Additive Manufacturing of 316L Stainless Steel for Nuclear · 2016-07-29 · Additive Manufacturing...

Additive Manufacturing of 316L Stainless Steel for Nuclear

EPRI LWR Material Reliability, Chicago IL, August 2016

Myles Connor, Fran Bolger and Ron Horn

GE-Hitachi Nuclear Energy

Xiaoyuan Lou, Peter L. Andresen and

Evan Dolley

GE Global Research

2GEH/GRC 316L Additive

7/27/2016

Topics of Discussion

• Additive Manufacturing Overview

• Why Additive Manufacturing

• Material Properties

– Focus on 316L

Objective: GEH Additive Manufacturing progress.

Feedback, insights, questions, etc…

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Additive (3D Printing) Process

Post Processing (HIP, Heat Treat, Machining, etc.)

Direct Material Laser Melting (DMLM)

Ref: UTEP

Ref. Within Labs, UK

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Value of Additive/3D Metal Printing

Speed of Delivery: Condensed supply chain enables quick response to emergent needs

• No tooling required: fast turnaround time

Design for Performance: Fewer manufacturing limitations allow new designs

• Design-driven manufacturing as opposed to manufacturing-constrained design

Equivalency to Wrought Properties

Enhanced chemistry control: Powder atomization Low Cobalt

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When to Apply Additive• Functional prototypes

• Design for performance enhancement where conventional manufacturing is difficult or not possible

• Weight reduction

• Geometric features enable enhancements

• Cost reduction for complex multi-component assemblies

• High-value products for low volume, specialized or unique components

• Customized designs

AM316L Material Properties

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Summary of Tests To Date

Microstructure Characterization

Tensile Properties

Charpy Fracture Toughness

Stress Corrosion Cracking

AM316L Stainless Steel for Nuclear Environment

Microstructure Characterization1) As-built2) Stress relief3) Solution annealing4) HIP+Annealing

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Top View 2 Top View 2

Cross-section View 4

1

2

3 4

Building

Direction

Stress ReliefAs-built

Cross-section View 4

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Top View 2 Top View 2

Cross-section View 2 Cross-section View 4

1

2

3 4

Building

Direction

Anneal HIP+Anneal

Good density, low porosity

100% Austenitic

Grain size 5 or finer

Microstructure similar to wrought

Tensile and Charpy Impact Test

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Tensile and Charpy Specimen Orientation

Specimens were oriented along vertical, 0 degree

horizontal, and 45 degree horizontal

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Tensile and Charpy Properties

Good ductility (>40%El)

Good yield strength

20

40

60

80

100

120

140DMLS 316L (Vertical)DMLS 316L (Horizontal)Wrought 316LNitronic 50

UTS 0.2% YS Elongation

Stre

ss, k

si o

r Elo

ngat

ion,

%

HIP+Anneal

0

20

40

60

80

100

120

140

Vertical 0 degree 45 degree

Orientation

Toug

hnes

s (ft-

lb)

HIP+Anneal

Typical charpy toughness for annealed

316L @RT: 65~100 ft-lb

AM 316L mechanical properties similar to Wrought 316L

Stress Corrosion Cracking

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20%

Cold Work

Specimen Testing Orientation

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SCC Crack Growth Rate

2ppm O2 (mm/s) 63ppb H2 (mm/s)

HIP+SA, Z-X

Orientation

3.4 X 10-7 1.1 X 10-8

Wrought ~3 X 10-7 ~1 X 10-8

SCC crack growth rate:AM 316L ≤ wrought 316L

25ksi√in, 20%CW, 20 ppb SO42-

Irradiated Properties

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Irradiated Property Strategy

Strong technical basis for wrought 316L similarity

NEET project lead by Dr. Lou (GRC), ORNL, Dr. Was (Univ. Michigan)

• Proton irradiation of DMLM 316L benchmarked against wrought 316L

• Alternate processing property investigation

NSUF ATR irradiation and testing at INL, lead by GEH and INL

Commercial nuclear irradiation of DMLM 316L component and PIE testing

Inspection and AM Standards

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Inspection• Ultrasonic Test (UT) and Radiography Test (RT) similar to

wrought 316L

• Complex geometry = complex inspection

• Only simplest parts can be UT inspected

• Computed Tomography (CT) scan can be used for dimensional validation

• Produce test specimens as part of each build

Cut up, SEM, and mechanical testing of selected complete parts

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Standards AcceptanceASTM draft spec in review

• WK48732- New Standard Additive Manufacturing Stainless Steel Alloy (UNS S31603) with Powder Bed Fusion

• GEH has seat on ASTM F42 committee

– GE Aviation and GE O&G also active on F42 and SAE (aviation)

– GEH also sitting in AWS D20 committee

BWRVIP-84 requirements

Conclusions

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For all the tested material properties (porosity, tensile, charpy, corrosionfatigue, SCC),

AM 316L stainless steel performs similar or better than wrought 316Lstainless steel.

Conclusions

Continue building material property database

• Fatigue, high temp tensile, irradiated, etc.

Qualification/inspection techniques

Material acceptance (ASTM/ASME, BWRVIP, etc.)

Reactor applications

Future Work