On microstructural and mechanical properties of 21-4-N nitronic steel joint developed using microwave energy

In the current experimental work, an effort has been made to explore the feasibility of fusion joints of 21-4-N nitronic steel employing microwave heating. These fusion joints were developed inside a domestic microwave applicator operating at 900 W. Microwave energy was used to fabricate the joints in hybrid heating mode by converting electromagnetic energy into heat at 2.45 GHz. Charcoal and SiC plates were used as susceptor and separator, respectively, and nickel powder was used as the interface material. The developed joints were characterized for their microstructural and mechanical properties. The microstructures indicate a complete fusion of nickel interfacing powder with the faying surfaces. XRD results show the formation of metallic nitrides and carbide phases (Cr2N, Fe3N, and Fe2C) and the FeNi phase at the weld zone. Furthermore, the observed average tensile strength of the fusion joints was approximately 61% of base metal. The reduction in the stress and elongation compared to the base metal were 38.67% and 12.68%, respectively. The average microhardness of the microwave joints was monitored as 407 ± 69.27 HV. The results indicate the feasibility of fusion joints of nitronic steel using microwave energy.