Abstract
Novel 12Cr-W-Mo-Co heat resistance steels (HRSs) with excellent mechanical properties have been developed for ultra-supercritical (USC) applications above 923 K (650 °C). The thermal analysis of the present steels indicates that the remelting temperature of secondary phases is increased by Co alloying, resulting in the improvement of microstructural stability. Delta ferrite in these HRSs is completely suppressed as the content of Co is increased up to 5 pct. The room temperature tensile strength (TS), yield strength (YS), and the elongation (EL) of the HRS with 5 pct Co reach 887.9, 652.6 MPa, and 21.07 pct, respectively. At 948 K (675 °C), the TS and YS of the HRS with 5 pct Co attain 360 and 290 MPa, respectively, which are higher than those of T/P122 steel by 27.4 and 22.1 pct, respectively. TEM study of the microstructure confirmed that the strengthening effects for these 12Cr-W-Mo-Co HRSs are attributed to the suppression of delta ferrite, the formation of fine martensitic laths with substructure, dislocation networks and walls, and the precipitation of second nanoscale phases.
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Acknowledgments
This research was supported by the National Natural Science Foundation of China (Nos. 51071018, 51271018), and also in part by the National Nature Science Foundation of China (No. 51010001), 111 project (No. B07003), and Program for ChangJiang Scholars and Innovative Research Team in University.
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Manuscript submitted October 26, 2013.
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Wang, S., Chang, L., Lin, D. et al. High Temperature Strengthening in 12Cr-W-Mo Steels by Controlling the Formation of Delta Ferrite. Metall Mater Trans A 45, 4371–4385 (2014). https://doi.org/10.1007/s11661-014-2411-1
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DOI: https://doi.org/10.1007/s11661-014-2411-1