TSS
ASM Thermal Spray Society
An Affiliate Society of ASM International ®
SM
November 2007
Volume 2 • Issue 4
Your Thermal Spray
Information Partner
I N T E R N A T I O N A L
Thermal Spray &
Surface Engineering
TM
T H E O F F I C I A L N E W S L E T T E R O F T H E A S M T H E R M A L S P R AY S O C I E T Y
Basics of
Thermal Barrier
Coatings
Metallizing Steel
Structures for
Corrosion
Resistance
Industry News
Thermal Spray
Tips
www.asminternational.org/tss
NOVEMBER 2007 • Volume 2 • Issue 4
TM
8 Thermal Spray Tip: Metallography
Editor Christopher C. Berndt
Managing Editor Ed Kubel
Art Director Barbara L. Brody
12 Thermal Spray Tip: DE
Production Manager Joanne Miller
Publisher Joe Zion
13 Thermal Barrier Coatings:
The Basics
Coating samples from
high velocity oxygen
fuel processes.
Sales
Mike Sellaroli
Columbus, Ohio
tel: 614/268-5260;
email: mike.sellaroli@asminternational.org
Erik Klingerman
North Royalton, Ohio
440-338-5151, ext. 5574
Erik.klingerman@asminternational.org
16 Thermal Spray Coatings
Protect Steel Structures
from Corrosion
Air bridges docked to aircraft;
bridges are given a thermal
spray coating to protect the
steel structure from corrosion.
Thermal Spray Society
Executive Committee
Peter Hanneforth, President
Richard Knight, Past President
Mitchell Dorfman, Vice President
Charles Kay, Secretary/Treasurer
Thomas S. Passek, Executive Director
About the cover
Thermal spray coatings are used to protect
the Emsworth Lock and Dam on the Ohio
River in the U.S. from corrosion. Courtesy
of Metallisation Ltd., West Midlands, UK.
International Thermal Spray & Surface EngineeringTM is
published quarterly by ASM International®, 9639
Kinsman Road, Materials Park, OH 44073; tel:
440/338-5151; www.asminternational.org. Vol. 2, No.
3. Copyright© 2007 by ASM International®. All rights
reserved.
Departments
2
3
16
18
From the Editor
Industry News
ASM Thermal Spray Society News
JTST Highlights
20
Calendar
ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
The acceptance and publication of manuscripts in
International Thermal Spray & Surface Engineering
does not imply that the editors or ASM International®
accept, approve, or endorse the data, opinions, and
conclusions of the authors. Although manuscripts
published in International Thermal Spray & Surface
Engineering are intended to have archival significance,
author’s data and interpretations are frequently
insufficient to be directly translatable to specific design,
production, testing, or performance applications
without independent examination and verification
of their applicability and suitability by professionally
qualified personnel.
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FROM THE
EDITOR
Thermal Spray:
The Best Thing Since Sliced Bread?
H
ow many times have you been placed in the position of (a) having to describe what thermal
spray (TS) is all about, (b) defending the physical attributes of a thermal spray coating with respect to another product or process, or (c) arguing the attributes of thermal spray on the
basis of life cycle costs? And sometimes all of these topics might be discussed within a single
business exchange.
There are many pragmatic answers to these questions. There are many resources that discuss
the TS process including conferences, web sites, peer-reviewed literature, patents, private databases,
and professional societies.
In some cases, the honest answer is “Yes, I fully understand where you are coming from. Thermal
spray may not be the specific solution that your company needs for this particular application.” In such
instances, your expertise in understanding the entire array of surfacing solutions can be brought to
bear. The outcome is that the customer may very well be satisfied with the alternative solution and your
own credibility as an expert will be reinforced. Thus, this person will feel comfortable in coming back
to you, even though TS was not the solution for that particular application.
A more difficult circumstance is where you are placed in the position of defending the microstructure of TS coatings. Remember viewing your own coating under the microscope where the eyes focused on a structure of pores, inclusions, and cracks. It is not hard to see then that persons trained
as engineers, scientists, and technologists would find it difficult to understand how such structures
can function as coatings under actual engineering conditions. It’s easy to foresee the many questions
that might arise about coating strength vs. fully dense materials, the effects of surface roughness, and
mechanical properties including yield and ultimate tensile strengths, fatigue strength, and modulus.
As practitioners, we know that TS coatings do in fact perform more than satisfactorily in many adverse mechanical and corrosive environments. So we are able to defend the microstructure largely
through the many successful case histories and extensive industrial practices that are available.
Finally, the cost of TS coatings apparently is favorable since a global market of several billion dollars
exists for thermal spray. The high capital equipment cost can be amortized over 5 to 10 years, so the
major cost is people — engineers who can specify coatings and skilled operators who can program
manufacturing cells and/or hand spray complex geometries.
Is thermal spray the best thing since sliced bread? I have had experiences where thermal spray has
been over-sold, leaving the client cautious about repeating a negative experience. However, in the past
decade, the database of successful examples of thermal spray and other coating technologies has
increased significantly to build a high confidence level that the coatings will perform in accordance to
the required specification.
Thermal spray is a competitive technology for many applications. Whether TS is better than sliced
bread should not be based on what we are told to believe, but on the basis of solid engineering results
and hard data. There is a strong need for unbiased results and data, and many people are striving to
fill this need. I urge you to praise the success of all coating technologies so that we can, to paraphrase
local jargon, “not only make our bread, but serve it to our customers as well.”
Chris Berndt, FASM, Editor
Editor Emeritus: The Journal of Thermal
Spray Technology
Tel: +61 (07) 4781 6489
Fax: +61 (07) 4775 1184
Mobile: 0428 237 638
christopher.berndt@jcu.edu.au
cberndt@notes.cc.sunysb.edu
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ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
Xiom Corp., West Babylon, N.Y., a manufacturer of polymer
powder spray systems and polymer-based coatings, has developed a technology that is said to significantly reduce both the
risk of bridge deterioration and the costs involved in maintaining
bridges.
There is growing concern over the safety of bridges in the U.S.
Of the nation’s 600,000 bridges, it is estimated that more than
100,000 are structurally deficient. Corrosion is a major cause of
bridge failure, and Xiom’s polymer powder coatings offer good
corrosion-fighting ability.
After testing various coating formulations, the company determined that an 85%zinc-15% aluminum coating provides good
corrosion protection, and a hard polymer top coat provides a
more durable, weather-resistant coating than paint or other competitive coatings.
The coatings, which also can be used to coat concrete and the
rebar embedded in concrete, don’t drip and there are no overspray problems and no VOCs (volatile organic chemicals). The
coatings cure instantly; no oven-curing is required, thus enabling
bridges to reopen more quickly. www.xiom-corp.com.
Ceramic-Coated Bearings Prevent Fan-Motor Failings
SKF Ltd., Bedfordshire, UK, offers ceramic-coated bearings
to prevent fan motors from failing due to stray electric currents.
Many motors in manufacturing plants can be affected by stray
currents that leak through generators and associated equipment.
The stray currents can damage the rolling elements and raceways of steel bearings and rapidly degrade the lubricant, resulting in unplanned downtime and increased costs related to
bearing replacement and lost productivity. Alleviating the
problem by insulating the housing or shaft can be expensive and
time consuming, and may not yield optimum results. SKF’s Insocoat bearings are said to solve these problems.
The bearings are standard, all-steel bearings plasma sprayed
with a ceramic coating. The coating is applied to the outside surface of the inner or outer ring, depending on the application, and
sealed to protect against the conductive effects of water and
moisture. As well as being environmentally friendly, the coating
provides a consistent insulation layer that is virtually insensitive to high operating temperatures and chemicals.
Well-suited to medium and large sized motors, the bearings
have the same boundary dimensions as standard
bearings so do not require special installation procedures or expensive modifications. They also offer a number of advantages over other methods used
to prevent stray currents including:
• Extended bearing service life
• Increased machine uptime
• Reduced maintenance and
repair costs
• Cost effective compared
with other insulating methods
• Drop-in replacement for easy
installation
• No degradation of the lubricant
caused by current discharges
• Virtual elimination of bearing damage
from stray electric currents
To illustrate, an integrated pulp and carton-board
mill was losing productivity due to bearing problems in the pulp
boiler flue gas recirculation fan motors. The 400 kW ac motors
with frequency converters were running at 950 rpm with an operating temperature in excess of 100°C (212°F). The motors were
equipped with standard bearings, which lasted only six months
on average due to damage caused by stray electric currents.
The company installed Insocoat bearings to improve reliability and reduce fan maintenance and repair costs. Since installing the bearings, there have been no failures. The mill realized dramatic savings in maintenance and repair costs, along
with additional benefits in reduced downtime and increased productivity. www.skf.com.
