Structural Integrity Assessment of Inconel 617/P92 Steel Dissimilar Welds Produced Using the Shielded Metal Arc Welding Process

The present investigation is conducted to study the effect of the varying filler composition on microstructure and mechanical properties of the dissimilar metal welds of heat-resistant P92 steel and Ni-based superalloy Inconel 617 used for producing the boiler components in advanced ultrasupercritical (AUSC) power units. The dissimilar joint is prepared using the shielded metal arc welding (SMAW) technique using the electrode metals of Inconel 617 (ENiCrCoMo-1), Inconel 625 (ENiCrMo-3), and Inconel 82 (ENiCrFe-3). All the welds were made with the same welding parameters. It was witnessed from macrostructure and microstructural characterization that there was no evidence of cracks in weldments obtained by Inconel fillers. The EDS observation of the weld showed the presence of Ti(C, N) and NbC in ENiCrFe-3 weld, NbC and laves phase ENiCrMo-3 weld and Cr and Mo-rich phases (M23C6 and Mo6C) in ENiCrCoMo-1 weld. The room temperature tensile test showed the maximum (664 ± 11 MPa) and minimum (590 ± 10 MPa) ultimate tensile strength for the ENiCrCoMo-1 weld and ENiCrFe-3 weld, respectively. However, the ENiCrCoMo-1 weld showed failure from P92 BM, while in the other two welds, failure occurred in the weld metal. The hardness of the weld metal varied from top to root area as well as in transverse direction for each weld joint. The maximum hardness of the weld was 297 ± 12 HV for the ENiCrMo-3 weld and the minimum was 219 ± 9 HV for the ENiCrFe-3 weld. The microstructural characterization and mechanical testing confirmed that ENiCrCoMo-1 filler was the best choice among all the fillers for making the dissimilar joint of P92 and Inconel 617.