Itsse: Advanced Processes and Applications for Thermal Spray

FEBRUARY 2015 | VOL. 10 | ISSUE 1 Thermal Spray Society ASM International

THE OFFICIAL NEWSLETTER OF THE ASM THERMAL SPRAY SOCIETY Thermal Spray Coatings in Aerospace and MILITARY ApplicationS

SOCIETY NEWS 2 JTST HIGHLIGHTS 15

tss.asminternational.org

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THE OFFICIAL NEWSLETTER OF THE ASM THERMAL SPRAY SOCIETY

Editors Robert Gansert Rajan Bamola Managing Editor Julie Lucko Art Director Barbara L. Brody Production Manager Annie Beck National Account Manager Kelly Thomas, CEM.CMP Materials Park, Ohio 440.338.1733 8

[email protected] Low Pressure and Vacuum Plasma Spray Build iTSSe Thermal Spray Society Executive Committee Better Coatings for Engine Applications Christian Moreau, President Luc Pouliot, Immediate Past President Douglas G. Puerta, Vice President Ann Bolcavage, Secretary/Treasurer

International Thermal Spray & Surface EngineeringTM is published quarterly by ASM International®, 9639 Kinsman Road, Materials Park, OH 44073; 440.338.5151; asminternational.org. Vol. 10, No. 1. Copyright© 2015 by ASM International®. All rights reserved. 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, 11 13 author’s data and interpretations are frequently insufficient to be directly translatable to specific design, Orion Heat Shield TECHNICAL SPOTLIGHT production, testing, or performance applications without independent examination and verification Handles EXTREME Surface Coatings of their applicability and suitability by professionally qualified personnel. TEMPS Offer Protection in Harsh Environments EDITORIAL OPPORTUNITIES FOR iTSSe IN 2015 iTSSe’s editorial focus reflects established DEPARTMENTS applications of thermal spray technology 2 | EDITORIAL as well as emerging applications. | ASM THERMAL SPRAY SOCIETY NEWS May Energy & Power Generation 3 August Automotive & Industrial 15 | JTST HIGHLIGHTS Applications November Emerging Technologies/ Applications and Case Studies ABOUT THE COVER The Orion Multi-Purpose Crew Vehicle is intended to carry a crew of up to four astronauts to destinations To contribute an article, contact Julie Lucko at [email protected]. at or beyond low Earth orbit. During re-entry into Earth’s atmosphere, the Orion heat shield protected the To advertise, contact Kelly Thomas, vehicle from external temperatures of 4000°F. Courtesy of NASA. nasa.gov. [email protected].

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All for one and one for all!

t’s not The Three Musketeers cry; it’s structural parts; bond coat development for TBCs, engineer- | FEBRUARY 2015 FEBRUARY | the 2015 International Thermal Spray ing TBCs and abradables, and much more. A special combined Conference and Exposition! This year, plenary session is also being planned on the expo show floor. Ifor the price of one registration fee, ITSC The opening keynote session features Dr. John Grotzing- attendees will gain access to technical er, chief scientist and head of strategic science planning for processes programming for three conferences: ITSC NASA’s $2.5 billion Curiosity rover mission to Mars. Dr. Grot- & 2015, AeroMat 2015, and an IMS topi- zinger is the lead scientist for Curiosity’s mission to explore the christian cal event. The theme of AeroMat 2015 is past climate and geology of Mars. He will describe what the moreau TSS PRESIDENT “Shape the Future of Your Industry,” while rover has discovered since landing on the Red Planet, and how IMS focuses on the “Microstructural Char- the Mars Science Laboratory onboard Curiosity will continue materials

acterization of Aerospace Materials and Coatings.” Between the search for signs of extraterrestrial life. all three conferences, attendees will have access to more The show also features a special event on the historic than 400 technical presentations. Queen Mary where attendees will have the opportunity to Attendees will also learn about the latest research and build business relationships and network with key contacts.

