Improving thermal conductivity of a nickel-based alloy through advanced electromagnetic coupling treatment

In this study, in response to the requirement for a higher heat transfer efficiency of the small-scale nuclear power reactors, a novel material treatment method in the form of electromagnetic coupling treatments (EMCT) was studied and applied to improve the thermal properties of a nickel-based austenitic alloy - Alloy 690, often used for the heat transfer tube of the steam generator. The effect of the EMCT on the thermal properties of Alloy 690 was investigated and the evolution of microstructure and texture under the influences of the electromagnetic coupling field was studied. These were compared with that produced by the treatments with electric field only and magnetic field only respectively. The results showed that the thermal conductivity of Alloy 690 could be improved by 17.5% by the EMCT approach. The further study revealed that the migration and annihilation of dislocations and the precipitation of the M23C6 phase are the key factors influencing the changes of the thermal conductivity, and the magnetoplastic and electroplastic effects provide the impetus to the evolution of the microstructure. The proposed and proven electromagnetic coupling treatment technology provides a novel method for improving the thermal conductivity of nickel-based superalloys and the study provides an important technical guidance to the design and research of critical nickel-based alloy components, such as that used in small-scale nuclear power reactors. At the same time, the work reported in this paper demonstrates a new approach that could also be used for the study of the thermal properties of other superalloys.