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Short-term heat treatments of tool steels, such as inductive hardening, target the martensitic hardening of functional surfaces from a metastable microstructural state of the multiphase system. Understanding the kinetics of the carbide dissolution, precipitation, growth, and coarsening, and their effect on the austenitic matrix is, thus, instrumental to designing optimal heat treatments. The present work investigates the influence of such processes on the powder-metallurgically produced high-speed steel DIN EN 1.3377 (PM HS 3-3-4). Starting from the as-delivered soft-annealed state, the microstructural evolution during the heat treatment was investigated. The heat treatments were simulated experimentally in a quenching dilatometer and numerically within the software package MatCalc. SEM and XRD provided detailed information about the microstructure, whereas hardness measurements deliver insights into mechanical properties. The developed MatCalc model can predict the carbide dissolution and the associated change in the chemical composition of the matrix during austenitizing as a function of temperature and time. The results in terms of the measured and computed martensite start temperature demonstrated good agreement between the experimental and simulation campaigns. [ABSTRACT FROM AUTHOR]

Large volume bone defects that do not spontaneously heal despite surgical stabilization ("critical-sized" defects) remain a challenge to treat clinically. Recent research investigating bone regenerative implants made from 3D printed materials have shown promise as a potential alternative to current treatment methods, such as autografting, allografting, and multi-step surgical interventions. Recent work has shown that implanting 3D printed calcium phosphate cement (CPC) scaffolds loaded with bone morphogenetic protein-2 (BMP-2) can provide a one-step surgical intervention that has similar bone healing outcomes to a popular two-step intervention: the Masquelet technique. The aim of this study was to investigate whether a 3D printed CPC scaffold loaded with a lyophilized polyplex gene-delivery formulation could serve as an alternative to loading BMP-2 protein onto such scaffolds. We 3D printed CPC scaffolds, hardened them with multiple methods, and explored the impact of these hardening methods on surface texture, mechanical strength, osteogenic differentiation, and ion flux. We then gene-activated these materials with cationic polyplexes containing plasmid DNA encoding reporter genes to investigate transfection from the gene-activated scaffolds. We found that incubating CPC scaffolds in aqueous solutions after initial hardening in a humid environment could enhance scaffold mechanical strength (compressive strength of 21.28 MPa vs. 6.54 MPa) and osteogenic differentiation. We also found that when we increased the total surface area of the CPC material exposed to polyplex solutions, there was a reduction in transfection via adsorption of polyplexes to the CPC surface. This study shows that 3D printed, gene-activated CPC scaffolds are a promising avenue for future exploration in the field of bone regeneration, though the level of gene expression induced by the scaffolds must be improved. [ABSTRACT FROM AUTHOR]

Inconel 601 alloy is a material widely used at high temperatures. One of the most important mechanical properties to consider for some of the materials used in these areas is wear. Wear that occurs at the contact points between parts both causes material loss and reduces material performance. For this reason, coatings and new lubricants are used on material surfaces to reduce wear. In this study, nanoparticle and cryogenic lubricants with different viscosities were prepared to reduce the wear of Inconel 601. Additionally, the surface is hardened by the pack aluminizing. With the 100 µm thick NiCrAl intermetallic coating layer formed on the surface by the aluminizing process, an improvement was achieved in the hardness (2.9 times) and elasticity modulus values (15%) of the surface. The wear behavior of Inconel 601 was investigated under different loads (15 N, 25 N, 35 N) and using different lubricants (Dry, Nano-MQL-Mix, Cryo-MQL, Cryo-Nano-MQL) in a ball-on-flat wear device. In the studies conducted, the lowest volume loss, friction coefficient and wear depth were achieved in Cryo-Nano-MQL conditions and aluminized samples, while the highest values occurred in a dry environment. When the volume loss results are examined, the average volume loss in the as received samples occurred in a dry environment with 2.76 mm3. When switching from dry environment to Cryo-Nano-MQL at a load of 35 N, a decrease of 96.85% is observed. In alumination samples, the average volume loss occurred in a dry environment with 1.74 mm3. When switching from dry environment to Cryo-Nano-MQL at a load of 35 N, a decrease of 97.70% is observed. Tribological performance was improved by increasing the viscosity of the lubricants used and by using the pack aluminization method. [ABSTRACT FROM AUTHOR]

AISI 1045 steel is widely used in mechanical parts of industrial equipment. However, its surface mechanical properties can be improved to increase this steel's applicability and service life. This study proposes an evaluation of the feasibility of duplex treatment concerning plasma nitriding (PN) and cathodic cage plasma deposition (CCPD) for reducing wear on AISI 1045 steel. X-ray diffraction, roughness, Vickers hardness, scanning electron microscopy, and wear test results showed that duplex treatment (PN + CCPD) caused the formation of nitride phases responsible for surface hardening, a significant increase in wear resistance for samples subjected to PN and duplex treatment. However, the sample subjected to duplex treatment showed a hardness 77.2% higher than that of the sample that was only nitrided and a greater depth of surface modification, giving the duplex treatment mechanical advantages due to the longer period of time required for AISI 1045 mechanical parts. [ABSTRACT FROM AUTHOR]