advanced development efforts in their specific field while gaining a Crowds will gather on the show floor to learn the latest indus- | | global perspective from leading scientists and engineers from try trends across the thermal spray, aerospace, and metallur- around the world. AeroMat and ITSC are working together to gy industries. New products and services will be discovered, present a special joint symposium on advanced coatings for while business relationships are built. iTSSe the aerospace industry. Topics include thermal barrier coat- On top of all of that, the show is taking place in beau- ings (TBCs); engineering, protection, and repair of aircraft tiful Long Beach, California, May 11-14—a prime West Coast

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EDITORIAL PRESIDENTIAL PROFILE iTSSe | TSS ADVANCED MATERIALS & PROCESSES | FEBRUARY 2015 |

location that is part of the Southern California aerospace Ala., continues to serve as chair of the TSS Awards Com- corridor—and is sure to attract a large cohort of aerospace mittee. Shari Fowler-Hutchinson, Saint-Gobain, Boston, engineers and researchers. We hope to see you in Long serves as chair of the Exposition Committee and Marcel Beach in May! To learn more and to register, visit asminter- van Wonderen, KLM Royal Dutch Airlines, Amsterdam, was national.org/web/itsc-2015. named chair of the Accepted Practices Committee. If you are interested in serving on an affiliate society committee, contact the respective committee chair or email joanne.miller@ asminternational.org.

President’s Profile: Christian Moreau christian Moreau, FASM, Ph.D., has advanced the understanding and development of thermal Pouliot Tucker Sharma spray technology through his significant role in the development of optical systems for the measure-

ment of the plasma effluent and particle tempera- iTSSe ture, velocity, and size distribution. Dr. Moreau is currently a professor in the Department of Mechan- ical and Industrial Engineering at Concordia Univer- sity in Montreal. He has been an active member of Puerta Wuest McDonald the Thermal Spray Society and a member of the TSS Nominating Committee from 2010 to 2012. In addition, he has been a member of both the TSS Publica- tions and Communications Committee as well as the TSS Program Committee from 1999 to 2013. He was a TSS Board Member from 2006 to 2012, and also a member of TSS Information Develop- ment/Delivery. He became an ASM Fellow in 2006 McKechnie Fowler- van and was inducted into the Thermal Spray Hall of Hutchinson Wonderen Fame in 2013. He is presently Editor-in-Chief of the Journal of Thermal Spray Technology and has been a TSS committee chairs named for member of the JTST Committee since 1999. 2014-2015 term “I am much honored to have the opportunity the ASM Thermal Spray Society Board appointed chairs to contribute to the TSS as the newly elected pres- to each of its committees for the 2014-2015 term. Christian ident. In this capacity, I will invest my efforts to Moreau, FASM, Concordia University, Montreal, was elected make sure our Society continues providing mem- as president of TSS. Luc Pouliot, Tecnar Automation Ltd., bers with high quality publications, conferences, Quebec, Canada, currently serves TSS as immediate past and services in the most efficient and pertinent president and chair of the Nominating Committee. Robert manner possible,” says Moreau. “I would like to C. Tucker, Jr., FASM, The Tucker Group, continues as chair recognize the exceptional job my predecessor Luc of the Journal of Thermal Spray Technology Committee. Pouliot has done over the last two years and thank Atin Sharma, Oerlikon Metco, Westbury, N.Y., serves as chair him on behalf of all TSS members and on my own of the Membership, Marketing and Outreach Committee. behalf. I would also like to thank all volunteers Douglas Puerta, Elementals Materials Technology, Port- who contributed and will continue to contribute land, Ore., serves as vice president of TSS and chair of the to the life of our Society by their dedicated work TSS Program Committee. Greg Wuest, Oerlikon Metco, con- and efforts. Nothing would be possible without tinues to serve as chair of the TSS Safety Committee while you. A special welcome to the new members of Andre McDonald, University of Alberta, Edmonton, Canada, the TSS Board and Committees! I look forward to continues as chair of the TSS Training Committee. Timothy working with all of you in the coming years.” N. McKechnie, FASM, Plasma Processes Inc., Huntsville,

