Microdrill with variations in thickness of diamond coating

Abstract

In this study, microcrystalline diamond films with varied thicknesses (1·2, 2·5, 4 and 7 μm) are deposited on flat samples and microdrills. The Raman results show that the top layer of thicker diamond films on flat samples exhibit relatively lower compressive residual stress and favourable diamond purity. However, with increased thickness, the multiple radial and diagonal microcracks along with significant diamond coating detachment are easier to be formed in thicker diamond coatings. These results can be applied for analysing the mechanisms on the coating delamination for the thicker diamond coatings and the worse wear resistance for the thinner ones deposited on microdrills during graphite machining processes. The microcrystalline diamond coated microdrill with 2·5 μm coating thickness reveals the best cutting performance due to its robust rigidity for preventing the detachment of diamond films as well as the relatively good wear resistance.

Keywords:

• Diamond
• Microdrill
• Graphite
• Thickness

Acknowledgements

This research is supported by the National Natural Science Foundation of China (nos. 51275302, 51375011 and 51005154), the Chenguang Program of Shanghai Municipal Education Commission (no. 12CG11), the Natural Science Foundation of Jiangsu Province (no. BK2012203) and the Technical Innovation Funds for the Sci-Tech Enterprise of Jiangsu Province (no. BC2012124).