Enhancement Of Surface Quality Research Articles

Exploring the mechanism of gallium nitride surface quality enhancement by green organic additives in chemical mechanical polishing

This study presents a novel approach using colloidal silica and organic salt additives for ultra-precision processing of GaN films. The chemical mechanical polishing (CMP) process significantly reduced the surface roughness (Sq) to a minimum of 0.63 nm, while improving the material removal rate by 60 % (from 70 nm/h to 112 nm/h). Contact angle experiments confirmed enhanced slurry wettability due to the organic salts, reducing the contact angle between the polishing slurry and GaN surface from 20° to less than 10°. Additionally, X-ray photoelectron spectroscopy (XPS) and quantum chemical calculations explained the inhibition of the oxide layer through adsorption energy. These insights contribute to optimizing GaN CMP processes for fabricating high-performance GaN devices.

Influence of NaAlO2 Concentration on the Characteristics of Micro-Arc Oxidation Coating Fabricated on a ZK60 Magnesium Alloy

This study investigated the impact of NaAlO2 concentration in electrolytic solutions on micro-arc oxidation (MAO) coatings, focusing on their surface quality enhancement and corrosion resistance improvement. The surface morphology and microstructure of these coatings were assessed using scanning electron microscopy. Mechanical properties, such as hardness and wear resistance of MAO coatings, were tested. The hardness of the 6 g/L group was 411.2 HV. X-ray photoelectron spectroscopy examinations showed that MgAl2O4, CaMgP2O7, and MgSiO4 were the phases in the MAO coating. Antibacterial assessments were performed to evaluate the influence of NaAlO2 concentration, and the antibacterial rate of the 6 g/L group reached 97.08%. The hydrophilicity of the coatings was determined using water contact angle measurements, wherein the water contact angle of the 6 g/L was the lowest, at 58.25°. Corrosion resistance was evaluated with an electrochemical workstation. The findings revealed that the MAO coatings prepared with a NaAlO2 concentration of 6 g/L exhibited superior uniformity with fewer defects, enhanced corrosion resistance, and increased adhesive strength compared to other concentration groups. The 6 g/L NaAlO2 concentration MAO coating demonstrated the highest fitting coating resistance R3 (8.14 × 104 Ω∙cm2), signifying better corrosion resistance.

Surface quality enhancement by constant scallop-height in three-axis milling operations

The quality of machined part surfaces are under the impact of scallop height which should be analyzed and minimized. Achieving a uniform scallop-height is important for ensuring a smooth surface finish and maintaining consistent material removal across the machined surfaces during CNC machining operations. This approach helps to reduce material waste, tool wear and part production errors while ensuring consistent and high-quality of machined parts. Maintaining a constant scallop height can also help to reduce chatter and vibration during milling operations. The research work develops a virtual machining methodology to produce constant scallops through three-axis milling operations. The proposed approach examines free-form surfaces of workpiece in order to obtain free form surfaces curvatures. Then, free-form surfaces are separated into flat, convex and concave surfaces to provide optimized cutting tool variables in order to provide constant scallop height during CNC cutting tool paths. Achieving a constant scallop height involves optimizing cutting parameters such as feed rate, spindle speed, and step over. To calculate the optimized machining parameters of feed rate, speed of spindle and step over, the Taguchi optimization methodology is utilized in the study. Then, the machining variables of feed rate, speed of spindle and step over are optimized to achieve the uniform scallop height during milling potations of free-form surfaces. As a result, using optimized machining parameters during machining operations, the surface roughness of machined components are reduced by 23.8%. So, the proposed virtual machining method can enhance surface quality of machined parts during CNC milling operations of free-from-surfaces.

Pulsed Laser Ultrasonic Vibration-Assisted Cutting of SiCp/Al Composites through Finite Element Simulation and Experimental Research

Silicon carbide particle-reinforced aluminum matrix composites (SiCp/Al) find diverse applications in engineering. Nevertheless, SiCp/Al exhibit limited machinability due to their special structure. A pulsed laser ultrasonic vibration assisted cutting (PLUVAC) method was proposed to enhance the machining characteristics of SiCp/Al and decrease surface defects. The finite element model was constructed, considering both the thermal effect of the pulsed laser and the location distribution of SiC particles. The model has been developed to analyze the damage forms of SiC particles and the formation mechanisms for the surface morphology. The influence of pulsed laser power on average cutting forces has also been analyzed. Research results indicate that PLUVAC accelerates the transition from the brittleness to the plastic of SiC particles, which helps to reduce surface scratching caused by fragmented SiC particles. Furthermore, the enhancement of surface quality is attributed to the decrease in surface cracks and the beneficial coating effect of the Al matrix. The accuracy of the simulation is verified by experiments, and the feasibility of PLUVAC method to enhance the surface quality of SiCp/Al is confirmed.

