ULTRA-HIGH TEMPERATURE THERMAL BARRIER COATINGS Maurice Gell, Eric Jordan, Jeffrey Roth, Rishi Kumar University of Connecticut

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DOE STTR Phase II Grant # DE-SC0007544 DOE UTSR 2014 Presentation

Jiwen Wang, Balky Nair HiFunda LLC

SPPS TBCs: Presentation Outline • Background Processing, Microstructure & Properties

• SPPS YAG Thermal Barrier Coatings Benefits Processing & Microstructure Engine Critical Properties Industry Collaboration

• Summary & Conclusions

Liquid reservoir

Plasma gun Droplets Coating Substrate

Temperature control unit

Solution Precursor Plasma Spray (SPPS) Process

A B

Liquid injector

Solution Precursors

• A, B or A+B

• Multiple composition

Solution Precursor Plasma Spray: Unique Microstructural Features

100 μm

1 μm

Through-thickness vertical cracks

Varied nano/micro-scale porosity: 0~40%

Splat diameter < 2 μm Splat thickness < 1 μm Splat area is 1/2500 of that in APS TBCs

Layered porosity: inter-pass boundaries.

SPPS YAG TBCs: Project Objectives

• Develop a Higher Temperature (+200oC), Lower Thermal Conductivity Thermal Barrier Coating Using Yttrium Alumina Garnet (YAG) and the Solution Precursor Plasma Spray Process (SPPS)

• Demonstrate That YAG’s Greater Thermal Expansion Mismatch Strains Can be Overcome By The Strain-Tolerant Microstructure of SPPS TBCs

Anticipated Benefits • A New TBC That Can Tolerate Surface

Temperatures of 1500oC Can Be Game-Changing For the Gas Turbine Industry Due to Higher Turbine Efficiencies and Lower Fuel Consumption

Processing & Microstructure

Yttria-Alumina Phase Diagram

M. Shojaie-Bahaabad et al, Ceramics Intl.,Vol 35, 2009

0

10000

20000

30000

40000

50000

60000

70000

80000

20 25 30 35 40 45 50 55 60 65 70

M: YAM P: YAP

M P

As-Sprayed SPPS YAG

0

20000

40000

60000

80000

100000

120000

140000

20 25 30 35 40 45 50 55 60 65 70

2θ (°)

Intensi

ty

As-Sprayed SPPS YAG with Excess Al3+ in precursor

• Predominantly YAG Phase with Minor Amounts of YAM and YAP

• Pure YAG phase

Stoichiometric YAG Deposited By SPPS Process

Inte

nsity

SPPS YAG TBC: Processing • Over 100 Plasma Spray Trials • Sulzer-Metco 9MB Plasma Torch • 42-45 KW Power • Aqueous Precusor: Yttrium Nitrate,

Aluminum Nitrate, Urea

• Key Processing Variables: Precusor Energetics, Cation Loading, Viscosity Stand-Off Distance Atomizing Pressure

SPPS YAG TBCs: Effect of Precursor Concentration

SPPS YAG 5 wt% urea, 1.375”, on SS.

SPPS YAG 5 wt% urea, 10% H2O dilution, 1.375”, on SS.

SPPS YAG 5 wt% urea, 20% H2O dilution, 1.375”, on SS.

SPPS YAG precursors without dilution

227 210

149

0

50

100

150

200

250

300

1.375" 1.44" 1.5"

Mic

rohard

ness (

HV

)

SPPS YAG precursors with 10% H2O dilution

450

327

218

0

100

200

300

400

500

600

1.375" 1.44" 1.5"

Mic

rohard

ness (

HV

)

SPPS YAG precursors with 20% H2O dilution

373 380

228

0

100

200

300

400

500

1.375" 1.44" 1.5"

Mic

rohard

ness (

HV

)

