Proceedings of the 3rd International Conference on Advanced Surface Enhancement (INCASE) 2023

Laser peening (LP) processing is one of surface technologies in which a metal material placed in water is irradiated with a pulse laser and peened by the generated shock wave. Since conventional laser peening requires large-scale and high-cost laser equipment, smaller and cheaper pulse laser oscillators have been desired for further industrial applications. In recent years, some handheld pulse laser oscillators have been developed by the ImPACT Program in Japan. In this study, in order to investigate the effectiveness of the new handheld laser device for LP treatment, rotating bending high cycle fatigue tests were conducted on A7075BE-T6511 aluminum alloy. As a result, the high cycle fatigue properties were significantly improved by LP treatment. The fatigue strength at 107 cycles is improved by about 1.5 times, and the fatigue life is extended by about 100 times than those of base metal specimens. In this study, the improvement of fatigue properties by laser peening treatment with a handheld laser oscillator was investigated from the viewpoint of peening effect and fracture mechanism.

This paper proposed a vibrofinisher with a unique design—domeless, non-elevating and circular bowl vibrofinisher to be used for the aerospace industry. Compared to conventional circular dome vibrofinishers, this new setup could be more effective for material removal and surface roughness improvement than current industrial practices because of its better accessibility to annular geometries. There was limited literature to support this statement. In this paper, a model of a cuboid-body vibration system was proposed and a numerical analysis of this design with reference to past papers of standard design was conducted. The theoretical analysis showed a high potential for faster material removal rate due to an increase of 80.5% in the excitation force and excitation moment of up to 144.6%. Both displacement and rotational angle increased by 68% and 47% respectively, which suggests a higher amplitude. Using the theoretical results, the law of abrasive law and a roughness model was used to substantiate the effectiveness of the domeless bowl as a potential replacement to both the trough and dome bowl.

Three dimensional additively manufactured metallic materials, i.e., 3D-Metal, are attractive materials. However, the fatigue strength of as-built 3D-metal is nearly half of bulk metals. In order to enhance the fatigue strength of 3D-metal, a combined process of blasting and cavitation peening (CP) was proposed. In the process, the blasting makes smoother surface by collisions of abrasives, and introduces compressive residuals stress in the sub-surface region. After the blasting, CP using a submerged water jet introduces compressive residual stress into the deeper region. In the present paper, titanium alloy Ti6Al4V manufactured by direct metal laser sintering (DMLS) was treated by the combined process of blasting and CP. The fatigue strength was evaluated by torsion fatigue testers of a torsion-controlled type and an angle-controlled type. To make clear the mechanism of the improvement of fatigue strength, surface roughness and surface residual stress were measured. It was revealed that the blasting introduced the compressive residual stress while decreasing the surface roughness, and the fatigue strength was improved by about 33% compared with as-built specimen. When the specimen was treated by CP after blasting, the fatigue strength was improved by 58%, which was larger than that of CP only.

Laser shock peening process generally introduces compressive residual stresses on a component by targeting laser beam normal to the surface. However, geometrical complexity of components necessitates laser beam to be delivered at an angle other than normal. In such cases, the peening effect is not optimal. In this study, the effect of varying incident angles on residual stresses of Ti-6Al-4V components after laser shock peening is investigated. The results revealed a decrease in residual stress magnitude and depth with an increase in incident angle. The degree of reduction is especially obvious when the angle exceeds 20°. Peening at a constant laser fluence produced similar levels of residual stress as in normal peening. However, at very large angles, peening effect was still slightly lower despite using same fluence, possibly due to other losses. It was found that increasing the laser fluence can compensate for the reduction in peening effect at large angles.

Direct energy deposition Inconel 718 is increasingly explored and used for various industrial applications due to its near net shape and ability to build complex geometries. For post-processing, hammer peening process is a well-established surface finishing step to enhance the compressive stress of the metal, reducing and preventing cracks. Increasingly, laser has been explored for post-processing additive manufactured metal as an in-situ heat treatment process to relieve tensile stresses formed during the process. In this paper, an investigation into the effects of hammer peening in conjunction with laser is performed. Microstructural analysis, hardness values and tribological properties will be used to observe these effects. It was found that hammer peening increased the hardness of Inconel 718, and when used in tandem with laser, the hardness decreased, albeit higher than the non-post processed sample. Lastly, there is a disconnect between the correlation of higher hardness values with lower wear rate, as the lowest hardness value sample has the lowest wear rate in this study, and that hammer peening itself did not reduce the wear rate of direct energy deposited Inconel 718.

In the paper, 1.06 µm picosecond (ps) laser is employed to fabricate micro/nano surface textures on Al2024-T3 substrate. The effects of different laser parameters including laser fluence, repetition rate, scanning speed, pulse number, focal position, etc. on the topography, feature profile, feature dimensions of the induced surface textures have been studied. The optimum laser parameters have been identified and the uniform-distributed 2 scale micro-nano hierarchical bump array, sub-micron-ripple and micro-dimple array surface patterns are fabricated on the Al2024-T3 substrates. The laser textured Al2024-T3 sample shows stable superhydrophobic property with a water contact angle (WCA) of more than 150 degree and contact angle hysteresis (CAH) of less than 10 degree. The mechanism involved in the process is discussed in terms of surface morphology and surface chemistry. The developed process has the potential to be applied in improving the performance of the Al-based components and/or products in terms of superhydrophobicity and easy cleaning.

