Creep Properties of Hastelloy-X in Impure Helium Environments

Nakanishi, Tetsuya; Kawakami, Haruo

doi:10.13182/nt84-a33430

Cited by 13 publications

(6 citation statements)

References 4 publications

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“…Moreover, the creep strain is strongly affected by carburisation [11,12]. However it is worth noticing that the creep rupture lifetime of Hastelloy X under "carburising" helium is not far below the one in air [13].…”

Section: Corrosion Damage Of Ni-cr-mo Alloys In Gcr Heliummentioning

confidence: 99%

High temperature corrosion of structural materials under gas‐cooled reactor helium

Cabet¹,

Terlain

Lett

et al. 2006

Materials & Corrosion

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The Generation IV International Forum has selected six promising nuclear power systems for further collaborative investigations and development. Among these six concepts, two candidates are Gas Cooled Reactors (GCR), namely the Very High Temperature Reactor (VHTR) and the Gas-cooled Fast Reactor (GFR). The CEA has launched a R&D program on the metallic materials for application in an innovative GCR. Structural GCR alloys have been extensively studied in the past three decades. Some critical aspects for the steels and nickel base alloys resistance under the service conditions are microstructural stability, creep strength and compatibility with the cooling gas. The coolant, namely helium, proved to contain impurities mainly H 2 , CO, CH 4 , N 2 and steam in the microbar range that interact with metals at high temperature. Surface scale formation, bulk carburisation and/or decarburisation can occur, depending on the atmosphere characteristics, primarily the effective oxygen partial pressure and carbon activity, on the temperature and on the alloys chemical composition. These structural transformations can notably influence the mechanical properties: carburisation may induce a loss in toughness and ductility whereas decarburisation impedes the creep strength.There is a valuable theoretical as well as practical knowledge on the corrosion of high temperature alloys in the primary circuit of a GCR but this past experience is not sufficient to qualify every component in a future reactor. On the one hand, the material environment could be significantly different from the former GCR's, especially regarding the higher temperature. On the other hand, the materials of interest are partly different. Ni-Cr-W alloys, for instance, may offer significant improvement in the maximum operating temperature as far as the mechanical properties are concerned. However, their corrosion resistance toward the GCR atmosphere is still unknown.We describe here our first corrosion tests of Haynes 230, a high strength Ni base alloy containing tungsten, under low oxidising helium at 750 C or 950 C. The experiments were carried out in a purposely-designed device that allows controlling low impurity partial pressure. The test duration was up to 1000 h. The corrosion behaviour was assessed through gravimetry and microscopy. Some specimens were investigated using EDS and DRX. The results under low oxidizing potential are compared to the oxidation kinetics in air. Tentative interpretations are proposed based on published models.

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Section: Corrosion Damage Of Ni-cr-mo Alloys In Gcr Heliummentioning

confidence: 99%

High temperature corrosion of structural materials under gas‐cooled reactor helium

Cabet¹,

Terlain

Lett

et al. 2006

Materials & Corrosion

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show abstract

“…If the carbon concentration locally reaches the solubility limit, coarse internal carbides precipitate that embrittle Ni-Cr-Mo alloys at low temperature [15]. Moreover, carburization strongly lowers the creep strain [16,17] even if it is said to have few effects on the creep rupture life [18]. Decarburization: Carbon removal from the surface causes a transport of carbon to the surface.…”

Section: Corrosion Effectsmentioning

confidence: 99%

High temperature reactivity of two chromium-containing alloys in impure helium

Cabet

Chapovaloff²,

Rouillard

et al. 2008

Journal of Nuclear Materials

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“…If the carbon solubility limit is locally reached in the solid solution, coarse internal carbides precipitate that embrittle the metal alloys at low temperature (ennis and lupton, 1980). moreover, carburisation strongly lowers the creep strain (mcCoy et al, 1984;Cook, 1984) even if it is said to have few effects on the creep rupture life (Nakanishi and Kawakami, 1984).…”

Section: Carburisationmentioning

confidence: 99%