Research on microstructure and crack of EBW of cemented carbide and 40CR steel

The microstrutures of the WC-Co/40Cr joint were formed by martensite and η phase. Due to the different spread intensity of the interface elements, the center of the joint got different morphology and the η phase distributed differently in the weld when the welding beam was changed. Two kinds of typical cracks generated under the force of the microstructures and the tensile stress, one was crystalline crack and the other was quenching embrittlement crack. Carbon depleted environment was formed at the interface due to the C element diffusion and η phase will be formed under the appropriate temperature gradient. Mechanical properties of the joints were carried out that average shear strength exceeded 506 MPa. Fracture occured through the carbide heat affected zone, interface, and weld, which present the characteristics of intergranular fracture, quasi cleavage fracture and cleavage fracture features.