Rough Morphology Research Articles

Surface Modification of Bioactive Glasses by Femtosecond and CO2 Lasers

This study explores the potential of laser surface modification (LSM) to enhance the biological properties of melt-derived bioactive glasses, specifically 45S5 and ICIE16, which are key in medical implants due to their bone-regenerating capabilities. Despite their bioactivity, these materials have limitations in cellular adhesion due to their smooth surfaces. LSM enables the creation of precise surface patterns that could improve interactions with biological environments. This study involved surface texturing bioactive glass (BG) samples using CO2 and femtosecond (fs) laser systems, modifying the laser average power, scanning speed, line spacing, and number of passes. Characterization methods included optical and stereoscopic microscopy, profilometry, and solubility tests in Tris-HCl buffer to evaluate surface roughness evolution, morphology, and bioactive behavior. The findings demonstrated significant modifications in surface properties post-texturing. The CO2 laser-treated surfaces preserve the increased roughness values after 75 days of immersion in Tris-HCl buffer for both 45S5 and ICIE16 melt-quenched bioactive glasses, showing a potential long-term osteoconductivity enhancement. On the contrary, the femtosecond laser-treated surfaces revealed a preferential apatite precipitation ability at the pattern grooves. Femtosecond laser modification stands as a suitable technique to provide preferential osteoconductivity characteristics when conducted on the surface of bioactive glass with moderate reactivity, such as ICIE16 bioactive glass.

Signal response and energy evolution of separated sandstone

This study aims to establish a precise prediction system for strong rockbursts and mine earthquakes caused by high-hard roof fractures. A three-point bending test was conducted on separated sandstone (SS) to analyze deformation field changes under the influence of digital image correlation (DIC) and acoustic emission (AE) signals during rock fracture. Microscopic fracture modes and energy evolution patterns of SS are investigated using scanning electron microscopy and Particle Flow Code in 2 Dimension, revealing the internal mechanisms linking fracture modes, crack classifications, and energy evolution. The results show that the AE signals and DIC deformation fields are highly correlated. Tensile cracks are the primary indicator of damage to SS during the strong contact phase. Complete failure occurs at peak load, driven by a combination of tensile and shear cracks. Increasing the precast crack length (b) or the upper-to-lower rock layer thickness ratio (U/L) enhances tensile failure sensitivity, whereas simultaneous increases reduce it. Macroscopically, this is reflected in variations of AE peak frequency and the primary fracture's peak frequency. Microscopically, it appears as changes in fracture surface roughness and grain fracture morphology. Energetically, this is evident in changes to the ratios of strain energy and slip energy relative to total energy. Additionally, as b and U/L increase, the primary crack location and AE energy density concentration shift progressively from the lower to the upper rock layers. Meanwhile, total input energy decreases with increasing b or as U/L deviates from 1.

Experimental Study on Efficient Short Electric Arc Turning of Titanium Alloy

This study investigates a novel short electric arc vertical turning method for machining titanium alloy shafts. The method was successfully applied to titanium alloy rods, and its effects on material removal rate (MRR), surface roughness, roundness, and cross-sectional morphology were analyzed at varying processing voltages. The results indicate that the MRR and surface quality improve with increased voltage, reaching a maximum of 231 mm3/min and 26 μm surface roughness at 32 V. However, surface roughness deteriorates with higher duty cycles and voltages due to unstable discharges. Roundness deviations are minimized with higher rotational speeds, which enhance uniform material removal and arc stability. Metallographic analysis revealed an increased heat-affected zone and recast layer thickness at higher voltages. This method demonstrates high machining efficiency and improved surface quality, making it suitable for titanium alloy shaft manufacturing in advanced engineering applications.

Physicochemical properties and in vitro hypolipidemic activities of three different bonding state pectic polysaccharide fractions extracted sequentially from pear pulp.

