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

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 1hbox { HV})), the lowest porosity (5.6%), wear rate ((3.1 imes 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.