Joining of polyamide material by friction stir spot welding

This study investigates the effects of Friction Stir Spot Welding (FSSW) on the mechanical, thermal, and microstructural properties of PA6, a widely used engineering plastic. PA6 plates (5 mm thick, 30 mm wide, 150 mm long) were welded using an Optimum BF20L milling machine, examining key parameters: rotational speed (762, 1146, 1560 rpm), pin diameter (M10, M12), and dwell time (15 s, 60 s). A full factorial design was employed to analyze their effects. Rotational speed emerged as the most significant factor influencing tensile strength, with an optimal speed of 1146 rpm yielding 72.4 MPa. Dwell time also played a major role, improving flexural strength by 56.5% as it increased from 15 to 60 seconds (40.6 MPa to 63.6 MPa). Although pin diameter had limited influence on tensile performance, larger pins (M12) promoted higher crystallinity (up to 26.77%) and better thermal distribution. The specimen PA6-09 (1146 rpm, M10, 60 s) stands out as the most balanced and optimal sample in terms of mechanical, thermal, and morphological properties, demonstrating high strength, high fracture resistance, and acceptable ductility. In addition, PA6-10 also exhibits superior performance in terms of tensile and fracture strength, indicating that the specimen possesses a balanced and tough structure. The SEM micrographs are observed to be consistent with the mechanical and thermal data. These findings highlight the potential of friction stir spot welding (FSSW) to enhance the performance characteristics of PA6, thereby rendering it a promising joining technique for high-performance applications in the automotive, aerospace, and electronics industries.