Improvement in tool life of electroplated diamond tools by Ni-based carbon nanotube composite coatings

•Ni-based CNT composite coatings were applied for improving the grain bonding strength of electroplated diamond tools.•The effects of the amount of CNTs in the plating bath on the hardness and grain bonding strength of Ni-based CNT composite coatings were evaluated.•The Vickers hardness of Ni-based CNT composite coatings electroplated in a bath that contained more than 1-g/l CNTs exceeded 500HV.•The grain bonding strength can be improved by codepositing CNTs in Ni coatings and was almost 1.3 times in our estimations.•In the case of the side machining of glass plates, electroplated diamond tools composed of the Ni-based CNT composite coatings had a tool life approximately eight times longer than that of normal tools. Ni-based CNT composite (Ni-CNT) coatings were applied for improving the grain bonding strength of electroplated diamond tools. Further, since it is extremely important for the coatings to have good surface roughness for applications to micro-electroplated diamond tools, ultrasonic-vibration stirring was employed for improving the surface roughness of the coatings. The effects of the amount of CNTs in the plating bath on the hardness and grain bonding strength of Ni-CNT coatings were evaluated. Finally, we evaluated the tool life of microelectroplated diamond tools comprising Ni-CNT coatings as the topcoat layers by conducting experiments involving side machining and hole-drilling. The Vickers hardness of Ni-CNT coatings electroplated in a bath that contained more than 1-g/l CNTs exceeded 500HV. The grain bonding strength can be improved by codepositing CNTs in Ni coatings and was almost 1.3 times in our estimations. In the case of the side machining of glass plates, electroplated diamond tools composed of the Ni-CNT coatings had a tool life approximately eight times longer than that of normal tools. Moreover, micro electroplated diamond tools also had a longer tool life for drilling holes in fused quartz glass. This represents the first experimental verification of the efficacy of Ni-CNT coatings in improving the grain bonding strength. In this manner, we have demonstrated that Ni-CNT coatings are extremely effective for improving the grain bonding strength of electroplated diamond tools.