Abstract:Ni-W-P layers were formed on a low-carbon steel substrate by direct-current electroplating method. The effects of current density, pH value and bath temperature on the composition, surface morphology, and microstructure of Ni-W-P layers were studied by X-ray fluorescence (XRF), scanning electron microscope (SEM), auger electron spectroscopy (AES) and X-ray diffraction (XRD). The results indicate that the change of current density and pH value influenced the composition of Ni-W-P layer greatly, but the change of current density, pH value and bath temperature hardly influenced the thickness of Ni-W-P layer. As current density and bath temperature increased, current efficiency decreased and increased, respectively, and current efficiency reached the maximum value when pH value is 7.0. The structure of Ni-W-P layer was greatly influenced by pH value, and a well-preferred orientation along Ni (111) direction was shown when pH value was 8.0. Synchronously, the microhardness of Ni-W-P layer reached the maximum value of 7130 MPa. At last, electroplating mechanism of Ni-W-P layer was discussed further.