Plasma-enhanced titanium and vanadium nitrides form hardest thin films ever
March 12, 2019
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Lehigh University, Pa., announces that its researchers have developed plasma-enhanced atomic layer deposited titanium and vanadium nitrides that are said to be harder than commercial coatings “by orders of magnitude.â€
Titanium and vanadium nitride films are already known to be extremely hard and wear resistant. Traditionally, they're grown by sputtering, pulsed laser deposition, or chemical vapor deposition methods. In a first, the Lehigh group's collaborators at Veeco/CNT grew their nitride films via plasma-enhanced atomic layer deposition, or PE-ALD. Veeco/CNT is a leading supplier of ALD systems based in Waltham, Massachusetts.
The technique involves a vapor process in which two or more self-limiting chemical reactions grow one layer of film at a time. In this case, a titanium precursor enters the system's chamber as a gas, reacts with the substrate, and forms a monolayer. Excess titanium is pumped out, then the second gas, nitrogen plasma, is pumped in. It bonds with the titanium, and forms a second monolayer. This two-step process is repeated until the film reaches the specified thickness. The technique is enhanced by a plasma generator, hence the PE in the PE-ALD.
"For growing nitrides, you need a lot of thermal energy, like 800°C," says Dr. Nicholas Strandwitz. "Or, you need a plasma to make the nitrogen more reactive. Generating plasma means we're knocking electrons off the nitrogen molecules as they're flying around in the gas, making the nitrogen more reactive so it will bond to the surface and become part of the film. If you just float nitrogen gas through there, nothing would happen, because the nitrogen molecule is super stable. So with plasma, we can grow these films at 50°C, just slightly above room temperature."
The ability to grow films at that temperature is key. Too-high temps can melt sensitive materials like plastic and aluminum and make even fairly stable metals more brittle. "Having the capability to deposit at low temperatures opens up more materials that you can deposit on," says Dr. Strandwitz.
www.lehigh.edu
Lehigh University, Pa., announces that its researchers have developed plasma-enhanced atomic layer deposited titanium and vanadium nitrides that are said to be harder than commercial coatings “by orders of magnitude.”
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European team produces 3D printed titanium pressure vessel for space exploration
March 11, 2019
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A European aerospace production team comprising Thales Alenia Space, Cranfield University, and Glenalmond Technologies announces the completion of the first full-scale prototype of an additively manufactured titanium pressure vessel to be used in future manned missions for space exploration.
The vessel is approximately 39 inches high and weighs about 19 pounds. Made of the titanium alloy Ti-6Al-4V, it was manufactured by the â€wire plus arc†additive manufacturing (WAAM) process, which Cranfield University has pioneered over the last decade. Thanks to being able to go straight from digital drawing to final structure, WAAM has integrated two individual pieces into a single part; eliminated the need for long-lead-time forgings; and substantially reduced the amount of waste material removed by machining.
If manufactured traditionally, the component would have required about 30 times more raw material than its final mass. By using the WAAM process, more than 440 pounds of Ti-6Al-4V has been saved for each component. There is room to improve this further, and Cranfield is working on innovative methods to deposit closer to the final thickness.
The WAAM shape was manufactured at Cranfield and then sent to Glenalmond Technologies, where it was stress-relieved, laser-scanned, machined, and inspected by an ultrasonic method. The final inspection was carried out by Agiometrix with a computer tomography scan for internal quality analysis and then an optical scanner, with Thales Alenia Space ensuring that the part met the mechanical requirements and specifications.
Following the checks, the project team was satisfied that the vessel fulfils the driving technical and quality requirements. The team is now proceeding to the building of a second prototype, to carry out a fine tuning of the whole manufacturing cycle, to demonstrate the repeatability and reliability of the process, and to push the implementation of the new approach into the flight hardware.
http://www.cranfield.ac.uk
A European aerospace production team comprising Thales Alenia Space, Cranfield University, and Glenalmond Technologies announces the completion of the first full-scale prototype of an additively manufactured titanium pressure vessel to be used in future manned missions for space exploration.
