Comprehensive influence of Y on K417 superalloy: Purification, interactions among the alloy elements and high temperature properties.

This study investigated the effects of yttrium addition (0wt%–0.5wt%) on the purification, microsegregation and mechanical properties of K417 cast superalloy. The results showed that the addition of Y could significantly reduce the content of oxygen. Purified K417 superalloy with 4∼7ppm O content was obtained after adding a moderate amount of Y. With the increasing Y addition, the segregation degrees of alloying elements (Ti, V and Mo) dropped as a whole, γ′ phase was refined, and the size and volume fraction of γ/γ′ eutectic increased. The decrease in the degree of Ti segregation and the solid solution of Y in carbide periodicity changed the morphology of carbide. When the Y addition increased from 0wt% to 0.1 wt%, the decrease of O content, the refinement of γ′ phase and the formation of rod carbides increased the high temperature tensile strength of the alloy. When the Y addition increased from 0.2wt% to 0.5 wt%, the production of large-size Y-rich phase reduced the mechanical properties of the alloy. The plasticity of the alloy rised and then decreased with increasing Y addition. The appropriate amount of Y addition was about 0.01wt% to 0.05wt%. • The addition of Y hindered the segregation of alloying elements. • High purity K417 alloy with oxygen and nitrogen content of 5ppm was obtained. • Yttrium addition caused the carbide shape to exhibit periodic change in the shape of a block and a rod. • The formation of rod-shaped carbide promoted the improvement of high temperature tensile strength. [ABSTRACT FROM AUTHOR]