Effect of AlTiN Coating Structure on the Cutting Performance of Cemented Carbide PCB Microdrills

The preparation of high-performance hard coatings on the surface of cemented carbide PCB (printed circuit board) microdrills can effectively decrease the rapid tool wear that occurs during cutting. In this study, arc ion plating technology was employed to deposit conventional AlTiN columnar crystal single-layer coatings and AlTiN nanocrystalline single-layer coatings on the cemented carbide substrates of PCB microdrills. Additionally, a novel AlTiN composite coating with alternating columnar and nanocrystalline layers was designed and deposited. The mechanical properties and morphological characteristics of the three coating structures were analyzed using an indentation tester and scanning electron microscopy. The above three coated PCB microdrills were tested under the same conditions, and the cutting performance and tool wear mechanisms were compared and analyzed. The results show that the primary wear mechanisms for AlTiN-coated PCB microdrills are abrasive wear and coating flaking, and that the microdrill with the AlTiN columnar/nanocrystalline multilayer composite coating has the longest tool life. The novel AlTiN columnar/nanocrystalline composite coating exhibits superior interfacial adhesion strength, higher toughness, and better surface quality, and, hence, is more suitable for the high-speed drilling of PCB microholes.