Conventional airflow is the most widely used drying process, although it has several drawbacks that affect the performance and quality of the final product. Investigators have operated various innovative drying techniques to improve the process's efficiency and the product's quality. For several years, our research team has defined new intensification drying processes such as swell drying (including Instant Controlled Pressure Drop (DIC)), Multi-Flash Autovaporization (DDS), and other intermittent drying processes. These operations, generally based on interrupting product exposure to heat, can improve energy efficiency and product quality. They have solved some of the problems of conventional continuous drying, such as long time, high-energy consumption, surface hardening, shrinkage, and poor-quality attributes. However, the definition of active and tempering periods in conventional intermittent drying has been empirical due to the lack of fundamental studies. Recently, we defined highly activated interval drying operations as an innovative drying process that intensifies drying performance and improves the quality of finished products. It aims to ideally separate the transfer phenomena during drying, exclusively dedicating the active period (tON) to surface evaporation and the tempering period (tOFF) to the diffusion of water within the product. Internal and superficial water transfer mechanisms during conventional convective drying (CCD), conventional intermittent drying (ICD), and Interval Starting Accessibility Drying (ISAD). [ABSTRACT FROM AUTHOR]

Traditional railway substructure materials (i.e., natural crushed rock aggregates used for ballast and capping layers) degrade under service loads, incurring higher periodic maintenance costs compared to recycled materials. Using recycled waste materials such as coal wash and rubber crumbs for infrastructure upgrades not only reduces construction and maintenance costs but also supports environmental sustainability. By exploring unconventional avenues, earlier studies have delved into the viability of blending rubber crumbs (RC) and coal wash (CW) as an innovative substitute for traditional railway substructure materials, with a specific focus on the capping layer. This study introduces a semi-empirical constitutive model to simulate the response of mixtures of coal wash and rubber crumbs (CWRC) using the bounding surface plasticity framework. The novelty of this study is that a modified volumetric strain expression is introduced to capture the compressibility of rubber, thus enabling a more accurate representation of the internal deformation of rubber within the granular matrix. The variation of rubber content in the mixture is captured by the corresponding critical state void ratio surface and the hardening modulus. The theoretical model is then calibrated and validated using static drained triaxial test data for CWRC mixtures as well as mixtures of steel furnace slag, coal wash, and rubber crumbs (SFS + CW + RC). [ABSTRACT FROM AUTHOR]

Laser hardening is used for surface hardening of wear parts. Laser equipment is suitable for hardening small and geometrically complex elements. The hardening depth is 0.1 - 1.5 mm. Experimental studies using the robot KUKA KR120 have shown that the process of laser hardening does not always lead to positive results under certain conditions of parts processing, so there is a need to create a calculation base for rational choice of parameters of the process. On the basis of the considered assumptions and limitations, a mathematical model is formulated, which is a boundary value problem for calculating the unsteady thermal state of a metal plate and determining the depth of its heating and possible penetration when the laser beam moves along its surface. A numerical algorithm is proposed that allows to approximate solve the boundary value problem of the plate warm state, to determine the depth of the hardened layer and rational parameters of metal cooling. The calculation of non-stationary temperature fields in a 40X steel plate when exposed to a laser beam with two modes of cooling it with water is shown. The depth of metal penetration and the depth of its hardening are determined. [ABSTRACT FROM AUTHOR]

This study aimed to develop an alternative surface hardening technique for low-carbon steel alloy type 20Ch using plasma electrolytic oxidation (PEO). The surface hardening of 20Ch alloy steel samples was achieved through PEO in a Na2CO3 electrolyte solution. Optimal processing parameters were determined experimentally by measuring voltage and applied current. Quenching was performed in the electrolyte stream, and plasma was ionised through excitation. A mathematical model based on thermal conductivity equations and regression analysis was developed to relate the key parameters of the hardening process. The results from both the experimental and mathematical models demonstrated that PEO significantly reduces hardening time compared to traditional methods. The microstructural images revealed the transformation of the coarse-grained pearlite–ferrite structure into quenched martensite. Vickers microhardness tests indicated a substantial increase in surface hardness after PEO treatment, compared to the untreated samples. The major advantages of PEO include lower energy consumption, high quenching rates, and the ability to perform localised surface treatments. These benefits contribute to overall cost reduction, making PEO a promising surface hardening method for various industrial applications. [ABSTRACT FROM AUTHOR]

In this study, anisotropic non-proportional hardening behaviour of the sheet metals with different crystalline structures is investigated. The investigated materials particularly exhibit the Bauschinger effect and complex transient hardening behaviour during loading path change. Furthermore, the finite element simulations are carried out to evaluate the performance of the distortional and multi-surface-kinematic hardening models in flow stress prediction under loading path change. Both models can well reproduce the measured anisotropic hardening, but the distortional hardening concept shows better predictive capability for flow stresses. The improved accuracy of the flow stress prediction with the distortional hardening model compared to the kinematic hardening is attributed to its flexibility in distortion of the yield surface following microstructure deviator independent on the initial yield surface. In contrast, the initial size of the yield surface in the kinematic hardening significantly affects the determination of the re-yielding stress at load reversal. [ABSTRACT FROM AUTHOR]

The cutting characteristics of Inconel 718 alloy are high hardness and surface hardening, causing fast tool wear, severe chipping, and inadequate machining accuracy. In order to overcome the existing challenges, this study proposes a method to enhance the cutting performance by injecting fullerene C60 nanoparticle cutting fluid with minimum quantity lubrication (MQL) into the cutting zone. Leveraging the Johnson–Cook constitutive model and the imaginary heat source method, this study simulates the cooling effect and friction reduction characteristics of the cutting contact interface under minimum quantity lubrication conditions, and assessment of cutting energy consumption using predicted and measured specific cutting energy (SCE). Through friction wear tests, the friction coefficient changes under various lubrication conditions are measured. The impact of lubrication conditions on friction and wear mechanism is analyzed. The cutting test results demonstrate that variations in cutting parameters significantly influence energy efficiency, with specific cutting energy exhibiting a downward trend as the material removal rate (MRR) increases. Notably, C60 nanoparticle minimum quantity lubrication (NMQL) stands out excellent friction reduction and cooling effects among other lubrication methods. Experimental data indicate that NMQL compared with dry cutting, flood cutting, and pure MQL, the specific cutting energy is reduced by 31.3%, 19.13%, and 17.37%, respectively, and that the cutting energy performance is significantly improved. The maximum error of the SCE prediction model is 17.5%, and the prediction results align well with the experimental findings. Moreover, this study provides novel insights for advancing machining theory and exploring sustainable green machining of nickel-based alloys. [ABSTRACT FROM AUTHOR]

