Nanostructured Ni-AlN composite coatings

Electrodeposited Ni composite coatings embedded with AlN particles were deposited on mild steel substrates. AlN whiskers of 40-150 nm size were successfully prepared by nitriding method. Coatings were produced from Ni Watt's bath and the optimum conditions of plating process were determined. The wear resistance and friction coefficients of Ni-AlN composite coatings containing various amounts of AlN have been studied. The corrosion rates of composite coatings were measured in 1 M HCl solution. Surface morphology of the coatings was analyzed by using a scanning electron microscope (SEM). Thermal stability of the pure Ni and composite coatings were studied at 900-1100 degrees C. The thermal expansion coefficients of the coatings were investigated in the temperature range of 100-650 degrees C. The results referred that increasing the incorporation rate of AlN particles leads to an increase in both of the hardness and friction coefficients of the films. The composite coatings containing 41 wt.% of AlN exhibited high resistance against wear and corrosion. The addition of low expansion AlN particles restricted the expansion of matrix through interfaces. (c) 2006 Elsevier B.V. All rights reserved.