Intergranular precipitation evolution and its effect on the impact toughness of Super304H austenitic stainless steel weld metal during long-term aging at 650 °C
The microstructural evolution and its effect on the impact toughness of Super304H austenitic stainless steel weld metal during long-term aging at 650 °C was investigated in detail. The fractography and precipitation evolution in the aged samples were characterized by scanning electron microscope (SE...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2025-05-01
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| Series: | Journal of Materials Research and Technology |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2238785425011330 |
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| Summary: | The microstructural evolution and its effect on the impact toughness of Super304H austenitic stainless steel weld metal during long-term aging at 650 °C was investigated in detail. The fractography and precipitation evolution in the aged samples were characterized by scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS) and transmission electron microscope (TEM). During the aging process, the impact toughness of the weld metal decreased continuously over time, exhibiting a significantly more pronounced tendency towards long-term aging embrittlement compared to the base metal. The main reason for this was the continuous precipitation of M23C6 along the grain boundaries, which formed a network structure distribution. Furthermore, electron backscatter diffraction (EBSD) analysis revealed that the orientation relationship between the M23C6 precipitates along the grain boundaries and the matrix changed from a semi-coherent relationship in the as-welded metal to a non-coherent relationship in the aged metal, which also had an adverse effect on the impact toughness. The precipitation kinetics curve of M23C6 phase in the weld metal during aging was established for investigating the evolution of impact toughness after long-term exposure. Moreover, a novel model between the impact toughness W of weld metal and the M23C6 phase parameter (grain boundary equivalent width, B) was proposed to further reveal the mechanism for the intergranular fracture caused by the increase of the grain boundary equivalent width (i.e., carbide coarsening) and provide guidance for predicting changes in weld metal toughness during long-term aging. |
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| ISSN: | 2238-7854 |