩾ 1.5. The structural evolution is hierarchical as the structural variations have their cause in a different macroscopic orientation of the cementite in the initial (patented) structure with respect to the wire axis. The through...

  15. Reheating Austenitizing Temperature of Spring Steel 60Si2MnA for Railway

    Institute of Scientific and Technical Information of China (English)

    CUI Juan; LIU Ya-zheng; PAN Hui; GAO Li-feng

    2008-01-01

    The microsturctural transformation of austenite grain,pearlite interlamellar spacing,and lamellar cementite thickness of spring steel 60Si2MnA for railway were studied in the hot-rolled and reheated states.Furthermore,the effect of microstructural characterization on its final mechanical properties was discussed.The results showed that as far as 60Si2MnA,the pearlite interlamellar spacing determined the hardness,whereas,the austenite grain determined the toughness.Compared with microstructure and mechanical properties in the hot-rolled state,after reheating treatment at 950℃,its average grain sizes are apparently fine and the pearlite interlamellar spacing and lamellar cementite thickness coarsen to some extent,but both hardness and impact toughness increase to HRC 48 and 8.5 J.respectively.In the course of making spring,the optimum reheating austenitizing temperature for the 60Si2MnA steel is 950℃.

  16. Effect of annealing cooling rate on microstructure and mechanical property of 100Cr6 steel ring manufactured by cold ring rolling process

    Institute of Scientific and Technical Information of China (English)

    魏文婷; 吴敏

    2014-01-01

    Pre-heat treatment is a vital step before cold ring rolling and it has significant effect on the microstructure and mechanical properties of rolled rings. The 100Cr6 steel rings were subjected to pre-heat treatment and subsequent cold rolling process. Scanning electron microscopy and tensile tests were applied to investigate microstructure characteristic and mechanical property variations of 100Cr6 steel rings undergoing different pre-heat treatings. The results indicate that the average diameter of carbide particles, the tensile strength and hardness increase, while the elongation decreases with the decrease of cooling rate. The cooling rate has minor effect on the yield strength of sample. After cold ring rolling, the ferrite matrix shows a clear direction along the rolling direction. The distribution of cementite is more homogeneous and the cementite particles are finer. Meanwhile, the hardness of the rolled ring is higher than that before rolling.

  17. Mechanical properties and fracture characteristics of high carbon steel after equal channel angular pressing

    International Nuclear Information System (INIS)

    The ultra-microduplex structure was fabricated in a fully pearlitic Fe–0.8 wt% C steel after equal channel angular pressing (ECAP) at 923 K via the Bc route. The microstructures and mechanical properties, before and after deformation, were investigated using scanning electron microscopy and mini-tensile tests. The cementite lamellae are gradually spheroidized by increasing the number of ECAP passes. After four passes, the cementite lamellae are fully spheroidized. Microhardness and the ultimate tensile strength of pearlite increase with the strain, up to a peak value (after two passes) and then decrease significantly. The yield strength, elongation and percentage of reduction in area increase with the number of ECAP passes. The tensile fracture morphology changes gradually from brittle cleavage to typical ductile fracture after four passes

  18. Study on deformation and microstructure characterizations of mild steel joints by continuous drive friction welding

    Institute of Scientific and Technical Information of China (English)

    Li Wenya; Yu Min; Li Jinglong; Gao Dalu

    2009-01-01

    Macro-deformation characteristics of continuous drive friction welded mild steel joints were examined by using one deformable workpiece (objective) and the other undeformable one (rigid). The microstructure evolution and hardness change across the joint were studied. The results show that the axial shortening and radial increment of joints increase with increasing the friction time at 1 200rpm. The cementite particles of pearlites in the weld center are uniformly distributed on the ferrite matrix, while the cementites of the pearlite in the thermal-mechanically affected zone are broken and discontinuously dispersed in the pearlite. The hardness decreases rapidly from the weld center to the parent metal under the coupled effects of heat and deformation during the rapid heating and cooling processes.

  19. Nanostructure and mechanical properties of heavily cold-drawn steel wires

    International Nuclear Information System (INIS)

    The effects of microstructure on the mechanical properties of the high-carbon steel wires were investigated. The wires were fabricated with carbon content of 0.82 and 1.02 wt.% and drawing strain from 4.12 to 4.32. The bending fatigue resistance and torsion ductility were measured by a Hunter fatigue tester and a torsion tester specially designed for fine wires. As the carbon content and drawing strain increased, the fatigue resistance and the torsional ductility of the steel wires decreased, and the tensile strength increased. To elucidate the causes of these behaviors, the microstructure in terms of lamellar spacing (λP), cementite thickness (tC) and morphology of cementite was observed using transmission electron microscopy (TEM) and 3-dimensional atom probe (3-DAP).

  20. Super-heater tube failure due to overheating when using bagasse as fuel

    OpenAIRE

    John Jairo Coronado Marín

    2010-01-01

    A super-heater’s boiler tubes presented external longitudinal cracks. The tubes’ external surfaces presented a reddish-white layer consisting of paraffin chains: CH, functional groups: CO, NH and sulphur compounds. This brittle layer prevented heat transfer, thereby causing increased tube temperature. Creep led to failure due to long-term overheating. The steel tubes’ microstructure presented grain growth, cementite globulisation and intergranular cracks on the external surface. The foregoing...

  1. Influence of Ferrite Content on Fatigue Strength of Quenched and Tempered 42CrMoS4 Steel

    OpenAIRE

    Hanno, Mithaq Elias

    2012-01-01

    Specimens of steel 42CrMoS4 were quenched from the austenite (γ) and the ferrite (α) + austenite + cementite phase fields to produce fully martensitic matrices with 0 – 14 % ferrite dispersed in the matrix. After tempering at 300°C or 600°C mechanical and fatigue properties were determined. As expected yield strength, tensile strength and hardness decreased with increased tempering temperature and ferrite content. Quite unexpected, the fatigue properties were mildly affected. A small amount o...

  2. The microstructure of continuously cooled tough bainitic steel

    OpenAIRE

    García Caballero, Francisca; Capdevila, Carlos; Chao, Jesús; Cornide, J.; García Mateo, Carlos; Roelofs, H; Hasler, St; Mastrogiacomo, G.

    2010-01-01

    The influence of bainite morphology on the impact toughness behaviour of a continuously cooled cementite free low carbon C-Mn-B type of steel has been examined. Different bainite morphologies were obtained by cooling from the austenite regime to ambient temperature with different cooling rates. The resulting microstructures have been quantitatively analysed using light optical microscopy (LOM), scanning electron microscopy (SEM) and electron back scatter diffraction (EBSD) techniques. The rel...

  3. ATOM PROBE MICROANALYSIS OF WELD METAL IN A SUBMERGED ARC WELDED CHROMIUM-MOLYBDENUM STEEL

    OpenAIRE

    Josefsson, B.; Kvist, A.; Andrén, H.

    1987-01-01

    A submerged arc welded 2.25Cr - 1Mo steel has been investigated using electron microscopy and atom probe field ion microscopy. The bainitic microstructure of the as-welded steel consisted of ferrite and martensite. During heat treatment at 690°C the martensite transformed to ferrite and cementite and needle-shaped (Cr,Mo)2C carbides precipitated. Together with a substantial decrease in dislocation density, this resulted in an improvement of the toughness.

  4. Microstructure and transformation kinetics in bainitic steels

    OpenAIRE

    Luzginova, N.V.

    2008-01-01

    With the aim of reaching a better understanding of the microstructure evolution and the overall phase transformation kinetics in hyper-eutectoid steels a commercial SAE 52100 bearing steel and 7 model alloys with different concentrations of chromium, cobalt and aluminum have been studied in this work, both experimentally and theoretically. The effect of alloying elements, Cr, Co and Al, on different processes occurring during heat treatment of hyper-eutectoid steels (cementite spheroidization...

  5. Influences of Short Discrete Fibers in High Strength Concrete with Very Coarse Sand

    OpenAIRE

    Mahyuddin Ramli; Kwan W. Hoe

    2010-01-01

    Problem statement: High Strength Concrete (HSC) normally content high cementitous amount and low water binder ratio. However, these would cause substantial volume changes to the concrete and therefore affected the strength development. In addition, the brittleness of HSC was increased when silica fume used as partial cement replacement to achieve high strength. Approach: This study discussed the effects of incorporated short discrete Coconut Fibers (CF), Barchip Fibers ...

  6. MORPHOLOGY MODIFICATION OF CARBON CHROME MOLYBDENUM STEEL STRUCTURE INFLUENCED BY HEAT TREATMENT

    Directory of Open Access Journals (Sweden)

    V. A. Lutsenko

    2011-01-01

    Full Text Available The influence of temperature and time parameters of thermal treatment on structural change and properties of carbon chromium molybdenum steel has been studied. It has been shown that there are considerable areas with grainy morphology of cementite after high temperature tempering in the structure of steel. It assures reduction of steel microhardness by 25%, and there are no substantial structural changes after medium temperature tempering.

  7. CHANGE OF MORPHOLOGY OF THE CARBON CHROME-MOLYBDENUM STEEL STRUCTURE UNDER THE INFLUENCE OF THERMAL TREATMENT

    Directory of Open Access Journals (Sweden)

    V. A. Lutsenko

    2010-01-01

    Full Text Available Influence of temperature-temporal parameters of thermal treatment on changing of structure and characteristics of carbon chrome-molybdenum steel is studied. It is shown that there are considerable areas with granular morphology of cementite in metal structure after high-temperature tempering, what provides lowering of microhardness of steel by 25%, and after medium-temperature tempering there are no essential structural changes.

  8. MORPHOLOGY MODIFICATION OF CARBON CHROME MOLYBDENUM STEEL STRUCTURE INFLUENCEDBY HEAT TREATMENT

    OpenAIRE

    Lutsenko, V.; Anelkin, N.; Golubenko, T.; Scherbakov, V.; Lutsenko, O.

    2011-01-01

    The influence of temperature and time parameters of thermal treatment on structural change and properties of carbon chromium molybdenum steel has been studied. It has been shown that there are considerable areas with grainy morphology of cementite after high temperature tempering in the structure of steel. It assures reduction of steel microhardness by 25%, and there are no substantial structural changes after medium temperature tempering.

  9. CHANGE OF MORPHOLOGY OF THE CARBON CHROME-MOLYBDENUM STEEL STRUCTURE UNDER THE INFLUENCE OF THERMAL TREATMENT

    OpenAIRE

    V. A. Lutsenko; N. I. Anelkin; T. N. Golubenko; Shcherbakov, V. I.; O. V. Lutsenko; L. A. Drobyshevskij

    2016-01-01

    Influence of temperature-temporal parameters of thermal treatment on changing of structure and characteristics of carbon chrome-molybdenum steel is studied. It is shown that there are considerable areas with granular morphology of cementite in metal structure after high-temperature tempering, what provides lowering of microhardness of steel by 25%, and after medium-temperature tempering there are no essential structural changes.

  10. Morphology modification of carbon chrome molybdenum steel structure influenced by heat treatment

    OpenAIRE

    V. A. Lutsenko; N. L. Anelkin; T. N. Golubenko; Scherbakov, V. I.; O. V. Lutsenko

    2011-01-01

    The influence of temperature and time parameters of thermal treatment on structural change and properties of carbon chromium molybdenum steel has been studied. It has been shown that there are considerable areas with grainy morphology of cementite after high temperature tempering in the structure of steel. It assures reduction of steel microhardness by 25%, and there are no substantial structural changes after medium temperature tempering.

  11. Compatibilités et incompatibilités liants cimentaires / superplastifiants

    OpenAIRE

    Nicolas, Edwige

    2010-01-01

    Currently required concrete strength imposes a lower water/cement ratio and use of superplasticizer to make easier the fresh material implementation. Polycarboxylate type products are very effective in the short term but can lead to a fast loss of workability in case of binder/superplasticizer incompatibility. The object of this work is the identification of cementitous phases involved in these rheological variations. Initially, flow of various superplasticized pastes is evaluated by a rheome...

  12. The Correlation of Chloride Diffusion Coefficient and Concrete Maturity Value and Its Application in Hong Kong–Zhuhai–Macao Bridge Engineering

    OpenAIRE

    Li, Pengping; Wang, Shengnian; Xiong, Jianbo; Chai, Rui; Yan, Yu

    2014-01-01

    The correlation of chloride diffusion coefficient and concrete maturity value within 56 days of curing was investigated by the chemically combined water content method, rapid chloride migration (RCM) test, and concrete maturity test. The experimental results showed that chloride diffusion coefficient of concretes decreased not only with increasing curing ages but also with increasing curing temperature, which can promote the hydration degree of cementitous materials. There is a significant co...

  13. Effect of cutting parameters on chip formation in orthogonal cutting

    OpenAIRE

    Ben Salem, S.; E. Bayraktar; M. Boujelbene; D. Katundi

    2012-01-01

    Purpose: of this paper is to study the chip formation to obtain the optimal cutting conditions and to observe the different chip formation mechanisms. Analysis of machining of a hardened alloy, X160CrMoV12-1 (cold work steel: AISI D2 with a ferritic and cementite matrix and coarse primary carbides), showed that there are relationships between the chip geometry, cutting conditions and the different micrographs under different metallurgical states.Design/methodology/approach: Machining of harde...

  14. Microstructure evolution during laser-aided direct metal deposition of alloy tool steel

    International Nuclear Information System (INIS)

    Laser-aided direct metal deposition has been used to form an alloy tool steel coating. The microstructure of the deposited material was analyzed by means of scanning electron microscopy and transmission electron microscopy. The formation relationships among martensite, ε-carbide, cementite and austenite in the coating are discussed. The effect of rapid solidification associated with direct metal deposition on lattice parameters is also reported.

  15. Flexural reinforcement of concrete with textile reinforced mortar TRM

    OpenAIRE

    Gil Espert, Lluís; Escrig Pérez, Christian; Bernat Masó, Ernest

    2013-01-01

    This work presents a method of strengthening concrete structures based on textiles of high strength and mortars. The combination of textiles and mortars produces a new composite material of cementitic matrix. This material can be used for the reinforcement of concrete beams under bending loads. We tested several combinations of fibers: glass, PBO, steel and carbon fibers with mortar and we used them to reinforce precast concrete beams. All the specimens were tested with a four-point load test...

  16. Effects of MC-Type Carbide Forming and Graphitizing Elements on Thermal Fatigue Behavior of Indefinite Chilled Cast Iron Rolls

    Science.gov (United States)

    Ahiale, Godwin Kwame; Choi, Won-Doo; Suh, Yongchan; Lee, Young-Kook; Oh, Yong-Jun

    2015-11-01

    The thermal fatigue behavior of indefinite chilled cast iron rolls with various V+Nb contents and Si/Cr ratios was evaluated. Increasing the ratio of Si/Cr prolonged the life of the rolls by reducing brittle cementites. Higher V+Nb addition also increased the life through the formation of carbides that refined and toughened the martensite matrix and reduced the thermal expansion mismatch in the microstructure.

  17. Numerical modeling and experimental validation of microstructure in gray cast iron

    DEFF Research Database (Denmark)

    Jabbari, Masoud; Davami, Parviz; Varahram, Naser

    2012-01-01

    To predict the amount of different phases in gray cast iron by a finite difference model (FDM) on the basis of cooling rate (R), the volume fractions of total γ phase, graphite, and cementite were calculated. The results of phase composition were evaluated to find a proper correlation with cooling...... to correlate the phase volume fraction to hardness. The results are compared with experimental data and show reasonable agreement....

  18. Rationalisation of Austenite Transformation to Upper or Lower Bainite in Steels

    Directory of Open Access Journals (Sweden)

    Ławrynowicz Z.

    2014-06-01

    Full Text Available The paper presents an analytical evaluation of transition temperature from upper to lower bainite in Fe-C-Cr steel. The calculations was based on the model constructed by Matas and Hehemann which involves a comparison between the times needed to precipitate cementite within the bainitic ferrite plates (tθ, with the time required to decarburise supersaturated ferrite plates (td. The transition between upper and lower bainite is found to occur over a narrow range of temperatures (350-410°C and depends on the thickness of bainitic ferrite laths and the volume fraction of precipitated cementite. On comparing the td and tθ times it was found that the transition temperature from upper to lower bainite reaction (LS of about 350oC could be predicted if the thickness of bainitic ferrite laths is set as wo = 0.1 μm and volume fraction of cementite is set as ξ = 0.01

  19. Atom Probe Tomography Examination of Carbon Redistribution in Quenched and Tempered 4340 Steel

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, Amy J. [Los Alamos National Laboratory; Miller, Michael K. [ORNL; Alexander, David J. [Los Alamos National Laboratory; Field, Robert D. [Los Alamos National Laboratory; Clarke, Kester D. [Los Alamos National Laboratory

    2012-08-07

    Quenching and tempering produces a wide range of mechanical properties in medium carbon, low alloyed steels - Study fragmentation behavior as a function of heat-treatment. Subtle microstructural changes accompany the mechanical property changes that result from quenching and tempering - Characterize the location and distribution of carbon and alloying elements in the microstructure using atom probe tomography (APT). Perform complementary transmission electron microscopy (TEM). Tempering influences the mechanical properties and fragmentation of quenched 4340 (hemi-shaped samples). APT revealed carbon-enriched features that contain a maximum of {approx}12-14 at.% carbon after quenching to RT (the level of carbon is perhaps associated with the extent of autotempering). TEM confirmed the presence of twinned martensite and indicates {var_epsilon} ({eta}) transition carbides after oil quenching to RT. Tempering at 325 C resulted in carbon-enriched plates (> 25 at.% C) with no significant element partitioning (transition carbides?). Tempering at 450 C and 575 C resulted in cementite ({approx} 25 at.% C) during late stage tempering; Cr, Mn, Mo partitioned to cementite and Si partitioned to ferrite. Tempering at 575 C resulted in P segregation at cementite interfaces and the formation of Cottrell atmospheres.

  20. Inoculation Effects of Cast Iron

    Directory of Open Access Journals (Sweden)

    E. Fraś

    2012-12-01

    Full Text Available The paper presents a solidification sequence of graphite eutectic cells of A and D types, as well as globular and cementite eutectics. The morphology of eutectic cells in cast iron, the equations for their growth and the distances between the graphite precipitations in A and D eutectic types were analyzed. It is observed a critical eutectic growth rate at which one type of eutectic transformed into another. A mathematical formula was derived that combined the maximum degree of undercooling, the cooling rate of cast iron, eutectic cell count and the eutectic growth rate. One type of eutectic structure turned smoothly into the other at a particular transition rate, transformation temperature and transformational eutectic cell count. Inoculation of cast iron increased the number of eutectic cells with flake graphite and the graphite nodule count in ductile iron, while reducing the undercooling. An increase in intensity of inoculation caused a smooth transition from a cementite eutectic structure to a mixture of cementite and D type eutectic structure, then to a mixture of D and A types of eutectics up to the presence of only the A type of eutectic structure. Moreover, the mechanism of inoculation of cast iron was studied.

  1. cs of abrasive-reactive nanocomposite powder synthesis in the SiO2 − C/S system

    Directory of Open Access Journals (Sweden)

    Faryt Urakaev

    2015-03-01

    Full Text Available In this study, the syntheses of cementite (Fe3C and pyrite (FeS2 have been performed by mechanical activation of a mixture of graphite or sulfur with amorphous or crystalline silica in a planetary ball mill AGO-2 with steel fittings. XRD analysis was used to record products and changes of systems components after mechanical activation of the studied systems. The formation of nanocomposites based on cementite (or pyrite has been recorded and the quantitative characteristics of abrasive-reactive wear of steel milling tools have been evaluated. It has been demonstrated the possibility of steel material reaction of milling tools for direct mechanochemical preparation of composite based on cementite using abrasive properties of silica modifications. It has obtained nanocomposites based on pyrite and glass matrix during mechanical activation of quartz glass and sulfur in a time of 1-2 orders of magnitude lower than traditional mechanical alloying powders of iron and sulfur. It can be noted that any scrap metal and ceramic products can be used as milling tools. This significantly enhances the ability of the proposed method of abrasive-reactive nanowear of milling tools materials of mechanochemical reactors and processed materials.

  2. The Relationship Between Microstructural Evolution and Mechanical Properties of Heavy Plate of Low-Mn Steel During Ultra Fast Cooling

    Science.gov (United States)

    Wang, Bin; Wang, Zhao-dong; Wang, Bing-xing; Wang, Guo-dong; Misra, R. D. K.

    2015-07-01

    We describe here the electron microscopy and mechanical property studies that were conducted in an industrially processed 20- and 40-mm C-Mn thick plates that involved a new approach of ultrafast cooling (UFC) together with significant reduction in Mn-content of the steel by ~0.3 to 0.5 pct, in relation to the conventional C-Mn steels, with the aim of cost-effectiveness. The study demonstrated that nanoscale cementite precipitation occurred during austenite transformation in the matrix of heavy plate during UFC, providing significant precipitation strengthening. With decrease in UFC stop temperature and consequent increase in the degree of undercooling, there was a transition in the morphology of cementite from lamellar to irregular-shaped nanoscale particles in the 20 mm heavy plate. With the increase in plate thickness, nanoscale cementite precipitated in bainitic lath at the surface of 40 mm heavy plate, which significantly increased the strength and decreased the elongation. Simultaneously, microstructural evolution in hot-rolled sheets was studied via simulation experiments using laboratory rolling mill to define the limits of microstructural evolution that can obtained in the UFC process and develop an understanding of the evolved microstructure in terms of process parameters.

  3. Effect of cyclic heat treatment on microstructure and mechanical properties of 50CrV4 steel

    Institute of Scientific and Technical Information of China (English)

    李红英; 韩茂盛; 李德望; 李俊; 徐德超

    2015-01-01

    An annealed 50CrV4 steel was subjected to cyclic heat treatment process that consists of repeated short-duration (200 s) held at 840 °C (aboveAc3 temperature of 790 °C) and short-duration (100 s) held at 700 °C (belowAc1 temperature of 710 °C). The spheroidization ratio of cementite and the average size of particles increase with increasing the cyclic number of heat treatment. After 5-cycle heat treatment, the spheroidization ratio of cementite is 100%, and the average size of the cementite particles is about 0.53μm. After cyclic heat treatment, the hardness, ultimate tensile strength and yield strength of the experimental steel gradually decrease with increasing cyclic number of heat treatment. The elongation of the as-received specimens is about 7.4%, the elongation of the 1-cycle specimen is 14.3%, and the elongation of 5-cycle specimen reaches a peak value of 22.5%, thereafter marginally decreases to 18.3% after 6-cycle heat treatment. Accordingly, the fractured surface initially exhibits the regions of wavy lamellar fracture. By increasing the cyclic number of heat treatment cycles, the regions of dimples consume the entire fractured surface gradually. Some large dimples can be found in the fracture surface of the specimen subjected to six heat treatment cycles.

  4. Residual stress analysis of cold-drawn pearlite steel wire using white synchrotron radiation

    International Nuclear Information System (INIS)

    Measurement of the residual stresses in cold-drawn pearlitic steel wire was conducted using an energy dispersive X-ray diffraction technique. The residual stresses of the ferrite and cementite phases were determined for different crystal orientations and large residual stresses were found to exist in the cold-drawn pearlitic steel wire. The residual stresses in the ferrite phase were compressive in the axial direction but nearly zero in the hoop and radial directions. In addition, the residual stresses of the reflection indices for the ferrite phase were similar to one another. For the cementite phase, while tensile residual stress existed in the axial direction, compressive residual stress existed in the hoop and radial directions. These stresses in the ferrite phase in the axial direction and cementite phase in all directions decreased along the radial positions. A residual stress state model was proposed on the basis of the aligned lamellar structure along the drawing direction; the model explains the effect of the lamellar direction on residual stress. Reanalysis of the wire sample using the proposed model provided residual strains and stresses in the lamellar direction that were different from the average values estimated using the simple stress analysis method. (author)

  5. Effect of phosphorous and boron addition on microstructural evolution and Charpy impact properties of high-phosphorous-containing plain carbon steels

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Seokmin [Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Shin, Sang Yong [Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf D-40237 (Germany); Lee, Junghoon [Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Lee, Chang-Hoon [Next Generation Products Research Group, Technical Research Laboratories, POSCO, Pohang 790-785 (Korea, Republic of); Lee, Sunghak, E-mail: shlee@postech.ac.kr [Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)

    2013-03-01

    Four plain carbon steels were fabricated by controlling the addition of P and B, and then isothermal heat-treatments were conducted at 550 °C and 650 °C for 3 h on these steels to make ferrite–pearlite-based or ferrite–bainite-based microstructures, respectively. B was added for controlling the reduction in toughness due to grain boundary segregation of P because B was readily distributed on grain boundaries. In the 550 °C-treated steels, bainite grains were refined by the B addition, whereas the 650 °C-treated steels did not show the grain refinement due to the B addition. According to the critical time analysis for non-equilibrium grain boundary segregation of P and B, the present isothermal treatment time of 3 h was too short for the grain boundary segregation of P, and thus the fracture occurred mostly in a cleavage mode, instead of an intergranular mode. Since this 3 h-treatment time was too long for the grain boundary segregation of B, the grain boundary segregation of B was reduced, and the precipitation of cementites was promoted. In the 550 °C-treated steels, the area fraction of intergranular fracture increased with increasing volume fraction of grain boundary cementites, as they played an important role in initiating the intergranular fracture, although the area fraction of intergranular fracture was lower than 5%. In the 650 °C-treated steels having coarse grains, however, grain boundary cementites did not work for intergranular fracture because the crack readily propagated in a cleavage mode.

  6. Phase transformation in Fe-Mo-C and Fe-W-C steels. 1: The structural evolution during tempering at 700 C

    International Nuclear Information System (INIS)

    Mechanism and kinetics of carbide transformation during tempering at 700 C have been studied in Fe-Mo-C and Fe-W-C steels (with up to 2.5% W or Mo) by transmission electron microscopy (TEM) and X-ray diffraction. The sequence of carbide formation is Fe3C→Mo2C→(Fe2MoC, M23C6) in molybdenum steels and Fe3C→M6C→M23C6 in tungsten steels. Increasing the alloying element level increases the rate of carbide replacement reaction. In Fe-Mo-C steels the Fe2MoC carbides nucleate preferentially at the Fe3C-α interface and grow into cementite, whereas in Fe-W-C steels the Me2C carbides usually precipitate inside cementite giving rise to the in situ transformation Fe3C→M6C. The software DICTRA and THERMO-CALC were used to simulate cementite growth and to show the possibility of the in situ transformation. The M23C6 carbide is first confined to prior austenite grain boundaries and penetrates into the grains with increasing tempering time. During growth the M23C6 carbide absorbs surrounding pre-existing carbides. As a result, after tempering for 500 h, patches of two-phase areas with (M23C6 + α) are observed in tungsten steels, and patches of (M23C6 + α) or (Fe2MoC + α) in molybdenum steels. The alloying element partitioning between α and precipitated carbides was determined using TEM-EDS. It was established that the M23C6 carbide is stable at 700 C in both investigated steels. The Fe2MoC carbide is stable in the Fe-Mo-C system at this temperature. The MC carbide was not observed even after tempering for 3,000 h

  7. CO2 corrosion resistance of carbon steel in relation with microstructure changes

    International Nuclear Information System (INIS)

    The microstructural effects on the corrosion resistance of an API 5L X42 carbon steel in 0.5 M NaCl solution saturated with CO2 was investigated. Four microstructures were considered: banded (B), normalized (N), quenched and tempered (Q&T), and annealed (A). Electrochemical measurements (polarization curves and electrochemical impedance spectroscopy) were coupled with surface analyses (scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS)) to characterize the formation of the corrosion product layers. Electrochemical results revealed that corrosion resistance increased in the following order: B < N < Q&T < A. From the polarization curves it was shown that specifically, cathodic current densities were affected by microstructural changes. SEM images indicated that ferrite dissolved earlier than cementite and a thin layer of corrosion products was deposited on the steel surface. XPS analyses revealed that this layer was composed of a mixture of iron carbonate and non-dissolved cementite. It was also found that the quantity of FeCO3 content on the steel surface was greater for Q&T and A microstructures. These results, in agreement with the electrochemical data, indicate that the deposition mechanism of iron carbonate is closely related to the morphology of the non-dissolved cementite, determining the protective properties of the corrosion product layers. - Highlights: • The effect of change in microstructure on CO2 corrosion resistance was evaluated. • An API 5LX 42 carbon steel was immersed in a 0.5 M NaCl solution saturated with CO2. • Banded, normalized, quenched-tempered and annealed microstructures were considered. • Electrochemical measurements were coupled with surface analysis. • Morphology and distribution of undissolved Fe3C control corrosion kinetics

  8. The effects of vanadium on the microstructure and wear resistance of centrifugally cast Ni-hard rolls

    International Nuclear Information System (INIS)

    Highlights: • V addition changed the pro-eutectic phase from austenite to vermicular (V,Nb)C. • Pro-eutectic (V,Nb)C particles were segregated to the inner part of the roll. • Wear loss was inversely proportional to MC fraction under the same graphite fraction. • Cementite particles acted as the initiation site and propagation path of cracks. • High-temperature wear sequence of centrifugally cast Ni-hard rolls was suggested. - Abstract: The effects of V on the microstructure and wear resistance of centrifugally cast Ni-hard rolls are investigated under a constant fraction of graphite using electron microscopes and a revolving disk-type high-temperature wear tester. The volume fraction of (V,Nb)C particles was increased at the expense of the volume fraction of cementite with an increase in the V concentration. However, the volume fraction of graphite was held nearly constant by controlling the concentration ratio of Si and Cr. As the V concentration was higher than 3 wt.%, the pro-eutectic phase was changed from austenite to (V,Nb)C carbide. The pro-eutectic vermicular (V,Nb)C particles were segregated to the inner part of the roll during centrifugal casting. The wear resistance was improved with an addition of V due to the high volume fractions of the coarse eutectic and pro-eutectic (V,Nb)C particles and the precipitation hardening of fine (V,Nb)C particles in the martensitic matrix. The worn surface showed that cementite particles acted as the initiation site and propagation route of cracks

  9. Induction Tempering vs Conventional Tempering of a Heat-Treatable Steel

    Science.gov (United States)

    Sackl, Stephanie; Zuber, Michael; Clemens, Helmut; Primig, Sophie

    2016-07-01

    An induction heat treatment is favorable compared to a conventional one mainly due to significant time and cost savings. Therefore, in this study, the microstructure property relationships during induction and conventional heat treatment of a heat treatable steel 42CrMo4 is investigated. The yield strength and hardness is slightly higher for the conventionally heat-treated steel, whereas the induction heat-treated condition exhibits a roughly 30 J/cm2 higher impact energy. In a previous investigation of the authors, it has been proved that the difference in yield strength originates from the smaller block size of the conventionally heat-treated steel, which was already present after hardening. In the present work, it can be shown that during tempering the martensitic blocks become equi-axed ferrite grains due to recrystallization as revealed by electron back scatter diffraction. Nevertheless, a larger grain size usually is less favorable for the impact toughness of steels. Therefore, another mechanism is responsible for the higher impact energy of the induction hardened and tempered steel. With the aid of transmission electron microscopy a finer distribution of cementite was observed in the induction heat-treated samples. The delay of recovery is the reason for the presence of finer cementite in case of the induction heat-treated steel. Here, the higher heating rates and shorter process times reduce the annihilation of dislocation and as a consequence provide more nucleation sites for precipitation of cementite during tempering. From the obtained experimental results, it is believed that the finer distribution of carbides causes the observed higher impact toughness.

  10. The effects of vanadium on the microstructure and wear resistance of centrifugally cast Ni-hard rolls

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Minwoo, E-mail: aonia@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Suh, Yongchan, E-mail: ycsuh@hyundai-steel.com [Roll Development Team, HYUNDAI STEEL, 444 Songnae-dong, Nam-gu, Pohang, Gyeongbuk 790-785 (Korea, Republic of); Oh, Yong-Jun, E-mail: yjoh@hanbat.ac.kr [Department of Advanced Materials Science and Engineering, Hanbat National University, Daejeon 305-719 (Korea, Republic of); Lee, Young-Kook, E-mail: yklee@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2014-10-01

    Highlights: • V addition changed the pro-eutectic phase from austenite to vermicular (V,Nb)C. • Pro-eutectic (V,Nb)C particles were segregated to the inner part of the roll. • Wear loss was inversely proportional to MC fraction under the same graphite fraction. • Cementite particles acted as the initiation site and propagation path of cracks. • High-temperature wear sequence of centrifugally cast Ni-hard rolls was suggested. - Abstract: The effects of V on the microstructure and wear resistance of centrifugally cast Ni-hard rolls are investigated under a constant fraction of graphite using electron microscopes and a revolving disk-type high-temperature wear tester. The volume fraction of (V,Nb)C particles was increased at the expense of the volume fraction of cementite with an increase in the V concentration. However, the volume fraction of graphite was held nearly constant by controlling the concentration ratio of Si and Cr. As the V concentration was higher than 3 wt.%, the pro-eutectic phase was changed from austenite to (V,Nb)C carbide. The pro-eutectic vermicular (V,Nb)C particles were segregated to the inner part of the roll during centrifugal casting. The wear resistance was improved with an addition of V due to the high volume fractions of the coarse eutectic and pro-eutectic (V,Nb)C particles and the precipitation hardening of fine (V,Nb)C particles in the martensitic matrix. The worn surface showed that cementite particles acted as the initiation site and propagation route of cracks.

  11. An Atom Probe Tomographic Investigation of High-Strength, High-Toughness Precipitation Strengthened Steels for Naval Applications

    Science.gov (United States)

    Hunter, Allen H.

