Upload
rea
View
37
Download
1
Tags:
Embed Size (px)
DESCRIPTION
Strength of Energy Engineering Materials. Abdel-Fatah M HASHEM Professor of materials science South Valley University, EGYPT. April 2009, Japan. Collaborative Research Centre SFB 651 at the AU and SVU. Turbines Fluid dynamics Phys. chemistry Metal physics Materials Casting Coating - PowerPoint PPT Presentation
Citation preview
Strength of Energy Engineering Materials
Abdel-Fatah M HASHEM
Professor of materials scienceSouth Valley University, EGYPT
April 2009, Japan
Collaborative Research Centre SFB 651 at the AU and SVU
%65
%58
TurbinesFluid dynamicsPhys. chemistryMetal physicsMaterialsCastingCoatingWeldingMetal formingLaser techn.
12 years15 Professors and their co- workers20 Million € =150 Million Egypt. pounds
Inlet Temperature of Gas turbines: from 1230 °C to 1320 °C
Inlet Temperature of Steam Turbines: from 600 °C to
700 °C
Steam turbine (Siemens)
<1990 560 °C 12% Cr, 1% Mo (X20CrMoV12-1)>1990 600 °C 9% Cr-Steels P91 +0% W
E911 +1% W P92: +2% W>2000 625 °C NF12: 12% Cr, 3% W, 3% Co Goal 700 °C Nickel-Base-Alloys
E9110.40
0.42
0.44
0.46
0.48
150 200 250 300
650 °C
700 °C
450°C
500 °C
550 °C
600 °C
Pressure, bar
The
rmal
Effi
cie
ncy
T
h
Steam Turbine: Increase of efficiency
X20CrMoV12-1 12C1Mo-VP91: 9Cr-1Mo-VNbE911 X12CrMoWVNbN10-1-1P92 (NF616) 9Cr-0,5Mo-1.8W-V-NbNF12: 12Cr-2.6W-2.5Co-0.5Ni-V-Nb
Steam Turbine: Cooling system
Laboratory experimentsReality: Multi-axial stress state with stress components varying with timeData available: Uni-axial experiments with simple time functionsTherefore, Modelling is essential
Strain
Str
ess
Low cycle fatigue test
= const.T = const.
Time
Cre
ep
Str
ain
Creep test
= const.T = const.
Time
Str
ess
Relaxation test
= const.T = const.
Strain rate
Str
ess
Tensile Test
d/dt = const.T = const.
Influence of Temperature on the Stress strain Curve
200 °C - 700 °C Intercrystalline damage
< 700° C Dynamic recrystallisation
0
100
200
300
400
500
600
700
0 10 20 30
b)
AA7075-T7351
250 °C
200 °C
150 °C
100 °C
20 °C
300 °C
Engineering Strain , %
Eng
inee
ring
Str
ess
, M
Pa
0
200
400
600
800
1000
0 20 40 60
a)
- 50
/ °C =
X6CrNi18-11
1000900
- 100- 150
400
800
700650
500600
200100
23
Engineering Strain , %
Eng
inee
ring
Str
ess
, M
Pa
23 °C – 150 °C Dynamic recovery
200 °C - 300 °C Intercrystalline damage
Flow curve: Description and Influence of strain rate
4321
2
21
/exp(1:
MagdEl)1(/
KocksMecking/
CCCCaGb
kckdd
kkdd
?10nKK
0
200
400
600
800
1000
0 0.1 0.2 0.3
293 K373 K473 K573 K873 K923 K773 K973 K1073 K1173 K
X6CrNi18-11
True Strain
Tru
e S
tre
ss,
M
Pa
0
100
200
300
400
500
0 0.1 0.2 0.3
1.7 10-5
1.7 10-6
1.7 10-4
1.7 10-3
d/dt / s-1
=
True StrainT
rue
Sre
ss ,
MP
a
Power law ?
