Laser Surface Texturing Research Articles

High‐Speed Laser Surface Structuring for Thermal Spray Coating Preparation

The preparation of surfaces for coating processes is indispensable for maximal adhesion and good coating results. These technical surfaces can be treated by chemical, mechanical, or physical procedures. In thermal spray coating, grit blasting is a standard process for surface preparation. This mechanical roughening and activation of the surfaces is fast and easy to handle. On the negative side, the grit gets wasted and the generated pattern is inflexible. Therefore, attempts to substitute grit blasting with a laser application is discussed in this article. Herein, a theoretical evaluation of high‐speed laser surface texturing (LST) is performed to find limits and points for the optimization of these processes. To estimate the surface processing rates, continuous wave, nanosecond, and ultrashort pulse laser machined dimples and grooves are investigated, and results of the spray coatings are presented afterward. The steel substrates are coated with Stellite 6 and tungsten. Adhesion tests and coating structures are analyzed. In terms of the optimization of the laser texturing, in situ temperature measurements show the influence of the laser process speed on the thermal load of the substrate. The influence of the number of scanning repetitions on heat accumulation during LST is also analyzed.

Enhancing heat transfer at low temperatures by laser functionalization of the inner surface of metal pipes

The latent heat transfer during vapour condensation in the condenser section of passive heat transport devices such as the two-phase closed thermosiphon is limited by film condensation. Dropwise condensation provides an increase of the heat transfer coefficient by up to one order of magnitude and can be achieved with a water-repellant surface. The inner surface of pipes made from stainless steel was functionalized by laser surface texturing with ultrashort laser pulses and subsequent storage in a liquid containing long-chained hydrocarbons. The pipes were separated into half-pipes by wire eroding to enable laser texturing of the inner surface, and were then joined by electron beam welding after laser texturing. As a result, superhydrophobic and water-repellent surfaces with a contact angle of 153° were obtained on the inner surface of the pipes with a length of up to 1 m. The functionalized pipes were used in the condenser section of a two-phase closed thermosiphon to demonstrate a heat transfer rate of 0.92 kW at 45 °C, which is approximately three times the heat transfer rate of 0.31 kW of a smooth reference pipe.

Improvement of the deposition efficiency and adhesion strength of cold sprayed fluoropolymer coating by laser surface texturing of the substrate

High-performance polymer cold-spraying is attracting the interest of many for its economical, time-saving, and environmentally safe features in comparison to traditional thermal spraying processes. The cold spray process allows applying functional polymer coatings on a similar or dissimilar material surface for protective measures or additional functionalities. However, its practical use has been restricted by inherently low deposition efficiency associated with a weak interfacial adhesion strength.In this study, fluoropolymer powder mixed with 5 wt% of nano-alumina was cold-sprayed on laser-textured carbon steel substrates. A thorough analysis of the particle deposition as a function of the spray parameters (gas temperature, pressure, pass number, traverse speed) was performed to highlight the effect of the laser-texturing (groove geometry, laser pitch, pattern) on the deposition efficiency and adhesion strength. By laser-texturing the substrate, the deposition efficiency increases up to 60 %, and the adhesion strength reaches 1.25 MPa. Thus, while the addition of nano-alumina enhances the interparticle cohesion, a laser-textured substrate promotes the mechanical interlocking at the particle/substrate interface.

Combining laser surface texturing and double glow plasma surface chromizing to improve tribological performance of Ti6Al4V alloy

