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Friction involved in metal-forming processes typically leads to the wear of tool and die surfaces, and in turn shortens the tool's service life. A thriving need for reducing surface friction requires the tool surface to be modified. This paper presents the surface modification of SKH51 tool steel, on which the hexagonal array of micro-dimples is fabricated by a nanosecond pulse laser. Using the average laser power of 25 W can create decent dimples for trapping lubricant and enabling hydraulic pressure at the surfaces in contact. The effect of dimple density and sliding speed on the coefficient of friction was examined in this study through the pin-on-disc test, in which a stainless steel pin was applied against the tool steel disc with a constant load. The laser-textured tool steel surface with a dimple density of 35% had a friction coefficient of 0.087, which was lower than that of the untextured surface by 12.6% when using a sliding speed of 15 cm/s. In addition to friction reduction, there was no substantial wear found on the laser-textured surface compared to the untextured sample. The findings of this study can be a processing guideline and benefit the treatment of tool and die surfaces for friction and wear reduction in metal-forming and related processes. [ABSTRACT FROM AUTHOR]

Laser texturing process is a promising method to alter the wettability of metal surface on which micro/nano rough structures are created for changing the contact angle between the textured surface and liquid droplet. This paper aims at fabricating a superhydrophobic surface on AISI316L stainless steel, and a nanosecond pulse laser was employed for texturing line and point patterns on the metal surface. The influences of texturing patterns, laser power, scan speed, irradiation duration, and aging hours on the water contact angle and morphology of workpiece surface were investigated. According to the results, the hydrophilic surface was obtained right after the texturing process, and the surface turned to be hydrophobic after being left in ambient air for 15 days. The aging of laser-textured surface was also performed to induce the chemisorption of hydrocarbons toward the surface. This post process was able to shorten the hydrophilic-to-hydrophobic transition from days to a few hours. The aging duration of 2 and 0.5 h was respectively recommended for yielding and stabilizing the superhydrophobicity on line- and point-patterned surfaces. The maximum contact angle of 159.61° was achievable when the point pattern was textured on the stainless steel surface by using the laser power of 10 W and irradiation duration of 0.18 ms. [ABSTRACT FROM AUTHOR]

The first-generation semiconductor materials represented by silicon (Si) and germanium (Ge) still hold a dominant position in many fields, including micro-electromechanical systems (MEMS) and integrated circuits (ICs). The processing of these materials continues to attract significant research attention for improvements in quality and efficiency. This study proposes a novel hybrid laser-enhanced particle-laden electrochemical machining (LEPL-ECM) process, whereby pulsed laser irradiation is utilized to selectively and locally enhance the electrical conductivity of Ge at specific locations. A neutral electrolyte jet, containing abrasive diamond particles, is applied to the location on the wafer surface opposite the laser irradiation, facilitating a localized and enhanced electrochemical dissolution. The effect of micro-particle erosion effectively removes the generated oxides and potential passivation layers, ensuring continuous and efficient electrochemical reactions. Consequently, high-quality micro-dimples with an entrance diameter of about 380–800 μm, a depth of around 138–300 μm, and a quasi-mirror surface with the roughness (Sa) of as low as 59.8 nm can be achieved within 90 s. Furthermore, the effects of the applied voltage, laser power and processing time on the resulting dimple characteristics and surface quality are discussed, along with a detailed morphology characterization. Dense micro-pits, radial streamlined micro-grooves and a special transitional region have been observed on dimple center, sidewall and near the edge, respectively, and the formation mechanism have been analyzed. Finally, a simulation of the electrolyte jet induced fluid pressure and velocity as well as the particle trajectory and distributions within and surrounding the dimple structure was conducted, which reveals that the synergistic mechanism associated with the hybrid material removal process involves both electrochemical corrosion and abrasive erosion. [Display omitted] • A novel LEPL-ECM method is proposed for high quality micro-dimpling of Ge. • A quasi-mirror dimple surface with the Sa of 59.8 nm can be achieved within 90 s. • Influences of several key processing parameters have been experimentally studied. • Synergistic effects exist between electrochemical corrosion and abrasive erosion. • Distributions of flow velocity, pressure and particle trajectory are calculated. [ABSTRACT FROM AUTHOR]

