单一 MX型析出相强化马氏体耐热钢力学性能及蠕变行为

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 700^oC for 1, 10, 100, and 1000 h were tested at 700^oC 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 Zr_0.46Nb_0.14C_0.4 and the volume fraction is 0.29%. According to the creep test results, the threshold stresses at 650 and 700^oC are 54.5 and 28.4 MPa, respectively.