Method for manufacturing a turbine wheel

Abstract

A method for manufacturing a turbine wheel comprising casting the turbine wheel from an austenitic nickel-chromium-based superalloy, subjecting the cast turbine wheel to hot isostatic pressing and then subjecting a surface of the hot isostatically pressed turbine wheel to plastic deformation, wherein said hot isostatic pressing is effected at a pressure of 98 to 200 MPa and a temperature of 1160 to 1220° C. for a time period of 225 to 300 minutes. There is further described a hot isostatically pressed cast turbine wheel manufactured from an austenitic nickel-chromium-based superalloy, the turbine wheel having a plastically deformed surface; and a turbocharger incorporating such a turbine wheel.

What is claimed is: 
     
         1 . A hot isostatically pressed cast turbine wheel manufactured from an austenitic nickel-chromium-based superalloy, wherein the hot isostatic pressing is effected at a pressure of 98 to 200 MPa and a temperature of 1160 to 1220° C. for a time period of 225 to 300 minutes, and wherein the turbine wheel has a plastically deformed surface. 
     
     
         2 . A turbine wheel according to  claim 1 , wherein the plastically deformed surface of the turbine wheel exhibits a residual compressive stress of −1000 to −1500 MPa at a depth of 25 to 90 microns below said surface of the turbine wheel. 
     
     
         3 . A turbine wheel according to  claim 1 , wherein the plastically deformed surface of the turbine wheel exhibits a residual compressive stress of −1100 to −1500 MPa at a depth of 30 to 60 microns below said surface of the turbine wheel. 
     
     
         4 . A turbine wheel according to  claim 1 , wherein the plastically deformed surface of the turbine wheel exhibits a residual compressive stress of −500 to −1200 MPa at a depth of 100 to 190 microns below said surface of the turbine wheel. 
     
     
         5 . A turbine wheel according to  claim 1 , wherein the plastically deformed surface of the turbine wheel exhibits a residual compressive stress of −600 to −900 MPa at a depth of 112 to 160 microns below said surface of the turbine wheel. 
     
     
         6 . A turbocharger comprising: a housing; a turbine wheel supported on a shaft within said housing for rotation about a turbine axis; and a compressor wheel supported on said shaft within said housing, wherein said turbine wheel is a hot isostatically pressed cast turbine wheel manufactured from an austenitic nickel-chromium-based superalloy, wherein the hot isostatic pressing is effected at a pressure of 98 to 200 MPa and a temperature of 1160 to 1220° C. for a time period of 225 to 300 minutes, and wherein the turbine wheel has a plastically deformed surface. 
     
     
         7 . A turbocharger according to  claim 6 , wherein the turbine wheel is in accordance with any one of  claims 2  to  5 .