Defects Modification of TiB₂–TiC Composite Phase Coating Resistance Spot Welding Electrode via Friction Stir Processing

Abstract

In this work, surface modification was carried out using friction stir processing (FSP) technique to investigate on the electro-spark deposited (ESD) TiB₂–TiC coated electrode caps for resistance spot welding. The morphology, microstructure, phase composition and resulting mechanical properties of the electrode were examined and characterized. The results showed that treatment with FSP significantly reduced the number of cracks formed on TiB₂–TiC coating and enhanced the interfacial binding force between the TiB₂–TiC coating and the substrate. The micro-hardness and bonding strength of the TiB₂–TiC coating were also improved and the heat affected zone (HAZ) of the substrate disappeared due to the influence of FSP. The improvement mechanism are attributed to a decrease in the number of coating cracks, improved delamination, and refined substrate grains size near the interface.