Implementation Challenges for Sintered Silicon Carbide ... · MS&T 2011, Columbus, OH, Oct. 16-20th, 2011 Implementation Challenges for Sintered Silicon Carbide Fiber Bonded Ceramic

Invited Lecture International Symposium in honor of Prof. K.K. Chawla

MS&T 2011, Columbus, OH, Oct. 16-20th, 2011

Implementation Challenges for Sintered Silicon Carbide Fiber Bonded Ceramic Materials for High Temperature Applications

M. Singh Ohio Aerospace Institute

NASA Glenn Research Center Cleveland, OH 44135 (USA)

Abstract

During the last decades, a number of fiber reinforced ceramic composites have been developed and tested for various aerospace and ground based applications. However, a number of challenges still remain slowing the wide scale implementation of these materials. In addition to continuous fiber reinforced composites, other innovative materials have been developed including the fibrous monoliths and sintered fiber bonded ceramics. The sintered silicon carbide fiber bonded ceramics have been fabricated by the hot pressing and sintering of silicon carbide fibers. However, in this system reliable property database as well as various issues related to thermomechanical performance, integration, and fabrication of large and complex shape components has yet to be addressed. In this presentation, thermomechanical properties of sintered silicon carbide fiber bonded ceramics (as fabricated and joined) will be presented. In addition, critical need for manufacturing and integration technologies in successful implementation of these materials will be discussed.

https://ntrs.nasa.gov/search.jsp?R=20150009974 2020-07-01T11:34:55+00:00Z

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National Aeronautics and Space Administration

Implementation Challenges for Sintered Silicon Carbide Fiber Bonded Ceramic Materials for

High Temperature Applications

M. SinghM. SinghOhio Ohio Aerospace Aerospace InstituteInstitute

NASA Glenn Research CenterNASA Glenn Research CenterCl l d OH 44135Cl l d OH 44135

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Cleveland, OH 44135Cleveland, OH 44135


Outline

• Introduction and Background

• Fiber Bonded Ceramics: Overview• Materials and Manufacturing

• Microstructure (SEM, TEM)

• Thermal Properties

• Key Implementation Challenges• Thermomechanical Performance

• Integration Technologies

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g g

• Robust Manufacturing and Cost

• Concluding Remarks

• Acknowledgments

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Ceramic Matrix Composites (CMCs): Past, Present and Future ?

• Tremendous potential for use of ceramic matrix composites in aerospace and ground-based applications.

• Many intrinsic advantages over other material classes.

• Unique capabilities relative to certain applications.

• Substantial, long-term government funding for research and development in these materials worldwide.

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• But many scientific, technical, economic, and cultural problems still remain in wide scale use of these materials.


Timescale for Development and Applications of CMCs

Introduction/Background

Fiber Bonded Ceramics

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1960 1970 1980 1990 2000 2015Ceramic Fibers

MatricesInterphases

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Although more complex and more expensive than monolithic ceramics, the added “toughness” of CMCs make them more

inherently damage tolerant than monolithic ceramics.(Fiber Bonded Ceramics Could Play a Key Role)

Introduction/Background

Monolithic Ceramics -brittle, catastrophic failure

C it (CMC)

Suts

sile

Str

ess

sile

Str

ess Fiber Bonded Ceramics -

tough, “graceful” failure

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Composite (CMC) -tough, “graceful” failure

Longitudinal StrainLongitudinal Strain

PL=oTen

sT

ens


SiC Fiber Bonded Ceramics

Processing and Microstructure

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Synthesis of Amorphous Si-Al-C-O Fiber

Polyalumino-Polyalumino-carbosilane

Melt spinning

@220°C

Curing

in Air @160°C

Firingin Ar gas

up to 1300°C

phou

sC

-O f

iber

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Formingcontinuouslyto fiber shape

Changing toceramic fiber A

mor

pSi

-Al-

C

T. Ishikawa, Ube Industries


Fabrication of SiC Fiber Bonded Ceramics (SA-Tyrannohex)

AmorphousSi-Al-C-O fiber

Cut & Lamination

SA-Tyrannohex™

Fabric(8-harness satin)

Hot Pressing

Si1C1.5O0.4Al0.014Si C O Al

53 33 13.3 0.7

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at ~1900 ,50MPa,1h in Ar gas

Ube Industries

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Forming Process of SA-Tyrannohex during Hot Pressing

11 22 33

44 55

Under high pressure & high temp.in a hot press

Deforming fibers & Evaporating SiO and CO gas

Closed-pack hexagonal columnarstructure

C layer

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Carbon diffusion from the center of fibers to its surface

