Spray Tips: Temperature, Dwell Time, and Velocity in the Thermal Spray Jet

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Spray Tips: Temperature, Dwell Time, and Velocity in the Thermal Spray Jet

Temperature and velocity vary considerably within the jet, because of several factors. The most significant of these is the difference in temperature between the hot core of the jet and its relatively cold surrounding environment.

The diagram schematically illustrates the dwell time of hypothetical particles, indicating how different particle trajectories lead to a range of dwell times and temperatures. A range of dwell times is characteristic of a spray process or a set of spray parameters. It should be emphasized that for thermal spray processes, single, specific dwell times and temperatures do not exist. Instead of absolute numbers, dwell times and temperatures are dealt with in terms of average values for the distributions.

Plasma jets are confined by water-cooled anodes/nozzles. Flame-driven processes, with a few exceptions, are air-cooled devices operating at ambient conditions. The temperature drop from the jet core to the boundary between the nozzle and the environment is typically several thousand degrees over a few millimeters. This drop in temperature causes a corresponding drop in gas velocity and an increase in gas viscosity toward the outer boundaries.

Temperature and velocity also decay as the jet exits the nozzle, so there are both radial and axial gradients of gas temperature, gas velocity, and gas viscosity. Into those complex distributions, a distribution of powder is injected. On the surface the process seems chaotic; however, these interactions are favorable, whether by design or chance.

Volume 5A, Thermal Spray Technology -> Thermal Spray Processes and Coatings -> Thermal Spray Processes -> Processing characteristics 

Message from the President: Thermal Spray of Suspensions & Solutions Symposium (TS4)

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MESSAGE FROM THE PRESIDENT

Thermal Spray of Suspensions & Solutions Symposium (TS4)

For the first time in North America, a special symposium dedicated to this emerging thermal spray process will bring together scientists and engineers from academia, national laboratories, and industry for a two-day information-exchange event. Presentations from internationally recognized leaders will enable participants to learn about the most recent advances in this exciting new technology, and to identify key challenges that must be solved if it is to be fully deployed in new markets.

Check out the program, scrutinize the speaker list, and consider registering right away to take advantage of the early bird registration rates. The Symposium will be held in Montreal December 2-3, 2015. Visit the event site here.  

Enjoy the Joie de vivre of Montreal, and meet with colleagues who are eager to take advantage of the latest advances in thermal spray, above all, one that is very likely to generate significant opportunities for the thermal spray industry!

Christian

Christian Moreau, President
ASM Thermal Spray Society

NanoSteel BLDRmetal powders for binder jet 3D printing make parts that resist wear

October 2, 2015
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NanoSteel, Providence, R.I., introduces its first powders designed for the binder jet 3D printing of parts having three times the wear and impact resistance of an equivalently infiltrated 420 stainless steel. BLDRmetal J-10 and BLDRmetal J-11 enable the 3D printing of components for highly abrasive environments that can benefit from additive manufacturing's ability to eliminate tooling, create advanced geometries, and build custom parts on demand.

Industrial components made using J-10 feature twice the elongation and three times the wear and impact resistance of an equivalently infiltrated 420 stainless steel. NanoSteel demonstrated this capability working with 3DX Industries, an additive manufacturing service provider, to print a security tool used by a global avionics company for removing and replacing aircraft panels.

In this commercial application, the tools made with J-10 lasted five times longer than the previous solution, significantly reducing the risk of delays in servicing the aircraft.

"The NanoSteel solution enabled us to create a tool that delivered the durability and reliability the customer required in a fast turnaround environment," said Roger Janssen, President and CEO of 3DX. The avionics service team is planning further adoption of this new technology across the global operation.

The BLDRmetal product line of binder jet powders also includes J-11, which is designed for extreme wear low-impact applications. Components made with J-11 provide ten times the wear resistance of an equivalently infiltrated 420 stainless steel. The exceptional performance of both NanoSteel products is based on the combination of complex metallic phases that provide wear resistance and a steel matrix that delivers ductility and toughness.

Binder jetting is a powder bed process in which a binder is used to selectively ‘print' the part shape by adhesively joining the metal particles. After the jetting process, the green part is sintered in a furnace to burn off the binder. Then an infiltrant, typically bronze, is melted and drawn into the part to fill in the remaining spaces within the sintered metal powder skeleton to create a dense component. The resulting parts combine properties from both the metal powder and the infiltrant. 

www.nanosteelco.com

Zircotec coatings protect Bloodhound land-speed record car from high temperatures

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Zircotec Ltd., England, has provided its ThermoHold ceramic coating for the exhaust system and a zirconia-based coating for the composite front structure of the British Bloodhound, a car being designed to reach 1000 mph and break the land speed record.  Because the exhaust system is a prime source of heat in proximity to the fuel tank, the Bloodhound team specified Zircotec's ThermoHold ceramic coating. Plasma-sprayed at twice the speed of sound, the coating can reduce surface temperatures by at least 30%, ensuring that the tank remains stable even as heat builds up during the two runs needed for the record to be validated.

