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A large variety of ultrafast laser‐matter interaction regimes and different processed surface finishing qualities of stainless steel can be achieved by varying the laser processing parameters. The optimization of the laser fluence to the most efficient ablation also leads to the lowest surface roughness of the ablated material. High laser fluence together with a high pulse repetition rate leads to heat accumulation, which results in the formation of microstructures with various morphology and scales. The use of GHz bursts allows a rough stainless‐steel surface to be smoothed and even polished. In this work, the fast and high‐quality milling of 2.5D cavities is demonstrated. Laser beam spot optimization is used to increase the throughput of the high‐power femtosecond laser (67.8 W), resulting in an ablation rate of 13 mm3 min−1. The complex cavities are produced by laser milling and cutting in layers. The formation of surface structures on stainless steel because of laser irradiation has been demonstrated. The possibilities of further GHz burst polishing are examined on previously laser‐milled stainless steel using with lowest possible surface roughness. The ability to polish the surface with microstructures below the original roughness is demonstrated by bursts of ultrashort pulses with a repetition rate in the GHz range. It has been demonstrated that mold milling in stainless steel designed for LED diffusers can be fabricated using a modern femtosecond laser source together with beam size optimization technique for efficient ablation with low surface roughness, layer‐by‐layer milling techniques, and GHz burst polishing techniques. [ABSTRACT FROM AUTHOR]

With the gradual increase of the demand for wooden products, people's requirements for processing quality of wooden products become higher. In this work, the dimension of groove micro‐texture is determined by finite element simulation analysis of tool structure strength. In this article, by designing milling experiments, the wood surface quality and wood surface morphology after milling with ordinary tools, micro‐textured tools, coated tools and micro‐textured coated tools are compared. The experimental results show that the quality of wood surface after milling with micro‐texture coating tool is better than that of the other three kinds of tools. And the wood surface after milling with micro‐texture coating tool is smooth, and the processing defects, such as burr and crack are less. In other words, micro‐texture technology combined with surface coating technology can effectively improve the surface quality of wood after milling. [ABSTRACT FROM AUTHOR]

The plasma-material interaction and evolution mechanism of a solitary crater governs the nature of the surface, either plain or textured, created through the electrical discharge micromachining (EDMM) process. Therefore, it is indispensable to understand the fundamentals of a single crater evolution, which involves melt pool hydrodynamics and material vaporization under intense plasma pressure. The plasma pressure during the workpiece heating phase alters the vaporization phenomenon and melt ejection, warranting an in-depth understanding. In light of this, the current work proposes a two-dimensional (2-D) multiphysics numerical model of the melt pool hydrodynamics during EDMM. The model incorporates thermal evolution along with the effects of active plasma pressure during the heating phase of the substrate with the help of a coupled thermo-fluidic model. The simulation results reveal the predominant role of plasma pressure on the crater morphology evolution, plasma flushing efficiency (PFE) and recast layer thickness (RLT). The predicted single crater profile is validated using single-spark experiments with reasonable agreement. Thereafter, the formation mechanism of a single crater has been extended to multi-crater creation for textured surface generation. [Display omitted] • A multiphysics model of the EDMM implementing plasma pressure is developed. • Maximum liquid-vapour interface temperature increases with active plasma pressure. • Plasma pressure plays a major role in determining crater morphology, PFE and RLT. • The predicted crater dimensions match the single-machined crater on Ti-6Al-4 V. • Single crater model is extended to multi-crater formation for surface texturing. [ABSTRACT FROM AUTHOR]

Amused with the blissful benefits of micro-textures, researchers consider it a promising option for improving cutting tool performance, especially during machining superalloys. Through this study, the machining performance of two homothetic and six hybrid micro-textured tungsten carbide inserts have been comparatively assessed while dry turning Inconel-718. Dimple and channel micro-textures were the two independent homothetic textures. Dimple and channel micro-textures with 0°, 45°, and 90° orientation angles and a combination of triangle, square, and dimples constituted six different hybrid micro-textures. Micro-textures were fabricated on the rake face of inserts using a Ti-sapphire fired, nanosecond pulsed, infrared fiber laser. Dimple and channel micro-textured tools at 90° texture angle on rake face performed exceptionally well. Improvements in average tool life, cutting forces, and surface finish have been reported. Adhesion and attrition were the predominant forms of tool wear. Chip morphology study revealed long helical and continuous but segmented chips. [ABSTRACT FROM AUTHOR]

