Cutting performance of CrN-based coatings tool deposited by hybrid coating method for micro drilling applications

This paper describes the results of application of CrN based coatings to micro drilling operation for deep and small boreholes machining. Four different CrN, Cr–Al–N, Cr–Si–N, and Cr–Al–Si–N coatings were successfully deposited on WC–Co substrates by a hybrid coating system. Their microstructure and mechanical and tribological properties were systematically investigated. The hardness values of the Cr–Si–N (~ 35 Gpa) and the Cr–Al–Si–N (~ 55 Gpa) coatings were significantly increased compared with those of CrN (~ 23 GPa) and Cr–Al–N (~ 25 GPa) coatings. Besides, the average friction coefficients of the Cr–Si–N (~ 0.30) and the Cr–Al–Si–N (~ 0.57) coatings with Si content of 9 at.% were largely decreased compared with those of CrN (~ 0.50) and Cr–Al–N (~ 0.84) coatings. And then, high-speed through-hole drilling tests were performed on circuit board workpiece to investigate the machining performance of coated micro drills. The experimental results show that the Cr–Al–Si(8.7 at.%)–N has excellent microstructure, microhardness, and tribological properties and represents the optimal coatings for micro drilling applications.