An experimental investigation of the cutting performance in hybrid laser–waterjet (or laser-assisted waterjet) micro-grooving of germanium wafers is presented, with a view to eliminate or minimize the laser-induced thermal damages to the workpiece. Various process parameters are considered, such as water pressure, laser pulse overlap, pulse energy and focal plane position. It is found that the hybrid laser–waterjet is a viable technology for micromachining of germanium with negligible thermal damage. A Raman spectroscopy study did not reveal any crystalline change in the material on the machined surfaces. The effects of process parameters on the heat-affected zone and groove characteristics are amply discussed. It is shown that good grooves of within 100 µm in top width and up to 300 µm in depth can be machined with high material removal rates, and the heat-affected zone size can be controlled to within 20 µm on each side of the grooves. Recommendations are also made on the appropriate process parameters that may be used in the process. [ABSTRACT FROM AUTHOR]

This paper provides a convenient, efficient and repeatable method for the preparation of flexible PDMS superhydrophobic films. The stainless steel template was etched with picosecond laser to create textures, which was then filled with PDMS and thermally cured to produce PDMS superhydrophobic films featuring corresponding microstructures. By constructing computational models of the microstructures and exploring the influence of laser scanning spacing on contact angle, the process parameters were optimized to obtain superhydrophobic PDMS films while ensuring the stability of microstructures. The microstructures showed straight lines spaced 55 μm apart, with each line connected by regular truncated cone structures. These structures formed Cassie contacts with the droplets, exhibiting a contact angle of 152.1° and a sliding angle of 9°. In addition, this study demonstrates the reproducibility of the PDMS superhydrophobic film preparation method and its effectiveness in delaying icing. The results indicate that the templates can be used for more than twenty replications, and the obtained PDMS superhydrophobic films have a delayed icing time of 3.3 times. These findings suggest that the PDMS superhydrophobic films have excellent performance and repeatable characteristics, making them suitable for various applications. • Preparation of PDMS superhydrophobic films with repeatable demoulding function • A wettability calculation model for multiple types of microstructures • Excellent application of flexible surfaces and delayed icing performance [ABSTRACT FROM AUTHOR]

A novel Fe Ni coating with refined grain size and alternated distribution of element content was designed via laser-assisted electrochemical deposition. The formation of this microstructure is attributed to a specific laser scanning strategy, forming the periodic current waveform. This novel coating is expected to enhance the microhardness and wear performance within the grain size range of the inverse Hall–Petch (HP) relationship. The critical size of the HP relationship was estimated at 13 nm based on the relationship between different grain sizes and microhardness. Compared to the coating prepared by electrochemical deposition, the average grain sizes decrease from 8.4 ± 1.4 nm to 4.5 ± 1.6 nm. In addition, the microhardness was enhanced by approximately 28 %; the wear rate was decreased by approximately 58 %. The main mechanisms include abrasive, fatigue, and slight oxidation wear. This unique structure may enhance the resistance to grain boundaries mediated plastic deformation. • The critical HP size of Fe Ni coating is approximately 13 nm. • Average grain size decreases from 8.4 ± 1.4 to 4.5 ± 1.6 nm. • The microhardness and the wear resistance are enhanced. • The wear mechanism includes abrasive, fatigue, and slight oxidation wear. • GBs mediation is the main plastic deformation mechanism. [ABSTRACT FROM AUTHOR]

This study developed a new electrodeposited Fe–Ni coatings using the laser-induced current waveform. This process refined grains accomponied with a mixed nanocrystalline size and alternate element content. The electrochemical and immersion corrosion performance at 3.5 wt% NaCl was improved, which is still pitting corrosion. The corrosion pits are more likely to spread around rather than in the depth direction. The enhancement mechanism is mainly attributed to the richer grain boundaries. This microstructure increases the interface transfer resistance and makes the corrosion more uniform. This study provides a potential process for preparing nanocrystalline coatings with better performance. [Display omitted] • Laser-induced current waveform refines grains with a mixed size. • The element content is distributed alternately along the cross-section. • The electrochemical and immersion corrosion properties are improved. • The enhance mechanism is mainly attributed to the rich grain boundaries. [ABSTRACT FROM AUTHOR]

