Recent advancements in polymers, metals, and composites are taking the manufacturing industry in bold, often unexpected directions
Humans began turning metals into useful shapes millennia ago, first with copper and gold, then bronze, followed by iron and steel. Polymers have a far shorter history—just over a century—but have since become every bit as important as their metallic counterparts.
Then there are the newcomers to the materials evolution, among them carbon-fiber-reinforced plastics (CFRP) and metal-matrix composites, which have grown increasingly popular in recent years due to their strength and stiffness, relatively low weight, and “tunability” for various applications.
Innovations continue across the materials spectrum, yielding an eclectic mix of advanced formulations with application-specific properties to enhance strength, durability, and formability, while reducing weight and improving sustainability. Not that there was ever much doubt, but modern materials development truly is a science.
Ironically, one of the most established players in this materials menagerie, steel, is once again striving to lead the pack—at least in the automotive world. That’s because advanced high-strength steel (AHSS) and ultra-high-strength steel (UHSS) have taken the driver’s seat in many car and truck designs, thanks to their weight and environmental benefits.
So-called 3rd-generation steels “can reduce a vehicle’s structural weight by as much as 25 percent and cut total lifecycle CO2 emissions by up to 15 percent more than any other automotive material,” according to the American Iron and Steel Institute (AISI), Washington, D.C.
Chris Kristock, vice president of AISI’s automotive program, noted that the steel industry has experienced several distinct phases on the road to these high-strength steels. “Some of us might recall the virtually indestructible Checker Cabs of the fifties, whose body panels were made of heavy gage carbon-manganese alloys,” he said. “Back then, strength was achieved by using thicker materials, a practice that’s unheard of nowadays.”
The first step toward thinner metals came with the addition of columbium, titanium, vanadium, and similar alloying elements, all of which serve to increase strength while maintaining good ductility. Not all improvements are purely metallurgical, however. Automakers soon developed the hot-stamping process, where steel containing slightly higher amounts of carbon and manganese (and a bit of boron) is heated to 1,800° F (982° C) during forming, then quenched while still in the die. And while this process produced strong, high-quality parts, automakers wanted more.
Kristock explained that Gen3 steels are dual-phase in nature, with a ferritic–martensitic microstructure that significantly increases their mechanical properties.
“Traditional low-carbon steel has yield strength for forming around 210 megapascals (MPa), or 30,000 psi,” he said. “Yet steelmakers have begun distributing commercial alloys that can be cold stamped with yield strength in the 800 MPa range and associated tensile strength of 1,180 MPa, with some hot stamping grades able to achieve yield strength levels in finished parts up to 1400 MPa or up to seven times that of mild steel with associated tensile strength up to 1500 MPa. And they’re not done—we see that steels with 10 times the strength level are on the horizon.”
As stated at the outset, humans have been making steel for millennia. So what’s changed? Are these huge improvements due to newly discovered alloying elements, or some drastically different manufacturing method?
The answer, Kristock explained, is neither. “Thanks to advanced process controls and a host of technology improvements, we’re better equipped to manipulate the thermal processing that goes on during steelmaking,” he said. “We can heat and cool the steel in such a way that it breaks the traditional relationship of strength versus ductility.”
But there’s much more to this steelmaking story. Kristock went on to describe the continuous annealing furnaces and gas quenching systems that allow mill operators to produce AHSS and UHSS, not to mention a host of advanced forming and joining methods that AISI and its member companies have developed to successfully manufacture products from these high-strength steels. Simply put, the steelmaking industry is alive and well, and continues to provide automakers and other market segments with the alloys they need to deliver high-quality wares.
QuesTek Innovations LLC has extensive experience in developing and deploying novel alloys. The Evanston, Illinois, company has been providing integrated computational materials engineering (ICME) services for more than 25 years, and will soon offer its proprietary materials toolkits, models, and databases via a cloud-based, software-as-a-service (SaaS) subscription under the trademarked brand name ICMD (integrated computational materials design).
But as solutions architecture director Keith Fritz explained, QuesTek’s services go well beyond development to include product-specific material optimization and manufacturing support, what the company calls “materials concurrency.”
“Let’s say you need to design the landing gear for an aircraft,” Fritz said. “One of the first things you’ll do is look for an alloy that offers the necessary performance characteristics, then design the parts around those specifications. In other cases, you might design a product before finding, or possibly developing, a material that will meet your requirements,” he continued. “The idea with materials concurrency is that both of those processes start at the same time. You can develop the material and product in parallel with one another, which is a radical departure from how parts have been designed in the past.”
Examples of this include a project with the U.S. Army, which sought to replace the legacy 8620 and 9310 steels used in its helicopter rotor gear trains with novel alloys that would exhibit “a combination of increased bending and contact fatigue resistance, enhanced core strength with good toughness, higher temperature resistance, and excellent hardenability.”
