Untextured Specimens Research Articles

Single‐ and Multiscale Laser Patterning of 3D Printed Biomedical Titanium Alloy: Toward an Enhanced Adhesion and Early Differentiation of Human Bone Marrow Stromal Cells

AbstractThis study explores the enhancement of biocompatible titanium‐based implants through surface functionalization for improved bone healing. Specifically, a near‐beta type Ti‐13Nb‐13Zr alloy is 3D printed using laser powder bed fusion and subsequently textured using nanosecond (ns) and picosecond (ps) direct laser interference patterning (DLIP) to create single‐scale and multi‐scale surface textures. On these textures, the cell behavior, morphology, metabolic activity and osteogenic differentiation potential of human bone marrow stromal cells are assessed using fluorescence microscopy and MTS assays. Moreover, tissue non‐specific alkaline phosphatase activity served as an early osteoblast production marker. Compared to untextured specimens, both types of textures exhibited higher metabolic activity and cell proliferation. Single‐scale ns‐DLIP textures encouraged cell extensions anchored in groove regions, while ps‐DLIP textures with hierarchical structures promoted cell extensions attaching to nanostructures on sidewalls. The groove width and nanotopographies in groove areas facilitated cell spreading. Surface topography, roughness, and surface chemistry (surface energy, wettability) influenced cell adhesion, proliferation, and differentiation. A comprehensive evaluation of DLIP‐generated surface textures, including their topography and chemical states, complements the factors affecting in vitro cell behavior. Overall, this research demonstrates the potential of surface‐functionalized 3Dprinted titanium for a novel generation of biocompatible implants.

Study on the Influence of Surface Texture Parameters of Oil Production Screw Motor Rotor on the Tribological Properties of Its Friction Pair

By researching the influence of micro-groove texture on the surface tribological properties of the stator and rotor pair of oil production hydraulic motors, this paper aims to reduce the frictional resistance moment of the spiral pair of hydraulic motors, and further solve the problem of the difficult restart of the pump of a certain type of hydraulic-driven screw pump. According to the spiral pair of screw motors, a metal-rubber flat plate reciprocating friction model is established, and rectangular micro-grooves with different texture angles and depths are machined on the surface of the metal specimen. A combination of finite element simulation and tribological tests is used to carry out a study on the influence of different texture parameters on the friction performance of the hydraulic motor spiral pair. The results showed that at a certain texture angle, the friction coefficient of each specimen basically increases with the texture depth. When the texture depth is constant, the friction coefficient increases first and then decreases with the increase of the texture angle. The texture angle is the main factor affecting the friction coefficient. Under the same test conditions, the friction coefficient of the textured specimen can be reduced by 20.2% compared with the untextured specimen. In the metal-rubber contact pair of the stator and rotor of the hydraulic motor, the friction reduction mechanism of the texture mainly transport the lubricating medium through the micro-grooves to improve the lubricating conditions. Samples with a reasonable design of texture parameters can effectively reduce the friction coefficient of the friction pair without reducing the service life of the hydraulic motor, which is conducive to the smooth restart of the oil production system of the hydraulically driven screw pump.

Experimental study on laser peen texturing and tribological properties of E690 high-strength steel

