Breakdown of Protective Cr-Rich Oxide Scale Formed on Heat-Resistant Steels for Superheater Tubes in a Waste Power Generation Boiler

Furugaki, Takashi; Takahashi, Hiromitsu; Hayashi, Shigenari

doi:10.1007/s11085-023-10184-0

Cited by 4 publications

References 13 publications

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The Impact of HCl on Alkali-Induced Corrosion of Stainless Steels/FeCrAl Alloy at 600 °C: The Story After Breakaway

Ssenteza,

Jonsson,

Nockert

et al. 2024

High Temperature Corrosion of mater.

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The impact of Cl on alkali-induced high-temperature corrosion of stainless steels/FeCrAl alloys after breakaway oxidation was investigated in a simulated biomass- and waste-fired boiler environment at 600 °C. For this investigation, three alloys were exposed to low Cl load environment (H2O+KCl) and to high Cl load (H2O+KCl+HCl). Post-exposure analysis showed that the stainless steel SVM12 experiences fast oxidation and forms thick double-layered Fe-rich oxide scales. The corrosion attack is further accelerated with addition of HCl for this material with the effect being more pronounced in the inward-growing scale. The FeCrAl and FeCrNi alloys exhibit slower oxidation kinetics after the breakaway corrosion compared to SVM12 in the H2O+KCl exposure. Furthermore, in contrast with SVM12, the addition of HCl did not accelerate the corrosion attack on these alloys. It is argued that the properties of the secondary oxide layer formed after breakaway corrosion are important in the continued corrosion resistance against chlorine-induced corrosion attack. Especially, the Cr content in the inner scales is suggested to be important in corrosion mitigation.

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The Impact of HCl on Alkali-Induced Corrosion of Stainless Steels/FeCrAl Alloy at 600 °C: The Story After Breakaway

Ssenteza,

Jonsson,

Nockert

et al. 2024

High Temperature Corrosion of mater.

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High-Temperature Corrosion Behavior of Superheater Materials at 600 °C: Insights from Laboratory and Field Exposures

Ssenteza,

Olausson,

Eklund

et al. 2024

Energy Fuels

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Combustion of biomass and waste results in release of corrosive species, such as alkali chlorides and water vapor, which accelerate the corrosion of superheaters in the boiler. To improve our understanding of alkali-induced corrosion, long-term corrosion investigations are needed. This study utilizes a systematic approach based on long-term corrosion studies (up to 8000 h) in a wellcontrolled laboratory environment to understand the corrosion behavior and protectiveness of oxide scales formed on a FeCr alloy (marginal chromia former) and three overlay weld coating systems (lean FeCrAl, FeCrAl, and Ni-based alloy) in a KCl-rich environment at 600 °C. The results show that all the alloys undergo fast breakaway corrosion and form duplex-layered scales consisting of outward-and inward-growing oxide scales. The marginal chromia former exhibits parabolic oxidation kinetics and forms Fe-rich oxides in the outer scale and mixed Fe-and Cr-oxides in the inner layer. These oxide microstructures are compared to the scales formed on probe-exposed samples in boilers, and similar microstructures are typically found after exposures. The FeCrAl coatings form Fe-rich oxides in the outer layer and Fe-, Cr-, and Al-oxides in the inner layer. All alloy systems except the Ni-based coating show corrosion rates in the boiler in good agreement with the laboratory test prediction. The Ni-based coating exhibits the slowest oxidation kinetics in the laboratory, forming thin oxide scales with Ni-rich oxides in the outer layer and Cr-rich oxides in the inner layers, while this is not the case in the waste-fired boiler.

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Comparative erosion performance of HVOF and LVOF sprayed NiCrSiBCFe-WC-Co coating

Yadav,

Mishra

2024

Surface Engineering

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Thermal spray coatings enhance one or more surface properties of engineering components. In this work, NiCrSiBCFe-WC-Co composite coating powder is deposited over SA213-T12 boiler steel using the high velocity oxy fuel spraying (HVOF) and low velocity oxy fuel spraying (LVOF) thermal spray methods to improve erosion performance. XRD and scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) were used to examine the surfaces and constituents of as-deposited specimens, whereas SEM was used to investigate the eroded specimens. The erosion behaviours of developed coatings were investigated at 30° and 90° impact angles, 53 m/s and 400°C. XRD analysis of the HVOF coating showed an additional peaks of NiCo2O4, SiC and Ni2B with common peaks Ni, WC, W2C, Cr23C6 and C6(Cr,Co,Ni)23 to that of LVOF coating. HVOF-sprayed coating demonstrated higher microhardness and adhesion strength with lower porosity than LVOF-sprayed coating. The HVOF-sprayed NiCrSiBCFe-WC-Co coating demonstrated comparatively better erosion resistance than LVOF-sprayed NiCrSiBCFe-WC-Co coating, attributed to its superior properties. The mechanism of erosion, concerning the different characteristics of the coatings, is discussed.

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Breakdown of Protective Cr-Rich Oxide Scale Formed on Heat-Resistant Steels for Superheater Tubes in a Waste Power Generation Boiler

Cited by 4 publications

References 13 publications

The Impact of HCl on Alkali-Induced Corrosion of Stainless Steels/FeCrAl Alloy at 600 °C: The Story After Breakaway

The Impact of HCl on Alkali-Induced Corrosion of Stainless Steels/FeCrAl Alloy at 600 °C: The Story After Breakaway

High-Temperature Corrosion Behavior of Superheater Materials at 600 °C: Insights from Laboratory and Field Exposures

Comparative erosion performance of HVOF and LVOF sprayed NiCrSiBCFe-WC-Co coating

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