The Microstructure Stability of Super304H Steel Aging at 750°C

Abstract:

The microstructure stability and the effect of microstructure evolution on the properties of Super304H steel aged at 750°C for different time were investigated. The results showed that the microstructure of the Super304H steel after aging at 750°C consists of primary matrix and large amount of precipitated phases. The main precipitates were Cu-rich phase, MX phase and M₂₃C₆ carbides in austenitic matrix during aging. The M₂₃C₆ carbides precipitate preferentially at grain boundaries, and then coarsening remarkably with increasing aging time. The MX phase was stable during the whole aging process. The Cu-rich particle is smaller than 10 nm at the initial aging stage, and then coarsen with increasing aging time. The strength and hardness increase obviously at the initial stage due to the interaction of Cu-rich phase, MX phase and M₂₃C₆ carbides precipitation strength, in which Cu-rich phase strengthen action is the dominant. Coarsening M₂₃C₆ carbides weaken the strength during aging.

• Periodical: Materials Science Forum (Volume 898)
• Pages: 730-734
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.898.730
• Online since: June 2017
• Authors: Bao Lan Gu*, Jian Xin Dong, Tong Xu
• Keywords: Cu-Rich Phase, High Temperature Stability, Precipitate Strengthen, Super304H Steel

References

[1] Sawaragi Y, Ogawa K, Kato S, et al. Development of the economical 18-8 stainless steel (SUPER 304H) having high elevated temperature strength for fossil fired boilers, J. The Sumitomo Search. 48-1 (1992) 50.

[2] Zhao Q X, Gu H F, Lu Y S, et al. Advances in Heat Resistant Steels for Power Boilers, J. Power Engineering, 18-1 (1998) 74-83.

[3] M. Igarashi: 18Cr-9Ni-3Cu-Nb-N steel, Springer Berlin Heidelberg, (2004) 260-264.

[4] T. Kan, K. Sawaragi, Y. Yamadera and H. Okada. Materials for advanced power engineering, (Julich, Germany; Forschungszentrum Julich; 1998, Conference; 6th: Liege; Belgium, (1998) 441-450.

[5] Sun Y M, Zhou X P. The comment of Super304H Stainless Steel Boiler Tube, J . Boiler Technology. 38-1 (2007) 52-55.

[6] Lu Y S．Urgency of R&D of new materials-seen from the development of super-critical power generating units. J. Power General Equipment, 3 (2006) 149-151.

[7] Fang X D, Wang H J, Tian X Q, eta1. Development of heat-resistant steel S30432 tube for 1000MW supercritical (ultrasuper critica1) boiler.J. Taigang Sci Technol. 2 (2007) 22-27.

[8] Wang J Z，Luo S Q, Huang X B. Trial production of S30432 tubes for supercritical (ultrasupercritica1) boiler .J. Iron Steel. 41-1 (2006) 43-46.

[9] Gong Z H, Ding W, Wang B F. Influence of precipitates on high temperature mechanical properties of S30432 steel with long-time aging. J. Transactions of Material and Heat Treatment. 36-11 (2015) 83-87.

[10] Zhao Q X, Zhu L H. Research of heat resistant steel for ultra super critical boiler. 1st Ed. Beijing: China Machine Press. (2010) 272.

[11] Jiang J, Zhu L H. Strengthening mechanisms of precipitates in S30432 heat resistant steel during short term aging. J. Materials Science and Engineering A. 539 (2012) 170-176.

DOI: 10.1016/j.msea.2012.01.076

[12] Bai J W, Zhan Q, Chi C Y. Strengthening effect of precipitate phase in Super304H austenitic heat-resistant steel after long-term aging. J. The Chinese Journal of Nonferrous Metals. 24-12(2014) 3042-3050.

[13] OU P, Xing H, Wang X L. Coarsening and Hardening Behaviors of Cu-Rich Precipitates in Super304H Austenitic Steel. J. Metallurgical and Materials Transactions A. 46-9 (2015) 3909-3916.

DOI: 10.1007/s11661-015-3004-3

[14] P. Ou, H. Xing , X.L. Wang. Tensile yield behavior and precipitation strengthening mechanism in Super304H steel. J. MaterialsScience&EngineeringA600. (2014) 171-175.

DOI: 10.1016/j.msea.2014.01.085