To refine the grain organization of the coating and improve the quality of the fused coating, ultrasound-assisted laser cladding technology was used to prepare WC-Fe60 composite coating on the surface of 16Mn steel. With the help of a metallurgical microscope, microhardness tester, scanning electron microscope, energy spectrum analyzer, ray diffractometer, friction and wear testing machine, and other means of characterization, the physical composition of the coating, macroscopic morphology, microstructure, hardness distribution, friction factor, and other parameters were analyzed and tested. The results indicate that the surface of the cladding layer prepared with ultrasonic vibration became smoother, and the slag reduced in size and quantity. The cavitation effect and acoustic streaming generated by ultrasonic vibration refine the coating grains, primarily composed of small equiaxed crystals with a minor amount of dendrites. There was a significant reduction in pores and cracks within the coating, and the intense high-frequency vibration homogenized the distribution of coating elements. The coating phase consists of α-Fe, γ-Fe, M23C6 (M: Cr, W, or Fe), and WC. Following the application of ultrasonic vibration, the average microhardness of the coating reached 1150HV0.5, marking a 30% increase compared to the coating without ultrasonic vibration. The friction coefficient stood at 0.60, a decrease of ∼14%, resulting in improved wear resistance. Ultrasound-assisted laser cladding notably enhances the quality of the prepared coating, densifies the microstructure, and boosts hardness and wear resistance. This study offers a theoretical foundation for the advancement of wear-resistant materials and the refinement of surface hardening techniques. [ABSTRACT FROM AUTHOR]

To broaden the process understanding with regard to a tool concept for finishing operations based on soft foams coated with diamonds, the application behaviour with respect to the surface preparation of a ground hardened steel surface is considered. By analysing the surface on the basis of established roughness parameters, the material removal behaviour is investigated in dependence on the process parameters and tool specifications. Furthermore, the influence on the micro roughness superimposed on the roughness profile can be analysed. The recorded process forces serve as a basis for understanding the underlying mechanisms and for interpreting the results. [ABSTRACT FROM AUTHOR]

AISI 1045 steels are medium carbon steels used in applications that require greater strength and hardness such as gears, railway wheels and tracks, crankshafts, rolls, axles and other structural components. Although AISI 1045 steels are highly demanded engineering materials, they suffer from deformation and wear resistance when these applications are used. The hardness and wear resistance of the material are improved using a surface hardening method. Pack nitriding is the cheapest and easiest method of surface hardening method implemented in this work. The surface hardness of AISI 1045 steel is improved by the diffusion of nitrogen from the nitrogen-bearing material (melamine) to the surface of the steel and forms a metal nitride compound, which has strong hardness and wear resistance. This work reports that substantial surface hardening of AISI 1045 steel was achieved by the pack nitriding method using melamine obtained by in situ reaction of urea. The surface hardness increases manifold with the amount of melamine used, soaking time and temperature. The microscopic investigations of the nitrided surfaces of the metal show the formation of two distinct layers. The microstructural properties and hardness of the samples before and after nitriding were thoroughly investigated and interpreted. [ABSTRACT FROM AUTHOR]

Nitriding is a thermochemical surface hardening process, which can be used to improve the performance properties of gears. In particular, the tooth flank and tooth root load-carrying capacity can be significantly increased by nitriding. Previous work has shown that tribological dominated failure modes and limits, such as the micro-pitting and wear load-carrying capacity of gears, can be significantly increased by a suitable compound layer structure. In this work, the relationship between compound layer design and macro-pitting load-carrying capacity of nitrided gears is explored based on experimental investigations. For this purpose, the materials EN31CrMoV9 and EN42CrMo4 were nitrided under varying nitriding conditions to produce compound layers with different structures and properties. The characteristics of the compound layer such as phase composition, compound layer thickness and pore seam were extensively characterized by means of metallographic techniques, XRD, GDOES, and EBSD. Experimental investigations of the macro-pitting load-carrying capacity were carried out on an FZG back-to-back gear test rig with center distance a = 52 mm. It was shown that the pitting load-carrying capacity depends to a large extent on the characteristics of the compound layer, in particular on the formation of the pore seam. A minimum pore seam thickness of CLTP ≥ 1.8 µm has a positive effect on the pitting load-carrying capacity. The test results for the pitting load-carrying capacity are above (σH lim ≥ 1690 N/mm2) or, in some cases, significantly above (σH lim = 1979 N/mm2) the strength values specified in ISO 6336-5:2016 for nitrided nitriding steels (σH lim = 1450 N/mm2; material quality ME) and case-hardened alloy steels (σH lim = 1650 N/mm2; material quality ME). [ABSTRACT FROM AUTHOR]

