High temperature corrosion of cast alloys in exhaust environments. II-Cast stainless steels
Artikel i vetenskaplig tidskrift, 2008

This paper describes in detail the oxidation of two cast stainless steels in synthetic diesel and gasoline exhaust gases. One alloy was ferritic (Fe18Cr1.4Nb2.1Mn0.32C) and one austenitic (Fe20Cr9Ni1.9Nb2.7W0.47C). Polished sections were exposed, mostly for 50 h, at temperatures between 650 and 1,050 degrees C. The oxidation product was characterized by means of SEM/EDX, AES, and XRD. Inter-dendritic non-Cr carbides initiated thick oxides. The ferritic steel formed a rather thin and adherent oxide scale at all temperatures. It consisted of (Mn, Cr) oxide on top of Cr2O3 and, starting at 850 degrees C, a thin silica film at the metal-oxide interface. Chromium depletion triggered dissolution of carbides providing Cr to the oxide. Water vapor did not accelerate the attack since the outer (Mn, Cr) spinel oxide reduced the Cr evaporation. The austenitic grade was very sensitive to water vapor. Chromium segregation directed pitting to the dendrites up to 950 degrees C whereas uniform catastrophic oxidation occurred at 1,050 degrees C.

cast stainless steels

OXIDE

(Mn

Cr-evaporation

SILICON

BASE ALLOYS

Cr) spinel

FE-CR ALLOYS

OXYGEN

IRON

gas mixtures

KINETICS

high temperature corrosion

CHROMIUM

OXIDATION

MANGANESE ALLOYS

Författare

Frédéric Tholence

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. 69 37-62

Ämneskategorier

Materialteknik

DOI

10.1007/s11085-007-9082-x