20th International Forgemasters Meeting - IFM 2017

Ni-base superalloy LTES700R turbine rotors for advanced-ultra supercritical (A-USC) power generation was produced, and their microstructure, tensile, impact, and creep properties were evaluated. 10-ton class rotor forging was successfully produced through the double melting technique, which is the vacuum induction melting (VIM) followed by the electroslag remelting (ESR), and free forging with a 14,000 ton hydraulic press. Fine grain microstructure of which grain size number was approximately 3 to 4 at the surface and the center of the rotor, this result indicated that the conditions of the forging and solution heat treatment were appropriate. Fine grain microstructure improved the permeability of the ultrasonic wave in the ultrasonic inspection test, resulting in small minimum detectable flaw size (MDFS) of under 1.6mm. The tensile strength at 700 °C was adequate, without large difference among the position of the rotor. The creep test at 700 °C revealed that the 105 h rupture stress at 700 °C was estimated to be sufficiently higher than 100 MPa, which is thought as an industrial target in service. The results of the present production expressly demonstrated that it is possible to manufacture 10-ton class A-USC turbine rotors of LTES700R with excellent mechanical properties and good permeability of the ultrasonic wave.