Surface Degradation of Composites Prepared by Al2 O3 and Ni Nanopowders
Material Science and Engineering with Advanced Research
Nowadays, in most engineering fields, there is a high need for the development of new products with improved properties and innovative functionalities that can with stand aggressive environmental and high load conditions. Towards this need, the fabrication of materials composed of nanostructured ceramics and metals is a promising option, as they combine the high strength of ceramics with the crack deflection toughening attained by the nanostructure and the metallic phase. Within the above
... hin the above framework, Al 2 O 3 -(5-50) wt.% Ni composites have been manufactured by powder metallurgy processing of Al 2 O 3 and Ni nanopowders. The attained microstructure consists of a metallic network enclosing Al 2 O 3 grains. The latter are composed of Al 2 O 3 nanosized sub grains. Ni nanoparticles are dispersed in the Al 2 O 3 grains, whilst they are mostly located in pores. Nanostructured Ni-Al-O zones have been formed between Al 2 O 3 and Ni phases. Cyclic potentiodynamic polarization showed that the composites present passivation and high resistance to localised corrosion in 3.5 wt.% NaCl. Surface films are analysed by SEM/EDX and Raman spectroscopy. A mechanism of corrosion is proposed. Sliding wear testing (ball-on-disk) revealed that Ni improves the wear resistance of Al 2 O 3 . The maximum improvementis observed at 20 wt.% Ni addition. The roles of Ni on the corrosion and sliding wear performance of the composites are discussed and elucidated.