Process-structure-property Relationships in the Coating of ... Presentation_5.pdf · Flaw-free...
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1
Process-structure-property Relationships in the Coating of Stelliteon Inconel 718 by Directed Energy Deposition Process
08/14/2019SFF 20191045 Hrs.
Room 416 AB
Ziyad SmoqiJordan Severson
Joshua ToddyHarold Halliday
Tom CobbsPrahalad Rao
[email protected] and Materials Engineering
University of Nebraska-Lincoln
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2Acknowledgements
Mr. Josh Brown
Stellite Powder Material for this research was donated by
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3Acknowledgements
MECH 498/898 Additive Manufacturing Project Team
Adam Bartels, Ethan Blayney, Elijah Elmshaeuser, Chris Fisher, Evan Penington, Joe Swenson, Charles Krueger, and Arsen Slonsky.
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4Acknowledgements
National Science Foundation
CMMI 1719388
CMMI 1739696
CMMI 1752069 (CAREER, Smart Additive Manufacturing)
4
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5Goal
Flaw-free deposition of Stellite 21 wear coating on Inconel 718
No Preheat and High Power High Preheat and High PowerLow Preheat and Low Power
1 mm
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6Objectives
1) Understand and explain the metallurgy and processing science of flaw formation.
2) In-process detection and prevention of flaw formation
Flaw-free deposition of Stellite 21 wear coating on Inconel 718
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7Outline
• Background and Prior Work
• Methods
– Experimental Plan & Setup
– Instrumentation of Sensor Array
• Results
– Microstructure characterization (Optical, XCT, SEM)
– Hardness testing
• Summary & Future Work
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8Outline
• Background and Prior Work
• Methods
– Experimental Plan & Setup
– Instrumentation of Sensor Array
• Results
– Microstructure characterization (Optical, XCT, SEM)
– Hardness testing
• Summary Future Work
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9Directed Energy Deposition of Stellite 21
• Stellite is a cobalt-based ceramic material. Trademark of Kennametal.
• Application: Wear-resistant coating for parts operating in high-temperature conditions. E.g., automotive valves, machine gun barrels, and cutting tools.
• Directed Energy Deposition (DED), allows cladding Stellite onto free-form surfaces, and apply a graded coating.
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10Effects of Preheating
Brueckner, F., Lepski, D., Nowotny, S., Leyens, C., and Beyer, E., 2012, "Calculating the stress of multi-track formations in
induction-assisted laser cladding," International Congress on Applications of Lasers & Electro-Optics, pp. 176-182.
Preheating reduces crack formation.
Laser cladding of Stellite 20 on Ck45 (carbon steel)
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11Energy density is a key determinant of coating wear resistant
Stellite 6 coatings on cutting tools.
Traxel, Kellen D., and Amit Bandyopadhyay. “First Demonstration of Additive Manufacturing of Cutting Tools Using Directed Energy Deposition System: Stellite™-Based Cutting Tools.” Additive Manufacturing, vol. 25, 2019, pp. 460–468., doi:10.1016/j.addma.2018.11.019.
Laser Power (P): 410 WScan Speed (V): 5.5 mm/secHatch Spacing (H): 0.5 mmLayer thickness (T): 0.5 mm
EV =P
V × T × H= 300
J
mm3
We used 225 and 280𝐽
𝑚𝑚3 as starting points
DED-based Stellite coating for cutting tool applications.
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12Energy density is related to hardness and flaw formation
P = Laser Power [W]; V = Scan Rate [mm/s]; and D = Laser Spot Diameter [mm]
We used 30 and 40J
mm2 as starting points
EA =P
V × D
J
mm2
Low energy density correlated to higher micro-hardness, reduced particle erosion, but increase in flaws.
Raghuvir Singh, Damodar Kumar, S.K. Mishra, S.K. Tiwari, Laser cladding of Stellite 6 on stainless steel to enhance solid particle
erosion and cavitation resistance, Surface and Coatings Technology, Volume 251, 2014, Pages 87-97,
ISSN 0257-8972, https://doi.org/10.1016/j.surfcoat.2014.04.008.