To investigate how laser peen texturing (LPT) parameters affect the patterns formed on the surface of E690 high-strength steel, and how these patterns subsequently influence tribological properties, the LPT process, including multiple shocks, was simulated by ABAQUS and verified by experiments. The residual stress and microstructure on the surface of micro-dimples after LPT were measured and observed by X-ray stress analyzer and transmission electron microscope. The tribological properties of specimens with different LPT density and depth were tested by reciprocating friction experiments, and the worn surfaces were observed using a scanning electron microscope. The experimentally obtained plastic deformation depths of the micro-dimples were − 8.82 μm, −18.31 μm, −28.72 μm and − 36.34 μm when the shock number was varied from 1 to 4. The simulation and experiment results were within 3.3 %, verifying the accuracy and reliability of the simulation. When the shock number was ≥ 2, the residual stress values in all directions at the test points within the micro-dimples tended to be consistent, and the full width at half maximum (FWHM) values gradually increased with increasing shock number. The TEM images and electron diffraction pattern of the specimen after three shocks showed that nanocrystals are formed on the bottom surface of the micro-dimple. In the friction experiments, the average friction coefficient first decreased and then increased with increasing LPT density. The average friction coefficient was the lowest when the LPT density was 20 %, for a constant micro-dimple depth. When the LPT density was 20 %, increasing the micro-dimple depth had little effect on the average friction coefficient, but the stability time of the specimens increased substantially. The wear surface of the untextured specimen showed deep and wide wear marks, and serious abrasive wear and adhesive wear occurred.Suggested LPT parameters for optimum wear resistance are an LPT density of 20% and shock number of 3.

Laser surface texturing inhibits Biofilm formation

Biofilm development on surfaces leads to biofouling, which is an undesirable phenomenon in the marine industry. Marine fouling leads to an increase in fuel consumption and corrosion of propeller blades. Most of the antifouling technologies available today are chemical methods that have detrimental effects on the environment. The current work focused on producing non-toxic and effective antifouling systems to control biofilm formation on the titanium alloy surfaces, which has potentially wide range of applications in the marine industry, such as propeller blades, the hull of the ships, heat exchangers, and offshore piping systems. A laser micro-machining was used in this study for the generation of surface texture patterns on the titanium specimens. The contact angle of the untextured surface was 28°, but the wettability of the textured surface increased with a contact angle of 134° for a square pit and 112° for a triangular pit. Surface roughness of the untextured sample showed Ra = 3.811 μm, but post-laser-texturing, the Ra value increased to 10.66 μm and 9.55 μm for the square pit pattern and triangular pit pattern, respectively. Microbes formed biofilm on the untextured specimen but, the square textured surface showed no apparent biofilm formation, while the biofilm was found in triangular textured surface as seen under the fluorescence and scanning electron microscope. The biofilm biomass was significantly reduced in the square textured surface. This work showed that laser textured surfaces might be potentially used to reduce biofilm development on the surfaces. Unlike most methods used for reducing bacterial adhesion, this kind of physical alteration of the surface topography is non-toxic, and it will help to prolong the life of the components used in the marine environment.

Effects of oil retention property for sinusoidal textures on tribological characteristics under scarcity oil supply

Continuous and proper oil lubrication between the friction pair can reduce wear and increase service life of mechanical components. In this paper, the friction experiment and finite element analysis method are combined to study the tribological properties and oil retention mechanism of sinusoidal textured under various width-depth ratios and oil supply. The results indicate that the sinusoidal texture can improve tribological property. ST-3 (the width-to-depth ratio is 1.35) has optimal oil retention property. Compared with untextured specimens (UT), the wear and friction coefficient of ST-3 are reduced by 74% and 7.7%, respectively. Furthermore, the maximum positive pressure is proportional to the non-friction area. This research provides a basis for the optimization design of texture.

Experimental investigation of the effect of typical surface texture patterns on mechanical seal performance

Different types of surface texture patterns such as microgrooves and microdimples have a significant effect on mechanical seal performance. However, these patterns have been studied individually for improved performance in previous publications. The purpose of this paper is to investigate the effect of microgrooves and microdimples on friction coefficient and leakage rate. The micro-textured specimens (rotor ring, 304 stainless steel) are prepared by photolithography combined with electrolytic etching technology. The stator specimens are made of silicon carbide (SiC).The experiments are conducted by using a ring-on-ring type high-speed seal test apparatus. Experimental results indicate that the friction coefficient of all textured surfaces is lower than untextured specimens with increasing area density and texture depth, but the reduction of friction is always companied with increased leakage rate. In general, the optimum area density and texture depth are around 15% and 5 µm, respectively. When the area density, Sp < 10%, microgrooves result in lower friction coefficient, but when the area density exceeds 10%, elliptical dimples has the lowest friction coefficient. Moreover, microgrooves interpenetrated the inner radius of the rotor ring with α = 45° can obtain lower friction coefficient and leakage rate. These findings provide a design reference for surface texturing on practical engineering applications.

