Finishing Process Research Articles

Study on improving surface integrity for additively manufactured Inconel 718 via high-speed micromilling

ABSTRACT The surface finish required for the application of products to aerospace and defense sectors cannot be produced by additive manufacturing (AM), and hence, a secondary finishing process is required post-additive manufacturing. Consequently, the current study analyses the ability of micromilling to enhance surface integrity for AM Inconel 718. Micromilling has been performed at three different levels of cutting conditions. The force induced during micromilling, surface finish, and top burr width for machined workpieces has been analyzed. A minimum value of 50 nm has been achieved for surface finish post-machining at a feed of 2 µm/flute and a speed of 50,000 rpm. An upmilling strategy has been found to be generating a lower top burr width compared to downmilling with a minimum value of 141 µm. A stability plot has also been constructed for the micromilling of AM Inconel 718 and compared with the stability lobe for wrought Inconel at different cutting speeds.

Experimental investigation of pool boiling on Ti-Cu composite coated surfaces prepared using Electric Discharge Coating

Boiling heat transfer has become a very potent two-phase heat transfer mechanism for cooling high heat-producing devices such as microelectronic devices, fusion reactors or turbine blades. Increasing research has shown that micro/nano-structures on surfaces increase the number of nucleation sites for bubble formation, which ultimately results in a major improvement in boiling performance. This led to studies on developing various coated surfaces in order to generate micro/nano-structures on surfaces. In the current study, microstructured boiling surfaces were prepared using the Electric Discharge Coating (EDC) process. Titanium-copper (Ti-Cu) composite microparticles were coated on copper surface under reverse polarity in the Electric Discharge Machine. Four surfaces were prepared by using current settings of 3 A, 4 A, 5 A and 6 A. It was followed by characterisation of the surfaces which included, wettability analysis, porosity, pore size estimation, mean roughness measurement and elemental analysis, in order to better understand the boiling results on the surfaces. The surfaces formed were hydrophilic in nature, with contact angles varying from 47° to 65°. Pool boiling were performed with the developed surfaces and critical heat flux (CHF) and nucleate boiling heat transfer coefficient (NBHTC) improvement of 37.17 % and 172 % respectively were observed with the best performing surface compared to the bare surface. The best performing surface was also compared with relevant published literature to determine its standing against the present state of the art.

Study on the hydrolysis characteristics of polymeric aluminum chloride forced by fine bubbles and its key factors affecting the efficiency and capacity of forcing hydrolysis

Enhanced coagulation is an important way to remove natural organic matter and reduce disinfection by-products in traditional water treatment processes, in which the micromolecular organic matter that is difficult to be removed during conventional coagulation can be enhanced more conveniently by modulating the dominant Al species in the traditional metal salt coagulants (e.g., polymeric aluminum chloride, PACl). Based on the forcing hydrolysis characteristics of fine bubbles due to the adsorption of hydroxide ions on their surfaces, this study verified the adaptability of the forced PACl hydrolysis by fine bubbles under different operating conditions objectively and comprehensively. The morphological changes of PACl before and after forced hydrolysis by fine bubbles were characterized figuratively, and the evolution of the dominant Al species before and after forced hydrolysis by fine bubbles was reasonably elaborated. The experimental results showed that fine bubbles had the effect of forcing the hydrolysis of PACl with different degrees of alkalinity and modulating the dominant Al species. It was innovatively found that the mass transfer efficiency of the fine bubbles determined their efficiency in forcing PACl hydrolysis (Pearson's r = -0.9423) and the concentration of fine bubbles affected their capacity to force PACl hydrolysis (Pearson's r = 0.8189). At pH = 7 and an air flow rate of 20 mL/min, the DOC concentration of micromolecular organics and the DOC removal efficiency of total organics could be reduced by 0.54 mg/L and enhanced by 12.6 %, respectively, after forced PACl hydrolysis by fine bubbles. While deepening the mechanism of forced PACl hydrolysis by fine bubbles, the above results preliminarily verified the relevance and feasibility of modulating the dominant Al species through forced PACl hydrolysis by fine bubbles to improve the coagulation efficiency, which provided theoretical and data support for the construction of a fine bubble-enhanced coagulation process for drinking water treatment plants.

