www.cranfield.ac.uk
Wire plus Arc Additive built multi-alloystructural component for the marineenvironment
Offshore structural steels generally conform to various designstandards, e.g. BS EN 10025. However, design flexibility is oftencompromised to maintain a single material grade. For complex bespokecomponents forgings/castings are often used, but are expensive andlogistically complicated. WAAM is a cutting-edge technology capable ofsignificant component design improvement, reduced delivery timethrough reduced material usage and environmentally sustainable.Material selection allows the use of different materials depending onthe application and stress analysis, reducing operating expenditures(Opex). A drawback of the technique is structure surface wavinessproduced by the deposition process which may cause undesirablestress concentration.
To understand the suitability of the WAAM processin developing bespoke parts/components to exploit design flexibility.However, for cost effective application further machining andprocessing needs to be optimised.
Introduction
• ER120S-G & ER90S-B3 are more sensitive to surface waviness ascompared to ER70S-6 that possesses some damage toleranceattributes (Fig. 6).
• EBSD analysis reveals moderate anisotropy in the WAAM alloys andthese properties could be advantageous for utilisation in gradedstructures (Fig. 8).
• The EDS line scanning at the ER90S-B3 /ER70S-6 interface reveals avariation of alloying element across the interface, the content ofchromium decrease significantly near the fusion line than that ofnickel with hardness measurements following the same trend(Fig.10)
• Notches associated with waviness serve as stress risers andtherefore reduce the fatigue life of the structure (Fig. 11).
• WAAM of multi grade possesses similar properties as single gradesand both mechanical properties meets the minimum required bystandard (Fig. 6&7).
• Ongoing work to determine fracture toughness and crack growthrate in single and multi graded WAAM structure for both machinedand as deposited condition is in progress.
Methodology
Results and discussion
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Unmachined Machined Unmachined Machined Unmachined Machined
ER120S-G ER120S-G ER70S-6 ER70S-6 ER90S-B3 ER90S-B3
Elo
ng(
%)
MP
a
UTS(Mpa) Rp(Mpa) Elong(%)
Summary and ongoing work
Wind turbinemain frame
Mild steel
High strengthsteel
Ultra fatigueresistance steel
Ultra wearresistance steel
=200 µm; Map4; Step=0.2709 µm; Grid1774x1330
Philip Dirisu- [email protected], REMS Centre, Cranfield University, UK, MK43 0ALAcademic Supervisors: Dr. Supriyo Ganguly & Dr. Filomena MartinaIndustrial Supervisor: Juan Carlos Ceballos (Vestas)
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Max
stre
ss(M
Pa)
Number of cycle to fracture
ER70S-6 (Machinedcondition)
ER70S-6(Aswelded condition)
70% 0f Rp 70% of UTS 80% of UTS 90% of UTS 50% UTS 22.5% of PS
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Har
dn
ess
HV
Distance from the bottom of test piece(mm)
ER90S-B3 ER70S-6
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Max
stre
ss(M
Pa)
Number of cycle to fracture
ER120S-G (Aswelded condition)
ER70S-6 (Aswelded condition)
Fig 10: Hardness variation and EDS line scanning at the ER90S-B3 /ER70S-6 interface of a mixed grade WAAM structure
=200 µm; Map4; Step=0.2709 µm; Grid1774x1331
=200 µm; Map4; Step=0.27 µm; Grid1780x1336
Fig 6: Average mechanical properties of machined Vs as- depositedcondition for WAAM ER70S-6, ER90S-B3 & ER120S-G – X direction
Fig 5: WAAM set up (a) & multi grade built structure (b)
WA
AM
Single grade
Machined ER70S-6 ER90S-B3 ER120S-G
As deposited
Peening ER70S-6 ER90S-B3 ER120S-G
Rolling
Multi grade
Machined ER120S-G/ER70S-6 ER90S-B3/ER70S-6 ER120S-G/ER90S-B3
As deposited
Peening ER120S-G/ER70S-6 ER90S-B3/ER70S-6 ER120S-G/ER90S-B3
Rolling
MIG-cold metaltransfer process
(CMT)
DepositionParameters
optimisation
Parallel + oscillatorydeposition strategies
InstrumentedWAAM for thermalcycles monitoring in
each layer
Microstructural+
metallurgicalcharacterisation
Static + dynamicmechanicalproperties
characterisation
project aims
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(ER70S-6 + ER90S-B3) VERT
(ER70S-6 + ER90S-B3)HORZ
(ER90S-B3)HORZ (ER100S-G +ER90S-B3)HORZ
Elo
ng
(%)
MP
a
Rp(MPa) UTS(MPa) Elong(%)
ER70S-6
Fig 1: Project targeted component Fig 2: WAAM steel post processing
Fig 4: Test matrix
Fig 3: Sequence of experimental process
The methodology adopted for the project is highlighted in Fig.3. Fig.4 shows thetest matrix. The set up and built multi grade structure is shown in Fig 5 (a & b)
Fig 7: Mechanical properties of multi graded structure
Fig 9: Pole figure & inverse pole figure images of ER120S-G WAAM structure
ER90S-B3ER120S-G
Fig 8: Electron backscatter diffraction (EBSD) images of ER120S-G, ER90S-B3 & ER70S-6 WAAM structure
{111}Y0
X0
Pole Figure
[ER120 H-X(r) Site 6 Map Data 8.cpr]
Iron bcc (old) (m3m)
Complete data set
1721502 data points
Equal Area projection
Upper hemisphere
Half width:10°
Cluster size:5°
Exp. densities (mud):
Min= 0.32, Max= 2.22
1
{111}Y0
X0
Pole Figure
[EK120 V-2 Site 4 Map Data 5.cpr]
Iron bcc (old) (m3m)
Complete data set
1857979 data points
Equal Area projection
Upper hemisphere
Half width:10°
Cluster size:5°
Exp. densities (mud):
Min= 0.07, Max= 3.20
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2
Z1001
1-11
101
111
Inverse Pole Figure
(Extended)
[ER120 H-X(r) Site 6 Map Data 8.cpr]
Iron bcc (old) (m3m)
Complete data set
1721502 data points
Equal Area projection
Upper hemisphere
Half width:10°
Cluster size:5°
Exp. densities (mud):
Min= 0.66, Max= 1.34
Cr
ER90S-B3
ER120S-G
a) b)
Fig 11 : Effect of stress concentration on dynamic performance of WAAM steel machined in Z-direction, R = 0.1 , Freq = 15HZ
Recommended
