Surface Finishing Process Research Articles

Spot conductance measurement of aluminum alloys at cryo-temperatures under varying pressure conditions

Thermal contact conductance (TCC) is a key parameter, which influences the reliability of various cryogenic systems. The accurate estimation of TCC is a basic requirement for the optimal design of cryogen-free conduction cooling systems. The lack of reliable TCC results for bare demountable aluminium contacts in the sub-ambient temperature range (50–300 K) prompted us to undertake the systematic experimental investigations. A unique experimental setup has been fabricated to carryout axial heat transfer experiments, which is used for the estimation of TCC between aluminum contacts in the temperature range of 50–300 K. The influence of changing interfacial temperature (50–300 K), interfacial pressure (0.5–12 MPa), and surface roughness parameters (σ = 1.51 to 11.06 μm), as well as the surface finishing process on TCC have been investigated systematically. The finite element (FE) rough surface contact analysis has also been carried out, and real contact area and the TCC has been estimated over the range of interfacial pressure and temperature under considerations. The real contact area was found to be less than 0.1% of the nominal area, even at 12 MPa, and it varies almost linearly with temperature and pressure. The FE estimates of TCC has shown a good agreement with experimental TCC results. Finally, an empirical correlation of TCC has been proposed by incorporating three of the functional parameters, while considering temperature-dependent thermo-mechanical properties into the analysis.

A profile shaping and surface finishing process of micro electrochemical machining for microstructures on microfluidic chip molds

In the lithography-based fabrication process of microstructures on microfluidic chip molds, the shortcoming of limited substrate materials seriously shortens the service lifetime of the mold. This research focuses on a profile shaping and surface finishing process of micro electrochemical machining (ECM) for microstructures with targeted dimensional and geometrical characteristics on the mold steel S136H. The effects of parameters on the material removal region and single-layer depth are firstly investigated. The sidewall taper of the machined groove increases with the machining voltage and decreases with the scanning velocity. Besides, the bottom surface quality is improved with increasing path spans. Then, the mathematical models of the material removal region and single-layer depth are analyzed, which are regarded as guidance for path planning and parameter optimization. In ECM experiments, a relatively higher machining voltage (20 V) is utilized to rapidly machine basic profiles of the designed flow resistor in the profiles shaping procedure. Sloping sidewalls and rough surfaces are finished by using a lower machining voltage (14 V) and a higher scanning velocity (500 μm s−1) in the surface finishing procedure. As a result, the specially designed flow resistor with a dimensional deviation < 10 μm, and surface roughness Ra < 500 nm is obtained. The proposed ECM process is proved to machine microstructures with high precision and curve profiles on the mold steel.

Review on Surface Quality Improvement of Additively Manufactured Metals by Laser Polishing

Additive manufacturing enables the manufacturing of parts with complex geometries that are not easy to be manufactured by conventional methods such as machining or forging. Despite their numerous advantages, additive manufacturing methods have some drawbacks, such as poor surface quality as a primary concern. Parts with high surface roughness tend to show poor fatigue resistance; thus, they cannot be reliable under dynamic load conditions. Therefore, additively manufactured parts should be subjected to additional surface finish operations to improve surface quality and eliminate the negative effects of surface roughness. In this review, one of the most popular methods among modern surface finish processes, known as laser polishing, has been discussed. Process parameters, changes in processed part morphology, and applications along with the advantages and limitations of the method have also been explained to have a good understanding of the importance of this promising method.