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Nominations Sought for processes including plas- ASM Thermal Spray Society Board ma spray, high velocity the ASM TSS Nominating Committee is currently oxy-fuel, and detonation gun deposition, as well | FEBRUARY 2015 FEBRUARY | seeking nominations to fill two board member positions. Candidates for these director positions may come from as a description of coat- any segment of the thermal spray community, but ideally ing properties and their will have a focus on the service or government research wear, corrosion, and ther- segments. mal barrier characteris- processes tics. Principles, types of Nominees must be a member of the ASM Thermal Spray & coatings, applications, Society and must be endorsed by five TSS members. Board performance, and test- members whose terms are expiring may be eligible for nom- ing/analysis are also cov- ination and possible reelection on an equal basis with any ered. A greatly expanded other candidate. Nominations must be received no later

materials selection of applications than March 1. Forms can be found at tss.asminternational. includes examples and org. Contact Luc Pouliot, ASM TSS Nominating Committee figures from various industries, including electronics and Chair, at [email protected] for more information. semiconductors, automotive, energy, and biomedical. Emerging thermal spray market sectors such as aero- advanced

| | ASM Handbook, Volume 5A: space and industrial gas turbines, and important areas of Thermal Spray Technology growth such as advanced thermal barrier materials, wear Volume 5A is a replacement for the Handbook of coatings, clearance control coatings, and oxidation/hot

iTSSe Thermal Spray Technology, edited by J.R. Davis (2004) corrosion resistant alloys are also reviewed. Visit asmint- and provides an introduction to modern thermal spray ernational.org to learn more.

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SOCIETY NEWS SOCIETY NEWS iTSSe | TSS ADVANCED MATERIALS & PROCESSES | FEBRUARY 2015 |

July Thermal Spray Join the TSS Discussion Group the TSS email discussion group is an email-based discussion list, where only Education Courses subscribers may post messages to the group. Messages are relayed as they come in, Please look for these upcoming or subscribers may choose a once-daily digest instead. Individuals may subscribe courses at ASM Headquarters, and unsubscribe as they wish. Visit asminternational.org/web/tss/membership/ Materials Park, Ohio, in July. Visit forum to learn more. asminternational.org/education for more information.

Introduction to Thermal Spray July 6-7 Instructor: Richard A. Sayman This course focuses on the five critical areas of thermal spray: Safety, preparation, troubleshooting, spraying, and keeping records. Safety standards for thermal spray operators and the evaluation process required in

various practical applications are iTSSe an important part of the course.

Thermal Spray Technology July 8-9 Instructor: Christopher C. Berndt, HoF, FASM This course provides a thorough grounding and understanding of thermal spray processes, depicts complex scientific concepts in terms of simple physical models, and integrates this knowledge into practical engineering applications and commonly accepted thermal spray practices. Participants also receive the Handbook of Thermal Spray Technology.

Thermal Spray for Gas and Oil Industries July 10 Instructor: André McDonald Given the special needs of the oil and gas sector for wear and corrosion-resistant coatings with high longevity, the certification and validation process differs significantly from other industries. This course includes training and testing information that applies specifically to the oil and gas sector.

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Lwo Pressure and Vacuum Plasma

| FEBRUARY 2015 FEBRUARY | Spray Build Better Coatings for Engine Applications Ludwig Guggenheim, Ralph Herber, and Silvano Keller, AMT AG, Dottingen, Switzerland

processes Robert Gansert*, Advanced Materials & Technology Services Inc., Simi Valley, Calif. & ow pressure and vacuum plasma spray technologies are Lwo pressure and vacuum plasma spray making headway in many emerging industries, along coating properties with their primary use in commercial and military aero- Low pressure and vacuum plasma spray produce coat-

materials L space gas turbine engine applications. Vacuum plasma has ings with better performance properties than those made also been implemented in biomedical and electronics appli- by traditional air plasma spray (APS). By carefully controlling cations. Figures 1 and 2 show a vacuum plasma system, while the processing environment, exceptional coating properties Figs. 3 and 4 show a low pressure coating system (LPCS) man- with regard to microstructure (porosity, oxide content, den-