INDUSTRY NEWS
Xiom Corp. Develops Coating Technology for Bridge Repairs
BTU International,
DEK International Partner
for Solar-Cell Metallization
Solutions
BTU International Inc., Billerica, Mass., a supplier of advanced
thermal processing equipment for the electronics manufacturing and alternative energy markets, entered a
strategic partnership with DEK International, a
business of Dover Corp., New York, N.Y., a
provider of printing equipment and processes
for the high-accuracy mass imaging of
electronic materials. The partnership will
provide complete in-line metallization
process solutions to photovoltaic (PV)
manufacturers.
The alliance combines DEK International’s next-generation printing technologies and handling solutions with BTU International’s high-performance drying and firing
technologies to form a complete turn-key metallization line for solar cells. This broadens BTU’s
product offerings to the solar industry, which also
includes integrated in-line diffusion and anti-reflective
coating systems. BTU’s goal is to offer customers the lowest
cost per watt process. www.btu.com; www.dek.com.
International Thermal Spray Conference & Exposition (ITSC 2008)
June 2-4, 2008 • Maastricht, Netherlands
Organized by the German Welding Society (DVS), the ASM Thermal Spray Society (TSS) and the International Institute of Welding (IIW).
For more information, visit www.dvs-ev.de/itsc2008; or contact Cust. Srvc. Ctr., ASM Intl., Matls. Park, Ohio; tel: 800/336-5152 (ext. 0) or
440/338-5151 (ext. 0); fax: 440/338-4634; e-mail: customerservice@asminternational.org; Web: www.asminternational.org.
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INDUSTRY NEWS
Rolls Royce Links with Universities
to Advance Jet-Engine Technologies
Rolls-Royce plc, Derby, UK, opened a new University Technology Centre (UTC) at Karlsruhe University in Germany to research cooling in gas turbine combustors and turbines and related technologies required to improve the fuel efficiency and
environmental performance of future aero engines. The latest
UTC is the fourth to be established in Germany.
The economic and environmental demands on the aviation
industry call for aero engines to operate at higher fuel efficiencies, which means running at higher temperatures. Efficient
cooling systems are vital to prevent combustion and turbine components—even those made of the most advanced alloys—from
melting, and the UTC will take a holistic approach to maximize
the use of air for cooling. Using less air for cooling and more
in the combustion process will help to further reduce engine
emissions.
The University has proven academic capability in the research
areas of combustion cooling in very hot environments, film
cooling, and two-phase-flow; plus a range of rigs and sophisticated hardware, innovative methods, and measurement techniques. It is expected that Karlsruhe will work closely with a
number of existing Rolls-Royce UTCs in the UK—notably those
based in Surrey, Loughborough, and Nottingham Universities,
and the Osney Laboratory in Oxford—that collectively focus on
research into heat transfer, combustion, computational fluid dynamics (CFD), aerothermal techniques, and component interactions; and provide highly specialized modeling, validation,
and testing capabilities. www.rolls-royce.com.
In another area, Rolls-Royce Corp. acquired exclusive rights
to use a coating invented by Iowa State University (Ames, Iowa)
researchers that helps turbines stand up to the heat in jet engines.
The unique bond coating will be applied to engine turbine
blades made of nickel-base superalloys. The superalloys are designed for strength, but need help withstanding metal temperatures approaching 2100°F (1150°C) inside the hot section of a
jet engine, says Brian Gleeson, Iowa State’s Alan and Julie
Praxair and FMC
Technologies Sign
Agreement for Thermal
Spray Coatings Service
Praxair Surface Technologies, Indianapolis, Ind., a wholly owned
subsidiary of Praxair Inc., reached an agreement with FMC
Technologies, Houston, Tex., a global provider of technology
solutions for the energy industry and other industrial markets,
to supply thermal spray coatings for gate-valve components
used in oil and natural gas production. The agreement includes
plans for Praxair to establish a facility at Coimbatore in southern
India that is expected to be in full production by mid-2008. The
facility will include a manufacturing plant for coating oil-field
gate-valve components manufactured in India. Praxair’s thermal
spray coating provides wear and corrosion protection for
gate valves in critical service applications. Praxair also
provides FMC with thermal spray coating from its operations
in Houston and St. Etienne, France. www.praxair.com, or
www.praxairsurfacetechnologies.com.
The Rolls-Royce LiftSystem for the F-35B Joint Strike Fighter
consists of the Rolls-Royce LiftFan, the 3 Bearing Swivel Module
(3BSM), and the roll posts. Courtesyof Rolls Royce plc, Derby, UK.
Renken Professor in Materials Science and Engineering and a
co-inventor of the coating. The bond coating improves the durability and reliability of a ceramic thermal barrier applied over
the bond coat, and offers significant advantages over existing
coating technologies.
The coating is based on a composition consisting of platinum,
nickel, aluminum, and hafnium. A key advantage to this technology is that it is mechanically compatible with the superalloys it covers and protects. It reacts to the heat and stress of an
engine about the same way the superalloy does, which gives the
coating composition—and therefore the engine parts—better
performance and a longer life.
The Iowa State researchers continue to work on the coating
composition project, with the intent to develop a better, less expensive way to produce the coating, and are looking for new
coating compositions and new ways to deposit them on materials.
Rolls-Royce will have an exclusive license to commercialize
the inventions. Patents are pending for the inventions, and the
term of the license agreement is for the life of any patents. Also,
the license has the potential to be an important source of revenue for the research foundation. www.iastate.edu.
Optomec Develops
Deposition System for
Solar-Cell Production
Optomec, Albuquerque, N. Mex., a provider of additive manufacturing systems for high-performance applications in the
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ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
Linde Gas Cools Off Spray
Coating Technology
Linde Gas, Murray Hill, N.J., a North American subsidiary
and affiliate of The Linde Group, a global engineering
and industrial gases company, designed a turnkey,
high-pressure gas delivery system capable of delivering
pressures above the 50 bar required to use nitrogen in
the cold-spray process. Cold spray enables manufacturers
to achieve coatings that are compatible with traditional
thermal spray technologies, such as plasma and flame
spraying. However, cold spray has relied on scarce,
expensive helium to propel the powder coating material on
to surfaces.
Linde’s high pressure delivery system has been optimized
to support cold spray gun technology called Kinetiks 4000,
manufactured by CGT GmbH, based in Ampfing, Germany.
Cold spray converts the kinetic energy of solid particles to
thermal energy as they hit the surface to be coated, forming
a nearly impermeable bond. Cold spray is being used in industries such as aerospace, oil and gas, and power; where
coated materials are subject to extreme mechanical and
physical demands.
Cold spray’s lower thermal load results in lower porosity
and oxygen content. The coated surface has deposition
rates that can exceed 95%, and is durable with respect to
surfaces coated using other technologies. Having fewer oxides implies that the surface will have electrical and thermal
conductivity. www.linde.com.
INDUSTRY NEWS
electronics, biomedical, and aerospace & defense markets, introduced its M3D Aerosol Jet Deposition system, which is said to improve photovoltaic cell efficiencies. The M3D system is a printing
platform used in the development of next-generation devices such
as high density circuitry for photovoltaic cells, fuel cells, and printable electronics.
The system, used in conjunction with a light-induced plating
process, significantly increases overall photovoltaic wafer efficiencies. In preproduction trials, M3D technology produced printed
collector lines as small as 45 Pm by using new and modified versions of screen-printing material.
The M3D Aerosol Jet is a Direct Write™ process that first
aerosolizes conductive photovoltaic inks or pastes and then forms
an aerodynamically focused droplet stream of the material. This
Direct Write capability eliminates the need for screens or stencils required by traditional contact deposition processes while also
enabling much finer feature sizes.
In addition to the wide variety of materials and substrates
supported and the finer feature sizes, the additive process used
by M3D reduces environmental impact by minimizing the waste
and chemicals that are part of more traditional manufacturing
processes.
An additional benefit of the process is that the non-contact aerosol
jet feature enables the deposition of photovoltaic materials onto
extremely thin, non-planar substrates. New silicon wafer manufacturing technologies generate very thin, non-planar wafers that
can be produced far less expensively than traditional, ingot-based
silicon-wafer technology. www.optomec.com.
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INDUSTRY NEWS
Cold Spray at TWI Yorkshire
Cold spray, or more precisely cold gas dynamic spray (CGDS),
is a high-rate material deposition process in which powder particles (typically 1 to 50 Pm) are accelerated to velocities in the
range of 200 to 1000 m/s in a supersonic jet of compressed gas
at a temperature far below the melting point of the feedstock
powder (ambient temperature to 700°C, or 1290°F). Upon impact with a target surface, the solid particles experience plastic
deformation that disrupts thin surface films (such as metal oxides) and provides intimate conformal contact between the clean
metal surfaces under high local pressure. This permits bonding
to occur and rapid layer build-up of deposited material.
