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2University Bayreuth Uwe Glatzel, Metals and Alloys
Single Crystal Nickel Based Superalloys
for High Temperature Applications- Microstructure, Properties, Anisotropy -
Uwe GlatzelUwe GlatzelMetals and Alloys
University Bayreuth
3University Bayreuth Uwe Glatzel, Metals and Alloys
Content• motivation: history, application field
• processing
• microstructure, misfit
• anisotropic properties(modulos, creep behavior)
• dislocations, stress induced diffusion
• Outlook (alloys with reduced density, platinum basedsuperalloys)
TU-Berlin (SFB 339)Uni Jena
4University Bayreuth Uwe Glatzel, Metals and Alloys
Superalloys for Extreme Demands
Single crystal nickel based superalloys as material for firstrotating blades after thecombustioncombustion chamberchamber in aircraft flight engines.
fan(thrust)
compressor (titanium)
gas temp.: 1500°C
material: 1100°C
⇒ const. stress of about 100 MPa
(≈ 1 car/cm2)
20.000 rpm
5University Bayreuth Uwe Glatzel, Metals and Alloys
Big, Single Crystal Blade
Blade forstationarygas turbinefor powerproduction
≈ $ 40.000
6University Bayreuth Uwe Glatzel, Metals and Alloys
Coefficient of Efficiency
in
outinmax.theor T
TT −=η
regular fuel car engine: 23%
diesel car engine: 27%
aircraft turbine: 30-35%
stationary gasturbine: 40%
gas and steam generation: 54%
gas + steam + long distance heating: 87%
increase of Tin increasescoefficient of efficiency
7University Bayreuth Uwe Glatzel, Metals and Alloys
Increase in Temperature due to Improved Construction and Material
constantimprovement5-10°C/year
ceramics??platinumbase alloys?
year1950 1960 1970 1980 1990 2000
tem
pera
ture
[°
C]
500
1000
1500
2000
improved materials
improved coolingcivilianmilitary
material temperature
gas temperature
polycrystalline
directional solidified
single crystal
iron base
nickel base alloys
8University Bayreuth Uwe Glatzel, Metals and Alloys
Why nickel based superalloys?Anomalous flow stress behavior of the
intermetallic phase Ni3Al:
temperature [°C]
0 200 400 600 800 1000
flow
str
ess
[M
Pa]
0
100
200
300
400
500
superalloy as cast
superalloy heat treated
Ni3Al
nickel solid solution0 %
100 %
70 %
Copley and Kear, Trans. AIMEVol. 239 (1967), 984-992
9University Bayreuth Uwe Glatzel, Metals and Alloys
History
≈ 1980: Inconel 738 (polycrystalline) => 738 LC (single crystal)50-60vol.% γ' phase, 3wt.% W, 0% Re
SRR 99, CMSX-6 (first generation)60-70% γ', 9% W, 0% Re
≈ 1990: CMSX-4 (second generation)> 70 % γ', 6% W, 3% Re
≈ 1995: CMSX-10 (third generation)> 70 % γ', 6% W, 6% Re
Costly and time intensive heat treatment:3-stage homogenization, controlled rapid cooling2-stage aging
10University Bayreuth Uwe Glatzel, Metals and Alloys
Content• motivation: history, application field
• processing
• microstructure, misfit
• anisotropic properties(modulos, creep behavior)
• dislocations, stress induced diffusion
• Outlook (alloys with reduced density, platinum basedsuperalloys)
11University Bayreuth Uwe Glatzel, Metals and Alloys
Single Crystal Growing
R = ∆T/∆x
v = ∆x/∆tR⋅v = ∆T/∆t
determines the dendrite spacing
[001] crystaldirection
alternative: seeding technique
12University Bayreuth Uwe Glatzel, Metals and Alloys
Heat Treatment
example: CMSX-4 standard heat treatment
homogenization:1 h @ 1280°C, 2 h @ 1290°C, 6 h @ 1300°Ccooling rate 150-400°C/min.
