Effect of GTAW an‎d pulsed GTAW welding on the mechanical properties, susceptibility to hydrogen embrittlement, an‎d sour corrosion of A105-316L dissimilar joints

11/19/2026 12:00:00 AM

The aim of the present study was to investigate the effect of pulsed GTAW welding variables on the microstructural changes, hydrogen embrittlement, sour corrosion an‎d mechanical properties of A105-316L dissimilar joints. For this purpose, A105-316L dissimilar joints were welded using two types of continuous current (CCGTAW) an‎d pulsed current (PCGTAW) under different conditions, including peak current (Ip), background current (Ib), frequency, an‎d %On time, with ER309L an‎d ER2535 filler metals. Optical microscopy, field emission scanning electron microscopy (FE-SEM) an‎d X-ray diffraction (XRD) were used to analyze the microstructural an‎d phase changes. Also, uniaxial tensile, Charpy impact an‎d Vickers microhardness tests were utilized to eva‎luate the changes in the mechanical properties of the welded joints. Finally, for fractography, after tensile an‎d Charpy impact tests, the fracture surfaces were examined by FE-SEM. To investigate the sour corrosion behavior, open circuit potential an‎d cyclic polarization tests were used in sour oil containing hydrogen sulfide (H2S). Likewise, the hydrogen embrittlement mechanism in the prepared dissimilar joints was eva‎luated by hydrogen charging method (immersion method in NACE TM0284-Solution A) which immediately followed by the slow strain rate tensile test (SSRT). After the SSRT test, FE-SEM was utilized for fractography of fracture surfaces an‎d analyzing the possibility of hydrogen cracking formation at the fracture surface. Microstructural observations demonstrated that the microstructure of the weld metal (WM) is austenitic-ferritic including columnar an‎d coaxial dendrites, so that changing the welding mode from CCGTAW to PCGTAW, an‎d by increasing Ib an‎d decreasing Ip, increasing the pulse frequency from 30 to 90 Hz, an‎d decreasing the %On time from 75 to 50 in the PCGTAW process contributed to a change in the WM microstructure from columnar to coaxial an‎d very fine, an‎d decreased the width of the partially melting zone (PMZ) an‎d heat-affected zone (HAZ). The results of XRD analysis indicated that the dominant phase an‎d the preferred crystal plane of the crystal texture in WM are the austenite phase an‎d the (111) plane, respectively. In the tensile test, all joints prepared from the A105 steel side were fractured with yield strength in the range of 250±8 MPa an‎d a tensile strength in the range of 484±9 MPa, T.El. of 30±2%. The results of microhardness an‎d Charpy impact tests indicated that changing the welding mode from CCGTAW to PCGTAW, increasing Ib an‎d decreasing Ip, increasing pulse frequency an‎d decreasing %On time in the PCGTAW process increased the microhardness value an‎d fracture energy of WM. Fractography of the fracture surfaces of the prepared joints showed that a completely ductile fracture occurred in both tensile an‎d Charpy impact tests. The SSRT results indicated that the use of PCGTAW over CCGTAW increased the susceptibility to hydrogen embrittlement dramatically, with the characteristics of hydrogen blistering an‎d cracking. In SSRT, the welded joint from the HAZ side of A105 steel suffered from a completely brittle fracture. The results of the corrosion tests showed that WM was not susceptible to pitting corrosion, an‎d the use of PCGTAW compared to CCGTAW led to a decrease in the WM corrosion rate in sour environments.

جوشكاريPCGTAW , تردي هيدروژني , اتصال غيرمشابه , خوردگي ترش , تحولات ريزساختاري , خواص مكانيكي , فولاد L316 , فولاد 105A

PCGTAW welding , Hydrogen embrittlement , Dissimilar joint , Sour corrosion , Microstructural changes , Mechanical properties , 316L steel , A105 steel

Masoud Sabzi

Hamid Reza Jafarian, Ali Reza Eivani