Effects of gravitational orientation on surface deformation and weld pool geometry during gas tungsten arc welding

Effects of gravitational orientation on gas tungsten arc (GTA) welding of nickel were studied to determine the impact of free-surface deformation on weld-pool shape. This was accomplished through GTA welding and a numerical study of the welding process. Welding was conducted by varying scan velocity and gravitational orientation, e.g.,,welding upward opposing gravity (parallel-up weld), welding downward with gravity (parallel-down weld), and welding perpendicular. to gravity (perpendicular weld). Slower scan velocity produced more significant free surface deformation. Gravitational orientation caused 21% deeper penetration in the parallel-up weld compared with the parallel-down weld (resulting from 50% or more maximum surface deformation). Weld penetration of the perpendicular weld was between that of parallel-up and parallel-down cases. A model of the welding process, in which an experimentally generated free surface was implemented as a boundary condition, supported the results by showing similar trends.