Physico-chemical Modeling of Phase Separation in Fe-21.4 Cr Steel with 1.14 Mo Using the Provisions of Non-equilibrium Thermodynamics
Serhii V. Bobyr,
Dmitro V. Loshkarev
Issue:
Volume 5, Issue 2, June 2021
Pages:
23-28
Received:
18 May 2021
Accepted:
8 June 2021
Published:
21 June 2021
Abstract: The use of ferritic-martensitic steels, for example, Fe-Cr and Fe-Cr-Al alloys as structural material for fast neutron reactors has been advocated due to their relatively low rate of swelling at elevated temperatures. Because of the high Cr-content, the Fe-Cr alloys are not suitable for use at temperatures around 500°С due to the miscibility gap in the Fe-Cr system. Phase separation in such alloys can also be prevented by doping with elements that impede the segregation of chromium. In solid state physics for calculating phase separation in similar metal systems are used physicochemical and phase-field modeling. The aim of the work is the physicochemical modeling of diffusion phase transformation and determination of the long-term microstructural stability of the Fe-21.4 Cr-1.16 Mo. A conventional Fe-21.4 Cr alloy is used as a reference material. The article proposes an integral approach to modeling phase separation in chromium alloys, combining the determination of diffusion coefficients and fluxes of elements, taking into account their dependences on the concentration and an assessment of the mutual diffusion of elements, using the provisions of nonequilibrium thermodynamics. The calculated values of diffusion fluxes are used to calculate the current concentrations of carbon and chromium in the alloy and the size of chromium formations. They show that the thermal stability of the Fe - 21.4% Cr alloy with 1.16% Mo is much higher than without molybdenum. In alloy Fe – 21,4% Cr – 1,16% Mo at a temperature of 973°K, the chromium concentration during the same operation time decreases three times slower with the formation of inclusions of the σ-phase about 6 microns in size.
Abstract: The use of ferritic-martensitic steels, for example, Fe-Cr and Fe-Cr-Al alloys as structural material for fast neutron reactors has been advocated due to their relatively low rate of swelling at elevated temperatures. Because of the high Cr-content, the Fe-Cr alloys are not suitable for use at temperatures around 500°С due to the miscibility gap in...
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Influence of Temperature on Wax Deposit on Corrosion of Crude Oil Pipeline
Nnorom Obinichi,
Alexander Nwachukwu Okpala,
Tolumoye Johnnie Tuaweri
Issue:
Volume 5, Issue 2, June 2021
Pages:
29-34
Received:
25 May 2021
Accepted:
11 June 2021
Published:
25 June 2021
Abstract: The paper aims to study the effect of temperature on wax deposition on corrosion of crude oil pipeline at different flow rate with time. The waxy crude oil sample is pumped into the design and fabricated experimental flow-loop set up under different operating conditions. The effect of temperature on corrosion at different flow rate of wax deposition during the corrosion inhibition were studied at flow rate of 10.21, 20.37, 30.45, 40.28 and 50.70 L/min and time at 3, 6, 9, 12, 15 and 18 min while keeping temperature constant for each of the experimental run at 15, 20, 25, 30 and 35°C, to determine the corrosion rate against time. The results showed that at flow rate of 10.21 L/min and time 18 min at constant temperature of 15°C, the corrosion rate is 0.11 mpy. At flow rate of 10.21 L/min and time 18 min at constant temperature of 20°C, the corrosion rate is 0.08 mpy. At flow rate of 10.21 L/min and time 18 min at constant temperature of 25°C, the, corrosion rate is 0.12 mpy. Based on the results, a significant reduction of corrosion rates and excellent corrosion protection is achieved while others provided only moderate or negligible protection to the crude oil pipeline. However, the wax layer becomes thicker with time, if the temperature stays below the WAT for extended period of time and can in the long run, cause partial or total blockage of the pipe. Hence, as the deposition of the paraffin wax increases the corrosion rate decrease. The paraffin wax film presence on the surface promotes a significant reduction of general corrosion rates on the pipeline, although localized corrosion was observed due to loss of integrity of the paraffin layer. It means that deposition of paraffin wax inhibit corrosion and also give protection to the pipeline layer. Finally, due to the long chain paraffin layer being physically removed from the surface most of the corrosion protection has been lost during the periods of increased flow rate or temperature.
Abstract: The paper aims to study the effect of temperature on wax deposition on corrosion of crude oil pipeline at different flow rate with time. The waxy crude oil sample is pumped into the design and fabricated experimental flow-loop set up under different operating conditions. The effect of temperature on corrosion at different flow rate of wax depositio...
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The Technology of Programmed Thermo-mechanical Processing for Structural Steel
Radkevich Mikhail Mikhailovich
Issue:
Volume 5, Issue 2, June 2021
Pages:
35-38
Received:
2 December 2020
Accepted:
4 January 2021
Published:
28 June 2021
Abstract: This paper discusses the technology that allows to obtain high-strength products made of structural carbon and alloy steels with hardening processing named the technology of programmed thermo-mechanical processing (PTMP). Targeted material structure research of hot deformation processing makes possible creation of new important technologies of thermo-mechanical processing (TMP). The programmed thermo-mechanical processing objective is to intense growing process of imperfections during thermal processing and plastic deformation of crystalline lattice, which improves structural conditions and mechanical properties of the product. The desired results achieved only by full realignment of the crystal lattice and micro-grain structures, caused by combined mechanical and thermal processing. Therefore, the objective of the programmed thermo-mechanical processing is to combine two technologies: thermal- and mechanical- processing, into a single production process that allows obtaining of rational micro-grain structural conditions of alloy and the appropriate density of crystalline lattice imperfections that increase forges mechanical properties. To achieve fine alloy structure on various levels (sub-, macro- and micro-grain) PTMP technology must provide regulation of deformation intensity and thermal impact to forged material with programmed manufacturing working algorithm. Designed technology aimed to form a crystalline lattice with desired properties, and fixed chemical composition. The combined mechanical and thermal effect, not only leading to a high density of crystalline structure imperfections but also the most importantly provides homogenous recrystallization process throughout the volume of a workpiece, which provides significantly increased mechanical properties of forgings processed by PTMP.
Abstract: This paper discusses the technology that allows to obtain high-strength products made of structural carbon and alloy steels with hardening processing named the technology of programmed thermo-mechanical processing (PTMP). Targeted material structure research of hot deformation processing makes possible creation of new important technologies of ther...
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