advanced ufactured by AMT AG. sity), phase composition, and mechanical attributes may be | | Both systems pump down the atmosphere to <0.1 torr achieved. It is also possible to hold oxide content to less than and backfill to processing pressure in a short time. Stable at- 1% and reach coating densities near 99%. mospheric pressure regulation and reliable part handling are Plasma coatings of NiCrAlY, shown in Fig. 5, are produced iTSSe critical for proper coating quality. Therefore, state-of-the-art in a low pressure plasma spray atmosphere. These coatings control software and hardware is used as well as a new robotic exhibit enhanced oxidation protection and increased resis- and computer numerical control (CNC) technique. tance to spallation in gas turbine engines.

Fig. 2 — Vacuum plasma spray in operation.

Fig. 1 — Vacuum plasma spray system. Fig. 3 — Low pressure coating system *Member of ASM International and ASM Thermal Spray Society (LPCS).

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FEATURE iTSSe | TSS ADVANCED MATERIALS & PROCESSES | FEBRUARY 2015 |

A range of coating operations and system configura- tions are possible using low pressure and vacuum plasma spray. Figure 1 illustrates a vacuum plasma spray process during a batch operation where parts (ranging from IGT turbine components to titanium implants) are coated using a vacuum rated turntable and robot system located in- side the chamber. With LPCS, continuous production is performed in contrast to a batch operation. This is common in high-volume production spray of thermal barrier coatings, such as NiCrAlY for aerospace turbine engine components. Figure 3 shows a main process low pressure chamber located between two load-locks, which enable part loading and unloading for spraying coatings in the main chamber. The main process chamber is able to maintain low pressure, while parts (e.g., turbine blades) are loaded into the load-locks and pumped down to match the pressure of the process chamber for the coating operation. Two work-piece manipulators (stings)

move parts into and out of the main process chamber and iTSSe manipulate components to be coated in the plasma process stream. A gun drive (sting) further enables gun motion for coating all desired surfaces of a component, in addition to the two stings already mentioned. In LPCS, a higher-power Fig. 4 — LPCS plasma plume (dummy part).

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5 iTSSe | TSS CASE STUDY Y 201 AR U R B E

Fig. 5a — NiCrAlY, 200x. Fig. 5b — NiCrAlY, 500x.

plasma gun is enabled with the use of 2000 amperage pow- content and high density. Applications include various tur- er supplies in contrast to the type of gun typically used in a bine engine components, as well as biomedical and elec- vacuum plasma spray process. tronics components. | advanced materials & processes | F | & processes materials advanced | Conclusions For more information: Robert Gansert is president of Ad- Vacuum plasma and low pressure plasma spray tech- vanced Materials & Technology Services Inc., 67 W. Easy St., nologies each provide unique solutions for achieving supe- Simi Valley, CA 93065, 805.581.6045, [email protected], iTSSe rior properties in metallic coatings that require low oxide www.adv-mts.com.

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CASE STUDY iTSSe | TSS ADVANCED

ORION HEAT SHIELD HANDLES extreme temps MATERIALS

ave you ever imagined how hot it would be at the Earth’s core? What about stepping on molten lava?

The Orion spacecraft built by Lockheed Martin endured &

Hthose temperatures (and higher) when re-entering the terres- PROCESSES trial atmosphere late last year. Boosted to an altitude of 3604 miles, Orion fell back to Earth on December 5 at nearly 20,000 mph. During re-entry, Orion’s heat shield protected the vehicle from external temperatures of 4000°F—nearly half the heat of the sun’s surface. | F E

The heat shield is the forebody or wind-facing side of an B R

aeroshell system. Due to its size, the aeroshell experiences U tremendous entry loads as a result of dynamic pressures from AR

