Design Window for Tungsten Alloys - ENEA WINDOW FOR TUNGSTEN ALLOYS S. Sharafat , R. Martinez N. M. Ghoniem ... Stanford Press, CA, 1965, p. 315) Creep stress vs. Rupture time for

DESIGN WINDOW FORDESIGN WINDOW FOR

TUNGSTEN ALLOYSTUNGSTEN ALLOYS

S.S. Sharafat Sharafat , R. Martinez , R. MartinezN. M.N. M. Ghoniem Ghoniem

The University of California at Los Angeles (UCLA)The University of California at Los Angeles (UCLA)Los Angeles, CA. 90095-1597, USALos Angeles, CA. 90095-1597, USA

APEX STUDY GROUP MEETINGPPPL

May 12-14, 1999

UCLA: SS/NG 05-12-99 APEX 2

PRESENTATION OUTLINE

•High Temperature Creep Strength Limits of W-Alloys

•Effects of Fabrication, Alloying, and Irradiation on the DBTT of W-Alloys.

•Estimates for DBTT Shifts based on a Phenomenological Model

•Oxidation limits for 1ppm O2

•Recommendations of Design Windows for W-Alloys


Physical and Mechanical Properties of ITER ConsideredW-Alloys Unirradiated Properties

After: I. Smid, et al., J. Nucl. Mater., 258-263(1998)160


0

100

200

300

400

500

600

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Temperature (C)

W Ta

Cb Mo

COMPARISON OF TENSILE BEHAVIOR OFREFRACTORY METALS

MoTa

Nb

W

Reference: Tietz, Behavior and Properties of Refractory Metals, Stanford Press, Stanford, p. 195

Ulti

mat

e Te

nsile

Str

ess

(MP

a)


HIGH TEMPERATURE CREEP STRENGTHOF REFRACTORY METALS

(100 Hour Test Results)

0

50

100

150

200

250

800 900 1000 1100 1200 1300 1400

Temperature (C)

W Mo

Cb Ta

Mo

Ta

Nb

W

Reference: Tietz, Behavior and Properties of Refractory Metals, Stanford Press, Stanford, p. 195

Str

ess

(MP

a)


HIGH TEMPERATURE CREEP STRENGTH LIMITS

• Limited data base requires the use of Larson Millerparameters (m) to correlate Temperature (T) with the timeto failure (tr)at constant engineering stress (σ):

MATERIAL LARSON-MILLERC

Various Steels ~20

S-590 Alloys 17

A-286 SS 20

Nimonic 81A 18

1-Cr-1Mo-0.25V Steel 22

T(log tr + C) = m

Ref.: M. A. Meyers, “Mechanical Behavior of Materials,” Prentice Hall, UK, 1998, p. 550.


DESIGN STRESS LIMITS

• A simplified TENSILE DESIGN STRESS can be defined as theminimum value of 1/3 of the ULTIMATE or 2/3 of the YIELDstrength, which ever is smaller:

= yieldultimatedesign σσσ

32

;31

min

THE DESIGN-STRESS LIMIT IS CHOSEN TO BE THE LESSEROF THE 10 year CREEP STRESS LIMIT AND THE TENSILE

STRESS-LIMIT σdesign .


CREEP-RUPTURE DATA OF PURE W

Creep stress vs. Rupture time for recrystallizedtungsten at four temperatures

(Tietz, T.E., “Behavior and Properties of Refractory Metals,”Stanford Press, CA, 1965, p. 315)

Creep stress vs. Rupture time for recrystallizedtungsten in inert atmosphere.

(Tietz, T.E., “Behavior and Properties of Refractory Metals,”Stanford Press, CA, 1965, p. 315)


LARSON-MILLER BASEDCREEP-RUPTURE OF PURE W

(Arc-Melted, Recrystallized)

0

20

40

60

80

100

120

140

160

180

200

0 500 1000 1500 2000 2500

Temperature (C)

1 year creep life span



2/3 yield stress

1/3 ultimate stress

Design Stress Limit

References: Sims, “Properties of Refractory Alloys Containing Rhenium”, Trans. ASM, 52 (1960) p. 929- 941Shin, “High Temperature Properties of Particle Strengthened W-5Re”, JOM August 1990, p. 12-15

Str

ess

(MP

a)


LARSON-MILLER BASEDCREEP-RUPTURE OF PURE W(Wrought, Arc-Cast, Tested in Hydrogen)

0

100

200

300

400

500

600

700

800

0 500 1000 1500 2000 2500 3000

Temperature (C)




1/3 ultimate stress

design stress limit

References: Tajime, “The Tensile Strength of Tungsten Wires at High Temperatures”, Hantaro Nagaoka Anniversary Volume, Tokyo (1925);Flagella, “High Temperature Creep Rupture Behavior of Unalloyed Tungsten”, GE-NMPO, GEMP-543

