Embed Size (px)
Citation preview
OCAS: a joint venture betweenArcelorMittal and the Flemish Region
Ann De Vyt
Micro-analytical instruments: Indispensable in the
development of steel
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
OCAS
Applications
& Solutions
Surfaces
Metallurgy
Energy Durability EnvironmentTechnical Support
& Entrepreneurial
R&D
Materials
characterisation
& testing
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Materials Characterisation and Testing
• MC&T is an internal operational "shared services platform”, which provides technical and scientific support to all departments of OCAS
• Use of various testing and analysis equipment
• Through Hercules program access to:
TEM JEOL ARM 200F @ KULeuven via a bilateral contractAPT Cameca LEAP 5000 XR @ KULeuvenTOF-SIMS IonTOF TOF.SIMS 5@ IMEC
3
All work together to support the development of steel
Two case studies coming up
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Case study 1: Metallic coatings
• Problem: crystal (spangle) size variations across the sheet. Very visible resulting in an esthetic problem for example in building applications.
• What is causing this?
4
small normal
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Steel surface
• Used rolling emulsions degrade• Free fatty acids are formed• They react with the fresh steel surface (before coating application) and
remain there as a contamination• Functional groups are detected at the steel surface by FTIR and XPS
5*
fresh emulsion used emulsion
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Different coated surfacesLow carboxyl load at
steel surface
High carboxyl load at
steel surface
Normal crystals
ASTM 0,3
Small crystals
ASTM 1,1
Digital camera
Optical microscope
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Cross sections
• SEMThickness of intermetallic layer can be correlated to the
surface cleanliness of the sheet and thus the spangle sizeSo we dig further into the intermetallic layer
steel substrate
coating
intermetallic layer
Span
gle
size
incr
ease
Car
bo
xyl l
oad
de
crea
ses
Intermetallic layer thickness (µm)
2,3
2,0
2,1
1,9
1,6
1,7
1,2
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Intermetallic layer• FIB/TEM
88
“normal” “small”
steel
IMC overlayer
overlayersteel
IMC
Al/Fe ≈ 2,5 - 3
Al/Fe ≈ 2-2,5 increasing
to 2,5-3
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
-0,5 0,5 1,5 2,5
Al/
Fe r
atio
distance, mm
lg1
lg2
lg3
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Small crystals Al Si Fe
Zn Mn O
2µm
Intermetallic layer
• Two layers are present• Mn rich oxide particles at the surface of the intermetallic layer• Zn segregation at the grain boundaries
This is seen only in the ‘small’ grain samples and clearly indicates that the presence of fatty acids interferes in the solidification of the metallic coating.
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Case study 2: Maraging steels• Name comes from the combination of
"martensite" and subsequent "aging“ for precipitation strengthening
• Simple process Austenitising Quenching Ageing
• Originally: Ultra Low C grades for ductile martensite Precipitates = intermetallics Ni3(X,Y)
high Ni, Co, Mo, Ti contents• “M250” 18Ni-8Co-5Mo-0.5Ti • PH17-4 17Cr-4Ni & Ph15-5 15Cr-5Ni (stainless)
Hugely expensive! Research for cheaper possibilities
• Mechanical• Strength (>1500MPa)• Superior fracture toughness
Transformation• Formability & Machinability in pre-aged
state• Weldability
• End-use• Very stable at high T up to 400C• Hydrogen and SCC resistance
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Maraging steels: hardening
Inserts/casts
1
2
3
4
95442 samples
00-047-1417 (N) - Taenite, syn - gamma-(Fe,Ni) - Y: 29.18 % - d x by: 1. - WL: 1.78897 - Cubic - a 3.597
00-048-1816 (*) - Cobalt Iron - Co3Fe7 - Y: 35.42 % - d x by: 1. - WL: 1.78897 - Cubic - a 2.86340 - b 2.
00-037-0474 (*) - Kamacite - (Fe,Ni) - Y: 13.31 % - d x by: 1. - WL: 1.78897 - Cubic - a 2.86810 - b 2.868
00-006-0696 (*) - Iron, syn - Fe - Y: 9.59 % - d x by: 1. - WL: 1.78897 - Cubic - a 2.86640 - b 2.86640 - c
Operations: Background 1.000,1.000 | Import
File: sample4.raw - Type: 2Th/Th locked - Start: 25.000 ° - End: 125.000 ° - Step: 0.020 ° - Step time: 5.
Operations: Background 1.000,1.000 | Import
File: sample3.raw - Type: 2Th/Th locked - Start: 25.000 ° - End: 125.000 ° - Step: 0.020 ° - Step time: 5.
Operations: Background 1.000,1.000 | Import
File: sample2.raw - Type: 2Th/Th locked - Start: 25.000 ° - End: 125.000 ° - Step: 0.020 ° - Step time: 5.
Operations: Background 1.000,1.000 | Import
File: sample1.raw - Type: 2Th/Th locked - Start: 25.000 ° - End: 125.000 ° - Step: 0.020 ° - Step time: 5.
Lin
(C
ounts
)
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
11000
12000
13000
2-Theta - Scale
47 48 49 50 51 52 53 54 55
1
2
3
4
γ
α
• Shift of the α peak during aging: reverted austenite
• Not possible to detect the intermetallics by XRD
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
STEM BF image STEM HAADF image
Martensite
In the martensite phase, a lot of needle-like precipitates are visible.
Maraging steels: precipitates
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Maraging steels: precipitates
By EDX mapping, the precipitates are identified as Ni-Ti
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Clustering
Matrix Intermetallics
Fe 70% 58%
Ni 16% 29%
Co 9% 7%
Mo 3% 4%
Ti 0.6% 2%
AQ
Clustering
Coarsening/optimum?
Coarsening/optimum
MatrixLarge &
rodSmaller & spherical
Fe 71% 32% 32%
Ni 14% 41% 41%
Co 9% 6.6% 6.4%
Mo 3.2% 11.5% 9%
Ti 0.5% 8.5% 11%
Evolution of the Ni3(Ti,Mo): more Mo Ni3(Ti,+Mo)
Maraging steels: precipitates
APT
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Maraging steels: reverted austenite
Ni
FEG-EPMA shows the Ni diffusion in the light grey areas of the back scatter image, proving the existence of the reverted austenite.
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Maraging steels
• Combining various techniques to analyse commercial material leads to the confirmation of the maraging mechanism by showing:Clustering into precipitatesCoarsening of precipitatesDiffusion of Ni driven reverted austenite
• This methodology can be transferred to understand new grades with other intermetallics
© 2
011
–O
CA
S –
All rig
hts
rese
rve
d fo
r all c
ou
ntrie
sC
an
no
t be
dis
clo
se
d, u
se
d, o
r rep
rod
uce
d w
itho
ut p
rior w
ritten
sp
ecific
au
thoriz
atio
n o
f OC
AS
CO
NF
IDE
NT
IAL –
Priv
ileg
ed
Info
rma
tion
–O
CA
S’ p
rop
rieta
ry in
form
atio
n
Summary
• Two case studies were presented showing the strength of combining various techniques in understanding the properties of materials.
• Thanks to• Hui Shi, Laura Moli Sanchez, Annick Dhont, Franz
Horzenberger, ZAC association, Hercules program• The entire SMACH group• Jan Scheers
