Laser Surface Textured PTFE Inhibitation for Stick-Slip Phenomenon Under Boundary Lubrication

When the machine tool is in the start-and stop-stages,the stick-slip phenomenon will be observed and highprecision positioning,machining accuracy and fretting feed will not be guaranteed. The most critical reason is that there is the difference between the dynamic and the static friction coefficients. Textures with different area ratios are fabricated on the surfaces of the upper PTFE-based composite and the friction tests are carried out on a reciprocating tribotester under the boundary lubrication and flat-on-flat contact conditions. The results show that there exists an optimal textured area ratio of 19.6% that can minimize the difference between the dynamic and the static friction coefficients.

Effect of laser textured surface with different patterns on tribological characteristics of bearing material AISI 52100

Chrome steels are used in bearings since they possess high strength and wear resistance.However,when those parts are in service,failure happens due to sliding friction before the lifetime.To improve the durability of the American Iron and Steel Institute(AISI)52100 chromium steel,in this work,the effect of laser surface texturing(LST)was analyzed.With the different patterns of circle and ellipse comparing with the untextured samples,the wear behavior was investigated using the pin-on-disc tribometer.The lubricant used for wear analysis is semisolid lithium grease National Lubricating Grease Institute lubricant(SKF NLGI-3).Sliding wear analysis was conducted at different loads of 10 N,30 N and 50 N for the sliding speed of 750 r/min and 1400 r/min.The wear morphology was analyzed using a scanning electron microscope(SEM).The roughness of the samples was found using a white light interferometer.The effect of different patterns like circle and ellipse,alter the friction and wear properties of chromium alloy was observed compared with the untextured samples.LST shows considerable reduction in friction and wear for ellipsoidal pattern compared with the circular pattern because of wear debris and lubricant getting trapped.

Impressive strides in amelioration of corrosion behavior of Mg-based alloys through the PEO process combined with surface laser process: A review

The unsatisfactory corrosion properties of Mg-based alloys pose a significant obstacle to their widespread application. Plasma electrolytic oxidation(PEO) is a prevalent and effective coating method that produces a ceramic-like oxide coating on the surface of Mg-based alloys,enhancing their resistance to corrosion. Research has demonstrated that PEO treatment can substantially improve the corrosion performance of alloys based on magnesium in the short term. In an effort to enhance the corrosion resistance of PEO coatings over an extended period of time, researchers have turned their attention to the use of laser processes as both pre-and post-treatments in conjunction with the PEO process. Various laser processes, such as laser shock melting(LSM), laser shock adhesion(LSA), laser shock texturing(LST), and laser shock peening(LSP), have been investigated for their potential to improve PEO coatings on Mg substrates and their alloys. These laser melting processes can homogenize and alter the microstructure of Mg-based alloys while leaving the bulk material unchanged, thereby modifying the substrate surface. However, the porous and rough structure of PEO coatings, with their open and interconnected pore structure, can reduce their long-term corrosion resistance. As such, various laser processes are well-suited for surface modification of these coatings. This study will first examine the PEO process and the various types of laser processes used in this process, before investigating the corrosion behavior of PEO coatings in conjunction with laser pre-and post-treatment processes.

Mechanical Properties and Microstructure of Bionic Non-Smooth Stainless Steel Surface by Laser Multiple Processing

Laser multiple processing, i.e. laser surface texturing and then Laser Shock Processing (LSP), is a new surface processing technology for the preparation of bionic non-smooth surfaces. Based on engineering bionics, samples of bionic non-smooth surfaces of stainless steel 0Crl 8Ni9 were manufactured in the form of reseau structure by laser multiple processing. The mechanical properties (including microhardness, residual stress, surface roughness) and microstructure of the samples treated by laser multiple processing were compared with those of the samples without LSP The results show that the mechanical properties of these samples by laser multiple processing were clearly improved in comparison with those of the samples without LSP The mechanisms underlying the improved surface microhardness and surface residual stress were analyzed, and the relations between hardness, comnressive residual stress and roughness were also presented.

