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

Bała P., Krawczyk J., Hanc A.

Archives of Materials Science and Engineering

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2008

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Vol. 32, nr 2

95-98

EN

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 900°C 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.

2

FMR study of nanocarbon materials obtained by carburisation of nanocrystalline iron

Narkiewicz U., Arabczyk W., Pełech I., Guskos N., Typek J., Maryniak M., Woźniak M. J., Matysiak H., Kurzydłowski K. J.

Materials Science Poland

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2006

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Vol. 24, No. 4

1067--1075

EN

Samples of nanocrystalline iron were carburised with ethylene and next reduced with hydrogen. Both carburisation and reduction were monitored by the thermogravimetry. The obtained samples were characterised using X-ray diffraction, high-resolution transmission electron microscopy and ferromagnetic resonance. The samples after carburisation contained cementite (Fe3C) and carbon deposit (nanofibres and nanotubes). As the result of reduction with hydrogen at 450 or 500 °C cementite was reduced to iron. A major part of carbon was also hydrogenated, only thin carbon nanotubes remained. The FMR spectra of the prepared samples were recorded at room temperature. The sample after carburisation has shown a wide FMR line with weak intensity while the resonance field has been shifted to lower magnetic field. This spectrum has been attributed to the presence of cementite. The FMR lines corresponding to samples after reduction are more intense and are connected with the presence of alfa-Fe nanoparticle conglomerates.

3

Exfoliated graphite-based composites with iron and chromium carbides exhibiting enhanced oxidation resistance

Skowroński J. M., Walkowiak M.

Karbo

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2004

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Nr 1

52-55

EN

The process of oxidation of two composite materials obtained by heat-treatment of graphite intercalation compounds is investigated using thermal gravimctry and differential thermal analysis techniques. The first material consisted of exfoliated graphite and chromium carbide Cr3C2, whereas the second material was composed of exfoliated graphite, metallic iron and iron carbide Fe3C. It was found that the temperature at which burning-out begins to start is nearly 200°C higher for composite containing Cr2C2 as compared to pure exfoliated graphite. A characteristic feature of composite containing metallic and iron Fe3C is an anomalously slow kinetics of oxidation.

PL

Dwa rodzaje materiałów kompozytowych wytworzonych na drodze obróbki cieplnej interkalacyjnych związków grafitu badane były metodami termograwimetrii i różnicowej analizy termicznej. Pierwszy z materiałów składał sic z eksfoliowanego grafitu i węgliku chromu, zaś drugi złożony był z eksfoliowancgo grafitu, węgliku żelaza i metalicznego żelaza. Stwierdzono, że temperatura, przy której rozpoczyna się proces spalania, jest około 200°C wyższa dla kompozytu zawierającego węglik chromu Cr3C2/, w porównaniu z czystym eksfoliowanym grafitem. Charakterystyczną właściwością kompozytu zawierającego metaliczne żelazo i Fe3Cjest anomalnie wolna kinetyka procesu utleniania.

4

Studies of the kinetics of CH4 decomposition to Fe3C on the promoted iron catalysts

Arabczyk W., Narkiewicz U., Konicki W., Grzmil B.

Polish Journal of Chemical Technology

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2002

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Vol. 4, nr 3

1-4

EN

The decomposition of methane on the doubly- (A1,O,, CaO) and triply- (K,O, A1,O,, CaO) promoted iron catalyst has been investigated using the thermobalance (considered as an differential reactor). The process of decomposition results in the formation of iron carbide and carbon deposit subsequently. The process was carried out under atmospheric pressure in the temperature range of 500 - 600°C. The rate of Fe3C formation in the kinetic region of the reaction was written using the following expression: r = k-pCH . The apparent activation energy of methane decomposition to Fe,C is equal to 158 kJ/mol for both doubly and triply promoted iron catalysts. The pre-exponential factor k() equals to 1.77-10* and 5.71 105 for doubly and triply promoted catalyst, respectively.