摘要
In order to improve the lifespan of spot-welding electrodes used for welding zinc coated steel sheets, titanium diboride was deposited onto their surface after precoating nickel as an intermediate layer. The microstructures and phase compositions of TiB2 and Ni coatings were characterized by SEM and XRD. The coating hardness was measured using a microhardness tester. The results indicate that a satisfactory TiB2 coating is obtained as a result of the intermediate nickel layer acting as a good binder between the TiB2 coating and the copper alloy substrate. Owing to its capacity of deforming, the precoated nickel layer is dense and crack free, while cracks and pores are observed in the TiB2 coating. The hardness of the TiB2/Ni coating decreases with the increase of voltage and capacitance because of the diffusion of copper and nickel and the oxidation of the coating materials. Because of the good thermal and electrical conductivities and high hardness properties of TiB2, the deformation of the electrode with TiB2/Ni coating is reduced and its spot-welding life is by far prolonged than that of the uncoated one.
为了提高镀锌钢板用点焊电极的使用寿命,在铜电极表面涂覆过渡层Ni后沉积了TiB2涂层。通过SEM和XRD分析了Ni和TiB2涂层的物相和微观结构,并测试了其显微硬度。结果表明:由于材料具有良好的塑性,预涂覆的Ni涂层结构致密无裂纹,与基体Cu无分层;而TiB2涂层内存在裂纹和孔洞。通过过渡层Ni将TiB2涂层和基体Cu粘结起来,获得了较理想的涂层。随着电火花放电电容和电压的增加,TiB2的氧化程度增强,Cu和Ni大量扩散进入涂层表面,使TiB2/Ni涂层的硬度降低。由于TiB2良好的导电和导热性能及高的硬度,TiB2/Ni涂层电极在点焊时的塑性变形降低,寿命比无涂层电极和TiC涂层电极得到了明显提高。
基金
Project (50575069) supported by the National Natural Science Foundation of China