With CGDS, various materials can be sprayed without exposing them (or the substrate) to high thermal loads. Compared
with other thermal spray processes (e.g. plasma spray and flame
spray), CGDS allows coatings to be made having extremely low
porosity and oxygen content.
TWI uses the latest, highest specification commercial system
(CGT GmbH Kinetiks 4000, 47 kW) that can achieve process
gas temperatures up to 800°C (1470°F) and process gas pressures up to 40 bar. The feed-stock powder can be heated to temperatures over 500°C (930°F), resulting in improved adhesion
for some specific coating systems. The Active Jet Cold Spray
Gun can be operated with or without preheating the gas. This
enables the system to be configured for the application of tailored coatings.
Several materials have proven to be suitable for cold spray
including:
• Metals (Al, Cu, Ni, Ti, Ag, Zn, Ta, Nb)
• Refractory metals (Zr, W, Ta)
• Alloys (steels, Ni alloys, MCrAlYs)
• Composites (Cu-W, Al-SiC, Al-Al2O3)
With these materials in mind, a wide range of applications can
be explored, with possible end uses in a number of industry sectors, such as aerospace, automotive, oil and gas, power generation, motorsport, medical, petrochemical, and electronics.
www.twi.co.uk.
Sulzer Reports
Higher Sales and Earnings
for First Half of 2007
Sulzer, Winterthur, Switzerland, achieved strong growth and
substantially higher results in the first half of 2007, with divisions
increasing operating income by 46%. Orders, sales, operating
income, and net income were well above the previous year’s results.
All key markets and regions remained in a positive condition. The
outlook for the full year is encouraging, with strong gains expected in
orders and sales. In 2007, results are anticipated to be above those
of the previous year due to operating improvements and volume
leverage.
For Sulzer Metco, the first six months of 2007 depicted considerable impact from the operational improvement measures that were
started some years ago. Orders increased by 18.8% and sales improved by 23.1% to US $311 million. The operating income was up
64.8% to US $31 million. Return on sales reached 9.8%, compared
with 7.3% in the previous year’s first half. The key segments were in
a good condition. Although the positive trend is likely to continue over
the next few years, Sulzer Metco does not expect to develop at the
same pace as in this reporting period. www.sulzer.com
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Entegris Acquires
High-Purity Semiconductor
Coatings Business
Entegris, Chaska, Minn., acquired the assets of the high-purity semiconductor coatings business of Surmet Corp.,
Burlington, Mass. The acquisition is said to help strengthen
the company’s ability to deliver solutions that purify, protect,
and transport critical materials in semiconductor applications,
and gives Surmet customers access to a wider range of global
resources.
Surmet is a pioneer in high-performance, high-purity coatings that protect wafer handling and equipment components,
such as electrostatic clamps, in the semiconductor manufacturing process, and reduce contamination of wafers from the
components themselves. These microparticle-free and corrosion-resistant, high-performance coatings use an innovative low-temperature plasma process that can be applied on
a wide range of substrates.
Entegris sees the potential to extend the application of
Surmet’s technologies beyond the semiconductor industry.
The terms of the transaction were not disclosed. www.
entegris.com; www.surmet.com.
Nanowire Coating
for Bone Implants, Stents
Researchers at University of Arkansas, Fayetteville, Ark., discovered a simple, inexpensive way to create a nanowire coating
on the surface of biocompatible titanium, which can be used to
create more effective surfaces for hip replacement, dental reconstruction, and vascular stenting. Further, the material can
easily be sterilized using ultraviolet light and water or using
ethanol, making it useful in hospital settings.
The researchers use an alkali and heat to create titanium
oxide-based ceramic nanowires that coat the surface of a titanium medical device. They can control the length, height,
pore openings, and pore volumes within the nanowire scaffolds by varying the time, temperature, and alkali concentration in the reaction, says Z. Ryan Tian, assistant professor of
chemistry and biochemistry in the J. William Fulbright College of Arts and Sciences. The process is extremely sustainable, requiring only that the device be rinsed in reusable water
after the heating process.
Reconstructive bone surgeries such as hip replacements use
titanium implants. However, muscle tissue may not adhere well
to titanium’s smooth surface, causing the implant to fail after
a decade or so and requiring the patient to undergo a second
surgery.
A nanowire-coated joint placed in mice had tissue adhering
to the joint after four weeks. Because the researchers can control the size and shape of the pores in the nanowire scaffold, the
material also could be coated onto stents used in patients with
coronary artery disease and in potential stroke victims. Conventional stents sometimes become reclogged with fat after implantation.
The researchers have applied for a provisional patent for the
multifunctional nanowire bioscaffolds on titanium or titaniumcontaining alloys such as Nitinol. www.uark.edu.
ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
Reactive NanoTechnologies Inc. (RNT), Hunt Valley, Md.,
developer and manufacturer of its patented NanoFoil, partnered with the Kurt J. Lesker Co., (Clairton, Pa.;
www.lesker.com) to expand worldwide sales and distribution of NanoFoil and its accompanying NanoBond process.
Key markets to benefit from this partnership include semiconductor manufacturing, LCD and flat panel displays, advanced
displays, glass coatings, film coatings, and other vacuum industries using sputtering targets. Nanofoil precisely controls
the instantaneous release of heat energy for joining and reaction initiation applications. NanoBond produces a virtually
void-free solder bond having low residual stress and higher
melting temperatures; resulting in potentially higher sputter
powers, and greater film deposition rates.
Kurt J. Lesker Co. will serve as RNT’s exclusive distributor
in North America and Europe, offering NanoBond bonding
service for customer supplied materials, as well as full target assemblies incorporating NanoBond. www.rntfoil.com.
nCoat Involved in Various Activities
nCoat Inc.,Whitsett, N.C., announced through its operating
subsidiary High Performance Coatings (HPC) the formation of
a customer relationship with SoCal Diesel (Valencia, Calif.;
www.socaldiesel.com), which specializes in Duramax diesel
performance components. HPC applies heat and corrosion management and friction reduction coatings to internal diesel engine
components.
HPC coats the skirts of SoCal Diesel pistons with improved
S Series fluoropolymer dry film coating containing PTFE (polytetrafluoroethylene) additives. HPC’s lubricating coatings reduce metal-to-metal surface friction, thereby reducing wear
on the piston, and helping seat the piston during the break in period on the engine. HPC also coats the combustion sides of the
diesel engine pistons with H Series heat-management coatings,
which distribute combustion cycle heat evenly across the entire
crown of the piston. This reduces any hot spots and thermal oxidation affecting piston top surfaces. H Series is an inorganic ceramic metallic coating that also provides excellent thermal shock
characteristics when tested at temperatures greater than 1000
down to 65°F (540 down to 18°C) in water quench tests.
nCoat acquired Metallic Ceramic Coatings Inc. (MCC), King
of Prussia, Pa., which conducts business under the brand of JetHot coatings. The business combination is said to strengthen the
market position of both companies. MCC offers thermal barrier,
lubricating, and corrosion resistance coatings applied on autos
and bikes ranging from street rods and dragsters to classics, exotics, snowmobiles, and over-the-road trucks.
MCC claims to be a market leader in header coatings appli-
ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
INDUSTRY NEWS
RNT, Kurt J. Lesker Co. to Expand Market Reach
for Sputtering Targets
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INDUSTRY NEWS
cations producing low emissivity and ceramic insulating characteristics, which create thermal barriers on both the interior and
exterior surface of headers. In accelerated salt-spray tests conducted in accordance with ASTM B117, Jet-Hot corrosion barrier coatings last over 14 times longer than chrome and more
than 140 times longer than high-temperature paint, enduring
more than 5,000 hours.
nCoat announced that its newly acquired Pennsylvania-based
operating subsidiary, Jet-Hot Inc., opened a new production plant
in Quakertown, Pa., a high-volume, automated automotive
aftermarket coating facility in the northeast United States. In
its current configuration, the plant increases capacity at Jet-Hot
by 30%.
Jet-Hot Inc. announced a new high-temperature, high-gloss
coating known as Extreme Sterling. The coating uses near-molecular (nano-scale) ceramic particulates in its binder formulation that provides the coating with an exceptional binding capability. Extreme Sterling coatings serve as a thermal barrier to
reduce pipe skin temperatures up to 400°F (220°C), reducing
the need for higher grade pipes and thermal wrap insulation materials under the hood.
nCoat announced it received the Frost and Sullivan 2007 North
American Product Innovation of the Year Award for nCoat’s
thermal barrier coatings (TBCs). The coatings, developed at
nCoat subsidiary nTech Inc., are nano-formulated surface treatments. The award recognized the high-temperature resistant
nanoslurry coatings, which have low porosity, high density, good
strength and flexibility at temperatures to 4200°F (2310°C). The
Metallography of NiCrAl/Bentonite
Abradable Coatings
Abradable coatings (such
as Ni-4Cr-4Al/Bentonite) entail a family of coatings that
are used throughout jet engines, primarily as sacrificial
coatings into which moving
components wear. The coatings generally consist of a
metallic phase and a nonmetallic phase, and contain
Typical microstructure for Ni-4Crrelatively high porosity levels
4Al/Bentonite.
