Increase In Hardness Research Articles

Polyvinyl acetate wood adhesive stabilized with hydroxyethyl cellulose: synthesis and characterizations

Specifically, the conventional wood adhesive uses polyvinyl alcohol (PVA) as colloid to stabilise the polyvinyl acetate (PVAc) emulsion. Green materials are being used as a result of recent study on chemicals and alternative sources. This factor has made the substitution of sustainable biopolymers for petrochemicals considerably more important. An emulsifier, sodium lauryl sulphate (SLS), was used during the addition polymerization process to produce a hydroxyethyl cellulose-grafted-poly (vinyl acetate) (HEC-g-P(VAc)) emulsion from HEC and VAc. The purpose of the study was to increase the content of renewable materials in the emulsion. The adhesive films glass transition temperatures (Tg) have been identified via Differential Scanning Calorimetry (DSC). The performance of the PVAc emulsion-based adhesive in accordance with EN 204 and EN 205 standards was evaluated by measuring the tensile shear strength of wood joints under both dry and wet conditions. The viscosity of the adhesives significantly increased along with the addition of HEC. The application of HEC led to an increase in PVAc film hardness, which was confirmed by the film’s glass transition temperature. In an environment that was wet, after 24 h, the tensile strength of the sample containing HEC increased by 54% compared to a pristine sample, as per EN 204 and EN 205. Water resistance significantly increased in sample with HEC, as was found by measuring the water contact angle which is in line with wet strength. The overall study conclusion emphasises the superior water resistance and increased adhesion capabilities of PVAc emulsion-based wood adhesives stabilised by HEC.

The microstructure evolution and mechanical properties of WC-cu-10Ni-5Mn-3Sn cemented carbides containing NbC prepared by pressureless melt infiltration

WC-based cemented carbides with different contents of NbC (0, 0.6, 0.8, 1.0, 1.2, and 1.4 wt%) are prepared via pressureless melt infiltration at 1200 °C for 1.5 h. Microstructure evolution regularity of WC-based cemented carbide is investigated to establish the effect of NbC addition and microstructure peculiarities on mechanical properties (flexural strength, hardness, and impact toughness) of final product. Experimental results reveal that NbC firstly dissolves in binder alloy during melt infiltration, which slows down dissolution-precipitation reaction of WC, thus refining WC grains. With the increase in NbC content, average WC grain size shows varying trend, achieving the minimum (3.779 μm) at NbC addition of 1 wt%. When NbC is added in smaller amounts, Nb is mainly distributed throughout binder alloy. With the increase in NbC content, Nb elements tend to form aggregates and attach to WC particle boundaries. Some WC and NbC also decompose under experimental conditions. At NbC addition greater than 1 wt%, decomposition products (Nb, W, and C) combine with other elements in binder phase to form new phases such as (Nb,W)C, Ni2W4C, Nb2C, and Nb4Ni2C. These phases further act as bridges for WC grain coarsening. Meanwhile, excessive NbC is detrimental to mechanical properties of the alloy. With the increase in NbC content, hardness and flexural strength of the alloy increase and then decrease, reaching the maximum values of 93.4 HRA and 1808.786 MPa, respectively, at 1 wt% NbC addition. In turn, impact toughness of the alloy shows consistently downward trend. Therefore, changes in mechanical properties of WC-based cemented carbides are mainly related to WC grain size, the appearance of new phases in binder phase, and their morphology.

Microstructure, crystallographic texture and mechanical properties of the Zn–1%Mg–1%Fe alloy subjected to severe plastic deformation

The paper covers the production, analysis of the microstructure, crystallographic texture and deformation mechanisms of the ultrafine-grained (UFG) Zn–1%Mg–1%Fe zinc alloy demonstrating unique physical and mechanical properties compared to its coarse-crystalline analogs. The zinc alloy with improved mechanical properties was developed in two stages. At the first stage, based on the analysis of literature data, an alloy with the following chemical composition was cast: Zn–1%Mg–1%Fe. Then, the alloy was subjected to high-pressure torsion (HPT) to improve mechanical properties due to grain structure refinement and implementation of dynamic strain aging. The conducted mechanical tensile tests of the samples and assessment of the alloy hardness showed that HPT treatment leads to an increase in its tensile strength to 415MPa, an increase in hardness to 144HV, and an increase in ductility to 82%. The obtained mechanical characteristics demonstrate the suitability of using the developed alloy in medicine as some implants (stents) requiring high applied loads. To explain the reasons for the improvement of the mechanical properties of this alloy, the authors carried out comprehensive tests using microscopy and X-ray diffraction analysis. The microstructure analysis showed that during the formation of the ultrafine-grained structure, a phase transition is implemented according to the following scheme: Zneutectic + Mg2Zn11eutectic + FeZn13 → Znphase + Mg2Zn11phase + MgZn2particles + Znparticles. It was found that as a result of high pressure torsion in the main phases (Zn, Mg2Zn11), the grain structure is refined, the density of introduced defects increases, and a developed crystallographic texture consisting of basic, pyramidal, prismatic, and twin texture components is formed. The study showed that the resistance of pyramidal, prismatic and twin texture components at the initial stages of high-pressure torsion determines the level and anisotropy of the strength properties of this alloy. The relationship between the discovered structural features of the produced alloy and its unique mechanical properties is discussed.