    Novel high-strength high-toughness alloys strengthened by precipitation are investigated for use in naval applications. The mechanical properties of an experimental steel alloy, NUCu-140, are evaluated and are not suitable for the naval requirements due to poor impact toughness at -40°C. An investigation is conducted to determine optimum processing conditions to restore toughness. A detailed aging study is conducted at 450, 500, and 550°C to determine the evolution of the microstructure and mechanical properties. A combination of transmission electron microscopy (TEM), synchrotron X-ray Diffraction (XRD), and Local electrode atom probe (LEAP) tomography are used to measure the evolution of the Cu precipitates, austenite, NbC, and cementite phases during aging. The evolution of the Cu precipitates significantly affects the yield strength of the steel, but low temperature toughness is controlled by the cementite precipitates. Extended aging is effective at improving the impact toughness but the yield strength is also decreased due to coarsening of the Cu precipitates. To provide a foundation for successful welding of NUCu-140 steel, an investigation of the effects of gas metal arc welding (GMAW) are performed. The microstructures in the base metal (BM), heat affected zone (HAZ), and fusion zone (FZ) of a GMAW sample are analyzed to determine the effects of the welding thermal cycle. Weld simulation samples with known thermal histories are prepared and analyzed by XRD and LEAP tomography. A significant loss in microhardness is observed as a result of dissolution of the Cu precipitates after the weld thermal cycle. The cooling time is too rapid to allow significant precipitation of Cu. In addition to the NUCu-140 alloy, a production HSLA-115 steel alloy is investigated using TEM, XRD, and LEAP tomography. The strength of the HSLA-115 is found to be derived primarily from Cu precipitates. The volume fractions of cementite, austenite, and NbC are measured by XRD

  12. CO{sub 2} corrosion resistance of carbon steel in relation with microstructure changes

    Energy Technology Data Exchange (ETDEWEB)

    Ochoa, Nathalie, E-mail: nochoa@usb.ve [Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Aptdo., 89000, Caracas (Venezuela, Bolivarian Republic of); Vega, Carlos [Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Aptdo., 89000, Caracas (Venezuela, Bolivarian Republic of); Pébère, Nadine; Lacaze, Jacques [Université de Toulouse, CIRIMAT, UPS/INPT/CNRS, ENSIACET, 4 Allée Emile Monso, CS 44362, 31030 Toulouse Cedex 4 (France); Brito, Joaquín L. [Laboratorio de Físico-química de Superficies, Centro de Química, Instituto Venezolano de Investigaciones Cientificas (IVIC), Carretera Panamericana, Km 11, Altos de Pipe, Estado Miranda (Venezuela, Bolivarian Republic of)

    2015-04-15

    The microstructural effects on the corrosion resistance of an API 5L X42 carbon steel in 0.5 M NaCl solution saturated with CO{sub 2} was investigated. Four microstructures were considered: banded (B), normalized (N), quenched and tempered (Q&T), and annealed (A). Electrochemical measurements (polarization curves and electrochemical impedance spectroscopy) were coupled with surface analyses (scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS)) to characterize the formation of the corrosion product layers. Electrochemical results revealed that corrosion resistance increased in the following order: B < N < Q&T < A. From the polarization curves it was shown that specifically, cathodic current densities were affected by microstructural changes. SEM images indicated that ferrite dissolved earlier than cementite and a thin layer of corrosion products was deposited on the steel surface. XPS analyses revealed that this layer was composed of a mixture of iron carbonate and non-dissolved cementite. It was also found that the quantity of FeCO{sub 3} content on the steel surface was greater for Q&T and A microstructures. These results, in agreement with the electrochemical data, indicate that the deposition mechanism of iron carbonate is closely related to the morphology of the non-dissolved cementite, determining the protective properties of the corrosion product layers. - Highlights: • The effect of change in microstructure on CO{sub 2} corrosion resistance was evaluated. • An API 5LX 42 carbon steel was immersed in a 0.5 M NaCl solution saturated with CO{sub 2}. • Banded, normalized, quenched-tempered and annealed microstructures were considered. • Electrochemical measurements were coupled with surface analysis. • Morphology and distribution of undissolved Fe{sub 3}C control corrosion kinetics.

  13. Super-heater tube failure due to overheating when using bagasse as fuel

    Directory of Open Access Journals (Sweden)

    John Jairo Coronado Marín

    2010-04-01

    Full Text Available A super-heater’s boiler tubes presented external longitudinal cracks. The tubes’ external surfaces presented a reddish-white layer consisting of paraffin chains: CH, functional groups: CO, NH and sulphur compounds. This brittle layer prevented heat transfer, thereby causing increased tube temperature. Creep led to failure due to long-term overheating. The steel tubes’ microstructure presented grain growth, cementite globulisation and intergranular cracks on the external surface. The foregoing observations support microstructure deterioration facilitated by the presence of unsuitable super-heater tube material when just using bagasse as fuel.

  14. Interactions of hydrogen with the iron and iron carbide interfaces: a ReaxFF molecular dynamics study.

    Science.gov (United States)

    Islam, Md Mahbubul; Zou, Chenyu; van Duin, Adri C T; Raman, Sumathy

    2016-01-14

    Hydrogen embrittlement (HE) is a well-known material phenomenon that causes significant loss in the mechanical strength of structural iron and often leads to catastrophic failures. In order to provide a detailed atomistic description of HE we have used a reactive bond order potential to adequately describe the diffusion of hydrogen as well as its chemical interaction with other hydrogen atoms, defects, and the host metal. The currently published ReaxFF force field for Fe/C/H systems was originally developed to describe Fischer-Tropsch (FT) catalysis [C. Zou, A. C. T. van Duin and D. C. Sorescu, Top. Catal., 2012, 55, 391-401], and especially had been trained for surface formation energies, binding energies of small hydrocarbon radicals on different surfaces of iron and the barrier heights of surface reactions. We merged this force field with the latest ReaxFF carbon parameters [S. Goverapet Srinivasan, A. C. T. van Duin and P. Ganesh, J. Phys. Chem. A, 2015, 119, 1089-5639] and used the same training data set to refit the Fe/C interaction parameters. The present work is focused on evaluating the applicability of this reactive force field to describe material characteristics and study the role of defects and impurities in the bulk and at the precipitator interfaces. We study the interactions of hydrogen with pure and defective α-iron (ferrite), Fe3C (cementite), and ferrite-cementite interfaces with a vacancy cluster. We also investigate the growth of nanovoids in α-iron using a grand canonical Monte Carlo (GCMC) scheme. The calculated hydrogen diffusion coefficients for both ferrite and cementite phases predict a decrease in the work of separation with increasing hydrogen concentration at the ferrite-cementite interface, suggesting a hydrogen-induced decohesion behavior. Hydrogen accumulation at the interface was observed during molecular dynamics (MD) simulations, which is consistent with experimental findings. These results demonstrate the ability of the Reax

  15. Microstructure and Wear Behavior of TiC Coating Deposited on Spheroidized Graphite Cast Iron Using Laser Surfacing

    OpenAIRE

    E. R. I. Mahmoud; H. F. El-Labban

    2014-01-01

    Spheroidal graphite cast iron was laser cladded with TiC powder using a YAG fiber laser at powers of 700, 1000, 1500 and 2000 W. The powder was preplaced on the surface of the specimens with 0.5 mm thickness. Sound cladding and fusion zones were observed at 700, 1000 and 1500 W powers. However, at 2000 W, cracking was observed in the fusion zone.  At 700 W, a build-up zone consisted of fine TiC dendrites inside a matrix composed of martensite, cementite (Fe3C), and some blocks of retaine...

  16. Friction stir processing on high carbon steel U12

    Energy Technology Data Exchange (ETDEWEB)

    Tarasov, S. Yu., E-mail: tsy@ispms.ru; Rubtsov, V. E., E-mail: rvy@ispms.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Melnikov, A. G., E-mail: melnikov-ag@tpu.ru [National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation)

    2015-10-27

    Friction stir processing (FSP) of high carbon steel (U12) samples has been carried out using a milling machine and tools made of cemented tungsten carbide. The FSP tool has been made in the shape of 5×5×1.5 mm. The microstructural characterization of obtained stir zone and heat affected zone has been carried out. Microhardness at the level of 700 MPa has been obtained in the stir zone with microstructure consisting of large grains and cementitte network. This high-level of microhardness is explained by bainitic reaction developing from decarburization of austenitic grains during cementite network formation.

  17. Structural Parameters and Strengthening Mechanisms in Cold-Drawn Pearlitic Steel Wires

    DEFF Research Database (Denmark)

    Zhang, Xiaodan; Godfrey, Andy; Huang, Xiaoxu; Hansen, Niels

    2012-01-01

    Pearlitic steel wires have a nanoscale structure and a strength which can reach 5 GPa. In order to investigate strengthening mechanisms, structural parameters including interlamellar spacing, dislocation density and cementite decomposition, have been analyzed by transmission electron microscopy and...... high resolution electron microscopy in wires cold drawn up to a strain of 3.7. Three strengthening mechanisms, namely boundary strengthening, dislocation strengthening and solid solution hardening have been analyzed and good agreement has been found between the measured flow stress and the value...

  18. Enhanced thermal stability in nanostructured bainitic steel

    International Nuclear Information System (INIS)

    We report an attempt at increasing the thermal stability of nanocrystalline bainite to tempering heat treatments by enhancing the silicon concentration of the alloy. Validation experiments have been conducted using synchrotron X-irradiation during tempering heat treatment. It is found that the change in alloying successfully stabilizes the austenite at elevated temperatures by retarding cementite formation to temperatures as high as 500 °C. Other changes reflected in the lattice parameters of the major phases have revealed further information about the mechanisms involved

  19. Moessbauer spectroscopic investigation of retained-austenite content of high-carbon tool steel during isothermal tempering of as-quenched samples

    Energy Technology Data Exchange (ETDEWEB)

    Bala, Piotr, E-mail: pbala@agh.edu.pl; Krawczyk, Janusz [AGH University of Science and Technology, Faculty of Metals Engineering and Industrial Computer Science (Poland); Hanc, Aneta [University of Silesia, Faculty of Computer and Materials Science (Poland)

    2009-04-15

    This work presents the results of investigations using Moessbauer spectroscopy technique and their interpretation concerning retained austenite (RA) and its transformation during tempering in relation to previously conducted dilatometric, microscopic and mechanical investigations. This research was conducted on a new high-carbon alloy steel 120 MnCrMoV8-6-4-2, which was designed in 1998, in Phase Transformations Research Group at the AGH UST. The influence of the tempering time on the mechanical and chemical stability of retained austenite and on the products of its transformation, nucleation and solubility of {epsilon} carbides and cementite nucleation and growth, was determined.

  20. Moessbauer spectroscopic investigation of retained-austenite content of high-carbon tool steel during isothermal tempering of as-quenched samples

    International Nuclear Information System (INIS)

    This work presents the results of investigations using Moessbauer spectroscopy technique and their interpretation concerning retained austenite (RA) and its transformation during tempering in relation to previously conducted dilatometric, microscopic and mechanical investigations. This research was conducted on a new high-carbon alloy steel 120 MnCrMoV8-6-4-2, which was designed in 1998, in Phase Transformations Research Group at the AGH UST. The influence of the tempering time on the mechanical and chemical stability of retained austenite and on the products of its transformation, nucleation and solubility of ε carbides and cementite nucleation and growth, was determined.

  1. Dislocation-based plasticity and strengthening mechanisms in sub-20 nm lamellar structures in pearlitic steel wire

    DEFF Research Database (Denmark)

    Zhang, Xiaodan; Hansen, Niels; Godfrey, Andrew; Huang, Xiaoxu

    2016-01-01

    The tensile properties and the deformation microstructure of pearlitic steel (0.8 wt % C) have been quantified in wires drawn to strains in the range from 3.7 to 5.4, having a flow stress in the range from 3.5 to 4.5 GPa. With increasing strain the interlamellar spacing (ILS) decreases from about...... 20 to 10 nm and the thickness of the cementite lamellae decreases from about 2 nm to about 0.7 nm, representing a structure, which breaks up at large strains, decomposes and releases carbon to the ferrite lamellae. The dislocation density increases continuously with strain and reaches about 5 1016 m2...

  2. Searching for high magnetization density in bulk Fe: the new metastable Fe$_6$ phase

    OpenAIRE

    Umemoto, Koichiro; Himmetoglu, Burak; Wang, Jian-Ping; Wentzcovitch, Renata M.; Cococcioni, Matteo

    2014-01-01

    We report the discovery of a new allotrope of iron by first principles calculations. This phase has $Pmn2_1$ symmetry, a six-atom unit cell (hence the name Fe$_6$), and the highest magnetization density (M$_s$) among all known crystalline phases of iron. Obtained from the structural optimizations of the Fe$_3$C-cementite crystal upon carbon removal, $Pmn2_1$ Fe$_6$ is shown to result from the stabilization of a ferromagnetic FCC phase, further strained along the Bain path. Although metastable...

  3. Effect of post-weld heat treatment on hydrogen-assisted cracking behavior of high-strength process pipe steel in a sour environment

    International Nuclear Information System (INIS)

    The influence of post-weld heat treatment on hydrogen-assisted cracking of process pipe steel is investigated in terms of change in hydrogen trapping site. This study reports that, contrary to other microstructures, in acicular ferrite, cementite bodies acting as reversible trapping sites for hydrogen atoms are newly precipitated along the grain boundary by the post-weld heat treatment conducted at 620 °C. This leads to an increase in diffusible hydrogen content in the steel that makes it more susceptible to hydrogen-induced cracking.

  4. Influence of supersaturated carbon on the diffusion of Ni in ferrite determined by atom probe tomography

    KAUST Repository

    Kresse, T.

    2013-09-01

    In patented and cold-drawn pearlitic steel wires dissociation of cementite occurs during mechanical deformation. In this study the influence of the carbon decomposition on the diffusion of nickel in ferrite is investigated by means of atom probe tomography. In the temperature range 423-523 K we observed a much smaller activation energy of Ni diffusion than for self-diffusion in body-centered cubic iron, indicating an increased vacancy density owing to enhanced formation of vacancy-carbon complexes. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  5. Mathematical Model of the Processoof Pearlite Austenitization

    Directory of Open Access Journals (Sweden)

    Olejarczyk-Wożeńska I.

    2014-10-01

    Full Text Available The paper presents a mathematical model of the pearlite - austenite transformation. The description of this process uses the diffusion mechanism which takes place between the plates of ferrite and cementite (pearlite as well as austenite. The process of austenite growth was described by means of a system of differential equations solved with the use of the finite difference method. The developed model was implemented in the environment of Delphi 4. The proprietary program allows for the calculation of the rate and time of the transformation at an assumed temperature as well as to determine the TTT diagram for the assigned temperature range.

  6. Friction stir processing on high carbon steel U12

    International Nuclear Information System (INIS)

    Friction stir processing (FSP) of high carbon steel (U12) samples has been carried out using a milling machine and tools made of cemented tungsten carbide. The FSP tool has been made in the shape of 5×5×1.5 mm. The microstructural characterization of obtained stir zone and heat affected zone has been carried out. Microhardness at the level of 700 MPa has been obtained in the stir zone with microstructure consisting of large grains and cementitte network. This high-level of microhardness is explained by bainitic reaction developing from decarburization of austenitic grains during cementite network formation

  7. Hybrid Friction Stir Welding of High-carbon Steel

    Institute of Scientific and Technical Information of China (English)

    Don-Hyun Choi; Seung-Boo Jung; Chang-Yong Lee; Byung-Wook Ahn; Jung-Hyun Choi; Yun-Mo Yeon; Keun Song; Seung-Gab Hong; Won-Bae Lee; Ki-Bong Kang

    2011-01-01

    A high-carbon steel joint, SK5 (0.84 wt% C), was successfully welded by friction stir welding (FSW), both without and with a gas torch, in order to control the cooling rate during welding. After welding, the weld zone comprised gray and black regions, corresponding to microstructural variation: a martensite structure and a duplex structure of ferrite and cementite, respectively. The volume fraction of the martensite structure and the Vickers hardness in the welds were decreased with the using of the gas torch, which was related with the lower cooling rate.

  8. The role of C and Mn at the austenite/pearlite reaction front during non-steady-state pearlite growth in a Fe–C–Mn steel

    International Nuclear Information System (INIS)

    The role of C and Mn during the growth of pearlite under non-steady state conditions is analyzed by comparing phase compositions of austenite, ferrite and cementite (γ+α+θ) through the use of transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and atom probe tomography (APT) measurements across the austenite/pearlite interface. A local Mn enrichment and C depletion at the austenite/pearlite interface has been measured, which causes a change in the transformation driving force with time during divergent pearlite growth

  9. Microstructure and mechanical properties of a low carbon carbide-free bainitic steel co-alloyed with Al and Si

    International Nuclear Information System (INIS)

    Highlight: ► A low carbon carbide-free bainitic steel was produced. ► Co-alloying with Al and Si suppresses the precipitation of cementite. ► Fine carbide-free bainite laths and thin film-like retained austenite obtained. ► Excellent combination of strength, ductility and toughness enabled. -- Abstract: A low carbon, low alloy steel has been investigated for producing low carbon carbide-free bainitic microstructure by co-addition of alloying elements of aluminum and silicon. The influence of heat treatment process on microstructure, impact toughness as well as tensile properties was investigated by light optical microscopy, transmission electron microscopy, X-ray diffraction and mechanical property tests. The results demonstrate that the co-addition of aluminum and silicon in the investigated steel plays an effective role in suppressing the precipitation of cementite. A desired microstructure consisting of mainly fine-scale carbide-free bainitic ferrite and thin film-like retained austenite located between the ferrite laths was obtained and accordingly an excellent combination of toughness, ductility and strength was achieved by optimized heat treatments, i.e. by isothermal treatment at 320 °C for ∼84 min or more. The microstructure-mechanical property relationships are discussed.

  10. Influence of Post-Weld Heat Treatment on the Microstructure, Microhardness, and Toughness of a Weld Metal for Hot Bend

    Directory of Open Access Journals (Sweden)

    Xiu-Lin Han

    2016-03-01

    Full Text Available In this work, a weld metal in K65 pipeline steel pipe has been processed through self-designed post-weld heat treatments including reheating and tempering associated with hot bending. The microstructures and the corresponding toughness and microhardness of the weld metal subjected to the post-weld heat treatments have been investigated. Results show that with the increase in reheating temperature, austenite grain size increases and the main microstructures transition from fine polygonal ferrite (PF to granular bainitic ferrite (GB. The density of the high angle boundary decreases at higher reheating temperature, leading to a loss of impact toughness. Lots of martensite/austenite (M/A constituents are observed after reheating, and to a large extent transform into cementite after further tempering. At high reheating temperatures, the increased hardenability promotes the formation of large quantities of M/A constituents. After tempering, the cementite particles become denser and coarser, which considerably deteriorates the impact toughness. Additionally, microhardness has a good linear relation with the mean equivalent diameter of ferrite grain with a low boundary tolerance angle (2°−8°, which shows that the hardness is controlled by low misorientation grain boundaries for the weld metal.

  11. Effect of initial microstructure on mechanical properties in warm caliber rolling of high carbon steel

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Y.S. [National Research Laboratory for Computer Aided Materials Processing, Department of Mechanical Engineering, KAIST, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Son, I.H. [Wire Rod Research Group, Technical Research Laboratories, POSCO, 1 Goedong-dong, Nam-gu, Pohang, Gyeongbuk 790-785 (Korea, Republic of); Jung, K.H.; Kim, D.K. [National Research Laboratory for Computer Aided Materials Processing, Department of Mechanical Engineering, KAIST, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Lee, D.L. [Wire Rod Research Group, Technical Research Laboratories, POSCO, 1 Goedong-dong, Nam-gu, Pohang, Gyeongbuk 790-785 (Korea, Republic of); Im, Y.T., E-mail: ytim@kaist.ac.kr [National Research Laboratory for Computer Aided Materials Processing, Department of Mechanical Engineering, KAIST, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2011-07-15

    Highlights: {yields} The effect of initial microstructure on change of micro-hardness, tension, and Charpy tests were investigated by warm caliber rolling (WCR). {yields} Smaller ferrite grain and dispersed cementite particles with smaller interspacing increased the strength and toughness. {yields} In WCR, elongation hardly decreased compared to the conventional hot rolling. {yields} Depending on the microstructure change, WCR guaranteed higher impact energy and the mode of fracture varied as well. - Abstract: In this study, the effect of initial microstructure on change of mechanical properties was investigated by warm caliber rolling (WCR) of high carbon steel. Experiments were carried out with two different kinds of initial microstructures of pearlite and tempered martensite at the temperature of 500 deg. C. For comparison, the microstructure of austenite phase obtained from the conventional hot rolling at the temperature of 900 deg. C up to about 83% of the accumulative reduction in area was assumed to be a reference case. It was found that the WCR provided better mechanical properties in terms of strength and toughness compared to the conventional hot rolling based on experimental results of micro-hardness, tension, and Charpy impact tests. The improvement of strength and toughness was attributed to smaller ferrite grain and dispersed cementite particles with smaller interspacing aligned to the rolling direction after the WCR owing to field emission scanning electron microscopy. The investigated WCR might be useful in obtaining the high strength material with better toughness without adding new alloying elements for industrial applications according to the present investigation.

  12. Structure–property relationship in a 960 MPa grade ultrahigh strength low carbon niobium–vanadium microalloyed steel: The significance of high frequency induction tempering

    International Nuclear Information System (INIS)

    The present study describes the microstructure and precipitation behavior in an ultra-high strength low carbon niobium–vanadium microalloyed steel that was processed by quenching and high frequency induction tempering. Ultrahigh yield strength of ∼1000 MPa with high elongation of ∼15% and high low temperature toughness of 55 J (half thickness) at −40 °C was obtained after quenching from austenitization at 900 °C for 30 min, and tempering at 600 °C for 15 min by induction reheating with a reheating rate of ∼50 °C/s. While the yield strength increase on tempering was similar for both induction reheating and conventional reheating (electrical resistance reheating), there was ∼100% increase in low temperature toughness in induction reheated steel compared to the conventional reheating process. The underlying reason for the increase in toughness was attributed to the transformation of cementite film observed in conventional reheating and tempering to nanoscale cementite in induction reheating and tempering. The precipitation of nanoscale carbides is believed to significantly contribute to ultra-high strength, good ductility, and high toughness in the high frequency induction reheating and tempering process

  13. Laser transformation hardening of a high-purity iron-carbon-chromium alloy

    International Nuclear Information System (INIS)

    Successful laser transformation hardening of steel surfaces requires that the absorbed laser energy is sufficient to austenitize the initial microstructure to a depth of 0.5 mm or more. Hardening is accomplished when rapid cooling by conduction of heat away from the surface causes transformation of the austenite layer to martensite. Heating and cooling rates of 104 K/s or greater are typical of the laser hardening process and the entire thermal cycle may be accomplished in less than 0.1 s. In an earlier study, laser surface hardening of commercial plain carbon and chromium alloyed steels was examined. It was shown that in the alloyed steel chromium enrichment of the cementite in the initial microstructure could prevent complete transformation of pearlite to asutenite during the very rapid laser heating cycle. However, interpretation of the results was complicated somewhat by the fact that manganese was also partitioned to the cementite. The purpose of this work was to conduct selected identical laser heating experiments on a high-purity Fe-C-Cr alloy to test the effect of chromium unequivocally, i.e., in the absence of manganese and other elements normally present in commercial steels

  14. Effect of Mn and Cr addition on the properties of extra heavy gauge Mn-Mo-Ni steel plates for pressure vessels

    International Nuclear Information System (INIS)

    Effects of Mn and Cr addition on tensile properties and low temperature toughness have been investigated with extra heavy gauge pressure vessel steel plates that have the chemical composition of 0.12%C-1.4%Mn-0.3%Mo-0.75%Ni, then the results have been discussed with metallurgical view points. The Cr addition, not less effectively than the increase of Mn content, increases the tensile strength at both room temperature and 350degC, with less deterioration of Charpy absorbed energy. With the cooling rates that are equivalent to those at quenching of such extra heavy gauge plates as 150mm thick, the Cr addition works to suppress the elevation of starting temperatures of bainitic transformation (Bs). This suppression of elevation of Bs could be the reason for the improvement of tensile strength with Cr addition. The Cr addition also changes the morphology of cementite in the region surrounded by acicular ferrite (carbide free bainite) from lamellar one to small sized granular one. This morphological change of cementite could lighten the deterioration of the Charpy absorbed energy through lowering the possibilities of crack initiation. (author)

  15. Deviations from cooperative growth mode during eutectoid transformation: Insights from a phase-field approach

    International Nuclear Information System (INIS)

    The non-cooperative eutectoid transformation relies on the presence of pre-existing cementite particles in the parent austenitic phase and yields a product, popularly known as the divorced eutectoid. Under isothermal conditions, two of the important parameters that influence the transformation mechanism and determine the final morphology are undercooling (below the A1 temperature) and interparticle spacing. Although the criteria that govern the morphological transition from lamellar to divorced is experimentally well established, numerical studies giving a detailed exposition of the non-cooperative transformation mechanism have not been reported extensively. In the present work, we employ a multiphase-field model that uses thermodynamic information from the CALPHAD database to numerically simulate the pulling-away of the advancing ferrite–austenite interface from cementite, which results in a transition from lamellar to divorced eutectoid morphology in Fe–C alloy. We also identify the onset of a concurrent growth and coarsening regime at small interparticle spacing and low undercooling. We analyze the simulation results to unravel the essential physics behind this complex spatial and temporal evolution pathway and amend the existing criteria by constructing a Lamellar-Divorced-Coarsening (LDC) map

  16. Chemical and morphological changes during production of conducting carbons from ferrocene-poly (furfuryl alcohol)

    International Nuclear Information System (INIS)

    Carbons are obtained by heating organic substances up to 1000 deg C under inert atmosphere. The electronic properties of carbons change dramatically during this carbonisation process. By controlled preparation, it is possible to obtain electronically functional materials. The addition of iron to the organic starting material has a strong modifying effect and, in particular, carbonising a ferrocene-poly(furfuryl alcohol) (PFA) mixture at 700 deg C produces a carbon with a comparable electron transfer rate to platinum. 57 Moessbauer spectra showed that the first transformation of the ferrocene is to magnetite, at 200-300 deg C. At 600 deg C, the magnetite is converted to wustite, while at 650 deg C α-iron starts to appear. The final products at 800 deg C were α-iron, γ-iron and cementite, Fe3C. Morphological changes were studied by SEM. The tentative explanation for these results is that the iron promotes the elimination of oxygen from the initial PFA structure to produce magnetite. At 600-650 deg C , the magnetite is carbothermically reduced to wustite and α-iron, forming glassy carbon. Above 700 deg C, the iron dissolves carbon atoms to make a solid solution. On cooling, some of this fractionates into graphitic carbon, cementite and γ-iron stabilised by the carbon atoms. We believe that the furry surface is produced in this cooling process

  17. Effect of initial microstructure on mechanical properties in warm caliber rolling of high carbon steel

    International Nuclear Information System (INIS)

    Highlights: → The effect of initial microstructure on change of micro-hardness, tension, and Charpy tests were investigated by warm caliber rolling (WCR). → Smaller ferrite grain and dispersed cementite particles with smaller interspacing increased the strength and toughness. → In WCR, elongation hardly decreased compared to the conventional hot rolling. → Depending on the microstructure change, WCR guaranteed higher impact energy and the mode of fracture varied as well. - Abstract: In this study, the effect of initial microstructure on change of mechanical properties was investigated by warm caliber rolling (WCR) of high carbon steel. Experiments were carried out with two different kinds of initial microstructures of pearlite and tempered martensite at the temperature of 500 deg. C. For comparison, the microstructure of austenite phase obtained from the conventional hot rolling at the temperature of 900 deg. C up to about 83% of the accumulative reduction in area was assumed to be a reference case. It was found that the WCR provided better mechanical properties in terms of strength and toughness compared to the conventional hot rolling based on experimental results of micro-hardness, tension, and Charpy impact tests. The improvement of strength and toughness was attributed to smaller ferrite grain and dispersed cementite particles with smaller interspacing aligned to the rolling direction after the WCR owing to field emission scanning electron microscopy. The investigated WCR might be useful in obtaining the high strength material with better toughness without adding new alloying elements for industrial applications according to the present investigation.

  18. Microstructure of high strength niobium-containing pipeline steel

    Energy Technology Data Exchange (ETDEWEB)

    Shanmugam, S. [Center for Structural and Functional Materials, Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504-4130 (United States); Misra, R.D.K. [Center for Structural and Functional Materials, Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, LA 70504-4130 (United States)]. E-mail: dmisra@louisiana.edu; Hartmann, J. [Mittal Steel, Indiana Harbor Works, 3001 Dickey Road, East Chicago, IN 46312 (United States); Jansto, S.G. [Reference Metals, 1000 Old Pond Road, Bridgeville, PA 15017 (United States)

    2006-12-15

    The paper describes the microstructural constituents in a industrially processed Nb-microalloyed pipeline steel having yield strength of {approx}620 MPa. The microstructure of base, heat affected zone (HAZ), and weld metal of the fabricated steel pipe was examined by optical and transmission electron microscopy. The microstructure of thermomechanically processed pipeline steel primarily consisted of non-equiaxed ferrite of mixed morphologies with small fraction of degenerated pearlite. The microstructure contained high dislocation density, sub-boundaries and dislocation substructures. The HAZ was characterized by a combination of fine and coarse grained polygonal ferrite structure with high density of dislocations and fine cementite particles. In the weld metal, the constituents of complex ferrite were low temperature transformation products formed during continuous cooling such as quasi-polygonal or massive ferrite, acicular ferrite, bainitic ferrite and dispersion of coarse and fine cementite particles in the ferrite matrix. The precipitates in the investigated pipeline steel were of duplex type containing either Nb and Ti or Ti and Mo, even though the steel contained low concentration of titanium. Precipitates of different morphology and size range were observed and include rectangular ({approx}100-130 nm), cuboidal/spherical ({approx}20-100 nm), fine ({approx}10-20 nm) and very fine (<10 nm). They were MC type of carbides.

  19. Microstructure of high strength niobium-containing pipeline steel

    International Nuclear Information System (INIS)

    The paper describes the microstructural constituents in a industrially processed Nb-microalloyed pipeline steel having yield strength of ∼620 MPa. The microstructure of base, heat affected zone (HAZ), and weld metal of the fabricated steel pipe was examined by optical and transmission electron microscopy. The microstructure of thermomechanically processed pipeline steel primarily consisted of non-equiaxed ferrite of mixed morphologies with small fraction of degenerated pearlite. The microstructure contained high dislocation density, sub-boundaries and dislocation substructures. The HAZ was characterized by a combination of fine and coarse grained polygonal ferrite structure with high density of dislocations and fine cementite particles. In the weld metal, the constituents of complex ferrite were low temperature transformation products formed during continuous cooling such as quasi-polygonal or massive ferrite, acicular ferrite, bainitic ferrite and dispersion of coarse and fine cementite particles in the ferrite matrix. The precipitates in the investigated pipeline steel were of duplex type containing either Nb and Ti or Ti and Mo, even though the steel contained low concentration of titanium. Precipitates of different morphology and size range were observed and include rectangular (∼100-130 nm), cuboidal/spherical (∼20-100 nm), fine (∼10-20 nm) and very fine (<10 nm). They were MC type of carbides

  20. Surface treatment of 0.20% C carbon steel by high-current pulsed electron beam

    Institute of Scientific and Technical Information of China (English)

    XU Guo-cheng; FU Shi-you; GUAN Qing-feng

    2006-01-01

    A high-current pulsed electron beam(HCPEB) generated on the system of Nadezhda-2 was applied to improve the microstructure and performance of 0.20% C low carbon steel. Surface layers of the samples bombarded by explosive electron beam at different pulses was observed by using electron microscopy. The physical model of the thermal-stress process and related modification mechanism as a result of HCPEB irradiation was also investigated. After HCPEB post treatments, obvious changes in microstructure and significant hardening occur in the depth of 200-250 μm from the surface after HCPEB irradiation. Rapid heating and subsequent rapid solidification induce heavy plastic deformation, which results in that the laminated structure of pearlite is substituted by dispersive rounded-like cementites in the near-surface. The effect of HCPEB treatment can reach more than 500 m depth from the surface. The original crystalline structure is changed to a different degree that grows with the numbers of bombardment, and in the surface layer amorphous states and nanocrystaline structures consisting of grains of γ-phase and cementite are found. The violent stress induced by HCPEB irradiation is the origin of the nanostructured and amorphous structure formation.

  1. Application of headed studs in steel fiber reinforced cementitious composite slab of steel beam-column connection

    Science.gov (United States)

    Yao, Cui; Nakashima, Masayoshi

    2012-03-01

    Steel fiber reinforced cementitous composites (SFRCC) is a promising material with high strength in both compression and tension compared with normal concrete. The ductility is also greatly improved because of 6% volume portion of straight steel fibers. A steel beam-column connection with Steel fiber reinforced cementitous composites (SFRCC) slab diaphragms is proposed to overcome the damage caused by the weld. The push-out test results suggested that the application of SFRCC promises larger shear forces transferred through headed studs allocated in a small area in the slab. Finite element models were developed to simulate the behavior of headed studs. The failure mechanism of the grouped arrangement is further discussed based on a series of parametric analysis. In the proposed connection, the SFRCC slab is designed as an exterior diaphragm to transfer the beam flange load to the column face. The headed studs are densely arranged on the beam flange to connect the SFRCC slab diaphragms and steel beams. The seismic performance and failure mechanism of the SFRCC slab diaphragm beam-column connection were investigated based on the cyclic loading test. Beam hinge mechanism was achieved at the end of the SFRCC slab diaphragm by using sufficient studs and appropriate rebars in the SFRCC slab.