(to 40%). Typical locations
for application of an abradable coating include the fan, and lowand high-pressure compressor sections.
The composite nature of abradable coatings presents unique challenges from a metallography standpoint. Due to thickness and
porosity considerations, vacuum impregnation with a low-viscosity
cold mount epoxy is the recommended mounting method. To facilitate impregnation with fast-cure epoxies (which are typically
more viscous than slow-cure epoxies), the resin can be heated to
approximately 150°F (150°C) prior to mixing with the hardener.
Holding the epoxy at elevated temperature for 15 to 20 minutes
should result in a significant improvement in the viscosity of the
epoxy.
Thermal Spray Accepted Practices Committee
www.asminternational.org/tss.
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NanoSteel Redefines
Hardfacing
NanoSteel Co., Providence, R.I., a producer of nano-structured steel alloys for industrial applications, announced the commercial availability of its latest alloy line using the company’s
patented super hard steel (SHS) technology. SHS 9700 features
an ultrarefined crystalline microstructure, up to a thousand times
finer than existing compositions, and extreme hardness up to 69
HRC without the use of nickel, molybdenum, or tungsten. SHS
9700, produced in a range of cored-wire diameters suitable for
metal inert gas (MIG)/open-arc/submerged-arc welding applications and as an atomized powder for plasma-transferred arc
(PTA) welding applications, provides exceptional wear resistance in severe abrasion environments up to five times that of traditional chrome carbide and complex carbide materials.
The improved hardness/wear performance and cost-effective
pricing of SHS 9700 makes it an attractive hardfacing and wearplate welding material for commercial end users needing to extend the service life of mission-critical parts and components on
ground engaging tools and materials processing equipment used
in industries such as mining, construction, and oil and gas.
www.nanosteelco.com.
Purdue Makes Precision Parts
Via Laser and Machining
THERMAL SPRAY TIP
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nanoscale particulates in the slurry efficiently bind with the
substrate materials, which minimizes the risk of delamination
problems. www.ncoat.com.
Researchers at Purdue University, West Lafayette, Ind., are
perfecting a technique to manufacture parts that have complex
shapes and precision internal features by depositing layers of
powder materials, melting the powder with a laser, and immediately machining each layer. The method can be used to create
parts made of advanced materials such as ceramics, which are
difficult to manufacture and cannot be machined without first
using a laser to soften the material, according to Yung Shin, professor of mechanical engineering and director of Purdue’s Center
for Laser-Based Manufacturing.
Because the technique enables parts to be formed one layer
at a time, it promises new industrial applications for manufacturing parts containing myriad internal features. Although the
basic laser deposition technique is not new, the researchers have
increased its precision by adding the machining step. The method
is about 20 times more accurate by adding the ability to machine
the part while it is being formed. They have developed a facility
that can actually deposit the powder, heat it with the laser, and
machine it at the same time.
The new technique could be ideal for manufacturing certain
kinds of ceramic components that are not produced in large
enough quantities to justify the expense of designing costly dies.
Components made in small lot sizes might be produced far more
economically by machining instead of using dies. But there
has been no practical way to machine the brittle ceramic
materials economically with the high precision needed for many
applications.
The technique is potentially practical for industry because it
does not require expensive clean room environments. Rolls-
ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
Mechanical engineering doctoral student Kevin Schoeffel controls a laser-cladding system
developed as part of research led by Yung Shin, a professor of mechanical engineering and
director of Purdue’s Center for Laser-Based Manufacturing. A powdered material is deposited
and then melted by a direct-diode laser, producing coatings in a one-step process that is less
expensive and faster
Royce Corp. is evaluating the machining method for potential medium- and long-range
applications.
Purdue’s Office of Technology Commercialization has filed patents in connection with the
laser-deposition-machining technique, which is available for licensing. www.purdue.edu.
Raymor Industries Inc., Boisbriand, Quebec, Canada, a developer and producer of singlewalled carbon nanotubes,
nanomaterials, and advance
materials, announced that
its wholly-owned subsidiary,
Raymor Aerospace has signed
a conditional agreement for the
acquisition of a company specializing in manufacturing and
repairing precision parts the
aerospace and industrial sectors. The strategic acquisition
allows Raymor Aerospace to
rapidly implement a one-stop
shop for its specialized coating
services in these sectors.
www.raymor.com.
INDUSTRY NEWS
Raymor
Industries
Acquisition
Bolsters
Its Coating
Division
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ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
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TSS News
Members of the TSS Board
Reelected to a Second Term
The TSS electorate, consisting of active TSS Board and Committee members, has re-elected the following people to the TSS Board for 2007-2010,
effective October 1, 2007:
Mr. Peter Heinrich, Manager, Thermal Spray, Linde Gas AG, Germany
Mr. William J. Lenling, Vice President and Materials Engineer, Thermal
Spray Technologies, Inc., Sun Prairie, Wis.
Dr. Roland D. Seals, FASM, Senior Staff Scientist, BWXT Y12
National Security Complex, Oak Ridge, Tenn.
Continuing in their leadership roles on the TSS Board are Mr. Peter Hanneforth, president; Mr. Mitchell Dorfman, vice president; Mr. Charles Kay,
secretary/treasurer; and Dr. Richard Knight, FASM, immediate past president.
Other TSS board members include:
Mr. Richard Bajan
Mr. Thomas S. Passek
Dr. Basil R. Marple
Executive Director
Dr. Christian Moreau, FASM
Mrs. Sarina Pastoric
Ms. Lysa Russo
Staff Liaison
Mr. Raymond J. Sinatra
Dr. Mark F. Smith, FASM
Board Liaison
Dorfman
Hanneforth
Heinrich
Knight
Lenling
Seals
Kay
International Thermal Spray
Conference & Exposition
(ITSC 2008)
June 2-4, 2008
Maastricht, Netherlands
Organized by the German Welding Society (DVS),
the ASM Thermal Spray Society (TSS)
and the International Institute of Welding (IIW).
For more information, visit www.dvs-ev.de/itsc2008;
or contact Cust. Srvc. Ctr., ASM Intl., Matls. Park, Ohio;
tel: 800/336-5152 (ext. 0) or 440/338-5151 (ext. 0);
fax: 440/338-4634;
e-mail: customerservice@asminternational.org;
Web: www.asminternational.org.
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ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
Register Today.
2008 Surface Engineering for Aerospace
and Defense Conference and Exposition
January 21-22, 2008
Coronado Springs Resort
Walt Disney World • Orlando, FL
This two day event will bring together surface engineering
professionals from a wide variety of disciplines – electroplating,
PVD, CVD, thermal spray, ion implantation – focused on problems
facing the aerospace and defense industries. Topics include:
•
•
•
•
Green Manufacturing and De-Manufacturing
Engineered Materials for Harsh Environments
Extending Service Life and Enhancing Performance
Surface Engineering and Global Climate Change
If your organization is involved in any aspect of surface finishing,
you won’t want to miss this unique opportunity! In addition to
the technical excellence of this conference, the networking
opportunities are invaluable.
To register for Surface Engineering for Aerospace and Defense visit
www.asminternational.org/surfaceengineering
ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
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THERMAL SPRAY TIP
Measuring Deposition Efficiency
Definition: Deposition efficiency (DE) is defined as an idealized measure of the percentage of particles introduced into
a spray jet that actually deposits onto a flat substrate without
overspray considerations.
Measurement: Deposition efficiency (DE) can be measured
according to the following procedure:
• Determine the mass (X ) of a clean, grit blasted 4 in. × 6 in.
× 0.125 in. (100 × 150 × 3 mm) flat steel plate
• Place powder into the powder feeder
• After stabilization of the spray parameters and powder feed,
spray material onto the steel plate for a known period of time
(e.g., 60 s) at a predetermined feed rate (e.g., 20 g/min) ensuring
that the spray pattern remains on the plate at all times. (The
plate may be cooled using air/gas jets directed at the rear face
of the plate.)
• Measure the mass (Y ) of the plate plus the coating.
• Determine the gain in mass due to the coating deposited (Z
= Y - X ).
• Divide the mass deposited in one minute (Z) by the powder
feed rate and multiply by 100 to give DE in %.
