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A case of nitridation, carburization and oxidation on a stainless steel
Author(s) -
Grabke H. J.
Publication year - 2005
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.200403849
Subject(s) - nitriding , metallurgy , materials science , carburizing , austenite , carbide , oxide , nitride , corrosion , decarburization , oxidizing agent , precipitation , spall , layer (electronics) , sulfidation , microstructure , sulfur , composite material , chemistry , physics , organic chemistry , meteorology
A case of corrosion was studied on stainless steel tubes, exposed to a nitriding, carburizing and oxidizing environment (mainly NH 3 and CO 2 ) at 390–450°C. Due to the high nitriding potential prior formation of internally nitrided layers occurs, at higher temperatures (> about 425°C) under precipitation of CrN in the layer and at lower temperatures under formation of the γ N ‐phase, i.e. austenite with high N‐content and expanded lattice. The latter process causes more severe corrosion, due to the high expansion, the stresses in the nitrided layers lead to bursting and repeated spalling of the scales. Carburization and oxidation are less important. The carburization is slower than nitridation, Fe 3 C formation is observed and carbon deposition. Also the oxidation by CO 2 is slow and converts the nitrides and carbides formed before, to unprotective oxide flakes.