Additive manufacturing processes face challenges when producing complex metallic components. Surface defects, such as incomplete melting, balling, and geometric inaccuracies, are common in printed metallic components with complex structures, such as lattice structures. These defects make it unfeasible to use these components commercially without further processing. Limitations such as inaccessibility and limited improvement in surface quality in existing post-processing techniques make the motivation for this study. This paper is largely based on the partial results of an ongoing thesis in the development of a novel hybrid process. The hybrid process combines electrochemical polishing (ECP) and ultrasonic cavitation abrasive peening (UCAP). It takes advantage of ECP's ability to brighten and smoothen surfaces and UCAP's ability to generate compressive residual stresses, enhance surface hardness, and improve the efficiency of ECP synergistically. The first part of this paper gives an overview of the need for an alternative post-processing technique and the benefits of a hybrid process. Further, results and discussion of investigative experimentation will be highlighted describing the effects and mechanisms of the hybrid process.

In this paper, the previously presented theoretical equations governing the utilization of a new sensor to measures peening intensity will be expanded to include the effect of impingement angle. The equations are derived from the Impulse–Momentum principle and use the input velocity, the coefficient of restitution, the media particle mass and the impact impulse time to determine the maximum impact force at any angle. The equations are verified with results from experimental testing at impingement angles of 85°, 65°, 55°, 45° and 35° at five different input velocities using AWCR28 media propelled from a Shockform designed single particle cannon. Results show that for all angles, the sensor output offers a good linear correlation with the input velocity. The sensor can be used to assess the quality of the particle stream when peening at different angles and with different media flow rates. Examples of sensor output graphs will be presented showing how collisions between incoming and outgoing media particles can affect the distribution of impacts on a part.

Tungsten carbide coating deposited by High Velocity Oxy-Fuel (HVOF) spray process possesses high microhardness and dense coating structure. It has very good wear and corrosion resistant properties which are used on components in various industries such as aerospace, marine, offshore, oil and gas. Beside these known properties, there is one interesting surface property—the coating surface has potential to reach near superhydrophobic state which enable a durable antistick surface. This experimental study revealed that the HVOF sprayed WC-CoCr coating transiting from hydrophilicity during as-sprayed to hydrophobicity after 15 days of exposure to atmospheric condition.

Laser peening (LSP) is a surface enhancement technology that utilizes a short-pulsed laser to improve the fatigue life of components. With the advent of additive manufacturing (AM), there has been an interest in studying LSP of AM parts. In this experimental work, we examine the effect of LSP on the microstructure and surface morphology of AM 316L stainless steel. LSP at moderate and extreme peak power densities of 7.86 and 17.68 GW/cm2 respectively, was performed on a 316L steel sample fabricated by directed energy deposition (DED). The samples were characterized for their surface morphology and near-surface microstructure using a range of analytical techniques. The results indicate that all LSP conditions had no significant effect on the surface topography or oxide level. When no ablative coating was used, the surface residual stress was tensile whilst with coating the surface residual stress state was compressive. The plastic strain (as measured by EBSD) was not significantly different for all LSP conditions. The use of extremely high peak power density (17.68 GW/cm2) showed no significant increment in plastic strain, hardness or surface residual stress compared to moderate peak power density (7.86 GW/cm2) possibly due to the dielectric breakdown of water. The findings indicate that a very high peak power density does not necessarily translate to larger peening effects and may not be required for material processing.

A two-step process of the mechanical surface treatments (MST) on Ti-6Al-4 V using a deep cold rolling (DCR) followed by a metal shot peening (MSP) was studied to understand the complementary effect of MSP over DCR. DCR was used for the introduction of higher and deeper compressive residual stress on the Ti-6Al-4 V coupons while MSP was used for the further improvement of the compressive residual stress near the surface of the coupons. The study shows that the two-step process reduces the anisotropy of Ti-6Al-4 V in both surface roughness and compressive residual stress compared the standard single step DCR process. Furthermore, the two-step process improves the near-surface compressive residual stress owing to the secondary MSP process without compromising the depth of influence by the first DCR treatment.

Fluidic flow in micro-channels is driven by capillary filling actuation mechanism. Therefore, surface hydrophobicity plays a significant role in controlling the fluidic flow. Surface hydrophobicity can be tuned by depositing hydrophobic material onto the surface, or by creating surface micro-/nano-textures that follow Cassie-Baxter model (hydrophobic). To facilitate fluidic flow in a microchannel, it is critical to design and create superhydrophobic surfaces with high contact angle and low contact angle hysteresis, which require accurate control of two-scale micro-/nanostructures. In this study, we propose to use laser interference to create deterministic micro- and or nano-level patterns on a metal mold surface. Femtosecond laser is chosen due to its high machining precision and minimum heat-affected zone. The surface structures are characterized by optical and scanning electron microscopy. The surface wettability is analyzed by measuring surface water contact angles. Through hot embossing, the surface structures are replicated onto surfaces of polymer microfluidic channels. The proposed method is shown to be effective and easy to implement for microfluidic applications.