During the moulding of polymeric pieces, the important temperatures involved, and the gases produced by decomposition of components from the polymer can induce corrosion on the working surface of the steel mould. Polymers can also stick to the mould surface, being their separation (demoulding) one of the critical aspects in their processing. Demoulding agents typically used in this process are expected to contribute in some extend to protect the mould against corrosion. In this work, hybrid sol–gel technology for anti-adherent coatings presented in previous papers is extended to formulations doped with different metallic precursors of proven chemical and wear resistance such as Zn, Ti, and Zr, with the aim to increase the corrosion resistant at the same time that keep good demoulding properties. Different synthetic routes one-pot or two components were followed depending on the doped agent. Sol–gel formulations were applied onto steel substrates by controlled dip coating technique, resulted in ultra-thin films of ∼0.15 µm, being capable to protect micro texturized steel moulds. Hardness of these films was superior (10H) to those formulations with fluorosilane and PDMS used as reference. Corrosion protection was evaluated obtaining good results in both polarization resistance and corrosion rate for Zn (5232 Ω × cm2, 0.08 mm/year), protecting the bare steel up to 6.5 times more in terms of annual corrosion, followed by Zr and Ti. Their behaviour as anti-adherent coating was also discussed and compared with fluorosilane and PDMS-based coatings. [ABSTRACT FROM AUTHOR]

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TiB-TiC/Co-based coatings with different surface micro-texturing were prepared on the sliding bearing by laser cladding and fiber pulse laser under the help of E-RSC-100 rotary workbench. The effect of different shape surface micro-texturing on the tribological properties of the Co-based coatings was systematically investigated. The results showed that the constituent phases of the coatings were not changed after surface micro-texturing. With the increase in the rotation speed and loading, the friction coefficient of the coatings with different shape surface micro-texturing was all reduced. The friction coefficient of the coatings with triangular surface micro-texturing was the smallest and followed by the circular and square surface micro-texturing. The microhardness of the coatings was not changed after surface micro-texturing. Compared with the coatings without surface micro-texturing, the mass loss of the coatings with surface micro-texturing was all reduced, and the mass loss of the coatings with the square, circular and triangular surface micro-texturing was reduced by 7.6, 21.7 and 31.5%, respectively. The wear mechanism of the coatings without and with surface micro-texturing was the typical abrasive wear and combined effect of the adhesive wear and the abrasive wear, respectively. [ABSTRACT FROM AUTHOR]

In articular joint implants, polymeric inserts are usually exploited for on-contact sliding surfaces to guarantee low friction and wear, a high load-bearing capacity, impact strength and stiffness, and biocompatibility. Surface micro-structuring can drastically reduce friction and wear by promoting hydrostatic friction due to synovial fluid. Ultra-High Molecular Weight Polyethylene (UHMWPE) is a suitable material for these applications due to its strong chemical resistance, excellent resistance to stress, cracking, abrasion, and wear, and self-lubricating property. However, surface micro-texturing of UHMWPE is hardly achievable with the currently available processes. The present study investigates UHMWPE's micro-textured surface replication capability via injection molding, comparing the results with the more easily processable High-Density Polyethylene (HDPE). Four different micro-texture cavities were designed and fabricated on a steel mold by micro-EDM milling, and used for the experimental campaign. Complete samples were fabricated with both materials. Then, the mold and samples were geometrically characterized, considering the dimensions of the features and the texture layout. The replication analysis showed that HDPE samples present geometrical errors that span from 1% to 9% resulting in an average error of 4.3%. In comparison, the UHMWPE samples display a higher variability, although still acceptable, with percentage errors ranging from 2% to 31% and an average error of 11.4%. [ABSTRACT FROM AUTHOR]