Unique SA-Tyrannohex structure

5µmSiC fiber

C layer

T. Ishikawa, Ube Industries


Unique MicrostructureHexagonal columnar SiC

polycrystalline fibers

Microstructure of Fiber Bonded Ceramics

C layerpolycrystalline fibers 10-20 nm turbostratic carbon

interfacial layers

Good PropertiesHigh density (~98-99%)High thermal conductivity

(33 W/mK @ 1600°C)

5µmSiC fiber

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( @ )High strength sustained up to

1600°CFlexural strength~300 MPa

High fracture toughness (1200 J/m2 @ RT)

SiCSiC

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Thermomechanical Properties

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Thermomechanical Evaluation of Flexural Stress Rupture Behavior (time-to-failure)

3mm × 4mm × 50 mm

Applied stress

SA-THX

20

Pre-heat treatment @1400°Cfor 10h in air

1µm outer silica coating

Time

Tem

pera

ture Desired test temp.

30minto equilibratethe temperature

pp

FracturedFractured

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Fractography of tested specimens in SEM

Focused on the tensile side40mm

20mm

50mm

3mm α-SiC

SA-THX

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Stress versus Lifetime Behavior for SA-Tyrannohex™ Tested up to 1150 C in air

400

500

ApparentThreshold

300

200

pp

lied

str

ess,

MP

a

700°C950°C

500°C

ThresholdStress: 200-225 MPa

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10-2 10-1 100 101 102 103 10410-3

Time to failure, h

1009080

Ap

70

950 C1150°C No distinguishable

difference existed in the stress-dependence


Stress versus Lifetime Behavior for SA-Tyrannohex™ Tested up to 1400°C in Air

400

500

Apparent

300

200

pp

lied

str

ess,

MP

a

700°C950°C

500°C

ThresholdStress: 175 MPa

The time-to-failure ≥

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10-2 10-1 100 101 102 103 10410-3

Time to failure, h

1009080

Ap

70

950 C1150°C

1400°C1300°C

The time to failure ≥ 1300°C exhibited a stress-dependence

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Stress versus Lifetime Behavior of MI SiC/SiCand SA-Tyrannohex up to 1300°C in Air

in air400

500

700°CSintered SiCHi-Nic-MISiC

300

200

pp

lied

str

ess,

MP

a

700°C

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700 C950°C1150°C1300°C

10-2 10-1 100 101 102 103 10410-3

Time to failure, h

1009080

Ap

70

700 C950°C1150°C1300°C


Fractography of SA-Tyrannohex after the Rupture Tests between 700-1400°C

250MPa @700˚C 265MPa @1150˚C

250MPa @1300˚C 250MPa @1400˚C

500nm 500nm

2µm 2µm

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2µm 2µm

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Joining and Integration Technologies

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Critical Needs for Integration Technologies

• A wide majority of CMC components have to be integrated with existing metallic constituents or components either during component manufacturing or co po e ts e t e du g co po e t a u actu g oin service.

• It is important to understand the technical issues among the different material systems

• Robust integration technologies can also play a key role in manufacturing of large size components (beyond existing manufacturing capabilities) utilizing building

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existing manufacturing capabilities) utilizing building block approach.

• Building Block approach has been used through the ages and currently quite effectively in metal, polymer, and electronic industry.

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• Materials– SA-Tyrannohex with two

orientations• Parallel type• Perpendicular type

• Procedure

Active Metal Brazing of Fiber Bonded Ceramics

Cusil-ABATi il– AgCuTi brazing alloy

• Cusil-ABA• Ticusil

• Conditions– Temperature: 10-15°C above

liquidus– Hold time: 5 min– Vacuum level: 10-6Torr

Assembly

Load: 0.3-0.4N

VacuumSA-THX

Ticusil

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• Characterization– Mounted in epoxy, and

polished– Optical microscopy– SEM-EDS

NameComposition(wt%)

TL

(K)TS

(K)

CTE (×10-6K-

1)

Cusil-ABA

63.0Ag-35.25Cu-1.75Ti

1088 1053 18.5

Ticusil68.8Ag-26.7Cu-4.5Ti

1173 1053 18.5


Brazing of SA-Tyrannohex Material to Itself using the AgCuTi Brazing Alloy

SA-Tyrannohex

AgCuTi alloy

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50µm

Uniform joint microstructure and good bonding

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Joining of SA-Tyrannohex Material to Itself using the AgCuTi Brazing Alloy (Cusil-ABA & Ticusil)

