Microstructure and wear behaviour of graphene–$\hbox {Si}_{\mathrm {3}}\hbox {N}_{\mathrm {4}}$ binary particle-reinforced aluminium hybrid composites

Abstract

In this study, $\hbox {Si}_{\mathrm {3}}\hbox {N}_{\mathrm {4}}$ and graphene-reinforced aluminium matrix composites (AMCs) with various contents ($\hbox {Si}_{\mathrm {3}}\hbox {N}_{\mathrm {4}}$: 1, 3, 6, 9 wt%; graphene: 0.1, 0.3, 0.5 wt%) were produced by the powder metallurgy method. The phase and microstructure analyses of the composites were performed by X-ray diffractometry and scanning electron microscopy, respectively. To investigate the tribological behaviour of Al–$\hbox {Si}_{\mathrm {3}}\hbox {N}_{\mathrm {4}}$ and Al–$\hbox {Si}_{\mathrm {3}}\hbox {N}_{\mathrm {4}}$–graphene composites, pin-on-disc experiments were conducted with different loads ($F = 10$, 20 and 30 N) at a constant sliding speed (200 rpm). Thus, the effects of $\hbox {Si}_{\mathrm {3}}\hbox {N}_{\mathrm {4}}$ and graphene contents on microstructure, Vickers hardness, apparent density, porosity, wear rate and friction coefficient of AMCs were investigated. Test results reveal that the highest Vickers hardness ($66 \pm 1\hbox { HV}$), the lowest porosity (5.6%), wear rate ($3.1 \times 10^{\mathrm {-5}}\hbox { mm}^{\mathrm {3}}\hbox { N}^{\mathrm {-1}}$ $\hbox {m}^{\mathrm {-1}})$ and friction coefficient (0.13) were obtained for Al–9$\hbox {Si}_{\mathrm {3}}\hbox {N}_{\mathrm {4}}$–0.1 graphene. After attaining 0.1% graphene content, agglomeration was detected from the microstructure images of $\hbox {Si}_{\mathrm {3}}\hbox {N}_{\mathrm {4}}$–graphene-reinforced AMCs. It was concluded that $\hbox {Si}_{\mathrm {3}}\hbox {N}_{\mathrm {4}}$ had an outstanding wear resistance and graphene was a good solid lubricant for AMCs.