Fig. 1 — At 16.5 ft in diameter, the Orion heat shield is the largest Y 201 the atmosphere and the high velocity of vehicle descent. Lock- composite version ever made. heed Martin constructed all eight of the aeroshells that have protected NASA’s Mars-bound space- 5 |

craft—but Orion is unique. iTSSe At 16.5 ft in diameter, it is the largest composite heat shield ever made. Orion is also designed for long-duration, human exploration of deep space. That means the shield will play a critical role in pro- tecting future astronauts on their return to Earth. Not only is the new heat shield the largest ever built, it also features a unique resin system that can withstand higher temperatures and landing impact. After testing in extreme environments and simulating Fig. 2 — Engineers attach the heat shield to the Orion spacecraft. re-entry, engineers verified that the thermal insulator on the outside of the composite material over the skin, and each of its 320,000 cells is filled with a ma- could be thinner, making the spacecraft lighter and allowing terial called Avcoat. The surface is designed to burn away, or more payload to join the mission. The resin was developed ablate, as the material heats up, rather than transfer heat back by the Lockheed Martin Orion thermal protection system into the crew module. At its thickest, the heat shield is 1.6-in. team in partnership with TenCate Advanced Composites, thick, and about 20% of the Avcoat will erode as Orion travels Morgan Hill, Calif. through Earth’s atmosphere. The heat shield is built around a titanium skeleton and carbon-fiber skin that gives the shield its shape and provides Taest par meters structural support for the crew module during descent and During the high orbital test flight, Orion traveled a total splashdown. A fiberglass-phenolic honeycomb structure fits of 60,000 statute miles and as far out as 3600 statute miles

Orion heat shield details: • The Orion heat shield is the largest ever made. • The melting point for titanium is about 3000°F and the surface temperature of the sun is about 10,000°F. Orion can handle temperatures around 5000°F. • Orion must withstand landing loads of 300,000 to 400,000 lb, roughly equivalent to the mass of a school bus crashing into the ocean at 20 mph.

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Fig. 3 — The Orion Multi-Purpose Crew Vehicle is intended to carry iTSSe a crew of up to four astronauts to destinations at or beyond low Earth orbit. Fig. 4 — During re-entry into Earth’s atmosphere, the Orion heat shield protected the vehicle from external temperatures of 4000°F.

above the Earth’s surface. This generated a re-entry velocity exceeding 20,000 mph. For extra strength and stiffness, the heat shield features a titanium backbone structure enabling Orion to withstand landing loads of 300,000-400,000 lb. The December flight tested all of Orion’s re-entry systems—including testing the heat shield, jettisoning the forward bay cover, and deploying parachutes—and gauged the effective- ness of the software driving numerous functions across mul- tiple systems. Data collected from Exploration Flight Test-1 provides engineers with information about fluctuations between the temperatures and pressures across the heat shield during re-entry, Avcoat performance, and accelerations and strain during splashdown. Even with deployment of 11 parachutes to help slow the spacecraft to a safe splashdown, the heat shield must protect the crew and capsule from landing loads and turbulent sea conditions, which could vary significantly during different missions. Comprehensive test flight data, including information about the heat shield, will guide design decisions most critical to crew safety, ultimately lowering risks and costs for future space missions.

For more information: Allison Rakes is Orion public relations officer, Lockheed Martin Space Systems Co., 6801 Rockledge Dr., Bethesda, MD 20817-1803, 303.977.7135, [email protected], lockheedmartin.com.

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TECHNICAL SPOTLIGHT iTSSe | TSS ADVANCED

SURFACE COATINGS OFFER PROTECTION MATERIALS IN HARSH ENVIRONMENTS &

lasma spray coatings are increasingly used to solve a PROCESSES range of engineering issues for military suppliers, including heat, wear, electrical insulation, and the re- Pplacement of more harmful coatings. Plasma spray coatings

now offer the potential to solve electro-mechanical interfer- | F ence on composites. E B

Novel surface technology derived from experience in the R U

nuclear industry is enabling engineers to solve many perfor- AR

mance issues in a range of harsh environments. Zircotec Ltd., Y 201 UK, originally developed its technologies for use in nuclear reactors. During the last decade, its coatings have been used 5 | in several other applications, including orthopedic implants,

and the company has expanded into the defense sector with iTSSe a greater emphasis on heat protection. Anti-abrasive coatings, electrically insulating formulas, and cadmium-free options are also available.

