Performance evaluation of DLC coated tools in high-speed micromilling of carbon fibre reinforced plastic

Carbon fibre reinforced plastic (CFRP) is highly desirable for applications in strategic sectors such as aerospace, defence, etc., because of its high tensile strength, stiffness, lightweight nature, low thermal expansion, and high modulus of elasticity. The demand for miniature complex 3D features in CFRP composites is also gradually increasing. Micromilling is one of the micromachining processes that can create microfeatures on CFRP components with high material removal rates and surface finish. However, challenges like non-homogeneous structure and abrasive nature of the CFRP composites can lead to issues such as fibre delamination and tool wear. The localized heat buildup in the machining zone caused by the low thermal diffusivity of CFRP can also result in accelerated tool wear. There is a lack of research work in the area of micromilling of CFRP, which is essential for strategic sectors such as aerospace, semiconductor, defence, etc. Therefore, this study investigates the micromachinability of CFRP composites using high-speed micromilling with diamond-like carbon (DLC) coated tools. Experiments were conducted using uncoated and DLC coated tungsten carbide endmills at different feeds per flute and spindle speeds. The critical cutting zone and behavior of fibre delamination in CFRP were analyzed. Lower fibre delamination and lower cutting forces were observed for DLC coated tools. The DLC coated tools exhibited better surface quality and superior machining performance. Delamination of the coating at the rake face on the DLC coated tool was observed with an increase in feed per flute.