Alloy Design for γ′ Precipitation Hardening Nickel-base Superalloys Containing Ti, Ta, and W

Abstract

The increase in the inlet gas temperature of a gas turbine is the most effective to raise the output efficiency of the turbine. For this purpose, blade materials having superior creep strength and hot corrosion resistance are required.
In this study, γ′ precipitation hardening nickel-base superalloys being superior in the above two properties have been developed by a computer-aided alloy design. The outline of the computer-aided alloy design is as follows.
At first, compositions of γ and γ′ which are in a state of equilibrium each other, both highly solid solution hardened, and have a small lattice mismatch are selected. Compositions of alloys with optimum amount of γ′ can be calculated by the application of the lever rule to the selected γ and γ′ compositions and the addition of carbides and boride compositions.
The evaluation of the alloy was made by creep rupture tests and a crucible test using a molten Na₂SO₄+25% NaCl Salt mixture.