Influence of Duty Cycle on the Phosphorus Content and Hardness of the Ni-P Coatings Produced by Pulse-Current Electroplating

Ni-P coatings were prepared on low carbon steel substrates using the pulse electrodeposition method. The influence of the pulse duty cycle on the phosphorus content and hardness of the Ni-P coatings was investigated. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were employed to examine the surface morphology and chemical composition of the Ni-P coating layers. The results showed that an increased pulse duty cycle (20% - 80%) led to a decreased phosphorus content from 17.81 wt.% to 13.71 wt.%. The microhardness values were found to have an inverse relationship with the phosphorus content. The highest hardness of 538.22 ± 12.92 HV0.1 was obtained from the sample produced with a duty cycle of 80%, which had the lowest P content of 13.71 wt.%.