In this study, water-soluble fraction (WSF), chelator-soluble fraction (CSF), and sodium carbonate-soluble fraction (NSF) were sequentially fractionated from pear pulp, of which physicochemical properties and hypolipidemic activities in vitro were evaluated. They showed distinct monosaccharide composition, surface morphology, nuclear magnetic resonance (NMR), and Fourier transform infrared (FT-IR) spectrums. WSF and NSF were identified as high methyl-esterified pectic polysaccharides with degrees of methyl esterification (DM) of 85.71 % and 66.67 %, respectively, whereas CSF was low methyl-esterified pectic polysaccharides (47.83 %). WSF, CSF, and NSF all demonstrated low molecular weight, desirable rheological, thermal, antioxidant, and hypolipidemic effects in vitro. It was remarkable that WSF displayed the most excellent inhibition capacity of cholesterol micelles (26.63 %), pancreatic lipase (PL) (91.13 %)/cholesterol esterase (CEase) (53.10 %) activity inhibition, attributed to its highest DM and roughest morphology. CSF and NSF exhibited stronger cholate-binding capacity than WSF, inseparable from higher apparent viscosity and gel ability. On these grounds, different bonding state pectic polysaccharide fractions from pear presented some distinctions in their structural characteristics and functional properties, which might endow them with exploitation in health promotion and dietary supplements.

Electrochemical Performance of Guanidinium Salt-Added PVP/PEO Solid Polymer Electrolyte with Superior Power Density.

Solid polymer electrolytes (SPEs) for symmetrical supercapacitors are proposed herein with activated carbon as electrodes and optimized solid polymer electrolyte membranes, which serve as the separators and electrolytes. We propose the design of a low-cost solid polymer electrolyte consisting of guanidinium nitrate (GuN) and poly(ethylene oxide) (PEO) with poly(vinylpyrrolidone) (PVP). Using the solution casting approach, blended polymer electrolytes with varying GuN weight percentage ratios of PVP and PEO are prepared. On the blended polymer electrolytes, structural, morphological, vibrational, and ionic conductivity are investigated. The solid polymer electrolytes' morphology and level of roughness are examined using an FESEM. The interlinking bond formation between the blended polymers and the GuN salt is verified by FTIR measurements, indicating that the ligands are chemically complex. We found that, up to 20 wt.% GuN, the conductivity value increased (1.84 × 10-6 S/cm) with an increase in mobile charge carriers. Notably, the optimized PVP/PEO/20 wt.% solid polymer electrolyte was fabricated into a solid-state symmetrical supercapacitor device, which delivered a potential window of 0 to 2 V, a superior energy density of 3.88 Wh kg-1, and a power density of 1132 W kg-1.

Newly identified c-di-GMP pathway putative EAL domain gene STM0343 regulates stress resistance and virulence in Salmonella enterica serovar Typhimurium

S. Typhimurium is a significant zoonotic pathogen, and its survival and transmission rely on stress resistance and virulence factors. Therefore, identifying key regulatory elements is crucial for preventing and controlling S. Typhimurium. We performed transcriptomic analysis and screened for a c-di-GMP pathway key gene STM0343, a putative EAL domain protein with an unknown function. Our findings revealed that the deletion of this gene (269ΔSTM0343) led to a 29.85% increase in c-di-GMP. In terms of stress resistance, the strain 269ΔSTM0343 showed significant improvements compared to the wild strain WT269. Specifically, it exhibited increases of 95.74% in extracellular protein and 35.96% in exopolysaccharide production by upregulating the expression of relevant genes. As a result, the biofilm formation ability of 269ΔSTM0343 was enhanced by 21.54%, accompanied by a more pronounced red, dry, and rough colony morphology. 269ΔSTM0343 also showed a 19.03% decrease in motility due to the downregulation of flhD expression. As a result, 269ΔSTM0343 increased resistance to various antibiotics, as well as to acidic conditions, oxidative stress, and disinfectants. In terms of virulence, compared to WT269, the adhesion and invasive ability of 269ΔSTM0343 to HeLa cells was enhanced by onefold and 25.67%, respectively. In in vivo experiments, mice challenged with 269ΔSTM0343 experienced greater weight loss, and the bacterial loads in the spleen, liver, and intestines were elevated by fivefold, 30-fold, and 21-fold, respectively, accompanied by more severe pathological damage. Mechanistic studies revealed that the adhesion and invasion capacities of 269ΔSTM0343ΔCsgB decreased by 29.41% and 68.58%, respectively, compared to 269ΔSTM0343. Additionally, LacZ gene reporting indicated that STM0343 inhibited the expression of CsgB. This suggests that STM0343 suppresses virulence by downregulating CsgB expression. This study provides insights into the regulatory mechanisms by which STM0343 reduces the stress resistance and pathogenicity of S. Typhimurium.

