Evolution of Microstructure and Texture in UNS S32750 Super Duplex Stainless Steel Weldments

Super duplex stainless steel (UNS S32750) butt joints were prepared using ER2594 and ER2595 electrodes by shielded metal arc welding (SMAW) process. The heat input used during welding was in the range of 0.75-0.81 kJ/mm. Microstructure and texture across the weldments were investigated using optical microscope, scanning electron microscope, and electron backscattered diffraction. The solidification mode in the fusion zone (FZ) was found to be ferritic, and the microstructure mainly consisted of Widmanstatten austenite (WA), grain boundary austenite (GBA), and inter-granular austenite (IGA). The base metal (BM) had similar to 50% ferrite and 50% austenite. The ferrite proportion changed significantly in FZ and heat-affected zone (HAZ) after welding. Austenite in the BM showed strong Brass ({110} < 112 >), Cu ({112} < 111 >), Goss ({110} < 110 >), and S ({123} < 634 >) components, while ferrite showed strong alpha (RD// < 110 >) and gamma (ND// < 111 >) fibres. The texture of ferrite was stronger than that of austenite. The austenite and ferrite in the FZ (cap pass) obeyed Kurdjumov-Sachs (K-S) orientation relationship. Further, the hardness of ER2595 weldments was found to be higher than that of ER2594 weldments.