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Tungsten-based alloy withstands radiation in nuclear fusion devices without damage
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Los Alamos National Laboratory, New Mexico, announces that its scientists have developed a tungsten-based alloy that can withstand unprecedented amounts of radiation without damage. The material, created as a thin film, is a quaternary nanocrystalline tungsten-tantalum-vanadium-chromium alloy that has been characterized under extreme thermal conditions and after irradiation.
Essential for extreme irradiation environments such as the interiors of magnetic fusion reactors, previously explored materials have thus far been hobbled by weakness against fracture, but this new alloy seems to defeat that problem.
“This material showed outstanding radiation resistance when compared to pure nanocrystalline tungsten materials and other conventional alloys,†said Osman El Atwani, the lead author of the paper and the principal investigator of the “Radiation Effects and Plasma Material Interactions in Tungsten Based Materials†project at Los Alamos. “Our investigations of the material mechanical properties under different stress states and response of the material under plasma exposure are ongoing.â€
“We have never seen before a material that can withstand the level of radiation damage that we have observed for this high-entropy [four or more principal elements] alloy,†says principal investigator Enrique Martinez Saez, a coauthor of the paper at Los Alamos. “It seems to retain outstanding mechanical properties after irradiation, as opposed to traditional counterparts, in which the mechanical properties degrade easily under irradiation.â€
www.lanl.gov
Los Alamos National Laboratory, New Mexico, announces that its scientists have developed a tungsten-based alloy that can withstand unprecedented amounts of radiation without damage.
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Asylum Research Jupiter AFM provides 200-mm sample access and higher resolution
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Oxford Instruments Asylum Research, Santa Barbara, Calif., announces the new Jupiter XR Atomic Force Microscope, the first and only large-sample AFM to offer both high-speed imaging and extended range in a single scanner. Jupiter provides complete 200 mm sample access and delivers higher resolution, faster results, a simpler user experience, and the versatility to excel in both academic research and industrial R&D laboratories.
Jupiter XR features a fully-addressable 200 mm sample chuck, and simple and intuitive software control of system setup. This includes laser and detector alignment, automated optimization of imaging parameters, automated multi-site imaging and analysis, and Asylum Research’s unique blueDrive tapping mode for improved tip lifetime and measurement repeatability.
It is also the world’s most versatile large-sample AFM, incorporating Asylum Research’s extraordinary range of capabilities and accessories, and a modular design that supports future expansion. It works well in research environments, high-throughput industrial applications, and failure analysis labs. No matter the application, this large-stage AFM provides ease of use, speed, performance, and flexibility.
https://afm.oxinst.com/products/jupiter-family-of-afms/jupiter-xr-afm
Oxford Instruments Asylum Research, Santa Barbara, Calif., announces the new Jupiter XR Atomic Force Microscope, the first and only large-sample AFM to offer both high-speed imaging and extended range in a single scanner.
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Mineral and organic acids extract rare earth elements from phosphate rock waste
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Researchers from Rutgers University-New Brunswick, N.J., and members of the Critical Materials Institute in Ames, Iowa, announce that they have found a possible new source of rare earth elements in phosphate rock waste, and have developed an environmentally friendly way to extract the elements. Results of their study were published in the Journal of Chemical Thermodynamics.
The research team explored using mineral and organic acids, including a bio-acid mixture, to extract six rare earth elements (yttrium, cerium, neodymium, samarium, europium, and ytterbium) from synthetic phosphogypsum. Scientists led by David Reed at Idaho National Laboratory produced the bio-acid mixture - consisting primarily of gluconic acid, found naturally in fruits and honey - by growing the bacteria Gluconobacter oxydans on glucose.
The results suggest that the bio-acid did a better job extracting rare earth elements than pure gluconic acid at the same pH (2.1), or degree of acidity. The mineral acids (sulfuric and phosphoric) failed to extract any rare earth elements in that scenario. When the four acids were tested at the same concentration, only sulfuric acid was more effective than the bio-acid.
