Dry sliding wear behaviour of single and dual ceramic reinforcements premixed with Al powder in AA6061 matrix

Abstract

This work highlighted the preparation of a hybrid of AA6061/Al2O3/graphite composite by additionally incorporating Si3N4 nanoparticles in the material system. The reinforcements were premixed with Al metal powder to improve their diffusion into the matrix during manufacturing of composites. The composites were manufactured by stir casting method. The pin on disc wear test was carried out as per ASTM G99 standard. Field emission scanning electron microscope (FESEM) and energy dispersive spectroscopy (EDS) analysis were conducted on worn out surface and subsurface of the composite specimens to determine the wear mechanism. From the results, it was found that the wear behaviour of Al powder premixed reinforcement was superior to unmixed reinforcements. The composites with dual ceramic reinforcement have shown lesser wear rate and coefficient of friction than composites with single ceramic reinforcement. Abrasive wear and grain structure refinement just beneath the worn out surface were noted in composites with Si3N4 nanoparticles. Single ceramic reinforcement of Al premixed Al2O3 was identified with abrasive wear, micro cuts and formation of mechanically mixed layer on the worn out surface. Single ceramic reinforcement of unmixed Al2O3 exhibited abrasive wear and severe plastic deformation on worn out surface. Porosity, particle fracture and particle pull out were noticed in the subsurface of the composites with unmixed single ceramic reinforcement of Al2O3. Keywords: Metal–matrix composite, Wear testing, Electron microscopy, Surface analysis