The Sandia team notes that the impressive properties of 9 to 1 platinum-gold alloys are already well documented. Their formulation’s exceptional resistance comes from the unique way they are created: very thin layers of platinum-gold are deposited, one at a time, on top of a high-purity platinum-gold base using a vacuum-sealed magnetic chamber. The inspiration to use this fabrication method came from computer models of how individual atoms would interact.
Although the stability under mechanical stress was predicted by their simulations, the platinum-gold alloy also had some unexpected benefits. In an experiment documented in the journal Carbon, the material spontaneously created its own lubricant – a coating of DLC – during a wear test. DLC is one of the best lubricants because it has the hardness of diamond but slickness of graphite.
“We believe the stability and inherent resistance to wear allows carbon-containing molecules from the environment to stick and degrade during sliding to ultimately form diamond-like carbon,” first author John Curry explained. “Industry has other methods of doing this, but they typically involve vacuum chambers with high-temperature plasmas of carbon species. It can get very expensive.”