Metallurgical aspects and electrical resistivity of hardfaced pure copper layers over AISI 347 with cold metal transfer process

Abstract

Pure Copper having excellent electrical conductivity was deposited over AISI 347 substrate using Cold Metal Transfer (CMT) process to obtain quality weld overlays without defects. To improve the electrical conductivity post heat-treatment was performed. The microstructural examination revealed the presence of Cu-FCC and Fe-FCC along with retained delta ferrite at the bi-metallic interface. Also, the existence of bi-phasic spherulites rich in Fe and Cr were noticed in the weld overlay side while Cu spherulites were observed in the AISI 347 substrate adjacent to the bi-metallic interface. Energy Dispersive X-Ray Spectroscopy (EDS) elemental mapping and line scan data confirmed the presence of spherulites due to solid-state diffusion near the interface. The spherulite size was reduced in the heat-treated weld overlays and a small fraction of Cu spherulites were observed in the interface. The microhardness of the as-deposited and heat-treated weld overlays revealed the transition of elements at the bi-metallic interface. Post heat-treatment of Cu weld overlays improved the electrical conductivity significantly in comparison to the as-deposited ones. These electrical measurements suggest that pure Cu weld overlays with sufficient conductivity shall be attained with the CMT process for electrical and power generation applications.