[Display omitted] • The laser activated the crystal modifier to form a cellular structure. • The cellular structure increases the surface potential inhomogeneity. • The electrochemical corrosion rate decreases by approximately 4 times. • Corrosion mechanism changes from stress corrosion to pitting corrosion. • The improvement of corrosion resistance is caused by micro corrosion cells. Laser irradiation was applied to a Ni–P electrolyte containing a crystal modifier. This produced a Ni–P alloy surface prepared via electrodeposition that was composed of numerous three-dimensional microcellular structures. The coating maintained its original amorphous structure while reducing the residual tensile stress. This structure replaced the surface crack structure, thus reducing the corrosion rate by nearly a factor of four. The main corrosion mechanism corresponding to the conventional method was stress corrosion, whereas the proposed method involved pitting corrosion. This was primarily because of the formation of corrosion microcells owing to the electrochemical non-uniformity caused by the structures. [ABSTRACT FROM AUTHOR]

To achieve superamphiphobic properties on the surface of copper, a novel strategy for fabricating multi-level micro-nano superamphiphobic membranes by laser-electrochemistry subtractive-additive manufacturing method is explored. To test the properties of the metal surface prepared by this method, a variety of testing experiments are carried out. The experiment results shows that the contact angle (CA) of water and oil droplets are 161° ± 4° and 151° ± 4°, while those rolling CAs are 2° and 10°, which shows that the prepared surface had excellent superamphiphobic properties. Through the wettability test at different temperatures, the surface hydrophobicity of the prepared samples at low temperature 5 °C is worse than that at a room temperature 25 °C. According to droplet bounce test, the water drops experiences two complete bouncing processes on the surface of the prepared samples when the laser scanning interval is equal to the laser spot diameter, which indicates that the stable Cassie state is related to the multi-level micro-nano structures. In addition, the superamphiphobic surfaces fabricated in this paper have perfect functionality and stability, which provides a novel method for the potential application in the automotive, aerospace, and shipbuilding industries. [Display omitted] [ABSTRACT FROM AUTHOR]

This study proposed a new process strategy to obtain Fe-Ni multilayer gradient structure. Laser irradiation was introduced into the electrochemical deposition (ECD) process. Based on activation and diffusion control steps, the regulation of element content is realized by adjusting laser parameters. In addition, the surface quality, internal structure, and performance of the coating prepared by laser-assisted ECD were evaluated. The results show that laser irradiation can reduce surface defects and roughness without changing the internal structure. Laser irradiation improves the uniformity of element content distribution and reduces the Fe content. In the same deposition time, the coating's thickness increased by approximately 91.2 %. The element content delamination was successfully achieved by changing the laser parameters without changing the electrochemical parameters. The main mechanism is that laser irradiation increases the limiting current density and inhibits diffusion control. Compared with monolithic ECD coatings, the mechanical properties and corrosion resistance are improved. According to the control mechanism, the preparation of gradient structures along the horizontal direction of the substrate is verified. [Display omitted] • Element content gradient is realized by adjusting laser parameters. • Laser irradiation increases the coating's thickness by approximately 91.2 %. • Laser irradiation makes the difference of Fe content reach approximately 20 wt%. • LECD produces transverse/longitudinal multilayer gradient structures. • LECD improves wear and corrosion resistance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Laser irradiation realizes ultra-thin localized Au Coating. • Laser irradiation increases the electrodeposition efficiency. • Laser irradiation improves the surface quality of Au coating. • Laser irradiation achieves precise regulation of dimensional accuracy. • Laser irradiation improves corrosion resistance of Au coating. Traditional electrodeposition requires auxiliary technologies such as mask to realize localized deposited layer. In this paper, ultra-thin Au coating can be obtained selectively by laser-induced electrodeposition without mask, which has advantages in dimensional accuracy, brightness, good compactness. The deposition rate, dimensional accuracy, density, roughness, and corrosion resistance were evaluated under different laser single pulse energy (4.5, 5, 5.5, 6, 6.5, 7, 7.5, and 8 μJ). Furthermore, the spatial distribution of the transient temperature field and the change law of the cathode substrate current under laser irradiation were detected to explore the mechanism induced by laser thermal effect. The results show that laser irradiation can increase the cathode limit current density to reach the Au precipitation potential. Besides, the electrodeposition rate increases with the increase of laser single pulse energy. When the laser single pulse energy is 6 µJ, the electrodeposition rate reaches 0.167 mg/min. Meanwhile, the electrodeposition accuracy and surface density are better, and surface roughness (Sa) is 0.98 μm. Moreover, compared with the Au coating product provided by an electroplating enterprise, the coating prepared by laser-induced electrodeposition has better corrosion resistance. When the laser single pulse energy is 6 µJ, self-corrosion potential (φ corr) is −0.3059 V, and self-corrosion current density (j corr) is 5.066 × 10−5 A/cm2. [ABSTRACT FROM AUTHOR]