• Increased Precursor Dilution Produces Denser Harder TBCs

SD (cm) : 3.2 3.5 3.6 4.1

6/27/2013 spray trials, 10 psi atomizing pressure

382

290226

161

0

100

200

300

400

500

06272013AA 06272013AB 06272013AC 06272013AD

Microh

ardnes

s (HV)

SPPS YAG TBCs: Stand-Off Distance

• Decreased Stand-off Distance Increase Plasma and Substrate Temperature; Produces Denser, Harder YAG TBCs

YAG, different atomizing pressure, SD = 1.44"

145

273

572

0100200300400500600700800900

15 psi 10 psi 5 psi

Microh

ardnes

s (HV

)

SPPS YAG TBCs: Atomizing Pressure

• Reduced Atomizing Pressure Increases Plasma Temperature, Droplet Penetration and TBC Hardness

Engine-Critical Properties

SPPS YAG TBCs: Standard Microstructure --Used for Engine-Critical Properties Tests--

SPPS YAG

APS YSZ

Bond Coat

Superalloy

• Vickers Hardness: 200-400 • Porosity: 15-20%

SPPS YAG 1600ºC 100h

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20 30 40 50 60 702θ (º)

Intensit

y

SPPS YAG TBCs: Phase Stability

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20 25 30 35 40 45 50 55 60 65 70

• SPPS YAG TBCs Are Phase Stable To At Least 1600oC

M: YAM P: YAP M

P

SPPS YAG 1500°C 100h

0

10000

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70000

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20 25 30 35 40 45 50 55 60 65 70

2 Theta (°C)

Intensit

y

M: YAM P: YAP

M P

1500ºC 100 hr

As-sprayed SPPS YAG

M P

1600ºC 100 hr M: YAM P: YAP

As-sprayed 1500ºC 100h 1600ºC 100h

SPPS YAG TBCs: Sintering Resistance

HV = 324±122 HV = 380±185 HV = 378±139

Sintering Effects Are Small Up to 1600oC

0

10

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1100 1150 1200 1250 1300 1350 1400 1450 1500 1550

Perc

ent I

ncre

ase

in th

erm

al c

ondu

ctiv

ity

Sintering Temperature ˚C

SPPS YSZ: 50 hrs SPPS YAG: 20 hrs

SPPS TBCs: Sintering & Thermal Conductivity

SPPS YSZ

SPPS YAG

• SPPS YAG TBCs More Sinter Resistant Than SPPS and APS YSZ

CMAS Reactivity Study: YSZ & YAG Powders of YSZ, YAG, 50:50 w/o YSZ & CMAS, 50:50 w/o YAG & CMAS Prepared • Powder Size: YAG 2-5 microns, YSZ 50 microns

• CMAS Powder: Industry Standard Composition,

1170oC Melting Temperature • Powders Exposed For 24 hours at 1100o to 1500oC • X-Ray Diffraction, SEM and EDAX Evaluations

Being Conducted

G: YAG

1500 ◌֯C 1400 ◌֯C 1300 ◌֯C 1200 ◌֯C 1100 ◌֯C

1500 °C

Phase Stability: 50:50 w/o YAG/CMAS Powder

• YAG Phase Stable To 1500oC In Presence of CMAS

SPPS YAG TBCs: Thermal Cycle Life vs Hardness

MAX

• SPPS Strain-Tolerant Microstructure Overcomes Higher Thermal Expansion Mismatch Stresses

MIN

AVERAGE

SPPS YAG TBCs: Erosion Rate vs Hardness (Tests Performed at Penn State Univ. By Dr. D Wolfe)

90º, 80 m/s

y = 0.6x + 0.0022

y = 0.39x + 0.0005

y = 0.23x + 0.0004

y = 0.175x + 0.00040

0.0010.0020.0030.0040.0050.0060.0070.0080.0090.01

0 0.002 0.004 0.006 0.008 0.01 0.012

Erodent Feed (kg)

Coa

ting

Mas

s Lo

ss (g

)

