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The roles of CO2 and water vapour on the high temperature corrosion of a type 430 stainless steel as an interconnect of bio-gas fuel intermediate temperature SOFCs
(2025-12-01)
Thublaor, Thammaporn
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Srihathai, Padungaut
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Tengprasert, Watcharapon
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Suparapinyopapkul, Grid
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Yan, Jiayi
A Type 430 stainless steel was exposed to Ar-20 %CO<inf>2</inf> without and with water vapour at 800 °C up to 96 h. Increasing water vapour content from 5 % to 40 % helped reduce mass gain, enhance volatilisation, and improve scale adhesion with fewer pores at scale/steel interface. Mechanisms for Cr and Mn volatilisations including the direct reactions between Cr-containing oxide and CO<inf>2</inf> were suggested with the aid of the XPS results. Mathematical relations that express the role of water vapour on concentrations of defects responsible for scale growth were proposed to help explain the reduced oxidation rate.
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Novel Method for Determining Standard Enthalpy and Entropy of Volatilisation of Chromia Exposed to Humidified Oxygen at 298 K Based on Transport Theory of Multicomponent Gas Mixtures
(2025-02-01)
Thublaor, Thammaporn
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Tengprasert, Watcharapon
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Suparapinyopapkul, Grid
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Nilsonthi, Thanasak
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Chandra-ambhorn, Walairat
Based on the transport theory of multicomponent gas mixtures, we proposed an expression for determining the standard volatilisation enthalpy and entropy of chromia exposed to humidified oxygen at 298 K. The use of this expression could lead to the quantification of those thermodynamic quantities when the mass flux of Cr loss due to the volatilisation of chromia is determined. We thus experimentally measured the mass fluxes of Cr loss due to volatilisation in humidified atmospheres at 873–1073 K. As a result, the standard enthalpy and entropy of the volatilisation of chromia subjected to humidified oxygen at 298 K were quantified, giving the values of 61.1 ± 1.0 kJ mol−1 and −43.0 ± 1.9 J K−1 mol−1, respectively. The measured and calculated mass fluxes of Cr loss due to volatilisation tended to be related to absolute temperature in the Arrhenius-like form. We proposed the use of the line of the mass flux of Cr loss due to volatilisation in an Arrhenius-like diagram, which was shifted by the different thermodynamic data used to graphically assess the reliability of the thermodynamic data obtained from this work and the literature.
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Microstructure and high-temperature oxidation behaviour of AISI 304L stainless steel welds produced by gas tungsten arc welding using the Ar–N2–H2shielding gas
(2025-01-01)
Chueaprakha, Sompong
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Thublaor, Thammaporn
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Siripongsakul, Thamrongsin
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Wiman, Panya
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Chandra-Ambhorn, Walairat
In the present work, we added 1.5 and 5% v/v hydrogen gas to an Ar–7% N<inf>2</inf> shielding gas for the gas tungsten arc welding of AISI 304L stainless steel to investigate its effect on the weld microstructure and oxidation rate. By using Ar–7% N<inf>2</inf> as a shielding gas, the weld metal contained 2.1% of delta ferrite in an austenite matrix. The addition of 1.5 and 5% hydrogen gas in the shielding gas provided the welds with a higher ratio of delta ferrite to austenite matrix, ranging from 3.8 to 6.9%, thus helping reduce the risk of hot cracks. The weld metals were further subjected to an oxidation test in synthetic air at 700°C, and the parabolic oxidation kinetics were observed. The parabolic rate constant of the weld metal produced using the Ar–7% N<inf>2</inf> shielding gas was 5.44 × 10–13 g2 cm–4 s–1. When 1.5 and 5% hydrogen gas was added to the Ar–7% N<inf>2</inf> shielding gas, the rate constants were reduced to 64% and 24% of that of the weld produced using only Ar–7% N<inf>2</inf> shielding gas, indicating the promising role of the presence of hydrogen in the Ar–7% N<inf>2</inf> shielding gas on improving the weld metal oxidation resistance for high temperature services.
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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
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Tengprasert, Watcharapon
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Thublaor, Thammaporn
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Wiman, Panya
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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
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Muengjai, Angkana
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Srihathai, Padungaut
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Thublaor, Thammaporn
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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–2. 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.
