Advanced Oxide Material Systems For 1650 C Thermal/Environmental Barrier Coating Applications

2004·1.4 MB·English

by  Zhu, Dongming

ADVANCED OXIDE MATERIAL SYSTEMS FOR
1650°C THERMAL/ENVIRONMENTAL BARRIER
COAT IN G AP PL I C AT ION S
Dongming Zhu, Dennis S. Fox,
Narottam P. Bansal, and Robert A. Miller
NASA John H. Glenn Research Center
Cleveland, OH 44135, USA
This work was supported by NASA Ultra-Efficient Engine Technology (UEET) Program
Fifth International Conference on High Temperature Ceramic Matrix Composites
September 12-1 6,2004, Seattle, Washington, USA
Abstract
Advanced thermallenvironmental barrier coatings (T/EBCs)
are being developed for low emission SiCISiC ceramic matrix
composite (CMC) combustor and vane applications to extend the
CMC liner and vane temperature capability to 1650OC (3000°F) in
oxidizing and water-vapor containing combustion environments.
The 165OOC T/EBC system is required to have better thermal
stability, lower thermal conductivity, and improved sintering and
thermal stress resistance than current coating systems.
In this paper, the thermal conductivity, water vapor stability
and cyclic durability of selected candidate zirconia-/hafnia-,
pyrochlore- and magnetoplumbite-based TlEBC materials are
evaluated. The test results have been used to downselect the T/EBC
coating materials, and help demonstrate advanced 1650OC coatings
feasibility with long-term cyclic durability.
0b jectives
-
Thermal conductivity and sintering behavior of
advanced oxide coating materials
ZirconiaJhafnia-, pyrochlore- and magnetoplumbite-based T/EBC
materials studied
Hot-pressed specimens and plasma-sprayed coatings
investigated
-
Water vapor stability of the advanced oxides at
temperatures of I6 50°C (3000°F)
-
Hf0,=Y20, coating system 1650°C (3000°F) cyclic
dura biI i t y

Thermal Conductivity Measurements of Hot-
Pressed Hf0,-Y,03 Coatings
-
Temperature dependence can be determined using the laser heat-flux
test approach
.o
0.0 0.5 1 1.5
Surface temperature, "C
Time, hours
Thermal Conductivity of Hot-Pressed
Pyrochlore Oxides
-
Thermal conductivity can increase by more than 100% at high
temperature due to the increased radiation heat-transfer under thermal
grad ient conditions
The multiple rare earth oxide co-doped pyrochlore oxides showed lower
conductivity as compared to the undoped La2Zr20,
5
4
3
2
hot-pressed (sol-gel powder)
1 La2Zr207h ot-pressed (sol-gel powder)
---.e-L-a2-Z r207h ot-pressed (spray-dried powder)
0 0
200 400 600 800 1000 1200 1400 1600
200 400 600 800 1000 1200 1400 1600
Surface temperature, "C Surface temperature, "C
Thermal Conductivity of Hot-Pressed Pyrochlore
Oxide and Plasma-Sprayed Coating Specimens
-
Plasma-sprayed coatings showed significantly lower radiation
conductivity due to the increased scattering and reflectivity of micro-
porosity
Hot-pressed dense zirconate material ZrO -8wt%Y 203pl asma-sprayed porous coating
2
5
k measured
3
b4
k fit due to lattice conduction k fit due to lattice conduction-radiation
s6 4
i;
.,>-I 3
*
.,Y-I
TJ
sF:
2
d2
3 1 lattice conduction lattice conduction
b
0
200 400 600 800 1000 1200 1400 200 400 600 800 1000 1200 1400 1600 1800
Surface temperature, "C Surface temperature, "C
Thermal Conductivity of Magnetoplumbites
-
Thermal conductivity of LaMgAl, ,01,,S mMgAl,, 0,, and GdMgAI, ,O,,
The Gd,O, and Yb,O, co-doped oxides showed the lowest conductivity
4.0 fi 4.0
3.5 bi 3.5 t
6
3.0 5 3.0
2.5 2.5
2.0 2.0
1.5 1.5
.o .o
1 1
0.5 0.5
0.0 0.0
200 400 600 800 1000 1200 200 400 600 800 1000 1200
Temperature, "C Temperature, "C
Thermal Conductivity of Advanced Oxide
Coatings
-
Thermal conductivity of plasma-sprayed HfO2=Y2O3z,i rconate/hafnate
and magnetoplumbite coatings tested at 1650°C
-
2.0 2.5
--
-
5YSHf
-
A
15YSHf 2.0
25YSHf ‘3
1.5 25YSHf s
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1
42
2
0.5
-A- Ld’Ll_ehl 0
0.5 0.0
0 5 10 15 20 0 5 10 15 20 25
Time, hours Time, hours
The Water Vapor Stability of Selected Hf0,-
and Pyrochlore Oxides
-
The water vapor stability of selected Hf02-based oxides and pyrochlore
oxides, determined by the TGA tests in a 50-50% flowing water vapor-
oxygen environment at 1650°C.
0.20
L
0.1 5
0.1 0
0.05
5
1 3
Q) 0.00
3
0
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0
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rn -0.05