Combating hot corrosion of boiler tubes – A study

Kumar, Santosh; Kumar, Manoj; Handa, Amit

doi:10.1016/j.engfailanal.2018.08.004

Cited by 152 publications

(45 citation statements)

References 73 publications

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“…Owing to the excellent strength and corrosion resistance at higher temperatures, nickel-based superalloys are widely used as the materials for the hot components in aero-engines and land-based gas turbines, such as blades, turbine discs, and combustion chambers [1][2][3]. However, due to the existence of various impurities such as sulfur, sodium, potassium, and vanadium in the fuels, SO 2 and SO 3 gases will be generated during the combustion process at high temperatures, which then react with oxygen and NaCl to form a layer of molten Na 2 SO 4 on the surfaces of the hot components, thereby accelerating hot corrosion attack and the degradation of the alloys [4][5][6]. At high temperatures, the sulfur in the sulfate penetrates the oxide film and diffuses into the alloy to make it porous.…”

Section: Introductionmentioning

confidence: 99%

Hot Corrosion and Mechanical Performance of Repaired Inconel 718 Components via Laser Additive Manufacturing

Zhang

Zhuang

et al. 2020

Materials

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Hot corrosion is one of the crucial failure modes of Ni-based superalloy components operating at high temperatures, which inevitably affects the subsequent mechanical properties of the alloys. In this research, damaged Inconel 718 alloy components with a pre-made trapezoid groove are repaired using laser additive manufacturing technique, and the change mechanisms of the microstructure and tensile properties of the repaired Inconel 718 alloy due to the hot corrosion in the salt mixture of 87.5 wt.% Na2SO4 + 5 wt.% NaCl + 7.5 wt.% NaNO3 at 650 °C for different durations are investigated. The results show that oxidation and Cr-depletion occur on the repaired components due to the hot corrosion, and the corrosion products are mainly composed of Cr2O3, Fe3O4, and Ni3S2. The tensile strength and elongation of the as-repaired specimens are 736.6 MPa and 12.5%, respectively. After being hot corroded for 50 h, the tensile strength increases to 1022.9 MPa and elongation decreases to 1.7%. However, after being hot corroded for 150 h, both tensile strength and elongation of the repaired specimens drop to 955.8 MPa and 1.2%, respectively. The mechanical performance alteration is highly related to thermal effects instead of the molten salt attack.

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Section: Introductionmentioning

confidence: 99%

Hot Corrosion and Mechanical Performance of Repaired Inconel 718 Components via Laser Additive Manufacturing

Zhang

Zhuang

et al. 2020

Materials

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“…The selection of AISI304 as the substrate of choice was due to its wide application in erosion-corrosion environment at high (>600°C) service temperatures [8]. Particularly, the 304 variant is the most common boiler steel under both high temperature and oxidising environment [42,43]. The coating surface of the substrate was manually grit blasted at 320-500 μm resulting in a surface roughness of approximately 9±1 μm.…”

Section: Substrate and Coating Feedstockmentioning

confidence: 99%

Effect of nano-Al₂O₃ addition on the microstructure and erosion wear of HVOF sprayed NiCrSiB coatings