Time-Dependent Evolution of Al-Al4C3 Composite Microstructure and Hardness during the Sintering Process.

In this study, Al-Al4C3 compounds were manufactured by mechanical milling followed by heat treatment. To analyze the microstructural evolution, the composites were sintered at 550 °C at different sintering times of 2, 4 and 6 h. The mechanical results suggest that dislocation density and crystallite size primarily contribute to hardening before the sintering process, with a minimal contribution from particle dispersion in this condition. The compound exhibited a significant 75% increase in hardness after 2 h of sintering, primarily attributed to the nucleation and growth of Al4C3 nanorods. The HRTEM analysis, combined with geometric phase analysis (GPA) at and near the Al-Al4C3 interface of the nanorods, revealed strain field distributions primarily associated with partial screw dislocations and the presence of closely spaced dislocation dipoles. These findings are consistent with the microstructural parameters determined from X-ray diffraction pattern analysis using the convolutional multiple whole profile (CMWP) method. This analysis showed that the predominant dislocation character is primarily of the screw type, with the dislocation dipoles being closely correlated. Based on these results, it is suggested that samples with a lower weight percentage of reinforcement and longer sintering times may experience reduced brittleness in Al/Al4C3 composites. Strengthening contributions were calculated using the Langford-Cohen and Taylor equations.

INNOVATIVE APPROACH TO ENSURING THE QUALITY OF GAS TURBINE ENGINE PARTS PRODUCED BY SELECTIVE LASER SINTERING FOR UAV

The research objects are gas turbine engines parts, manufactured using an innovative method of additive manufacturing – selective laser sintering. The main problem solved in this work is the low quality of the surface layer and the residual porosity of the parts obtained by this method, which significantly limits their operational characteristics and durability. As a result of the experimental studies, rational operating parameters of diamond smoothing were established. This allowed to significantly improve the surface quality and increase the operational characteristics of parts made of heat-resistant alloys INCONEL 718 and an intermetallic alloy based on titanium aluminide OX45-3ODS. The effectiveness of diamond smoothing is explained by local plastic deformation and compaction of the surface layer of parts under the influence of high contact pressures and temperatures. This leads to a significant reduction in surface roughness, an increase in the surface hardness due to strain hardening and a significant reduction in the size and number of residual pores. A characteristic feature of the obtained results is the ability to control the quality parameters of the surface layer by varying the diamond smoothing operating parameters – smoothing force, feed, radius, and geometry of the smoother's working part. The established regularities of the smoothing operating parameters have an impact on the quality characteristics of the surface. This information can be utilized in the development of highly efficient technological processes for the production and restoration of gas turbine engines, critical components of unmanned aerial vehicles, obtained through selective laser sintering. Implementing the elaborated technological recommendations will permit broadening the range of goods produced by additive manufacturing and enhancing their capacity and dependability during operation under conditions of cyclical loads and extreme temperatures.

Microstructure-thermal transport property correlation after cold/cryo rolling deformation of alloy D9

ABSTRACT Plastic deformation alters the microstructure of a material due to the formation of twins, high density of dislocations and strain-induced phases and grain refinement. Such microstructural modifications can affect thermal transport properties of a material. In this work, variation in thermal diffusivity (TD) was investigated in cold worked (CW) and cryo rolled (CR) alloy D9 (ASTM designation A771/UNS S38660), using laser flash analyser after 20–80% thickness reduction. Deformed samples were characterised using XRD and microscopy techniques for structure and microstructure modifications besides correlating with the change in hardness. Temperature dependence of thermal diffusivity was measured from room temperature up to 1273 K. Microstructural features confirmed the formation of deformation-induced martensite in CR specimen. This was accompanied by up to 172% increase in hardness in 80% CR compared to annealed specimen. The dislocation density estimated from XRD structural profile showed an increase with the percentage of deformation. For all specimens, thermal diffusivity showed an increasing trend with temperature but decreased with deformation. The reduction in thermal diffusivity was non-negligible beyond 40% thickness reduction for all deformed specimen and was substantial specifically for CR alloy D9.