Gold, Silver, and Electrum Electroless Plating on Additively Manufactured Laser Powder-Bed Fusion AlSi10Mg Parts: A Review

Additive manufacturing (AM) revolutionary technologies open new opportunities and challenges. They allow low-cost manufacturing of parts with complex geometries and short time-to-market of products that can be exclusively customized. Additive manufactured parts often need post-printing surface modification. This study aims to review novel environmental-friendly surface finishing process of 3D-printed AlSi10Mg parts by electroless deposition of gold, silver, and gold–silver alloy (e.g., electrum) and to propose a full process methodology suitable for effective metallization. This deposition technique is simple and low cost method, allowing the metallization of both conductive and insulating materials. The AlSi10Mg parts were produced by the additive manufacturing laser powder bed fusion (AM-LPBF) process. Gold, silver, and their alloys were chosen as coatings due to their esthetic appearance, good corrosion resistance, and excellent electrical and thermal conductivity. The metals were deposited on 3D-printed disk-shaped specimens at 80 and 90 °C using a dedicated surface activation method where special functionalization of the printed AlSi10Mg was performed to assure a uniform catalytic surface yielding a good adhesion of the deposited metal to the substrate. Various methods were used to examine the coating quality, including light microscopy, optical profilometry, XRD, X-ray fluorescence, SEM–energy-dispersive spectroscopy (EDS), focused ion beam (FIB)-SEM, and XPS analyses. The results indicate that the developed coatings yield satisfactory quality, and the suggested surface finishing process can be used for many AM products and applications.

Fluidised bed finishing process for aeronautical applications: Environmental and technical-economic assessment

The manual surface finishing process of aeronautical stators is time consuming and expensive. Moreover, this process is difficult to control and automate. To overcome these problems, this paper presents an innovative fluidised bed finishing process applied to turbine blades capable of guaranteeing compliance with the specifications in the absence of processing waste. Compared to the manual process performed by an individual operator, the fluidised bed process ensures the same quality in terms of surface roughness, with values of approximately 1 μm. It reduces the finishing costs of a single stator by approximately 80%, i.e., from € 769 to € 159, and increases productivity from approximately 42 units per year by manual processing to approximately 372 units. The significant increase in productivity is due to the possibility of processing an entire stator within the designed fluidised bed system. Despite an increase in the required investment costs, i.e., € 35,200 against € 1,000, the fluidised bed process guarantees a reduction in the main production cost items compared to that cost of a manual process, i.e., in terms of manpower (€ 2,703 vs. € 23,097) and processing materials (€ 4,346 € vs. € 6,906); this result, in combination with a significant increase in productivity, allows us to realise much cheaper processing than that with traditional methods. The performed life cycle assessment shows the excellent eco-sustainability of the fluidised bed process, and the corresponding environmental impact is much lower than that of the studied manual process, with a reduction of approximately 45% in the overall damage score, i.e., 11.598 pt vs. 21.094 pt. The traditional process is penalised above all by the considerable consumption of raw materials, i.e., 12.125 pt vs. 6.030 pt, which strongly affects the overall environmental impact. The fluidised bed process overcomes this problem and does not produce waste thanks to its high degree of automation and repeatability, therefore improving profits.

Novel Approach to Improve the Optical Performance by Machining Process Without Surface Finishing

With the increase in dimensions of optical elements in addition to ever rising demand for aspherical optics, the millimeter-scale periodic waviness that is naturally produced by machining (such as diamond turning) process in precision optical engineering has been one of the most crucial issues in the development of high surface quality optical elements. Even an extremely small waviness can affect the laser beam profile significantly through interference caused by Bragg scattering. This paper presents a novel method for improving a laser beam profile by utilizing the characteristics of Bragg scattering without requiring established final surface finishing processes such as optical polishing. By engraving an artificial periodic structure with a period of a few hundred microns, the Bragg scattering angle that influences the formation of interference fringes in the laser beam profile was drastically enlarged. Consequently, the quality of the beam profile was improved at a propagation distance where the 0th and 1st (− 1st) order beam modes are spatially separated, only by diamond turning machining without the surface finishing process. In addition, this approach represents an important contribution to green technology, which seeks energy saving and waste reduction in the optical surface manufacturing process.