Process capability Plasma spray technology works by injecting powder particles into a nitrogen or argon plasma with a flame temperature of roughly 20,000K and a gas velocity of Mach 2-3. Therefore, particles spend a short time in the flame while spray parameters are adjusted, and an extensive range of Zircotec’s plasma spraying process safely coats materials may be sprayed. These range from nylon at the Fig. 1 — composites, enabling use in high temperature environments. lower end of the temperature spectrum to beryllia at the top. Provided the material does not sublime nor is transparent to UV, particles will melt and quench as splats onto the cut, folded, and bent to fit any shape and offers surface tem- substrate. Control of overall spray parameters to predefined perature reductions of 64%. The newest derivative, ZircoFlex tolerances ensures that coatings are evenly built-up in mul- FORM, will enable structural heat shields to be made from a tiple thin layers—a method that helps to reduce stress in the flexible and bendable sheet. final coating. The material is produced as a thin aluminum or gold backed foil that is easily bent and manipulated to suit dif- A range of plasma spray coatings is already being suc- ferent geometries, and can even be folded tightly through cessfully applied to metallic components, reducing metal 180° without damaging the thermal barrier. It weighs only surface temperatures by more than 170°C in some applica- 0.46kg/m2 (0.23kg/m2 for ZircoFlex Gold). The material is ex- tions such as automotive exhaust systems. Zirconia has a tremely thin—at 0.25 mm overall, it requires only minimal thermal efficiency of less than 1.7 W/m K (compared with 4 space for installation. In addition, the metal backing makes W/m K for alumina), enabling coatings that are highly effec- it robust, easy to handle and cut, and simple to install by tive at inhibiting surface heat radiation. This coating is also a hand or machine. suitable choice for thermal management. The defense sector has adopted another technology— a flexible ceramic supplied on an aluminum foil. ZircoFlex Enabling greater use of composites solves heat issues without components needing to be re- Zircotec has pioneered the use of plasma spray coat- moved from service for spraying, making it easy to retrofit, ings on composite substrates to enable use in environments even during use. ZircoFlex is a flexible ceramic heat shield where they would have previously failed due to delamina- material, offering superior thermal barrier performance at tion or heat damage. Formula One racing is an area where minimal weight and thickness. Supplied in sheets, it can be these coatings are increasingly popular to prevent such

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5 iTSSe | TSS JTST HIGHLIGHTS Y 201 AR U R B E | advanced materials & processes | F | & processes materials advanced | Fig. 2 — Coatings can reduce the heat and electrical signals Fig. 3 — ZircoFlex is used in the field in defense applications to emitted from vehicles. solve heat issues without removing vehicles from duty.

iTSSe failures. In fact, 85% of the F1 grid is now using a Zircotec These coatings could also boost composites growth in coating to protect composite parts. electrical applications. Electromagnetic interference (EMI) can interrupt or degrade transmitted data signals. Carbon- composite materials, known to be relatively transparent to radio frequency signals, require bulky metal heat shields to provide the right level of shielding. However, the added weight and bulk has deterred composite use in such applications. Zircotec addressed this problem with a highly conductive aluminum-based material that is lightweight yet thin—typically applied at less than 0.3 mm. Because carbon is an excellent electrical conductor, a less conductive sub-layer is applied be- fore the EMC top coating to prevent electrical contact with the components themselves. For design engineers, this means considerably more scope for positioning electrical or electronic parts within a vehicle and the option to use more composites in vehicle design as well. Zircotec’s research suggests that engineers would like to use composites for housing electronics, but poor EMC performance has restricted usage due to the bulky metal shielding required to protect electrical components.

Looking forward In defense applications, heat management coatings from Zircotec could be used reduce the thermal footprint of vehicles, lowering the temperature emitted and making them less detectable.

