Co-electrodeposition of Functionally Graded Ni-NCZ (Nickel Coated ZrO2) Composite Coating

摘要

In this study, functionally NCZ (electroless nickel plated ZrO2) content graded Ni-NCZ composite coating has been successfully co-electrodeposited from a bath with gradually increasing of stirring rate. For this, different composite coatings were electroplated in the same bath with different stirring rates to find the optimum condition. SEM, XRD, EDX and electrochemical studies showed that co-electrodeposition in a bath with stirring rate of 250 rpm results in the maximum co-electrodeposited particle content and the best particle distribution and corrosion resistance. Also, this sample had the highest wear resistance with respect to the other samples. To produce NCZ content graded Ni-NCZ composite coating, the stirring rate was continuously increased from 0 to 250 rpm. The electroplated coating had a continuous gradient increasing of co-electrodeposited NCZ content from substrate toward the surface. This distribution of NCZ particles results in a gradient increasing of the microhardness in the cross section of the coating. Bend test revealed that the functionally graded composite coating shows better adhesion to the substrate compared with the uniformly distributed Ni-NCZ on the same substrate. This result has been attributed to lower mechanical mismatch between coating and substrate in the functionally graded composite coating with respect to the uniformly distributed one.