Microstructure and mechanical properties of ferritic-martensitic steel EP-823 after high-temperature thermomechanical treatment

2019 ◽  
Author(s):  
K. V. Almaeva ◽  
N. A. Polekhina ◽  
V. V. Linnik ◽  
I. Yu. Litovchenko
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Thermomechanical Treatment ◽  
Martensitic Steel ◽  
Microstructure And Mechanical Properties

scholarly journals The Microstructure and Mechanical Properties of Ferritic-Martensitic Steel EP-823 after High-Temperature Thermomechanical Treatment

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 79
Author(s):  
Igor Litovchenko ◽  
Kseniya Almaeva ◽  
Nadezhda Polekhina ◽  
Sergey Akkuzin ◽  
Valeria Linnik ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Plastic Deformation ◽  
High Temperature ◽  
Thermomechanical Treatment ◽  
Martensitic Steel ◽  
Rolling Plane ◽  
Dynamic Strain ◽  
Temperature Range ◽  
Microstructure And Mechanical Properties

The effect of high-temperature thermomechanical treatment (HTMT) with plastic deformation by rolling in austenitic region on the microstructure and mechanical properties of 12% chromium ferritic-martensitic steel EP-823 is investigated. The features of the grain and defect microstructure of steel are studied by Scanning Electron Microscopy with Electron Back-Scatter Diffraction (SEM EBSD) and Transmission Electron Microscopy (TEM). It is shown that HTMT leads to the formation of pancake structure with grains extended in the rolling direction and flattened in the rolling plane. The average sizes of martensitic packets and ferrite grains are approximately 1.5–2 times smaller compared to the corresponding values after traditional heat treatment (THT, which consists of normalization and tempering). The maximum grain size in the section parallel to the rolling plane increases up to more than 80 µm. HTMT leads to the formation of new sub-boundaries and a higher dislocation density. The fraction of low-angle misorientation boundaries reaches up to ≈68%, which exceeds the corresponding value after HTMT (55%). HTMT does not practically affect the carbide subsystem of steel. The mechanical properties are investigated by tensile tests in the temperature range 20–700 °C. It is shown that the values of the yield strength in this temperature range after HTMT increase relative to the corresponding values after THT. As a result of HTMT, the elongation decreases. A significant decrease is observed in the area of dynamic strain aging (DSA). The mechanisms of plastic deformation and strengthening of ferritic-martensitic steel under the high-temperature thermomechanical treatments are also discussed.

scholarly journals The Effect of Quenching and Partitioning (Q&P) Heat Treatment on the Microstructure and Mechanical Properties of High Boron Steel

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1556
Author(s):  
Zhao Li ◽  
Run Wu ◽  
Mingwei Li ◽  
Song-Sheng Zeng ◽  
Yu Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Volume Fraction ◽  
Martensitic Steel ◽  
Boron Steel ◽  
Quenching And Partitioning ◽  
Effect Mechanism ◽  
Microstructure And Mechanical Properties ◽  
High Boron ◽  
Cast Condition

High boron steel is prone to brittle failure due to the boride distributed in it with net-like or fishbone morphology, which limit its applications. The Quenching and Partitioning (Q&P) heat treatment is a promising process to produce martensitic steel with excellent mechanical properties, especially high toughness by increasing the volume fraction of retained austensite (RA) in the martensitic matrix. In this work, the Q&P heat treatment is used to improve the inherent defect of insufficient toughness of high boron steel, and the effect mechanism of this process on microstructure transformation and the change of mechanical properties of the steel has also been investigated. The high boron steel as-casted is composed of martensite, retained austensite (RA) and eutectic borides. A proper quenching and partitioning heat treatment leads to a significant change of the microstructure and mechanical properties of the steel. The net-like and fishbone-like boride is partially broken and spheroidized. The volume fraction of RA increases from 10% in the as-cast condition to 19%, and its morphology also changes from blocky to film-like. Although the macro-hardness has slightly reduced, the toughness is significantly increased up to 7.5 J·cm−2, and the wear resistance is also improved.

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