Abstract
A Ni-based superalloy named "TOS1X-2" has been developed as a material for A-USC turbine rotors. TOS1X-2 is based on Inconel Alloy 617 and has a modified chemical composition to achieve the higher strength needed for over 700°C-class A-USCs. Aging heat treatment conditions were determined from the mechanical properties and microstructure. We manufactured an actual-scale rotor model made of TOS1X-2. A 31 ton ingot was manufactured, followed by forging of the model rotor with a diameter of 1100 mm and length of 2400 mm without any defects. Metallurgical and mechanical analyses of the model rotor were carried out. All metallurgical and mechanical features of the TOS1X-2 rotor model satisfied the requirements for not only 700°C-class but also over 700°C-class A-USC turbine rotor.