Intensity is an indirect quantification of the kinetic energy in the air-media stream through the usage of Almen strips in shot peening. However, intensity does not give an insight to the energy transferred into the material nor the compressive residual stress (CRS) on different materials. Previous studies have been done on individual materials but few serve to investigate and compare across materials. In this study, the effect of Shot Peening on common aerospace materials Al7075-T6, IN718, SUS304 and Ti-6Al-4 V were investigated to assess residual stress distribution and other material properties such as hardness across different material properties for the same peening intensity. Through this work, the authors aim to elucidate the mechanism of differences in residual stress distribution by establishing a relationship with the different material properties studied. Specimens were shot peened using ASR70 media, while residual stress and hardness measurements were conducted at various depths thereafter. It was found that the variation in pre-peened material hardness from all materials does not correlate to obtaining higher work hardening and deeper residual stresses under the same shot peening intensity and coverage. Among the materials studied, Al7075-T6, the softest, exhibited the highest post-peening surface roughness, but showed limited work hardening and induced residual stresses. In contrast, Ti-6Al-4 V, the hardest material, demonstrated the lowest post-peening surface roughness, with relatively minor work hardening and residual stresses compared to Inconel 718 and SS304. These differences can be attributed to the distinctive material properties and microstructure, leading to varying deformation behavior when subjected to cold work processes like shot peening.

In recent years, many problems have arisen, such as increased power consumption in commercial refrigerators due to water droplets on aluminum alloy surfaces, increased frost formation due to bacteria and mold, and increased transportation costs for bullet trains. To solve these problems, we turned our attention to surface texturing technology and shot blasting, a new surface component that can switch between hydrophobic and hydrophilic properties. Shot blasting can be applied to large areas at a lower cost than laser processing and can be used for surface texturing. This study reports the results of an evaluation of the effect of shot blasting on the surface wettability of aluminum alloys. Shot blasting was performed on aluminum alloy A5052 using various particles, and the wettability of the specimens was evaluated. It was found that the wettability after shot blasting varied with the particle material and particle size as in previous studies. Using the aspect ratio (dent depth/dent width) calculated from the surface roughness, it was found that the specimens became hydrophilic to hydrophobic up to an aspect ratio of 7 or less, and that the contact angle gradually increased to hydrophobic at an aspect ratio of 7 or greater.

Silicon is one of the most commonly used semiconductor materials. However, working with silicon presents challenges due to its high brittleness and hardness. Drilling, milling, dicing, and surface treatment require careful handling. Fortunately, laser processing technology offers a solution. With its high energy density and smaller heat-affected zone, laser processing is well-suited for working with silicon materials. This paper reviews the interaction mechanism between laser and silicon material and its applications. The surface and subsurface treatments are introduced. The surface roughness, microstructure, residual stress, and electrical properties of silicon material after laser microprocessing are investigated. Based on the current research status, we summarize some of the challenges that must be overcome to allow a wider application of laser in the new generation of semiconductor materials.

This study aimed to achieve a polished surface on the internal channel of Ti-6Al-4V, a popular titanium alloy in the 3D printing industry, using electrochemical polishing (ECP). We used a custom functionalised cathode and less toxic electrolyte to achieve this goal. We found that a smooth surface with a minimum roughness of Ra value 9.9 µm could be achieved, and localised polishing of channels could be done without masking the workpiece itself. The study investigated the interaction between the workpiece, cathode, and electrolyte within the internal channel and found that the formation and removal of a viscous layer during ECP affected the polishing effect, as well as the bubbling produced at the cathode. The optimal process parameters are expected to vary for different geometries and could be determined through a linear sweep voltammetry test followed by ECP at a constant voltage. This research provides useful insights and methods for achieving ECP on the internal surface of Ti-6Al-4 V components which could have significant implications for the design of more complex components for applications of 3D printing in the aerospace, marine or med-tech industries.

Hydraulic fracturing is widely accepted and has become the most useful method to increase exploiting production of shale oil and gas in more complex geological environment. As the key component of the hydraulic fracturing, fracturing pump bears high cyclic pressure and is prone to fatigue failure around intersection line of the fluid cylinder, which is closely associated with the material surface state. In this paper, residual stress and axial tension fatigue test are investigated on the specimens with and without Laser Shock Peening (LSP) treatment. Numerical simulation is conducted to identify stress distribution and LSP region of fracturing pump, which is then subjected to LSP and fatigue performance test. Results showed that LSP produced a maximum compressive residual stress (CRS) of up to 730 MPa on the specimen surface and a CRS layer with a thickness of 1.5 mm under the upper surface. Tension-tension fatigue life was increased by 141.08% at 800 MPa after LSP treatment. Stress concentration of the fracturing pump was located at intersection line according to finite element analysis. And then, LSP region was designated as the area where Mises stress larger than 80% of Max. The service life was increased by 68.3% with subsequent LSP which was attributed to the compressive residual stress.

Plasma electrolytic polishing (PEP) is a technology with high efficiency, environmental friendly, simple manufacturing process, high quality and ability to improve corrosion resistance. Plasma electrolytic polishing improves corrosion resistance by forming oxides on the surface of workpieces and achieving passivation. In this study, the SUS 316 was polished with different plasma electrolytic polishing electrolytes. We observed the influence of electrolyte on the ratio of chromium to iron to understand the effect of plasma electrolytic polishing technology on improving the corrosion resistance of materials. After plasma electropolishing of SUS 316 using different electrolytes (voltage: 320 V; time: 180 s; temperature: 80 °C), it was found that the surface components were mainly oxides of iron and oxides of chromium. The oxide is concentrated on the surface of the workpiece with a thickness of about 3–750 nm. Plasma electrolytic polishing with different electrolytes will produce oxide layers with different thicknesses. After plasma electrolytic polishing, the stainless steel workpiece has a surface chromium-iron ratio of 1.64 (optimal condition). This study shows that plasma electrolytic polishing technology can optimize the oxide layer on the surface of stainless steel and achieve the effect of improving corrosion resistance.