aging6 h @ 1140°C für 6 h, 870°C für 16 h
if possible, combined with coating treatment
13University Bayreuth Uwe Glatzel, Metals and Alloys
Content• motivation: history, application field
• processing
• microstructure, misfit
• anisotropic properties(modulos, creep behavior)
• dislocations, stress induced diffusion
• Outlook (alloys with reduced density, platinum basedsuperalloys)
14University Bayreuth Uwe Glatzel, Metals and Alloys
Microstructuretwo-phase, single crystal:
face-centred-cubicmatrix(nickel solid solution)
Ni3Al => fcc, but superlatticeordering, L12 or γ' Phase dislocation free
15University Bayreuth Uwe Glatzel, Metals and Alloys
Ni3Al ⇔ nickel solid solution
nickel atoms in face centre
aluminium atoms on cube corners
in nickel solid solution statistical distribution of atoms
dNi3Al = 358,0 pm dnickel solid sol. = 358,7 pm
16University Bayreuth Uwe Glatzel, Metals and Alloys
Optimal Precipitation Hardening
• round particles(better than needle-shaped)
• high volume fraction• finely dispersed• small particles ( )• hard precipitates,
soft matrix
500 nm
in text books no information given on optimum misfit
17University Bayreuth Uwe Glatzel, Metals and Alloys
Constrained ↔ UnconstrainedMisfit
Matrix
γ' Phase
Matrix
γ' Phase
high compression stresses in matrix parallel to interface
Small difference in lattice parameter, ∆d/d ≈ - (1 – 3)·10-3
resulting in a coherent interface and internal stresses:
MPa300100d
dE −≈∆
=σ
isotropic misfitmisfit dependent of planes taken for Bragg reflection
18University Bayreuth Uwe Glatzel, Metals and Alloys
Two-Phase but 100% Coherent=> Internal Stresses
19University Bayreuth Uwe Glatzel, Metals and Alloys
Stress Distribution
two views of 1/8 of the γ' cube with surrounding matrix
stress σxx [MPa]
20University Bayreuth Uwe Glatzel, Metals and Alloys
Stress Distribution Schematical
compressiontension
in matrix
in γ' phase
21University Bayreuth Uwe Glatzel, Metals and Alloys
"Macrostructure"
single crystal,but no hgomogeneousdistribution of tungstenand rhenium
[001][010]
dendrite spacing≈ 1/4 mm
⇒ therefore local variation of misfit
22University Bayreuth Uwe Glatzel, Metals and Alloys
Variation of Misfit due to Dendritic Segregation
• negative misfit in dendrite
• close to zero in interdendritic region
[10-3]
-5
-4
-3
-2
-1
0
1
DendritInterdendrit Interdendrit
Fehlpassung gemessen mit CBED
Neutronenstreuung
Völkl, Glatzel, Feller-Kniepmeier; Acta mat. 46 (1998) 4395
23University Bayreuth Uwe Glatzel, Metals and Alloys
200 400 600 800
-300
-250
-200
-150
-100
-50
Local Stress Variation
up to 300 MPa compression stress in matrix channels in dendrite
Spa
nnun
g [
MP
a]
spacing ≈ 250 µm
dendrite
interdendritic region
5 10 15 20
-17.5-15
-12.5-10-7.5-5
-2.5
spacing ≈ 0,5 µm
24University Bayreuth Uwe Glatzel, Metals and Alloys
Content• motivation: history, application field
• processing
• microstructure, misfit
• anisotropic properties(modulos, creep behavior)
• dislocations, stress induced diffusion
• Outlook (alloys with reduced density, platinum basedsuperalloys)
25University Bayreuth Uwe Glatzel, Metals and Alloys
Elastic Anisotropy togetherwith Misfit:
Explanation for cuboidal γ' precipitates, with {100} phase boundary planes
thereby very high volume fractionsachievable
