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Abstract for submission to Fall MS&T06 Symposium ”Phase Stability, Diffusion and Their Applications”
Phase Stability of a Powder Metallurgy Disk Superalloy
T. P. Gabb, J. Gayda, P. Kantzos, J. Telesman Advanced powder metallurgy superalloy disks in aerospace turbine engines now entering service can be exposed to temperatures approaching 700°C, higher than those previously encountered. They also have higher levels of refractory elements, which can increase mechanical properties at these temperatures but can also encourage phase instabilities during service. Microstructural changes including precipitation of topological close pack phase precipitation and coarsening of existing γ ′ precipitates can be slow at these temperatures, yet potentially significant for anticipated disk service times exceeding 1,000 h. The ability to quantify and predict such potential phase instabilities and degradation of capabilities is needed to insure structural integrity and air worthiness of propulsion systems over the full life cycle. A prototypical advanced disk superalloy was subjected to high temperature exposures, and then evaluated. Microstructural changes and corresponding changes in mechanical properties were quantified. The results will be compared to predictions of microstructure modeling software.
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esea
rch
Cen
ter
Phas
e St
abili
ty o
f a P
owde
r Met
allu
rgy
Dis
k Su
pera
lloy
Tim
Gab
b, J
. Gay
da, J
. Tel
esm
an, A
. Gar
g, P
. Kan
tzos
Phas
e St
abili
ty, D
iffus
ion
and
Thei
r App
licat
ions
Mat
eria
ls S
cien
ce &
Tec
hnol
ogy
2006
O
ctob
er 1
8, 2
006
2
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iona
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onau
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e Ad
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esea
rch
Cen
ter
Bac
kgro
und
-Pow
der m
etal
lurg
y pr
oces
sing
of d
isk
supe
rallo
ysal
low
s hi
gher
le
vels
of s
tren
gthe
ning
ele
men
ts fo
r inc
reas
ed te
mpe
ratu
re
capa
bilit
ies
-Adv
ance
d du
al m
icro
stru
ctur
e he
at tr
eatm
ents
(DM
HT)
can
als
o be
app
lied
to p
rodu
ce o
ptim
al g
rain
siz
e vs
. loc
atio
n an
d as
soci
ated
tem
pera
ture
/str
ess
1)Fi
ne g
rain
siz
e in
bor
e an
d w
eb s
ectio
ns fo
r hig
h st
reng
th
and
fatig
ue re
sist
ance
up
to 5
00°C
2)C
oars
e gr
ain
size
in th
e rim
for h
igh
cree
p an
d cr
ack
grow
th re
sist
ance
at 7
00°C
+
DM
HT
Dis
k10
mm
Gra
in S
ize
= 4
.5 μ
mG
rain
Siz
e =
34 μ
m
Supe
rsol
vus
Rim
Subs
olvu
sB
ore
10 μ
m10
μm
3
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iona
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Cen
ter
Stat
emen
t of P
robl
em
The
long
term
sta
bilit
y of
a D
MH
T ri
m’s
mic
rost
ruct
ure
at70
0°C
+ is
a c
once
rn-
Com
mer
cial
sof
twar
e pr
edic
ts p
reci
pita
tion
of h
arm
ful p
hase
s fo
rDM
HT
allo
y (L
SHR
)-
Cha
nges
of γ
′pre
cipi
tate
siz
es a
lso
pred
icte
d-
Thes
e ef
fect
s m
ight
be
acce
lera
ted
at g
rain
bou
ndar
ies
How
wou
ld th
ese
chan
ges
effe
ct m
echa
nica
l pro
pert
ies?
-Te
nsile
pro
pert
ies
need
to b
e st
able
-Ti
me-
depe
nden
t pro
pert
ies
coul
d lim
it lif
e at
thes
e te
mpe
ratu
res
-G
rain
bou
ndar
ies
are
ofte
n fa
ilure
site
s he
re :
enha
nced
effe
cts?