Surface quality enhancement of cold work tool steel by GOV (flow peening) process versus abrasive flow machining

Surface quality enhancement of cold work tool steel by GOV (flow peening) process versus abrasive flow machining

Feasibility and mechanism of atmospheric pressure cold plasma jet (APCPJ) assisted micro-milling of bulk metallic glasses (BMGs)

The unique microstructures of bulk metallic glasses (BMGs) provide them with excellent mechanical, physical, and chemical properties, having important applications in the fields of medical devices, military equipment, aerospace, etc. However, the superb mechanical properties also contribute to poor machinability of the BMGs. Currently, researchers have proposed to improve the machinability by single-point diamond turning, laser-assisted machining and ultrasonic vibration-assisted machining, but their plasticity and viscous flow remain unchanged, thus restraining further enhancement of surface quality. Atmospheric pressure cold plasma jet (APCPJ), which is rich in active particles, can effectively ameliorate material machinability by modulating material properties. In this paper, we propose to use the APCPJ to regulate the properties of BMGs, and carry out nanoindentation, nanoscratching, and micro-milling experiments to investigate the influence mechanisms of APCPJ on the material properties and cutting process. The results demonstrate that after modified by APCPJ, plastic deformability of the BMGs is improved due to the increase of free volume content; meanwhile, the viscous flow is inhibited. The micro-milling experiments indicate that under the conditions of feed rate Vf = 500 μm/s, spindle speed n = 30,000 rpm, and cutting depth ap = 5 μm, the improvement effect of APCPJ on the cutting process is relatively optimum. The surface roughness Ra of the Zr-based BMG and Ti-based BMG obtained by APCPJ are respectively 0.076 μm and 0.081 μm, which can be reduced by 37.7 % and 38.2 % compared with dry micro-milling. The cutting forces Fz in the direction of cutting depth are also reduced by 30.9 % and 23.3 %, respectively. The APCPJ-assisted micro-milling method proposed in this work may ameliorate the machining quality of BMGs and promote the application of BMGs and APCPJ-assisted machining technology in aerospace and precision machining.

Preliminary Parametric Investigations into Macro-Laser Polishing of Laser-Directed Energy Deposition of SS 304L Bulk Structures

The higher surface roughness of laser-directed energy deposition (LDED)-built components necessitates advanced and sustainable surface quality enhancement techniques like laser polishing. In the present work, a parametric study involving experimental investigation and numerical analysis is conducted to determine the effect of macro-laser polishing on LDED-built SS 304L structures. A thermophysical model is developed to simulate the effect of laser power and scan speed on the melt pool depth of the LDED-built samples. The simulated melt pool depth is compared with experimental results and is found to be in good agreement. Further, the correlation between the melt pool depth and surface behaviour is studied based on shallow surface melting and shallow over-melting mechanisms. A maximum reduction in surface roughness from 21.3 µm to 9 µm (~57%) is achieved with laser polishing, and process parameters’ effect on the surface roughness is investigated. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) mapping, and X-ray diffraction (XRD) are used to further characterize the laser-polished surface. SEM-EDS analysis shows that the segregation is more evident in laser-polished samples, while the XRD results indicate the absence of phase change during the process. This study paves the way to a greater understanding of the effect of macro-laser polishing on LDED-built SS 304L structures.

Milling surface quality enhancement through encoder micro-cyclic error compensation in an ultraprecision machine tool

Milling surface quality enhancement through encoder micro-cyclic error compensation in an ultraprecision machine tool

Surface quality enhancement of warm incremental forming process using solid lubricant with varying etching period

The warm incremental forming process is an effective and flexible approach for forming magnesium alloy (AZ31B) sheets, which usually is difficult to deform at room temperature. However, friction increases drastically at elevated temperatures during the forming process. In order to reduce friction, liquid lubricants are generally applied on the sheet’s surface; however, the liquid lubricant usually thins out during the warm incremental forming process. To address this problem, solid lubricants such as graphite and molybdenum disulfide have been used as better alternative lubricants for forming the parts at elevated temperatures. In addition, an increase in surface roughness, either by depositing porous film or by creating micro or nanostructures, can help better the surfaces’ lubrication by solid lubricants. In this work, a facile etching method is used to treat a pre-formed sheet and solid lubricants to improve the surface quality and reduce the part’s wear during the warm incremental forming process. The combined effect of the type of solid lubricant and etching time is studied in detail. The quality of the magnesium alloy sample and its morphology before and after the forming process has been examined using various characterization tools, including a surface roughness tester, a tribometer, and scanning electron microscopy (SEM). The results reveal that the magnesium alloy sample etched for 5 min and lubricated with graphite powder showed significantly low weight loss and better surface quality. Overall, the results revealed that the etching of samples could be highly beneficial for the warm incremental forming process.