Fretting friction properties of laser surface texture microfilaments

PurposeThis paper aims to improve the wear resistance of metal rubber microfilaments and the service life. The effect of surface texture by laser processing on the fretting friction properties of metal rubber microfilaments was studied.Design/methodology/approachThe LQL-F20A laser marking machine was used to fabricate a ring groove array with equal spacing and dense arrangement on the surface of metal rubber microfilaments. The test was carried out with a self-made micro-dynamic frictional tester. The topography of the microfilaments was observed by scanning electron microscopy and analyzed.FindingsIt has shown that laser surface texturing can improve the wear performance of microfilaments. Under the same experimental conditions, the microfilaments of textured surface has a smaller depth of wear than un-textured specimen. The wear resistance increases with the increase of texture density. The friction coefficient of textured specimen is significantly reduced compared with un-textured specimen, and the surface texture density of microfilaments has little influence on the friction coefficient after stabilization. In the stage of stable fretting wear, the wear depth will be more with the increase of the load.Originality/valueThere is little research on metal rubber microfilaments tribological properties. In this paper, the effect of laser texturing of microfilaments on micro-dynamic friction properties was studied by friction machine to provide a reference for the application of metal rubber in aerospace, medical and other fields.

Tribological characteristics of a cemented carbide friction surface with chevron pattern micro-texture based on different texture density

Abstract The influence of the drawing area on the tribological properties was studied using femtosecond laser processing of four kinds of chevron pockets of cemented carbides with 5.05%, 9.5%, 13.02%, and 15.2% texture density. The results show that the chevron pattern texture with a certain texture density helps decrease the friction of a YT15 cemented carbide surface compared with un-textured specimens. This surface texture minimizes and stabilizes the friction coefficient, while the fluid dynamic pressure increased in the specimen with 9.5% texture density. Wear occurs due to abrasive and adhesive wear. Therefore, designing a reasonable shape and selecting appropriate texture density will be the focus of further research on surface micro-texture.

Influence of laser processing conditions for texturing on ultra-high-molecular-weight-polyethylene (UHMWPE) surface

Surface modification of Ultra-High Molecular Weight Polyethylene (UHMWPE) for improving tribological performance is difficult due to its high melt viscosity. Therefore, the potential of laser processing to produce textures on the surface of this material in specific dimensions was evaluated in this study. The influence of several conditions and laser processing parameters was determined. The laser texturing at room temperature, freezing temperature, and producing distilled water layer on UHMWPE disks was not helpful to produce the textures in required dimensions. The textures in specific dimensions were produced at 2 overscan times, 25 mm/s scanning speed and 30 MHz laser intensity using aluminum foil. The coefficient of friction (COF) versus time data under different concentrations of Bovine Serum Albumin (BSA) was recorded for textured and un-textured specimens. The wear performance in term of wear track depth was also compared for textured and un-textured specimens using a confocal microscope.

Effect of laser surface texturing on wear resistance of nickel based superalloy

PurposeThis paper aims to investigate the effect of laser surface texturing (LST) on the wear behavior of C-263 nickel-based superalloy and to identify the optimum wear operating condition.Design/methodology/approachC-263 nickel-based superalloy was selected as substrate material and pico-second Nd-YAG laser was used to fabricate the waviness groove texture on their surface. Wear experiments were designed based on Box-Bhenken design with three factors of sliding velocity, sliding distance and applied load. Wear experiments were performed using pin on disc tribometer. Morphologies of textures and worn-out surfaces were evaluated by scanning electron microscopy and energy dispersive spectroscopy. Surface topographies and surface roughness of the textures were evaluated by weight light interferometry. The response surface methodology was adopted to identify the optimum wear operating condition and ANOVA to identify the significant factors.FindingsLST improves the wear resistance of C-263 nickel-based superalloy by appeoximately 82 per cent. Higher wear rate occurs at maximum values of all operating conditions, and applied load affects the coefficient of friction. Applied load significantly affects the wear rate of un-textured specimen. The interaction of sliding velocity and applied load also affects the wear rate of textured specimens. The optimum parameters to get minimum wear rate for un-textured specimens are 1.5 m/s sliding velocity, 725 m sliding distance and 31 N of applied load. For textured specimens, the optimum values are 1.5 m/s sliding distance, 500 m sliding distance and 40 N of the applied load.Originality/valueLiterature on laser texturing on nickel-based superalloy is very scarce. Specifically, the effect of laser texturing on wear behavior of the nickel-based superalloy C-263 alloy is not yet reported.

