Jet Engine MaterialsJet Engine Materials

A quick overview of the materials requirements,

the materials being used, and the materials being developed

Motivation for Materials Motivation for Materials DevelopmentDevelopment

Higher Operating Temperatures

Higher Rotational Speeds Lower Weight Engine

Components Longer Operating Lifetime Decreased Failure

Occurrence

This all adds up to: Better Performance Lower Life Cycle Costs

Materials RequirementsMaterials Requirements

thousands of operating hours at temperatures up to 1,100°C (2000 °F)

high thermal stresses caused by rapid temperature changes and large temperature gradients

high mechanical stresses due to high rotational speeds and large aerodynamic forces

low- and high-frequency vibrational loading

oxidation

corrosion

time- , temperature- and stress-dependent effects such as creep, stress rupture, and high- and low-cycle fatigue.

Regions of the EngineRegions of the Engine

Cold Sections Inlet/Fan Compressor Casing

Hot Sections Combustor Turbine/Outlet

Cold Section Materials Cold Section Materials RequirementsRequirements

High Strength (static, fatigue) High Stiffness Low Weight Materials:

Titanium Alloys Aluminum Alloys Polymer Composites Titanium intermetallics and composites

Applications of Polymer Applications of Polymer CompositesComposites

Fiber Reinforced Polymer Fiber Reinforced Polymer Composite Properties - Composite Properties - Graphite/KevlarGraphite/Kevlar

Very high strength-weight ratios Very high stiffness-weight ratio (graphite) Versatility of design and manufacture Specific gravity: ~1.6 (compared to 4.5 for

titanium & 2.8 for aluminum) Can only be used at low temperatures

< 300 °C (600 °F)

Titanium alloys used for critical Titanium alloys used for critical cold section componentscold section components

Fan disks/blade Compressor

disks/blades Typical Alloy:

Ti-6Al-4V

Titanium PropertiesTitanium Properties High strength & stiffness to weight ratios

> 150 ksi, E = 18 Msi Specific gravity of 4.5 ( 58 % that of steel) Titanium alloys can be used up to temperatures of ~

590 °C (1100 °F) Good oxidation/corrosion resistance (also used in

medical implants) High strength alloys hard to work - therefore many

engine components are cast

Metallurgy of disks critical to Metallurgy of disks critical to achieve desired properties achieve desired properties and to eliminate defectsand to eliminate defects

Accident occurred JUL-19-89 at SIOUX CITY, IAAircraft: MCDONNELL DOUGLAS DC-10-10, Injuries: 111 Fatal, 47 Serious, 125 Minor, 13 Uninjured.

A FATIGUE CRACK ORIGINATING FROM A PREVIOUSLY UNDECTECTED METALLURGICAL DEFECT LOCATED IN A CRITICAL AREA OF THE STAGE 1 FAN DISK THAT WAS MANUFACTURED BY GENERAL ELECTRIC AIRCRAFT ENGINES. THE SUBSEQUENT CATASTROPHIC DISINTEGRATION OF THE DISK RESULTED IN THE LIBERATION OF DEBRIS IN A PATTERN OF DISTRIBUTION AND WITH ENERGY LEVELS THAT EXCEEDED THE LEVEL OF PROTECTION PROVIDED BY DESIGN FEATURES OF THE HYDRAULIC SYSTEMS THAT OPERATED THE DC-10'S FLIGHT CONTROLS.

Aluminum alloys can reduce Aluminum alloys can reduce weight over titaniumweight over titanium

Conventional alloys have lower strength/weight ratios than Ti but more advanced alloys approach that of Ti.

Specific gravity: 2.8 ( 62 % that of Ti) Lower cost than Ti Max temp for advanced alloys: ~ 350 °C

(600 °F) Lower weight & rotating part inertia

Titanium Aluminide TiTitanium Aluminide Ti33AlAl

An intermetallic alloy of Ti and Al Extends the temperature range of Ti from

1100 °F to 1200-1300 °F Suffers from embrittlement due to exposure

to atmosphere at high temperature - needs to be coated.

Titanium Composites (MMC)Titanium Composites (MMC)

Titanium matrix with SiC fibers Decreases weight while increases strength

and creep strength

TYPICAL Ti/SiC COMPOSITE100X

Hot Section Materials Hot Section Materials RequirementsRequirements

High Strength(static, fatigue, creep-rupture)

High temperatureresistance 850 °C - 1100 °C (1600 °F - 2000 °F)

Corrosion/oxidation resistance Low Weight

High Temperatures - 1100 °C (2000 °F)High Temperatures - 1100 °C (2000 °F)

Creep becomes at factor for conventional metals when the operating temperature reaches approximately 0.4 Tm

(absolute melting temp.) Conventional engineering metals at 1100 °C:

Steel ~0.9 Tm

Aluminum ~1.4 Tm

Titanium ~0.7 Tm

Conclusion: We need something other than conventional materials!

Unconventional metal alloys - or superalloys

Ceramics

High Temperatures - 1100 °C (2000 °F)High Temperatures - 1100 °C (2000 °F)

What Materials Can Be Used?What Materials Can Be Used?

