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Results for “High Temperature Oxidation”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

High Temperature Oxidation Behavior of Aluminized Haynes 230

The effect of reactive air aluminizing (RAA) on the high-temperature oxidation behavior of the H230 superalloy is studied at 850 °C for 600 hours. Mass gain values are measured and microstructure is studied by XRD, SEM, and EDX. Post oxidation mass gain for the aluminized alloy is reduced compared to wrought alloy. A three-zone microstructure of diffusion coating is observed in RAA H230. Formation and growth of alumina scale during RAA process and oxidation is attributed to the complementary roles of ß-NiAl + ?'-Ni3Al phases in the composite coating.

Rashidi, S↗
DOE OSTI2017

Structural Evolution of a Ni Alloy Surface During High-Temperature Oxidation

We show that considerable structural transformations occur at a Ni alloy surface during the transient stages of high-temperature oxidation. This was demonstrated by exposing the alloy to high-temperature CO 2 for short times at both atmospheric and supercritical pressures. A protective Cr-rich oxide layer formed after only 5 min at 700 °C and persisted for longer exposures up to 500 h. Voids formed and grew over time by the condensation of metal vacancies generated during oxidation, while the alloy surface recrystallized after sufficient oxidation had occurred. The oxygen potential established at the oxide/alloy interface led to oxidation along the newly formed grain boundaries as well as adjacent to and inside of the voids. Al, the most stable oxide-former and present at low concentration in the alloy, was preferentially oxidized in these regions. Furthermore, the results provide an improved understanding of the internal oxidation of Al and its role in enhancing scale adhesion for this class of Ni alloys.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2021

High temperature oxidation of corrosion resistant alloys from machine learning

Parabolic rate constants, k p , were collected from published reports and calculated from corrosion product data (sample mass gain or corrosion product thickness) and tabulated for 75 alloys exposed to temperatures between ~800 and 2000 K (~500–1700 °C; 900–3000°F). Data were collected for environments including lab air, ambient and supercritical carbon dioxide, supercritical water, and steam. Materials studied include low- and high-Cr ferritic and austenitic steels, nickel superalloys, and aluminide materials. A combination of Arrhenius analysis, simple linear regression, supervised and unsupervised machine learning methods were used to investigate the relations between composition and oxidation kinetics. The supervised machine learning techniques produced the lowest mean standard errors. The most significant elements controlling oxidation kinetics were Ni, Cr, Al, and Fe, with Mo and Co composition also found to be significant features. The activation energies produced from the machine learning analysis were in the correct distributions for the diffusion constants for the oxide scales expected to dominate in each class.

Materials Science↗
DOE OSTI2016

Nanocarbon synthesis by high-temperature oxidation of nanoparticles

High-temperature oxidation of silicon-carbide nanoparticles (nSiC) underlies a wide range of technologies from high-power electronic switches for efficient electrical grid and thermal protection of space vehicles to self-healing ceramic nanocomposites. Here, multimillion-atom reactive molecular dynamics simulations validated by ab initio quantum molecular dynamics simulations predict unexpected condensation of large graphene flakes during high-temperature oxidation of nSiC. Initial oxidation produces a molten silica shell that acts as an autocatalytic ‘nanoreactor’ by actively transporting oxygen reactants while protecting the nanocarbon product from harsh oxidizing environment. Percolation transition produces porous nanocarbon with fractal geometry, which consists of mostly sp 2 carbons with pentagonal and heptagonal defects. Furthermore, this work suggests a simple synthetic pathway to high surface-area, low-density nanocarbon with numerous energy, biomedical and mechanical-metamaterial applications, including the reinforcement of self-healing composites.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

High temperature oxidation behavior of a high Al-containing ferritic heat-resistant stainless steel

