Ni-base superalloy and manufacturing method thereof

Abstract

According to the present invention, a Ni-base superalloy is comprised 2.0 to 6.0 wt. % of cobalt (Co), 8.0 to 12.0 wt. % of chromium (Cr), 5.0 to 9.0 wt. % of tungsten (W), 3.5 to 6.0 wt. % of aluminum (Al), 3.0 wt. % or less of titanium (Ti), 5.0 to 10.0 wt. % of tantalum (Ta), 0.05 to 0.15 wt. % of carbon (C), 0.02 wt. % or less of boron (B), 0.05 wt. % or less of zirconium (Zr), with the remainder being composed of nickel (Ni) and unavoidable impurities.

What is claimed is: 
     
         1 . A Ni-base superalloy comprising:
 2.0 to 6.0 wt. % of cobalt (Co), 8.0 to 12.0 wt. % of chromium (Cr), 5.0 to 9.0 wt. % of tungsten (W), 3.5 to 6.0 wt. % of aluminum (Al), 3.0 wt. % or less of titanium (Ti), 5.0 to 10.0 wt. % of tantalum (Ta), 0.05 to 0.15 wt. % of carbon (C), 0.02 wt. % or less of boron (B), 0.05 wt. % or less of zirconium (Zr), with the remainder being composed of nickel (Ni) and unavoidable impurities.   
     
     
         2 . A Ni-base superalloy comprising:
 4.0 wt. % of cobalt (Co), 10.0 wt. % of chromium (Cr), 7.0 wt. % of tungsten (W), 5.0 wt. % of aluminum (Al), 1.0 wt. % of titanium (Ti), 7.5 wt. % of tantalum (Ta), 0.07 wt. % of carbon (C), 0.015 wt. % of boron (B), 0.01 wt. % of zirconium (Zr), with the remainder being composed of nickel (Ni) and unavoidable impurities.   
     
     
         3 . The Ni-base superalloy of  claim 1 ,
 wherein the Ni-base superalloy has M 23 C 6 - and M 6 C-type precipitates at a grain boundary, and uniformly distributed γ′ precipitates of 0.3 to 0.4 μm in average size within a γ matrix.   
     
     
         4 . The Ni-base superalloy of  claim 3 ,
 wherein the Ni-base superalloy has a creep life of 600 hours or more under the creep conditions of 871° C./310 MPa.   
     
     
         5 . The Ni-base superalloy of  claim 3 ,
 wherein the Ni-base superalloy has a creep life of 150 hours or more under the creep conditions of 982° C./187 MPa.   
     
     
         6 . The Ni-base superalloy of  claim 3 ,
 wherein the Ni-base superalloy has a change in weight of 10 mg/cm 2  or less when an cyclic oxidation test, in which the Ni-base superalloy is kept at 1100° C. for 1 hour and cooled to room temperature, is repeated 200 times.   
     
     
         7 . A manufacturing method of for preparing a Ni-base superalloy, comprising:
 performing a material preparing step comprising preparing an alloy comprised of 2.0 to 6.0 wt. % of cobalt (Co), 8.0 to 12.0 wt. % of chromium (Cr), 5.0 to 9.0 wt. % of tungsten (W), 3.5 to 6.0 wt. % of aluminum (Al), 3.0 wt. % or less of titanium (Ti), 5.0 to 10.0 wt. % of tantalum (Ta), 0.05 to 0.15 wt. % of carbon (C), 0.02 wt. % or less of boron (B), 0.05 wt. % or less of zirconium (Zr), with the remainder being composed of nickel (Ni) and unavoidable impurities;   performing a casting step comprising manufacturing a casting through a directional solidification process with the alloy;   performing a solution treatment step comprising performing a homogenization heat treatment on the casting at 1280° C. for 4 hours;   performing a first aging step comprising performing an aging heat treatment on the casting at 1080° C. for 4 hours; and   performing a second aging step comprising heat treating the casting at 871° C. for 24 hours to complete the Ni-base superalloy.   
     
     
         8 . The manufacturing method of  claim 7 , wherein the heat treatment steps are carried out in a vacuum or an inert gas atmosphere. 
     
     
         9 . The manufacturing method of  claim 8 , wherein in the first aging step and the second aging step, M 23 C 6 - and M 6 C-type carbides are precipitated at a grain boundary, and a γ matrix has uniformly distributed γ′ precipitates having an average size of 0.3 to 0.4 μm. 
     
     
         10 . The Ni-base superalloy of  claim 2 , wherein the Ni-base superalloy has M 23 C 6 - and M 6 C-type precipitates at a grain boundary, and uniformly distributed γ′ precipitates of 0.3 to 0.4 μam in average size within a γ matrix.