  2. Strength and ductility of medium carbon steel after equal channel angular pressing

    International Nuclear Information System (INIS)

    Upon the ECA pressing at 4000C of the AISI 1045 steel with 0.45% C, the processes of dynamic recovery are developed with the formation of subgrains of ∼320 nm in size and isolated grains of submicron size with high-angle boundaries. The fragmentation and partial spheroidization of the cementite lamellae is observed within the pearlite colonies. Deformation in pearlite grains is not sufficient, either to break down the cementite lamellae structure or to produce the refinement of ferrite grains. Annealing of the deformed steel with 0.45%C after ECA pressing causes the perfection of the recovered structure in ferrite and further processes of fragmentation, spheroidization, and coagulation of carbide phase. Annealing at T = 5500C for 5 h leads to almost complete spheroidization of carbides with an average size of ∼280 nm and increases to some extent the average ferrite grain (subgrain) size to ∼410 nm. The submicron grain-subgrain structure of the steel with 0.45%C causes a significant strengthening (YS = 960 MPa) at a retention of satisfactory elongation (EL = 8%). Subsequent annealing at T 5500C for 5 h increases ductility to EL = 14% and decreases the yield strength to YS = 745 MPa.

  3. Response of cold briquetted iron (CBI to high temperatures treatment

    Directory of Open Access Journals (Sweden)

    Ibitoye S.A.

    2010-01-01

    Full Text Available This investigation was carried out to assess the behaviours of Cold Briquetted Iron (CBI when exposed to increasing temperature changes up to its complete melting. High-temperature behaviours and melting characteristics of CBI were studied. Ground as-received CBI briquette and those heated to temperatures ranging from 500°C to 1000°C were sieved to maximum of 30 microns diameter size and their room-temperature x-ray diffraction (XRD measured. CBI was found to contain among others, α-iron, cementite and silica phases. Cementite was found to commence decomposition at 500°C - 600°C and completed by 700°C with conspicuous increase in the concentration of α-iron phase. Only α-iron and silica phases were sustained in CBI at temperatures above 700°C. In an inert atmosphere, it was discovered that CBI melted over a temperature range of 1527.3°C to 1536.96°C accompanied by an irrecoverable weight loss of 9.6 wt.% of the starting material. It was concluded that melting CBI would require charging along it appropriate fluxes to take care of the unreduced iron oxide and incorporation into facility for melting CBI an effective deslagging mechanism to remove unavoidable possible voluminous slag that would be formed.

  4. Microstructure of as-quenched 3. 5 NiCrMoV rotor steel. Pt. 2. Double diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Gates, J.D.; Atrens, A.; Smith, I.O.

    1987-06-01

    In a study of the microstructural features of 3.5 NiCrMoV steam turbine rotor steel in the as-quenched state, correct interpretation of selected area electron diffraction patterns has been found to be nontrivial. A major complicating factor is the widespread occurrence of double diffraction associated with micro-twins in the martensite. The resulting diffraction patterns are similar to those expected from cementite and may even suggest an orientation relationship consistent with the Bagaryatskii relationship. Moreover in the as-quenched steel they are the only well-developed diffraction patterns observed. Cases of failure to recognise double diffraction, with misinterpretation as evidence for the presence of cementite, have been brought to light. Double diffraction also occurs in regions containing retained austenite. A notation of the form d-dsub(hkl/sub ..cap alpha../) is proposed for diffraction spots due to double diffraction micro-twins, based on the observed relationship between the reciprocal lattice spacings of the double diffraction spots and those of the matrix spots.

  5. Structure–property relationship in a 960 MPa grade ultrahigh strength low carbon niobium–vanadium microalloyed steel: The significance of high frequency induction tempering

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Z.J.; Fang, Y.P.; Han, G.; Guo, H. [School of Materials Science and Engineering, University of Science and Technology, 30 Xueyuan Road, Haidian Street, Beijing 100083 (China); Misra, R.D.K. [Department of Metallurgical and Materials Engineering, University of Texas at El Paso, El Paso, TX 79968 (United States); Shang, C.J., E-mail: cjshang@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology, 30 Xueyuan Road, Haidian Street, Beijing 100083 (China)

    2014-11-17

    The present study describes the microstructure and precipitation behavior in an ultra-high strength low carbon niobium–vanadium microalloyed steel that was processed by quenching and high frequency induction tempering. Ultrahigh yield strength of ∼1000 MPa with high elongation of ∼15% and high low temperature toughness of 55 J (half thickness) at −40 °C was obtained after quenching from austenitization at 900 °C for 30 min, and tempering at 600 °C for 15 min by induction reheating with a reheating rate of ∼50 °C/s. While the yield strength increase on tempering was similar for both induction reheating and conventional reheating (electrical resistance reheating), there was ∼100% increase in low temperature toughness in induction reheated steel compared to the conventional reheating process. The underlying reason for the increase in toughness was attributed to the transformation of cementite film observed in conventional reheating and tempering to nanoscale cementite in induction reheating and tempering. The precipitation of nanoscale carbides is believed to significantly contribute to ultra-high strength, good ductility, and high toughness in the high frequency induction reheating and tempering process.

  6. Microstructural evolution of AISI 4340 steel during Direct Metal Deposition process

    International Nuclear Information System (INIS)

    Research highlights: → 4340 steel was successfully deposited using diode laser DMD system on mild steel. → Ferrite, martensite and cementite microstructural phases were identified in the clad. → Lattice parameters of identified phases are shorter than reported lattice parameters. → Microhardness of the clad decreases down the clad layers. → Decrease in microhardness corresponds to degree of tempering of martensite phase. - Abstract: In the current investigation AISI 4340 steel was laser deposited on a rolled mild steel substrate by Direct Metal Deposition (DMD) technology. The microstructural investigation of the clad was performed using optical and electron microscopes and X-ray diffraction techniques. The microstructure consisted of ferrite, martensite and cementite phases. Two types of martensite, lathe-type and plate-type, were observed in the microstructure. Decrease in microhardness values from the top layer to the alloy layer proves that the degree of tempering of the martensite phase increases in the same direction. The lattice parameters of the identified phases were found to be shorter than those reported in literature. The reported parameters in literature are from samples processed under equilibrium conditions.

  7. Optimization of chemical compositions in low-carbon Al-killed enamel steel produced by ultra-fast continuous annealing

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Futao, E-mail: dongft@sina.com [The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Du, Linxiu; Liu, Xianghua [The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819 (China); Xue, Fei [College of Electrical Engineering, Hebei United University, Tangshan 063000 (China)

    2013-10-15

    The influence of Mn,S and B contents on microstructural characteristics, mechanical properties and hydrogen trapping ability of low-carbon Al-killed enamel steel was investigated. The materials were produced and processed in a laboratory and the ultra-fast continuous annealing processing was performed using a continuous annealing simulator. It was found that increasing Mn,S contents in steel can improve its hydrogen trapping ability which is attributed by refined ferrite grains, more dispersed cementite and added MnS inclusions. Nevertheless, it deteriorates mechanical properties of steel sheet. Addition of trace boron results in both good mechanical properties and significantly improved hydrogen trapping ability. The boron combined with nitrogen segregating at grain boundaries, cementite and MnS inclusions, provides higher amount of attractive hydrogen trapping sites and raises the activation energy for hydrogen desorption from them. - Highlights: • We study microstructures and properties in low-carbon Al-killed enamel steel. • Hydrogen diffusion coefficients are measured to reflect fish-scale resistance. • Manganese improves hydrogen trapping ability but decrease deep-drawing ability. • Boron improves both hydrogen trapping ability and deep-drawing ability. • Both excellent mechanical properties and fish-scale resistance can be matched.

  8. Distribution and anisotropy of dislocations in cold-drawn pearlitic steel wires analyzed using micro-beam X-ray diffraction

    International Nuclear Information System (INIS)

    To characterize the distribution and anisotropy of dislocations in cold-drawn pearlitic steel wires, X-ray diffraction line-profile analysis was performed using synchrotron radiation micro-beams. An analytical procedure for correcting the instrumental line broadening for highly directional micro-beams was developed using diffraction profiles of standard CeO2 powder. Although the CeO2 powder line profile includes line broadening due to its microstructural imperfections, the instrumental broadening can be obtained by estimating the effect of the microstructural imperfections on the line broadening. The plastic shear strain was generally more severe near the surface than the center of the wire, whereas the dislocation density distribution was almost constant from the center to the surface. On the other hand, the dislocation rearrangement, which evolves the dislocation cell structure, progressed closer to the surface. It was also revealed that a difference between the hardness in axial and transverse wire directions could be explained by anisotropic dislocation density. Line-profile analysis based on diffraction data at elevated temperatures was performed. Whereas the cementite recovery progressed at a constant rate, the ferrite phase recovery rate was temperature-dependent, suggesting that the ferrite phase recovery was less related to that of the cementite phase. (author)

  9. Optimization of chemical compositions in low-carbon Al-killed enamel steel produced by ultra-fast continuous annealing

    International Nuclear Information System (INIS)

    The influence of Mn,S and B contents on microstructural characteristics, mechanical properties and hydrogen trapping ability of low-carbon Al-killed enamel steel was investigated. The materials were produced and processed in a laboratory and the ultra-fast continuous annealing processing was performed using a continuous annealing simulator. It was found that increasing Mn,S contents in steel can improve its hydrogen trapping ability which is attributed by refined ferrite grains, more dispersed cementite and added MnS inclusions. Nevertheless, it deteriorates mechanical properties of steel sheet. Addition of trace boron results in both good mechanical properties and significantly improved hydrogen trapping ability. The boron combined with nitrogen segregating at grain boundaries, cementite and MnS inclusions, provides higher amount of attractive hydrogen trapping sites and raises the activation energy for hydrogen desorption from them. - Highlights: • We study microstructures and properties in low-carbon Al-killed enamel steel. • Hydrogen diffusion coefficients are measured to reflect fish-scale resistance. • Manganese improves hydrogen trapping ability but decrease deep-drawing ability. • Boron improves both hydrogen trapping ability and deep-drawing ability. • Both excellent mechanical properties and fish-scale resistance can be matched

  10. Transient liquid phase bonding of carbon steel tubes using a Cu interlayer: Characterization and comparison with amorphous Fe–B–Si interlayer bonds

    Energy Technology Data Exchange (ETDEWEB)

    Di Luozzo, Nicolas, E-mail: nicolasdiluozzo@gmail.com [Laboratorio de Sólidos Amorfos, INTECIN, Facultad de Ingeniería, Universidad de Buenos Aires – CONICET, Paseo Colón 850, C1063ACV Buenos Aires (Argentina); Laboratoire des Matériaux et du Génie Physique (CNRS UMR 5628), Grenoble Institute of Technology, MINATEC, Grenoble Cedex 1 (France); Boudard, Michel; Doisneau, Béatrice [Laboratoire des Matériaux et du Génie Physique (CNRS UMR 5628), Grenoble Institute of Technology, MINATEC, Grenoble Cedex 1 (France); Fontana, Marcelo; Arcondo, Bibiana [Laboratorio de Sólidos Amorfos, INTECIN, Facultad de Ingeniería, Universidad de Buenos Aires – CONICET, Paseo Colón 850, C1063ACV Buenos Aires (Argentina)

    2014-12-05

    Highlights: • Cu and Fe–B–Si foils were used as interlayers to bond steel tubes by TLPB process. • The microstructure and mechanical properties were characterized. • In Cu bonded samples, the solidification process was not systematically completed. • When using Cu foils, evidences of epitaxial solidification were observed. • Tensile tests show that Cu and Fe–B–Si bonded samples failed away from the joint. - Abstract: In the present work the transient liquid phase bonding process was performed to join seamless carbon steel tubes using commercially pure Cu interlayers. The structural and mechanical characteristics of the resulting bonds are compared with those achieved using amorphous Fe–B–Si interlayers, under the same process parameters: a holding temperature of 1300 °C, a holding time of 7 min and an applied pressure of 5 MPa. The joined tubes microstructures were characterized by direct observations – scanning electron microscopy – and diffraction techniques – electron backscatter diffraction. Chemical analysis was performed using electron probe microanalysis. Whereas the amorphous Fe-B-Si interlayer leads to a completion of the bonding process over the whole bonding area, the bond performed using a Cu interlayer achieved the completion of the bonding process only partially. As the Cu is a cementite promoter, the amount of cementite coexisting with ferrite grains is higher in the joint region (JR) – corresponding to the higher concentration of Cu – as compared with the heat affected zone (HAZ) and the base metal (BM). An opposite effect is observed when using Fe-B-Si interlayers due to the fact that the cementite is unable to form in Si enriched zones – the microstructure at the JR presents only ferrite grains. Tensile tests show that the joined tubes using Cu or Fe–B–Si interlayers failed away from the bond, at the HAZ, attaining almost the same ultimate tensile strength of the BM, in the as-received condition. Hardness

  11. Transient liquid phase bonding of carbon steel tubes using a Cu interlayer: Characterization and comparison with amorphous Fe–B–Si interlayer bonds

    International Nuclear Information System (INIS)

    Highlights: • Cu and Fe–B–Si foils were used as interlayers to bond steel tubes by TLPB process. • The microstructure and mechanical properties were characterized. • In Cu bonded samples, the solidification process was not systematically completed. • When using Cu foils, evidences of epitaxial solidification were observed. • Tensile tests show that Cu and Fe–B–Si bonded samples failed away from the joint. - Abstract: In the present work the transient liquid phase bonding process was performed to join seamless carbon steel tubes using commercially pure Cu interlayers. The structural and mechanical characteristics of the resulting bonds are compared with those achieved using amorphous Fe–B–Si interlayers, under the same process parameters: a holding temperature of 1300 °C, a holding time of 7 min and an applied pressure of 5 MPa. The joined tubes microstructures were characterized by direct observations – scanning electron microscopy – and diffraction techniques – electron backscatter diffraction. Chemical analysis was performed using electron probe microanalysis. Whereas the amorphous Fe-B-Si interlayer leads to a completion of the bonding process over the whole bonding area, the bond performed using a Cu interlayer achieved the completion of the bonding process only partially. As the Cu is a cementite promoter, the amount of cementite coexisting with ferrite grains is higher in the joint region (JR) – corresponding to the higher concentration of Cu – as compared with the heat affected zone (HAZ) and the base metal (BM). An opposite effect is observed when using Fe-B-Si interlayers due to the fact that the cementite is unable to form in Si enriched zones – the microstructure at the JR presents only ferrite grains. Tensile tests show that the joined tubes using Cu or Fe–B–Si interlayers failed away from the bond, at the HAZ, attaining almost the same ultimate tensile strength of the BM, in the as-received condition. Hardness

  12. Investigation on tempering of granular bainite in an offshore platform steel

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yanlei; Jia, Tao; Zhang, Xiangjun [The State Key Laboratory of Rolling and Automation, Northeastern University, P.O. Box 105, No. 11, Lane 3, Wenhua Road, HePing District, Shenyang 110819 (China); Liu, Zhenyu, E-mail: zyliu@mail.neu.edu.cn [The State Key Laboratory of Rolling and Automation, Northeastern University, P.O. Box 105, No. 11, Lane 3, Wenhua Road, HePing District, Shenyang 110819 (China); Misra, R.D.K. [Department of Metallurgical and Materials Engineering, University of Texas at El Paso, 500 W. University Avenue, El Paso, TX 79968-0521 (United States)

    2015-02-25

    Granular bainite, where M-A constituents dispersed in bainitic ferrite matrix usually presents at the half thickness region in thermo-mechanically processed heavy gauge offshore platform steel. In the present work, the decomposition of M-A constituents during tempering at 600 °C was firstly revealed by transmission electron microscopy (TEM) analysis, which primarily involves the precipitation of cementite, recovery and recrystallization of highly dislocated ferrite matrix. Then, the effect of tempering on mechanical properties was investigated by tempering at different temperature for 60 min. Results indicated that, at tempering temperature of 500–600 °C, large quantity of micro-alloying carbides precipitated and partially compensated the loss of strength mainly due to the decomposition of M-A constituents. Compared with the as-rolled state, the decomposition of M-A constituents and softening of bainitic ferrite matrix after tempering have resulted in higher density of microvoids and substantial plastic deformation before impact failure.

  13. Plastic Deformation and Softening of the Surface Layer of Railway Wheel

    Directory of Open Access Journals (Sweden)

    Ławrynowicz Z.

    2015-12-01

    Full Text Available In this study scanning electron microscope (SEM and optical micrograph observations were used to investigate the plastic deformation near the surface of the worn railway wheel following service. Microstructure, plastic deformation and micro-hardness of the material in the outermost tread layer of used passenger railway wheel were characterised. It was found that the material in the contact surface of wheel undergoes severe plastic deformation. Vickers micro-hardness measurements in the highly deformed layer could be correlated with softening of the outer wheel rim and the spheroidisation of the cementite phase. Examination of worn, railway wheel taken out of service, has indicated that cracks are predominantly initiated at the wheel surface down the edges of highly strained, pro-eutectoid ferrite zones (situated along prior austenite grain boundaries and that such pro-eutectoid ferrite zones also facilitate crack propagation.

  14. Study on microstructure and hardness uniformity of non-quenched prehardened steel for large section plastic mould

    International Nuclear Information System (INIS)

    Microstructures throughout a 460 mm x 800 mm cross-section of non-quenched prehardened (NQP) steel for plastic mould were characterized by optical microscopy, scanning electronic microscopy and transmission electronic microscopy. Strength and hardness of the NQP steel block was also tested. It is found that mechanical properties at core are close to that at surface and hardness distributes between 37 and 40 HRC through the whole section. Grains at core are coarser and deformation bands are observed at surface, while microstructures both at core and at surface are composed of bainitic ferrite laths with high dislocation density and interlath cementite and/or residual austensite. Considering continuous cooling transformation of the NQP steel, the small variation in hardness throughout the section is caused by the main microstructure bainite which possesses high hardenability. Moreover, the differences of the lath widths and dislocation density in baintic ferrite lath make hardness at surface a little higher than that at core

  15. Simulation of the kinetics of precipitation reactions in ferritic steels

    International Nuclear Information System (INIS)

    Computer simulations of diffusion-controlled phase transformations in model alloys of Fe-Cr-C, Fe-Cr-W-C, Fe-Cr-Si-C, and Fe-Cr-Co-V-C are presented. The compositions considered are typical for ferritic steels. The simulations are performed using the software DICTRA and the thermodynamic calculations of phase equilibria are performed using Thermo-Calc. The thermodynamic driving forces and the kinetics of diffusion-controlled precipitation reactions of M23C6, M7C3, cementite and Laves-phase (Fe, Cr)2W are discussed. The simultaneous growth of stable and metastable phases is treated in a multi-cell approach. The results show remarkable effects on the growth kinetics due to the competition during simultaneous growth

  16. Hirarchical structures and strength in cold-drawn pearlitic steel wire

    DEFF Research Database (Denmark)

    Zhang, Xiaodan; Hansen, Niels; Godfrey, Andrew; Huang, Xiaoxu

    2014-01-01

    and the cementite decomposition, have been analyzed and quantified by scanning electron microscopy, transmission electron microscopy and high resolution electron microscopy for wires cold drawn up to a strain of 3.68. Three strengthening mechanisms, boundary strengthening, dislocation strengthening...... and solid solution hardening, have been analyzed based on the microstructural analysis. The individual and combined contributions, of these mechanisms to the wire strength have been estimated and good agreement has been found between the measured flow stress and values estimated based on an assumption...... of linear additivity of the three strengthening mechanisms. Mechanisms behind the higher strength of about 6.4 GPa in the wires drawn to higher strains and to a finer microstructural scale is also discussed....

  17. A microstructure based analysis of cyclic plasticity of pearlitic steels with Hill's self-consistent scheme incorporating general anisotropic Eshelby tensor

    Institute of Scientific and Technical Information of China (English)

    Xuesong Long; Xianghe Peng; Wenli Pi

    2008-01-01

    A pearlitic steel is composed of numerous pearlitic colonies with random orientations,and each colony consists of many parallel lamellas of ferrite and cementite.The constitutive behavior of this kind of materials may involve both inherent anisotropy and plastic deformation induced anisotropy.A description of the cyclic plasticity for this kind of dual-phase materials is proposed by use of a microstructure-based constitutive model for a pearlitic colony,and the Hill's self-consistent scheme incorporating anisotropic Eshelby tensor for ellipsoidal inclusions.The corresponding numerical algorithm is developed.The responses of pearlitic steel BS11 and single-phase hard-drawn copper subjected to asymmetrically cyclic loading are analyzed.The analytical results agree very well with experimental ones.Compared with the results using isotropic Eshelby tensor,it is shown that the isotropic approximation can provide acceptable overall responses in a much simpler way.

  18. Anti-seismic behavior of HRB400 reinforced steel bars

    Institute of Scientific and Technical Information of China (English)

    QIN Bin; SHENG Guang-min; GONG Shi-hong

    2005-01-01

    The properties of anti-seismic HRB400 steel bars with 25 mm diameter were systematically investigated. The results showed that the properties of the HRB400 reinforced steel bars had been greatly enhanced comparing with HRB335 steel bars, i.e. coordination of strength and ductility, strain-aging sensibility, low temperature impact toughness, weld ability and high strain low cycle fatigue. The ductile-brittle transit temperatures of hot-rolled and strain-aged steel bars were evaluated as -17℃ and-8℃ respectively, and the low temperature impact toughness of HRB400 steel bars remains to be improved. Transmission electron microscopy (TEM) and electron diffraction showed little vanadium existed in ferrite as VN, most of which existed in pearlite as alloy cementite which resulted in the declination of impact toughness. Methods were suggested to improve the anti-seismic properties of steel bars.

  19. Microstructure and Mechanical Properties of Granular Pearlite Steel After Equal Channel Angular Pressing

    Science.gov (United States)

    Xiong, Yi; He, Tiantian; Li, Pengyan; Chen, Lufei; Ren, Fengzhang; Volinsky, Alex A.

    2015-07-01

    Equal channel angular pressing (ECAP) of granular pearlite high carbon steel was carried out at room temperature via the Bc route. The microstructure evolution was investigated by means of scanning and transmission electron microscopy, and the mechanical properties of granular pearlite steel were measured by tensile and microhardness testing. After four passes, the microstructure was obviously refined. An ultrafine microduplex structure with 400 nm equiaxed ferrite grains and 200 nm cementite particles were formed. The yield strength, ultimate tensile strength, microhardness, and the ratio of the yield to tensile strength increased with the number of ECAP passes, however, the elongation slightly reduced. The tensile fracture morphology changes gradually from ductile fracture to ductile and quasi-cleavage mixed fracture.

  20. Monitoring iron carbide production from iron ore by quantitative Moessbauer spectroscopy

    International Nuclear Information System (INIS)

    The process of converting iron ore (principally Fe2O3 or Fe3O4) into iron carbide (Fe3C) to be used as feedstock for steel-making yields complex mixtures of several iron containing compounds as a function of processing conditions. In addition to the above compounds (hematite, magnetite and cementite), the mixtures typically contain wustite (FeO) and metallic iron (Fe). Moessbauer spectroscopy has been developed into a quantitative analytical method for monitoring the degree of conversion to carbide from samples periodically extracted from a fluidized bed reactor type of pilot plant. Emphasis has been placed on standardizing and simplifying the analysis procedure for routine use in an industrial environment. (orig.)

  1. The Moessbauer spectroscopy studies of matrix changes during continuous heating from as-quenched state of high carbon tool steel

    International Nuclear Information System (INIS)

    This work presents the results of investigations carried out using Moessbauer spectroscopy technique, and their interpretation concerning ferrite or martensite matrix and its changes during tempering. The changes in the matrix are brought about by the stress relaxation, retained austenite transformation, nucleation and solubility of ε carbides as well as cementite nucleation and growth. This research was conducted on a new high-carbon alloy 120MnCrMoV8-6-4-2 steel, which was designed by the Phase Transformations Research Group, AGH UST, in 1998. Moessbauer spectroscopy was applied not only for magnetic hyperfine field studies, but also for analysis of the values of quadrupole splitting and isomeric shift, what resulted in significant conclusions concerning the changes in matrix chemical composition, microstructure, and the level of stresses being present in it.

  2. The Moessbauer spectroscopy studies of matrix changes during continuous heating from as-quenched state of high carbon tool steel

    Energy Technology Data Exchange (ETDEWEB)

    Krawczyk, Janusz, E-mail: jkrawczy@ruczaj.pl; Bala, Piotr [AGH University of Science and Technology, Faculty of Metals Engineering and Industrial Computer Science (Poland); Hanc, Aneta [Institute of Materials Science, University of Silesia (Poland)

    2009-04-15

    This work presents the results of investigations carried out using Moessbauer spectroscopy technique, and their interpretation concerning ferrite or martensite matrix and its changes during tempering. The changes in the matrix are brought about by the stress relaxation, retained austenite transformation, nucleation and solubility of {epsilon} carbides as well as cementite nucleation and growth. This research was conducted on a new high-carbon alloy 120MnCrMoV8-6-4-2 steel, which was designed by the Phase Transformations Research Group, AGH UST, in 1998. Moessbauer spectroscopy was applied not only for magnetic hyperfine field studies, but also for analysis of the values of quadrupole splitting and isomeric shift, what resulted in significant conclusions concerning the changes in matrix chemical composition, microstructure, and the level of stresses being present in it.

  3. Electromagnetic nondestructive evaluation of tempering process in AISI D2 tool steel

    Science.gov (United States)

    Kahrobaee, Saeed; Kashefi, Mehrdad

    2015-05-01

    The present paper investigates the potential of using eddy current technique as a reliable nondestructive tool to detect microstructural changes during the different stages of tempering treatment in AISI D2 tool steel. Five stages occur in tempering of the steel: precipitation of ɛ carbides, formation of cementite, retained austenite decomposition, secondary hardening effect and spheroidization of carbides. These stages were characterized by destructive methods, including dilatometry, differential scanning calorimetry, X-ray diffraction, scanning electron microscopic observations, and hardness measurements. The microstructural changes alter the electrical resistivity/magnetic saturation, which, in turn, influence the eddy current signals. Two EC parameters, induced voltage sensed by pickup coil and impedance point detected by excitation coil, were evaluated as a function of tempering temperature to characterize the microstructural features, nondestructively. The study revealed that a good correlation exists between the EC parameters and the microstructural changes.

  4. Combinatorial optimization of carbide-free bainitic nanostructures

    International Nuclear Information System (INIS)

    Thermodynamic calculations in combination with a neural network model are employed to predict the conditions under which nanostructured carbide-free bainite can be formed. The method recovers well the conditions under which the alloys reported in the literature display such features. Aluminium and silicon are shown to be equally effective in suppressing cementite. Manganese reduction appears to be the most effective means to accelerate bainite formation at low temperatures. A new low-manganese high-chromium steel grade capable of transforming into a nanostructured carbide-free structure is proposed, in which thermokinetic calculation and experiment show that low-temperature bainite forms faster and displays greater hardness than the alloys previously reported in the literature

  5. Studying the Hall-Petch effect regarding sub-micrometer steel (0.6% C

    Directory of Open Access Journals (Sweden)

    Rodolfo Rodríguez Baracaldo

    2011-08-01

    Full Text Available This paper study the synthesis and mechanical characterisation of steel (0.6% C having lower than 1 micron grain size. There was severe plastic deformation in high pressure planetary ball milling and consolidation for obtaining bulk samples at temperatures between 350°C and 500°C. Studying grain size evolution showed that samples without subsequent heat treatment retained their nanocrystalline structure. Grain growth was controlled in heat-treated samples due to many nucleation points and the presence of cementite precipitates. The results obtained regarding hardness and grain size satisfactory agreed with the Hall- Petch ratio. The influence of the synthesis and mechanical characterisation techniques used in this work were compared to results mentioned in several references.

  6. Effect of Cr and Mo on strain ageing behaviour of low carbon steel

    International Nuclear Information System (INIS)

    This work explores the effects of Cr (0.26-0.74 wt%) and Mo (0.09-0.3 wt%) additions on the kinetics of strain ageing process in low carbon steel. The strain ageing behaviour of the steels was investigated by using tensile tests and transmission electron microscopy. The results have shown that Mo-alloyed steels undergo the same four stages of ageing as unalloyed low carbon steel, whereas Cr-alloyed steels exhibit only three stages of ageing. At the same time, the addition of Mo accelerates the ageing response, while alloying with Cr reduces the rate of strain ageing by ∼3 times in comparison with non-alloyed low carbon steel. It especially delays the offset of Stage III. This is explained by the reduction of carbon content in ferrite due to the enrichment of cementite with Cr leading to the reduction of its equilibrium solubility in ferrite.

  7. The CCT diagrams of ultra low carbon bainitic steels and their impact toughness properties

    International Nuclear Information System (INIS)

    The CCT diagrams of ULCBNi steels, HN3MV, HN3MVCu having 5.1% Ni and 3.5% Ni and Cu bearing steels; HN3M1.5Cu, HSLA 100 have been determined. The reduced carbon concentration in steel, in order to prevent the formation of cementite, allowed for using nickel, manganese, chromium and molybdenum to enhance hardenability and refinement of the bainitic microstructures by lowering BS temperature. Copper and microadditions of vanadium and niobium are successfully used for precipitation strengthening of steel both in thermomechanically or heat treated conditions. Very good fracture toughness at low temperatures and high yield strength properties of HN3MVCu and HN3MV steels allowed for fulfillment of the requirements for steel plates for pressure vessels and cryogenic applications. (author)

  8. Influence of long-term thermal aging on the microstructural evolution of nuclear reactor pressure vessel materials: An atom probe study

    International Nuclear Information System (INIS)

    Atom probe field ion microscopy (APFIM) investigations of the microstructure of unaged (as-fabricated) and long-term thermally aged (∼ 100,000 h at 280 C) surveillance materials from commercial reactor pressure vessel steels were performed. This combination of materials and conditions permitted the investigation of potential thermal-aging effects. This microstructural study focused on the quantification of the compositions of the matrix and carbides. The APFIM results indicate that there was no significant microstructural evolution after a long-term thermal exposure in weld, plate, or forging materials. The matrix depletion of copper that was observed in weld materials was consistent with the copper concentration in the matrix after the stress-relief heat treatment. The compositions of cementite carbides aged for 100,000 h were compared with the Thermocalc trademark prediction. The APFIM comparisons of materials under these conditions are consistent with the measured change in mechanical properties such as the Charpy transition temperature

  9. In situ neutron diffraction of heavily drawn steel wires with ultra-high strength under tensile loading

    International Nuclear Information System (INIS)

    To make clear the strengthening mechanism of heavily drawn steel wires exhibiting ultra-high strength, in situ neutron diffraction during tensile loading was performed. A ferrite steel (FK) subjected to a true strain of 6.6 and a pearlite steel (PS) subjected to 4.0 were extended on a tensile tester and (1 1 0) diffraction profiles were measured at various holding stresses. Tensile strengths of steel FK and PS are 1.7 and 3.7 GPa, respectively. The change in (1 1 0) spacing with tensile stress is reversible, i.e., elastic, close to the relevant tensile strength. A stress versus (1 1 0) lattice plane strain is linear for steel FK while evidently nonlinear at higher stresses for steel PS. In steel PS in which cementite peaks were hardly observed, the strengthening mechanism is postulated to be different from that for as-patented pearlite steels

  10. Low temperature superplasticity and thermal stability of a nanostructured low-carbon microalloyed steel

    Science.gov (United States)

    Hu, J.; Du, L.-X.; Sun, G.-S.; Xie, H.; Misra, R. D. K.

    2015-12-01

    We describe here for the first time the low temperature superplasticity of nanostructured low carbon steel (microalloyed with V, N, Mn, Al, Si, and Ni). Low carbon nanograined/ultrafine-grained (NG/UFG) bulk steel was processed using a combination of cold-rolling and annealing of martensite. The complex microstructure of NG/UFG ferrite and 50-80 nm cementite exhibited high thermal stability at 500 °C with low temperature elongation exceeding 100% (at less than 0.5 of the absolute melting point) as compared to the conventional fine-grained (FG) counterpart. The low temperature superplasticity is adequate to form complex components. Moreover, the low strength during hot processing is favorable for decreasing the spring back and minimize die loss.

  11. Effect of cutting parameters on the chip formation in orthogonal cutting

    Science.gov (United States)

    M'hamdi, M.; BenSalem, S.; Boujelbene, M.; Katundi, D.; Bayraktar, E.

    2011-01-01

    This paper aims to study the chip formation to obtain the optimal cutting conditions by observing the different chip formation mechanisms. Analysis of machining of a hardened alloy, X160CrMoV12-1 (cold work steel: AISI D2 with a ferritic and cementite matrix and coarse primary carbides), showed that there are relationships between the chip geometry, cutting conditions and the different micrographs under different metallurgical states. For the experimental study here, various cutting speeds and feed rates have been applied on the work material. The "saw-tooth type chips" geometry has been examined and the chip samples were metallographically processed and observed under scanning electronic microscope (SEM) to determine if white layers are present.

  12. Tool steels

    DEFF Research Database (Denmark)

    Højerslev, C.

    2001-01-01

    On designing a tool steel, its composition and heat treatment parameters are chosen to provide a hardened and tempered martensitic matrix in which carbides are evenly distributed. In this condition the matrix has an optimum combination of hardness andtoughness, the primary carbides provide...... resistance against abrasive wear and secondary carbides (if any) increase the resistance against plastic deformation. Tool steels are alloyed with carbide forming elements (Typically: vanadium, tungsten, molybdenumand chromium) furthermore some steel types contains cobalt. Addition of alloying elements...... serves primarily two purpose (i) to improve the hardenabillity and (ii) to provide harder and thermally more stable carbides than cementite. Assuming proper heattreatment, the properties of a tool steel depends on the which alloying elements are added and their respective concentrations....