APS YSZ Baseline

SPPS YAG #9, 230 VHNSPPS YAG #8, 290 VHN

SPPS YAG #11, 500 VHN

90º, 80 m/s

0.00.10.20.30.40.50.60.70.80.91.0

APS YSZ Baseline SPPS YAG, #9, 230VHN

SPPS YAG, #8, 290VHN

SPPS YAG, #11, 500VHN

Coa

ting

Loss

Rat

e (m

m/k

g)

YSZ

YAG

hardness

SPPS YAG TBCs: Erosion Rate vs Hardness (Tests Performed at Penn State Univ. By Dr. D Wolfe)

SPPS YAG TBCs: Erosion Rate vs Hardness -30º Impingement-

(Tests Performed at Penn State Univ. By Dr. D Wolfe)

• SPPS YAG Has Superior Erosion Resistance To APS YSZ In Both 30º 90º Impingement Erosion Tests.

Erosion Test 30º impingement, 100 m/s

0

0.1

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0.5

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APS YSZ Baseline SPPS YAG 230 VHN SPPS YAG 290 VHN

Eros

ion

Rate

(g/k

g)

Erosion Test 30º Impingement, 100 m/s

0

0.2

0.4

0.6

0.8

1

1.2

APS YSZ Baseline SPPS YAG 230 VHN SPPS YAG 290 VHN

Coat

ing

Loss

Rat

e (m

m/k

g)

0

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0.8

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1.6

1.8

0 200 400 600 800 1000 1200

The

rmal

Con

duct

ivity

W/m

-K

Temperature ◌֯ C

Experimental Data Using LaserFlash

Extrapolation Using Data ofPadture and Klemens For DenseYAG

Thermal Conductivity of SPPS YAG TBCs

• SPPS YAG TBC Th. Conductivity Estimated To Be Lower Than APS YSZ At Elevated Temperatures

APS YSZ

HV= 324±60

SPPS YAG TBCs with IPBs

• Further Reductions in Thermal Conductivity Possible With IPBs & Small Compositional Modifications

Industry Partners

Engine Manufacturers • Solar Turbines • Siemens Energy • Pratt & Whitney

TBC Coating/Equipment Manufacturers • Praxair • Progressive Surface

Industry Partner Coordination

• Solar and Siemens Provided Baseline and Bond Coated Superalloy Specimens Used In Program

• Solar and Siemens Supplied Specimens For SPPS YAG TBC Coating For Their Internal Evaluations

• Technology Transfer Initiated With Praxair & Progressive Engineering Teams Visiting UConn For Full-Day Briefings

• Praxair & Progressive Will Demonstrate Production Process & Economics For SPPS YAG TBCs

Solar Turbines Demonstration Component --Fuel Nozzle Igniter--

• Coordination Meeting Held with Praxair, Solar & UConn, 8-11-14

Summary & Conclusions-I • SPPS YAG TBCs Show Potential For >1500oC

Operation Based On Phase Stability, Sinter and CMAS Resistance

• This Represents A >200oC Advantage Over APS YSZ • Durability of SPPS YAG TBCs Shown To Be Equal

Or Greater Than APS YSZ In Thermal Cycle and Erosion Tests

• Initial Measurements Indicate SPPS YAG TBC Thermal Conductivity of 0.7 Watt/moK at 1000oC (40% reduction compared to APS YSZ)

Summary & Conclusions-II • Engine Manufacturers Continue To Show Strong

Interest In SPPS YAG TBCs; Will Conduct In-House Testing

• Technology Transfer Being Conducted With TBC Coating Suppliers; They Will Conduct Demonstration Trials and Provide Process Economics

• SPPS YAG Continues to Show Strong Promise As Higher Temperature, Sinter-Resistant, Durable TBC

Acknowledgements

• Patcharin Burke, DOE Program Manager, DOE STTR Phase I & II Programs on SPPS YAG TBCs • Our Industrial Partners: Solar Turbines, Siemens

Energy, Pratt & Whitney, Praxair and Progressive Surface