Air‐processed perovskite solar cells are desirable for the large‐scale manufacturing application in the future, yet the presence of moisture and oxygen goes against perovskite crystallization and deteriorates phase stabilization, leading to the formation of substantial defective nano‐impurities, especially on the vulnerable surface. Here, we propose a strategy to simultaneously remove superficial defect layer and solidify the surface by soaking air‐fabricated perovskite film into low‐polar organic esters at elevated temperature to trigger an in situ dynamic surface lattice disassemble and reconstruction process. Molecular dynamics simulations and experimental results indicate that the inorganic CsPbI2Br perovskite is first dissolved and then the Br‐rich phase is recrystallized at solid–liquid interface owing to the balance between weak solubility and high‐temperature induced annealing process, thus hardening the soft surface and releasing the lattice tensile stress, which benefits the minimization of interfacial recombination and improvement of the structural stability. As a result, we prepare a carbon‐based CsPbI2Br device in complete air without precise control on humidity, achieving a champion efficiency of 15.37 % with excellent resistance to harsh attackers. This method offers a promising avenue for overcoming the limit of processing conditions on advancing perovskite‐based optoelectronic devices. [ABSTRACT FROM AUTHOR]

This study examines the effect of gallium doping on the phase transformation, transmission, and hardness of commercial multispectral-grade ZnS specimens exposed to Ga2S3 vapor. Using secondary ion mass spectrometry, we show that Ga diffusion extends into the subsurface down to several tens of microns. X-ray diffraction patterns reveal minimal to no precipitation of wurtzite, resulting in limited infrared transmission loss after treatment. We report a monotonic increase in Vickers surface microhardness with increasing Ga concentration, reaching values more than double those of untreated windows. Future work will focus on optimizing this process and evaluating its effectiveness in enhancing the durability of ZnS windows under harsh environmental conditions. [ABSTRACT FROM AUTHOR]

This paper explains about the mechanical insertion of graphite particles into aluminum (Al-1100) surface for forming composites on the surface through an electrical resistance heat-supported pressing procedure. The surface of the aluminum is first graphite coated by solution casting. To achieve impregnation, the graphite–aluminum interface is locally heated with the assistance of electrical resistance heating followed by mechanical pushing. The degree to which aluminum surface softens can be regulated by process factors like current and heating time. Microstructural characterization of aluminum–graphite composite was carried out with SEM, TEM, Raman spectroscopy and XRD. It was revealed from the microstructural characterization that graphite particles were impregnated into the aluminum surface without agglomeration. Raman spectroscopy of graphite-impregnated surface shows a shift in major graphite peaks and an increased ratio of intensity ( I D / I G ). The presence of carbide compound (Al4C3) was not detected from the XRD and TEM studies. The mechanical property examination of the surface was carried out by nanoindentation and the subsurface was characterized by microhardness tests. It was observed that surface mechanical property and reduced Young's modulus were improved by more than 200% and 150%, respectively. The projected method can be utilized as a surface modification technique in solid-state by fabricating surface composites fabricated through mechanical insertion of particulate reinforcement at sub-melting temperatures of substrate and under an open producing environment. [ABSTRACT FROM AUTHOR]

The publication presents the results of research on the influence of hydrostatic burnishing process on the value of selected parameters of surface roughness, material ratio and surface hardness. The process was carried out on shafts made of the X5CrNi18-10 stainless steel. The prepared samples were subjected to a finishing turning process with constant cutting parameters, and then hydrostatic burnishing was performed on the surface. The tests determined the influence of the variable pressure exerted by the ball on the shaft surface. The evaluation of the research results showed a significant increase in hardness in the surface layer and an improvement in surface roughness parameters and material ratio. The machining process was carried out on a conventional lathe. [ABSTRACT FROM AUTHOR]

The double-connection structure of bionic joints of mining drill pipes has solved the problem of drill drop caused by fatigue cracks. However, with low-melting-point elastic–ductile alloy filling in the bionic joint, the thread on the joint cannot be hardened by high-temperature surface hardening treatments such as quenching and nitriding, making it prone to thread gluing or excessive wear. In this paper, the feasibility of diamond-like film deposition on the surface of a bionic drill pipe thread was studied. A tungsten transition film was used to improve the thickness of the film and the interfacial bond strength between the film and the substrate. The test results show that the total thickness of the DLC film is about 3~5 μm, the roughness is less than 2 μm, the hardness of the film reaches 24.4 GPa, the friction coefficient is 0.04, and the critical load is 56 N. SEM and EDS analyses show that the tungsten film and the bionic joint thread form a metallurgical structure. The morphology of the diamond-like carbon film is uniform and dense, and there is no obvious stratification between the substrate material. The joint with a diamond-like coating treatment has a longer service life than joints receiving conventional high-temperature nitriding treatment. [ABSTRACT FROM AUTHOR]

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The interaction of laser radiation with matter is considered. Marking of non-metallic materials re- quires heating below the softening point, heat treatment requires heating to temperatures above the phase transformation temperature, laser cutting of metals occurs with heating above the melting point, and engraving occurs above the melting or evaporation point. The choice of a laser for a certain type of processing is determined by the specific impact of laser radiation on a given material and the characteristics of the technological task at hand. Laser radiation in the UV range with a wavelength of λ = 355 nm, which can be obtained through third harmonic generation, is increasingly used in industry. Recommendations are pro- vided for the use of low-power pulsed UV lasers for marking, engraving, cutting of metallic and non- metallic materials and surface hardening of steels. The paper presents the results of a study of the effect of laser radiation wavelength on metal engraving. The studies show that engraving with a beam with a radiation wavelength of λ = 0.355 µm allows obtaining a high-quality image without melting the surface. Due to the fact that radiation with a wavelength of λ = 0.35 µm is equally well absorbed by metals and dielectrics, UV-lasers can be used for separation operations in microelectronics, for example, for cutting flexible printed circuit boards with high quality. Reducing the diameter of the focus spot of the UV-laser compared to the focus of the CO2-laser makes it possible to reduce the radiation power and perform better cutting. Comparison of thermal strengthening of steels by volume hardening, laser hardening with melting, laser hardening by UV-radiation showed high efficiency of hardening by UV-radiation. Laser processing in the UV-range is rationally used for local surface hardening of fuel equipment parts, cutting tools [ABSTRACT FROM AUTHOR]

