A possibility study on plasma-assisted synthesis of hybrid multi-scale Al-(Al2O3+AlxTiy) nanocomposite coatings for wear resistance applications: A look at microstructure evolution mechanism

As a new-emerging and recently uncovered ceramic, aluminum titanate (Al2TiO5) has been exploited as a facile chemical source to develop a multi-scale blend of metal-based reinforcing particles suitable for metal matrix nanocomposites. In this work, the authors have performed a possibility study on whether the tailorable phase transformation between sol-gel synthesized Al2TiO5 nanostructure and chemically activated aluminum following the plasma-assisted ultrarapid compaction technology can bring up a fully dense hybrid nanocomposite coating for the engineering applications in which a high degree of wear resistance and hardness are considerably required. Through the successful diffusive deposition of thermomechanically synthesized Al2O3 + AlxTiy phase blend on 1050 aluminum alloy sheets, the present work evolved a fully dense coating with a uniform distribution of multi-scale reinforcements with pore-free interfaces, thereby persuading the wear resistance of the aluminum matrix. The microstructure of the nanocomposite coatings was composed of homogeneously distributed dark and bright regions with high and low microhardness, respectively, resembling islands engulfed by the grey regions with a river-like pattern and a medium microhardness. This pattern may originate from the plastic flow of plasma-affected semi-solid composite particles perpendicular to the applied pressure during the compaction process. Moreover, the microstructure evolution mechanism of the prepared hybrid nanocomposite coating was investigated. The results illustrated that the obtained microstructure with a hierarchical nature could guarantee a combination of ductility and strength for the hybrid nanocomposite coating. Also, the synergistic effects of the hybridized reinforcing nanoparticles resulted in a significantly higher sliding wear resistance than Al2O3 conventional counterparts by up to 70 %. It is also more than three times higher than that of bare substrate. Finally, abrasive wear was reported as the dominant mechanism for the nanocomposite coatings based on friction coefficient values and micromorphology study of wear tracks.