Difference in hot deformation behavior of a Ni–Fe based superalloy through cast-wrought and additive manufactured processes

Abstract

Traditional cast-wrought superalloys have been challenging in cogging due to element segregation. However, additive manufacturing technology is anticipated as a novel method for producing low-segregation superalloys. A set of isothermal compression tests were conducted on a Ni–Fe based superalloy GH4169 in various processing conditions, including as-cast and as-homogenized alloy produced by triple melting (Alloy TMC and TMH), as well as additive manufactured alloy (Alloy AM). Flow stresses were examined to develop activation energy maps and processing maps. Additionally, microstructure evolutions were observed to investigate the mechanisms of recrystallization nucleation and grains refinement during hot deformation. Under specific deformation conditions, three alloys have developed to varying refinement stages. As Zener-Hollomon parameter Z decreases, the nucleation mechanism shifts from continuous to discontinuous dynamic recrystallization. Alloy TMH exhibits enhanced hot workability compared to TMC, which is attributed to its lower activation energy Q and more limited instability region. Q value of Alloy AM is slightly higher than that of TMH; however, it demonstrates a wider processing window. Utilizing AMed superalloys for hot deformation not only provides advantages in low segregation and fine grains, but also simplifies the process sequences. This is expected to break through the current technical bottleneck associated with higher performance superalloy turbine disks.