Surface Processing Method Research Articles

Transitions in the sliding wear mechanisms of binary Cu-Al alloys having a range of solute contents and microstructures

Sliding wear damage to non-lubricated metallic bearing surfaces results from the dissipation of frictional work. Damage features at or near worn surfaces depend on alloy-specific modes of deformation that are influenced by stacking fault energy (SFE) and other microstructural properties. Metal pairs having similar friction coefficients do not necessarily wear equally due to differences in energy partition. Dissipative mechanisms include highly-deformed layer (HDL) formation, deformation twinning, recrystallization, amorphization, and texturing. In some tribosystems, a portion of the frictional work is dissipated in third-body layers. HDL thickness can vary from grain-to-grain, depending on crystallographic orientation relative to the sliding direction. Thus, the energy used in texturing can also vary grain-by-grain. Composition and surface processing methods affect the manner and degree of friction/wear correlation. Transitions in wear mechanisms are investigated in a series of Cu-Al binary alloys ranging from 0 to 15 wt% Al that are processed by different routes. These bronzes were worn against bearing steels in a non-lubricated block-on-ring configuration. Application of established and less common imaging methods supports the transition from sharpened dislocation cell formation at higher SFE to deformation twinning at lower SFE. At the wear process level, primary and secondary wear debris affect model development because their relative influence changes over time.

Selective Plasma Etching of Polymer-Metal Mesh Foil in Large-Area Hydrogen Atmospheric Pressure Plasma

We present a novel method of surface processing of complex polymer-metal composite substrates. Atmospheric-pressure plasma etching in pure H2, N2, H2/N2 and air plasmas was used to fabricate flexible transparent composite poly(methyl methacrylate) (PMMA)-based polymer film/Ag-coated Cu metal wire mesh substrates with conductive connection sites by the selective removal of the thin (~10–100 nm) surface PMMA layer. To mimic large-area roll-to-roll processing, we used an advanced alumina-based concavely curved electrode generating a thin and high-power density cold plasma layer by the diffuse coplanar surface barrier discharge. A short 1 s exposure to pure hydrogen plasma, led to successful highly-selective etching of the surface PMMA film without any destruction of the Ag-coated Cu metal wires embedded in the PMMA polymer. On the other hand, the use of ambient air, pure nitrogen and H2/N2 plasmas resulted in undesired degradation both of the polymer and the metal wires surfaces. Since it was found that the etching efficiency strongly depends on the process parameters, such as treatment time and the distance from the electrode surface, we studied the effect and performance of these parameters.

THEORETICAL AND EXPERIMENTAL STUDIES ON SLIDING AT LOW SPEEDS WITH INTERMITTENCIES

The guides of the machine tools, brakes, clutches there is the possibility of the intermittent movement of stick-slip. This opens in the case of frictional couples with sliding motion, due to the low sliding speeds. Intermittent slip introduces vibrational phenomena and influences the uniformity of movement and the state of the surface of the couples due to their use. In this respect, the concerns related to the study of this phenomenon represent an interest in the machine building industry. The paper aims to achieve an original theoretical model for calculating the static and kinetic friction coefficients and its experimental verification on a stick-slip stand. The proposed theoretical model establishes the calculation relations of the static and kinetic friction coefficient and the connection between them taking into account the surface processing method. The originality of the approach is that the model is considered friction between the conical penetrator (steel material) and a polymer material. In the literature, the stick-slip phenomenon is approached only in terms of the analysis of flat surfaces. The torques of said materials is frequently used on the parts of sliding machines where this phenomenon is possible. The paper highlights the influence of exploitation factors (load, speed), the processing of surfaces, and the quality of the lubricating liquid on the stick-slip phenomenon, for a friction coupling of polymeric material / metallic material.

