Cobalt-Free Ni-Base Superalloy

Abstract

There is provided a Co-free Ni-base superalloy having a composition containing 1.0 to 10.0 wt % of Cr, 0.1 to 3.5 wt % of Mo, 7.5 to 10.0 wt % of W, 4.0 to 8.0 wt % of Al, 12.0 wt % or less of at least one species of Ta, Nb and Ti, 0 to 2.0 wt % of Hf, 0.1 to 5.0 wt % of Re and the remainder comprised of Ni and unavoidable impurities. The Co-free Ni-base superalloy exhibits high composition stability over a long period of time and is excellent in creep properties at high temperature, and also suitable as a turbine blade or turbine vane of atomic power generation in which maintenance for radioactive contamination and so forth are easy.

1 - 6 . (canceled) 
   
   
       7 . An Ni-base superalloy, having a composition containing 1.0 to 10.0 wt % of Cr, 0.1 to 3.5 wt % of Mo, 7.5 to 10.0 wt % of W, 4.0 to 8.0 wt % of Al, 12.0 wt % or less of at least one species of Ta and Nb, 0 to 2.0 wt % of Hf. 0.1 to 5.0 wt % of Re and the remainder comprised of Ni and unavoidable impurities. 
   
   
       8 . The Ni-base superalloy of  claim 7 , having a composition containing 4.0 to 6.0 wt % of Cr, 1.0 to 3.0 wt % of Mo, 7.6 to 8.5 wt % of W, 4.5 to 6.0 wt % of Al, 4.0 to 10.0 wt % or less of at least one species of Ta and Nb, 0.1 to 1.6 wt % of Hf. 1.5 to 3.5 wt % of Re and the remainder comprised of Ni and unavoidable impurities. 
   
   
       9 . The Ni-base superalloy of  claim 7 , wherein the composition further contains at least one species of 0.3 wt % or less of Si and 0.5 wt % or less of Ti. 
   
   
       10 . A method of manufacturing a Ni-base superalloy, wherein any of the Ni-base superalloys of  claim 7  is cast by a normal casting method, a one-direction solidifying method or a single crystal solidifying method. 
   
   
       11 . The method of manufacturing an Ni-base superalloy of  claim 10 , comprising:
 performing a preliminary heat treatment at 1260 to 1300° C. for 20 minutes to 2 hours after casting; and   performing a solution treatment at 1300 to 1350° C. for 3 to 10 hours, a first aging treatment at 1050 to 1150° C. for 2 to 8 hours and a second aging treatment at 800 to 900° C. for 10 to 24 hours.   
   
   
       12 . A turbine blade or turbine vane part, wherein any Ni-base superalloy of  claim 7  is at least a part of its structure.