Effect of Alloying Elements, Water Vapor Content, and Temperature on the Oxidation of Interstitial-Free Steels

Abstract

The present study is an investigation of the surface and subsurface oxidation of Mn solidsolution-strengthened interstitial-free (IF) steels with the objective of elucidating the surface evolution before coating. Thermogravimetric (TG) analysis was carried out under 95 vol pct Ar + 5 vol pct (H 2 + H 2 O) atmospheres with P H 2 O =P H 2 ranging from 0.01 to 0.13 and temperatures ranging from 800°C to 843°C. Post-exposure characterization was carried out through scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and glancing-angle X-ray diffraction (XRD) to study the external and internal oxide evolution. The oxidation proceeds as a combination of the internal and external formation of Mn oxides. Decreasing the P H 2 O =P H 2 ratios or temperature has the effect of decreasing the amount of oxidation, which is a combination of internal and external oxidation controlled by solid-state oxygen and manganese diffusion, respectively. External oxides are not continuous; they are instead concentrated near the intersection of alloy grain boundaries with the external surface. Internal oxides are concentrated along the grain boundaries. The effects of Sb (0.03 wt pct), B (10 ppm), P (0.04 and 0.08 wt pct), and Si (0.06 to 1.5 wt pct) on the oxidation were investigated. It is found that small amounts of Sb and B have a significant effect on decreasing both the external and internal oxidation, whereas Si and P increase the external and internal oxidation.

Effect of Dew Point and Gas Flow Rate on the Surface Oxidation of Advanced High Strength Steels

“…It is well known that, in the absence of a continuous external scale, higher dew points cause internal oxidations as a result of increased dissolved oxygen concentration at the surface. 16) In agreement with other reported results, 6) it was observed that the internal oxidation developed at dew points of 0°C or higher in this study under 100 l/min flow rate. What is noteworthy however is that the appearance of internal oxides shifted to lower dew points when the gas flow rate was decreased.…”

“…[3][4][5][6][7][8][9][10][11] To identify ways to reduce surface oxides, studies were carried out in various annealing conditions; such as the influence of oxygen partial pressure or H 2 /N 2 ratio in atmosphere, Si/Mn ratio or trace elements in steel compositions etc. Most of these investigations were focused on the reaction of metals with oxygen in atmospheres that were assumed to be under (or near) thermodynamic equilibrium conditions wherein the oxygen partial pressure in atmosphere was determined by gas phase equilibrium.…”

Investigation of the Effect of Alloying Elements and Water Vapor Contents on the Oxidation and Decarburization of Transformation-Induced Plasticity Steels

“…The experimental procedures have been described in an earlier article, [13,17] and will be briefly summarized here. A TG analysis setup (SETARAM Instrumentation, Caluire, France) was mainly used in the present experiments.…”

“…[11] To improve the wettability of TRIP steels, some researchers tried to suppress the oxidation by adding some surface active elements, one of which is Sb. An addition of Sb has been found to significantly affect the recrystallization of steels [12] and to suppress internal oxidation, [13] as well as to improve the texture of nonoriented Si steels. This was due to the formation of a texture rich in (100) grains in Si steels caused by the presence of Sb.…”

“…[13,16,17] The articles elucidated the evolution of internal oxidation, external oxidation, and decarburization and their interdependence under different P H 2 O =P H 2 ratios for TRIP steels, and the effect of water vapor content, temperature, and alloying elements on the oxidation of IF steels. It was found that Si increases the internal oxide density and causes Fe extrusion to the surface, and that Sb addition suppresses both the internal and external oxidation of IF steels.…”