Effect of pulsed electric-current on densification behavior of bonded interlayer of oxide-dispersion-strengthened superalloys joint

In order to clarify the rapid densification behavior during pulsed electric-current sintering (PECS) bonding process, the kinetics of densification behaviors were investigated by,comparing PECS bonding process with direct electric-current sintering (DECS) and hot pressing (HP) bonding processes. The ODS alloy powders of MA956 (Fe based alloy) and MA754 (Ni based alloy) were packed between bonding specimens as insert material. Bonding experiments showed that the completion time for fully densification in bonded interlayer on PECS bonding was about 1/2-1/3 times as short as those on DECS and HP bondings under the same conditions. The kinetics of the densification of bonded interlayer during all the three bonding processes could be expressed by a sequential kinetic equations of the grain boundary diffusion creep and volume diffusion. The densification rates controlled by creep were increased in order, PECS > DECS > HP. These results indicated that the rapid densification in PECS was attributed to the local rise in temperature on the neck region by joule heat generation.