Injectable Hydrogel-Loaded Rough Heterostructured Nanoparticles for Multi-Procedural Promotion of Diabetic Wound Healing

Wound healing is a complex, multifaceted biological process broadly divided into four overlapping phases: hemostasis, inflammation, proliferation, and remodeling. Each stage of wound healing is critical to successfully restoring tissue integrity, and disruption or delay in any of these stages can lead to delayed healing. Various existing nanomaterials only promote a single stage. In this study, Au-CuS nanoparticles (Au-CuS NPs) with rough surfaces were formed by using gold nanorods (Au NRs) as templates on which copper sulfide (CuS) was grown and transported in an injectable hydrogel (Au-CuS@Gel). Au-CuS@Gel can accelerate all stages of diabetic wound healing. The rough surface of Au-CuS@Gel and the injectable property of hydrogel can adhere to close the wound and generate reactive oxygen species (ROS) under near infrared (NIR) light to effectively kill bacteria in diabetic wounds. Meanwhile, the rough morphology effectively polarizes macrophages to M2 phenotype and accelerates collagen deposition. Au-CuS@Gel can be programmed to promote all stages of diabetic wound healing. It provides a new paradigm for the healing of the special wounds represented by diabetes.

Porous Carbon Fabricated by Microbial Pretreatment of Brewer's Grain for the Improvement of Toluene Adsorption Performance.

Porous activated carbons (AC-AN and AC-AO) for toluene adsorption were prepared starting from brewer's grain biomass pretreated with microorganisms (Aspergillus niger van Tieghem for AC-AN and Aspergillus oryzae RIB40 for AC-AO). The structures and chemical properties of the three activated carbon materials (AC-AN, AC-AO, and AC that was not pretreated with microorganisms) were characterized by N2 adsorption-desorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The adsorption behavior of the three activated carbons for toluene was studied and correlated with the physical and chemical properties of these materials. The results suggested that the activated carbons prepared by microbial pretreatment had a rougher morphology, higher specific surface area, richer pore structure, fewer oxygen-containing functional groups on the surface, and better adsorption performance for toluene (increased by 31.5% and 18.3% with AC-AN and AC-AO, respectively) compared with the untreated activated carbon (AC). The Thomas model was used to fit the toluene adsorption data, indicating that the rich pore structure accelerated the kinetic process of toluene adsorption. Therefore, appropriate microbial pretreatment of the feedstock that is used to prepare activated carbon can effectively improve its adsorption capacity towards toluene.

Functional role of the biofilm regulator CsgD in Salmonella enterica sv. Typhi

IntroductionTyphoid fever is an infectious disease primarily caused by Salmonella enterica sv. Typhi (S. Typhi), a bacterium that causes as many as 20 million infections and 600,000 deaths annually. Asymptomatic chronic carriers of S. Typhi play a major role in the transmission of typhoid fever, as they intermittently shed the bacteria and can unknowingly infect humans in close proximity. An estimated 90% of chronic carriers have gallstones; biofilm formation on gallstones is a primary factor in the establishment and maintenance of gallbladder carriage. CsgD is a central biofilm regulator in Salmonella, but the S. Typhi csgD gene has a mutation that introduces an early stop codon, resulting in a protein truncated by 8 amino acids at the C-terminus. In this study, we investigate the role of role of CsgD in S. Typhi. MethodsWe introduced a fully functional copy of the csgD gene from S. Typhimurium into S. Typhi under both a native and a constitutive promoter and tested for red, dry, and rough (Rdar) colony morphology, curli fimbriae, cellulose, and biofilm formation. Results and discussionWe demonstrate that although CsgD-regulated curli and cellulose production were partially restored, the introduction of the S. Typhimurium csgD did not induce the Rdar colony morphology. Interestingly, we show that CsgD does not have a significant role in S. Typhi biofilm formation, as biofilm-forming capacities depend more on the isolate than the CsgD regulator. This data suggests the presence of an alternative biofilm regulatory process in this human-restricted pathogen.