Laser-etching technology can perform micro-nano processing on the sub-surface of composite, thereby enhancing its mechanical interlocking to improve the adhesive performance. However, it can easily cause surface fiber damage and destroy the integrity of composite. Hence, the influences of surface micro-texturing and laser-etching effect on the adhesive property and failure behaviors of basalt fiber reinforced polymer (BFRP) composite single-lap-joint are investigated. Here, different surface micro-texturing of BFRP with different laser-etching power and line space are processed by laser-etching. The surface morphology and wetting property of experimental samples are characterized, and single lap tests are conducted to evaluate the adhesive properties. Results show that the adhesive property firstly increases and then decreases with the laser power increase, where the samples etched with 10 W and line space of 0.1 mm perform the best. It is found that the epoxy on the surface is removed by laser-etching to improve the contact area, but the fiber damage is formed to affect the adhesive property. When the laser-etching reaches a certain depth in spite of fiber damage, it can achieve the best bonding performance with the balance of performance and structural integrity. Finally, the multi-scale simulations are conducted to effectively demonstrate the laser-etched interface bonding behavior and damage evolution process of BFRP single lap joints. [ABSTRACT FROM AUTHOR]

Despite numerous experimental and theoretical studies reported in the literature, surface micro-texturing to control friction and wear in lubricated tribo-contacts is still in the trial-and-error phase. The tribological behaviour and advantageous micro-texture geometries and arrangements largely depend on the contact type and the operating conditions. Industrial scale implementation is hampered by the complexity of numerical approaches. This substantiates the urgent need to numerically design and optimize micro-textures for specific conditions. Since these aspects have not been covered by other review articles yet, we aim at summarizing the existing state-of-the art regarding optimization strategies for micro-textures applied in hydrodynamically and elastohydrodynamically lubricated contacts. Our analysis demonstrates the great potential of optimization strategies to further tailor micro-textures with the overall aim to reduce friction and wear, thus contributing toward an improved energy efficiency and sustainability. [ABSTRACT FROM AUTHOR]

Acrylonitrile-butadiene-styrene (ABS plastic) is one of the most widely used thermoplastic resins for electroplating. In electroplating, a glossing metallic layer is coated on the ABS plastic surface. Yet, the electroplated coating has poor adhesion to ABS plastics. Thus, polymer producers strive to develop more adhesive electroplating grades of ABS plastic. Unfortunately, there is no reliable method to quantify the polymer chemistry-induced adhesion to electroplated coating separately from the interlocking. Herein, the chemical adhesion at the metal-polymer is measured via precision manipulation with the actual surface area of the ABS plastic, without introducing interlocking and chemical modifications. We fabricated 9 moulds with 2, 4 and 6 µm wide and 2, 4 and 6 µm deep pillars, hot-embossed the pillars into ABS plastic, electroplated the ABS plastic with a copper coating, peeled the copper coating to measure the adhesion strength, and observed the micro-textured ABS plastic/copper interface in SEM. We found that the adhesion strength at the ABS plastic/copper interface is linearly proportional to the actual surface area of the texture (1), independent of the non-interlocking texture size (2), and strongly depends on the grade of the ABS plastic (3). The method can be employed to compare the adhesivity of different polymers while developing a new electroplating grade of ABS plastic. [ABSTRACT FROM AUTHOR]

The present work consists of large-area surface texturing through die-sinking electrical discharge machining (EDM) using compound tool electrodes. The compound tools were machined through the wire electrical discharge machining (WEDM). The micro-textured surfaces incorporating array of nearly square/circular-shaped micro-dimples, rectangular micro-channels and square micro-pillars were analysed for their wetting properties. An increase in water contact angle (CA) indicated higher water repellence for textured surfaces with respect to the untextured ones. Further, improved frictional behaviour was elicited through tribological analysis via the ball-on-disc test, revealing a lower average coefficient of friction (CoF) compared to the untextured surface. The wear volume of textured surfaces (micro-channels and micro-pillars) exhibited a slightly higher value with respect to the untextured surface, which can be ascribed to the stress concentration from microfeatures. However, the micro-dimpled textured surface showed a relatively lower wear volume, presenting a suitable micro-texture for improved tribological characteristics. [ABSTRACT FROM AUTHOR]

