点焊电极表面超声波辅助电火花原位沉积鳞片状ZrB2-TiB2复相涂层及涂层改性的研究

With the development of automotive lightweight, the applications of aluminum alloy on car body have become more and more popular. In order to obtain good welding quality, a large welding current and short welding time in the resistance spot welding of aluminum alloy are usually used, which in turn results in the serious reduction of spot welding electrode life. In order to solve this problem, this project will carry out the study on the scalelike ZrB2-TiB2 double-phases coating on welding electrode surface by ultrasonic- assisted electrospark in situ deposition and modification of coating. The emphasis is on the discharging electrode ingredients in electrospark deposition and the fabrication technology, the formation process and mechanism of scalelike double-phases coating in ultrasonic-assisted electric sparking deposition method will be studied, the mechanism of modification of scalelike ZrB2-TiB2 double-phases coating by ultrasonic friction stir surface treatment will be carried out. The effects of discharging electrode ingredients and fabrication technology, the technology of ultrasonic-assisted electrospark in situ deposition, and the technology of ultrasonic friction stir surface treatment on properties of the scalelike double-phases coating will be researched. The mechanism of scalelike double-phases coating improving the welding electrode life will also be studied. Finally, the technology of scalelike ZrB2-TiB2 double-phases coating by ultrasonic-assisted electrospark in situ deposition and modification of coating by ultrasonic friction stir surface treatment will be obtained. These studies not only will provide a new process and a new discharge electrode material for electrospark deposition to improve the surface properties of copper alloys，but also have the innovations.

随着汽车轻量化的发展，铝合金在车身上的应用越来越多。由于在点焊铝合金时采用大的点焊电流和较短的焊接时间才能保证接头性能，这使点焊电极寿命大大降低。本项目针对这一问题开展点焊电极表面超声波辅助电火花原位沉积鳞片状ZrB2-TiB2复相涂层及涂层改性的研究，重点研究电火花原位沉积用放电电极的成分及制造工艺，研究超声波辅助电火花原位沉积鳞片状复相涂层的工艺和机理；研究复相涂层的超声波搅拌摩擦表面改性机制；研究放电电极的成分及制造工艺、超声波辅助电火花原位沉积工艺、超声波搅拌摩擦表面改性处理工艺对点焊电极表面鳞片状复相涂层性能的影响；研究鳞片状复相涂层提高点焊电极寿命的机理；最后预期获得点焊电极表面超声波辅助电火花原位沉积鳞片状ZrB2-TiB2复相涂层的工艺及涂层的超声波搅拌摩擦表面改性处理工艺。这些研究不仅可为电火花沉积提高铜合金表面性能提供新的工艺和新的放电电极,而且也具有创新性。

为提高点焊电极使用寿命，本项目通过超声辅助电火花沉积工艺在点焊电极表面原位沉积制备了ZrB2-TiB2复相涂层。项目研究了新的电火花原位沉积鳞片状ZrB2-TiB2 复相涂层用放电电极，并建立成分、机械合金化工艺及冷成型工艺和放电电极性能之间的关系；研究了一种新的点焊电极表面超声波辅助电火花原位沉积鳞片状ZrB2-TiB2 复相涂层的方法，并建立超声波辅助电火花原位沉积工艺与鳞片状ZrB2-TiB2 复相涂层性能之间的关系；探讨了一种涂层改性的新方法──超声波搅拌摩擦表面改性处理，并开发了两套设备；涂层电极寿命达到预期，是无涂层电极寿命的6倍。最后，重点探讨了涂层电极点焊过程中的寿命提高机理及失效原因，通过实验发现，点焊电极主要失效机制包括塑性变形、合金化 。涂层电极寿命提高的主要原因是涂层能改善点焊电极表面硬度、减缓点焊电极端部塑性变形以及电极表面合金化。涂层与基体间较差的结合力，是导致ZrB2-TiB2涂层电极寿命低于ZrB2-TiB2/Ni涂层电极寿命之主要因素。对于无涂层电极、ZrB2-TiB2涂层电极，电极塑性变形、合金化是其失效主要形式；对于ZrB2-TiB2/Ni涂层电极，涂层作用一直持续至电极失效，电极失效形式主要表现为塑性变形。达到了预期目标. 项目资助发表SCI/EI收录论文12 篇，核心论文9篇，授权发明专利5项，出版专著一部；培养博士研究生1名，硕士研究生3名，在读硕士研究生1名；项目投入经费85万元，累计支出77.0206万元，结余7.9794万元，剩余经费将用于本项目相关研究。