26University Bayreuth Uwe Glatzel, Metals and Alloys
Temperature Dependence of Elastic Constants
T [K]
200 300 400 500 600 700 800 900 1000 1100 1200 1300
E<
100>
[
GP
a]
80
90
100
110
120
130
140
E<100>
γ'
MatrixCMSX-4
ultrasonic speed measurements at RTMatrix
CMSX-4
Siebörger, Knake, Glatzel; Mat. Sci. Eng. A298 (2001) 26
Important: anisotropy stays on the same high level of ≈ 2.8
T [K]
200 300 400 500 600 700 800 900 1000 1100 1200 1300
G[1
00]
85
90
95
100
105
110
115
120
125
130
135
140
145
150
G<100>
CMSX-4
Matrix
γ'
[GPa
]
ultrasonic speed measurements at RT
27University Bayreuth Uwe Glatzel, Metals and Alloys
Creep Deformation
28University Bayreuth Uwe Glatzel, Metals and Alloys
High TemperatureDeformation up to 1400°C
temperature and load are kept constant
29University Bayreuth Uwe Glatzel, Metals and Alloys
Orientation Dependenceat 850°C
(T = 850°C) l0
Single crystal with load axis parallel to [001]
constant load of 500 MPa
"horizontal" / "vertical" matrix channels
CMSX-41123K, 500MPa
Strain [%]0 1 2 3
Str
ain
Rat
e [
1/s]
10-8
10-7
10-6
+
A 1
A 2B 1
M
+
B 2
C 1
+ Fracture
C1
[001] [011]
[111]
A 1
A 2M
B 2
B 1
→ [001] orientation shows best creep performance
30University Bayreuth Uwe Glatzel, Metals and Alloys
Orientation Dependenceat 980°C
A
C
C
A
anisotropy has less influence at higher temperatures
strain
stra
inra
te [
s-1]
31University Bayreuth Uwe Glatzel, Metals and Alloys
Changes in Morphology980°C, 350 MPa, 28 h
[001]
[100][010]
[100][110]
[110]
rafts with planes normal to theexternal [001] load axis
bars with long axisparallel to <100>
σ σ
32University Bayreuth Uwe Glatzel, Metals and Alloys
[001] crystal orientation:
• fastest growing direction +
• elastic soft +
• leads to {001} phase boundaries of the cuboidal γ' particles +
• direction of best creep properties +
33University Bayreuth Uwe Glatzel, Metals and Alloys
Content• motivation: history, application field
• processing
• microstructure, misfit
• anisotropic properties(modulos, creep behavior)
• dislocations, stress induced diffusion
• Outlook (alloys with reduced density, platinum basedsuperalloys)
34University Bayreuth Uwe Glatzel, Metals and Alloys
FEM calculation of stress distribution (pure elastic)
No external loadhigh compression stresses in
matrix channels parallel to thephase boundaries
With an external load (500 MPa)high stress levels in horizontal
channels; low stress levels in vertical channels
compressiontensionσ
pure elastic at time t = 0
35University Bayreuth Uwe Glatzel, Metals and Alloys
FEM calculations of stress distributionafter creep (plastic deformation)
(Matrix according to Norton creep, γ' phase yields plastisch)
tension
dislocations networks:
horizontaler channel:High density of edgedislocations with additional half plane within γ' phase
hydrostatic tension p ≈ σext.
vertical channel:network of LH- and RH-screw dislocations,1/3 density
σext.
36University Bayreuth Uwe Glatzel, Metals and Alloys
TEM Dislocation Structure:
load axis
longitudinal sectionε = 1 %
cross section, ε = 2.1 %external load normal to view plane
look onto horizontal matrixchannels, vertical channels edge-on.
horizontal
channel
37University Bayreuth Uwe Glatzel, Metals and Alloys
Stress Induced Diffusion (EDX-TEM)
Large atoms diffuse from vertical to horizontal channel.
