Study of the high temperature oxidation and Kirkendall porosity in dissimilar welding joints between FE-CR-AL alloy and stainless steel AISI 310 after isothermal heat treatment at 1150 °C in air

Abstract

Dissimilar welded joints of Fe-Cr-Al alloy (23Cr-7Al) and AISI 310 austenitic stainless steel (25Cr-20Ni) were studied and characterized, before and after the isothermal heat treatment (IHT) of oxidation at 1150 °C for 936 h in air. The Fe-Cr-Al alloy was used as the welding consumable and the welding process used was gas-shielded tungsten arc welding (GTAW) with currents of 60, 80 and 130 amps, and welding speed 1, 1.1 and 1.3 mm/s. In the heat treated specimens, pore formation was observed as well as significant variations of Al contents in all-welded metals and formation of protective layer of alumina-Al2O3 on the oxidized surfaces particularly in the sample 1, welded at 60 amps and welding speed of 1 mm/s, that showed higher pore index and a greater deflection in the decrease of the Al content. The formation of Kirkendall pores occur due to the rapid diffusion of the aluminum from the all weld metals to the AISI 310 austenitic stainless steel, as was detected by the sample 1 mainly and especially by identifying the chromium content of the dissimilar alloy and the stainless steel. Keywords: GTAW, Kirkendall porosity, Alloys Fe-Cr-Al, AISI 310