Ni基単結晶超合金のクリープ疲労強度特性

抄録

Much interest in new alloys is being taken at present. The improvement by chemical yeast has almost reached the limit for developing a superalloy used for high-temperature components. Accordingly, attention is being paid to the progress of directionally solidified and single crystal casting processes. High-temperature strength of a single crystal superalloy is superior to those of conventionally and directionally solidified cast ones for the following reasons: (1) A high incipient melting temperature by not intentional adding grain boundary strengthening elements, (2) High creep strength by a high gamma prime solution temperature, and (3) Improved properties by a high solution heat treatment temperature.
This paper describes an experimental study on the creep-fatigue strength of a Ni-base single crystal superalloy, CMSX-2, for the purpose of applying it to turbine blade and vane in a coal-gasification combined-cycle plant. The experimental results displayed clearly the following points: (1) The lives under PP strain wave became longer in comparison to those under other strain waves, PC, CP and CC. (2) CMSX-2 has excellent creep-fatigue strength in comparison to those of Ni-base conventionally and directionally solidified cast superalloys, Mar-M247. (3) The creep-fatigue strength of CMSX-2 could be sensitive to the gamma prime size, especially under PP strain wave.