Polysiloxane-Based Composite Coatings with Bactericidal Additives

This paper examines the effect of both natural and synthetic additives of different concentrations to a polysiloxane matrix in order to obtain bactericidal composites. Natural additives such as black cumin, cloves, and turmeric were compared with silver, a well-known antiseptic, and with graphene, which has potential bactericidal properties. The first stage of the research included the production of polysiloxane composites with the above-mentioned powders in the form of bulk solid samples, and then a series of tests were carried out on them to not only assess their bactericidal properties but also determine their effect on physicochemical properties such as chemical structure, surface wettability, roughness, hardness, and surface morphology. Based on the obtained results, the most promising composite recipes were selected, and coatings were produced from them on a super-smooth substrate, which had been previously cleaned using a plasma chemical method. The obtained results indicated that all obtained materials were characterized by high bactericidal activity. The conducted studies also showed a significant effect of the introduced additives on the mechanical properties of the polysiloxane matrix, including graphene, which improved the hardness of the composites. Plasma chemical modification of the substrates increased the adhesion of the tested coatings to them. In addition, the effect of the used additive was also visible in this area.

A Study of the Effect of Roughness on the Three-Body Wear Mechanism from a Microscopic Point of View: Asperity Peak Removal

The presence of particles leads to varying degrees of mass loss on a metal sealing surface, which severely affects the seal’s lifespan. Understanding the complex wear mechanism and optimizing the surface roughness morphology are particularly important in engineering. By characterizing the surface of the metal (SS 304) with different roughness parameters Ra, Rp, Rpk, Rpc and Rku, the variation mode of mass loss under abrasive wear conditions was revealed. Unlike traditional two-body wear, the involvement of abrasive particles significantly impacts surface Ra and other surface morphologies (asperity peak features). A contact model for metal rough surfaces, distinct from two-body contact, was established to clarify the changes in removal mechanisms. It was found that the change in the contact between the particle and the asperity peak led to a change in the mass loss and guided the appropriate metal roughness range: Ra 0.05 μm and Ra 0.6–0.8 μm. In addition, it was found that the removal of asperity peaks is holistic under low roughness, and only parts of asperity peaks are removed under high roughness. Notably, the metrological methods used in this study supplement existing roughness measurements. By exploring the complex removal mechanism of asperity peaks, micro-scale guidance for surface (texture) design, machining, and optimization is provided.

Towards sustainable machining: an experimental study of eco-friendly MQL and its impact on machinability and future opportunities

Abstract Enforcement of stricter environmental policies calls for alternative methods that could reduce the usage of cutting fluid during machining. Thus, dry machining and minimum quantity lubrication (MQL) machining are gaining practical importance. From this perspective, the development of new biodegradable MQL fluids and their performance assessment during machining is acquiring global attention. In this work, Jatropha crude oil (JCO) is chemically transformed into an epoxidized product and used as a MQL fluid. The turning experiments are conducted on Nimonic 80A under varying cutting speeds, and feed rates with constant depth of cut to examine the effects on machinability characteristics. The experiments are conducted under three different environments viz. dry, conventional minimum quantity lubrication (CMQL) and epoxidized minimum quantity lubrication (EMQL). The cutting force, tool flank wear, surface roughness and chip morphology are used as performance indicators. Regarding environmental concerns, the EMQL proved to be a viable substitute for CMQL as it demonstrated the lowest cutting force, tool wear and surface roughness. EMQL can reduce tool wear and surface roughness to the extent of about 54% and 22% as compared to the dry machining environment. The cutting force is reduced by about 13% and 34% by adopting CMQL and EMQL respectively even under the high feed (f = 0.45 mm min−1) condition. The sustainability assessment model developed using the Pugh matrix environmental approach disclosed EMQL system helps in attaining the desired machinability qualities while offering environmental friendliness and cleaner production.

Removal of ofloxacin and inhibition of antibiotic resistance gene spread during the aerobic biofilm treatment of rural domestic sewage through the micro-nano aeration technology.

