How to measure the real contact area? A simple marker and relocation foot-printing approach

• Marker and relocation foot-printing approach to determine the contact area.
• Four different experimental techniques were used.
• For polished surfaces, all techniques resulted in similar contact areas.
• For laser-patterned surfaces, just image segmentation led to reliable results.
• This technique can estimate contact areas comprising several sub-contacts of any shape.

A marker layer (Au80Pd20) combined with four different techniques was used in order to estimate the real contact area between static steel–steel contact pairing (substrate: AISI304 and ball: AISI 52100). The experiments were done with polished references (substrate and ball) and with substrates having a laser-patterned line-like surface topography using two loads (1 and 5 N) and two pattern periodicities (9 and 15 µm). Irrespective of the normal load, all techniques led to the same results within the standard deviation for the polished surfaces. For the laser-patterns, only the combination of foot-printing, scanning electron microscopy and image segmentation is capable to provide meaningful results, since the other techniques significantly overestimate the real contact area.