Cr-based alloys have potential as heat-resistant materials due to the higher melting point and lower density of Cr. Although oxidation and nitridation at high temperatures are one of the drawbacks of Cr and Cr-based alloys, addition of Si has been reported to enhance the oxidation and nitridation resistance. This study focuses on the microstructure and mechanical properties in the Cr-Si binary alloys with the Cr ss + Cr 3 Si two-phase structure. The Cr-16at.%Si alloy showed an eutectic microstructure and hypoeutectic alloys with the lower Si composition exhibited a combination of the primary Cr ss and the Cr ss /Cr 3 Si eutectic microstructure. Compression tests at elevated temperatures were conducted for the hypoeutectic and the eutectic alloys in vacuum environment. Among the investigated alloys, the Cr-13at.%Si hypoeutectic alloy including the Cr 3 Si phase of about 40% was found to show the highest 0.2% proof stress of 526 MPa at 1000 °C. Its specific strength is 78.1 Nm/g which is roughly twice as high as that of Ni-based Mar-M247 alloy. It was also confirmed that the 0.2% proof stress at 1000 °C depends on not only the volume fraction of the Cr 3 Si phase, but also the morphology of the Cr ss + Cr 3 Si two-phase microstructure.

A new Ni-base superalloy has been developed for Advanced Ultra Super Critical (A-USC) power plants operating above 750°C, targeting reduced CO 2 emissions through improved efficiency. While existing research focuses on 700°C-class materials, this study presents a novel alloy design for higher-temperature applications. Using the CALPHAD method, a prototype alloy (Ni-23Co-18Cr-8W-4Al-0.1C) was developed by eliminating Ti, Nb, and Ta to improve hot-workability while maintaining strength. The resulting alloy demonstrates twice the creep strength of Nimonic 263, with an estimated 10 5 h steam turbine creep resistance temperature of 780°C, marking a significant advancement in A-USC material capabilities.