High-current gas tungsten arc welding of Ni-base superalloy Haynes 282: correlating heat input with weld profile, microstructure, hardness and indentation size effect

Increasing the linear heat input during high-current gas tungsten arc welding (GTAW) of Haynes 282 leads to a progressive change from conduction mode welding to one with keyhole formation. It coincides with changes in the melt pool geometry and spatial variation of microhardness in the heat affected zone (HAZ). The latter originates from heat input dependent changes in the heating/cooling rates which alter the dissolution/re-precipitation characteristics of fine grain boundary carbides. The load-dependence of microhardness of all weld zones is shown to follow a type-I indentation size effect (ISE). Nanoindentation experiments are carried out to quantify the ISE and extract local plastic properties, demonstrating a qualitatively different mechanical response of the FZ compared to the base metal and the HAZ.