A new, scalable process chain for the fabrication of curved micro-structured metallic tools is developed and evaluated. Arrays of arrows, circles, semicircles and rings with final lateral dimensions of 124 to 819 µm are realised on the tools and successfully transmitted in one process step to stainless steel workpieces with a functional area of 6.5 cm2 using pulsed electrochemical machining. Photolithography-etching or micromilling are applied as initial micro-structuring processes, resulting in micro-structured master forms. These forms are copied into reusable silicon forms. This is followed by epoxy casting and electroforming to obtain the final tools. The tools are made of Nickel and have a diameter of 34 mm. Whilst micromilling, photolithography, silicon casting, epoxy casting and electroforming copy the structures very precisely, the wet etching process induces a widening of the dimensions due to the isotropic character of the process. The advantage of the process chain is the reusability of the master as well as of the silicone forms, which can be copied very precisely and easily with scalable processes to get precision tools with relatively large micro-structured areas. The reusability of the forms makes the fabrication of micro-structured tools relatively cost-efficient. The use of photolithography as the initial structuring process enables the generation of arbitrary, user-defined geometries for the micro-structures on the tool surface. The process chain described has the potential to fabricate lateral structure sizes on tools down to one micrometre. [ABSTRACT FROM AUTHOR]

In articular joint implants, polymeric inserts are usually exploited for on-contact sliding surfaces to guarantee low friction and wear, a high load-bearing capacity, impact strength and stiffness, and biocompatibility. Surface micro-structuring can drastically reduce friction and wear by promoting hydrostatic friction due to synovial fluid. Ultra-High Molecular Weight Polyethylene (UHMWPE) is a suitable material for these applications due to its strong chemical resistance, excellent resistance to stress, cracking, abrasion, and wear, and self-lubricating property. However, surface micro-texturing of UHMWPE is hardly achievable with the currently available processes. The present study investigates UHMWPE’s micro-textured surface replication capability via injection molding, comparing the results with the more easily processable High-Density Polyethylene (HDPE). Four different micro-texture cavities were designed and fabricated on a steel mold by micro-EDM milling, and used for the experimental campaign. Complete samples were fabricated with both materials. Then, the mold and samples were geometrically characterized, considering the dimensions of the features and the texture layout. The replication analysis showed that HDPE samples present geometrical errors that span from 1% to 9% resulting in an average error of 4.3%. In comparison, the UHMWPE samples display a higher variability, although still acceptable, with percentage errors ranging from 2% to 31% and an average error of 11.4%.

In the present research, the carbon fiber reinforced thermoplastic (CFRTP) was laser joined with the Al alloy whose joining interface was pretreated by laser micro-texturing, anodizing, and hybrid of laser micro-texturing and anodizing. The surface morphology of the pretreated Al joining interface and bonding strength of the corresponding Al/CFRTP butt joint were investigated. The results show that the laser micro-texturing has fabricated the micro-pit or micro-furrow in the Al joining interface. With the increasing of laser scanning times, the size of the micro-pit or micro-furrow decreases, when the laser scanning distance is constant. The bonding strength of the Al/CFRTP butt joint with Al joining interface pretreated by micro-texturing fluctuates with the increasing of laser scanning distance and times, reaching the maximum value of 20 MPa at laser scanning distance of 0.1 mm and 1 time. The anodizing pretreatment has formed the Al2O3 oxide layer on the Al joining interface. The Al/CFRTP butt joint with Al joining interface pretreated by anodizing obtains the maximum bonding strength of 11 MPa at anodizing time of 10 min. The hybrid pretreatment of micro-texturing and subsequent anodizing fabricates the regular grid structure with smooth micro-furrow and micro-pit, while the hybrid pretreatment of anodizing and subsequent micro-texturing fabricates the Al joining interface with explosive micro-pit and micro-furrow. The bonding strength of the Al/CFRTP butt joint with hybrid-pretreated Al joining interface is relative better than that of the Al/CFRTP butt joint with anodizing-pretreated Al joining interface but almost lower than that of the Al/CFRTP butt joint with micro-texturing pretreated Al joining interface. Such results should be attributed to the surface morphology of the Al joining interface.

