Self Healing in Coatings at High Temperatures

Sloof, W.G.

doi:10.1007/978-1-4020-6250-6_14

Cited by 15 publications

(14 citation statements)

References 14 publications

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“…The optimum Cr 3+ content in the bath was found to be 80 g/L, which was very close to literature. This value was found by analysing the EDS spectra of the coating cross-sections; 80 g/L of Cr 3+ in the bath allowed the Cr content in the coating to exceed 20 wt.%, which is the minimum needed for protective chromia scale to cover the coating (Sloof, 2008). The effects of the deposition technique on the coating quality are discussed in Sections 3.2.1 and 3.2.2.…”

Section: Electroplating Processmentioning

confidence: 99%

“…If a coating is applied to improve the oxidation resistance, such that the material can operate at 900 o C, then the Carnot efficiency increases from approximately 69% to 75% (assuming a T 0 of 25 o C). Such efficiency increases can lead to a significant reduction in fuel consumption and CO 2 emissions (Sloof, 2008;Young, 2008).…”

Section: Introductionmentioning

confidence: 99%

“…However, this scale has a tendency to crack and spall due to growth and thermal stresses. The thermal stress is due to the different thermal expansion of the oxide to the underlying coating and substrate (Sloof, 2008;Wang, Wang, Yu, Zhu, 2008). Previous studies have found that scale adhesion can be improved by the addition of small quantities of rare earth elements, such as yttrium, or their corresponding compounds.…”

Section: Introductionmentioning

confidence: 99%

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Oxidation Behaviour of Ni-Cr-Y2O3 Composite Coatings Synthesised by Sol Enhanced Pulse Electroplating

Hoye¹,

Gao²

2012

JMSR

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The objective of this study was to improve the oxidation resistance of electroplated Ni-Cr coatings by introducing a fine dispersion of yttria (Y 2 O 3 ) nanoparticles to the coatings. A technique was developed to produce Y 2 O 3 nanoparticles nm in size. Electroplating conditions were also investigated and it was found that pulse plating could produce high quality coatings without cracking. The Y 2 O 3 nanoparticles were then co-deposited with Ni-Cr and formed a fine dispersion in the coating. The Ni-Cr-Y 2 O 3 composite coatings had improved oxidation resistance compared with the conventional Ni-Cr coatings. It is believed that this is due to Y 2 O 3 nanoparticles causing finer grains to occur, thereby improving oxide scale adhesion.

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Section: Electroplating Processmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Oxidation Behaviour of Ni-Cr-Y2O3 Composite Coatings Synthesised by Sol Enhanced Pulse Electroplating

Hoye¹,

Gao²

2012

JMSR

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“…If the reaction product has poor mechanical properties, blocking of the original crack could still be desirable as it will 'heal' the protective character of this ceramic material when it is used as an antioxidation coating on top of an underlying metallic substrate. Self-healing of ceramic oxide scales, such as Al 2 O 3 , SiO 2 and Cr 2 O 3 , which offer protection against corrosion of an underlying metallic component, is well known (Sloof 2007). In particular, for applications at elevated or high temperature, damage in terms of cracking or delamination of the protective oxide scale occurs due to stresses generated by mismatch of the coefficients of thermal expansion between the oxide scale and the metallic component upon thermal cycling.…”

Section: Ceramics and Ceramic Coatingsmentioning

confidence: 99%

Self-healing behaviour in man-made engineering materials: bioinspired but taking into account their intrinsic character

Zwaag

Dijk

Jonkers

et al. 2009

Phil. Trans. R. Soc. A.

108

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Man-made engineering materials generally demonstrate excellent mechanical properties, which often far exceed those of natural materials. However, all such engineering materials lack the ability of self-healing, i.e. the ability to remove or neutralize microcracks without (much) intentional human interaction. This inability is the unintentional consequence of the damage prevention paradigm underlying all current engineering material optimization strategies. The damage management paradigm observed in nature can be reproduced successfully in man-made engineering materials, provided the intrinsic character of the various types of engineering materials is taken into account.

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“…Currently the lifetime of TBC systems is limited by failure of the brittle ceramic top coating, which occurs through continuous development and coalescence of thermally induced cracks, eventually leading to spallation of parts of the coating [36]. In order to reduce ultimate failure by spallation and to increase the lifetime of TBC systems, new self-healing TBC systems are currently being studied [37], where one of the promising concepts focuses upon the local healing of cracks in the ceramic top coating through sintering at high operational temperatures. If the self-healing mechanism examined in the present study is adequately applied within a TBC system, it may lead to a substantial improvement of the overall thermo-mechanical performance of a turbine engine.…”

Section: Concluding Remarks and Applicationmentioning

confidence: 99%

Self-healing of damaged particulate materials through sintering

Luding¹,

Suiker²

2008

Philosophical Magazine

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Particulate materials loaded under uniaxial compression and tension are studied using the Discrete Element Method (DEM). Self-healing of the damaged samples is activated through sintering, a process that effectively increases the contact adhesion (i.e., the tensile strength) between particles. The initial sample is prepared from spherical particles by applying high (isotropic) pressure, where particles in contact deform plastically and adhere to each other due to increased van der Waals forces. The result of this pressure-sintering is a solid sample from which the stress is released before uniaxial tension or compression is applied. Damage occurs "microscopically" through loss of contacts and thus loss of adhesion. In order to "self-heal" (part of) this damage, the mechanical loading is stopped. The system is then sintered again, so that the adhesion at existing contacts in the damaged sample becomes stronger than originally. Subsequently, mechanical loading is continued. The stress-strain curves for the mechanically loaded samples are characterized by a peakstrength followed by a softening branch. Self-healing of an originally "weak" sample, up to a "strong" adhesion level, leads to qualitatively different stress-strain behavior, dependent on the strain at which self-healing is applied. Interestingly, the response of the "weak" self-healed material is bounded by the damage response of the "strong" material. For an optimal self-healing of the particulate material, it is preferable to initiate the healing mechanism during the early stage of damage development, before the peakstrength is reached.

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Self Healing in Coatings at High Temperatures

Cited by 15 publications

References 14 publications

Oxidation Behaviour of Ni-Cr-Y2O3 Composite Coatings Synthesised by Sol Enhanced Pulse Electroplating

Oxidation Behaviour of Ni-Cr-Y2O3 Composite Coatings Synthesised by Sol Enhanced Pulse Electroplating

Self-healing behaviour in man-made engineering materials: bioinspired but taking into account their intrinsic character

Self-healing of damaged particulate materials through sintering

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