Pulsing-induced healing of a surface crack of a nickel-based alloy

Abstract

In this work, we demonstrate the feasibility of applying electric pulses to heal surface cracks on nickel-based alloy GH4169 under compressive load. There exists an incubation time for the onset of the healing of a crack, which is associated with local temperature at the crack tip. The crack size decreases with increasing the pulsing time at a constant healing rate prior to complete healing of the crack. Increasing compressive load accelerates the healing process. The electric pulsing leads to the formation of an influential zone surrounding the crack with the finest grain sizes in the healed crack and the coarsest grain sizes away from the influential zone. The indentation hardness increases with the increase the distance to the crack tip of the healed crack. A model of viscous flow in the crack channel is proposed for the crack healing. The resultant force on the crack faces due to the crack healing increases with the increase of the healing time and the decrease of the crack width.