October_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | O C T O B E R 2 0 2 0 2 0 Hanwha was looking for, the part ge- ometry was extremely complex and the material itself proved difficult to ma- chine. In this case, 3D printing was a logical alternative choice, providing de- sign freedom and avoiding welding and brazing of separate parts (Fig. 1b). Sur- face finish directly out of the advanced AM system was also exceptionally high, reducing post-processing steps. Ti-6Al-4V— KW Micro Power is de- veloping small, powerful, affordable hy- brid-electric microturbines for drones and portable power generation. Their microturbine generator can produce more power than systems 10 times as large. At the heart of the company’s tur- bine technology is a titaniumdisc with a 10-in. diameter and 4-in. height, whose interior contains a complex labyrinth that channels exhaust gases far more efficiently than conventional systems. The Ti-6Al-4V alloy the compa- ny chose for its desirable weight and strength characteristics can be a chal- lenge to work with. It is prone to crack- ing when 3D printed in many current systems. The material is ideal for build- ing the microturbine’s elaborate in- ternal structures and zero-degree overhangs—although most AM tech- nologies would require numerous scaf- fold-like supports to keep theworkpiece from drooping and warping during the build process. In this case, a next-gen AM system enabled the part to be print- ed on the very first run—with a bare minimum of support structures (Fig. 2). Software, hardware, and process con- trol overcame the technical challen- ges of printing this complex titani- um part. Aluminum F357 —In another sce- nario, aluminum F357, a foundry-grade aluminum alloy with attractive thermal characteristics, can be used to 3D print parts traditionally manufactured. While there are other aluminum alloys such as AlSi10Mg that are more commonly used in metal additive manufacturing, the high silicon content of this alloy means it cannot be anodized. In contrast, 3D parts printed from aluminum F357 can be anodized, thus inhibiting corrosion and providing greater durability in the field. This is a highly desirable attribute for heat exchangers in mission-critical applications—for which F357 has al- ready been certified. That’s why PWR , a global supplier of advanced cooling solutions to For- mula 1, NASCAR, and other racing se- ries—along with custom automotive, military, and aerospace heat-exchang- er applications—chose this material (Fig. 3). The company worked with an advanced AM system provider to de- velop the process for 3D printing F357. Of particular importance are thin walls that are leak-tight, fully dense with no porosity, and have a good surface fin- ish, all of which work together to en- able thermal conductivity. Because this advanced AM technology allows the creation of extremely free-form and lightweight structures, PWR now has both the material and technolo- gy resources to further improve perfor- mance and packaging in a wide variety of heat-transfer applications. Hastelloy X —The final example in- volves Hastelloy X, a nickel-base alloy exceptionally resistant to stress corro- sion cracking and oxidation. It is most Fig. 2 — The as-printed KWMicro Power diffuser housing, top view (left) and bottom (right). Fig. 3 — A variety of 3D-printed heat exchanger components (both whole and in cross section) demonstrate the design freedom provided by advanced AM technology. Note the ultrathin features in the core (cross section image). Such complexity is nearly impossible to attain with existing AM technologies. Fig. 4 — Unicore of a 20-kWmicroturbine engine, being developed by Sierra Turbines, 3D printed on an advanced metal AM system. The nickel-base alloy is exceptionally resistant to stress corrosion cracking and oxidation and is most often used to manufacture parts for combustion- zone gas turbine engines due to its high temperature strength.