Microstructure and wear behaviour of graphene-Si3N4 binary particle-reinforced aluminium hybrid composites

In this study, Si3N4 and graphene-reinforced aluminium matrix composites (AMCs) with various contents (Si3N4: 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-Si3N4 and Al-Si3N4-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 Si3N4 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 +/- 1 HV), the lowest porosity (5.6%), wear rate (3.1 x 10(-5) mm(3) N-1 m(-1)) and friction coefficient (0.13) were obtained for Al-9Si(3)N(4)-0.1 graphene. After attaining 0.1% graphene content, agglomeration was detected from the microstructure images of Si3N4-graphene-reinforced AMCs. It was concluded that Si3N4 had an outstanding wear resistance and graphene was a good solid lubricant for AMCs.