8th Charles Parsons Turbine Conference

Transcription

1 U.S. Department of Energy/Fossil Energy Materials Research Development for Power and Steam Turbines 8th Charles Parsons Turbine Conference Robert Romanosky Advanced Research Technology Manager September 5-8, th Charles Parsons Turbine Conference (September 5-8, 2011)

2 Power Turbine Program Goals Improving IGCC Performance with CCS Develop advanced coal power systems capable of 45-50% efficiency, and offer near zero emissions with multi-product production (electricity and hydrogen) 2015 Contribution to Goals H 2 turbine w/ 3 5 % pts. improvement in CC H 2 Turbine IGCC with 2 ppm NO x (@15 % O 2 ) 2020 Commercial Demonstration of Advanced H2 Turbine in Coal Based IGCC with CCS 2

3 Overview of the Advanced Power Turbine Materials Program Key research Areas Novel coatings for unique Thermal Barrier Coating (TBC) bond coat architecture Bond coats and rare-earth element effects Novel bond coats systems and the development of diffusional barrier coatings Photo courtesy of N. Padture 3

4 Novel TBCs Novel TBCs are required for: Combustors Airfoils Shrouds APS or HVOF Photo courtesy of S. Sampath Stonybrook Efforts underway to: Develop reduced-cost diffusion bond coat (BC) systems Develop diffusion barrier coating (DBC) systems Investigate multiple compositions. Conduct applied microstructural research with a science focus. 4

5 Novel TBCs - Composition TBC compositions of interest include: 1. Stabilized Zirconia lack thermal stability above 1400 C High-purity important 2. La- & Gd- Zirconate Pyrochlores Resistant to ash deposition w/ high T stability Less erosion resistant TGO interactions suggest multi-layer structure required 3. Stabilized Hafnia High melting point suggests good thermal stability Cost could be an issue Additional toughness for Foreign Object Damage resistance desirable 5

6 Novel TBCs - Microstructure TBC Microstructural Features Thermal and mechanical properties heavily influenced by microstructural features Stonybrook developing process maps to correlate processing conditions to thermal conductivity & elastic modulus Fundamental science improves component reliability by increasing partto-part consistency. Figures courtesy of S. Sampath Stonybrook 6

7 Bond Coats Oxidation-resistant bond coats needed to protect expensive substrates. Thermally-grown oxides must be adherent Focused on MCrAlY coatings applied via APS or HVOF Efforts Underway Effects of rare-earths in CMSX-4 superalloys were quantified via thermal cycling at 1100 C MCrAlY bond coatings with Hf and Si additions showed longer lifetimes compared to MCrAlY La additions are also being studied Studies being conducted on moisture effects on TBC coatings 7

8 Thermal Cycle Lifetimes Bond Coats Moisture Effects of moisture being quantified at lab scale Pt-based diffusion and aluminides complete MCrAlY coatings underway Unclear if issue or not Bond Coat Roughness Evidence for mechanism building Rumpling appears to play some role in some cases Not clear if mechanism is same in MCrAlY coatings Working on mitigation strategy Figures courtesy of B. Pint ORNL 8

9 Plant Thermal Efficiency (%) Advanced Ultra Supercritical Power Plant Operating up to 5,000 psi and 1,400 F psi 3500 psi Ultrasupercritical (USC) DOE goal for higher efficiency and much lower emissions, materials capable of: 760 C (1400 F) 42 Birks and Ruth 5,000 psi Oxygen firing Temperature ( F) Plant efficiency can be improved to Ultrasupercritical (USC) CO 2 Emissions are reduced by 15 to 22% Lower balance of plant cost means smaller coal handling and pollution controls for the same net plant output Meeting these targets requires: The use of new materials Novel uses of existing materials 9

10 A-USC Steam Turbine Materials Program Research Areas Materials for non-welded Rotors, Buckets and Bolting Coating for Steam Oxidation and Solid Particle Erosion Resistance Energy Erosion Resistant Coatings Study for USC Steam Turbine 760 C Department of Energy Initiative Process Development for Welded Rotors Cast Ni-based Superalloys for Turbine Casing Application 10

11 Turbine Material Candidate List Assessed mechanical and other physical properties, processing and manufacturing capability of 25 candidate alloys Five alloys were identified as candidate materials for a rotor forging: 1. Nimonic 105 (N105) 2. Haynes 282 (H282) 3. Udimet 720Li (U720Li) (Not Tested) 4. Inconel 740 (IN740) 5. Waspaloy 11

12 Temperature Capability (Deg F) Initial Material Selection for A-USC Turbine Temperature Capability for HP/IP Rotor Alloys Best Candidates: Nimonic 105, Haynes 282, Temperature and Waspalloy Capability - (not HP/IP shown) Rotor Alloys HP Typical IP Typical CrMoV Cost E IN625HT IN718 U720Li IN901 IN740 H282 N ,000 10,000 15,000 20,000 25,000 30,000 Operating Stress (psi) 760 C 12

