Internal Oxidation of Fe–Mn–Cr Steels, Simulations and Experiments

Abstract

A multi-element and multi-phase internal oxidation model that couples thermodynamics with kinetics is developed to predict the internal oxidation behaviour of Fe-Mn-Cr steels as a function of annealing time and oxygen partial pressure. To validate the simulation results, selected Fe-Mn-Cr steels were annealed at 950°C for 1-16 h in a gas mixture of Ar with 5 vol% H 2 and dew points of -30, -10 and 10°C. The measured kinetics of internal oxidation as well as the concentration depth profiles of internal oxides in the annealed Fe-Mn-Cr steels are in agreement with the predictions. Internal MnO and MnCr 2 O 4 are formed during annealing, and both two oxides have a relatively low solubility product. Local thermodynamic equilibrium is established in the internal oxidation zone of Fe-Mn-Cr steels during annealing and the internal oxidation kinetics are solely controlled by diffusion of oxygen. The internal oxidation of Fe-Mn-Cr steels follows the parabolic rate law. The parabolic rate constant increases with annealing dew point, but decreases with the concentration of the alloying elements.

Effect of minor Zr on oxidation resistance and mechanical property of nickel-saving austenitic heat-resistant cast steel

“…Figure 5 . It indicates that the oxide scales formed on two experimental steels are of a stratified structure, which is consistent with many researchers' literatures on Mn-containing austenitic steels [10][11][12][13]. As shown in figure 6, after oxidation for 100 h, the oxide scale of two experimental steels were severely spalled during the cooling process.…”

Metal‐Matrix Materials for High‐Temperature Applications with Liquid Aluminum

“…The oxygen is introduced by the starting metal powder through the formation of an oxide layer during processing in air (powder mixing, extrusion, debindering). The formation of these particulate inclusions during sintering cannot be prevented at the applied sintering temperature and atmosphere . However, their presence is of minor significance on the mechanical and corrosive properties, since all the material variants were prepared from one steel powder batch and, therefore, they were also expected to exist in all the materials tested.…”

“…Delamination or broken‐out particles were hardly detected, which indicates the firm bonding at the metal/ceramic interfaces, although the formation of distinct interlayers was not detected by the used methods. The interactions are the result of an intensive diffusion of the steel alloying elements and oxygen and of the reaction with the ceramic components during sintering . These mechanisms are widely known from MMC materials with additions of zirconia or alumina with the intensive formation of spinel or silicate structures .…”

“…The formation of these particulate inclusions during sintering cannot be prevented at the applied sintering temperature and atmosphere. [36][37][38][39] However, their presence is of minor significance on the mechanical and corrosive properties, since all the material variants were prepared from one steel powder batch and, therefore, they were also expected to exist in all the materials tested. The characteristic microstructures of composite variants with additions of TiO 2 are shown in Figure 3.…”

“…The interactions are the result of an intensive diffusion of the steel alloying elements and oxygen and of the reaction with the ceramic components during sintering. [36,38] These mechanisms are widely known from MMC materials with additions of zirconia or alumina with the intensive formation of spinel or silicate structures. [6,18,[40][41][42] Yet, the low Si concentrations in the used powders are assumed to limit the silicate formation to a not adequately measurable quantity.…”