Friction and Wear of Silicon Nitride and Silicon Carbide in Water: Hydrodynamic Lubrication at Low Sliding Speed Obtained by Tribochemical Wear

Abstract

This report describes experiments on friction of Si₃N₄ and SiC sliding against themselves and against each other in water at room temperature. The friction coefficient of Si₃N₄ against itself is f = 0.7 at low speeds (0.2 cm/s). At speeds above 6.5 cm/s and 4.91-N load, hydrodynamic lubrication sets in, with f = 3N₄ which occurs by dissolution in water and an absence of wear particles. The friction coefficient of SiC, against SiC or Si₃N₄ in water at low speeds is f = 0.26. Wear occurs by dissolution and fracture pitting. Small wear particles are observed. The friction coefficient of SiC against SiC is independent of sliding velocity between 0.2 and 20 cm/s. Hydrodynamic lubrication is obtained with a Si₃N₄ pin on SiC plate near 10 cm/s, mixed lubrication is obtained with a SiC in on Si₃N₄ plate at v < 20 cm/s.