Heat resistance improvement of Ni-based alloys
In aircraft and gas turbine power plants, a nickel-based heat-resistant alloy called Alloy 718 is used for the compressor rear-stage discs, blades, and turbine discs. This alloy is strengthened by finely dispersing the γ"-Ni3Nb phase with a D022 structure within the Ni solid-solution. However, the γ" phase is a metastable phase, and when it is held at temperatures above 600°C for prolonged period, it transitions to a coarser stable phase (δ), thus limiting the service temperature. Therefore, our laboratory is conducting research to improve the heat resistance of 718-type Ni-based alloys by enhancing the stability of the γ" phase.
So far, we have found that by partially replacing Nb with Ta and V, the stability of the γ" phase is increased (see Figure 7), and the heat resistance is improved (see Figure 8). Currently, in addition to our fundamental understanding, we are exploring applications in material design.
