Relationships between the microstructure and properties of thermally sprayed deposits

Thermally sprayed deposits have layered structure composed of individual splats. The individual splats have quenching microstructure of quasi-stable preferred fine grains. However, this fine-grained microstructure of the deposits is usually not reflected by improved performance of the deposits becau...

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Bibliographic Details
Published in:Journal of thermal spray technology 2002-09, Vol.11 (3), p.365-374
Main Authors: LI, C.-J, OHMORI, A
Format: Article
Language:English
Subjects:
Condensed matter: structure, mechanical and thermal properties
Deposition
Deposits
Exact sciences and technology
Lamellar structure
Mathematical models
Mechanical and acoustical properties
Microstructure
Physical properties of thin films, nonelectronic
Physics
Porosity
Sprays
Surfaces and interfaces
thin films and whiskers (structure and nonelectronic properties)
Voids
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Summary:Thermally sprayed deposits have layered structure composed of individual splats. The individual splats have quenching microstructure of quasi-stable preferred fine grains. However, this fine-grained microstructure of the deposits is usually not reflected by improved performance of the deposits because a layered structure with two-dimensional voids occurs between lamellar interfaces. The microstructure of the thermal spray deposits with the emphasis on the layer structural parameters is reviewed. Conventionally, one of the most common quantitative parameters used to characterize the microstructure of the thermally sprayed deposits is the porosity, measured by different methods. However, it is illustrated that the relationships between properties and porosity for bulk porous materials processed by conventional processes cannot be applied to thermally sprayed deposits owing to the two-dimensional characteristics of voids. The total porosity in the deposits is not meaningful from the viewpoint of prediction of the deposit properties. An idealized structural model and related parameters, instead of porosity, are proposed to characterize quantitatively the microstructure of the thermally sprayed deposit. The relationships between the properties and the structural parameters are presented for the plasma-sprayed ceramic deposits based on the proposed microstructure model. The properties include the Young's modulus, fracture toughness, erosion resistance, and thermal conductivity of the plasma sprayed ceramic deposits. The correlations of theoretical relationships with reported experimental data are discussed. An agreement of theoretical with observed values suggests that the lamellar structure of the deposit with limited interface bonding is the dominant factor controlling the performance of the deposit. [The experimental procedure involves the copper electroplating for an alumina deposit.]
ISSN:1059-9630
1544-1016
DOI:10.1361/105996302770348754