Tribological Behaviour of Hot Extruded Al6061-Si₃N₄ Composite

Silicon nitride (Si₃N₄) possesses excellent hot hardness, wear resistance coupled with good corrosion resistance. Further, it possesses high anti friction properties making it an ideal reinforcement in developing high quality light weight, metal matrix composites for tribological applications. Silicon nitride has been successfully dispersed in aluminum alloy matrices. Their tribological properties with the beneficial effect of silicon nitride in enhancing the wear resistance of metal matrix composite have been reported by several researchers. Most of the researchers have focused on development of silicon nitride reinforced aluminum composite by powder metallurgy and casting route. However, meager information is available as regards the secondary processing of these composites in particular hot extrusion. Several researchers have reported an improved tribological behaviour in composites after extrusion. Hot extrusion of light weight metal matrix composites is very challenging. In the light of the above, this paper discusses the tribological behaviour of hot extruded Al6061 aluminum composites, which were initially developed by stir casting technique. Nickel coated silicon nitride particles were dispersed in Al6061 alloy using stir casting process. The cast composites were extruded at an extrusion ratio of 1:10 adopting a temperature of 550°C. The hot extruded composite (6Wt% Si₃N₄) and the matrix alloy were subjected to metallographic studies, microhardness and friction and wear tests using a pin on disc machine. Friction and wear test were carried out at loads ranging from 10 to 60 N at a sliding velocity of 0.314m/s. The worn surfaces and wear debris analysis have been carried out to understand the mechanism of wear in the developed hot extruded composites. The developed hot extruded composites exhibited lower coefficient of friction and wear rates when compared with matrix alloy.