Oxidation Resistance Of Stainless Steel Research Articles

Fabrication of yttria-stabilized zirconia/La2O3 composite coating by electrophoretic deposition to improve high-temperature oxidation resistance of stainless steel

Nanoscale yttria-stabilized zirconia (YSZ) and La2O3 were used to prepare a composite coating by electrophoretic deposition (EPD) and sintering to improve the high-temperature oxidation resistance of AISI430 stainless steel. SEM, XRD, and TEM were used to identify the microstructure of the YSZ/La2O3 composite coating and the oxide film formed at 900 °C. The effect of the EPD voltage on the coating thickness was studied. The microstructure properties and phase transition of the composite coatings during sintering were identified. The oxidation behavior of the composite coating at 900 °C was investigated by analyzing the oxidation kinetics curve, oxidation spallation, the formation of the interfacial oxide film, and the evolution of the coating microstructure. A model of the microstructure evolution of the YSZ/La2O3 composite coating during EPD, sintering, and high-temperature oxidation was proposed and discussed.

Effect of laser shock peening and surface mechanical attrition treatment on the oxidation resistance of a 20Cr-25Ni-Nb stainless steel

In this study, the effects of laser shock peening (LSP) and surface mechanical attrition treatment (SMAT) were comparatively investigated on the oxidation behaviors of 20Cr-25Ni-Nb stainless steel in a high-temperature (650 °C) CO2 environment up to 1000 h. The results show that the oxidation resistance of stainless steel can be improved by LSP but deteriorated by SMAT. LSP promoted the formation of a thin and uniform Cr-rich oxide layer on the 20Cr-25Ni-Nb stainless steel instead of a thick duplex oxide layer with Fe-rich outer layer and Cr-rich inner layer which appeared on the untreated sample. For the SMAT-treated sample, besides the oxide scale, a thick internal oxidation zone (IOZ) and oxides spallation were also observed. The formation of a Cr-rich oxide layer was facilitated by the enhancement of the Cr diffusion within the LSP-induced hardened layer. The unsatisfying oxidation performance of the SMAT-treated sample is due to the surface micro-cracks and significant grain refinement which synergistically contributed to the visible carburization and oxidation in a high-temperature CO2 environment.

Analysis on Oxidation Behavior of HR3C Steel at 700°C in Water Vapor

HR3C is an advanced heat-resistant alloy, and its high-temperature oxidation resistance directly determines the service performance of the material. Therefore, exploring the high-temperature oxidation behavior of HR3C is of great significance for the theoretical research and practical application of the material. The oxidation kinetic curve, oxide film morphology, oxide film composition, and oxide film phase composition of HR3C samples in the supply state after being oxidized in water vapor at 700°C for 50h, 150h, 250h, 350h, 450h, 550h and 600h were analyzed by SEM (Scanning Electron Microscopy), EDS (Energy Dispersive Spectroscopy) and XRD (X-ray diffraction). The results show that the oxidation kinetic curve of the material conforms to the parabolic law, the oxide film first forms a lamellar oxide, and the lamellar oxide film grows alternately to form a loose and porous oxide film surface, the oxide is composed of three oxides: Fe₃O₄, FeCr₂O₄ and Fe₂O₃. The FeCr₂O₄ is a spinel compound, which can form a dense oxide film, and the diffusion coefficient of metal ions in it is small, which hinders the diffusion and mass transfer of ions, thereby improving the high temperature oxidation resistance of stainless steel. The element Cr is mainly enriched in the inner oxide layer, and the element Fe is relatively high in the outer oxide layer.

Clarifying the mitigation effect of proton irradiation on the intergranular oxidation of 316L stainless steel in high temperature water

