The improvement of cutting performance in semi-dry condition by the combination of DLC coating and CVD smooth surface diamond coating

The authors have recently developed a finely crystallized smooth surface diamond coating. Using this coating, the anti-sticking property of cutting tools was significantly improved in comparison to conventional rough surface diamond coatings. However, small crystal apices still remained. When aluminum alloy is cut by the tools with this coating, small amount of aluminum alloy still sticks in the valleys in between the apices of diamond crystals and causes friction loss. To solve this problem, we tried to apply DLC (Diamond like carbon) coating over CVD diamond coatings on cutting tools. DLC coating has very smooth surface and shows excellent performance in solid lubrication. But it does not have enough durability in the case being in contact with highly abrasive materials. On the other hand, the fine crystal diamond coating produced by the authors has great durability against highly abrasive materials. By putting them together, both the excellent lubrication performance and durability of coating were compatibly achieved. These new combinations of coatings lead to a better anti-sticking property of cutting tools for aluminum alloy and successfully increased the tool endurance.