Effect of vacuum level on the interfacial reactions between K417 superalloy and Y2O3 crucibles

Abstract This study investigates the influence of vacuum level on the interfacial reactions between K417 melt and Y2O3 crucibles. The results indicate that the interactions between Y2O3 crucibles and the K417 melt include the physical erosion of the crucible inner wall by the melt, and the chemical dissolution of Y2O3 particles in the melt. During the melting process, the vacuum level significantly affects the interface reaction and composition of the alloy. With the vacuum level increasing from 500 Pa to 0.03 Pa, the content of dissolved Y in the alloy increases from 4 ppm to 600 ppm, the thickness of interface reaction layer increases from 0 μm to 213 μm, and the actual sample composition including for uptake of residual gas contamination gradually decreases. Furthermore, the results strongly indicate that, because of the dissolution of Y element in the melt, the segregation of alloying elements (Ti and V) generally decreases, and the morphology of primary carbide transfers from continuous rods and platelets to discrete blocks. The K417 superalloy ingot melted with Y2O3 crucibles at 0.03 Pa has the best composition and the most stable microstructure.