Nanoscale structural defects in electrodeposited Ni/Al2O3 composite coatings

This article attempts to explain how Al2O3 nanoparticles and saccharin added to and dispersed in an electrolytic bath affect the microstructure of electrodeposited composite coatings. The micro- and nanoscale observations of the structure of the pure Ni and Ni/Al2O3 coatings revealed the presence of numerous growth type faults in the Ni matrix, including dislocations and high density (111) nanotwins along the [011] zone axis. The addition of alumina nanoparticles and saccharin to the electrolyte caused an increase in the density of the nanotwins and refinement of the Ni grains, which improved the mechanical properties of the coatings. The highest values of microhardness were reported for the Ni/Al2O3 coating obtained from the bath containing the organic compound. The presence of alumina nanoparticles in the electrolyte changed the texture component of the Ni deposit. The addition of both the ceramic and saccharin did not affect the preferred crystallographic orientation of the Ni grains but resulted in a lower level of residual stresses in the coatings. (C) 2017 Elsevier B.V. All rights reserved.