For more information: Peter Whyman is sales director at Zircotec Ltd., 22 Nuffield Way, Abingdon Oxon, OX14 1RL, +44 1235 546050, zircotec.com.

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JTST HIGHLIGHTS iTSSe | TSS ADVANCED

The Journal of Thermal Spray Technolo- quantitative evaluation of

gy (JTST), the official journal of the ASM wear tests, while analysis of MATERIALS Thermal Spray Society, publishes con- wear tracks is used for qual- tributions on all aspects—fundamental itative evaluation. Both eval- and practical—of thermal spray science, uation methods can only be

including processes, feedstock manu- used after wear testing and & facture, testing, and characterization. results can only be present- Schematic representation of PROCESSES As the primary vehicle for thermal spray ed in the final outcome of the surface fatigue around a information transfer, its mission is to syn- wear tests. However, chang- pit on a coating’s surface. ergize the rapidly advancing thermal spray industry and relat- es during the wear test and ed industries by presenting research and development efforts time-dependent wear mechanisms are also of great interest.

leading to advancements in implementable engineering appli- A running wear test in a large chamber scanning electron | F

cations of the technology. Articles from the January issue, as microscope (SEM) offers the first opportunity to observe the E B

selected by JTST Editor-in-Chief Christian Moreau and Lead Ed- wear process in situ. Different wear mechanisms, such as the R U

itor Armelle Vardelle, are highlighted here. This issue features adhesive, abrasive wear, surface fatigue, and tribochemical AR

papers based on presentations at ITSC 2014. In addition to the reaction, can be recorded with high magnification. A special Y 201 print publication, JTST is available online through springerlink. pin-on-disk testing device was designed for a vacuum envi-

com. For more information, visit asminternational.org/tss. ronment. Using this device, arc-sprayed NiCrBSi coatings and 5 |

HVOF-sprayed WC-12Co coatings were tested in a large cham- iTSSe “Thermal Spray Coatings for High-Temperature Corrosion ber SEM with Al2O3 ceramic balls as wear counterparts. During Protection in Biomass Co-Fired Boilers” wear testing, different wear mechanisms were determined M. Oksa, J. Metsäjoki, and J. Kärki and processes were recorded in short video streams. There are over 1000 biomass boilers and roughly 500 plants us- “Columnar-Structured Mg-Al-Spinel Thermal Barrier ing waste as fuel in Europe, and Coatings (TBCs) by Suspension Plasma Spraying (SPS)” numbers are increasing. Many N. Schlegel, S. Ebert, G. Mauer, and R. Vaßen encounter serious problems with Suspension plasma spray (SPS) was developed to per- high-temperature corrosion due mit feeding of sub-micrometer-sized powder into the plasma to detrimental elements such as plume. In contrast to electron beam-physical vapor deposi- chlorides, alkali metals, and heavy tion and plasma spray-physical vapor deposition, SPS enables metals. HVOF spray produces very 550 MWth circulating cost-efficient deposition of columnar-structured coatings. fluidized bed boiler test dense and well-adhered coatings, Due to their strain tolerance, these coatings play an import- facility with the probe which can be applied for corro- ant role in the field of thermal barrier coatings (TBCs). Yttria measurement location. sion protection of heat exchanger partially stabilized zirconia (YSZ) is commonly used as TBC surfaces in biomass and waste-to-energy power plant boilers. material. However, its long-term application at temperatures Four HVOF coatings and one arc sprayed coating were exposed higher than 1200°C is problematic. At these high temperatures, to actual biomass co-fired boiler conditions in a superheater phase transitions and sintering effects lead to the degradation area with a probe measurement installation for 5900 h at 550° of the TBC system. To overcome those deficits, Mg-Al-spi- and 750°C. Coating materials include Ni-Cr, IN625, Fe-Cr-W-Nb- nel was used as a TBC material. Even though it has a lower Mo, and Ni-Cr-Ti. CJS and DJ Hybrid spray guns were used for melting point (~2135°C) HVOF spray to compare the corrosion resistance of Ni-Cr coat- and higher thermal con- ing structures. Reference materials were ferritic steel T92 and ductivity (~2.5 W/m/K) nickel super alloy A263. The circulating fluidized bed boiler than YSZ, Mg-Al-spinel burnt a mixture of wood, peat, and coal. Coatings show excel- provides phase stability at lent corrosion resistance at 550°C compared to ferritic steel. At higher temperature, NiCr sprayed with CJS had the best corrosion resistance. IN625 was consumed almost completely during exposure at 750°C.

