ABSTRACT
In summary, a novel nanocomposite coating with nanoporous alumina as a matrix with aligned metal nanorod has been developed. This was achieved by optimally modifying the barrier layer (BL) without sacrificing the interfacial strength. For filling metal into the porous structure, we have tried three different electrodeposition processes: DC, AC and pulse electrodeposition. We have found that the use of pulse electrodeposition is a highly efficient and well-suited method for metal filling into the pores. After developing the uniform nanocomposite coating, we have evaluated the tribological performance of the nanocomposite coating by measuring friction and wear in a reciprocating wear test. The coefficient of friction for NPA and Al samples were high, while it was 30% less for NPA/Cu. In NPA, crack formation occurs at the top layer, but the sub-layers remain unaffected. From the SEM images, wear and crack were found to be less in porous alumina/copper than in porous alumina and aluminium. A thin transfer layer of copper/steel gets coated on alumina. At a low thickness of porous alumina/copper nanocomposite coating, few cracks are found on the wear track area. At a high thickness of porous alumina/copper nanocomposite coating, no cracks are found. By optimising the nanoporous structure and tuning the electrodeposition process, we uniformly filled ordered pores with copper. Uniform coating has been achieved over an area. The coating is found to have good tribological properties of low friction and high wear resistance. Uniform coating has been achieved over an area of 10 mm × 10 mm. The coating is found to have higher hardness and higher wear resistance.