SuperalloysSuperalloys Nickel (or Cobalt) based materials Can be used in load bearing applications up

to 0.8Tm - this fraction is higher than for any other class of engineering alloys!

High strength /stiffness Specific gravity ~8.8 (relatively heavy) Over 50% weight of current engines

Typical Compositions of Typical Compositions of SuperalloysSuperalloys

Ni Cr Co Mo W Ta

TURBINE BLADE ALLOYS

ALLOY 713C BAL 12.5 4.2 2.0

MAR-M 247 BAL 8.2 10.0 0.6 10.0 3.0

CMSX - (SC) BAL 8.0 4.6 0.6 8.0 6.0

TURBINE DISK ALLOYS

WASPALOY BAL 19.5 13.5 4.3

RENE’ 95 BAL 14.0 8.0 3.5 3.5 3.5

COMBUSTOR ALLOYS

HASTELLOY X BAL 22.0 1.5 9.0 0.6

INCONEL 617 BAL 22.0 12.5 9.0

Cb Al Ti C Zr Hf

2.0 6.1 0.8 0.12 0.10

5.5 1.0 0.20 0.09 1.5

5.6 1.0 0.1

1.3 3.0 0.006 0.06

3.5 3.5 2.5 0.01 0.05

1.0

CHEMICAL COMPOSITION, WEIGHT PERCENT

Chromium yields corrosion resistance

Microstructure of a SuperalloyMicrostructure of a Superalloy

Superalloys are dispersion hardened Ni3Al and Ni3Ti

in a Ni matrix Particles resist

dislocation motion andresist growth at hightemperatures

Creep - RuptureCreep - Rupture

Strain increases over time under a static load - usually only at elevated temperatures (atoms more mobile at higher temperatures)

The higher energy states of the atoms at grain boundaries causes grain boundaries - particularly ones transverse to load axis - to creep at a rate faster than within grains

Can increase creep-rupture strength by eliminating transverse grain boundaries

Controlled grain structure in Controlled grain structure in turbine blades:turbine blades:

Equi-axed Directionally solidified (DS)

Single Crystal (SX)

Performance of superalloy Performance of superalloy parts enhanced with parts enhanced with thermal thermal barrier coatingsbarrier coatings

Thin coating - plasma sprayed MCrALY coating materials Increased corrosion/oxidation resistance Can reduce superalloy surface temperature

by up to 40 °C (~100 °F)

Non-metallics - CeramicsNon-metallics - Ceramics• Cobalt

• Nickel

• Chromium

• Tungsten

• Tantalum

• Silicon

• Nitrogen

• CarbonSUPERALLOY

CERAMIC

Ceramics - AdvantagesCeramics - Advantages

Higher Temperatures Lower Cost Availability of Raw Materials Lighter Weight Materials:

Al2O3, Si3N4, SiC, MgO

Ceramics - ChallengesCeramics - Challenges

SuperalloysCeramics

DUCTILITY

TOUGHNESS

IMPACT

CRITICAL FLAW SIZE

Ceramic CompositesCeramic Composites

Ceramic Fiber Reinforced Ceramic Matrix Improve toughness Improve defect

tolerance Fiber pre-form

impregnated with powder and then hot-pressed to fuse matrix

Carbon-Carbon compositeCarbon-Carbon composite

Carbon fibers in a carbon matrix Has the potential for the highest

temperature capability > 2000 °C (~4000 °F)

Must be protected from oxidation (e.g. SiC) Currently used for nose-cone for space shuttle

which has reentry temperatures of 1650 °C (3000 °F)

Trends in turbine materialsTrends in turbine materialsT

UR

BIN

E R

OT

OR

IN

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TT

EM

P, F

Materials for F109 engineMaterials for F109 engineF109 FAN MODULE MATERIALS

F109 HP COMPRESSOR MATERIALS

Ti 6-4 INCO 718 Ti 6-2-4-2

INCO 625 (side plates)INCO 718 (vanes)

201-T6 Aluminum

17-4 PHHAST X

F109 COMBUSTOR/MIDFRAME MATERIALS

INCO 600HAST XHAST S

INCO 718INCO 718INCO 718

HS 188+ TBC HS 188 300 SS

HS 188

WASP BINCO 718HAST X

HAST XMAR-M 247

DS HAST S

MAR-M 247DS

INCO 738

MAR-M 247DS

MAR-M 247

INCO 738

F109 HP TURBINE MATERIALS

WASPALOY

WASPALOY

WASPALOY

WASPALOY

WASPALOY

HAST X BACK WITH HAST X0.032 CELL. HONEYCOMB

EQUIAXED MAR-M 247COATED WITH RT-21

EQUIAXED MAR-M 247

HASTELLOY X

HAST X BACK WITH HAST X0.032 CELL. HONEYCOMB

INCONEL 625

HAST X BACK WITHHAST X0.032 CELL.HONEYCOMB

EQUIAXED MAR-M 247 COATED WITH RT-21

INCONEL 625

HAST X BACK WITH HAST X0.032 CELL. HONEYCOMB

F109 LP TURBINE MATERIALS