Evolution of mechanical behavior in granular soil during fine particle loss simulated by salt dissolution: Insights from ring shear tests

Fine particle loss in soil is one of the main causes of slope instability and geotechnical structure failure. Loss of fines can cause instability in granular assembles by changing the fabric and microstructure of the sample. However, real-time monitoring of the evolution of mechanical behavior in granular soils during the particle loss process is still poorly explored. This study presents a novel approach by simulating fine particle loss through salt dissolution in ring-shear tests, offering real-time insights into the mechanical evolution of granular soils under realistic stress conditions. Meanwhile, the shear resistance, shear displacement, vertical displacement, salt content, and acoustic emissions were simultaneously recorded. The test results showed that the instability of the sample was triggered by the loss of fine particles. With a gradual loss of fine particles, both the vertical and shear deformations and the void ratio increased. The evolution of shear resistance in the sample can be divided into three stages: stress weakening, then strengthening, and finally recovery to the initial value. We infer that the evolution of shear resistance originated from the collapse and rearrangement of its granular fabric and microstructure. Additional evidence for this hypothesis was provided by high-frequency acoustic emissions (approximately 150 kHz), suggesting buckling of the force chains accompanying the particle loss process. Furthermore, the sample experienced greater shear deformations and stress weakening that developed under a larger initial fine content or a higher normal stress. This finding may provide valuable insights into the mechanical behavior of granular soil during the fine particle loss process.

Research on machining technology of stepped boring for intersecting holes in aircraft

Abstract During the assembly process of a large-scale aircraft fuselage, critical bearing areas require the drilling of intersecting holes, which are commonly processed using traditional single-edged reamers by most domestic manufacturers. To improve the efficiency and accuracy of the finishing process for these holes, enhance the quality of the assembly, and further shorten the construction cycle for precision processing, improvements need to be made to traditional single-edge reamer machining methods. This paper proposes a new approach that uses stepped reamers to machine intersecting holes. By setting up an experimental platform to simulate actual processing conditions and optimize processing parameters, the study analyzes and compares the quality and efficiency of traditional reaming and stepped reaming modes. The results show that stepped reaming can improve processing efficiency by 50.6% compared to traditional machining while also reducing human intervention and minimizing quality risks. The findings from this research project can be extended to various aircraft fuselages or wings for precise drilling of intersecting holes, providing significant guidance for efficient and high-quality delivery of aircraft.

Development of Electron Beam Physical Vapor Deposition Coating Process for YSZ Material Using Domestic Equipment Technology

Development of Electron Beam Physical Vapor Deposition Coating Process for YSZ Material Using Domestic Equipment Technology

Fabrication of Zinc Oxide Thin Films by Sol-Gel Dip Coating Process

Zinc oxide (ZnO) is a non-toxic material known for its distinctive physical and chemical properties, including a direct band gap energy of 3.37 eV and a large exciton binding energy of 60 meV, which contribute to its significant thermal and chemical stability at room temperature. Due to these characteristics, ZnO plays a critical role in various applications, such as UV light emitters, transparent conducting thin films in electronic devices, gas sensors, piezoelectric materials, transducers, and as a transparent conductive oxide (TCO) layer in thin-film photoelectrochemical cells. Numerous fabrication techniques have been employed to produce ZnO thin films. However, many of these methods require costly equipment, high vacuum environments, and elevated temperatures. In contrast, the sol-gel process stands out as a convenient, cost-effective, and versatile method for ZnO thin film fabrication. It offers advantages such as simplicity, low crystallization temperature, ease of reproducibility, molecular-level homogeneity, and precise compositional control. In this study, ZnO thin films were deposited onto Indium Tin Oxide (ITO) glass substrates using the sol-gel dip coating method, with varying preparative parameters: sol concentrations and annealing temperatures. The resulting samples were characterized using a UV-visible spectrophotometer, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDX). The results demonstrated that the unique properties of ZnO thin films are highly dependent on the preparative parameters. Specifically, the band gap energy decreased from 3.25 eV to 3.18 eV with increasing sol concentration and also showed a similar decline with higher annealing temperatures. XRD patterns revealed a smaller full width at half maximum (FWHM) of the most intense peak (002) at higher sol concentrations and annealing temperatures, indicating an increase in crystallite size. FESEM images highlighted distinct morphological changes corresponding to the variations in sol precursor concentration and annealing temperature, while EDX analysis confirmed the formation of highly pure ZnO thin films on ITO glass substrates.

