Binder Effect on Microstructure and Mechanical Properties of NbC Cermet

Abstract

Niobium Carbide (NbC) has emerged as a potential candidate for the replacement of Tungsten Carbide – Cobalt (WC-Co) cermet. Over the past decade, NbC has attracted a lot of attention due to its promising mechanical properties. Modification of binder that can lead to enhanced mechanical properties of NbC with reduced material cost is the most desirable path. In this thesis, Iron was selected as an alloying element in the Nickel binder of NbC. Iron being nontoxic and cheap, will serve as suitable candidate. High Vacuum Liquid Phase Sintering Technique was used for the fabrication of NbC-FeNi cermet. The XRD analysis showed the presence of the taenite phase of FeNi alloy. A significant change in the crystal structures of binder was observed along different compositions of FeNi alloy through major shifts in the XRD peaks. The SEM analysis of the microstructure showed that with the addition of Iron in the Nickel, NbC grain growth was restricted due to the lower solubility of NbC in Iron. A decreasing trend of NbC grain size over the increasing addition of Iron content in Nickel binder is observed. There was a significant increase of 36% in the hardness of NbC-FeNi cermet with a moderate fracture toughness of 8.54 (𝐾𝐼𝐶). The NbC-FeNi cermet recorded a highest hardness value of 1450 HV30 while the NbC-Ni cermet recorded the lowest hardness value of 1105 HV30 in this study. NbC-FeNi cermet also showed the improved flexural strength of 680 MPa, while NbC-Ni had the lowest Flexural Strength of 550 MPa but had the highest strain. The performance of the NbC-FeNi cermet showed promising properties as a cutting tool. The NbC-FeNi has the potential to replace WC-Co and NbC-Ni cermet in the industry. This novel binder can open a new era in the field of cermet by inhibiting carbide grain growth.