Improving the surface quality and mechanical properties of selective laser sintered PA2200 components by the vibratory surface finishing process

This paper attempts to improve the physical and mechanical properties of selective laser sintered polyamide PA2200 components through a vibratory surface finishing process by inducing severe plastic deformation at the outer surface layers. The industrial target of additive manufacturing components is to obtain structures having surface roughness, hardness, and other mechanical properties equivalent to or better than those produced conventionally. Compared to the as-built SLS PA2200 samples, vibratory surface finishing treated specimens exhibited a smooth surface microstructure and more favorable roughness, hardness, and tensile strength. Also, the duration of the vibratory surface finishing process showed a further improvement in the surface roughness and hardness of the SLS samples. Compared to the as-built state, the roughness and hardness of the surface-treated samples improved by almost 90% and 15%, respectively. Consequently, microstructural analysis indicates that lower surface roughness and enhanced surface hardness is a crucial factor in influencing the overall tensile strength of SLS-PA2200 components. We consider that the combination of VSF and SLS processes can successfully handle a wide range of potential applications. This study also highlights the efficiency and applicability of the vibratory surface finishing process to other additive manufacturing processes and materials.Graphic abstract

Experimental studies on material removal behavior in MRAH based finishing technique

ABSTRACT Since the invention of Magneto-rheological abrasive honing (MRAH), it is realized as one of the innovative ultra-precise surface finishing techniques employed for finishing of external intricate surfaces. In this technique, required level of finishing is achieved by assigning simultaneous rotation and reciprocating motion to the workpiece and magneto-rheological fluid, respectively. To recognize the surface finishing process, detailed understanding of material removal mechanism with consequences of various machining parameters on material removal (MR) is essential. Planned experiments (using response surface methodology) were conducted on the brass workpiece with varying rotational speed, finishing time, and magnetic field strength. ANOVA was employed to investigate the influence of chosen parameters on response. From experiments, rotational speed was detected as the most influencing parameter trailed by magnetizing current and finishing time. This paper presents material removal behavior and its mechanism in case of brass workpiece finished by MRAH process.

Experimental study on the cutting responses and surface integrity of side milled in situ TiB2/Al composites

Research on the machinability of particle-reinforced Al matrix composites (PRAMCs) is significant to their industrial applications. In the present article, the side milling process of two in situ TiB2/Al composites (in situ 6% TiB2/2024 Al composite and in situ 4% TiB2/7075 Al composite) and the corresponding Al alloys (2024 Al alloy and 7075 Al alloy) were investigated. Cutting responses, including milling force and temperature, were monitored and analyzed. Surface integrity, including roughness, topology, morphology, microstructure, and residual stress of the machined samples, was comprehensively characterized and analyzed. Results showed that, by adjusting the process parameters in appropriate ranges, the milling force and temperature of in situ TiB2/Al composites can be controlled at almost the same level of those of conventional Al alloys. Besides, in situ TiB2/Al composites showed better surface finish and larger process window than conventional Al alloys, which can be helpful for the side milling of precision parts, especially for ensuring the high surface quality of the workpiece without special setting of the process parameters. It is worthy to be noticed that side milling can make the TiB2 particles distribute more evenly on the sample surface, which can be beneficial to the comprehensive surface mechanical properties of the in situ TiB2/Al composites.

Multi-Response Optimization of Magnetic Abrasive Flow Finishing Process on Aluminum (6061-T6) Using Utility Concept Embedded Firefly’s Algorithm

Surface finish is the most desired properties of any sophisticated machinery parts for its proper functioning and long endurance. The surface finish must be in the order of micrometer to nanometer for most of the machinery parts. The nontraditional surface finish processes prepare these parts; in these processes, the uses of electromagnet play a vital role in the surface finishing mechanism. Magnetic abrasive flow finishing (MAFF) is such a hybrid process, which gives a combined effect of abrasive flow finishing (AFF) and magnetic abrasive finishing (MAF). In this method, a pair of electromagnets are attached to the AFF setup. By using electromagnet in the AFF process, it enhanced material removal and surface finishing. The main process parameters selected in the MAFF process were magnetic flux density, number of cycles, percentage abrasive content, piston speed, and corresponding responses selected were material removal, percentage improvement in surface finish. In this research paper, the responses were optimized by a combination of utility theory and meta-heuristic firefly’s algorithm. The utility theory based-firefly algorithm’s predicted global optimum parameters set, which was more suitable for reducing the finishing time and required surface finish. The confirmatory test validated this optimized parameter set and it was revealed that the meta-heuristic firefly algorithm embedded with utility theory had given optimized results in the MAFF process.

