REVISTA DYNA NEW TECHNOLOGIES

Key words:

Recubrimiento de barrera térmica, esfuerzos residuales, rociado térmico y óxidos fundidos de calcio, magnesio, aluminio y silicio (CMAS), Thermal barrier coating (TBC), residual stresses, thermal spraying, region of interest (Roi) and molten calcium-magnesium-alumino-silicate, Thermal barrier coating, TBC, residual stresses, thermal spraying, and molten calcium–magnesium–alumino–silicate, CMAS.

Article type:

ARTICULO DE INVESTIGACION / RESEARCH ARTICLE

Section:

RESEARCH ARTICLES

ABSTRACT:
I This work is part of an Inter-Institutional project to understand the problem of degradation suffered by thermal barrier coatings of gas turbines. Thermal barrier coatings (TBC) were manufactured by deposition of two layers of different chemical composition, namely CoNiCrAlY and yttria-stabilized zirconia (YSZ) on an AISI 304 stainless steel substrate. Both layers were deposited by employing thermal spraying processes, the bonding metallic layer (BC) was deposited by employing an HVOF gun, whereas the ceramic component (TC) by atmospheric plasma spray (APS). The TBCs were heat treated at 1200 °C, with CMAS attack with a concentration of 35 mg/cm2 for different soaking times in order to evaluate the effect of CMAS attack on the magnitude of the state of residual stresses in the coating at high temperature, as a function of exposure time. The coatings´ stress state was determined by employing the Modified Layer Removal Method for Duplex Coatings (MLRMDC) and an adaptation of the stress equation due to the difference of thermal expansion coefficients.. The residual stress profile of a TBC was successfully determined by employing both methods; it was found that longer exposure times at high temperature resulted in an increased compressive residual stress state on the TC by the CMAS effect. The result of this work may be of great interest in the determination of new TBCs for better and more durable protection of aircraft turbine blades. They are also a reference point for the use and calibration of new techniques to determine residual stresses such as the Electronic Speckle Pattern Interferometry (ESPI).

Keywords: Thermal barrier coating (TBC), residual stresses, thermal spraying, and molten calcium–magnesium–alumino–silicate (CMAS).