Multiobjective optimization of magnetic abrasive finishing process with periodic re-distribution of magnetic abrasive particles on 17-4PH stainless steel

Magnetic abrasive finishing (MAF) exhibits considerable potential as a promising process for enhancing surface finish quality for softer as well as harder materials. This work proposes a novel approach to harness the potential of MAF for obtaining superior surface quality of precipitation-hardening martensitic steel (17-4PH steel) while performing periodic re-distribution of magnetic abrasive particles. The experiments were conducted using the Box-Behnken design of experiments and response surface methodology (RSM). RSM-based desirability function approach and genetic algorithms were used for multiobjective optimization. The set of pareto-optimal solutions obtained through multiobjective optimization were ranked using the Technique for Order of Preference by Similarity to an Ideal Solution (TOPSIS) by assigning equal importance to the selected performance parameters (percentage change in surface roughness (PCSR) and material removal rate (MRR)). The optimized values of PCSR and MRR obtained through the desirability function of RSM and genetic algorithm were validated experimentally and compared with the predicted values obtained through the regression model. Results showed that the desirability function of RSM provided better results than the genetic algorithm for the selected conditions and confirmed the effectiveness of the proposed approach.

Neurotrophic extracellular matrix proteins promote neuronal and iPSC astrocyte progenitor cell- and nano-scale process extension for neural repair applications.

The extracellular matrix plays a critical role in modulating cell behaviour in the developing and adult central nervous system influencing neural cell morphology, function and growth. Neurons and astrocytes, play vital roles in neural signalling and support respectively and respond to cues from the surrounding matrix environment. However, a better understanding of the impact of specific individual extracellular matrix proteins on both neurons and astrocytes is critical for advancing the development of matrix-based scaffolds for neural repair applications. This study aimed to provide an in-depth analysis of how different commonly used extracellular matrix proteins- laminin-1, Fn, collagen IV, and collagen I-affect the morphology and growth of trophic induced pluripotent stem cell (iPSC)-derived astrocyte progenitors and mouse motor neuron-like cells. Following a 7-day culture period, morphological assessments revealed that laminin-1, fibronectin, and collagen-IV, but not collagen I, promoted increased process extension and a stellate morphology in astrocytes, with collagen-IV yielding the greatest increases. Subsequent analysis of neurons grown on the different extracellular matrix proteins revealed a similar pattern with laminin-1, fibronectin, and collagen-IV supporting robust neurite outgrowth. fibronectin promoted the greatest increase in neurite extension, while collagen-I did not enhance neurite growth compared to poly-L-lysine controls. Super-resolution microscopy highlighted extracellular matrix-specific nanoscale changes in cytoskeletal organization, with distinct patterns of actin filament distribution where the three basement membrane-associated proteins (laminin-1, fibronectin, and collagen-IV) promoted the extension of fine cellular processes. Overall, this study demonstrates the potent effect of laminin-1, fibronectin and collagen-IV to promote both iPSC-derived astrocyte progenitor and neuronal growth, yielding detailed insights into the effect of extracellular matrix proteins on neural cell morphology at both the whole cell and nanoscale levels. The ability of laminin-1, collagen-IV and fibronectin to elicit strong growth-promoting effects highlight their suitability as optimal extracellular matrix proteins to incorporate into neurotrophic biomaterial scaffolds for the delivery of cell cargoes for neural repair.

