Effect of milling time and sintering temperature on the microstructure and binder distribution of spark plasma sintered NbC-Ni cermets

Niobium carbide (NbC) based cermets are emerging as strong contenders to replace conventional tungsten carbide (WC) based cermets for applications involving abrasion and wear resistance due to their superior mechanical, physical, and chemical properties. NbC cermets with various binders have been explored in literature and nickel has emerged as a promising candidate binder material. Mechanical mixing (MM) followed by spark plasma sintering (SPS) has been shown to be one of the effective methods to synthesize NbC-Ni cermets. However, the effect of certain crucial process parameters during the MM + SPS process on the end product have not been established. To address this, the present study reports the effect of ball milling time and the effect of sintering temperature on the microstructure, binder distribution, hardness, and indentation fracture toughness of NbC - 16 vol% Ni cermets synthesized using MM + SPS. Insufficient milling time resulted in inhomogeneous binder distribution in the consolidated cermets and sintering above a certain temperature resulted in complete loss of binder. Therefore, the combination of sufficient milling time and an appropriate sintering temperature was essential to obtain a consolidated cermet with homogeneous microstructure and uniform mechanical properties.