The dependence of the structure and mechanical properties of thin ta-C coatings deposited using electromagnetic venetian blind plasma filter on their thickness

In this paper, we present the results of studies determining the optimum thickness of amorphous tetrahedral carbon (ta-C) thin films for industrial applications. ta-C coatings from 50 to 1000 nm thickness were synthesized by a pulsed vacuum-arc method using a water-cooled electromagnetic Venetian blind plasma filter. Systematic studies of the thickness dependence of the microstructure and mechanical properties showed that the content of sp3 bonds in all the deposited coatings are equal (about 68%), but the 300 nm thick coatings exhibited the best mechanical properties (hardness H > 50 GPa, adhesion Lc2 = 48 N). These coatings were deposited on industrial cutting taps with 2 and 2.5 mm diameters and tested in industrial conditions. The results of the threading tests performed with Inox stainless steel showed that the durability of the ta-C coated tools were significantly higher compared with the uncoated ones. These real-world industrial tests confirmed the usefulness of the electromagnetic Venetian blind plasma filter for synthesizing thin ta-C coatings with excellent physico-mechanical characteristics.