The paper refers to previous publications of the author, focused on criteria of casting feeding, including the thermal criterion proposed by

Niyama. On the basis of this criterion, present in the post-processing of practically all the simulation codes, danger of casting compactness

(in the sense of soundness) in form of a microporosity, caused by the shrinkage phenomena, is predicted. The vast majority of publications

in this field concerns shrinkage and feeding phenomena in the cast steel castings – these are the alloys, in which parallel expansion

phenomenon does not occur as in the cast irons (graphite crystallization). The paper, basing on the simulation-experimental studies,

presents problems of usability of a classic, definition-based approach to the Niyama criterion for the cast iron castings, especially of

greater massiveness, for prediction of presence of zones of dispersed porosity, with relation to predictions of the shrinkage type defects.

The graphite expansion and its influence on shrinkage compensation during solidification of eutectic is also discussed.

Turbine blades have complex geometries with free form surface. Blades have different thickness at the trailing and leading edges as well

as sharp bends at the chord-tip shroud junction and sharp fins at the tip shroud. In investment casting of blades, shrinkage at the tip-shroud

and cord junction is a common casting problem. Because of high temperature applications, grain structure is also critical in these castings

in order to avoid creep. The aim of this work is to evaluate the effect of different process parameters, such as, shell thickness, insulation

and casting temperature on shrinkage porosity and grain size. The test geometry used in this study was a thin-walled air-foil structure

which is representative of a typical hot-gas-path rotating turbine component. It was observed that, in thin sections, increased shell

thickness helps to increase the feeding distance and thus avoid interdendritic shrinkage. It was also observed that grain size is not

significantly affected by shell thickness in thin sections. Slower cooling rate due to the added insulation and steeper thermal gradient at

metal mold interface induced by the thicker shell not only helps to avoid shrinkage porosity but also increases fill-ability in thinner

sections.