Synthesis and cutting performance of NiMoCoAlTi high‐entropy alloy‐reinforced Ti(C,N) cermet cutting tool materials

Abstract To enhance the mechanical properties of Ti(C,N)‐based cermets cutting tools for high‐speed cutting applications, this study incorporated five types of metal powders into Ti(C,N) powder, followed by uniform dispersion and high‐energy ball milling. Subsequently, spark plasma sintering was employed to in situ synthesize high‐entropy alloy (HEA)‐toughened Ti(C,N)‐based cermets cutting tools [HEA‐Ti(C,N)]. Compared with the conventional method of directly adding pre‐fabricated HEAs, the in situ generation of HEAs ensured a more uniform distribution of the HEA phase within the ceramic matrix, while also eliminating the need for a separate HEA preparation process. The results indicated that the in situ synthesized NiMoCoAlTi HEA‐reinforced Ti(C,N)‐based cermets exhibited a core‒shell microstructure composed of Ti(C,N)‒(Ti,Mo)(C,N) multiple solid solution. The HEA phase and ceramic matrix exhibited grain boundary anchoring effect, which enhanced interfacial bonding strength and significantly improved flexural strength and fracture toughness. The Vickers hardness, flexural strength, and fracture toughness of the material reached 15.12 ± 0.11 GPa, 1653 ± 21 MPa, and 13.78 ± 0.33 MPa·m 1/2 . Dry cutting test on 40Cr steel revealed that the cutting life of the HEA‐Ti(C,N) tool exceeded 20 000 m, representing a 43.2% improvement over conventional Ti(C,N) cermet tools, with a surface roughness of only 0.89 µm. Analysis indicated that the enhanced cutting performance of the HEA‐Ti(C,N) tools was primarily attributed to grain boundary anchoring effect of the HEA phase and multiple solid solution, which improved mechanical properties. Furthermore, during the cutting test, the surface of the cutting tool was consistently protected by a dense film of metal oxide, which slowed down the wear of the tool and improved microchipping.