Composition, Microstructure, and Water Vapor Effects on Internal/External Oxidation of Alumina-Forming Austenitic Stainless Steels

Durable alloy foils are needed for gas turbine recuperators operating at 650°–700°C. It has been established that water vapor in the exhaust gas causes more rapid consumption of Cr in austenitic stainless steels leading to a reduction in operating lifetime of these thin-walled components. Laboratory testing at 650°–800°C of commercial and model alloys is being used to develop a better understanding of the long-term rate of Cr consumption in these environments. Results are presented for commercial alloys 709, 120 and 625. After 10,000h exposures at 650° and 700°C in humid air, grain boundary Cr depletion was observed near the surface of all these materials. In the Fe-base alloys, 709 and 120, this depletion led to localized Fe-rich nodule formation. This information then can be used to develop low-cost alternatives to currently available candidate materials.

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Accelerated Oxidation of Type 347 Stainless Steel Primary Surface Recuperators Operating Above 600°C

Volume 3: Turbo Expo 2007 ◽

10.1115/gt2007-27190 ◽

2007 ◽

Cited By ~ 4

Author(s):

Wendy J. Matthews ◽

Karren L. More ◽

Larry R. Walker

Keyword(s):

Stainless Steel ◽

Water Vapor ◽

Stainless Steels ◽

National Laboratory ◽

Austenitic Stainless Steels ◽

Operating Conditions ◽

Accelerated Oxidation ◽

Oak Ridge ◽

Compositional Changes ◽

Operating Temperatures

Type 347 stainless steel has traditionally been used in the manufacture of microturbine primary surface recuperators. It has been established during the past few years that the water vapor present in the microturbine exhaust gas causes accelerated oxidation of austenitic stainless steels at operating temperatures above ∼600°C (∼1110°F), which has resulted in the replacement of austenitic stainless steels with more highly alloyed Fe-based alloys and Ni-based alloys in microturbine recuperators. The effect of water vapor on type 347 stainless steel primary surface recuperators has been studied extensively by Capstone Turbine Corporation in collaboration with Oak Ridge National Laboratory. Several recuperators exposed in a Capstone C60 MicroTurbine™ under different steady-state and cyclic operating conditions, have been microstructurally characterized. Evaluation of surface oxide scale formation and associated compositional changes has been carried out on representative sections from recuperators with operating lives ranging from ∼2,000–15,000 hours. Results from the microstructural and compositional analyses of the engine-tested recuperators illustrate the progression of accelerated oxidation of type 347 stainless steel at recuperator operating temperatures above 600°C.

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Local Surface Phase Stability during Cyclic Oxidation Process

Materials Science Forum ◽

10.4028/www.scientific.net/msf.879.855 ◽

2016 ◽

Vol 879 ◽

pp. 855-860

Author(s):

Mattias Calmunger ◽

Robert Eriksson ◽

Guo Cai Chai ◽

Sten Johansson ◽

Jan Högberg ◽

...

Keyword(s):

Phase Transformation ◽

Water Vapor ◽

Chemical Composition ◽

Martensitic Transformation ◽

Thermal Cycling ◽

Stainless Steels ◽

Austenitic Stainless Steels ◽

Surface Phase ◽

Local Surface ◽

Aisi 304

Surface properties are essential for many engineering material ́s design issues, such as fatigue and corrosion performances. Austenitic stainless steels used in high-temperature applications, as for instance components in biomass-fired power plants, need sufficient corrosion resistance. At temperatures above 600 °C and in water vapor environment, Cr-vaporization will create Cr-depletion, causing a local change in chemical composition. This local change in chemical composition leads to phase transformation in some austenitic stainless steels. This paper reports the surface properties regarding the local phase transformation during thermal cycling in water vapor environment. Three commercial austenitic stainless steels are investigated, AISI 304, AISI 316L and Sandvik SanicroTM 28. The thermal cycling was performed up to 650 °C in a 15 mol.% water vapor environment. AISI 304 shows local surface phase transformation related to martensitic transformation due to locally changed chemical composition and increase in the martensitic transformation temperature (Ms). However, the other two austenitic stainless steels don’t show this martensitic transformation. The phase transformation and oxidation is discussed using microstructural investigations methods such as x-ray diffraction (XRD), electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS).

