Simultaneous optimization of weld bead geometry and weld strength during gas tungsten arc welding of Inconel 825 strips using desirability function coupled with grey relational analysis (DF-GRA)

Abstract

Inconel 825 is a prominent Ni-Fe-Cr based superalloy finds application in aerospace, defense, automotive, nuclear, marine industries. This article investigates ‘weld strength’ and ‘weld bead characteristics’ of Inconel 825 weld specimens welded using the gas tungsten arc welding (GTAW) process. The welding speed (V), welding current (I), gas flow rate (GFR) and arc length (N) are considered as GTAW parameter and their effect has been examined on the weld characteristics. Welding speed and welding current has been identified as the most influential factor on process characteristics. Increased heat input from increased welding current and decreased welding speed initially improves weldment penetration (P) and ultimate tensile strength (UTS). However, at the highest heat input condition, the formation of root cracks is observed, resulting in nominal weld strength deterioration. To obtain a favorable parameters setting that satisfies both the criterion simultaneously i.e. maximizing weld strength for optimum weld bead geometry, a hybrid optimization approach employing desirability function coupled with grey relational analysis (DF-GRA) is proposed. Satisfying all the objectives simultaneously, the approach provides an optimum weld parameters setting of (I 3−V 1−GFR 2−N 1:120 A−180 mm min−1−9 l/min−2 mm) resulting an improvement of 4.15% in penetration (P), 5.12% in front width (W), 19.74% in reinforcement (R), 1.29% in ultimate tensile strength (UTS), and 2.9% in percentage elongation (%E) on validation. Upon comparison, the algorithm outperforms the optimization results of both DF and GRA approach suggesting its robust nature. Overall, the DF-GRA hybrid approach is found simple and effective that includes the ignored robustness of the desirability approach.