Abstract
The tensile properties of Inconel 718 and Udimet 720 Ni-base alloys being used for liquid hydrogen fueled rocket engine materials were investigated in a high pressure hydrogen of 19.7MPa at room temperature. The results obtained are as follows;
(1) Elongation, reduction of area and ultimate tensile strength in hydrogen were smaller than those in argon for both Inconel 718 and Udimet 720. The effect of hydrogen on the tensile properties increased with decreasing strain rate.
(2) Dimple rupture was mainly observed in argon both of Inconel 718 and Udimet 720. In hydrogen, the fracture along the interface between δ phase and γ matrix for Inconel 718 and that along the interface between γ' phase and γ matrix for Udimet 720 were observed on the fracture surface, respectively.
(3) For Inconel 718, the crack initiation occurred at carbide and then the crack propagated along the interface between δ phase and γ matrix in hydrogen. For Udimet 720, the crack initiation occurred at precipitate and then the crack propagated along the interface between γ' phase and γ matrix in hydrogen.
