Researchers at Sandia National Laboratories (Albuquerque, New Mexico, USA) recently engineered a platinum-gold alloy believed to be the most wear-resistant metal in the world. According to the research team, the alloy is 100 times more durable than high-strength steel, making it the first alloy, or combination of metals, in the same class as diamond and sapphire.
Although metals are typically thought of as strong, they can wear down, deform, and corrode when repeatedly rubbed against other metals, such as in an engine, the researchers explain. This is unless they have a protective barrier, like additives in motor oil.
In electronics, moving metal-to-metal contacts receive similar protections with outer layers of gold or other precious metal alloys. But these coatings are expensive, and eventually they can wear out, as connections press and slide across each other. These effects are exacerbated when connections are smaller, because reduced initial material means there is less wear and tear that each connection can endure.
With Sandia’s platinum-gold coating, made of 90% platinum and 10% gold, the researchers say only a single layer of atoms would be lost after a mile of skidding on hypothetical tires. The coating could make electronics of all sizes and across many industries more cost-effective.
While conventional wisdom says a metal’s ability to withstand friction is based on its hardness, the Sandia team proposed a new theory that wear is related to how metals react to heat, not their hardness. In turn, they handpicked metals, proportions, and a fabrication process to prove their theory. The theory arose from computer simulations that calculated how individual atoms were affecting the large-scale properties of a material.
“Many traditional alloys were developed to increase the strength of a material by reducing grain size,” says John Curry, a postdoctoral appointee. “Even still, in the presence of extreme stresses and temperatures, many alloys will coarsen or soften, especially under fatigue. We saw that with our platinum-gold alloy, the mechanical and thermal stability is excellent, and we did not see much change to the microstructure over immensely long periods of cyclic stress during sliding.”
Source: Sandia National Laboratories, www.sandia.gov.