Praveen

Arjunan

2019

Mater. Res. Express

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Development of nanostructured high velocity oxy-fuel (HVOF) coatings with low porosity, high strength and increased wear resistance is still in its infancy. Combining nanoparticles with conventional microscale powders are increasingly being investigated to use with feedstock materials for thermal spray processes. Accordingly, this work investigates the addition of nano-Al 2 O 3 particles on the microstructure and erosion wear of NiCrSiB HVOF coating in a stainless steel (AISI 304) substrate. Particle analysis of the NiCrSiB feedstock was conducted and the maximum allowable addition of Al 2 O 3 nanoparticles have been identified using the 'mass mixture ratio' model considering both the particle size and density. Consequently, two cases are considered and their performance analysed: a maximum allowable case of 1.4 wt%, followed by a 0.17 wt% addition of nano-Al 2 O 3 with NiCrSiB. Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and x-ray Diffraction (XRD) analysis were employed to inform the microstructure, material composition and phase spectrum of the resulting coatings. Subsequently, the nanostructured coating was exposed to both a pull-off adhesion strength test and hot air jet (450°C) hard particle erosion to characterise its performance. It was found that the microhardness of the HVOF NiCrSiB coating improved from 576 HV 0.3 to 748 HV 0.3 with the addition of 1.4 wt% nano-Al 2 O 3 . Furthermore, the nanostructured coating also exhibited high erosion resistance at a 90°erodent impact angle. The increase in erosion wear resistance was due to the increase in the hardness as a result of the nano-Al 2 O 3 addition. IntroductionSolid particle erosion wear plays an important role in the material degradation process of engineering components [1-3], including turbines, thermal power plants, pipelines, hydropower machinery and combustion systems [4,5]. According to Martinella [6], one of the major industries affected by solid particle erosion are coal based electric power plants. This is caused as a result of the fly ash interaction with the wall surfaces facilitated by the high-temperature flue gases. The prolonged effect of this causes the boiler components to fail and currently account for ∼25% of the down time [7]. The subsequent cost effect of erosion wear damage in such cases is often as high as 54% of the overall maintenance cost [8,9]. Consequently, coatings that can improve the surface resistance to solid particle erosion wear along with high-temperature oxidation protection systems are increasingly being sought.Among the numerous solution available to prevent or control the fly ash erosion, surface coatings [10] are the most widely adopted technique [11][12][13]. When it comes to coating methodology, several techniques are available including vapour deposition [14], electrochemical, sol-gel [14] and thermal spraying [14]. Among these different coating techniques, thermal spray techniques [15,16] have received increased attention largely due to their capacity to accommodate a range of ...

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“…As already known, the main deterioration mechanisms in power plant boilers are creep damage, microstructural degradation, erosion by fly-ash and high-temperature fatigue, embrittlement, carburization, hydrogen damage, graphitization, thermal shock, liquid metal embrittlement, and high-temperature corrosion of various types [3][4][5] . These mechanisms are associated with long-term exposure to high-temperatures, strain generated by particle`s impact, and corrosive action of combustion products, which can be intensified due to high temperatures 5,6 . The expected service life of applied materials is 20 years for boilers operating under standard conditions.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Fly Ash and a Protective Coating for Brazilian Thermal Power Plant Boilers

et al. 2020

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Thermoelectric power plants that use mineral coal show high wear in heat exchanger due to the action of several damage mechanisms associated with the impact of hard particles from the residue of burnt coal, the ashes. The employment of coatings should be given into consideration particularly for critical components, which are subject to severe erosive conditions is one of the solutions. However, the choice of material will depend on several factors, including the properties of aggressive ashes. This paper aims to characterize ashes generated by a Brazilian coal-based power plant and a FeCrNbNi-based metallic coating obtained by the electric arc spraying process. No trace of sulfur content was found in fly ashes and it was defined that wear is mainly related to the impact and energy of hard particles are the leading causes of degradation in coal-fired boiler equipment. According to the assessment, applied coating showed (5 ± 2)% by volume of pores and cracks, with 1.6% of oxides after the spraying process and hardness 35% greater than ash particles. Preliminary results in field operation suggest that the material showed relatively low wear compared to the original substrate and showed great applicability in controlling material deterioration for this purpose.

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Combating hot corrosion of boiler tubes – A study

Cited by 152 publications

References 73 publications

Hot Corrosion and Mechanical Performance of Repaired Inconel 718 Components via Laser Additive Manufacturing

Hot Corrosion and Mechanical Performance of Repaired Inconel 718 Components via Laser Additive Manufacturing

Effect of nano-Al₂O₃ addition on the microstructure and erosion wear of HVOF sprayed NiCrSiB coatings

Characterization of Fly Ash and a Protective Coating for Brazilian Thermal Power Plant Boilers

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Combating hot corrosion of boiler tubes – A study

Cited by 152 publications

References 73 publications

Hot Corrosion and Mechanical Performance of Repaired Inconel 718 Components via Laser Additive Manufacturing

Hot Corrosion and Mechanical Performance of Repaired Inconel 718 Components via Laser Additive Manufacturing

Effect of nano-Al2O3 addition on the microstructure and erosion wear of HVOF sprayed NiCrSiB coatings

Characterization of Fly Ash and a Protective Coating for Brazilian Thermal Power Plant Boilers

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Effect of nano-Al₂O₃ addition on the microstructure and erosion wear of HVOF sprayed NiCrSiB coatings