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13Outline
• Background and Prior Work
• Methods
– Experimental Plan & Setup
– Instrumentation of Sensor Array
• Results
– Microstructure characterization (Optical, XCT, SEM)
– Hardness testing
• Summary & Future Work
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14Key Process Parameters
• Preheating
– Use the laser (suitable for small parts)
– Separate heating element (difficult to scale)
• Energy Density (Ev)
– Laser Power and Velocity are machine constraints.
– Ev is more transferable
• Flow Rate
– Material is ejected from the meltpool
– Forced convection pushes material away
– Powder bounces from the substrate
EV =P
V × T × H
J
mm3
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15Experimental Plan
Inconel 718 coupon
(37.5 mm 37.5 mm × 4.76 mm)
Coating thickness 12 layers
(3 mm total coating, 0.250 mm layer height)
• Preheating begins with counterclockwise
contour scan starting from the datum.
• Preheating (2 passes) is done with the laser
• Rectilinear scan path, no overlap.
• Start and end at the same point.
• Laser turns off at the end of the scan.
Datum
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16Experimental Plan
• Anti-clockwise contour between layers starting at the datum
• 12 deposition passes, rectilinear scan path, 95% overlap between hatches.
• Start and end at the same point.
• Laser turns off at the end of the scan
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17Setting the Energy Density Parameters
𝐸𝑉 =𝑃
𝑉×𝑇×𝐻(J/mm3 )
Length scanned in one second (V)
Layer Thickness (T)
Hatch Spacing (H)
(center-to-center distance
between adjacent hatches)
Pass #1Pass #2
Process StepLaser Power
P [W]Scan Speed V
[mm/s]Hatch Spacing
H [mm]
Layer Thickness T
[mm]
Preheat (2 layers)
Varied(NP, 300, 350, 400)
12 0.7
(laser spot size)N/A
Print (12 layers)
Varied(200, 225, 250, 275)
10.6(recommended)
0.38(1.5 × T)
0.25
EV used in this experiment 200 J
mm3 to 275 J
mm3
Approximate printing time 60 minutes to 75 minutes
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18Setting Flow Rate
Minimum Flow Rate = Volume of Material Deposited in one minute × Density
= 𝑉 × 𝑇 × 𝐻 𝜌= 10.6 × 0.25 × 0.38 × 8.33 × 10−3
≈ 0.500 [g·s-1 ]
Minimum flow rate possible on the machine is 1.8 g.s-1
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19Outline
• Background and Prior Work
• Methods
– Experimental Plan & Setup
– Instrumentation of Sensor Array
• Results
– Microstructure characterization (Optical, XCT, SEM)
– Hardness testing
• Summary & Future Work
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20Fixture and Setup
Inconel 718 clad K type Thermocouples (TC)
Tapped holes for
clamping screws
Slots for thermocouple probes
Positioning screw
Plywood insulation
1.5”
Sample
Fro
nt
of
Machin
e
Left of Machine
Near
TC
Substr
ate
TC
Far
TC
2.5 × 2.5 × 1.125
Build plate fixture inside the Optomec LENS machine
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21Fixture and Setup
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22In-process Sensing Setup
Multiple sensors were instrumented on the machine, including a
photodetector array, infrared thermal cameral, and a meltpool camera.