Highlights: • Oxidation kinetics has been analyzed by discontinuous weighing. • Microstructure and phase composition of oxide films were investigated by SEM, EDS and XRD analysis. • The oxidation resistance of 1000 °C is obviously deteriorated comparing with that at 800 °C and 900 °C. • The oxidation mechanism has been discussed. - Abstract: The high temperature oxidation behavior of a high Al-containing ferritic heat-resistant stainless steel at temperatures of 800, 900, and 1000 °C in air were studied in isothermal oxidation tests. The results showed that the isothermal oxidation kinetic curves obtained at different temperatures followed the parabolic law, and the weight gain per unit at 1000 °C was significantly higher than that at 800 and 900 °C. The oxidation rate at 1000 °C was about three times faster than that at 800 and 900 °C. Continuous and compact multicomponent oxide films mainly composed of Cr{sub 2}O{sub 3}, Al{sub 2}O{sub 3}, spinel MnFe{sub 2}O{sub 4}, and MnCr{sub 2}O{sub 4} were obtained at 800 and 900 °C. The oxide film started delaminating at 1000 °C; the outer layer was composed of Cr{sub 2}O{sub 3}, spinel MnCr{sub 2}O{sub 4}, and MnFe{sub 2}O{sub 4}, the middle layer was composed of Fe{sub 2}O{sub 3} and Fe-Cr matrix, and the inner layer was composed of Al{sub 2}O{sub 3} and SiO{sub 2}. Oxidation resistance at 1000 °C was reduced mainly because of porous Fe{sub 2}O{sub 3} and inner oxidation of Al and Si. In addition, the oxidation mechanism was discussed based on kinetic and morphological observations.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Radiation Tolerance of Controlled Fusion Welds in High Temperature Oxidation Resistant FeCrAl Alloys

High temperature oxidation resistant iron-chromium-aluminum (FeCrAl) alloys are candidate alloys for nuclear applications due to their exceptional performance during off-normal conditions such as a loss-of-coolant accident (LOCA) compared to currently deployed zirconium-based claddings [1]. A series of studies have been completed to determine the weldability of the FeCrAl alloy class and investigate the weldment performance in the as-received (non-irradiated) state [2,3]. These initial studies have shown the general effects of composition and microstructure on the weldability of FeCrAl alloys. Given this, limited details on the radiation tolerance of FeCrAl alloys and their weldments exist. Here, the highest priority candidate FeCrAl alloys and their weldments have been investigated after irradiation to enable a better understanding of FeCrAl alloy weldment performance within a high-intensity neutron field. The alloys examined include C35M (Fe-13%Cr-5% Al) and variants with aluminum (+2%) or titanium carbide (+1%) additions. Two different sub-sized tensile geometries, SS-J type and SS-2E (or SS-mini), were neutron irradiated in the High Flux Isotope Reactor to 1.8-1.9 displacements per atom (dpa) in the temperature range of 195°C to 559°C. Post irradiation examination of the candidate alloys was completed and included uniaxial tensile tests coupled with digital image correlation (DIC), scanning electron microscopy-electron back scattered diffraction analysis (SEM-EBSD), and SEM-based fractography. In addition to weldment testing, non-welded parent material was examined as a direct comparison between welded and non-welded specimen performance. Both welded and non-welded specimens showed a high degree of radiation-induced hardening near irradiation temperatures of 200°C, moderate radiation-induced hardening near temperatures of 360°C, and almost no radiation-induced hardening at elevated temperatures near 550°C. Additionally, low-temperature irradiations showed the non-welded specimens to exhibit strain-induced softening (decrease in the true stress level) with increasing plastic strain during tensile testing. Fracture for the weldments was found to occur exclusively within the fusion zone. The mechanical performance of the weldment was speculated to be directly linked to variances in the radiation-induced microstructure including the formation of dislocation loops and precipitation of the Cr-rich α' phase. The localized microstructural variation within the weldments, including grain size, was determined to play a significant role in the radiation-induced microstructure. The results summarized within highlight the need for additional data on the radiation tolerance of weldments as the mechanical performance of the fusion zone was shown to be the limiting factor in the overall performance of the weldments.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Manufacturability of U{sub 3}Si{sub 2} and its high temperature oxidation behaviour

