一方向凝固Ni基超合金MarM247LCDSの室温高圧水素環境下における引張性質(フラクトグラフィ特集)

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Tensile properties of the directionally solidified Ni-base superalloy MarM247LCDS used for the turbine blades of the fuel and oxidizer turbopumps installed in the liquid hydrogen fueled rocket engine, LE-7 engine, of H-II rocket were investigated in a high pressure hydrogen of 19.7 MPa at room temperature. The results obtained are as follows ; (1) The 0.2% proof stress, ultimate tensile strength, elongation and reduction of area in hydrogen were smaller than those in argon. The effect of hydrogen on the tensile properties increased with decreasing strain rate. Hydrogen environment embrittlement depended little on the solidified direction. (2) The crack initiation occurred at carbides in the area between dendrites both in argon and hydrogen. Then the crack propagated in γ matrix between γ' and γ' with ductile fracture in argon and with brittle fracture in hydrogen, respectively.
1994-05-15