Effects of nitriding on salt spray corrosion resistance of additively manufactured 17-4 PH steels

• Published in: Materials letters Vol. 330; p. 133258
• Main Authors: Jessy Michla, J.R., Rajini, Nagarajan, Oluwarotimi Ismail, Sikiru, Ram Prabhu, T., Mohammad, Faruq, Siengchin, Suchart, Indira Devi, M.P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2023
• Subjects: Additive manufacturing; Corrosion; Grain boundaries; Microstructure; Nitriding; Grain boundaries; Nitriding; Additive manufacturing; Corrosion; Microstructure
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2022.133258

•Study on effects of nitriding temperatures on NSS corrosion on AM 17-4 PH steel material.•Larger red rust formation was observed on as-built when compared with nitrided samples.•Higher volume of reduced grain size with precipitates was observed in the microstructure of nitrided samples.•Passive protective film with chromium and iron nitrides exhibited the best corrosion resistance at 580 °C. This work addresses the effects of varying nitriding temperatures of 530, 560 and 580 °C for 2 h on corrosion resistance of additively manufactured (AM) 17-4 PH steels, using neutral salt spray (NSS) method for 104 h. The morphological analysis indicated the presence of columnar grains along the built direction of additive manufacturing process. The refined grain size and the amount of the precipitates increased with an increasing nitriding temperature. The results of the analysis showed that a minimum weight loss was observed at 580 °C, due to the formation of passive oxide layer and nitrogen rich precipitates on the surface. The X-ray diffraction (XRD) showed the presence of these compounds: Cr2N, (Fe, Cr)4N, (Fe, Cr)2-3N, Fe2O3, FeOOH, and Cr2O3 on the nitrided sample after the salt spray test.