Nowadays, AISI 304 stainless steel plays a crucial role in industry. However, stainless steel exhibits limited wear resistance as it is used in parts with relative motion. Laser treatment emerges as a promising approach to improve its superficial properties. Using a laser as a heat source presents unique properties for heating surfaces, as the first atomic layers of the material absorb the radiation from the laser beam. In this study, we used a low-cost 100 W CO2 laser with carbon black powder to treat the surface of AISI 304 steels. In addition, the reflectance of irradiation on steel is 90%. We used carbon black powder as a photo-absorbing material for radiation to overcome this obstacle. The characterization included field emission gun–scanning electron microscopy, energy dispersive x ray, microhardness, and pin-on reciprocation tribometer. The results showed a significant increase in surface hardness after laser treatment compared to the untreated substrate at a magnitude of 3.8 times. Elemental mapping analysis revealed carbon's presence on the substrate's surface. In addition to increasing surface hardness, we observed a decrease in the friction coefficient of the laser-treated samples compared to the reference substrate. Finally, it could be concluded that carbon black powder had a triple function; it acted as a photo-absorbent material, a carbon source to increase surface hardness, and a solid lubricant. These results show the predictions of using a low-cost CO2 laser with carbon black powder as an efficient, versatile, and fast alternative. [ABSTRACT FROM AUTHOR]

In recent years, the industry has demanded high hardness, wear resistance, corrosion resistance, and other properties for critical components made of steel and its alloys. Enhancing the surface properties of a part by applying modification techniques to its surface is considered to be an economical and efficient method. Laser hardening, as a new surface modification technology, has received more and more attention due to its high hardening efficiency, fast cooling rate, and excellent surface properties. Laser hardening technology has good application prospects in surface modification, and significant progress has been made in the exploration of laser hardening strengthening mechanisms, optimization of process parameters, high-quality preparation of hardened layers, and theoretical simulation. However, some problems need to be addressed in the practical application of the technology. This paper reviews the research progress of the laser surface hardening process for steel and its alloys, including numerical investigation, process optimization, hardening performance analysis, and external field-assisted laser hardening technology. It also discusses the problems and challenges faced by the technology and gives an outlook on its development trend. [ABSTRACT FROM AUTHOR]

Aluminum alloy 7075 is utilized widely across marine, aerospace, and automotive sectors. However, its surface wear resistance has hindered its application in certain tribological environments. Addressing this challenge, the current study examines a hybrid laser method to increase surface wear resistance by combining two techniques: ultrafast laser texturing and laser‐based surface hardening. Ultrafast laser processing is conducted using 3 W laser power, 100 kHz pulse repetition rate, 4 mm s−1 scanning speed, and three different scan patterns. After the texturing operation, laser‐based surface hardening is then performed on these textures using a continuous wave laser. The laser heat treatment is conducted using laser powers of 400 and 500 W with three different scan speeds of 1, 2, and 3 mm s−1. Microhardness evaluations show a notable increase in hardness, with the hardest sample exhibiting a 17.8% increase compared to the pristine sample. The laser‐textured and laser heat‐treated samples exhibit a significant reduction in the average coefficient of friction and wear volumes compared to samples that were laser‐textured but not laser heat‐treated. The investigated laser processing strategy offers a promising approach for surface modification, enhancing both mechanical properties and wear resistance of aluminum alloy 7075 surfaces. [ABSTRACT FROM AUTHOR]

Jimibong is a north-facing horseshoe-shaped scoria cone in the northeast of Jeju Island that released lava flows to form a semicircular lava plateau. Sixty volcanic hummocks comprising scoria, spatter, and volcanic bombs are found on the lava plateau. The hummocks can be classified into Type 1 and Type 2 according to clast components, distance from the vent, and internal structure. Type 1 hummocks, distributed within approximately 1,000 m of the vent, comprise scoria deposits mixed with volcanic bombs and relatively few dykes that rise from the underlying lava. In contrast, Type 2 hummocks, distributed 1,000–1,300 m from the vent along the coast, comprise spatter/scoria and volcanic bomb deposits. The spatter/scoria of the Type 2 hummocks is highly agglutinated with abundant squeezing dykes that originated from the underlying lava and locally extruded over the hummocks. Although both the Type 1 and Type 2 hummocks comprise parts of the collapsed and rafted spatter/scoria blocks, their differences in shape, clast components, and structures are explained by changes in the eruption style (from spatter to scoria) and rheological changes in the lava with distance from the vent. Lava flows breached the cone following spatter-dominated eruptions in the early stages of Hawaiian eruption. Through this partial cone collapse, spatter blocks were transported with the lava flow away from the cone. The lava surface then cooled and hardened as the lava temperature decreased and viscosity increased. The contraction of the lava due to cooling caused the rafted cones to fragment into various sizes as they cracked, fractured, and rotated. Hot liquid lava from within the flow was squeezed-up because of the volcanic load of the rafted blocks, intruding into the fractures in the rafted blocks before locally flowing over them, creating the characteristic Type 2 hummocks. In contrast, Type 1 hummocks formed in the later stages of Strombolian activity, when scoria-dominant eruptions caused collapsed scoria blocks to be rafted with the lava flow. These scoria blocks were deposited in areas proximal to the cone and show few dyke intrusions due to the limiting effects of edifice load on dyke development. The Jimibong volcano provides an example of changing hummock structures in relation to changing eruption styles of scoria cones, deepening our understanding of the geomorphic development in volcanic regions. [ABSTRACT FROM AUTHOR]

