Bulk Metallic Glass Gears

BMG Gears

(a) Schematic showing the motivation for developing bulk metallic glass (BMG) gears. Crystalline metals tend to exhibit poor wear while ceramics are brittle. BMGs offer wear resistance similar to ceramics but with up to two orders of magnitude higher toughness. (b) Micrograph showing the teeth of a BMG gear. (c) Two BMG gears in a spur gear test where their performances were shown to be up to three times better than the best steel alloys. (d) Cast BMG gears integrated into a working gearbox. (e) A handful of cast BMG gears demonstrating the ease with which they can be fabricated. Images credit: NASA

NASA needs heaterless gearboxes to enable cold capable mechanisms for missions to icy bodies and extreme cold environments like Europa; missions like a Europa lander will not have solar panels or nuclear sources for power generation and will have to meet mission objectives on battery power.

The problem to be solved is to make metal alloys that combine the benefits of metals and ceramics into a single material, optimally suited for wear-resistant applications. Such an optimal material would (1) have a higher toughness than ceramics, (2) have higher wear-resistance than any metals (approaching ceramics), (3) have low processing temperatures so that net-shaped forming is possible, (4) be machinable, and (5) be robust to extreme environments.

BMG Gears project’s unique material solution is a metallic glass with mechanical properties very similar to ceramics; it is high in strength, wear resistant, and holds up to extreme temperatures. Bulk metallic glass is moldable for reduced component cost after the initial tooling investment, and existing industry infrastructure supports alloy and component supply change, providing another opportunity for cost savings as well as opportunities for partnering with industry.

Keith Belvin ( w.k.belvin@nasa.gov) Robert Dillon (robert.p.dillon@jpl.nasa.gov)

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