Cooperative effect of surface alloying and laser texturing on tribological performance of lubricated surfaces

The cooperative effect of laser surface texturing(LST) and double glow plasma surface alloying on tribological performance of lubricated sliding contacts was investigated.A Nd:YAG laser was used to generate microdimples on steel surfaces. Dimples with the diameter of 150μm and the depth of 30-35μm distributed circumferentially on the disc surface.The alloying element Cr was sputtered to the laser texturing steel surface by double glow plasma technique.A deep diffusion layer with a thickness of 30μm and a high hardness of HV900 was formed in this alloy.Tribological experiments of three types of samples(smooth,texturing and texturing+alloying) were conducted with a ring-on-disc tribometer to simulate the face seal.It is found that,in comparison with smooth steel surfaces,the laser texturing samples significantly reduce the friction coefficient.Moreover,the lower wear rate of the sample treated with the two surface techniques is observed.

Tribological Properties of Dimpled Surface Alloying Layer on Carbon Steel

The effect of surface structure and coating on tribological properties of 45^# carbon steel disc was analyzed. A Nd：YAG laser was used to generate rnicrodirnples on steel surfaces. Dimples with diameter of 150 rn and depth of 50 rn were distributed in an orbicular array on disc surface. Then the alloying element Mo was sputtered to 45# carbon steel disc surface by means of double glow plasma technology. Diffusion Mo alloying layer with 30min thickness and high hardness up to 0.025 was formed on the disc surface. Tribological experiments of three types samples （smooth, texturing and texturing＋alloying） were conducted with a pin-on-disc tribometer. It is found that the dimpled-samples are most effective for reducing friction in comparison with smooth steel surthces, improving the lubricating state from boundary to hydrodynamic region.

Laser Surface Texturing of Co–Cr–Mo Alloy for Biomedical Applications:A Case Study for the Effects of Process Parameters on Surface Properties

This study presents a comprehensive approach to applying texturing processes created by engraving on the surface of CoCr28Mo alloy workpieces using a 20 W pulsed nanosecond fiber laser.The hatch strategy and distance,frequency,and scan speed were control parameters for texturing applications.The effectiveness of the parameters in terms of roughness and contact angle of the texturized surface was investigated.Surface roughness and contact angle were analyzed using variance analysis to identify each variable's influence.It has been determined that the roughness of the texture defined by the hatch strategy plays a decisive role in the wettability behavior of the surface;however,the scan speed,frequency,and hatch distance which are among the laser surface texturing conditions are influential in the roughness and contact angle.Increasing scan speed and hatch distance while decreasing frequency resulted in smoother surfaces,increasing the contact angle.Textures having rough surfaces produced with different processing conditions exhibit a super hydrophilic behavior.The contact angle is most sensitive to the hatch distance;however,the frequency has the least influence on the contact angle.The most and least efficient surface roughness parameters are revealed to be scan speed and hatch distance,respectively.

Experimental study on bumps formation textured by nanosecond laser on Ti6Al4V alloy

The surface properties of biomaterials are the key factors for the success of artificial implants in the body.The creation of patterns on titanium alloys by laser surface texturing techniques can modify the surface to make it multifunctional.The evolution of the surface morphology of Ti6Al4V alloy textured by a nanosecond laser with 1064 nm wavelength in the air is studied.Laser surface texturing treatment is performed on the titanium alloy through different pulse numbers,power,pulse width and scan times to obtain different morphologies.The 2D cross-section profile shows that the morphology can be divided into three types in the evolution process of various pulse numbers,powers and pulse widths:bump-shaped,hump-shaped and crater-shaped.It is found that the effect of pulse width on morphology mainly depends on power.The effects of laser parameters on the height of bumps and the evolution of morphology are the main research points to analyse the topography evolution.The causes of bumps are also analysed.Energy dispersive spectrometer measures the area irradiated by the laser,and it is found that the oxygen content of the bump is up to 43.1%,which can speculate that the bump is the result of the oxidation reaction.

A synergetic strategy based on laser surface texturing and lubricating grease for improving the tribological and electrical properties of Ag coating under current-carrying friction

Herein,a series of Ag coatings with different micro‐dimples were fabricated on copper surfaces by laser surface texturing(LST)and magnetron sputtering.Multilayer graphene lubricating grease(MGLG)was prepared using multilayer graphene as an additive.The textured Ag coatings and MGLG were characterized.Moreover,the tribological and electrical performances of the textured Ag coatings under MGLG lubrication were investigated in detail.Results demonstrated that the textured Ag coating with an appropriate dimple diameter could exhibit improved tribological and electrical properties when compared to the non‐textured Ag coating under MGLG lubrication.The characterization and analysis of the worn surfaces suggest that the synergetic effect of LST and MGLG contributes to these excellent tribological and electrical properties.