Wax warm additives are widely used in asphalt mixture production due to their energy savings and low cost. However, the compatibility problem between waxes and asphalt binders leads to wax precipitation and asphalt low-temperature cracking. Plasma treatment technology can modify the surface of waxes. In this study, plasma technology was used to modify Fischer Tropsch (FT) wax surfaces, linear aliphatic hydrocarbon wax, and two plastic cracking waxes. The effects of waxes on the high-temperature performance, fatigue performance, low-temperature physical hardening, and wax precipitation temperature of asphalt binders were evaluated by the multistress creep recovery (MSCR) test, linear amplitude sweep (LAS) test, extended bending beam rheometer (ExBBR) test, and dynamic shear rheometer (DSR) viscosity test. In addition, the effect of plasma treatment on waxes in terms of low-temperature physical hardening and wax precipitation temperature was explored. The results showed that the effect of waxes on the high-temperature properties of asphalt binders was related to wax type, dosage, and stress level. Within the allowable dosage range, waxes improve the fatigue properties of asphalt binders. After plasma treatment, the surface roughness and activity of waxes were increased, resulting in the alleviation of physical hardening of waxed asphalt binders and a decrease in wax precipitation temperature. Among them, plastic cracking waxes were more sensitive to the plasma treatment technique. [ABSTRACT FROM AUTHOR]

Granular crushing significantly changes mechanical behaviours, especially under elevated stress levels. Therefore, this study aims to develop a model to simulate the constitutive behaviours of granular materials at the crushing-dominant stage. Firstly, the contour of elastic potential energy is demonstrated and employed to derive the yield surface or function, acknowledging that the stored elastic energy dominates the breakage yield criterion. The versatility of the proposed yield function in accurately capturing the features of yield surfaces is verified with three cases, including Cam-clay models, test results, and an empirical yield function. Next, a hardening parameter, H, is formulated, considering the extent of crushing, B, and the void ratio, e, to reflect the expansion of the yield surface during hardening. The proposed simple hardening formulation favourably represents compression characteristics under elevated stress levels. Combining the above results of yield and hardening functions, a new elastic–plastic-crushing constitutive model is developed; the model's capability to describe crushable granular material behaviours is validated against experimental counterparts. [ABSTRACT FROM AUTHOR]

Anti-fatigue design in the machining process of aviation material requires advanced processes to enhance the surface integrity and a holistic model which can optimize the process aiming at maximum fatigue life. In the present study, the axial ultrasonic assisted milling process was utilized to machine the Inconel 718 while the process executes the thermomechanical cutting and peening action simultaneously. To optimize the process factors, a hybrid model using a combination of regression analysis and an analytical model was developed to correlate the machining factors, i.e., vibration amplitude, cutting velocity and feed rate to fatigue life. Herein, the former was used to map the process inputs to surface integrity aspects (SIAs), viz. roughness, hardness and residual stress; then, the SIA was mapped to fatigue life through a stress-based approach. The obtained results revealed that there is close agreement between the measured and predicted values of fatigue life where the prediction error is less than two times the dispersion. On the other hand, applying ultrasonic vibration at the highest amplitude together with the maximum feed rate and cutting velocity yield significant improvement in fatigue life, i.e., three times the same condition without ultrasonic vibration in light of the enhancement of compressive residual stress and work hardening of the surface layers. [ABSTRACT FROM AUTHOR]

Modern mechanical engineering faces high competition in global markets, which requires manufacturers of process equipment to significantly reduce production costs while ensuring high product quality and maximum productivity. Metalworking occupies a significant part of industrial production and consumes a significant share of the world's energy and natural resources. Improving the technology of manufacturing parts with an emphasis on more efficient use of metalworking machines is necessary to maintain the competitiveness of the domestic machine tool industry. Hybrid metalworking systems based on the principles of multi-purpose integration eliminate the disadvantages of monotechnologies and increase efficiency by reducing time losses and intermediate operations. The purpose of this work is to develop and implement a hybrid machine tool system and an appropriate combined technology for manufacturing machine parts. Theory and methods. Studies of the possible structural composition and layout of hybrid equipment at integration of mechanical and surface-thermal processes were carried out, taking into account the basic provisions of structural synthesis and componentization of metalworking systems. Theoretical studies were carried out using the basic provisions of system analysis, geometric theory of surface formation, design of metalworking machines, methods of finite elements, and mathematical and computer modeling. The mathematical modeling of thermal fields and structural-phase transformations during HEH HFC was carried out in ANSYS (version 19.1) and SYSWELD (version 2010) software packages using numerical methods of solving differential equations of unsteady heat conduction (Fourier equation), carbon diffusion (2nd Fick's law) and elastic–plastic behavior of the material. The verification of the modeling results was carried out using in situ experiments employing the following: optical and scanning microscopy; and mechanical and X-ray methods of residual stress determination. Formtracer SV-C4500 profilograph profilometer was used in the study for simultaneous measurement of shape deviations and surface roughness. Surface topography was assessed using a Walter UHL VMM 150 V instrumental microscope. The microhardness of the hardened surface layer of the parts was evaluated on a Wolpert Group 402MVD. Results and discussion. The original methodology of structural and kinematic analysis for pre-design studies of hybrid metalworking equipment is presented. Methodological recommendations for the modernization of multi-purpose metal-cutting machine tool are developed, the implementation of which will make it possible to implement high-energy heating with high-frequency currents (HEH HFC) on a standard machine tool system and provide the formation of knowledge-intensive technological equipment with extended functionality. The innovative moment of this work is the development of hybrid metalworking equipment with numerical control and writing a unique postprocessor to it, which allows to realize all functional possibilities of this machine system and the technology of combined processing as a whole. Special tooling and tools providing all the necessary requirements for the process of surface hardening of HEH HFC were designed and manufactured. The conducted complex of works and approbation of the technology of integrated processing in real conditions in comparison with traditional methods of construction of technological process of parts manufacturing allowed to obtain the following results: increase in the productivity of processing by 1.9 times; exclusion of possibility of scrap occurrence at finishing grinding; reduction in auxiliary and preparatory-tasking time; and reduction in inter-operational parts backlogs. [ABSTRACT FROM AUTHOR]

