EFFECT OF SURFACE ORIENTATION ON CHARACTERISTIC WELD MICROSTRUCTURE EVOLUTION OF Ni-BASE SUPERALLOY SINGLE CRYSTAL

摘要

The weldability of Ni-base superalloy single crystal was investigated under various laser welding conditions by using the specimens with characteristic surface orientations. The conditions for prevention of cracks and/or different crystals evolution were established. The evolution of different crystals increased with increases in welding speed and laser power. This was attributed to the suppression of solid-solution of carbides during welding. Different crystals were formed due to easier heterogeneous nucleation from the vicinity of carbides at the fusion boundary. The effect of crystallographic surface orientation on the occurrence or prevention of different crystals was confirmed and interpreted in terms of different angles between [100] orientations and thermal gradient direction.