Photodetector Array
Meltpool Camera
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23Evolutionary Optimization Experimental Plan
FPreheat: N/A
Printing: 275 W (206 W)Sample 4
PPreheat: N/A
Printing: 225 W (150 W)Sample 2
B
Preheat: 300 W (234 W)
Printing: 225 W (150 W)Sample 5
GPreheat: 300 W (234 W)
Printing: 275 W (206 W)Sample 3
Q & J
Preheat: 400 W (345 W)
Printing: 225 W (150 W)Samples 1 and 6
OPreheat: 400 W (345 W)
Printing: 275 W (206 W)Sample 8
IPreheat: 350 W (290 W)
Printing: 250 W (180 W)Sample 7
NPreheat: 350 W (290 W)
Printing: 200 W (123 W)Sample 9
Preheat Laser Power
PrintLaser
Pow
er
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24Outline
• Background and Prior Work
• Methods
– Experimental Plan & Setup
– Instrumentation of Sensor Array
• Results
– Microstructure characterization (Optical, XCT, SEM)
– Hardness testing
• Summary & Future Work
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25
I
Preheat: 350 W;
Printing: 250 W
F
Preheat: N/A; Printing: 275 W
P
Preheat: N/A
Printing: 225 W
B
Preheat: 300 W
Printing: 225 W
G
Preheat: 300 W; Printing: 275 W
Q
Preheat: 400 W
Printing: 225 W
O
Preheat: 400 W; Printing: 275 W)
N
Preheat: 350 W
Printing: 200 WPreheat
Pri
nting L
ase
rP
ow
er
Surface Optical Microscopy (As deposited)
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26
F Preheat: N/A; Printing: 275 W)
PPreheat: N/A; Printing: 225 W
BPreheat: 300 WPrinting: 225 W
GPreheat: 300 W; Printing: 275 W)
QPreheat: 400 WPrinting: 225 W
O(Preheat: 400 W; Printing: 275 W)
I Preheat: 350 W; Printing: 250
N Preheat: 350 WPrinting: 200 W
Preheat Laser Power
Dep
osi
tio
n L
aser
Pow
er
Surface SEM (as-deposited)
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27
FNo Preheat
Printing: 275 W (206 W)
PNo Preheat
Printing: 225 W (150 W)
BPreheat: 300 W (234 W)Printing: 225 W (150 W)
GPreheat: 300 W (234 W)Printing: 275 W (206 W)
J & QPreheat: 400 W (345 W)Printing: 225 W (150 W)
OPreheat: 400 W (345 W)Printing: 275 W (206 W)
IPreheat: 350 W (290 W)
Printing: 250 W
NPreheat: 350 W (290 W)Printing: 200 W (123 W)
Preheat
Pri
nt
Lase
rP
ow
er
Most Cracking Most Warping
N
G O
P
Crack0.2 mm to
0.5 mm
I
J
Optimal Condition. Devoid of Cracks.
F
B
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28Cracking is related to the scanning direction
F N
o P
reh
eat
Pri
nti
ng:
275
W (
206
W)
OP
reheat: 400 W
(345 W)
Prin
ting: 275 W
(206 W)
F O
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29Cracks cross the scan vector at nearly 45°
F No Preheat
Printing: 275 W (206 W)
OPreheat: 400 W (345 W)Printing: 275 W (206 W)
45 °
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30Samples Chosen for Microstructural Characterization
FPreheat: N/APrinting: 275 W Sample 4
PPreheat: N/APrinting: 225 W Sample 2
BPreheat: 300 W Printing: 225 W Sample 5
GPreheat: 300 W)Printing: 275 W Sample 3
Q Preheat: 400 WPrinting: 225 W
Samples 1 and 6
OPreheat: 400 W Printing: 275 W Sample 8
IPreheat: 350 W Printing: 250 W Sample 7
NPreheat: 350 W Printing: 200 W Sample 9
Preheat Power
Dep
osi
tio
nLa
ser
Pow
er Scale bars= 500 µm
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32Sample Preparation
• Small samples ≈ 0.5 inch X 0.5 inch were cut by EDM
• Top surface, and exposed cross sections of the coating were ground mechanically using 400, 600, 800, and 1200 grit SiC sandpaper.
