Ni-W/BN(h) electrodeposited nanocomposite coating with functionally graded microstructure

The aim of this research is study the pulse electrodeposition of functionally graded (FG) Ni-W/BN(h) nanocomposite coatings in which the content of the incorporated BN(h) nanoparticles changes along the thickness. To make the FG structure, pulse parameters (pulse frequency/duty cycle) were changed in four stages. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis were performed to investigate the microstructure and elemental analysis of the composite coatings, respectively. Electrochemical tests and wear tests were used to study corrosion resistance and wear behavior of the coatings. Measurements of microhardness were carried out on a cross-section of the FG coatings to study mechanical properties. The results revealed that with increasing frequency or reduction of duty cycle along the four-layer structure, the content of BN(h) nanoparticles and tungsten increased in different extent. And the wear resistance and microhardness of FG Ni-W/BN(h) coatings were significantly improved compared to that of uniform Ni-W/BN(h) coatings. Moreover, results showed that the corrosion resistance of the FG coatings increased due to the increase of BN(h) nanoparticles content inside the deposits.