Tribological behaviour of Si 3 N 4 -hBN ceramic materials against metal with different sliding speeds

Abstract The tribological behaviours of Si3N4-hBN (the content of the hBN is 0%, 5%,10%,20% and 30%) composites sliding on metal under dry friction condition at different sliding speeds were investigated by using an MMW-1 type vertical universal friction and wear tester. Research shows that the friction coefficients of the sliding pairs represent a downward trend with the increase of the sliding speed. And the addition of hBN could effectively improve the tribological performance of the Si3N4-hBN/ASS tribocouple. Especially, for the SN10 (Si3N4-10%hBN)/ASS pair, the friction coefficient decreased from 0.69 at a sliding speed of 0.52 m/s to 0.51 at a sliding speed of 0.86 m/s, and continuously decreased to 0.12 at a speed of 1.73 m/s. However, the negative wear which closed to zero appeared on the SN10 pin mated with the ASS disc at a speed of 1.73 m/s. During the friction process, higher sliding speed provided a favourable condition for the chemical reaction between the worn surface of the friction pairs and the air. Meanwhile the surface analysis indicated that a surface film consisting of Fe2O3, SiO2 and B2O3 was formed on the worn surface of the SN10/ASS tribocouple also at a speed of 1.73 m/s. The surface film lubricated the worn surfaces and protected both of pin and disc from being further wore. Compared with Si3N4-hBN/ASS pairs, the tribological properties of Si3N4-hBN/45# pairs were poor under the same experimental conditions.