Effect of Nanodiamond Concentration and the Current Density of the Electrolyte on the Texture and Mechanical Properties of Ni/Nanodiamond Composite Coatings Produced by Electrodeposition

An Ni/nanodiamond composite coating was deposited on carbon steel in a traditional Watt's solution without additives via direct current (DC) electroplating. The effects of the nanodiamond concentration and current density in the plating solution on the morphology, grain size, and texture of the Ni/nanodiamond composite coating were observed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The distribution of the nanodiamond particles in the composite coating was investigated by Raman spectra and SEM. The mechanical properties of the composite coating, such as its elastic modulus and hardness, were examined using a Nano Indenter XP nanometer mechanical test system. The coefficient of friction was tested using a Universal Micro-Tribotester. The results demonstrated that the preferential orientation of the Ni/nanodiamond composite coating varied from the (111) crystal orientation of the pure nickel coating to the (200) crystal orientation. When the nanodiamond concentration in the plating solution was 8.0 g/L and the current density was 3.0 A/dm², the hardness of the composite coating reached the maximum value of 5.302 GPa and the friction factor was maintained at around 0.1. The average grain size of the composite coating was reduced to 20.4 nm.