Micro-textures were engineered on titanium samples by a rapid, highly repeatable, and cost effective nanosecond laser texturing process. The controlled and repeatable micro-texture was effective in the reduction of adhesion and proliferation of Staphylococcus aureus. However, the adhesion and proliferation of human bone marrow mesenchymal stem cells were found unaffected. The authors observed time-delayed saturation of oxidation on laser micro-textured Ti6Al4V as compared to pristine material yielding a super-hydrophobic surface (contact angle of ∼158.2°). An in-house setup was designed to expose a three-dimensionally laser micro-textured Ti6Al4V sample to S. aureus-spiked nutrient broth for 24 h in a closed loop continuous flow system. The authors observed a 50% reduction of S. aureus adhesion and proliferation over the laser micro-textured surface compared to pristine samples. In vitro tests confirmed that blood coagulation remains largely unaffected, while protein adsorption was decreased by fourfold on the micro-textured surfaces, a desirable property for surgical tools. Nanosecond laser micro-textured surfaces were effective in reducing S. aureus adhesion and its proliferation due to phase evolution, oxidative transformation of Ti6Al4V, and reduction of surface potential. In addition, laser based micro-texturing is a nontoxic, environment friendly green process that is also a cost effective alternative to conventional surface modification techniques such as mechanical micromachining and chemical treatments. [ABSTRACT FROM AUTHOR]

Packaging using thermoplastic molding for hollowed GaN chips were requested for a leak-proof micro-joining between plastic molds and copper-based substrates. The design and engineering of micro-textures is a key technology for putting leak-proof packaging into practice. In the present paper, a micro-meshing punch array was prepared using plasma-nitriding-assisted printing. Two-dimensional original patterns were screen-printed onto an AISI316 die substrate and plasma nitrided at 673 K for 14.4 ks (or 4 h). The unprinted surfaces were selectively nitrogen super-saturated to have more nitrogen content than 5 mass% and a higher hardness than 1200 HV. The printed surfaces were selectively sand blasted to fabricate the micro-meshing punch array for micro-embossing. A computer numerically controlled stamping system was utilized to describe the micro-embossing behavior onto copper substrates and to investigate how the micro-textures on the array was transcribed onto the copper. Reduction of takt time as well as flexibility in the micro-grooving were discussed with reference to the picosecond laser machining and mechanical milling processes.

Surface micro/nano-texturing combined with the presence of fluorine atoms can result in superhydrophobicity. Different strategies are investigated in order to determine the critical parameters to reach such properties. On the one hand, fluorine atoms were grafted by direct fluorination of carbon nanofibers (treatment with gaseous F 2 resulted in samples denoted F-CNF), and on the other hand, fluorinated polymers such as polyvinylidene fluoride PDVF or poly(ethylene oxide) PEO fluorinated with F 2 as well as commercial hydrophobic polymers like polystyrene (PS) were used as binders and/or polymer matrix to produce nanocomposites. Stable superhydrophobic properties are obtained with F-CNF/PVDF nanocomposites micro-textured with femtosecond laser ablation and F-CNF/PS nanocomposites, with water contact angles of 157° and 155° respectively. Polystyrene was also covalently grafted onto the nanofiber surface through a two-step process: fluorination followed by monomer grafting. The polymerization of styrene ensures both covalent grafting onto the carbonaceous surface and a good dispersion of nanofibers inside the polymer lattice. Moreover, C F bonds exhibit a covalent nature in fluorinated nanofibers, in PVDF, in fluorinated PEO and in the fluorinated resin and ensure an improved chemical stability for the studied nanocomposites and micro-textured resin. Comparison of the water contact angles for nanocomposites with PS, PVDF, PEO and fluorinated PEO highlights that the polymer matrix imposes its surface chemistry whereas the emergence of nanofibers results in a necessary nano-texturing. [ABSTRACT FROM AUTHOR]

Laser surface texturing of materials potentially offers precise control of surface structure and mechanical properties. This has a wide range of applications such as control of frictional forces, control of bond strength in interference fit joints, and production of antifouling surfaces. To achieve such texturing in a well-defined, useful manner, precise control of the applied laser processing parameters over a sizeable surface area is required. This paper presents the development of a method for creating highly repeatable and predetermined moiré textured patterns on metallic samples via laser processing. While the method developed is broadly applicable to various materials and laser systems, in the example detailed here the surfaces of cylindrical stainless steel samples were processed with a pulsed CO 2 laser. The resulting modified surfaces contained texture geometries with pre-definable peak-to-peak widths, valley-to-peak heights, and texture directions. The method of achieving this theoretically and experimentally is detailed in this paper. The relationship between the laser processing parameters and resulting diameter increase was confirmed via Design of Experiment response surface methodology. Precise control of the laser textured cylindrical surface outer diameter and texture pattern are key factors in determining the potential suitability of this process for application to the production of interference fit fasteners. The effects of the laser processing parameters and topologies of the resulting re-solidified metal profile on the surfaces were assessed in detail with a focus on this application. [ABSTRACT FROM AUTHOR]

