Tensile and creep deformation of a newly developed Ni-Fe-based superalloy for 700 °C advanced ultra-supercritical boiler applications

Abstract

A new Ni-Fe-based superalloy, HT-X, has been developed for applications in 700°C advanced ultra-supercritical (A-USC) boilers. The HT-X alloy is subjected to various heat treatments. Tensile tests are conducted at room temperature (RT), 700°C and 750°C. Creep tests are carried out under conditions of 700°C/300 MPa and 750°C/150 MPa. After aging treatment, the yield strength of the HT-X alloy at RT and 750°C is 787 MPa and 624 MPa, respectively. When additional thermal exposure at 750°C for 5400 h is applied, the yield strength is decreased to 656 MPa at RT and 480 MPa at 700°C. For an aged specimen, the a/2<110> dislocation shearing process occurs when tensile testing is conducted at RT and 750°C. As the γ' precipitate size increases in the specimen that is thermally exposed at 750°C for 5400 h, Orowan bowing is the dominant dislocation process, and stacking faults develop in the γ' precipitates at both RT and 700°C. Dislocation slip combined with climb is the dominant mechanism under the creep testing conditions. The factors that affect the mechanical properties and deformation mechanisms are discussed.

Archives of Metallurgy and Materials

“…However, it has poor oxidation and mechanical properties compared to intermetallic compounds [4][5][6]. As a result, Mo alloys, composed of an Mo phase and Mo-Si intermetallic compounds phases such as MoSi 3 and Mo 5 Si 3 , have been stud-ied with the aim of improving their mechanical properties and oxidation resistance [7][8][9]. However, despite the improvement of the mechanical or oxidation properties of Mo alloys, machining this alloy is difficult because of poor ductility of the alloys at room temperature.…”

Thermal Characteristics of Tube Bundles in Ultra-Supercritical Boilers

“…They concluded that steam temperatures up to 750 • C are Energies 2016, 9, 779 3 of 14 allowable in service. Yuan et al [20] analyzed the tensile and creep deformation for a newly-developed Ni-Fe-based superalloy. They found that the new material can endure 750 • C for 5400 h.…”