Electrode life evaluation for varied electrode material composition and geometry in resistance spot welding of aluminum alloys

This study addresses the effects of alloying elements and radius curvature of the electrode on the degradation behavior during resistance spot welding (RSW) of A6451-T4. The importance of electrode characteristics is emphasised according to changes in hardness and electrical conductivity by electrode composition and radius curvature. The electrodes that were alloyed with Ag, Cr, and Be with varied radii were used in this study. The endurance limit of electrode was investigated by producing 100 welds with the optimised welding parameters. In addition to mechanical characterisation of the weld samples, comprehensive analyses of the electrode surfaces were carried out by carbon imprint, 3D digital microscope profiling, and electron microscopy. A computational analysis using the commercialised SORPAS software was also conducted to analyse heat generation according to the electrode characteristics. The results demonstrate that the electrode degradation proceeds by four discrete stages: aluminum pick-up and alloying, contact area increase, pitting, and cavitation. It was confirmed that load-bearing capacity and nugget diameter also change in proportion to the generated heat between the electrode and welded sheet. Among the physical properties of the electrode, the hardness and electrical conductivity most influence the electrode wearing behavior.