HIGH POWDER CO2 AND ND-YAG LASER-WELDING OF WROUGHT INCONEL-718

High power laser welding techniques and related metallurgy have been i nvestigated on Inconel 718 sheets, 4 mm and 8 mm of thickness, in anne aled and aged states. The CO2 CW laser welded joint, with high depth t o width ratio, is suitable for post welding machining. The uniform bea d profiles were acheived by using an Nd-YAG pulsed laser, which have a n overlapping rate of about 85%. Wrought Inconel 718 can be welded by laser in both annealed and aged states, but the grain size must be AST M 10 or finer in order to control the microffissuring. The microfissur es relate to the delta phase at fine grain boudaries (ASTM 9-12) and t he NbC phase at large grain boundaries (ASTM 6) in particular, which o ccur in the delta phase band. The eutectic of the Gamma/NbC was suppre ssed by rapid solidification in the fusion zone. Many delta phases pre cipitate at interdendrites with 960 degrees C post welding solution tr eatment. Above 1038 degrees C the laves phase dissolves completely and only NdC is present.