am part integrity: the ndt in-process and post-build...

AM part integrity: the NDT in-process

and post-build perspectives

Ben Dutton

EIS Seminar - AM

18-06-2019

MTC, Coventry

Contents

In-process NDT

Post built NDT

Post built Metrology

NDT standard

AFRCAdvanced Forming Research Centre

CPICentre for Process Innovation

NAMRCNuclear Advanced ManufacturingResearch Centre

AMRCAdvanced Manufacturing Research Centre

MTCManufacturing Technology Centre

WMGWarwick Manufacturing Group

NCCThe National Composites Centre

MTC also hosts the European Space Agency (ESA) AM Benchmarking Centre since May 2017

HIGH VALUE MANUFACTURING CATAPULT

MTC has become the first ASTM AM Center of Excellence (CoE) in Europe since July 2018

MANUFACTRUING INNOVATION

Dimensional & surface Metrology and NDT

M&NDT: TECHNOLOGY COVERAGE HIGHLIGHTS

High-precision tactile instruments High-precision optical instruments Portable tactile instruments Portable optical Instruments

Tactile surface measurement Optical surface measurement Portable surface measurement Microscopes

3D Computed Tomography Computed Radiography

Portable NDT (phased array ultrasound, eddy current flexible array, x-ray backscatter and GPR)

Non-contact laser ultrasound inspection

Dimensional Metrology

Surface Metrology

Non-destructive Testing

In-process NDT

Potential advantages

• As other manufacturing processes, additive manufacturing (AM) inspection has typically relied on post-process/post build NDE, but due to AM’s geometrical complexity, surface finish, material density and in particularly large parts, ideally NDE would be better placed at an earlier stage.

• AM process has a unique advantage due to its build process: layer-by-layer or bead-by-bead, hence both process monitoring and inspection may be exploited.

• Current AM in-process monitoring relies mainly on surface measurements, potentially missing subsurface defects. Additionally AM processes are at high temperatures. NDE methods such as Laser Ultrasound Testing (LUT) have the potential to detect both surface and sub-surface defects making it ideal for AM.

In-process NDT

LUT on calibration and real Powder Bed AM samples

Courtesy AMAZE EU project

Calibration and real samples tested

• Calibration samples consisted of Ti64 cuboids with dimensions (10 x 10 x 30 mm) with Electric Discharge Machining (EDM) through holes (400 µm diameter) representing subsurface defects.

• AM part with process subsurface isolated 200 µm and 300 µm gas pores.

Why LUT

• LUT, being a non-contact ultrasound testing method, is capable to work at elevated temperatures of at around 1000 C, and the system at the MTC is capable to work on rough samples which are expected to be in AM process.

• Research based unit with capability for integration to industrial applications

• MTC has been working on projects showing LUT capability for some AM industrial applications.

In-process NDT

LUT on a DED AM Titanium sample with LOF defects

Capable to detect fusion irregularities between side by side and top and bottom beads.

Sample and scan details A-Scans B-ScansCourtesy AMAZE EU project

In-process NDT

LUT integrated demonstration

Courtesy AURORA IUK project

In-process NDT

LUT integrated demonstration

Courtesy AURORA IUK project

Video

LUT in-process inspection - MTC.mp4

In-process NDT

LUT detection of isolated bulk pores in laser powder DED

Courtesy OpenHybrid EU project

Scan

dir

ecti

on

15

mm

Rayleigh wave

Diameter: 0.270 mmDepth: 0.330 mm



XCT vertical slice

LUT B-scan

Sample picture

• LUT showing capability to detect isolated pores in a TiDED as built sample

Post built NDT Potential

Methods capability: selector tool output for a simple block with machined surface finish


Class Type Sub-type Including… Surf

ace

brea

king

crac

ks /

lack

-of-

fusi

on

Surf

ace

brea

king

void

s

Inte

rnal

cra

cks

/

lack

-of-

fusi

on /

laye

r def

ects

Isol

ated

/

clus

tere

d

poro

sity

Inte

rnal

voi

ds,

incl

. cro

ss-l

ayer

defe

cts

Incl

usio

ns

Trap

ped

pow

der

(Pow

der B

ed

Fusi

on o

nly)

Nea

r sur

face

mic

rost

ruct

ure

vari

atio

n

Sub-

surf

ace

mic

rost

ruct

ure

vari

atio

n

Nea

r sur

face

resi

dual

str

ess

Sub-

surf

ace

resi

dual

str

ess

Contact or near-contact (a i r-

coupled)

Single / twin / array probe,

Time of Fl ight Di ffraction

Immers ion

Vibration analysis Resonance testing

Acoustic pattern

recognition

SimpleAids such as l ighting /

boroscope etc.