Str

ess

(MP

a)


LARSON-MILLER BASEDCREEP-RUPTURE OF W-5Re


0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000 2500 3000

Temperature (C)




2/3 yield stress

1/3 ultimate stress

1/3 ultimate stress (W-3Re Recrystallized, PM,Taylor)design stress limit

References: Vandervoort, “Creep Behavior of W-5Re”, Met. Trans., 1 (1970), p. 857-864;Shin, “High Temperature Properties of Particle Strengthened W-5Re”, JOM August 1990, p. 12-15;

Taylor, “Tensile Properties of W-3%Re in a Vacuum”, J. of the Less Common Metals, 7 (1964), p. 27

Str

ess

(MP

a)


LARSON-MILLER BASEDCREEP-RUPTURE OF W-26Re and W-24Re

(Arc-Melted, Recrystallized and Annealed)

0

20

40

60

80

100

120

140

0 500 1000 1500 2000 2500

Temperature (C)




1/3 ultimate stress (W-24Reannealed 1hr. 1982 C)

design stress limit

References: Klopp, Refractory Metals and Alloys IV-Research and Development, Gordon-Breach, New York, 1967, p. 557;Shin, “High Temperature Properties of Particle Strengthened W-5Re”, JOM August 1990, p. 12-15

Str

ess

(MP

a)


LARSON-MILLER BASED CREEP-RUPTURE OFW-4Re-0.26HfC and W-3.6Re-0.26HfC


0

20

40

60

80

100

120

140

160

180

200

0 500 1000 1500 2000 2500

Temperature (C)

1 year creep life span (W-4RE-0.26HfC)



2/3 yield stress (W-3.6Re-0.26HfC)

1/3 ultimate stress (W-3.6Re-0.26HfC)

design stress limit

References: Shin, “High Temperature Properties of Particle Strengthened W-5Re”, JOM August 1990, p. 12-15

Str

ess

(MP

a)


LARSON-MILLER BASED CREEP-RUPTURE OFW-23.4Re-0.27HfC(Arc-Melted, Swaged)

0

200

400

600

800

1000

1200

1400

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Temperature (C)

1 year life span

3 year life span

10 year life span

1/3 ultimate stress

2/3 yield stress

design stress limit

References: Klopp, “Mechanical Properties of a Tungsten 23.4%Re-0.27%HfC Alloy”, J. of the Less Common Metals, 24 (1971) p. 427-442; Shin,“High Temperature Properties of Particle Strengthened W-5Re”, JOM August 1990, p. 12-15

Str

ess

(MP

a)


LARSON-MILLER BASED CREEP-RUPTURE OFW-23.4Re-0.27HfC


0

100

200

300

400

500

600

700

800

0 500 1000 1500 2000 2500

Temperature (C)




1/3 ultimate stress (annealed)

2/3 yield stress (annealed)

design stress limit

References: Witzke, “Mechanical Properties of a Tungsten 23.4%Re-0.27% HfC Alloy”, J. of the Less Common Metals, 24 (1971), p. 427-442

Str

ess

(MP

a)


LARSON-MILLER MASTER PLOT FORPure W, W-4Re-0.26HfC, W-23.4Re-0.27HfC

(All Recrystallized)

y = -0.0069x + 419

y = -0.0216x + 1132.3

y = -0.0017x + 107.39

0

50

100

150

200

250

300

350

400

0 10000 20000 30000 40000 50000 60000 70000

Larson Miller Parameter

W Recrystallized

W-4Re-0.26HfC Recrystallized

W-23.4- Re-0.27HfCRecrystallized

Linear (W-4Re-0.26HfCRecrystallized)

Linear (W-23.4- Re-0.27HfCRecrystallized)

Linear (W Recrystallized)

Str

ess

(MP

a)


Comparison of Design Stress Limits of W-Alloys(All Recrystallized)

0

100

200

300

400

500

600

700

800

0 500 1000 1500 2000 2500

Temperature (C)

W Recrystallized

W Wrought

W-5Re Recrystallized

W-50Mo Swaged

W-23.4Re-0.27HfC Swaged

W-23.4Re-0.27HfC Recrystallized



2/3 yield stress W-1%La2O3

Str

ess

(MP

a)


Comparison of High Temperature Design Stress Limitsof W-Alloys

0

20

40

60

80

100

120

1000 1200 1400 1600 1800 2000 2200 2400

Temperature (C)

W Recrystallized

W Wrought


W-50Mo Swaged

W-23.4Re-0.27HfC Swaged

W-23.4Re-0.27HfC Recrystallized



2/3 yield stress W-1 La2O3

Str

ess

(MP

a)


A NEWLY SUGGESTED W-ALLOY

W-23.4Re-0.27HfC

This Ductile W-23.4Re-0.27HfC Alloy has been consolidated byArc-Melting and Fabricated into Sheets and Rods

Particle (HfC) strengthening providesW with high temperature strength

High Re content provides substantiallow temperature ductility to W

COMBINATION OF THESE

• A TUNGSTEN-Alloy Which Exhibits Good HighTemperature Strength and Excellent Low TemperatureDuctility– At 1650oC the tensile strength is 432 MPa which is

double the strength of W-24Re alloys (194 MPa).


