Comparison of the High Temperature Surface Reactivity in Impure Helium of Two Materials for Gas Cooled Reactors

2008 ◽  
Vol 595-598 ◽  
pp. 439-448 ◽  
Author(s):  
Céline Cabet ◽  
Gouenou Girardin ◽  
Fabien Rouillard ◽  
Jerome Chapovaloff ◽  
Krzysztof Wolski ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
High Temperature ◽  
Surface Reactivity ◽  
Haynes 230 ◽  
Partial Pressures ◽  
Basic Equilibrium ◽  
Inconel 617 ◽  
Nickel Base ◽  
Temperature Surface

Nickel base alloys Haynes 230 and Inconel 617 are of interest for gas cooled reactors. At high temperature in impure helium, they generally form surface chromium-rich oxides. However above a critical temperature called TA, the scales are not stable anymore and the chromia destruction comes with a production of carbon monoxide. Reactivity tests on model alloys, with and without carbon, prove that chromia is reduced by the carbon from the alloy. TA vs P(CO) curves were also plotted for the two commercial alloys based on the experimental determination of TA in various atmospheres with increasing partial pressures of carbon monoxide. Unexpectedly, both materials exhibit an almost identical behavior although a basic equilibrium approach suggests that the chromia scale would be reduced in different conditions due to the thermodynamic particularity of the interfacial alloy/scale system.

Corrosion Issues of High Temperature Reactor Structural Metallic Materials

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Celine Cabet ◽  
Fabien Rouillard
Keyword(s):  
High Temperature ◽  
Structural Materials ◽  
Surface Reactivity ◽  
Surface Oxide ◽  
Gas Composition ◽  
Helium Atmosphere ◽  
High Temperature Process ◽  
Partial Pressures ◽  
Nickel Base ◽  
Alloy Properties

Cooling helium of high temperature reactors (HTRs) is expected to contain a low level of impurities: oxidizing gases and carbon-bearing species. Reference structural materials for pipes and heat exchangers are chromia former nickel base alloys, typically alloys 617 and 230. And as is generally the case in any high temperature process, their long term corrosion resistance relies on the growth of a surface chromium oxide that can act as a barrier against corrosive species. This implies that the HTR environment must allow for oxidation of these alloys to occur, while it remains not too oxidizing against in-core graphite. First, studies on the surface reactivity under various impure helium containing low partial pressures of H2, H2O, CO, and CH4 show that alloys 617 and 230 oxidize in many atmosphere at intermediate temperatures (up to 890–970°C, depending on the exact gas composition). However when heated above a critical temperature, the surface oxide becomes unstable. It was demonstrated that at the scale/alloy interface, the surface oxide interacts with the carbon from the material. These investigations have established an environmental area that promotes oxidation. When exposed in oxidizing HTR helium, alloys 617 and 230 actually develop a sustainable surface scale over thousands of hours. On the other hand, if the scale is destabilized by reaction with the carbon, the oxide is not protective anymore, and the alloy surface interacts with gaseous impurities. In the case of CH4-containg atmospheres, this causes rapid carburization in the form of precipitation of coarse carbides on the surface and in the bulk. Carburization was shown to induce an extensive embrittlement of the alloys. In CH4-free helium mixtures, alloys decarburize with a global loss of carbon and dissolution of the pre-existing carbides. As carbides take part in the alloy strengthening at high temperature, it is expected that decarburization impacts the creep properties. Carburization and decarburization degrade rapidly the alloy properties, and thus result in an unacceptably high risk on the material integrity at high temperature. Therefore, the purification system shall control the gas composition in order to make this unique helium atmosphere compatible with the in-core graphite, as well as with structural materials. This paper reviews the data on the corrosion behavior of structural materials in HTRs and draws some conclusions on the appropriate helium chemistry regarding the material compatibility at high temperature.

Corrosion Issues of HTR Structural Metallic Materials

2008 ◽  
Author(s):  
Celine Cabet ◽  
Fabien Rouillard ◽  
Gouenou Girardin ◽  
Martine Blat
Keyword(s):  
High Temperature ◽  
Structural Materials ◽  
Surface Reactivity ◽  
Surface Oxide ◽  
Gas Composition ◽  
Helium Atmosphere ◽  
High Temperature Process ◽  
Partial Pressures ◽  
Nickel Base ◽  
Alloy Properties

