Abstract
The modern nickel based superalloys for aircraft engine applications are nanostructured materials. A large number of intermetallic nanosized particles in these alloys provide them high strength and heat resistance, but cause great difficulties for processing. The article discusses various methods of forming axisymmetric parts for rotors of gas turbine engines such as discs and shafts out of nickel based superalloys. The superplastic process of roll-forming the disc is carried out at one passage with a large cogging of blanks in thickness, for example. A variety of hollow shafts can be roll-formed using a different scheme, which allows making long shafts and their combination with the disc. It is shown that the rotary method of disc forming - roll-forming has a high value of the rotary mode of deformation. The roll-forming method provides large strain of the workpiece material, which is obtained as a result of the fine-grained homogeneous structure, which is important to achieve high and isotropic mechanical properties. An important advantage of roll-forming is that the accumulation of large strain in this method is due to rotational components, which does not change the size of the workpiece. Fine-grained alloys, depending on the operating temperature, can be used directly after roll-forming or additional heat treatment. Long-term strength at 500°C and a load of 1050 MPa of a sample out of superalloy EP962 with fine-grained structure survived without failure more than 3,000 hours. Meanwhile, typically such test is provided for 100 hours only. This fine-grained alloy showed a high strength of about 1600 MPa at room temperature. Another fine-grained superalloy Inconel 718 revealed strength over 2000 MPa, and high fatigue strength.
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