Changes in porosity and Young’s Modulus due to sintering of plasma sprayed thermal barrier coatings

Siebert, Barbara; Funke, Claudia; Vaβen, R.; Stöver, D.

doi:10.1016/s0924-0136(99)00243-5

Cited by 128 publications

(69 citation statements)

References 4 publications

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“…In fact, a rise of the porosity was observed because it was measured by image analysis and very fine pores were hardly identified by this technique. However, previous works, where the porosity was measured by mercury porosimetry, revealed that porosity was reduced at high soak times but the mean void size was increased [20]. Other authors noted that a cracking during isothermal treatment is formed due to the TGO thickening that promotes out of plane stresses at the TGO and ceramic layer interfaces [21].…”

Section: Isothermal Treatmentmentioning

confidence: 94%

“…The formation of sintering necks causes a closing of the cracks, as a consequence, the smooth and straight cracks were separated into smaller parts and a reduction of crack ratio was determined, as reflected in Fig. 5 [20]. The reduction of porosity and cracks in the coatings caused hardening so that the coating hardness rises during the first 20 h of thermal treatment.…”

Section: Isothermal Treatmentmentioning

confidence: 97%

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Thermal behaviour of multilayer and functionally-graded YSZ/Gd2Zr2O7 coatings

Carpio

Salvador

Borrell

et al. 2017

Ceramics International

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Zirconates with pyrochlore structure, such as Gd2Zr2O7, are new promising thermal barrier coatings because of their very low thermal conductivity and good chemical resistance against molten salts. However, their coefficient of thermal expansion is low, therefore their thermal fatigue resistance is compromised. As a solution, the combination of yttria-stabilised zirconia (YSZ) and Gd2Zr2O7 can reduce the thermal contraction mismatch between the thermal barrier coating parts.In the present study, two possible designs have been performed to combine YSZ/ Gd2Zr2O7. On the one hand, a multilayer coating was obtained where YSZ layer was deposited between a Gd2Zr2O7 layer and a bond coat. On the other hand, a functionallygraded coating was designed where different layers with variable ratios of YSZ/Gd2Zr2O7 were deposited such that the composition gradually changed along the coating thickness.Multilayer and functionally-graded coatings underwent isothermal and thermally-cycled treatments in order to evaluate the oxidation, sintering effects and thermal fatigue resistance of the coatings. The YSZ/Gd2Zr2O7 multilayer coating displayed better thermal behaviour than the Gd2Zr2O7 monolayer coating but quite less thermal fatigue resistance compared to the conventional YSZ coating. However, the functionally-graded coating displays a good thermal fatigue resistance. Hence, it can be concluded that this kind of design is ideal to optimise the behaviour of thermal barrier coatings.

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Section: Isothermal Treatmentmentioning

confidence: 94%

Section: Isothermal Treatmentmentioning

confidence: 97%

Thermal behaviour of multilayer and functionally-graded YSZ/Gd2Zr2O7 coatings

Carpio

Salvador

Borrell

et al. 2017

Ceramics International

View full text Add to dashboard Cite

show abstract

“…A widely reported fact about plasma sprayed ceramic coatings is the closure of pores and cracks due to sintering upon prolonged exposure to high temperatures [28,39]. This can reduce the overall coating porosity compared to the as-sprayed coating [39].…”

Section: Microstructural Changes After Heat Treatmentmentioning

confidence: 99%

“…In view of its importance, the influence of high temperature exposure in terms of sintering of the ceramic-layer, pore closure etc. has been well-studied in case of both APS [28][29][30] and EB-PVD [31][32][33] TBCs. However such studies on SPS TBCs have been rare as per the author's knowledge and, therefore, an attempt has been made to specifically address this issue in the present work.…”

Section: Introductionmentioning

confidence: 99%

Influence of Isothermal Heat Treatment on Porosity and Crystallite Size in Axial Suspension Plasma Sprayed Thermal Barrier Coatings for Gas Turbine Applications

2016

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Axial suspension plasma spraying (ASPS) is an advanced thermal spraying technique, which enables the creation of specific microstructures in thermal barrier coatings (TBCs) used for gas turbine applications. However, the widely varying dimensional scale of pores, ranging from a few nanometers to a few tenths of micrometers, makes it difficult to experimentally measure and analyze porosity in SPS coatings and correlate it with thermal conductivity or other functional characteristics of the TBCs. In this work, an image analysis technique carried out at two distinct magnifications, i.e., low (500×) and high (10,000×), was adopted to analyze the wide range of porosity. Isothermal heat treatment of five different coatings was performed at 1150 • C for 200 h under a controlled atmosphere. Significant microstructural changes, such as inter-columnar spacing widening or coalescence of pores (pore coarsening), closure or densification of pores (sintering) and crystallite size growth, were noticed in all the coatings. The noted changes in thermal conductivity of the coatings following isothermal heat treatment are attributable to sintering, crystallite size growth and pore coarsening.

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“…The Vickers indentation were performed on the polished cross section of the coating, which were measured at least 20 times in random different areas with a load of 2.94 N and 10 s holding time and keeping at least five times greater than the diagonal length of indentation between consecutive indentations. The Weibull statistical analysis was used to analyze the scatter of micro-hardness data, which distribution characteristic of the mechanical property can reflect the microstructural characteristic of the as-sprayed coatings [17][18][19].The fracture toughness of as-sprayed coatings was determined by [20],…”

Section: Indentation Tests and Weibull Analysismentioning

confidence: 99%

Particle in-flight behavior and its determining the microstructure and mechanical properties of zirconia based thermal barrier coatings

Liu¹,

Ma²,

Bai³

2018

Proceedings of the 4th Annual International Conference on Material Engineering and Application (ICMEA 2017)

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Abstract-The present study aims to elaborate the particle inflight behavior during plasma spraying and its significance in determining the microstructure and mechanical properties of plasma sprayed yttria partially stabilized zirconia (YSZ) thermal barrier coatings (TBCs). The as-sprayed YSZ coatings were characterized in terms of the defects (such as pores, unmelted particles and cracks here), hardness and fracture toughness. The results showed that, due to the higher temperature and velocity of in-flight particles in SAPS than that of APS, denser coatings were formed leading to better mechanical properties, including Vickers hardness and fracture toughness. The percentage of defects of microstructure was similar to the temperature and velocity of particles in-flight during plasma spraying. Again, the results were in agreement with that the structural defects had an strongly effect on its mechanical behavior.

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Changes in porosity and Young’s Modulus due to sintering of plasma sprayed thermal barrier coatings

Cited by 128 publications

References 4 publications

Thermal behaviour of multilayer and functionally-graded YSZ/Gd2Zr2O7 coatings

Thermal behaviour of multilayer and functionally-graded YSZ/Gd2Zr2O7 coatings

Influence of Isothermal Heat Treatment on Porosity and Crystallite Size in Axial Suspension Plasma Sprayed Thermal Barrier Coatings for Gas Turbine Applications

Particle in-flight behavior and its determining the microstructure and mechanical properties of zirconia based thermal barrier coatings

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