Does laser surface texturing really have a negative impact on the fatigue lifetime of mechanical components?

Laser surface texturing(LST)has been proven to improve the tribological performance of machine elements.The micro-scale patterns manufactured by LST may act as lubricant reservoirs,thus supplying oil when encountering insufficient lubrication.However,not many studies have investigated the use of LST in the boundary lubrication regime,likely due to concerns of higher contact stresses that can occur with the increasing surface roughness.This study aims to examine the influence of LST on the fatigue lifetime of thrust rolling bearings under boundary lubrication.A series of periodic patterns were produced on the thrust rolling bearings,using two geometrically different designs,namely cross and dimple patterns.Base oil ISO VG 100 mixed with 0.05 wt%P of zinc dialkyldithiophosphate(ZDDP)was supplied.The bearings with cross patterns reduce the wear loss by two orders of magnitude.The patterns not only retain lubricant in the textured pockets but also enhance the formation of an anti-wear tribofilm.The tribofilm generation may be improved by the higher contact stresses that occur when using the textured surface.Therefore,in contrast to the negative concerns,the ball bearings with cross patterns were instead found to increase the fatigue life by a factor of three.

Fast laser surface texturing of spherical samples to improve the frictional performance of elasto-hydrodynamic lubricated contacts

Textured surfaces offer the potential to promote friction and wear reduction by increasing the hydrodynamic pressure,fluid uptake,or acting as oil or debris reservoirs.However,texturing techniques often require additional manufacturing steps and costs,thus frequently being not economically feasible for real engineering applications.This experimental study aims at applying a fast laser texturing technique on curved surfaces for obtaining superior tribological performances.A femtosecond pulsed laser(Ti:Sapphire)and direct laser interference patterning(with a solid‐state Nd:YAG laser)were used for manufacturing dimple and groove patterns on curved steel surfaces(ball samples).Tribological tests were carried out under elasto‐hydrodynamic lubricated contact conditions varying slide‐roll ratio using a ball‐on‐disk configuration.Furthermore,a specific interferometry technique for rough surfaces was used to measure the film thickness of smooth and textured surfaces.Smooth steel samples were used to obtain data for the reference surface.The results showed that dimples promoted friction reduction(up to 20%)compared to the reference smooth specimens,whereas grooves generally caused less beneficial or detrimental effects.In addition,dimples promoted the formation of full film lubrication conditions at lower speeds.This study demonstrates how fast texturing techniques could potentially be used for improving the tribological performance of bearings as well as other mechanical components utilised in several engineering applications.

Metal surface wettability modification by nanosecond laser surface texturing:A review

Laser surface texturing(LST)is a non-contact manufacturing process for fabricating functional surfaces in a manner that improves the corresponding wettability,and is widely used in biomedicine and industry.Laser surface texturing is a facile approach that is compatible with various materials,can result in a hierarchical texture,and enables a high degree of surface wetting(i.e.,extreme wetting).In addition to surface structures,surface chemical modification is a primary factor in producing extreme wetting surfaces.This review discusses the effects of various surface textures and surface chemistries on wettability.Optimal laser parameters for the desired surface texture are based on the fundamental wettability and laser mechanism.In particular,bumps in the morphology are conducive to obtaining extreme wetting.Diverse surface chemical strategies result in extreme wetting by different mechanisms.This paper makes a rigorous evaluation of the laser parameters and optimal surface chemical modifications by elucidating the relationships between the surface structure,surface chemical modification,and wettability,and in so doing,determines the final wettability.The unresolved problems of LST are presented in the conclusion.This review provides guidance,development directions,and an integrated framework for LST,which will be useful for fabricating extreme wetting surfaces on various metals.

