High Temperature Hardness of Electrodeposited Nickel-based Carbon Nanotube Composite Coatings

The Vickers hardness of Ni-based coatings was improved by codepositing carbon nanotubes (CNTs) as reinforcements in the nickel matrix and over 500 HV at room temperature. The purpose of this study was to reveal the Vickers hardness at high temperature range. The normal nickel coatings and the Ni-based CNT composite coatings were formed by ultrasonic assisted electroplating using a horn sonicator. Nickel sulfamate plating bath adding 1.6 g/L CNTs which was 9.5nm in diameter and 1.5 mu m in average length was used for depositing Ni-based CNT composite coating. At room temperature, the Vickers hardness of Ni-based CNT composite coatings was about three times that of normal nickel coatings. However, The Vickers hardness of Ni-based CNT composite coatings steeply decreased with increasing temperature. At high temperature range from 400 to 600 degrees C, The Vickers hardness of Ni-based CNT composite coatings was about 50HV and lower than that of normal coatings.