Prediction of tensile strength of polymer carbon nanotube composites using practical machine learning method

This paper is devoted to the development and construction of a practical Machine Learning (ML)-based model for the prediction of tensile strength of polymer carbon nanotube (CNTs) composites. To this end, a database was compiled from the available literature, composed of 11 input variables. The input variables for predicting tensile strength of nanocomposites were selected for the following main reasons: (i) type of polymer matrix, (ii) mechanical properties of polymer matrix, (iii) physical characteristics of CNTs, (iv) mechanical properties of CNTs and (v) incorporation parameters such as CNT weight fraction, CNT surface modification method and processing method. As the problem of prediction is highly dimensional (with 11 dimensions), the Gaussian Process Regression (GPR) model was selected and optimized by means of a parametric study. The correlation coefficient (R), Willmott’s index of agreement (IA), slope of regression, Mean Absolute Percentage Error (MAPE), Root Mean Squared Error (RMSE) and Mean Absolute Error (MAE) were employed as error measurement criteria when training the GPR model. The GPR model exhibited good performance for both training and testing parts (RMSE = 5.982 and 5.327 MPa, MAE = 3.447 and 3.539 MPa, respectively). In addition, uncertainty analysis was also applied to estimate the prediction confidence intervals. Finally, the prediction capability of the GPR model with different ranges of values of input variables was investigated and discussed. For practical application, a Graphical User Interface (GUI) was developed in Matlab for predicting the tensile strength of nanocomposites.

Impact Study of Electron-Beam Heating on the Structure and Properties of Boroaluminized Layers Aimed at Producing New Composite Coatings with Special Properties

Abstract Electron-beam processing is a promising method of surface processing. Electron-beam processing can involve surface melting accompanied by adding alloying elements into the melt (electron-beam alloying), or it can be applied to preliminary obtained diffusion layers on a material’s surface (electron-beam chemical thermal processing). Electron-beam heating both increases the temperature and initiates diffusion processes in the metal. By regulating parameters of electron-beam processing, different types of layers—diffusion, diffusion-crystalized, or liquid phase—are formed. The paper presents the study of the impact of electron-beam heating on the structure and properties of boroaluminized layers in carbon steel 60 (0.6 % carbon), obtained by thermochemical processing (solid-phase boroaluminizing in powder mixture 98 % (70 % aluminum oxide Al2O3) + 10 % boron oxide (B2O3) + 20 % aluminum (Al) + 2 % sodium fluoride (NaF) at T = 950°C, τ = 4 h). The authors studied the influence of electron-heat processing modes on the formation of boroaluminized layers’ structure. The parameters of electron-beam heating were beam current Ic = 20–60 mA and time of impact τ = 15–120 s. The authors conducted metallographic and X-ray microscopic analysis and measured microhardness of boroaluminized layers obtained with a combined method (thermochemical processing and electron-beam heating). It was shown that electron-beam heating of boroaluminized layers leads to changes in the structure and properties as well as in the layer’s morphology. Aluminum is spread evenly in the depth of the layer. The layer’s microhardness changes and the brittleness decreases. The obtained results led to the conclusion that electron-beam heating can be recommended to improve properties of boroaluminized layers and used as a foundation for producing new composite coatings with special properties.

Laser-interference pulse number dependence of surface chemistry and sub-surface microstructure of AA2024-T3 alloy

The laser-based treatment of a metal surface is an intrinsically non-chemical technique that can alter both the topology and chemistry of surfaces. A laser-based treatment for coating and joining applications can offer alternative surface preparations to the chemically-based surface preparation techniques, which are subject to severe environmental protection and hazardous-waste management considerations. In this study, the surface chemistry and sub-surface microstructural changes are investigated for a novel surface processing method using laser interferometry produced by two beams of a pulsed Nd:YAG laser. The two-beam laser-interference allowed the structuring of the surface at length scales much less than that of the laser beam spot. Surface chemistry changes in the oxide layer of AA 2024-T3 aluminum alloy rolled sheet due to laser processing were investigated using x-ray photoelectron spectroscopy (XPS). Near surface microstructural changes have been investigated with scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM/EDS), and scanning transmission electron microscopy (STEM) as a function of number of interfering laser shots. SEM microstructure pictures of the top surface shows the minimization of surface defects, as all of the sharp features from a rolled sheet surface were smoothed by laser-structuring. STEM images indicate that the laser-interference processing reduced the formation of CuMn-rich precipitates over a 500–800 nm depth from the top surface. XPS data indicated that the Al oxide layer is modified compared to that of the baseline specimen and that the oxide thickness increases with the number of shots per spot. The additional thicker oxide on Al alloys is expected to increase the corrosion resistance of the coated Al 2024.