Bulge micro-textures influence on tribological performance of ultra-high-molecular-weight-polyethylene (UHMWPE) under phosphatidylcholine (Lipid) and bovine serum albumin (BSA) solutions

Ultra-High Molecular Weight Polyethylene (UHMWPE) is an engineering polymer used as a bearing material with metallic or ceramics counter surfaces in orthopedic implants because of its high ductility, compatibility and impact resistance. Several methods, including cross-linking, surface texturing and particle or fiber reinforcement have been employed to improve the tribological performance of UHMWPE. In this study, square and rectangular bulge textures were introduced on UHMWPE and their influence on friction and wear properties under Phosphatidylcholine (Lipid) and Bovine Serum Albumin (BSA) solutions were investigated. The laser texturing was performed under different conditions such as using distilled water layer, aluminum foil and at freezing and room temperature with varying laser processing parameters including scanning speed, pulse frequency, and laser intensity. The textures in the required dimension were produced using only aluminum foil by controlling melt viscosity. The ball-on-disk tribometer was used for tribological tests. The reduction in coefficient of friction (COF) was recorded in case of textured specimens as compared to un-textured specimens at low concentration of BSA and at higher concentration of lipid. However for both cases, the square texturing was proved optimal as compared to rectangular texturing because of the higher area ratio of square textures.

Experimental investigation of disc partial surface texture on the generation of hydrodynamic lubricating performance under conformal contact condition

A series of experiments is conducted to investigate the hydrodynamic lubricant characteristics of partial surface textured specimens. The specimens are fabricated with partial surface texture. Two dimple shapes are adopted: circular and elliptic. Four kinds of texture arrangements of elliptic dimples are designed. During each test, different rotating speeds and gaps between the tested specimen and the geometric probe are set to explain the relationship between the operation condition and load-carrying capacity. We found that the load-carrying capacity is strongly affected by the operation condition, i.e. by both speed and gap. The surface textured specimens generate large hydrodynamic lift force compared with the untextured specimen. In addition, the texture arrangements exhibit a significant impact on the lubrication property.

Enhancing tribological performance by anodizing micro-textured surfaces with nano-MoS2 coatings prepared on aluminum-silicon alloys

Abstract Aluminum-silicon alloys exhibit poor tribological performance and suffer from severe adhesive wear. The single surface treatment has demonstrated unsatisfactory anti-friction performances. In this paper, the synergistic effect of the surface micro-texturing and nano-solid lubricant improved the tribological performance of aluminum-silicon alloys effectively. The anodizing micro-textured surface with nano-MoS2 coatings was fabricated by micro-milling, anodizing and ultrasonic impregnation. Pin-on-disc tribological tests revealed that the friction coefficient of the anodizing micro-textured surface with nano-MoS2 coatings decreased by 22.6% compared with that of the untextured specimen. The anti-friction characteristic was attributed to the synergistic effect of the entrapping wear debris of dimple structure, the high hardness of porous anodic aluminum oxide films and the self-lubricating property of nano-MoS2 coatings.