Sub-nanoporous polyimide membrane with selective and fast K+ transport

Biological ion channels have excellent monovalent ion separation performance, and it is of great significance to develop artificial membrane materials with monovalent ion selectivity based on their mechanism. The latent-track method is a new technology to prepare sub-nanometer channels on polymer membranes by swift heavy ion irradiation. This method has been widely applied in the study of mono/divalent ion separation membranes, but its application in monovalent ion separation membranes still needs to be explored. In this work, polyimide (PI) film was irradiated by swift heavy ion, then water rinsed, and the sub-nanoporous PI membrane with effective channel size in the range of 0.30 and 0.66 nm was fabricated, then its electrical and transport properties were studied. Due to the smaller hydrated diameter and lower hydration energy of K+, the membrane exhibited good selectivity for K+. The selectivity ratio of K+/Li+ is 3.4–3.9, and the maximum K+ flux can reach 0.44 mol m−2 h−1 at 55℃. The sub-nanoporous PI membranes are expected to be applied in salt lake lithium extraction, fine processing of potassium and lithium, and other relevant scenarios.

Developing Screen-Printing Processes for Silver Electrodes Towards All-Solution Coating Processes for Solar Cells.

In recent years, third-generation solar cells have experienced a remarkable growth in efficiency, making them a highly promising alternative energy solution. Currently, high-efficiency solar cells often use top electrodes fabricated by thermal evaporation, which rely on high-cost and high energy-consumption vacuum equipment, raising significant concerns for mass production. This study develops a method for fabricating silver electrodes using the screen-printing process, aiming to achieve solar cell production through an all-solution coating process. By selecting appropriate blocking-layer materials and optimizing the process, we have achieved device efficiencies for organic photovoltaics (OPVs) with screen-printed silver electrodes comparable to those with silver electrodes fabricated by thermal evaporation. Furthermore, we developed a method to cure the silver ink using near-infrared (NIR) annealing, significantly reducing the curing time from 30 min with hot air annealing to just 5 s. Additionally, by employing sheet-to-sheet (S2S) slot-die coating, we scaled up the device area and completed module development, successfully verifying stability in ambient air. We have also extended the application of screen-printed silver electrodes to perovskite solar cells (PSCs).

Electrolytic silver-tin (AgSn20) process for electronic finishing

Electrolytic silver-tin (AgSn20) process for electronic finishing

Experimental investigations of chemo-mechanical magneto-rheological finishing of Al-6061 via composite magnetic abrasive

ABSTRACT To achieve flawless soft material surfaces, defects and irregularities must be eliminated. Traditional abrasive-mixing techniques frequently produce surface flaws as a result of abrasive embrittlement, resulting in poor surface-quality. As a result, ensuring an immaculate finish is critical for these surfaces. In contrast, the chemo-mechanical magneto-rheological finishing (CMMRF) process, which employs a composite magnetic abrasive (CMA)-based smart fluid, has proven to be extremely effective at producing nano-finished surfaces. This study used a central-composite-rotatable design (CCRD) based on response surface methodology (RSM) to analyze how CMAs variables, slurry-based parameters, and polishing time affect final surface roughness (R a ) and percentage change in roughness (%∆R a ) for Al-6061. The CMMRF process resulted in a superior Al-surface finish (R a ) of 29 nm and a %∆R a of 91.23%. Statistical models predicted R a and %∆R a values, which matched experimental results. Characterization tests on the final Al-surface revealed significant reduction in initial machining scratches and valleys, resulting in a superior mirror-polished surface via CMA-based polishing.

On the Role of Substrate in Hydroxyapatite Coating Formation by Cold Spray

The deposition of agglomerated hydroxyapatite (HAp) powders by low-pressure cold spray has been a topic of interest in recent years. Key parameters influencing the deposition of HAp powders include particle morphology and impact kinetic energy. This work examines the deposition of HAp powders on various metal surfaces to assess the impact of substrate properties on the formation of HAp deposits via cold spray. The substrates studied here encompass metals with varying hardness and thermal conductivities, including Al6061, Inconel alloy 625, AISI 316 stainless steel, H13 tool steel, Ti6Al4V, and AZ31 alloy. Single-track experiments offer insights into the initial interactions between HAp particles and different substrate surfaces. In this study, the results indicate that the ductility of the substrate may enhance HAp particle deposition only at the first deposition stages where substrate/particle interaction is the most critical factor for deposition. Features on the substrate associated with the first deposition sprayed layer include localized substrate deformation and the formation of clusters of HAp agglomerates, which aid in HAp deposition. Furthermore, after multiple spraying passes on the various metallic surfaces, deposition efficiency was significantly reduced when the build-up process of HAp coatings shifted from ceramic/metal to ceramic/ceramic interactions. Overall, this study achieved agglomerated HAp deposits with high deposition efficiencies (30–60%) through single-track experiments and resulted in the preparation of HAp coatings on various substrates with thickness values ranging from 24 to 53 µm. These coatings exhibited bioactive behavior in simulated body fluid.

