NASA Technical Reports Server (NTRS) 20150010092: Mechanical Properties of Air Plasma Sprayed Environmental Barrier Coating (EBC) Materials

6.4 MB·English

by  NASA Technical Reports Server (NTRS)

National Aeronautics and Space Administration
Mechanical Properties of
Air Plasma Sprayed
Environmental Barrier
Coating (EBC) Materials
Bradley Richards1,2, Dongming Zhu1, Louis Ghosn1, and
Haydn Wadley2
1NASA Glenn Research Center, Cleveland, OH 44135
2University of Virginia, Charlottesville, VA 22903
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Outline: testing of relevant mechanical
properties of APS EBCs: Yb Si O and Si
2 2 7
1.  Very brief introduction
2.  Methodology
3.  APS Yb Si O properties
2 2 7
1.  APS structure
2.  Elastic modulus, flexure strength, K
IC
3.  Isothermal creep
4.  Laser thermal gradient creep
4.  APS Si properties
1.  APS structure
2.  Elastic modulus, flexure strength, K
IC
3.  Laser thermal gradient creep
4.  Interlaminar/interfacial toughness
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Yb Si O /Si EBC Property Testing Goals
2 2 7
g
n Provide insight into how
i
t
a APS processing can alter
o
C
mechanical properties

d
e
l
a
e
n
Provide thermophysical data
n
A
for modeling efforts of EBC
systems
s
e
l
c
y
C
Understand mechanical
Yb Si O
m
2 2 7
a properties of a relevant EBC
e
Si
t
S system

0
SiC
0
0
2
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Methodology
•  Refine spray parameters
APS YbS2 stand-alone
•  Deposit APS stand-alone
material:
Yb Si O and Si
2 2 7
@ 130 x 65 x 13mm
•  Machine (grind) APS stand-
alone material into test bars
Machined APS Si bars
15 YbS2 and and 15 Si
@ 50 x 5 x 4mm
•  Test density, size, elastic
modulus for all specimens
•  Perform mechanical tests
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4pt flexure- isothermal & thermal gradient
Convenient for determining
many mechanical properties
Low temperature
configuration (ASTM C1161)
High temperature
configuration (ASTM C1211)
Laser/cooling air induced
thermal gradient
configuration
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Creep Equations and Testing
Primary
dε/dt = A * exp(-E /RT) * σn * t-s
a
key parameters E , n, s
a

Secondary
dε/dt = C * exp(-E /RT) * σn
a
key parameters E , n
a

Data recorded in creep test is actuator or mid-point displacement,
load, and time. Models are used to calculate strain (see Hollenberg
et. al. 1970).

For low n (~1), elastic strains from Euler-Bernoulli beam theory
happen to be accurate.

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APS Yb Si O
2 2 7
Properties
Elastic Modulus, Flexure Strength, Toughness,
Isothermal Creep, Laser Thermal Gradient Creep
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Yb Si O Microstructure
2 2 7
APS structure crack-free and 90-91% dense
(archimedes density and image analysis)
Pores loosely spherical
Some Si loss occurred during APS processing (quantity
still undetermined, pending analysis)
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Yb Si O Properties
2 2 7
•  Elastic Modulus- impulse excitation E = 33.4 GPa, σ = 2.53
13 specimens @ 25°C
(~170-180GPa bulk: X-ray, nanoindentation)

•  Low Temperature K = 0.925 MPa*m0.5, σ = 0.05
IC
3 specimens @ 25°C
(dense material 2 MPa*m0.5)

•  Low Temperature Flexure Strength = 19.7 MPa, σ = 0.62
4 specimens @ 25°C
(dense & stoichiometric: ~100MPa Yb Si O , ~15MPa Yb SiO )
2 2 7 2 5

•  High Temperature Flexure Strength = 24.3 MPa, σ = 0.42
2 specimens @ 900°C

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Isothermal Creep Behavior
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