Micro-nano aeration (MNA) has great potential for emerging contaminant removal. However, the mechanism of antibiotic removal and antibiotic resistance gene (ARG) spread, and the impact of the different aeration conditions remain unclear. This study investigated the adsorption and biodegradation of ofloxacin (OFL) and the spread of ARGs in aerobic biofilm systems under MNA and conventional aeration (CVA) conditions. Results showed that the MNA increased OFL removal by 17.27 %-40.54 % and decreased total ARG abundance by 36.37 %-54.98 %, compared with CVA. MNA-induced biofilm rough morphology, high zeta potential, and reduced extracellular polymeric substance (EPS) secretion enhanced OFL adsorption. High dissolved oxygen and temperature, induced by MNA-enriched aerobic bacteria and their carrying OFL-degrading genes, enhanced OFL biodegradation. MNA inhibited the enrichment of ARG host bacteria, which acquired ARGs possibly via horizontal gene transfer (HGT). Functional profiles involved in the HGT process, including reactive oxygen species production, membrane permeability, mobile genetic elements (MGEs), adenosine triphosphate synthesis, and EPS secretion, were down-regulated by MNA, inhibiting ARG spread. Partial least-squares path modeling revealed that MGEs might be the main factor inhibiting ARG spread. This study provides insights into the mechanisms by which MNA enhances antibiotic removal and inhibits ARG spread in aerobic biofilm systems.

Tailoring Optical Performance of Polyvinyl Alcohol/Crystal Violet Band-Pass Filters via Solvent Features.

Optical filters are essential components for a variety of applicative fields, such as communications, chemical analysis and optical signal processing. This article describes the preparation and characterization of a new optical filter made of polyvinyl alcohol and incremental amounts of crystal violet. By using distinct solvents (H2O, dimethyl sulfoxide (DMSO) and H2O2) to obtain the dyed polymer films, new insights were gained into the pathway that underlies the possibility of tailoring the material's optical performance. The effect of the dye content on the sample's main properties was inspected via UV-VIS spectroscopy analysis combined with colorimetry, refractometry and atomic force microscopy experiments. The results revealed that the colorimetric parameters are affected by the dye amount and are dramatically changed when the solvent used for film preparation is different. The rise in the refractive index upon polymer dyeing was due to the synergistic effect of the larger polarizability of the dye and the occurrence of hydrogen bonds among the system components. Spectral data evidenced that samples prepared in H2O and DMSO preserve the absorption characteristics of the added dye, whereas H2O2 acts as an oxidizing agent and enhances transparency. Also, for the first two solvents, multiple absorption edges were noted as a result of dye incorporation, which was responsible for the occurrence of new exciton-like states, hence the band gap reduction. The films processed in H2O were able to block radiations in the 506-633 nm range while allowing other wavelengths to pass with a transmittance above 90%. The samples attained in DMSO presented similar properties, with the difference that the domain of light attenuation was shifted towards higher wavelengths. Atomic force microscopy showed the dye's effect on the level of surface roughness uniformity and morphology isotropy. The dyed polymer foils in non-oxidizing agents have suitable features for use as band-pass filters.

Magnetic hydrogel scaffold based on hyaluronic acid/chitosan and gelatin natural polymers

Owing to their native extracellular matrix-like features, magnetic hydrogels have been proven to be promising biomaterials as tissue engineering templates In the present work, magnetic hydrogels scaffold based on chitosan, gelatin, hyaluronic acid, containing Fe3O4 as magnetic nanoparticles (IONPs) were prepared. The prepared hydrogels were loaded with ciprofloxacin hydrochloride as a model drug. The magnetic hydrogel was prepared using different volumes of chitosan, 1%, gelatin, 10%, and hyaluronic acid, 1% in glutaraldehyde as the crosslinking agent and Fe3O4 as magnetic nanoparticles. The hydrogel scaffold and magnetic scaffold hydrogel samples were characterized by scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), and Fourier-transform infrared spectroscopy (FTIR). The porosity, mechanical properties, swelling degree, and antibacterial activity of the hydrogel scaffold were also determined as well as the drug release profiles of the hydrogels. SEM imaging revealed that the magnetic hydrogel scaffold showed a relatively rough morphology with an irregular surface. The data obtained indicated that the hydrogel surface has three-dimensional porous microstructures and the porosity varied depending on the hydrogel formulation. The breaking load of the hydrogel scaffold increased from 1.361 Kgf to 4.98 Kgf by increasing the glutaraldehyde concentration from 0.2 mL to 0.8 mL. Swelling degree values in water were from 250 to 2000% after 24 h. The antibacterial activity of the hydrogel scaffold ranged from 54% to about 97% for Gram-positive bacteria (S. aureus) and from about 26–92% for Gram-negative bacteria (E. coli). The ciprofloxacin hydrochloride loaded hydrogel has a sustained release of ciprofloxacin hydrochloride over 10 h. The presence of IONPs gave a faster release of ciprofloxacin hydrochloride.

