Moisture-induced delayed spallation and interfacial hydrogen embrittlement of alumina scales

Smialek, James L.

doi:10.1007/s11837-006-0064-2

Cited by 39 publications

(40 citation statements)

References 33 publications

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“…This had been discussed in prior works [5,12,15,16] where there is general agreement that moisture causes a decrease in interfacial toughness between the scale and metal. The mechanism accounting for the decrease is under investigation, and one proposition is hydrogen embrittlement at the interface [17]. The rationale stems from the close analogy to moisture-induced hydrogen embrittlement features for intermetallic compounds.…”

Section: High Temperature Corrosion and Protection Of Materialsmentioning

confidence: 99%

“…The rationale stems from the close analogy to moisture-induced hydrogen embrittlement features for intermetallic compounds. To test this hypothesis, very adherent pre-oxidized samples of Rene′N5+80 ppmw Y, hydrogen annealed at 1250°C for 100 hr., were subjected to an electrolytic cathodic hydrogen charging procedure [17]. The current-voltage response profile was first established, showing relatively low 1 mA currents at less than 2.0 V cathodic (-) polarization or less than 1.3 V anodic (+) for coupons It can be seen that only eqn.…”

Section: High Temperature Corrosion and Protection Of Materialsmentioning

confidence: 99%

“…The current-voltage response profile was first established, showing relatively low 1 mA currents at less than 2.0 V cathodic (-) polarization or less than 1.3 V anodic (+) for coupons It can be seen that only eqn. [1], for metallic hydroxylization, produces hydrogen. Indeed, there is indication from preliminary proton induced gamma emission (PIGE) studies that some hydrogen does exist at the metal interface of oxidized alumina-formers [18].…”

Section: High Temperature Corrosion and Protection Of Materialsmentioning

confidence: 99%

“…According to many treatises on hydrogen embrittlement, a number of common aspects are in play that have parallels in the MIDS phenomenon, as discussed previously in [17]: a multi-axial tensile stress state exists which promotes hydrogen interstitial diffusion; embrittlement is maximized near room temperature, where hydrogen diffusion is sufficient to enter the material, but not so fast as to escape immediately; time delays for crack propagation are caused by this diffusion interval; and, finally, a negative synergy with interfacial sulfur exists, both experimentally and in theoretical quantum chemistry models, showing decreased M-Al 2 O 3 interfacial bond strength. This is in contrast with relatively slow moisture-induced crack growth (stress corrosion, static fatigue) for bulk alumina occurring by eqn.…”

Section: High Temperature Corrosion and Protection Of Materialsmentioning

confidence: 99%

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Enigmatic Moisture Effects on Al2O3 Scale and TBC Adhesion

Smialek

2008

MSF

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Abstract. Alumina scale adhesion on high temperature alloys is known to be affected primarily by sulfur segregation and reactive element additions. However adherent scales can become partially compromised by excessive strain energy and cyclic cracking. With time, exposure of such scales to moisture can lead to spontaneous interfacial decohesion, occurring while the samples are maintained at ambient conditions. Examples of this Moisture-Induced Delayed Spallation (MIDS) are presented for NiCrAl and single crystal superalloys, becoming more severe with sulfur level and cyclic exposure conditions. Similarly, delayed failure or Desk Top Spallation (DTS) results are reviewed for TBC's, culminating in the water drop failure test. Both phenomena are discussed in terms of moisture effects on bulk alumina and bulk aluminides. A mechanism is proposed based on hydrogen embrittlement and is supported by a cathodic hydrogen charging experiment. Hydroxylization of aluminum from the alloy interface appears to be the relevant basic reaction.

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Section: High Temperature Corrosion and Protection Of Materialsmentioning

confidence: 99%

Section: High Temperature Corrosion and Protection Of Materialsmentioning

confidence: 99%

Section: High Temperature Corrosion and Protection Of Materialsmentioning

confidence: 99%

Section: High Temperature Corrosion and Protection Of Materialsmentioning

confidence: 99%

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Enigmatic Moisture Effects on Al2O3 Scale and TBC Adhesion

Smialek

2008

MSF

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“…1 This is a serious concern that needs to be addressed. Another major issue with respect to durability is the build up and relaxation of thermal stresses within the multilayers of TBCs upon thermal cycling of these components.…”

Section: Oxide Layersmentioning

confidence: 99%

Challenges in oxidation resistant coatings

Ramanathan¹

2007

Surface Engineering

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Degradation of materials at high temperatures is a major concern in many sectors, including power generation, refinery and petrochemicals, chemical processing, metallurgical processing, paper and pulp, automotive, aerospace and defence. This degradation manifests itself mainly as oxidation, although solid particle erosion, phase transformation, hot corrosion, spalling of surface oxides and volatilisation are also encountered. Materials exposed to industrial atmospheres must be resistant to attack by the environment, and if the component is load bearing also to deformation. For many such components it is possible to choose a material with a suitable combination of properties. However, as mechanical loads and the severity of attack increase, the range of materials with an acceptable combination of properties becomes more limited. A solution to this problem is to design the material such that the surface is optimised to resist attack by the environment and the bulk is optimised to bear the mechanical load.Coatings are widely used to protect metallic components and are ideally specified to ensure the component is capable of operating efficiently throughout its design life. Oxidation resistant coatings are generally metallic or ceramic and should:

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Influence of water vapour on the oxidation behaviour of a conventional aluminide and a new thermal barrier coating system sintered from a slurry

Brossard

Bouchaud

Pedraza

2013

Materials & Corrosion

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In this work, the effect of water vapour on a new thermal barrier coating system synthesised from a slurry containing Al microparticles was studied under isothermal regime at 1100 °C for short oxidation times (50 h). Both dry air and argon gas atmospheres were investigated with increasing water vapour contents (0, 5, 10% RH, relative humidity) and the oxidation mechanisms and growth kinetics of the oxide scales were compared to conventional aluminide coatings up to 50% RH. The phase transformations occurring in the coating were characterised by local Raman micro‐spectrometry with complementary analytical techniques (X‐ray diffraction and FEG‐ESEM/EDS). The results demonstrated that water vapour does not exert a great influence on the oxidation of this type of coatings once an α‐Al2O3 scale is stabilised after an appropriate sintering of the coating. In contrast the combined effect of water vapour and oxidation onto oxide scales grown from raw aluminide coatings was shown to trigger delayed transformation of θ into α‐Al2O3, the appearance of pores and spallation, in particular in air + x %RH.

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Moisture-induced delayed spallation and interfacial hydrogen embrittlement of alumina scales

Abstract: High-Temperature Protection Research Summary

Cited by 39 publications

References 33 publications

Enigmatic Moisture Effects on Al<sub>2</sub>O<sub>3</sub> Scale and TBC Adhesion

Enigmatic Moisture Effects on Al<sub>2</sub>O<sub>3</sub> Scale and TBC Adhesion

Challenges in oxidation resistant coatings

Influence of water vapour on the oxidation behaviour of a conventional aluminide and a new thermal barrier coating system sintered from a slurry

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