Grain Selection in Spiral Selectors During Investment Casting of Single-Crystal Components: Part II. Numerical Modeling

Abstract

In this article, grain selection in spiral selectors during investment casting of single-crystal (SX) components is simulated using a cellular automaton grain structure model (CAFE) within a finite element thermal model (PROCAST). The models were validated against experimental observations and then were applied to model the effect of geometry of the spiral selectors on grain selection through a systematic approach. It was found that the efficiency of the spiral selector is significantly dependent on its geometry; the spiral becomes more efficient in selecting single grain with a smaller wax wire diameter; larger spiral rotation diameter, and smaller takeoff angle. Recommendations for optimizing the spiral geometry are provided.

Modeling of Directional Solidification of Columnar Grain Structure in CMSX-4 Nickel-Based Superalloy Castings

“…The basic function of starter is the formation of lowest quantity of columnar grains on the inlet of the selector, while maintaining the minimum deviation of crystallographic orientation from the [001] axis. On the basis of the analysis of calculation results and literature survey (Ref 18,19) it has been established that application of grain starter of height exceeding 35 mm does not cause the significant decrease of grain quantity and the deflection angle. However, it leads to the reduction of blade casting height in the model assembly and, as a consequence, to a rise of production costs.…”

Removal of casting defects from CMSX-4®and CMSX-10®alloys by electropolishing in a novel electrolyte; Deep Eutectic Solvent

“…In order to measure these dissolution rates over much larger distances and longer times we have very recently used focus variation microscopy using the Zeta Instruments Zeta 200 3D optical profiler. Here a 3D topographical image can be obtained over areas of several mm 2 and height ranges of mm. A typical 3D image and profile plot of the step can be seen in Fig.…”

“…Typical single crystal superalloys castings are manufactured using the vacuum investment casting process; during this process the molten superalloy is poured in a ceramic mould that has been fabricated via the lost wax method [1][2][3][4][5]. The single crystal growth is controlled in part by the speed and temperature at which this mould is removed from the furnace.…”

Single-Crystal Casting/Directional Solidification

“…Improvement of creep ductility and thermal fatigue resistance by orientating the preferred <001> crystallographic growth direction, which coincides with the elastically soft direction, parallel to the maximum loading direction (64)(65)(66). In order to grow single-crystal component, a grain selector is implemented into the directional solidification process in a modified Bridgman furnace to ensure that only one grain can survive in the final structure ( Figure 16) (25,26). Different single crystal (SX) selector designs have been employed ( Figure 17) (26,67) to select a single grain.…”