The existence of a lateral size effect and the relationship between indentation and scratch hardness in copper

AbstractIndentation size effects (ISEs) are well known in static indentation of materials that deform by dislocation-based mechanisms. However, whilst instrumented indentation techniques have become rapidly established as a means of determining the near-surface mechanical properties of materials, scratch testing has been much less widely used. Hardness is used in wear models as a proxy for the yield stress, and the design of materials and hard coatings has often sought to exploit size-derived performance enhancements through length-scale engineering. Yet, it is not known directly whether (or not) length-scale effects also apply to scratch (and thus wear) performance at small scales, or what the functional form of this effect is. This work directly demonstrates that there is a lateral size effect (LSE) and shows that there are questions to be answered if the use of hardness as an indicator of wear performance is to remain valid. We report on constant load scratch experiments using a Berkovich indenter on s...