The tribological phenomena of a new type of TiN/a-C:H multilayer coatings

• Deposition of new kind of multilayer coatings TiN/a-C:H for tribological applications.
• Analysis of hardness and elasticity modulus based on nanoindentation results.
• Effect of bilayer period and TiN to a-C:H layers thickness ratio on mechanical properties.
• Analysis of fracture toughness and wear mechanisms.
• Discussion on optimization coatings architecture to obtain an excellent mechanical and tribological properties.

The paper presents the results of mechanical and tribological tests of new TiN/a-C:H multilayer coatings, which were compared with the properties of single TiN and a-C:H coatings. The effects of the bilayer period and thickness ratio of ceramic and carbon layers on the hardness, resistance to scratching, fracture, wear and coefficient of friction, of such coatings were analyzed. The optimal properties were exhibited by coatings with a 125 nm bilayer period and a TiN/a-C:H thickness ratio of 1:1 and 1:2. The test results showed that there is no reason to reduce the multilayer period to 30 nm and increase the amount of carbon layers to a 1:4 ratio, because such coatings are brittle and exhibit poor adhesion to the substrate. On the other hand, coatings with a higher ratio of ceramic layers have a higher coefficient of friction.

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