Design strategies for Fe-based diamond composites with nanocrystalline/amorphous composite interfacial structure for high bending strength

The weak interfacial bonding between Fe and diamond has long been a critical constraint on the performance enhancement of Fe-based diamond composites. In this study, an innovative active Mo2B5/a-BxC coating was pre-coated on the diamond surfaces. During the sintering process of the composite, the coating undergoes an in-situ reaction with Fe, resulting in the formation of a nanocrystalline/amorphous composite interfacial structure between the diamond and the matrix. This unique interface comprises of hard phases (Mo2FeB2, FeMo, and Fe2B) and amorphous carbon layers. The synergistic effect between the nanocrystalline and amorphous phases, along with the controlled diffusion of Fe within the interface, effectively alleviates interfacial stress concentration. Additionally, the amorphous layers suppress crack initiation and facilitate crack deflection, thereby hindering crack propagation along the interface. These multi-mechanism interactions collectively enhance the interfacial bonding between the diamond and the Fe-based matrix. As a result, the composite exhibits exceptional crack propagation resistance and achieves a notable bending strength (919 MPa, a 16.5 % increase compared to composite with uncoated diamonds). This work proposes a novel and effective interface engineering strategy for the design of high-performance Fe-based diamond composites.