The role of proton irradiation in the intergranular oxidation of 316L stainless steel after long-term immersion in simulated PWR primary water was clarified by comparing the microstructural and microchemical features of oxide between the irradiated grain boundary (GB) and its un-irradiated counterpart. As such, the interference from difference in GB structure can be ruled out. Surprisingly, the results reveal that the intergranular oxide penetration in the irradiated region is shallower than that in the un-irradiated region. It is found that Si segregated at the irradiated GB diffuses outwards preferentially and gets oxidized due to its high diffusivity and affinity to oxygen. The Si-enriched oxide in the intergranular oxide tip of irradiated GB can act as a temporary diffusion barrier for oxygen, although it tends to dissolve near the sample surface. Meanwhile, the efficiency of elements (especially Cr) transport along irradiated GB to the oxidation front is promoted mainly due to the vacancies created by preferential diffusion of Si, resulting in higher Cr content at the intergranular oxide tip. The combination of Si and Cr enrichments in the intergranular oxide tip can enhance the resistance to oxidation and eventually leads to a lower oxidation rate for the irradiated GB. For the first time, our study determines that irradiation can enhance the intergranular oxidation resistance of stainless steel after long-term immersion in simulated PWR primary water when the sample is not stressed.

Effect of Mullite Film Layers on the High-Temperature Oxidation Resistance of AISI 304 Stainless Steel

Protective coating is an effective way to extend materials’ high-temperature service life. In order to improve the high-temperature oxidation resistance of AISI 304 stainless steel, mullite films with different layers were successfully prepared by the sol-gel method and the sintering process on the surface of stainless steel. The effect of the film layers on the high-temperature oxidation resistance of stainless steel at 900 °C for 100 h was studied. The analysis results of oxidation kinetics, X-rays diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis (EDS) show that Al1.4Si0.3O2.7 mullite film effectively improved the high-temperature oxidation resistance of stainless steel. The sample with three-layer mullite film has the best high-temperature oxidation resistance. The mass gain and oxidation spalling mass are only 4.6% and 34.5% of those of the uncoated sample after 100 h cyclic oxidation at 900 °C. A chromium oxide layer was formed at the interface of mullite film and the substrate during the sintering process. The generation of selective Cr2O3 scale was promoted at the cyclic oxidation stage so that the sample with three-layers has excellent high-temperature oxidation resistance.

Elucidating the grain-orientation dependent corrosion rates of austenitic stainless steels

The dependence of oxidation rates on grain orientation has been observed for austenitic alloys suggesting crystallographic control of such processes. To better understand these observations, the active and transpassive oxidation behaviors of an austenitic AISI 316L stainless steel were investigated using vertical scanning interferometry (VSI). The oxidation rates of >100 unique grains were measured and related to their crystallographic orientations (i.e., with respect to the surface normal direction) as identified using electron backscatter diffraction (EBSD). The oxidation rates follow a scaling that is given by: {001} < {101} < {111} for grains undergoing both active and transpassive oxidation. The corrosion tendencies of {001} and {101} grains indicate that the activation energy of dissolution follows a scaling similar to that of the surface energy. However, the high corrosion rates of {111} grains, which feature a surface energy lower than those of the {001} and {101} grains, is attributed to their lower tendency to adsorb passivating species, from solution, that leads to a net reduction in the activation energy of oxidation. These insights provide improved understanding of the crystallographic controls of oxidation processes, and thereby suggest processing pathways for enhancing the oxidation resistance of stainless steels.

Microstructure and Oxidation Behavior of Ni–TiO2 Composite Coating at High Temperature

Ni-based composite coatings are considered to improve the oxidation resistance of stainless steel. In this study, Ni–TiO2 composite coatings were electrodeposited onto the AISI 430 stainless steel. The isothermal oxidation of bare steel and steel with Ni–TiO2 coating was performed at 800 °C for 200 h. Moreover, cyclic oxidation of the coated and bare steel was performed up to 50 cycles. The coating layer and oxide scales were investigated by X-ray diffraction and scanning electron microscopy. All the coated specimens showed good oxidation resistance during the oxidation tests. The TiO2 particles in the coating affected the stability of the protective oxide scale. Furthermore, the coated steel showed a lower oxidation rate compared with the bare steel. It is concluded that TiO2 increases oxidation resistance by blocking the outward diffusion of Cr cations.

Grain orientation dependent Nb–Ti microalloying mediated surface segregation on ferritic stainless steel

Surface segregation and oxide formation anisotropy on Ti–Nb stabilized ferritic stainless steel (EN 1.4521) were studied by XPS and Electron Backscatter Diffraction. Competitive surface segregation of Si, Nb and Ti was initiated at ∼550°C, and segregation was favored to the open surface sites of 〈111〉 oriented grains. Furthermore, the surface segregation of Cr was strongly limited at the locations of stable Ti(CN)- and (NbTi)C-type precipitates. Consequently, the oxidation resistance of stainless steels can be enhanced cost-efficiently, without alloy additions, by optimizing the microstructure to facilitate the fast and uniform growth of protective oxide scale.

