Can the H/E ratio be generalized as an index for the wear resistance of materials?

Hardness (H) is the main mechanical property which determines the wear resistance of materials. Young's modulus (E) has also been shown to influence the wear resistance. The H/E ratio is often used as an index to represent wear resistances of materials and coatings. The larger the H/E ratio, the higher the wear resistance. However, though this ratio is shown to be a measure of the wear resistance for reported cases, whether or not it can be generalized as an index of wear resistance is questionable. In this study, we investigate the wear behaviors of strain-hardened Cu and Mg, and demonstrate the H/E ratio markedly overestimates the wear resistance. Although the cold-work increases hardness, it deteriorates the material integrity with introduced lattice imperfections, which negatively influence the atomic bonding, thus decreasing the benefit of strain-hardening to the wear resistance.