Effect of yttrium addition on microstructural evolution and high temperature mechanical properties of Ni-based superalloy produced by selective laser melting

Abstract

The effects of Y addition on the microstructural evolution and room/high temperature mechanical properties of SLM Ni-based superalloy were investigated. Y-free and Y-added SLM Ni-based superalloy as two alloys for comparison. In the Y-added superalloy, the main reasons for the denser microstructure are a flat melt pool and epitaxial growth of columnar dendrites with <001> orientation. Moreover, the Y-added SLM specimens have superior hot tensile performance due to high density dislocation and the formation of Y2O3-oxides. Analysis of microstructural evolution under elevated temperatures showed that the interaction between dislocation and oxide could pin dislocation at the grain boundary and increase the annihilation temperature of dislocation. We also examined the high temperature fracture morphology of Y-added specimens, and found that their excellent performance is primarily because of tenacity nests and serpentine sliding originating from the oxide and dislocation, as well as their impediment to microvoid extension.