Electrodeposition and characterization of Ni–Co/SiC nanocomposite coatings

Ni–Co/SiC nanocomposite coatings were electrodeposited in a modified watt type of Ni–Co bath containing 20 nm SiC particles to be codeposited. Potentiodynamic polarization tests were conducted to study the effect of the SiC particulates on the electrodeposition of Ni and Co. Scanning electron microscopy was used to assess the morphology of the Ni–Co alloy and Ni–Co/SiC nanocomposite coatings. The distribution of the particulates in the matrix was considered by means of transmission electron microscopy. Applying nanomechanical testing instruments coupled to atomic force microscopy, mechanical properties of the alloy and composite coatings were studied and compared. The presence of 11 vol.% SiC in the Ni–Co matrix increased hardness more than 60%. The average depth of scratch in the mentioned composite coating was about 15% less than that of the Ni–Co alloy coating. The corrosion penetration rate (CPR) of the Ni–Co alloy coating in a 3.5 wt.% NaCl solution was more than 17 times greater than that of the Ni–Co/SiC coating with 30.5 vol.% SiC.

► The addition of SiC nano particles to the deposition bath leaded to the positive displacement of the Ni–Co polarization curve.
► The presence of 11 vol.% SiC in Ni–Co matrix increased the hardness from 2.1 GPa to 3.43 GPa, i.e. more than 60%. The average depth of scratch for the mentioned composite coating was about 15% less than that of the Ni–Co coating.
► The corrosion penetration rate (CPR) of the Ni–Co/SiC coating with 30.5 vol.% SiC was more than 17 times less than the Ni–Co alloy in the 3.5 wt.% NaCl solution.