Experimental investigation on the dynamic tensile characteristics and microstructure of recycled coral aggregate concrete(RCAC)

This study investigates the use of waste coral aggregate to produce recycled coral aggregate concrete (RCAC) for sustainable island construction. The recycled coral coarse aggregates (RCCA) were characterized by their crushing index, water absorption, and apparent density. Various RCAC mixtures were prepared with different RCCA substitution rates, and their mechanical properties under impact loading were tested using a Ф100mm Split Hopkinson Pressure Bar(SHPB) setup. Additionally, the microstructure of RCAC was analyzed using X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The results showed that the quasi-static splitting strength of RCAC with 50 % and 100 % RCCA substitution decreased by 32.8 % and 46.8 %, respectively, compared to 0 % substitution. The tensile-to-compressive strength ratios ranged from 1/21 to 1/13. Under impact loading, the split tensile strength of RCAC increased with strain rate. The recycled coral aggregates exhibited a porous, rough morphology, while the interfacial transition zone with the cement mortar was denser. Despite the brittleness of RCCA compared to natural aggregates, this study provides a viable path toward sustainability in island and reef construction.

Nanofoamed Polyamide Membranes: Mechanisms, Developments, and Environmental Implications.

Thin film composite (TFC) polyamide membranes have been widely applied for environmental applications, such as desalination and water reuse. The separation performance of TFC polyamide membranes strongly depends on their nanovoid-containing roughness morphology. These nanovoids not only influence the effective filtration area of the polyamide film but also regulate the water transport pathways through the film. Although there have been ongoing debates on the formation mechanisms of nanovoids, a nanofoaming theory─stipulating the shaping of polyamide roughness morphology by nanobubbles of degassed CO2 and the vapor of volatile solvents─has gained much attention in recent years. In this review, we provide a comprehensive summary of the nanofoaming mechanism, including related fundamental principles and strategies to tailor nanovoid formation for improved membrane separation performance. The effects of nanovoids on the fouling behaviors of TFC membranes are also discussed. In addition, numerical models on the role of nanovoids in regulating the water transport pathways toward improved water permeance and antifouling ability are highlighted. The comprehensive summary on the nanofoaming mechanism in this review provides insightful guidelines for the future design and optimization of TFC polyamide membranes toward various environmental applications.

Investigation of the Anticorrosive Activity of Piper divaricatum Essential Oil on Steel in 1 M HCl.

Piper divaricatum essential oil (PDEO), extracted from plants of the Brazilian Amazon, was investigated for the first time as a novel green or eco-friendly inhibitor for steel corrosion in 1 M HCl at 25 °C. Our electrochemical studies demonstrate that for different PDEO concentrations, lower E corr and i corr values were obtained. The influence of the oil concentration on corrosion inhibition, 0.5-4 g/L, was determined for 1 and 7 days of immersion. The corrosion rate (CR) and inhibition efficiency (IE) were determined by mass loss. The steel surface in the presence and absence of oil was investigated by scanning electron microscopy (SEM). The main PDEO compounds, determined by gas chromatography-mass spectrometry (GC-MS), were methyleugenol (20.68%) and eugenol (15.42%). The CR and IE for 2 g/L PDEO exhibited an optimal value of 4.31 mm/year and 98.3% for 7 days of immersion, respectively. The surface with 2 g/L oil for 7 days exhibited a less rough morphology, which was attributed to the corrosion inhibitory effect of PDEO. In addition, the PDEO adsorption process on the steel surface obeyed the Langmuir isotherm model. Negative values found for free standard energy ( < 0 kJ·mol-1) were attributed as a favorable process, i.e., an indicative of physisorption and chemisorption between the PDEO components and the steel surface. Our results reveal that the PDEO has a promising character for anticorrosive steel applications and metal coating in industries.