The document discusses advances in low-temperature nitriding and carburizing of stainless steels and metallic materials to enhance their surface properties. By using low-temperature treatments, expanded phases can be formed in stainless steels, improving surface hardness, wear and fatigue resistance, and corrosion resistance. These treatments have been successful in various stainless steel grades, as well as non-ferrous alloys, and have been applied to additively manufactured parts. The research aims to provide valuable insights for scientists and engineers involved in surface engineering processes for stainless steels and metallic materials. [Extracted from the article]

Following sustainability in manufacturing, the machining chain can be optimized by either reducing the time and energy consumption of each operation or eliminating the unnecessary operations subjected to keeping the quality of the final product as consistent. However, the roadblock in designing an optimum machining chain is lack of prediction tool to interact between the included operations. In this paper, an integrated algorithm is developed to simulate the surface roughness generation and following modification caused by milling and burnishing, respectively. Predict the surface roughness generation by milling process and its alternation after burnishing. The algorithm works on the basis of clouds of points which were generated in the engagement region of tool and workpiece and their transformation from tool to workpiece coordinate systems. Moreover, some mechanical attributes of the process regarding effect of surface work hardening and elastic rebound were added to the algorithm to enhance the accuracy of simulation. To verify the results, a series of burnishing experiments with multi-roller rotary tool have been carried out on the surface of the finish-milled samples and the surface roughness change was taken into investigation. The obtained results showed that by applying the work hardening and springback effect to predictive algorithm the prediction accuracy of roughness at submicron level enhances up to 50%. It was also found that the most influential parameters influencing the surface roughness after milling-burnishing sequence are milled surface roughness, burnishing force and pass number. In addition, results showed that applying burnishing after rough machining consumes lots of energy to achieve nanoscale surface finish. Accordingly, the sequence of rough-milling, finish-milling and burnishing results in achieving sound surface finish within significantly shorter period of time and applied force. [ABSTRACT FROM AUTHOR]

Nowadays, emerging of new technologies causes implicitly the increased requirements for conventional methods and materials. Literature survey shows that combined thermomechanical processes of surface hardening and finishing using highly-concentrated energy sources are promising to enhance the surface integrity and operational properties of structural steels. Some surface-related and microstructural factors can be considered crucial for properties’ enhancement, viz., surface roughness and waviness, grain size and phase composition, residual macro stresses, and microhardness. In this work, a laser heat treatment (LHT) followed by an ultrasonic impact treatment (UIT) also known as high-frequency mechanical impact (HFMI) treatment is sequentially applied to the AISI 1045 steel to demonstrate the efficiency of their combined influence. The near-surface microstructure formed after the combined LHT + UIT process is observed by optical microscopy, transmission electron microscopy, and x-ray diffraction analysis. The surface residual macro stresses, microhardness, roughness, and waviness are also evaluated. The results show that the combined LHT + UIT-treatment induces phase transformation and severe plastic deformation, forming layered hardening and grain structure refinement in the near-surface layers of medium-carbon steel. The subsurface microhardness at a depth up to ≈50 µm after the combined treatment is significantly increased (>10 GPa) due to the severe plastic deformation of the LHT-formed martensitic lamellas, providing the Nano equiaxed grain microstructure in the subsurface layer. The hardening depth (140–440 µm) in the LHT + UIT-treated samples depends on the LHT speed (40–140 mm/min) and the heating temperature (1200–1300 °C) by scanning laser beam. Additionally, taking into account the sur - face residual compressive macro stresses (>400 MPa), smoother microrelief on the surface, and reduced roughness parameters (Ra < 0.5 µm) formed by UIT, the studied steel functionality is expected to be improved. The combined laser–ultrasonic surface hardening and finishing process can be used for large-size steel product treatment. [ABSTRACT FROM AUTHOR]

High-entropy alloys exhibit great potential for cryogenic applications. This study investigates the nano-scratching behavior of CuCoCrFeNi high-entropy alloy at a cryogenic temperature (77 K) using molecular dynamics. Results show that compared with the single-grain model, the average friction coefficient (AFC) increases for all three polycrystalline models with different grain sizes d, but the anti-wear property can be improved by 28.5%, when grain size d = 10.7 nm. The smaller friction on the scratching surface of the single-grain model (AFC is 15.5% less than that of the model with d = 8.2 nm), which makes the overall temperature rise lower compared to that of the polycrystalline models. However, due to the stress concentration released when a complete stacking fault tetrahedron is produced, the single-grain model cannot significantly harden the surface and subsurface to a greater degree. In the polycrystalline models, dislocations are blocked at grain boundaries (GBs). However, the introduction of GBs changes the von Mises stress distribution. Finally, an attempt was made to reveal the role of yield pressure H3/E2 (H—hardness, E—elastic modulus) in friction-reducing and anti-wear properties. [ABSTRACT FROM AUTHOR]

The article presents the test results on the technology of surface hardening of castings from unalloyed and low-alloy nodular cast iron using the method of surface heat treatment, i.e., induction surface hardening and methods of thermochemical treatment, i.e. gas nitriding, nitrocarburizing, and nitrocarburizing with oxidation. The scope of research included macro- and microhardness measurements using Rockwell and Vickers methods, respectively, as well as metallographic microscopic examinations using a light microscope. Furthermore, abrasive wear resistance tests were performed using the pin-on-disk method in the friction pair of nodular cast iron – SiC abrasive paper and the reciprocating method in the friction pair of nodular cast iron – unalloyed steel. Analysis of the test results shows that the size and depth of surface layer hardening strongly depend on the chemical composition of the nodular cast iron, determining its hardenability and its ability to create diffusion layers. Medium induction surface hardening made it possible to strengthen the surface layer of the tested nodular cast irons to the level of 700 HV0.5 with a hardening depth of up to approximately 4000μm, while various variants of thermochemical treatment provided surface hardness of up to 750 HV0.5 with a hardening depth of up to approximately 200μm. Furthermore, induction surface hardening increased the resistance to abrasive wear of nodular cast iron castings, depending on the test method, by an average of 70 and 45%, while thermochemical treatment on average by 15 and 60%.

