FORGED TiAl COMPONENTS, AND METHOD FOR PRODUCING SAME

Abstract

The present invention relates to a method for producing forged components of a TiAl alloy, in particular turbine blades, wherein the components are forged and undergo a two-stage heat treatment after the forging process, the first stage of the heat treatment comprising a recrystallization annealing process for 50 to 100 minutes at a temperature below the γ/α transition temperature, and the second stage of the heat treatment comprising a stabilization annealing process in the temperature range of from 800° C. to 950° C. for 5 to 7 hrs, and the cooling rate during the first heat treatment stage being greater than or equal to 3° C./sec, in the temperature range between 1300° C. to 900° C.

1 .- 7 . (canceled) 
     
     
         8 . A method for producing a forged component of a TiAl alloy, wherein the method comprises forging the component and thereafter subjecting it to a two-stage heat treatment, and wherein (i) a first stage of the heat treatment comprises recrystallization annealing for 50 to 100 minutes at a temperature below a γ/α transition temperature, (ii) a second stage of the heat treatment comprises stabilization annealing in a temperature range of from 800° C. to 950° C. for 5 to 7 h, and (iii) a cooling rate during the first stage of the heat treatment is greater than or equal to 3° C./s in a temperature range of from 1300° C. to 900° C. 
     
     
         9 . The method of  claim 8 , wherein the component is a turbine blade. 
     
     
         10 . The method of  claim 8 , wherein recrystallization annealing is carried out for 60 to 90 minutes. 
     
     
         11 . The method of  claim 8 , wherein recrystallization annealing is carried out for 70 to 80 minutes. 
     
     
         12 . The method of  claim 8 , wherein stabilization annealing is carried out in a temperature range of from 825° C. to 925° C. 
     
     
         13 . The method of  claim 8 , wherein stabilization annealing is carried out in a temperature range of from 850° C. to 900° C. 
     
     
         14 . The method of  claim 8 , wherein stabilization annealing is carried out for 345 to 375 minutes. 
     
     
         15 . The method of  claim 8 , wherein a temperature during the heat treatment is set and held with an accuracy of a 5° C. to 10° C. upward or downward deviation from a desired temperature. 
     
     
         16 . The method of  claim 8 , wherein the TiAl alloy further comprises niobium and molybdenum. 
     
     
         17 . The method of  claim 16 , wherein the TiAl alloy comprises from 42 to 45 atom % of aluminum, from 3 to 5 atom % of niobium and from 0.5 to 1.5 atom % of molybdenum. 
     
     
         18 . The method of  claim 16 , wherein the TiAl alloy comprises from 42.8 to 44.2 atom % of aluminum, from 3.7 to 4.3 atom % of niobium and from 0.8 to 1.2 atom % of molybdenum. 
     
     
         19 . The method of  claim 8 , wherein the TiAl alloy further comprises from 0.05 to 0.15 atom % of boron. 
     
     
         20 . The method of  claim 18 , wherein the TiAl alloy further comprises from 0.07 to 0.13 atom % of boron. 
     
     
         21 . The method of  claim 8 , wherein the component is produced by drop forging in an α-γ-β temperature range. 
     
     
         22 . The method of  claim 8 , wherein cast or hot-isostatically pressed blanks are used as the starting materials for forging the component. 
     
     
         23 . A method for producing a forged component of a TiAl alloy, wherein the method comprises forging the component and thereafter subjecting it to a two-stage heat treatment, and wherein (i) a first stage of the heat treatment comprises recrystallization annealing for 70 to 80 minutes at a temperature below a γ/α transition temperature, (ii) a second stage of the heat treatment comprises stabilization annealing in a temperature range of from 850° C. to 900° C. for 345 to 375 minutes, and (iii) a cooling rate during the first stage of the heat treatment is greater than or equal to 3° C./s in a temperature range of from 1300° C. to 900° C., a temperature during the heat treatment being set and held with an accuracy of a 5° C. to 10° C. upward or downward deviation from a desired temperature. 
     
     
         24 . The method of  claim 23 , wherein the TiAl alloy comprises from 42.8 to 44.2 atom % of aluminum, from 3.7 to 4.3 atom % of niobium and from 0.8 to 1.2 atom % of molybdenum. 
     
     
         25 . The method of  claim 24 , wherein the TiAl alloy further comprises from 0.07 to 0.13 atom % of boron. 
     
     
         26 . The method of  claim 25 , wherein the component is produced by drop forging in an α-γ-β temperature range. 
     
     
         27 . A forged component of a TiAl alloy, wherein the component is obtainable by the method of  claim 8 .