SA-THX

Cusil-ABA SA-THX

Ticusil Despite orientation of fiber and Ti content, microstructures of the joints were very similar

pe

4.5%Ti (Ticusil)1.75%Ti (Cusil-ABA)

5µm

SA-THX

Cusil-ABA

5µm

SA-THX

Ticusil

ar t

ype

Par

alle

l typ

SA-THXTicusil

Rea

cted

Rea

cted

inte

rlaye

rin

terla

yer

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5µm 5µmPer

pen

dic

ula Magnified

2µm


• Interlayer of SA-THX/Ticusil • EDS mapping result

Microstructure of the Joint Interfaces

SA-THX

iCla

yer

mp

ou

nd CCPhase diagramPhase diagram

1

23 5

4

2µmAg (Cu)

Cu (Ag)

T

Ti-S

i co

m

atomic %

SiSi TiTi

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Pos. Al Si Ti Cu Ag

1 23 4 5

0000

1.1

00

39.08.0

98.5

00

50.187.9

0

16.098.510.94.10

84.01.5000

CuCu AgAg

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• Schematic • Effect of Ti on the thickness of TiC layer on SA-Tyrannohex

Summary of Joint Microstructure of SA-THXMaterials using AgCuTi Alloy Brazes

SA-THXAg (Cu)

1.2

m

• In the interface between SA-T h d th t l thi TiC

Cu (Ag)

TiC layerGranular

Ti-Sicompound

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6

TiC

laye

r th

ickn

ess,

µm

Ti content %

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Tyrannohex and the metals, thin TiClayer and granular Ti-Si compound (could be Ti5Si3) were formed regardless of the orientation and Ti content.

• The joint microstructure of the SA-Tyrannohex using Ag-Cu-Ti alloy brazes was very similar regardless of the orientation and Ti content.

Ti content, %

Ti content Orientation Ti-Si region (µm)

1.75 wt%Parallel 0.82 ± 0.20Perpendicular 1.60 ± 0.68

4.5 wt%Parallel 2.16 ± 0.88Perpendicular 1.42 ± 0.45


• Joint Materials– SA-THX( & ǁ)/Cusil-ABA

• Testing Machine– Capacity: 22.5 kN– Crosshead speed:

0 5mm/min

Procedure for Mechanical Evaluation

• Single lap offset shear test– Modified ASTM D905– R.T., 250, 650 and 750°C

• Melting point: 815°C

0.5mm/min– Atmosphere: air

Joint

Pushing rod

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Heater

StageFixture

Thermocouples

sample

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30

Mechanical Behavior SA-THX Joints as a Function of Test Temperature

Failed withinFailed withinSASA--THX ≤250THX ≤250°°CC

10

15

20

25

Lo

ad a

t fa

ilure

, kN

Perpendiculartype

Parallel-type

Failed in jointsFailed in joints≥650≥650°°CC

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0

5

0 200 400 600 800 1000

L

Temperature, °C

yp

Failed withinFailed withinSASA--THX ≤750THX ≤750°°CC


25

30

Shear Strength of the Perpendicular-Type SA-THX Joints as a function of Test Temperature

The perpendicular type SA-THX joints tested above 650°C fractured100

120

Pa

Perpendicular-type

Failed withinFailed withinSATHX ≤250SATHX ≤250°°CC

Failed in JointsFailed in Joints

5

10

15

20

Load

at f

ailu

re, k

N

Perpendiculartype

Parallel-type

joints tested above 650 C fractured at the metal. The others joints while failed within the SA-THX materials.

In terms of these samples, shear strength can be obtained via this formula;

F20

40

60

80

She

ar s

tren

gth

of jo

int,

MP

The shear strength decreased with increase in temperatures

Failed in JointsFailed in Joints≥650≥650°°CC

Fractographiccharacterization

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00 200 400 600 800 1000

Temperature, °C

F

A00 200 400 600 800

Temperature, °C

with increase in temperatures

Failed withinFailed withinSATHX ≤750SATHX ≤750°°CC

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Summary of Fractography• Failure occurred between the filler

metal and TiO2 interaction layer

– TiO2 layer may be caused by oxidation of TiC, which was formed

SA

-TH

X

SA

-TH

X

TiC

Ag-

Cu

Ag

& C

u2

O

Cu

O

TiO 2

Cra

ckin

g pa

th

Ti-S

i

Ti-S

i-O

ack

s

by the reaction between Ti in the filler metal and C in SA-Tyrannohexduring the brazing.

• There are micro-cracks in SA-Tyrannohex in the vicinity of the interaction phase.

