Method for producing a part made from a superalloy based on nickel and corresponding part

Abstract

A method for manufacturing a blank part in Ni-base superalloy, wherein an alloy is prepared and heat treatments are conducted characterized in that: the said superalloy contains at least a total of 2.5% of Nb and Ta; heat treatment is conducted comprising a plurality of steps: a first step at between 850 and 1000° C. held for at least 20 minutes to precipitate the δ phase at the grain boundaries; a second step held at a temperature higher than the temperature of the first step allowing partial dissolution of the δ phase obtained at the first step; ageing treatment comprising a third step and optionally one or more additional steps at a temperature below the temperature of the first step and allowing precipitation of the hardening phases γ′ and γ″. Part thus obtained.

1 . A method for manufacturing a blank of a part in Ni-base superalloy comprising at least 50 Ni in weight percent, comprising:
 preparing an alloy of said superalloy, and   conducting heat treatments of said alloy, wherein:
 said superalloy in weight percentage comprises at least a total of 2.5% Nb and Ta; 
 heat treatment is applied to said alloy, comprising a plurality of steps distributed as follows:
 in a first step, during said alloy is held at between 850 and 1000° C. for at least 20 minutes, precipitating a δ phase at grain boundaries; 
 in a second step, during said alloy is held at a temperature higher than the temperature of the first step, allowing partial dissolution of the δ phase obtained at the first step, and after the second step to obtain a δ phase quantity of between 2 and 4%, the first and second step being conducted without intermediate cooling; and 
 in ageing treatment comprising a third step and optionally one or more additional steps conducted at a temperature lower than that of the first step, allowing precipitation of γ′ and/or γ″ hardening phases; 
 
 the first step being conducted between 900 and 1000° C. for at least 30 min, and the second step at between 940 and 1020° C. for 5 to 90 min, the difference in temperature between the two steps being at least 20° C. 
   
     
     
         2 . The method according to  claim 1 , wherein an Al content of the alloy is equal to or less than 3%. 
     
     
         3 . The method according to  claim 1 , wherein a ratio (Nb+Ta+Ti)/Al of the alloy is equal to or more than 3. 
     
     
         4 . The method according to  claim 1 , wherein a grain size obtained at the end of the alloy treatment is between 7 and 13 ASTM. 
     
     
         5 . The method according to  claim 1 , wherein distribution of the δ phase is homogeneous at the grain boundaries after the ageing treatment. 
     
     
         6 . The method according to  claim 1 , wherein after the second step a δ phase quantity is obtained of between 2.5 and 3.5%. 
     
     
         7 . (canceled) 
     
     
         8 . The process according to  claim 1 , wherein a changeover from the first step to the second step is performed at a rate of 4° C./min or less. 
     
     
         9 . (canceled) 
     
     
         10 . The process according to  claim 1 , wherein the alloy comprises by weight:
 between 50 and 55% nickel,   between 17 and 21% chromium,   less than 0.08% carbon,   less than 0.35% manganese,   less than 0.35% silicon,   less than 1% cobalt   between 2.8 and 3.3% molybdenum,   at least one of the elements niobium or tantalum, such that the sum of niobium and tantalum totals between 4.75 and 5.5% with Ta less than 0.2%,   between 0.65 and 1.15% titanium,   between 0.20 and 0.80% aluminium,   less than 0.006% boron,   less than 0.015% phosphorus,   the residual percentage being iron and impurities resulting from processing.   
     
     
         11 . The method according to  claim 10  wherein the first step is conducted at between 920 and 990° C. for at least 30 min and the second step is conducted at a temperature of between 960 and 1010° C. for 5 to 45 min. 
     
     
         12 . The method according to  claim 11 , wherein the total content of Nb and Ta of the alloy is between 5.2 and 5.5%, in that the first step is conducted at between 960 and 990° C. for 45 min to 2 h, and in that the second step is conducted at between 990 and 1010° C. for 5 to 45 min. 
     
     
         13 . The method according to  claim 11 , wherein a total content of Nb and Ta of the alloy is between 4.8 and 5.2%, in that the first step is conducted at between 920 and 960° C. for 45 min to 2 h, and in that the second step is conducted at between 960 and 990° C. for 5 to 45 min. 
     
     
         14 . The method according to  claim 1 , wherein the alloy comprises a weight content of:
 between 55 and 61% nickel,   between 19 and 22.5% chromium,   between 7 and 9.5% molybdenum,   at least one of the elements niobium or tantalum, such that the sum of niobium and tantalum is between 2.75 and 4% with Ta less than 0.2%,   between 1 and 1.7% titanium,   less than 0.55% aluminium,   less than 0.5% cobalt,   less than 0.03% carbon,   less than 0.35% manganese,   less than 0.2% silicon,   less than 0.006% boron,   less than 0.015% phosphorus,   less than 0.01% sulphur,   the residual percentage being iron and impurities resulting from processing.   
     
     
         15 . The method according to  claim 1 , wherein the alloy comprises by weight:
 between 12 and 20% chromium,   between 2 and 4% molybdenum,   at least one of the elements niobium or tantalum, such that the sum of niobium or tantalum is between 5 and 7% with Ta less than 0.2%,   between 1 and 2% tungsten,   between 5 and 10% cobalt,   between 0.4 and 1.4% titanium,   between 0.6 and 2.6% aluminium,   between 6 and 14% iron,   less than 0.1% carbon,   less than 0.015% boron,   less than 0.03% phosphorus   the residual percentage being nickel and impurities resulting from processing.   
     
     
         16 . The method according to  claim 1 , wherein the alloy has a weight percent content of phosphorus of more than 0.007%. 
     
     
         17 . The method according to  claim 1 , wherein the first step and the second step are conducted at sub-solvus temperatures of the δ phase of the alloy, the first step being conducted at a temperature between 50° C. below the δ solvus temperature and 20° C. below the δ solvus temperature, and the second step being conducted at a temperature between 20° C. below the δ solvus temperature and the δ solvus temperature. 
     
     
         18 . The method according to  claim 1 , wherein a temperature of the hot-worked blank part is held constant during at least one of the said steps. 
     
     
         19 . The method according to  claim 1 , wherein the said third step is conducted at between 700 and 750° C. for 4 to 16 h and in that a fourth step is conducted at between 600 and 650° C. for between 4 and 16 h, cooling at 50° C./h to +/−10° C./h being carried out between the said third and fourth steps. 
     
     
         20 . The method according to  claim 1 , wherein between the first and second steps, the hot-worked alloy is held at least at one intermediate temperature between the temperatures of the first and second steps for no more than 1 h. 
     
     
         21 . The method according to  claim 1 , wherein said blank part was prepared in ingot form and then hot-worked. 
     
     
         22 . The method according to  claim 1 , wherein said blank part was prepared using a powder metallurgy method. 
     
     
         23 . A part in nickel-base superalloy wherein it is obtained from a blank part manufactured using the method according to  claim 1 . 
     
     
         24 . The part according to  claim 23 , wherein it is an aeronautic or land-based gas turbine part.