Abstract
In order to promote the development of ultra-supercritical technology, the optimum composition design of three new alumina-forming austenitic heat-resistant steels, based on Fe–22Cr–25Ni (wt. %), with low cost and excellent performance, and used for 700 °C ultra-supercritical unit was carried out using Thermo-Calc software. A comparison of the mechanical properties presented that with increasing Al content, the plasticity of the system was further improved. Based on the composition system, a systematic investigation regarding the structure stability, thermodynamic properties, and mechanical properties of these new steels was carried out to reveal possible strengthening and toughening mechanisms by employing the first-principles method. Calculation results showed that when Al existed in the Fe–Cr–Ni alloy system as a solid solution, the new structures were stable, especially under high temperature. The solution of Al and Al + Si could increase the value of B/G, namely improving the plasticity of the system, particularly in case of alloying with Al + Si. The inclusion of Si in the Fe–Cr–Ni–Al system was conducive to further improving the plasticity without affecting the strength, which provided references for the subsequent optimum composition design and performance regulation of alumina-forming austenitic heat-resistant steels.
Highlights
Environmental protection and energy conservation have been regarded as international issues in recent years
Fe–22Cr–25Ni steels system, optimum of three such new alumina-forming heat resistant by the adjusting the composition proportion ofdesign alloy elements alumina-forming austenitic by adjusting the proportion alloy elements such as as Nb, Al, Cu, and
Fe8 Cr4 Ni4, it was clearly seen that the part of Totaldensity density of of states states (TDOS) below the Fermi level was mainly contributed to by
Summary
Environmental protection and energy conservation have been regarded as international issues in recent years. Conventional austenitic heat-resistant steels, such as HR3C, TP310HCbN, SUPER304H, and NF709, are commonly used in 600–650 ◦ C ultra-supercritical (USC) conditions as superheater tubes and reactor pressure vessels with excellent high-temperature creep property and oxidation stability [3,4,5,6,7]. These steels face challenges in water–steam environments when the service temperature is higher than 650 ◦ C, including the sharply deteriorated oxidation resistance caused by the formation. The results could provide suggestions for the rational design of high-performance stainless steel to be used in advanced ultra-supercritical boilers
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