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).