Abstract
The LE-7 engine, the first stage main engine for the H-II rocket, has been developed in Japan. During the development, there were some troubles in the various welded joints. In the previous report, the tensile properties of the Inconel-718 welded joints, solution treated at 1228K, were reported. In this report, the micro-structures, the hardnesses and the tensile properties of the Inconel-718 welded joints with various solution treatment conditions were investigated and compared with the previous results. It was observed that the dissolution of Ni3Nb phases in the welded metal, which reduced the ductility, and the grain growth in the parent metal occurred simultaneously, and that the break point in the specimen shifted from the welded metal to the parent metal as the solution treatment temperature increased from 1228K to 1338K.