Cooling helium of HTRs is expected to contain a low level of impurities: oxidizing gasses and carbon-bearing species. Reference structural materials for pipes and heat exchangers are chromia-former nickel base alloys — typically alloys 617 and 230 — and, as is generally the case in any high temperature process, their long term corrosion resistance relies on the growth of a surface chromium-oxide that can act as a barrier against corrosive species. This implies that the HTR environment must allow for oxidation of these alloys to occur, while it remains not too oxidizing against in-core graphite. First, studies on the surface reactivity under various impure helium containing low partial pressures of H2, H2O, CO and CH4 show that alloys 617 and 230 oxidize in many atmospheres from intermediate temperatures up to 890–970°C, depending on the exact gas composition. However when heated above a critical temperature, the surface oxide becomes unstable: it was demonstrated that at the scale/alloy interface the surface oxide interacts with the carbon from the material. These investigations have established an environmental area that promotes oxidation. When expose in oxidizing HTR helium, alloys 617 and 230 actually develop a sustainable surface scale over thousands of hours. On the other hand if the scale is destabilized by reaction with the carbon, the oxide is not protective anymore and the alloy surface interacts with gaseous impurities. In the case of CH4-containg atmospheres, this causes rapid carburization in the form of precipitation of coarse carbides on the surface and in the bulk. Carburization was shown to induce an extensive embrittlement of the alloys. In CH4-free helium mixtures, alloys decarburize with a global loss of carbon and dissolution of the pre-existing carbides. As carbides take part to the alloy strengthening at high temperature, it is expected that decarburization impacts the creep properties. Carburization and decarburization degrade rapidly the alloy properties and thus result in an unacceptably high risk on the material integrity at high temperature. Therefore, the purification system shall control the gas composition in order to make this unique helium atmosphere compatible with the in-core graphite as well as with structural materials. This paper reviews the data on the corrosion behavior of structural material in HTR and draws some conclusion on appropriate helium chemistry regarding the material compatibility at high temperature.

Chromium Activity Measurements in Nickel Based Alloys for Very High Temperature Reactors: Inconel 617, Haynes 230, and Model Alloys

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Stéphane Gossé ◽  
Thierry Alpettaz ◽  
Sylvie Chatain ◽  
Christine Guéneau
Keyword(s):  
High Temperature ◽  
Heat Exchangers ◽  
Mass Spectrometric ◽  
Operating Conditions ◽  
Pure Substance ◽  
Haynes 230 ◽  
Inconel 617 ◽  
High Temperature Reactor ◽  
High Temperature Reactors ◽  
Very High

The alloys Haynes 230 and Inconel 617 are potential candidates for the intermediate heat exchangers (IHXs) of (very) high temperature reactors ((V)-HTRs). The behavior under corrosion of these alloys by the (V)-HTR coolant (impure helium) is an important selection criterion because it defines the service life of these components. At high temperature, the Haynes 230 is likely to develop a chromium oxide on the surface. This layer protects from the exchanges with the surrounding medium and thus confers certain passivity on metal. At very high temperature, the initial microstructure made up of austenitic grains and coarse intra- and intergranular M6C carbide grains rich in W will evolve. The M6C carbides remain and some M23C6 richer in Cr appear. Then, carbon can reduce the protective oxide layer. The alloy loses its protective coating and can corrode quickly. Experimental investigations were performed on these nickel based alloys under an impure helium flow (Rouillard, F., 2007, “Mécanismes de formation et de destruction de la couche d’oxyde sur un alliage chrominoformeur en milieu HTR,” Ph.D. thesis, Ecole des Mines de Saint-Etienne, France). To predict the surface reactivity of chromium under impure helium, it is necessary to determine its chemical activity in a temperature range close to the operating conditions of the heat exchangers (T≈1273 K). For that, high temperature mass spectrometry measurements coupled to multiple effusion Knudsen cells are carried out on several samples: Haynes 230, Inconel 617, and model alloys 1178, 1181, and 1201. This coupling makes it possible for the thermodynamic equilibrium to be obtained between the vapor phase and the condensed phase of the sample. The measurement of the chromium ionic intensity (I) of the molecular beam resulting from a cell containing an alloy provides the values of partial pressure according to the temperature. This value is compared with that of the pure substance (Cr) at the same temperature. These calculations provide thermodynamic data characteristic of the chromium behavior in these alloys. These activity results call into question those previously measured by Hilpert and Ali-Khan (1978, “Mass Spectrometric Studies of Alloys Proposed for High-Temperature Reactor Systems: I. Alloy IN-643,” J. Nucl. Mater., 78, pp. 265–271; 1979, “Mass Spectrometric Studies of Alloys Proposed for High-Temperature Reactor Systems: II. Inconel Alloy 617 and Nimomic Alloy PE 13,” J. Nucl. Mater., 80, pp. 126–131), largely used in the literature.

