application of nickel nanoparticles in diffusion bonding of stainless steel surfaces
DESCRIPTION
Application of Nickel Nanoparticles in Diffusion Bonding of Stainless Steel Surfaces. Santosh Tiwari and Brian K. Paul School of Mechanical, Industrial and Manufacturing Engineering Oregon State University. Microfluidic Technology. Micro Total Analysis Systems (µTAS). - PowerPoint PPT PresentationTRANSCRIPT
Application of Nickel Nanoparticles in Diffusion Bonding of Stainless
Steel Surfaces
Santosh Tiwari and Brian K. Paul
School of Mechanical, Industrial and Manufacturing Engineering
Oregon State University
Microfluidic Technology
Micro Energy and Chemical Systems (MECS)Micro Total Analysis Systems (µTAS)
BIOMEDICAL
MEMS
CHEMICAL
BIOLOGICALCHEMICAL
ENERGY
Cell sorting
DNA Diagnostics
Inkjet Print Heads
Drug Delivery
MicroelectronicCooling Automotive Heat
Pumps
Portable Power Generation
Fuel ReformingPoint-of-use
Nanomaterial Synthesis
BiodieselSynthesis
Lab-on-a-chip
ProteomicsSingle Cell Analysis
Cytosensors
KidneyDialysis
BiopolymerSynthesis
Water Purification
Person Portable Cooling
Blood Processing
At-Home Sensors
>> 100 mL/minpL or nL
higherlower
25 µm < Channel Height < 250 µm
Fluid Volume
Application Temperature
Channel Dimensions < 100 µm
Analytical Microfluidics Arrayed Microfluidics
Emerging Industry
Fuel Processing
Chemical Processing
Heating & Cooling
Nanomaterial Synthesis
Separations
200 µm wide channels
“Number Up” Channels
channel header
channels
Single Lamina
• Channels – 200 µm wide; 100 µm deep
– 300 µm pitch
• Lamina (24” long x 12” wide)– ~1000 µchannels/lamina
– 300 µm thickness
Patterning: • photochemical machining
“Number Up” Laminae
• Device (12” stack)~ 1000 laminae= 1 x 106 reactor µchannels
• Laminae (24” long x 12” wide)– ~1000 µchannels/lamina
– 300 µm thickness Bonding: • diffusion bonding
Patterning: • photochemical machining
24”
12”
12”
12”
24”Cross-section of Microchannel Array
Outline
• Motivation and Objective
• Approach
• Results
• Summary
Diffusion Bonding: Concept Diffusion Bonding: Concept
a
b
c
d
e
a) Initial 'point' contact
b) Yielding and creep leading to reduced voids
c) Final yielding and creep (some voids left)
d) Continued vacancy diffusion, leaving few small voids
e) Bonding is complete
Diffusion Brazing of SS 316L
• Filler materials such as Ni, Cu, Au etc.• Nickel
– Almost 100 % solid solubility in Fe – Good corrosion and wear resistance– Compatible with stainless steel
• Temperature depressant materials (TDMs) like Si, B, P etc. added to reduce the melting temperature– Transient liquid phase bonding
• Adverse effect of TDMs– Formation of secondary phases– Bond strength and ductility ▼– Additional heat treatment cycle ~ up to 24 hrs– Time and Cost ▲
Analysis of Microchannel Samples
ObjectiveObjective• To Compare the diffusion bonded and
Nickel-Phosphorous (NiP) diffusion brazedsamples to obtain
– the characteristics of bonding – effect of NiP interlayer
• Bonding conditions
Sample Diffusion BondedDiffusion Brazed with
NiP
Patterning Laser micromachining Chemical etching
Laminae Thickness 0.028” 0.025”
BondingParameters
Temperature (oC) 1000 1000
Pressure (psi) 1000 1000
Ramp rate (oC/min) 20 15
Dwelling Time (hrs) 2 2
Diffusion Heating Cycle
0
200
400
600
800
1000
1200
0 100 200 300 400 500 600
time, min
tem
pe
ratu
re,
°C
diffusion boded
diffusion brazed
Scanning Electron Microscopy
200 µm 100 µm
SEM image of bond line for diffusion bonded sample
50 µm
SEM image of bond line for diffusion brazed sample
10 µm
10 µm
two phases present
intermetallic?