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Fabrication of Mn–Co Alloys Electrodeposited on AISI 430 Ferritic Stainless Steel for SOFC Interconnect Applications
(2023-03-01)
Thanedburapasup, Saravut
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Wetchirarat, Nattapol
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Muengjai, Angkana
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Tengprasert, Watcharapon
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Wiman, Panya
Mn–Co alloys were electroplated on AISI 430 stainless steel using an electrodeposition technique with the aim to reduce oxidation and chromium volatilization. The electroplating parameters were designed to improve the coating quality. The increased current density with decreased MnSO<inf>4</inf> content resulted in a denser coating layer. A sample coated with 0.10 M CoSO<inf>4</inf> and 0.50 MnSO<inf>4</inf> at 350 mA cm−2 showed the best oxidation resistance after being oxidized at 800 °C for 90 h. The X-ray diffraction (XRD) result revealed that the oxide growth on the surface of the coated samples mainly formed oxides of MnCo<inf>2</inf>O<inf>4</inf>, MnCr<inf>2</inf>O<inf>4</inf>, and Cr<inf>2</inf>O<inf>3</inf>. The chromium volatilization was evaluated by exposing the coated samples to humidified synthetic air at 800 °C for 96 h. The mass flux of Cr volatilization was on the order of 10−11 g cm−2 s−1. Furthermore, different heat treatments in O<inf>2</inf> and CO<inf>2</inf> atmospheres were compared. Annealing in CO<inf>2</inf> at 800 °C for 4 h helped increase the Mn–Co coating density. The relationship between the porosity and its failure behavior was also discussed.
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Corrosion behaviour of AISI 430 stainless steel in O2-40%H2O at 800 °C
(2022-07-15)
Wiman, Panya
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Thublaor, Thammaporn
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Rojhirunsakool, Tanaporn
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Bidabadi, Mohammad Hassan Shirani
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Yang, Zhi Gang
Less mass gain and poorer scale adhesion assessed by the tensile test of the AISI 430 stainless steel exposed to O<inf>2</inf>-40%H<inf>2</inf>O at 800 °C were observed in comparison with the exposure to O<inf>2</inf>. The reduced mass gain was partly due to Cr-species volatilisation while the worse scale adhesion related to pores formed at scale/steel interface. The Brouwer diagrams were proposed to help discuss the water vapour effect on altering defect concentrations that could affect the oxidation rate and scale adhesion of the studied steel.
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Evidence for chromium, cobalt and molybdenum volatilisations during high temperature oxidation of Co-27Cr-6Mo Alloy
(2022-07-01)
Wongpromrat, Patthranit
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Galerie, Alain
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Thublaor, Thammaporn
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Chandra-ambhorn, Walairat
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Ponpo, Phisan
A Co-27Cr-6Mo alloy was oxidised in pure O<inf>2</inf> between 800 and 1000 °C for durations up to 96 h. The flow rate was varied between 2 and 5 cm.s–1. In these conditions, volatilisations of chromium, cobalt and molybdenum were observed. The chromium volatilisation values were in good agreement with calculations assuming (CrO<inf>3</inf>)g volatilisation limited by diffusion in the gas boundary layer. On the contrary, the measured flux of evaporated Co was higher than the calculated Co volatilisation flux from the metallic Co. The theoretical relation between the solid Co particle size and its vapour pressure was suggested to help explaining such difference.
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Oxidation and volatilisation behaviour of a type 430 stainless steel coated by Mn-Co oxide by slurry method with pre-oxidation for SOFC interconnect application
(2021-07-15)
Chandra-ambhorn, Somrerk
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Homjabok, Wanna
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Chandra-ambhorn, Walairat
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Thublaor, Thammaporn
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Siripongsakul, Thamrongsin
An AISI 430 stainless steel was coated by Mn-Co spinel using a slurry method. Pre-oxidation before the coating helped reduce the oxidation rate of the coated steel at 800 °C in O<inf>2</inf>-5%H<inf>2</inf>O, relating to the formation of the continuous chromia layer which inhibited the outward diffusion of iron to the coating layer. It also helped reduce the mass flux of Cr loss due to the volatilisation. The combined molecular and Knudsen diffusion of the volatile species through the coating layer was suggested to explain the reduced volatilisation rate of the coated sample with pre-oxidation.
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Characterisation of thermal oxide scales on stainless steels
(2020-01-01)
Srisrual, Anusara
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Thublaor, Thammaporn
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Wongpromrat, Patthranit
This chapter aims at reviewing the characterisation techniques that are commonly used for high temperature oxidation study, especially on stainless steels. In addition, the experimental studies about the high temperature oxidation i.e. thermogravimetric method and chromium volatilisation measurement are explained. The various kinds of characterisation techniques for physico-chemical and electronic properties of thermal oxide scales are reviewed, starting from optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), focused ion beam coupled with scanning electron microscope (FIB/SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy (RS), and photoelectrochemical characterisation (PEC). The review focuses on the basic concepts and shows how the characterising tools can be applied to thermal oxide characterisation.

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