Ti6Al4V (TC4) alloy has been widely applied in the military, industrial, chemical, and medical fields due to their excellent thermal stability, corrosion resistance, and biocompatibility. However, titanium alloys are notorious for their poor tribological properties, such as their high friction coefficients and low surface bearing capacities. To tackle this problem, combination of laser surface texturing (LST) and double glow plasma chromizing was conducted to improve the wear resistance of TC4. LST was first conducted to produce uniform dimples with a diameter of 300 μm and gradient density of 11 % on the Ti6Al4V substrate. A chromizing coating (Cr-coating) was subsequently deposited on the surfaces of the textured and raw Ti6Al4V alloy by double glow plasma surface alloying (DGPSA). A continuous and compact Cr-coating with a thickness of about 55 μm was formed on TC4 after being maintained at a temperature of 850 °C, and the coating was mainly composed of a solid solution and intermetallic compounds of Cr2Ti phases. The surface hardness after alloying was two times higher than that of the TC4 substrate. Comparative assessments on the wear resistance of the Cr-coatings with and without LST treatment and the TC4 alloy were carried out using a ball-on-disk wear tester. The results showed that the mass loss and specific wear rate of the duplex-treated sample were 1.54 mg and 7.14 × 10−4 mm3·N−1·m−1. The mass loss and specific wear rate of the TC4 were 4.32 mg and 1.62 × 10−3 mm3·N−1·m−1. The specific wear rates of the four tested samples were in the following order: the duplex-treated TC4 < textured TC4 < chromized TC4 < polished TC4. The coating obtained by LST-double glow plasma chromizing duplex treatment exhibited an outstanding durability and the best mechanical performance. Thus, this approach be used for the protection of Ti6Al4V surface in engineering components and medical instruments.

Effect of laser surface texturing on the corrosion behaviour and biocompatibility of zinc hydroxyapatite implant material

The demand to optimize pure zinc with adjustable rates of corrosion and biocompatibility has recently increased, and metal matrix composites offer a promising solution. In this study, an optimized Zinc-Hydroxyapatite combination was prepared through a powder metallurgy process, and surface modifications were performed using Laser Surface Texturing. The feasibility of the composite in corrosive and cell culture environments was systematically evaluated through physical and mechanical tests, revealing properties matching those of bone tissue. Three different textures were tested, and textured samples showed better resistance to corrosion and higher cell viability than non-textured ones, with hexagonal texture being the most effective. Contact angle measurements were performed to analyse the sample's hydrophilic nature, which improved with the texturing process. These results suggest that texturing increased the surface area and surface wettability, leading to better biocompatibility results. This study highlights the potential of metal matrix composites for in-vivo conditions and calls for further investigation.

Parametric investigation of ultrashort pulsed laser surface texturing on aluminium alloy 7075 for hydrophobicity enhancement

Hydrophobicity plays a pivotal role in mitigating surface fouling, corrosion, and icing in critical marine and aerospace environments. By employing ultrafast laser texturing, the characteristic properties of a material’s surface can be modified. This work investigates the potential of an advanced ultrafast laser texturing manufacturing process to enhance the hydrophobicity of aluminium alloy 7075. The surface properties were characterized using goniometry, 3D profilometry, SEM, and XPS analysis. The findings from this study show that the laser process parameters play a crucial role in the manufacturing of the required surface structures. Numerical optimization with response surface optimization was conducted to maximize the contact angle on these surfaces. The maximum water contact angle achieved was 142º, with an average height roughness (Sa) of 0.87 ± 0.075 µm, maximum height roughness (Sz) of 19.4 ± 2.12 µm, and texture aspect ratio of 0.042. This sample was manufactured with the process parameters of 3W laser power, 0.08 mm hatch distance, and a 3 mm/s scan speed. This study highlights the importance of laser process parameters in the manufacturing of the required surface structures and presents a parametric modeling approach that can be used to optimize the laser process parameters to obtain a specific surface morphology and hydrophobicity.

Laser Surface Texturing for Ground Surface: Frictional Effect of Plateau Roughness and Surface Textures under Oil Lubrication

Laser surface texturing has proven beneficial in improving tribological performance in different lubrication regimes. However, the interaction between plateau roughness and surface texture remains to be further investigated, even though rough surfaces are common in engineering applications. In the present study, we investigated the frictional influence of surface texturing of ground surfaces under different lubrication conditions. Channel textures with different depths and area ratios were fabricated on ground surfaces, and their friction was tested in reciprocating tests. The experimental findings indicate that the textures caused increased friction for ground surfaces under boundary or mixed lubrication when the interface is well lubricated. Nevertheless, when the oil supply was limited, an up to 40% friction reduction was observed under test conditions.

