Composite turbine wheel and process for making same

Claim 1

A process for making a composite turbine wheel or the like comprising a plurality of blades connected to the periphery of a hub which comprises the steps of forming a plurality of blade elements composed of a high temperature strength and fatigue resistant material including a blade section having an integrally-connected root section extending axially of the base of said blade section, finishing said blade elements to accurate final dimensions, positioning said blade elements in a mold in radially-oriented accurately-spaced circumferential relationship with said root sections thereof extending inwardly of a mold cavity defining the profile of the hub of said turbine wheel, filling said mold cavity with a superalloy metal powder of a particle size less than about 100 mesh and an oxygen content of less than about 200 ppm in a manner to achieve a loose powder packing density of at least about 60 percent of theoretical 100 percent density and effecting an embedment of said root sections in said metal powder, heating said mold and the assembled said blade elements and said metal powder in vacuum to an elevated temperature to effect a sintering of said metal powder into a coherent mass and a bonding thereof to said root sections, continuing said heating and sintering until the sintered said powder attains a density of at least about 90 of 100 percent theoretical density and to form a metallurgical diffusion bond between said root sections and the sintered said metal powder forming an integral assembly, and thereafter hot isostatically pressing said integral assembly at an elevated temperature under sufficient pressure for a period of time to effect a further densification of the sintered said powder defining the hub to a density approaching 100 percent of theoretical density.