Improving Precision in Aluminum Alloy Machining Due to the Application of Diamond-Like Carbon Thin Film

Abstract

Cutting precision is extremely affected by a phenomenon known as built up edge (BUE) that occurs on tungsten carbide tools during low cutting speed of aluminum alloy. BUE is responsible for early tool breakage due to excessive material build up from the machined part on the cutting face, leading to problems of shape irregularity and tool-tip breakage. Thus, diamond-like carbon (DLC) was deposited and tested to verify cutting precision in aluminum alloy by using tungsten carbide tools. The characterizations of the film were morphology analysis through scanning electron microscopy (SEM), structural atomic analyze of chemical bond from Raman backscatter spectroscopy, the distribution of carbon atoms on the film surface by X-ray photoelectron spectroscopy (XPS), and the evaluation of Young’s modulus and hardness using the Oliver–Pharr method. To analyze the cutting precision, drilling tests were performed on coated/uncoated drills at two cutting speeds (340 and 430 m/min). As an evaluation parameter in the aluminum alloy, the hole diameter deviation was measured after pre determined numbers of drilling operations. Statistical comparisons between the diameter deviation as a function of the number of drilling test indicated better cutting accuracy for the DLC-coated tool. The factors identified in this work, such as the reduction of the friction coefficient, and the hardness and Young’s modulus of the DLC helped in the performance of the tool, mainly in the lower cutting speed.