Study on the subsurface characteristics of textured surfaces under EHL condition

PurposeThe purpose of this study is to investigate the influence of surface texture on the subsurface characteristics of contact interfaces under elastohydrodynamic lubrication condition. As a typical contact form of gears and bearings, the optimization of friction characteristics at the elastohydrodynamic lubrication (EHL) interface has attracted the attention of scholars. Laser surface texturing is a feasible optimization solution, but there have been concerns about whether the surface texture of high-pair parts will affect their fatigue life.Design/methodology/approachTo examine the impact of texture preparation on the subsurface characteristics of high-pair interfaces under EHL conditions, a point contact EHL model is developed that takes into account the effect of textured surface topography. The pressure and thickness of the oil film are calculated as input parameters under different loads and entrainment velocities. The finite element method is used to simulate the impact of textures with varying diameters, densities and depths on the subsurface characteristics of the elastohydrodynamic interface. According to ISO 25178, analyze the relationship between 3D topography parameters and subsurface characteristics and study the trend of friction characteristics and subsurface characteristics based on the results of the ball on disc friction tests.FindingsThe outcomes suggest that under different rotational velocity and load conditions, the textured surfaces exhibit improved friction reduction effects; however, the creation of textures can result in significant subsurface plastic deformation and local peeling. The existence of texture makes the larger stress zone in the subsurface layer closer to the surface, leading to fatigue failure near the surface. Reasonable design parameters can help enhance the attributes of the subsurface. A smaller Sa and a Str greater than 0.5 can achieve ideal subsurface properties on the textured surface.Originality/valueThis paper investigates the influence of surface texture on the friction and subsurface characteristics of EHL interfaces and analyzes the impact of surface texture on interface contact performance while achieving lubrication improvement functional characteristics. The results provide theoretical support for the optimization design and functional regulation of surface texture in EHL interfaces.Peer reviewThe peer review history for this article is https://publons.com/publon/10.1108/ILT-10-2023-0324/

Alumina/GNPs coating on textured WC/Co substrate: microstructure and tribology

This work aims to provide a method for improving the tribological properties of WC/Co substrates. Laser surface texturing technology was employed to fabricate micro-grooves on the substrate surfaces. Suspension high velocity oxy fuel thermal spraying technique was used to deposit 99 wt-% alumina + 1 wt-% graphene nanoplatelets (GNPs) coating on the substrate surface with micro-grooves. Characterisations such as micromorphology, composition analysis and tribological performance were examined. Results showed that the morphology of the laser prepared micro-groove consisted of two hills and one valley. The grid-textured samples sprayed with alumina/GNPs coating showed the lowest coefficient of friction and wear rate, which was benefited from the larger texture density and the friction reduction of GNPs lubrication film.

Numerical simulation and experimental investigation on the friction reduction properties of ZrO$$_2$$ by laser surface texture

Numerical simulation and experimental investigation on the friction reduction properties of ZrO$$_2$$ by laser surface texture

Tribological Performance of Laser‐Based Surface Textured Nonconformal Contacts

The benefits of surface textures on rolling and sliding tribological contacts have been an exciting field of study over the last three decades. Laser surface texturing (LST) is a comparatively newer texturing methodology that yields repeatable precise microtextures. A detailed overview of the available literature on the various works in this field is consolidated in this review. The main focus is on the effect of surface textures (with focus on laser ablation) for nonconformal contacts with elastohydrodynamic lubrication (EHL), as in rolling element bearings. A review of literature on textured contacts for the EHL regime, emphasizing its effect on friction, wear, rolling contact fatigue, vibration, texture geometry, and numerical simulation studies, is carried out with possibilities of future works. Basic details on LST processes and various parameters of the laser beam that determine the texture geometry are discussed. Being a field of continuing research, the review paper will aid in understanding the present developments and future directions in laser‐based surface texturing for nonconformal tribological contacts.

Measurement of frictional torque of a directacting valvetrain using a shaft-to-shaft torque transducer to study the effect of Laser Surface Texturing on friction reduction

The study of tribological applications requires measuring various parameters, including RPMs, friction, and wear. The useful information is sometimes not readily available in a measurement and requires further postprocessing to extract that information. In this research, a production engine test rig has been developed to study a direct-acting valvetrain’s tribological performance for various operating conditions. The measurement of the drive torque is carried out by using a shaft-to-shaft torque transducer. The total drive torque is a combination of geometric torque and frictional torque. The geometric torque is not affected by changes in parameters such as surface modification or lubricant chemistry but the frictional torque changes. We need to extract the frictional torque from the total drive torque to study the effect of any parameter or operating condition change on friction. As variation in frictional torque helps the tribologists to compare the performance of different parameter changes. This paper explains the complete procedure of measuring the experimental frictional torque from drive torque data. In this study, the frictional torque variation between an untextured and a textured tappet shim is studied for a direct acting cam tappet contact of a real production engine.

