[PPT] - High Temperature Lightweight Self- Healing Ceramic Composites for PowerPoint Presentation

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NARI

High Temperature Lightweight Self- Healing Ceramic Composites for Aircraft Engine Applications

S. V. Raj1 (PI), M. Singh2 and R. Bhatt2

Glenn Research Center, Cleveland, OH Ohio Aerospace Institute, Cleveland, OH

NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar

Acknowledgements

Technicians: Mr. Ray Babuder (CWRU); Mr. Robert Angus (GRC) Program Manager: Dr. Koushik Datta (ARC) Funding: ARMD Seedling Fund Phase I

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Introduction

Advanced aircraft engines require the use of reliable,

lightweight, creep-resistant and environmentally durable materials.

Silicon carbide-based ceramic matrix composite (CMC)

technology is being developed to replace nickel-based superalloy blades and vanes.

Near term 1589 K (2400 ºF) (cooled).
Medium term 1755 K (2700 ºF) (cooled).
Long term 1922 K (3000 ºF) (uncooled).

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar 2

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Rule of Mixtures (ROM) Composite Theory

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Pi = Property of the ith component (e.g. strength). Vi = Volume fraction of the ith component .

Properties of the composite are determined by the

properties of the fiber and the matrix and their relative volume fractions. P = PfiberVfiber + PmatrixVmatrix Vfiber + Vmatrix = 1

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Objectives

Develop a new class of ceramic composites –

Engineered Matrix Ceramics (EMCs).

Design different engineered matrices.
Demonstrate thermal strain compatibility with

SiC.

Evaluate oxidation and mechanical properties.
Fabricate engineered matrix composites.
Evaluate self-healing properties.

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar 4

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5

SiC Fiber

Preform

Reactor

CVI BN

Interface Infiltration

CVI-MI CMC

0/90 Fabric Weaving

CVI Preform

CVI SiC Preform

Slurry Infiltration Si Melt Infiltration

Full CVI CMC

Current SiC/SiC CMC Fabrication Processes

Reactor

CVI SiC

Matrix Infiltration

PIP PIP or CVI- PIP CMC

(courtesy R. Bhatt)

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar

Preform Compression

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Current Generation of CMCs: Matrix Microstructure

Silicon carbide (SiC).
Unreacted or free carbon and silicon.
Porosity:

~10-25 vol.% for chemical vapor infiltration (CVI). ~10-25 vol.% for polymer infiltration and pyrolysis (PIP). ~3-10 vol.% for Melt Infiltration (MI).

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar 6

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Typical Microstructure of As-Processed BN-Coated Hi-Nicalon MI SiC Composites

Density ~ 96-97 % fiber SiC

10 µm

Si SiC

40 µm

Porosity

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar

(Courtesy M. Singh)

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Current SiC/SiC CMC Matrix Capabilities

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Brittle at all temperatures.
No crack tip blunting – fast crack propagation.
No self-healing.
Oxygen ingress to fibers shortens fiber life.
Free Si in the matrix limits temperature usage

to below 1588 K (2400 ºF).

Low matrix cracking strength

(proportional limit - 69 MPa/10 ksi)

Matrix fills space and provides a

thermally conductive path.

Fracture toughness due to crack

bridging and interface debonding.

SiC fibers SiC matrix Crack Interface debonding

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Recession of BN and Formation of Glassy Phase in BN-Coated Hi-Nicalon MI SiC Composites

T = 973 K; σ = 250 MPa;1000 h in air 2BN (s) + 3/2 O2 (g) = B2O3 (l) +N2 (g) B2O3 - SiO2: Low eutectic temperature of 372 ºC

Glass

5 mm

BN

10 µm

Glass

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar

(Courtesy M. Singh)

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Important Question

Can the matrix properties be suitably engineered to ensure certain desirable characteristics?