Tribological properties of acid and alkali solutions on glass surface were studied in aqueous environment using a ball-on-disc reciprocating configuration. Interactions between lubricants and sliding surfaces produce different surface topographies. The lubricating ability of each kind of surface topography was evaluated using the same base oil. Wear tracks which were smooth or with grooves on the surfaces had high coefficient of friction in reciprocating sliding tests. However, surfaces with pits exhibited much lower friction than that the others. Low friction coefficients could be achieved after the running-in process with acidic solutions, accompanied by the formation of a pitted topography on the wear tracks. Especially, the friction coefficient was found to be below 0.01 during the steady sliding period, except at the reversal positions. Such good lubricity could be attributed to the micro-sized pits. [ABSTRACT FROM AUTHOR]

To improve the long-term tribological properties of precision moving parts in aerospace, MoS 2 -Ti film was applied on a low-density micro-textured surface of the most commonly used 9Cr18 steel. The 1.0, 1.5, 2.0 and 3.0 % dimple densities of micro-textured surfaces were produced by an Nd: YAG femtosecond pulse laser system. The effects of different micro-textured densities surface with MoS 2 -Ti films on friction properties and wear mechanisms were investigated. Tribological results showed that all the micro-textured surfaces with MoS 2 -Ti films had a lower friction coefficient and wear rate than the un-textured surfaces with MoS 2 -Ti films. The wear performance was enhanced by increasing the density of the micro-textured surface. The friction coefficient and wear rate after 3.6 × 105 lap rotation were reduced to below 0.018 and <1.0 × 10−7 mm2/N•m, respectively, when the density of micro-texture was 3.0 %. It was found that the friction coefficient and wear rate increased with increasing sliding laps, but the 3.0 % density surface with MoS 2 -Ti film after a lap rotation of 9.0 × 105 still had a lower wear rate than the un-textured surface, indicating an excellent long-term wear resistance. The function of micro-textures is not only to capture wear debris and store lubrication films but also to form a moderate transfer layer on the friction pair, all of which could help to prolong the wear life of MoS 2 -Ti films. • Different densities of micro-textured 9Cr18 surfaces were coated with MoS 2 -Ti (11 %) films. • Micro-textured surface of density 3 % has a prominent positive impact on the tribological properties. • Titanium introduced to the MoS 2 film was totally oxidized during the film's deposition process. • The MoS 2 film evolved to MoO 3 and MoS 2- x during long-term friction in vacuum. • Wear mechanism changed from plow of un-textured to adhesive wear of micro-textured density of 1.5 %. [ABSTRACT FROM AUTHOR]

Diamond-Like Carbon (DLC) and Chemical Vapor Deposition (CVD)-diamond films have been widely utilized not only as a hard protective coating for molds and dies but also as a functional substrate for bio-MEMS/ NEMS. Micro-texturing into these hard coated molds and dies provides a productive tool to duplicate the original mother micro-patterns onto various work materials and to construct any tailored micro-textures for sensors and actuators. In the present paper, the high density oxygen plasma etching method is utilized to make micro-line and microgroove patterns onto the DLC and diamond coatings. Our developing oxygen plasma etching system is introduced together with characterization on the plasma state during etching. In this quantitative plasma diagnosis, both the population of activated species and the electron and ion densities are identified through the emissive light spectroscopy and the Langmuir probe method. In addition, the on-line monitoring of the plasmas helps to describe the etching process. DLC coated WC (Co) specimen is first employed to describe the etching mechanism by the present method. Chemical Vapor Deposition (CVD) diamond coated WC (Co) is also employed to demonstrate the reliable capacity of the present high density oxygen plasma etching. This oxygen plasma etching performance is discussed by comparison of the etching rates. [ABSTRACT FROM AUTHOR]