Tailoring Resin–Metal Adhesion by Femtosecond Laser Surface Texturing

Epoxy resin wettability and adhesion on metal surfaces are of interest to composite manufacturing processes in two aspects: while higher adhesion is desired for composite to metal part bonding, lower adhesion is expected for metal tools used in the composite fabrication process. Among several surface modification techniques to achieve such increased/decreased adhesion strengths, femtosecond laser micromachining is a sustainable and scalable technique. Therefore, this study aims to explore epoxy resin adhesion behavior against femtosecond laser micromachined aluminum surfaces as a function of different microscale topographies. The texture types include microscale hexagonal and cylindrical hole patterns with different solid/air surface fractions and comparatively smaller‐scale laser‐induced periodic surface structures. Based on polished metal contact angle results, desired texture geometries are selected in a range to theoretically favor or inhibit resin penetration into microcavities. Theoretical predictions are derived from the capillary effect and Gibb's energy difference. The adhesion strength of resin to metal is examined by tensile tests. All the laser‐textured surfaces show considerably increased adhesion strengths compared to polished surfaces. Scanning electron microscopy and laser profilometry analysis on failed surfaces confirm resin penetration into all textures. Nevertheless, hexagonal holes, which exhibit the highest microcavity volume, show potential for air trapping.

Innovative Fabrication of Metal Alloy Structures via Laser-Induced Forward Transfer on Flexible Substrates.

Laser-induced forward transfer is a contactless, nozzle free process which enables accurate, precise and fast development of 3D structures. However, a number of shortcomings such as shockwave generation, poor adhesion to receiver substrates and uniform depositions limit LIFT to be utilized. Therefore, this research tends to put forward easy and effective solutions for successful mitigation of the LIFT limitations. Receiver surface modifications and low-pressure conditions are introduced through laser surface texturing (LST) and a vacuum pump. A number of textures and orientations are investigated for determining the optimal copper (Cu) deposition. Furthermore, utilization of the same laser system for LST enables the manufacturing process cost and time effective. In addition to Cu depositions, additive layers of silver (Ag) and platinum (Pt) are deposited. Finally, Ag and Pt micropillars are fabricated on their respective additive layers leading to formation of Cu-Ag and Cu-Pt alloys structure. Subsequently, electrical and material characterizations are made to validate for potential applications. Experimental evidence shows greater adhesion with electrical properties for LST-based LIFT in low pressure conditions. Finally, an energy analysis is performed based on theoretical and finite element methods (FEM) to gain greater insights into mechanics of the LIFT process.

Biofouling and Corrosion Protection of Aluminum Alloys Through Ultrafast Laser Surface Texturing for Marine Applications

AbstractSurface biofouling, corrosion, and wettability are important parameters to understand and characterize aluminum alloys to prevent the failure in marine environments. Antifouling technologies predominantly encompass chemical and biocidal approaches with negative environmental consequences. Therefore, this study focuses on a new method of producing non‐toxic and effective antifouling and corrosion‐resistant surfaces. In this study, ultrafast laser texturing is used to modify the surface of an aluminum alloy using a femtosecond laser system. Five different unique texture patterns are designed and fabricated using 3 W laser power, 100 kHz pulse repetition rate, and 4 mm s−1 scanning speed in order to make the aluminum surface antifouling and corrosion resistant. The non‐textured sample has a contact angle of 85° while the textured samples have contact angles of up to 157°. The contact angle increased with time up to 90 days of aging. Biofouling assessment is conducted using marine algae Nitzschia ovalis as a marine fouling test organism. A reduction of biofilm coverage of 79% is recorded from the laser‐produced star pattern texture. This study demonstrates that laser‐textured surfaces have the potential to mitigate the formation of biofilms on the surfaces while also providing a mechanism to control the relative level of corrosion.

