A New Way to Improve the Superalloys

Abstract

A metallography coupled with the microprobe method was used to study the solidification process of superalloys. It was found that the final solidification temperatures of the conventional superalloys are generally very low, about lOtSO-112OC, the solidification ranges are large enough, reaching 180-24OC, that makes the solidification segregation serious. Strictly controlling the contents of the minor elements P,Zr,B and Si in superalloys can raise the final solidification temperature to 1180-1280°C and contract the solidification temperature range to 50-12O"C, that results in alleviating the solidification segregation obviously. After controlling the contents of the minor elements, a series of new superalloys with low segregation and excellent properties have been developed.

Solute Redistribution during Planar and Dendritic Growth of Directionally Solidified Ni-Base Superalloy CMSX-10

“…It was also found that γ′ particles precipitated near γ/γ′ eutectic pools before the final solidification occurs (Figure 3(a)). This result agrees quite well with the microstructural observation of Zhu et al [20], who reported that large amounts of γ′ particles precipitate at the periphery of γ/γ′ eutectic in IN738 alloy before the final solidification occurs. It can be also seen that thin γ layer formed ahead of coarse γ/γ′ eutectic pools in the fully solidified microstructure of the alloy CMSX-10 ( Figure 3(b)).…”

Eta Phase and Boride Formation in Directionally Solidified Ni-Base Superalloy IN792 + Hf

“…[13] who reported that large amounts of c¢ particles are precipitated at the periphery of c/c¢ eutectic in IN738 alloy before the final solidification occurs. Note that the DSC exothermic peak at 1402 K could not be observed in the DSC curve of the alloy CM247LC, whose as-cast microstructure is composed of primary c, MC carbide, c/c¢ eutectic, and c¢ precipitates.…”

Influence of solidification conditions on the castability of nickel-base superalloy IN792

“…Grain boundary elements such as B and Zr or impurities such as P and S are potentially harmful for castability. [15,21,22] Their concentration in the grain boundary must decrease when the grain size decreases. The grain boundary may become more tortuous with increasing withdrawal speed, as shown previously; it results in stronger interlocking, and therefore, increased cohesion.…”