1. Jet Engine Materials A quick overview of the materials requirements, the materials being used, and the materials being developed

2. Motivation for Materials Development u Higher Operating Temperatures u Higher Rotational Speeds u Lower Weight Engine Components u Longer Operating Lifetime u Decreased Failure Occurrence u This all adds up to: u Better Performance u Lower Life Cycle Costs

3. Materials Requirements u thousands of operating hours at temperatures up to 1,100°C (2000 °F) u high thermal stresses caused by rapid temperature changes and large temperature gradients u high mechanical stresses due to high rotational speeds and large aerodynamic forces u low- and high-frequency vibrational loading u oxidation u corrosion u time-, temperature- and stress-dependent effects such as creep, stress rupture, and high- and low-cycle fatigue.

4. Regions of the Engine u Cold Sections u Inlet/Fan u Compressor u Casing u Hot Sections u Combustor u Turbine/Outlet

5. Cold Section Materials Requirements u High Strength (static, fatigue) u High Stiffness u Low Weight u Materials: u Titanium Alloys u Aluminum Alloys u Polymer Composites u Titanium intermetallics and composites

6. Applications of Polymer Composites

7. Fiber Reinforced Polymer Composite Properties - Graphite/Kevlar u Very high strength-weight ratios u Very high stiffness-weight ratio (graphite) u Versatility of design and manufacture u Specific gravity: ~1.6 (compared to 4.5 for titanium & 2.8 for aluminum) u Can only be used at low temperatures < 300 °C (600 °F)

8. Titanium alloys used for critical cold section components u Fan disks/blade u Compressor disks/blades u Typical Alloy: Ti-6Al-4V

9. Titanium Properties u High strength & stiffness to weight ratios  > 150 ksi, E = 18 Msi u Specific gravity of 4.5 ( 58 % that of steel) u Titanium alloys can be used up to temperatures of ~ 590 °C (1100 °F) u Good oxidation/corrosion resistance (also used in medical implants) u High strength alloys hard to work - therefore many engine components are cast

10. Metallurgy of disks critical to achieve desired properties and to eliminate defects u Accident occurred JUL-19-89 at SIOUX CITY, IA Aircraft: MCDONNELL DOUGLAS DC-10-10, Injuries: 111 Fatal, 47 Serious, 125 Minor, 13 Uninjured. u 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.

11. Aluminum alloys can reduce weight over titanium u Conventional alloys have lower strength/weight ratios than Ti but more advanced alloys approach that of Ti. u Specific gravity: 2.8 ( 62 % that of Ti) u Lower cost than Ti u Max temp for advanced alloys: ~ 350 °C (600 °F) u Lower weight & rotating part inertia

12. Titanium Aluminide Ti 3 Al u An intermetallic alloy of Ti and Al u Extends the temperature range of Ti from 1100 °F to 1200-1300 °F u Suffers from embrittlement due to exposure to atmosphere at high temperature - needs to be coated.

13. Titanium Composites (MMC) u Titanium matrix with SiC fibers u Decreases weight while increases strength and creep strength TYPICAL Ti/SiC COMPOSITE 100X

14. Hot Section Materials Requirements u High Strength (static, fatigue, creep-rupture) u High temperature resistance 850 °C - 1100 °C (1600 °F - 2000 °F) u Corrosion/oxidation resistance u Low Weight

15. High Temperatures - 1100 °C (2000 °F) u Creep becomes at factor for conventional metals when the operating temperature reaches approximately 0.4 T m (absolute melting temp.) u Conventional engineering metals at 1100 °C: u Steel ~0.9 T m u Aluminum~1.4 T m u Titanium ~0.7 T m u Conclusion: We need something other than conventional materials!

16. u Unconventional metal alloys - or superalloys u Ceramics High Temperatures - 1100 °C (2000 °F) What Materials Can Be Used?

17. Superalloys u Nickel (or Cobalt) based materials u Can be used in load bearing applications up to 0.8T m - this fraction is higher than for any other class of engineering alloys! u High strength /stiffness u Specific gravity ~8.8 (relatively heavy) u Over 50% weight of current engines

18. Typical Compositions of Superalloys CHEMICAL COMPOSITION, WEIGHT PERCENT Chromium yields corrosion resistance

19. Microstructure of a Superalloy u Superalloys are dispersion hardened u Ni 3 Al and Ni 3 Ti in a Ni matrix u Particles resist dislocation motion and resist growth at high temperatures

20. Creep - Rupture u Strain increases over time under a static load - usually only at elevated temperatures (atoms more mobile at higher temperatures) u 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 u Can increase creep-rupture strength by eliminating transverse grain boundaries

21. Controlled grain structure in turbine blades: Equi-axed Directionally solidified (DS) Single Crystal (SX)

22. Performance of superalloy parts enhanced with thermal barrier coatings u Thin coating - plasma sprayed u MCrALY coating materials u Increased corrosion/oxidation resistance u Can reduce superalloy surface temperature by up to 40 °C (~100 °F)

23. Non-metallics - Ceramics Cobalt Nickel Chromium Tungsten Tantalum Silicon Nitrogen Carbon SUPERALLOY CERAMIC

24. Ceramics - Advantages u Higher Temperatures u Lower Cost u Availability of Raw Materials u Lighter Weight u Materials: u Al 2 O 3, Si 3 N 4, SiC, MgO

25. Ceramics - Challenges Superalloys Ceramics DUCTILITY TOUGHNESS IMPACT CRITICAL FLAW SIZE

26. Ceramic Composites u Ceramic Fiber Reinforced Ceramic Matrix u Improve toughness u Improve defect tolerance u Fiber pre-form impregnated with powder and then hot- pressed to fuse matrix

27. Carbon-Carbon composite u Carbon fibers in a carbon matrix u Has the potential for the highest temperature capability > 2000 °C (~4000 °F) u Must be protected from oxidation (e.g. SiC) u Currently used for nose-cone for space shuttle which has reentry temperatures of 1650 °C (3000 °F)

28. Trends in turbine materials TURBINE ROTOR INLET TEMP, F

29. Materials for F109 engine F109 FAN MODULE MATERIALS

30. 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 PH HAST X

31. F109 COMBUSTOR/MIDFRAME MATERIALS INCO 600 HAST X HAST S INCO 718 HS 188 + TBC HS 188 300 SS HS 188

32. WASP BINCO 718HAST X MAR-M 247 DS HAST S MAR-M 247 DS INCO 738 MAR-M 247 DS MAR-M 247 INCO 738 F109 HP TURBINE MATERIALS

33. WASPALOY HAST X BACK WITH HAST X 0.032 CELL. HONEYCOMB EQUIAXED MAR-M 247 COATED WITH RT-21 EQUIAXED MAR-M 247 HASTELLOY X HAST X BACK WITH HAST X 0.032 CELL. HONEYCOMB INCONEL 625 HAST X BACK WITH HAST X0.032 CELL. HONEYCOMB EQUIAXED MAR-M 247 COATED WITH RT-21 INCONEL 625 HAST X BACK WITH HAST X 0.032 CELL. HONEYCOMB F109 LP TURBINE MATERIALS