Nickel Base Superalloys Single Crystal Growth Technology for Large Size Buckets in Heavy Duty Gas Turbines

Abstract

A larger size bucket with superior high temperature strength is required for future land based gas turbines. From the viewpoint of high temperature mechanical properties, single crystal alloys are rather promising. To grow larger sized single crystals of nickel base superalloys, a two stage heating and bypass process in which single crystal growth paths are incorporated into large cross sectional positions such as platforms has been developed. It results in successful single crystal growth of alloys for buckets with a total length of 170mm and large lateral cross section. Characteristics of single crystal buckets made by the bypass process and properties of an alumina mold prepared for a single crystal casting are described herein.

Evolution mechanism of crystallographic orientation in grain continuator bars of a Ni-based single-crystal superalloy prepared by Bridgman technology during directional solidification

“…These defects result in an obvious deterioration of the blades' performance. To avoid the solidification defects mentioned above, a grain continuator (GC) technique was developed to prepare the single-crystal turbine blades [10][11][12] .…”

Processing of a Single Crystal Casting for Heavy-Duty Gas Turbine Blades: Creep and Metal/Mould Reaction Behavior of Al2O3-SiO2 Shell Mould

“…The moulds were fired at 1500 to 15501 for 20 to 30 min to form 3AI2Os • 2SiO2. The identification of 3AI2O3 • 2SiO2 and AI203 was made by X-ray diffraction (Yoshinari et al,1991). The Al203-SiO2 equilibrium phase diagram is shown in Fig.1 (Aksay and Pask, 1975).…”