Oxidation of high-temperature alloys (superalloys) at elevated temperatures in air: I

Hussain, Nazar; Shahid, K. A.; Khan, Iqra Haider; Rahman, S.

doi:10.1007/bf01080783

Cited by 65 publications

(32 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The temperature range of interest and the temperature range of these experiments was 1173 K to 1573 K (900 "C to 1300 "C) in increments of 100 K. There was considerable evidence in the published literature that, over this range of temperature, the rate of oxidation of superalloys exhibits a parabolic rate dependence [4][5]. Parabolic rate dependence refers to a phenomenon in which transport (mass, momentum or energy) is diffusion-controlled and the solution to the parabolic differential equation results in a time-dependence in which the rate of change of the dependent variable is proportional to the square root of time.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

Oxidation of Inconel 718 in Air at Temperatures From 973k to 1620k.

Greene¹,

Finfrock²

2000

View full text Add to dashboard Cite

As part of the APT project, it was necessary to quantify the release of tungsten from the APT spallation target during postulated accident conditions in order to develop accident source terms for accident consequence characterization. Experiments with tungsten rods at high temperatures in a flowing steam environment characteristic of postulated accidents revealed that considerable vaporization of the tungsten occurred as a result of reactions with the steam and that the aerosols which formed were readily transported away from the tungsten surfaces, thus exposing fresh tungsten to react with more steam. The resulting tungsten release fractions and source terms were undesirable and it was decided to clad the tungsten target with Inconel718 in order to protect it from contact with steam during an accident and mitigate the accident source term and the consequences.As part of the material selection criteria, experiments were conducted with Inconel 718 at high temperatures to evaluate the rate of oxidation of the proposed clad material over as wide a temperature range as possible, as well as to determine the high-temperature failure limit of the material. Samples of Inconel718 were inserted into a preheated furnace at temperatures ranging from 973 K to 1620 K and oxidized in air for varying periods of time. After oxidizing in air at a constant temperature for the prescribed time and then being allowed to cool, the samples would be reweighed to determine their weight gain due to the uptake of oxygen. From these weight gain measurements, it was possible to identify three regimes of oxidation for Inconel 718: a lowtemperature regime in which the samples became passivated after the initial oxidation, an intermediate-temperature regime in which the rate of oxidation was limited by diffusion and exhibited a constant parabolic rate dependence, and a high-temperature regime in which material deformation and damage accompanied an accelerated oxidation rate above the parabolic regime.At temperatures below 1173 K, the rate of oxidation of the Inconel 718 surface was found to decrease markedly with time; the parabolic oxidation rate coefficient was not a constant but decreased with time. This was taken to indicate that the oxide film on the surface was having a passivating effect on oxygen transport through the oxide to the underlying metal. For temperatures in the range 1173 K to 1573 K, the time-dependent rate of oxidation as determined once again by weight-gain measurements was found to display the classical parabolic rate behavior, indicating that the rate of transport of reactants through the oxide was controlled by diffusion through the growing oxide layer. Parabolic rate coefficients were determined by least-squares analysis of time

show abstract

Section: Discussion Of Resultsmentioning

confidence: 99%

Oxidation of Inconel 718 in Air at Temperatures From 973k to 1620k.

Greene¹,

Finfrock²

2000

View full text Add to dashboard Cite

show abstract

“…Therefore, further studies are needed on the oxidation behavior of complex commercial alloys, particularly those used for high-temperature applications. [11] The objective of this work is to characterize the hightemperature corrosion mechanisms for 2.25Cr-1Mo. T22 ASTM SA213 of unweld and welded steel was subjected to hot corrosion in an aggressive environment of molten salt (Na 2 SO 4 -60 pct V 2 O 5 ).…”

Section: Introductionmentioning

confidence: 99%

Studies on Hot Corrosion of the 2.25 Cr-1Mo Boiler Tube Steel and Its Weldments in the Molten Salt Na2SO4-60 pct V2O5 Environment

Kumar

Tewari

Prakash

2007

Metall Mater Trans A

View full text Add to dashboard Cite

Hot corrosion is mainly due to the dissolution of protective oxides in the molten salt at the metal surface and their reprecipitation at some other sites as nonprotective porous mass. The hot corrosion attack along the grain boundaries leading to subsurface precipitation of oxides and sulfides also contributes to weakening of material. Ferritic steel with 2.25Cr 1Mo is used widely as a candidate material in the steam generating system of power plants. Hot corrosion studies were conducted on 2.25Cr-1Mo unwelded as well as welded steel specimens with molten salt coated after exposure at 900°C under cyclic conditions. The thermogravimetric technique was used to establish the kinetics of corrosion X-ray diffraction (XRD); scanning electron microscopy/energy-dispersive analysis (SEM/EDAX) was used to analyze the corrosion products.

show abstract

“…In this sense, as the Al content of these superalloys is too low to ensure the formation of an external, continuous, thermodynamically stable and adherent alumina scale, it is necessary to circumscribe the life service effects by enriching the surface with an Al ''reservoir'' [2,[14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Cyclic and Isothermal Oxidation at 1,100 °C of a CVD Aluminised Directionally Solidified Ni Superalloy

2008

View full text Add to dashboard Cite

CVD aluminide coatings deposited on a Directionally Solidified (DS) substrate were oxidized at 1,100°C up to 240 h under isothermal and cyclic oxidation conditions to study the growth mechanisms of the oxide scales and the possible degradation of the coatings. The specimens were investigated using light and scanning electron (SEM) microscopy, energy-dispersive spectrometry (EDS) and X-Ray Diffraction (XRD). The results indicate that the coatings provide a much greater beneficial effect under isothermal conditions than upon cycling. The cycled specimens undergo oxide-scale spallation and increased roughening, which can derive from growth and thermal stresses as well as from the NiAl ? Ni 3 Al phase transformation associated with Al depletion. Under isothermal conditions, typical oxide scales formed with the appearance of some rumples. However, the origin of rumpling is uncertain from these experimental results.

show abstract

Oxidation of high-temperature alloys (superalloys) at elevated temperatures in air: I

Cited by 65 publications

References 12 publications

Oxidation of Inconel 718 in Air at Temperatures From 973k to 1620k.

Oxidation of Inconel 718 in Air at Temperatures From 973k to 1620k.

Studies on Hot Corrosion of the 2.25 Cr-1Mo Boiler Tube Steel and Its Weldments in the Molten Salt Na2SO4-60 pct V2O5 Environment

Cyclic and Isothermal Oxidation at 1,100 °C of a CVD Aluminised Directionally Solidified Ni Superalloy

Contact Info

Product

Resources

About