Study on micro-hardness of Ni-Co-SiC nano-composite coatings by high-frequency pulse

Ni-Co-SiC nano-composite coatings were prepared by pulse electroplating at high frequency (20-140 kHz). The effects of pulse frequency, mass concentration of SiC and heat treatment temperature on the morphology and micro-hardness of deposit were studied. The Ni-Co-SiC obtained by high-frequency pulse electroplating features higher compactness, better uniformity, lower porosity and higher micro-hardness as compared with that DC electroplated. Ni-Co-SiC coating is increased with increasing pulse frequency or CoSO₄ content in plating bath. The micro-hardness increased with increasing heat treatment temperature from 200 to 400°C, but decreased with further increasing temperature over 400°C. The micro-hardness of deposit prepared at pulse frequency 120 kHz and 140 kHz is decreased with increasing heat treatment temperature.