A study on the machinability of advanced arc PVD AlCrN-coated tungsten carbide tools in drilling of CFRP/titanium alloy
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Carbon Letters https://doi.org/10.1007/s42823-020-00180-8
ORIGINAL ARTICLE
A study on the machinability of advanced arc PVD AlCrN‑coated tungsten carbide tools in drilling of CFRP/titanium alloy stacks Dave Kim1 · Sam R. Swan2 · Bin He3 · Viktor Khominich4 · Eric Bell4 · Seok‑Woo Lee5 · Tae‑Gon Kim5 Received: 5 June 2020 / Revised: 20 July 2020 / Accepted: 19 August 2020 © Korean Carbon Society 2020
Abstract This study aims to investigate the effect of an aluminum chromium nitride (AlCrN) coating on tool wear and hole quality in the conventional drilling process of carbon fiber-reinforced plastic (CFRP) composites, titanium alloy (Ti), and CFRP–Ti stack workpieces popular in the aerospace industry. The advanced arc plasma acceleration (APA) method of physical vapor deposition (PVD) was used for all AlCrN coatings. The drilling experiments were conducted with uncoated drills as well as AlCrN-coated drills. When drilling CFRP only, the AlCrN coating was removed at the drill cutting edges and the margin area, which suggests the carbon fibers abraded the coatings. When drilling Ti only, the AlCrN-coated drill mitigated the Ti adhesion formation, which resulted in less tool wear. In addition, hole quality for both CFRP and Ti was improved when the coating was used versus the uncoated tool. The machinability of CFRP–Ti stacks in the drilling process was improved by utilizing the advanced AlCrN coating on the WC tool in terms of drilling forces and hole quality parameters such as average hole size, average hole roundness, hole surface roughness, and Ti exit burr height. Keywords CFRP–titanium alloy stacks · Carbon fibers · Drilling · Tool wear · AlCrN coating · Hole quality
1 Introduction Carbon Fiber-Reinforced Polymer (CFRP), a polymer matrix composite material reinforced by carbon fibers, offers high modulus of elasticity exceeding that of typical metals such as steels, high tensile strength, low density, and high chemical inertness [1, 2]. Aircraft and automotive manufacturers increase the usage of carbon fiber-reinforced plastics (CFRP) [1] and assemble with metallic structures (e.g., Boeing 787 and 777X, BMW i3 and i8) to improve fuel efficiency [2]. One of the popular hybrid material systems in the aerospace industry is CFRP/Titanium alloy (Ti) stacks, * Tae‑Gon Kim [email protected] 1
School of Engineering and Computer Science, Washington State University, Vancouver, WA, USA
2
Carbon Nexus at the Institute for Frontier Materials, Deakin University, Geelong, Australia
3
Precision Castparts Co., Portland, OR, USA
4
Phygen Coatings, Inc., Minneapolis, MN, USA
5
Korea Institute of Industrial Technology (KITECH), Cheonan‑si, Republic of Korea
primarily in the form of CFRP atop Ti plates, which offer a higher strength-to-weight ratio and corrosion/heat resistance than CFRP alone. The advent of CFRP–Ti stacks into the aircraft industry has led to a need for specialized tools and machining techniques to manufacture near-net-shaped CFRP–Ti stack products for the final assembly. To maximize the pro
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