High density fuels, such as uranium silicide (U{sub 3}Si{sub 2}), are being considered alongside improved cladding materials to develop new fuels which are both economic to manufacture and demonstrate enhanced accident tolerance. Through a collaborative programme led by Westinghouse and involving national laboratories in the US and UK, efforts are being made to establish a viable route by which U{sub 3}Si{sub 2} can be manufactured and to test its suitability as a fuel. In the UK work has focused on routes to convert UF{sub 6} and UF{sub 4} to U{sub 3}Si{sub 2} directly, without needing to reduce the uranium to its metallic state. Experimental observations of reactions between UF{sub 4} and Si indicate the formation of a USi{sub 2-x} phase at a temperature of 1000 C. degrees, consistent with thermodynamic assessments. Work on the construction of a rig which will pass UF{sub 6} heated to 1000 C. degrees through a bed of finely divided Si powder, is also reported. At Westinghouse, U{sub 3}Si{sub 2} fabricated by the arc-melting process has been subjected to high temperature steam and synthetic air tests and the reaction rate measured as a function of temperature using differential scanning calorimetry. The rates are compared to UO{sub 2} and UN (Uranium mononitride). At Idaho National Laboratory irradiation testing of U{sub 3}Si{sub 2} fuel is in progress. Fuel specimens were prepared by conventional arc melting process to formulate the U{sub 3}Si{sub 2} followed by conventional powder metallurgy processes to create pellets. These irradiation tests are intended to help resolve questions concerning the swelling of U{sub 3}Si{sub 2} under conditions representative of LWR fuel. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Effect of water vapor on high-temperature oxidation of NiAl alloy

The high-temperature oxidation of NiAl is studied with dry oxygen and water vapor. The oxidation in H 2 O results in a thicker Al 2 O 3 oxide scale than that in O 2 . The oxide scale formed initially is a single layer of γ-Al 2 O 3 that subsequently transforms into a α-Al 2 O 3 /γ-Al 2 O 3 bilayer structure, in which the inner α-Al2O3 layer formed in H2O has a higher porosity than that in O 2 . Finally, further density functional theory calculations show that H protons derived from H 2 O molecules penetrate into the oxide lattice and boost the formation of lattice vacancies in both α-Al 2 O 3 and γ-Al 2 O 3 , thus enhancing the oxide scale growth.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Combined Raman imaging and {sup 18}O tracer analysis for the study of high temperature oxidation of pre-oxidized Zircaloy-4 in spent fuel pool accident - 6.4 STP-2016-0037

Oxidation at high temperature of Zr-based cladding materials is expected to be the primary cause of the fuel assemblies' degradation in Spent Fuel Storage Pool loss of cooling accidents. Differently from Loss Of Coolant Accident (LOCA) in reactor vessel, presence of air in the atmosphere in case of a spent fuel pool accident is known to be an aggravating factor because of the 'catalytic' role of nitrogen on the oxidation. 'Low temperature' oxidation scales simulating corrosion oxide formed during normal operation have been observed to have a protective effect regarding subsequent high temperature oxidation, in steam as well as in air and air + steam atmospheres. However, in the presence of nitrogen, this protective effect is lost much earlier than in pure steam or pure oxygen. We present results on oxygen transport through such corrosion oxide layers studied using an {sup 18}O tracer technique. Experiments were performed in {sup 18}O{sub 2} alone as well as in mixed {sup 18}O{sub 2} + N{sub 2} atmospheres, at 850 deg. C, a temperature for which nitrogen is known to have a strong effect on the Zr-based alloys oxidation. Post-test investigations of the specimens were performed by means of micro-Raman profiling or imaging, giving simultaneous information on the {sup 18}O distribution and on structural factors such as composition and stresses in the scales. Raman imaging gave clear evidence for different characteristic distributions of {sup 18}O in the scales. Some of them have been correlated with the development of cracks and porosity in the oxide which allows oxygen to locally penetrate in the scales. Although nitrogen appears to have no or limited influence on the oxygen diffusion, it is observed to reach the metal/oxide interface much faster than oxygen. A mechanism explaining the role of nitrogen on the loss of the protective effect and the kinetic acceleration observed by TGA is proposed. (authors)