Silver Surface Treatment of Cu(In,Ga)Se2 (CIGS) Thin Film: A New Passivation Process for the CdS/CIGS Heterojunction Interface

The interface engineering of Cu(In,Ga)Se2 (CIGS)‐based solar cells is challenging for high‐efficiency devices, especially for the CdS/CIGS heterojunction interface. Recently, post‐treatment of the CIGS surface, as an efficient approach to passivate the defects at the CdS/CIGS interface, has attracted widespread attention. Here, a simple Ag surface treatment process is used to realize the passivation of interface defects and the enhancement of the CdS/CIGS heterojunction. This process not only reduces the surface roughness of CIGS films significantly, but also contributes to controlling the Ga composition in the surface layer. Furthermore, characterization techniques reveal that Ag surface treatment can effectively decrease the defect concentrations at the heterojunction interface and enhance the CdS/CIGS heterojunction quality with appropriate Ag deposition duration. Further investigations on the changed defect level caused by the Ag surface treatment indicate that the increased defect level is likely related to the shift of valence band maximum. Eventually, the efficiency of the optimum device has a relative increase of about 18% compared with that of the reference solar cell. This work focuses on revealing the differences of the CIGS surface and CdS/CIGS interface caused by Ag, which provides a new surface processing method for the passivation of the CdS/CIGS heterojunction.

Research on VOCs Treatment of Electrophoresis Coating Process

The coating process is the main source of VOCs emissions in the aluminium profile industry. The electrophoretic coating process is a surface processing method widely used by aluminium profile companies. However, the electrophoretic coating process generates a large amount of exhaust gas, and the main component of the exhaust gas is VOCs. This paper combined with the monitoring of the exhaust gas treatment project of an electrophoresis coating workshop of a large aluminium profile company, and found that the main component is xylene. The exhaust gas treatment process uses “activated carbon adsorption + spray absorption” and more than 97% of emissions could be achieved.

Improved fatigue strength of additively manufactured Ti6Al4V by surface post processing

A major challenge for additively manufactured structural parts is the low fatigue strength connected to rough as-built surfaces. In this study, Ti6Al4V manufactured with laser powder bed fusion (L-PBF) and electron beam powder bed fusion (E-PBF) have been subjected to five surface processing methods, shot peening, laser shock peening, centrifugal finishing, laser polishing and linishing, in order to increase the fatigue strength. Shot peened and centrifugal finished L-PBF material achieved comparable fatigue strength to machined material. Moreover, the surface roughness alone was found to be an insufficient indicator on the fatigue strength since subsurface defects were hidden below smooth surfaces.

Verification of stiffness and surface treatment of axial bearing levers by static tests

To eliminate misalignment between stator and rotor (especially in large rotary machines) the thrust bearing with a system of very precise manufactured levers has started to be used. The article deals with the static tests of self-equalizing elements (levers) made of 34CrNiMo6 steel, which are the critical parts of a newly developing self-equalizing thrust bearing. To verify the stiffness of the newly designed levers by static tests, the real levers were produced, which according to preliminary experiments and numerical simulations have the potential to be used the most in turbines. Based on basic tests of the pairs samples, that represent types of geometries going in contact within real conditions, it was found out that in terms of the surface treatment, the best results show electroless nickel-plated samples. So, due to this reason, the real levers were produced and their surfaces were processed in this way by electroless nickel-plating. Within the presented research, they were statically tested intending to determine the surface integrity and whether there was any development of damage to the surface layer. The evaluation was done using a stereomicroscope and a scanning electron microscope. The tests confirm sufficient rigidity of the levers including a suitable method of surface processing. Although, in some cases, these were surface defects caused by surface treatment technology, but no defects were found after static loading.

