The fabrication of hierarchical periodic microstructures on metals by means of direct laser interference patterning was investigated. A nanosecond pulsed Nd:YAG laser at 355 nm wavelength was used to produce the microstructures with grating periods ranging from 1 micron to 10 micron on stainless steel, titanium, and aluminum. The results indicate that the geometrical characteristics of the interference patterns as well as the thermal properties of the substrates determine the quality of the fabricated structures. In particular, the best structures were obtained when the material at the interference minima position remained in the solid state and the temperature at the interference maxima is below the vaporization temperature. Thermal simulations by finite element method were carried out modeling photothermal interactions of the interference pattern with the metallic substrates to evaluate laser induced thermal effects, such as temperature distribution and temperature gradients and, thus, enabling to explain the obtained results
This study discusses the effects of surface topographies on the frictional behavior of 100Cr6 bearing steel. A solid state laser with nanosecond pulses is used to produce one-and two-dimensional periodic micropatterns using direct laser interference patterning. Line-, cross-, and dot-like patterns with pitches of 5 mm, and aspect ratios (AR) between 0.02 and 0.17 are fabricated. The friction tests of the surface textured samples are performed under lubricating conditions using a ball-on-disk configuration in rotating mode. The results show that through the surface structure a reduction of the friction coefficient from 25 to 65% can be achieved compared to unstructured surfaces. The smallest coefficients of friction are obtained for ARs between 0.07 and 0.11.
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