• Repeat the measurement a minimum of three times and take
the average.
Note: Deposition efficiency is only useful insofar as it provides
a measure for optimizing spray parameters.
Source: Handbook of Thermal Spray Technology, Ed. J.R.Davis,
ASM International, Materials Park, OH, 2004.
Thermal Spray Accepted Practices Committee
www.asminternational.org/tss.
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ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
Thermal Barrier
Coatings: The Basics
Andrea Scrivani and Gabriele Rizzi
Turbocoating S.p.A, Parma, Italy
hermal barrier coatings (TBCs) are widely used surface
treatments typically consisting of a top coat of Y2O3 air
plasma sprayed partially stabilized ZrO2, and a MCrAlY
bond coat (where M is Ni, Co, or NiCo), which can be
deposited using different thermal spray processes such as air plasma
spray (APS), vacuum plasma spray (VPS), and high-velocity oxyfuel (HVOF) [1-3]. Another example is a top coat of Y2O3 partially
stabilized ZrO2 deposited using electron-beam physical vapor deposition (EBPVD), and an aluminum alloy bond coat deposited using
chemical vapor deposition (CVD).
For many metallic components, adequate creep properties (creep
resistance, thermal efficiency, thermal shock resistance, etc.) can
only be achieved with the use of nickel and cobalt superalloy base
material plus adequate coatings and surface treatments to obtain resistance to oxidation and corrosion at high temperature. Repair of
components means restoring their original properties. Therefore,
these surface treatment processes are not only used during manufacture, but also during repair.
T
Mechanics of Thermal Spray
Thermal spray processes are widely used to coat components because they can deposit a range of materials and obtain thicknesses
from 80 to 2,000 Pm. The main stages of a thermal spray coating
deposition are:
• Feeding the coating material into the spray gun
• Heat transfer from plasma or combustion gas to melt coating
material
• Transport of melted particles on to the substrate surface
• Heat transfer from the melted particles to the substrate and solidification
• Coating formation by means of overlapping of several coating
material layers
The particles assume a splat configuration and solidify and transfer
the heat to the base material. The final coating consists of several
layers of coating materials. The bonding is generally mechanical,
created by local melting and diffusion.
Surface preparation is critical so that the spray particles can adhere and establish an integral coating. For thermal spray, the most
common surface preparation method is grit blasting the surface using
a suitable abrasive material such as corundum or silicon carbide.
The main parameters to be considered are the type of blasting machine, blasting media (type, grain size distribution, shape, and hardness), working pressure, and hardness of substrate materials. Tuning
of blasting parameters is crucial to obtain good surface preparation
without causing contamination from the blasting particles.
In the case of plasma spraying under a vacuum, the coating process
is carried out at reduced pressure (about 10 to 50 mbar). The jet velocity is higher because of the absence of air resistance, and the lack
of oxygen results in oxide-free coatings[3,4]. The higher jet velocity
and less cooling result in a higher-energy deposition, which creates
coatings that are denser and have higher chemical purity.
In turbine applications, air plasma spray is used to spray yttria
partially stabilized zirconia (functioning as the TBC) and also aluminum on the “fir-tree” section of blades to serve as a seal with
the rotor when the part is assembled. (The fir-tree section refers to
the bottom part of a blade that slots into the rotating assembly.)
Vacuum plasma spray is used to spray MCrAlY alloys as a bond
coat and a high-temperature corrosion- and oxidation-resistant
coating.
The HVOF process is used to deposit several anti-wear and anticorrosion coatings. The coatings are dense and the splat on the surface is ideal. The powder is injected into the flame by a suitable carrier gas (usually nitrogen), melted, and projected on to the substrate
surface. The most common materials sprayed using this technology
are metals, carbides, cermets, and some polymers[5-8].
Applying MCrAlY Coatings
Studies have been carried out to compare HVOF and LPPS-VPS
technologies by evaluating their MCrAlY bond coats[1, 3]. Commercial powder (AMDRY 995, a widely used coating) was used in tests
and deposited-film quality was assessed. Coatings from the two
processes were compared in terms of their microstructural (porosity,
oxide concentration, presence of unmelted particles ) and mechanical characteristics (hardness). The surface composition and morphology of the coatings were also determined, and specific efficiency tests were performed for the three technologies.
Vacuum plasma sprayed technologies are currently the state-ofthe-art for the production of MCrAlY alloy coatings, which serve
as oxidation-resistant material and the bond coat in TBC systems.
The quality of the coatings obtained by VPS is better than that obtained by means of HVOF (Fig. 1). Nevertheless, HVOF coatings
demonstrate a good porosity level due to the high flame velocity,
but the oxide content is slightly higher than in VPS coatings. Hardness is the same for both processes.
Prior to coating, serviced gas turbine components usually go
through repair processes. Factors that should be considered before
thermal spraying include:
• The extent of and quality of potential damage to the base material
Porosity, %
Oxides, %
Hardness, HV300
LPPS
Nearly zero
Nearly 0
370-450
HVOF
<1
<1
400-450
Fig. 1 — Coating samples from low pressure plasma spray (left) and
high velocity oxygen fuel processes (right).Scales at top right are 50Pm.
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ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
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13
Set A
Set C
Parameter set
A
B
C
D
Porosity, %
11-14
17-19
21-23
26-28
Set B
Set D
Fig. 2 — Sets A, B, C, and D refer to increasing power level of the
plasma. The porosity varies; however, the pores are uniformly distributed for all the parameters.
• The presence of various kinds of materials that are carried over
from any repair processes. For example, the bulk material, and
welding and brazing materials having different thermal expansion
coefficients will influence the properties of the coating.
• The risk of cracks or damage from preheating by plasma spray
Possible solutions are HVOF technology, or using an improved
preheating procedure for LPPS coatings. The HVOF process is a
relatively cold process; i.e., preheating the components to high temperature is not needed, and the coatings have less oxides (similar to
LPPS). This process is also more economical.
Preheating to high temperature is needed for vacuum plasma spray
processes. The plasma jet generates a local overheating and the
inhomogeneous temperature sometimes reopens cracks or damage
in repaired areas. Therefore, an improved preheating procedure is
needed to minimize the contact between the plasma and the components. Turbocoating has designed an inert gas furnace for preheating.
Applying Top Coats
After deposition of metallic MCrAlY bond coats, a ceramic layer
could be deposited to reduce the life-service temperature of components. Usually yttria partially stabilized zirconia (YPSZ) is used
as a coating material and deposited by APS.
Typically, OEM specifications classify the ceramic top coat according to thickness. A thin TBC, usually applied to blades and
vanes, is defined as a 200 to 800Pm thick coating having from 5 to
20% porosity. A thick TBC, usually applied to stationary gas turbine components such as the combustion chamber or segments and
liner that cover turbine internal walls, is generally a 1.5 to 2.0mm
thick zirconia coating having up to 28% porosity.
Zirconium oxide (ZrO2) is selected due to its properties of low
heat conduction coefficient (making it useful as a thermal barrier)
and a higher coefficient of thermal expansion than that of most
oxides (such as alumina and chromia), which makes the deposition
of the ceramic coating on a metal alloy substrate easier. Furthermore, the relatively poor mechanical stability of ZrO2 caused by a
4% volume increase during transformation from tetragonal to monoclinic phase, has been substantially improved in recent years. This
is accomplished by partially stabilizing the tetragonal phase at room
temperature by adding suitable stabilizers such as calcium oxide
(CaO), magnesium oxide (MgO) and yttrium oxide (Y2O3). Yttria
is normally preferred since CaO and MgO tend to vaporize at high
temperatures[9, 10].
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YPSZ is a multiphase material. At room temperature, the stable
cubic phase coexists with the tetragonal phase (metastable at room
temperature) and a small percentage of the monoclinic phase. This
structure produces better mechanical properties in terms of mechanical strength and fracture toughness[11].
The presence of monoclinic phase in the coating should be avoided
as much as possible to prevent the volume variation induced by
phase transformation, which could occur during the service of the
coating. Therefore, powders having low monoclinic content are preferred, and phase content in the coating after deposition has to be
checked carefully.
Comparing Porosity
Besides several applications of both thin and thick TBCs, Turbocoating studies have been carried out to develop a thick TBC to
resist to thermal cycling fatigue (TCF), paying attention to the microstructure and the coating porosity[12]. This development has been
engineered for application on gas turbine combustion chambers,
mainly on heat shields and liners.
Tests on APS sprayed yttria partially stabilized zirconia produced
using four different sets of parameters (with increasing level of
power) show that porosity varies from 11 to 28%. The coating structure is homogeneous (Fig. 2) with fine pores uniformly dispersed
in the coating matrix. In a TCF test, the coating samples passed 1,000
thermal cycles (from 1,000 to 20°C, or 1,830 to 68°F) with good
performance. This result shows that high coating cohesion coupled
with good structure is more important than absolute TBC porosity.
