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Superalloys
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Liburdi Engineering Limited
Liburdi Engineering Ltd Liburdi Turbine Services Inc Liburdi Automation Inc Liburdi Dimetrics Corp
Dundas, Ontario Davidson, North Carolina St Petersburg, Russia
Liburdi Group of Companies
Dundas, Ontario Canada
Davidson, NC, USA
2Turbomachinery
Conference Houston, TX September 13-17, 2009
PowerGen
Conference Las Vegas, NV December 7-10, 2009
3Superalloys
4Typical Gas Turbine Component Materials
Turbine Stationary300SS, 400SSN-155, M509, HS-188,L605X-40, X-45, FSX-414, ECY-768IN738, R80, GTD222, GTD444
Turbine Rotating
Waspalloy, U-500, U520, U700, U710, U720, INX750, IN738, Rene80, GTD111, M247, M002,PWA1483, CMSX4, ReneN5
Piping, tubing, valves, etc.Steel
Compressor CasingsGrey Cast IronCarbon Steel
Turbine ShellsDuctile Cast Iron
Compressor Wheels/DisksNi-Cr-MO-VForging
Turbine Wheels/DiscsNi-Cr-MO-V Steel Cr-Mo-V Forging12Cr StainlessDiscalloyA286IN718
CompressorSome 300SS403, 410, 422, 450 StainlessIN718Ti64 titanium
Combustor300SSHastelloy-X, RA-33 L-605IN-600, IN-617Nimonic 75, Nimonic 263Haynes 230
5SUPERALLOYS
1. Definition and Properties2. Strengthening Mechanisms
- Solid Solution Hardening- Precipitation Hardening and Heat Treatment- Grain Boundary Hardening and Control
3. Surface Stability: Oxidation and Hot Corrosion
6SUPERALLOY DEFINITION
Superalloys have remarkable mechanical strength at high temperatures -- up to 80% of their incipient melting point.
Superalloys exhibit the highest surface stability in air at elevated temperatures of engineering alloys.
Superalloys are also exotic as they can contain up to 12 elements And they can have as many elements specifically excluded.
7ALLOY PROPERTIES
Metals and their alloys have varying strength andoxidation resistance (and cost)
Alloys used for Turbine Blades/Buckets
8MECHANICAL PROPERTIES
Fe/Ni-based superalloys are economical, high strength forging alloys for low and intermediate temperatures
Ni-based superalloys can withstand high creep stresses at intermediate and high temperatures
Co-based superalloy are castable, weldable, and useful at very high temperature and corrosive environments
9Compositions and Properties - Nickel Based Alloys
Sheet alloys like Hasteloy X have low Aluminum + Titanium content have excellent formability
Forged alloys like Udimet 520, Nimonic105, X750 have a moderate Aluminum + Titanium content, have good mechanical properties but are forgeable. Used for intermediate-temperature buckets.
Cast alloys like CMSX, GTD111, IN738, MM247 have a high Aluminum + Titanium content, have excellent mechanical properties at elevated temperature and are used for the highest temperature blades.
10
SUPERALLOY PROPERTIES
Excellent mechanical properties in the service temperature and stress range that gas turbine blades operate in, even after prolonged service
Excellent creep strength
Useful mechanical strength
Good fatigue and thermal fatigue properties
Adequate ductility and toughness (low crack growth rates)
Useful thermal expansion characteristics
Excellent resistance to oxidation and corrosion
Alloy additions form self-healing protective scales
Fabricability (forging, casting, welding, machining, coating)
11
SUPERALLOY DESIGN
Solvent can be cobalt, iron or nickel (usually a mixture of nickel and cobalt)
Oxidation protection provided by aluminum & chromium
Solutes, molybdenum, niobium, rhenium, tantalum, tungsten
Precipitation formers: aluminum, titanium, niobium
Grain strengtheners: carbon, hafnium, zirconium, boron
Tramp elements: silver, boron, silicon
12
Cast Nickel Based Alloy Compositions
Alloy Ni Cr Co Mo W Ta Cb Al Ti Fe Mn Hf C B Zr Others
Ni-Base Alloys
Alloy 713C 74 12.5 0.0 4.2 0.0 0.0 2.0 6.1 0.8 0.0 0.0 0.0 0.12 0.012 0.10
B-1900 64 8.0 10.0 6.0 0.0 4.0 0.0 6.0 1.0 0.0 0.0 0.0 0.10 0.015 0.10
C-1023 58 15.5 10.0 8.5 0.0 0.0 0.0 4.2 3.6 0.0 0.0 0.0 0.16 0.006 0.00
CMSX- 2 66 8.0 4.6 0.6 7.9 5.8 0.0 5.6 0.9 0.0 0.0 0.0 0.00 0.000 0.00
GTD-111 60 14.0 9.5 1.5 3.8 2.8 0.0 3.0 4.9 0.0 0.0 0.0 0.10 0.01 0.03
GTD-222 51 22.5 19.0 0.0 2.0 1.0 0.8 1.2 2.3 0..0 0.0 0.0 0.10 0.010 0.01
IN-100 60 10.0 15.0 3.0 0.0 0.0 0.0 5.5 4.7 0.0 0.0 0.0 0.18 0.014 0.06 1.0 V
IN-738LC 61 16.0 8.5 1.7 2.6 1.7 0.9 3.4 3.4 0.0 0.0 0.0 0.11 0.010 0.05
IN-939 48 22.5 19.9 0.0 2.0 1.4 1.0 1.9 3.7 0.0 0.0 0.0 0.15 0.009 0.09
IN-792 61 12.4 9.0 1.9 3.8 3.9 0.0 3.1 4.5 0.0 0.0 0.0 0.12 0.020 0.10
MarM-002 61 9.0 10.0 0.0 10 2.5 0.0 5.5 1.5 0.0 0.0 1.5 0.14 0.015 0.05
MarM-247 60 8.3 10.0 0.7 10 3.0 0.0 5.5 1.0 0.0 0.0 1.5 0.10 0.015 0.05
PWA-1483 61 12.8 9.0 1.9 3.8 4.0 0.0 3.6 4.0 0.0 0.0 0.0 0.07 0.0 0.0
Rene-N5 62 7.0 8.0 2.0 5.0 7.0 0.0 6.2 0.0 0.0 0.0 0.2 0.0 0.0 0.0 3.0 Re
13
PRECIPITATION STRENGTHENING
Superalloys are strengthened by carbide and gamma-prime () precipitates Substitution of aluminium for nickel in lattice results in phase of the
composition Ni3Al. Titanium and niobium can substitute for aluminium in The volume fraction of phase formed is a function of the hardener content
Increasingcreep
strength
Increasing volume
phase in Ni-based superalloy
14
Gamma Prime () Strengthening (cont.)
