On the use of LIPSS in single- and multi-scale laser-structured tool surfaces under lubricated conditions

Abstract

To use water as lubricant, suitable conditions must be created on the process side to compensate its low viscosity. Here, tool surfaces functionalized by micro dimples and laser induced periodic surface structures (LIPSS) in conjunction with high process velocities could play an essential role. This work shows that laser hardened LIPSS wear out in direct water lubricated sliding contact between strip drawing tools and workpiece. Thus, these structures are applied as hierarchical structures to the bottoms of dimples. Though LIPSS' hydrophilicity is preserved, strip drawing tests reveal that the nanostructures do not influence the coefficient of friction as comparisons with dimpled tools without LIPSS show. Instead, the achieved coefficients of friction are in the range of those from tools used in dry condition. Thus, the expected positive influence of functionalized surfaces on lubricated metallic friction couples due to direct as well as in hierarchical structures in water lubricated sliding conditions could not be confirmed.