Each year, an estimated 250 million tons of phosphate rock are mined to produce phosphoric acid for fertilizers. In the United States, approximately 28 million metric tons were mined in 2017. Rare earth elements generally amount to less than 0.1 percent in phosphate rock. But worldwide, about 100,000 tons of these elements per year end up in phosphogypsum waste. That's almost as much as the approximately 126,000 tons of rare earth oxides produced worldwide each year.
www.newbrunswick.rutgers.edu
https://cmi.ameslab.gov/
Researchers from Rutgers University-New Brunswick, N.J., and members of the Critical Materials Institute in Ames, Iowa, announce that they have found a possible new source of rare earth elements in phosphate rock waste, and have developed an environmentally friendly way to extract the elements.
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Kermetico makes specialized HVAF systems for a wide variety of powders and substrates
March 8, 2019
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Kermetico, Benicia, Calif., makes specialized HVAF systems to spray metal coatings and alloyed powder compositions onto uncommon substrates such as acme threads, thin walls, and temperature-sensitive materials. The HVAF process is extremely stable due to the utilization of micro-flame combustion technology enhanced with a catalytic insert.
Modular hardware design makes it possible to build specialized equipment: engineers adjust combustion chambers, nozzles, and powder injectors to achieve optimized results. A variety of fuel gases and the possibility of multiple additional gas injections make the process even more versatile and efficient.
The company offers several systems optimized to spray particular powders. For example, the Kermetico SL HVAF system provides an option to spray low melting point materials such as zinc at up to 22 pounds per hour, without oxidation and with an applied cost not substantially higher than twin-wire arc spray.
When working with precious metals, it is critical to have a stable and predictable technological process. The Kermetico SP High Velocity Air Fuel (HVAF) gun heats silver or gold powder to just below the melting point, which prevents material evaporation. Then it delivers hot powder to the solid metal substrate at supersonic speed and deposits it densely. This system prevents loss of precious metals due to evaporation. Most of it will be deposited as a high-quality coating; the remainder will go into the filtration system.
www.kermetico.com
Kermetico, Benicia, Calif., makes specialized HVAF systems to spray metal coatings and alloyed powder compositions onto uncommon substrates such as acme threads, thin walls, and temperature-sensitive materials.
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Spray Tips: Cold spray particle velocity and temperature
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The diagram compares the particle velocity and gas temperature ranges of cold spray and other thermal spray processes: In the cold spray process, the gas and particle temperatures are much lower and the gas and particle velocity are much higher than in other thermal spray processes.
There typically are four regions of particle/substrate interactions that can be defined by particle velocity. In the first region, the particle velocity (Vp) is too low for a given coating/substrate combination to form a coating, and the feedstock particles are reflected from or bounce off the surface and do not form a contiguous coating or deposit.
When the particles impinge at moderate velocities, solid particle erosion of the substrate surface occurs, but no coating is deposited.
When the particles reach a critical velocity (Vcrit), the particles begin to plastically deform, adhere to the substrate, and form a coating. The critical velocity varies with particle and substrate material. As Vp increases, the particles undergo more deformation, typically leading to higher coating densities. At very high velocities, the solid particles start to erode the surface of the substrate. When this occurs, the particle velocity is called the erosion velocity (Verosion).
https://dl.asminternational.org/books/book/12/chapter/133714/Cold-Spray-Process
The diagram compares the particle velocity and gas temperature ranges of cold spray and other thermal spray processes: In the cold spray process, the gas and particle temperatures are much lower and the gas and particle velocity are much higher than in other thermal spray processes.
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How cold spray technology improves the electrical and erosion properties of polymers
March 7, 2019
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Metallization of polymers is an attractive way of improving their electrical and erosion properties, but it is still challenging to achieve a dense metal coating on polymer surfaces by thermal spray processes, due to excessive surface erosion during processing.
Depositing Metallic Coatings on Polymer Substrates by the Cold Spray Process was presented at the Thermal Spray of Suspensions and Solutions Symposium 2018.
Following is the abstract of the presentation:
Cold spray (CS) is a successful and promising coating technique for many engineering applications due to its high-rate and high-dense coating development abilities. Nevertheless, its practical use in polymer substrates is still in the fledgling phase.
