Evolution of carbides and Charpy toughness in a low alloy bainitic steel during step-up aging process

IF 6.6 2区材料科学 Q1 MATERIALS SCIENCE, MULTIDISCIPLINARY

npj Materials Degradation Pub Date : 2024-10-21 DOI:10.1038/s41529-024-00527-w

Long Jin, Kun Zhang, Ming-Liang Zhu, Fu-Zhen Xuan

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Abstract

The low alloy bainitic steel used in reactor pressure vessels deteriorates during thermal service while the macroscopic thermodynamic parameters that cause thermal aging remains unknown. In this work, a thermal aging restructuring scheme was proposed by step-up aging the steel from 350 °C to 490 °C, with a total duration of 7500 hours. Samples from varied thickness of the steel were characterized in terms of carbides evolution and Charpy impact toughness at 20 °C. The carbide size and its fraction were statistically analyzed showing partial coarsening and dissolution during aging, while the carbide fraction was found linearly correlated with the impact energy for the first time. The critical transition temperature parameter of the aging process was found to be 470 °C for the steel. The macroscopic thermodynamic parameters, including the thermal aging time and temperature, facilitate a comprehensive understanding of the material degradation mechanism and provide a basis for long-term safety of equipment.

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低合金贝氏体钢在阶跃时效过程中的碳化物演变和夏比韧性

反应堆压力容器中使用的低合金贝氏体钢在热使用过程中会发生劣化，而导致热老化的宏观热力学参数仍然未知。在这项工作中，提出了一种热老化重组方案，将钢材从 350 °C 逐步老化到 490 °C，总持续时间为 7500 小时。对不同厚度的钢材样品进行了碳化物演变和 20 °C 时夏比冲击韧性的表征。对碳化物尺寸及其组分进行了统计分析，结果表明碳化物在时效过程中发生了部分粗化和溶解，同时首次发现碳化物组分与冲击能量呈线性相关。发现该钢的时效过程临界转变温度参数为 470 ℃。包括热老化时间和温度在内的宏观热力学参数有助于全面了解材料的降解机理，为设备的长期安全提供依据。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

npj Materials Degradation MATERIALS SCIENCE, MULTIDISCIPLINARY-

CiteScore

7.80

自引率

7.80%

发文量

审稿时长

6 weeks

期刊介绍： npj Materials Degradation considers basic and applied research that explores all aspects of the degradation of metallic and non-metallic materials. The journal broadly defines ‘materials degradation’ as a reduction in the ability of a material to perform its task in-service as a result of environmental exposure. The journal covers a broad range of topics including but not limited to: -Degradation of metals, glasses, minerals, polymers, ceramics, cements and composites in natural and engineered environments, as a result of various stimuli -Computational and experimental studies of degradation mechanisms and kinetics -Characterization of degradation by traditional and emerging techniques -New approaches and technologies for enhancing resistance to degradation -Inspection and monitoring techniques for materials in-service, such as sensing technologies