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The present work seeks to develop a novel and systematic approach to quantifying the repeatability of textured surfaces, a relevant property for several technological fields. Specifically, aluminum alloy and stainless steel specimens were subject to nanosecond pulsed laser texturing to produce arrays of ablation craters in a typical configuration employed to improve wettability and tribological performance. Feature repeatability was firstly assessed in terms of crater volume and interfacial area, after which an additional parameter was developed based on the Pearson's Correlation Coefficient (PCC). Within the tested laser parameter range, the crater volume exhibited highest repeatability in the high energy dose regime on aluminum alloy specimens, while the crater volume was more repeatable in the low energy dose regime on stainless steel specimens. This difference was attributed to the development of an oxide ring surrounding the craters on stainless steel at high energy dose. This outcome was confirmed through analysis of the point-to-point repeatability, where process repeatability was determined for different portions of the ablation craters.

Detailed analysis and characterization of injection-molded polypropylene (PP) specimens produced with laser-textured molds has been performed. Ultrashort pulsed laser surface structuring was exploited to produce sub-micrometric surface features on injection molds over areas of 2400 mm2, including two-dimensional hole and cone arrays, and ridges parallel and perpendicular to the injection direction. Replication effectiveness was evaluated in terms of surface roughness parameters, Filling Volume Fraction (FVF) and Power Spectral Density (PSD), after which detailed comparison of the topography in the same region on plastic samples and molds was performed. A scatterometry setup was employed based on optical diffraction of a probe laser beam to assess replication fidelity over the entire surface of each PP sample with a measurement technique suitable for optimization and quality control in an industrial production environment. Of the tested surface morphologies, greatest replication effectiveness was achieved with LIPSS oriented parallel to the injection direction, where the arithmetic mean height of plastic samples (Sa = 37 ± 4 nm) was 97 % of the corresponding value of the mold (Sa = 38 ± 6 nm), while the average FVF was 86 ± 9 % and the PSD indicated ripple-like features with a spacing of λ ≃ 0.9 μm. Direct comparison of the topography in selected regions highlighted local variability in the transfer effectiveness of individual surface features. The investigation demonstrated that micro and nanoscale morphology can effectively be transferred via injection molding over large areas relevant to industrial applications, while careful attention must be paid to the size and nature of defects in relation to the specific functional surface under consideration.

Laser induced micro-nano texture formation on the surface of solid materials has become a research hotspot in the field of material surface modification. However, due to its extremely easy crystallization characteristics, the study of laser-induced surface modification of bulk amorphous alloy lags behind. In this study, femtosecond laser was used to induce one-dimensional LIPSS (Laser-induced periodic surface structures), SWPSS (Super-wavelength periodic surface structure), a mixed state structure of LIPSS + SWPSS and two-dimensional self-organized microholes structure on surface of the Zr55Cu16Ni15Ti10Al4 bulk amorphous alloy. The numerical difference between LIPSS, SWPSS and self-organized microholes structure in different dimensions such as period, groove width, profile height, etc. were compared, and the roughness of different micro-nano textures and the size of surface undulations were evaluated. The effects of different process parameters on the formation and transformation of micro-nano texture on the surface of zirconium bulk amorphous alloys were investigated. The mechanism of the transformation from LIPSS to SWPSS and finally to two-dimensional self-organized microholes structure was analyzed in detail. Finally, Escherichia coli was cultured on the amorphous surface of Zr-based metallic glasses with different structure. To examine the effect of micro-nano texture on the antibacterial properties of Zr-based metallic glasses surfaces. It is found that the self-organized microholes structure has the best effect in reducing the adhesion of bacteria on the surface of the material.