A Review of Additive Manufacturing Post-Treatment Techniques for Surface Quality Enhancement

Additive manufacturing (AM), also known as 3D printing, produces an object layer by layer with the application of a computer-controlled method. AM creates an object by adding material to a solid block until the finished product is created. AM manufacturing benefits including design flexibility, creativity, rapid prototyping, high productivity, reduced manufacturing cycle, etc. However, AM products have physical quality flaws such as surface roughness, inaccurate dimensioning, porosity, staircase effects, etc. Therefore, there is a need to carry out post-treatment on the AM fabricated components to correct their flaws before they can be used. Seventeen different post-treatment methods (PTM) on AM fabricated components were discussed in this review study. Each of these PTMs, however, has its advantages and disadvantages. The results obtained from the study show that chemical PTM has the ability to improve surface roughness easily, laser polishing can be used to reduce the staircase effects, and thus reduce surface roughness significantly and increase the hardness of AM fabricated component parts. Mechanical PTM helps to join the layers of AM components and improve their toughness, while subtractive machining PTM improves surface quality. Thermal PTMs are used to improve corrosion resistance, reduce surface roughness, eliminate staircase effects, etc. The discussion of various PTMs is clearly highlighted to serve as a guide for AM stakeholders.

IMPROVING CORROSION RESISTANCE OF MAGNESIUM NANOCOMPOSITES BY USING ELECTROLESS NICKEL COATINGS

The present study aims at improving corrosion resistance of magnesium nanocomposites through autocatalytic Ni-P coating. Electroless Ni-P coatings with different concentration of sodium hypophosphite are deposited on 2% WC incorporated magnesium nanocomposites (AZ31-2WC) and the coated samples are further heat-treated. Basic characterizations and compositional analyses are done by using scanning electron microscope (SEM), energy dispersive x-ray analysis (EDAX), and X-ray diffraction analysis (XRD). Microhardness values of the developed materials are also evaluated. The attempt is made to improve corrosion resistance of AZ31-2WC by modifying surface roughness. Corrosion characteristics of Ni-P coated AZ31-2WC nanocomposites are examined by performing potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). Corrosion resistance improves with enhancement of surface quality. Corrosion resistance of AZ31-2WC nanocomposite also improves due to application of Ni-P coating. Finally, corrosion morphologies are scrutinized by SEM micrographs of corroded surface.

Enhancement of surface quality in the electrochemical milling of 316L using a novel cathode structure

In electrochemical jet milling (EJM), enhancing the current density at the trail edge of a workpiece can improve the surface quality. In this study, a novel rectangular cathode tool structure insulated at one side was designed to reinforce the current density at the trail edge of a workpiece to improve the machined surface quality. Numerical simulation was performed to analyse the current density distribution with respect to various parameters, and experiments were conducted to verify the simulation results. The simulation results showed that the current density could be strengthened by utilising the tool with an insulated frontal nozzle tip, which can improve the surface quality during the machining process. Meanwhile, the experimental results revealed that a mirror-like surface could be obtained when utilising the tool under favourable conditions. Compared to other tools, the surface machined by the tool with an insulated frontal nozzle tip had minimum roughness, defects, and overcut.

Investigations on a hybrid chemo-magnetorheological finishing process for freeform surface quality enhancement

Surface roughness improvement of the freeform surfaces is essential for the enhanced functionality of the components, including implants, turbine blades, microchannels, etc. The exclusion of human involvement during the finishing of freeform surfaces prevents hazardous exposure to particulate and provides uniform surface quality. Different surface finishing techniques, including vibratory finishing, Abrasive Flow Finishing (AFF), Electron Beam (EB) Irradiation, Electrolytic in-process Dressing (ELID) grinding, etc., have been developed to automate the finishing operation. However, some limitations are associated with the preexisting techniques, e.g., the process controllability of AFF and vibratory finishing, recast layer formation during EB irradiation, and low productivity of ELID grinding. Hence, a novel method for surface improvement, namely, Hybrid Chemo-Magnetorheological Finishing (HC-MRF), is proposed in the present study to reduce the surface roughness (Ra) (~up to a few nanometer) without affecting the surface topography of the workpiece. HC-MRF simultaneously utilizes the synergic action between Magnetorheological Finishing (MRF) and chemical etching to reduce surface finishing time and escalate process efficiency. Herein, the carrier medium of the Magnetorheological (MR) fluid is replaced by a reagent to facilitate the chemical etching process, and its synchronized action with mechanical abrasion reduces surface irregularities. Furthermore, the design of the developed apparatus to enable the HC-MRF process, where permanent magnets are used to produce the desired external magnetic field, is also discoursed. A case study on the surface roughness enhancement through the HC-MRF on the WC-Co (tungsten carbide in a cobalt-rich matrix) is investigated using Response Surface Methodology (RSM). Herein, Murakami's reagent is used as the carrier medium in the MR fluid, and a reduction in surface roughness (Ra) from an initial value of 312.87 nm to a final value of 34.50 nm is noticed. Moreover, the inclusion of Murakami's reagent enhances the process efficiency. The change in surface roughness with and without Murakami's reagent in the MR fluid is 88.97 % and 43.12 %, respectively, for a constant finishing time.

