Effect of low-energy pulse current on the microstructure and properties of a Ni-based superalloy

Abstract

This study proposes a low-energy pulse current (LEPC) rapid solution treatment method, which can dissolve more primary γ′ phase in a shorter time and effectively suppress abnormal growth of grain, thereby successfully achieving microstructure optimization and property enhancement. The microstructure analysis showed that, compared with the 62.5% dissolution rate of the standard traditional solution treatment (1100 ℃/4 h), LEPC achieved an 88.9% dissolution of the primary γ′ phase in just 5 minutes at the same temperature. Furthermore, due to the rapidity of the LEPC treatment and its “targeted dissolution effect” on the γ′ phase, excessive growth of grain was effectively suppressed, resulting in grain sizes comparable to those obtained with traditional solution treatment. Mechanical property testing indicated that the alloy treated with LEPC had a hardness of 531 HV at room temperature, while the yield strength, tensile strength, and maximum strain reached 993 MPa, 1030 MPa, and 5.1% at the service temperature (750°C). Compared to the standard traditional solution treatment, these properties were improved by 10.4%, 11.1%, 10.4%, and 17.5%, respectively. Finally, theoretical calculations revealed that the non-thermal effects of LEPC reduced the dissolution-free energy by approximately 49.4 kJ/mol and increased the diffusion coefficient by about 76 times, which was the fundamental reason for the accelerated dissolution of the primary γ' phase.