  13. Microstructural features responsible for the combined high strength and ductility properties in CA processed HSLA steels

    Energy Technology Data Exchange (ETDEWEB)

    Michal, G.M. (Case Western Reserve Univ., Cleveland, OH (USA))

    Under a variety of CA processing conditions HSLA steels can develop superior combined strength and ductility properties compared to the same steels subject to BA processing. To determine the possible causes of the better properties of CA processed HSLA steels, a detailed optical and TEM evaluation of a series of Cb and Cb-V steels cold rolled 62% and annealed at 705 C to 871 C for 1 to 10 minutes was performed. Steels that developed yield strengths above 414 MPa (60 KSI) were often found to contain isolated regions of nonrecrystallized ferrite. These regions caused increases in yield strengths of as much as 75 MPa (11 KSI) with only a slight loss in ductility compared to fully recrystallized steels. Cementite inherited from the hot band spheroidized under certain annealing conditions. These and other results are presented and their ramifications for developing improved CA processing schemes are discussed.

  14. The application of metallographic techniques to the study of the tempering of HSLA-100 steel

    Energy Technology Data Exchange (ETDEWEB)

    Varughese, R.; Howell, P.R. (Pennsylvania State Univ., Univ. Park (United States))

    1993-06-01

    A study of a quenched, and a quenched and tempered low-carbon, copper-containing steel (HSLA 100) was conducted. The primary investigation technique employed was transmission electron microscopy. Quenching the steel from the austenitizing temperature yielded a microstructure that was predominantly lath martensite. However, a significant amount of retained austenite was also present.Niobium carbide particles were also documented in the as-quenched structures. Tempering at 605C for 1-3h yielded a heterogeneous distribution of [var epsilon]-Cu, much of which was associated with the lath boundaries. The austenite was highly resistant to decomposition during tempering at 605C and, as a consequence, little evidence of cementite precipitation was found.

  15. Tailoring the gradient ultrafine-grained structure in low-carbon steel during drawing with shear

    Directory of Open Access Journals (Sweden)

    G. I. Raab

    2016-04-01

    Full Text Available Conventional drawing and drawing with shear were conducted on the rods of low-carbon steel. Deformation by simple drawing forms basically a homogenous structure and leads to a uniform change in microhardness along the billet volume. A comparative analysis of the models of these processes showed that shear drawing of steel at room temperature reduces energy characteristics in half, normal forces on the die – by 1,8, and enhances the strain intensity from 0,5 to 1,6. During drawing with shear, strain-induced cementite dissolution occurs and a gradient structure is formed, which increases the microhardness of the surface layer up to values close to 7 000 MPa.

  16. The influence of drawing speed on structure changes in high carbon steel wires

    Directory of Open Access Journals (Sweden)

    M. Suliga

    2015-01-01

    Full Text Available In the paper the influence of the drawing speed on structure changes has been assessed. The Scanning Electron Microscope investigation confirmed that for wires drawn with high total draft, exceeding 80 %, makes it impossible to clearly assess the impact of drawing technology on structural changes in the drawn wires. Thus, to assess the structural changes necessary to apply quantitative methods. On the basis of examination of the wire structure by measuring of electrical resistance, the structure changes in drawn wires has been determined. It has been shown that the increase of drawing speed, especially above 15 m/s, causes an increase in structure defect, with a decline in platelet orientation of cementite in drawn wires.

  17. A thermally coupled flow formulation with microstructural evolution for hypoeutectic cast-iron solidification

    Energy Technology Data Exchange (ETDEWEB)

    Celentano, D.; Cruchaga, M. [Univ. de Santiago de Chile (Chile)

    1999-08-01

    A thermally coupled incompressible flow formulation, including microstructural phase-change effects, is presented. The governing equations are written in the framework of the finite-element method using a generalized streamline operator technique. In particular, a hypoeutectic cast-iron microstructural model accounting for primary austenite and eutectic solidification is considered. An inverse level rule has been employed to describe the austenite formation, while the eutectic (graphite and cementite) fractions are assumed to be governed by nucleation and growth laws. The application of this methodology in the area of casting solidification constitutes an original contribution of this work. Further, an enhanced staggered scheme is also proposed in order to solve the resulting strongly coupled discretized equations. The analysis of a solidification problem, with particular interest in the influence of the natural convection on the microstructural formation, is performed. The numerical results obtained with the present formulation allow prediction of the flow patterns, volume-fraction distributions, and recalescences developed during the process.

  18. Investigation of Transformation for Ultrahigh Strength Steel Aermet 100

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@The heat-stagnation curves of two quenched and cryogenically treated ultrahigh strength AF1410and Aermet 100 steels during heating and cooling in furnace have been measured. The results showed that the curve displayed an abnormal terrace in the course of heating, and within the temperature range corresponding to the terrace, the formation and growth of both cementite Fe3C and secondary hardening phase M2C in the steel make the carbon content in matrix obviously vary. It is in the region of terrace that the optimum combination of tensile strength and fracture toughness is obtained because of secondary hardening. Based on the measured heat-stagnation curve, several transformation points have been determined and the correctness was also verified by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Furthermore, the influence of heating rate and tempering temperature on the crystal structure and stability of austenite has been studied.

  19. Fading of inoculation effects in ductile iron

    Directory of Open Access Journals (Sweden)

    E. Fraś

    2008-03-01

    Full Text Available In work i t has bccn shown rcsults or invcsligations of influcncc of rime Iapsed form inoculation proccss on graphitc nucleation potentialrcprcscntcd by: numbcr of graphitc nodulcs N and N,, maximum undercooling AT,, during solidification of gmphile eutcct ic. abmlutcchilling tcndcncy CT and critical casting diametct dh. undcr which cementite euteclic occur (so-callcd chills. Morcovcr it has hccncstima~cd raic of changc of N and N, AT,,,. CT and dk,. Also, it has bccn provcd that altcr onc minutc sincc rhc momcnt of inocuIationproccss nhout 35% of prnphttc nucIeation potenrial is tost. by 40% chitking tendency, by 70% incrcascs maximum undcrcmling forgraphitc ci~tccrica nd by nearly 40% caging diameter has to bc incrcascd in ordcr to avoid chills.

  20. Fracture Mechanisms in Steel Castings

    Directory of Open Access Journals (Sweden)

    Z. Stradomski

    2013-07-01

    Full Text Available The investigations were inspired with the problem of cracking of steel castings during the production process. A single mechanism of decohesion - the intergranular one - occurs in the case of hot cracking, while a variety of structural factors is decisive for hot cracking initiation, depending on chemical composition of the cast steel. The low-carbon and low-alloyed steel castings crack due to the presence of the type II sulphides, the cause of cracking of the high-carbon tool cast steels is the net of secondary cementite and/or ledeburite precipitated along the boundaries of solidified grains. Also the brittle phosphor and carbide eutectics precipitated in the final stage solidification are responsible for cracking of castings made of Hadfield steel. The examination of mechanical properties at 1050°C revealed low or very low strength of high-carbon cast steels.

  1. Design of a low-alloy high-strength and high-toughness martensitic steel

    Science.gov (United States)

    Zhao, Yan-jun; Ren, Xue-ping; Yang, Wen-chao; Zang, Yue

    2013-08-01

    To develop a high strength low alloy (HSLA) steel with high strength and high toughness, a series of martensitic steels were studied through alloying with various elements and thermodynamic simulation. The microstructure and mechanical properties of the designed steel were investigated by optical microscopy, scanning electron microscopy, tensile testing and Charpy impact test. The results show that cementite exists between 500°C and 700°C, M7C3 exits below 720°C, and they are much lower than the austenitizing temperature of the designed steel. Furthermore, the Ti(C,N) precipitate exists until 1280°C, which refines the microstructure and increases the strength and toughness. The optimal alloying components are 0.19% C, 1.19% Si, 2.83% Mn, 1.24% Ni, and 0.049% Ti; the tensile strength and the V notch impact toughness of the designed steel are more than 1500 MPa and 100 J, respectively.

  2. Effect of annealing on mechanical properties of ledeburitic cast steel

    Directory of Open Access Journals (Sweden)

    E. Rożniata

    2007-01-01

    Full Text Available Purpose: The paper presents evaluation of influence of grain normalization (refinement as a result of repeatedaustenitizing, and the inclination to precipitate the hypereutectoid cementite in Widmannstätten structure inG200CrMoNi4-6-3 cast steel. Four temperatures of heat refining have been applied.Design/methodology/approach: Basic research of G200CrMoNi4-6-3 cast steel included metallographicanalysis, and hardness and impact strength tests. The heat treatment has been planned on the basis of CCTdiagram prepared for that alloy cast steel.Findings: The test material has been G200CrMoNi4-6-3 hypereutectoid cast steel. The evaluation has beencarried out for four annealing temperatures, i.e. 850°C, 900°C, 950°C and 1050°C. At all annealing temperaturesin the structure of cast steel the precipitation of hypereutectoid cementite along grain boundaries of formeraustenite took place. At the temperature of 850°C one may observe the coagulated hypereutectoid cementiteprecipitates inside of primary grains of austenite. Whereas beginning from the temperature of 900°C thecementite in G200CrMoNi4-6-3 cast steel forms distinct „subgrains” inside of primary grains of austenite.Research limitations/implications: Research financed by the Ministry of Scientific Research and InformationTechnology, grant No. 3 T08B 057 29.Practical implications: G200CrMoNi4-6-3 cast steel of ledeburite class is used mainly for rolls production.Any data related to the structure and mechanical properties of that cast steel are precious for the manufacturersand users of the mill rolls.Originality/value: The new heat treatment of G200CrMoNi4-6-3 cast steel

  3. Study of the effect of nano-sized precipitates on the mechanical properties of boron-added low-carbon steels by neutron scattering techniques.

    Science.gov (United States)

    Seong, B S; Cho, Y R; Shin, E J; Kim, S I; Choi, S-H; Kim, H R; Kim, Y J

    2008-10-01

    Small-angle neutron scattering (SANS) and neutron powder diffraction (ND) techniques were used to study quantitatively the effect of nano-sized precipitates and boron addition on the mechanical properties of low-carbon steels. SANS was used to evaluate nano-sized precipitates, smaller than about 600 A in diameter, and ND was used to determine the weight fraction of the cementite precipitates. Fine core-shell structured spherical precipitates with an average radius of ~50 A, such as MnS and/or CuS, surrounded by BN layers were observed in the boron-added (BA) low-carbon steels; fine spherical precipitates with an average radius of ~48 A were mainly observed in the boron-free (BF) low-carbon steels. In the BA steels, the number of boron precipitates, such as BN, Fe(3)(C,B) and MnS, surrounded by BN layers increased drastically at higher hot-rolling temperatures. The volume fraction of the fine precipitates of the BA steels was higher than that of the BF steels; this difference is related to the rapid growth of the BN layers on the MnS and CuS precipitates. Boron addition to low-carbon steels resulted in a reduction in strength and an improvement in elongation; this behaviour is related to the reduction of the solute carbon and the nitrogen contents in the ferrite matrix caused by the precipitation of BN, as well by the increase in the volume fraction of the cementites. PMID:19461851

  4. Microstructural and mechanical characterizations of steel tubes joined by transient liquid phase bonding using an amorphous Fe–B–Si interlayer

    International Nuclear Information System (INIS)

    Highlights: • We joined steel tubes by means of TLPB process using a Fe–B–Si foil as interlayer. • We characterized both microstructure and mechanical properties of the joint. • The microstructure at the joint consists only of ferrite grains. • Evidences of non-epitaxial solidification were found. • Both tensile and hardness tests show the soundness of the joint. - Abstract: In this work the transient liquid phase bonding process was successfully used to join seamless carbon steel tubes using an amorphous Fe–B–Si foil as interlayer. The tubes were aligned with their butted surfaces in contact with the interlayer and the entire assembly was heated by means of an induction furnace under a reducing atmosphere. The temperature was raised to the process temperature (≈1300 °C) and then held for 7 min. The joining process was performed under a pressure of 5 MPa. The joined tubes microstructures were characterized by direct observations – scanning electron microscopy – and diffraction techniques – electron backscatter diffraction. Chemical analysis was performed by electron probe microanalysis. The joint region (JR) presents only ferrite grains - in contrast with the heat affected zone (HAZ) and the base metal (BM), whose microstructures consist of ferrite and cementite. Si content at the JR was precisely determined by chemical profiling, showing higher concentrations of Si compared with the HAZ and BM. These results are in accordance with the fact that the cementite is unable to form in Si enriched zones. Also, ferrite grains at the JR present high-angle grain boundaries with respect to the grains of the HAZ. Tensile tests show that the joined tubes failed away from the bond, at the HAZ, and reached 96% of the ultimate tensile strength of the BM, in the as-bonded condition. Microindentation hardness profiles across the bonding zone are in agreement with the observed microstructures at the different zones of the bond region

  5. Microstructural and mechanical characterizations of steel tubes joined by transient liquid phase bonding using an amorphous Fe–B–Si interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Di Luozzo, Nicolas, E-mail: nicolasdiluozzo@gmail.com [Laboratorio de Sólidos Amorfos, INTECIN, Facultad de Ingeniería, Universidad de Buenos Aires – CONICET, Paseo Colón 850, C1063ACV Buenos Aires (Argentina); Laboratoire des Matériaux et du Génie Physique (CNRS UMR 5628), Grenoble Institute of Technology, MINATEC, Grenoble Cedex 1 (France); Doisneau, Béatrice; Boudard, Michel [Laboratoire des Matériaux et du Génie Physique (CNRS UMR 5628), Grenoble Institute of Technology, MINATEC, Grenoble Cedex 1 (France); Fontana, Marcelo; Arcondo, Bibiana [Laboratorio de Sólidos Amorfos, INTECIN, Facultad de Ingeniería, Universidad de Buenos Aires – CONICET, Paseo Colón 850, C1063ACV Buenos Aires (Argentina)

    2014-12-05

    Highlights: • We joined steel tubes by means of TLPB process using a Fe–B–Si foil as interlayer. • We characterized both microstructure and mechanical properties of the joint. • The microstructure at the joint consists only of ferrite grains. • Evidences of non-epitaxial solidification were found. • Both tensile and hardness tests show the soundness of the joint. - Abstract: In this work the transient liquid phase bonding process was successfully used to join seamless carbon steel tubes using an amorphous Fe–B–Si foil as interlayer. The tubes were aligned with their butted surfaces in contact with the interlayer and the entire assembly was heated by means of an induction furnace under a reducing atmosphere. The temperature was raised to the process temperature (≈1300 °C) and then held for 7 min. The joining process was performed under a pressure of 5 MPa. The joined tubes microstructures were characterized by direct observations – scanning electron microscopy – and diffraction techniques – electron backscatter diffraction. Chemical analysis was performed by electron probe microanalysis. The joint region (JR) presents only ferrite grains - in contrast with the heat affected zone (HAZ) and the base metal (BM), whose microstructures consist of ferrite and cementite. Si content at the JR was precisely determined by chemical profiling, showing higher concentrations of Si compared with the HAZ and BM. These results are in accordance with the fact that the cementite is unable to form in Si enriched zones. Also, ferrite grains at the JR present high-angle grain boundaries with respect to the grains of the HAZ. Tensile tests show that the joined tubes failed away from the bond, at the HAZ, and reached 96% of the ultimate tensile strength of the BM, in the as-bonded condition. Microindentation hardness profiles across the bonding zone are in agreement with the observed microstructures at the different zones of the bond region.

  6. On the Spheroidized Carbide Dissolution and Elemental Partitioning in High Carbon Bearing Steel 100Cr6

    Science.gov (United States)

    Song, Wenwen; Choi, Pyuck-Pa; Inden, Gerhard; Prahl, Ulrich; Raabe, Dierk; Bleck, Wolfgang

    2014-02-01

    We report on the characterization of high carbon bearing steel 100Cr6 using electron microscopy and atom probe tomography in combination with multi-component diffusion simulations. Scanning electron micrographs show that around 14 vol pct spheroidized carbides are formed during soft annealing and only 3 vol pct remain after dissolution into the austenitic matrix through austenitization at 1123 K (850 °C) for 300 seconds. The spheroidized particles are identified as (Fe, Cr)3C by transmission electron microscopy. Atom probe analysis reveals the redistribution and partitioning of the elements involved, i.e., C, Si, Mn, Cr, Fe, in both, the spheroidized carbides and the bainitic matrix in the sample isothermally heat-treated at 773 K (500 °C) after austenitization. Homogeneous distribution of C and a Cr gradient were detected within the spheroidized carbides. Due to its limited diffusivity in (Fe, Cr)3C, Cr exhibits a maximum concentration at the surface of spheroidized carbides (16 at. pct) and decreases gradually from the surface towards the core down to about 2 at. pct. The atom probe results also indicate that the partially dissolved spheroidized carbides during austenitization may serve as nucleation sites for intermediate temperature cementite within bainite, which results in a relatively softer surface and harder core in spheroidized particles. This microstructure may contribute to the good wear resistance and fatigue properties of the steel. Good agreement between DICTRA simulations and experimental composition profiles is obtained by an increase of mobility of the substitutional elements in cementite by a factor of five, compared to the mobility in the database MOBFE2.

  7. The ternary iron aluminum carbides

    International Nuclear Information System (INIS)

    Research highlights: → Carbides present in ternary Fe-Al-C were investigated. → Presence of carbides Fe3C, M23C6, and/or κ-Fe3AlC depends on the Al and C concentration. → The existence of M23C6 ternary carbide in the Fe-Al-C system is recognized for first time. → Solubility of Al in M23C6 is low and negligible in the cementite. - Abstract: Carbides present in ternary Fe-Al-C were investigated by the combined utilization of an X-ray diffractometer and a scanning electron microscope equipped with an energy dispersive X-ray spectrometer. The alloys were prepared by arc melting and the microstructure was homogenised by a solution annealing treatment in the temperature range 950-1050 deg. C for 15 min. The diffraction patterns of resulting materials were analysed using a multiphase Rietveld refinement. The steel is composed of a ferritic matrix with carbides Fe3C, M23C6, and/or κ-Fe3AlC depending on the Al and C concentration. It is the first time that the existence of M23C6 ternary carbide in the Fe-Al-C system is recognized. Microprobe analyses performed revealed that the solubility of Al in M23C6 is low, with an Fe/Al ratio (in at.%) higher than 15. On the other hand, the amount of Al in the cementite is negligible and hence its lattice parameters do not depend on the Al concentration of the alloy.

  8. Metal Dusting-Mechanisms and Preventions

    Institute of Scientific and Technical Information of China (English)

    J.Q.ZHANG; D.J.YOUNG

    2009-01-01

    Metal dusting attacks iron, low and high alloy steels and nickel-or cobalt-base alloys by disintegrating bulk metals and alloys into metal particles in a coke deposit. It occurs in strongly carburising gas atmospheres (carbon activity aC>1) at elevated temperatures (400℃~1000℃). This phenomenon has been studied for decades, but the detailed mechanism is still not well understood. Current methods of protection against metal dusting are either directed to the process conditions-temperature and gas composition-or to the development of a dense adherent oxide layer on the surface of the alloy by selective oxidation. However, metal dusting still occurs by carbon dissolving in the base metal via defects in the oxide scale. The research work at UNSW is aimed at determining the detailed mechanism of metal dusting of both ferritic and austenitic alloys, in particular the microprocesses of graphite deposition, nanoparticle formation and underlying metal destruction. This work was carried out using surface observation, cross-section analysis by focused ion beam and electron microscopic examination of coke deposits at different stages of the reaction. It was found that surface orientation affected carbon deposition and metal dusting at the initial stage of the reaction. Metal dusting occurred only when graphite grew into the metal interior where the volume expansion is responsible for metal disintegration and dusting. It was also found that the metal dusting process could be significantly changed by alterations in alloy chemistry. Germanium was found to affect the iron dusting process by destabilising FeC but increasing the rate of carbon deposition and dusting, which questions the role of cementite in ferritic alloy dusting. Whilst adding copper to iron did not change the carburisation kinetics, cementite formation and coke morphology, copper alloying reduced nickel and nickel-base alloy dusting rates significantly. Application of these fundamental results to the dusting

  9. Influence of activation modes on diametral tensile strength of dual-curing resin cements Influência dos métodos de ativação na resistência à tração diametral de cimentos resinosos duais

    Directory of Open Access Journals (Sweden)

    Renata Garcia Fonseca

    2005-12-01

    Full Text Available In metallic restorations, the polymerization of dual-curing resin cements depends exclusively on chemical activation. The effect of the lack of photoactivation on the strength of these cements has been rarely studied. This study evaluated the influence of activation modes on the diametral tensile strength (DTS of dual-curing resin cements. Base and catalyst pastes of Panavia F, Variolink II, Scotchbond Resin Cement, Rely X and Enforce were mixed and inserted into cylindrical metal moulds (4 x 2 mm. Cements were either: 1 not exposed to light (chemical activation = self-cured groups or 2 photoactivated through mylar strips (chemical and photo-activation = dual-cured groups (n = 10. After a 24 h storage in 37ºC distilled water, specimens were subjected to compressive load in a testing machine. A self-curing resin cement (Cement-It and a zinc phosphate cement served as controls. Comparative analyses were performed: 1 between the activation modes for each dual-curing resin cement, using Student’s t test; 2 among the self-cured groups of the dual-curing resin cements and the control groups, using one-way ANOVA and Tukey’s test (alpha = 0.05. The dual-cured groups of Scotchbond Resin Cement (53.3 MPa, Variolink II (48.4 MPa and Rely X (51.6 MPa showed higher DTS than that of self-cured groups (44.6, 40.4 and 44.5 MPa respectively (p 0.05. The self-cured groups of all the dual-curing resin cements presented statistically the same DTS as that of Cement-It (44.1 MPa (p > 0.05, and higher DTS than that of zinc phosphate (4.2 MPa. Scotchbond Resin Cement, Variolink II and Rely X depended on photoactivation to achieve maximum DTS. In the absence of light, all the dual-curing resin cements presented higher DTS than that of zinc phosphate and statistically the same as that of Cement-It (p > 0.05.Em restaurações metálicas, a polimerização dos cimentos resinosos duais depende exclusivamente da ativação química. Há poucas pesquisas sobre o efeito

  10. 位错及掺杂对球铁冲击韧性影响的电子机理%Electronic Mechanism of Dislocation and Doping for Impact Toughness of Ductile Cast Iron

    Institute of Scientific and Technical Information of China (English)

    杨忠华; 刘贵立; 曲迎东; 李荣德

    2015-01-01

    Atom module of α⁃Fe [ 100 ] ( 010 ) edge dislocation is built in metallic matrix of ductile cast iron. Density functional theory CASTEP method is employed to calculate energy parameters of carbon doping edge dislocation system including atom embedded energy, affinity energy and Mulliken population. It shows that there exist C2v symmetry group in structure of α⁃Fe [100] (010) edge dislocation and localized effect of dislocation happens in limited range. Energy valley attracts light impurity carbon which forms atom clusters in dislocation corn. Interaction between C and Fe atoms is strengthened with charge transportation between C⁃4s and Fe⁃2p obtains which pins dislocation slipping. Mulliken population of Fe atom and C atom is high. Length is short. Iron carbide could be produced. Binding energy and PDOS of carbon doping cementite system show that silicon promotes cementite decomposing and nicalon becomes corn of graphite ball, which improve impact toughness of ductile cast iron.%在球墨铸铁金属基体中建立α⁃Fe[100](010)刃型位错原子模型,利用基于密度泛函理论的CASTEP方法计算C原子在位错芯区的埋置能、亲和能、电荷布居数等电子参数。结果表明:α⁃Fe[100](010)刃型位错芯区局域效应集中范围较小并具有C2v点群对称性。位错芯区的能量低谷吸引轻质杂质C原子偏聚,C原子的2p轨道与刃型位错尖端Fe原子的4s价轨道之间发生电荷转移,具有较强的相互作用,使位错运动受阻。 Fe⁃C原子间布居数较大、原子间距离较小表明,Fe⁃C原子间有生成渗碳体化合物的倾向。 Si原子掺杂渗碳体的结合能及各原子轨道分波态密度表明,Si原子能够促使渗碳体分解,析出碳硅化合物成为石墨球化的核心,从而改善球墨铸铁的冲击韧性。

  11. Magnetic Characterization to Asses the Efficiency of In-vivo Settlement of Magnetic Nanoparticles in Rat Livers

    Science.gov (United States)

    Senn, Nico; Hirt, Ann; Herrmann, Inge; Schlegel, Andrea

    2013-04-01

    Magnetic nanoparticles (MNP) are used in a broad range of disciplines that include magnetic actuators, data storage, resonance imaging, as well as a range of applications in biomedicine. This study employs magnetic methods to assess the efficiency of delivering MNP into an isolated rat liver. MNP were injected into the portal vein in vivo, where they should be taken up from the blood by liver sinusoidal voids before procurement. Carbon-encapsulated, spherical cementite (Fe3C) MNP were synthesized via flame spray pyrolysis, and have an average diameter of 30 nm. The acquisition of isothermal remanent magnetization (IRM) was used to estimate the concentration of particles in the livers. Ten samples of pure cementite of varying concentration were prepared. Six were measured at 77 K and four at room temperature. These samples show a linear relationship between the saturation IRM and particle concentration. Three untreated liver samples, five blood samples and four empty holders were analyzed to establish the base magnetic signal. Subsequently IRM acquisition was measured on 18 liver samples that were treated with MNP. The IRM in fresh tissue was measured at 77 K to prevent chemical alteration within the tissue; the sample was subsequently freeze-dried and remeasured at 77 K and room temperature. No alteration of the remanent magnetic properties occurred during freeze-drying. Calculations of the MNP content in the tissue show that all MNP injected into the system settle directly inside the liver, distributing themselves very heterogeneously. The fact that all MNP remain in the liver indicates that once the particle-containing blood flows through the liver, the MNP settle into the tissue, so that the time in which the particles remain in the blood circulation is limited. The heterogeneous distribution of the MNP makes it difficult to calculate the total MNP content that settles in the liver. However, modification of the system by positioning a magnet near a specific part

  12. Microstructure and Wear Behavior of TiC Coating Deposited on Spheroidized Graphite Cast Iron Using Laser Surfacing

    Directory of Open Access Journals (Sweden)

    E. R. I. Mahmoud

    2014-10-01

    Full Text Available Spheroidal graphite cast iron was laser cladded with TiC powder using a YAG fiber laser at powers of 700, 1000, 1500 and 2000 W. The powder was preplaced on the surface of the specimens with 0.5 mm thickness. Sound cladding and fusion zones were observed at 700, 1000 and 1500 W powers. However, at 2000 W, cracking was observed in the fusion zone. At 700 W, a build-up zone consisted of fine TiC dendrites inside a matrix composed of martensite, cementite (Fe3C, and some blocks of retained austenite was observed. In this zone, all graphite nodules were totally melted. In the fusion zone, some undissolved and partially dissolved graphite nodules appeared in a matrix containing bainite, ferrite, martensite and retained austenite. At 1500 W, the fusion zone had more iron carbides and ferrite, and the HAZ consisted of martensitic structure. At 2000 W, the build-up zone was consisted of TiC particles precipitated in a matrix of eutectic carbides, martensite plus an inter-lamellar retained austenite. The hardness of the cladded area was remarkably improved (1330 HV in case of 700 W: 5.5 times of the hardness of substrate

  13. Effect of Initial Microstructure on Impact Toughness of 1200 MPa-Class High Strength Steel with Ultrafine Elongated Grain Structure

    Science.gov (United States)

    Jafari, Meysam; Garrison, Warren M.; Tsuzaki, Kaneaki

    2014-02-01

    A medium-carbon low-alloy steel was prepared with initial structures of either martensite or bainite. For both initial structures, warm caliber-rolling was conducted at 773 K (500 °C) to obtain ultrafine elongated grain (UFEG) structures with strong //rolling direction (RD) fiber deformation textures. The UFEG structures consisted of spheroidal cementite particles distributed uniformly in a ferrite matrix of a transverse grain size of about 331 and 311 nm in samples with initial martensite and bainite structures, respectively. For both initial structures, the UFEG materials had similar tensile properties, upper shelf energy (145 J), and ductile-to-brittle transition temperatures 98 K (500 °C). Obtaining the martensitic structure requires more rapid cooling than is needed to obtain the bainitic structure and this more rapid cooling promote cracking. As the UFEG structures obtained from initial martensitic and bainitic structures have almost identical properties, but obtaining the bainitic structure does not require a rapid cooling which promotes cracking suggests the use of a bainitic structure in obtaining UFEG structures should be examined further.

  14. Effects of alloying elements on fracture toughness in the transition temperature region of base metals and simulated heat-affected zones of Mn-Mo-Ni low-alloy steels

    Science.gov (United States)

    Kim, Sangho; Im, Young-Roc; Lee, Sunghak; Lee, Hu-Chul; Kim, Sung-Joon; Hong, Jun Hwa

    2004-07-01

    This study is concerned with the effects of alloying elements on fracture toughness in the transition temperature region of base metals and heat-affected zones (HAZs) of Mn-Mo-Ni low-alloy steels. Three kinds of steels whose compositions were varied from the composition specification of SA 508 steel (grade 3) were fabricated by vacuum-induction melting and heat treatment, and their fracture toughness was examined using an ASTM E1921 standard test method. In the steels that have decreased C and increased Mo and Ni content, the number of fine M2C carbides was greatly increased and the number of coarse M3C carbides was decreased, thereby leading to the simultaneous improvement of tensile properties and fracture toughness. Brittle martensite-austenite (M-A) constituents were also formed in these steels during cooling, but did not deteriorate fracture toughness because they were decomposed to ferrite and fine carbides after tempering. Their simulated HAZs also had sufficient impact toughness after postweld heat treatment. These findings indicated that the reduction in C content to inhibit the formation of coarse cementite and to improve toughness and the increase in Mo and Ni to prevent the reduction in hardenability and to precipitate fine M2C carbides were useful ways to improve simultaneously the tensile and fracture properties of the HAZs as well as the base metals.

  15. On the Effect of Manganese on Grain Size Stability and Hardenability in Ultrafine-Grained Ferrite/Martensite Dual-Phase Steels

    Science.gov (United States)

    Calcagnotto, Marion; Ponge, Dirk; Raabe, Dierk

    2012-01-01

    Two plain carbon steels with varying manganese content (0.87 wt pct and 1.63 wt pct) were refined to approximately 1 μm by large strain warm deformation and subsequently subjected to intercritical annealing to produce an ultrafine grained ferrite/martensite dual-phase steel. The influence of the Mn content on microstructure evolution is studied by scanning electron microscopy (SEM). The Mn distribution in ferrite and martensite is analyzed by high-resolution electron backscatter diffraction (EBSD) combined with energy dispersive X-ray spectroscopy (EDX). The experimental findings are supported by the calculated phase diagrams, equilibrium phase compositions, and the estimated diffusion distances using Thermo-Calc (Thermo-Calc Software, McMurray, PA) and Dictra (Thermo-Calc Software). Mn substantially enhances the grain size stability during intercritical annealing and the ability of austenite to undergo martensitic phase transformation. The first observation is explained in terms of the alteration of the phase transformation temperatures and the grain boundary mobility, while the second is a result of the Mn enrichment in cementite during large strain warm deformation, which is inherited by the newly formed austenite and increases its hardenability. The latter is the main reason why the ultrafine-grained material exhibits a hardenability that is comparable with the hardenability of the coarse-grained reference material.

  16. Electrochemical method pits generation and its application in crack initiation in pipeline steel in near-neutral pH environment

    Energy Technology Data Exchange (ETDEWEB)

    Fang, B. [Alberta Univ., Edmonton, AB (Canada). Dept. of Chemical and Materials Engineering]|[Chinese Academy of Sciences, Shenyang (China). Inst. of Metal Research, Environmental Corrosion Center; Eadie, R.L.; Chen, W. [Alberta Univ., Edmonton, AB (Canada). Dept. of Chemical and Materials Engineering; Elboujdaini, M. [Natural Resources Canada, Ottawa, ON (Canada). CANMET Materials Technology Lab

    2008-07-01

    Pit nucleation is related to the electrochemical processes that can occur during corrosion. This paper discussed an electrochemical technique developed to produce pits on X-52 steel samples. Dog-bone-shaped specimens were machined from X-52 steel pipes. The pitted samples were then subjected to cyclic loading in a nearly neutral pH solution at a peak normal stress of 93.6 per cent of the yield strength (YS) with a stress ratio of 0.8. After a period of 76.5 days and 661 cycles, cracks were initiated on many of the pits. Additional cracks were formed by preferential dissolution associated with pearlite colonies. The cracks were hemispherical and growth morphology was similar but more rapid than growth observed using passivation and immersion methods. It was concluded that the cracks advance across the cementite lamellae, which indicates that hydrogen-assisted cracking is involved when cracks exceed a specific threshold size. 29 refs., 1 tab., 11 figs.

  17. Influences of Short Discrete Fibers in High Strength Concrete with Very Coarse Sand

    Directory of Open Access Journals (Sweden)

    Mahyuddin Ramli

    2010-01-01

    Full Text Available Problem statement: High Strength Concrete (HSC normally content high cementitous amount and low water binder ratio. However, these would cause substantial volume changes to the concrete and therefore affected the strength development. In addition, the brittleness of HSC was increased when silica fume used as partial cement replacement to achieve high strength. Approach: This study discussed the effects of incorporated short discrete Coconut Fibers (CF, Barchip Fibers (BF and Glass Fibers (GF into HSC to enhance the performance of concrete while kept the binder content at moderate level. Additional specialty to this HSC was casted with very coarse sand with fineness modulus of 3.98. A total of thirteen mixes were casted and tested for slump, density, compressive strength, flexural strength and ultrasonic pulse velocity in accordance with British Standards. Results: The slump was slightly reduced by the short discrete fibers. All of the fibrous specimens had lower density than control. However, the compressive strength of the HSC had increased from 71.8-79.0 MPa using 1.8% of BF, while flexural strength had increased from 5.21-6.50 MPa. All specimens showed that ultrasonic velocity higher than 4.28 km sec-1. Conclusion/Recommendations: In short, combination of incorporated short discrete fibers and applied very coarse sand to produce HSC showed very satisfying results and improvements. Further assessment on durability and impact resistivity will be verified in the coming research.