Optimizing textile dyeing and finishing for improved energy efficiency and sustainability in fleece knitted fabrics

In the industrial range, optimizing dyeing and finishing energy is important to control environmental pollution. In the Dyeing stage to finishing of textiles gas, electricity, steam, and water are used 260 m3/hour, 591 kWh, 1.2 pounds/hour, and 8.69 tons/hour respectively. If textile professionals do not match the desired shade and quality of fabrics with the use of minimal resources the energy cost will be multiple times higher. This study investigates the change in the shade of fleece knitted fabrics from the dyeing unload to the finish stage and assumes a dyeing recipe adjustment, focusing on the impact of optimized dyeing and finishing processes. Also, it focuses on qualitative changes in properties across various color variations. Identical dyeing recipes for light, medium, and dark shades of red, blue, and navy. Properties such as GSM (grams per square meter), width, color strength, shade (darker/lighter, red/green, blue/yellow), shrinkage, spirality, pilling, bursting strength, and color fastness were analyzed. Dyeing to post-finishing, an increase in color strength (K/S) values was observed, with examples including minimum increases from 2.9 to 3.18 for light red and maximum from 19.3 to 22.9 for dark navy shade. Darker shades (DL*) were observed after stenter 1st pass (among all variants, red: 1.2 % to 8.1 %, blue: 4.5 % to 6.7 %, navy: 1.6 % to 2 %), while lighter shades (DL*) were observed following sueding and napping (among all variants, red: 3.1 % to 19.7 %, blue: 11.8 % to 19.7 %, navy: 14.8 % to 27.6 %). Greenish (Da*) and yellowish (Db*) tones are prominent across all colors in the finishing stages. Besides, other properties shrinkage, spirality, pilling, bursting strength, and color fastness significantly changed. These findings offer valuable guidance for dyeing professionals aiming to achieve the desired adjustment of shades that match the quality standard and produce sustainable fleece fabrics. To compensate for the shade lightening that occurs during the finishing process, it is recommended to keep the fabric shade slightly darker (5.70 % to 23.10 %) at the dyeing stage.

An equivalent model of horizontal vibratory finishing process: Model construction and analysis based on similarity theory

The manufacturing cost of parts and experimental equipment seriously limits the development of experimental research on mass finishing. To tackle this issue, an equivalent model construction method was proposed based on similarity theory. First, the similarity criterion of relevant physical quantities in horizontal vibratory finishing was determined, and the calculation formula of the distortion coefficient was derived to correct the prediction results. Second, the effects of vibration parameters on the characteristics and similarities of particle velocity and normal force were analyzed by DEM simulation. Finally, the validity of the equivalent model was proved by PIV and force tests. The results show that the equivalent model can be used to reflect the variation of the actual model and anticipate the particle velocity and normal force. And the prediction accuracy can reach 99.56 % and 97.46 %, respectively. The research results provide a new efficient and low-cost method for researching the mass finishing process.

Effect of diffusion barriers on steam oxidation properties and interface evolutions of Cr coating for zirconium alloy at 1200 °C

Currently, Cr-based coatings are considered the most promising protective coatings for zirconium alloy claddings under the ATF design concept. However, the primary factor affecting the oxidation resistance of Cr coatings is the interdiffusion of Cr and Zr. In this study, Cr coatings with three refractory metal interlayers of Nb, Mo, and Ta were deposited on zirconium alloy surfaces using closed-field unbalanced magnetron sputtering. The study investigated the effects of different interlayers on the microstructure, oxidation properties, and interface evolution process of Cr coatings under steam conditions at 1200 ℃, and compared them with Cr coatings without intermediate layers. The results indicate that the refractory metal interlayer influences the orientation and growth rate of Cr coating grains. The formation of a Laves phase mixed layer in the interlayer during oxidation effectively hinders the diffusion of O and Cr to the zirconium alloy matrix, enhancing its oxidation resistance. Furthermore, the diffusion rate and vacancy concentration of Mo and Ta elements to the Zr layer exceed that of diffusion to the Cr layer. During the cooling process, a precipitate phase forms in the Zr-4 matrix, while the Nb coating forms an infinite solid solution in the β-Zr.

