Development of TiN based composite coatings for tribological applications

Nitrides exhibit strong bonds which are responsible for elevated stability at high temperatures, along with superior hardness, wear resistance, and chemical durability, which explains the extensive use of nitrides as protective and wear resistant coatings. These coatings are commonly fabricated using thin film deposition techniques (PVD, CVD etc.); however, such Methods are limited by achievable coating thicknes (<10 µm) and the size of the components that can be coated. In order to deposit thick layers, thermal spraying offers advantages with its flexibility, high deposition rate and possibility of local material deposition. Nevertheless, thermal spraying of non-oxides poses some limitations, either due to a high oxidation tendency or the lack of a congruent melting point. A possible approach is to deposit these materials together with a chemical compatible binder phase allowing partial incorporation of non-oxides while enhancing coating properties. In this project, TiN/Al2O3 composite coatings were developed using High Velocity Suspension Flame Spraying (HVSFS) and evaluated regarding their phase composition, wear resistance, microstructure and mechanical properties. The HVSFS process enables the incorporation of a high TiN content and well-distributed nitride particles within the coating.