Enhancing the tribological properties of CrN/NbN nanoscale multilayer PVD coatings.

This research developed a CrN/NbN coating with promising properties for tribological applications where corrosion plays a big role. Building on this knowledge base a novel approach to the surface treatment was selected, in which multiple layers, each chosen for a specific purpose, were optimised to combine the best properties of each. In this approach a careful consideration of macro- and microstructure of each layer is required in order to extract the good properties of each layer while eliminating the negative ones. It was shown in the work that, if such consideration is neglected, a catastrophic failure may follow. For example poor adhesion may cause a total failure of the coating. As the number of layers and interfaces increase a good understanding on the structure and the properties of each layer becomes very important as the number of parameters and possible combinations increase many times.In this whole work the intention was to take a very practical approach to the coating.The objective was to combine different approaches, such as duplex treatments and multi layering and investigate the specific interactions that are not otherwise apparent.The results of this work show that such an approach is viable and should lead to excellent results as long as the wear mechanisms of the coating are understood and the coating is correctly engineered for the application.