The presence of fine, uniformly distributed pores contributes to TCF
resistance, but the number of pores (the overall porosity) is of less
importance.
While thermal spray processes are versatile and widely used, they
cannot be used in some situations such as the coating of internal
cooling passages. In such cases, an aluminum coating is deposited
using the chemical vapor deposition process.
Conclusions
Thermal spray processes are widely used in gas turbine application thanks to their versatility. In particular, vacuum plasma spray
technologies currently remain the state of the art for the production
of MCrAlY alloy coatings to be used as oxidation-resistant material and bond coats in TBC systems. Nevertheless, HVOF coatings
demonstrate an acceptably low porosity level due to the high impact conditions during impingement and, additionally, the oxide
content is slightly higher with respect to VPS. On the other hand,
the HVOF process is less expensive than a VPS process.
The TBC developed and presented in this paper exhibited good
behavior with regard to thermal cycling tests. The process is robust
and produces a high-performance TBC coating having low sensitivity to variations in the process parameters.
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References
1. A. Scrivani, et. al., A Comparative Study on HVOF, Vacuum Plasma
Spray and Axial Plasma Spray for CoNiCrAlY Alloy Deposition, Proc.
ITSC2001, Singapore, 28-30 May 2001.
2. A. Scrivani, et. al., On the Experimental Correlation Between The Properties of Yttria Partially Stabilized Zirconia Coatings And The Process Characteristics, Proc. ICCE/8, Tenerife, Spagna, 5 -11 August 2001.
3. A. Scrivani, et. al., A Comparative Study of High Velocity Oxygen Fuel,
Vacuum Plasma Spray (VPS) and Axial Plasma Spray (AxPS) for The Deposition of CoNiCrAlY Bond Coat Alloy, J. of Thermal Spray Tech., Vol.
12(3), Sept. 2003-1.
4. A. Scrivani, Thermal Spray Coatings: Introduction and Application to
ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
the Power Generation Field,” Proc. of II course, Intl. Summer School on
Advanced Matl. Sci. & Tech., Advanced Coating Technologies, 28 Aug.1 Sept. 2000. Jesi-Ancona (Italy) p 124-133.
5. A. Scrivani, et. al., Resistance of Thermal Spray Coatings in Sour Environments: A Comparison of Tungsten Carbide, Chromium Carbide and
Inconel 625, Proc. EUROPM 99, Advances in Hard Materials Production,
Torino, Italia, 8-10 Nov. 1999.
6. A. Scrivani, et. al., A Contribution to the Surface Analysis and Characterization of HVOF Coatings for Petrochemical Application, Wear, Vol.
250/1-12, p 107-113, 2001.
7. A. Scrivani, et. al., A Comparative Study of the Deposition of Spray and
High Velocity Oxygen Fuel, Proc. ITSC2001, Singapore, 28-30 May 2001.
8. A. Scrivani, M. Rosso, and L. Salvarani, Performances and Reliability
of Thermal Spray Coatings WC Based Materials, Proc. 15th Plansee Seminar, Reutte, Austria, 28 May - 1 June 2001.
9. A. Scrivani, et. al., On The Experimental Correlation Between Plasma
Spray Process Conditions and Yttria Partially Stabilized Zirconia Coating
Properties, Thermal Spray, Surface Engineering via Applied Research,
Proc. ITSC2001, Ed. C. Berndt, ASM International, Materials Park, OH,
USA, p 1207-1210, 2001.
10. D.S. Suhr, T.E. Mitchell, and R.J. Keller, Microstructure and Durability
of Zirconia Thermal Barrier Coatings, Advances in Ceramics,” Vol. 3,
Ed. A. H. Hueur and L.W. Hobbs, American Ceramic Soc., USA, p 503517, 1982.
11. G.N. Heintze and R. McPherson, Structures of Plasma-Sprayed Zirconia Coatings, Advances in Ceramics, Vol. 24, Ed. S. Somiya, H. Yanagida,
and N. Yamamoto, American Ceramic Soc., USA, p 431-437, 1988.
12. A. Scrivani, H.K. Pugsley, and G. Rizzi, Development of Thick Thermal
Barrier Coating With Varying Porosities and Continually High Functional
Properties, Proc. ITSC2004, Osaka, Japan, 10-12 May 2004.
For more information: Andrea Scrivani is technical director, and Gabriele
Rizzi is R&D manager for long-term research projects (e-mail:
gabrielerizzi@turbocoating.it), Turbocoating S.p.A., Parma, Italy; Web
site: www.turbocoating.com.
CALENDAR
3–4 Dec. Surface Tech. & Functional Coatings, a European Exec. Seminar: Ermatingen, Switzerland. Contact Deutsche Gesellschaft für Materialkunde e.V., Frankfurt, Germany; tel: +49-(0)69-75306-757; fax: +49(0)69-75306-733; e-mail: np@dgm.de; Web site: www.dgm.de.
2008
21–22 Jan. Engrd. Surfaces for Aerospace & Defense: Lake Buena Vista,
Fla. Sponsored by ASM Intl. Contact Cust. Srvc. Ctr., ASM Intl., Matls.
Park, Ohio; tel: 800/336-5152 (ext. 5900) or 440/338-5151; fax: 440/3384634; e-mail: customerservice@asminternational.org; Web site: www.asminternational.org.
27–30 Jan. Paint & Coatings Expo (PACE 2008): Los Angeles, Calif.
Web site: www.pace2008.com.
28 Jan.–1 Feb. 32nd Intl. Conf. & Expo on Advanced Ceramics &
Composites: Daytona Beach, Fla. Contact Megan Mahan, mktg. dir., Amer.
Ceramic Soc., Westerville, Ohio; tel: 614/794-5894; e-mail:
mmahan@ceramics.org; Web site: www.ceramics.org/acc.
8-9 Feb. WTS 2008 (Workshop on Thermal Spray): New Delhi, India.
Organized by Metallizing Equipment Co. Pvt. Ltd., Jodhpur, India); Contact Mr. Girish Mathur; tel: +91 9351509835; or Mr. Noman M. Shaikh; tel:
+91-291-2747601; Web site: www.mecpl.com/wts-2008.
12–13 Feb. ShipTech: Biloxi, Miss. Contact Tricia Wright, event coord.,
Concurrent Technologies Corp., Johnstown, Pa.; tel: 814/269-2567; e-mail:
wright@ctc.com.
27–28 Feb. 48th Israel Ann. Conf. on Aerospace Sciences: Tel Aviv and
Haifa, Israel. Contact Dan Knassim Ltd., Ramat Gan, Israel; tel: 972-36133340, ext. 207; fax: 972-3-7604829; Web site: www.aeroconf.org.il.
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Thermal Spray Coatings Protect
Steel Structures from Corrosion
etal spray, or thermal spray, is commonly used today
to protect steel structures from corrosion. In excess of
200 metric tons of zinc wire is sprayed annually in
New Zealand to protect steel structures in many different types of environments, from inland to submerged conditions.
This represents an area of 200,000 m2 (2.1 million square feet) with
a coating thickness of 75 Pm or 100,000 m2 (1.07 million square
feet) with a coating thickness of 150 Pm.
In one of those applications, Metallisation Ltd.’s, (Dudley, West
Midlands, UK) New Zealand distributor, Metal Spray Suppliers
(NZ) Ltd., supplied equipment and supplies to Edmonds Industrial
Coatings Ltd of Wanganui to apply a coating system for airport air
bridges in New Zealand. Typically, Pacific Rim airports are often
located on the coast and air bridges are exposed to the harsh marine
environment. Coating systems have to provide long-term, advanced
corrosion protection and be visually attractive. J & D McLennan
Ltd (ael.co.nz), responsible for maintenance of Airport equipment
for the whole of the South Pacific specified a finish and quality to
the same high standard as automotive bodywork. This meant creating a zinc anti-corrosion coating that was smooth enough to facilitate a functional, yet decorative, paint system, and protect the air
bridge against the elements.
Requirements for the job included an arc-spray system that would:
• Apply a smooth, high-quality zinc layer at the fastest rate possible without having to sand the surface smooth after spraying
• Be flexible enough to minimize equipment repositioning and
allow the operator good access to the air bridge
• Be reliable in a hostile blast and spray environment
• Be economical to use and easy to operate and maintain
Edmonds selected the Metallisation Arc 170 push/pull system,
which provided the required spray rates, as well as the necessary
10-m (33 ft) reach for convenient positioning. The Arc 170 is fast
and provides a high deposition rate and efficiency that doesn’t compromise the coating quality or integrity. The spray system’s fast
spray rate ensures that blast-prepared surfaces are coated as quickly
as possible, keeping oxidization and contamination of the interface
to a minimum. This is critical to achieve the strongest possible bond
to the surface. With the system, processing time for all anti-corrosion surface treatments has been cut by half to two days, and eliminated time consuming manual sanding.
