Wear behavior of metal matrix nanocomposites

Metal matrix nanocomposites (MMNCs), a unique class of metallic materials having superior mechanical, chemical, thermal or tribological properties, are commonly used in critical applications Those light-weight aluminum and magnesium alloys usually working in harsh wear conditions are susceptible to surface attacks. Although a lot of investigations have already been performed on those conventional composites reinforced by micro-particles, the wear behavior of the nanocomposites has not yet been fully understood. The surface properties associated with MMNCs are presented in this paper focusing mostly on manufacturing & processing routes, nano-particles as well as the dominant wear mechanisms. Studying wear behavior of MMNCs shows that no quantitative comparison of different existing studies is available as it is aimed to be done in the present review. To this end, wear reports have been categorized and discussed wherein the following results has been obtained: (i) it is found that ceramics reinforced composites usually exhibit a relatively better wear resistance behavior compared to those filled by carbon-based nanomaterials, (ii) hybrid MMNCs with two or more reinforcement types are promising materials to improve the surface resistance, particularly when the combination of ceramic and carbon-based particles are employed, (iii) solid-state processes like powder metallurgy usually provide superior wear resistance as compared to those liquid processing methods like casting, (iv) the use of smaller reinforcement size may almost always result in superior response, (v) abrasion is the most governing wear mechanism amongst the abrasion, adhesion and delamination mechanisms being frequently observed in MMNCs. A comprehensive review is made with particular attention on the composites reinforced by nano-sized reinforcing agents in order to evaluate the current research activities, discuss the pitfalls and provide a roadmap for future endeavors. It is believed that still countless research opportunities exist in order to fill the existing voids and fulfill the challenges with MMNCs.