Microhardness and Corrosion Resistance of Electrodeposited Ni–SiC–BN Composite Coatings

Ni–SiC–BN composite coatings were electrodeposited on H13 steel in a Watt's bath with SiC and BN particles. The effects of SiC and BN concentration in the bath on the microtructure, microhardness and corrosion resistance of the composite coatings were investigated. The results revealed that the coating grains were refined by adding the concentration of SiC and BN particles. The content of these particles embedded in the composite coating increased until the particles concentration reached 37.5 g/L. Ni– SiC–BN composite coating exhibited the highest microhardness (403.0 ± 21.2 HV 0.2 ) when the particles concentration was 37.5 g/L, which was due to the superior dispersion strengthening, fine grain strengthening, high density dislocation strengthening and the supporting effect of high-hardness particles. The composite coating with the maximum capacitance arc radius and R ct value (2.518×10 5 Ω·cm 2 ) was obtained at 25 g/L, showing the highest corrosion resistance, which was attributed to the compact and uniform microstructure. And these particles that act as a barrier limited the exposed area of Ni matrix to the corrosive electrolyte.