Prediction Model of Material Removal for Polishing Single Crystal Silicon by Cluster Magnetorheological Finishing with Dynamic Magnetic Fields Based on BP Neural Network

Magnetorheological Finishing (MRF) is a new optical surface processing method, which has the advantages that good polishing effect, no subsurface damage, and suitable for complex surface processing. However, the interaction mechanism between the MRF pad and the workpiece is very complicated, so that the existing MRF material removal theoretical model is not accurate enough to establish the relationship between polishing parameters and material removal. In order to improve the processing efficiency and explore the material removal mechanism, a cluster magnetorheological finishing (CMRF) with dynamic magnetic fields method was proposed. Studying CMRF with dynamic magnetic fields material removal model is helpful to explain the removal mechanism more deeply, and improve the processing efficiency. In this study, the CMRF method was used to conduct a multi-factor orthogonal test on 2-inch single crystal silicon wafers. Based on the empirical Preston equation, the relationship between the machining gap and the polishing pressure was explained. Orthogonal experiments were done for a series of speeds, and obtaining the order of the influence of various factors on the average surface roughness <i>Ra</i> of the workpiece was: workpiece rotation speed > polishing disk speed > magnetic poles rotation speed > oscillating speed; the material removal rate (<i>MRR</i>) was: polishing disk speed > workpiece rotation speed > magnetic poles rotation speed > oscillating speed. Then combining with the orthogonal experimental data, and taking the surface roughness <i>Ra</i> and <i>MRR</i> as evaluation criteria, using Adam (Adaptive momentum) optimization algorithm to build a prediction model of <i>Ra</i> and <i>MRR</i> for polishing single crystal silicon by CMRF with dynamic magnetic fields based on BP neural network. For the prediction result, <i>Ra</i> of the maximum error was 7.05%, the minimum was 0.31%; <i>MRR</i> of the maximum error was 10.22%, the minimum was 1.32%. Therefore, the feasibility of this model for predicting the results of CMRF was verified, and it laid a good foundation for the development of CMRF technology and its industrial application.

Flexible Insole Sensors with Stably Connected Electrodes for Gait Phase Detection.

Gait analysis is an important assessment tool for analyzing vital signals collected from individuals and for providing physical information of the human body, and it is emerging in a diverse range of application scenarios, such as disease diagnosis, fall prevention, rehabilitation, and human–robot interaction. Herein, a kind of surface processed conductive rubber was designed and investigated to develop a pressure-sensitive insole to monitor planar pressure in a real-time manner. Due to a novel surface processing method, the pressure sensor was characterized by stable contact resistance, simple manufacturing, and high mechanical durability. In the experiments, it was demonstrated that the developed pressure sensors were easily assembled with the inkjet-printed electrodes and a flexible substrate as a pressure-sensitive insole while maintaining good sensing performance. Moreover, resistive signals were wirelessly transmitted to computers in real time. By analyzing sampled resistive data combined with the gait information monitored by a visual-based reference system based on machine learning method (k-Nearest Neighbor algorithm), the corresponding relationship between plantar pressure distribution and lower limb joint angles was obtained. Finally, the experimental validation of the ability to accurately divide gait into several phases was conducted, illustrating the potential application of the developed device in healthcare and robotics.

Surface nanocrystallization of sintered Nd-Fe-B magnet by HDDR process

A novel practice of surface nanocrystallization (SNC) to protect sintered Nd-Fe-B magnet from corrosion was achieved by a controlled hydrogenation-disproportionation-desorption-recombination (HDDR). The SNC magnet showed much better corrosion resistance compared with the originally unprocessed. The nanocrystallized surface of 50 μm thick layer with dispersed Nd-rich intergranular phases played crucial role in blocking intergranular corrosion. For SNC magnet, corrosion test showed a highly oxidized and chemically homogeneous film had formed preventing corrosion deep inwards. Hardness testing revealed the surface was strengthened showing a totally different cracking pattern. To verify its applicable ability, the influences of hydrogen reaction with bulk magnet on microstructures and magnetic properties in different depth were studied. For a large-sized magnet, the detrimental effects were almost negligible. This technique could be a possible new method of surface processing utilized in large bulk Nd-Fe-B magnet for good corrosion resistance and surface strength.

