Electrode degradation mechanism during resistance spot welding of zinc coated steel using Cu-TiB2 electrodes

The TiB2 dispersion-reinforced copper-matrix composite used as electrode material in resistance spot welding of zinc coated steels was studied. The service life of the composite electrode reaches 7700 welds, which is 4 times that of the conventional Cu-Cr-Zr electrode. Little gross deformation is observed on the composite electrodes because of the higher thermal strength; therefore, it is believed that wear is the only mechanism for the composite electrode deterioration. However, both wear and plastic deformation are responsible for the large increase in the tip diameter of the Cu-Cr-Zr electrodes. Moreover, the large deformation of the Cu-Cr-Zr electrodes may contribute to the increased wear rate of the tips.