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Open AccessArticle

Microstructure of Low-Temperature Gas-Carbonitrided Layers on Austenitic Stainless Steel

Institute of Materials Science and Engineering, West Pomeranian University of Technology, 70-310 Szczecin, Av. Piastów 19, Poland
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Metals 2019, 9(8), 817; https://doi.org/10.3390/met9080817
Received: 14 June 2019 / Revised: 22 July 2019 / Accepted: 23 July 2019 / Published: 25 July 2019
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Abstract

This paper presents the results of microstructural examinations on gas carbonitrided layers using scanning electron microscopy (SEM), wavelength dispersive spectrometry X-ray microanalysis (WDS), magnetic force microscopy (MFM), electron backscattered diffraction (EBSD), and X-ray diffraction. The main objective of the work is to discuss the microstructural and morphological changes occurring in the layers depending on the process parameter such as temperature and atmosphere composition. The carbonitrided layers comprise two sublayers: an outer layer enriched in nitrogen and an inner layer enriched in carbon. It is found that both the microstructure and the thickness depend on the technological parameters of the thermochemical treatment. The treatment temperature is particularly important, increasing both the total and the nitrogen-rich sublayer thickness regardless of the atmosphere type. The nitrogen potential has a positive influence on the thickness of the nitrogen-stabilised S-phase sublayer. Layers treated for 5 h at temperatures of 400 and 450 °C are composed of an internal carbon-enriched S-phase sublayer and an outer nitrogen-enriched S-phase sublayer that can be divided into ferromagnetic and paramagnetic zones. In the outer sublayer, symmetry distortion of the fcc crystal system is observed and stacking faults may have occurred. With layers produced at 500 °C for 5 h, the outer nitrogen-enriched sublayer contains fine precipitates of nitrides and carbides. View Full-Text
Keywords: carbonitriding; nitrocarburizing; S-phase; low-temperature thermochemical treatment; austenitic stainless steel carbonitriding; nitrocarburizing; S-phase; low-temperature thermochemical treatment; austenitic stainless steel
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MDPI and ACS Style

Kochmański, P.; Baranowska, J.; Fryska, S. Microstructure of Low-Temperature Gas-Carbonitrided Layers on Austenitic Stainless Steel. Metals 2019, 9, 817.

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