Method of making cast metal turbine wheel with integral radial columnar grain blades and equiaxed grain disc

Abstract From the Canadian patent

Abstract of the Disclosure:, A cast metal turbine wheel is made comprising a cylindrical disc with equiaxed grains and integral blades with columnar grains oriented substantially parallel to the leading and trailing blade edges. The blades are solidified unidirectionally by withdrawing heat through chill means located adjacent the mold at the blade tips. Cooling is inhibited from other blade surfaces by retaining cast metal in mold portions located above and below the blades. The disc portion of the mold is insulated so that it cools slowly to promote grain nucleation throughout the metal therein and equiaxed grain growth.