Improvement in load support capability of a-C(Al)-based nanocomposite coatings by multilayer architecture

Due to severe operating conditions and long lifetime requirements for mechanical components, the great challenge is to develop coatings with anti-wear and high load support capability. The designs for nanocomposite protective coatings are very promising and provide an attractive alternative to take into account the multilayer architecture. In this work, a-C(Al)-based nc-TiC/a-C(Al), nc-CrC/a-C(Al) and nc-WC/a-C(Al) nanocomposites were constructed by Cr/CrN/CrCN multilayer. The microstructure, mechanical properties, friction and wear behaviors for these multilayer coatings were systemically investigated. Results showed that the top-layered nc-TiC/a-C(Al), nc-CrC/a-C(Al) and nc-WC/a-C(Al) nanocomposites were dominated by typically nanocrystallite/amorphous microstructure, and these nanocomposites constructed by multilayer approach presented superior mechanical properties which possessed relatively high hardness, low internal stress as well as high adhesion strength. Particularly, the as-fabricated nc-TiC/a-C(Al), nc-CrC/a-C(Al) and nc-WC/a-C(Al) multilayer coatings exhibited superior anti-wear capability under relatively high applied Hertzian contact pressure compared to corresponding monolayer coatings. The improvement in friction and wear performances of as-fabricated multilayer coatings was mainly attributed to superior mechanical properties and formation of graphitized tribofilm as well as high load support capability by multilayer architecture, indicating that these coatings might be good candidates as solid lubrication materials in engineering applications.