High-temperature oxidation of a nickel base superalloy at different oxygen partial pressures

2016 ◽  
Vol 51 (7) ◽  
pp. 513-521 ◽  
Author(s):  
F. A. Pérez-González ◽  
J. H. Ramírez-Ramírez ◽  
M. Terock ◽  
N. F. Garza-Montes-de-Oca ◽  
U. Glatzel ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Nickel Base Superalloy ◽  
Temperature Oxidation ◽  
Partial Pressures ◽  
Nickel Base ◽  
Base Superalloy

High Temperature Behavior of Candidate VHTR Heat Exchanger Alloys

2008 ◽  
Author(s):  
Richard Wright ◽  
Joel Simpson ◽  
Alan Wertsching ◽  
W. David Swank
Keyword(s):  
High Temperature ◽  
Good Deal ◽  
Carbon Activity ◽  
Haynes 230 ◽  
Environmental Resistance ◽  
Principal Candidates ◽  
Inconel 617 ◽  
Series Of Experiments ◽  
Term Response

Several nickel based solid solution alloys are under consideration for application in heat exchangers for very high temperature gas cooled reactors. The principal candidates being considered for this application by the Next Generation Nuclear Plant (NGNP) project are Inconel 617 and Haynes 230. While both of these alloys have an attractive combination of creep strength, fabricability, and oxidation resistance a good deal remains to be determined about their environmental resistance in the expected NGNP helium chemistry and their long term response to thermal aging. A series of experiments has been carried out in a He loop with controlled impurity chemistries within the range expected for the NGNP. The influence of oxygen partial pressure and carbon activity on the microstructure and mechanical properties of Alloys 617 and 230 has been characterized. A relatively simple phenomenological model of the environmental interaction for these alloys has been developed.

Study on Comparison Between Inconel 617 and GH3128 as Structural Material Candidates for Intermediate Heat Exchanger

2013 ◽  
Author(s):  
Yunbai Shi ◽  
Kun Yuan ◽  
Xi Zhao ◽  
Yannan Wu
Keyword(s):  
High Temperature ◽  
Structural Material ◽  
Operation Temperature ◽  
Nickel Chromium ◽  
Nuclear Heat ◽  
Intermediate Heat Exchanger ◽  
Inconel 617 ◽  
Heat Application ◽  
Long Lifetime ◽  
Nickel Base

Intermediate heat exchangers (IHXs) are applied to transfer high-temperature heat generated in high-temperature gas-cooled reactor (HTGR) core to the secondary circulation loop. The requirements for IHXs are harsh due to its high operation temperature up to 900–1000°C, as well as long lifetime expectation. Inconel 617, an austenitic alloy based on nickel-chromium, is considered the primary candidate as IHX structural material for application in NGNP program in USA. This paper compares the characteristics of two nickel-base super alloys, namely GH3128 and Inconel 617, in terms of chemical composition, tensile strength and creep behavior. The result shows that GH3128, which was originally developed and deployed for aeronautic blast chamber in China, is also promising for IHXs in nuclear heat application, but much tests have to be done in the future before its successful application in nuclear high-temperature IHXs.

Direct Measurements of the Chromium Activity in Complex Nickel Base Alloys by High Temperature Mass Spectrometry

2008 ◽  
Vol 595-598 ◽  
pp. 975-985 ◽  
Author(s):  
Stéphane Gossé ◽  
Thierry Alpettaz ◽  
Fabien Rouillard ◽  
Sylvie Chatain ◽  
Christine Guéneau ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
High Temperature ◽  
Surrounding Medium ◽  
Operating Conditions ◽  
Primary Circuit ◽  
Haynes 230 ◽  
Temperature Range ◽  
High Temperature Mass Spectrometry ◽  
Inconel 617 ◽  
Chromium Activity

Chromium rich, nickel based alloys Haynes 230 and Inconel 617 are candidate materials for the primary circuit and intermediate heat exchangers (IHX) of (Very)-High Temperature Reactors. The corrosion resistance of these alloys is strongly related to the reactivity of chromium in the reactor specific environment (high temperature, impure helium). At intermediate temperature – 900°C for Haynes 230 and 850°C for Inconel 617 – the alloys under investigation are likely to develop a chromium-rich surface oxide scale. This layer protects from the exchanges with the surrounding medium and thus prevents against intensive corrosion processes. However at higher temperatures, it was shown that the surface chromia can be reduced by reaction with the carbon from the alloy [1] and the bare material can quickly corrode. Chromium appears to be a key element in this surface scale reactivity. Then, quantitative assessment of the surface requires an accurate knowledge of the chromium activity in the temperature range close to the operating conditions (T ≈ 1273 K). High temperature mass spectrometry (HTMS) coupled to multiple effusion Knudsen cells was successfully used to measure the chromium activity in Inconel 617 and Haynes 230 in the 1423- 1548 K temperature range. Appropriate adjustments of the experimental parameters and in-situ calibration toward pure chromium allow to reach accuracy better than ± 5%. For both alloys, the chromium activities are determined. Our experimental results on Inconel 617 are in disagreement with the data published by Hilpert [2]. Possible explanations for the significant discrepancy are discussed.

Sign in / Sign up

Export Citation Format

Share Document