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The Kansai Electric Power Company, Co., Inc. (KEPCO), Nagoya Univ. and Hitachi, Ltd. have
jointly developed a new Ni-based superalloy with excellent heat resistant characteristics which are usable in the 1500 or even higher class industrial gas turbine for power generation.
There has been a great demand to raise thermal efficiency and to reduce CO2 emission in power generation systems. In combined Gas Turbine generating systems, it is necessary to raise the turbine inlet gas temperature as high as possible.
In order to make it possible, we have been conducting a research on Ni based superalloys for gas turbine blades since 1997 with the aid of the d-electron concept. We have successfully found a new superalloy that can be applicable both to gas turbines and jet engines for airplanes. |
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Overview of the single-crystal
model bucket ( length :170mm) |
« Features of the alloy »
1. Chemical composition
It is a single crystal Ni based superalloy composed of Ni, Co, Cr, W, Al, Ti, Ta, Re, Hf, and etc.
2. Heat Resistant Characteristics
It has high tensile strength, excellent creep strength, hot corrosion resistance, good oxidation resistance, high fatigue strength and stable microstructure. No TCP phases or undesirable phases are observed even after a long term creep test.
3. Castabity
There is no inherent problem of castability in thealloy. A single crystal model bucket 170mm in length is grown for use in the first stage blade of 25MW class industrial gas turbine. |
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SEM micrographs of the
alloy
after the heat treatment |
« Comparison of other alloys »
The developed alloy possesses about 30 higher temperature capability than the second generation superalloy used practically in the world. The developed alloy has no problems of oxidation resistance and phase stability in the temperature above 1000 different from the 3rd and 4th generation alloys recently developed.
« Research plan for the future »
It is one of the most advanced technology in the world to develop a large gas turbine blade of Ni based single crystal superalloys. There are still many technical issues to be solved.
KEPCO continues to research on the Ni based superalloys developed this time about the material characteristics for the purpose of practical use and also conducting a research to improve the single crystal alloy into directionally solidified one in order to make it easier to cast a large gas turbine blade.
It is our final goal to make it possible to apply it to the gas turbines and reduce the cost of power generation and continue to contribute to the environmental issues of global warming.
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