“In Situ Wear Test on Thermal Spray Coatings in a Large Suspension-feeder developed at Forschungszentrum Jülich Chamber Scanning Electron Microscope” GmbH (Germany), showing the monitoring and control unit Weifeng Luo, Wolfgang Tillmann, and Ursula Selvadurai (a), and injection of suspension into the plasma jet with a two- Currently, mass loss determination is usually used for phase atomizer (b).

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5 iTSSe | TSS JTST HIGHLIGHTS Y 201

AR high temperatures in contrast to YSZ. Mg-Al-spinel deposition of the plasma jet U

R by SPS results in columnar-structured coatings, which were (velocity, enthalpy, B

E tested for their thermal cycling lifetime. The influence of and stability) as well substrate cooling during the spray process on thermal cy- as those of droplets cling behavior, phase composition, and stoichiometry of (trajectories, num- Mg-Al-spinel was also investigated. ber, and size) and particles (velocity) “Tailoring the Spray Conditions for Suspension Plasma were measured and Spraying” correlated to the A. Joulia, W. Duarte, S. Goutier, M. Vardelle, A. Vardelle, coating microstruc- and S. Rossignol ture. The operating SEM micrograph of YSZ splats collected Plasma spray using suspensions as liquid feedstock al- conditions neces- at 30 mm from nozzle exit. Arc current: lows deposition of finely structured coatings with improved sary for obtaining 600 A. Plasma gas composition: Ar properties compared to that of coatings deposited by con- disk-shape splats (77%)-He (33%). Substrate: 400°C. ventional plasma spray techniques. The evaporation of the and achieving ho- solvent, acceleration, heating, and melting of fine solid par- mogeneous coatings are described including plasma jet ticles within the plasma jet take place in a shorter time, as properties and substrate parameters. the substrate is located closer to the plasma torch when a

| advanced materials & processes | F | & processes materials advanced | mono-cathode mono-anode plasma torch is used, while “Interface Characterization and Bonding Mechanisms of Cold liquid material processing globally consumes more energy Gas-Sprayed Al Coatings on Ceramic Substrates” than powder materials. In this study, a large range of plasma R. Drehmann, T. Grund, T. Lampke, B. Wielage, K. Manygoats,

iTSSe spray conditions were used to achieve yttria-stabilized zir- T. Schucknecht, and D. Rafaja conia coatings by suspension plasma spray. The properties Research aims to contribute to the understanding of adhesion mechanisms, which take effect at the interface of cold gas-sprayed metallic coatings on ceramic substrates. Former investigations reveal the possibility to deposit well-adhering metallic coatings on atomically smooth ce- ramics, meaning that mechanical interlocking is not al- ways a necessary precondition for bonding. A combination of recrystallization processes induced by adiabatic shear processes and heteroepitaxial growth might explain high observed adhesion strengths. The present work examines the interface area of cold gas-sprayed aluminum on various ceramic substrates using SEM and HRTEM. Besides sintered corundum plates, single-crystalline sapphire substrates with defined lattice orientations were used as substrates for coating deposition. In addition to Al2O3 substrates, aluminum coatings were also deposited on AlN, Si3N4, and SiC to investigate whether different amounts of ionic bonds in these substrate materials influence the substrate/coating interface formation. Interface of (0001)-oriented sapphire with (111)-oriented PVD Al coating (TEM image). Directions normal to the lattice planes (determined by XRD pole figures) are indicated by arrows.

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