Micro-texturing method has grown up to be one of the most promising procedures to form micro-lines, micro-dots and micro-grooves onto the mold-die materials and to duplicate these micro-patterns onto metallic or polymer sheets via stamping or injection molding. This related application requires for large-area, fine micro-texturing onto the martensitic stainless steel mold-die materials. A new method other than laser-machining, micro-milling or micro-EDM is awaited for further advancement of this micro-texturing. In the present paper, a new micro-texturing method is developed on the basis of the plasma assisted nitriding to transform the two-dimensionally designed micro-patterns to the three dimensional micro-textures in the martensitic stainless steels. First, original patterns are printed onto the surface of stainless steel molds by using the dispenser or the ink-jet printer. Then, the masked mold is subjected to high density plasma nitriding; the un-masked surfaces are nitrided to have higher hardness, 1400 Hv than the matrix hardness, 200 Hv of stainless steels. This nitrided mold is further treated by sand-blasting to selectively remove the soft, masked surfaces. Finally, the micro-patterned martensitic stainless steel mold is fabricated as a tool to duplicate these micro-patterns onto the plastic materials by the injection molding. [ABSTRACT FROM AUTHOR]

As an approach to enhance the tribological performance of diamond like carbon (DLC) coating films for dry microforming operations, the present study applied the micro-textured structures to the DLC films. Micro-texturing was realized by using stainless steel wire mesh as a masking during the ionized physical vapor deposition (I-PVD) of DLC films. Tribological performance of fabricated micro-textured structures with a width of 40 and 80 μm and an interval of 30 and 40 μm were evaluated by the ball-on-disk type friction tester. To simulate the severe contact state of dry microforming operation, normal pressure of 1.2 GPa was applied for 100,000 times rotations under unlubricated condition. As results, the micro-textured DLC films with structure size of 40 μm showed the excellent stable variation with relatively low coefficient of friction (COF) of μ = 0.01-0.06, while the conventional non-textured DLC films showed the significantly large deviation with high COF of μ > 0.25. In comparison between the different micro-texture sizes, the smaller structure size of 40 μm showed the lower COF than that of 80 μm, although the larger amount of wear debris from DLC films were generated. Additional wear track observation after the friction tests revealed that the stable tribological properties of textured DLC films were attributed to the promotion of wear debris ejection, which can prevent the plowing inside the apparent area of contact. [ABSTRACT FROM AUTHOR]

Micro-texturing method has grown up to be one of the most promising procedures to form micro-lines, micro-dots and micro-grooves onto the mold-die materials and to duplicate these micro-patterns onto metallic or polymer sheets via stamping or injection molding. This related application requires for large-area, fine micro-texturing onto the martensitic stainless steel mold-die materials. A new method other than laser-machining, micro-milling or micro-EDM is awaited for further advancement of this micro-texturing. In the present paper, a new micro-texturing method is developed on the basis of the plasma assisted nitriding to transform the two-dimensionally designed micro-patterns to the three dimensional micro-textures in the martensitic stainless steels. First, original patterns are printed onto the surface of stainless steel molds by using the dispenser or the ink-jet printer. Then, the masked mold is subjected to high density plasma nitriding; the un-masked surfaces are nitrided to have higher hardness, 1400 Hv than the matrix hardness, 200 Hv of stainless steels. This nitrided mold is further treated by sand-blasting to selectively remove the soft, masked surfaces. Finally, the micro-patterned martensitic stainless steel mold is fabricated as a tool to duplicate these micro-patterns onto the plastic materials by the injection molding.

Diamond-Like Carbon (DLC) and Chemical Vapor Deposition (CVD)-diamond films have been widely utilized not only as a hard protective coating for molds and dies but also as a functional substrate for bio-MEMS/NEMS. Micro-texturing into these hard coated molds and dies provides a productive tool to duplicate the original mother micro-patterns onto various work materials and to construct any tailored micro-textures for sensors and actuators. In the present paper, the high density oxygen plasma etching method is utilized to make micro-line and micro-groove patterns onto the DLC and diamond coatings. Our developing oxygen plasma etching system is introduced together with characterization on the plasma state during etching. In this quantitative plasma diagnosis, both the population of activated species and the electron and ion densities are identified through the emissive light spectroscopy and the Langmuir probe method. In addition, the on-line monitoring of the plasmas helps to describe the etching process. DLC coated WC (Co) specimen is first employed to describe the etching mechanism by the present method. Chemical Vapor Deposition (CVD) diamond coated WC (Co) is also employed to demonstrate the reliable capacity of the present high density oxygen plasma etching. This oxygen plasma etching performance is discussed by comparison of the etching rates.

