Hardening Mechanisms of 12% Chromium Ferritic-Martensitic Steel EP-823
Based on experimental data on microstructure parameters of the reactor heat-resistant high-chromium (12% Cr) ferritic-martensitic steel EP-823, the main factors responsible for its strength properties have been identified. An analysis of the hardening mechanisms of this steel after processing is car...
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Published in | Steel in translation Vol. 52; no. 12; pp. 1135 - 1141 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Moscow
Pleiades Publishing
01.12.2022
Springer Nature B.V |
Subjects | |
Online Access | Get full text |
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Summary: | Based on experimental data on microstructure parameters of the reactor heat-resistant high-chromium (12% Cr) ferritic-martensitic steel EP-823, the main factors responsible for its strength properties have been identified. An analysis of the hardening mechanisms of this steel after processing is carried out according to the modes that provide a different level of its strength properties. Traditional heat treatment (THT) and advanced modifying high-temperature thermomechanical treatment (HTMT) are considered. The main mechanisms of steel hardening, regardless of the processing mode, are: dispersed hardening with nanosized particles of the
MeX
type (
Me
= V, Nb, Mo;
X
= C, N) according to the Orowan mechanism; grain-boundary hardening by high-angle boundaries of martensitic blocks and ferrite grains; substructural hardening by low-angle boundaries of martensitic lamellae; dislocation hardening due to the increased density of dislocations. The HTMT mode, which includes hot deformation in the austenitic region, leads to a significant modification of the structural-phase state of steel relative to THT: a decrease in the average sizes of martensite blocks and lamellae, as well as ferrite grains, an increase in the dislocation density and the volume fraction of nanosized particles of the
MeX
type. In this case, the corresponding contributions to the value of the yield strength of steel from grain boundary, substructural and disperse hardening increase in comparison with THT by 1.2, 1.3, and 1.8 times. The relative contributions of the considered hardening mechanisms to the yield strength of ferritic-martensitic steel EP-823 are discussed. It is shown that the closest to the experimental yield strength values after the two studied machining modes are obtained by using the Langford-Cohen model to estimate the value of substructural hardening. |
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ISSN: | 0967-0912 1935-0988 |
DOI: | 10.3103/S0967091222120026 |