PARAMETRIC STUDY OF DRY SLIDING WEAR BEHAVIOUR OF FUNCTIONALLY GRADED Al LM25/Si3N4 COMPOSITE BY RESPONSE SURFACE METHODOLOGY

Functionally graded aluminium LM25/silicon nitride composite was produced through stir casting followed by centrifugal casting and obtained a hollow cylindrical cast component with dimensions of 150 x 150 x 20 mm. The microstructural examination and the hardness test were carried out on the outer (1 mm) and inner surface (17 mm) as the function of radial distance from the outer periphery. The outer surface was observed with particle enriched region compared to inner surface and exhibited higher hardness. Hence the outer surface of the functionally graded composite was only further subjected to sliding wear test in pin-on-disc tribometer. The Central Composite Design in Response Surface Methodology was used to design the experiments for the selected parameters such as load (15-45 N), velocity (0.5-2.5 m/s) and sliding distance (500-2000 m). Regression test and Analysis of Variance were conducted to check the adequacy of the constructed model. The surface plots for wear rate showed that wear rate increased with increase in load and non-linearly varied with increase in velocity and sliding distance. Scanning Electron Microscopy analysis was conducted on the worn-out surfaces and observed mild to severe wear transition on increase of load.