Abstract

The lifetime of the high temperature ceramic coating 7 wt.% yttria-stabilized zirconia (7YSZ) is reduced when calcium-magnesium-alumino-silicate (CMAS) particulates enters aero-engines during operation in a sandy or dusty environment, melts, and infiltrates into the coating. 7YSZ undergo both chemical and mechanical degradation from CMAS infiltration during cycling. Characterization methods with synchrotron X-ray diffraction (XRD) provides a non-destructive means to measure the impact of time and temperature on coating degradation with high spatial resolution of 7YSZ coatings infiltrated and annealed by CMAS for 1 hour and 10 hours as well as at 1225 °C and 1250 °C. Additionally, qualitative results of cross-sectional scanning electron microscopy (SEM) allows for the additional observation and validation of the extent of degradation the coatings experience from CMAS infiltration. The XRD measurements show the extent of degradation is more sensitive to temperature around the melting range of CMAS with an increase of approximately 42.8% in the concentration of the monoclinic phases present in the coating at the surface when increasing the annealing temperature from 1225 °C to 1250 °C. It was also found that the degradation was more significant in the first hour of infiltration. There was an increase of 21.5% in the concentration of the monoclinic phases present within the coating at the surface when increasing the annealing time from 1 hour to 10 hours. The results presented within this thesis resolve the impact of time and temperature on the infiltration kinetics of CMAS in coatings which are important considerations in mitigating CMAS infiltration.

Thesis Completion

2020

Semester

Spring

Thesis Chair

Raghavan, Seetha

Co-Chair

Ghosh, Ranajay

Degree

Bachelor Science in Aerospace Engineering (B.S.A.E.)

College

College of Engineering and Computer Science

Department

Mechanical and Aerospace Engineering

Degree Program

Aerospace Engineering

Language

English

Access Status

Campus Access

Length of Campus-only Access

1 year

Release Date

5-1-2021

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