Boron and carbon behavior in the cast Ni-base superalloy EP962

Abstract

The results of investigations of boron and carbon segregations, boride and carbide phases forming in various elements of the structure of ingots of the Ni-base superalloy EP962 have been presented. The methods of light metallography (LM), scanning electron microscopy (SEM), X-ray spectral microanalysis (XRSMA), high sensitive track autoradiography on boron via the nuclear reaction 10B(n, α) 7, Li and activation autoradiography on carbon via the reaction 12C(d, n) 13N were used. Boron segregation and precipitation of boride phase in interdendritic regions and on the grain boundaries were established. Composition of boride phase was found to be (Ni 0.32Cr 0.22Nb 0.14Mo 0.11Co 0.13W 0.02Al 0.02Ti 0.01)B 0.67, which is of M 3B 2 type. Formation of the non-equilibrium γ′–γ eutectic in interdendritic regions causes microliquation of Cr, Nb, Mo, Co, W and B in the crown of γ′–γ eutectic that results in formation of boride particles in the crown of γ′–γ eutectic. Carbon was found mainly forming carbide particles in interdendritic regions. Composition of carbide particles was found by the XRSMA as (Nb 0.61Ti 0.22Ni 0.10Cr 0.02W 0.01Hf 0.01)C.