Weld performance of joints using stirring pins coated with high-entropy alloy carbonitride coating in friction stir welding of SiCp/Al composites

Friction stir welding (FSW) of silicon carbide particle-reinforced aluminum matrix (SiCp/Al) composites faces significant challenges due to severe tool wear caused by the hard SiC particles, which ultimately degrades joint quality. Previously, high-entropy alloy carbonitride (HEANC) coated tools were successfully fabricated, and the wear mechanism was studied. However, the impact of the HEANC coated tools on joint quality is still unclear. In this paper, FSW of dissimilar materials (SiCp/6092Al composite and 6061Al alloy) was performed using stirring pins deposited with HEANC coatings. The effects of the coatings on the microstructure, mechanical properties, and corrosion resistance of the postweld joints were analyzed. The results show that when the C target power is 200 W, the coating exhibits higher hardness, a lower friction coefficient, and better wear resistance. All coated stirring tools successfully achieved dissimilar material welding. The joint welded with the HEANC200-coated stirring pin has the smallest grain size, and the average hardness of the weld nugget zone is 20.37% higher than that of the joint welded with the uncoated stirring pin. Its tensile strength reaches 198.48 MPa, and the fracture behavior shows typical ductile fracture characteristics. Electrochemical tests indicate that the corrosion current density of the joint welded with the HEANC coated pin decreases, with a slight improvement in corrosion resistance.