– The micro-cracks could be brought about by degradation of SA-

SA

-TH

X

SA

-TH

X

TiC

Ag-

Cu

TiC

Cra

ckin

g p

ath

Ti-S

i

Ti-S

i

cks

Mic

ro-c

ra

Obtained representative microstructure

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Tyrannohex strength, which would be caused by C migration in SA-Tyrannohex to form TiC.

• Since Cu reacts with O2, CuO and Cu2O phases were formed during the cooling after the test at 750˚C.

Mic

ro-c

rac

Predicted microstructure as the joint failure occurred at high temperatures


Joining with Eutectic Phase Tapes (1 layer and 2 layers)

• SA-Tyrannohex (parallel) and SA-Tyrannohex (perpendicular)

• Joined with 2 mm offset for mechanical tests.

• Testing at R.T., 700ºC and 1200ºC

Ceramic Joining and Integration- Joining with Si-Hf Eutectic Phase Tape

Spot C Si Al Hf

1 63.12 36.88

2 64.30 35.70

3 67.75 32.25

4 63.82 35.40 0.78

5 55.93 44.07

6 56.83 43.17

7 55.28 44.72

8 32.89 67.11

40

60

80

100

120

140

ent Shear Strength, Mpa

8a 100.00

9 32.92 67.08

9a 100.00

10 32.34 67.66

10a 100.00

Spot C Si Hf

1 61.71 38.29

2 61 81 38 19

SEM and EDS of joints for parallel and perpendicular

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0

20

40

Appare

‖SA‐Tyrannohex 1 layer

‖SA‐Tyrannohex 2 layers

┴ SA‐Tyrannohex 1 layer

┴ SA‐Tyrannohex 2 layers

Apparent Shear Strength at Room Temperature

2 61.81 38.19

3 57.41 42.59

4 57.63 42.37

5 53.25 46.75

6 65.12 34.88

7 100.00

7a 31.28 68.72

8 100.00

8a 32.32 67.68

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Long Term Challenges

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Environmental Issues in Manufacturing and Product Life Cycle Management

• ISO 14000 Standard for Environmental Management.

ISO 14001 d ISO 14004 d l ith E i t l• ISO 14001 and ISO 14004 deal with Environmental Management System (EMS)- 1996.

• EMS provides a framework for an organization to manage the impact of its activities on the environment.

• Provides tools to help companies realize their own environmental policies, objectives, and targets.

• In Europe, European Community (EC) has established an

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p , p y ( )Eco Management and Audit Scheme (EMAS) in 1997.

In Global Economy, Consumer Demand of High Quality Products with In Global Economy, Consumer Demand of High Quality Products with Low or No Environmental Impact, Standards Will Play Major RoleLow or No Environmental Impact, Standards Will Play Major Role

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Performance vs Cost Issue

• It is quite clear that CMC industry is in a real dilemma

CMC ( t ) d d f t t b t- CMC users (customers) demand performance at cost, but cost is typically driven by market volume.

- Small market volume means high cost and small number (or no) customers.

• Users (customers) are willing to pay the COST if the CMC is truly enabling.

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Concluding Remarks

• Fiber Bonded Ceramics have a lot of potential for niche high temperature applications but the manufacturing processes are still evolutionary. Their use has been limited due to limited manufacturing base and costdue to limited manufacturing base and cost.

• For the wide scale applications of these materials, reliable processes and properties have to be demonstrated at various levels (coupons to full scale components). In addition, multiscale modeling tools have to be developed and effectively utilized.

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• The CMC community has to leverage their resources and make a concerted effort in finding out multiple applications and educating customers. High market volume will drop the cost and will be able to sustain the supplier base.

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Acknowledgments

• Drs. T. Ishikawa and T. Matsunaga, Ube Industries, Inc., Japan

• Mr. Michael Halbig, NASA Glenn Research Center

• Mr. Craig E. Smith, Ohio Aerospace Institute

• Mr. Ray Babuder, Case Western reserve University

• Mr. Ronald E. Phillips, ASRC Corp., Cleveland, OH

• Dr. H-T. Lin, Oak Ridge National Laboratory, TN

• Prof. Julian Martinez-Fernandez, University of Seville, S i

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Spain

• Prof. Rajiv Asthana, University of Wisconsin-Stout, WI

Documents

Implementation Challenges for Sintered Silicon Carbide ... · MS&T 2011, Columbus, OH, Oct. 16-20th, 2011 Implementation Challenges for Sintered Silicon Carbide Fiber Bonded Ceramic