Elimination of hot cracking in the laser surface re-melting of the IC10 superalloy by controlling the heat input

Hot cracking is a severe defect that occurs during the repair or manufacturing of directionally solidified superalloy by laser metal deposition. In this study, the hot cracking sensitivity of a directionally solidified superalloy, IC10 alloy, in the laser surface re-melting was evaluated and the effects of heat input on the hot cracking was investigated. It is found that the crack number density and the crack length density first increase and then decrease with the increase of heat input under studied conditions, and the crack-free re-melted sample can be achieved under the heat input of 50 J/mm. Meanwhile, the cracks display a typical characteristic of liquation cracks. The formation of liquid film can be ascribed to the liquation of γ-γ' eutectic phases, γ' phases and carbides. The liquation height and the maximum width of liquid channel increase with the increase of heat input, and they are used to describe the capability of liquid feeding. Furthermore, the driving force for crack initiation and propagation induced by thermomechanical conditions are also discussed. These findings provide technical support for achieving successful repair or manufacturing methods of the non-weldable directionally solidified superalloys.