Unlike previous record-challenging cars, a large proportion of the Bloodhound front structure is made of composites. Chosen for excellent strength-to-weight ratio, the drawback of composites is poor resistance to heat compared to metallic options.  Zircotec proposed ThermoHold for Composites, a zirconia-based coating that is applied at temperatures exceeding 18,000°F, but in such a way that the substrate is not affected.

In addition, the Bloodhound team has chosen Zircoflex, a hybrid aluminum/ceramic heatshield, to be applied at a thickness of just 0.3 mm around any areas of the vehicle where heat must be resisted. "With ZircoFlex, we can bend and mold it to shape. It is lightweight, and with self-adhesive backing, it is good for up to 900°F," says Tony Parraman of the sponsorship liaison team. "For example, after a two minute run, the internal temp of the jet or rocket might be 5400°F, but the externals are 400°F. We can manage that heat with ZircoFlex protecting wiring looms and composite panels."

http://www.zircotec.com/news/3/227

RIT chosen to lead university-industry consortium to advance additive manufacturing

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Rochester Institute of Technology, Rochester, N.Y., announces that it has been chosen to lead a consortium of universities and corporations in establishing a New York State Center for advanced technology in additive manufacturing and functional printing. The award is $921,000 per year for the center, with annual renewal for up to ten years, subject to annual performance evaluations.

These focus areas are the key in the market growth in functional 3D printing—improvements to print equipment, new nano-ink materials development, and applications for products built using functional 3D-print technologies. RIT has made significant inroads into training both its students and industry professionals in using functional 3D-printing technologies. The lab partnerships also have expanded to include capabilities in chemical processing, new materials development, and expanded prototyping work for startup companies. 

The center, to be called the AMPrint Center for Advanced Technology, will be based at RIT. Its focus will be to conduct research and development in 3D printing and additive manufacturing—an industry seen as a key economic driver for the Finger Lakes region and New York state because of its application to a wide range of companies and products.

Denis Cormier, RIT's Earl W. Brinkman Professor and a national expert on 3D printing and additive manufacturing, will lead the AMPrint Center. The consortium's university partners include RIT, Clarkson University, and SUNY New Paltz. Corporate partners include Xerox Corp., GE Research, Corning Inc., Eastman Kodak, and MakerBot. Smaller regional companies will also collaborate with the center.

Research partners in the consortium will develop next-generation polymer, metal, and composite technologies, and will use the new facility to synthesize advanced functional materials, develop additive manufacturing technologies, and design novel devices using the new materials and technologies.

Each of the partners brings unique capabilities to the consortium in areas such as printable nano-inks and devices that use these inks. RIT's has a pulsed photonic curing system capable of fusing the inks into solid form through thermal processing that makes the materials and devices operational. The advanced curing system for printed materials can thermally process and fuse high-temperature metals and ceramics onto low-temperature paper or plastic. These are the foundational materials being used for flexible electronics, considered a targeted growth market for New York state.

www.rit.edu

Market analysis predicts thermal spray coatings market to reach $12 billion by 2022

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Grand View Research Inc., San Francisco, has published a thermal spray coating market analysis that predicts the market is expected to reach $12.29 billion by the year 2022. The study says that the growing need for corrosion-resistant coatings in aerospace and industrial gas turbines is expected to fuel demand over the next seven years. Replacement of hard chrome by thermal spray coatings in various aerospace and automotive applications is also expected to result in high growth.

In addition, stringent government regulations, particularly in North America and Europe, have led to an increasing need for environmentally friendly and sustainable coatings. North America and Europe are expected to witness substantial market growth in bioceramic coatings that are both biocompatible and corrosion-resistant for medical implants. 

Ceramics are expected to be the fastest growing segment in terms of revenue, at a rate of 7.0% from 2015 to 2022. Aerospace was the largest application segment in 2014, valued at $2.55 billion. Increasing government expenditures, particularly in the civil aviation sector, will propel thermal spray coating market over the next seven years. Furthermore, the growing need for wear- and corrosion-resistant products that can withstand high temperatures is expected to have a positive impact on the industry.

North America was the largest regional consumer of thermal spray coatings, with revenue valued at over $2.10 billion in 2014. In Mexico, rapid urbanization as a result of growing population and increasing disposable income is expected to augment the automobile industry in Mexico. This in turn is expected to increase industry growth over the next seven years.

http://www.grandviewresearch.com/industry-analysis/thermal-spray-coatings-market