Surface patterning has been used to enhance the fracture toughness of adhesive joints. In this study, the effect of the variable bondline thickness introduced by the patterns and the effect of pattern geometry on the fracture behaviour of adhesive joints were analysed. Surface patterns including longitudinal grooves, transverse grooves, dimples and grids were fabricated by means of laser texturing. The patterned surfaces were bonded using a tough structural adhesive and the mode I fracture toughness was measured using the J-integral method. The toughness of the patterned joints was compared with the results from bonding with control surfaces and with grit blasted in combination with chromic acid etched (GB-CAE) surfaces. It was shown that both longitudinal and transverse grooves led to the highest value of toughness. Grid patterns yielded a toughness close to the GB-CAE treatment, both of which were higher than the dimple patterns. It was also shown that the variable bondline thickness due to the existence of surface patterns, which influences the size of the plastic zone, reduced rather than increased the fracture toughness.

International audience; Thermal barrier coating systems are usually build-up with bond coats to ensure a good adhesion of the ceramic top coat and to protect the substrate against oxidation and corrosion. Such system is often subjected to complex thermo-mechanical loading. Because of the very different damage processes encountered during service operations, a simplified system was investigated by removing the bond-coat. Recently adhesion bond strength was enhanced using laser surface texturing of the substrate in thermal spraying processes. Atmospheric plasma spray yttria-stabilized-zirconia thermal barrier coating system was deposited on the Ni-based AM1 single crystalline superalloy without bond coat. Adhesion bond strength was already increased compared to conventional processing method. Top coat durability was evaluated at high temperature and damage mechanisms were studied. Isothermal and cyclic oxidation tests showed durability of 1000 h and 400 cycles at 1100 °C. The oxidation mechanisms at the substrate/top coat interface changed due to fast solidification during the laser texturing process. Then, TBC system was studied under high temperature mechanical solicitation in tension creep. The textured interfaces were not damaged after 1% creep strain while top-coat/substrate interfacial cracking was observed for grit-blasted specimens. Moreover, no preferential crack development in the substrate was observed. Patterns provided an enhanced adhesion by changing the stress distribution near the interface.

The present study is aimed at investigating the influence of the main process parameters on the mechanical behavior and morphology of friction assisted joints made on aluminum and PVC sheets. To ensure the successful achievement of the joint, the aluminum sheets were pre-treated by means of laser texturing process. Thus, an instrumented prototypal apparatus was developed to produce these joints under load control. The main process parameters were, the plunging load and dwell time. Mechanical characterization of the joints was performed by means of single lap shear tests. In addition, morphological analysis was performed by means of optical Microscopy and Scanning Electron Microscopy to evaluate the dimension of the joined area as well as to evaluate the possible degradation of the polymer. Infrared analysis was also performed to evaluate the variation and distribution of temperature during the joining process. According to the achieved results, the maximum shear strength (16 MPa) was reached (that is 75% of the shear strength of the base material) by the employment of the maximum plunging load with an interaction time of 20 s. Higher dwell time resulted in development of material degradation with consequent reduction in the joints strength.

Laser welding of dissimilar metals (steel and aluminium) was investigated with the aim to increase the maximum tensile shear load of the Fe-Al joints. The increase was achieved by texturing the surface of steel prior to the laser spot welding process which was performed in a lap-joint configuration with the steel positioned on top of the aluminium and with a texture faced down to the aluminium surface. This configuration enabled an increase of the bonding area of the joints, because the molten aluminium filled in the gaps of the texture, without the need of increasing the process energy which typically leads to the growth of the intermetallic compounds. Different textures (containing hexagonally arranged craters, parallel lines, grid and spiral patterns) were tested with different laser welding parameters. The Fe-Al joints obtained with the textured steel were found to have up to 25% higher maximum tensile-shear load than the joints obtained with the untextured steel.

Significant effort has been undertaken to study the effects of engineered surfaces, such as those developed through laser texturing, and the potential tribological benefits that can arise. However, the theoretical models can be contradictory, and few good experimental studies of such systems exist. In this work, dimpled surfaces were created using laser surface texturing (LST) which were tested in a reciprocating wear tester. Friction and wear coefficients were measured and compared to surfaces without dimples for both metal-on-metal and metal-on-plastic contacts. The geometry of the dimple to accommodate unidirectional sliding was considered. The results showed a positive effect of surface texturing on the friction coefficients and wear rates of the textured surfaces, consistent with increased distance between asperities due to improvements in lubrication.

