Hot Deformation Behavior of GH738 for A-USC Turbine Blades

The hot deformation characteristics of GH738 superalloy over the temperature range of 1000 °C to 1200 °C and strain range of 0.01 s−1 to 10.0 s−1 under a strain of 1.0 s−1 were investigated through hot compression tests with a Gleeble-1500 simulation machine. The flow stress reached peak value before flow softening occurred. The average apparent activation energy (Q) of GH738 was calculated to be 430 kJ/mol, and the stress index (n) is approximately 4.08. The processing map was developed based on flow stress data and dynamic materials model (DMM). The map shows a dynamic recrystallization (DRX) domain in 1050 °C to 1150 °C and 0.01 s−1 to 1.0 s−1 strain rate range with a peak efficiency of 45%, which is considered to be the optimum region for hot working. Moreover, the materials undergo flow instability in the temperature range of 1000 °C to 1050 °C and strain range of 1.0 s−1 to 10.0 s−1, and adiabatic shear bands can be observed in this domain.