Experimental Analysis and Computer Simulation of Inward Oxide Growth during High-Temperature Corrosion of Low-Alloy Boiler Steels

Krupp, Ulrich; Trindade, Vicente Braz; Hanjari, Behzad Zandi; Yang, Shihao; Christ, H.‐J.; Buschmann, U.; Wiechert, Wolfgang

doi:10.4028/www.scientific.net/msf.461-464.571

Cited by 6 publications

(4 citation statements)

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“…As the oxygen potential increases, part of FeCr 2 O 3 will be further oxidized to form Fe 3 O 4 . The depth of the Fe 3 O 4 precipitation front is responsible for the thickness of the inner scale; it was found that after 20 h exposure, the thickness of the inward oxidation layer is about 8 lm, which is in a very good agreement with the experimental results [7].…”

Section: Kinetics Calculationsupporting

confidence: 80%

Optimisation of in-service performance of boiler steels by modelling high-temperature corrosion

Heikinheimo¹,

Baxter

Hack

et al. 2006

Materials and Corrosion

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The main objective of the EU OPTICORR project is the optimisation of in-service performance of boiler steels by modelling hightemperature corrosion, the development of a life-cycle approach (LCA) for the materials in energy production, particularly for the steels used in waste incinerators and co-fired boiler plants. The expected benefits of this approach for safe and cost effective energy production are: -control and optimisation of in-service performance of boiler materials, -understanding of high-temperature corrosion and oxidation mechanisms under service conditions, -improvement of reliability to prevent the failure of components and plant accidents and -expanding the limits of boiler plant materials by corrosion simulations for flexible plant operation conditions (steel, fuel, temperature etc.).The technical aim of the EU OPTICORR project is the development of modelling tools for high-temperature oxidation and corrosion specifically in boiler conditions with HCl-and SO 2 -containing combustion gases and Cl-containing salts. The work necessitates thermodynamic data collection and processing. For development and modelling, knowledge about the corrosion mechanisms and exact data are needed. The kinetics of hightemperature oxidation and corrosion are determined from laboratory thermo-gravimetric tests (TG) and multi-sample exposure tests. The materials studied are typical boiler tubes and fin-steels: ferritic alloys, the austenitic steel T347 and the Ni-based alloy Inconel 625. The exposure gases are dry air, air with 15 vol-% H 2 O, and with 2000 ppm HCl and 200 ppm SO 2 . The salt deposits used are based on KCl-ZnCl 2 and Ca, Na, K, Pb, Zn-sulfates. The test temperatures for exposures with deposits are 320 and 420 C and, for gas exposures, 500 to 600 C.At present the tools being developed are ChemSheet based programmes with a kinetic module and easy-to-use interface and a more sophisticated numerical finite-difference-based diffusion calculation programme, InCorr, developed for prediction of inward corrosion and internal corrosion.The development of modelling tools for oxidation and high-temperature corrosion was started with thermodynamic data collection for relevant systems and thermodynamic mappings. Further, there are needs to develop the simulation model and tool for salt-induced hot corrosion based on the ChemSheet approach. Also, the work on modelling and simulating with the InCorr kinetic modelling tool will be continued to demonstrate the use of the tool for various steels and alloys in defined combustion environments.

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Section: Kinetics Calculationsupporting

confidence: 80%

Optimisation of in-service performance of boiler steels by modelling high-temperature corrosion

Heikinheimo¹,

Baxter

Hack

et al. 2006

Materials and Corrosion

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show abstract

“…Oxidation of the austenitic steel TP347 and the Ni-base alloy under oxidizing conditions (He-O 2 +H 2 O) and temperatures between 550°C and 650°C was negligible and characterized by a very slow-growing Cr 2 O 3 scale. [7,8]. The effects of HCl-and SO 2 -additions to the gas system on the oxidation kinetics and mechanisms are discussed in more detail in the paper of [7].…”

Section: Corrosion and Oxidation Modellingmentioning

confidence: 99%

“…Within the grains the diffusion coefficient was supposed to be isotropic. Thus, it was possible to simulate intergranular oxidation as it was observed experimentally in low-alloy steels [8]. In order to define the initial oxygen concentration, local equilibrium at outer / inner oxide layer interface was assumed.…”

Section: Incorr Model For Modelling Internal Oxidation -mentioning

confidence: 99%

Optimisation of In-Service Performance of Boiler Steels by Modelling High Temperature Corrosion – EU FP5 OPTICORR Project

Heikinheimo

Hack²,

Baxter³

et al. 2004

MSF

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The paper summarises the aims and development of EU-OPTICORR project in modelling of high temperature oxidation and corrosion. The work necessitates thermodynamic data collection and processing for the modelling tools. At present the tools are two ChemSheet based programmes with a kinetic module and easy to use interface and a more sophisticated numerical finite-difference based diffusion calculation programme, InCorr, developed for prediction of internal corrosion.

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“…To model inward oxide scale growth on low-alloy steels, the above-mentioned approach had to be extended by taking two-dimensional grain boundary and bulk diffusion of oxygen in the substrate and in the scale into account [10]. Furthermore, the substrate-metal interface has to be considered as moving inward (inward scale growth).…”

mentioning

confidence: 99%

The Effect of Grain-Boundary Diffusion on the Oxidation of Low-Chromium Steels

Krupp

Trindade²,

Schmidt

et al. 2005

DDF

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Even though the oxidation behavior of steels is generally considered as to be widely understood, a closer look reveals some open questions, e.g. regarding the influence of the substrate grain size on the overall oxidation kinetics. At temperatures below 570°C the main constituent of the oxide scale formed on top of low alloy steels is magnetite. As shown by gold marker experiments it grows outward and inward at the same time, the latter exhibiting a gradual transition to the more stable spinel compound FeCr2O4. As indicated by intergranular-oxidation attack below the superficial scale, inward oxide growth seems to be driven by oxygen transport along the grain boundaries serving as fast diffusion paths. This is supported by thermogravimetric oxidation tests in air on low-Cr steels with varying grain size: The smaller the grains the higher the oxidation rate. Recently, a numerical model for the diffusive transport processes based on the finite-difference approach has been developed, which distinguishes between fast grain-boundary diffusion and bulk diffusion. Qualitatively, it is capable to predict the relationship between substrate grain size and inward oxide growth kinetics. Together with the thermodynamic tool ChemApp and in combination with a data set for the Fe-Cr-O system the mechanism-based simulation of the overall oxidation process of low-Cr steels is possible.

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Experimental Analysis and Computer Simulation of Inward Oxide Growth during High-Temperature Corrosion of Low-Alloy Boiler Steels

Cited by 6 publications

References 0 publications

Optimisation of in-service performance of boiler steels by modelling high-temperature corrosion

Optimisation of in-service performance of boiler steels by modelling high-temperature corrosion

Optimisation of In-Service Performance of Boiler Steels by Modelling High Temperature Corrosion – EU FP5 OPTICORR Project

The Effect of Grain-Boundary Diffusion on the Oxidation of Low-Chromium Steels

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