Microstructure of 11%Cr ferritic/martensitic steel in normally heat-treated state before and after irradiation

doi:10.13251/j.issn.0254-6051.2025.01.001

Abstract

Abstract: The microstructure of 11%Cr ferritic/martensitic steel in the normally heat-treated state before and after irradiation was experimentally studied by using transmission electron microscopy and energy dispersive spectroscopy. The results show that the primary microstructure of the 11%Cr ferritic/martensitic steel before and after irradiation consists of tempered martensitic along with a small amount of δ-ferrite. Before irradiation, a small amount of precipitates with a relatively small size are present at martensite boundaries and within martensite laths. Some irregular, blocky, large black particles are present at the interface of δ-ferrite and matrix. There are no precipitates within δ-ferrite grains. After irradiation, a large number of rod-like and blocky precipitates appear at the boundaries and interior of the martensitic lath, while the number and size of precipitates significantly increase compared to that before irradiation. The number of irregular blocky black particles at the interface of δ-ferrite and matrix increase compared to that before irradiation. Inside the δ-ferrite, a large number of blocky and needle-like precipitates are formed which may be Cr-rich nitrides, Cr-rich carbonitrides and Fe-W type precipitates. After irradiation, the precipitates inside the martensitic laths are Cr-rich M₂₃C₆ phase. Compared with the Cr-rich M₂₃C₆ phase before irradiation, the Cr and Ta contents in the M₂₃C₆ phase slightly decrease, while the Fe and Nd contents slightly increase after irradiation. However, overall, the changes in the average metal element composition of the Cr-rich M₂₃C₆ phase are relatively small.

Key words: high-Cr ferritic/martensitic steel, microstructure, precipitated phase, high-temperature irradiation

CLC Number:

TG142.73

Wo Jianxing, Shen Yinzhong. Microstructure of 11%Cr ferritic/martensitic steel in normally heat-treated state before and after irradiation[J]. Heat Treatment of Metals, 2025, 50(1): 6-11.

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