Adhesion of tungsten particles on rough tungsten surfaces using Atomic Force Microscopy

Adhesion forces between tungsten spherical microparticles and tungsten substrates with different roughnesses have been measured using the Atomic Force Microscopy (AFM) colloidal probe technique. Mean roughnesses of the tungsten substrates were measured by AFM and were ranked in three categories i.e. nanoscale, sub-microscale and microscale roughnesses. Experimental Hamaker constant of 37±3.5×10−20 J has been obtained using a spherical tungsten particle of 10.5 μm in radius and a tungsten substrate with nanoscale root-mean-square roughness of rms=11.5 nm. It was shown that larger roughness of the order rms=712 nm induces a two order of magnitude decrease on the adhesion of tungsten microparticles compared to a smooth tungsten surface with nanoscale roughness. Comparison with the van der Waals-based adhesion force model of Rabinovich which integrates the roughness of surfaces showed good agreement with experimental pull-off forces even when roughness of the substrate is close to the micrometer range. In such case, measurements have shown that dependency of adhesion force with particle size (in the micrometer range) has a secondary influence compared to the roughness of surfaces. •AFM measurements between tungsten particles and tungsten substrates are presented..•A strong effect of roughness (versus the size of the particle) in the reduction of adhesion on real surfaces is observed.•Comparison between experiments and adhesion models emphasis the relevance of using rms roughness of surfaces in contact.•Experimental value for the Hamaker constant of tungsten has been found in good agreement with theoretical values.