Performance of thermally sprayed Si/mullite/BSAS environmental barrier coatings exposed to thermal cycling in water vapor environment

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Journal titleSurface and Coatings Technology
Pages215223; # of pages: 9
SubjectAir plasma sprayed; Bond coats; BSAS; Controlled conditions; Crack-healing; Crack-resistant; Deposition conditions; Elastic modulus values; Environmental barrier coatings; Functionally graded; High temperature; High temperature structural applications; High-temperature water; Hot zone; Influence of water; Microstructural characteristics; SiC substrates; Silicon-based ceramics; Structural and mechanical properties; Thermal cycle testing; Thermal exposure; Top-coats; Water vapor atmosphere; Aluminosilicates; Ceramic matrix composites; Cracks; Elastic moduli; Gas turbines; High temperature applications; Signal encoding; Silicate minerals; Silicon; Silicon carbide; Thermal barrier coatings; Thermal cycling; Vapors; Sprayed coatings
AbstractThe ongoing development of environmental barrier coatings (EBCs) offers the prospect to implement the full potential of silicon-based ceramic matrix composites (CMCs) for high temperature structural applications, more specifically the hot zones of gas turbine engines. The current state-of-the-art EBC system comprises a Si bond coat, a mullite (Al6Si2O13) interlayer and a barium-strontium aluminosilicate (BSAS) (Ba1-xSrxAl2Si2O8; 0<x<1) crack-resistant and water vapor attack resistant top coat. In this study, fully crystalline air plasma sprayed Si/mullite/BSAS-celsian EBCs were engineered under controlled conditions on SiC substrates. The influence of water vapor corrosion on the structural and mechanical properties of a Si/Mullite/BSAS EBC architecture was assessed by furnace thermal cycle testing (i.e.; 50 and 100cycles, 2h/cycles at 1300°C in water vapor atmosphere). The elastic modulus values of the as-sprayed BSAS top coat (~75±6GPa as determined via indentation) did not exhibit major changes after thermal exposure (~78±8GPa). In addition, the BSAS layer exhibited crack healing at high temperatures, the density of cracks decreasing from 15cracks/cm in the as-sprayed state to 2cracks/cm after thermal cycling. These characteristics of the BSAS top coat were related to its glass-ceramic nature, the phase/chemical stabilities of the BSAS-celsian at high temperatures and the engineered deposition conditions at which it was deposited. The overall performance at high-temperature of this functionally graded EBC architecture is discussed and correlated to its microstructural characteristics. © 2012.
Publication date
AffiliationNational Research Council Canada (NRC-CNRC)
Peer reviewedYes
NPARC number21270710
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Record identifier83cfe009-e0b5-4c6d-869b-25d820857197
Record created2014-02-17
Record modified2016-05-09
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