Performance of Cr 3 C 2 -Ti-DLC coated tools in dissimilar friction stir welding

Friction stir welding (FSW) is an effective joining approach for dissimilar base metals, such as aluminum alloys (AA) and advanced high-strength steels. However, tool degradation during the process can compromise weld quality, shorten tool life, and increase production costs. This study evaluates the performance and durability enhancement of the tool through the FSW of AA6022-T4 and galvanized DP600 steel by applying Cr 3 C 2 -Ti-DLC thin-film coatings on H13 tool steel and WC-10% Co tools. The surface finish quality of the welds was quantitatively evaluated using a 3D white light interferometer, while real-time thermal profiles were captured using an infrared thermography camera. Tool degradation patterns and performance were assessed through optical microscopy, SEM coupled with EDS, and precise weight loss measurements. The uncoated H13 tool exhibited significant degradation, including thread flattening, micro-abrasion, and material pickup. In contrast, the uncoated WC-10% Co tool demonstrated improved wear resistance. The deposition of thin-film surface coatings significantly reduced tool degradation by 26% for H13 and 23% for WC-10% Co tools in comparison with uncoated tools. These findings demonstrate the effectiveness of thin-film surface coatings in improving tool performance and durability, particularly in dissimilar material friction stir welding.