Defect QuantificationDefect Quantification
Diffusion Bonded SSDiffusion Bonded SS Diffusion Brazed SS – NiPDiffusion Brazed SS – NiP
µm, %
Wavelength Dispersive X-ray Spectroscopy Wavelength Dispersive X-ray Spectroscopy
-20
0
20
40
60
80
100
0 10 20 30 40 50 60 70
distance, µm
wei
gh
t %
ele
men
t
Ni_bonded Ni_brazedFe_bonded Fe_brazedP_bonded P_brazed
bo
nd li
ne
Elemental concentration across the bond line in diffusion bonded and diffusion brazed sample
Nanoscale Materials in Chemistry, Wiley, 2001Q Jiang, Materials chemistry and physics, v. 83, 2003, pp. 225-227
Au
Ag
“As the size decreases beyond a critical value, due to the surface –to-volume ratio, the melting temperature decreases and becomes size dependent”
Nano Al : 2nm (200oC) and 9nm (660oC) Generally, critical value is ~10nm
Effect of NP Size on Properties
Role of NanoparticlesRole of Nanoparticles
• Nano-sized particles – exhibit lower melting temperature than the bulk material – lower activation energy required to liberate atoms from the
surface– tremendously high surface area causing higher diffusion rate
• The densification rate during sintering
3 3
1.s sv vdV g Dk
dt kTG t G
Ω: geometric correction factor
sv: interfacial energyDv: volume diffusion co-efficientG: grain sizeVs: fractional porosity
Outline
• Motivation and Objective
• Approach
• Results
• Summary
Objective and ProtocolObjectives
• to compare NiNP-brazed samples with diffusion bonded and NiP diffusion brazed samples
• to investigate the microstructural evolution and bond strength of the stainless steel shims bonded using a Ni NP interlayer
Sample Preparation
• Materials– Stainless steel 316L shims of 1.0 mm thickness (1”x1”) – Suspension: Nicrobraz binder mixed with Ni nanoparticles
• Processing – Laser machining and deburring– Coating of NiNPs: ~5 µm thick– Drying: 200°C for 30 min– Diffusion bonding
Deposition from NP suspension
Spin CoatingSpin Coating• Small capital cost
• Faster Process
• Low contamination
• Patterned surface
• Edge effect
• Wastage of material
Sample Coating material RPM Time
Stainless steel lamina NiNP added in Nicrobraz cement 1500 20 sec
+
_
Drip CoatingDrip Coating • Small capital cost
• Patterned surface
• Less wastage of material
• Non-uniformity of the coating
• Agglomeration
• Very crude method
+
_
Nicrobraz Binder
• A commercially available water based binder (Wall Colmonoy Corporation)– Low viscosity: better for deposition – Readily wets the surface of clean metal substrates– Excellent adherence and a relatively short drying time– Low content of binder material to minimize outgassing
during the bonding cycle– All binding material volatilizes by 540°C leaving behind
the compact layer of particles– No residue remains on the parts after brazing, when
using nickel-based filler metals • Ideally suited for application of nickel-based brazing
filler metals
Film Characterization
(a) Continuous and uniform film
(b) Nanoparticle film (50 to 100 nm dia.) implying that high diffusion rate still achievable at relatively lower temperatures
200 µm
SEM images of the (a) coated and (b) dried (200°C, 30 min) nickel nanoparticles film on SS substrate
a b
Experimental DesignIndependent variables Dependent variables
Bonding temperatureBonding pressure
Bonding timeSurface condition
Bonding environment
Void fraction
Warpage
sample temperature (°C) Pressure (psi) Time (min)
SS 1000 1000 120
SS-NiP 1000 1000 120
SS – NiNP interlayer 750 1000 60
SS – NiNP interlayer 750 1000 120
SS – NiNP interlayer 800 1000 60
SS – NiNP interlayer 800 1000 120
SS – NiNP interlayer 900 1000 60
SS – NiNP interlayer 900 1000 120
SS – NiNP interlayer 1000 1000 60
SS – NiNP interlayer 1000 1000 120
Outline
• Motivation and Objective
• Approach
• Results
• Summary
Bonded and Brazed Samples
(a) diffusion bonded SS at 1000°C, 2 hrs (b) NiP diffusion brazed at 1000°C, 2 hrs and (c) NiNP diffusion brazed SS at 1000°C, 2 hrs
20 µm
a
10 µm
b
20 µm
c
Surface etched with “Aqua-Regia” (3HCl + HNO3)
Evidence of phase change!
Experimental Design
Process flow chart for bonding of Process flow chart for bonding of SS with NiNP interlayerSS with NiNP interlayer
CharacterizationCharacterizationSEM
MaterialsMaterials Nicrobraz cement with NiNP
Solution PreparationSolution Preparation 30 min ultrasonic stirring
30 min electromagnetic stirring
Spin CoatingSpin Coating1500 rpm, 20 sec
Diffusion BondingDiffusion Bonding 700°C - 900°C, 1000psi,
60 - 120 min
Void Fractions
Key findings• 2X time makes
no statistical difference
• Temperature above 800 C makes little difference
• Major advantage going from 750 and 800 C
750°C
800°C900°C
1000°C
Bondline Characterization 50 nm Ni on SS
1000X – X-section of nano Ni bonded SS; 750 C, minutes
500X – X-section of nano Ni bonded SS; 800 C, minutes
Evidence of phase change between 750 and 800 C!
Summary
• A 50 nm+ dia. nickel nanoparticle (NiNP) interlayer has been shown to:– lower the bonding temperature for diffusion brazing – eliminate the use of melting temperature depressants
• NiNP-brazing yielded – low void fractions– no deleterious secondary phases– expected require less time at lower temperature than
conventional diffusion techniques• 50 nm+ dia. NiNPs appear to have gone through
phase change between 750 and 800 C• Currently evaluating shear strength of joints
Acknowledgments
This research is sponsored by the National Science Foundation CTS.