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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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