LAUSR

Abstract This work investigates the reverse thermodynamic dissolution of the topologically closed-packed (TCP) phases in the deteriorated nickel-based superalloy using the pulsed electric current. The mechanical properties cannot be restored directly by the conventional heat treatment because the dissolution temperature (1130 °C) of the TCP phases is higher than the initial solvation temperature (950 °C) of the γ′ phase. Here it was found that the TCP phases can be selectively dissolved under the pulsed electric current at a relative low temperature (800 °C), and the volume fraction of γ′ phase is unchanged. It means the pulsed processing is a lossless performance regeneration method. The count of TCP phases decreased from 3.49 × 109/m2 to 1.24 × 109/m2, accounting for only 35.5% of the thermal exposure sample. Correspondingly, the mechanical properties change toward the young stage. By the HRTEM, the TCP phases initially interrupted at stacking faults have been observed, and the stacking faults are basically aligned along the (111)TCP direction. Subsequently, the interrupted TCP phases dissolved from both ends to the middle. The solute elements can be rapidly diffused into the γ-matrix and γ′ phase using the high current density regions that caused by conductivity discrepancies.