Dye-penetrant Fluorescent / vis ible

Conventional , 2D

Fi lm / Computed / Real -

time / Digi ta l

Computed Tomography

2D (fan beam) / 3D (cone

beam) CT / Laminography

Diffraction

Flash

Laser

Electrically excited Induction-heated

Vibrationally excited Thermosonics

Eddy current Single / array probe

Magnetic particle

Barkhausen

Alternating Current Field

Measurement

Eletromagnetic-MechanicalElectromagnetic Acoustic

Transducer Ultrasound

Laser Ultrasound

Spatia l ly Resolved Acoustic

Spectroscopy

Shearography

Electronic speckle pattern

interferometry

Laser Speckle Photometry

Grazing Incidence

Ultrasound MicroscopyOptical-MechanicalMixed

Electromagnetic Magnetic field

Thermal

Optically excited

Radiographic X-ray

Optical / visible

light

Mechnical

Ultrasonic


The tool shows that commonly used NDE methods such as Contact/immersion UT and die penetrant for bulk and surface breaking defects respectively, would be capable.

Post built NDT PotentialMethods capability: selector tool output for a complex lattice structure and as built surface condition


The tool shows that the most appropriate NDT method for the majority of defects is X-ray computed tomography and resonance testing.

Class Type Sub-type Including… Surf

ace

brea

king

crac

ks /

lack

-of-

fusi

on

Surf

ace

brea

king

void

s

Inte

rnal

cra

cks

/

lack

-of-

fusi

on /

laye

r def

ects

Isol

ated

/

clus

tere

d

poro

sity

Inte

rnal

voi

ds,

incl

. cro

ss-l

ayer

defe

cts

Incl

usio

ns

Trap

ped

pow

der

(Pow

der B

ed

Fusi

on o

nly)

Nea

r sur

face

mic

rost

ruct

ure

vari

atio

n

Sub-

surf

ace

mic

rost

ruct

ure

vari

atio

n

Nea

r sur

face

resi

dual

str

ess

Sub-

surf

ace

resi

dual

str

ess

Contact or near-contact (a i r-

coupled)

Single / twin / array probe,

Time of Fl ight Di ffraction

Immers ion

Vibration analysis Resonance testing

Acoustic pattern

recognition

SimpleAids such as l ighting /

boroscope etc.

Dye-penetrant Fluorescent / vis ible

Conventional , 2D

Fi lm / Computed / Real -

time / Digi ta l

Computed Tomography

2D (fan beam) / 3D (cone

beam) CT / Laminography

Diffraction

Flash

Laser

Electrically excited Induction-heated

Vibrationally excited Thermosonics

Eddy current Single / array probe

Magnetic particle

Barkhausen

Alternating Current Field

Measurement

Eletromagnetic-MechanicalElectromagnetic Acoustic

Transducer Ultrasound

Laser Ultrasound

Spatia l ly Resolved Acoustic

Spectroscopy

Shearography

Electronic speckle pattern

interferometry

Laser Speckle Photometry

Grazing Incidence

Ultrasound MicroscopyOptical-MechanicalMixed

Electromagnetic Magnetic field

Thermal

Optically excited

Radiographic X-ray

Optical / visible

light

Mechnical

Ultrasonic


Post build NDT

Current method (XCT) limits of detection assessment

Microscope image of cut-up and polish sectionL-PBF of a calibration sample X-ray CT image (slice) using 225 kV XCT

system

• X-ray Computed Tomography

(XCT) and cut-ups comparison

where defects that are present in

both are circled in green and

defects that are present only on

cut-up are circled in red.

