Electrodeposition of REACH compliant boron carbide reinforced nickel composites for wear protection

Due to European regulations like REACH, hard chromium plating is gradually being replaced with other, more environmentally friendly, procedures. Nickel-based nanocomposite coatings, obtained by co-deposition of nanoparticles (NPs) of different nature (typically hard ceramics) within nickel matrix, are considered a practical alternative to hard chromium. However, to operate with a nickel REACH compliant electrolyte, boric acid must be replaced. In this study, boric acid was substituted with succinic acid to operate in line with the constraints of REACH regulation. The REACH compliant nickel electrolyte was tested, demonstrating the buffering capacity of succinic acid and its ability to produce bright and uniform nickel coatings in a wide range of current densities (10–60 mA/cm 2 ), even though the new formulation caused an increase of the mean grain size and a subsequent decrease of hardness. Moreover, boron carbide was added to the solution in different concentrations (1, 2, 3.5, 5 and 10 g/L) in order to study the effect on hardness and tribological properties such as the coefficient of friction in relation to the content of B 4 C inside the coating. The tribological properties of the composite coatings were assessed by modified ASTM G75 , mini traction machine (MTM) and Basalt N2 tests. The hardness increased up to values of 1215 HV 0.1 with a concentration of boron carbide in the coating up to 2.71 wt% for the samples produced with a concentration of 10 g/L of nanoparticles in the bath. Furthermore, the same sample exhibited a constant coefficient of friction of 0.12 for more than 100 cycles. • A commercial nickel electrolyte is modified to make it REACH compliant. • Succinic acid is proposed as REACH compliant buffer for nickel composite plating. • A nickel/B 4 C hard composite is deposited without boric acid for the first time. • The obtained hardness exceeds 1215 HV 100 . • Tribological properties of the composite support its use as anti-wear coating.