United Technologies Corporation

Marvin Martin Allen

John A Miller

Ralph E Anderson, Jr

Bruce Edward Woodings

An integrally bladed bimetallic rotor for high temperature operation having airfoils with good stress rupture and creep strength and a hub with high tensile strength and good low cycle fatigue resistance is made from a preform of two concentric cylinders of different superalloy metals metallurgically bonded to each other at their interface, both materials being in such a condition that they exhibit superplastic behavior at a certain, controlled strain rate and temperature without incurring substantial grain growth. The metal of the outer cylinder is selected such that it has a lower gamma prime solvus temperature than the metal of the inner cylinder. The preform is isothermally forged at the controlled strain rate and temperature to form the airfoils from the alloy of the outer cylinder and to form the hub from the alloy of the inner cylinder. A sharp, reproducible interface is created between the two alloys. After forging, the rotor is heated to a temperature between the gamma prime solvus temperatures of the alloys and under conditions which cause full gamma prime solutioning of the airfoils up to the interface but only partial gamma prime solutioning of the rotor hub. The resulting airfoils have coarse grains and the hub has fine equiaxed grains.

Process for fabricating integrally bladed bimetallic rotors

A thermomechanical treatment for producing useful microstructures in the nickel base superalloys is described. The process is applied to material which has been placed in a condition of super-plasticity, and utilizes isothermal hot deformation under conditions which produce a uniform dislocation density and a resultant propensity for abnormal grain growth. The material is then recrystallized in a thermal gradient to produce a final structure consisting of elongated grains.

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W. Palm Beach, FL, United States of America

Marvin Martin Allen