Effect of solidification parameters on the microstructures of a single crystal Ni-based superalloy AM3

Abstract

A single crystal Ni-based superalloy AM3 was processed at withdraw rates of 3.5, 10, 50, 100, 200, and 500 μm•s-1, respectively. The as-cast microstructures and solidification segregation ratio were characterized with various withdraw rates. The shape and size of carbide microstructures were determined. As expected, the primary and secondary dendrite arm spacings (PDAS and SDAS) decrease with the increase of withdraw rate. The highest volume fraction of eutectic γ/γ′is observed at the 100 μm•s-1 withdraw rate. The volume fraction of eutectic γ/γ′does not appear to be a strong function of the withdraw rate. With increasing withdraw rate, interface morphologies change in the sequence of planar, cellular, and dendrite. There is a general refinement of the microstructure as the withdraw rate increases. EPMA analysis showed that withdraw rate does not have obvious influence on the segregation of elements.

Keywords

• Ni-based superalloy
• single crystal
• withdraw rate
• solidification
• PDAS
• SDAS