NiTi laser textured implants with improved in vivo osseointegration:An experimental study in rats

Laser surface texturing is a versatile approach for manufacturing implants with suitable surfaces for os-seointegration.This work explores the use of laser to fabricate NiTi textured implants,testing two dif-ferent groove-based designs.Their performance was evaluated in vivo through implantation in Sprague Dawley rats’femur,being then analyzed after 4 and 12 weeks of implantation.Push-out experiments and histological characterization allowed to assess bone-implant bond and osseointegration and to compare the laser textured solutions with non-textured NiTi.Histology showed that,at 4 weeks of implantation,mainly immature woven bone was present whilst at 12 weeks a more mature bone had developed.Con-sidering the largest implantation time(12 weeks),results showed extraction forces considerably higher for textured implants(G2 and G3).Moreover,when comparing G2 and G3,it was found that G2(having the highest textured surface area)displayed the maximum extraction force among all groups,with an increase of 212%when compared to non-textured implants(G1).These results prove that the design and manufacturing technology are effective to promote an im-proved bone-implant bond,aiming the development of orthopedic implants.

Assessment of wear micromechanisms on a laser textured cemented carbide tool during abrasive-like machining by FIB/FESEM

The combined use of focused ion beam(FIB)milling and field-emission scanning electron microscopy inspection(FESEM)is a unique and successful approach for assessment of near-surface phenomena at specific and selected locations.In this study,a FIB/FESEM dual-beam platform was implemented to docment and analyze the wear micromechanisms on a laser-surface textured(LST)hardmetal(HM)tool.In particular,changes in surface and microstructural integrity of the laser-sculptured pyramids(effective cutting microfeatures)were characterized after testing the LST-HM tool against a steel workpiece in a workbench designed to simulate an external honing process.It was demonstrated that:(1)laser-surface texturing does not degrade the intrinsic surface integrity and tool effectiveness of HM pyramids;and(2)there exists a correlation between the wear and loading of shaped pyramids at the local level.Hence,the enhanced performance of the laser-textured tool should consider the pyramid geometry aspects rather than the microstructure assemblage of the HM grade used,at least for attempted abrasive applications.

Laser pattern-induced unidirectional lubricant flow for lubrication track replenishment

Effective oil replenishment to the lubrication track of a running bearing is crucial to its sustainable operation.Reliable practical solutions are rare despite numerous theoretical studies were conducted in the last few decades.This paper proposes the use of surface effect,wettability gradient,to achieve the goal.This method is simple and can be nicely implemented using femtosecond laser ablation.A periodic comb-tooth-shaped pattern with anisotropic wetting capability is devised and its effect on the anisotropic spreading behaviour of an oil droplet is studied.Results show that the comb-tooth-shaped pattern enables the rearrangement of oil distribution,thereby escalating oil replenishment to the lubrication track.The effect is due to the unbalanced interfacial force created by the surface pattern.The influence of the shape and the pitch of teeth,which are the two governing factors,on oil transport is also reported.The effects of the newly devised surface pattern on lubrication are experimentally evaluated under the conditions of limited lubricant supply.These results are promising,demonstrating the reduction in bearing friction and the increase in lubricating film thickness.

Tribological properties of textured stator and PTFE-based material in travelling wave ultrasonic motors

This study fabricated textures on the stator surface of a traveling wave ultrasonic motor(USM)using laser and investigated the tribological behavior of a polytetrafluoroethylene(PTFE)composite friction material and stator.Initially,the effect of textures with different densities was tested.As the results suggested,the generation of large transfer films of PTFE composite was prevented by laser surface texturing,and adhesive wear reduced notably despite the insignificant decrease in load capacity and efficiency.Next,the 100-h test was performed to further study the effects of texture.Worn surface and wear debris were observed to discuss wear mechanisms.After 100 h,the form of wear debris changed into particles.The wear mechanisms of friction material sliding against the textured stator were small size fatigue and slight abrasive wear.The wear height of friction material decreased from 3.8μm to 1.1μm.This research provides a method to reduce the wear of friction materials used in travelling wave USMs.

Is laser surface texturing good or bad for rolling element bearings?--Comments on: “Does laser surface texturing really have a negative impact on the fatigue lifetime of mechanical components?” by Hsu et al. and “An exploration of frictional and vibrational behaviors of textured deep groove ball bearing in the vicinity of requisite minimum load” by Vidyasagar et al.

A short commentary on the two research articles published in Friction in 2021 is presented.Both articles reported experimental results of applications of laser surface texturing technology to the raceway of rolling element bearings.After briefly reviewing the main findings of the articles,the arguable problems and distinctions between the two articles are pointed out.