Method and apparatus for improving turbocharger components

Abstract

In one form, a turbocharger component, such as a compressor wheel or an impeller, formed of a cast material or a material made using a powder metal process, includes a surface having at least a portion thereof treated by a thermo-mechanical treatment process, such as friction stir processing. At the treated portion, the material forming the component includes a microstructure that is different than the microstructure of the material throughout the rest of the component. For example, in one form the material at the treated portion includes a homogenous microstructure while the material throughout the rest of the component includes a cast microstructure. In one or more forms, the treated portion exhibits at least one of increased strength, ductility and fatigue-resistant properties. In another form, a method is directed to providing components for a turbocharger which exhibit enhanced structural properties. However, other embodiments, forms and applications are also envisioned.

1 . An apparatus, comprising:
 a turbocharger for an internal combustion engine, said turbocharger including a compressor wheel coupled with a first end of a shaft and a turbine coupled with an opposite second end of said shaft, said compressor wheel including a first surface facing said turbine and a second surface including a plurality of vanes and facing away from said turbine;   wherein said compressor wheel comprises a material having a first microstructure; and   wherein at least a portion of said first surface comprises a second microstructure, said second microstructure being formed by a localized friction stir processing treatment.   
     
     
         2 . The apparatus of  claim 1 , wherein said compressor wheel is formed of a material selected from the group consisting of a cast material and a material made using a powder metal process. 
     
     
         3 . The apparatus of  claim 2 , wherein said second microstructure comprises a homogenized microstructure containing a reduced number of casting defects relative to said first microstructure. 
     
     
         4 . The apparatus of  claim 1 , wherein:
 said portion includes a stir zone defined by said friction stir processing;   said stir zone comprises said second microstructure;   said first microstructure of the material lies beneath said stir zone; and   said material includes a gradual transition between said stir zone and said first microstructure.   
     
     
         5 . The apparatus of  claim 1 , wherein said material is selected from the group consisting of aluminum and aluminum alloys. 
     
     
         6 . The apparatus of  claim 1 , wherein at least a portion of said first surface comprising said second microstructure includes an alloying material incorporated therein by said localized friction stir processing treatment. 
     
     
         7 . A method, comprising:
 providing a cast component of a turbocharger for an internal combustion engine, said component comprising a material including a cast microstructure; and   applying a friction stir processing treatment to at least a portion of a surface of said component and thereby altering the cast microstructure of the material at said portion.   
     
     
         8 . The method of  claim 7 , wherein said cast component is selected from the group consisting of a turbine wheel and a compressor wheel. 
     
     
         9 . The method of  claim 7 , wherein said component is a compressor wheel including a plurality of vanes and said surface is positioned opposite said plurality of vanes. 
     
     
         10 . The method of  claim 9 , wherein the material is selected from the group consisting of aluminum and aluminum alloys. 
     
     
         11 . The method of  claim 7 , wherein:
 treating said portion with said friction stir processing treatment defines a stir zone at said portion;   said cast microstructure lies beneath said stir zone; and   the material includes a gradual transition between said stir zone and said cast microstructure.   
     
     
         12 . The method of  claim 11 , wherein said stir zone extends from said surface to a depth of from about 0.5 mm to about 150 mm. 
     
     
         13 . The method of  claim 7 , wherein said applying said friction stir processing comprises incorporating an alloying material into the stir zone. 
     
     
         14 . The method of  claim 13 , wherein said alloying material comprises a form selected from the group consisting of a thin sheet, a wire and a powder. 
     
     
         15 . The method of  claim 7 , wherein altering the cast microstructure of the material at said portion includes at least one of homogenizing the cast microstructure, removing casting defects from the cast microstructure at said portion and incorporating an alloying material into said portion. 
     
     
         16 . The method of  claim 15 , wherein removing casting defects includes substantially eliminating at least one of voids, dendrites, microstructural segregation and inclusions from the material at said portion. 
     
     
         17 . The method of  claim 7 , wherein said providing includes inspecting a preassembled turbocharger for defects and removing a cast component from said preassembled turbocharger as a result of detecting at least one defect in said cast component. 
     
     
         18 . The method of  claim 7 , further comprising identifying at least one highly stressed area of said cast component and wherein said applying said friction stir processing treatment comprises applying said friction stir processing treatment to at least one of said at least one highly stressed areas of said cast component. 
     
     
         19 . A cast impeller for a turbocharger compressor, comprising a body having a cast microstructure extending between a first surface and a second surface, wherein at least one of said first and second surfaces includes at least a portion treated by a friction stir processing treatment and having a second microstructure exhibiting at least one of increased strength, ductility and fatigue-resistant properties relative to the cast microstructure. 
     
     
         20 . The impeller of  claim 19 , wherein said first surface includes a plurality of vanes and said second surface includes said portion. 
     
     
         21 . The impeller of  claim 19 , wherein said body comprises a material selected from the group consisting of aluminum and aluminum alloys.