Structural and piezoelectric properties of &lt;001&gt; textured PZT‐PZNN piezoelectric ceramics

AbstractRhombohedral 0.69Pb(Zr0.47Ti0.53)‐0.31Pb(Zn0.6Ni0.4)NbO3 (PZT‐PZNN) ceramics were textured using 10.0 vol. % BaTiO3 (BT) platelets along the &lt;001&gt; direction at 950°C with a high Lotgering factor of 95.3%. BT platelets did not react with the PZT‐PZNN ceramics, and the textured PZT‐PZNN ceramic had a tetragonal structure. The PZT‐PZNN ceramics exhibited a strain of 0.174% with a piezoelectric strain constant (d*33) of 580 pC/N at 3.0 kV/mm. The textured PZT‐PZNN ceramic showed an increased strain of 0.276% and d*33 of 920 pC/N at 3.0 kV/mm, which can be explained by the domain rotation. However, the d33 values of the textured specimens are smaller than those of the untextured specimens because of the small remanent polarization and relative dielectric constant of BT platelets. The textured PZT‐PZNN ceramic synthesized in this work can be used for piezoelectric multilayer actuators because of its large strain and low sintering temperature.

Effects of micro-milled malposed dimple structures on tribological behavior of Al-Si alloy under droplet lubricant condition

To solve the problem of undesired rapid wear of the piston and high leakage in the combustion chamber, various technical approaches have been presented to decrease the friction between internal compression piston ring and cylinder liner. Surface micro-texturing is one of the most efficient methods to mitigate parasitic losses. In this paper, surface micro-textures with different dimple distribution angles (15°, 45°, 60°, and 90°) were fabricated by micro-milling on Al-Si alloy ZL109. Pin-on-disc reciprocating tribometer was utilized to investigate the effects of the malposed rectangle dimple structures on the tribological behaviors of ZL109. The friction coefficient and wear topographies of the textured specimens with different distribution angles were examined. The possible friction reduction and wear resistant mechanisms were analyzed. The results indicated that the friction performance of machined surface could be enhanced by the malposed rectangle dimple micro-textures. The average friction coefficient of dimple distribution angle θ = 45° reduced by 6.93% in comparison to the untextured specimens. Furthermore, optical micrographs indicated that the micro-textured specimens with distribution angle θ of 60° exhibited the narrowest and shallowest wear track.

Improved Tribological Behavior of Grey Cast Iron Under Low and High Viscous Lubricants by Laser Surface Texturing

Abstract The main objective of this paper was to investigate the effect of laser surface texturing (LST) on the friction and wear behavior of gray cast iron in lubricated conditions. The dimples with a diameter of 54 μm and depth of about 10 μm were produced with various dimple densities in the range from 5 to 35 %. Ball-on-disc friction tests were carried out for all the specimens in low and high viscous oils. The friction coefficient was reduced by about 35 % after the LST compared with the untextured specimen at a load of 5 N and speed of 5 cm/s. The textured specimen with a dimple density of 10 % possessed the lowest friction coefficient of all the dimpled specimens in both low and high viscous oils. However, the high viscous oil was found to be more effective to achieve a lower friction coefficient compared to the low viscous oil. The friction coefficient reduced by about 46 % in high viscous oil compared to the low viscous oil. Similarly, the lower wear was noticed for the specimen with a dimple density of 10 % and 5 % among all the specimens in both low and high viscous oils. The resistance to wear of the specimens was also found to be enhanced in high viscous oil compared to those in low viscous oil.