Stress peening is a modern technique to enhance the durability of spring. The springs are shot peened under prestress, and after unloading, the residual stress will increase significantly. The same procedure can also be done by deep rolling. The difference is that deep rolling has two different residual stress directions (amounts) if you look along or perpendicular to the rolling track. Therefore, you get in sum four totally different residual stress distributions if you take into consideration that the prestress (before rolling) is along or perpendicular to the track. The residual stress distributions in the dependence of the above-explained facts, and different prestresses are investigated. The different depths of the interaction zones are shown. Also, the limit of the theoretical inducible residual stresses is compared with the experimental results. Last, but not least, a practical application of a torsion bar is presented.

Distortion of machined parts is still a big issue not only in the aircraft parts industry but also in any machine industry. Compressive residual stress is favorable compared with tensile residual stress after machining for fatigue and stress corrosion properties. However, it is not easy to get compressive residual stress on the surface after machining. Cutting is the main machining process for various machine parts including aircraft parts. Therefore, in this research, we try to find out the appropriate cutting condition to obtain compressive residual stress after cutting. Especially cutting conditions of up-cut and down-cut methods are compared from the viewpoint of residual stress after the cutting. The residual stress was measured by X-ray diffraction method using the μ-X360 device of Pulstec Industrial Co., Ltd. The results confirm that up-cut tends to generate compressive residual stress. On the other hand, down-cut tends to generate tensile residual stress. The details including the effect of repetitive processing are also discussed.

Burnishing is a process in which a cylindrical or hemispherical tool made of a hard material is pressed against a workpiece with a rough cut surface to obtain a smooth surface. Compared to shot peening, the process stress is easier to control and more precise. Burnishing is usually used to improve surface roughness. Depending on the processing conditions, it is possible to affect the interior of the material and obtain an effect similar to shot peening. Electromagnetic steel sheet is a material that is easy to observe changes in crystal characteristics because it is close to pure iron in terms of material composition and has large crystal grains. When the crystals change, the magnetic properties also change. Therefore, it is a material that is easy to evaluate in various aspects. In this study, the changes that occur when electromagnetic steel sheets are processed by inclined burnishing was investigated.

Laser peening without coating (LPwC) was invented in Japan in the 1990s. After confirming the effect of reducing the stress corrosion cracking (SCC) susceptibility of sensitized materials, LPwC has been applied to operating nuclear power reactors as a countermeasure against SCC of in-core components. Meanwhile, fiber-delivery technology for high-power laser pulses has been developed to expand the applicability of LPwC. In parallel, the effect of LPwC to improve fatigue properties has been investigated and then applied to the inside of the connecting pinholes at the root of nuclear steam turbine blades. In the last decade, various technological developments have been made to further expand the applications, such as dry LPwC, which does not use water as a confinement medium, and handheld LPwC, which uses a finger-sized microchip laser mounted directly on a robot. The author reviews the activities in LPwC over the past 30 years, focusing on the underlying physics, inventions, applications, and future developments.

Electrochemical corrosion tests were conducted on 13Cr steel for steam turbine blade material of power plants in the simulated boiler water containing chloride ions (Cl−) and formic acid (HCOOH). The corroded surfaces were observed and analyzed in detail. In the boiler waters containing 100 ppm Cl−, the formation of corrosion products as passivation films on the specimen surfaces inhibited the occurrence of pitting corrosion by the additions of 25–75 ppm HCOOH.

In this study, it was elucidated that the fatigue failure mechanism of glass-fiber reinforced plastics (GFRP) with different fiber orientations, and the relationship between the fiber orientation and the failure mechanism by using a simple unidirectional fiber orientation. Fatigue tests exhibited that GFRP, whose glass fiber oriented parallel to the load direction showed high fatigue strength. Furthermore, as a result of observing the fatigue fracture, in the case of GFRP containing fibers oriented parallel to the loading direction, fatigue cracks occur at the fiber edges, propagated through between the glass fibers and the matrix. After that, the fatigue crack propagation rate gradually decreases, the fatigue crack growth stopped, and finally, GFRP material was statically fractured. Therefore, this suggests that the increase in fiber length of fibers oriented parallel to the loading direction extends the fatigue crack propagation life, leading to an increase in total fatigue life.

Porosity has long been observed in manufacturing metal alloys, which is much more frequent in additively manufactured (AM) alloys than in those manufactured by traditional methods such as cast and wrought. The common origin of porosity is strongly depending on specific manufacturing process parameters and conditions. In general, pore structures can originate from a variety of factors, including trapped gas, incomplete fusion, cooling rate, feedstock quality, processing parameters and conditions, etc. By carefully controlling the manufacturing process and conditions, the porosity in AM-alloys can be mitigated. Besides, post-AM treatment, e.g., hot isostatic pressing and/or cold working, can reduce the porosity (in both the size and density) through plastic deformation and materials flow. Here, we present a glimpse on porosity and its effect on mechanical performance of AM alloys. Mitigation and closure of porous structures will also be discussed mainly based on recent observations in aluminum- and nickel-based AM alloys, representing high-temperature high-strength and low-density applications, respectively.