The interaction between liquid flow and solid boundary can result in cavitation formation when the local pressure drops below vaporization threshold. The cavitation dynamics does not depend only on basic geometry, but also on surface roughness, chemistry and wettability. From application point of view, controlling cavitation in fluid flows by surface functionalization is of great importance to avoid the unwanted effects of hydrodynamic cavitation (erosion, noise and vibrations). However, it could be also used for intensification of various physical and chemical processes. In this work, the surfaces of 10-mm stainless steel cylinders are laser textured in order to demonstrate how hydrodynamic cavitation behavior can be controlled by surface modification. The surface properties are modified by using a nanosecond (10–28 ns) fiber laser (wavelength of 1060 nm). In such a way, surfaces with different topographies and wettability were produced and tested in a cavitation tunnel at different cavitation numbers (1.0–2.6). Cavitation characteristics behind functionalized cylindrical surfaces were monitored simultaneously by high-speed visualization (20,000 fps) and high frequency pressure transducers. The results clearly show that cavitation characteristics differ significantly between different micro-structured surfaces. On some surfaces incipient cavitation is delayed and cavitation extent decreased in comparison with the reference – a highly polished cylinder. It is also shown that the increased surface wettability (i.e., hydrophilicity) delays the incipient cavitation.

Adhesion is one of the most important characteristics of coating on cutting tools. Poor coating adhesion on the tool favors fragmentation and release of hard abrasive particles between the tool and the workpiece. These particles interact with the surfaces of the tool, accelerating its wear and decreasing tool life. One possible solution is the use of laser texturing prior to coating in order to achieve a desired surface topography with enhanced adhesion properties. In the texturing, a high-frequency short-pulse laser changes surface characteristics, generating resolidified material and selective vaporization. This work evaluated the effectiveness of laser texturing in improving the substrate–coating adhesion of PVD coated cemented carbide tools. To this end, the substrates were textured with a Nd:YAG laser, in four different intensities, and then coated with a PVD TiAlN film. To ascertain the effectiveness of laser texturing, Rockwell C indentation and turning experiments were performed on both textured tools and conventional unlasered tools. The PVD coated laser-textured tool showed better performance in the indentation and turning tests than the standard tools. A comparative evaluation of tool wear mechanisms indicated that texturing did not change the wear mechanisms, but altered their importance to tool wear. The anchoring provided by the higher roughness of the textured surface increased the adhesion of the coating on the substrate, thus increasing tool life. Additionally, the chemical modification of the carbide grains due to the laser heating might be responsible for an enhanced adhesion between coating and substrate.

The main obstacle to calculate the 'feel' of a product from its surface properties is the ill-defined surface topography that is encountered after the most surface finishing processes. In this work this obstacle was avoided by producing well-defined surface topographies by laser texturing. The friction of textures having surface features with varying radii and spacings was investigated by measuring friction against the fingerpad. Within the range of conditions tested the coefficient of friction decreased with increasing normal load. The relation between the surface texture parameters and the coefficient of friction is influenced by the scale-dependent elastic behaviour of the skin top layer. © 2012 Elsevier Ltd. All rights reserved.

Surface texturing is gaining interest in the field of surface engineering. Enhancements can be obtained by carefully creating textures with arrangement of 3D-cavities; such textures retain lubricant and enhancing the hydrodynamic effect, reducing therefore the friction coefficient and wear of sliding contact surfaces 3D-cavities may have flat or curved shapes. In this investigation a picosecond pulsed laser with 1030nm and 343nm has been used to develop precise surface textures with triangular and flat shaped profiles. Tribological essays showed improvements in the tribological behavior of textured surfaces, triangular profile cavities obtained a friction coefficient < 0.03 doubling the wear resistance compared to reference surface without texture.