Role of Nitrogen Uptake During the Oxidation of 304L and 904L Austenitic Stainless Steels
Artikel i vetenskaplig tidskrift, 2013

Nitrogen uptake affects corrosion of stainless steel in diesel exhaust systems where urea is injected to reduce NO (x) . This was examined by exposing plasma nitrided 304L and 904L to humid air at 450-600 A degrees C. The samples were characterized primarily by using XRD, AES and XPS. The as-nitrided samples had 10-20 at.% N in 3-40 mu m layers dominated by expanded austenite supersaturated with N, or the S-phase. Nitrogen was detrimental, with oxide thicknesses about 70-100 times thicker than on as-received 304L and 2-5 times thicker on 904L. In the S-phase the Cr activity is reduced by short-range ordering with N, hampering formation of protective oxides. On 304L the fraction of thick oxides decreased significantly with increasing temperature, despite formation of CrN, since formation of bcc promotes Cr diffusion. For 904L the S-phase is more stable and the corrosion less severe due to its alloying content. At 500 A degrees C formation of CrN enhanced the corrosion.

molybdenum

water-vapor

oxide hydroxide evaporation

high-temperature oxidation

Oxidation

Nitriding

Stainless steel

behavior

aisi 316l

Expanded austenite

corrosion

microstructure

Författare

Yu Cao

Chalmers, Material- och tillverkningsteknik, Yt- och mikrostrukturteknik

Mats Norell

Chalmers, Material- och tillverkningsteknik, Yt- och mikrostrukturteknik

Oxidation of Metals

0030-770X (ISSN) 1573-4889 (eISSN)

Vol. 80 479-491

Ämneskategorier

Metallurgi och metalliska material

Styrkeområden

Materialvetenskap

DOI

10.1007/s11085-013-9391-1