Tribological Properties of Functionally Graded Ni-Al2O3 Nanocomposite Coating

The main challenge in producing metal matrix composite coatings is achieving a homogeneous distribution of the second phase particles and avoiding the particle agglomeration. Despite all the works done up to now, the effect of the particles' distribution in the matrix of composite coatings on the tribological properties has rarely been reported. The primary concern of the present study is to investigate the tribological behavior of functionally graded nickel-Al2O3 nanocomposite coating produced at different duty cycles in 3.5% wt NaCl solution. Before starting the tribocorrosion test, the open circuit potential variations are small and reached stable values which followed by a negative shift during and after the tribocorrosion test. SEM and EBSD images showed that by decreasing the duty cycle the width of the wear track decreased because of more incorporated particles and changing of the (001) structure to compact random texture. Although the EIS results show the corrosion resistance decreased by increasing the embedded particles, higher hardness and compact structure result in better tribocorrosion properties of samples prepared at lower duty cycle. The adhesive wear was the dominant mechanism for coatings plated at high duty cycle and it changed to the abrasive wear in sample prepared at lower duty cycle. (C) 2017 The Electrochemical Society. All rights reserved.