Effect of the Shot Peening Process on the Corrosion and Oxidation Resistance of AISI430 Stainless Steel

Ferritic stainless steels are used in specific applications where corrosion resistance, oxidation resistance and a high mechanical resistance are required. Shot peening is a process applied to add residual compression stresses in metallic surfaces with the intent of improving the material when exposed to corrosion due to stress and fatigue. Some studies about the effect of the shot peening process on the fatigue resistance, bending fatigue behavior, and residual surface stress in the ferritic stainless steels have been performed. However, the effect of the shot peening process on the corrosion and oxidation resistance of the stainless steel is not well known. In this context, the purpose of this study is to evaluate the effect of the shot peening process on these superficial properties of ferritic AISI430 stainless steel. The obtained results showed that the ferritic AISI430 stainless steel samples treated with shot peening presented a significant modification on the surface morphology and an important decrease of oxidation and corrosion resistance, evidencing that the shot peening process compromises the chemical and physical properties of the surface.

Stainless Steel - A Versatile Engineering Material for Critical Applications

Stainless Steel is a family of versatile materials that has been put into a wide variety of application by mankind. Stainless steels are iron-based alloys containing minimum 12% chromium and upto 25% nickel with minor additions of carbon, nitrogen, molybdenum, tungsten, titanium, niobium, copper and selenium. It has a wide range of applications from small pins to the construction of automobiles, petrochemical, space, aeronautical, ship building industries, nuclear and thermal power stations. Certain grades of stainless steels, because of their biocompatibility are used for manufacture of biomedical implants. In fact steel touches every sphere of our daily life. By and large stainless steel family consists of hundreds of grades with varieties of compositions and a large spectrum of mechanical properties. The corrosion and oxidation resistance of stainless steels have been significantly improved through fine-tuned chemical compositions and microstructural constituents, leading to the evolution of super stainless steels. Stainless steel development from design to application is a long-term continuous effort. The recent advances in stainless steels are mainly due to new ways of manufacture, processing and usage of advanced equipments. In spite of inroads by a range of competing materials, stainless steels occupy an important place as structural materials, because of their outstanding strength to weight ratios, ductility, fracture toughness, repairability, corrosion, etc for a given cost. Over the years, MIDHANI has catered to the requirements of Indian Space, Nuclear, Thermal, aeronautical and Defence sector for many high performance materials. A wide range of special stainless steels many of them being tailor made to customers specific needs have been developed and supplied. This has been possible with the help of state of the art facility and excellent quality assurance system available in MIDHANI. The presentation will high light MIDHANI role in development and commercial production of different varieties of stainless steels for critical applications.

Role of nanoceria coatings on the high temperature oxidation of stainless steels: An atomistic simulation

Computer simulations using the Density Functional Theory and GAUSSIAN 03 were implemented in predicting potential mechanisms that can be associated with the high temperature oxidation of stainless steels. In particular, the role of nanoceria protective coatings on the induced diffusional mechanisms at 1273K was satisfactorily predicted. Atomistic calculations were made on computed activation energies for oxygen inward diffusion and for iron outward diffusion through the nanoceria coating and the chromium oxide scale, respectively. In addition, it was assumed that when nanoceria coatings are present in stainless steels, cerium ions can be incorporated in the Cr2O3 scale as dopants. Computer simulations indicate that in the absence of Ce ions in the chromia scale lattice Fe outward diffusion is dominant and accounts for the relatively high oxidation rates. It was found that in a Ce-doped Cr2O3 scale the predicted activation energies exhibit appreciable changes. Under these conditions the activation energies for both, iron and oxygen diffusion increase in magnitude. However, the activation energy for O inward diffusion falls below the one corresponding to Fe outward diffusion. In turn, oxygen inward diffusion becomes rate limiting accounting for the role of nanoceria coatings on the high temperature oxidation resistance of stainless steels.

