Microstructural optimization by two-step tempering treatment and quantitative analysis of microstructure effect on the toughness at −40 °C in CrNiMoV steel
30CrNiMoV steel is widely used in engineering applications, where, in addition to high strength requirements, the demand for enhanced toughness is increasingly critical for safety. This study proposes a novel two-step tempering process that optimizes the microstructure by shortening tempering time a...
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Elsevier
2025-03-01
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| Series: | Journal of Materials Research and Technology |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2238785425002339 |
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| author | Li Wang Junwei Qin Yuzhi Zhu Kaixuan Chen Yanlin Wang Zidong Wang |
| author_facet | Li Wang Junwei Qin Yuzhi Zhu Kaixuan Chen Yanlin Wang Zidong Wang |
| author_sort | Li Wang |
| collection | DOAJ |
| description | 30CrNiMoV steel is widely used in engineering applications, where, in addition to high strength requirements, the demand for enhanced toughness is increasingly critical for safety. This study proposes a novel two-step tempering process that optimizes the microstructure by shortening tempering time and accelerating cooling, effectively avoiding the strength-ductility trade-off. Specifically, the intrinsic relationship between −40 °C impact resistance and microstructure were quantitatively investigated using CVN impact tests, SEM, EBSD, and TEM characterization. The results showed that the optimal new process increased the ultimate tensile strength (UTS) and yield strength (YS) from 1380 MPa to 1173 MPa – 1445 MPa and 1212 MPa respectively, and increased the −40 °C impact energy from 19.0 to 47.5 J. The ductile-to-brittle transition temperature (DBTT) was reduced from −6.5 °C to −21.5 °C. The excellent low temperature toughness achieved by this novel process could be attributed to the following reasons: Firstly, the QTwTa process optimizes the morphology and size of the carbides, significantly increasing their number density. This improves the coordinated deformation between the carbides and the matrix, reduces stress concentration during fracture, raises the crack initiation threshold σIC, and delayed the initiation of cracks, thereby enhancing fracture toughness. Secondly, the uniform and refined the block lead to a reduction in DBTT. Moreover, the more uniform and finer the block, the higher the proportion of high-angle grain boundaries, which increases the frequency of crack deflection, preventing rapid crack propagation and thereby enhancing energy absorption. In conclusion, the synergistic effect of carbide dimensions, number density of, and high-angle grain boundary and block dimensions are crucial for achieving excellent mechanical properties with the novel two-step tempering process. |
| format | Article |
| id | doaj-art-59a92f0372ed4458a2b75c4f7c92ca0c |
| institution | Kabale University |
| issn | 2238-7854 |
| language | English |
| publishDate | 2025-03-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Journal of Materials Research and Technology |
| spelling | doaj-art-59a92f0372ed4458a2b75c4f7c92ca0c2025-02-04T04:10:27ZengElsevierJournal of Materials Research and Technology2238-78542025-03-013527812790Microstructural optimization by two-step tempering treatment and quantitative analysis of microstructure effect on the toughness at −40 °C in CrNiMoV steelLi Wang0Junwei Qin1Yuzhi Zhu2Kaixuan Chen3Yanlin Wang4Zidong Wang5School of Material Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, PR ChinaSchool of Mechanical Engineering, University of Science and Technology Beijing, Beijing, 100083, PR ChinaSchool of Material Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, PR ChinaSchool of Material Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, PR ChinaSchool of Material Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, PR China; Corresponding author.School of Material Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, PR China; Corresponding author.30CrNiMoV steel is widely used in engineering applications, where, in addition to high strength requirements, the demand for enhanced toughness is increasingly critical for safety. This study proposes a novel two-step tempering process that optimizes the microstructure by shortening tempering time and accelerating cooling, effectively avoiding the strength-ductility trade-off. Specifically, the intrinsic relationship between −40 °C impact resistance and microstructure were quantitatively investigated using CVN impact tests, SEM, EBSD, and TEM characterization. The results showed that the optimal new process increased the ultimate tensile strength (UTS) and yield strength (YS) from 1380 MPa to 1173 MPa – 1445 MPa and 1212 MPa respectively, and increased the −40 °C impact energy from 19.0 to 47.5 J. The ductile-to-brittle transition temperature (DBTT) was reduced from −6.5 °C to −21.5 °C. The excellent low temperature toughness achieved by this novel process could be attributed to the following reasons: Firstly, the QTwTa process optimizes the morphology and size of the carbides, significantly increasing their number density. This improves the coordinated deformation between the carbides and the matrix, reduces stress concentration during fracture, raises the crack initiation threshold σIC, and delayed the initiation of cracks, thereby enhancing fracture toughness. Secondly, the uniform and refined the block lead to a reduction in DBTT. Moreover, the more uniform and finer the block, the higher the proportion of high-angle grain boundaries, which increases the frequency of crack deflection, preventing rapid crack propagation and thereby enhancing energy absorption. In conclusion, the synergistic effect of carbide dimensions, number density of, and high-angle grain boundary and block dimensions are crucial for achieving excellent mechanical properties with the novel two-step tempering process.http://www.sciencedirect.com/science/article/pii/S2238785425002339Low-temperature toughnessHigh-angle grain boundariesCarbidesBlock width |
| spellingShingle | Li Wang Junwei Qin Yuzhi Zhu Kaixuan Chen Yanlin Wang Zidong Wang Microstructural optimization by two-step tempering treatment and quantitative analysis of microstructure effect on the toughness at −40 °C in CrNiMoV steel Journal of Materials Research and Technology Low-temperature toughness High-angle grain boundaries Carbides Block width |
| title | Microstructural optimization by two-step tempering treatment and quantitative analysis of microstructure effect on the toughness at −40 °C in CrNiMoV steel |
| title_full | Microstructural optimization by two-step tempering treatment and quantitative analysis of microstructure effect on the toughness at −40 °C in CrNiMoV steel |
| title_fullStr | Microstructural optimization by two-step tempering treatment and quantitative analysis of microstructure effect on the toughness at −40 °C in CrNiMoV steel |
| title_full_unstemmed | Microstructural optimization by two-step tempering treatment and quantitative analysis of microstructure effect on the toughness at −40 °C in CrNiMoV steel |
| title_short | Microstructural optimization by two-step tempering treatment and quantitative analysis of microstructure effect on the toughness at −40 °C in CrNiMoV steel |
| title_sort | microstructural optimization by two step tempering treatment and quantitative analysis of microstructure effect on the toughness at 40 °c in crnimov steel |
| topic | Low-temperature toughness High-angle grain boundaries Carbides Block width |
| url | http://www.sciencedirect.com/science/article/pii/S2238785425002339 |
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