Effect Of Widmanstatten Eta Phase On Tensile Shear Strength Of Resistance Spot Welding Joints Of A286 Superalloy

This work aims to study the effect of Widmanstatten eta phase on tensile shear strength (TSS) of resistance spot welding joints (RSW) of A286 superalloy subjected to post-weld high temperature aging treatment. The tensile shear test specimens were welded in the solution treated condition, and then subjected to six different post-weld aging treatments (at an aging temperature of 840 degrees C for six different aging times). The as-cast dendritic microstructure of the weld nugget and the austenite equiaxed-grain microstructure of the base metal have a different response to the post-weld high temperature aging treatment. Growth of Widmanstatten eta phase in the weld nugget is faster than in the base metal. While in the base metal the Widmanstatten eta phase precipitates into the grain, in the weld nugget precipitates at the interdendritic region because of the segregation of Ti towards the last-to-solidify interdendritic regions (studied by performing SEM/EDX analysis). Although the hardness increases with the presence of Widmanstatten eta phase, the increase in hardness does not necessarily imply an increase in the experimental TSS.