A Comparative Analysis of Chemical, Thermal, and Mechanical Post-Process of Fused Filament Fabricated Polyetherimide Parts for Surface Quality Enhancement.

Additive manufacturing technologies are increasingly being used in production systems because they shorten product development time and production cost, but surface integrity remains a limitation to meet the standards set by conventional manufacturing. In this research article, two chemical, one thermal, and three mechanical finishing operations are proposed to post-process fused filament fabricated Ultem 9085 parts. Their effects on the parts’ surface quality and dimensional accuracy (changes in their width, height, length, and mass) are examined through optical and electron scanning microscopy, and the advantages and disadvantages of each method are discussed. Microscope evaluation has proven to be a powerful tool to observe apparent differences and understand the nature of different morphological changes. Results indicate that chemical and thermal treatments and ball burnishing are good candidates to significantly enhance the finish of the parts, despite requiring the use of solvents or provoking dimensional changes to the parts. The effects of abrasive mechanical treatments are more moderate at a macroscopic scale, but the surface of the filaments suffers the most remarkable changes.

Enhancement of Surface Quality of DMLS Aluminium Alloy using RSM Optimization and ANN Modelling

Direct Metal Laser Sintering (DMLS) is an additive manufacturing technology gaining popularity due to its ability to produce near net-shaped functional components. As there is a great need to improve the surface quality of DMLS components to upgrade their dynamic properties, an attempt was made to study the influence of process parameters like laser power, scan speed, and overlap rate on the surface quality of DMLS Aluminum alloy (AlSi10Mg) in as-built condition. The optimized process window to generate the best surface quality was achieved using Response Surface Method (RSM). Artificial Neural Network (ANN) modeling is also developed to map the influence of process parameters on surface quality. Conclusively, Scan speed is found to be most influential over surface quality as per the F and P test results. The optimized process parameters for best surface quality (3.52 µm) were 300 W laser power, 600 mm/sec scan speed, and 25% overlap rate. Both RSM and ANN models were accurate in prediction. However, ANN is recorded as superior with the highest coefficient of correlation (R).

Crack Elimination and Surface Quality Enhancement of the Wear-resistant Layer on Guide Slippers of Coal Cutting Machines

In order to enhance the surface quality and avoid the cracking problem of the wear-resistant layer on guide slippers of coal cutting machines, an automatic welding system was employed for the overlaying welding production. By regulating the welding parameters, including the welding path and speed, the surface flatness and quality were greatly reduced. The cracks at the arc extinguishing positions were effectively eliminated. As compared to the conventional manual welding, the automatic welding not only reduced the machining allowance, but also increased the production rate and the service life of the guide slippers.

Study on application of laser in maskless localized electrodeposition and surface quality enhancement

To obtain electrodeposited layers with different patterns, the additional auxiliary measures such as mask prepared by photoresist are usually required for traditional electrodeposition (ECD) technology, which may reduce the flexibility and convenience of this method. Meanwhile, the ultrashort pulsed laser can be introduced into ECD process and increase current density in the selected area on cathode, and has potential in helping achieve maskless localized ECD. In this paper, the picosecond (ps) laser-assisted ECD (LECD) method is studied, in which a cyclic laser scanning scheme is used to produce different electrodeposited layers on the cathode substrate. In addition, the realizing mechanism of localized ECD is discussed, and the surface quality of Ni-P coating prepared by LECD is evaluated. The results show that the electrodeposited layers with different sizes (1 × 1 mm, 2 × 2 mm and 3 × 3 mm) can be obtained by laser selective irradiation on the copper substrate (10 × 10 mm), demonstrating that the critical current can be increased to reach the reaction conditions in the irradiated zone by the laser-caused thermal effects. Analysis also shows that the theoretical diameter of zigzag edge can be calculated, which is consistent with that of actual electrodeposited layer, indicating that the precision and localization of electrodeposited layer is controllable by adjusting laser processing parameters. Furthermore, measurement shows that a surface roughness of 0.012 μm and better surface flatness can be obtained by LECD under a pulse energy of 16 μJ, and the amorphous degree Ni-P can be increased by the thermal and photoelectric effects of ps laser irradiation. Besides, the corrosion potential and current density are −0.19 V and 3.83 × 10−6 A/cm2, respectively, and the AC impedance spectrum also indicates a higher electron transfer resistance, illustrating better corrosion resistance can be achieved by LECD (16 μJ).

