Predicting Changes in Structure and Properties During Wear in Metallic Systems

University Of California-Irvine, Irvine CA

Investigators

Abstract

Wear is generically defined as the loss or displacement of material during sliding contact, and is an engineering topic of great practical importance. Material loss during service can result in reduced component performance or even catastrophic failure of a device. Nanostructured metals, where internal structural features have dimensions in the nanometer range, are promising materials for wear-resistant coatings and engineering components because of their extremely high hardness and strength. However, the unique nanostructure that imparts excellent strength also accumulates wear damage in unique ways. This award supports a systematic investigation of wear loss and damage in such nanostructured metallic materials. The research combines mechanical engineering with materials science and physics, while also utilizing a combination of cutting-edge experimental and computational techniques. Of specific interest is the identification of the effect of operating conditions on the accumulation of wear damage. Therefore, this project will benefit the U.S. economy by allowing for the design of better wear-resistant materials that extend product lifetime and limit wear failures. In addition, educational and research opportunities will be created for students from diverse backgrounds, broadening participation in scientific research. This award supports an innovative study to reveal the mechanisms of structural evolution and damage during wear of nanocrystalline metals, and to understand how these changes affect subsequent mechanical response. Molecular dynamics simulations will first be used to explore how abrasive sliding drives grain boundary migration, grain growth, and grain boundary relaxation. Of specific interest will be the connection between continuum predictions of stress fields, local atomic stress distributions, and structural evolution. The effects of alloy chemistry and grain boundary energy will also be probed. These simulations will be used to guide wear experiments and inform site-specific structural characterization, in order to study the evolution of near-surface microstructure as a function of grain size, wear cycle, applied load, and sliding speed. This data will be used to create "structural evolution maps," to improve the field's understanding of how nanocrystalline materials respond to complex deformation conditions and help in the future design of damage-resistant nanostructured materials. The study will also quantify how the mechanical properties of the near-surface material evolve with wear damage.