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Present Concept

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Crack Tip Blunting and Self-Healing

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SiC fibers Engineered matrix Crack Crack blunting due to matrix plasticity slows crack growth SiC fibers Engineered matrix Crack Self-healing of fine cracks minimizes

xygen ingress

to fibers

Increased reliability and load carrying capacity

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Innovation: Desired Characteristics of the Engineered Matrix (EM)

 Thermal strain compatibility of the matrix with the SiC fibers.  Plastically compliant matrix to blunt cracks.  Self-healing crack capabilities to minimize ingress of oxygen.  Minimize the volume fraction of unreacted silicon to prevent corrosive attack of fibers and incipient melting.  Dense matrix to increase thermal conductivity.

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar 13

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Expected Impact of Innovation

Matrix plasticity - increased reliability, compliant matrix.
Self-healing matrix - prevents or minimizes oxygen ingress.
Low free Si - reduces fiber attack, reduces incipient melting,

increased high temperature capability.

Dense matrix - High thermal conductivity.

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar 14

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Fabrication and Testing of Engineered Matrix Composites (EMC)

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Hot-Pressed Plate and Optical Micrograph

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50 x 50 x 4 mm

Optical micrograph

CrMoSi-EM

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Proof-of-Concept: Thermal Strains

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar 17

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Optical Macrographs of MoSi2 Engineered Matrix

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Thermally cycled between room temperature and 1500 K (2240 ºF) three times.

Thermal cycling resulted in

cracking.

No longer considered in the

program.

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Isothermal Oxidation Behavior

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar 19

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Bend Stress-Strain Curves for CrMoSi-EM

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Bend Stress-Strain Curves for CrSi2-EM

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Bend Stress-Strain Curves for WSi2-EM

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Catastrophic oxidation occurred during heat-up to 1473 K.

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23

SiC Fiber

SiC fiber Preform Fabrication

Reactor

CVI BN

Interface Infiltration

EMC

0/90 Fabric Weaving

CVI Preform

CVI SiC Preform

Engineered Matrix Infiltration Melt Infiltration

Engineered Matrix Composites Fabrication

Reactor

CVI SiC

Matrix Infiltration

(courtesy R. Bhatt)

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar

Fiber coating

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Microstructures of Particulate-Infiltrated SiC Fiber Preform

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Particulates Coated Preform Fibers tows Voids

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CT Scans of Particulate Infiltrated Preform

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Particulate Infiltrated As-received Preform Area fraction of porosity ~ 0.9% Area fraction of porosity ~ 21-23%

NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar

The red regions are voids

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Summary and Conclusions

Bend, CTE, isothermal oxidation and thermal cycling tests were

conducted on several engineered silicide/SiC/Si3N4 matrices.

Two promising engineered matrix compositions were down-selected

for further development.

Trials to infiltrate one of these engineered matrices into SiC-coated

fiber preforms have been completed. Microstructural analysis and CT scans demonstrated almost complete infiltration of the preform.

Efforts are underway to produce Engineered Matrix Composites

(EMCs) specimens to determine self-healing capabilities.

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Summary of Phase I Accomplishments: TRL 2

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Milestone Status Demonstrate thermal strains for engineered matrices match those of SiC. Completed. Generation of matrix properties and down-selection of promising compositions. Completed. Demonstrate high temperature matrix plasticity. Completed. Develop processing techniques for fabricating EMCs. Particulate infiltration trials completed; melt infiltration trials to be completed. Evaluate mechanical properties

f EMCs and demonstrate self-

healing capabilities. To be completed.

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Next Steps

Complete tensile tests of monolithic specimens.
Particulate and melt infiltrate bend specimens.
Mechanical testing of EMC bend specimens.
Evaluate self-healing properties in EMCs.
Write and submit final report.
Submit Phase II proposal.

June 5-7, 2012 NASA Aeronautics Mission Directorate FY11 Seedling Phase I Technical Seminar 28

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Distribution and Dissemination

Submitted NF 1679 to GRC patent attorney (LEW-

18964-1).

Submit papers to journals/NASA TMs after receiving

approvals.

Present papers at conferences after receiving

approvals depending on the availability of travel funds.

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