  18. Retained austenite thermal stability in a nanostructured bainitic steel

    International Nuclear Information System (INIS)

    The unique microstructure of nanostructured bainite consists of very slender bainitic ferrite plates and high carbon retained austenite films. As a consequence, the reported properties are opening a wide range of different commercial uses. However, bainitic transformation follows the T0 criteria, i.e. the incomplete reaction phenomena, which means that the microstructure is not thermodynamically stable because the bainitic transformation stops well before austenite reaches an equilibrium carbon level. This article aims to study the different microstructural changes taking place when nanostructured bainite is destabilized by austempering for times well in excess of that strictly necessary to end the transformation. Results indicate that while bainitic ferrite seems unaware of the extended heat treatment, retained austenite exhibits a more receptive behavior to it. - Highlights: • Nanostructured bainitic steel is not thermodynamically stable. • Extensive austempering in these microstructures has not been reported before. • Precipitation of cementite particles is unavoidable at longer austempering times. • TEM, FEG-SEM and XRD analysis were used for microstructural characterization

  19. 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.

  20. Stabilization of in-tank residual wastes and external-tank soil contamination for the tank focus area, Hanford tank initiative: Applications to the AX Tank Farm

    International Nuclear Information System (INIS)

    A combined engineering and geochemistry approach is recommended for the stabilization of waste in decommissioned tanks and contaminated soils at the AX Tank Farm, Hanford, WA. A two-part strategy of desiccation and gettering is proposed for treatment of the in-tank residual wastes. Dry portland cement and/or fly ash are suggested as an effective and low-cost desiccant for wicking excess moisture from the upper waste layer. Getters work by either ion exchange or phase precipitation to reduce radionuclide concentrations in solution. The authors recommend the use of specific natural and man-made compounds, appropriately proportioned to the unique inventory of each tank. A filler design consisting of multilayered cementitous grout with interlayered sealant horizons should serve to maintain tank integrity and minimize fluid transport to the residual waste form. External tank soil contamination is best mitigated by placement of grouted skirts under and around each tank, together with installation of a cone-shaped permeable reactive barrier beneath the entire tank farm. Actinide release rates are calculated from four tank closure scenarios ranging from no action to a comprehensive stabilization treatment plan (desiccant/getters/grouting/RCRA cap). Although preliminary, these calculations indicate significant reductions in the potential for actinide transport as compared to the no-treatment option

  1. Carbon partitioning during quenching and partitioning heat treatment accompanied by carbide precipitation

    International Nuclear Information System (INIS)

    Carbon partitioning from martensite into austenite in the quenching and partitioning (Q&P) process has been suggested to be controlled by the constrained carbon equilibrium (CCE) criterion. It defines an approach for predicting the carbon concentration in austenite under the condition that competing reactions such as carbide formation and bainite transformation are suppressed. Carbide precipitation in martensite is, however, often observed during the partitioning step, even in low-carbon steels as well as in high-carbon steels, even when containing a high amount of Si. Therefore, carbon partitioning from martensite into austenite is studied here, considering carbide precipitation in martensite. Carbon partitioning was investigated by means of a field-emission electron probe micro analysis (FE-EPMA) and atom probe tomography (APT), using 1.07 wt.% and 0.59 wt.% carbon steels with various martensite volume fractions. Carbon partitioning from martensite to austenite was clearly observed in all specimens, even though a considerable amount of carbide precipitated inside the martensite. The austenite carbon concentration after the partitioning step was not influenced by either the martensite volume fraction or the bulk carbon content. A modified model for predicting the austenite carbon concentration after the partitioning step was proposed to explain the experimental results by assuming carbon equilibria between austenite, ferrite and cementite under a constrained condition

  2. The comparison of the structure and microhardness of the tool steel C90 and HS 6-5-2 remelted with the electric arc

    Directory of Open Access Journals (Sweden)

    A. Dziedzic

    2010-04-01

    Full Text Available The examination of the structure and microhardness of surface layer of C90 non-alloy steel and HS 6-5-2 high speed steel after electric arc treatment are presented in the paper. The comparison has been presented due to the similar content of the carbon in both steels. The structure of the remelted zone of the steel C90 before the conventional tempering consists of the cells, dendritic cells surrounded with the cementite, there is a plate martensite and retained austenite inside them, whereas the structure of the steel HS 6-5-2 is consistuted with cells, dendritic cells and dendrites surrounded with the eutectic system, inside of which there is a plate martensite and retained austenite. Such structure is characterized by the similar microhardness (790-800 HV0,065 and intensity of the tribiological wear. The tempering causes the decrease of the microhardness in non-alloy steel and the increase of the microhardness in high speed steel.

  3. Electromagnetic nondestructive evaluation of tempering process in AISI D2 tool steel

    Energy Technology Data Exchange (ETDEWEB)

    Kahrobaee, Saeed, E-mail: saeed.kahrobaee@yahoo.com; Kashefi, Mehrdad, E-mail: m-kashefi@um.ac.ir

    2015-05-15

    The present paper investigates the potential of using eddy current technique as a reliable nondestructive tool to detect microstructural changes during the different stages of tempering treatment in AISI D2 tool steel. Five stages occur in tempering of the steel: precipitation of ε carbides, formation of cementite, retained austenite decomposition, secondary hardening effect and spheroidization of carbides. These stages were characterized by destructive methods, including dilatometry, differential scanning calorimetry, X-ray diffraction, scanning electron microscopic observations, and hardness measurements. The microstructural changes alter the electrical resistivity/magnetic saturation, which, in turn, influence the eddy current signals. Two EC parameters, induced voltage sensed by pickup coil and impedance point detected by excitation coil, were evaluated as a function of tempering temperature to characterize the microstructural features, nondestructively. The study revealed that a good correlation exists between the EC parameters and the microstructural changes. - Highlights: • D2 steel parts were tempered at 200-650 °C to produce various microstructures. • Precipitation of ε and Fe{sub 3}C carbides and spheroidization of carbides were detected. • Retained austenite decomposition and secondary hardening effect were determined. • Variations of electrical resistivity (ρ) and magnetic saturation (Bs) were studied. • Combined effects of ρ and Bs on the EC outputs were evaluated.

  4. Electromagnetic nondestructive evaluation of tempering process in AISI D2 tool steel

    International Nuclear Information System (INIS)

    The present paper investigates the potential of using eddy current technique as a reliable nondestructive tool to detect microstructural changes during the different stages of tempering treatment in AISI D2 tool steel. Five stages occur in tempering of the steel: precipitation of ε carbides, formation of cementite, retained austenite decomposition, secondary hardening effect and spheroidization of carbides. These stages were characterized by destructive methods, including dilatometry, differential scanning calorimetry, X-ray diffraction, scanning electron microscopic observations, and hardness measurements. The microstructural changes alter the electrical resistivity/magnetic saturation, which, in turn, influence the eddy current signals. Two EC parameters, induced voltage sensed by pickup coil and impedance point detected by excitation coil, were evaluated as a function of tempering temperature to characterize the microstructural features, nondestructively. The study revealed that a good correlation exists between the EC parameters and the microstructural changes. - Highlights: • D2 steel parts were tempered at 200-650 °C to produce various microstructures. • Precipitation of ε and Fe3C carbides and spheroidization of carbides were detected. • Retained austenite decomposition and secondary hardening effect were determined. • Variations of electrical resistivity (ρ) and magnetic saturation (Bs) were studied. • Combined effects of ρ and Bs on the EC outputs were evaluated

  5. A micro-mechanical analysis and an experimental characterisation of the behavior and the damaging processes of a 16MND5 pressure vessel steel at low temperature; Etude micromecanique et caracterisation experimentale du comportement et de l'endommagement de l'acier de cuve 16MND5 a basses temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Pesci, R

    2004-06-15

    As part of an important experimental and numerical research program launched by Electricite De France on the 16MND5 pressure vessel steel, sequenced and in-situ tensile tests are realized at low temperatures [-196 C;-60 C]. They enable to associate the observation of specimens, the complete cartography of which has been made with a scanning electron microscope (damaging processes, initiation and propagation of microcracks), with the stress states determined by X-ray diffraction, in order to establish relevant criteria. All these measurements enable to supply a two-scale polycrystalline modeling of behavior and damage (Mori-Tanaka/self-consistent) which is developed concurrently with the experimental characterization. This model proves to be a very efficient one, since it correctly reproduces the influence of temperature experimentally defined: the stress state in ferrite remains less important than in bainite (the difference never exceeds 150 MPa), whereas it is much higher in cementite. The heterogeneity of strains and stresses for each crystallographic orientation is well rendered; so is cleavage fracture normal to the {l_brace}100{r_brace} planes in ferrite (planes identified by electron back scattered diffraction during an in-situ tensile test at -150 C), which occurs sooner when temperature decreases, for a constant stress of about 700 MPa in this phase. (author)

  6. Correlations between fracture toughness and microstructure in 4140 steel. MRL E-113

    International Nuclear Information System (INIS)

    Correlations between the microstructure of an ultra-high strength steel and material resistance to fracture, as measured by blunt notch Charpy impact tests and sharp crack K/sub IC/ tests, were investigated for a standard 8700C/oil and an experimental 11750C/oil austenitizing treatment. The increase in sharp crack toughness with higher temperature austenitizing treatments, for the as-quenched and 2000C/oil temper conditions, was rationalized by a fracture criterion based on the notion that for fracture to occur, a critical strain, epsilon/sub f/, must be achieved over some critical distance, delta. The lath colonies were identified as the fracture controlling microstructural unit, and hence, their size was considered to be the critical distance, delta. Toughness in the 3000C/l hour and 4000C/l hour temper conditions, for which the mechanical data indicated an embrittlement, was clearly controlled by the cementite morphology in conjunction with the prior austenite grain size. Attempts to rationalize toughness in these temper conditions, using a stress-controlled fracture criterion, were unsuccessful and led to physically unreasonable results. In the 5000C/l hour temper condition, stable crack growth and periodic ridge patterns were observed. Fracture toughness differences between the 8700C and 11750C austenitizing treatments were qualitatively rationalized by the nature of the respective fracture morphologies. Good correspondence between J/sub IC/ and the so-called tearing modulus, T, as indicators of sharp crack fracture toughness, was observed

  7. Microstructures and Toughness of Weld Metal of Ultrafine Grained Ferritic Steel by Laser Welding

    Institute of Scientific and Technical Information of China (English)

    Xudong ZHANG; Wuzhu CHEN; Cheng WANG; Lin ZHAO; Yun PENG; Zhiling TIAN

    2004-01-01

    3 mm thick 400 MPa grade ultrafine grained ferritic steel plates were bead-on-plate welded by CO2 laser with heat input of 120~480 J/mm. The microstructures of the weld metal mainly consist of bainite, which form is lower bainite plates or polygonal ferrite containing quantities of dispersed cementite particles, mixed with a few of low carbon martensite laths or ferrite, depending on the heat input. The hardness and the tensile strength of the weld metal are higher than those of the base metal, and monotonously increase as the heat input decreases. No softened zone exists inheat affected zone (HAZ). Compared with the base metal, although the grains of laser weld are much larger, the toughness of the weld metal is higher within a large range of heat input. Furthermore, as the heat input increases, the toughness of the weld metal rises to a maximum value, at which point the percentage of lower bainite is the highest, and then drops.

  8. Radio-induced brittleness of austenitic stainless steels at high temperatures

    International Nuclear Information System (INIS)

    In a first part, the author recalls some metallurgical characteristics and properties of iron (atomic properties, crystalline structure, transformation), of iron carbon systems and steels (ferrite, austenite, cementite, martensite, bainite, phase diagrams of iron chromium alloy and iron nickel alloy), aspects regarding the influence of addition elements in the case of stainless steels (mutual interaction of carbon, chromium and nickel in their iron alloys, indication of the various stainless steels, i.e. martensitic, ferritic, austenitic, austenitic-ferritic, and non ferrous), and presents and discusses various mechanical tests (tensile tests, torsion tests, resilience tests, hardness tests, creep tests). In a second part, he discusses the effects of irradiation on austenitic stainless steels: irradiation and deformation under low temperature, irradiation at intermediate temperature, irradiation at high temperature. The third part addresses mechanisms of intergranular fracture in different temperature ranges (400-600, 700-750, and about 800 C). The author then discusses the effect of Helium on the embrittlement of austenitic steels, and finally evokes the perspective of development of a damage model

  9. Electrical resistivity and dechanneling study of radiation defects in iron by 235U fission fragments (F.F.). I - Study of damage induced by F.F. Irradiation at 20K. II - Recovery of radiation defects

    International Nuclear Information System (INIS)

    The irradiation by 235U fission fragments (F.F.) of two iron samples of different purities (the essential impurity being C) have been studied. Comparative measurements of electrical resistivity and dechanneling of 5 MeV α-particles have been made during irradiation and subsequent recovery. The production curves provide, from their slopes at the origin, the following informations: 14000 Frenkel pairs by F.F. (from electrical resistivity); aggregate's rate: 5 per mille (from dechanneling). These curves do not follow a simple law: it seems that one observes the superposition of two saturation mechanisms with very different kinetics. During recovery, the same stages that after electrons or neutrons irradiation are observed, but with very different proportions. Dechanneling puts in evidence: -great modifications in cementite precipitation of an Fe-C alloy, by irradiation; - the recovery stage of loops starting from 800 K and with an activation energy approximately 1 eV; - the preponderant effect of clustering during stages Isub(D), Isub(E), IIsub(C) and IIsub(D)

  10. Additional heat treatment of non-porous coatings obtained on medium carbon steel substrates by electron beam cladding of a Ti-Mo-C powder composition

    Science.gov (United States)

    Mul, D. O.; Drobyaz, E. A.; Zimoglyadova, T. A.; Bataev, V. A.; Lazurenko, D. V.; Shevtsova, L. I.

    2016-04-01

    The structure and microhardness of surface layers, obtained by non-vacuum electron beam cladding of Ti-Mo-C powder mixture on a steel substrate after different types of heat treatment, were investigated. After cladding samples were heat treated in a furnace at 200...500 °C, as well as quenched at 860 ° C and then underwent high-temperature tempering. Heat treatment of cladded coatings induced tempering of martensite and precipitation of cementite particles (Fe3C). Transmission electron microscopy of the samples after heating and holding at 300 ° C revealed precipitation of nanosized cubical TiC particles. The formation of hard nanosized particles led to the surface layer microhardness growth. The highest level of microhardness (which was 1.2...1.5-fold higher in comparison with coating microhardness after heat treatment) was achieved after heating of the claded material at 300 °C and 400 °C Additional quenching of samples at 860 °C did not increase the microhardness level.

  11. Structural tale of two novel (Cr, Mn)C carbides in steel

    International Nuclear Information System (INIS)

    Chromium (Cr), manganese (Mn) and carbon (C) are well known alloying elements used in technologically important alloy steels and advanced high strength steels. It is known that binary CrCx and MnCx carbides can be formed in steels, but in this study we reveal for the first time that Cr and Mn were found combined in novel ternary cementite type (Cr, Mn)C carbides. Electron diffraction experiments showed that Cr, Mn and C formed two distinct carbide phases possessing orthorhombic and monoclinic crystal structures. Density functional theory calculations were performed on these phases and excellent agreement was found between calculations and experiments on the lattice parameters and relative atomic positions. The calculations showed that the combination of Mn and Cr resulted in a very high thermodynamic stability of the (Cr, Mn)C carbides, and that local structural relaxations are associated with carbon additions. Possible implications of these ternary carbides for novel applications in steel design and manufacturing are discussed

  12. Parameters Optimization of Low Carbon Low Alloy Steel Annealing Process

    Institute of Scientific and Technical Information of China (English)

    Maoyu ZHAO; Qianwang CHEN

    2013-01-01

    A suitable match of annealing process parameters is critical for obtaining the fine microstructure of material.Low carbon low alloy steel (20CrMnTi) was heated for various durations near Ac temperature to obtain fine pearlite and ferrite grains.Annealing temperature and time were used as independent variables,and material property data were acquired by orthogonal experiment design under intercritical process followed by subcritical annealing process (IPSAP).The weights of plasticity (hardness,yield strength,section shrinkage and elongation) of annealed material were calculated by analytic hierarchy process,and then the process parameters were optimized by the grey theory system.The results observed by SEM images show that microstructure of optimization annealing material are consisted of smaller lamellar pearlites (ferrite-cementite)and refining ferrites which distribute uniformly.Morphologies on tension fracture surface of optimized annealing material indicate that the numbers of dimple fracture show more finer toughness obviously comparing with other annealing materials.Moreover,the yield strength value of optimization annealing material decreases apparently by tensile test.Thus,the new optimized strategy is accurate and feasible.

  13. A micro-mechanical analysis and an experimental characterisation of the behavior and the damaging processes of a 16MND5 pressure vessel steel at low temperature

    International Nuclear Information System (INIS)

    As part of an important experimental and numerical research program launched by Electricite De France on the 16MND5 pressure vessel steel, sequenced and in-situ tensile tests are realized at low temperatures [-196 C;-60 C]. They enable to associate the observation of specimens, the complete cartography of which has been made with a scanning electron microscope (damaging processes, initiation and propagation of microcracks), with the stress states determined by X-ray diffraction, in order to establish relevant criteria. All these measurements enable to supply a two-scale polycrystalline modeling of behavior and damage (Mori-Tanaka/self-consistent) which is developed concurrently with the experimental characterization. This model proves to be a very efficient one, since it correctly reproduces the influence of temperature experimentally defined: the stress state in ferrite remains less important than in bainite (the difference never exceeds 150 MPa), whereas it is much higher in cementite. The heterogeneity of strains and stresses for each crystallographic orientation is well rendered; so is cleavage fracture normal to the {100} planes in ferrite (planes identified by electron back scattered diffraction during an in-situ tensile test at -150 C), which occurs sooner when temperature decreases, for a constant stress of about 700 MPa in this phase. (author)

  14. Hydrogen Embrittlement of a 1500-MPa Tensile Strength Level Steel with an Ultrafine Elongated Grain Structure

    Science.gov (United States)

    Nie, Yihong; Kimura, Yuuji; Inoue, Tadanobu; Yin, Fuxing; Akiyama, Eiji; Tsuzaki, Kaneaki

    2012-05-01

    A deformation of a tempered martensitic structure ( i.e., tempforming) at 773 K (500 °C) was applied to a 0.6 pct C-2 pct Si-1 pct Cr steel. The hydrogen embrittlement (HE) property of the tempformed (TF) steel was investigated by a slow strain rate test (SSRT) and an accelerated atmospheric corrosion test (AACT). Hydrogen content within the samples after SSRT and AACT was measured by thermal desorption spectrometry (TDS). The tempforming at 773 K (500 °C) using multipass caliber rolling with an accumulative are reduction of 76 pct resulted in the evolution of an ultrafine elongated grain (UFEG) structure with a strong //rolling direction (RD) fiber deformation texture and a dispersion of spheroidized cementite particles. The SSRT of the pre-hydrogen-charged notched specimens and the AACT demonstrated that the TF sample had superior potential for HE resistance to the conventional quenched and tempered (QT) sample at a tensile strength of 1500 MPa. The TDS analysis also indicated that the hydrogen might be mainly trapped by reversible trapping sites such as grain boundaries and dislocations in the TF sample, and the hydrogen trapping states of the TF sample were similar to those of the QT sample. The QT sample exhibited hydrogen-induced intergranular fracture along the boundaries of coarse prior-austenite grains. In contrast, the hydrogen-induced cracking occurred in association with the UFEG structure in the TF sample, leading to the higher HE resistance of the TF sample.

  15. Carburisation of stainless steel caused by oil in sodium

    International Nuclear Information System (INIS)

    The primary objectives of this work were to investigate the kinetics of austenitic stainless steel carburisation in sodium caused by oil in sodium, and to measure the corresponding 'sodium carbon activity' (a quantitative measure of sodium steel carburisation potential). For comparative purposes, the steel carburising effects of chemically simpler carbon sources have also been studied. The specific experimental investigations have involved: (i) A study of the kinetics of stainless steel carburisation at 5500C caused by oil in sodium; (ii) A determination of the effective steel carburisation potential (carbon activity) arising from oil ingress, and its persistence with time, and (iii) A comparison of oil and chemically simpler carbon sources, namely graphite and cementite (as carburised iron, Fe-Fe3C), with regard to both kinetics of steel carburisation and sodium carbon activities produced. In all cases, the nature and extent of carburisation has been determined by optical metallography, X-ray and nuclear microprobe analysis. Preliminary studies on the mutual effect of steel surfaces in close proximity have also been conducted. Previous studies on steel carburisation in sodium are outlined, and the present results are discussed in the context of available thermodynamic and kinetic data pertaining to the carbon-steel and carbon-sodium systems. (author)

  16. Effect of scanning speed during PTA remelting treatment on the microstructure and wear resistance of nodular cast iron

    Institute of Scientific and Technical Information of China (English)

    Hua-tang Cao; Xuan-pu Dong; Qi-wen Huang; Zhang Pan; Jian-jun Li; Zi-tian Fan

    2014-01-01

    The surface of nodular cast iron (NCI) with a ferrite substrate was rapidly remelted and solidified by plasma transferred arc (PTA) to induce a chilled structure with high hardness and favorable wear resistance. The effect of scanning speed on the microstructure, micro-hardness distribution, and wear properties of PTA-remelted specimens was systematically investigated. Microstructural characterization in-dicated that the PTA remelting treatment could dissolve most graphite nodules and that the crystallized primary austenite dendrites were transformed into cementite, martensite, an interdendritic network of ledeburite eutectic, and certain residual austenite during rapid solidifica-tion. The dimensions of the remelted zone and its dendrites increase with decreased scanning speed. The microhardness of the remelted zone varied in the range of 650 HV0.2 to 820 HV0.2, which is approximately 2.3-3.1 times higher than the hardness of the substrate. The wear re-sistance of NCI was also significantly improved after the PTA remelting treatment.

  17. Analysis of a New High-Toughness Ultra-high-Strength Martensitic Steel by Transmission Electron Microscopy and Atom Probe Tomography

    Science.gov (United States)

    Hartshorne, Matthew I.; McCormick, Caroline; Schmidt, Michael; Novotny, Paul; Isheim, Dieter; Seidman, David N.; Taheri, Mitra L.

    2016-04-01

    The microstructure of a new martensitic high-strength steel (Fe-0.40C-3.81Ni-1.31Cr-1.50Si-0.75Mn-0.52Mo-0.51Cu-0.30V) with high fracture toughness is characterized by transmission electron microscopy and atom probe tomography (APT). MC, M6C, and M23C6 precipitates form inside the martensitic lath matrix. The fracture toughness is insensitive to the dissolution of M23C6 precipitates at austenitizing temperatures above 1164 K (891 °C). APT reveals that solute segregation at the prior austenite grain boundaries (PAGB) is not uniform, with C, Mo, Si, Ni, and/or P enrichment varying at different areas of the PAGB. Si depletion is detected in the same area as the highest C enrichment. Carbon also segregates at lath boundaries. Segregation of C indicates the presence of retained austenite films at both PAGB and lath boundaries. Regions enriched in C up to 10 pct were found within the laths; however, no regions were enriched to the level expected of cementite or ɛ-carbide. The observed C distribution and high fracture toughness indicates that the tempering behavior is significantly different than that observed in 300M steel. The effect of Si, Ni, and Cu on the formation and stabilization of the regions of C enrichment and retained austenite require further study, as it may be key to the increased toughness.

  18. Anti frictional materials iron-pig iron-brass manufacture using shaving waste products of pig-iron

    International Nuclear Information System (INIS)

    Parts based on iron and steel powders are widely used in the manufacture of automobile and domestic equipment. This work was done to study the anti-friction properties of iron-pig iron-brass compositions of materials which were obtained by pressing and sintering from a mix of iron powders and industrial by products of cast-iron turnings, brass, talc and technical sulphur. Experiments were performed using cold pressure technology in the flowing matrix of the powder composite without solid lubricants. The subsequent sintering was carried out at 1200 degree centigree under isothermal conditions in a nitrogen atmosphere in the sintering zone during 1 h. The physical-mechanical and anti-friction properties were almost double by the active drainage of the gases from the compression mould. The study of the microstructure of the sintered materials showed that free cementite existed between the particle limits and around the pores. large agglomerations of dark inclusions could be observed, consisting of graphite, zinc and iron oxides, which were points of tension in the materials that reduce its durability and, therefore, its wear resistance to dry friction. (Author) 34 refs

  19. Coatings and Films analyzed and optimized by Moessbauer Spectroscopy

    International Nuclear Information System (INIS)

    Thin Films, multilayers and coatings are playing a steadily increasing role for most advanced technical applications and the development of new materials. For the improvement of corrosion, friction and wear properties of machine and tool surfaces, carbides and nitrides are especially interesting. Here we present the effects of pulsed laser irradiation of iron in methane atmosphere and their analysis by Moessbauer spectroscopy. The dependence of the phase formation and the resulting properties are given in relation to the laser treatment parameters, such as number of laser shots and reactive gas pressure. For example, the irradiation of pure iron in methane atmosphere at low pressures or low number of laser pulses results in the formation of an amorphous carbon surface layer and hexagonal FexC, which is more and more transformed into Fe3C cementite when increasing the number of pulses or the gas pressure. It will be demonstrated that Moessbauer spectroscopy is well suited to analyze the processing and to give valuable hints for its optimization

  20. The structural-phase state of iron-carbon coatings formed by the ultradispersed particles

    Energy Technology Data Exchange (ETDEWEB)

    Manakova, Irina A., E-mail: manakova@inp.kz; Ozernoy, Alexey N., E-mail: manakova@inp.kz; Tuleushev, Yuriy Zh., E-mail: manakova@inp.kz; Vereshchak, Mikhail F., E-mail: manakova@inp.kz; Volodin, Valeriy N., E-mail: manakova@inp.kz; Zhakanbayev, Yeldar A., E-mail: manakova@inp.kz [Institute of Nuclear Physics, 050032 Almaty (Kazakhstan)

    2014-10-27

    The methods of nuclear gamma-resonance spectroscopy, elemental microanalysis, and X-ray diffraction were used to study nanoscale coatings. The samples were prepared by magnetron sputtering of carbon and iron particles. They alternately were deposited on monocrystalline silicon or polycrystalline corundum substrate moving relative to the plasma flows in the form of sublayers with a thickness of less than 0.6 nm up to the total thickness of 150-500 nm. Solid solutions with the carbon concentrations of up to 7.5, 12.0, 17.6, and 23.9 at% were produced by co-precipitation of ultradispersed particles of iron and carbon. Using method of conversion electron Mössbauer spectroscopy, we detected the anisotropy of orientation of magnetic moments of iron atoms due to texturing of the formed coatings. The deviation of the crystallite orientation from the average value depends on the degree of carbonization. At 550°C, the pearlite eutectic α‐Fe(C)+Fe{sub 3}C is formed from the amorphous structure without formation of intermediate carbides. The relative content of cementite correlates with the amount of carbon in the coating. The formation of the solid solutions-alloys directly during the deposition process confirms the theory of thermal-fluctuation melting of small particles.

  1. CRYSTALLOGRAPHIC RELATIONS OF CEMENTITE–AUSTENITE–FERRITE IN THE DIFFUSIVE DECOMPOSITION OF AUSTENITE

    Directory of Open Access Journals (Sweden)

    BOLSHAKOV V. I.

    2016-05-01

    Full Text Available Summary. It was made a search for new and more accurate orientation relations between the crystal lattice in the pearlite and bainite austenite decomposition products. Methods. It were used the methods: transmission electron microscopy, the micro-, mathematical matrix and stereographic analysis. The purpose of the research is with theoretical, numerical and experimental methods to set up to a 0.2 degree angular orientation relations between the lattices of ferrite and cementite in the austenite decomposition products in the temperature range 400 ... 700С. Results. It was established a new, refined value for grids in the diffusion decay of γ → α + (α + θ. Practical significance. It was proposed a new oriented dependence and the corresponding double gnomonic projection with poles to planes α and θ phases, which can be used in patterns of crystallographic lattices relations studies at phase transitions, as well as the subsequent modeling of complex physical processes of structure formation in metals and binary systems.

  2. Pearlite transformation in high carbon steels deformed in metastable austenite region; Jun`antei austenite iki de kakoshita kotansoko no pearlite hentai

    Energy Technology Data Exchange (ETDEWEB)

    Daito, Y.; Aihara, K.; Nishizawa, T. [Sumitomo Metal Industries, Ltd., Osaka (Japan)

    1997-09-01

    Pearlite structure was discussed noticing particularly on the state of nucleus composition, for the case when high carbon steels mainly structured by pearlite was processed in metastable austenite region below the point A1 which is thought a non-recrystallized region. When the processing amount is increased in the metastable austenite region, the size of pearlite colonies decreased. This is because of increase in nucleus producing site as a result of the processing. Even with a steel of eutectoid carbon concentration of an equilibrium diagram, proeuctoid ferrite is produced if the processing is given in the metastable austenite region. Furthermore, the production amount of the proeuctoid ferrite increased with increasing processing amount. If the processing is given in the metastable austenite region, the region that becomes a single pearlite structure shifted to hypereuctoid carbon concentration side as the transformation temperature has fallen. The result of an experiment performed in carbon concentration at which the single pearlite structure is obtained agreed well with drive force equilibrium line of ferrite and cementite as calculated based on the Gibbs energy. 18 refs., 11 figs., 1 tab.

  3. New low carbon Q and P steels containing film-like intercritical ferrite

    International Nuclear Information System (INIS)

    In this work, the application of the Quenching and Partitioning (Q and P) process to two low-carbon steels has led to the development of a new kind of steel microstructure formed by laths of martensite separated by films of intercritical ferrite and retained austenite. The chemical compositions of the steels have been specially designed for this process, containing 3.5 wt.% Mn to retard the formation of bainite and combinations of Si and Al to avoid cementite precipitation. The microstructural changes occurring during the application of the heat treatments are discussed in terms of the current knowledge of the Q and P process and the experimental observations. A significant amount of retained austenite has been obtained in both steels after application of appropriate heat treatments, especially in the steel alloyed with higher amount of Si, in which the volume fraction of retained austenite reached values up to 0.19. Tensile tests in some selected specimens of both materials have shown outstanding combinations of strength and ductility, indicating that the designed Q and P steels are a promising candidate for the development of a new generation of advanced high strength steels.

  4. Effects of Nitrogen Content and Austenitization Temperature on Precipitation in Niobium Micro-alloyed Steels

    Institute of Scientific and Technical Information of China (English)

    Lei CAO; Zhong-min YANG; Ying CHEN; Hui-min WANG; Xiao-li ZHAO

    2015-01-01

    The influences of nitrogen content and austenitization temperature on Nb(C,N)precipitation in niobium micro-alloyed steels were studied by different methods:optical microscopy,tensile tests,scanning electron mi-croscopy,transmission electron microscopy,physicochemical phase analysis,and small-angle X-ray scattering. The results show that the strength of the steel with high nitrogen content is slightly higher than that of the steel with low nitrogen content.The increase in the nitrogen content does not result in the increase in the amount of Nb(C,N) precipitates,which mainly depends on the niobium content in the steel.The mass fraction of small-sized Nb(C,N) precipitates (1-10 nm)in the steel with high nitrogen content is less than that in the steel with low nitrogen con-tent.After austenitized at 1 150 ℃,a number of large cuboidal and needle-shaped particles are detected in the steel with high nitrogen content,whereas they dissolve after austenitized at 1 200 ℃ and the Nb(C,N)precipitates become finer in both steels.Furthermore,the results also show that part of the nitrogen in steel involves the formation of al-loyed cementite.