Plasma electrolytic oxidation (PEO) is a promising technology to improve the durability of aluminum alloys. However, herein we find that PEO process reduces the fatigue strength of the aluminum substrate, and the reduction varies with the PEO coating process. Detailed surface and sub-surface characterizations are conducted to understand the mechanism. Our study provides in-depth understanding on the effect of PEO coating on the properties of the base material, thus has important implications on their applications.

Aluminum (Al) alloys with low density are extensively used in ground transport and aerospace applications to attract fuel energy savings. While the additive manufacturing of Al alloys is not new, precipitation hardened alloys pose severe challenges due to their susceptibility to high residual stress and cracking. This study aims to report on the influence of heat treatment in minimizing the surface residual stress and improving the room temperature tensile response of a precipitation hardened high strength Al alloy (Al2139). The changes to mechanical properties will be presented by invoking the process-microstructure-property relationships.

Amorphous alloys with no crystal structure, particularly Fe-based ones, exhibit excellent soft magnetic properties and are expected to be applied to motor cores because of their high magnetic flux density. However, they are difficult to machine because of their mechanical properties, such as high strength and toughness, owing to their unique structure. These mechanical properties of amorphous alloys change due to thermal microstructural changes, that is, structural relaxation and crystallization; however, the excellent magnetic properties also degrade. Therefore, this study proposes a new blanking method that improves the machinability of amorphous alloys without degrading their magnetic properties by thermally changing the microstructure of the local area where blanking is performed. This study investigated the effectiveness of ultrashort pulsed lasers, which have little thermal effect, on the local heat treatment of amorphous alloys. Furthermore, blanking tests were performed on the locally heat-treated amorphous alloys, and the blanking resistance values and characteristics of the blanked surfaces were evaluated.

Shot peening is a common surface treatment technique used to improve the fatigue life of aerospace materials such as Titanium-64. However, shot peening increases the surface roughness of the part and hence, an additional vibratory polishing process is usually employed as a post-treatment step to reduce the surface roughness. Unfortunately, vibratory polishing is a material removal process, and its effect on the residual stress and cold work in the part is not well understood. In this paper, we explore the impact of prolonged vibratory polishing on shot peened coupons. The study focuses on the residual stress, cold work, and microstructure of the test coupons.

Powerful tools for improving the layer thickness distribution in electroplating are available through simulation techniques for calculating the electric field. To get the best out of these simulation technologies, a good knowledge of the possibilities of simulation tools, the needed requirements as well as typical, proven workflows are important. This paper uses an industrial case study to cover, present and discuss the above-mentioned points as well as the used approach used and the achieved results. Both the individual results achieved and the improved understanding of the process noticeably improve the efficiency in electroplating.

Three dimensional numerical simulations of micro shot peening process are carried out for different operating and nozzle surface conditions. The influence of two different turbulence model variants namely the SKE model and AKN model are employed to investigate their capability to accurately predict the shot peening process. Nozzle surface is assumed to be both smooth and rough and their influence on the solid discrete particle dynamics is investigated. Particle velocity and splat sizes resulting from the shot peening process are numerically simulated and compared against the measurements. It is inferred from simulations that the AKN turbulence model predicts the surface deposition characteristics both qualitatively and quantitatively closer to the measurements than that of the SKE model. Nozzle surface roughness is found to influence the particle velocity, particle rebounding angles and therefore resulting in wider particle dispersion leading to larger particle splats on the target substrate.

The present study extends a previously calibrated rheology and wall slip model to computational fluid dynamics (CFD) simulations of material removal distribution over the surface of a fairway golf club undergoing the stream finishing process. Simulations were undertaken for the cases of the golf club immersed in a stream finishing drum, fixed for two different orientations and with the drum rotated either clockwise or counterclockwise. Owing to the complex media flow over the golf club resulting from the interaction between the media and the three-dimensional surface of the golf club, predicted values of wall pressure and slip velocity distributions span over a wide range of magnitudes, implying that achieving uniform material removal would be a particularly interesting challenge. Lastly, insights gained from the present study will inform a careful design of the physical experiments, which are meant to further improve the stream finishing material models.

The paper presents many study cases on the effect of shear viscosity on the deformation and jet formation posterior to the impact of copper powder onto copper substrates. Thanks to a physics-based plasticity model dedicated to high strain rates processes, we performed a batch of numerical finite element simulations in order to understand the way copper particle flatten and expulse material outside the zone of contact. We considered a continuous function of viscosity as a first shot followed by other cases where temperature thresholds are considered to enable the action of shear viscosity. In the present paper we are not aiming to compare numerical results to experimental data rather than depicting the influence and the importance of physical parameters such as shear viscosity on the development of jetting in impacted copper.

Surface modification treatments using particle impact, such as shot peening and fine particle peening, are used in many parts such as automotive gears. However, the surface modification effect is affected by many factors such as the material of the projectile, particle size, and nozzle diameter. In the case of the air injection type, the airflow inside and outside the nozzle has a particularly large effect. However, few studies have examined the effects of airflow inside and outside the nozzle. In this study, the airflow inside and outside the nozzle was analyzed using the finite element method. As a result, it was found that the airflow velocity increases as the nozzle diameter increases. It was also clarified that the factors causing this increase were the lengthening of the potential core section and the deceleration caused by the wall resistance.