Microstructure evolution and degradation process of AlCrTiSiN coatings with different Si contents at high temperatures

The microstructure evolution of AlCrTiN and AlCrTiSiN coatings containing 4, 6.8, and 10.6 at.% Si was studied at temperatures ranging from 800 to 1100 °C. The AlCrTiN coating exhibits a single-phase fcc-(Al,Cr,Ti)N structure, while the AlCrTiSiN coatings transition from a nanocomposite structure, composed of fcc-(Al,Cr,Ti)N and amorphous a-SixNy, to a fully amorphous structure as the Si content increases. The hardness and adhesion strength of coatings initially rise, peaking at 24 GPa and 44 N respectively, due to the formation of the nanocomposite structure. However, these properties decline as the coatings become fully amorphous. At elevated temperatures, severe oxidation leads to the gradual formation of layered oxides. Concurrently, phase transformation, spinodal decomposition, and crystallization occur within the nitride layer. The addition of Si enhances oxidation resistance by promoting the rapid formation of a dense and protective oxide layer, and by reducing nitrogen release and TiO2 formation. However, at 1000 and 1100 °C, the coating with 10 at.% Si exhibits slightly faster oxidation compared to the 6.8 at.% Si coating, as the increased Si content reduces the Al content, limiting the coating's ability to regenerate the protective oxide layer.

Mass finishing of additively manufactured AISI 316L using pecan nutshells as sustainable abrasive media

Abrasive processes represent the main methods for obtaining high-quality surface finish in metal parts. As one main characteristic, these processes have a relatively high consumption of energy per material volume removed, as well as many inputs, such as abrasive tools and equipment, and, consequently, a high associated environmental impact. Additive manufacturing is becoming a competitive method to produce customized parts, but the surface finish is often not good enough for the application, and post-processing is needed. In this work, a mass finishing process using a planetary mill with abrasive media made of sustainable materials (pecan nutshells) was used on AISI 316L stainless steel samples manufactured by selective laser melting (SLM). The main goal was to perform a multicriteria analysis of the sample surface before and after post-processing. Through the analysis, it could be observed that the nutshell abrasive media has results close to those of traditional ceramic media. The increase in the rotation speed of the planetary mill, increase of finishing time, and use of abrasive pastes can further increase the effectiveness of the process.

Improvement of fatigue life by aluminizing of additive manufactured Fe- and Ni-base alloy

Laser powder bed fusion (PBF-LB/M) is used in various industries to manufacture complex parts with high precision. High surface roughness and porosity have a negative impact on fatigue resistance. This work presents aluminum pack cementation as a method to reduce surface roughness and improve fatigue resistance of AM parts. An Fe-base alloy (Alloy 800H) and a Ni-base alloy (Alloy 699XA) are selected. Some of the specimens made from PBF-LB/M were treated by pack cementation with aluminum, while others were subjected to the vibratory finishing process. The surface roughness, microhardness distribution and the microstructure of the interface zone were measured and analyzed for the as-built, vibratory finished and aluminized specimens. Rotating bending fatigue test was performed at room temperature. Conventionally fabricated specimens of both investigated alloys were tested under the same conditions to evaluate the effects of pack cementation. The aluminized samples (PBF-LB/M) show a significant reduction in surface roughness with a decrease of 45 % for Alloy 800H and 65 % for Alloy 699XA. This leads to an improvement in fatigue life for both Alloy 800H and Alloy 699XA. In contrast, the conventionally fabricated specimens exhibited increased surface roughness after pack cementation compared to their initial condition and showed a significant reduction in fatigue resistance.