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The high-hardness diamond-like carbon (DLC) films synthesized by filtered cathodic vacuum arc (FCVA) deposition may have high residual stress, which will cause the DLC film/substrate interfacial crack and film failure. Therefore, it is essential to analyze and control the residual stress during the DLC deposition. In this paper, the low-hardness DLC monolithic layer films (rich in sp2 content, soft DLC), the high-hardness DLC monolithic layer films (rich in sp3 content, hard DLC), and a series of soft/hard DLC multilayer films with modulation ratio of 1 : 1 and modulation periods ranging from 70 to 280 nm are deposited, respectively, on Si (100) wafer and Ti-6Al-4V by FCVA technology with periodic adjustments of the substrate negative bias. The effects of modulation periods (bilayer thickness) on residual stress and wear resistance of multilayer DLC films are studied. The results show that the residual stress decreases in soft/hard multilayer DLC films with decreasing modulation periods, and the films with modulation period of 140 nm have excellent wear resistance. ANSYS finite-element software is used to simulate the residual stress generation during FCVA deposition in the DLC film on a silicon substrate. The result of the finite-element simulation is consistent with that of the experiment, and the finite-element technique has a potential application in the optimization process of DLC multilayer films.
Date of Publication: Sept. 2012