铜电极表面电火花沉积TiB2/TiC复层涂层的微观结构及成因

采用电火花沉积工艺将烧结二硼化钛和碳化钛涂覆到铜电极表面形成TiB2/TiC复层涂层,通过扫描电镜(SEM)结合能谱分析研究涂层和界面的微观结构及成分。结果表明,涂层电极横截面分为多个区域,涂层内有裂纹,与基体无明显分层;基体热影响区出现细晶和柱状晶,主要化学成分为铜。细晶区的形成主要是电火花放电过程中快速冷凝时高的形核率所致,并可能与电火花放电的脉冲能量有关。柱状晶区主要是因单向散热引起晶体的定向生长而产生的。

Microstructure and formation mechanism of TiB2/TiC bilaminar coatings deposited on copper electrode surface by electrosparking

TiB2 and TiC bilaminar coatings were deposited by electrosparking onto the surface of copper alloy electrodes used for spot welding of zinc-coated steel.The coating structure and compositions were characterized by SEM and XRD.The results suggest that the TiB2 and TiC bilaminar coatings consist of multi-layers,cracks appear in the top surface of the coating and no delamination is observed at the interface of the coating and the heat affected zone(HAZ),whereas fine and columnar crystals appear in the HAZ with copper as the major composition.The formation of fine crystal results from the high nucleation rate of substrate during rapid solidation,and may relate to pulse energy of electrospark as well.The oriented growth of the fine crystal owing to unidirectional heat dispersing forms the columnar crystal.