High-temperature forging, particularly of titanium aluminides

Abstract

The present invention relates to a method for forging a component, in particular a component made of a TiAl material, in which the die for forging is heated to a specified first temperature prior to the forging, and in which a preform of the component to be forged is preheated to a specified second temperature, wherein the first temperature is lower than the second temperature, and first and second temperatures are selected so that during the forging, the surface temperature of the preform does not fall below a minimum forging temperature, and the temperature of the die does not increase above a maximum die temperature.

What is claimed is: 
     
         1 . A method for forging a component, in which the die for forging is heated to a specified first temperature prior to the forging, and in which a preform of the component to be forged is preheated to a specified second temperature prior to the forging, wherein the first temperature is lower than the second temperature, and first and second temperatures are selected so that during the forging, the surface temperature of the preform does not fall below a minimum forging temperature, and the temperature of the die does not exceed a maximum die temperature. 
     
     
         2 . The method according to  claim 1 , wherein the die is heated during the forging so that the surface temperature of the preform does not fall below a minimum forging temperature and the temperature of the die does not exceed a maximum die temperature during the forging. 
     
     
         3 . The method according to  claim 1 , wherein the difference between first and second temperatures is less than or equal to 320° C., in particular less than or equal to 200° C., and preferably less than or equal to 150° C. 
     
     
         4 . The method according to  claim 1 , wherein the minimum forging temperature and the maximum die temperature are the same or differ by less than ±50° C. 
     
     
         5 . The method according to  claim 1 , wherein the preform is preheated in a preheating furnace and is transferred therefrom directly into the die just before the forging. 
     
     
         6 . The method according to  claim 1 , wherein the forging takes place under a protective gas atmosphere. 
     
     
         7 . The method according to  claim 1 , wherein the forged component is formed from a TiAl alloy and/or is a turbine blade or vane. 
     
     
         8 . The method according to  claim 1 , wherein a reshaping rate lies in the range of 1×10 −4  to 0.5 1/s, in particular of 5×10 −3  to 1×10 −1  1/s. 
     
     
         9 . The method according to  claim 1 , wherein a TiAl alloy containing niobium and molybdenum is used containing 42 to 45 at. % aluminum, 3 to 5 at. % niobium, and 0.5 to 1.5 at. % molybdenum. 
     
     
         10 . The method according to  claim 9 , wherein the alloy used contains 0.05 to 0.15 at. % boron. 
     
     
         11 . The method according to  claim 9 , wherein the alloy used, in addition to unavoidable impurities, contains at least one additional constituent from the group that comprises carbon, oxygen, nitrogen, hydrogen, chromium, silicon, iron, copper, nickel and yttrium, wherein the content therein can amount to: ≤0.05 wt. % chromium, ≤0.05 wt. % silicon, ≤0.08 wt. % oxygen, ≤0.02 wt. % carbon, ≤0.015 wt. % nitrogen, ≤0.005 wt. % hydrogen, ≤0.06 wt. % iron, ≤0.15 wt. % copper, ≤0.02 wt. % nickel, and ≤0.001 wt. % yttrium. 
     
     
         12 . The method according to one of  claim 9 , wherein the alloy that is used has a chemical composition that comprises titanium in a quantity such that the alloy containing the remaining constituents comprises 100 at. %. 
     
     
         13 . The method according to  claim 1 , wherein the first temperature lies in the range between 1080° C. and 1220° C. and/or the second temperature lies in the range between 1220° C. and 1400° C. 
     
     
         14 . The method according to  claim 1 , wherein, during the forging, the temperature of the preform or of the component and the temperature of the die are equilibrated to one another so they both lie in the temperature range of the α-γ-β phase region of the TiAl alloy and at a temperature between 1100° C. and 1240° C.