Characterization of Oxidation Resistance of Stainless Steels at High Temperature by Metallographic Examinations and In-Situ Electrical Resistance Measurements

Abstract Practically all metals and alloys survive high-temperature exposure by growing oxide scales and/or by precipitation of the oxide particles in the matrix. Formed products can grow in shape of external oxide layers on surfaces, or as discrete oxide particles precipitated in a metal matrix. The first case represents external oxidation, and the other case is called internal oxidation. These processes are very important, because they determine the properties and applicability of metallic materials. Generally, they are undesired, because they cause deterioration of the mechanical properties and decomposition of metallic material. On the other side, the controlled process of external oxidation could be used for formation of protective coatings and the internal oxidation for dispersion strengthening of materials. In this paper we present monitoring of high-temperature oxidation of X12Cr13 stainless steel by in-situ electrical resistance measurements at different annealing temperatures in the air atmosphere. We determined the kinetics of oxide scale formation and its morphology with additional metallographic examination made by optical and scanning electron microscopy. The results of this research work show that in-situ monitoring and characterization of high-temperature oxidation present a strong tool that will contribute to a better fundamental understanding of the phenomena that occur during high-temperature oxidation of metallic materials.

Improving Oxidation Resistance of Stainless Steel (AISI 316L) by Pack Cementation

Improving Oxidation Resistance of Stainless Steel (AISI 316L) by Pack Cementation

Improvement in Oxidation Resistance of Stainless Steel by Molten-Salt Electrodeposition of La

Improvement in the oxidation resistance of SUS304 stainless steel was accomplished by electrodeposition of La in a molten salt. The electrolysis of La was conducted using a potentiostatic-polarization method in an equimolar NaCl–KCl melt containing 3.5 mol. LaF 3 at 1023 K. Observation of the specimen surface after polarization at −1.8 V (vs. Ag/Ag+ (0.1)) for 0.18 ks showed that La particles were uniformly dispersed on the surface. The oxidation resistance of the electrodeposited stainless steel was significantly improved as compared with the untreated stainless steel. The scale formed on the untreated stainless steel after oxidation was thick and consisted of Fe2O3 and Fe3O4, whereas the scale formed on the elecrodeposited stainless steel was extremely thin, and mainly consisted of Cr2O3.

ステンレススチール薄板上にスラリーコートしたγ‐Ａｌ２Ｏ３層の耐熱性

Technology of porous alumina coating on stainless steel substrate was examined for the development of the environmental catalytic part, which was used under heat condition. Although oxidation resistance of stainless steel (SUS304) was not so high, the stable coat layer was made through a simple dipping-drawing procedure of γ-Al2O3 slurry. Thermal stability of the coat layer on stainless steel was examined by the change about surface area, XRD, and SEM morphology in the temperature range of 500-1100°C. The surface area was 108m2/g and 96m2/g after heat treatment in 0.2%O2-99.8%N2 at 900°C and 1000°C, respectively. The coat layer was stable with porous structure on stainless steel below the temperature of 1000°C.

Effect of alloy grain size on oxidation resistance of silica-coated stainless steel

Oxidation resistance of stainless steels, which rely on the formation of a Cr2O3 (chromia) scale, can be further improved through minor alloying additions such as Al or Si, or by application of coatings to the exposed surfaces. Although, additions of Si to austenitic steels have demonstrated an improvement in oxidation resistance, high Si contents can be detrimental to the mechanical properties of these alloys. The application of a silica coating on the surface of the stainless steel provides improved oxidation resistance without detrimental effects on the mechanical properties. This study examines the effect of the grain size of the stainless steel on the effectiveness of a silica coating as an oxidation barrier.Fully austenitic stainless steel of composition Fe-18(wt%)Cr-20Ni-1.5Mn was produced in both coarsegrained and fine-grained form. The coarse-grained alloy, with a grain size of approximately 100 μm, was produced by casting and hot rolling. The fine-grained alloy, with a grain size of approximately 5 μm, was produced by rapid solidification powder processing, followed by consolidated by hot isostatic pressing and swaging.

Improvement of oxidation resistance of stainless steels by laser surface melting

Improvement of oxidation resistance of stainless steels by laser surface melting