US Department of Energy scientists at the Oak Ridge National Laboratory (ORNL) have developed a coating based on carbon nanotubes that promises to drastically reduce the friction experienced by moving parts like turbines and drivetrains.
Friction is the enemy of most moving parts, with it causing a loss of efficiency and component wear that ultimately leads to failure. It is thought, for example, to cost the US economy a trillion dollars each year. Dry metals sliding against each other usually incur a friction coefficient of around 0.5, but using a lubricant like the Castrol Magna slideway oil can slash this to around 0.1 while also protecting against wear. The new coating developed by ONRL goes far beyond this, however, with it achieving a coefficient of friction of about 0.001, which is below the superlubricity threshold of 0.01.
This does not mean an oil-based lubricant is no longer needed, however, as the leader of the research group, Jun Qu, explained:
“We tried it without oil; it didn’t work. The reason is, without oil, friction removes the carbon nanotubes too aggressively. Then the tribofilm cannot form nicely or survive long. It’s like an engine without oil. It smokes in a few minutes, whereas one with oil can easily run for years.”
The main advantage of the new coating is that it has the potential to bring superlubricity, which has previously been confined to nanoscale and other niche applications, to common applications like turbines and gears, potentially enabling systems to run at new levels of efficiency and reliability.
