Microstructure and Solidification Characteristics and Segregation Behavior of Superalloy K4169

The solidification process and segregation feature of K4169 alloy is studied by DSC, Thermo-Calc simulation and isothermal solidification analyses. The segregation and precipitation behavior of superalloy K4169 during isothermal solidification at 1360 and 1120 degrees C have been observed by the means of optical microscopy (OM), electron probe microanalysis (EPMA), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The results stated that the solidification began with the formation of primary gamma dendrites, and accompanied by the formation of MC carbides. During the solidification, Nb, Mo and Ti were enriched in the residual liquid phase, which eventually lid to the formation of MC carbides and Laves phases. The liquidus of K4169 was 1354 degrees C, and the solidus was 1240 degrees C. Its solidification sequence can be identified as follows: L -> gamma at 1354 degrees C; L -> gamma + MC at 1290 degrees C; L -> gamma + Laves at 1120 degrees C.