Dissimilar Welding Between 1.4742 Ferritic and 310S Austenitic Stainless Steels: Assessment of Oxidation Behaviour

Abstract

In the present work, the isothermal and cyclic oxidation behaviour of the 1.4742 ferritic and 310S austenitic stainless steels together with their dissimilar metal welds was investigated in the air with the humidity of 30 ± 3%. The welding was performed by the gas tungsten arc welding process utilizing ER310, ERNiCr-3, and ER446 filler metals. In the isothermal conditions, all the tested specimens followed the parabolic rate law. The maximum and minimum kp values were related to the 310S-BM, 1.89 × 10−1 mg2 cm−4 h−1, and the 1.4742-BM, 0.03 × 10−2 mg2 cm−4 h−1, respectively. Due to the formation of a dense and thin mono-layer of Cr–Fe–Al spinel ((Cr,Fe,Al)3O4) on the surface of the 1.4742 stainless steel alongside the lowest coefficients of the thermal expansion (CTE), it exhibits a highly satisfying oxidation resistance in both isothermal and cyclic conditions. In the cyclic conditions, except for the 1.4742-BM, the other specimens encountered the oxide scale cracking and spallation. The large CTE mismatch between the underlying 310S-BM, -BMS, and ER310-WM with the multi-layer chromia (Cr2O3) and Cr–Mn spinel ((Cr,Mn)3O4) oxide scale caused extensive spallation and mass loss in cyclic conditions. The ERNiCr-3-W in comparison with the two other weldments, by reducing the thermal expansion mismatch between the adjacent underlying metals and the better oxidation resistance of the nickel-base ERNiCr-3-WM, showed better oxidation resistance in both isothermal and cyclic conditions.