Abstract:Based on a 5% (mass fraction) Re-containing single crystal nickel-based superalloy with 3% (mass fraction) Cr, the microstructural variation with Cr addition was investigated. The experimental results show that segregation of alloying elements was enhanced in as-cast microstructure with Cr addition; and the volume fraction of eutectic is increased. However, the solidus and liquidus temperatures are remarkably reduced. With the increase of Cr content, the average γ¢ size and volume fraction are decreased in the fully heat treated microstructure. X-ray diffraction results indicate that γ/γ¢ lattice misfit becomes more negative. According to the energy dispersive spectroscopy (EDS) results, Cr is mainly distributed in the γ matrix; and more γ-forming elements, such as Re and W, enter the γ matrix, while the γ/γ¢ partition ratio of Cr is inversely decreased.

Key words: Cr; Re; single crystal superalloy; misfit; microstructure