NASA’ s space goals include a permanent presence on the Moon and an expedition to Mars. The success of habitats and vehicles on the Moon and Mars — and ultimately, of the human exploration of and permanent human presence on the Moon and Mars — is critically dependent on the correct and reliable operation of many moving mechanical assemblies. These harsh environments include severe dust, extreme cold and heat, and high vacuum, which make the use of liquid lubrication systems impractical. Potential threats common to both the Moon and Mars are low ambient temperatures, wide daily temperature swings (thermal cycling), solar flux, cosmic radiation, and large quantities of dust. The surface of Mars provides the additional challenges of dust storms, wind, and a carbon dioxide atmosphere. It is essential, therefore, to develop specialized mechanical components, such as bearings and gears, and to develop proper, long-life solid lubrication systems/coatings for each application.

This will require designing new solid lubricants and completing design validation efforts in these applications where liquid lubricants are ineffective and undesirable. Solid lubricants and coatings are needed for lunar and Martian applications where liquid lubricants are ineffective and undesirable, and these lubricants must perform well in the extreme environments of the Moon, Mars, and space, as well as on Earth where they will be assembled and tested. No solid lubricants and coatings and their systems currently exist or have been validated that meet these requirements, so new solid lubricants must be designed and validated for these applications. This program addresses the limitations through microstructural control and advanced application process development.

The purpose of this work was to develop and characterize nanostructured self-lubricated coatings with low coefficient of friction and high wear resistance. This was enabled through the use of a revolutionary combination of hard materials such as nitrides, and self-lubricated materials including molybdenum and molybdenum disulfide. PComP™ coatings are ceramic-metallic (cermet) composites fabricated into a hierarchical structure engineered down to the nanoscale. They are manufactured by thermally spraying cermet powders with a nanocomposite core and a clad coat. This coat is manufactured using a combination of high-wear-resistant and low-friction materials. The nanocomposite core provides high wear resistance through nitride particles and low friction through solid lubricants, while the binders and clad coat provide toughness, ductility, resiliency, and improved deposition efficiency through thermal spray processing.

Nanosized hard particles have a well-defined morphology and composition within the nanometric scale that serve as building blocks for the microscale particles. The microscaled metallic alloys bind individual nano-nitrides and solid lubricants in the core and encapsulate/clad the entire core.

The coating demonstrated substantial 1 to 2 orders of magnitude improvement in wear resistance over uncoated materials and commercially available coatings in dry conditions. The material also performed exceptionally in the presence of diesel fuel. The fabrication capabilities were shown by production of more than 10 lb (≈4.5 kg) of powder batches.

This work was done by Evelina Vogli, Gabriel Santillan, and Andrew Sherman of MesoCoat Inc. for Glenn Research Center. NASA is seeking partners to further develop this technology through joint cooperative research and development. For more information about this technology and to explore opportunities, please contact here . LEW-19278-1

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This article first appeared in the October, 2017 issue of Tech Briefs Magazine.

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