Climate change and intensified human activities have disrupted the natural hydrological regime and rhythm of river-connected lakes, extending the dry season, increasing water loss, and exposing previously submerged lake floors. This exposure has led to significant sediment hardening, which directly impacts submerged macrophytes. However, strategies to mitigate the negative effects of hardened sediments and promote the growth and development of submerged macrophytes remain largely unexplored. In this study, we selected typical hardened sediment from Dongting Lake to investigate the response of different growth forms of submerged macrophytes to multiple sediment remediation measures (loosening and litter addition) using a mesocosm experiment. The results indicated that loosening alone uniformly benefited all submerged macrophytes by increasing total biomass, relative growth rate (RGR), and the root/shoot ratio. Additionally, loosening altered the root traits of submerged macrophytes, promoting maximum root length (MRL) while reducing average root diameter (ARD). Moreover, different submerged macrophytes exhibited species-specific responses to the combination of loosening and litter addition. Notably, the combination of loosening and adding Miscanthus lutarioriparius litter had an antagonistic effect on the growth of Potamogeton wrightii and Myriophyllum spicatum. The response of functional traits of submerged macrophytes with similar growth forms to the same treatment was consistent. Our findings suggest that future sediment remediation efforts should consider matching specific treatments with the growth forms of submerged macrophytes to achieve optimal outcomes. [ABSTRACT FROM AUTHOR]

The work deals with the influence of the reach of the applied tool holder on the edge wear, dimensional accuracy and surface quality defined by the topography as well as the roughness of the machined surface. The research has been conducted on specimens made of Inconel 718 in the configuration of sleeves, within the scope of finish turning with constant cutting parameters, vc = 85 m/min; f = 0.14 mm/rev; ap = 0.2 mm. The material under machining has undergone heat treatment procedures such as solution treatment and precipitation hardening, resulting in a hardness of 45 ± 2 HRC. Two kinds of turning holders have been used with the reaches of 120 mm and 700 mm. The tools are intended for turning external and internal surfaces, respectively. The tests have been conducted using V-shaped cutting inserts manufactured by different producers, made of fine-grained carbide with coatings applied by the PVD (Physical Vapour Deposition) and CVD (Chemical Vapour Deposition) methods. The edge wear has been evaluated. The value of the achieved diameter dimensions has also been assessed in relation to the set ones, as well as the recorded values of surface roughness and the surface topography parameters have also been assessed. It has been determined that the quality of the manufactured surface evaluated by the 2D and 3D roughness parameters, as well as the dimensional quality are influenced by the kind of the applied tool holder. The influence is also visible considering the edge wear. The smallest values of the deviations from the nominal dimensions have been obtained for the coated inserts of the range of higher abrasion resistance (taking into account information from the producers). The obtained results show that in predicting the dimensional accuracy in the process of turning Inconel 718 alloy with long-overhang tools, one should consider the necessity of correction of the tool path. Taking into account the achieved surface roughness, it should be pointed out that not only the kind of the tool coating but also the character of its wear has a great influence, particularly, when a long cutting distance is required. [ABSTRACT FROM AUTHOR]

The paper focuses on plasma cutting of AA5056 and AA2024 aluminum alloy sheets. It is shown that at the minimum thicknesses, the upper edge of the sheet tends to undercut when using reverse polarity. This phenomenon considerably diminishes when using the best cutting conditions. In the case of the AA2024 alloy, most of the material remains in the cutting zone, adhering to the surface and forming a substantial zone of melting or beading. The AA2024 alloy demonstrates a greater oxidation and hardening of the cutting surface. Degraded material layers and surface roughness reduce when using the best cutting conditions. The upper edge of both alloys is more homogeneous and exhibits less roughness than the lower edge. This is attributed to a more complex displacement of the metal relative to the lower edge undercut. [ABSTRACT FROM AUTHOR]

The present study aims to predict the fatigue strength of ion-nitrided 42CrMo4 steel, using multiaxial high cycle fatigue (HCF) criteria and considering the effects of stabilized residual stresses and surface hardening. The predicted fatigue strength was compared to experimental data obtained after three-points bending fatigue tests at two stress ratios (0.1 and 0.5) and for notched (Kt = 1.6) nitrided and untreated specimens. A 3D finite element (FE) model of a three-point bending fatigue test was developed under ABAQUS software in order to determine the actual applied cyclic stress state at the notch. The results show that ion-nitriding treatment led to 32% improvement in the fatigue strength at 106 cycles compared to the untreated material. This improvement is explained by the advantageous effect of ion-nitriding treatment in terms of compressive residual stresses and surface layer hardening. Both stabilized residual stress state and hardening effects were successfully implemented into various multi-axial HCF criteria, including Sines, Crossland, Dang Van and Matake criteria. A sensitivity analysis has shown that Crossland criterion has permitted to predict the fatigue limits in accordance with the experimental results. [ABSTRACT FROM AUTHOR]