Abstract
The drilling of carbon fiber reinforced plastics (CFRP) is a significant topic for the aircraft industry. However, CFRP are materials which are difficult to cut due to their unique properties. This paper studies tools with excellent cutting performance in machining CFRP. The microcrystalline diamond (MCD), nanocrystalline diamond (NCD), and dual-layer composite MCD/NCD coatings are deposited on Co-cemented tungsten carbide (WC-Co) drills. The morphology of MCD shows pyramidal grains and the NCD and MCD/NCD coatings present cauliflower-like morphology. The cutting performances of coated tools are checked in CFRP drilling tests by the drilling force and tool wear. According to the results, the dual-layer composite MCD/NCD coated tools present the best cutting performance with the lowest drilling force. Meanwhile, the MCD/NCD coated tools display high resistance to wear and adhesive strength.
Highlights
Carbon fiber reinforced plastics (CFRP) are widely used in the aerospace industry with the combination of high hardness, high strength, and being lightweight [1,2]
Three types of diamond coatings are deposited on the WC-Co drills using the hot filament Chemical vapor deposition (CVD) (HFCVD) method: (I) microcrystalline diamond (MCD), (II) nanocrystalline diamond (NCD), and (III) MCD/NCD
As for dual-layer composite diamond coatings, the MCD coatings are deposited on the drill surfaces for 4 h, the NCD coatings are deposited in situ for 2 h by adjusting the deposition parameters
Summary
Carbon fiber reinforced plastics (CFRP) are widely used in the aerospace industry with the combination of high hardness, high strength, and being lightweight [1,2]. The main problems encountered in CFRP drilling are rapid tool wear and insufficient hole quality, including inter-layer damage, fiber pullout, and exit burrs. This can be attributed to the abrasive nature of the fiber reinforcement, and the anisotropic and heterogeneous nature of the CFRP structure. Chemical vapor deposition (CVD) diamond coatings are famous for their unique characteristics such as high hardness, good wear resistance, low friction coefficient, and high thermal conductivity. The mechanical properties of diamond coated tools depend mainly on the coating structure, such as its thickness and surface morphology. In the case of cutting composite materials, diamond coatings have a positive effect, due to their excellent mechanical and physical properties. The drilling force and tool wear are investigated employing dynamometer and SEM
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