Preparation and properties of electroless Ni–P–SiO2 composite coatings

Dispersible SiO2 nanoparticles were co-deposited with electroless Ni–P coating onto AISI-1045 steel substrates in the absence of any surfactants in plating bath. The resulting Ni–P/nano-SiO2 composite coatings were heat-treated for 1 h at 200 °C, 400 °C, and 600 °C, respectively. The hardness and wear resistance of the heat-treated composite coatings were measured. Moreover, the structural changes of the composite coatings before and after heat treatment were investigated by means of X-ray diffraction (XRD), while their elemental composition and morphology were analyzed using an energy dispersive spectrometer (EDS) and a scanning electron microscope (SEM). Results show that co-deposited SiO2 particles contributed to increase the hardness and wear resistance of electroless Ni–P coating, and the composite coating heat-treated at about 400 °C had the maximum hardness and wear resistance.