Shot peening is a surface treatment technique that can improve the fatigue performance of metallic materials by introducing compressive residual stresses and modifying the microstructure via grain refinement, phase transformation, texture and/or dislocation structure changes. In this study, a multi-scale modelling framework is developed to understand the evolution of dislocation structures during shot peening of a nickel-based single crystal superalloy. Firstly, explicit finite-element (FE) simulations of the shot peening process are carried out using a Johnson–Cook model calibrated on reported mechanical properties of PWA1484 (Walston et al. In Superalloys 2004 (Tenth International Symposium). TMS, pp 15–24 [1], Cetel and Duhl In Superalloys 1988 (Sixth International Symposium). TMS, pp 235–244 [2]). Instead of using a systematically pre-defined distribution of shots, a random distribution of shot is adopted for these simulations. An Avrami-type equation is used to relate the surface coverage to the necessary peening time and corresponding number of shots (Kirk and Abyaneh in Shot Peen 9:28–30 [3], Pham et al. in Surf Eng 33:687–695 [4]). Various shot peening coverage is modeled by identifying the peening time required for 100%, then using a linear relationship between peening time and coverage. In order to study the effect of shot peening intensity, the initial velocities of shot are chosen according to experimentally measured average shot velocities applied at varying levels of intensity. Figure 1 shows the von Mises stress distribution on shot-peened surface with intensity of 0.15 mmA. During the shot peening process, specimens experience large plastic strain and strain gradient, which induced localized dislocation activity and complex dislocation pattern near the surface. A significant gradient in Geometrically Necessary Dislocations (GND) induced by shot peening from the surface to the bulk has been widely reported (Breumier et al. in Mater Sci Eng A 816 [5]), which is usually correlated to experimentally measured hardening gradient. Thus, in this study, the discrete dislocation plasticity (DDP) model (Giessen and Needleman in Model Simul Mater Sci Eng 3:689 [6]) is adopted in order to explicitly model the activities of individual dislocations in the region of substrate near the peened surface. The DDP model is coupled to the FE simulations of the shot peening process by applying boundary conditions corresponding to the displacement on the top surface, as shown in Fig. 2. The surface strengthening mechanisms of the nickel-based single crystal superalloy under different shot peening conditions are investigated by analyzing the resultant dislocation structures (i.e. Figure 3), dislocation density, slip field and lattice orientations.

In the age of machine learning, data-driven approaches with hybrid data (a mixture of real images and simulation images) are getting increasingly popular. One major issue with creating a realistic simulation for surface engineering is that the surface of the mesh model used in the simulation is smooth. Often, this mesh does not contain information on surface texture; thus, simulating an object based on these meshes may not represent an actual surface texture of a real component. This article presents a novel technique for introducing surface roughness onto a smooth mesh object to facilitate engineering simulation by using a conditional Generative-Adversarial Network (cGAN) that is trained on real height maps to generate random 2D height maps that represents a realistic texture of a typical upskin and downskin surface of an additively manufactured (AM) part. This approach extracted the past scans of AM components from the Focus Variation microscopy. The 3D surface deviation is extracted as height maps and used as the training data for the generative network. This paper will also discuss the structural similarities between the synthetic and real data using standard descriptors for surface texture characterisation, such as $$S_{a}$$ S a , $$S_{q}$$ S q and $$S_{dq}$$ S dq .

An impact of a bubble induced by a submerged pulsed laser is utilized for improvement of fatigue strength of metallic materials. As the bubble induced by the pulsed laser behaves like a cavitation bubble, the laser induced bubble is called as “laser cavitation”. The mechanical surface treatment using the laser cavitation impact is named as “laser cavitation peening”. At laser cavitation peening, the impact induced by laser cavitation collapse strongly depends on the bubble geometry. There are two typical mode at the bubble collapse. One mode is “microjet mode”, at which bubble develops near the target and is collapsed with generating a microjet in the bubble. The other mode is “hemispherical mode”, at which a hemispherical bubble develops on the target surface and is collapsed on the surface. As the bubble collapse of microjet mode is interesting phenomenon, a lot of researchers investigate “microjet mode”. However, impact induced by “hemispherical mode” is significantly larger than that of “microjet mode”. In the present paper, to optimize laser cavitation peening condition, a fluid/material coupled numerical simulation of a bubble collapse near a wall was carried out changing with standoff distance from wall. It was revealed that the equivalent stress induced by hemispherical mode was larger than that of microjet mode.

High entropy alloy nanoparticles (HEA NPs) have recently found tremendous popularity as effective catalysts in water splitting applications, such as oxygen evolution reactions (OERs). HEA NPs that contain expensive and less sustainable noble metals, such as platinum and iridium, as constituent elements are extensively investigated. With consideration of environmental friendliness, we propose a novel and facile approach for the fabrication of CoCuFeMnNi HEA NPs upon conventional carbon cloth (CC) substrates using laser irradiation. Noble metal-free CoCuFeMnNi HEA NPs were synthesized on CC substrates. Characterization using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) confirmed the successful synthesis of the HEA NPs on CC. Preliminary electrochemical results show that CoCuFeMnNi HEA NPs on CC display promising catalytic performance of lower overpotentials during OER tests. These results are competitive with traditionally used RuO2, IrO2, and other novel nanocatalysts in research today. This work can provide evidence that CoCuFeMnNi HEA NPs synthesized by laser irradiation can still perform comparably to conventional noble metal catalysts. It also provides insights into using more sustainable and cheaper nanomaterials as electrocatalysts.

