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Journal of Materials Engineering and Performance

, Volume 27, Issue 9, pp 4392–4404 | Cite as

Investigation on Microstructural Evolutions and Mechanical Properties of P92 Steel During Thermal Processing

  • Jichao Wang
  • Pulin Nie
  • Shangfei Qiao
  • O. A. Ojo
  • Chengwu Yao
  • Zhuguo Li
  • Jian Huang
Article

Abstract

The evolution of the microstructure of P92 steel during heat processing has a significant effect on the final performance of steel products and is thus an area of critical interest. Accordingly, the grain growth behavior of austenite and δ-ferrite changes in P92 steel is comprehensively investigated in this study through thermodynamic calculations and physical simulation. The results show that the AC1, AC3 and γδ transformation temperatures of P92 steel are 841 °C, 878 °C and 1095 °C, respectively, which are comparable to the measured values of 850 °C, 879 °C and 1175 °C, respectively. When the temperature exceeds the AC1 temperature, the austenite grain size increases with increasing temperature and longer holding times, and the growth rate of austenite grains increases with higher temperatures but decreases with holding time at a certain temperature. A model that shows the austenite grain growth kinetics is established: Dn − D 0 n  =  2.03 × 1016exp(− 498,770/RT)t, in which the time exponent n decreases from 4.52 to 2.11 with an increase in temperature from 1000 °C to 1200 °C due to the reduced pinning effect resultant of the dissolution of precipitates, M23C6, VX and NbX at 887 °C, 1073 °C and 1200 °C, respectively. The formation of δ-ferrite at 1200 °C when held for 600 s and 1300 °C when held for 60 ~ 600 s causes a smaller austenite grain size. The relationship between the evolution of the microstructure of P92 steel and the mechanical properties is also studied. The results show that the prior austenite grain size has an inverse relationship with impact energy and ultimate tensile strength at 620 °C, while the presence of soft δ-ferrite leads to a reduction in the microhardness, impact energy and ultimate tensile strength at 620 °C.

Keywords

δ-ferrite austenite grain growth mechanical properties P92 steel physical simulation thermodynamic calculations 

Notes

Acknowledgments

Financial support provided by the National Natural Science Foundation of China [Grant No. 51775338] is acknowledged. We would also like to acknowledge the valuable advice and support for the thermodynamic calculations and physical simulation in this study by Dr. Feng Sun and Mr. Yihua Chen.

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Copyright information

© ASM International 2018

Authors and Affiliations

  • Jichao Wang
    • 1
  • Pulin Nie
    • 1
  • Shangfei Qiao
    • 2
  • O. A. Ojo
    • 3
  • Chengwu Yao
    • 1
  • Zhuguo Li
    • 1
  • Jian Huang
    • 1
  1. 1.Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghaiPeople’s Republic of China
  2. 2.Shanghai Turbine PlantShanghai Electric Power Generation Equipment Co. Ltd.ShanghaiPeople’s Republic of China
  3. 3.Department of Mechanical and Manufacturing EngineeringUniversity of ManitobaWinnipegCanada

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