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Author: search.filters.author.Wiman, PanyaSubject: search.filters.subject.Oxidation

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    Effects of temperature and water vapour on Cr-species volatilisation, oxidation and scale adhesion of a Type 409L stainless steel for application as interconnect of low temperature solid oxide fuel cells
    (2024-06-01)
    Homjabok, Wanna
    ;
    Tengprasert, Watcharapon
    ;
    Thublaor, Thammaporn
    ;
    Wiman, Panya
    ;
    Nilsonthi, Thanasak
    Though the classical transport theory does not mathematically express the Arrhenius-like relation between Cr-loss flux due to volatilisation and absolute temperature, such relation was experimentally observed for 409L stainless steel exposed at 600–750 °C. Volatilisation calculation in the present cases can be estimated giving such relation because of the nearly linear relation between mass transfer coefficient and temperature. Cr-loss fluxes in O<inf>2</inf> with 20 and 40 % H<inf>2</inf>O are close to or coincided with the fluxes calculated from MnCr<inf>2</inf>O<inf>4</inf> evaporation. Increasing water vapour could enhance volatilisation contributed from the raised CrO<inf>2</inf>(OH)<inf>2</inf> pressure, reduce oxidation rate, and worsen scale adhesion.
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    Oxidation and Scale Adhesion of a Type 430 Stainless Steel in Ar–CO2 Gas Mixtures at 800 °C
    (2023-04-01)
    Wiman, Panya
    ;
    Muengjai, Angkana
    ;
    Srihathai, Padungaut
    ;
    Thublaor, Thammaporn
    ;
    Siripongsakul, Thamrongsin
    Biogas is an alternative source of fuel potentially used to run solid oxide fuel cells (SOFCs). It mainly consists of CH<inf>4</inf> and CO<inf>2</inf> which can degrade the SOFC interconnect, which is typically made of stainless steel. To investigate the effect of each gas constituent, we focussed here on the effect of CO<inf>2</inf> on high-temperature oxidation behavior of and scale adhesion on the stainless steel interconnect, Type 430 stainless steel. The samples studied were oxidised in CO<inf>2</inf> at contents of 5–100% at 800 °C. The oxidation kinetics were found to be parabolic with the rate constant increasing when the CO<inf>2</inf> content increased. The scale adhesion was assessed using a tensile-test method. The scale formed in the atmosphere containing higher CO<inf>2</inf> content exhibited poorer scale adhesion, as indicated by a lower strain initiating the first spallation and a larger spallation percentage after the first spallation took place. The worsened scale adhesion relates to pores formed at the scale/steel interface. The adhesion energies were further quantified giving the values of about 40–100 J m<sup>–2</sup>. Oxidation mechanisms were suggested based on the dependence of the parabolic rate constant on the oxygen partial pressure and the inward diffusion of carbon-bearing species.