Performance enhancement of diamond-coating on step drill for machining CFRPs

Because of the high strength of fibers used in CFRPs, rapid tool wear is a key issue in CFRP machining. Therefore, to overcome this problem, a diamond coating was applied on the step drill via CVD. To increase the tool life for CFRP machining, retardation of the delamination of diamond coated layer must be performed, which requires the higher adhesion force and proper thickness of coated layer. However, a relatively thick coating is more likely to cause delamination of the coating due to high thrust forces. Therefore, in this study, an experiment was conducted to find the optimal coating thickness. For this purpose, 5 types of diamond coatings with different particle sizes and thicknesses of diamond coating are applied. As a result, the best performance of the coated tool was obtained about 2.5 times the lifetime to the worst tool based on flank wear and about 2.2 times based on the delamination factor, which are performed by controlling CH4 concentration for adhesion force and coating time for the thickness of layer.

Automated summary

In order to increase the tool life for CFRP machining, this study applied diamond coatings via CVD and conducted experiments to find the optimal coating thickness. The best performance was achieved by controlling CH4 concentration for adhesion force and coating time for the thickness of layer, leading to 2.5 times longer lifetime based on flank wear and 2.2 times longer based on the delamination factor compared to the worst tool.