目的 了解TiB2-ZrB2/Ni涂层电极点焊镀锌钢板时的失效机理。方法 通过扫描电镜（SEM）、X射线衍射仪（XRD）、显微硬度测试等表征方法，研究TiB2-ZrB2/Ni涂层点焊电极点焊镀锌钢板时表面结构、物相及性能的变化。结果 TiB2-ZrB2/Ni涂层电极对提高点焊电极寿命有很大帮助，点焊电极寿命可提高5倍左右。涂层使点焊电极表面的硬度得以明显提高，减缓了点焊电极端部塑性变形的进程。ZrB2-TiB2/Ni涂层在一定程度上减缓了钢板镀层与点焊电极产生合金化反应的进程。结论 ZrB2-TiB2/Ni涂层电极由于具有一定的塑性，点焊过程中涂层不会出现完全脱落现象。涂层作用一直持续至电极失效，电极失效的形式主要表现为塑性变形。

The work aims to reveal failure mechanism of electrodes with TiB2-ZrB2/Ni coatings for spot welding galvanized steel sheet. Changes in surface structure, phase and properties of the coatings for spot welding galvanized steel sheet were characterized with scanning electron microscopy, X-ray diffractometer and microhardness test, respectively. Applying TiB2-ZrB2/Ni coatings to electrodes could significantly improve service life of spot-welding electrodes by nearly 5 times. Surface hardness of electrodes was obviously increased by the ZrB2-TiB2/Ni coatings, which slowed down plastic deformation on tips of coated elec?trodes. In addition, the ZrB2-TiB2/Ni coatings could mitigate alloying reaction between steel sheet coatings and spot-welding electrodes to some extent. The coatings will not drop off completely during the process of spot welding as ZrB2-TiB2/Ni-coated electrodes are of certain plasticity. The coatings acts until the electrodes fail, and primary form of electrode failure is plastic deformation.