Bi-metal impeller rotor

1 . A method of manufacturing a dual alloy impeller for a compressor section of an aircraft engine, the method comprising:

obtaining a first workpiece of a first metal alloy;

obtaining a second workpiece of a second metal alloy, the second workpiece defining a cavity for receiving the first workpiece in a complementary fashion, the second metal alloy being more creep resistant than the first metal alloy, the first metal alloy being more cold dwell resistant than the second metal alloy;

inserting the first workpiece into the cavity of the second workpiece and joining the first workpiece to the second workpiece to create a pre-joined dual alloy workpiece; and then

forging the pre-joined dual alloy workpiece, wherein the forging the pre-joined dual alloy workpiece comprises using flow maps from forge modelling to create a non-linear interface between the first metal alloy and the second metal alloy.

2 . The method of claim 1 , wherein the creating the non-linear interface comprises creating a curved interface between the first metal alloy and the second metal alloy.

3 . The method of claim 2 , wherein the curved interface gradually curves radially away from a central axis of the dual alloy impeller in an aft direction towards a back face of the dual alloy impeller.

4 . The method of claim 1 , wherein creating the non-linear interface comprises deforming a weld line between the first metal alloy and the second metal alloy.

5 . The method of claim 1 , wherein the joining the first workpiece to the second workpiece comprises friction welding the first workpiece to the second workpiece to form a weld joint therebetween, and wherein the forging the pre-joined dual alloy workpiece comprises deforming the weld joint to create the non-linear interface between the first metal alloy and the second metal alloy.

6 . The method of claim 5 , wherein the weld joint is formed between a radially outer surface of the first workpiece and a radially inner surface of the second workpiece.

7 . The method of claim 1 , wherein the forging comprises forging a friction weld joint between the first metal alloy and the second metal alloy.

8 . The method of claim 7 , comprising changing a metal grain direction of the first metal alloy and the second metal alloy at the friction weld joint.

9 . A method of manufacturing an impeller for a compressor section of a gas turbine engine, the method comprising:

forging a dual alloy workpiece having an inner portion welded to an outer portion along a conical weld line, the forging including deforming the conical weld line to provide a non-linear interface between the inner portion and the outer portion;

wherein the forging the dual alloy workpiece comprises using flow maps from forge modelling to create the non-linear interface.

10 . The method of claim 9 , wherein prior to forging, the method comprises:

obtaining a first alloy stock to form the inner portion of the dual alloy workpiece;

obtaining a second alloy stock to form the outer portion of the dual alloy workpiece;

wherein the second alloy stock is more creep resistant than the first alloy stock, the first alloy stock being more cold dwell resistant than the second alloy stock.

11 . The method of claim 10 , wherein prior to forging, the method comprises friction welding a radially outer conical surface of the inner portion to a complementary radially inner conical surface of the outer portion.

12 . The method of claim 11 , wherein deforming the conical weld line includes changing a metal grain structure of both the first alloy stock and the second alloy stock during a common forging operation.

13 . The method of claim 12 , wherein the forging comprises placing the first alloy stock and the second alloy stock in a die and then squeeze forming the first alloy stock and the second alloy stock together.