In a previous study, micro-scale pyramid structures were produced on cemented carbide grades to form cutting edges (in the range 50 μm–100 μm) on their cutting surfaces. The pyramids were machined by an ultrashort pulse laser, exhibiting excellent surface integrity and defined geometric features. They are similar in size and shape to the abrasives used in grinding tools. In this study, hexagonal- and square-shaped pyramid structures are produced on four different cemented carbide grades. The wear of these textured cemented carbide tools was quantitatively and qualitatively assessed after grinding-like service conditions. More precisely, the geometric feature changes were measured, and cross-sectional characterization was conducted to reveal wear modalities of the cutting edges. Wear was detected mainly on the pyramids in the effective contact area of the tools, in the form of material loss resulting from grain cracking and adhesion. Hardness was a decisive factor in wearing the pyramids, and tools with hardness more than 1100 HV30 showed reduced wear. Pyramid shape also influenced the degree of wear, as the hexagon pyramids experienced less height reduction (up to 5%) than the square ones. Adhesion turned out to be significant on the cemented carbide grades with high binder content (about 30 wt%). • Wear occurred only on the pyramids mostly in the middle area of the tools. • Wear was mainly in the form of gradual material loss on pyramid top surfaces related to grain cracking and adhesion. • Hardness was a decisive factor in pyramid wear; less wear occured on the tools with a hardness more than 1100 HV30. • Pyramid shape influenced the wear degree: hexagon pyramids had less height reduction (up to 5%) than square ones. • Adhesion was more significant on cemented carbide grades with high binder content (about 30 wt%). [ABSTRACT FROM AUTHOR]

• Picosecond laser beam irradiation is employed for micro texturing on mesoporous silicon surface. • The laser beam parameters, fluence and number of shots are leading to create micron-sized and uniform spikes. • Absorption enhancement and ablation are the main phenomena in the creation of microspikes. • Large surface texturing allows the study of reflectivity change in the IR range versus the laser process parameters. • The absorption in the IR range is enhanced. Conical spikes with sizes ranging between 0.2 and 5 µm were formed on a mesoporous silicon surface under ultraviolet picosecond laser irradiation in ambient air. Scanning electron microscopy was employed to visualize the successive steps in the formation of the spikes. On increasing the number of shots (up to 1000) at a fluence of 400 mJ/cm2, an increase in the size and an enhancement in the distribution of spikes were observed. The experimental observations revealed that the formation and the growth of these structures were mainly due to material ablation and removal mechanisms. FTIR analysis on several large (5 × 5 mm2) irradiated zones showed an enhancement in the absorption coefficient mainly in the IR range from 1 to 8 µm versus the size of the microstructures. [ABSTRACT FROM AUTHOR]

Packaging using thermoplastic molding for hollowed GaN chips were requested for a leak-proof micro-joining between plastic molds and copper-based substrates. The design and engineering of micro-textures is a key technology for putting leak-proof packaging into practice. In the present paper, a micro-meshing punch array was prepared using plasma-nitriding-assisted printing. Two-dimensional original patterns were screen-printed onto an AISI316 die substrate and plasma nitrided at 673 K for 14.4 ks (or 4 h). The unprinted surfaces were selectively nitrogen super-saturated to have more nitrogen content than 5 mass% and a higher hardness than 1200 HV. The printed surfaces were selectively sand blasted to fabricate the micro-meshing punch array for micro-embossing. A computer numerically controlled stamping system was utilized to describe the micro-embossing behavior onto copper substrates and to investigate how the micro-textures on the array was transcribed onto the copper. Reduction of takt time as well as flexibility in the micro-grooving were discussed with reference to the picosecond laser machining and mechanical milling processes. [ABSTRACT FROM AUTHOR]