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John Shingledecker, Ph.D.Sr. Program Manger, EPRI Cross Sector TechnologiesDan Purdy, Cara Libby (EPRI)Jack deBarbadillo, Brian Baker (SMC)

Solar Energy Technologies Office (SETO) CSP Program Summit 2019: Oakland, CA – March 19, 2019

Improving Economics of Generation 3 CSP System Components Through Fabrication and Application of High Temperature Nickel-based AlloysDE-EE0008367 (DOE SETO: GEN3 CSP SYSTEMS)

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Unanticipated materials challenges in first-of-a-kind applications and demonstrations in power generation

Materials Selection &Environmental Effects

Fabrication challenges

Materials research during Design and continuing through Demonstration reduces overall project risk

Codes, Standards, and Specifications

New Environments New Materials

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40

60

80

100

300

500

550 600 650 700 750 800

1100 1200 1300 1400

6

8

10

30

50

70

Stre

ss (M

Pa)

Average Temperature for Rupture in 100,000 hours (oC)

9-12Cr Creep-Strength Enhanced Ferritic Steels (Gr. 91, 92, 122)

Nickel-BasedAlloys

Std. 617CCA617

Inconel 740

Haynes 230

Advanced Austenitic Alloys (Super 304H, 347HFG, NF709, etc.)

Haynes 282

Average Temperature for Rupture in 100,000 hours (oF)

Stre

ss (k

si)

Materials Selection for Gen 3 CSP Goal: >715oCHigh Temperature Strength, Corrosion Resistance, Ductility, Fatigue, etc. = Age-HardenableNickel-Based Alloys will be utilized

°

/740H

§ Current Gen 2 Materials (limited solid solution alloys) are not governed by creep§ Time dependent (creep) behavior must be considered for Gen 3

Increased creep strength

= Higher allowable

stress à

enables thinner walls =

lower cost, more cyclic flexibility

Relative Pipe Thickness at 700°C per ASME Allowable Stress

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Nickel-Based Materials will be needed for all pathways

R&D GAPS

§ Low-cost manufacture

§ Data for Codes and

Standards

§ Fabrication/Welding

Trials

§ Gen 3 Environments

§ Potential damage

interactions: Creep-

fatigue, TMF, etc.

Product Forms:

§ Thin-wall tubing

(receivers, HX)

§ Large diameter pipe

(piping, downcomers)

§ Thin sheets and plates

(HXs)

§ Forgings/castings

(valves)

§ Welded structures

(headers, HX, piping)

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Research Goals:

§ Enable reduced Nickel-based alloy cost through– Materials Selection

§ Use of higher-strength alloys to minimize overall material usage§ 740H up to 50% less expensive than 230 for pressure boundary components

– Innovative manufacturing§ Rolled & welded tubing up

to 30% less expensive compared to seamless

§ Challenges (some)– Processing of new alloy grade– Weld structure and performance– Code acceptance

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Project Organization & Team – Key Areas of Progress § Task 1: Project Management - EPRI§ Task 2: Collaboration with Gen 3 CSP Teams & Code Interactions – EPRI

– Materials for testing, test conditions, specific design and component requirements – Engage codes and standards to ensure testing will address current deficiencies

§ Task 3: Manufacturing – Special Metals (and partners)– Baseline materials– Welded tube (thin wall)– Welded pipe (Large diameter)– Subcomponent manufacture (bending, welding)– Techno-economics (enable cost estimates and savings for design teams)

§ Task 4: High-Temperature Mechanical Testing & Data Analysis – EPRI– Tensile/Fatigue (time independent)– Creep (time dependent): determination of weld strength reduction– Pressurized creep of welded tubing – Unique to CSP receivers to gain code acceptance

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Tube Processing

Primary Melt + Remelt(VIM + ESR)

Cold roll to sheet coil,

anneal, pickle, and

slit

Cut Multsand Extrude

Cold Draw or Pilger

Anneal, Age, & Pickle

Final Straighten & Test Final Product

Forge to Tube

Round

Hot roll slab ingot to hot

band

Weld Tube

In-line / Off-line Anneal

and Age (if

required)

Test Final Product

Redraw, Anneal,

and Age (if Required)

Test Final

Product

Seamless Tube Production

Welded Tube Production

x4-6

Multiple steps: High energy use, lower yield

Images Courtesy: RathGibson Welded Tube Production

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Successful Welded Tube Production: Inconel® Alloy 740H®

§ Two successful trials:– Passed flattening tests– Passed non-destructive

evaluation requirements (eddy current) – no cracks or discontinuities

Coil Weight kg (lbs) Coil Thickness mm(in) Coil Width mm(in) Produced Tube Diameter mm(in)

ASTM Grain Size

Trial 1 112 (247) 1.65 (0.065) 76.7 (3.02) 25.4 (1) 7.5Trial 2 230 (508) 1.65 (0.065) 157 (6.19) 50.8 (2) 7.5

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Tensile Test Results

§ Yield and Tensile Strength of Mill Annealed Tubes was equivalent to starting coil stock– After aging, all tubes met ASME minimum criteria

§ Tensile Ductility (Elongation)– Mill Annealed tube & aged tubes > Coil– All materials exceed ASME Min Requirement

§ Pressurized room temperature burst test à failures outside of weld

Coil-

MA,

47.0

Coil-

MA+

Age,

30.

3

T1-M

A, 55

.0

T1-M

A, 54

.0

T1-F

A, 5

0.0

T1-FA

, 60.

0

T1-F

A+Ag

e, 34

.0

T1-F

A+Ag

e, 37

.0

T2-M

A, 5

6.0

T2-M

A, 5

6.0

T2-F

A+Ag

e, 32

.5

T2-F

A+Ag

e, 44

.0

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

Elon

gatio

n (%

)

ASME Min. (Aged)

Weld Seam

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Key next steps for tubing§ Room temperature properties ≠ high-

temperature behavior§ How will these tubes perform at Gen 3 CSP

Conditions (~700oC)?– Creep Considerations:

§ Processing (heat-treatment)§ Grain Size§ Weldments

– Fatigue

10 100 1000 10000 100000 100000010

100

1000

10000

100000

1000000 Grain Size < 100µm Grain Size > 100µm

Pred

icte

d R

uptu

re L

ife (h

rs) -

eq.

1

Rupture Life (hrs)

Slope = 0.93

+/- factor of 2

Open Symbols = Ongoing Test

Research on alloy 740H shows grain-size effect on long-term creep in typical wrought product with lower-

scatter band (weaker) properties when grain size is finer than ASTM 3.5

After Shingledecker, et al. 2013

EPRI Facility for Pressurized Creep Testing of CSP Thin-walled tubes

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Summary

§ Age-hardenable nickel-based alloys

are key candidates for Gen 3 CSP Systems

§ Reduced alloy (product form) cost through advanced manufacturing is needed

to improve overall economics

§ Ongoing research to evaluate Inconel® Alloy 740H®

– Production of: Welded tube, welded pipe, CSP specific processes

– Long-term data: Creep of welds, pressurized creep, low cycle fatigue

– Validate economic assumptions

– Gain code acceptance for new processes

Research to date on welded tubing shows promising results

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