36 MATERIALS SCIENCE↗
DOE OSTI2023

Phase-field modeling of alloy oxidation at high temperatures

Oxide growth is a complex process involving transport of reactive species, heterogeneous reactions, and microstructure evolution. Predicting oxidation kinetics and especially the oxide morphological change has been a long-standing challenge. Here we develop a phase-field model for predicting the oxide growth kinetics of a multicomponent alloy during high temperature oxidation, focusing on internal oxidation (non-protective) and its transition to external oxidation (protective). In this work, the predicted kinetics and oxide morphology are analyzed and compared to the classical Wagner’s theory and an existing analytical model by Zhao and Gleeson. Some assumptions used in the analytical models and the limitation are discussed. In addition, it is demonstrated that the morphology and distribution of the initial oxide nuclei play an important role in the later stage oxide connectivity and thus the transition to external oxidation.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Aluminizing on the High-Temperature Oxidation Behavior of an Alumina-Forming Austenitic Stainless Steel

Due to their excellent oxidation resistance and creep resistance at elevated temperatures, alumina forming austenitic (AFA) stainless steels have emerged as potential alloys for high temperature applications. In this study, a Reactive Air Aluminizing (RAA) method was used to aluminize the surface of AFA25 stainless steel. The high temperature oxidation behavior of both as-received and aluminized AFA25 was investigated at 850 °C in dry air. The mass gain per unit area was higher for the aluminized AFA25 than for the as-received material. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS), performed on the oxide scales following the high temperature oxidation tests, confirmed the formation of alumina scale on both as-received and aluminized AFA. However, the aluminized alloy exhibited a thicker alumina scale on the surface, as well as more extensive penetration of the scale into the subsurface region of the alloy.

Rashidi, S.↗
DOE OSTI2016

Combined Raman imaging and {sup 18}O tracer analysis for the study of zircaloy-4 high-temperature oxidation in spent fuel pool accident - 2016-0037

Oxidation at high temperature (HT) of cladding materials is expected to be the primary cause of the fuel assemblies degradation in spent fuel storage pool loss of cooling accidents. Unlike a loss-of-coolant accident (LOCA) in a reactor vessel, the presence of air in the atmosphere is expected in a spent fuel pool accident and is known to be an aggravating factor because of the 'catalytic' role of nitrogen on the oxidation. In steam LOCA conditions, a low-temperature (LT) oxidation scale simulating the corrosion oxide formed during in-service use of the assemblies has been observed to have a protective effect regarding subsequent HT oxidation. In the presence of nitrogen, HT oxidation kinetic experiments show that the protective effect of an LT corrosion scale also exists but is lost much earlier than in pure steam. Oxygen transport through LT oxide layers has been studied using the {sup 18}O tracer technique. We performed experiments in {sup 18}O{sub 2} alone as well as in mixed {sup 18}O{sub 2}+N{sub 2} atmospheres, at 850 deg. C. Micro-Raman imaging, both at the specimen surfaces and on cross sections gave clear evidence for different characteristic distributions of {sup 18}O in the scales. Some of these distributions have been correlated with the presence of cracks and porosity in the LT oxide, which allows oxygen to locally penetrate in the scales. In cases in which no radial crack is present, apparent oxygen diffusion coefficients in the oxide were derived from fitting {sup 18}O diffusion profiles. Nitrogen appears to have no or only a limited influence on the oxygen diffusivity, but it is observed to reach the metal-oxide interface faster than oxygen, at which point it reacts with the metal and the sub-stoichiometric oxide to form zirconium nitride.The later conversion of the ZrN into ZrO{sub 2} might lead to the destabilization of the LT scale and to the loss of its protective effect. (authors)

