O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI 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 ASME Turbo Expo Vienna, Austria June 16, 2004

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI Page 20 of 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

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

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

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

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

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

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

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

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

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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI Page 30 of mm 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)

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

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

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

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

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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI Page 36 of 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)

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

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

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

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

O AK R IDGE N ATIONAL L ABORATORY U. S. D EPARTMENT OF E NERGY Lara-Curzio et al. IGTI Page 41 of 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.)

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

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

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

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