Mechanical Properties and Creep Behavior of MX-Type Precipitates Strengthened Heat Resistant Martensite Steel
Received date: 2021-10-15
Revised date: 2021-11-28
Online published: 2022-03-18
Supported by
National Natural Science Foundation of China(52004224);China Postdoctoral Science Foundation(2020M683559)
There has been a push in the past few decades to increase the operating temperature of steam generators to the ultra-supercritical (USC) regime. This requires that creep-resistant alloys can operate at 650-700°C for 30 years. P91 and P92 steels are commercially applied in USC steam generator applications. However, these steels fail due to the coarsening of M23C6 and Laves phases during long-term service. Therefore, it is significant to restrict the formation of easily coarsened precipitates. In this study, a martensitic heat-resistant steel strengthened by single MX precipitates is designed using the Thermo-Calc software, as Fe-0.03C-10Cr-0.2Zr-0.3V. The yield strength, tensile strength, and elongation at room temperature are 266 MPa, 413 MPa, and 38%, respectively. The high-temperature hardnesses of specimens aged at 700oC for 1, 10, 100, and 1000 h were tested at 700oC after normalizing treatment, which illustrates that the high-temperature hardness of the specimens remains stable with increased aging time. In addition, TEM was used to characterize the precipitates in the heat-resistant steel aged for different times. It is found that with the increase of aging time (1-1000 h), the average size of the precipitates increases from 10.8 to 17.8 nm. The composition of MX precipitates in the specimens aged for 1000 h is Zr0.46Nb0.14C0.4 and the volume fraction is 0.29%. According to the creep test results, the threshold stresses at 650 and 700oC are 54.5 and 28.4 MPa, respectively.
Xiaolin LI , Linxi LIU , Yating LI , Jiawei YANG , Xiangtao DENG , Haifeng WANG . Mechanical Properties and Creep Behavior of MX-Type Precipitates Strengthened Heat Resistant Martensite Steel[J]. Acta Metall Sin, 2022 , 58(9) : 1199 -1207 . DOI: 10.11900/0412.1961.2021.00432
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