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Precipitates evolution during tempering of 9CrMoCoB (CB2) ferritic heat-resistant steel

Journal Article


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.

Publication Date


  • 2019

Citation


  • Jia, C., Liu, Y., Liu, C., Li, C., & Li, H. (2019). Precipitates evolution during tempering of 9CrMoCoB (CB2) ferritic heat-resistant steel. Materials Characterization, 152, 12-20. doi:10.1016/j.matchar.2019.04.006

Scopus Eid


  • 2-s2.0-85063981928

Web Of Science Accession Number


Start Page


  • 12

End Page


  • 20

Volume


  • 152

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.

Publication Date


  • 2019

Citation


  • Jia, C., Liu, Y., Liu, C., Li, C., & Li, H. (2019). Precipitates evolution during tempering of 9CrMoCoB (CB2) ferritic heat-resistant steel. Materials Characterization, 152, 12-20. doi:10.1016/j.matchar.2019.04.006

Scopus Eid


  • 2-s2.0-85063981928

Web Of Science Accession Number


Start Page


  • 12

End Page


  • 20

Volume


  • 152