Katsumi Iijima

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

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.Copyright

CHARACTERISTICS OF TITANIUM ALLOY 40 INCH LAST STAGE BLADE OF STEAM TURBINE

ABSTRACT Enlargement of the last stage blade (LSB) is one of the most effective ways to improve thermal efficiency. This requires development or selection of the materials which have a high tensile strength-to-weight ratio suitable for long low pressure LSBs of the steam turbine. It was confirmed that Ti-6Al-4V alloy was suited to a 40 inch last stage blade for 3600 rpm turbine instead of 12Cr materials. Shot peening was effective to improve high cycle fatigue strength. A trial 40 inch blade which was manufactured from Ti-6Al-4V alloy had offered excellent characteristics to satisfy the specified requirements.