Black nickel plating is a decorative coating typically electrodeposited from an electroplating bath containing nickel and zinc cations. To ensure coating quality, chemical composition and pH value of plating bath should be closely monitored and maintained within the working ranges, especially when an inert anode is used. With plating by using an inert anode, both pH and bath composition will change and eventually drift out of the working range, leading to coating defects. In this paper, we propose a new methodology to tune the black nickel plating bath back to its usable range, by identifying the critical parameters and their limits, and give a recommended sequence for facile tuning to obtain optimal performance in terms of uniform black appearance. The recommended sequence of tuning is to first adjust the pH value, then the zinc concentration, and finally the nickel concentration when they reach their critical limits. The deposited black nickel coatings are characterized using sphere spectrophotometer and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy where the ratio of deposited zinc to nickel is found to be critical for obtaining a uniform and consistent black appearance.

Nickel (Ni) alloy coating with high phosphorus (P), P > 10wt.%, is usually deposited by electroless and electrolytic plating processes and has been widely used for corrosion and wear resistance applications. However, the deposition rate is low and plating tanks with temperature control are required, and not viable for on-site coating and coating repair. The tank-free brush plating is usually controlled by constant voltage and featured with high deposition rate due to high current density (>100 A/dm2), while the current density of conventional tank plating is usually lower than 10 A/dm2. However, the high current density of brush plating leads to a challenge to deposit a high phosphorus (Hi-P) Ni alloy, as the P content in the nickel phosphorus (NiP) alloy coating is inversely proportional to the operating current density based on the tank plating practices. In this paper, we report a brush plating process to deposit high phosphorous nickel thin film on carbon steel coupons. Design of experiments (DOE) was used to optimize the brush plating process, including plating bath formation, and plating parameters. It is found that low pH value and high phosphorous acid (H3PO3) concentration in the plating bath are beneficial for high P content in the NiP deposit. High pH value and low 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) concentration are beneficial for high current efficiency. By using the optimized bath chemistry and plating parameters, NiP coating with P content of 13.7 wt% was deposited on carbon steel coupons with a current efficiency as high as 19.4%.

Electroplated hard metal coatings are sought after for their anti-wear properties and cost-effective deposition process. However, traditional choices like hard chrome and tungsten present challenges in terms of fabrication and environmental concerns. To address this, we explored the electroplating process under a binary sulfamate system to produce a hard Ni-Co alloy coating on metal surfaces. Our findings revealed that the electroplating current density predominantly influenced the hardness of the Ni–Co alloy, with higher current densities resulting in lower Co concentrations. Surprisingly, the composition of the alloy remained consistent regardless of the current density and showed little sensitivity to the Co2+ concentration. The highest hardness value of 608.1 HV0.05, with a Co concentration of 34%, was achieved at a current density of 3 ASD. These results highlight the potential of electroplated Ni–Co alloy coatings as alternatives to traditional options, offering controlled hardness properties and stable compositions. Further research is needed to assess their mechanical properties and applicability in various industries.

Metallisation is the process of applying a metallic coating on the surface of a non-metallic component for structural, functional, or decorative purposes. It can be used to replace metallic parts with metallic-coated polymers with the objective of weight and cost reduction, or to extend the field of application of polymeric components granting them thermal or electrical conductivity. For example, it is used in aerospace applications to provide conductivity as protection against lighting strikes. Cold Spray was demonstrated to be suitable for the deposition of metallic coatings on polymer-based substrates without any prior surface treatment. It can be considered as an environmentally friendly alternative for the traditional electroplating metallisation practices and thermal spray coatings technologies as it is a non-combustion process and any unadhered powder residues can be easily disposed of while the metallisation via Cold Spray of thermoplastic polymers was reported by various authors in the last few years, the coating of thermosetting presents additional challenges that have yet to be fully resolved. In this work, a low-pressure Cold Spray system with a maximum pressure of 6 bar was employed to investigate the challenges associated with the metallisation of an epoxy resin.

Global climate changes and worldwide sustainability are pushing the requirement for advanced manufacturing and remanufacturing in various areas, including aerospace, sea- and land-transport, infrastructure, low-carbon energy, etc. Surface engineering and protective coating (SEPC) are a typical area that deals with the surface finishing and enhancement of metallic components. SEPC has long been developed in traditional manufacturing but attracted increasing interest in recent years along with the rapid advancing in additive manufacturing and remanufacturing. For example, surface enhancement process, when introduced into interpass additive manufacturing, can significantly enhance the whole components with reduced necessity for post-manufacturing treatment. Here, we present and discuss a few surface engineering techniques as well as their potential applications in protective coatings produced by direct energy depositions.

