Al元素对20Cr25NiNb耐热钢热老化行为的影响研究

舒茗; 周钦; 李刚; 刘肖; 孙永铎; 赵可; 肖军

doi:10.13832/j.jnpe.2023.06.0140

Al元素对20Cr25NiNb耐热钢热老化行为的影响研究

doi: 10.13832/j.jnpe.2023.06.0140

舒茗^{1, 2,},
周钦²,
李刚¹,
刘肖¹,
孙永铎¹,
赵可¹,
肖军¹

1.
中国核动力研究设计院，成都，610213
2.
清华大学核能与新能源技术研究院，北京，100084

基金项目: 四川省自然科学基金（2022NSFSC1191）；中国核动力研究设计院原创基金（YF9722003）

详细信息

作者简介:
舒　茗（1990—），男，助理研究员，现主要从事先进反应堆结构材料研究，E-mail：shum09@163.com

中图分类号: TG14；TL424
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- 文章访问数: 163
- HTML全文浏览量: 110
- PDF下载量: 37
- 被引次数: 0
出版历程
- 收稿日期: 2023-06-20
- 修回日期: 2023-07-31
- 网络出版日期: 2023-12-11
- 刊出日期: 2023-12-15

Effect of Al Element on Thermal Aging Behavior of 20Cr25NiNb Heat-Resistant Steel

Shu Ming^{1, 2
,},
Zhou Qin²,
Li Gang¹,
Liu Xiao¹,
Sun Yongduo¹,
Zhao Ke¹,
Xiao Jun¹

1.
Nuclear Power Institute of China, Chengdu, 610213, China
2.
Institute of Nuclear and New EnergyTechnology, Tsinghua University, Beijing, 100084, China

摘要

摘要: 为深入研究超临界气冷堆包壳材料的高温热老化行为以及Al元素对力学性能退化的影响，本文对添加Al元素和不含Al元素的2种20Cr25NiNb奥氏体耐热钢进行了750℃热老化试验，并开展了相应的微观组织分析和力学性能测试。研究发现，固溶态合金基体为奥氏体相，并含有少量微米级NbC。热老化后合金基体中析出了Laves相和σ相，而含Al钢中还观察到了NiAl相的析出。Al元素对20Cr25NiNb的热老化行为产生了双重影响，一方面，Al元素具有固溶强化效果，同时使得热老化后析出的Laves相尺寸更小、数密度更高，从而提升了高温拉伸强度；另一方面，蠕变裂纹主要沿晶界萌生并扩展，热老化后含Al合金中σ相体积分数更高，粗化更严重，严重降低了蠕变断裂寿命。不含Al合金晶界处析出的细小Laves相能有效阻止σ相生长，提升材料的蠕变性能。因此，本研究为超临界气冷堆包壳材料的成分优化提供了有力的支持。
- 20Cr25NiNb /
- 热老化 /
- 高温强度 /
- 蠕变 /
- Al元素
Abstract: In order to comprehensively investigate the high-temperature thermal aging behavior of supercritical gas-cooled reactor (SCGCR) cladding materials and the impact of Al element on the degradation of material mechanical properties, the thermal aging experiments at 750℃ were conducted on two types of 20Cr25NiNb austenitic heat-resistant steels: the alloy doped with Al and the Al-free one. Subsequently, corresponding microstructure analysis and mechanical property tests were carried out. The results revealed that the as-solutionized steels consisted of austenite along with a minor amount of micro-sized NbC carbides. After thermal aging, the matrix exhibited the precipitation of Laves and σ phases, while the alloy containing Al additionally showed the emergence of NiAl precipitates. The presence of Al element induced dual effects on the thermal aging behavior of 20Cr25NiNb. On one hand, Al element exhibited a solid solution strengthening effect and led to a reduction in size and an increase in number density of Laves particles after thermal aging, thereby enhancing high-temperature tensile strength. On the other hand, creep cracks predominantly initiated and propagated along grain boundaries. After thermal aging, the volume fraction of σ phase in Al steel was higher and the coarsening was more serious, consequently resulting in a notable reduction in creep fracture life. The fine Laves phase precipitated at grain boundaries in the Al-free alloy effectively suppressed the growth of σ phase, thus enhancing creep resistance. As a conclusion, this study offers robust support for the optimization of cladding material composition for SCGCR applications.
- 20Cr25NiNb /
- Thermal aging /
- High temperature strength /
- Creep /
- Al element

HTML全文

图 1 固溶态2025WMo的基体组织和析出相

Figure 1. Matrix and Precipitates of As-solutionized 2025WMo　　　　　　

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图 2 固溶态和热老化态合金XRD图像

Figure 2. XRD Pattern of Solid Solution and Aged Alloys

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图 3 750℃下1000 h热老化后微观组织形貌

Figure 3. Microstructure after Thermal Aging at 750℃ for 1000 h　　　　　　

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图 4 热老化后改进型20Cr25NiNb不锈钢主要析出相能谱分析结果

Figure 4. Energy Dispersive Spectroscopy Analysis of Precipitated Phases for Advanced 20Cr25NiNb Stainless Steels after Thermal Aging

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图 5 750℃、3000 h热老化后微观组织形貌

Figure 5. Microstructure after Thermal Aging at 750℃ for 3000 h　　　　　　

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图 6 750℃、3000 h热老化后2025AFA基体中析出相伴生（BSE）

Figure 6. Accompanying Precipitation Behavior in Matrix of 2025AFA after Thermal Aging at 750℃ for 3000 h (BSE)

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图 7 750℃下合金工程应力-工程应变曲线图

Figure 7. Engineering Stress vs. Engineering Strain Curves of Alloys Tested at 750℃

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图 8 不同状态下2025WMo和2025AFA材料强度对照

Figure 8. Comparison of Strength for 2025WMo and 2025AFA Alloys under Different Heat Treatment State

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图 9 750℃蠕变应变-试验时间曲线图

Figure 9. Creep Strain versus Test Time Curves of Tested Alloys at 750℃

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图 10 2025AFA试样蠕变后微观组织图像

Figure 10. Microstructure of 2025AFA Sample after Creep　　　　　　　

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图 11 750℃、3000 h热老化后2025WMo析出相分布

Figure 11. Precipitates Distribution of 2025WMo after Thermal Aging at 750℃ for 3000 h

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图 12 750℃下试验合金热力学稳定相

Figure 12. Thermodynamically Stable Phases of Alloys Tested at 750℃

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表 1 试验用合金化学成分

Table 1. Chemical Composition of Alloys for Test

编号	元素质量分数/%
编号	Ni	Cr	Nb	Si	Mn	W	Mo	C	Al	Fe	其他
2025WMo	23.50	20.0	0.76	0.5	0.7	2	1.0	0.047		余量
2025AFA	23.44	19.4	0.83	0.2	0.6	2	1.1	0.057	2.5	余量	B＜0.0025

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表 2 热老化后合金Laves相和σ相尺寸和体积分数

Table 2. Size and Volume Fraction of Laves and σ Phases of the Tested Alloys after Thermal Aging

样品		2025WMo		2025AFA
热老化时间/h		1000	3000	1000	3000
Laves相	平均尺寸d/μm	0.2823	0.4107	0.2315	0.2480
Laves相	f /%	1.03	1.82	1.28	1.34
σ相	平均尺寸d /μm	1.2779	1.2536	1.2251	1.4899
σ相	f /%	1.52	2.92	9.65	17.04

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