Optical inspection of cutting parts by 3D scanning

In this paper was presented 3D scanning application of dimensional inspection of parts obtained by cutting process. The dimensional and geometric deviations of cylindrical shoots of aluminum alloy parts, machined by applying different milling parameters, were measured using the coordinate measuring machine (CMM), PC DMIS software, three different optical scanners and GOM Inspect software. Results obtained using CMM were selected for reference and their comparison with the results obtained with scanners was conducted. It was noted that the differences between measured deviations exist and that further research should be focused on more precise defining and monitoring of conditions in measurement environment as well as the selection of the method of approximation and surface processing in order to increase the accuracy of the inspection with the 3D scanning device. A brief overview of the inspection procedure, inspection devices, scanning and surface reconstruction was also provided as well as the existing software applications for inspection.

Numerical analysis of T-groove dry gas seal with orientation texture at the groove bottom

The influences of groove bottom texture, in the form of orientation structure with various width, depth, spacing, and different operation parameters, on orientation effect have been investigated by numerical analysis. The results show that the existence of texture and the change of direction have strong impacts on the orientation effect, and opening force and leakage increase due to the effect. The increment in the opening force and leakage is more remarkable when film thickness is small and the shaft speed or medium pressure is high. The orientation texture makes the performance of dry gas seal more stable, which is more significant for extreme working conditions. An optimal texture model was built and an efficient and cost-saving method of laser surface processing for the orientation texture was put forward.

Friction stir vibration processing: a new method to improve the microstructure and mechanical properties of Al5052/SiC surface nanocomposite layer

Friction stir processing (FSP) is a surface processing method to modify the microstructure and enhance the mechanical properties of metal surface. This process is also numerated as a method to incorporate second-phase nanoparticles into microstructure and form surface composites. In the current research, the work specimen is vibrated normal to processing line during FSP. Transverse and rotation movements of shoulder are accompanied with vibration motion of specimen. This new process is entitled FSVP (friction stir vibration processing). The effect of FSP and FSVP processes on microstructure and mechanical properties of Al5052 alloy matrix composite incorporated SiC nanoparticles is analyzed. The results show that the presence of vibration during FSP leads to the grain size decrease in the stir zone and it enhances the homogeneity of particle distribution. The results indicate that strength and ductility of friction stir (FS) processed specimens are lower than those processed by FSVP. These are related to increased deformation and strain of soft material in the stir zone as vibration is applied which promotes the dynamic recovery and recrystallization during FSP. The results also imply that the microstructure is refined more and the strength and the hardness of friction stir vibration (FSV) processed specimens increase as vibration frequency enhances.

Modifying the electrode-electrolyte interface of anode supported solid oxide fuel cells (SOFCs) by laser-machining

The NiO-yttrium stabilized zirconia (YSZ) anode substrates prepared by tape casting are modified via laser-machining technique in mesoscale for electrode-electrolyte interface modification. Two different surface processing methods are applied: (i) scanning the whole surface with continuous tracks to produce a “coarser” surface; (ii) engraving spots on the substrates surface forming “pits array”. The microstructure and electrical performance of the cells based on these anode substrates are investigated. For the scanned anode, confocal laser scanning microscope (CLSM) images show that the surface roughness increases with the laser intensity. The scanning electron microscopy (SEM) images of single cells show that electrode-electrolyte interface contact area is increased. Compared with the unmodified cell, the maximum power density of the cells fabricated with “coarser” anode substrates is improved by 47% at 800 °C. For the second case, the SEM images of cross-section of single cells show that the electrode-electrolyte interface is wavy, resulting increase in the electrochemically active area. It’s found that the degree of performance enhancement of the cells is related to the pits size, and a suitable diameter and depth of the pits are needed. The highest power density of the cells with “pits array” increases by 55% at 800 °C. In both cases, electrochemistry impedance spectroscopy (EIS) results show that ohmic and polarization resistances of single cells are decreased after modification.