  5. Time-dependent synchrotron X-ray diffraction on the austenite decomposition kinetics in SAE 52100 bearing steel at elevated temperatures under tensile stress

    International Nuclear Information System (INIS)

    We have studied the decomposition kinetics of the metastable austenite phase present in quenched-and-tempered SAE 52100 steel by in situ high-energy synchrotron X-ray diffraction experiments at elevated temperatures of 200–235 °C under a constant tensile stress. We have observed a continuous decomposition of austenite into ferrite and cementite. The decomposition kinetics is controlled by the long-range diffusion of carbon atoms into the austenite ahead of the moving austenite/ferrite interface. The presence of a tensile stress of 295 MPa favours the carbon diffusion in the remaining austenite, so that the activation energy for the overall process decreases from 138–148 to 82–104 kJ mol−1. Before the austenite starts to decompose, a significant amount of carbon atoms partition from the surrounding martensite phase into the metastable austenite grains. This carbon partitioning takes place simultaneously with the carbide precipitation due to the over-tempering of the martensite phase. As the austenite decomposition proceeds gradually at a constant temperature and stress, the elastic strain in the remaining austenite grains continuously decreases. Consequently, the remaining austenite grains act as a reinforcement of the ferritic matrix at longer isothermal holding times. The texture evolution in the constituent phases reflects both significant grain rotations and crystal orientation relationships between the parent austenite phase and the newly formed ferritic grains

  6. Searching for high magnetization density in bulk Fe: the new metastable Fe₆ phase.

    Science.gov (United States)

    Umemoto, Koichiro; Himmetoglu, Burak; Wang, Jian-Ping; Wentzcovitch, Renata M; Cococcioni, Matteo

    2015-01-14

    We report the discovery of a new allotrope of iron by first principles calculations. This phase has Pmn2(1) symmetry, a six-atom unit cell (hence the name Fe6), and the highest magnetization density (Ms) among all the known crystalline phases of iron. Obtained from the structural optimizations of the Fe3C-cementite crystal upon carbon removal, Pmn2(1) Fe6 is shown to result from the stabilization of a ferromagnetic FCC phase, further strained along the Bain path. Although metastable from 0 to 50 GPa, the new phase is more stable at low pressures than the other well-known HCP and FCC allotropes and smoothly transforms into the FCC phase under compression. If stabilized to room temperature, for example, by interstitial impurities, Fe6 could become the basis material for high Ms rare-earth-free permament magnets and high-impact applications such as light-weight electric engine rotors or high-density recording media. The new phase could also be key to explaining the enigmatic high Ms of Fe16N2, which is currently attracting intense research activity. PMID:25425567

  7. Common Quality Defects Analysis of SWRH82B Wire Rod%SWRH82B盘条常见质量缺陷分析

    Institute of Scientific and Technical Information of China (English)

    李文亚; 刘莉; 李智丽; 杨维宇

    2012-01-01

    The common surface defects of SWRH82B wire rod were summarized,including overlap,scab,microcrack,scratch and metallurgical defect.The causes were analyzed and prevention measures were proposed.The morphology of the inner defects including central netting cementite,central martensite,and central pipe was analyzed by SEM and OM,as well as the causes and harms;and corresponding solving programs and measures were put forward based on the actual production requirements.%综述了SWRH82B盘条常见的折叠、结疤、微裂纹、划痕等表面缺陷和冶金缺陷,分析了产生的原因并提出预防措施;采用SEM、OM分析了中心网状渗碳体、中心区域马氏体、中心缩孔等内部缺陷的组织形貌,分析产生的原因和危害,并根据生产实际要求提出相应的解决方案和措施。

  8. The structure, properties and a resistance to abrasive wear of railway sections of steel with a different pearlite morphology

    International Nuclear Information System (INIS)

    The article presents the characteristics of pearlite rail steels used in the construction of railways. The article discusses the influence of isothermal annealing process parameters on the pearlite morphology and properties of the R260 steel. The pearlite structure with a diverse pearlite morphology was obtained in the physical modeling of the isothermal annealing on the 3800 Gleeble Simulator. After the heat treatment, the existence of the pearlite microstructure with pearlite colonies was identified. They were smaller in relation to colonies after the hot rolling process. It was shown that the reduction of isothermal holding temperature influences the decrease of the interlamellar distance in the pearlite steel. On the basis of the received results, the dependences between the resistance to the abrasive wear and the pearlite morphology for operational conditions occurring in the switches were estimated. The resistance to the abrasive wear tests were conducted for steel with a different morphology of pearlite on the Amsler stand in conditions of rolling- sliding frictions. The resistance to the abrasive wear of R260 steel with a different pearlite morphology increases, when the interlamellar distance in cementite decreases and decreases as the load and slip increase.

  9. Ultrafine grained ferrite-martensite dual phase steels fabricated via equal channel angular pressing: Microstructure and tensile properties

    International Nuclear Information System (INIS)

    Ultrafine grained (UFG) ferrite-martensite dual phase steels containing different amounts of vanadium were fabricated by equal channel angular pressing (ECAP) and subsequent intercritical annealing. Their room temperature tensile properties were examined and compared to those of a coarse grained counterpart. The formation of UFG martensite islands of ∼1 μm was not confined to the former pearlite colonies but they were uniformly distributed throughout UFG ferrite matrix. A diffusion analysis showed that this specific microstructure may result from dissolution of carbon atoms from pearlitic cementite and their concurrent diffusion into UFG ferrite during ECAP, making the average carbon content reach the equilibrium content to form austenite during subsequent intercritical annealing. The strength of UFG dual phase steels was much higher than that of the coarse grained counterpart, but uniform and total elongations were not degraded. More importantly, the present UFG dual phase steels exhibited extensive rapid strain hardening unlike most UFG materials. The addition of vanadium slightly increased the strength and elongation of the present UFG dual phase steels, but it was found that excessive vanadium addition did not lead to further improvement of their mechanical properties. An excellent combination of strength, elongation and strain hardening of the present UFG dual phase steels was explained in terms of their specific microstructural features

  10. Segregation behavior of phosphorus in the heat-affected zone of an A533B/A182 dissimilar weld joint before and after simulated thermal aging

    International Nuclear Information System (INIS)

    Highlights: • Impacts of aging on P segregation in actual heat-affected zone were examined by 3D-APT. • Non-equilibrium segregation of P dominated in subsequent cooling after welding. • Equilibrium segregation of P prevailed in step-cooling heat treatment. • High enrichment of P at grain/packet boundaries occurred in CGHAZ and ICCGHAZ. • Level of P enrichment at precipitate/matrix interface seemed species-dependent. - Abstract: The segregation behavior of phosphorus (P) in the heat-affected zone (HAZ) of an A533B/A182 dissimilar weld joint before and after step cooling was investigated with atom probe tomography. At grain/packet boundaries, the final P segregation level consisted of non-equilibrium segregation that occurred during cooling after welding and post-weld heat treatment (PWHT) and equilibrium segregation that occurred during step cooling. In both processes, higher P coverage was observed in the coarse-grained and intercritically reheated coarse-grained HAZ than in the fine-grained HAZ and base material. The cooling after welding and PWHT seemed to have a pronounced impact on P segregation in the subsequent aging process. In addition, P segregation also occurred at the precipitate/matrix interfaces of cementite, Mo2C and Al–Si rich precipitates. The evolution of P coverage at these two types of sites suggested increasing risks of embrittlement with an increase in aging time

  11. Nano-sized precipitation and properties of a low carbon niobium micro-alloyed bainitic steel

    International Nuclear Information System (INIS)

    The present work focuses on microstructure evolution and precipitation strengthening during tempering at region of 550–680 °C to elucidate the structure–property relationship in the steel. The effect of tempering on the development of a 700 MPa grade high strength hot rolled cost-effective bainitic steel was studied for infrastructure applications. Granular bainite with dispersed martenisit–austenite (M–A) constituents in the bainitic ferrite matrix was obtained after hot rolling and air cooling to room temperature. The decomposition of M–A constituents to cementite carbides and the precipitation of nano-sized NbC carbides in bainitic matrix on tempering were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Nano-sized precipitates of NbC precipitated during tempering were in average diameter of ~4.1–6.1 nm. There were ~86–173 MPa increases in yield strength after tempering at region of 550–680 °C. It is noticeable that those nano-sized NbC precipitates provide an effective way to significantly increase the strength of the low carbon bainitic steel. High yield strength of 716 MPa with high ductility (uniform elongation of 9.3% and total elongation of 22.4%), low yield to tensile ratio of 0.9 and good low temperature toughness of 47 J (half thickness) at –40 °C was obtained after tempering at 680 °C for 30 min

  12. Effect of starting microstructure upon the nucleation sites and distribution of graphite particles during a graphitising anneal of an experimental medium-carbon machining steel

    International Nuclear Information System (INIS)

    The potential for using graphite particles as an internal lubricant during machining is considered. Graphite particles were found to form during graphitisation of experimental medium-carbon steel alloyed with Si and Al. The graphite nucleation sites were strongly influenced by the starting microstructure, whether ferrite–pearlite, bainite or martensite, as revealed by light and electron microscopy. Favourable nucleation sites in the ferrite–pearlite starting microstructure were, not unexpectedly, found to be located within pearlite colonies, no doubt due to the presence of abundant cementite as a source of carbon. In consequence, the final distribution of graphite nodules in ferrite–pearlite microstructures was less uniform than for the bainite microstructure studied. In the case of martensite, this study found a predominance of nucleation at grain boundaries, again leading to less uniform graphite dispersions. - Highlights: • Metallography of formation of graphite particles in experimental carbon steel. • Potential for using graphite in steel as an internal lubricant during machining. • Microstructure features expected to influence improved machinability studied. • Influence of pre-anneal starting microstructure on graphite nucleation sites. • Influence of pre-anneal starting microstructure on graphite distribution. • Potential benefit is new free-cutting steel compositions without e.g. Pb alloying

  13. Effects of sphere size on the microstructure and mechanical properties of ductile iron-steel hollow sphere syntactic foams

    Science.gov (United States)

    Sazegaran, Hamid; Kiani-Rashid, Ali-Reza; Khaki, Jalil Vahdati

    2016-06-01

    The effects of sphere size on the microstructural and mechanical properties of ductile iron-steel hollow sphere (DI-SHS) syntactic foams were investigated in this study. The SHSs were manufactured by fluidized-bed coating via the Fe-based commercial powder-binder suspension onto expanded polystyrene spheres (EPSs). Afterwards, the DI-SHS syntactic foams were produced via a sand-mold casting process. The microstructures of specimens were investigated by optical microscopy, scanning electron microscopy (SEM), and energy- dispersive X-ray spectroscopy (EDS). The microscopic evaluations of specimens reveal distinct regions composed of the DI matrix, SHS shells, and compatible interface. As a result, the microstructures and graphite morphologies of the DI matrix depend on sphere size. When the sphere size decreases, the area fractions of cementite and graphite phases are observed to increase and decrease, respectively. Compression tests were subsequently conducted at ambient temperature on the DI-SHS syntactic foams. The results reveal that the compression behavior of the syntactic foams is enhanced with increasing sphere size. Furthermore, the compressed specimens demonstrate that microcracks start and grow from the interface region.

  14. Study on carbides at grain boundary in micro-alloyed fire resistant steel%微合金耐火钢晶界处碳化物的研究

    Institute of Scientific and Technical Information of China (English)

    曹双梅; 张伟荣; 刘文庆

    2012-01-01

    Field ion microscope ( FIM) and transmission electron microscope ( TEM) were applied to characterize the carbides at grain boundary in micro-alloyed fire resistant steel tempered at 500 t for 0. 5 ~ 4 h after solution treatment at 1200 ℃ for 0. 5 h. Cementites were observed at the grain boundary with huge difference in the size, fine Nb-V-C clusters were detected to distribute uniformly within the grain. It indicates that the quicker diffusing velocity of carbon enhance the growth of Fe3 C, and fine Nb-V-C clusters is attributed to the slower diffusing velocity of niobium and vanadium.%将Nb-Mo-V微合金耐火钢在1200℃保温0.5h后淬火,在500℃回火0.5~4h,用场离子显微镜(FIM)和透射电子显微镜(TEM)研究晶界处的碳化物.结果发现,晶界处存在尺寸差异很大的Fe3C,晶粒内均匀分布着细小的Nb-V-C团簇.这是因为晶界处碳元素扩散速度快,很容易形核长大形成Fe3C,晶粒内合金元素扩散速度慢,只能形成Nb-V-C的团簇.

  15. Nano-sized precipitation and properties of a low carbon niobium micro-alloyed bainitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Z.J. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Department of Materials Science and Engineering, McMaster University, Hamilton L8S 4L8 (Canada); Ma, X.P. [Department of Materials Science and Engineering, McMaster University, Hamilton L8S 4L8 (Canada); Shang, C.J., E-mail: cjshang@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Wang, X.M. [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Subramanian, S.V. [Department of Materials Science and Engineering, McMaster University, Hamilton L8S 4L8 (Canada)

    2015-08-12

    The present work focuses on microstructure evolution and precipitation strengthening during tempering at region of 550–680 °C to elucidate the structure–property relationship in the steel. The effect of tempering on the development of a 700 MPa grade high strength hot rolled cost-effective bainitic steel was studied for infrastructure applications. Granular bainite with dispersed martenisit–austenite (M–A) constituents in the bainitic ferrite matrix was obtained after hot rolling and air cooling to room temperature. The decomposition of M–A constituents to cementite carbides and the precipitation of nano-sized NbC carbides in bainitic matrix on tempering were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Nano-sized precipitates of NbC precipitated during tempering were in average diameter of ~4.1–6.1 nm. There were ~86–173 MPa increases in yield strength after tempering at region of 550–680 °C. It is noticeable that those nano-sized NbC precipitates provide an effective way to significantly increase the strength of the low carbon bainitic steel. High yield strength of 716 MPa with high ductility (uniform elongation of 9.3% and total elongation of 22.4%), low yield to tensile ratio of 0.9 and good low temperature toughness of 47 J (half thickness) at –40 °C was obtained after tempering at 680 °C for 30 min.

  16. Influence of processing parameters on lattice parameters in laser deposited tool alloy steel

    International Nuclear Information System (INIS)

    Highlights: → Orientation relationships among phases in the DMD are given. → Martensite lattice parameters increased with laser specific energy. → Austenite lattice parameters decreased with laser specific energy. - Abstract: Laser aided direct metal deposition (DMD) has been used to form AISI 4340 steel coating on the AISI 4140 steel substrate. The microstructural property of the DMD coating was analyzed by means of scanning electron microscopy, transmission electron microscopy and X-ray diffractometry. Microhardness of the DMD was measured with a Vickers microhardness tester. Results indicate that DMD can be used to form dense AISI 4340 steel coatings on AISI 4140 steel substrate. The DMD coating is mainly composed of martensite and retained austenite. Consecutive thermal cycles have a remarkable effect on the microstructure of the plan view of the DMD coating and on the corresponding microhardness distribution. Orientation relationships among austenite, martensite and cementite in the DMD coating followed the ones in conventional heat treated steels. As the laser specific energy decreased, cooling rate increased, and martensite peaks broadened and shifted to a lower Bragg's angle. Also martensite lattice parameters increased and austenite lattice parameters decreased due to the above parameter change.

  17. Effect of microstructure on non-linear behavior of ultrasound during low cycle fatigue of pearlitic steels

    International Nuclear Information System (INIS)

    Research highlights: → Development of online NLU parameter determination system with proper calibration. → Correlation of microstructural changes with the variation of NLU parameter during low cycle fatigue in 0.3 wt.% carbon steel. → NLU parameter follows fatigue hardening and softening trends during low cycle fatigue in test material. → Before failure, fracture of cementite plates due to compressive stress causes a sharp increase in NLU parameter that could be the alarm for failure of components. Hence this technique may prevent catastrophic failure of components. - Abstract: Influence of microstructural changes on the second harmonics of sinusoidal ultrasonic wave during low cycle fatigue (LCF) deformation in pearlitic steel was studied. Fatigue tests were interrupted and at every interruption, non-linear ultrasonic (NLU) parameter (β) was determined. Microstructures of cyclically deformed specimens at various cycles were examined by transmission electron microscopy (TEM). The variation of β with fatigue cycles was correlated with the microstructural changes and the results were explained through the variation in dislocation morphology and carbon content of the steel.

  18. Molecular dynamics investigation of the interaction of dislocations with carbides in BCC Fe

    Science.gov (United States)

    Granberg, F.; Terentyev, D.; Nordlund, K.

    2015-06-01

    Different types of carbides are present in many steels used as structural materials. To safely use steel in demanding environments, like nuclear power plants, it is important to know how defects will affect the mechanical properties of the material. In this study, the effect of carbide precipitates on the edge dislocation movement is investigated. Three different types of carbides were investigated by means of molecular dynamics, with a Tersoff-like bond order interatomic potential by Henriksson et al. The obstacles were 4 nm in diameter and were of Fe3C- (cementite-), Fe23C6- and Cr23C6-type. The critical unpinning stress was calculated for each type at different temperatures, to get the temperature-dependent obstacle strength. The results showed a decreasing critical stress with increasing temperature, consistent with previous studies. The critical unpinning stress was seen to be dependent on the type of carbide, but the differences were small. A difference was also observed between the obstacles with the same structure, but with different composition. This study shows the relation between the existing Cr23C6 carbide and the experimentally non-existing Fe23C6 carbide, which needs to be used as a model system for investigations with interatomic potentials not able to describe the interaction of Cr in the Fe-C-system. We found the difference to be a between 7% and 10% higher critical unpinning stress for the chromium carbide, than for the iron carbide of the same type.

  19. The Determining Role of Finish Cooling Temperature on the Microstructural Evolution and Precipitation Behavior in an Nb-V-Ti Microalloyed Steel in the Context of Newly Developed Ultrafast Cooling

    Science.gov (United States)

    Li, Xiaolin; Wang, Zhaodong; Deng, Xiangtao; Wang, Guodong; Misra, R. D. K.

    2016-05-01

    We have studied here the impact of finish cooling temperature on the microstructural evolution and precipitation behavior in Nb-V-Ti microalloyed steel through thermo-mechanical simulation in the context of newly developed ultrafast cooling system. The microstructural evolution was studied in terms of morphology and crystallography of precipitates using high-resolution transmission electron microscopy. At finish cooling temperature of 933 K and 893 K (660 °C and 620 °C), the microstructure primarily consisted of polygonal ferrite, together with a small amount of wedge-shaped acicular ferrite and lamellar pearlite, while, at 853 K and 813 K (580 °C and 540 °C), the microstructure consisted of lath bainite with fine interlath cementite and granular bainite with martensite/austenite (M/A) constituent. In all the finish cooling temperatures studied, the near-spherical precipitates of size range ~2 to 15 nm were randomly dispersed in ferrite and bainite matrix. The carbide precipitates were identified as (Nb,V)C with NaCl-type crystal structure. With a decrease in the finish cooling temperature, the size of the precipitates was decreased, while the number density first increased with a peak at 893 K (620 °C) and then decreased. Using Ashby-Orowan model, the contribution of the precipitation strengthening to yield strength was ~149 MPa at the finish cooling temperature of 893 K (620 °C).

  20. Microstructural development of adiabatic shear bands in ultra-fine-grained low-carbon steels fabricated by equal channel angular pressing

    International Nuclear Information System (INIS)

    Microstructural development of adiabatic shear bands formed in ultra-fine-grained low-carbon steels fabricated by equal channel angular pressing (ECAP) was investigated in this study. Dynamic torsional tests were conducted on four steel specimens, two of which were annealed after ECAP, using a torsional Kolsky bar. The ECAP'ed specimen consisted of fine equiaxed grains of 0.2 μm in size, which were slightly coarsened and had an equiaxed shape after annealing. Some adiabatic shear bands were observed at the gage center of the dynamically deformed torsional specimen, and their width was narrower in the ECAP'ed specimen than in the 1-h annealed specimen. Detailed transmission electron microscopic analysis on adiabatic shear bands indicated that very fine equiaxed grains of 0.05-0.2 μm in size were developed within the adiabatic shear band, and that cell structures were formed in the shear band flank by partitioning elongated ferrites. These phenomena were explained by dynamic recovery and recrystallization due to the highly localized plastic deformation and temperature rise occurring in the shear band. The temperature rise in the shear band formation process was estimated to be above 540 deg. C by observing spheroidized cementites inside pearlite grains

  1. Microstructure-properties correlation in fiber laser welding of dual-phase and HSLA steels

    Energy Technology Data Exchange (ETDEWEB)

    Saha, D.C., E-mail: dcsaha@uwaterloo.ca [Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1 (Canada); Westerbaan, D.; Nayak, S.S. [Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1 (Canada); Biro, E. [ArcelorMittal Global Research, 1390 Burlington Street East, Hamilton, ON, Canada L8N 3J5 (Canada); Gerlich, A.P.; Zhou, Y. [Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1 (Canada)

    2014-06-01

    Similar and dissimilar welds of dual-phase (DP) and high strength low alloy (HSLA) steels were made by fiber laser welding (FLW). The welds were characterized with respect to microstructure, micro- and nano-hardness, and tensile properties. The fusion zone (FZ) in the DP welds consisted of fully martensitic structure; whereas HSLA and dissimilar weld FZ microstructure were mixture of martensite and bainite. Analytical transmission electron microscopy (TEM) confirmed bainite structures containing bainitic ferrite laths with intralath and interlath cementite. Precipitation of single variant carbides inside the bainitic ferrite laths were confirmed by measuring the interplanar spacing. The cooling rate in the FZ, estimated using Rosenthal equation, and continuous-cooling-transformation diagrams corroborated the microstructure formed. Nanoindentation was used to verify the hardness of these individual microconstituents, since a much lower nano-hardness for bainite (4.11 GPa) was observed compared to martensite (6.57 GPa) phase. Tensile failure occurred in the tempered area of the heat affected zone (HAZ) in the DP steel welded, which was confirmed by typical cup-like dimple fracture; likewise failure in the HSLA base metal, which occurred in dissimilar and HSLA welds, indicated distinctive dimple and shear dimple ductile morphology.

  2. Effects of cerium microalloying on the structure and properties of heat resistant steel of 4Kh4VMFS

    International Nuclear Information System (INIS)

    It is attempted to follow the peculiarity of structural-physical changes under high-temperature heating in subcritical region and on this base possible mechanisms of cerium effect on heat resistance increase of instrumental compos ition (0.42% C; 0.80% Si; 0.37% Mn; 4.0% Cr; 0.98% W; 1.55% Mo; 1.22% V; 0.01% Ca including the variant with 0.08% Ce) is chosen for investigation. Cerium microalloying is shown to result in advisability of precipitations in the 400-500 deg C tempering temperature range of cementite carbides on the boundaries and in the centre of matrix grains that is associated with liquating inhomogeneity by cerium and carbon. The noted inhomogeneity is levelled with the increase of tempering temperature above 500 deg C. Cerium inhibits the process of Fesub(α)-solid solution decomposition under tempering and its depletion by tungsten and molybdenum. Cerium microalloying of 4Kh4VMFS steel restrains carbide phase coagulation at high temperatures of tempering, it promotes inhibiting the recrystallization processes, assures increased fracture toughness

  3. Effect of substrates on microstructure and mechanical properties of nano-eutectic 1080 steel produced by aluminothermic reaction

    International Nuclear Information System (INIS)

    Nano-eutectic bulk 1080 carbon steel was prepared on glass and copper substrates by an aluminothermic reaction casting. The microstructure of the steel was analyzed by an optical microscope, transmission electron microscopy, an electron probe micro-analyzer, a scanning electron microscope and X-ray diffraction. Results show that the microstructure of the steel consisted of a little cementite and lamellar eutectic pearlite. Average lamellar spacing of the pearlite prepared on copper and glass substrates was about 230 nm and 219 nm, respectively. Volume fraction of the pearlite of the two steels was about 95%. Hardness of the steel was about 229 and 270 HV. Tensile strength was about 610 and 641 MPa and tensile elongation was about 15% and 8%. Compressive strength was about 1043 and 1144 MPa. Compared with the steel prepared on copper substrate, the steel prepared on glass substrate had smaller lamellar spacing of the pearlite phase and higher strength, and low ductility due to the smaller spacing. - Highlights: • 1080-carbon steels were successfully prepared by an aluminothermic reaction casting. • Lamellar spacing of the nanoeutetic pearlite is less than 250 nm. • The compressive strength of the steel is about 1144 MPa. • The tensile ductility of the steel is about 15%

  4. Effect of substrates on microstructure and mechanical properties of nano-eutectic 1080 steel produced by aluminothermic reaction

    Energy Technology Data Exchange (ETDEWEB)

    La, Peiqing, E-mail: pqla@lut.cn; Li, Zhengning; Li, Cuiling; Hu, Sulei; Lu, Xuefeng; Wei, Yupeng; Wei, Fuan

    2014-06-01

    Nano-eutectic bulk 1080 carbon steel was prepared on glass and copper substrates by an aluminothermic reaction casting. The microstructure of the steel was analyzed by an optical microscope, transmission electron microscopy, an electron probe micro-analyzer, a scanning electron microscope and X-ray diffraction. Results show that the microstructure of the steel consisted of a little cementite and lamellar eutectic pearlite. Average lamellar spacing of the pearlite prepared on copper and glass substrates was about 230 nm and 219 nm, respectively. Volume fraction of the pearlite of the two steels was about 95%. Hardness of the steel was about 229 and 270 HV. Tensile strength was about 610 and 641 MPa and tensile elongation was about 15% and 8%. Compressive strength was about 1043 and 1144 MPa. Compared with the steel prepared on copper substrate, the steel prepared on glass substrate had smaller lamellar spacing of the pearlite phase and higher strength, and low ductility due to the smaller spacing. - Highlights: • 1080-carbon steels were successfully prepared by an aluminothermic reaction casting. • Lamellar spacing of the nanoeutetic pearlite is less than 250 nm. • The compressive strength of the steel is about 1144 MPa. • The tensile ductility of the steel is about 15%.

  5. The structural-phase state of iron-carbon coatings formed by the ultradispersed particles

    Science.gov (United States)

    Manakova, Irina A.; Ozernoy, Alexey N.; Tuleushev, Yuriy Zh.; Vereshchak, Mikhail F.; Volodin, Valeriy N.; Zhakanbayev, Yeldar A.

    2014-10-01

    The methods of nuclear gamma-resonance spectroscopy, elemental microanalysis, and X-ray diffraction were used to study nanoscale coatings. The samples were prepared by magnetron sputtering of carbon and iron particles. They alternately were deposited on monocrystalline silicon or polycrystalline corundum substrate moving relative to the plasma flows in the form of sublayers with a thickness of less than 0.6 nm up to the total thickness of 150-500 nm. Solid solutions with the carbon concentrations of up to 7.5, 12.0, 17.6, and 23.9 at% were produced by co-precipitation of ultradispersed particles of iron and carbon. Using method of conversion electron Mössbauer spectroscopy, we detected the anisotropy of orientation of magnetic moments of iron atoms due to texturing of the formed coatings. The deviation of the crystallite orientation from the average value depends on the degree of carbonization. At 550°C, the pearlite eutectic α- Fe ( C )+ Fe3C is formed from the amorphous structure without formation of intermediate carbides. The relative content of cementite correlates with the amount of carbon in the coating. The formation of the solid solutions-alloys directly during the deposition process confirms the theory of thermal-fluctuation melting of small particles.

  6. Neutron irradiation effects on the microstructural dependence of mechanical properties of SA 508 Cl. 3 RPV steels

    International Nuclear Information System (INIS)

    Differences in the neutron-induced mechanical property change for four kinds of reactor pressure vessel (RPV) steels of different manufacturing process were investigated based on the differences in the unirradiated microstructure. Microvickers hardness, indentation, and miniature tensile specimen tests were conducted for mechanical property measurement and optical microscope (OM) and transmission electron microscope(TEM) were performed for microstructural characterization. Specimens were irradiated to a neutron fluence of 2.7 x 1019n/cm2 (E≥ 1 MeV) at 288 deg C. Investigation on the unirradiated microstructures showed largely the same microstructure in that tempered acicular bainite and ferrite with bainitic phase are prevailing. Noticiable differences were observed in the grain size and distribution of cementite, and bainitic lath microstructures. No noticiable changes were observed in the optical and thin film TEM microstructures after irradiation. Apparent differences, however, were observed in the results of mechanical testing after irradiation. Results of tensile testing and hardness measurement show that the present steel refined by vacuum carbon deoxidation(VCD) method exhibits exceptionally high radiation hardening behavior among the four kinds of steel of similar chemical composition examined in the present study. This observation implies that the current irradiation embrittlement prediction method based only on the major alloying elements and fluence could yield nonconservative prediction for this steel. The present results strongly suggest that a new material-specific embrittlement prediction method that considers the differences in the unirradiated microstructural state should be developed and applied

  7. First-principles elasticity of monocarboaluminate hydrates

    KAUST Repository

    Moon, J.

    2014-07-01

    The elasticity of monocarboaluminate hydrates, 3CaO·Al2O3·CaCO3·xH2O (x = 11 or 8), has been investigated by first-principles calculations. Previous experimental study revealed that the fully hydrated monocarboaluminate (x = 11) exhibits exceptionally low compressibility compared to other reported calcium aluminate hydrates. This stiff hydration product can contribute to the strength of concrete made with Portland cements containing calcium carbonates. In this study, full elastic tensors and mechanical properties of the crystal structures with different water contents (x = 11 or 8) are computed by first-principles methods based on density functional theory. The results indicate that the compressibility of monocarboaluminate is highly dependent on the water content in the interlayer region. The structure also becomes more isotropic with the addition of water molecules in this region. Since the monocarboaluminate is a key hydration product of limestone added cement, elasticity of the crystal is important to understand its mechanical impact on concrete. Besides, it is put forth that this theoretical calculation will be useful in predicting the elastic properties of other complex cementitous materials and the influence of ion exchange on compressibility.

  8. Structure of ductile iron in thin walled castings

    Directory of Open Access Journals (Sweden)

    M. Górny

    2007-12-01

    Full Text Available It this work it has been shown that it is possible to produce thin wall ductile iron (TWDI castings with considerably length using Archimedes spiral with wall thickness of 1, 2 and 3 mm. Inmould technique was used to produce TWDI. It has been estimated castability and metallographic investigations were made using different moulding materials. From castability measurements result that it is possible to obtain thin wall ductile iron castings with wall thickness down to 1 mm with castability of 200 mm. Using mould with small ability to absorb heat castability increases twice. At wall thickness equal 3 mm castability reaches 1000 mm and using LDASC sand its value increases to over 1500 mm. Structure parameters for different wall thickness and moulding materials (graphite nodule count, ferrite and cementite fraction are plotted versus distance from the beginning of spiral. It is shown strong influence of LDASC sand (material with small ability to absorb heat on structure parameters (NF, Vf i VC revealing gradient character of TWDI.

  9. Microstructure-properties correlation in fiber laser welding of dual-phase and HSLA steels

    International Nuclear Information System (INIS)

    Similar and dissimilar welds of dual-phase (DP) and high strength low alloy (HSLA) steels were made by fiber laser welding (FLW). The welds were characterized with respect to microstructure, micro- and nano-hardness, and tensile properties. The fusion zone (FZ) in the DP welds consisted of fully martensitic structure; whereas HSLA and dissimilar weld FZ microstructure were mixture of martensite and bainite. Analytical transmission electron microscopy (TEM) confirmed bainite structures containing bainitic ferrite laths with intralath and interlath cementite. Precipitation of single variant carbides inside the bainitic ferrite laths were confirmed by measuring the interplanar spacing. The cooling rate in the FZ, estimated using Rosenthal equation, and continuous-cooling-transformation diagrams corroborated the microstructure formed. Nanoindentation was used to verify the hardness of these individual microconstituents, since a much lower nano-hardness for bainite (4.11 GPa) was observed compared to martensite (6.57 GPa) phase. Tensile failure occurred in the tempered area of the heat affected zone (HAZ) in the DP steel welded, which was confirmed by typical cup-like dimple fracture; likewise failure in the HSLA base metal, which occurred in dissimilar and HSLA welds, indicated distinctive dimple and shear dimple ductile morphology

  10. Austenite formation during intercritical annealing

    Directory of Open Access Journals (Sweden)

    A. Lis

    2008-07-01

    Full Text Available Purpose: of this paper is the effect of the soft annealing of initial microstructure of the 6Mn16 steel on the kinetics of the austenite formation during next intercritical annealing.Design/methodology/approach: Analytical TEM point analysis with EDAX system attached to Philips CM20 was used to evaluate the concentration of Mn, Ni and Cr in the microstructure constituents of the multiphase steel and mainly Bainite- Martensite islands.Findings: The increase in soft annealing time from 1-60 hours at 625°C increases Mn partitioning between ferrite and cementite and new formed austenite and decreases the rate of the austenite formation during next intercritical annealing in the (α+γ temperature range at 700 and 750°C. The general equations for carbide dissolution and austenite formation in intercritical temperature range were established.Research limitations/implications: The final multiphase microstructure can be optimised by changing the time / temperature parameters of the intercritical heating in the (α+γ temperature range.Originality/value: The knowledge of partitioning of alloying elements mainly Mn during soft annealing and intercritical heating is very important to optimise the processing technology of intercritical annealing for a given amount of the austenite.

  11. A Study of the Influence of Thermomechanical Controlled Processing on the Microstructure of Bainite in High Strength Plate Steel

    Science.gov (United States)

    Liang, Xiaojun; DeArdo, Anthony J.

    2014-10-01

    Steels with compositions that are hot rolled and cooled to exhibit high strength and good toughness often require a bainitic microstructure. This is especially true for plate steels for linepipe applications where strengths in excess of 690 MPa (100 ksi) are needed in thicknesses between approximately 6 and 30 mm. To ensure adequate strength and toughness, the steels should have adequate hardenability (C. E. >0.50 and Pcm >0.20), and are thermomechanically controlled processed, i.e., controlled rolled, followed by interrupted direct quenching to below the Bs temperature of the pancaked austenite. Bainite formed in this way can be defined as a polyphase mixture comprised a matrix phase of bainitic ferrite plus a higher carbon second phase or micro-constituent which can be martensite, retained austenite, or cementite, depending on circumstances. This second feature is predominately martensite in IDQ steels. Unlike pearlite, where the ferrite and cementite form cooperatively at the same moving interface, the bainitic ferrite and MA form in sequence with falling temperature below the Bs temperature or with increasing isothermal holding time. Several studies have found that the mechanical properties may vary strongly for different types of bainite, i.e., different forms of bainitic ferrite and/or MA. Thermomechanical controlled processing (TMCP) has been shown to be an important way to control the microstructure and mechanical properties in low carbon, high strength steel. This is especially true in the case of bainite formation, where the complexity of the austenite-bainite transformation makes its control through disciplined processing especially important. In this study, a low carbon, high manganese steel containing niobium was investigated to better understand the effects of austenite conditioning and cooling rates on the bainitic phase transformation, i.e., the formation of bainitic ferrite plus MA. Specimens were compared after transformation from recrystallized

  12. Carbon-content dependent effect of magnetic field on austenitic decomposition of steels

    International Nuclear Information System (INIS)

    The transformed microstructures of the high-purity Fe–0.12C alloy and Fe–0.36C alloy heat treated without and with a 12 T magnetic field have been investigated to explore the carbon-content dependent field effect on austenitic decomposition in steels. Results show that, the field-induced transformed morphology characteristics in different alloys differ from each other. In the Fe–0.12C alloy, the pearlite colonies are elongated along the field direction, and shaped by the chained and elongated proeutectoid ferrite grains in the field direction. However, in the Fe–0.36C alloy, the field mainly reduces the amount of Widmänstatten ferrite and elongates the formed proeutectoid ferrite grains in the field direction. No clear field direction alignment is obtained. The magnetic field also demonstrates carbon-content dependent effect on the texture of the formed ferrite. It clearly enhances the 〈001〉 fiber of the ferrite in the transverse field direction in the Fe–0.36C alloy. This field effect is related to the crystal lattice distortion induced by carbon solution and this impact becomes stronger with the increase of the carbon content. For the Fe–0.12C alloy, this field effect is greatly reduced due to the reduced carbon oversaturation in ferrite and elevated formation temperature. The orientation relationships (ORs) between the pearlitic ferrite and the pearlitic cementite in both alloys are less affected by the magnetic field. No obvious changes in the either type of the appearing ORs and their number of occurrences are detected. - Highlights: ► The carbon-content dependent field effect on austenitic decomposition is studied. ► The field-induced morphology features vary with the carbon content. ► The field effect on ferrite texture is more pronounced in high carbon content alloy. ► Magnetic field hardly affects the orientation relationships between phases in pearlite.

