Performance of HIPIMS deposited CrN/NbN nanostructured coatings exposed to 650 degrees C in pure steam environment

Hovsepian, P. E., Ehisarian, A. P., Purandare, Y. P., Biswas, B., Pérez, F. J., Lasanta, M. I., De Miguel, M. T., Illana, A., Juez Lorenzo, M., Muelas, R., Agüero, A. 2016. Performance of HIPIMS deposited CrN/NbN nanostructured coatings exposed to 650 degrees C in pure steam environment. Materials Chemistry and Physics 179, 110-119, DOI: 10.1016/j.matchemphys.2016.05.017

In the current work, 4 mu m thick CrN/NbN coating utilising nanoscale multilayer structure with bi-layer thickness of Delta = 2.9 nm has been used to protect 9 wt% Cr steels such as P92 widely used in steam power plants. The uniquely layered coatings have a combination of nitrides of chromium and niobium which are not only resistant to aqueous corrosion and corrosion-erosion and have excellent tribological properties, but also have oxidation resistance in dry air up to a temperature of 850 degrees C. The novel High Power Impulse Magnetron Sputtering (HIPIMS) deposition technology has been used to deposit CrN/NbN with enhanced adhesion (critical load of scratch adhesion L-C2 = 80 N) and a very dense microstructure as demonstrated by Transmission Electron Microscopy (TEM) imaging. These superior coating properties are achieved due to the unique high metal ion content (up to 90%) in the HIPIMS plasma, which allows particle acceleration and trajectory control by external electrical and magnetic fields thus delivering highly energetic material flux on the condensing surface.

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