Microstructure and high-temperature oxidation behaviour of AISI 304L stainless steel welds produced by gas tungsten arc welding using the Ar–N ₂ –H ₂ shielding gas

Abstract

Abstract In the present work, we added 1.5 and 5% v/v hydrogen gas to an Ar–7% N 2 shielding gas for the gas tungsten arc welding of AISI 304L stainless steel to investigate its effect on the weld microstructure and oxidation rate. By using Ar–7% N 2 as a shielding gas, the weld metal contained 2.1% of delta ferrite in an austenite matrix. The addition of 1.5 and 5% hydrogen gas in the shielding gas provided the welds with a higher ratio of delta ferrite to austenite matrix, ranging from 3.8 to 6.9%, thus helping reduce the risk of hot cracks. The weld metals were further subjected to an oxidation test in synthetic air at 700°C, and the parabolic oxidation kinetics were observed. The parabolic rate constant of the weld metal produced using the Ar–7% N 2 shielding gas was 5.44 × 10 –13 g 2 cm –4 s –1 . When 1.5 and 5% hydrogen gas was added to the Ar–7% N 2 shielding gas, the rate constants were reduced to 64% and 24% of that of the weld produced using only Ar–7% N 2 shielding gas, indicating the promising role of the presence of hydrogen in the Ar–7% N 2 shielding gas on improving the weld metal oxidation resistance for high temperature services.