Microstructure and tribomechanical properties of (Cr, N)-DLC/DLC multilayer films deposited by a combination of filtered and direct cathodic vacuum arcs

• (Cr, N)-DLC/DLC multilayer films were deposited by FCVA combined with DCVA.
• The (Cr, N)-DLC layer consists of amorphous phase and nano-crystals.
• Co-doping could relieve DLC film's residual compressive stress effectively.
• The multilayers' toughness can be tuned by varying sp3 content in DLC layer.
• The multilayer films exhibited good wear resistance and high adhesion to YG8.

Alternating multilayer diamond-like carbon (DLC) films [(Cr, N)-DLC/DLC] with different sp3 contents in DLC layer have been prepared on YG8 (WC-Co) substrates by FCVA combined with DCVA technique. The structure was investigated by scanning electron microscopy and transmission electron microscopy. Chemical bonding was studied by Raman spectroscopy and X-ray photoelectron spectroscopy. Mechanical and tribological properties including residual stress, hardness, adhesion strength and wear resistance were evaluated by film stress tester, nanoindenter, scratch tester, ball-on-disk tribometer and surface profiler. The results showed that (Cr, N)-DLC layer had the composite structure of amorphous phase as base interspersed with a small amount of nano-crystals. The co-doping of Cr and N into DLC reduced the film's residual stress from − 1.62 GPa to − 0.99 GPa. For monolayer DLC, both the sp3 content and residual stress decreased as the substrate's bias voltage increased in the range of − 100 V to − 600 V. And the decrease of sp3 content contributed to an increase of the (Cr, N)-DLC/DLC films' toughness. In addition, the multilayer films presented good adhesion strength on YG8 substrates. The wear rates of all multilayer films belonged to the order of magnitude of 10− 7 mm3/Nm.Prime novelty statementMultilayer films consisting of DLC and DLC co-doped with metal and nonmetal atoms [(Cr, N)-DLC/DLC multilayer films] have been prepared by FCVA combined with DCVA technique and investigated systematically. The composite structure of the (Cr, N)-DLC layer is based on amorphous phase and contains a small number of nano-crystalline compounds of chromium.

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