Polymer composite is frequently coated with metals by various metallization processes, one of which is electroless nickel (EN) plating process. EN plating has been accepted by industry as a reliable method to produce the high quality, bright reflective surfaces. Aesthetically, the well-established bright metal finishes also offer plastic components with important functional advantages, such as wear resistance and hygienic properties. To improve EN coating adhesion on the polymer composite, chemical etching is used as the pre-treatment method prior to EN coating. However, the immediate consequence of the chemical etching is the exposure of the composite carbon fibre, leading to poor surface finish. To overcome the challenges, chemical-etching-free pre-treatment methods are desirable. In this paper, the key factors controlling the adhesion of EN coating on carbon fibre reinforced polyetherimide (CF-PEI) were investigated. Surface chemistry at different treatment stages was studied by X-ray photoelectron spectroscopy (XPS) analysis. It is found that reducing palladium (Pd) ions into Pd atoms on the composite surface takes a critical role to develop a good adhesion of EN coating to CF-PEI composite surface. When hypophosphite is used as a reducing agent, elevated temperature increases the density of catalytic Pd metal sites. With a stronger reducing agent sodium borohydride (NaBH4), more adsorbed Pd ions can be reduced at room temperature than the high temperature hypophosphite. Even though NaBH4 is used, there is still more than 30% adsorbed Pd ions yet to be reduced.

Additive manufactured (AM) aluminum alloys show good performance as lightweight critical parts for different industrial applications. However, the poor surface finish of as-printed parts due to the ‘‘Staircase Effect’’ is an obstacle to the implementation of AM for industry practice. In this study, a two-step post processing technique was developed to improve surface finish of 3D-printed AlSi10Mg. In the first step, the as-printed AlSi10Mg sample was chemically etched to remove the outer skin oxide layer and the dangling loose powder particles; in the second step, the chemically treated sample was electrochemically polished in an alkaline electrolyte to further smoothen the surface. The surface morphology of treated and reference parts were observed with SEM; the surface roughness (Ra) was measured with stylus profilometer to understand the smoothening mechanism and the effects of the process parameters. After this post processing treatment, the Ra was found to be typically decreased by at least 50%, for a much-improved surface finish.

The all solid-state lithium metal battery is considered a promising technology for electric vehicles due to its high theoretical capacity. However, during fast charging, the growth of lithium dendrites causes internal short circuits, which limits the charging rate. This study investigates the fast charging performance of sulfide and oxide solid electrolytes, which are representative solid electrolytes, by suppressing crack formation in the electrolyte through shot peening. The results show that shot peening did not increase the charging rate of sulfide solid electrolytes, but increased it by 10 times in the case of oxide solid electrolytes. Shot peening increased the fracture toughness of the oxide solid electrolyte by about 2 times, which is believed to have contributed to the increase in charging rate. The difference in the results for the sulfide and oxide solid electrolytes is due to the difference in their pellet production process. The oxide solid electrolytes are produced by high-temperature sintering, which results in compressive residual stresses that increase fracture toughness when shot peening is performed. However, the sulfide solid electrolytes are formed into pellets by cold pressing, and sintering is not performed after pressing, so there is residual stress by the pressing, resulting in no increase in fracture toughness due to shot peening.

Mechanical surface treatments, as for example machine hammer peening or deep cold rolling, are well known to increase the service life of dynamically loaded parts. Using this increased strength, a part can be designed more resource- or weight efficient. Both parameters are to reduce the carbon-footprint of the part. Within this presentation the effect of deep cold rolling on the overall CO2-footprint will be pointed out. The aim of this project is to identify the main effects on the carbon footprint. Using a life cycle assessment in- and output values are analyzed for different processes and are evaluated for their importance. Additionally, a method will be presented to quickly evaluate the benefits of mechanical surface treatments for any dynamically loaded part within the design phase for the whole life cycle. Within this framework different assumptions can be drawn to increase the quality of the prediction and it will be possible to quickly evaluate if a mechanical surface treatment will be beneficial for the CO2-footprint of a part.

Life Cycle Assessment (LCA) is a methodology employed to evaluate the environmental effects of goods or services over their complete life cycle. LCA reports are key for the industry to assess their contribution on the sustainability. It is a complex and time-consuming process that can be improved with the use of deep learning models due to a large amount of data are involved in prediction. Transformers have been successful in natural language processing and can also be applied to numerical data to predict environmental impacts. By detecting the phases in a product's life cycle that generate the most significant environmental consequences and automating the data compilation and analysis procedures, they can reduce the time and expense connected with LCA. The use of transformers for LCA analysis has the potential to improve the accuracy and efficiency of sustainability assessments, providing more comprehensive information about environmental impacts. Through experimenting with real-world datasets, the proposed transformer framework has been shown to effectively contribute to making informed sustainability-related decisions by providing comprehensive information about environmental impacts. This has the potential to benefit a wide range of industries and sectors, enabling more sustainable development and decision-making.

Surfaces that can keep themselves clean are described as self-cleaning surfaces. Such surfaces have drawn a lot of attention due to their numerous applications in food, aerospace, manufacturing and other industries. Self-cleaning for metals and alloys is usually achieved by creating hydrophobic textured surfaces. However, such surfaces obtained by texturing are unstable as their wettability changes over time. An alternative to creating self-cleaning surfaces is through the photocatalytic effect where a semiconductor material can generate radicals to remove organic contaminants upon the illumination of UV light. We studied the photocatalytic efficiency of TiO2 coating deposited on smooth and textured 316 stainless steel surfaces. Thermal oxidation at different temperatures was explored to study how it affects the photocatalytic efficiency of TiO2 coating. The results showed that the textured surfaces achieved a good bonding of TiO2 coating and a better self-cleaning effect as compared to the smooth samples. Generally, a better self-cleaning effect could be observed for TiO2 films that were obtained by thermally oxidising Ti films at around 500 °C.