Effects of foundry variables and refiners on cast structures of superalloy K4169II. Dendrite structures and granulation mechanisms

The effects of foundry variables and refiners on dendrite structures. micro segregation, inclusion and microporosity of cast superalloy 1 4169 have been studied. The results indicate that while keeping the other rocessing parameters invariant. both the average principal axis length of the primary dendrites (l(axis)) and the secondary dendrite arm spacing (SDAS) reduce with decreasing the pouring temperature. At the same pouring temperature. l(axis) shortened with the addition of refiners but the SDAS keeps almost unchanged. Meanwhile the microsegregation of main elements such as Fe, Cr. Nb,. Mo and Ti is alleviated with the decrease in rain size. and the grains have transformed from dendrite to granulation in fine-grained castings. Furthermore. it is found that trace addition of refiners to the melt did not form inclusion and change the phase constitution of the alloy. At high pouring temperature. the amount of microporosity in samples with the addition of refiners can be greatly reduced.