Investigation on Finishing Characteristics of Magnetic Abrasive Finishing Process Using an Alternating Magnetic Field

The magnetic abrasive finishing (MAF) process is an ultra-precision surface finishing process. In order to further improve the finishing efficiency and surface quality, the MAF process using an alternating magnetic field was proposed in the previous research, and it was proven that the alternating magnetic field has advantages compared with the static magnetic field. In order to further develop the process, this study investigated the effect on finishing characteristics when the alternating current waveform is a square wave. The difference between the fluctuation behavior of the magnetic cluster in two alternating magnetic fields (sine wave and square wave) is observed and analyzed. Through analysis, it can be concluded that the use of a square wave can make the magnetic cluster fluctuate faster, and as the size of the magnetic particles decreases, the difference between the magnetic cluster fluctuation speed of the two waveforms is greater. The experimental results show that the surface roughness of SUS304 stainless steel plate improves from 328 nm Ra to 14 nm Ra within 40 min.

Influence of the DIN 3962 Quality Class on the Efficiency in Honed Powder Metal and Wrought Steel Gears

To increase the efficiency of a gearbox, research on gear mesh loss is of importance. Britton et al. concluded that the surface finishing method affects the gear mesh efficiency. The efficiency benefits of superfinishing a surface and reducing the surface roughness have been reported by Kahraman. A novel method for calculating the bearing loss torque was proposed by Tu et al. Andersson et al. found that the efficiency can vary between 2 and 5% during repeated efficiency tests due to variations in the assembly process. This work investigates how the honing surface finishing process and DIN 3962 quality class affect the gear mesh efficiency by performing tests in an FZG back-to-back test rig. Two materials, a powder metal and a wrought steel, were tested. All gears were finished using a honing process and sorted according the measured quality class. Powder metal gears of class 6, 7, 8, and ≥9 and wrought steel gears of class 6, 7, and ≥9 were tested. The efficiency were calculated from measuring the torque required to maintain a constant velocity of the FZG test rig. The results from the efficiency tests showed no significant difference in efficiency between the wrought steel and powder metal steel gears. In addition, no obvious correlation between the DIN 3962 quality class and the gear mesh efficiency could be found. When examining the wrought steel material it was found that the reproducibility of the efficiency was comparable to the assembly error of the test rig, despite the variation in quality class.

Electrochemical deburring - A comprehensive review

Recent developments in precision manufacturing along with miniaturization of parts have put strict requirements on edge and surface finishing processes. It not only requires clean and defect free surfaces but also maintain previously generated precision dimensions on advance engineering material. The burr is undesired but inevitable, real productivity killer and amid the most worrying obstructions to mechanization of machining processes, hence affecting quality. Deburring and edge quality is of concern for the performance, cost, safety and appearance of the parts. Over the years electrochemical deburring (ECD) has emerged as a tool for removal of the burrs and retain the requisite edge tolerances exclusive of damaging formerly generated precision dimensions. Conventional ECD process working on the electrochemical principle has been now coupled with faradayic technology to enhance process capability. It is well known that ECD process works for conductive work materials and in specific applications. This review encompasses fundamental principle, parametric analysis and capabilities of the ECD processes that have been evolved through cross innovations. It also critically analyzes mathematical approaches for the modeling of the process in conjunction with their key formulations. Further it discusses the areas which need to be explored.

