Comparison of spot welding performance and failure analysis of CuNiCoBe and CuCrZr electrodes

The spot-welding performances of galvanized steel were compared between and CuNiCoBe and CuCrZr electrodes. The peeling of electrode surface, the degree of plastic deformation of the end portion and the composition and phases of the surface layer were studied by means of super depth of field microscope, Spectrometer, XRD and so on,and the failure mechanism of electrodes were analyzed. The results had shown that at the same parameters, the life of CuNiCoBe electrode is 3 500 points, which is 1.3 times higher than that of CuCrZr electrode, which mainly caused by the low intensity and hardness of CuCrZr alloy, large possibility to form peeling holes, the large size of plastic deformation and apparent increase of size of electrode tip. The compositions and products of surface layer of CuCrZr electrode is not the same as that of CuNiCoBe electrode.