J. DuPont, T. Anderson, Lehigh University, Bethlehem, PA
Melting efficiency is an important factor that controls the relative amount of melting and heat affected zone formation during welding. High melting efficiencies are typically desirable in order to reduce the extent of HAZ formation and associated degradation in properties of the base metal. In this work, the melting efficiency of laser and electron beam welds on a nickel base single crystal superalloy (CMSX4) were determined with metallographic methods. The influence of both beam power and travel speed were assessed along with variations in the crystallographic growth direction. The results showed that melting efficiency increased significantly with increasing beam power and travel speed. At low beam powers, a maximum melting efficiency was observed with increasing travel speed, beyond which the melting efficiency decreased with increasing beam velocity. At higher powers, the melting efficiency increased monotonically to near the theoretical maximum value of 0.5. The crystallographic growth direction had no significant effect, which indicates that heat flow in the single crystal is isotropic. The results were interpreted based on heat flow considerations using a recently published model and are useful for process optimization purposes.
Summary: Melting efficiency is an important factor that controls the relative amount of melting and heat affected zone formation during welding. In this work, the melting efficiency of laser and electron beam welds on a nickel base single crystal superalloy were determined with metallographic methods. The influence of beam power, travel speed, and crystallographic growth direction were assessed. The results were interpreted based on heat flow considerations using a recently published model and are useful for process optimization purposes.
