Co-growing mechanism of γ/γ′ eutectic on MC-type carbide in Ni-based single crystal superalloys

Abstract To clarify and comprehend the co-growing mechanism of γ/γ′ eutectic on MC-type carbide in a single crystal CM247LC superalloy, the interface and the elements' segregation between MC-type carbide and γ/γ′ eutectic was investigated in this paper. The results show that a semi-coherent boundary was observed having an orientation relationship of { 1 ¯ 1 ¯ 1 } MC ‖ { 1 ¯ 1 ¯ 1 } γ / γ ′ with MC || γ/γ′ . This interface structure resulted in a high interface energy, and a reduced preference of γ/γ′ eutectic's nucleation on MC-type carbide. However, this unfavorable interfacial feature was offset by the elements' segregation profile during the MC-type carbide's solidification, which is characterized by Al, Ni, Co and Cr enrichment and a co-growing mode.