Air bridges come in many forms to suit the diverse types of passenger aircraft. A complete air bridge can be up to 27 m (88 ft) long.
Using the Metallisation Arc 170 equipment, and the space available
at its extensive facility, Edmonds can complete the anti-corrosion
treatment of the air bridges in one process. The complete turnaround
time for an Apron drive air bridge is ten days. Resene Paints, working
in conjunction with McLennan, developed and specified the post
zinc arc spray paint system that would complement and work in synergy with the zinc layer. Resene proposed a low-build duplex paint
system that would incorporate all three methods of corrosion protection available; that is, sacrificial, inhibitive, and barrier. The
process sequence using the three-mode protection method was:
M
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Air bridges docked to aircraft; bridges are given a thermal spray coating
to protect the steel structure from corrosion.
• Surface preparation to SA3 abrasive grit blast
• Apply a 100 Pm zinc arc spray with one pass
• Seal/build coat (2 applications) using Resene’s zinc-phosphate
inhibitive epoxy system
• Resene’s low sheen urethane top coat (2 applications) developed to suppress reflection from lights at the airport to aid the pilot’s
vision when taxiing the aircraft to the bridge
The Resene paint system is sprayed directly on to the as-sprayed
zinc. The smoothness of the zinc coating eliminated the need for
any dressing or prepaint preparation, which saved time, labor, and
expense. The competed air bridge with its attractive and functional
anti-corrosion coating system is then ready for a very long service
at any of New Zealand’s airports.
The first air bridge using this innovative system was installed at
Wellington Airport in October 1997, and since then air bridges have
been coated and supplied to Auckland, Melbourne and Sydney, with
many more proposed for the Australasian region. Nearly a decade
on, the first air bridge coating system is performing with ease in the
harsh conditions. J & D McLennan Ltd. guarantees the air bridge
coating system for 20 years. Edmonds has now provided anti-corrosion protection for more than 40 air bridges.
Arc-sprayed zinc provides a thicker, greener alternative to galvanizing, and furthermore, is not limited by tank size and does not
distort the work piece. Coating thickness may be varied from place
to place to provide extra protection in critical areas. The process is
not limited to zinc and the coating material may be selected specifically for the environment. The coating can be applied on site, without
creating any effluent disposal problems. The system requires a reduced stock of zinc, which means working capital is not tied up in
a molten zinc bath. Further savings are made, as fuel is not needed
to keep zinc molten when the process is not operational. Metal
spraying is also used to restore corrosion protection on damaged
areas of welded galvanized steel.
ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
In another application, thermal spray coatings are used to protect
the Emsworth Lock and Dam on the Ohio River in the U.S. from
corrosion. Metallisation’s North American distributor, TMS Metalizing Systems Ltd., worked closely with its customer, Oregon Iron
Works (OIW) who has metal sprayed six dam gates with zincaluminum alloy.
The gates make up the bulkhead, which raise and lower the sluice
gate on the dam. This was part of an overhaul project to rehabilitate
the dam’s gate and mechanical electrical systems. OIW secured the
project with Pittsburgh’s District Office of the Corps.
The aim of the project was to metal spray the gates with zincaluminum coating to protect them from corrosion. Each of the six
gates measured 115 ft long and 12 to 14 ft high (35 m and 3.65 to
4.25 m). Consisting of steel T-bars and angle iron, they created
approximately 15,000 ft2 (1,400 m2) of surface area to be sprayed.
The job specifications required 85/15 zinc-aluminum material with
a minimum thickness of 16 mils (0.4 mm). The sheer size and shape
of the structure presented OIW with a number of challenges, especially having access to all surfaces.
TMS Metalizing Systems conferred with OIW to identify the
challenges and advise on the best possible approach to the project.
The outcome was to opt for two Metallisation Arc170 systems, a
700 A, high-production arc spray system with the required supplies
package reach of 33 ft (10 m).
TMS Metalizing Systems arranged on-site training to ensure the
metalizers were fully prepared prior to starting the project. To coincide with this training and preparation, OIW also enlisted the help
of SSPC ( the Society for Protective Coatings) to conduct the SSPC
Metallizing steel structures of the Emsworth locks on the Ohio River.
Thermal Spray Inspection Training Course, which supported OIW’s
ongoing commitment to quality and training of its staff.
The push/pull design of the arc spray system allows a 33 ft (10m)
supplies package, which enabled OIW to coat the top surfaces
without rotating the gate. The drum dispensers also resulted in
lower material costs, as spooling was not required. To protect
the gates from corrosion, they were metallized with 0.125 in. (3
mm) diameter, 85/15 zinc-aluminum alloy wire. The use of this
diameter wire also has the benefit of providing a good quality
coating at high throughputs with increased deposit efficiency.
www.metallisation.
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ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
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Calculated gas flow in a new powder port ring
holder designed and optimized to prevent
nozzle clogging and lump formation. Argon
flows through the circular ring channel and 16
convergent channels (in red) to form a gas
screen (in green) in front of the nozzle wall.
JTST
HIGHLIGHTS
The Journal of Thermal Spray
Technology (JTST), the official journal of
the ASM Thermal Spray Society,
publishes contributions on all aspects –
fundamental and practical – of thermal
spray science, including processes,
feedstock manufacture, testing, and
characterization. As the primary vehicle
for thermal spray information transfer, its
mission is to synergize the rapidly
advancing thermal spray industry and
related industries by presenting research
and development efforts leading to
advancements in implementable
engineering applications of the
technology.
JTST editor Christian Moreau has
announced that the December issue
16(4) is a special issue focusing on
thermal spray activities in the Nordic
countries of Europe. Guest editors for
this issue are Nicolaie Markocsan,
Per Nylén, Erja Turunen, Petri Vuoristo,
and Jan Wigren. Several articles are
highlighted here.
In addition to the print publication,
JTST is available online through
www.springerlink.com. For more
information, please visit
www.asminternational.org/tss.
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“Clogging and Lump
Formation during
Atmospheric Plasma
Spraying with Powder
Injection Downstream the
Plasma Gun”
Isabelle Choquet,
Stefan Björklund,
Jimmy Johansson, and Jan Wigren
This study numerically and experimentally investigates lump formation during atmospheric
plasma spraying with powder injection downstream the plasma gun exit. A first set of investigations focused on the location and orientation
of the powder port injector. It turned out to be impossible to keep the coating quality while avoiding
lumps by simply moving the powder injector. A
new geometry of the powder port ring holder was
designed and optimized to prevent nozzle clogging, and lump formation using a gas screen. This
solution was successfully tested for applications
with Ni-5 wt.%Al and ZrO2-7 wt.%Y2O3 powders used in production. The possible secondary
effect of plasma jet shrouding by the gas screen
and its consequence on powder particles prior to
impact was also studied.
“Laser Shock Flier Impact
Simulation of ParticleSubstrate Interactions in
Cold Spray”
M. Jeandin, S. Barradas,
V. Guipont, R. Molins, M. Arrigoni,
M. Boustie, C. Bolis, L. Berthe,
and M. Ducos
Coating-substrate adhesion in cold spray is a
paramount property, the mechanisms of which
are not yet well elucidated. To go into these mechanisms, due to the intrinsic characteristics of the
cold spray process (particle low-temperature and
high velocity) direct observation and control of
in-flight particles and related phenomena cannot
be done easily. For this reason, an experimental
simulation of the particle-substrate reactions at
the particle impingement was developed. This
Simulation of Cu particle (ø 15Pm, v = 800 m.s1) impingement on Al.
simulation is based on original flier impact experiments from laser shock acceleration. Relevant interaction phenomena were featured and
studied as a function of shearing, plastic deformation, and phase transformation, primarily.
These phenomena were shown to be similar to
those involved in cold spray. This was ascertained
by the study of the Cu-Al metallurgically-reactive system using SEM, TEM, EPMA, and energy balance and diffusion calculations. This simulation could also be used to feed finite element
(FE) modeling of cold spray and laser shock flier
impact.
