Corrosion Resistance of the Inconel 740H Nickel Alloy after Pulse Plasma Nitriding at a Frequency of 10 kHz
R. Sitek, J. Kaminski and J. Mizera
Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw, Poland
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The microstructure and corrosion resistance of the CrN, Cr2N layer produced by pulse plasma ion nitriding at a frequency of 10 kHz on the Inconel 740H nickel superalloy were examined. The microstructure of the layers were characterized by light microscope and scanning electron microscopy. The corrosion resistance was examined by the impedance and potentiodynamic methods in a 0.1 M Na2SO4 solution and an acidified (pH = 4) 0.1 M NaCl solution at room temperature. The layer obtained, about 4.5 µm thick, contains CrN, Cr2N phases. It is continuous on the entire cross-section of the sample and adheres well to the substrate. However, in the chloride environment it constitutes an inhomogeneous cathodic coating for corrosion and thereby intensifies pitting corrosion of the material. In chloride-less environment, on the other hand, the layer has no essential effect on the corrosion rate of the Inconel 740H nickel alloy.

DOI: 10.12693/APhysPolA.129.584
PACS numbers: 81.40.-z