Strain-rate hardening behavior of superalloy IN718

In order to produce superior feed stock for the forging of turbine disks and other components, it is necessary to better understand the effect of deformation parameters on the hot deformation behavior of IN718 during thermomechanical processing. Superalloy IN718 is a strain-rate sensitive material. In the present work, isothermal constant speed compression tests of superalloy IN718 were conducted using a computer-controlled MTS machine at temperatures of from 960 to 1040 degrees C, with initial strain rates of from 0.001 to 1.0s(-1), to engineering strains of from 0.1 to 0.7. The variation of flow stress with initial strain rate was analyzed in the paper. It was found that there was an obvious power-law relationship between how stress and initial strain rate. From the results of these tests, a mathematical model showing the strain-rate hardening behavior of superalloy IN718 at elevated temperatures was developed. At the same time, the flow stress calculated from the model was compared with experimental results and the effect of deformation parameters on the related coefficients was analyzed. (C) 1997 Elsevier Science S.A.