Influences of Boron Concentration on Mechanical Properties of Ni-W-B Composite Coatings

Abstract

Ni-W-B alloy coating containing amorphous boron particle were fabricated by direct current electrodeposition on low carbon steel substrates. The effect of boron concentration in the plating bath on the surface morphology, the overall boron content in the deposited layers and the hardness of the resulting coating layer were investigated. Scanning electron microscopy (SEM) revealed that the surface morphology of the Ni-W-B coating layer was largely modified by the boron particle loading in the electroplating suspension. Distinct nodular structures were observed in these samples. Energy dispersive X-ray spectroscopy (EDS) spectra suggested that the overall boron content in the coating layer increased with increasing boron particle loading from 1 to 3 g/L. Too high boron particle loading of 10 g/L resulted in lower overall boron content. The highest hardness of 680.86 ± 17.67 Hv was obtained from Ni-W-B/B coating layer fabricated using the boron particle loading of 5 g/L.

Effect of Amorphous Boron on the Microstructure and Corrosion Properties of Ni-W Coatings

“…The Ni-W coating has an average surface roughness (Ra) of 1.58 ± 0.1 µ m, while the Ni-W/B coatings have Ra values of 1.38 ± 0.05, 1.26 ± 0.07, and 0.93 ± 0.04 µ m, for boron concentrations of 0.5, 1, and 3 g/L in the plating solution, respectively. The incorporation of boron provided a smooth surface of the coatings because the incorporated particles act as nucleation sites and enable grain refinement, resulting in smaller grains [19,29,30], as shown in previous works [4,23,31]. In addition, boron particles retard the crystalline growth of the Ni-W matrix coating, leading to a smoother and more uniform surface [4,29,30].…”

“…In our previous work, we reported that the original Ni-W alloy coatings and composite Ni-W coatings modified by adding amorphous boron particles (Ni-W/B) can be successfully deposited on carbon steel using the electrodeposition method [4,23,24]. The hardness and wear resistance of the coatings are significantly improved via the incorporation of an appropriate content of amorphous boron particles because these particles uniformly distribute and provide a smooth surface [4,23]. Furthermore, the incorporated particles in Ni-W coatings can enhance the corrosion resistance [1][2][3][17][18][19].…”