ULTIMATE STRENGTH(As-Swaged and Annealed)

W-23.4Re-0.27HfC

V.BarabashITERJCT-Garching

0

500

1000

1500

Ulti

mat

e T

ensi

le S

tren

gth,

MPa

0 500 1000 1500 2000

Temperature, °C

UT

S/W

, W-L

aO, W

13I

W-13I, deformed rods; e=84%; Tdef. - 1100°C

W-1%La2O3, rod dia 40 mm, swaged, stress relieved


pure W, stress relieved

pure W, recrystallised

W-23.4Re-0.27Hf-C (As swaged)*2000

W-23.4Re-0.27Hf-C

(Annealed 1h 1892 C)*

}

*W.D.Klopp,J. Less-Common Metals,24(1971)427


TENSILE STRENGTH(As-Swaged and Annealed)

W-23.4Re-0.27HfC

0

500

1000

1500

Yie

ld S

tren

gth,

MPa

0 500 1000 1500 2000

Temperature, °C

YS,

W, W

-LaO

, W13

I

W-13I, deformed rods; e=84%; Tdef. - 1100°C



pure W, stress relieved

pure W, recrystallised

W-23.4Re-0.27Hf-C (As swaged)*2000

W-23.4Re-0.27Hf-C

(Annealed 1h 1892 C)*

}V.BarabashITERJCT-Garching

*W.D.Klopp,J. Less-Common Metals,24(1971)427


DUCTILE-TO-BRITTLE-TRANSITION TEMPERATURE(DBTT)

•• DBTT DEPENDS ON:DBTT DEPENDS ON:

– Production History (thermomechanical treatment)

– Alloying Elements

– Neutron Irradiation

– Irradiation Temperature


Effect Of Fabrication on the DBTT Of Refractory Metals

SWEB

AMPM

SRAN

DB

TT

TR

EN

D

ElectronBeam Arc-

Melted Sintered(PowderMetallurgy)

StressRelieved Recrsytallized

(annealed)

Swaged(rolled)


EFFECT OF ALLOYING ON THE DBTTOF W-ALLOYS

W-5Re W-HfC W-4Re-HfC

W-26 Re W-23.4Re-

HfC

As-Rolled

Re-crystallized

SA and Aged

-200

-100

0

100

200

300

400

500

DBTT(C)

SA &Aged


Effect of Neutron Irradiation on DBTT of W

• Only a few experimental W-data are available

• More work done on Mo-Alloys and TZM– A phenomenological approach based on Mo-data is presented– The Phenomenological Model is applied to W

• The effect of High Temperature Neutron Irradiation on theDBTT for W is estimated based on the Model.


PHENOMENOLOGICAL DBTT-MODEL

• Neutron irradiation increases DBTT because the resistance todislocation motion increases (neutron produced depleted zones).

• The shear stress (σi friction stress) necessary to move the dislocationsis the sum of long-range (σLR) and short range (σs)stresses:

σi = σLR+σs

• The increase in long range stress is proportional to N-1/2 (N: numberdensity of depleted zones), but the short range stress is proportionalto N+1/2 : 2

33

2

1

−=

c

oss T

Tσσ

Tc is the characteristic temperature at which the depleted zones are annealed out (about 0.44 Tm)


Were:α: number of cluster zones per neutron (~1); Σs macroscopic scattering cross-section; v: capturevolume around a depleted zone; Φ: neutron fluence.

PHENOMENOLOGICAL DBTT-MODEL (cont.)

( ) rN

GbUoo

s

21

21

21 2

23

1

324

=σ

Were:Uo: cutting energy for a dislocation; b: burgers vector; G:shear modulus; r: radius of obstacle todislocation motion; N: number density of depleted zones.

• Saturation of Radiation Hardening (in the absence of destructionmechanism) is based on the time rate of change of fast-neutron inducedclusters:

( )vNdtdN

s −ΦΣ= 1α


PHENOMENOLOGICAL DBTT-MODEL (cont.)