It was a tall order, but by leveraging its software tools and engineering expertise, QuesTek developed Ferrium C64 steel powder, allowing subcontractors Bell Helicopter and Sikorsky (part of Lockheed Martin) to 3D-print prototype parts that met the Army’s requirements.
A similar project with the U.S. Navy led to Ferrium N63, an equally tough, hardenable alloy suitable for a wide range of demanding defense and energy applications. But perhaps the best known of QuesTek’s success stories will hit home with anyone wearing an Apple Watch. Here, the manufacturer “acquired certain technology and know-how” from QuesTek and used it to develop a new grade of aluminum, one with elevated strength and surface hardness, excellent machining characteristics, and other properties that would help Apple maximize profitability and customer satisfaction.
“We also work with customers to optimize existing materials,” added QuesTek materials development lead Thomas Kozmel. “As many in the industry know, alloy specifications are typically quite broad, which means that one lot of material may be less machinable than another, even though they’re technically the same grade. For instance, we recently helped an aerospace client develop an improved formulation of Inconel 718 better suited to their specific application than the generic specification.”
Pin Lu, program manager and senior materials design engineer at QuesTek, agreed. “Our models, which may be considered digital twins, can simulate the various processes that an alloy might go through during manufacturing, whether that’s casting, heat treatment, post processing, surface finishing, and so on. We can model the effects those processes have on material properties, simulating what’s happening on the production floor and asking questions like: ‘What happens if I add more boron to the chemistry?’ Answering such questions on a digital model saves the manufacturer a great deal of trial and error development time and saves material testing costs, while also delivering a better outcome.”
Sometimes, product innovations don’t depend on novel materials at all, but a better understanding of existing ones. Such is the case for Milwaukee Tool, which has invested significant effort into data collection and advanced cloud-based analytics for this very purpose. That’s according to Max Sawa, senior manager of advanced engineering, who explained that the Brookfield, Wis.-based provider of job-site solutions for the mechanical, electrical, and plumbing trades leverages a broad range of prototyping and testing equipment in its Innovation Center.
“We have a front-end team within our advanced engineering group that designs and builds custom machines for prototyping and testing,” Sawa said. “These machines are equipped with sensors that collect data, which we then use to analyze product performance and make better design decisions. That might be information about how a metal responded to heat treating, or maybe it’s how an over-molded polymer performed after repeated cycles.
“At the end of the day,” he continued, “this type of information is crucial to any engineer that is designing new products. The faster we can get them this information, the faster they can iterate and bring products to market.”
One notable outcome of these efforts was when Milwaukee Tool engineers invented a more effective way to bond the carbide teeth to its Sawzall Torch brand of steel saw blades that reportedly yielded a fiftyfold increase in tool life. The company has also developed Nitrus Carbide blades for reciprocating saws, which promise faster cutting and longer life in cast-iron and thick metals. “Each of these is the direct result of collecting data from our prototyping processes (that) accelerates these types of material development,” Sawa noted.
John Barnes has plenty to say about product development, especially when it comes to those produced via 3D printing. As the founder and CEO of The Barnes Global Advisors, an additive manufacturing (AM) consulting firm in Pittsburgh, he recognized years ago the need for greater consistency in the metal and polymer powders used in laser-powder-bed fusion (LPBF), direct-energy deposition (DED), and supersonic-particle deposition (cold spray) AM methods.
Together with business partner Chris Aldridge, Barnes and his team developed an innovative technology that bypasses traditional atomization methods in favor of a mechanical powder-generation technique, one that uses commercially available bar stock and is performed at room temperature. In 2017, the pair took their process to market and founded Pittsburgh-based Metal Powder Works (MPW), a company that Barnes describes as an “alloy enabler” rather than an alloy developer.
“Today, there are 16 different AMS specifications for metal powder, but more than 2,000 specifications for bar stock,” Barnes said. “Our process enables conversion of bar stock to powder directly, and does so without changing their metallurgical properties, making 3D-printed part certification much easier.
“What’s more, we offer much greater yield and better powder consistency than that available through atomization, and have enhanced control over particle morphology and size distribution,” Barnes asserted. “I usually try to avoid terms like revolutionary or disruptive, but I have to say that no other process can deliver what ours does.”
Why is particle shape a big deal when those tiny bits of metal are just going to be melted, fused, or smashed together anyway? Barnes explained that every AM technology has its own distinct requirements, but one common thread among powder-bed and cold-spray processes is the need for consistency first, an attribute the MPW process inherently provides, along with the ability to tailor production to the specific manufacturing process to achieve density.
