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The present work deals with Niobcarbid (NbC). Strategic reflections on tungsten carbide and more and more stringent toxicological restrictions for cobalt associated for both with spiraling stock market prices have attracted recently some attention for Niobium carbide as a substitute for tungsten carbide in machining.
The aim of the study presented in this paper is to highlight the potential of niobium carbide cutting tool inserts for machining and to compare their performance to commercially available tungsten carbide inserts. In this work, a comparison between a conventional Wc-Co insert and NbC-Co inserts was carried out under hard machining conditions on specimens made of 100Cr6 bearing steel grade (SAE 52100).
The tribological profile of rotating disks made of binder-less niobium carbide (hot-pressed NbC) and cobalt-bonded NbC (NbC-8Co) mated against alumina (99.7%) were determined under unidirectional sliding tests (0.1 m/s to 8.0 m/s; 22°C and 400°C) as well as in oscillation tests (f= 20 Hz, Δx= 0.2 mm, 2/50/98% rel. humidity, n= 105/106 cycles) under un-lubricated (dry) conditions. In addition, the microstructure and mechanical properties of NbC and NbC bonded with 8% cobalt were determined as well. The tribological data obtained were benchmarked with different ceramics, cermets, hard metals and thermally sprayed coatings, where the NbC-8Co presented above 7 m/s the lowest wear rates so far in such a bench mark. NbC and NbC-8Co exhibited low wear rates under dry sliding associated with P·V high load carrying capacity. The tribological profile established revealed a strong position of NbC bearing materials under tribological considerations and for closed tribo-systems against traditional references.