Thermal Spray of Suspensions & Solutions Symposium (TS4)
December 2015, Montreal, Canada
Axial Suspension Plasma Spraying (ASPS)
Its Development and Application
Zhaolin Tang, PhD
Northwest Mettech Corp., North Vancouver, BC, Canada
• Introduction
• ASPS Technology
• ASPS Coating Development
- Solid Oxide Fuel Cells
- Semiconductor Equipment coatings
- Thermal Barrier Coatings
• Conclusions/challenges
Outline of the Presentation
2
Source: ITSA
Plasma Spraying
Radial InjectionAxial Injection
3
AXIAL III
Axial III plasma gun design
Benefits
High spray efficiency/spray rate
Improved coating quality
Advantages for liquid spraying
Features
•Axial powder injection
•High energy plasma
•Fully automatic control
Axial III Plasma Torch
4
Atomized liquid completely entrained in the plasma jets
5
NanoFeed Delivery
Liquid based delivery are precisely and automatically monitored and controlled.
Axial Injection
Reliable slurry delivery and injection are critical for coating production!
Gun Voltage and Current Suspension Delivery Test
Flow rate variation: <5%120 hours run without clogging
6
The plasma current and voltage were stable over 120h testing
Durability Test Over 120 hours
7
• SOFC Electrolyte
• Plasma etch resistant Y2O3 coatings
• Thermal barrier coatings (TBCs)
ASPS Coatings
Fuel
Air
O2－
e-
Anodeporous Ni-YSZ
Cu-SDC
Electrolytefully dense YSZ
CathodePorous LSM-YSZ
e-
O2+4e-→2O2-
2H2+ 2O2- →2H2O+4e-
O2-
Application #1: Solid Oxide Fuel Cells
8
Powder size
5-25 µm (powder feeding) 3-5 µm (powder feeding) <1 µm (suspension feeding)
20 µm
Finer particlesDenser coatings
YSZ Coatings - Different Powder Size
9
Microstructure of YSZ Electrolyte on Porous Anode Support
10
Leak Test Results at NRC-IFCI
0.50
0.22
0.14
0.11
0.000.00
0.10
0.20
0.30
0.40
0.50
0.60
Porous anode substrate (no electrolyte)
Regular sized Powder (June 2006)
Fine powder slurry (August 2007)
Fine powder slurry (October 2008)
Fine powder slurry (Feburary 2009)
Le
ak
ag
e r
ate
, S
CC
M/c
m2
Axial III Plasma sprayed Electrolyte
11
Application #2 : Semiconductor Equipment Coatings
12
J. Kitamura, ITSC2009
RFGas supply
RF Electrostatic chuck
(E-chuck)
Shower plate
Evacuate
Halogen
Plasma
Plasma Erosion Resistant Y2O3
Coating
13
Porosity 4.6% Porosity: 0.3%
Traditional
(37 mm)
Fine
(1 mm)
SEM images of specimens after plasma erosion test
Conventional Y2O3
coatingsASPS Y2O3 coatings
bulk Y2O3
14
• Low porosity: 0.3%• High hardness: 620 HV0.2g• Low erosion resistance: 65nm/min• Smaller particles generated
Properties close to bulk Y2O3
Application #3 : Thermal Barrier Coatings
15
N. Padture 12 APRIL 2002 VOL 296 SCIENCE
Commercial TBCs
16
A. Feuerstein et al, Journal of Thermal Spray Technology Volume 17(2) June 2008—199
EB-PVD TBCs
High durability, very expensive
APS TBCs
Low cost, low durability
ASPS TBC Structure
17
Effects of Parameters on TBCs
• Suspension parameters– Powder type and source– Particle size distribution– Concentration – Liquid base
• Process parameters:– Plasma parameters (current, gas composition)– Spray feed rate– Stand off distance– Traverse speed / rotation speed– Cooling method– Nozzle
• Substrate parameters:– Base alloys and bond coat type– Bond coat surface roughness
18
Standard APS Bond coat
+
ASPS Columnar TBCs
19
Surface modification study
Surface preparations:-1. As-produced2. Grit-blasted3. Polished & Grit Blasted4. Polished
Source: N. Curry, Surface & Coatings
Technology 268 (2015) 15–23)
Effect of Bond Coat Roughness on Coating Microstructure
20
Increased bond coat roughness, increased column size; SPS microstructure could be partially designed by controlling the bond
coat surface topography.
