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Precipitates evolution during tempering of 9CrMoCoB (CB2) ferritic heat-resistant steel.
- Source :
-
Materials Characterization . Jun2019, Vol. 152, p12-20. 9p. - Publication Year :
- 2019
-
Abstract
- In this paper, the evolution of precipitate phases in 9CrMoCoB (CB2) steel after tempering at 650 °C for different times has been investigated using transmission electron microscopy. As the tempering time prolonged from 0 to 100 h, four types of secondary phases consisting of M 3 C, M 2 X, M 7 C 3 and M 23 C 6 were identified in the experimental steel. It was found that the needle-like M 3 C carbides could be precipitated during both the air cooling process after austenization and the early stage of tempering. After tempering for 15 to 120 min, fine M 2 X particles were observed. The precipitation and growth of M 2 X were derived from the partially consumption of M 3 C carbides. After tempering for 50 h, M 2 X disappeared, while the rod-like M 7 C 3 carbides were observed to be precipitated independent of the early formed M 3 C precipitates. After tempering for 100 h, only M 23 C 6 carbides persisted, of which the number density and size kept increasing throughout 30 min to 100 h owing to their high thermostability. In addition, the precipitation mechanisms of the four types of precipitates were explained, and the relationship between the measured hardness values and microstructure was discussed. • Precipitates evolution in 9CrMoCoB (CB2) steel during tempering has been investigated. • M 3 C precipitated during both the air cooling process after austenization and the early stage of tempering. • The precipitation sequence can be given as follows: M 3 C → M 2 X → M 7 C 3 → M 23 C 6. • Hardness reduction rate of specimens decreased with the tempering time increasing. [ABSTRACT FROM AUTHOR]
- Subjects :
- *FERRITIC steel
*HEAT resistant alloys
*TRANSMISSION electron microscopy
Subjects
Details
- Language :
- English
- ISSN :
- 10445803
- Volume :
- 152
- Database :
- Academic Search Index
- Journal :
- Materials Characterization
- Publication Type :
- Academic Journal
- Accession number :
- 136464675
- Full Text :
- https://doi.org/10.1016/j.matchar.2019.04.006