Cuboidal primary phase
Spherical secondary phase
15
PRECIPITATION STRENGTHENING
For a given volume of in nickel superalloy, maximum strength is developed at anoptimum precipitate size
Heat treatments are used to create the optimum precipitate size(s).
In reality, it is both the size and spacing between precipitates that is responsible for strength.
16
ALLOY HEAT TREATMENT
17
GRAIN BOUNDARY HARDENING: BY CARBIDES
MC carbides form at high temperature and precipitate throughout the matrix with little influence on strength
M23C6 or M6C particles form preferentially along grain boundaries during aging cycles and service exposure
The particles inhibit grain boundary sliding and add to strength however there is an optimum carbon addition level (0.1-0.2%) beyond which properties degrade
Grain boundary carbide particles in IN939 alloy
18
GRAIN SIZE STRENGTHENING
Fine grain sizes provide high tensile and fatigue strengths, BUT lower creep strengths result
Fatigue of IN718, IN901 and Waspaloy
Creep of IN738
19
GRAIN ORIENTATION ADVANCED CASTING TECHNOLOGIES
Equiaxed
Directionally Single Cry
stal (SC)(polycrystalline] Solidified (DS) [monocrystalline]
20
GRAIN ORIENTATION
Grain boundaries are the weakest-link in polycrystalline superalloy behaviour. If the stresses are highly uniaxial, and the service temperature is very high, significant improvements can be made through controlling grain-boundary orientation or eliminating them altogether during casting.
equiaxed columnar single crystalPolycrystal DS Directional SX
Solidification
21
TRENDS IN TURBINE BLADE ALLOYS and GRAIN ORIENTATION
22
COMPARATIVE DS, SX AND POLYCRYSTAL PROPERTIES
23
SURFACE STABILITY: OXIDATION AND HOT CORROSION Engineering alloys are not stainless, they all form oxide
scales in air. Scale formation rate is a function of temperature and
environment Some native scales are not protective (Fe, Mg) Some native scales are protective (Al, Cr, Ti) Alloying enough protective element into non-
protective can impart protection (ie: 12+% chromium into iron makes stainless steel)
Protective elements can be added to base alloy or clad over as a coating
24
NATIVE OXIDE SCALES HIERARCHY FOR SUPERALLOYS AND COATINGS
Al2O3 Very Protective NiAl2O4 NiTa2O6
CrTaO4 Cr2O3 Protective
NiCr2 O4 CoCr2O4 NiTiO3
NiO Not helpfulCoOTiO2W, Mo, refractory oxides
25
Advanced Design Turbine Blades (Industrial Frame Engines Now Using Aero Cooling, Aero Alloys)
Manufacturer/Model First Stage Turbine Blade / Bucket
Alstom-GT24/26Single Crystal, Ni-BaseMatrix CooledVPS-NiCoCrAlY with APS-TBC
GE-Frame 7FADirectionally Solidified, GTD111Serpentine Cooling w/TurbulatorsLPPS-CoCrAlY/DVC-TBC, Plus Internal Coatings
Siemens V84.3ASingle Crystal PWA1480VPS-CoNiCrAlYSi
Plus Internal Coatings
Siemens- Westinghouse 501G
Directionally Solidified CM247Serpentine, Film & Showerhead VPS-NiCoCrAlY/TBC
GE LM2500+RR RB211 GT
Single Crystal N5 (GE), CMX4 (RR)Serpentine, Film & Showerhead PT Al Coating plus internal Coating (LM2500+)
Slide Number 1Slide Number 2SuperalloysTypical Gas Turbine Component MaterialsSUPERALLOYSSUPERALLOY DEFINITIONALLOY PROPERTIESMECHANICAL PROPERTIESCompositions and Properties - Nickel Based AlloysSUPERALLOY PROPERTIESSUPERALLOY DESIGNCast Nickel Based Alloy CompositionsPRECIPITATION STRENGTHENINGGamma Prime () Strengthening (cont.)PRECIPITATION STRENGTHENINGALLOY HEAT TREATMENTGRAIN BOUNDARY HARDENING:BY CARBIDESGRAIN SIZE STRENGTHENINGGRAIN ORIENTATION ADVANCED CASTING TECHNOLOGIESGRAIN ORIENTATIONSlide Number 21COMPARATIVE DS, SX AND POLYCRYSTAL PROPERTIESSURFACE STABILITY:OXIDATION AND HOT CORROSIONNATIVE OXIDE SCALES HIERARCHY FOR SUPERALLOYS AND COATINGSAdvanced Design Turbine Blades(Industrial Frame Engines Now Using Aero Cooling, Aero Alloys)