This paper presents the results on the potential of the CS process to produce metallic coatings on non-metallic surfaces such as polymers and composites. In order to rationalize the behavior of the high velocity particle with the substrates, three thermoplastic polymers were selected as a substrate, i.e., PEEK, ALTEM, and ABS. The result showed that the particle behaviors were unique with respect to the substrate. Also, it was clearly understood that the metal particles did not experience any plastic deformation due to the soft nature of the polymer substrates.
The properties of the coatings, such as adhesion strength, Vickers hardness and electrical resistivity, were measured and the influence of the coating thickness on the above properties and bonding behavior was also evaluated.
Paper authors:
Dr. M. Reza Rokni and Dr. Steven R Nutt, University of Southern California, Los Angeles
Dr. Christian A. Widener, South Dakota School of Mines and Technology, Rapid City
Mr. Robert Hrabe , VRC Metal Systems, Rapid City, South Dakota
www.vrcmetalsystems.com
Metallization of polymers is an attractive way of improving their electrical and erosion properties, but it is still challenging to achieve a dense metal coating on polymer surfaces by thermal spray processes, due to excessive surface erosion during processing.
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Super-fast high-energy X-rays reveal defects in 3D printed products as they are being built
March 6, 2019
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Engineers from Carnegie Mellon University and Argonne National Laboratory report that they have discovered defects in the products of the Laser Powder Bed Fusion (LPBF) process by taking videos of the products with super-fast high-energy x-rays as they are being built.
The research shows that keyhole defects form when a certain laser power density is reached that is sufficient to boil the metal. This, in turn, reveals the critical importance of the laser focus in the additive manufacturing process, an element that has received scant attention so far, according to the research team.
During the LBPF build process, lasers scan over each layer of powder to fuse metal where it is needed, creating the finished product from the ground up. Defects can form when pockets of gas become trapped into these layers, causing imperfections that could lead to cracks or other breakdowns in the final product.
Researchers were able to watch exactly what happens as the laser moves across the metal powder bed to create each layer of the product. Under perfect conditions, the melt pool shape is shallow and semicircular, called the “conduction mode.†But during the actual printing process, the high-power laser, often moving at a low speed, can change the melt pool shape to something like a keyhole in a warded lock: round and large on top, with a narrow spike at bottom, as shown in the image. Such “keyhole mode†melting can potentially lead to defects in the final product.
See the Science article here: http://science.sciencemag.org/content/363/6429/849
www.cmu.edu
www.anl.gov
Engineers from Carnegie Mellon University and Argonne National Laboratory report that they have discovered defects in the products of the Laser Powder Bed Fusion (LPBF) process by taking videos of the products with super-fast high-energy x-rays as they are being built.
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One Minute Mentor: Austenitizing ductile cast iron
March 4, 2019
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The usual objective of austenitizing is to produce an austenitic matrix with as uniform a carbon content as possible prior to thermal processing. The graph shows the 2% silicon section of the Fe-C-Si phase diagram.
For a typical hypereutectic ductile cast iron, an upper critical temperature must be exceeded so that the austenitizing temperature is in the two-phase (austenite and graphite) field. This temperature varies with alloy content. Equations to predict the location of the upper critical temperature with varying chemical compositions are found in the literature.
It also is clear from the graph that the “equilibrium†austenite carbon content in equilibrium with graphite increases with an increase in austenitizing temperature. This ability to select (within limits) the matrix austenite carbon content makes austenitizing temperature control important in processes that depend on carbon in the matrix to drive a reaction. This is true particularly in structures to be austempered, in which the hardenability (or austemperability) depends to a significant degree on matrix carbon content.
https://dl.asminternational.org/books/book/9/chapter-abstract/109877/Heat-Treating-and-Properties-of-Ductile-Iron?redirectedFrom=fulltext
The usual objective of austenitizing is to produce an austenitic matrix with as uniform a carbon content as possible prior to thermal processing. The graph shows the 2% silicon section of the Fe-C-Si phase diagram.
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