Fabrication and cutting performance of CrAlN/CrAl multilayer coatings deposited by continuous high-power magnetron sputtering

Continuous high-power magnetron sputtering (C-HPMS) is one of the desirable techniques to fabricate coatings with high hardness and a smooth surface to meet the demand by micro-millings for processing/cutting of printed circuit boards (PCBs). However, catastrophic failure can occur on the coatings because of the high residual stress in contact with hard glass fibers in PCBs at a high cutting speed. In this work, CrAlN/CrAl multilayer coatings consisting of thin CrAl interlayers are fabricated and characterized. The thin CrAl layers reduce the residual stress significantly from-6.7 GPa to-1.5 GPa, while the hardness of 35 GPa is preserved. Furthermore, the adhesion strength and wear resistance are improved appreciably by addition of the interlayers. The PCB cutting tests reveal that the CrAl layers mitigate sudden failure of the coatings and improve the cutting stability and service life by near two times.