1. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 1 of 45 Screening and Evaluation of Materials for Advanced Microturbine Recuperators Edgar Lara-Curzio, R. M. Trejo, K. L. More, P.A. Maziasz, B. A. Pint Metals & Ceramics Division Oak Ridge National Laboratory Oak Ridge, TN 37831-6069 ASME Turbo Expo Vienna, Austria June 16, 2004

2. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 2 of 45 Acknowledgments Research sponsored by the U.S. Department of Energy, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Power Technologies, Microturbine Materials Program, under contract DE-AC05-00OR22725 with UT-Battelle, LLC

3. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 3 of 45 Outline Background Microturbine Recuperator Testing Facility Test Procedure Results 347 Stainless Steel HR230® HR120® Summary, Current and Future Work

4. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 4 of 45 Outline Background

5. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 5 of 45 Background 200020022004 $500/kW 40% Efficiency 40,000-hr life 200620082010 U.S. DOE Advanced Microturbines Program

6. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 6 of 45 Background (cont.) 200020022004200620082010 higher TIT higher TET advanced materials U.S. DOE Advanced Microturbines Program $500/kW 40% Efficiency 40,000-hr life

7. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 7 of 45 Background (cont.) Temperature Environment (combustion gases can lead to corrosion) Mechanical Stress (pressure differential can induce creep deformation) Main parameters to consider for the selection of materials for microturbine recuperators

8. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 8 of 45 Outline Background Microturbine Test Facility Testing Procedure

9. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 9 of 45 Microturbine Test Facility gas compressor shelter housing instrumentation Capstone 60kW microturbine screenevaluate As part of the Advanced Materials for Recuperators Program, ORNL established a microturbine test facility to screen and evaluate candidate materials for advanced microturbine recuperators

10. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 10 of 45 ORNL’s Microturbine Test Facility (cont.) Modified Capstone C60 microturbine Higher TET (850°C) Placement of test specimens at the entrance of recuperator. thermocouples water-cooled block pressure transducer air line water lines sample holder

11. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 11 of 45 Microturbine Test Facility (cont.)

12. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 12 of 45 Four (4) laser-welded foils in each sample holder foil temperatures are monitored using type-K thermocouples sample holders are pressurized with air to simulate the pressure differential experienced by recuperator cells welded foils ORNL’s Microturbine Test Facility (cont.) sample holder thermocouples

13. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 13 of 45 Temperature distribution along sample holder TET=800°C

14. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 14 of 45 Effect of microturbine exposure on tensile properties Foils are removed from the sample holder and miniature test specimens, obtained by electric discharge machining, are evaluated in tension.

15. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 15 of 45 Temperature History for 500-hr test

16. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 16 of 45 Outline Background Microturbine Test Facility Testing Procedure Results 347 Stainless Steel

17. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 17 of 45 347-stainless steel after 500-hr exposure (TET=800°C) 0.089 mm A 758°C B 736°C C 697°C D 632°C 60 psi internal pressure -> 50 MPa hoop stress

18. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 18 of 45 Significant corrosion and spalling of oxidation products on foil exposed to highest temperature (758°C) 347-stainless steel after 500-hr exposure ballooning due to creep deformation

19. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 19 of 45 DC B A cool end 630°C hot end 758°C air side exhaust side Position D 500 h @ ~632°C very little corrosion Position C 500 h @ ~697°C thin scale Position B 500 h @ ~736°C ~3 µm scale Position A 500 h @ ~758°C ~20 µm scale 347-stainless steel after 500-hr exposure ballooning due to creep deformation “wart” cross-sectional analysis

20. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 20 of 45 347-stainless steel after 500-hr exposure FeNi Nb O Cr Foil A exhaust side air side Foil exposed at 758°C Multilayered oxide scale: Ni-Cr-O Fe-O Depletion of Cr at GBs Carbide formation

21. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 21 of 45 Tensile strength of as-processed 347-stainless steel

22. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 22 of 45 Tensile strength of 347-stainless steel

23. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 23 of 45 Tensile strength of 347-stainless steel

24. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 24 of 45 Tensile strength of 347-stainless steel

25. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 25 of 45 Tensile strength of 347-stainless steel

26. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 26 of 45 Tensile strength of 347-stainless steel Dimples characteristic of plastic deformation. Limited ductility 758°C 500 hrs 50 MPa (hoop stress due to 60 psi of internal pressure)

27. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 27 of 45 Tensile strength 347-stainless steel 500-hr test 60 psi internal pressure

28. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 28 of 45 Outline Background Microturbine Test Facility Testing Procedure Results 347 Stainless Steel HR230®

29. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 29 of 45 As-processed HR230® 89 µm 102 µm tungsten-rich particles

30. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 30 of 45 0.089 mm 0.102 mm A 752°C B 730°C C 700°C D 679°C 60 psi internal pressure HR230® after 500-hr exposure (TET=800°C)

31. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 31 of 45 DC B A cool end 679°C hot end 752°C Position C 500 h @ ~697°C Position B 500 h @ ~730°C Position A 500 h @ ~752°C cross-sectional analysis air side exhaust side Position D 500 h @ ~679°C HR230® after 500-hr exposure (TET=800°C)

32. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 32 of 45 Cr OWNi MoC Foil exposed at 752°C Limited corrosion products found on surface Significant cracking along grain boundaries Grain boundaries near surface are poor in Cr but rich in W and C. HR230® after 500-hr exposure (TET=800°C)

33. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 33 of 45 Tensile strength of HR230® after 500-hr exposure

34. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 34 of 45 Outline Background Microturbine Test Facility Testing Procedure Results 347 Stainless Steel HR230® HR120®

35. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 35 of 45 DC B A cool end 632°C hot end 745°C Position C 500 h @ ~700°C Position B 500 h @ ~730°C Position A 500 h @ ~745°C cross-sectional analysis air side exhaust side Position D 500 h @ ~632°C HR120® after 500-hr exposure (TET=800°C)

36. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 36 of 45 10 µm FeNiSiCr Foil exposed at 745°C Limited corrosion (oxides of Cr, Si and and Fe) Grain boundaries near surface are poor in Cr but rich in Ni HR120® after 500-hr exposure (TET=800°C)

37. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 37 of 45 Tensile strength of HR120® after 500-hr exposure

38. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 38 of 45 Tensile strength of metallic alloys after 500-hr exposure

39. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 39 of 45 Outline Background Microturbine Test Facility Testing Procedure Results 347 Stainless Steel HR230® HR120® Summary, Current and Future Work

40. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 40 of 45 A test facility was designed to screen and evaluate candidate materials for advanced microturbine recuperators. TET up to 850°C Mechanical stressing Foils of 347 stainless steel, HR230® and HR120® alloys have been evaluated Foils have been welded to sample holders by laser and e-beam. Summary, Current and Future Work

41. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 41 of 45 347 stainless steel347 stainless steel exhibited significant decrease in tensile strength and ductility, and severe corrosion after 500-hr exposure at 758°C. creepEvidence of creep deformation at temperatures above 700°C at 50 MPa. Corrosion products at highest temperature are a mixture of oxides of chromium, nickel and iron. chromiumDepletion of chromium from grain boundaries near interface between base metal and oxide layers. CarbideCarbide precipitation Summary, Current and Future Work (cont.)

42. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 42 of 45 HR230®HR230® retains 70% of its tensile strength after 500-hr exposure at 752°C. crackingLimited corrosion products found on surface but significant cracking along grain boundaries Grain boundaries near surface are poor in chromium but rich in tungsten and carbon. Summary, Current and Future Work (cont.)

43. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 43 of 45 HR120®HR120® exhibited good retention of mechanical properties (e.g.- 85% of its tensile strength) after 500-hr exposure at 745°C. Limited corrosion products in the form of oxide of chromium, silicon and iron. Depletion of chromium from grain boundaries close to surface exposed to exhaust gases. Summary, Current and Future Work (cont.)

44. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 44 of 45 Tests in progress to evaluate HR120®, HR214®, HR230®, ORNL-modified stainless steels, FeCrAlY alloys and alloy 625.Tests in progress to evaluate HR120®, HR214®, HR230®, ORNL-modified stainless steels, FeCrAlY alloys and alloy 625. Effect of intermittent operation on durability of candidate materialsEffect of intermittent operation on durability of candidate materials Summary, Current and Future Work (cont.)

45. O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI-2004. Page 45 of 45