  13. Variation of carbon concentration in proeutectoid ferrite during austenitization in hypoeutectoid steel

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Minsu; Cho, Wontae; Park, Jihye; Jung, Jae-Gil; Lee, Young-Kook, E-mail: yklee@yonsei.ac.kr

    2014-08-15

    The variation of the C concentration in proeutectoid ferrite (α{sub PF}) during austenitization in hypoeutectoid steels was quantitatively investigated using the massive transformation start temperature (T{sub m}) of α{sub PF} to austenite (γ) measured by high-temperature confocal laser scanning microscopy and hardness of α{sub PF}. The C concentration in α{sub PF} at T{sub m} in hypoeutectoid steels increased with increasing total C concentration up to approximately 0.2 wt.% during heating. The hardness of α{sub PF} with isothermal holding time at 775 °C in S20C steel revealed C enrichment in α{sub PF} at the early stage of isothermal holding and its reduction with further holding. These results explain the redistribution of the C in α{sub PF} during austenitization as follows: free C atoms released from cementite during pearlite decomposition diffuse excessively into neighboring α{sub PF} as well as pearlitic ferrite. The supersaturated C concentration in α{sub PF} is reduced during the long-range diffusive transformation of α{sub PF} to γ. However, some of the excess C atoms still remain in α{sub PF} until α{sub PF} starts to massively transform to γ. - Highlights: • Massive transformation of αPF to γ in hypoeutectoid steels was observed using CLSM. • C content in αPF during austenitization was analyzed by measured Tm and hardness. • Tm decreases and C content in αPF at Tm increases with increasing total C. • C atoms released from θ during formation of P to γ diffuse excessively into αPF. • Supersaturated C content in αPF is reduced during transformation of αPF to γ.

  14. Variation of carbon concentration in proeutectoid ferrite during austenitization in hypoeutectoid steel

    International Nuclear Information System (INIS)

    The variation of the C concentration in proeutectoid ferrite (αPF) during austenitization in hypoeutectoid steels was quantitatively investigated using the massive transformation start temperature (Tm) of αPF to austenite (γ) measured by high-temperature confocal laser scanning microscopy and hardness of αPF. The C concentration in αPF at Tm in hypoeutectoid steels increased with increasing total C concentration up to approximately 0.2 wt.% during heating. The hardness of αPF with isothermal holding time at 775 °C in S20C steel revealed C enrichment in αPF at the early stage of isothermal holding and its reduction with further holding. These results explain the redistribution of the C in αPF during austenitization as follows: free C atoms released from cementite during pearlite decomposition diffuse excessively into neighboring αPF as well as pearlitic ferrite. The supersaturated C concentration in αPF is reduced during the long-range diffusive transformation of αPF to γ. However, some of the excess C atoms still remain in αPF until αPF starts to massively transform to γ. - Highlights: • Massive transformation of αPF to γ in hypoeutectoid steels was observed using CLSM. • C content in αPF during austenitization was analyzed by measured Tm and hardness. • Tm decreases and C content in αPF at Tm increases with increasing total C. • C atoms released from θ during formation of P to γ diffuse excessively into αPF. • Supersaturated C content in αPF is reduced during transformation of αPF to γ

  15. Ferrite morphology and residual phases in continuously cooled low carbon steels

    International Nuclear Information System (INIS)

    Although much research has been conducted on the isothermal transformation products of medium to high carbon hardenable steels, relatively little has been reported for transformation of low carbon structural steels under continuous cooling conditions. The trend towards reduced carbon levels (less than about 0.1 wt% C) has been driven by demands for formability and weldability, challenging steel designers to maintain strength by microalloying and/or thermomechanical controlled processing. Although control of the ferritic products formed in low carbon steels after hot rolling, normalising and welding is essential in order to ensure adequate strength and toughness, understanding of the microstructures formed on continuous cooling is still limited. In addition, transformation mechanisms remain controversial because of polarisation of researchers into groups championing diffusional and displacive theories for the transformation of austenite over a wide range of cooling rates. The present review compares and draws together the main ferrite classification schemes, and discusses some critical issues on kinetics and mechanisms, in an attempt to rationalise the effects of cooling rate, prior austenite structure and composition on the resulting ferrite structure and its mechanical properties. It is concluded that with increasing cooling rate the ferritic product becomes finer, more plate-like, more dislocated, more carbon supersaturated, more likely to be formed by a displacive mechanism, harder and stronger. Other conclusions are that: (i) 'bainitic ferrite', which is a pervasive form of ferrite in continuously cooled low carbon steels, is different from the conventional upper and lower bainites observed in higher carbon steels, insofar as the co-product 'phase' is typically martensite-austenite islands rather than cementite; and (ii) low carbon bainite rather than martensite is the dominant product at typical fast cooling rates (<500K/s) associated with commercial

  16. Evolution of microstructure and mechanical properties during thermomechanical processing of a low-density multiphase steel for automotive application

    International Nuclear Information System (INIS)

    The evolution of the microstructure and mechanical properties in a low-density, low-alloy steel containing 6.57Al–3.34Mn–0.18C (wt.%) has been investigated as a function of processing. The steel was designed to have a duplex microstructure with ferrite as the major phase and austenite as the minor phase within the temperature range 800–1350 °C. The steel was processed to sheet form, which was thermomechanically treated and characterised by a variety of techniques such as optical metallography, scanning electron microscopy, electron backscatter diffraction, electron probe microanalysis, X-ray diffraction, transmission electron microscopy, tensile testing and density and elastic modulus measurements. The amount of austenite was found to decrease with an increase in the annealing temperature. While C and Mn partitioned into the austenite phase, Al partitioned into the ferrite. The tensile elongation increased with an increase in the amount of austenite in the microstructure. However, the austenite showed only a small transformation induced plasticity effect during tensile deformation due to its high stability. After annealing, mostly κ-carbide precipitates with a (Fe + Mn)/Al ratio of 3.6 appeared in the ferrite matrix, along with some cementite and complex carbides. These precipitates became coarser (330 nm) during a short time overageing treatment at 400 °C, causing a significant increase in elongation. The κ-carbides were found to have a close to Nishiyama–Wasserman type orientation relationship with the ferrite matrix. Although the Young’s modulus of the steel dropped due to the large amount of Al added, the reduced density was found to be beneficial for automotive applications, overriding the effect of a drop in Young’s modulus

  17. Simulation of paraequilibrium growth in multicomponent systems

    Science.gov (United States)

    Ghosh, G.; Olson, G. B.

    2001-03-01

    A methodology to simulate paraequilibrium (PE) growth in multicomponent systems using the DIC-TRA (Diffusion-Controlled Transformation) software is presented. For any given multicomponent system containing substitutional and interstitial elements, the basic approach is to define a hypothetical element Z, whose thermodynamic and mobility parameters are expressed in terms of the weighted average (with respect to site fraction) of the thermodynamic parameters and mobilities of the substitutional alloying elements. This procedure facilitates the calculation of PE phase diagrams and the PE growth simulations directly in the Thermo-Calc and DICTRA software, respectively. The results of two distinct case studies in multicomponent alloys are presented. In the first example, we simulate the isothermal growth of PE cementite in an Fe-C-Co-Cr-Mo-Ni secondary hardening steel during tempering. This is of practical importance in modeling the carbide precipitation kinetics during secondary hardening. In the second example, we have presented the results of PE ferrite growth during continuous cooling from an intercritical temperature in an Fe-Al-C-Mn-Si low-alloy steel. This is of importance to the design of triple-phase steels containing an austenite that has optimum stability, to facilitate stress-induced transformation under dynamic loading. The results of both simulations are in good accord with experimental results. The model calculations do not consider any resistive or dissipative forces, such as the interfacial energy, strain energy, or solute drag, and, as a result, the interface velocities represent an upper limit under the available chemical driving force.

  18. Comparison of solidification behavior between in situ observation and simulation of Fe–C–Si system

    Energy Technology Data Exchange (ETDEWEB)

    Henao, Hector M., E-mail: hector.henao0@gmail.com [Nihon Superior Centre for the Manufacture of Electronic Materials, School of Mechanical and Mining Engineering, The University of Queensland (Australia); Sugiyama, Akira [Department of Mechanical Engineering for Transportation, Osaka Sangyo University (Japan); Nogita, Kazuhiro [Nihon Superior Centre for the Manufacture of Electronic Materials, School of Mechanical and Mining Engineering, The University of Queensland (Australia)

    2014-11-15

    Highlights: • In situ time resolved X-ray imaging was obtained for solidification of Fe–C–Si alloy. • The techniques provided quantitative data of evolution and proportion of phases. • Thermo-Calc. and DICTRA was used to simulate the alloy solidification process. • Real-time observations were compared with the results of the simulation. • Further evaluation of DICTRA kinetic databases will be required. - Abstract: Over the last few years, important advances have been made in the understanding and modelling of phase transformations of metallic alloys including (a) the coupling of phase equilibria and kinetics for computerised simulation of multicomponent alloys and (b) in situ time resolved X-ray imaging of phase transformations in real time. Both techniques can be complementary. However the quality of the simulation relies to a large extent on the accuracy of phase equilibria and diffusion data obtained from existing experimental studies. In situ X-ray techniques provide quantitative information on the evolution and proportion of phases, and can validate the thermodynamic/kinetic packages. This validation in-turn improves the computational models and databases. In the present work, the phase transformation in the Fe–C–Si system from liquid to γ-Fe and the reaction liquid ↔ γ-Fe + Cementite was observed by using X-ray imaging at SPring-8 synchrotron. The relationship between fraction solid and temperature was obtained from the generated SPring-8 images. The results are compared with computer simulation using Thermo-Calc. and DICTRA. A critical analysis compares the results of the simulation with the real-time observations of the phase transformation.

  19. Systems design of high-performance stainless steels

    Science.gov (United States)

    Campbell, Carelyn Elizabeth

    A systems approach has been applied to the design of high performance stainless steels. Quantitative property objectives were addressed integrating processing/structure/property relations with mechanistic models. Martensitic transformation behavior was described using the Olson-Cohen model for heterogeneous nucleation and the Ghosh-Olson solid-solution strengthening model for interfacial mobility, and incorporating an improved description of Fe-Co-Cr thermodynamic interaction. Coherent Msb2C precipitation in a BCC matrix was described, taking into account initial paraequilibrium with cementite. Using available SANS data, a composition dependent strain energy was calibrated and a composition independent interfacial energy was evaluated to predict the critical particle size versus the fraction of the reaction completed as input to strengthening theory. Multicomponent Pourbaix diagrams provided an effective tool for evaluating oxide stability; constrained equilibrium calculations correlated oxide stability to Cr enrichment in the oxide film to allow more efficient use of alloy Cr content. Multicomponent solidification simulations provided composition constraints to improve castability. Using the Thermo-Calc and DICTRA software packages, the models were integrated to design a carburizing, secondary-hardening martensitic stainless steel. Initial characterization of the prototype showed good agreement with the design models and achievement of the desired property objectives. Prototype evaluation confirmed the predicted martensitic transformation temperature and the desired carburizing response, achieving a case hardness of Rsb{c} 64 in the secondary-hardened condition without case primary carbides. Decarburization experiments suggest that the design core toughness objective (Ksb{IC} = 65 MPasurdm) can be achieved by reducing the core carbon level to 0.05 weight percent. To achieve the core toughness objective at high core strength levels requires further analysis of an

  20. Intergranular brittle fracture of a low alloy steel induced by grain boundary segregation of impurities: influence of the microstructure

    International Nuclear Information System (INIS)

    The study contributes to improve the comprehension of intergranular embrittlement induced by the phosphorus segregation along prior austenitic grain boundaries of low alloy steels used in pressurized power reactor vessel. A part of this study was performed using a A533 steel which contains chemical fluctuations (ghost lines) with two intensities. Axi-symmetrically notched specimens were tested and intergranular brittle de-cohesions were observed in the ghost lines. The fracture initiation sites observed on fracture surfaces were identified as MnS inclusions. A bimodal statistic obtained in a probabilistic model of the fracture is explained by the double population of ghost lines' intensities. A metallurgical study was performed on the same class of steel by studying the influence of the microstructure on the susceptibility to temper embrittlement. Brittle fracture properties of such microstructures obtained by dilatometric experiments were tested on sub-sized specimens to measure the V-notched fracture toughness. Fraction areas of brittle fracture modes were determined on surface fractures. A transition of the fracture mode with the microstructure is observed. It is shown that tempered microstructures of martensite and lower bainite are more susceptible to intergranular embrittlement than tempered upper bainitic microstructure. The intergranular fracture is the most brittle mode. The analysis of crystalline mis-orientations shows a grain boundary structure appreciably more coherent for tempered microstructures of martensite and lower bainite. The higher density of random grain boundaries is susceptible to drag the phosphorus in the upper bainitic matrix and to make the quantity of free phosphorus decreasing. Microstructure observations show a difference in the size and the spatial distribution of carbides, essentially cementite, between tempered martensite and upper bainite. It can explain the bigger susceptibility of this last microstructure to cleavage mode

  1. Effect of double quenching and tempering heat treatment on the microstructure and mechanical properties of a novel 5Cr steel processed by electro-slag casting

    International Nuclear Information System (INIS)

    The effect of double quenching and tempering (DQT) treatment as well as conventional high temperature quenching and tempering (CQT) treatment on the microstructures and mechanical properties of low carbon 5Cr martensitic as cast steel produced by electroslag casting was investigated. The microstructure changes were characterized by optical microscope (OM), scanning electron microscope (SEM), electron back scatter diffraction (EBSD) and transmission electron microscopy (TEM). The characteristics of carbides precipitated during tempering were analyzed on both carbon extraction replica and thin foil samples by TEM. The mechanical performance was evaluated by Vickers hardness test, tensile test, and Charpy V-notch impact test at ambient temperature. The results of microstructure study indicated that DQT treatment led to a finer microstructure than that of CQT. The carbides of the tempered samples were identified as M7C3. The carbides along the prior austenite grain boundaries nucleated directly while those within the laths should be transformed from cementite which formed at the early tempering stage. Compared with CQT condition, yield strength slightly increased after DQT treatment, and impact toughness improved a lot. The strengthening mechanisms were analyzed and it was found that grain refining and precipitation strengthening were mainly responsible for the increase of strength. The superior toughness of DQT condition was attributed to the finer microstructure resulting in more frequent deflections of the cleavage crack and the smaller size of carbides along the prior austenite boundaries. EBSD analysis showed that both martensitic block and packet of low carbon 5Cr tempered martensitic steel could hinder crack propagation, while the latter was more effective

  2. Electrochemical Investigation of the Corrosion of Different Microstructural Phases of X65 Pipeline Steel under Saturated Carbon Dioxide Conditions

    Directory of Open Access Journals (Sweden)

    Yuanfeng Yang

    2015-05-01

    Full Text Available The aim of this research was to investigate the influence of metallurgy on the corrosion behaviour of separate weld zone (WZ and parent plate (PP regions of X65 pipeline steel in a solution of deionised water saturated with CO2, at two different temperatures (55 °C and 80 °C and at initial pH~4.0. In addition, a non-electrochemical immersion experiment was also performed at 80 °C in CO2, on a sample portion of X65 pipeline containing part of a weld section, together with adjacent heat affected zones (HAZ and parent material. Electrochemical impedance spectroscopy (EIS was used to evaluate the corrosion behaviour of the separate weld and parent plate samples. This study seeks to understand the significance of the different microstructures within the different zones of the welded X65 pipe in CO2 environments on corrosion performance; with particular attention given to the formation of surface scales; and their composition/significance. The results obtained from grazing incidence X-ray diffraction (GIXRD measurements suggest that, post immersion, the parent plate substrate is scale free, with only features arising from ferrite (α-Fe and cementite (Fe3C apparent. In contrast, at 80 °C, GIXRD from the weld zone substrate, and weld zone/heat affected zone of the non-electrochemical sample indicates the presence of siderite (FeCO3 and chukanovite (Fe2CO3(OH2 phases. Scanning Electron Microscopy (SEM on this surface confirmed the presence of characteristic discrete cube-shaped crystallites of siderite together with plate-like clusters of chukanovite.

  3. Tensile bond strength of indirect composites luted with three new self-adhesive resin cements to dentin

    Directory of Open Access Journals (Sweden)

    Cafer Türkmen

    2011-08-01

    Full Text Available OBJECTIVE: The aims of this study were to evaluate the tensile bond strengths between indirect composites and dentin of 3 recently developed self-adhesive resin cements and to determine mode of failure by SEM. MATERIAL AND METHODS: Exposed dentin surfaces of 70 mandibular third molars were used. Teeth were randomly divided into 7 groups: Group 1 (control group: direct composite resin restoration (Alert with etch-and-rinse adhesive system (Bond 1 primer/adhesive, Group 2: indirect composite restoration (Estenia luted with a resin cement (Cement-It combined with the same etch-and-rinse adhesive, Group 3: direct composite resin restoration with self-etch adhesive system (Nano-Bond, Group 4: indirect composite restoration luted with the resin cement combined with the same self-etch adhesive, Groups 5-7: indirect composite restoration luted with self-adhesive resin cements (RelyX Unicem, Maxcem, and Embrace WetBond, respectively onto the non-pretreated dentin surfaces. Tensile bond strengths of groups were tested with a universal testing machine at a constant speed of 1 mm/min using a 50 kgf load cell. Results were statistically analyzed by the Student's t-test. The failure modes of all groups were also evaluated. RESULTS: The indirect composite restorations luted with the self-adhesive resin cements (groups 5-7 showed better results compared to the other groups (p0.05. The surfaces of all debonded specimens showed evidence of both adhesive and cohesive failure. CONCLUSION: The new universal self-adhesive resins may be considered an alternative for luting indirect composite restorations onto non-pretreated dentin surfaces.

  4. Analysis on quenching crack of crankshaft for Toyota 3.8L car%丰田3.8L轿车曲轴淬火裂纹分析

    Institute of Scientific and Technical Information of China (English)

    邓军伟; 蔡婵婵; 高峰; 王磊

    2015-01-01

    对丰田3.8L曲轴裂纹进行了形貌及成分分析。结果表明,裂纹为淬火裂纹,主要原因是由于铸造时铁水均匀性差,元素沿晶界偏析,造成大量残留奥氏体和网状渗碳体。沿残留奥氏体晶界分布的网状渗碳体对基体起割裂作用;淬火冷却后期和回火时仍然有残留奥氏体转化为马氏体,曲轴体积发生膨胀,使表面承受过大的张应力,当张应力超过材料强度时,导致工件表面开裂。%Morphology and chemical composition of crankshaft crack for 3.8L car were analyzed.The results show that the crack is resulted from quenching.The main reason for the crack forming are poor uniformity of iron liquid and elements segregation along the grain boundary that results in a lot of retained austenite and cementite networks, which separates the matrix.The retained austenite transformed into martensite at the later stage of quenching and tempering, which causes crankshaft expansion, and the excessive tensile stress on the surface of the crankshaft, that induced the cracking.

  5. Effect of double quenching and tempering heat treatment on the microstructure and mechanical properties of a novel 5Cr steel processed by electro-slag casting

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jian, E-mail: healygo@163.com; Yu, Hao, E-mail: yuhao@ustb.edu.cn; Zhou, Tao, E-mail: zhoutao130984@163.com; Song, Chenghao, E-mail: songchenghao28@126.com; Zhang, Kai, E-mail: zhangkai8901@126.com

    2014-12-01

    The effect of double quenching and tempering (DQT) treatment as well as conventional high temperature quenching and tempering (CQT) treatment on the microstructures and mechanical properties of low carbon 5Cr martensitic as cast steel produced by electroslag casting was investigated. The microstructure changes were characterized by optical microscope (OM), scanning electron microscope (SEM), electron back scatter diffraction (EBSD) and transmission electron microscopy (TEM). The characteristics of carbides precipitated during tempering were analyzed on both carbon extraction replica and thin foil samples by TEM. The mechanical performance was evaluated by Vickers hardness test, tensile test, and Charpy V-notch impact test at ambient temperature. The results of microstructure study indicated that DQT treatment led to a finer microstructure than that of CQT. The carbides of the tempered samples were identified as M{sub 7}C{sub 3}. The carbides along the prior austenite grain boundaries nucleated directly while those within the laths should be transformed from cementite which formed at the early tempering stage. Compared with CQT condition, yield strength slightly increased after DQT treatment, and impact toughness improved a lot. The strengthening mechanisms were analyzed and it was found that grain refining and precipitation strengthening were mainly responsible for the increase of strength. The superior toughness of DQT condition was attributed to the finer microstructure resulting in more frequent deflections of the cleavage crack and the smaller size of carbides along the prior austenite boundaries. EBSD analysis showed that both martensitic block and packet of low carbon 5Cr tempered martensitic steel could hinder crack propagation, while the latter was more effective.

  6. Solid solutions between CrO4- and SO4-ettringite Ca6(Al(OH)6)2[(CrO4)x(SO4)(1-x)]3*26 H2O.

    Science.gov (United States)

    Leisinger, Sabine M; Lothenbach, Barbara; Le Saout, Gwenn; Kägi, Ralf; Wehrli, Bernhard; Johnson, C Annette

    2010-12-01

    Chromate is a toxic contaminant of potential concern, as it is quite soluble in the alkaline pH range and could be released to the environment. In cementitous systems, CrO4(2−) is thought to be incorporated as a solid solution with SO4(2−) in ettringite. The formation of a solid solution (SS) could lower the soluble CrO4(2−) concentrations. Ettringite containing SO4(2−) or CrO4(2−) and mixtures thereof have been synthesized. The resulting solids and their solubility after an equilibration time of 3 months have been characterized. For CrO4-ettringite at 25 °C, a solubility product log K(S0) of −40.2 ± 0.4 was calculated: log K(CrO4−ettringite) = 6log{Ca2+} + 2log{Al(OH)4(−)} + 3log{CrO4(2−)} + 4log{OH−} + 26log{H2O}. X-ray diffraction and the analysis of the solution indicated the formation of a regular solid solution between SO4- and CrO4-ettringite with a miscibility gap between 0.4 ≤ XCrO4 ≤ 0.6. The miscibility gap of the SO4- and CrO4-ettringite solid solution could be reproduced with a dimensionless Guggenheim fitting parameter (a0) of 2.03. The presence of a solid solution between SO4- and CrO4-ettringite results in a stabilization of the solids compared to the pure ettringites and thus in an increased uptake of CrO4(2−) in cementitious systems. PMID:21053912

  7. Rietveld and pair distribution function study of Hägg carbide using synchrotron X-ray diffraction.

    Science.gov (United States)

    du Plessis, Hester Esna; de Villiers, J P R; Kruger, G J; Steuwer, A; Brunelli, M

    2011-03-01

    Fischer-Tropsch (FT) synthesis is an important process in the manufacturing of hydrocarbons and oxygenated hydrocarbons from mixtures of carbon monoxide and hydrogen (syngas). The reduced iron catalyst reacts with carbon monoxide and hydrogen to form bulk Fe(5)C(2) Hägg carbide (χ-HC) during FT synthesis. Arguably, χ-HC is the predominant catalyst phase present in the working iron catalyst. Deactivation of the working catalyst can be due to oxidation of χ-HC to iron oxide, a step-wise decarburization to cementite (θ-Fe(3)C), carbon formation or sintering with accompanying loss of catalytic performance. It is therefore critical to determine the precise crystal structure of χ-HC for the understanding of the synthesis process and for comparison with the first-principles ab initio modelling. Here the results of high-resolution synchrotron X-ray powder diffraction data are reported. The atomic arrangement of χ-HC was confirmed by Rietveld refinement and subsequent real-space modelling of the pair distribution function (PDF) obtained from direct Fourier transformation. The Rietveld and PDF results of χ-HC correspond well with that of a pseudo-monoclinic phase of space group Pī [a = 11.5661 (6) Å, b = 4.5709 (1) Å, c = 5.0611 (2) Å, α = 89.990 (5)°, β = 97.753 (4)°, γ = 90.195 (4)°], where the Fe atoms are located in three distorted prismatic trigonal and one octahedral arrangement around the central C atoms. The Fe atoms are distorted from the prismatic trigonal arrangement in the monoclinic structure by the change in C atom location in the structure. PMID:21335915

  8. Molecular dynamics investigation of the interaction of dislocations with carbides in BCC Fe

    Energy Technology Data Exchange (ETDEWEB)

    Granberg, F., E-mail: fredric.granberg@helsinki.fi [Department of Physics, P.O. Box 43, FIN-00014 University of Helsinki (Finland); Terentyev, D. [Nuclear Materials Science Institute, SCK-CEN, Boeretang 200, B-2400 Mol (Belgium); Nordlund, K. [Department of Physics, P.O. Box 43, FIN-00014 University of Helsinki (Finland)

    2015-06-01

    Different types of carbides are present in many steels used as structural materials. To safely use steel in demanding environments, like nuclear power plants, it is important to know how defects will affect the mechanical properties of the material. In this study, the effect of carbide precipitates on the edge dislocation movement is investigated. Three different types of carbides were investigated by means of molecular dynamics, with a Tersoff-like bond order interatomic potential by Henriksson et al. The obstacles were 4 nm in diameter and were of Fe{sub 3}C- (cementite-), Fe{sub 23}C{sub 6}- and Cr{sub 23}C{sub 6}-type. The critical unpinning stress was calculated for each type at different temperatures, to get the temperature-dependent obstacle strength. The results showed a decreasing critical stress with increasing temperature, consistent with previous studies. The critical unpinning stress was seen to be dependent on the type of carbide, but the differences were small. A difference was also observed between the obstacles with the same structure, but with different composition. This study shows the relation between the existing Cr{sub 23}C{sub 6} carbide and the experimentally non-existing Fe{sub 23}C{sub 6} carbide, which needs to be used as a model system for investigations with interatomic potentials not able to describe the interaction of Cr in the Fe–C-system. We found the difference to be a between 7% and 10% higher critical unpinning stress for the chromium carbide, than for the iron carbide of the same type.

  9. Irradiation induced tensile property change of SA 508 Cl.3 reactor pressure vessel steels

    International Nuclear Information System (INIS)

    Irradiation induced tensile property change of four kinds of reactor pressure vessel steels manufactured by different steel refining process was compared based on the differences in the unirradiated and irradiated microstructure. Microvickers hardness, indentation, and miniature tensile specimen tests were conducted for mechanical property measurement and optical microscope (OM) and transmission electron microscope (TEM) were used for microstructural characterization. Specimens were 2 irradiated to a neutron fluence of 2.7x1019n/cm2 (E ≥ 1 MeV) at 288 deg. C. Investigation on the unirradiated microstructures showed largely a same microstructure in that tempered acicular bainite and ferrite with bainitic phase prevailing in the unirradiated condition. Band-shaped segregations were also clearly observed except a kind of materials. A large difference in the unirradiated microstructure appeared in the grain size and carbide microstructure. Of carbide microstructures, noticeable differences were observed in the size and distribution of cementite, and bainitic lath microstructures. No noticeable changes were observed in the optical and thin film TEM microstructures after irradiation. Complicated microstructural. state of heat treated bainitic low alloy microstructure prevents easy quantification of microstructural changes due to irradiation. Apparent differences, however, were observed in the results of mechanical testing. Results of tensile testing and hardness measurement show that a steel refined by vacuum carbon deoxidation(VCD) method exhibits the highest radiation hardening behavior. Some of mechanical testing results on irradiated materials were possible to understand based on the initial microstructure, but further investigations using a wide array of sophisticated tools (for example, SANS, APFIM) are required to understand and characterize irradiation induced defects that are responsible for irradiation hardening behavior but are not revealed by conventional

  10. Intergranular brittle fracture of a low alloy steel induced by grain boundary segregation of impurities: influence of the microstructure; Rupture intergranulaire fragile d'un acier faiblement allie induite par la segregation d'impuretes aux joints de grains: influence de la microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Raoul, St

    1999-07-01

    The study contributes to improve the comprehension of intergranular embrittlement induced by the phosphorus segregation along prior austenitic grain boundaries of low alloy steels used in pressurized power reactor vessel. A part of this study was performed using a A533 steel which contains chemical fluctuations (ghost lines) with two intensities. Axi-symmetrically notched specimens were tested and intergranular brittle de-cohesions were observed in the ghost lines. The fracture initiation sites observed on fracture surfaces were identified as MnS inclusions. A bimodal statistic obtained in a probabilistic model of the fracture is explained by the double population of ghost lines' intensities. A metallurgical study was performed on the same class of steel by studying the influence of the microstructure on the susceptibility to temper embrittlement. Brittle fracture properties of such microstructures obtained by dilatometric experiments were tested on sub-sized specimens to measure the V-notched fracture toughness. Fraction areas of brittle fracture modes were determined on surface fractures. A transition of the fracture mode with the microstructure is observed. It is shown that tempered microstructures of martensite and lower bainite are more susceptible to intergranular embrittlement than tempered upper bainitic microstructure. The intergranular fracture is the most brittle mode. The analysis of crystalline mis-orientations shows a grain boundary structure appreciably more coherent for tempered microstructures of martensite and lower bainite. The higher density of randomgrain boundaries is susceptible to drag the phosphorus in the upper bainitic matrix and to make the quantity of free phosphorus decreasing. Microstructure observations show a difference in the size and the spatial distribution of carbides, essentially cementite, between tempered martensite and upper bainite. It can explain the bigger susceptibility of this last microstructure to cleavage mode

  11. The effect of a non-circular drawing sequence on delamination characteristics of pearlitic steel wire

    International Nuclear Information System (INIS)

    Highlights: • A non-circular drawing (NCD) was applied to produce high-torsional ductility wire. • In the NCD, two processing routes were defined as the NCDA and NCDB, respectively. • The NCDB could impose relatively homogeneous plastic deformation on the wire. • A strength level of 2300 MPa wire was produced by the NCDB without delamination. - Abstract: In this study, a non-circular drawing (NCD) sequence was applied to investigate the effect of deformation behavior, microstructure and texture evolution on delamination characteristics of pearlitic steel wire under torsional deformation mode. The multi-pass NCD sequence was numerically and experimentally applied up to the 12th pass in comparison with conventional wire drawing (WD). For investigation of the deformation characteristics of the drawn wires, three-dimensional finite element and flownet analyses were carried out. These simulation results indicated that the NCD could impose relatively homogeneous plastic deformation on the wire compared to the WD. From the scanning electron microscopy and X-ray diffraction results, globular cementite and cylindrical texture component, which might increase likeliness of delamination fracture, were rarely observed in the NCD drawn wire. In the torsion test, the delamination fracture was observed in the WD drawn wire for the 10th pass while it did not occur for the 12th pass NCD. In addition, the ultimate tensile strength (UTS) of 2300 MPa grade wire was manufactured by the NCD and the UTS value was 257 MPa higher than the one of the WD. Therefore, it was demonstrated that the multi-pass NCD could impose relatively homogeneous plastic deformation on the wire, resulting in high-torsional ductility with better strength compared to the WD

  12. Coherent-Incoherent Transition of ɛ-Carbide in Steels Found with Mechanical Spectroscopy

    Science.gov (United States)

    Shimotomai, Michio

    2016-03-01

    Although a coherent-incoherent transition in the ɛ-carbide precipitated in steels is supposedly linked to hardening and microstructural changes, the existence of this transition has not yet been confirmed. In this paper, we investigate this subject using mechanical spectroscopy. By measuring mechanical loss spectra below room temperature of quench-aged Fe-C alloys, mild steel, and pearlitic steel, we reveal a new broad peak (NBP). This peak is related to thermal activation, and its line shape obeys the equation of the Debye peak with a distribution in relaxation time. The Arrhenius plot yielded a large activation energy and gigantic pre-exponential factor. Its intensity grew by aging at temperatures where precipitation of ɛ-carbide has been reported. However, it starts to decay at duration far too early for ɛ-carbide to transform to cementite. For isothermal aging at 393 K (120 °C), the intensity sharply decreased at durations over 3 hours. This decay was accompanied by appearance of another similar peak (NBP'), which had a peak frequency two orders higher than that of NBP. These peaks had comparable intensity. We attribute NBP and NBP' to coherent and incoherent ɛ-carbides, respectively. We produced a model that attributes the relaxation peaks to reorientations of extra carbon pairs in the ɛ-carbide. The extraordinary values of the Arrhenius parameters may be interpreted by using this model. Based on these results, we assert that mechanical spectroscopy can detect the coherent-incoherent transition in carbon steels. This method will be powerful in studying problems related to the coherency in carbon steels.

