IGTC-57 Single Crystal Casting Technology for Nickel Base Superalloy Buckets of Industrial Gas Turbines(Session C-1 MATERIALS AND FABRICATION)

概要

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Single crystal casting technology for nickel base superalloys was studied for buckets of industrial gas turbines. A mold withdrawal method was carried out for single crystal casting and the 'bypass-method' was introduced to eliminate nucleation of misoriented grains at overhanging portions of the bucket. The relationship between causes of grain defects in single crystal buckets and casting conditions was studied. Heating temperature of the mold and the velocity of mold withdrawal should be adjusted to eliminate grain defects. In case of higher heating temperature of the mold, a 'kiss-out defect' can be produced by deformation of the core. After surveying the casting conditions, 235mm-long single crystal buckets were successfully cast. Degradation due to casting defects was negligible for these single crystal buckets because the strength of these single crystal buckets was comparable to that of roundbar specimens.
公益社団法人日本ガスタービン学会の論文