High-temperature oxidation and spalling behavior of incoloy 825

Hussain, Nazar; Schanz, G.; Leistikow, S.; Shahid, K. A.

doi:10.1007/bf00665447

Cited by 20 publications

(9 citation statements)

References 3 publications

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“…On this basis, the values of the spallation constants q and q i are expected to be relatively insensitive to the temperature change, ⌬T, in the thermal cycle when T min is either constant or the oxide properties do not vary greatly with temperatures near T min . [30] In this case, Eq. Equation [36] indicates that f ϰ when bulk spallation is dominant m W g and P ϭ 0.…”

Section: Applications Of the Cyclic Oxidation Modelmentioning

confidence: 98%

“…[30] leading to The value of P is zero when the crack density in the interface, i0 , is zero and bulk spallation occurs by fracture within the oxide.…”

Section: Interface Spallationmentioning

confidence: 99%

“…In this regard, the proposed model is particularly attractive, because Eq. Equations [23] and [30] indicate that the q's (q and q i ) depend on elastic modulus, E ox ; fracture toughness of the oxide (K ox ) and the interface (K IN ); difference in the coefficients of thermal expansion, ⌬␣; the crack density parameters ( 0 and i0 ); and the crack orientation (). Equations [23] and [30] indicate that the q's (q and q i ) depend on elastic modulus, E ox ; fracture toughness of the oxide (K ox ) and the interface (K IN ); difference in the coefficients of thermal expansion, ⌬␣; the crack density parameters ( 0 and i0 ); and the crack orientation ().…”

Section: Calculated Cyclic Oxidation Behaviorsmentioning

confidence: 99%

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A mechanics-based approach to cyclic oxidation

Chan

1997

Metall Mater Trans A

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The failure process of cyclic oxidation, which involves both the formation and spallation of oxides, has been treated using a mechanics approach, in which oxidation is described via a parabolic growth law, while spallation is treated in terms of a power law derived from a fracture mechanics analysis. The spallation model is formulated on the basis that shear cracks are induced by thermal stresses during the cooldown period of a thermal cycle. Some of the shear cracks develop wing tip cleavage cracks, whose propagation and linkage with other shear cracks lead to the formation of oxide fragments that separate from the oxidizing surface during cooldown. Using a mass balance, quantitative relations are obtained between the process driving force, which is the thermal stress, and the response parameters such as the weight of oxide spalled, weight gain, and weight loss of the oxide-forming element. Applications of the proposed model for predicting the cyclic oxidation behavior of metal substrates and coating materials are demonstrated by comparing model calculations against experimental data as well as against other models in the literature.

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Section: Applications Of the Cyclic Oxidation Modelmentioning

confidence: 98%

“…[30] leading to The value of P is zero when the crack density in the interface, i0 , is zero and bulk spallation occurs by fracture within the oxide.…”

Section: Interface Spallationmentioning

confidence: 99%

Section: Calculated Cyclic Oxidation Behaviorsmentioning

confidence: 99%

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A mechanics-based approach to cyclic oxidation

Chan

1997

Metall Mater Trans A

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“…The exposure conditions were determined following a detailed investigation of the gaseous environments and deposit conditions that could be found around superheaters/reheaters in conventional pulverised coal-fired UK plants using various biomass-coal fuel combinations [8,10,16,17]. The gaseous conditions for the fireside tests were based on co-firing 80:20 wt% of a typical UK coal (Daw Mill) with cereal co-product (CCP).…”

Section: Exposure Conditionsmentioning

confidence: 99%

“…Fireside corrosion is defined as the loss of heat exchanger metal due to chemical reactions with the combustion gases and deposits at high temperatures [7][8][9]. Fireside corrosion is the single most reason for tube failures for pulverised fuel-fired power plants [8][9][10][11]. These failures are difficult to repair and result in unscheduled plant down time.…”

Section: Introductionmentioning

confidence: 99%

Modelling fireside corrosion of thermal sprayed coatings in co‐firing of coal/biomass

Hussain

Simms

Nicholls

2013

Materials & Corrosion

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This paper presents a development and evaluation of coating materials for advanced fossil fuel plants and addresses issues related to coal/biomass-derived flue gases. A selection of candidate coatings: 625, NiCr and NiCrAlY were deposited on superheater/reheater materials (T91) using high velocity oxy-fuel (HVOF) spraying. A series of laboratory-based fireside corrosion exposures have been carried out on these coated samples in controlled atmosphere furnaces for 1000 h. The tests were carried out with the ''deposit-recoat'' test method to generate the exposure conditions; the gaseous environment simulated that anticipated from air-firing 20 wt% cereal co-product (CCP) mixed with a UK coal. The exposures were carried out using various mixtures of Na 2 SO 4 , K 2 SO 4 , Fe 2 O 3 and kaolinite to produce different deposition fluxes at a test temperature of 650 8C. After the exposures, the samples were examined by environmental scanning electron microscope/energy dispersive X-ray analysis to characterise the damage. Pre-and post-exposure dimensional metrology was used to quantify the metal damage in terms of metal loss distributions. In all three coatings, the deposit targeted at forming undiluted alkali-iron tri-sulphate was found to be the most aggressive, causing the most corrosion damage to all alloys in simulated air-fired combustion gases. A corrosion model was proposed to predict the incubation time at different alkali deposition fluxes. The transition from incubation to propagation was found to be dependent on the chromium content of the alloys. The HVOF NiCr coating, with 46 wt% chromium, was found to be the best performing coating with the longest incubation times in these tests.

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