Tribology Study of Silicon Nitride-Based Nanocomposites with Carbon Additions

Abstract

Tribology tests were conducted on silicon nitride-based nanocomposites with various carbon additions to explore the effects of microstructure, the type and quantity of carbon additives and the preparation routes on the behavior. The nanocomposites consisted of Si3N4 and C in the proportions of 1 – 10 wt % carbon nanotube (CNT), or carbon black (CB), or graphite, or graphene. Specimens were produced by hot isostatic pressing. X-ray diffraction and scanning electron microscopy were used to reveal phase composition and microstructure. Unlubricated ball-on-disk tribology tests with silicon nitride counter face were carried out at room temperature in ambient atmosphere. Contact profilometer was used to profile the wear tracks. The friction coefficients of the pure Si3N4 and Si3N4 samples with 3% CNT varied between 0,77-0,81. Addition of 10% graphite and 3% CB to Si3N4 resulted in friction coefficients of 0,83 and 0,72 respectively. Si3N4 samples with 3% graphene showed distinctly lower friction levels of 0,52 and smaller scatter of the measured values. The wear track study revealed that high graphene content in the Si3N4 matrix caused relatively big wear particles and an uneven wear track.