The use of niobium carbide (NbC) as cutting tools and for wear resistant tribosystems

•Intrinsic wear resistances of binderless NbC and cobalt bonded NbCs.•Excellent elastic modulus and hardness make NbC a viable low weight candidate WC.•Wear resistances and PV-value increase significantly by increasing sliding velocity.•Binderless NbC wear rates compete with ceramics and hard metals (WC).•Low solubility of NbC in alloys qualifies NbC for machining operations.

The tribological profile of alumina (99.7%) mated against rotating disks made in binder-less niobium carbide (NbC) and cobalt-bonded NbC 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 unlubricated (dry) conditions. In addition, the microstructure and mechanical properties of binderless NbC and NbC bonded with 8% cobalt were determined as well. The reason for testing hot-pressed NbC was to avoid side effects generated by sintering additives and/or second phases. The tribological data obtained were benchmarked with different ceramics, cermets and thermally sprayed coatings. NbC and cobalt-bonded NbC exhibited low wear rates under dry sliding associated with 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, such as WC, Cr3C2 and (Ti,Mo)(C,N).