Effect of dilution on the behavior of solidification cracking in PTAW overlay deposit on Ni-base superalloys

In this study, the effects of dilution on the solidification cracking susceptibility of PTAW (Plasma Transferred Are Welding) Inconel 625 and 718 overlay on Nimonic 80A were observed. In order to evaluate solidification cracking susceptibility, the Varestraint test was utilized. A possible mechanism of solidification cracking was suggested on the basis of microstructural examination and thermal analysis. The present study showed that the solidification cracking of the diluted Inconel 625 and 718 with Nimonic 80A was closely related to the solidification temperature range and the amount and distribution of gamma/NbC and gamma/Laves eutectic phases formed along the solidification grain boundaries. As dilution increased, the C/Nb ratio increased and the amount of eutectic phases decreased. In addition, the solidification temperature range decreased with increasing dilution in each overlay.