Indentation hardness

Deformation (meteorology)

Contact area

Metallurgy

Materials science

Indentation

Nanoindentation

Microstructure

Scratch

Composite material

Tribology

Knoop hardness test

Hardness

Tribology International

Nanoindentation and scratch experiments probe the hardness by leaving a permanent imprint on the material’s surface. The scratch hardness, however, is less used due to its unclear relation to the nanoindentation hardness and discrepancies in the evaluation methods. We investigate which scratch hardness evaluation methods lead to consistent results and for which materials and load-ranges the contact area can be estimated by the Hertz solution or by the nanoindentation hardness. Finally, we address the relation of nanoindentation and scratch hardness. Secondary influences on the scratch hardness (tip size, scratch depth and elliptical shape) are addressed. To evaluate the general applicability of the findings, we study 5 materials with significantly different deformation behavior: aluminum, copper, soda-lime glass, cementite, and silicon.

Scratch hardness at a small scale: Experimental methods and correlation to nanoindentation hardness