Amorphous Ni-P alloys crystallize at high temperatures, which leads to the deterioration of resistivity and corrosion resistance. In this study, the use of laser irradiation with the electrodeposition (ECD) process for preparing amorphous Ni-P coatings was investigated; and the resistivity and corrosion resistance were analyzed, which is related to crystallization process, surface morphology, residual internal stress, and oxidation layer. The results indicates that the crystallization rate of Ni-P coating prepared by laser-assisted electrodeposition (LECD) was slower than that of ECD coating. With increasing ambient temperature, the internal tensile stress first decreased and then increased. The LECD coating has better oxidation resistance, with XPS indicating the oxide layer mainly comprised Ni-O compounds. At the same ambient temperature, the resistivity of the LECD coating was higher than that of the ECD coating. The Ni-P coating had better corrosion resistance after heating, and the corrosion mechanism changes from stress corrosion to pitting corrosion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magnetic field is introduced into ECD based on laser irradiation. • Transverse magnetic field has a better impact on properties of Fe-Ni coating. • The magnetic field affects the grain growth orientation and forms flow pattern. • The Fe content is affected due to the MHD effect on the diffusion degree. • Magnetic field can improve the properties of Fe-Ni coating. A steady-state magnetic field is introduced to prepare Fe-Ni coating based on laser-assisted electrodeposition (LECD) to control the change of element content and improve the surface quality. The internal structure, surface quality, and properties are tested to discuss under different magnetic field intensities. The results indicate that the comprehensive performance of Fe-Ni coating with a transverse magnetic field is better. The magnetohydrodynamic (MHD) and magnetization effect make the grain refinement and improve the surface quality of Fe-Ni coating. The surface morphology shows that the laser makes the surface denser, while the magnetic field causes the ions to magnetize so that the clusters form on the surface. The addition of the magnetic field does not change the grain structure, but the Fe content is increased because of the MHD effect on the diffusion degree. Besides, when the magnetic field intensity is 15 mT, the residual internal stress reaches 587 MPa in the form of compressive stress. Meanwhile, the test of micro-hardness, tensile strength, wear, and corrosion resistance indicates that the comprehensive performance of Fe-Ni coating by the magnetic field and laser-assisted electrodeposition (MLECD) is better than that of electrodeposition (ECD) and LECD. [ABSTRACT FROM AUTHOR]

Electrodeposited amorphous alloys require numerous nuclei and irregular atomic arrangements. In this study, the impact of processing parameters (e.g., a nanosecond laser) on the current density in the electroplating solution for an electrodeposited Ni P coating was tested using an electrochemical workstation. In addition, the effect of the laser on the temperature and micro-stirring caused by cavitation was simulated using COMSOL (version 5.4). The surface quality, wear, and corrosion resistance of the Ni P coating prepared by laser-assisted electrodeposition (LECD) at different laser repetition frequencies (picosecond laser, 0.5, 1, 1.5, 2, and 2.5 MHz) were evaluated. The results showed that the stability of current change was best when the laser frequency, pulse width, scanning line spacing, and irradiation area were 1 MHz, 200 ns, 20 μm, 1 mm2, respectively. Excessive laser energy destroys the balance of electrochemical deposition process. The simulation results showed that the maximum instantaneous temperature of the laser-irradiated solution was 123 °C. Cavitation increases the flow rate of the solution and produces a jet impact on the substrate. The maximum velocity and instantaneous pressure were 0.13 m/s and 7.26 × 108 Pa at 0.1 ns, respectively. At the laser frequency of 0.5 MHz, the P content increases by approximately 2% compared to that of the coating prepared by LECD (1–2.5 MHz). The residual internal stress decreased with increasing frequency, and it existed in the form of tensile stress. The wear and corrosion resistances of the Ni P coating were the best when the laser frequency was 1 MHz. [Display omitted] • Laser irradiation increases the current density of ECD. • Laser irradiation has a force impact on the solution. • Cavitation accelerates the flow velocity of solution and form jet impact. • Laser frequency affects the quality of electrodeposited layer. [ABSTRACT FROM AUTHOR]