IMPERMEABLE THIN Al{sub 2}O{sub 3} OVERLAY FOR TBC PROTECTION FROM SULFATE AND VANADATE ATTACK IN GAS TURBINES
To improve the hot corrosion resistance of YSZ thermal barrier coatings, a 25 {micro}m thick Al{sub 2}O{sub 3} overlay were deposited by HVOF thermal spray, respectively, onto to the surface of YSZ coating. In the next reporting period, we will measure or calculate the residue stress within Al{sub 2}O{sub 3} overlay and YSZ coating to study the mechanism of effect of Al{sub 2}O{sub 3} overlay on spalling of YSZ coating. However, due to the thermal expansion mismatch between YSZ coating and Al{sub 2}O{sub 3} overlay, such surface modification using Al{sub 2}O{sub 3} overlay might deteriorate strain tolerance of the TBC. In the present work, in order to investigate the effect of Al{sub 2}O{sub 3} overlay on residual stress developed in the samples during cooling after hot corrosion at high temperature, Finite Element method (FEM) was employed to determine the detailed stress states in the test specimens after cooling. The results showed that there is no high stress concentration at the interface between the YSZ and the bond coat for TBCs system without Al{sub 2}O{sub 3} overlay. On the other hand, the maximum compressive stress with a value of approximately, -330 MPa occurred within the Al{sub 2}O{sub 3} overlay. The maximum tensile stress in YSZ coat near the Al{sub 2}O{sub 3} overlay is in the range of 10-133 MPa. The maximum compressive stress of approximately -160 MPa occurred near the YSZ-bond coat interface. X axis stress play a dominant role in influencing the coating failure and spalling. In the next reporting period, we will study the thickness of Al{sub 2}O{sub 3} overlay on hot corrosion resistance and spalling of YSZ coating.
- Research Organization:
- University of Pittsburgh (US)
- Sponsoring Organization:
- (US)
- DOE Contract Number:
- FC26-01NT41189
- OSTI ID:
- 825293
- Resource Relation:
- Other Information: PBD: 31 Mar 2004
- Country of Publication:
- United States
- Language:
- English
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