The design and development of a water-cooled high temperature gas turbine has been under active investigation by the General Electric Gas Turbine Division for the past 15 years. The transition from testing small scale, laboratory-size experimental hardware to full scale industrial gas turbine components was initiated in 1975 by General Electric and extended further under the U.S. Department of Energy’s High Temperature Turbine Technology (HTTT) program. A key element in this transition was the identification of a composite (hybrid) design for the first stage nozzles. This design permits efficient heat transfer to the water-cooling passageways, thus lowering effective strains and increasing part life. This paper describes the metallurgical considerations and process technology required for such hardware. A review of the materials selection criteria utilized for the nozzle is presented, along with the results of several materials development programs aimed at determining metallurgical compatibility of the component materials, diffusion bonding behavior and both hot corrosion and aqueous corrosion performance of key materials. A brief description of the actual cascade testing of the part is given, along with results of a post-test metallurgical analysis of the tested hardware.

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