On Design and Tribological Behaviour of Laser Textured Surfaces

The paper reports an investigation into the functional response of textured surfaces with different designs that incorporated arrays of micro-dimples and grooves (40μm diameter/width and 15μm depth for both patterns) produced on tungsten carbide (WC) blocks by employing nanosecond (ns) and femtosecond (fs) lasers. In particular, the tribological performance of the textured WC blocks against stainless steel (SS316L) counterbody was evaluated in terms of friction and wear under dry condition compared to an untextured specimen. Friction tests were carried out on a reciprocating sliding tester while unidirectional ball-on-disc method was utilised to assess wear on the mating surfaces. The untextured surface exhibited a continuous rise in the friction coefficient from 0.15 to 0.5 from the start of the cycle to the end while the specimens textured with ns and fs lasers reached steady-state condition after 100 and 200 cycles with values between 0.35-0.45 and 0.3-0.4, respectively. Energy dispersive spectroscopy following wear tests showed a pronounced material transfer from the balls to the textured surfaces with stainless steel filling up some of the dimple and groove cavities; however, the reverse phenomenon was not apparent. Additionally, texturing with the fs laser exhibited formation of nano-ripples/structures in the produced dimples and grooves that can be further studied for creating nano-textured cutting tools or surfaces with super-hydrophobic/anti-ice properties.

Influence of groove surface texture on temperature rise under dry sliding friction

Parallel groove surface textures with different area densities were fabricated on ASTM 1045 steel. Friction tests were conducted under dry sliding condition. Temperature rise, friction coefficient and wear of both the textured and untextured specimens were studied. An embedded K-type thermocouple beneath the friction surfaces was employed to measure frictional temperature rise. The results indicated that the temperature rise of the textured specimen was obviously reduced compared with that of the untextured specimen, although the difference between the friction coefficients was not significant. The specimen with high texture density exhibited a small temperature rise. The difference in temperature rise between the specimens with different texture densities can be primarily attributed to differences in heat dissipation and energy allocation between the tribo-pairs caused by the textured structure. The energy consumed by wear and plastic deformation was small in comparison with the total energy input by friction, thus, the influence of these factors on temperature rise can be considered to be negligible.

Improving tribological performance of gray cast iron by laser peening in dynamic strain aging temperature regime

A high and stable brake disc friction coefficient is needed for automobile safety, while the coefficient degrades due to elevated temperature during the braking process. There is no better solution except changes in material composition and shape design optimization. In the dynamic strain aging(DSA) temperature regime of gray cast iron, micro-dimples with different dimple depth over diameter and surface area density are fabricated on the material surface by laser peening(LP) which is an LST method. Friction behavior and wear mechanism are investigated to evaluate the effects of surface texturing on the tribological performance of specimens under dry conditions. Through LP impacts assisted by DSA, the friction coefficients of the LPed specimens increase noticeably both at room temperature and elevated temperature in comparison to untreated specimens. Moreover, the coefficient of specimen with dimple depth over diameter of 0.03 and surface area density of 30% is up to 0.351 at room temperature, which dramatically rises up to 1.33 times that of untextured specimen and the value is still up to 0.3305 at 400°C with an increasing ratio of 35% compared to that of untreated specimen. The surface of textured specimen shows better wear resistance compared to untreated specimen. Wear mechanism includes adhesive wear, abrasive wear and oxidation wear. It is demonstrated that LP assisted by DSA can substantially improve wear resistance, raise the friction coefficient as well as its stability of gray cast iron under elevated temperatures. Heat fade and premature wear can be effectively relieved by this surface modification method.

Characteristic of Friction on Texturing Bearing Steel with Ultrasonic Hole Machine

We carry out experiments to characterize textured bearing steel with varying hole density and depth. Textured surface is believed to reduce the friction coefficient, and improve performance and wearing caused by third-body contact. We employ three lubrication regime conditions based on the Stribeck curve: boundary lubrication, mixed lubrication, and hydrodynamic lubrication. Ultrasonic machining is an untraditional machining method wherein abrasive grit particles are used. The hammering process on the work piece surface by abrasive provides the desired form. In this study, we create multi-holes on the bearing steel surface for texturing purposes. Holes are formed by an ultrasonic machine with a diameter of 0.534 mm and a depth of about 2-4 mm, and they are distributed on the contact surface with a density between 1.37-2.23%. The hole density over the surface area is an important factor affecting the friction. We test nine types of textured specimens using four times replication and compare them with the untextured specimen using graphs, as well as photographs taken using a scanning electron microscope. We use Analyzes variant in this experiment to find the correlation between each pair of treatments. Finally, we report the effect of hole density and depth on the friction coefficient.