Solidification Behavior Of Superalloy Research Articles

A Study of Sliver in C-Shaped Grain Selectors during Investment Casting of Single-Crystal Superalloy

In this study, the formation mechanism of sliver defects in C-shaped 2D grain selectors during investment casting of single-crystal superalloy was investigated by analyzing the effects of the C-shaped 2D grain selectors on the solidification behavior of superalloy. The physical field properties of the sliver formation and solidification characteristics of CM247LC nickel-based superalloy were determined. The temperature and stress fields were simulated using ProCAST. The results showed that the stress fields of solidification played an essential role in the formation of sliver, indicating that the solidification interval characteristics of the alloy and stress based on the geometry of the C-shaped 2D grain selector are crucial for the formation of sliver. In addition, the origin of sliver depended upon tensile stress during solidification, relying on the constraints of dendrite boundaries. The findings suggested that the joint sections of the starter block—i.e., selector and selector-casting joint of C-shaped selector sections—are stress-sensitive areas where sliver can form readily. Furthermore, sliver is formed in the final stages of solidification and especially originates in the grain selection part where the accumulated thermal stress is high, and there is only a small quantity of liquid phase with a low melting point between the dendrites. Therefore, the solidification and stress conditions generate thermal cracks, which can also cause sliver defects.

Solidification behavior of Pt-containing 718Plus superalloy

Solidification behaviors of Pt-containing 718Plus superalloyswere studied by scanning electron microscopy (SEM), energy dispersive spectrum (EDS), differential scanning calorimetry (DSC) and simulation calculations. It is found that Pt increases solidification range and decreases solidus temperature of the alloy and precipitation temperature of Laves + γ eutectic phase since Pt enlarges the region of γ phase by increasing Nb solubility. In addition, Pt segregates to the interdendritic region and increases the segregation of Nb and Tiin the interdendriticregion due to the strong attractive interactions between Pt and Nb/Ti. As a result, Pt promotes the precipitation of the Laves + γ eutectic phase and η phase around eutectic phase. The increase of solidification range and segregation degrees of Nb and Al caused by Pt also promotes the precipitation and growth of γ’ + γ” phase around eutectic phase. These results provide experimental bases for understanding the mechanism of Pt in solidification behavior of superalloys.

Solidification behavior of superalloy in 939 in melt spinning

The rapid solidification behavior of a Ni-base superalloy (IN 939) has been investigated by means of melt spinning. An attempt was made to determine the variation of the thermal parameters during the solidification in the melt puddle. The microstructure development, especially the segregationlessly solidified layer at the bottom of the ribbons, was studied. The absolute stability theory was used to calculate the critical condition for stability of the used alloy and then compared with the experimental results. By combination with the solidification data of the same alloy in the conventional regime a complete solidification diagram has been mapped out.