Electrodeposition of Ni–W–Al2O3 nanocomposite coating with functionally graded microstructure

• Functionally graded structures have been synthesized using adjusting pulse parameters.
• Al2O3 and W contents increases gradually as a function of coating thickness.
• Alumina increased the corrosion resistance by moderating icorr and Ecorr.
• Wear behavior has been enhanced in functionally graded structure.

Electrodeposition of functionally graded (FG) Ni–W–Al2O3 nanocomposite coatings is investigated in current research. These types of coatings were applied in a way that alumina content was increased from the substrate towards the surface of the coating; hence, Ni–W would possess improved wear and corrosion resistance properties. FG-coatings were developed by the variation of duty cycle and frequency. The microstructure and elemental analysis of the coating as a function of thickness was investigated using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis, respectively. The corrosion resistance of the FG-coatings was evaluated using potentiodynamic polarization and the wear behavior was also studied using pin-on-disk wear tests. In order to investigate hardness properties of the coating, microhardness measurements were carried out on cross-section of coatings. Results revealed that the alumina content and the microhardness increased towards the surface. Results also showed the corrosion and wear resistance of FG-coatings were significantly improved by addition of α-Al2O3 nanoparticles. Profilometery and AFM results also revealed that surface roughness was influenced by pulse plating parameters.

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