σext. ≈ 500 MPa
channelverticaltungsten
channelhorizontaltungsten c2.1c ⋅=
Schmidt and Feller-Kniepmeier, 1993 (SRR99, 760°C)
38University Bayreuth Uwe Glatzel, Metals and Alloys
additionally: compostion variation dendrite – interdendritic regionand morphology changes
γ'FEM+
TEM
TEM + FEM
γ'
W
W
W W
Re
Re Re
TEM +
EDX
γ'
+
-
neutron diffr.
dislocation networks in phase boundaries(plastic deformationaccording to localstress distribution)
=> high hydrostatic stress level in horizontal channel
=> stress induceddiffusion
change in latticeparameter (misfit). Change and reduction of stress level.
σext
Summary:changes occuring durig creep
39University Bayreuth Uwe Glatzel, Metals and Alloys
Content• motivation: history, application field
• processing
• microstructure, misfit
• anisotropic properties(modulos, creep behavior)
• dislocations, stress induced diffusion
• Outlook (alloys with reduced density, platinum basedsuperalloys)
40University Bayreuth Uwe Glatzel, Metals and Alloys
Outlook
• International patent (Glatzel, Mack, Wöllmer, Wortmann):Reduce W and Re content reduced density, improved phase stability, larger temperature window for solution heat treatment, cheaper LEK 94.Within GP 7000 engine for Airbus A 380.
• DFG-Project "Platinbasissuperlegierungen":Pt-Al-Cr-Ni (+ Ta, + Ti) alloys can copy successful system of nickel based superalloys (coherent L12 ordered, cuboidal γ' particles withhigh volume fraction embedded in fcc-matrix)
41University Bayreuth Uwe Glatzel, Metals and Alloys
LEK 94
Larsen-Miller-ParameterP = (T+273) [20+log tB] 10-3
25 26 27 28 29 30 31 32
stre
ss
[MP
a]
120
230
500CMSX-6 [Wortmann 88] 8.0 g/cm3
CMSX-4 [Erickson 94] 8.7 g/cm3
CMSX-4 [Frasier 90] 8.7 g/cm3
LEK-2 8.5 g/cm3
LEK-4 8.2 g/cm3
LEK-5 8.2 g/cm3
LEK-3 8.1 g/cm3
LEK-6 8.3 g/cm3
LEK-1C 8.4 g/cm3
LEK-1B 8.3 g/cm3
LEK-1A 8.2 g/cm3
∆T = 10 K
24 K
10 K
29 K
not corrected withdensity!
Patente: D, Europa, USA, Kanada, Japan
42University Bayreuth Uwe Glatzel, Metals and Alloys
MicrostructurePlatinum Based Superalloy
Pt77Al14Cr6Ni6
12h @1500°C + 120h @1000°C
CMSX-4, samemagnification
Hüller et al., Met.Mat.Trans. A, 36A (2005), 681
43University Bayreuth Uwe Glatzel, Metals and Alloys
MisfitPlatinum Based Superalloys
Pt80Al11Cr3Ni6
Pt84Al11Cr3Ni2
Pt77Al10Cr3Ni10
44University Bayreuth Uwe Glatzel, Metals and Alloys
Creep PropertiesPlatinum Based Superalloys
Maximum Stress inCompression withStrain Rate 10-5 s-1
Temperature [°C]
700 800 900 1000 1100 1200 1300 1400
Str
ess
10
100
1000
Pt82Al7Cr6+Ta5
Pt82Al7Cr6+Ti5
CMSX-4 (single crystal !)
Pt77Al12Cr6+Ni5Pt77Al12Cr6+Fe5
Pt77Al12Cr6+Co5
γ' precipitate dissolutionin Ni-base alloys
γ' precipitate dissolutionin Pt-base alloys
45University Bayreuth Uwe Glatzel, Metals and Alloys
Juni 2005 Bayreuth
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