The largely spherical shapes produced through gas atomization contact each of their neighbors in just one or two spots, limiting their ability to fuse with one another. Not so with MPW’s DirectPowder process, which through numerical control can be “programmed” to generate semi-spherical, disc-shaped, and even thread-like particles in a broad range of sizes.
“We can also produce material on demand directly at the point of use, what we call Sidecar or the trademarked Powder by the Hour,” Barnes added. “This reduces safety concerns. There’s little need for storage, eliminating the oxidation problems that are so common with powders. And it’s much less expensive—where a bar of 7075 aluminum today is around $5 a pound, a bucket of atomized powder costs 80 bucks a pound. So your accountants should be happier with this solution as well.”
Cost savings aside, Metal Powder Works might not have been the best name. Barnes admits the company has been too busy turning metal bars into powder to do much with polymers, but said the process can be applied here as well. That’s great news to Samuel Leguizamon, who knows all about polymer. In fact, upon meeting this senior scientist at Albuquerque-based Sandia National Laboratories, you might be greeted with, “Sam’s the name, advanced polymeric materials are the game.”
As with MPW, Leguizamon’s focus is on 3D printing. And while much of his time is spent on slurry and resin development for direct-ink-write (DWI) processing, he loves all polymers equally. When asked how he goes about inventing a new material, Leguizamon’s response was unsurprising: “It depends on the application. Does the polymer need to dissipate heat or radiation? What are the mechanical requirements? Do the molecules cross-link?
“Once you’ve answered as many of these questions as possible,” he continued, “it’s time to synthesize or hopefully buy the raw materials needed to make an initial formulation. You’ll then analyze its various properties, adjust as needed, and once everything is as close to desired as possible, print some test parts. It’s often a very iterative process.”
Currently, Leguizamon doesn’t use any software tools for this process, but he said this is “definitely a huge area of interest” for him and others in the materials development world.
That’s music to the ears of Greg Mulholland, CEO of Citrine Informatics Inc., who helped found the company based on the premise that where 3D design tools such as CAD and CAE revolutionized the geometric design of physical products, no one had yet developed the software tools needed to design the actual materials used in these products. That was 10 years ago, and the Redwood City, Calif.-based company is well on its way to changing this unfortunate situation.
“There’s been a lot of talk over the last decade and a half about using software to design materials, but until now, no one’s actually made good on it in any meaningful way,” Mulholland acknowledged.
Historically, manufacturers have developed new materials by tweaking existing ones, he explained. Companies might need an adhesive that sticks better at cold temperatures or an alloy that’s a bit harder or more ductile, which they then produce using the iterative process just described—through trial and error, by working from what you know, and making educated guesses.
“My co-founders and I created a platform that brings together materials data and machine learning, allowing the user to perform what a financier would call what-if analyses,” said Mulholland. “You can say to yourself: ‘If my material property goals are X, what process parameters, alloying elements, or chemical tuning can I utilize to achieve that outcome?’ You can then plug those variables into our software and iterate virtually rather than physically until you reach the desired results.”
Josh Tappan, Citrine’s marketing director, noted that many manufacturers are facing conflicts between performance, consumer preference, and regulatory pressure. Per- and poly-fluoroalkyl substances (PFAS) are one notorious example. These versatile coatings resist heat, oils, and water. They’re found in everything from clothing to cooking utensils, but according to the Centers for Disease Control, PFAS are also a forever chemical that accumulates over time and are suspected of causing a range of adverse and severe health effects.
“As with BPA [bisphenol A], materials that we’ve used in the past aren’t going to be allowed for very much longer, which is why chemical and metal manufacturers need a faster, more cost-effective way to formulate next-generation materials,” he said. “The good news is, we’re able to control material structures better today than ever before, to the point that we can literally manipulate individual atoms. The problem then becomes how to evaluate these novel structures and determine their performance characteristics without lengthy testing.”
Mulholland agreed, adding that the materials industry has never been very good at multi-objective optimization. “Everyone wants lighter and stronger, and while both are easy to achieve on their own, combining the two is quite difficult,” he laughed.
Mulholland used to work for a company that made gallium nitride, which is a semiconductor material used for blue light-emitting diodes. At the time, the material was considered the best solution for a wide variety of applications.
“If you asked me back then what (is) the best material for drill bits or light bulbs or shin guards for World Cup soccer players, I would have said gallium nitride,” Mulholland reflected.
That’s no longer the case, thanks to recent advances that have led to more alternatives. “Our software allows companies to leverage their people’s expertise but broaden it to domains beyond the ones they’re accustomed to working in,” Mulholland confided. “Because frankly, we’ve experienced a generational shift in operational requirements lately and require new materials to achieve the goals that we as a society need to accomplish. That’s what we bring to the table.”
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