Effects of boron or carbon on solidification behavior of Co-Ni-Al-W-based superalloys

Abstract

Effects of B or C on the solidification microstructures of Co-Ni-Al-W-based superalloys are studied. The addition of B from 0 to 0.50 at% significantly decreases the solidus temperature from 1270 to 1249 °C and enlarges the solidification temperature range from 87 to 96 °C. The addition of B increases the solidification segregation of Mo, Ta, Ti, Nb, Cr and W, and promotes the formation of Laves phase and (γ + γ′)e eutectic, but suppresses the formation of β phase. M3B2 forms at the final solidification stage when the content of B reaches 0.10 at%. The addition of C reduces the segregation of Ta, Ti, Nb, W; suppresses the formation of the Laves phase, (γ + γ′)e eutectic and β phase. Dot-shaped and rod-shaped MC carbides form when the content of C reaches 0.10 at%, and MC carbides can refine the primary dendrites arm spacing. The above results provide experimental basis for the composition design and heat treatment optimization of the Co-Ni-Al-W-based superalloys.