Effect of inclusions in joints on mechanical properties of cemented carbide/steel joints

YG8 Carbides and 45 steel were brazed with CuZnMn solder. The influence of inclusions in brazed joint on the mechanical properties of the joint was studied by using the metallographic microscope（ OM）, scanning electron microscopy（ SEM）, energy spectrum analyzer（EDS）, MTS universal mechanical testing machine and other means. The results show that the inclusions in brazed joint are oxides, sulfides,phosphide, silicate, boride etc. A wide range of lamellar tearing and partial dimple were observed in the shear fracture, which indicated that the fracture was ductile brittle mixed fracture. Fe-Co-0, MnO, FeS-MnS, FeP, 2MnO, SiO₂ and other non-metallic inclusions can be easily observed at the crack tip. Because of the high melting point and boiling point of non-metallic inclusions, their coefficient of thermal expansion are different from that of the base metal, it is easy to become the region of crack growth and expansion. The macroscopic performance is the reduction of shear strength.