Effect of substrate bias voltage on the mechanical properties of AlTiN/CrTiSiN multilayer hard coatings

Abstract

During physical vapor deposition (PVD), bias voltage is usually applied to the substrate for tuning the ion energies and tailoring the coating structure and mechanical properties of a protective hard coating for specific applications. In the present study, AlTiN/CrTiSiN multilayer coatings were deposited by a multisource cathodic arc ion deposition system with negative substrate bias voltages ranging from −20 to −180 V. During the coating process, graded CrN, CrN/AlTiN and CrTiSiN were deposited as interlayers to enhance adhesion strength of the coatings. Multisources of Cr, TiSi and AlTi alloy targets were used. Residual stresses and mechanical properties of AlTiN/CrTiSiN multilayer coatings deposited under various bias voltages were investigated. All the AlTiN/CrTiSiN multilayer coatings possessed higher hardness values (38.2–39.6 GPa) than AlTiN (32.5 GPa). As compared to the monolithic AlTiN, which had high residual stress of −9.8 GPa, the AlTiN/CrTiSiN multilayer coatings showed lower residual stresses of −2.4~ −9.1 GPa. The higher bias voltage was used the higher residual stress was observed. The AlTiN/CrTiSiN multilayer coating deposited at −20 V possessed the lowest residual stress (- 2.4 GPa). A cyclic impact test with high frequency were performed to evaluate the impact fatigue performance. The AlTiN/CrTiSiN multilayer coating deposited at −20 V showed the highest H/E (0.082) and H3/E2 (0.265) values to resist impact fatigue. The design of AlTiN/CrTiSiN multilayer coatings via low bias voltage can decrease residual stress and possessed good impact fatigue performance. Although the AlTiN/CrTiSiN coating deposited at high bias voltage of −180 V had similar hardness value to other AlTiN/CrTiSiN coatings under −20 V and −100 V, worse resistance to impact fatigue were found.