Influence of Hot Extrusion on Microstructure and Slurry Erosive Behaviour of Al6061-Si ₃ N ₄ -C _f Hybrid Composite (SAE Paper 2022-01-0049)

In recent decades, silicon nitride (Si₃N₄) and carbon fibres (C_f) have been the most popular candidate materials as reinforcements in the production of metal matrix composites (MMCs) due to their superior wear and corrosion resistance. Al6061 is the most sought after matrix alloy owing to its excellent formability among all class of aluminium alloys. Several researchers have reported on dry sliding wear and corrosion properties of cast composite with carbon fibres and silicon nitride as reinforcements but limited information is available related to the slurry erosive wear behaviour of hot extruded hybrid MMCs with carbon fibre as one of the reinforcement. In the light of the above, the current experimental work is aimed at investigating the slurry erosive wear behaviour of Al6061 dispersed with Si₃N₄ (6 wt %) and C_f (1 wt %) hybrid MMC after hot extrusion. Stir casting technique was used to disperse electroless nickel (Ni) deposited with Si₃N₄ and copper (Cu) coated with C_f in Al6061 followed by hot extrusion. Microstructural studies were conducted on specimens of cast and hot extruded base alloy, it’s composite & hybrid composite. Slurry erosive wear tests were performed by using 312 μm size silica sand particles in 3.5% NaCl solution. The tests were performed at rotational speed ranging from 300 rpm to 1200 rpm while the sand concentrations were varied between 10 gm/l to 40 gm/l. It is found from the experimental results that hybrid composite in hot extrusion condition exhibit better erosive wear resistance compared to that of base alloy in as-cast condition. A decrease in slurry erosive wear loss of 84.61% and 84.37% was found for hybrid composite in hot extruded condition compared to that of base alloy in as cast condition for sand concentration (10% and 40%), time (5 hrs) and speed (300 rpm). It is observed that a slurry erosive wear loss is reduced by 81.25% and 63.46% for hybrid composite in hot extruded condition compared to that of base alloy in as cast condition at speed (300 rpm and 1200 rpm), time (5 hrs) and sand concentration (30%). To understand the erosive wear mechanism, the eroded surfaces have been examined under SEM and EDS.