Influence of creep deformation on the corrosion behaviour of a CeO2 surface-modified alloy 800H in a sulphidising-oxidising-carburising environment

2009

Oxid Met

The effects of compressive stresses on the oxide-scale morphologies formed on an Fe-20Cr alloy were investigated by comparison of the oxidation behavior in air under classical conditions, i.e., without any applied mechanical stresses and under static compressive stresses, at 900°C. The study was carried out mainly by comparisons of oxidation kinetics gained by thermogravimetric analysis (TGA), surface morphologies of oxidized specimens observed by scanning electron microscopy (SEM), oxidized products examined by X-ray diffraction (XRD). It was found that the application of compressive stresses induced an increase in oxidation rate, but a decrease of oxide grain size. When the stresses are in the range of 5-8 MPa, both chromium-and iron-oxides formed but, at other stresses, only chromia was present. In particular, there was a maximum in oxidation rate when the applied stress was 5 MPa. The paper places emphasis on analyzing the cause of this phenomenon.

Section: Introductionmentioning

confidence: 73%

A Critical Compressive Stress for Increasing the Oxidation Kinetics of Fe–20Cr Alloy Oxidized at 900 °C

2009

Oxid Met

“…On the other hand, the stress state near the oxide-metal interface would change by the application of mechanical stresses. It was found [16] that 1% tensile strain rate accelerated the oxidation rate of IN800H. Rolls et al [17] also found that external stress accelerated oxidation rates suggesting that creep played a role.…”

Section: Oxidation Kineticsmentioning

confidence: 94%

Effect of Mechanical Loading on the Oxidation Kinetics and Oxide-Scale Failure of Pure Ni

2008

Oxid Met

The oxidation kinetics and mechanism of oxide-scale failure of pure Ni oxidized under external static compressive and tensile loads were studied. The results showed that both types of mechanical loads accelerated the oxidation rate, but the effect was different for the two types. Compressive loading (CL) affected it by improving the plasticity of oxide scales, and tensile loading (TL) affected it by amplifying the compaction of the oxide-metal interface. As for the oxide-scale failure, CL can delayed cracking, TL accelerated brittle failure. The study analyzed the effect of external load on the oxidation kinetics and the failure mechanism of oxide scales.

“…There are several ways [17] by which the oxide scale on a substrate can accommodate straining: (1) elastic deformation; (2) plastic deformation due to dislocation glide plasticity or creep; (3) cracking; (4) creep along the substrateoxide interface; (5) decohesion of the scale. Besides these mechanisms, healing processes, i.e., fast closure of cracks under a high oxidizing potential and low deformation rate, have been extensively investigated by Schütze [10,11].…”

Section: Discussionmentioning

confidence: 99%

Deformation of oxide scales on Fe‐20Cr alloy under compressive stress

2010

Materials & Corrosion

The behavior of oxide scales on Fe‐20Cr alloy was investigated in constant load at 1173 K in air. The objective was to understand the effect of mechanical loading on the deformation of oxide scales. It was carried out mainly by comparison of surface morphologies of oxidized specimens observed by scanning electronic microscope (SEM). In all cases, the oxide scales formed on specimens without stress showed a flat surface. However, oxide scales formed on specimens after 20 h of oxidation under a stress of 8 MPa (strain 3.07%) showed slip band characteristics. Furthermore, for longer oxidation time up to 65 h, slip bands formed under a low stress of 2 MPa (strain 1.19%), and grain boundary sliding became the main surface feature for the specimens subjected to a stress of 5 MPa (strain 2.53%). Two typical deformation forms are illustrated in the work.