TCP
Phas
esγ′C
oars
enin
g
4
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Cen
ter
Obj
ectiv
e
Ass
ess
the
long
term
sta
bilit
y of
rim
mec
hani
cal p
rope
rtie
s an
d m
icro
stru
ctur
eat
704
°C
-Te
nsile
and
tim
e-de
pend
ent p
rope
rtie
s-
Pres
ence
of h
arm
ful p
hase
s an
d co
arse
ning
of c
arbi
des
-C
hang
es o
f the
γ′p
reci
pita
te s
izes
and
con
tent
s
App
roac
h
Expo
se b
lank
s fr
om th
e he
at tr
eate
d rim
of a
DM
HT
disk
at t
hese
te
mpe
ratu
res;
then
mac
hine
, tes
t, an
d an
alyz
e sp
ecim
ens
-Te
nsile
, str
ess
rela
xatio
n, a
nd d
wel
l cra
ck g
row
th p
rope
rtie
s se
lect
ed fo
r tes
ting
-Pr
esen
ce o
f har
mfu
l pha
ses
and
chan
ges
in c
arbi
des
and γ′
prec
ipita
tes
scre
ened
usi
ng fi
eld
emis
sion
sca
nnin
g el
ectr
on
mic
rosc
opy
-In
itial
resu
lts fo
r exp
osur
es a
t 704
°C u
p to
5,0
00 h
will
be
pres
ente
d
5
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iona
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esea
rch
Cen
ter
Mat
eria
l and
Pro
cedu
reA
lloy:
NA
SA L
SHR
Con
solid
atio
n: A
rgon
ato
miz
ed p
owde
r, ho
t com
pact
ed, e
xtru
ded,
iso-
forg
edH
eat T
reat
men
t: D
MH
T +
Supe
rcoo
l®A
ir Q
uenc
h +
855°
C/4
h +
775°
C/8
hPr
oced
ure:
Bla
nks
(B) w
ere
extr
acte
d fr
om ri
m o
f uni
form
coo
ling
rate
and
gra
in
size
, exp
osed
in a
ir, m
achi
ned
and
test
ed
®La
dish
Co.
, Inc
.
78°C
/min
.
188°
C/m
in.
Rim
Bor
e
BB
BB
Coo
ling
Rat
es
Gra
in S
izes
10 m
m
Gra
in S
ize
= 4
.5 μ
mG
rain
Siz
e =
34 μ
m
BB
BB
Supe
rsol
vus
Rim
Subs
olvu
sB
ore
10 μ
m10
μm
6
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iona
l Aer
onau
tics
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e Ad
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esea
rch
Cen
ter
Effe
cts
of E
xpos
ures
at 7
04°C
on
Tens
ile P
rope
rtie
s
Incr
easi
ng e
xpos
ures
did
not
sev
erel
y de
grad
e pr
oper
ties
Res
ults
7
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iona
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rch
Cen
ter
Effe
cts
of E
xpos
ures
at 7
04°C
on
Subs
eque
nt
Stre
ss R
elax
atio
n
Incr
easi
ng e
xpos
ure
allo
wed
mor
e st
ress
rela
xatio
n
704°
C a
t 1%
Str
ain
8
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iona
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Cen
ter
Incr
ease
d ex
posu
re im
prov
ed d
wel
l cra
ck g
row
th re
sist
ance
Effe
cts
of E
xpos
ures
at 7
04°C
on
Subs
eque
nt
Dw
ell C
rack
Gro
wth
Res
ista
nce
0 h
1,00
0 h
5,00
0 h
-Pre
dom
inan
tly in
terg
ranu
larc
rack
gro
wth
in a
ll ca
ses
704°
C, 9
0 se
c D
wel
l
1.5-
3x
9
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iona
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onau
tics
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esea
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Cen
ter
Wha
t are
the
asso
ciat
ed m
icro
stru
ctur
alch
ange
s?
