Enhancement of Wear Properties of Chromium Layer by Using Nickel Middle Layer

In this study the wear properties of chromium deposit were improved by using the nickel electrodeposited middle layers. The nickel middle layers were formed by direct current (DC) and pulse current (PC) power supplies. The results showed that the surface morphology of a chromium layer in Ni/Cr coating (DC deposited) and Ni (duty cycle = 30%, frequency = 20 Hz, PC deposited) were compact, with small nodules. Also in these coatings the crack networks density of the chromium layer decreased when compared other coatings. The hardness step value profiles with the highest value of the chromium layer and the lowest value of the nickel middle layer occurred in the studied five samples. The compact surface morphology and the appropriate hardness step value profiles of the layers were two main reasons for improving the wear resistance of the chromium layer coated on the top of the nickel layers produced by DC and PC (duty cycle = 30% and frequency = 20 Hz) currents.