13 Large Forgings Research Requires an Understanding of Microstructure & Properties as a Function of Heat- Treatment 50 nm 50 nm Solution Annealed PA = SA C OV = PA C Studies on Haynes 282: Creep-rupture strength was relatively insensitive to heat-treatment Detailed microstructural studies on gamma prime precipitates after heattreatment and creep were conducted Both mechanical property data and microstructure studies suggest the alloy has a large processing window making it attractive for steam turbine forgings 13

14 Oxidation and Erosion Laboratory Screening Short- and Long-Term Steam oxidation testing of candidate nickel based alloys for A-USC steam turbine components and candidate coatings for SPE resistance. Screening tests in a thermo-gravimetric analyzer 10,000 hours in steam at atmospheric pressure and temperatures of 700, 760 and 800 C Substrate alloys Udimet 720LI, Waspaloy and 740 were the most resistant to steam oxidation Cross-sections of base metals after steam oxidation experiments CCA 617 Haynes 230 Haynes

15 Coatings Steam Oxidation Resistance (14 coatings tested) Stellite 6B, Tribaloy, T-400C and CrC-NiCr were the most resistant SPE Resistance Erosion testing on 12 coatings using the University of Cincinnati test rig. Silica sand and magnetite used as the erodent materials for this testing. A limited amount of testing was done with alumina as well. The top 4 coatings ranked according to their erosion rates and volume losses were: 1. Moly-Boride Cobalt Chromium 2. Zircoat 3. T400C (Tribaloy) 4. Conformaclad WC 15

16 Process Development for Welded Rotors I Assess the weldability of Nimonic 263, a typical precipitationstrengthened, wrought nickel-base alloy which is a candidate for highertemperature rotor applications Develop welding procedures for joining this alloy to Inconel 617 in thick sections. Assess the effect of long-term (10,000 hr) simulated service exposure at 725 C on the microstructure, hardness, tensile properties, and impact strength of the weld Results: There was little change in microstructure, hardness, or tensile properties of the thick-section weldment, but the impact strength was reduced in all microstructural zones of the weld. However, all zones had impact strengths sufficient to demonstrate adequate toughness, even after elevatedtemperature exposure 16

17 Process Development for Welded Rotors II The goal of this task was an electron beam welding feasibility study of Udimet 720Li to Haynes 282, and Haynes 282 to itself and to Inconel 617 welding trials were completed on simplified weld samples (small, flat samples) not entire rotors, as a feasibility study Weld process selection was electron beam welding due to weld penetration requirement, rigidity of post-weld component, base alloy selections, weld quality requirements and current available technologies which could accommodate the production size of the component. The final results of all three alloy combinations were favorable. It can be concluded that all three weld combinations attained favorable weld results via visual, ultrasonic immersion testing and metallographic evaluations on small, flat samples. Additional work is required for a full assessment of manufacturability and fitness for service. 17

18 Welded Rotor Concept Evaluation Various joint configurations were successfully demonstrated Alloy 263 to 617 Haynes 282 to Udimet 720Li Evaluation: tensile, creep-rupture, toughness, and aging response Udimet 720Li Trials Aging & Toughness Studies Trial I Trial II Trial III 18

19 Materials for Non-Welded Rotors, Buckets, and Bolting Identify suitable materials that can be made into a single piece rotor or the highest temperature portion of a mechanically coupled rotor, buckets and bolting operating in a steam turbine with an inlet temperature of 760 C (1400 F) Evaluation based on Rupture Strength, Yield Strength, Fracture Toughness Materials selected: Alloys 617 and 625 for turbine castings and rotor forgings Alloys 718 and 263 for rotor forgings Alloys 105 and Waspaloy for blades and bolting 19

20 Castings Casting are required for turbine shells, valve bodies, tees, etc. Traditionally air cast Screening study conducted by Oak Ridge National Laboratory and the National Energy Technology Laboratory Lab-scale castings, mechanical properties, microstructure, and heat-treatment were examined Cast Nimonic 105 and HR282 have much better creep resistance and rupture ductility than IN 740. Alloy 263 has much better strength and creep-rupture resistance than the other solid-solution cast alloys 20

21 Steam Turbine Phase II Work Tasks Using Selected Materials from Phase I: Rotor/Disc Testing (near full-size forgings) Blade/Airfoil Alloy Testing Valve Internals Alloy Testing Rotor Alloy Welding and Characterization Cast Casing Alloy Testing Casing Welding and Repair 21

22 Contact Information Robert R. Romanosky NETL Richard Dennis Patricia Rawls Office of Fossil Energy 22