• Polished using diamond paste (3, 1, and 0.5 microns)
• Etched with aqua regia (HCL:HNO3=3:1)
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33Effect of Preheat and Deposition Laser Power on Crack Density
17% Reduction
21%
Reduction
100% Reduction in crack density
F (Preheat: N/A; Printing: 275 W O (Preheat: 400 W; Printing: 275 W)
P (Preheat: N/A; Printing: 225 W)
45
% R
edu
ction
Q (Preheat: 400W; Printing: 225 W)
45
% R
edu
ction
N Preheat: 350W; Printing: 200 W
Preheat Laser Power
Dep
osi
tio
nLa
ser
Pow
er
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34Dendritic microstructure observed on the surface as function of preheat & deposition laser power
O
Q P
F
NPreheat: 350 WPrinting: 200 W
P P
reh
eat
: N/A
Pri
nti
ng:
225
WF
Pre
hea
t: N
/A P
rin
tin
g: 2
75 W
O P
reh
eat:
400
W P
rin
tin
g: 2
75 W
Q P
reh
eat
: 40
0 W
Pri
nti
ng:
225
W
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35Surface Microstructure under SEM
F O
P Q
P P
reh
eat:
N/A
Pri
nti
ng:
225
WF
Pre
hea
t: N
/A P
rin
tin
g: 2
75 W
O P
reh
eat:
400
W P
rin
tin
g: 2
75 W
Q P
reh
eat
: 4
00
W P
rin
tin
g: 2
25
W
N Preheat: 350 W
Printing: 200 W
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36Longitudinal cross-section
Cracks penetrate as much as 100 – 500 μm into the coating
O P
reh
eat:
400
W P
rin
tin
g: 2
75 W
P P
reh
eat:
N/A
Pri
nti
ng:
225
W
Q P
reh
eat
: 40
0 W
Pri
nti
ng:
225
W
F P
reh
eat:
N/A
Pri
nti
ng:
275
W
Coating Interface
CrackF
P
Interface
Q
OCrack
NPreheat: 350 WPrinting: 200 W
Coating
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37Transverse cross-section Penetration of the coating into the substrate increases
with preheat and deposition laser power
OF
P Q
P P
reh
eat:
N/A
Pri
nti
ng:
225
WF
Pre
hea
t: N
/A P
rin
tin
g: 2
75 W F
O P
reh
eat:
400
W P
rin
tin
g: 2
75 W
Q P
reh
eat
: 40
0 W
Pri
nti
ng:
225
W
NPreheat: 350 WPrinting: 200 W
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38Surface and Cross-sectional Microstructure
N Preheat: 350 W Printing: 200 W
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39HypothesisPreheating and low deposition power lead to smaller
thermal gradients, and hence minimize cracking.
F (P
reh
eat
: N
/A;
Pri
nti
ng:
27
5 W
)
F
N (
Pre
he
at: 3
50
; Pri
nti
ng:
20
0 W
)
N
N
F
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40X-Ray CT analysis of Surface and Interface
Interface
Surface
F Preheat: N/A Printing: 275 W
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41Outline
• Background and Prior Work
• Methods
– Experimental Plan & Setup
– Instrumentation of Sensor Array
• Results
– Microstructure characterization (Optical, XCT, SEM)
– Hardness testing
• Summary & Future Work
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42Surface Hardness Testing
Sample PreheatPreheat Laser
(W)
Print Laser
(W)Remarks
Mean Hardness
(HV)
Hardness
σ
P N - 225 High Cracking 435.4 47.5
G Y 300 275 427.8 26.7
F N - 275 High Cracking 430.4 28.4B Y 300 225 Less Cracking 419.4 24.5
O Y 400 275 High Warping 410 35.2
I Y 350 250 398.5 34.2
J Y 400 225 Less Cracking 438.4 16.9
Q Y 400 225 Less Cracking 541.8 39.9
N Y 350 200 Least Cracking 428.2 17.7
Vickers
Hardness
at 9 points
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43Outline
• Background and Prior Work
• Methods
– Experimental Plan & Setup
– Instrumentation of Sensor Array
• Results
– Microstructure characterization (Optical, XCT, SEM)
– Hardness testing
• Summary & Future Work
![Page 43: Process-structure-property Relationships in the Coating of ... Presentation_5.pdf · Flaw-free deposition of Stellite 21 wear coating on Inconel 718 Low Preheat and Low Power No Preheat](https://reader030.fdocuments.in/reader030/viewer/2022040819/5e650c94bbec3f5656355636/html5/thumbnails/43.jpg)
44No Preheat Preheat
Low Deposition Power (P=200W)
High Deposition Power (P=275W)
Medium Deposition Power (P=225)
Optical vs. SEM
(Optical vs. SEM)
(XCT Results:Near interface vs. Near surface
(Optical vs. SEM)
XCT Results:Near interface vs. Near surface
N
P Q
F G
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45Ongoing Work
1. EDS to characterize change in elemental composition
2. Mechanical characterization (wear and 3-point bending)
3. Modeling and In-process Data Analytics