Method for producing Ni based alloy and forging die

Abstract

A solution treatment is firstly performed for a non-heat-treated Ni based alloy having a composition equivalent to that of Inconel 718 (registered trademark). Subsequently, a primary aging treatment is applied by holding the Ni based alloy at 610° to 660° C. for 5 to 10 hours. After that, a secondary aging treatment is performed by holding the Ni based alloy at 710° to 760° C. for 5 to 10 hours. There are 700 or more precipitates per μm 2 , in which each precipitate has a longer diameter of not less than 0.5 nm, in a metal microstructure of the Ni based alloy. Some of the precipitates are large precipitates having average diameters of 25 nm to 1 μm. There are 10 or more large precipitates per μm 2 . A forging die can be produced with the Ni based alloy.

1 . A method of producing an Ni based alloy, wherein said Ni based alloy includes not less than 700 precipitates per μm 2  thereof when observed two-dimensionally with a transmission electron microscope having an electron beam transmission thickness normalized to 10 nm, each of said precipitates having a longer diameter of not less than 0.5 nm, said precipitates including a number of large precipitates having an average diameter of between about 25 nm to 1 μm, said average diameter defined as: (longer diameter+shorter diameter)/2, said method for producing said Ni based alloy comprising: 
 applying a solution treatment to a non-heat-treated Ni based alloy containing 50 to 55 wt % Ni, 17 to 21 wt % Cr, 2.8 to 3.3 wt % Mo, 4.75 to 5.5 wt % Ta and Nb in total provided that Ta is not more than 0.1 wt %, 0.65 to 1.15 wt % Ti, 0.2 to 0.8 wt % Al, and Fe and unavoidable impurity as a residue;    performing a primary aging treatment at a fist temperature after said solution treatment; and    performing a secondary aging treatment at a second temperature higher than said first temperature.    
   
   
       2 . The method according to  claim 1 , wherein said non-heat-treated Ni based alloy further contains not more than 0.08 wt % Co, not more than 0.01 wt % B, not more than 0.08 wt % Cu, not more than 0.08 wt % C, not more than 0.35 wt % Si, not more than 0.35 wt % Mn, not more than 0.015 wt % P, and not more than 0.015 wt % S.  
   
   
       3 . The method according to  claim 1 , wherein said first temperature is between 610 to 660° C., and said second temperature is between 710 to 760° C.  
   
   
       4 . The method according to  claim 1 , wherein said precipitates are primarily γ″ phase precipitates.  
   
   
       5 . The method according to  claim 1 , wherein the holding time associated with each of said primary aging treatment and said secondary aging treatment is between 5 to 10 hours.  
   
   
       6 . The method according to  claim 1 , wherein a crystal grain size of base metal in said non-heat-treated Ni based alloy is not less than ASTM No. 8.  
   
   
       7 . The method according to  claim 1 , wherein said Ni based alloy includes between 700 and 1,100 precipitates per μm 2 .  
   
   
       8 . A method of producing a forging die having improved physical properties, comprising: 
 providing a non-heat-treated Ni based alloy containing 50 to 55 wt % Ni, 17 to 21 wt % Cr, 2.8 to 3.3 wt % Mo, 4.75 to 5.5 wt % Ta and Nb in total provided that Ta is not more than 0.1 wt %, 0.65 to 1.15 wt % Ti, 0.2 to 0.8 wt % Al, and Fe and unavoidable impurity as a residue;    forming an unhardened forging die from said non-heat-treated Ni based alloy;    applying a solution treatment to said unhardened forging die;    subjecting said unhardened forging die to a primary aging treatment at a fist temperature after said solution treatment thereof; and    subjecting said unhardened forging die to a secondary aging treatment at a second temperature higher than said first temperature;    wherein the resulting alloy of said treated forging die includes not less than 700 precipitates per μm 2  thereof when observed two-dimensionally with a transmission electron microscope having an electron beam transmission thickness normalized to 10 nm, each of said precipitates having a longer diameter of not less than 0.5 nm, said precipitates including a number of large precipitates having an average diameter of between about 25 nm to 1 μm, said average diameter defined as: (longer diameter+shorter diameter)/2.    
   
   
       9 . The method according to  claim 8 , wherein said non-heat-treated Ni based alloy further contains not more than 0.08 wt % Co, not more than 0.01 wt % B, not more than 0.08 wt % Cu, not more than 0.08 wt % C, not more than 0.35 wt % Si, not more than 0.35 wt % Mn, not more than 0.015 wt % P, and not more than 0.015 wt % S.  
   
   
       10 . The method according to  claim 8 , wherein said first temperature is between 610 to 660° C., and said second temperature is between 710 to 760° C.  
   
   
       11 . The method according to  claim 8 , wherein said precipitates are primarily γ″ phase precipitates.  
   
   
       12 . The method according to  claim 8 , wherein the holding time associated with each of said primary aging treatment and said secondary aging treatment is between 5 to 10 hours.  
   
   
       13 . The method according to  claim 8 , wherein a crystal grain size of base metal in said non-heat-treated Ni based alloy is not less than ASTM No. 8.  
   
   
       14 . The method according to  claim 8 , wherein the alloy of said treated forging die includes between 700 and 1,100 precipitates per μm 2 .  
   
   
       15 . A method of producing an Ni based alloy having improved physical properties, comprising: 
 applying a solution treatment to a non-heat-treated Ni based alloy containing 50 to 55 wt % Ni, 17 to 21 wt % Cr, 2.8 to 3.3 wt % Mo, 4.75 to 5.5 wt % Ta and Nb in total provided that Ta is not more than 0.1 wt %, 0.65 to 1.15 wt % Ti, 0.2 to 0.8 wt % Al, and Fe and unavoidable impurity as a residue;    after said solution treatment, performing a primary aging treatment at a temperature of between 610 to 660° C. for between 5 to 10 hours; and    after said primary aging treatment, performing a secondary aging treatment at a temperature of between 710 to 760° C. for between 5 to 10 hours;    wherein the resulting Ni based alloy includes not less than 700 precipitates per μm 2  thereof when observed two-dimensionally with a transmission electron microscope having an electron beam transmission thickness normalized to 10 nm, each of said precipitates having a longer diameter of not less than 0.5 nm, said precipitates including a number of large precipitates having an average diameter of between about 25 nm to 1 μm, said average diameter defined as: (longer diameter+shorter diameter)/2.    
   
   
       16 . The method according to  claim 15 , wherein said non-heat-treated Ni based alloy further contains not more than 0.08 wt % Co, not more than 0.01 wt % B, not more than 0.08 wt % Cu, not more than 0.08 wt % C, not more than 0.35 wt % Si, not more than 0.35 wt % Mn, not more than 0.015 wt % P, and not more than 0.015 wt % S.  
   
   
       17 . The method according to  claim 15 , wherein said precipitates are primarily γ″ phase precipitates.  
   
   
       18 . The method according to  claim 15 , wherein a crystal grain size of base metal in said non-heat-treated Ni based alloy is not less than ASTM No. 8.  
   
   
       19 . The method according to  claim 15 , wherein said improved Ni based alloy includes between 700 and 1,100 precipitates per μm 2 .