Effect of modification and cooling rate on the macrostructure of IN-713C alloy

The results of investigations of the effect of modification and cooling rate on the macrostructure of castings made from IN-713C nickel superalloy were described. As a modifier, cobalt aluminate CoAl2O4 in composition with aluminium powder and colloidal silica was used. Changes in the cooling rate were obtained by the use of a stepped test piece with the steps of 6, 11, 17 and 23 mm thickness. As a criterion for the evaluation of casting macrostructure, the stereological parameters, like grain count, relative surface area, shape factor, and indeces of the grain size and shape homogeneity, were applied. The modification treatment was observed to change the grain type from columnar to equiaxial. The stereological parameters of the equiaxial grains depended to a great extent on the cooling rate of the individual elements of a cast stepped test piece.