Effect of Weld Metal Microstructure on the Fatigue and Corrosion-Fatigue Properties of GTA-Welded 304 Stainless Steel

In this research, two different filler metals, ERNiCrMo-3 and ER309L, were used for developing different microstructure, austenite (γ) and austenite and ferrite (γδ) in the weld metal and fatigue properties of welded samples were evaluated in the air and sea water environments. Microstructural studies indicated a good agreement between predicted microstructures via schiffler diagram and metallographic studies. Evaluation of fatigue properties in the air and sea water environments revealed the austenitic weld metal, like base metal microstructure, improved the fatigue strength of welded samples. Fractographic studies and FESEM-EDS analysis showed more ductile fracture of welded samples by using ERNiCrMo-3, formation of more uniform and deeper dimples in the final zone of fatigue fracture, than that of welded samples by using ER309L. Furthermore, unlike dimple formation centers in welded samples by using ER309L, Mo-Ti rich intermetallics caused formation of dimples in the welded sampled via ERNiCrMo-3.