As-received, Ra=11-12µmGrit blasted, Ra=6-8 µm
Polished, Ra:1-2µm Polished & grit blasted, Ra:3-4µmBond coat
Substrate
Top coat
Thermal Conductivity
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Polished Polished+Gritblasted
Grit Blasted Standard HVAF
The
rmal
Co
nd
uct
ivit
y (W
·m−1
·K−1
)
21(Laser Flash test condition: At room temperature in atmospheric pressure)
22
Thermo-cyclic Fatigue results
0
50
100
150
200
250
300
350
400
Polished Polished/Gritblasted
Grit blasted Standard HVAF
Cyc
les
to
Fai
lure
(Testing Conditions: Heating: 1 hour hold time at 1100°C, Cooling: 10 minutes with pressurised air (at room temperature) ; Temperature at end of cooling ~100°C)
Testing Conditions
Heating: Oxy-fuel flame
• Temperature (front): 1200 – 1300°C
• Temperature (back): ~1000 °C
• Heating time: 75s
• Cooling: Heated Pressurised Air
• Cooling temperature: ~ 450 °C
• Cooling time: 75s
Failure Criteria: >10% surface spallation
Thermal Shock TestingBurner Rig - GKN Aerospace
Thermal Shock Performance9903 thermal shock cycles
without failure!HVAF MCrAlY
Comparison of TBC Properties
25
Source: N. Padture 12 APRIL 2002 VOL 296 SCIENCEA. Feuerstein et al, Journal of Thermal Spray Technology Volume 17(2) June 2008—199R. Lima, SURFTEC Report 2006-2009, NRC-IMIMettech and customer’s test results
Properties APS ASPS EB-PVD
Bond Strength, MPa 20-40 50-82 65-75
Thermal Conductivity, W/mK
0.9-1.5 0.7-2 1.7-2
Furnace Cycling Test (FCT), h
n/a >700 >700
The properties of ASPS TBCS are comparable to EB-PVD like TBCs
ASPS TBC with High Spray Rate
26
Net powder feed rate of
60g/m
Suspension
NanoFeed
Axial III
TBC
CrystalArctm Powder• Micro / nano proprietary powder• Customize composition (low k)
CrystalArc tm Suspension• Organic or aqueous • Stable, long shelf life• Wide range of concentrations
NanoFeedtm Feeder• Closed loop PLC control• Explosion proof design• Axial III User Interface• Industry ready • Production and R&D models
ASPS Coating• Dense and vertically cracked• Columnar structure• Excellent adhesion
Axial IIItm Torch• Touch screen user interface• Robust, reliable torch construction• Axial injection• High deposition efficiency
ASPS Technology
27
Comparison of Costs
28
ASPS is shown to be an economical process to produce durable EB-PVD like TBCs
Cost ASPS EB-PVD
Capital cost ~$2 million >$20 million
Operating cost(no detailed data)
In air(Low cost)
In vacuum(High cost)
ASPS TBCs on blade
29
Concave face
Leading edge
Convex face
Trailing edge
Conclusions
1. Highly dense coatings were produced for the application of SOFC electrolyte and plasma erosion resistant coatings.
2. Columnar TBCs with properties similar to those of EB-PVD coatings have been developed. This coatings present an economical alternative to durable EB-PVD TBCs.
Axial Suspension Plasma Spraying Process was employed for spraying submicron powder slurries.
30
Challenges
However, suspension spraying is a very complex process.
1. A comprehensive approach is needed including materials, equipment and process in order to get consistent coatings for industrial application;
2. A close collaboration/ partnership with industry customers is necessary for engineering development and industry acceptance.
31
NRC-IMI, IFCI
UT, UBC (Canada), University West (Sweden)
Fujimi, Treibacher, Innonano
Various industrial partners
Acknowledgments
32
Thank you
Northwest Mettech Corp.467 Mountain HighwayNorth Vancouver, B.C
Canada V7J 2L3
Phone: +1.604.987.1668Fax: +1.604.987.1669
www.mettech.com
