Oscillating heat treatment method for a superalloy

Abstract

Superalloy solidified in a directional manner often cannot be subjected to heat treatment because the heat treatment leads to recrystallization. As a result of the temperature profile during a heat treatment according to the invention which oscillates in the manner of a pendulum, a recrystallization during heat treatment can be avoided because mechanical stresses are reduced thanks to the recurring succession of dissolutions and precipitations of the precipitate. The method can be applied to a Ni-based superalloy with γ-precipitates. After the cyclic heat treatment, the temperature can be adjusted to and maintained at a temperature which is the same as or higher than the complete dissolution temperature. An oscillating movement can also take place above the complete dissolution temperature.

1 .- 28 . (canceled) 
     
     
         29 . A method for heat treating a material having a precipitate that is dissolvable at least partially in a matrix of the material above a dissolution temperature, comprising:
 at least temporarily heat treating the material above the dissolution temperature via a temperature profile; and   at least temporarily oscillating the temperature profile for the heat treatment.   
     
     
         30 . The method as claimed in  claim 29 , wherein the temperature profile oscillates below the dissolution temperature and continues to increase at least temporarily above the dissolution temperature. 
     
     
         31 . The method as claimed in  claim 29 , wherein the temperature profile oscillates above the dissolution temperature. 
     
     
         32 . The method as claimed in  claim 29 , wherein the temperature profile initially rises to a temperature below the dissolution temperature and further oscillately rises. 
     
     
         33 . The method as claimed in  claim 29 , wherein the temperature profile initially rises at least to the dissolution temperature and further oscillately rises. 
     
     
         34 . The method as claimed in  claim 29 , wherein the temperature profile oscillates initially once or more than once from a temperature above the dissolution temperature to a temperature below the dissolution temperature. 
     
     
         35 . The method as claimed in  claim 29 , wherein the temperature profile oscillates from a temperature above the dissolution temperature to a temperature not below the dissolution temperature. 
     
     
         36 . The method as claimed in  claim 29 , wherein the oscillation is between two local maxima in the temperature profile and the temperature profile comprises at least two oscillations. 
     
     
         37 . The method as claimed in  claim 29 , wherein the temperature profile oscillates for at least one hour. 
     
     
         38 . The method as claimed in  claim 29 , wherein the temperature profile oscillates sinusoidally or triangularly. 
     
     
         39 . The method as claimed in  claim 29 , wherein the precipitate is dissolved completely in the matrix at a full solution annealing temperature. 
     
     
         40 . The method as claimed in  claim 39 , wherein the temperature profile oscillates between:
 the dissolution temperature and the full solution annealing temperature, or   a temperature above the dissolution temperature and the full solution annealing temperature, or   the dissolution temperature and a temperature below the full solution annealing temperature, or   a temperature above the dissolution temperature and a temperature below the full solution annealing temperature, or   a temperature below the dissolution temperature and the full solution annealing temperature.   
     
     
         41 . The method as claimed in  claim 39 , wherein the temperature profile initially rises to a temperature below the dissolution temperature and further oscillately rises to the full solution annealing temperature. 
     
     
         42 . The method as claimed in  claim 39 , wherein the temperature profile reaches the full solution annealing temperature during the oscillation at a specific time and is set constant at the full solution annealing temperature for the specific time. 
     
     
         43 . The method as claimed in  claim 42 , wherein the temperature profile stays at the full solution annealing temperature for at least one hour. 
     
     
         44 . The method as claimed in  claim 39 , wherein the temperature profile is set constant at a temperature above the full solution annealing temperature at a specific time. 
     
     
         45 . The method as claimed in  claim 39 , wherein the temperature profile overshoots the full solution annealing temperature at a specific time. 
     
     
         46 . The method as claimed in  claim 29 , wherein the temperature profile does not overshoot the full solution temperature. 
     
     
         47 . The method as claimed in  claim 29 , wherein a metallic element of the material is depleted before the heat treatment. 
     
     
         48 . The method as claimed in  claim 29 , wherein the precipitate is a γ-phase of a nickel-based superalloy.