Method for producing an impeller of an exhaust gas turbocharger and tial alloy for an impeller

Abstract

A method for producing an impeller of an exhaust gas turbocharger made of TiAl alloy by centrifugal casting, includes providing a TiAl alloy consisting of titanium, 43.7 at-% to 47.5 at-% aluminum, 1.9 at-% to 8.7 at-% niobium, 0.3 at-% to 0.6 at-% carbon, and at most 2.0 at-% others, heating a casting mold used for the centrifugal casting to a casting temperature of 500° C. to 800° C.; introducing the TiAl alloy into the heated casting mold; accelerating the casting mold about a rotation axis spaced apart from the casting mold with an angular acceleration to a rotational speed within an acceleration time period as soon as the TiAl has reached the casting temperature, wherein a rotary axis of the produced impeller is arranged perpendicular to the rotation axis during the centrifugal casting.

1 .- 10 . (canceled) 
     
     
         11 . A method for producing an impeller of an exhaust gas turbocharger made of a TiAl alloy by centrifugal casting, comprising:
 providing a TiAl alloy consisting of titanium, 43.7 at-% to 47.5 at-% aluminum, 1.9 at-% to 8.7 at-% niobium, 0.3 at-% to 0.6 at-% carbon, and at most 2.0 at-% others;   heating a casting mold used for the centrifugal casting to a temperature of 500° C. to 800° C.;   introducing the TiAl alloy into the heated casting mold;   accelerating the casting mold about a rotation axis spaced apart from the casting mold with an angular acceleration to a rotational speed within an acceleration time period as soon as the TiAl has reached the casting temperature, wherein a rotary axis of the produced impeller is arranged perpendicular to the rotation axis during the centrifugal casting   
     
     
         12 . The method of  claim 11 , wherein the TiAl alloy when being introduced into the casting mold has a casting temperature, which is higher by 40K to 150K relative to a liquidus temperature of the TiAl alloy. 
     
     
         13 . The method of  claim 11 , wherein the angular acceleration is between 1 s −2  to 100 s −2 , 
     
     
         14 . The method of  claim 11 , wherein the angular acceleration is from 1 s −2  to 10 s −2  or 
     
     
         15 . The method of  claim 11 , wherein the angular acceleration is from 10 s −2  to 100 s −2 . 
     
     
         16 . The method of  claim 11 , wherein the acceleration time period is between 0.05 s and 2.0 s, 
     
     
         17 . The method of  claim 11 , wherein the acceleration time period is from 0.5 s to 2.0 s. 
     
     
         18 . The method of  claim 11 , wherein the rotational speed is between 100 rpm and 500 rpm. 
     
     
         19 . The method of  claim 11 , wherein a distance between the casting mold and the rotation axis is between 200 mm and 1500 mm.