36 MATERIALS SCIENCE↗
DOE OSTI2016

Structure and high temperature oxidation of mechanical alloyed Fe-Al coating

The structure and high temperature oxidation resistance of Fe-Al coating on low carbon steel were investigated. The Fe-Al coating was deposited on the surface of low carbon steel using a mechanical alloying method. The coating was then annealed at 600°C for 2 hour in a vacuum of 5 Pa. The cyclic-oxidation tests of low carbon steel, Fe-Al coatings with and without annealing were performed at 600°C for up to 60h in air. The structure of oxidized samples was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy X-ray spectroscopy (EDS). The results show that the Fe-Al coatings exhibit high oxidation resistance compared to the uncoated steel. After 60 h exposure, the uncoated steel formed mainly Fe{sub 3}O{sub 4} and Fe{sub 2}O{sub 3} layers with the total thickness of around 75.93 µm. Fe-Al coating without annealing formed a thin oxide layer, probably (Fe,Al){sub 2}O{sub 3}. Meanwhile, for annealed sample, EDX analysis observed the formation of two Fe-Al layers with difference in elements concentration. The obtained results suggest that the deposition of Fe-Al coating on low carbon steel can improve the oxidation resistance of low carbon steel.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Chromium segregation-induced oxide evolution in Ni-10Cr alloys during high-temperature oxidation

The oxidation behavior of a Ni-10(wt%)Cr alloy under high-temperature O 2 conditions is investigated using transmission electron microscopy and first-principles calculations. Results reveal that chromium segregation plays a central role in driving the evolution of complex oxide phase structures during oxidation. At low Cr concentrations, Cr preferentially segregates to NiO grain boundaries or internal pores, substituting for Ni atoms and forming Ni(Cr)O solid solutions. As Cr content increases, enhanced diffusion promotes Cr penetration into the NiO lattice, leading to the formation of multiphase oxide structures. First-principles modeling corroborates these findings: at low Cr concentrations, Cr atoms favor surface and grain-boundary segregation, while higher concentrations lead to Cr aggregation within the NiO bulk. Furthermore, the integrated experimental-theoretical approach provides atomistic insights into Cr-mediated mass transport mechanisms during alloy oxidation and offers valuable guidance for controlling oxide growth kinetics and phase stability in Ni-Cr alloys, with implications for improving oxidation resistance in high-temperature structural applications.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The role of metal vacancies during high-temperature oxidation of alloys

An improved understanding of high-temperature alloy oxidation is key to the design of structural materials for next-generation energy conversion technologies. An often overlooked, yet fundamental aspect of this oxidation process concerns the fate of the metal vacancies created when metal atoms are ionized and enter the growing oxide layer. In this work, we provide direct experimental evidence showing that these metal vacancies can be inseparably linked to the oxidation process beginning at the very early stages. The coalescence of metal vacancies at the oxide/alloy interface results initially in the formation of low-density metal and eventually in nm-sized voids. The simultaneous and subsequent oxidation of these regions fills the vacated space and promotes adhesion between the growing oxide and the alloy substrate. These structural transformations represent an important deviation from conventional metal oxidation theory, and this improved understanding will aid in the development of new structural alloys with enhanced oxidation resistance.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Use of Modeling and Experiments to Assess the Effect of Minor Alloying Additions on Alumina Scale Formation during High-Temperature Oxidation

During the last decades, new generations of Ni-based superalloys have emerged with judiciously controlled chemistries. These alloys heavily rely on the addition of refractory elements to enhance their mechanical properties at elevated temperatures; however, a clear interpretation of the influence of these minor-element additions on the alloy's high-temperature oxidation behavior is still not well understood, particularly from the standpoint of predicting the transition from internal to external alumina formation. In this context, the present investigation describes a systematic study that addresses the intrinsic effects that minor element additions of Nb, Ta, and Re have on the oxidation behavior of alumina-scale forming γ-Ni alloys. By combining a novel simulation approach with high-temperature oxidation experiments, the present study evidences the generally positive effect associated with 2 at. % addition of Ta and Re as well as the detrimental consequences of Nb additions on the 1100 °C oxidation of (in at. %) Ni-6Al-(0,4,6,8)Cr alloys.

Rodriguez, Rafael↗