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

Shu Ming; Zhou Qin; Li Gang; Liu Xiao; Sun Yongduo; Zhao Ke; Xiao Jun

doi:10.13832/j.jnpe.2023.06.0140

Volume 44 Issue 6

Dec. 2023

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Article Navigation > Nuclear Power Engineering > 2023 > 44(6): 140-147

Shu Ming, Zhou Qin, Li Gang, Liu Xiao, Sun Yongduo, Zhao Ke, Xiao Jun. Effect of Al Element on Thermal Aging Behavior of 20Cr25NiNb Heat-Resistant Steel[J]. Nuclear Power Engineering, 2023, 44(6): 140-147. doi: 10.13832/j.jnpe.2023.06.0140

Citation:

Shu Ming, Zhou Qin, Li Gang, Liu Xiao, Sun Yongduo, Zhao Ke, Xiao Jun. Effect of Al Element on Thermal Aging Behavior of 20Cr25NiNb Heat-Resistant Steel[J]. Nuclear Power Engineering, 2023, 44(6): 140-147. doi: 10.13832/j.jnpe.2023.06.0140

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

doi: 10.13832/j.jnpe.2023.06.0140

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

Received Date: 2023-06-20
Rev Recd Date: 2023-07-31

Available Online: 2023-12-11

Publish Date: 2023-12-15

Abstract

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

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References(24)

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