Investigation of microstructure, mechanical properties and corrosion resistance of the joint between X70 low alloy steel and 2304 stainless steel by tungsten-gas arc welding

In this study, X70 low-alloy steel was jointed to the 2304 duplex stainless steel by tungsten-gas arc welding (GTAW) process and using ER316L filler metal. Each of the parameters of background current, maximum current, frequency and percentage of pulse on time were changed in three levels. Microstructure, mechanical properties (tensile, impact, hardness), fracture surfaces and corrosion resistance of weld metal for different samples were investigated. Based on the optical microscope observations the weld metal microstructure includes the predominant phase of austenite along with skeletal ferrite. Although in the tensile test due to the rupture of the samples from the 2304 stainless steel side the tensile properties of the samples are similar to each other, but the increase of background current, decrease of maximum current, increase of frequency and decrease of percentage of pulse on time increases the hardness and toughness of the joint. The scanning electron microscope observations of the weld metal fracture surface showed that the fracture mode is mixed (soft/brittle). The pulsed welding improves the corrosion resistance of the weld metal in comparison with the direct current.