  13. Comparison of solidification behavior between in situ observation and simulation of Fe–C–Si system

    International Nuclear Information System (INIS)

    Highlights: • In situ time resolved X-ray imaging was obtained for solidification of Fe–C–Si alloy. • The techniques provided quantitative data of evolution and proportion of phases. • Thermo-Calc. and DICTRA was used to simulate the alloy solidification process. • Real-time observations were compared with the results of the simulation. • Further evaluation of DICTRA kinetic databases will be required. - Abstract: Over the last few years, important advances have been made in the understanding and modelling of phase transformations of metallic alloys including (a) the coupling of phase equilibria and kinetics for computerised simulation of multicomponent alloys and (b) in situ time resolved X-ray imaging of phase transformations in real time. Both techniques can be complementary. However the quality of the simulation relies to a large extent on the accuracy of phase equilibria and diffusion data obtained from existing experimental studies. In situ X-ray techniques provide quantitative information on the evolution and proportion of phases, and can validate the thermodynamic/kinetic packages. This validation in-turn improves the computational models and databases. In the present work, the phase transformation in the Fe–C–Si system from liquid to γ-Fe and the reaction liquid ↔ γ-Fe + Cementite was observed by using X-ray imaging at SPring-8 synchrotron. The relationship between fraction solid and temperature was obtained from the generated SPring-8 images. The results are compared with computer simulation using Thermo-Calc. and DICTRA. A critical analysis compares the results of the simulation with the real-time observations of the phase transformation

  14. Irradiation induced tensile property change of SA 508 Cl. 3 reactor pressure vessel steels

    International Nuclear Information System (INIS)

    Irradiation induced tensile property change of four kinds of reactor pressure vessel steels manufactured by different steel refining process was compared based on the differences in the miniature tensile specimen tests were conducted for mechanical property measurement and optical microscope (OM) and transmission electron microscope (TEM) were used for microstructural characterization. Specimens were irradiated to a neutron fluence of 2.7 x 1019 n/cm2 (E ≥ 1 MeV) at 288 deg C. Investigation on the unirradiated microstructures showed largely a same microstructure in that tempered acicular bainite and ferrite with bainitic phase prevailing in the unirradiated condition. Ban-shaped segregations were also clearly observed except a kind of materials. A large difference in the unirradiated microstructure appeared in the grain size and carbide microstructure. Of carbide microstructures, noticeable differences were observed in the size and distribution of cementite, and bainitic lath microstructures. No noticeable changes were observed in the optical and thin film TEM microstructures after irradiation. Complicated microstructural state of heat treated bainitic low alloy microstructure prevents easy quantification of microstructural changes due to irradiation. Apparent differences, however, were observed in the results of mechanical testing. Results of tensile testing and hardness measurement show that a steel refined by vacuum carbon deoxidation (VCD) method exhibits the highest radiation hardening behavior. Some of mechanical testing results on irradiated materials were possible to understand based on the initial microstructure, but further investigations using a wide array of sophisticated tools (for example, SANS, APFIM) are required to understand and characterize irradiation induced defects that are responsible for irradiation hardening behavior but are not revealed by conventional TEM. (author)

  15. Effect of tool microstructure on the white layer formation

    Directory of Open Access Journals (Sweden)

    J. Krawczyk

    2006-04-01

    Full Text Available Purpose: Purpose of this paper: This work supplements the knowledge concerning formation of the white layer on the surface of the tools being utilized in high temperature metal forming processes. Eight iron-based materials were tested: 3 ledeburitic cast steels, 2 hypereutectoid cast steels, normalized and stress relief annealed steel, hardened and tempered steel and nodular mottled cast iron.Design/methodology/approach: The exploitation tests were performed on the hot rolling mills for selected rolled sections, rolling stands and roll passes. The samples were cut out of the roll in such a way that they contained the roll working surface and were used for metallographic observations of the subsurface zone.Findings: It was found, that uniform distribution of dispersed precipitates of hypereutectoid cementite in the alloy matrix prevents the formation of the white layer on the surface of the rolls.Research limitations/implications: The white layer definition was given. An influence of the microstructure of iron base alloys on the susceptibility to form the white layer on their surface due to tribological contact was also determined.Practical implications: The procedure for obtaining rolled products of better quality as well as for restricting the probability of roll cracking was proposed. Obtained results should allow proper design of the microstructure of the materials for tools.Originality/value: This work contains several new aspects, which are: the unique tribological conditions for performing the tests, wide range of investigated materials, and combining the microstructure of the material with the susceptibility of the formation of the white layer on its surface. The results of this research may be used by the producers of tools for high temperature metal forming.

  16. Solidification microstructures and mechanical properties of high-vanadium Fe-C-V and Fe-C-V-Si alloys

    International Nuclear Information System (INIS)

    Fe-C-V and Fe-C-V-Si alloys of various C, V and Si compositions were investigated in this work. It was found that the phases present in both of these alloy systems were alloyed ferrite, alloyed cementite, and VCx carbides. Depending on the alloy composition the solidified microstructural constituents were granular pearlite-like, lamellar pearlite, or mixtures of alloyed ferrite + granular pearlite-like or granular pearlite-like + lamellar pearlite. In addition, it is shown that in Fe-C-V alloys the C/V ratio influences (a) the type of matrix, (b) the fraction of vanadium carbides, fv and (c) the eutectic cell count, NF. In Fe-C-V alloys, a relationship between the alloy content corresponding to the eutectic line was experimentally determined and can be described by Ce=7.91Ve-0.635 where Ce and Ve are the carbon and vanadium composition of the eutectic. Moreover, in the Fe-C-V alloys (depending on the alloy chemistry), the primary VCx carbides crystallize with non-faceted or non-faceted/faceted interfaces, while the eutectic morphology is non-faceted/non-faceted with regular fiber-like structures, or it possesses a dual morphology (non-faceted/non-faceted with regular fiber-like structures + non-faceted/faceted with complex regular structures). In the Fe-C-V-Si system, the primary VCx carbides solidify with a non-faceted/faceted interface, while the eutectic is non-faceted/faceted with complex regular structures. In particular, spiral eutectic growth is observed when Si is present in the Fe-C-V alloys. In general, it is found that as the matrix constituent shifts from predominantly ferrite to lamellar pearlite, the hardness, yield and tensile strengths exhibit substantial increases at expenses of ductility. Moreover, Si additions lead to alloy strengthening by solid solution hardening of the ferrite phase and/or through a reduction in the eutectic fiber spacings with a decrease in the alloy ductility.

  17. Solidification microstructures and mechanical properties of high-vanadium Fe-C-V and Fe-C-V-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Fras, E.; Kawalec, M. [AGH - University of Science and Technology, Reymonta 23, 30-059 Krakow (Poland); Lopez, H.F., E-mail: hlopez@uwm.edu [Materials Department, University of Wisconsin-Milwaukee, 3200 N. Cramer Street, Milwaukee, WI 53211 (United States)

    2009-10-25

    Fe-C-V and Fe-C-V-Si alloys of various C, V and Si compositions were investigated in this work. It was found that the phases present in both of these alloy systems were alloyed ferrite, alloyed cementite, and VC{sub x} carbides. Depending on the alloy composition the solidified microstructural constituents were granular pearlite-like, lamellar pearlite, or mixtures of alloyed ferrite + granular pearlite-like or granular pearlite-like + lamellar pearlite. In addition, it is shown that in Fe-C-V alloys the C/V ratio influences (a) the type of matrix, (b) the fraction of vanadium carbides, f{sub v} and (c) the eutectic cell count, N{sub F}. In Fe-C-V alloys, a relationship between the alloy content corresponding to the eutectic line was experimentally determined and can be described by C{sub e}=7.91V{sub e}{sup -0.635} where C{sub e} and V{sub e} are the carbon and vanadium composition of the eutectic. Moreover, in the Fe-C-V alloys (depending on the alloy chemistry), the primary VC{sub x} carbides crystallize with non-faceted or non-faceted/faceted interfaces, while the eutectic morphology is non-faceted/non-faceted with regular fiber-like structures, or it possesses a dual morphology (non-faceted/non-faceted with regular fiber-like structures + non-faceted/faceted with complex regular structures). In the Fe-C-V-Si system, the primary VC{sub x} carbides solidify with a non-faceted/faceted interface, while the eutectic is non-faceted/faceted with complex regular structures. In particular, spiral eutectic growth is observed when Si is present in the Fe-C-V alloys. In general, it is found that as the matrix constituent shifts from predominantly ferrite to lamellar pearlite, the hardness, yield and tensile strengths exhibit substantial increases at expenses of ductility. Moreover, Si additions lead to alloy strengthening by solid solution hardening of the ferrite phase and/or through a reduction in the eutectic fiber spacings with a decrease in the alloy ductility.

  18. Influencia del revenido en la estructura y las propiedades de dureza, resistencia a la tracción y resiliencia del acero cubano al cromo-manganeso-silicio-níquel.

    Directory of Open Access Journals (Sweden)

    G. Tourón Alonso

    2009-09-01

    Full Text Available La actual demanda de herramientas y accesorios para maquinarias agrícolas se presenta como fuente creciente de nuevas aplicaciones del acero al Cr-Mn-Si-Ni. Este criterio justifica la práctica de tratamientos térmicos, para conseguir distintos valores de propiedades mecánicas, que orienten al material hacia las exigencias y circunstancias de aplicaciones concretas. El trabajo tiene como objetivo conocer la estructura del acero, heredadas de las transformaciones de fase en diferentes regímenes de tratamiento térmico de revenido, y la correlación entre dicha estructura y sus propiedades de dureza, resistencia a la tracción y resiliencia. Las observaciones al microscopio óptico de las muestras revenidas sugieren, en unos casos, una estructura compuesta por martensita revenida, en otros, indican la presencia de partículas de ferrita y cementita. Los ensayos de dureza y tracción revelaron una disminución de la dureza y de la resistencia a la tracción con el aumento de la temperatura de revenido. El ensayo de impacto reveló un aumento de la resiliencia con el aumento de la temperatura de revenido, aunque aparecen dos intervalos de temperatura en que la resiliencia disminuye.Specimens were tempered after being hardened into oil. Tempered specimens for tension tests, were heated from 200 to 500ºC, in an interval of 100ºC; while, specimens for hardness and resilience tests, were heated from 200 to 550ºC, in an interval of 50ºC. Tempering time, for tension and resilience tests, depends on specimens’ thickness, while, for hardness tests is 30, 60 and 90 minutes. Tempered specimens microstructures at 200 and 300ºC indicate the presence of carbide particles; it suggests a tempering martensite structure. Tempered specimens microstructures at 500ºC indicate the presence of ferrite and cementite particles. Both, hardness and strength decrease when the tempering temperature increases. The resilience increase with tempering temperature, but

  19. Development of a quantitative accelerated sulphate attack test for mine backfill

    Science.gov (United States)

    Shnorhokian, Shahe

    Mining operations produce large amounts of tailings that are either disposed of in surface impoundments or used in the production of backfill to be placed underground. Their mineralogy is determined by the local geology, and it is not uncommon to come across tailings with a relatively high sulphide mineral content, including pyrite and pyrrhotite. Sulphides oxidize in the presence of oxygen and water to produce sulphate and acidity. In the concrete industry, sulphate is known to produce detrimental effects by reacting with the cement paste to produce the minerals ettringite and gypsum. Because mine backfill uses tailings and binders---including cement---it is therefore prone to sulphate attack where the required conditions are met. Currently, laboratory tests on mine backfill mostly measure mechanical properties such as strength parameters, and the study of the chemical aspects is restricted to the impact of tailings on the environment. The potential of sulphate attack in mine backfill has not been studied at length, and no tests are conducted on binders used in backfill for their resistance to attack. Current ASTM guidelines for sulphate attack tests have been deemed inadequate by several authors due to their measurement of only expansion as an indicator of attack. Furthermore, the tests take too long to perform or are restricted to cement mortars only, and not to mixed binders that include pozzolans. Based on these, an accelerated test for sulphate attack was developed in this work through modifying and compiling procedures that had been suggested by different authors. Small cubes of two different binders were fully immersed in daily-monitored sodium sulphate and sulphuric acid solutions for a total of 28 days, after 7 days of accelerated curing at 50°C. In addition, four binders were partially immersed in the same solutions for 8 days for an accelerated attack process. The two procedures were conducted in tandem with leach tests using a mixed solution of

  20. 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

    region was characterised by complete precipitation of cementite. In general, the microstructure had a low dislocation density. (author)

  1. THE PROCESS OF FORMATION OF RAILWAY WHEEL DAMAGES AND TIRES IN OPERATION

    Directory of Open Access Journals (Sweden)

    N. A. Grischenko

    2015-01-01

    Full Text Available Purpose. The dependence analysis of structural changes in the metal of railway wheels and tires from indicated influences in operation, for the further development of strategy of service reliability growth. Methodology. Test materials are the details selected from railway wheels which were taken out of operation beforehand because of various damages. Micro-structural researches were made with the use of light microscope Epiquant and electron microscope. The sizing of structural elements was done by using the methods of quantitative metallography. Findings. Over the past few decades the rapid development of industry was supported by the steady growth of intensity of using railway transport. In this case simultaneous increase of load at wheel set axle, with the increase of speed was accompanied by natural increase of the amount of cases of premature wheels and tires’ withdrawing out of operation. Railway wheel, except the formation of metal layer at rolling surface with the high defects concentration of crystal structure and first of all dislocations, falls under thermal influence from interaction with break blocks. The nature of joint influence (cold deformation and heating on the metal rim of a wheel is conditioned by the appearance of sufficiently high gradients of structural changes that can be considered as the influence on the level of internal residual stresses. In case of the rise of volume part of carbide phase at a constant ferrite grain size, it is achieved only by the increasing of dislocation nucleation sources without changing the number of annihilation positions. In this case the accumulation of dislocations at the initial stages of plastic deformation (in metal volume in front of delta arm crack will lead to the formation of cementite globes around certain interlocked dislocation density. In contrast the sharp increase of deformation hardening carbon steel parameters is observed. Originality. During the braking of locomotive the

  2. Effect of cutting parameters on chip formation in orthogonal cutting

    Directory of Open Access Journals (Sweden)

    S. Ben Salem

    2012-01-01

    Full Text Available Purpose: of this paper is to study the chip formation to obtain the optimal cutting conditions and to observe the different chip formation mechanisms. Analysis of machining of a hardened alloy, X160CrMoV12-1 (cold work steel: AISI D2 with a ferritic and cementite matrix and coarse primary carbides, showed that there are relationships between the chip geometry, cutting conditions and the different micrographs under different metallurgical states.Design/methodology/approach: Machining of hardened alloys has some metallurgical and mechanical difficulties even if many successful processes have been increasingly developed. A lot of study has been carried out on this subject, however only with modest progress showing specific results concerning the real efficiency of chip formation. Hence, some crucial questions remain unanswered: the evolution of white layers produced during progressive tool flank wear in dry hard turning and to correlate this with the surface integrity of the machined surface. For the experimental study here, various cutting speeds and feed rates have been applied on the work material.Findings: The “saw-tooth type chips” geometry has been examined and a specific attention was given to the chip samples that were metallographically processed and observed under scanning electronic microscope (SEM to determine if white layers are present.Research limitations/implications: This research will be followed by a detail modelling and need more experimental results for a given a good prediction of the results occurred on the damage related to the microstructure by using the cutting parameters.Practical implications: A special detail was given to the mechanism of chip formation resulting from hard machining process and behaviour of steel at different metallurgical states on the material during the case of annealing and or the case of quench operations.Originality/value: For the sake of simplicity, ANOVA (Analysis of Variance was used to

  3. Influencia del revenido en la estructura y las propiedades de dureza, resistencia a la tracción y resiliencia del acero cubano al cromomanganeso- silicio-níquel. // Influence of tempering on structure and hardness, strength and resilience properties of ch

    Directory of Open Access Journals (Sweden)

    G. Tourón-Alonso

    2009-09-01

    Full Text Available La actual demanda de herramientas y accesorios para maquinarias agrícolas se presenta comofuente creciente de nuevas aplicaciones del acero al Cr-Mn-Si-Ni. Este criterio justifica la práctica detratamientos térmicos, para conseguir distintos valores de propiedades mecánicas, que orienten almaterial hacia las exigencias y circunstancias de aplicaciones concretas. El trabajo tiene comoobjetivo conocer la estructura del acero, heredadas de las transformaciones de fase en diferentesregímenes de tratamiento térmico de revenido, y la correlación entre dicha estructura y suspropiedades de dureza, resistencia a la tracción y resiliencia. Las observaciones al microscopioóptico de las muestras revenidas sugieren, en unos casos, una estructura compuesta por martensitarevenida, en otros, indican la presencia de partículas de ferrita y cementita. Los ensayos de dureza ytracción revelaron una disminución de la dureza y de la resistencia a la tracción con el aumento dela temperatura de revenido. El ensayo de impacto reveló un aumento de la resiliencia con elaumento de la temperatura de revenido, aunque aparecen dos intervalos de temperatura en que laresiliencia disminuye.Palabras claves: revenido, estructura, dureza, resistencia, resiliencia____________________________________________________________________________AbstractSpecimens were tempered after being hardened into oil. Tempered specimens for tension tests,were heated from 200 to 500ºC, in an interval of 100ºC; while, specimens for hardness andresilience tests, were heated from 200 to 550ºC, in an interval of 50ºC. Tempering time, for tensionand resilience tests, depends on specimens’ thickness, while, for hardness tests is 30, 60 and 90minutes. Tempered specimens microstructures at 200 and 300ºC indicate the presence of carbideparticles; it suggests a tempering martensite structure. Tempered specimens microstructures at500ºC indicate the presence of ferrite and cementite particles

  4. FLEXURAL AND TENSILE CHARACTERISTICS OF MICRO FIBER-REINFORCED VERY HIGH STRENGTH CONCRETE THIN PANELS

    Directory of Open Access Journals (Sweden)

    Taher M. Abu-Lebdeh

    2012-01-01

    Full Text Available The purpose of this research was to experimentally characterize the flexural and tensile characteristics of fiber-reinforced Very High-Strength Concrete (VHSC panels. The panels were made with a unique mix of cementitous materials achieving compressive strength of 26,000 psi (180 MPa or greater. VHSC panels were reinforced with polypropylene fibers of 1 inch (25.4 mm in length and Polyvinyl alcohol (PVA micro-fibers of ½ inch length, incorporated at 1.5% by volume. For the flexural behavior, 17×2×¾ inch flat panels were tested under third-point loading tests, while the direct tension experiments were tested on 10×3×½ inch tension panels under a direct tensile load. Flexural tests were conducted on three panels of plain VHSC, three panels of VHSC reinforced with polypropylene fibers and three panels of VHSC reinforced with ½ inch micro-fibers. Similar testing program was used to conduct the direct tension tests. Also, compression test conducted on 2×2×2 inch cubes and compressive test conducted on 4 inch by 8 inch cylinders test were used to establish compressive strength and modulus of elasticity respectively. Results show that the compressive strength, tensile strength and fracture toughness of the VHSC panels were much greater than those normally obtained by typical concrete material. The presence of fibers increases the toughness of VHSC specimens between 80 and 190% and increases the tensile strength by 23 to 47%. The modulus of elasticity and Poisson’s ratio recorded herein were determined according to ASTM C 469-02. Laboratory experiments on flexural and tensile properties of thin, very high-strength, fiber reinforced concrete panels, were used to study the material and characterize the panels’ reaction to load. Parameters such as compressive strength, tensile strength, toughness, elastic modulus, Poisson’s ratio and first-crack strength were determined and may be considered for potential use as

  5. Thermal sprayed iron base alloys coatings

    International Nuclear Information System (INIS)

    Particularities of thermal spraying of iron-based alloys coatings are associated with sufficiently great values of parameter of melting difficulty (for Fe D = 2.08 I-10/sup 10/ kJ.kg/sup -1/.m/sup -3/), and relatively low values of coefficients-of heat accumulation (for Fe b=C.raw.Lambda /sub 0.5/=108 W.m/sup -2/.K.sec/sup-0.5/). These materials are less inclined to form quality coating under the influence of the thermal activation and therefore it is reasonable to use in addition the mechanical activation of substrate surface. The powder of iron-base alloy FeSi/sub 7/AI/sub 3.5/C/sub 2/ was obtained by melt-atomization with water hardening of droplets. The main phase components of powder are alpha and gamma -solid solution on base of Fe (austenite), cementite (Fe/sub 3/C), metastable rhombic lattice x-phase, and possibly metastable carbide Fe/sub 2/C. When the powder particles shape is oval which axis dimensions about 80 and 300 micro meter, the main phase components of detonation sprayed coatings in case of oxy-acetylene gas mixture are alpha and gamma -phases, in case of oxy-propane-butane mixture the coating phase component the same as initial powder. When the powder particles size is 63-100 micro meter, the coatings phase components are alpha and gamma - solid solutions, Fe/sub 3/C, x-phase, Fe/sub 2/C, Fe/sub 3/0/sub 4/ and FeO. The main phase components of FeSi/sub 7/B/sub 12,6/ powder are alpha-solid solution, borides Fe/sub 2/B and FeB, X- phase. The sprayed coatings have the same phase composition. These types of Fe-base alloys powders have relatively low cost, easy available and can used for deposition of wear resistant coatings. (author)

  6. Reactive transport modelling of organic complexing agents in cement stabilized low and intermediate level waste

    Science.gov (United States)

    von Schenck, Henrik; Källström, Klas

    The Swedish final repository for short-lived radioactive waste (SFR 1) is located at Forsmark in Sweden. It holds low and intermediate-level operational waste from the Swedish nuclear power plants, as well as industrial, research-related, and medical waste. A variety of low molecular weight organic compounds are present in the waste or in its matrix. Such compounds can also be formed by chemical degradation of organic macromolecules. These organics can ligate to metal atoms forming stable complexes and also adsorb to the surface of cement, thereby influencing the net release of radionuclides from the repository. This motivates the study of the concentration distribution of complexing agents in the repository as a function of time. The following paper reports the results of mass transport modelling, describing the transport of complexing agents through the cementitous matrix in the rock vault for intermediate-level waste in the SFR 1 repository. Nitrilotriacetate (NTA) and isosaccharinate (ISA) have been investigated, where the former is considered to be non-sorbing and non-reacting, while the latter is produced from cellulose degradation and adsorbs strongly to cement. The 3D model considers advection, diffusion, and sorption of solvated species in cement pore water over a time period of 20,000 years. The model accounts for the spatial distribution of the flow field in the repository structure and also considers changing groundwater flow during the investigated time period. It is found that 99% of the NTA is removed after approximately 4000 years, while 90% of the ISA is retained in the rock vault after 20,000 years. The maximum pore water concentration of ISA is found to be 8.6 mol/m3 after approximately 2300 years, based on the degradation of the deposited amounts of cellulose. Over the investigated time scale, the ligands retained in the repository can redistribute across several waste compartments where the organic compounds were not originally deposited. In

  7. 利用APT对RPV模拟钢中富Cu原子团簇析出的研究%STUDY ON THE PRECIPITATION OF Cu-RICH CLUSTERS IN THE RPV MODEL STEEL BY APT

    Institute of Scientific and Technical Information of China (English)

    徐刚; 蔡琳玲; 冯柳; 周邦新; 刘文庆; 王均安

    2012-01-01

    from 1.5 nm to 2.4 nm, and the average Cu content in the Cu-rich clusters vary from 45% to 55 % (atomic fraction). The number density of the Cu-rich clusters in both types of the specimens is at the order of 1022 m-3. The Cu concentration in the ferritic matrix is (0.15±0.02)% for the specimen aged at 370℃ for 13200 h, which is still higher than the limitation of Cu solubility in the ferritic matrix at 370℃ . It means that the precipitation process of Cu-rich clusters does not reach the equilibrium state. The analysis results also show that Ni, Si, P atoms, but not Cu atoms, segregate near the interface between the cementite and the ferritic matrix, and Mn, Mo, S atoms are enriched in the cementite.%提高了Cu含量的核反应堆压力容器(RPV)模拟钢经过880℃水淬和660℃调质处理,在370℃时效不同时间后,利用原子探针层析技术(APT)进行分析.结果表明:样品经过1150 h时效后,富Cu团簇正处于析出过程的形核阶段;经过3000和13200 h时效后析出了富Cu团簇,团簇的平均等效直径分别为1.5和2.4 nm,团簇中Cu的平均浓度分别为45%和55%(原子分数),团簇的数量密度约为4.2×1022 m-3;样品经过13200 h时效后,α-Fe基体中的Cu含量为(0.15±0.02)%,仍然高于Cu在α-Fe中平衡固溶度的理论计算值,说明这时富Cu团簇的析出过程还没有达到平衡.对渗碳体的分析结果表明,Ni,Si和P偏聚在渗碳体和α-Fe基体的相界面附近,Mn,Mo和S富集在渗碳体中;并没有观察到Cu在相界面上偏聚的现象.

  8. Teknologi Pembuatan Material Shot Blast untuk Mendukung Industri Pengecoran Logam Nasional

    Directory of Open Access Journals (Sweden)

    Fajar Nurjaman

    2009-01-01

    Full Text Available Shot blast material is a supporting material in foundry which is used at surface finishing process of metal casting. Recently, there is no one of national industry that produce shot blast material, in consequence, the purpose of this research is to lessen the dependence of using shot blast material import by making a shot blast material which improve its hardness exceed the shot blast material import. This research use the raw material from scrap iron with the following composition: C (3.2%, Si (1.18%, Mn (6.1%, Cu (0.35%, Fe (88.7%. The scrap is melted in induction furnace untill melt (hot metal, then the hot metal (1200 oC is tilted into a runner which is connected with pan crucible, which is consisted of 107 holes with diameter of each holes is 10 mm. Hot metal that is leave from the holes, is injected by pressurized water 1.1 atm with the velocity 0.8 m/s, untill obtained grains of shot blast material, then these grains goes into the water tank which it has temperature 40oC. From thermodynamic study, to avoid the happening of the explosion that is arising out because the effect of high temperature difference at injection process beetween water and hot metal, hence the comparison value beetween the mass of water and hot metal equal to 1:4.6. From this research is obtained shot blast material Ø0.8-3.2 mm with the metallography structure with martensite domination and dispersion of cementite and a little austenit. The hardness value of this material is 54.8 HRC, where this value is larger than shot blast material import (45-50 HRC. Abstract in Bahasa Indonesia: Material shot blast merupakan material pendukung pengecoran logam yang digunakan pada proses surface finishing benda cor logam. Saat ini belum ada satupun industri nasional yang memproduksi material shot blast, karena itu tujuan penelitian ini untuk mengurangi ketergantungan penggunaan material shot blast impor dengan membuat material shot blast yang nilai kekerasannya melebihi material

  9. Effects and characterization of an environmentally-friendly, inexpensive composite Iron-Sodium catalyst on coal gasification

    Science.gov (United States)

    Monterroso, Rodolfo

    were studied through characterization tests. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Mossbauer spectroscopy, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), gas chromatography (GC-MS) and nuclear magnetic resonance spectroscopy (NMR) were used to perform the analyses. The XRD results are consistent with interactive mechanisms or the formation of Na-Fe oxides as the catalytic pathway. Activity of the iron catalyst during late stages of the gasification process was confirmed through XPS. Mossbauer spectroscopy also indicated the presence of metallic iron and cementite in the char at different stages. The Fe catalysts were better at tar decomposition than the Na catalysts, as indicated by GC-MS analyses. NMR spectra confirmed that tar compositions vary with the catalytic mechanism. FTIR analysis confirmed the presence of high yields of aromatic components and long aliphatic chains in the tar. Composite Fe-Na catalysts provide a method to tailor the amounts and composition of product generated during gasification.

  10. Effect of Si on Wear Resistance of Bainitic Cast Steel under High Stress Impact%硅对贝氏体铸钢高应力冲击磨损性能的影响

    Institute of Scientific and Technical Information of China (English)

    黄进峰; 方鸿生; 徐平光; 郑燕康

    2001-01-01

    The high stress-wear resistance and mechanism for bainitic cast steels with different Si content (0.7 %~2.4 %) have been studied systematically.The experiments have shown that the wear loss of high Si bainitic cast steels is only about 1/2 times as that of low Si baini tic cast steels, showing better wear resistance of the former under high stress impact.The reason is that the impact wear mechanism is different for low and hi gh Si bainitic cast steels.Low Si bainitic cast steel has poor wear resistance under high stress impact because of its low toughness, coarse dendrite and micro -segregation, etc.So the damage cracks are easily formed in the wear surface b efore formation of white layer, and propagate inside the deformation zone and ma trix, exhibiting mechanism of deformation zone and matrix delamination.The imp act toughness of high Si bainitic cast steels are improved apparently for the re ason that the brittle cementite is replaced by ductile retained austentite film, resulting in the brittle delamination of white layer.%研究了不同硅含量(0.7 %~2.4 %,质量分数,下 同)贝氏体铸钢的抗高应力磨损性能和失效机制。结果表明:高硅贝氏体铸钢的耐磨性能较 低硅钢显著提高,其磨损失重约是低硅贝氏体铸钢的1/2。这是因为硅使贝氏体铸钢在高应 力冲击磨损下表现出不同的失效机制。低硅(0.7 %)贝氏体铸钢由于韧性低、组织结构粗大 及树枝晶的微区成分偏析,故材料抵抗冲击的能力很低,常在表面还未形成强烈变形层(白 层)甚至变形层时,就在变形层和材料基体内产生裂纹并扩展,故低硅贝氏体铸钢的失效方 式为变形层和基体剥落机制。而硅含量为1.6 %~2.4 %的高硅贝氏体铸钢,因脆性的渗碳体 被韧性的残余奥氏体所代替,钢的韧性显著提高,失效方式表现为白层的剥落机制。

  11. Effect of microalloying on pearlite transformation of high carbon wire steels

    Science.gov (United States)

    Miller, Stephanie L.

    Microalloying has been shown to improve strength in eutectoid steels for wire applications, and previous work on vanadium-microalloyed eutectoid steels showed delayed pearlite transformation with additions of niobium and accelerated pearlite transformation with additional nitrogen. This study investigates the origin of the CCT shifts with microalloying additions and whether trends in hardness and microstructural feature sizes observed in continuous cooling tests persist through industrial hot rolling simulations. An industrially hot rolled 1080 wire rod with vanadium additions and three laboratory-prepared alloys were studied. The base alloy, denoted the V steel, had a composition of 0.80C-0.50Mn-0.24Si-0.20Cr-0.079V-0.0059N (wt pct). The V+N steel contained 0.0088 wt pct N, and the V+Nb steel contained an additional 0.010 wt pct Nb. All alloys were subjected to a GleebleRTM 3500 torsion hot rolling simulation based on industrial wire rod hot rolling parameters. Microstructural constituents, Vickers hardness, pearlite colony size, and pearlite interlamellar spacing (ILS) were characterized for each alloy. All alloys exhibited pearlitic microstructures with some proeutectoid ferrite at prior austenite grain boundaries, with no evidence of shear transformation products. The V steel has the lowest overall hardness, while both nitrogen and niobium additions increase hardness by approximately 15 HV, correlating to a 43 MPa increase in yield strength. Niobium additions refined ILS, with an average ILS of 92 +/- 3 nm for the V+Nb steel compared to 113 +/- 5 nm for the V steel and 113 +/- 3 nm for the V+N alloy. Vanadium additions produced precipitation strengthening for all alloys and heat treatments, and additional precipitation strengthening with nitrogen and niobium additions was not apparent based on a Taleff regression analysis. Atom probe tomography of an industrially processed wire rod with vanadium additions revealed vanadium enrichment of cementite, and vanadium

  12. Direct growth of carbon nanotubes on metal surfaces without an external catalyst and nanocomposite production

    Science.gov (United States)

    Baddour, Carole Emilie

    ), Transmission Electron Microscopy (TEM) and sonication. CNT purity up to 84% is attained and the catalyst is determined to be the faced-centred cubic structure of Fe in the austenite form (? Fe). In the case of the FBCVD technique, there are at least 30 mg of CNTs produced per total gram of sample made of CNT-coated SS particles. In addition, the recovery and reuse of the SS particles is demonstrated for a second growth sequence in the FBCVD setup. Detailed characterizations of the SS surface includes X-Ray Photoelectron Spectroscopy (XPS), grain size analysis, Atomic Force Microscopy-Kelvin Probe (AFM/Kelvin) and Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). In summary, XPS reveals that the etching process partially removes the Cr 2O3 passive oxide layer and results in the formation of Fe 2O3. Also, Fe3C is found on the surface beneath the CNTs. This iron carbide "cementite" phase is formed during the CNT growth process. Recrystallization occurs during the heat treatment step of the method and is followed by grain growth. The AFM study confirms that the etching process creates ripple-like features on the surface, which are 10-30 nm wide. In order to stabilize mechanically and structurally the CNT growth structure on the metallic support, the production of novel Diamond-like Carbon (DLC) / CNT and Titanium Nitride (TiN) / CNT nanocomposites having a porous three-dimensional architecture is also accomplished here. The "felt-like" CNTs produced in the first part of the thesis are "frozen" in DLC or TiN by Physical Vapour Deposition (PVD). The TiN/CNT nanocomposites are characterized by nanoindentation and contact angle measurements. An increase in contact stiffness values with TiN coating time is observed. The TiN coating on the non-wetting CNTs resulted in a wetting nanocomposite surface. The wetting property was found to be a function of the TiN coating thickness on the CNT structure.