In this study, grain boundary liquation phenomenon using two-dimensional model was calculated in order to estimate infiltration length of liquid phase around precipitate NbC on grain boundary as a function of the temperature. The high temperature ductility test was carried out as a verification of the numerical calculation, and the numerical calculation result was compared with the experimental result.
Grain boundary liquation start temperature calculated by the numerical analysis was well correspondent to the temperature measured by the experiment. In addition, the effect of heating and cooling speed, grain size and particle size of NbC on the liquid phase infiltration length to grain boundary in the laser welding was examined by the two-dimensional grain boundary liquation analysis. In Inconel 718, grain boundary liquation started in the heating process at 1434 K. The length of the liquid phase which infiltrates along grain boundary on the heating rate within 5000 K/s was not affected by heating rate. In addition, it was suggested that the liquation crack sensitivity be improved by decreasing grain size and doing the particle size of NbC under 1.0μm.
