抄録
In this study, the effect of titanium on the solidification brittle temperature range (BTR) of alloy 617 was evaluated, and the mechanism by which the eutectic reaction of titanium carbide influences the solidification cracking susceptibility of alloy 617 was clarified. The BTR was evaluated by the Varestraint test. Initially, the BTR decreased with increasing titanium content, reaching its minimum at 1.4% Ti, but further increased with additional Ti. Microstructural analysis of the quenched solidification microstructure of weld metal revealed the crystallization of Ti carbides during solidification.
To elucidate the mechanism by which Ti carbide formation during solidification influences the solidification cracking susceptibility of Alloy 617, a theoretical approach was conducted to understand the solidification brittle temperature range of Alloy 617. Ti carbide formation in the terminal stage of solidification reduced C concentration in the residual liquid and increased the solidification completion temperature. Excessive Ti addition causes an increase in Ti concentration in the terminal stage of solidification, which increases the BTR. Therefore, the existence of an appropriate range for the improvement of BTR by eutectic reaction of carbide using Ti was clarified. For the alloy 617 used in this study, the solidification cracking susceptibility was minimized when the Ti/C mass% ratio was around 30.
