Enhanced interfacial strength and cutting performance of Fe-based diamond composites via Ti-coating induced interfacial optimization

To address the insufficient strength and wear resistance of Fe-based diamond composites resulting from poor diamond–matrix interfacial wettability and the formation of brittle Fe–C reaction zones, this study used Ti-coated diamonds to optimize the interfacial structure. Fe-based diamond composites with uncoated diamonds (FDC) and Ti-coated diamonds (Ti-FDC) were prepared by hot-press sintering. A systematic comparison was conducted on their phase composition, densification degree, hardness, flexural strength, and wear ratio at sintering temperatures ranging from 850 to 950 °C. The results indicate that Ti-FDC exhibited a higher degree of densification and hardness at all temperatures. At 950 °C, the flexural strength of Ti-FDC reached 882 MPa, approximately 14% higher than that of FDC (776 MPa), while the wear ratio reached 1203, representing a 44% improvement compared with FDC (833). After wear testing, the average diamond protrusion height in Ti-FDC was approximately 32% higher than that in the uncoated sample, with the diamonds retaining sharp edges and intact surfaces. Interfacial characterization revealed the formation of a multilayer graded interfacial structure of “diamond/TiC/Ti/Ti-rich solid solution/Fe-based matrix” during sintering, thereby enabling reactive wetting and stable chemical bonding. This interfacial architecture effectively suppressed the formation of brittle Fe–C reaction zones, mitigated residual thermal stress, and reduced interfacial pores and microcracks. This study provides an effective strategy for the interfacial design of Fe-based diamond composites used in impregnated diamond bits.