Precise photorealistic visualization for restoration of historic buildings based on tacheometry data

This paper puts forward a 3D reconstruction methodology applied to the restoration of historic buildings taking advantage of the speed, range and accuracy of a total geodetic station. The measurements representing geo-referenced points produced an interactive and photorealistic geometric mesh of a monument named ‘Neoria.’ ‘Neoria’ is a Venetian building located by the old harbor at Chania, Crete, Greece. The integration of tacheometry acquisition and computer graphics puts forward a novel integrated software framework for the accurate 3D reconstruction of a historical building. The main technical challenge of this work was the production of a precise 3D mesh based on a sufficient number of tacheometry measurements acquired fast and at low cost, employing a combination of surface reconstruction and processing methods. A fully interactive application based on game engine technologies was developed. The user can visualize and walk through the monument and the area around it as well as photorealistically view it at different times of day and night. Advanced interactive functionalities are offered to the user in relation to identifying restoration areas and visualizing the outcome of such works. The user could visualize the coordinates of the points measured, calculate distances and navigate through the complete 3D mesh of the monument. The geographical data are stored in a database connected with the application. Features referencing and associating the database with the monument are developed. The goal was to utilize a small number of acquired data points and present a fully interactive visualization of a geo-referenced 3D model.

Comparative study of the heating surface impact on porous-material-involved spray system for electronic cooling – an experimental approach

A spray cooling system integrated with porous material was previously studied with an emphasis on the space-oriented application. As an extension, this paper presents a comparative study of cooling performances of three target surface processing methods (S1, S2 and S3). Among them S1 is a normal naked flat surface which functions as a reference. The latter two adopt phase-change microfluidic cooling tactics using porous foamed copper (PFC) which can realize liquid loop control and vapour-liquid separation in various gravitational field due to favourable characteristics possessed by porous meteal materials such as the capillary force and superhydrophilicity. Different from our previous study which centres on S3, the present one also includes thermal tests on S1 and S2. Results of the experiment and related comparative studies of the three surface processing methods are presented as well where effects of mass flow rate and spray distance upon heat transfer characteristics on the cooling performance are disclosed. Conclusions can be drawn that the S2 has the best cooling performance since the maximum heat flux can reach 470.9 W/cm2 under the given operation condition. An enhancement of 125.3% in terms of the maximum heat flux is attained compared with that for the S3 and 24.58% for the S1. The comparative study illustrates that the S2 is a relatively efficient form in cooling performance which retains properties that a space-oriented system should possess while eliminates the shortcomings such as reduced droplet impingement and huge thermal resistance when a layer of PFC is applied as well. In addition, empirical correlations based on experimental results for S2 and S3 are developed under the dimensionless study for the performance prediction with the relative errors of only ±1.84% and ±1.50% respectively.

Laser Microsphere Lens Array Fabrication of Micro/Nanostructures with Tunable Enhanced SERS Behavior in Dipole Superposition Plasmon Mode

Silicon-based surface-enhanced Raman scattering (SERS) substrates with high sensitivity and uniformity were obtained by a laser surface processing method utilizing microsphere sphere lens arrays followed by chemical etching and silver (Ag) deposition. High SERS performance of these substrates was demonstrated by their enhancement factor of up to 8.2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> for rhodamine 6G (R6G) as well as their ability to detect 1 nM of R6G and 10 ppm of fenthion by a rapid drop-evaporation detection method. A dipole superposition plasmon mode due to a novel Ag microflower structures formed on the top of microvolcano microstructures fabricated before Ag deposition was found to be responsible for the SERS enhancement. The height of the Ag microflowers was not determined by Ag deposition thickness but by the height of the microvolcanoes, which could be easily tuned by laser power, microsphere size, and alkali etching time; tunable SERS performance was also achieved. The developed approach provides a cost-effective way to prepare large-area 3-D solid SERS substrates to adapt to multiple species of probe molecules and different excitation wavelength ranges with high controllability and reproducibility.