The influence of ultrasonic vibration on parts properties during incremental sheet forming

The integration of ultrasonic vibration into sheet forming process can significantly reduce the forming force and bring benefits including the enhancement of surface quality, the enhancement of formability and the reduction of spring-back. However, the influencing mechanisms of the high-frequency vibration on parts properties during the incremental sheet forming (ISF) process are not well known, preventing a more efficient forming system. This paper comprehensively investigates the effects of different process parameters (vibration amplitude, step-down size, rotation speed and forming angle) on the micro-hardness, minimum thickness, forming limit and residual stress of the formed parts. First, a series of truncated pyramids were formed with an experimental platform designed for the ultrasonic-assisted incremental sheet forming. Then, micro-hardness tests, minimum thickness measurements and residual stress tests were performed for the formed parts. The results showed that the surface micro-hardness of the formed part was reduced since the vibration stress induced by the ultrasonic vibration within the material which eliminated the original internal stress. The superimposed ultrasonic vibration can effectively uniform the residual stress and thickness distribution, and improve the forming limit in the case of the small deformation rate. In addition, through the tensile fracture analysis of the formed part, it is shown that the elongation of material is improved and the elastic modulus and hardening index are decreased. The findings of the present work lay the foundation for a better integration of the ultrasonic vibration system into the incremental sheet forming process.

Performance analysis of copper-based MWCNT composite coated 316L SS tool in electro discharge machining

The tool material properties are essential key factors for the enhancement of electro discharge machining performance mainly, resistance to the wear of tool, removal of material from workpiece, and machined surface quality. In this study, copper-based multi-wall carbon nanotube (MWCNT) composite coated 316 L stainless steel electrode was fabricated by electrodeposition method and used in EDM operation for investigating machining performance. The agglomeration problem of MWCNTs was a critical issue for fabrication copper matrix composite, which was addressed with a cationic dispersing agent. The copper-based MWCNT composite coated electrode was used for machining of 304 SS workpiece. The experimental results show 57.11% reduction of tool wear rate (TWR) and 99.52% improvement of material removal rate (MRR) for copper-based MWCNT composite coated electrode compared to pure copper coated 316 L SS electrode. The enhancement of surface quality was also observed for the machined surface, which was generated during the machining with copper-based MWCNT composite coated electrode. The micro-crack formation was almost eliminated by using copper-based MWCNT composite coated electrode, which will enhance the strength and fatigue property of machined component. The enhancement of micro-hardness was also observed for the machined surface.

A study on tangential ultrasonic-assisted mirror grinding of zirconia ceramic curved surfaces

Zirconia ceramics have been used in the field of smartphone manufacturing, especially for the phone shells. To improve the machining efficiency and simultaneously obtain a mirror-surface quality on the curved surface made by zirconia ceramics, the tangential ultrasonic-assisted grinding (TUAG) was proposed, in which the ultrasonic vibrations of the grinding wheel are always in the direction tangential to the work surface at the grinding point. To reveal the fundamental grinding characteristics of the TUAG on the zirconia ceramic curved surface, the processing principle and according experimental setups were given out at first. The effects of the proposed method on the surface morphology and surface roughness were investigated experimentally and analyzed numerically under different process parameters for plane workpieces. Finally, a curved surface was successfully processed by the novel method with the optimized experimental conditions. The obtained results demonstrated that (1) typical sinusoidal cutting traces appeared on the work surface, which implied that the surface morphology was affected significantly by the ultrasonic vibrations; (2) the surface roughness was distinctly affected by the amplitude of the grinding wheel, and a higher efficiency was attained on the surface quality enhancement when the larger amplitude was applied, e.g., Ra was reduced by 58.3% when an amplitude of Ap–p = 4.66 μm was imposed; and (3) the Ra value in the direction vertical to the wheel feed direction on the curved surface decreased to 39.5 nm, implying that a mirror curved surface can be obtained by TUAG with the appropriate process conditions.