Microstructural and mechanical investigation of dissimilar joint of AISI 304L and UNS C70600 via pulsed gas tungsten arc welding

Abstract

In this paper, the microstructure and mechanical properties of dissimilar welding of AISI 304 L austenitic stainless steel and UNS C70600 copper-nickel alloy have been investigated. For this purpose, Tungsten-Gas Arc welding method with both pulse and non-pulse currenst and ERNiCr-3 welding wire was applied. The microstructures of different regions were evaluated using optical microscope and scanning electron microscope. The result showed that ERNiCr-3 filler metal has fully austenitic microstructure in both pulse and non-pulse modes, but in pulse mode, dendrites were found to be smaller than non-pulse mode. In both interfaces, between base and weld metal, partially melting zone was illustrated. Increasing grain size was more intense in the HAZ region of the copper-nickel base metal. In the tensile test, all samples were ruptured from the HAZ region of copper-nickel alloy with ductile fracture mode. According to the result of tensile test, tensile strength of the welded sample in pulse and non-pulse modes was 235 MPa and 268 MPa, respectively. The results of the hardness test showed that the hardness of the weld region in the pulse mode (75.3HRB) was slightly higher than hardness in non-pulse mode (71.6HBR). Minimum hardness number (17HRB) was related to the UNS C70600 alloy.