Mechanical and Tribological Properties of Ni-B and Ni-B-W Coatings Prepared by Electroless Plating

Abstract

Ni-B binary coating and Ni-B-W ternary coating were successfully prepared on titanium alloy (TC4) substrates by electroless plating to improve the hardness and wear resistance, followed by annealing treatment for better mechanical properties and tribological properties. The morphology, composition, microstructure, mechanical properties, and tribological behaviors of the coatings were characterized. Both as-plated coatings were amorphous, while the composition and morphology of the Ni-B-W coating differed from those of the Ni-B coating. Additionally, the Ni-B-W coating had better mechanical and tribological properties with a more considerable hardness (13.5 GPa), a minor friction coefficient (0.42), and a lower wear rate (0.10 × 10−7 cm3/(N·m)). After annealing, both coatings were crystalline. In parallel to the as-plated coating, the annealed coatings showed larger hardness values because of the formation of hard phases. Moreover, the crystalline grain of the coatings grew as the annealing temperature rose from 350 °C to 650 °C. Accordingly, the coatings showed a minor hardness value, a major friction coefficient, and severe wear under the same conditions. Above all, the Ni-B-W coating annealed at 350 °C showed the best performance, with an average grain size of 26.3 nm, hardness of 15.9 GPa, friction coefficient of 0.34, and wear rate of 0.09 × 10−7 cm3/(N·m).

Non-Precious Metals Catalysts for Hydrogen Generation

“…This electroless metal deposition method has proven successful due to its low initial investment, simple coating conditions, and good results. This method produced a uniform metallic coating with excellent properties on substrates of various shapes and sizes, such as Ni foam, stainless steel mesh, aluminum oxide membranes, carbon materials, Cu sheets, and foam [32,34,36,37,[40][41][42][43][44][45][46][47][48].…”

“…Electroless metal deposition covers many metals: Ni, Co, Cu, Pt, Pd, Ru, Rd, W, Ir, Zn, Ba, Mo, Au, and Ag [34,35,[41][42][43]. However, combining several metals in the same coating, especially non-noble metals, with an efficient activity for the reaction required remains a challenge for scientists.…”

“…There are currently four described Ni coatings combined with other metals: NiCu, NiCo, NiFe, and NiCoMo, investigated for hydrogen generation from sodium borohydride. However, the reported activation energy values are quite high [43][44][45][46]49]. J.C. Ingerloll et al report that the NiCo catalyst exhibits 62 kJ mol −1 activation energy for the borohydride hydrolysis reaction [31].…”

A Systematic Investigation of Lead-Free Electroless Ni-B-W Coating Properties Using Taguchi’s Methodology

“…The cross-section appears to have columnar growths for the lead nitrate-stabilized ENB-W coatings which reduces the actual contact area and prevents adhesion [11], resulting in enhanced performance. Apart from solid solution strengthening, the coating matrix can be also toughened by heat treatment within the range 350-650 • C [8,[12][13][14][15][16]. Heat treatment promotes the crystallization of the ENB-W coating matrix by inducing structural transformations.…”

“…This leads to marked improvement in both the hardness and wear resistance of the coating [4,5,8]. Post-heat treatment, hard boride phases are precipitated [13][14][15][16]. In fact, heat-treated ENB-W coatings were suggested to have better corrosion resistance [6].…”