Research status of laser surface texturing on tribological and wetting properties of materials: A review

Laser surface texturing (LST) holds great potential in fabricating precise and controllable micro/nanostructures, benefiting from its high processing resolution, flexible processing methods, and capability to handle a wide range of materials. This paper aims to comprehensively review the research status of LST in improving materials’ friction and wetting properties. Firstly, the significance of friction and wetting properties is outlined, followed by an introduction to commonly employed LST, including laser ablation, laser interference, and laser shock processing. Then, much emphasis has been placed on the impact of laser parameters and texture design on material properties. By manipulating laser parameters such as pulse width, pulse power density, and number of pulses, different effects can be generated on the geometric characteristics, pattern types, and distribution forms of surface textures, thereby altering the surface’s microscopic topography, roughness, hardness, and wettability to exhibit different friction and wetting performances. Next, the optimization methods for texture performance are discussed, encompassing the optimization of laser parameters and the texture itself. In particular, the fundamental theories and influencing mechanisms of LST on materials’ friction and wetting performance are elaborated in detail, followed by an overview of research conducted on metals, non-metals, and composite materials. Finally, a summary is provided on the application of LST in improving the friction and wetting performance of materials while pointing out the limitations of existing research and prospects for future research directions.

Laser surface textures enhance the friction and wear behaviour of orthodontic brackets

AbstractMinimising the friction force of the archwire‐bracket sliding contact is crucial for achieving a high‐quality orthodontic treatment. Micro‐dimples and micro‐grooves textures were successfully produced on the two slot surfaces of the stainless steel orthodontic brackets with the laser surface texturing technology. The effect of surface texture on reducing the friction and wear behaviour of the stainless steel archwire‐bracket sliding contact combinations in artificial saliva environment was investigated. Friction coefficients of less than 0.15 and mild wear were obtained by using the three rows micro‐grooves textured bracket with a width of 60 μm and a spacing of 150 μm. The friction and wear performance was further enhanced with the addition of orthodontic wax materials. It was strongly argued that the synergetic effects of the fabricated micro‐grooves texture and the added orthodontic wax materials leading to the outstanding friction and wear behaviour of the archwire‐bracket sliding contacts.

Improvement of the tribological behavior of high reinforcement concentration Al–SiC (63%) metal matrix composite through laser surface texturing

The tribological performance of high reinforcement concentration AlSiC-9 Metal Matrix Composite (63% reinforcement) can be improved by laser texturing. This research performs different topographies by changing the energy density and scanning speed parameters, which modify the liquid retention and wear resistance. Results demonstrated a reduction of up to 60% in the friction coefficient and up to 70% in wear volume. SEM/EDX analysis identified adhesive, abrasive, and plastic deformation as the main wear mechanisms. These results confirm that the main contribution of textures was to improve the lubrication retention and trap wear debris.

Tailoring the Coefficient of Friction by Direct Laser Writing Surface Texturing.

The modification of the surface topography at the micro- and nanoscale is a widely established as one of the best ways to engineering the surface of materials, to improve the tribological performances of materials in terms of load capacity and friction. The present paper reviews the state of the art on laser surface texturing by exploiting the technique of direct laser writing for tailoring the coefficient of friction, highlighting the effect of the textures' arrangement on the lubricated conformal and non-conformal contact behavior.

Adhesion Strength and Anti-Corrosion Performance of Ceramic Coating on Laser-Textured Aluminum Alloy

Laser surface texturing and micro-arc oxidation provide excellent approaches to enhance the adhesion strength and anti-corrosion performance of adhesive bonding interfaces in aluminum alloys, which can be applied in the field of automotive light weighting. Herein, micro-arc oxidation coatings were fabricated on the laser-textured aluminum surface under the voltage of 500 V for various treatment times (5 min, 15 min, 30 min, 60 min). The anti-corrosion performance of ceramic coatings on the laser-textured surface was analyzed using electrochemical measurements. The results of electrochemical measurement indicate that the coating on the sample surface presents two time constants corresponding to a dual-layer structure. The sample grown under 500 V for 60 min exhibits excellent protective performance with a value of 1.3 × 107 ohm·cm2. The adhesion strength of laser-textured ceramic coating is improved compared with the as-received substrate. The sample treated with 500 V for 30 min exhibits the highest bonding strength with a value of 52 MPa. The wider pores and bulges for the sample grown in 60 min would introduce microcracks and consequently reduce the adhesion strength.