Two-Layer Nanocomposite TiC-Based Coatings Produced by a Combination of Pulsed Cathodic Arc Evaporation and Vacuum Electro-Spark Alloying

A novel two-stage technology combining vacuum electro-spark alloying (VESA) and pulsed cathodic arc evaporation (PCAE) was approbated for the deposition of TiC-based coatings in inert (Ar) and reactive (C2H4) atmospheres. The deposition was carried out using a TiC-NiCr-Eu2O3 electrode and 5140 steel substrates. Structural, elemental, and phase compositions of the deposited coatings were investigated by scanning electron microscopy, energy-dispersive spectrometry, and X-ray diffraction. The mechanical properties of the coatings were measured by nanoindentation using a 4 mN load. The tribological properties of the coatings were measured using the pin-on-disc setup in air and in distilled water at a 5 N load. The experimental data suggest that VESA coatings are characterized by surface defects, a hardness of 12.2 GPa, and a friction coefficient of 0.4. To ensure good adhesion between the VESA coating and the upper layer containing diamond-like carbon (DLC), an intermediate layer was deposited by PCAE in the Ar atmosphere. The intermediate layer had a hardness of up to 31 GPa. The upper layer of the coating ensured a low and stable friction coefficient of 0.2 and high wear resistance due to the formation of an sp(2)-sp(3) bound carbon phase. Multilayer TiC-based coating with the upper DLC layer, in addition to high tribological properties, was characterized by the lowest corrosion current density (12 mu A/cm(2)).