Jet Engine Materials
A quick overview of the
materials requirements,
the materials being used,
and the materials being developed
Motivation for Materials
Development
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Higher Operating
Temperatures
Higher Rotational
Speeds
Lower Weight Engine
Components
Longer Operating
Lifetime
Decreased Failure
Occurrence
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This all adds up to:
Better Performance
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Costs
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Materials Requirements
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thousands of operating hours at temperatures up to 1,100°C (2000 °F)
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high thermal stresses caused by rapid temperature changes and large
temperature gradients
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high mechanical stresses due to high rotational speeds and large
aerodynamic forces
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low- and high-frequency vibrational loading
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oxidation
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corrosion
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time- , temperature- and stress-dependent effects such as creep, stress
rupture, and high- and low-cycle fatigue.
Regions of the Engine
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Cold Sections
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Inlet/Fan
Compressor
Casing
Hot Sections
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Combustor
Turbine/Outlet
Cold Section Materials
Requirements
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High Strength (static, fatigue)
High Stiffness
Low Weight
Materials:
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Titanium Alloys
Aluminum Alloys
Polymer Composites
Titanium intermetallics and composites
Applications of Polymer
Composites
Fiber Reinforced Polymer
Composite Properties Graphite/Kevlar
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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
cold section components
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Fan disks/blade
Compressor
disks/blades
Typical Alloy:
Ti-6Al-4V
Titanium Properties
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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
achieve desired properties and
to eliminate defects
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Accident occurred JUL-19-89 at SIOUX CITY, IA
Aircraft: MCDONNELL DOUGLAS DC-10-10,
Injuries: 111 Fatal, 47 Serious, 125 Minor, 13
Uninjured.
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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
weight over titanium
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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 Ti3Al
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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)
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Titanium matrix with SiC fibers
Decreases weight while increases strength
and creep strength
TYPICAL Ti/SiC COMPOSITE
100X
Hot Section Materials
Requirements
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High Strength
(static, fatigue,
creep-rupture)
High temperature
resistance
850 °C - 1100 °C
(1600 °F - 2000 °F)
Corrosion/oxidation resistance
Low Weight
High Temperatures - 1100 °C (2000 °F)
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Creep becomes at factor for conventional metals
when the operating temperature reaches
approximately 0.4 Tm (absolute melting temp.)
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Conventional engineering metals at 1100 °C:
Steel
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~0.9 Tm
~1.4 Tm
~0.7 Tm
Conclusion: We need something other than
conventional materials!
High Temperatures - 1100 °C (2000 °F)
What Materials Can Be Used?
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or superalloys
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metal alloys -
Superalloys
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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
Superalloys
CHEMICAL COMPOSITION, WEIGHT PERCENT
Ni
Cr
Co
Mo
W
Ta
Cb
Al
Ti
C
Zr
2.0
6.1
0.8
0.12
0.10
0.20
0.09
Hf
TURBINE BLADE ALLOYS
ALLOY 713C
BAL 12.5
4.2
MAR-M 247
BAL
8.2
10.0
0.6
10.0
3.0
5.5
1.0
CMSX - (SC)
BAL
8.0
4.6
0.6
8.0
6.0
5.6
1.0
WASPALOY
BAL 19.5
13.5
4.3
1.3
3.0
0.006 0.06
RENE’ 95
BAL 14.0
8.0
3.5
3.5
3.5
2.5
0.01
HASTELLOY X
BAL 22.0
1.5
9.0
0.6
INCONEL 617
BAL 22.0
12.5
9.0
0.1
TURBINE DISK ALLOYS
3.5
1.5
COMBUSTOR ALLOYS
1.0
Chromium yields corrosion resistance
0.05
Microstructure of a Superalloy
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Superalloys are dispersion hardened
Ni3Al and Ni3Ti
in a Ni matrix
Particles resist
dislocation motion and
resist growth at high
temperatures
Creep - Rupture
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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
turbine blades:
Equi-axed
Directionally Single Crystal
solidified (DS)
(SX)
Performance of superalloy
parts enhanced with thermal
barrier coatings
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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 - Ceramics
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SUPERALLOY
Cobalt
Nickel
Chromium
Tungsten
Tantalum
• Silicon
• Nitrogen
• Carbon
CERAMIC
Ceramics - Advantages
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Higher Temperatures
Lower Cost
Availability of Raw Materials
Lighter Weight
Materials:
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Al2O3, Si3N4, SiC, MgO
Ceramics - Challenges
DUCTILITY
IMPACT
Superalloys
Ceramics
TOUGHNESS
CRITICAL FLAW SIZE
Ceramic Composites
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Ceramic Fiber Reinforced Ceramic Matrix
Improve toughness
Improve defect
tolerance
Fiber pre-form
impregnated with
powder and then hotpressed to fuse matrix
Carbon-Carbon composite
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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)
TURBINE ROTOR INLET
TEMP, F
Trends in turbine materials
Materials for F109 engine
F109 FAN MODULE MATERIALS
F109 HP COMPRESSOR MATERIALS
201-T6 Aluminum INCO 625 (side plates)
INCO 718 (vanes)
17-4 PH
Ti 6-4
INCO 718
Ti 6-2-4-2
HAST X
F109 COMBUSTOR/MIDFRAME MATERIALS
HS 188
+ TBC INCO 718 HS 188
HS 188
HAST S
HAST X
300 SS INCO 718
INCO 718
INCO 600
F109 HP TURBINE MATERIALS
INCO 738
HAST X
HAST X
INCO 718
MAR-M 247
HAST S
DS
MAR-M 247
MAR-M 247
DS
WASP B
MAR-M 247
INCO 738 DS
F109 LP TURBINE MATERIALS
HAST X BACK WITH HAST X
0.032 CELL. HONEYCOMB
INCONEL 625
EQUIAXED MAR-M
247 COATED WITH
RT-21
INCONEL 625
HAST X BACK WITH HAST X
0.032 CELL. HONEYCOMB
HASTELLOY X
EQUIAXED MAR-M 247
WASPALOY
EQUIAXED MAR-M 247
COATED WITH RT-21
HAST X BACK WITH HAST X
0.032 CELL. HONEYCOMB
WASPALOY
WASPALOY
WASPALOY
HAST X BACK WITH
HAST X0.032 CELL.
HONEYCOMB
WASPALOY