Creep curves and creep rate curves
)]/(exp[),(min RTQSf
10-4
10-3
10-2
10-1
100
10-2
100
102
104
106
200190180160140130120110100 90 70
X6CrNi18-11: 700 °C
/MPa=
Time , h
Cre
ep
Str
ain
10-5
10-4
10-3
10-2
10-1
100
10-2
100
102
104
106
200190180160140130120110100 90 70
b)
/MPa=
Time , h
Cre
ep
Ra
te ,
h
-1
Minimum creep rate as stress function and creep fracture curve
10-5
10-4
10-3
10-2
10-1
100
100 200 300
C [sinh(/*)]N
C exp( )
C ( /*)N
X6CrNi18-11 = 700 °C
Creep Stress, MPa
Min
imum
Cre
ep
Rat
e ,
h-1
50
100
150
200
250
0.1 10 1000
X6CrNi18-11 = 700 °C
Fracture time , h S
tres
s ,
MP
a
Garofallo*
sinh
)exp(
BailyNorton
min
min
min
N
N
Soderberg
Up to 10000 h University laboratoryUp to 200000 h Industry, Standards
Proof stress and creep strength as Loading limitsDesign limits: with a factor of safety of 1.5
1 .Low Temperatures: 0,2% Proof Stress
2 .High Temperatures: Creep Strength= Stress for a fracture time of 100000 h
0
200
400
600
200 400 600 800 1000
Ni-Base Alloyaustenitic Steel12% Cr-SteelLA 2.25%Cr-SteelLA 1%Cr-SteelLA Mo-SteelLA Mn-Steelunalloyed Steel
Rp0,2
Rm 100000 h
Temperature oC
Rp
0,2
,
Rm
10
00
00
h ,
M
Pa
0
50
100
150
200
500 550 600 650 700
NF 616(9Cr-0.5Mo-1.8W-VNb)
X20CrMoV12-1(12Cr-1Mo-V)
E 911(10Cr-1Mo -1W-VNb)
T 91(9Cr-1Mo-VNb)
Temperature , °C
Cre
ep
Ste
ng
th
Rm
10
0 0
00
,
MP
a
Maximum service temperature: Creep strength for 100000 h = 100 MPa
Increase of creep strength1. Reducing grain boundary area per unit volume
Coarce grains Directional Single solidification crystals
10-8
10-7
10-6
10-5
10-4
10 20 50 100 200
Ilschner
= 704 oC
65
85
105130
0 / MPa =
austenitic Steel
Grain Size , µm M
inim
um
Cre
ep
Ra
te
, 1
/s
Increase of creep strength2. Precipitation hardening Barriers for the dislocation
10-7
10-5
10-3
10-1
10-1
101
103
105
/ MPa =
100110
130140
Alloy 800HT, solution annealed
=700°C
Time , h
Min
imu
m C
ree
p R
ate
, 1
/h
Influence of nitrides0.05 m% N
[Abe, F.: Sol.State.Phys. 8(2004)305 ]
Increase of creep strength3. Reinforcement by continuous fibres
10-7
10-6
10-5
10-4
10-3
10-2
100
101
102
103
FibreComposite
0
10.660.450.24
Vf=
Stress, MPa
Min
imu
m C
ree
p R
ate
, 1
/h
Not for cyclic compression !
Creep under stresses and temperatures
varying with time The Creep rate depends on the effective stress i.e. on the difference between Applied stress and internal back stress
niC )(
0
50
100
0 2 4 6 8
X6CrNi18-11690 °C
i
Time , h
App
lied
and
Bac
k S
tess
, M
Pa
0
50
100
0 2 4 6 8
X6CrNi18-11690 °C
i
Time , h
Concept of the internal back stress
i
niC
0
)(
10-5
10-4
10-3
10-2
10-1
5 10 20 50 100
/ °C =
800710
650
X6CrNi18-11
Effective Stress ( - is) , MPa
Min
imum
Cre
ep R
ate
,
h-1
-0.0002
-0.0001
0
0.0001
0.0002
0.0003
0 200 400 600 800 1000
X22CrMoV12-1T = 700 °C
30
50
60
80
90
95R / MPa =
0 = 100 MPa
Time , s
Cre
ep
Str
ain
aft
er
Str
ess
dro
