DEVELOPMENT OF ANODIZED Al-OXIDE WITH CNT/CNF IN NANOPORES AND ITS TRIBOLOGICAL BEHAVIOUR

Abstract

The replacement of materials in conventional components by lightweight aluminium, its alloys and composites based on these matrices has led to significant weight saving and consequently, improved fuel economy especially in space, aerospace, automotives and marine industries. In view of depleting fossil oil and its increasing cost, there is a need to pursue the objective of weight saving more aggressively by the materials and design engineers. Aluminium and its alloys have been extensively investigated because of their high strength to weight ratio, good corrosion resistance, and high thermal conductivity. However, these materials have shortcomings including low hardness, high friction coefficient, tendency of galling and difficulty in lubrication, which limit their extended applications. These shortcomings may be overcome by developing self-lubricated, hard and wear resistant coatings of nano-composites which has opened up new possibilities in extending material properties. The basic idea of the present work is to develop an oxide layer over the surface of aluminium of different levels of purity by anodizing process, a traditional and relatively simple way to impart hardness and thus improve wear and corrosion resistance of aluminium and its alloys. But the hard anodic oxide film surface does not provide a low friction lubricating surface. It is fortunate that the anodized surface has porosity and it is possible to generate self organized pores in this oxide layer by appropriate control of the anodization process. The porous anodic alumina films are potentially advantageous as lubricant reservoirs, although they have received only limited preliminary attention in tribology. The pores in the anodic aluminium layer could be impregnated by the lubricant (either in the liquid or solid state or both) and there will be slow dispensing of the lubricant on the sliding surface from the pores, which have very high aspect ratio (depth divided by diameter)......................