Novel binder for NbC-based cemented carbides prepared by spark plasma sintering

Abstract

The most advanced alternative to replace cobalt in cemented carbides is alloys based on the Fe-Ni-Co system due to their similar or superior properties to conventional Co-binder. However, recently, successful cermet alloys with Fe-Ni-Nb as a binder have been reported. In this work, cemented carbides NbC-10% wt Fe-Ni-Nb were prepared by solid state pulsed electrical current sintering (PECS), also known as spark plasma sintering (SPS), for 5 min, 40 MPa at temperatures 1280°C, 1300°C and 1350°C. The samples produced were investigated focusing on their structure, mechanical and thermal properties. All samples showed an increase in NbC crystallite size and n-phase formation. The processed NbC-FeNiNb cermet presented good densification and hardness of approximately 1726 HV30, fracture toughness 12.5 ± 0.1 MPa.m1/2, Young's modulus 385 ± 4 GPa, which is shown as a viable alternative composite in applications cemented carbide such as cutting tools. However, these cermets could have even better properties, eliminating the intermetallic phase present in the matrix and decreasing its particle size. TG and DSC analysis confirmed the formation of a liquid phase and more carbides contributing to the mechanical properties of the composite. The thermal properties showed that the thermal diffusivity and thermal conductivity for NbC-FeNiNb was lower than for WC-Co carbide.