• In the absence of destruction mechanisms:

21)]exp(1[ tv ss ΦΣ−−∝ ασ

• Thermal annealing of depleted zones at high temperatures significantlyaffects the zones number density at a decay time (τ) proportional to το

+ΣΦ−−

ΣΦ+

= tT

v

Tv

tTN ))(

1(exp1

)(1

1),(

τα

τα


0

IRRADIATED Mo-DATA

100

200

300

400

500

600

700

800

300 400 500 600 700 800 900 1000 1100

IRR. TEMPERATURE ( o C)

AV

ER

AG

E D

BTT

(o C

)

MoMo-05TiTZM

~ 11 dpa (EBR-II)

Cox&Wiffen (1979)*

AV

ER

AG

E D

BT

T (o C

)

*B. Cox, F. Wiffen “The Ductility in Bending of Molybdenum Alloys Irradiated Between 425 and 1000°C,” J. Nucl. Mat. 85&86(1979)901-905.


IRRADIATED W-DATATENSILE PROPERTIES OF TUNGSTEN

AS A FUNCTION OF TEMPERATURE AND IRRADIATION

0

50

100

150

200

250

0 200 400 600 800 1000 1200

TEMPERATURE (C)

YIE

LD S

TRE

NG

TH (

ksi)

Unirradiated

Irradiated

0

5

10

15

20

25

0 200 400 600 800 1000 1200

TEMPERATURE (C)

ELO

NG

ATI

ON

(%)

Unirradiated

Irradiated

Reference:Steichen, “TensileProperties of NeutronIrradiated TZM andTungsten”, Journal ofNuclear Materials, 60(1976) p. 13-19


PHENOMENOLOGICAL DBTT-MODELAPPLIED TO Mo-DATA

• The model was applied to the Mo neutron irradiated data:

300 400 500 600 700 800 900 1000 1100 1200 13000

100

200

300

400

500

600

700

800

900

2.5x1026n/m 2 (Wiffen1)1.0x1025n/m 2 (Abe2)

----- Model (Irradiation Data3 )

MOLYBDENUM: Ductile-To-Brittle-Transition Temperature Model

Irradiation Temperature, C

DB

TT, C


PHENOMENOLOGICAL DBTT-MODELAPPLIED TO W-DATA

300 400 500 600 700 800 900 1000 1100 1200 13000

20

40

60

80

100

120

140

160

180

200

5x1025n/m2 (Steichen*)(no thermomechanial history)

----- Model

*J.M.Steichen, JNM 60(1976)13

TUNGSTEN Ductile-To-Brittle Transition Temperature Model

Irradiation Temperature, C

Cha

nge

in D

BT

T, C


RECRYSTALLIZATION TEMPERATURE OFW-ALLOYS

RE-CRYSTALLIZATIONRE-CRYSTALLIZATIONALLOY ALLOY TEMPERATURE ( TEMPERATURE (ooCC))W 1150 - 1350(1)

W-5Re >1500(1)

W-24Re 1593(2)

W-1%La2O3 1200 - 1700(1)

W-23.4Re-0.27HfC 1704 (e-beam welded)(3)

(1) I. Smid, et al., J. Nucl. Mater., 258-263(1998)160(2) W.D.Klopp, Refractory Metals and Alloys IV, Gordon and Breach, NY, 1967, p.557(3) W.D.Klopp, J. Less-Common Metals,24(1971)427

Ave

rage

Gra

in S

ize,

cm

Annealing Temperature, oC

W-23.4Re-0.27HfC after 1 hr annealing at indicated Temp.


OXIDATION TEMPERATURE LIMITS BASEDON BOUNDARY LAYER EFFECTS

• Based on experimental data, the impingement rate of O2as a function of ppm was estimated for calculating theevaporation rate– Due to the BOUNDARY LAYER effect the

evaporation rate of W was estimated to be below1µm at 1 ppm O2 at 1500oC.


DESIGN WINDOW

• Based on the low DBTT, high re-crystallization temperature, hightemperature creep resistance the W-23.4Re-0.27HfC alloys should beconsidered as a candidate material.

• The Design Stress Limit based on the Tensile Design Limits and the 10year Creep Limit is:

– about 250 MPa at 1200oC (primary stress)

• The DBTT at elevated irradiation temperatures (>1000oC) for the W-alloy may be small.

• If the DBTT is shown to be larger than expected, annealing at elevatedtemperature is an option for the W-23.4Re-0.27HfC based on its highre-crystallization temperature (1703oC).

• Oxidation of W at 1ppm O2 content limits the evaporation rate to lessthan 1 µm per year at 1500oC

Documents

Design Window for Tungsten Alloys - ENEA WINDOW FOR TUNGSTEN ALLOYS S. Sharafat , R. Martinez N. M. Ghoniem ... Stanford Press, CA, 1965, p. 315) Creep stress vs. Rupture time for