Method of improving the mechanical properties of a component

Abstract

A method ( 40 ) of improving the mechanical properties of a component, for example a gas turbine engine turbine disc, ( 24 ) comprises isothermally forging ( 42 ) a preform to produce a shaped preform with a predetermined shape at a first predetermined temperature, solution heat treating ( 44 ) the shaped preform, quenching ( 46 ) the shaped preform, forging ( 48 ) the shaped preform at a second predetermined temperature to impart a predetermined residual strain in the shaped preform, ageing ( 50 ) the shaped preform and finally machining ( 52 ) the shaped preform to a finished shape. The second predetermined temperature is less than the first predetermined temperature.

1 . A method of improving the mechanical properties of a component comprising the steps of:—
 a) forging a preform to produce a shaped preform with a predetermined shape at a first predetermined temperature, 
 b) solution heat treating the shaped preform, 
 c) quenching the shaped preform, 
 d) ageing the shaped preform, 
 e) machining the shaped preform to a finished shape or a semi-finished shape, and 
 f) forging the shaped preform at a second predetermined temperature to impart a predetermined residual strain in the shaped preform after step c) and before step e), wherein the second predetermined temperature is less than the first predetermined temperature. 
 
     
     
         2 . A method as claimed in  claim 1  wherein step f) is after step c) and before step d). 
     
     
         3 . A method as claimed in  claim 1  wherein step f) is after step d) and before step e). 
     
     
         4 . A method as claimed in  claim 1  wherein step f) is concurrent with step d). 
     
     
         5 . A method as claimed in  claim 1  wherein the second predetermined temperature is between 700° C. and 870° C. 
     
     
         6 . A method as claimed in  claim 1  wherein the second predetermined temperature is between 750° C. and 850° C. 
     
     
         7 . A method as claimed in  claim 1  wherein the second predetermined temperature is between 760° C. and 810° C. 
     
     
         8 . A method as claimed in  claim 1  wherein the forging step f) imparts a predetermined residual tensile strain or a predetermined residual compressive strain. 
     
     
         9 . A method as claimed in  claim 1  wherein the forging step f) imparts a strain of less than 10%. 
     
     
         10 . A method as claimed in  claim 1  wherein the method comprises machining the shaped preform after step a) and before step b). 
     
     
         11 . A method as claimed in  claim 1  wherein step f) comprises isothermally forging. 
     
     
         12 . A method as claimed in  claim 1  wherein step f) comprises forging at a strain rate between 1×10 −4  and 1×10 −2  s −1 . 
     
     
         13 . A method as claimed in  claim 1  wherein step a) comprises isothermally forging. 
     
     
         14 . A method as claimed in  claim 1  wherein in step a) the first predetermined temperature is up to gamma prime solvus minus 25° C. to 50° C. 
     
     
         15 . A method as claimed in  claim 14  wherein step a) comprises forging at a strain rate between 1×10 −4  and 1×10 −2  s −1 . 
     
     
         16 . A method as claimed in  claim 1  wherein in step a) the first predetermined temperature is up to gamma prime solvus minus 55° C. to 110° C. 
     
     
         17 . A method as claimed in  claim 16  wherein step a) comprises forging at a strain rate between 1×10 −2  and 5×10 −1  s −1 . 
     
     
         18 . A method as claimed in  claim 1  wherein step b) comprises a subsolvus solution heat treatment and or a supersolvus heat treatment. 
     
     
         19 . A method as claimed in  claim 18  wherein step b) comprises a subsolvus solution heat treatment at 1120° C. for 4 hours. 
     
     
         20 . A method as claimed in  claim 18  wherein step b) comprises a subsolvus solution heat treatment at 1120° C. for 4 hours, followed by quenching, followed by a supersolvus heat treatment at 1204° C. for 1 hour. 
     
     
         21 . A method as claimed in  claim 18  wherein step b) comprises a supersolvus heat treatment at 1204° C. for 1 hour. 
     
     
         22 . A method as claimed in  claim 1  wherein step d) comprises an ageing heat treatment at 760° C. for 16 hours. 
     
     
         23 . A method as claimed in  claim 1  wherein the component is selected from the group consisting of a compressor disc, a turbine disc, a compressor cone and a turbine cover plate. 
     
     
         24 . A method as claimed in  claim 1  wherein the component is selected from the group consisting of a nickel base superalloy and a titanium base alloy.