Effect of Corrosion and Surface Finishing on Fatigue Behavior of Friction Stir Welded EN AW-5754 Aluminum Alloy Using Various Tool Configurations

In this study, fatigue behavior of surface finished and precorroded friction stir welded (FSW) specimens using various tool configurations were comparatively investigated by the load increase method. The FSW using conventional, stationary shoulder and dual-rotational configurations was carried out by a robotized tool setup on 2 mm EN AW-5754 aluminum sheets in butt joint formation. After extraction of the specimens, their weld seam and root surfaces were milled to two different depths of 200 µm and 400 µm to remove the surface and the FSW tool shoulder effects. This surface finishing process was performed to investigate the effect of the surface defects on the fatigue behavior of the FSW EN AW-5754 aluminum alloy sheets. It was found that material removal from the weld and root surfaces of the specimens, increased the fracture stresses of conventional and dual-rotational FSW from 204 to 229 MPa and 196 to 226 MPa, respectively. However, this increase could not be detected in stationary shoulder FSW. Specimens with finished surfaces, which showed superior properties, were used in salt spray and cyclic climate change test to investigate the effect of corrosion on the fatigue behavior of FSW specimens. It was shown that cyclic climate change test reduced the fatigue properties of the base material, conventional, stationary shoulder and dual-rotational FSW approximately 1%–7%. This decrease in the fatigue properties was greater in the case of the salt spray test, which was 7% to 21%.

Synthesis and Characterization of Sintered Magnetic Abrasives Used in Advance Finishing Processes Through Powder Metallurgy Route

The magnetic field-assisted surface finishing process needs a sintered magnetic abrasive powder which could be a mixture of SiC and CIP particles. Tube furnaces have been used to develop SiC-based sintered magnetic abrasives. The focus of this article is to investigate the anticipated results and to carry out the fabrication setup of sintered magnetic abrasive for the super-finishing of composite materials and their coating. The article depicts a significant effect on the mechanical properties such as microhardness and compressive strength and analyzes SiC and CIP composite-based microstructure. The synthesis of the powder involves four major processes like blending; compaction and sintering. Characterization of sintered magnetic abrasives has been done using SEM, EDS, XRD to study morphology, chemical composition, crystallography, and magnetic properties. The results have been compared with the un-bonded magnetic abrasives. This paper also presents a brief literature review of the state-of-the-art technology of high-performance surface finishing processes used in manufacturing industries. Finally, the downside and stray aspects of the related literature are spotlighted and a list of prospective issues for future research directions is recommended.

Study on improving hole quality of 7075 aluminum alloy based on magnetic abrasive finishing

Based on the mechanism of magnetic abrasive finishing, the 7075 aluminum alloy (Al7075) was used in the experimental study. In order to improve wall surface quality and to remove the edge burrs of the hole, a novel magnetic abrasive finishing process was proposed. First, the radial magnetizing pole for the inner surface finishing process was confirmed. The evaluation of magnet spinning speed, abrasive mesh, and abrasive filling amount on the diameter deviation of the hole and surface roughness of the inner wall was studied. According to the characteristics of magnetic abrasive finishing process, Taguchi’s method was used to carry out the test. Through the analysis of variance, the best process parameters were determined and verified. The inner surface roughness was further decreased and the surface morphology was more uniform after finishing process. Second, the edge burr removal process of the hole exit was also studied, and the geometry of the burrs was measured before and after the magnetic abrasive finishing process. The results show that the burrs were significantly removed and the burr removal efficiency was improved by 33.3% compared with the conventional magnetic abrasive finishing process. Finally, the improved magnetic abrasive finishing process is an effective method in improving finishing quality of the Al7075 holes.

Gold–Silver Electroless Plating on Laser Powder-Bed Fusion Additively Printed AlSi10Mg Parts

The current research presents a novel methodology for surface finishing of printed AlSi10Mg parts by electroless deposited gold–silver (electrum) alloys. The parts were printed by additive manufacturing laser powder-bed fusion (AM-LPBF). The electrum was chosen due to its appearance and good electrical and thermal properties and was deposited on disk-shaped specimens at 80 and 90 °C. The coating quality and appearance were studied by different methods for various deposition times and film thicknesses. The results indicate that Au–Ag coatings of AM-LPBF AlSi10Mg yield satisfactory results. The XRD analysis revealed that the coatings were composed of Au–Ag crystalline phases and beneath them, a quasi-amorphous or mixed quasi-amorphous and nanocrystalline Ni–P interlayer. The mechanism of electrum formation was studied based on the XPS analysis results as a function of the temperature and concentration. At 80 °C, the Ag was dominant at the beginning of the deposition process, while at 90 °C the Au was first detected on the interface. This result was explained by the electrochemical properties of alloying metals and the binding energies required to form metal–Ni and Au–Ag bonding. The results indicate that the electrum coatings are satisfactory, and the developed surface finishing process could be used for many applications.

