Patent ID: 8906174

Claim:
A heat treatment method of an Ni-base alloy comprising: not more than 0.1 wt % C., more than 16 wt % and not more than 50 wt % Fe, not more than 30 wt % Cr, Ti, Si, at least one of Nb and Al, and the balance being Ni and incidental impurities, the method comprising: subjecting the Ni-base alloy to a first solution heat treatment at a temperature of not lower than solid solution temperature of a η phase (Ni 3 Ti), a γ′ phase (Ni 3 Al), and a γ″ phase (Ni 3 Nb); subjecting the Ni-base alloy, processed by the first solution heat treatment, to a first aging treatment to precipitate the η phase at a temperature of 800° C. to 900° C.; subjecting the Ni-base alloy, processed by the first aging treatment, to a second solution heat treatment, at a temperature which is higher than the solid solution temperatures of the γ′ and γ″ phases, and higher than the solid solution temperature of the γ phase by 10° C., to cause the γ′ phase and the γ″ phase to again dissolve; and subjecting the Ni-base alloy, processed by the second solution heat treatment, to a second aging treatment to precipitate at least one of the γ′ phase and the γ″ phase at a temperature of 600-750° C.