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The Oxidation of Metal Alloy Foils in the Presence of Water Vapor

Volume 3: Turbo Expo 2003 ◽

10.1115/gt2003-38059 ◽

2003 ◽

Cited By ~ 4

Author(s):

James M. Rakowski

Keyword(s):

Water Vapor ◽

Elevated Temperature ◽

Chromium Oxide ◽

Stainless Steels ◽

Austenitic Stainless Steels ◽

Test Results ◽

Temperature Oxidation ◽

Chromium Oxide Layer ◽

Nickel Base

Water vapor can be detrimental to the elevated temperature oxidation resistance of alloys that rely on the formation of a protective chromium oxide layer. The resulting degradation can be significant, particularly when such alloys are in the form of light gauge sheet and strip. Long term test results will be presented for commercially available wrought austenitic stainless steels and for the nickel-base superalloys 625 and HX exposed at 1300°F and 1400°F in environments containing various levels of water vapor.

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Effect of Water-Vapor-Induced Cr Vaporization on the Oxidation of Austenitic Stainless Steels at 700 and 900°C

Journal of The Electrochemical Society ◽

10.1149/1.1644138 ◽

2004 ◽

Vol 151 (3) ◽

pp. B141 ◽

Cited By ~ 23

Author(s):

H. Asteman ◽

J.-E. Svensson ◽

L.-G. Johansson

Keyword(s):

Water Vapor ◽

Stainless Steels ◽

Austenitic Stainless Steels ◽

Effect Of Water

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The Oxidation of Metal Alloy Foils in the Presence of Water Vapor

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.1787508 ◽

2004 ◽

Vol 126 (4) ◽

pp. 867-873 ◽

Cited By ~ 1

Author(s):

James M. Rakowski

Keyword(s):

Water Vapor ◽

Elevated Temperature ◽

Chromium Oxide ◽

Stainless Steels ◽

Austenitic Stainless Steels ◽

Test Results ◽

Temperature Oxidation ◽

Chromium Oxide Layer ◽

Nickel Base

Water vapor can be detrimental to the elevated temperature oxidation resistance of alloys that rely on the formation of a protective chromium oxide layer. The resulting degradation can be significant, particularly when such alloys are in the form of light gauge sheet and strip. Long-term test results will be presented for commercially available wrought austenitic stainless steels and nickel-base superalloys exposed at 1300°F and 1400°F in environments containing various levels of water vapor.

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Radiation Damage Studies with the HVEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096655 ◽

1972 ◽

Vol 30 ◽

pp. 680-681

Author(s):

J. J. Laidler ◽

B. Mastel

Keyword(s):

Radiation Damage ◽

Stainless Steels ◽

Volume Expansion ◽

Austenitic Stainless Steels ◽

Test Facility ◽

Fast Breeder Reactors ◽

Breeder Reactors ◽

Under Construction ◽

Development Laboratory ◽

Insight Into

One of the major materials problems encountered in the development of fast breeder reactors for commercial power generation is the phenomenon of swelling in core structural components and fuel cladding. This volume expansion, which is due to the retention of lattice vacancies by agglomeration into large polyhedral clusters (voids), may amount to ten percent or greater at goal fluences in some austenitic stainless steels. From a design standpoint, this is an undesirable situation, and it is necessary to obtain experimental confirmation that such excessive volume expansion will not occur in materials selected for core applications in the Fast Flux Test Facility, the prototypic LMFBR now under construction at the Hanford Engineering Development Laboratory (HEDL). The HEDL JEM-1000 1 MeV electron microscope is being used to provide an insight into trends of radiation damage accumulation in stainless steels, since it is possible to produce atom displacements at an accelerated rate with 1 MeV electrons, while the specimen is under continuous observation.

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Strain-induced martensite effects on transgranular carbide precipitation in type 304 stainless steels

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087331 ◽

1991 ◽

Vol 49 ◽

pp. 604-605

Author(s):

A.H. Advani ◽

L.E. Murr ◽

D. Matlock

Keyword(s):

Heat Treatment ◽

Grain Boundary ◽

Stress Corrosion Cracking ◽

Stainless Steels ◽

Deformation Twin ◽

Austenitic Stainless Steels ◽

Carbide Precipitation ◽

Strain Induced Martensite ◽

Type 304

Thermomechanically induced strain is a key variable producing accelerated carbide precipitation, sensitization and stress corrosion cracking in austenitic stainless steels (SS). Recent work has indicated that higher levels of strain (above 20%) also produce transgranular (TG) carbide precipitation and corrosion simultaneous with the grain boundary phenomenon in 316 SS. Transgranular precipitates were noted to form primarily on deformation twin-fault planes and their intersections in 316 SS.Briant has indicated that TG precipitation in 316 SS is significantly different from 304 SS due to the formation of strain-induced martensite on 304 SS, though an understanding of the role of martensite on the process has not been developed. This study is concerned with evaluating the effects of strain and strain-induced martensite on TG carbide precipitation in 304 SS. The study was performed on samples of a 0.051%C-304 SS deformed to 33% followed by heat treatment at 670°C for 1 h.

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