Alloy Design of Ni-Cr-Mo Solid Solution Strengthened Superalloy

Abstract

In order to examine the possibility of developing an intermediate heat-exchanger material for the nuclear steel making which is cheaper than 23% Cr-18% W-Ni alloy developed in the previous study, an alloy design has been conducted with respect to austenitic Ni-Cr-Mo three component system.
Theoretically promising composition range is determined by the following conditions; (1) average electron vacancy number N_V is smaller than Barrows' critical electron vacancy number, (2) lattice parameter is greater than 3.580 Å, (3) N_V is greater than 1.90.
As a result of experimetal examination, it has been shown that 26% Cr-9.5% Mo is the best in the theoreti-cally promising composition range from 1000°C creep rupture strength point of view, and that an addition of about 0.07% carbon increases creep rupture strength at 1000°C. The target creep rupture strength, that is, higher than 1kg/mmmm² at 1000°C-10⁵ hours, however, is not satisfied.
26% Cr-9.5% Mo-Ti-Zr-C-Bal. Ni alloy which has been developed in the present study has almost the same creep rupture strength at 1000°C as that of Inconel 617, and seems to be applicable to various high temperature parts in nuclear power plants, because it contains no cobalt.