November 20, 2008: Friction is the bane of any machine. When moving parts are subject to friction, it takes more energy to move them, the machine doesn’t operate as efficiently, and the parts have a tendency to wear out over time. But if you could manufacture parts that had tough, “slippery” surfaces, there’d be less friction, requiring less input energy and the parts would last longer. Researchers at the US Department of Energy’s Ames Laboratory are collaborating with other research labs, universities, and industrial partners to develop just such a coating.
“If you consider a pump, like a water pump or a hydraulic pump, it has a turbine that moves the fluid,” said Bruce Cook, an Ames Laboratory scientist and co-principal investigator on the four-year, $3 million project. “When the rotor spins, there’s friction generated at the contacting surface between the vanes and the housing, or stator. This friction translates into additional torque needed to operate the pump, particularly at start-up. In addition, the friction results in a degradation of the surfaces, which reduces efficiency and the life of the pump. It takes extra energy to get the pump started, and you can’t run it at its optimum (higher speed) efficiency because it would wear out more quickly.”
Applying a coating to the blades that would reduce friction and increase wear resistance could have a significant effect in boosting the efficiency of pumps, which are used in all kinds of industrial and commercial applications. According to Cook, government calculations show that a modest increase in pump efficiency resulting from use of these nanocoatings could reduce US industrial energy usage by 31 trillion BTUs annually by 2030, or a savings of $179 million a year.
Photograph of an AlMgB14 coating on a steel substrate. The substrate is the mottled structure on the left-hand side of the photo and the coating is the thin, darker strip running along the edge of the steel. Blemishes on the steel are carbide inclusions. The coating has a thickness of approximately 2-3μm (about 1/10,000-in.)
The group is also working with Greenleaf Corp., a leading industrial cutting tool maker, to put a longer lasting coating on cutting tools. If a tool cuts with reduced friction, less applied force is needed, which directly translates to a reduction in the energy required for the machining operation.
To test the coatings, the project team includes Peter J. Blau and Jun Qu at one of the nation’s leading friction and wear research facilities at DOE’s Oak Ridge National Laboratory, or ORNL, in Tennessee. Initial tests show a decrease in friction relative to an uncoated surface of at least an order of magnitude with the AlMgB14-based coating. In preliminary tests, the coating also appears to outperform other coatings such as diamond-like carbon and TiB2.