A platinum-gold alloy engineered by scientists in New Mexico is 100 times more durable than high-strength steel and in the same class as diamond and sapphire.
The team at Sandia National Laboratories recently reported their findings in Advanced Materials, saying the discovery could save the electronics industry more than $US100 million a year in materials alone.
They also provided an unusual example of how durable a combination of 90% platinum with 10% gold can be. Apparently, if your car was fitted with tyres made of the material, you could skid – not drive – around the Earth’s equator 500 times before you needed a change.
“We showed there’s a fundamental change you can make to some alloys that will impart this tremendous increase in performance over a broad range of real, practical metals,” said materials scientist Nic Argibay, an author on the paper.
The combination of the two metals is not a new development. But the engineering and thinking behind the approach has propelled it forward as a new way to solve a modern problem.
They say wear is related to how metals react to heat, not their hardness, and they handpicked metals, proportions and a fabrication process to prove it.
Their alloy looks and feels like ordinary platinum, but is much better at resisting heat than other platinum-gold alloys and a hundred times more wear resistant.
Electronics companies used an ultra-thin coating of gold or other precious metals on their components to reduce wear as they constantly slide across each other, sometimes billions of times.
And the smaller the connections are, the less wear and tear they can endure before it all grinds to a halt.
With Sandia’s platinum-gold coating, only a single layer of atoms would be lost after a mile of skidding on the hypothetical tyres.
Traditionally, alloys work by reducing the grain size of raw materials, thereby producing a new stronger material. But those alloys will still eventually coarsen or soften under extreme stress and temperature.
But John Curry, a postdoctoral appointee at Sandia and first author on the paper, said the team “did not see much change to the microstructure over immensely long periods of cyclic stress during sliding”.
One more thing
As a bonus, testing also turned up a happy accident.
One day, while measuring wear on their alloy, a black film started forming on top. The team recognised it as diamond-like carbon, a coating slick as graphite and hard as diamond that usually requires special conditions to manufacture.
Under stress, their alloy was making its own lubricant, and a good one at that.
“Industry has other methods of doing this, but they typically involve vacuum chambers with high temperature plasmas of carbon species,” Curry says.
“It can get very expensive.”
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