Evolution of tool wear and machining quality during dry milling of AlCoCrFeNi2.1 eutectic high entropy alloy

AlCoCrFeNi2.1, a new class of eutectic high entropy alloy (EHEA) has drawn significant interest owing to the lamellar structure of alternating face-centered cubic (FCC) and B2 phases. Properties such as high strength and high plasticity render the machining of this alloy challenging. Addressing this issue, the milling experiments were conducted under dry conditions to investigate the machining quality of AlCoCrFeNi2.1 EHEA as well as the tool wear. The cutting temperature and cutting force were measured to explain the changes in tool wear and machining quality. The tool wear mechanisms and evolution modes were clarified. Finally, the change of surface roughness and surface morphology under different parameters were analyzed and the characterization method of plastic flow marked by B2 phase was proposed. Results showed that both the cutting temperature and cutting force increase as the milling parameters become larger. The width of flank wear increases with the increase of the cutting speed and the feed rate when the volume of material removal volume is constant. The tool wear modes evolved differently with different cutting parameters, for instance, abrasive wear dominated while the cutting speed was less than 80 m/min, but for higher speeds up to 110 m/min, adhesive wear and coating peeling occurred. As the cutting speed increases further, crater wear on the rake face starts to arise in addition to the flank wear. Abrasive wear and adhesive wear with increasing feed rate were dominant until a certain threshold (0.10 mm/tooth) beyond which the coating peels off the tool. Furthermore, chipping occurred for a higher feed rate of 0.14 mm/tooth. In particular, the formation of tool adhesive wear is mainly caused by the FCC phase adheres. In terms of machining quality, larger cutting parameters will worsen the surface roughness and morphology as well as lead to deeper subsurface plastic flow. The research will be conducive to promoting the applications of AlCoCrFeNi2.1 HEA.

High-speed turning of AISI 4340 alloy steel using carbide tools in a sustainable minimum quantity lubrication environment

Purpose This study aims to investigate the machining performance of CVD-coated carbide tools by considering most crucial machinability aspects: cutting force, tool life, surface roughness and chip morphology in high-speed hard turning of AISI 4340 alloy steel under a sustainable minimum quantity lubrication (MQL) environment. Design/methodology/approach The purpose of this study is to analyze the performance of coated carbide tools under MQL environment therefore, machining tests were performed in accordance with the Taguchi L9 orthogonal array, accommodating the three crucial machining parameters such as cutting speed (V = 300–400 m/min), feed rate (F = 0.1–0.2 mm/rev) and depth of cut (DOC = 0.2–0.4 mm). The measured or calculated values obtained in each experimental run were validated for normality assumptions before drawing any statistical inferences. Taguchi signal-to-noise (S/N) ratio and analysis of variance methodologies were used to examine the effect of machining variables on the performance outcomes. Findings The quantitative analysis revealed that the depth of cut exerted the most significant influence on cutting force, with a contributing rate of 60.72%. Cutting speed was identified as the primary variable affecting the tool life, exhibiting a 47.58% contribution, while feed rate had the most dominating impact on surface roughness, with an overall contributing rate of 89.95%. The lowest cutting force (184.55 N) and the longest tool life (7.10 min) were achieved with low machining parameters at V = 300 m/min, F = 0.1 mm/rev, DOC = 0.2 mm. Conversely, the lowest surface roughness (496 nm) was achieved with high cutting speed, low feed rate and moderate depth of cut at V = 400 m/min, F = 0.1 mm/rev and DOC = 0.3 mm. Moreover, the microscopic examination of the chips revealed a serrated shape formation under all machining conditions. However, the degree of serration increased with an incremental raise with cutting speed and feed rate. Research limitations/implications The study is limited to study the effect of machining parameters within the stated range of cutting speed, feed rate and depth of cut as well as other parameters. Practical implications Practitioners may consider to adopt this machining technique to create more sustainable working environment as well as eliminate the disposal cost of the used metal cutting fluid. Social implications By applying this machining technique, diseases caused by metal cutting fluid to the mechanist will be significantly reduced, therefore creating better lifestyles. Originality/value Hard turning is commonly carried out with advanced cutting tools such as ceramics, cubic boron nitride and polycrystalline cubic boron nitride to attain exceptional surface finish. However, the high cost of these tools necessitates exploration of alternative approaches. Therefore, this study investigates the potential of using cost-effective, multilayer-coated carbide tools under MQL conditions to achieve comparable surface quality. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0013/