-M
inor
pha
se c
hang
es-
Cha
nges
of t
he γ′p
reci
pita
te s
izes
and
con
tent
s w
ithin
gra
ins
-γ′p
reci
pita
te c
hang
es a
t the
gra
in b
ound
arie
s
Effe
cts
of e
xpos
ures
on
mec
hani
cal p
rope
rtie
s
-Te
nsile
pro
pert
ies:
sta
ble,
slig
htly
mor
e fo
rgiv
ing
-St
ress
rela
xatio
n: m
ore
rela
xatio
n al
low
ed-
Dw
ell f
atig
ue c
rack
gro
wth
: m
odes
t im
prov
emen
t
10
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iona
l Aer
onau
tics
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e Ad
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istra
tion
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rch
Cen
ter
Min
or P
hase
Siz
e D
istr
ibut
ions
and
Are
a Fr
actio
ns W
ere
Not
Sig
nific
antly
Cha
nged
By
Expo
sure
s
Expo
sure
s di
d no
t pro
mot
e ha
rmfu
l pha
se fo
rmat
ion
(Mo,
W,C
r)3B
2
(Ti,T
a,N
b)C
mic
rons
mic
rons
mic
rons
mic
rons
mic
rons
mic
rons
0 h
1,00
0 h
5,00
0 h
(Mo,
W,C
r)3B
2
(Ti,T
a,N
b)C
11
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iona
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Cen
ter
Seco
ndar
y γ′P
reci
pita
tes
Wer
e St
able
With
in G
rain
s
Tert
iary
γ′p
reci
pita
tes
coar
sene
d
Seco
ndar
yγ′
Tert
iary
γ′
mic
rons
mic
rons
mic
rons
mic
rons
mic
rons
mic
rons
0 h
1,00
0 h
5,00
0 h
Seco
ndar
yγ′
Tert
iary
γ′
12
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iona
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Cen
ter
Seco
ndar
y γ′W
as A
lso
Stab
le A
t Gra
in B
ound
arie
s
Tert
iary
γ′p
reci
pita
tes
also
coa
rsen
ed a
t gra
in b
ound
arie
s
Seco
ndar
yγ′
Tert
iary
γ′
mic
rons
mic
rons
mic
rons
mic
rons
mic
rons
mic
rons
0 h
1,00
0 h
5,00
0 h
Seco
ndar
yγ′
Tert
iary
γ′
13
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iona
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Cen
ter
Seco
ndar
y γ′
Com
paris
on o
f Mea
sure
men
ts In
dica
tes
Tert
iary
γ′
Coa
rsen
ing
Thro
ugho
ut M
icro
stru
ctur
e A
ppea
rs M
ost
Clo
sely
Ass
ocia
ted
With
The
Obs
erve
d Pr
oper
ty C
hang
es
Tert
iary
coa
rsen
ing
appe
ars
near
t1/3
LSW
* dep
ende
nce
Tert
iary
γ′
*Lifs
hitz
-Sly
ozov
-Wag
nert
heor
y
Gra
in
Bou
ndar
y Ef
fect
Gra
in
Bou
ndar
y Ef
fect
14
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iona
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Cen
ter
Sum
mar
y an
d C
oncl
usio
ns
The
long
term
, hig
h te
mpe
ratu
re s
tabi
lity
of th
e D
MH
T rim
’s
mic
rost
ruct
ure
at70
0°C
+ ap
pear
s pr
omis
ing
so fa
r:M
echa
nica
l Pro
pert
ies
-Te
nsile
pro
pert
ies,
tim
e-de
pend
ent p
rope
rtie
s in
dica
te
expo
sure
s pr
oduc
ed a
slig
htly
mor
e fo
rgiv
ing
mat
eria
lM
icro
stru
ctur
e-
No
harm
ful p
hase
s fo
und
so fa
r, de
spite
mod
el p
redi
ctio
ns-
γ′p
hase
fairl
y st
able
, with
onl
y te
rtia
ry p
reci
pita
te c
oars
enin
g-
Gra
in b
ound
ary
mic
rost
ruct
ure
likew
ise
stab
le s
o fa
r M
icro
stru
ctur
e-Pr
oper
ties
-Ex
posu
re e
ffect
s on
mec
hani
cal p
rope
rtie
s ap
pear
ass
ocia
ted
with
coa
rsen
ing
of te
rtia
ry γ′t
hrou
ghou
t mic
rost
ruct
ure
-Se
cond
ary γ′s
ize
appe
ars
larg
ely
set t
hrou
gh s
olut
ion
heat
tr
eat c
oolin
g pa
th, n
ote
this
was
pre
viou
sly
show
n to
als
o ef
fect
thes
e pr
oper
ties
-A
pplic
atio
n of
diff
eren
t sta
rtin
g he
at tr
eatm
ents
and
oth
ersu
bseq
uent
exp
osur
es a
nd s
tres
s co
uld
alte
r the
se fi
ndin
gs
15
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Cen
ter
Futu
re W
ork
-Tr
ansm
issi
on e
lect
ron
mic
rosc
opy
will
be
used
to m
ore
clos
ely
stud
y te
rtia
ry γ′c
hang
es-
Hig
her t
empe
ratu
res,
mor
e ex
posu
re ti
mes
will
be
expl
ored
-Ex
posu
res
unde
r str
ess
are
plan
ned,
to m
ore
clos
ely
sim
ulat
e st
ress
ed tu
rbin
e di
sk lo
catio
ns-
The
effe
cts
of d
iffer
ent h
eat t
reat
men
ts (c
oolin
g ra
tes
and
ages
) on
sub
sequ
ent e
xpos
ure
resp
onse
als
o ne
ed to
be
cons
ider
ed-
Mod
elin
g of
thes
e ef
fect
s is
als
o ge
tting
und
erw
ay
