Effect of current type on microstructure and corrosion resistance of super duplex stainless steel claddings produced by the gas tungsten arc welding process

In this research, super duplex stainless steel filler metals were clad on high strength low alloy steel substrates by the tungsten arc welding process using pulsed and constant currents. To characterize the pulsed current effect, the phase composition and microstructure of the claddings were compared, and the corrosion behavior of the claddings was evaluated using cyclic polarization, electrochemical impedance spectroscopy and critical pitting temperature measurements. The results showed that the slower cooling rate of the constant current cladding led to a higher total reformed austenite content and better corrosion resistance. It was also found that the formation of thermally-activated secondary austenite did not influence the corrosion behavior significantly. The electrochemical impedance spectroscopy indicated that the passive film formed on the pulsed current cladding was more defective. The constant current cladding also showed ten degree higher critical pitting temperature than the one which was produced by pulsed current.