“Microstructural Studies of
Cold Sprayed Copper,
Nickel, and Nickel30%Copper Coatings”
Heli Koivuluoto, Juha Lagerbom,
and Petri Vuoristo
Cold spraying enables production of metallic
coatings with low porosity level and low oxygen
content. Several material properties such as electrical conductivity and corrosion resistance rely
on these properties. The aim of this study was
to characterize microstructural properties of cold
sprayed copper, nickel, and nickel-30%copper
coatings. Microstructures, denseness, and deformation of particles were investigated. SEM
analysis and corrosion tests were done to get information about through-porosity. Open porosity
has an important role on the protectiveness of anodically protective coatings, such as copper and
nickel. In this study cold sprayed Cu coating was
fully dense. However, cold sprayed Ni and Ni30%Cu coatings seemed to be microstructurally
dense, but some porosity in some areas of the coatings, especially in some parts of the particle
boundaries was noticed after corrosion tests. Furthermore, the effect of annealing on microstruc-
Morphology of Cu powder (BSA -22+5 Pm).
ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
ture and corrosion test behavior was studied. Cold
sprayed Ni coating became denser during heat
treatment.
“A Method for
Characterizing the Degree
of Inter-particle Bond
Formation in Cold Sprayed
Coatings”
T.S. Price, P.H. Shipway,
D.G. McCartney, E. Calla,
and D. Zhang
The degree of bonding between particles within
cold sprayed deposits is of importance as it affects their mechanical and physical properties.
This paper describes a method for characterizing
the bonding between aluminium and copper particles following deposition by cold spraying. Aluminium and copper powders were blended in the
ratio 1:1 by volume, deposited onto a copper substrate, and subsequently heat treated at 400 °C for
15 minutes. An intermetallic layer formed along
some regions of the aluminium-copper boundaries, believed to be where true metal to metal
contact occurs. In other regions, metal to metal
contact was inhibited by the presence of oxide
films. Image analysis was employed to measure
the fraction of the aluminium–copper interface
covered with intermetallic phases and to estimate
intermetallic thicknesses. By increasing the primary gas pressure in the cold spray process an increase in the degree of inter-particle bond formation occurred.
BSE image of the heat treated Al-Cu deposit
sprayed at 29 bar at high magnification
showing Cu, bright, Al, dark, and three distinct
intermetallic layers at the interface. Spray direction top to bottom.
“Measuring Substrate
Temperature Variation
During Application of
Plasma Sprayed Zirconia
Coatings”
H.R. Salimijazi, L. Pershin,
T.W. Coyle, J. Mostaghimi,
S. Chandra, Y.C. Lau,
L. Rosenzweig, and E. Moran
Substrate temperature variation was measured
during plasma spraying of ZrO2 7%Y2O3 powder
using fast response thermocouples embedded
in the stainless steel surface. Coatings were deposited with both stationary and moving torches.
Particles velocity and temperature within the
plasma plume at 50 mm spray distance.
The substrate was either kept at room temperature at the start of coating deposition or pre-heated
to 270-300°C. Peak temperature during spraying
reached 450°C for a surface initially at room temperature, and 680°C for a surface preheated to
300°C before coating deposition. Preheating the
substrate reduced coating porosity by approximately 40%. The porosity at the center of the deposit was significantly lower than that at its periphery since particle temperature and velocity
were lower at the edges of the plasma plume than
along its axis. When a coating was applied with
a moving torch the substrate temperature did not
increase above 450°C, at which temperature heat
losses to the ambient equalled the heat supplied
by the plasma plume and particles. Coating
porosity decreased with distance from the substrate. As sequential layers of coating are applied
surface temperature increases and roughness decreases. Both of these factors suppress breakup of particles landing on the substrate and
thereby reduce coating porosity.
Hollis Joins
JTST Editorial Team
Dr. Christian Moreau, editor of the Journal of
Thermal Spray Technology, has announced that
Dr. Kendall Hollis, technical staff member, Los
Alamos National Laboratories (LANL), will join
Moreau
Hollis
ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007
Kuroda
the JTST editorial team as associate editor.
Dr. Hollis received his B.S. in nuclear engineering from the University of Illinois in 1990.
He did graduate study in plasma physics/material processing at the University of WisconsinMadison and performed graduate research at
Sandia National Laboratories with Mark Smith
and Richard Neiser, finishing his Ph.D. in 1995.
He became a staff member at LANL in the Materials Science and Technology group in 1996 and
has worked since then on the Powder Metallurgy
team and the Beryllium team. His areas of research at LANL have included arc physics, cathodic cleaning, powder atomization, powder
consolidation, fusion energy high heat flux components, inert ceramics for reactive molten metal
processing, thermal spray (plasma, wire arc,
flame), deposition welding, electro-spark deposition, laser and thermal emission diagnostics,
and process control.
Dr. Hollis will be responsible for the preparation of the front and back matter in the regular
issues of JTST. Dr. Jan Ilavsky had handled these
responsibilities as an associate editor for the past
four years.
Dr. Moreau said, “I want to thank Dr. Ilavsky
very much for the hard work he did consistently,
issue after issue, over those years. He and his team
of Jiri Matejicek, Andrew Gouldstone, and
Rogerio Lima were dedicated to producing high
quality materials for each JTST issue. It was a
great pleasure to work with him.
“Dr. Hollis is recognized for his high quality
contributions as a leading scientist in the field, his
good knowledge of the national and international
thermal spray community, his judgment, and his
long-term commitment to the ASM Thermal Spray
Society. We cannot get a better person to assume
these associate editor responsibilities.”
Dr. Hollis joins Dr. Seiji Kuroda and Prof.
Armelle Vardelle, who have been JTST associate
editors since 2005. Dr. Kuroda is the Director of
the Thermal Spray Group at the National Institute
for Materials Science (NIMS), Tsukuba, Japan,
and also a guest professor at Tokyo University of
Science and Chiba Institute of Technology.
Prof. Vardelle is a professor at the National Engineering School of Limoges, ENSIL, France,
where she is in charge of the research policy for
four departments, and chair of the Department of
Materials Engineering. She is a founding member
and administrator of CITRA, the Engineering
Center in Surface Finishing and Coatings.
Dr. Kuroda’s and Prof. Vardelle’s main responsibilities are the peer review process of papers
submitted by European and Asian authors as well
as papers in their respective fields of expertise.
Vardelle
Ilavsky
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TECHNICAL RESOURCES
The Cold Spray Materials Deposition Process:
Fundamentals and Applications
V.K. Champagne, U.S. Army Research Laboratory, USA, Woodhead Publishing Ltd., Cambridge, UK; 376 pages, September 2007;
Price: £135.00; EUR 195.00; US$255.00
This reference book examines the fundamentals of the cold spray
process, assesses how the technique can best be applied in practice,
and describes portable and stationary cold spray systems. The cold
spray process produces dense, low oxide coatings which can be used
in such diverse applications as corrosion control and metals repair. It has emerged as an important alternative to thermal spray
coating techniques in certain areas. This pioneering book reviews
both the fundamentals of the process and how it can best be applied
in practice.
The first part of the book discusses the development of the process
together with its advantages and disadvantages compared with
thermal spray coating techniques. Part 2 reviews key process parameters such as powders, nozzle design, particle temperature and
velocity, and particle/substrate interaction. It also describes portable
and stationary cold spray systems. The final part of the book discusses how the cold spray process can be applied in such areas as
improved wear, corrosion protection, electromagnetic interference
shielding and repair of damaged components.
The author is technical team leader of the Advanced Materials and
Processes Group within the Weapons and Materials Research Directorate of the U.S. Army Research Laboratory. For more information, visit www.woodheadpublishing.com.
Computer Methods and Experimental
Measurements for Surface Effects and
Contact Mechanics VIII
Edited by J.T.M. de Hosson, C.A. Brebbia, and
S.-I. Nishida, WIT Press, Ashurst Lodge, Ashurst,
Southampton, UK; 352 pages; Price: £115.00,
EUR 172.50, US$225.00
This volume contains most of the papers presented at the Eighth International Conference on
Computer Methods and Experimental Measurements for Surface
and Contact Mechanics, held in The New Forest, UK, May 16-18,
2007. The use of surface treatments can reduce the cost of components and extend the life of the elements. Their effect is of particular importance in the case of surfaces undergoing contact, a problem
which is addressed throughout the book. Topics covered include:
surface treatments, thin coatings, surface problems in contact
mechanics, contact mechanics, material surfaces in contact,
fracture and fatigue, and new applications. Full contents details
on the book can be found at http://www.witpressusa.com/acatalog/
9781845640736.html. Abstracts (free) and full text ($30 per paper)
of individual papers in the book are available through the electronic
edition of the Transactions at http://library.witpress.com/.
Available in North America from Computational Mechanics Inc.,
25 Bridge Street, Billerica, MA 01821; e-mail: marketingusa@
witpress.com; outside North America from WIT Press, Ashurst
Lodge, Ashurst, Southampton SO40 7AA, UK; e-mail:
marketing@witpress.com.
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ADVANCED MATERIALS & PROCESSES/NOVEMBER 2007