Abstract: A unitary turbine wheel for a gas turbine engine, the turbine wheel including a pair of initially separate discs which are diffusion bonded together and define air passageways which extend radially through the discs. A plurality of initially separate turbine blades are provided each of which defines cooling air passageways, and the turbine blades are diffusion bonded in angularly spaced relationship to the peripheral surfaces of the discs with the air passageways in the blades communicating with the air passageways defined by the discs. Means is provided for drivably connecting the turbine wheel to a turbine shaft, and in a preferred embodiment, the turbine blades have a thermally insulating coating on the exposed surfaces thereof.