Titanium-Aluminide Turbine Wheel and Shaft Assembly

Abstract

A titanium-aluminide turbine wheel ( 120, 220, 320, 420 ) is joined to the end of a shaft ( 110, 210, 310, 410 ) by utilizing a titanium surface on the end of the shaft to be joined to the wheel, and electron-beam welding the wheel onto the titanium surface on the shaft. A steel shaft ( 110, 310, 410 ) can have a titanium-containing end piece (130, 330, 430) mechanically joined (by brazing, bonding, or welding) to the end of the shaft, and the end piece can be directly electron-beam welded to the wheel. Alternatively, the shaft ( 210 ) can be formed as a titanium member and the end ( 212 ) of the shaft can be directly electron-beam welded to the wheel ( 220 ). In another embodiment, a ferrous end piece ( 330 ) is mechanically joined to the titanium-aluminide turbine wheel ( 320 ) and then the end piece is directly electron-beam welded to the end of a steel shaft ( 310 ). Alternatively, a silver-titanium alloy member ( 430 ) is sandwiched between the wheel ( 420 ) and a steel shaft ( 410 ) and is melted to join the parts together.

1 . A shaft assembly comprising: 
 a titanium-aluminide turbine wheel;    a steel shaft having opposite first and second ends, the shaft having a joint surface at the first end for attachment to the turbine wheel; and    a titanium alloy member sandwiched between a surface of the titanium-aluminide turbine wheel and the joint surface of the shaft, the titanium alloy member having a melting temperature of 650° C. to 750° C., which is lower than that of the titanium-aluminide turbine wheel and lower than that of the shaft;    the titanium alloy member being heated to cause melting of the titanium alloy member and then being allowed to cool and solidify so as to join the titanium-aluminide turbine wheel to the shaft.    
     
     
         2 . The shaft assembly of  claim 1 , wherein the titanium alloy member comprises a silver-titanium alloy member.