Design of Stable Nanocrystalline Alloys for Coating Applications

When the grain size of a metal is refined to a scale on the order of just a few nanometers, its strength, hardness, wear resistance, and other properties improve in dramatic ways. There is therefore significant interest in designing and deploying such nanocrystalline alloys for structural applications. However, refining the grain structure is a struggle against equilibrium, and nanocrystalline materials are often quite unstable; the grains grow given time even at room temperature, and the associated property benefits decline over time in service. In this talk, our efforts to design a stable family of nanocrystalline alloys will be described. We rely on selective alloying as a method to lower the energy of grain boundaries, brining the nanocrystalline structure closer to equilibrium. The result is a suite of coatings with highly desirable properties, easy processability, and with long-term stability against structural coarsening. The science of alloy design and characterization will be discussed, as will the commercial applications of the technology.