Prediction and compensation of material removal for abrasive flow machining of additively manufactured metal components

Abrasive flow machining (AFM) is a surface finishing process for internal channels and freeform surfaces that is based on the extrusion of an abrasive-laden viscoelastic media. AFM can be applied to additively manufactured (AM) components with high initial surface roughness, but the final geometry after AFM may not meet the required dimensional accuracy due to highly inhomogeneous material removal (MR). In this work, we developed a solution to predict the distribution of MR for a component, and then compensate by adding materials to the component during design. The feasibility and advantage of this new method were demonstrated on a laser sintered test coupon resembling a nozzle guide vane (NGV) section. First, a baseline for MR distribution was established by applying AFM was applied to the NGV without compensation. Profile measurements of an NGV blade before and after AFM showed that dimensional error was almost 600 μm at some region of the blade profile. Then, based on the measured MR distribution, the NGV design was revised to compensate for MR and then fabricated. With this revised design, profile measurements before and after AFM showed that dimensional error was reduced to less than 200 μm. The proposed solution of MR compensation has thus been successfully demonstrated. Lastly, to demonstrate the potential to scale this solution, computational fluid dynamics (CFD) simulation of the AFM process and an MR model were also developed. MR distribution predicted by the simulation showed a good agreement with experimental. Finally, pressure, media velocity and geometry were identified as key factors affecting the MR distribution on the NGV blades. The present CFD and MR model can be a tool to predict and compensate for MR during the component design phase, negating the need to obtain experimental MR distribution.

Fabrication of precision meso-scale diameter ZrO2 ceramic bars using new magnetic pole designs in ultra-precision magnetic abrasive finishing

Ultra-Precision Magnetic Abrasive Finishing (UPMAF) is a technique for enhancing the surface quality of products, such as medical devices. In the UPMAF process, magnetic poles connect magnets and magnetic abrasive particles to form magnetic abrasive brushes for controlling the surface finishing process. Different edge shapes of the magnetic pole achieve different surface finish results. In this study, three magnetic pole designs, with a sharp edge, a square edge, and a round edge, were studied regarding their resulting surface quality and roundness precision for meso-scale diameter ZrO2 bars. Experiments were conducted to quantify critical input parameters, including magnetic pole shape, diamond particle grain size, and magnetic pole vibration frequency at an ultra-high rotational speed of 35000 rpm. An FEM model for magnetic field is used to evaluate the magnetic flux density results of the different magnetic pole shapes. The results show that stock ZrO2 bars with an Ra surface roughness of 0.18 μm and a roundness error of 3.5 μm can be improved to 0.02 μm and 0.2 μm, respectively, with the following process parameters: magnetic poles with 2-mm square edges, 1-μm diamond abrasive particles, magnetic pole vibration frequency of 8 Hz, and a workpiece rotational speed of 35000 rpm for 40 s of finishing time.

Effect of ball burnishing medium on the surface characteristics of free machining brass

Burnishing is becoming a promising surface finishing process to enhance materials surface properties. The control of the various process parameters yields the desired surface characteristics in brass materials. In the current work, free machining brass specimens were burnished by Abrasive Assisted Burnishing(AAB) process and Plain Burnishing (PB) process using ball burnishing tool. Response Surface Methodology was used to design the experiments in which Burnishing Force, Speed, Feed and Number of Passes were chosen as the process parameters. The minimum surface roughness achieved by PB and AAB was 0.1451 µm and 0.1041 µm respectively. The maximum surface hardness achieved using PB and AAB on the brass specimen was 207 HV and 248 HV respectively. The ball burnishing of free machining brass by AAB resulted in better surface characteristics as compared to the PB process.