• The limits of detection, for this

particular sample and XCT

settings, which provided a voxel

resolution of 41 µm, is expected

to be at least twice the voxel

resolution (82 µm). No defects

were found at 82 µm, the closest

was 132 µm.


65.4 mm

Post build NDT

Emerging method non-linear resonance method assessment

Non-Linear

Resonance (NLR)

testing showing

identifiably different

responses for a

‘good’ and a ‘bad’

part (tests performed

by Theta Tech)

Corresponding non-linear responsesaPod 2 ‘good’ (top) and ‘bad’ (bottom) builds


Post build NDT

Emerging method, Process Compensated Resonance Testing (PCRT)

Courtesy of Vibrant for ISO TC 261 JG59, Additive manufacturing – General principles – Nondestructive evaluation of additive manufactured products, under development.

• PCRT has demonstrated capability to differentiate better between seeded (S1 & S2) and the non-seeded defects parts (S0).

Post build NDT

Automated hybrid NDT methods assessment

Courtesy RASCAL IUK project

• The robotic cell demonstrator was successful identifying the following defects in hinge brackets from the aerospace sector (validation was performed with X-ray CT):

Internal tight cracks via NLRExternal open cracks and notches via Thermography

• Capable to run and automatically indicate PASS/FAIL, generate a report and data can be accessed through the network.• The system will be used to demo at the MTC and/or other events.


Post-Processing: Geometrical effect from HIP on L-PBF

Build 1287 workflow: HIP only

Build plate bent inwards Build plate bent outwards



Post-Processing: Geometrical effect from Heat Treatment (HT) and part separation

Build 1289 workflow: HT and part separation

Build plate bent inwards Build plate bent outwards No part distortion



Post-Processing: Geometrical effect of Heat Treatment and HIP

Build 1377 workflow: Heat treatment and HIP

Build plate bent inwards Build plate bent outwards No part distortion No part distortion



Post-Processing: Geometrical effect of HIP

Defect before HIP Defect after HIP

Source: Brown, A., Jones, Z. Tilson, W., Classification, Effects, and Prevention of Build Defects in Powder-bed Fusion Printed Inconel 718, NASA Marshall Space Flight Center, 2016.

Defect morphology effect of HIPing: after HIP a defect becomes a crack like shape which may be more detrimental to the part integrity.

NDT Standard

ISO TC 261/ASTM F42 JG59 NP 52905

ISO/ASTM joint group activity led by MTC through British Standards Institute (BSI).

Ben Dutton, Technical Specialist at MTC is the convener.

This standard is to provide a best practice guide presenting NDT methods potential to detect defects which are not covered by current standards.

Post-built NDT

In-process NDT

Draft is under review.

Aim for final submission Sep. 2019.

MTC

Courtesy of ISO TC 261 JG59, ‘Additive Manufacturing — Non-Destructive Testing and Evaluation — Standard Guideline for Defect Detection in Metallic Parts’

Summary

In-process NDT

It is important to consider in-process inspection for AM since it has the potential to reduce or eliminate the need for inspection at the end of the build, reducing both cost for final part inspection and scrap of parts;

In some cases where NDT methods will not be capable to inspect the build parts due to their large or complex nature, in-process inspection may be the only option;

MTC’s work on LUT has showed good capability to detect surface and subsurface defects as small as 200 µm in diameter on as built L-PBF rough surface.

Post build NDT

The NDT selector tool showed an indication of how effective NDT methods will be on AM parts considering the level of geometrical complexity and surface finish;

XCT limits of detection highlights that the size of the part will influence the detection capability of even the ‘best’ NDT method currently available;

It is important to keep up-to-date of emerging and less used NDT methods, such as Non-linear Acoustics and PCRT which have shown promising results for AM part inspection.

Post built metrology and heating processes

Metrology showed good capability detecting geometrical deviations from the original CAD and actual build in addition to post processes such as HT and HIP have on AM part;

HT and HIP may be useful to reduce residual stresses and increase part density, respectively, but care must be taken that part quality is not reduced due to defects becoming more crack like.

NDT standard

MTC have been leading the development of NDT standards for AM, through ISO/ASTM JG59 and other ASTM participations, but more work is necessary to expedite the quality assurance of such parts.

Thank [email protected]

am part integrity: the ndt in-process and post-build...

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