p
Internal back stress
)/(exp1 11
1
1
C
C
d
d
is
i
iisi
/1
/1 ississis )/exp()( 0 TkTiss
0
100
200
800 900 1000 1100 1200
X8CrNi18-11X22CrMoV12-1X8CrNiMoNb16-16
iss
=k0exp(/T)
Temperature, K
Sat
urat
ion
Bac
k S
ress
is
s , M
Pa
0
100
200
0 100 200 300 400
700 °C
650 °C
710 °C
650 °CX22CrMoV12-1
X6CrNi18-11
Applied Stress , MPa
Inte
rna
l Bac
k st
ress
is ,
MP
a0
0.25
0.50
0.75
1.00
0 0.2 0.4 0.6 0.8 1.0
Pure AluminiumX8CrNiMoNb16-16X6CrNi18-11X22CrNiMoV 12 1
Relative Creep Strain / 1
Rel
ativ
e In
tern
al B
ack
Str
ess
i /
is
Cyclic creep: Life assessment
L= 0.6 under pulsating stressL= 0.8 under pulsating Temperature
10-5
10-4
10-3
10-2
10-1
0 200 400 600
= 150 MPa changing periodically
X6CrNi18-11
650 °C
635 °C
time , h
10-5
10-4
10-3
10-2
10-1
0 200 400 600
changing periodically650 °C
X6CrNi18-11
150 MPa
125 MPa
Time , h
Cre
ep
Ra
te,
h-1
Lt
t
f
Stress Relaxation: Basic equation
tt0
L0
elL
0
cL
0
el 0 L
0
),,(0
)()(
)()(
.00
tTE
tE
t
tt
const
cr
cr
crel
el
• Creep strain increases with time• Total strain remains constant• The elastic strain decreases• Stress decreases with time
Stress relaxation curves
Nickel-base alloy :Crystalline order changes around 550°C increases the specific volume And hence reduces relaxation
0
100
200
300
400
0 1000 2000 3000
X22CrMoV12-1
550 °C
600 °C
500 °C
Time , h
Str
ess
, M
Pa
0
100
200
300
0 10 20 30 40
0 / MPa =T = 650 °C
X6CrNi18-11
100150200250
300
Str
ess
,
MP
a
0
100
200
0 20 40 60 80
650 °C
600 °C
700 °C
X6 CrNi 18 11
0 = 200 MPa
0
100
200
300
400
500
0 1000 2000 3000
NiCr20TiAl
750 °C
650 °C
600 °C550 °C
500 °C
Time , h
Low Cycle Fatigue: Modelling
-400
0
400
-0.008 0 0.008
6
5
43
2
1
Total Strain tot
Str
ess
, M
Pa
-2000
-1000
0
1000
2000
-0.02 -0.01 0 0.01 0.02
1 tot
Tool Steel = 20 °CN=1
Re
Re
/
Total Strain
Str
ess
, M
Pa
-300
-150
0
150
300
-0.008 -0.004 0 0.004 0.008
50 20 10 9 8 7 6 5 4 3 2 1
N=X8CrNi18-10650 °C
Total Strain
Str
ess
, M
Pa
-1x105
0
1x105
2x105
3x105
-300 -150 0 150 300
6
5 4
3
21
2F
i
Stress , MPa
d/d to
t , M
Pa
Low Cycle Fatigue: Life assessment
0.002
0.005
0.01
0.02
0.05
101
102
103
104
105
106
t=0.18 N
- 0.6 + 0.026 N
- 0.14
pl=0.18 N
- 0.6 el=0.026 N
- 0.14
Schwingspielzahl N
Sch
win
gb
reite
de
r D
ehn
un
g
-2000
0
2000
-0.02 0 0.02
-2000
0
2000
-0.02 0 0.02
-2000
0
2000
-0.02 0 0.02
-2000
0
2000
-0.02 0 0.02
,
M
Pa
0
0
el/2
pl
el/2
t
Total strain
Str
ess
,
MP
a
Number of cycles at fracture
Voids: Growth by diffusion and by creep deformation
Void growth by Diffusion
Void growth by creep deformation of the surrounding materials
Wedge type micro-cracks
0.001
0.01
0.1
1
0 1 2 3 4 5 6 7 8
X8CrNiMoNb16-16
X6CrNi18-11
T = 700 °C = 80 MPa
Crack length classF
ract
ion
of
Cra
ck le
ng
th c
lass
X
n
61000 Cracks in X6CrNiMoNb16-1650000 Cracks in X6CrNi18-11
Material: Ni-based superalloy
Thank you for your attention