PREDICTION OF STRENGTH DEPENDING ON THE INFLUENCE OF THE CHEMICAL COMPOSITION IN THE 40КХНМ ALLOY

Introduction. The study is devoted to the analysis of the influence of the chemical composition of the 40КХНМ alloy on its hardness. The relevance of the work lies in the fact that mechanical tests require significant material and time costs. For the operational assessment of metal quality criteria, it is proposed to apply mathematical modeling in the work. Materials and methods. A study of the effect of the chemical composition on the hardness of the 40KHNM alloy, which meets the requirements of the state standard 51397, was carried out. The results of the experiment. In the course of research, it was found that changes in the chemical composition of the 40КХНМ alloy significantly affect its mechanical properties, including hardness and resistance to shock loads. An increase in the content of carbon, molybdenum and chromium in the alloy leads to an increase in its hardness. This is with the formation of stronger carbide and molybdenum phases in the structure of the alloy, which leads to an improvement in its mechanical properties. Increased hardness makes the alloy more resistant to wear and increases its durability in operating conditions. An increase in the nickel content in the alloy leads to an increase in its resistance to shock loads. This is caused by an increase in plasticity and impact toughness of the alloy with an increased nickel content. Higher resistance to shock loads makes the alloy suitable for use in conditions that require high resistance to shocks, for example, in the production of machine parts and equipment. A mathematical model of the dependence of the strength of the alloy on the percentage content of the components of the chemical composition was built, which allows to control the indicators of the strength of the alloy in the process of its manufacture. Conclusions. The research results confirm that changes in the chemical composition of the 40КХНМ alloy have a significant impact on its mechanical properties. As a result of the experiments, it was established that the chemical composition of the metal significantly affects the hardness of the material. By changing the composition of the metal, it was possible to achieve a significant increase in hardness to levels that meet the requirements of quality standards. These results are an important step in optimizing the production processes and improving the properties of the final products from the 40КХНМ alloy.

The Impact of Adding a Cationic Metal Salt and Curcumin to Monoammonium Glycyrrhizic Acid on Its Solubilizing Capacity and Gelation.

Monoammonium glycyrrhizic acid (MAG), a glycyrrhizic acid monoammonium salt, is a naturally derived low-molecular-weight gelling agent with surface-active properties. It has the capacity to individually facilitate the preparation of gel-solubilized drugs. As MAG is an anionic surfactant with carboxyl groups, the addition of counterions may affect micelle formation and gelation. In this study, the solubilization and gelling properties of MAG were investigated following the addition of metal salts (NaCl and KCl). The addition of metal salts resulted in a decrease in the critical micelle concentration and an increase in gel hardness. Supersaturation of curcumin (CUR) was maintained by the addition of metal salts because of increased micelle number and viscosity. When the gel hardness was compared between formulations with and without CUR, a significant reduction in hardness was observed with the solubilization of CUR. The addition of KCl prevented the decrease in the hardness of gels containing CUR compared to the addition of NaCl. Put together, the addition of metal salts had a noteworthy impact on micelle and gel formation of MAG. In particular, the addition of KCl was more effective in the preparation of gel-solubilized CUR.

THE INFLUENCE OF ELECTRON BEAM IRRADIATION ON THE TRIBOLOGICAL AND MECHANICAL PROPERTIES OF POLYTETRAFLUOROETHYLENE (PTFE) FOR ENGINEERING APPLICATIONS

The study demonstrates the significant effects of electron beam irradiation on the tribological and mechanical properties of polytetrafluoroethylene (PTFE). Electron beam irradiation, a method using highvelocity electrons to modify material properties, was applied to PTFE to potentially enhance its wear resistance and mechanical hardness, which are critical for applications under increased wear conditions. In the experiments, PTFE samples were irradiated at varying doses, and their wear resistance, microhardness, and surface roughness were evaluated post-irradiation. Tribological test results showed a notable improvement in wear resistance and microhardness with increasing radiation doses. Specifically, irradiated samples exhibited reduced wear volume and enhanced surface characteristics compared to the unirradiated sample. The irradiated sample (PTFE-2) showed the highest resistance to abrasive wear and a significant increase in surface hardness, indicating that electron beam irradiation effectively strengthens the material by inducing cross-linking and other structural modifications within the polymer matrix. Additionally, the study highlighted changes in surface roughness: irradiated samples exhibited altered roughness parameters that contributed to improved wear resistance. These changes can be explained by the physical and chemical transformations induced by electron beam exposure, which modify the surface and subsurface regions of the polymer. This study confirms that electron beam irradiation is an effective method for enhancing the mechanical and tribological properties of PTFE, making it more suitable for advanced engineering applications where high durability and resistance to extreme conditions are required. The findings open new avenues for the use of PTFE in sectors requiring high performance, extending its application beyond traditional fields.

The Influence of Oat β-Glucans of Different Molar Mass on the Properties of Gluten-Free Bread.

The influence of β-glucans on the properties of gluten-free dough and bread is still not fully explained, with the literature suggesting both positive and negative effects. The aim of this study was to investigate the effect of the molar mass of oat β-glucans on the properties of gluten-free bread. Gluten-free breads were baked under standardized conditions from a model gluten-free mix without and with a 1% or 2% share of oat β-glucans of a low molar mass of 24,540 g/mol, a medium molar mass of 85,940 g/mol and a high molar mass of 1,714,770 g/mol. The share of β-glucans affected the increase in water addition to the baking mix and dough yield proportionally to the molar mass and amount of β-glucans. The β-glucans of the highest molar mass, particularly at a 2% share, were most effective in increasing bread volume, reducing hardness and increasing the moisture content of the bread crumb on the day of baking, as well as reducing the increase in hardness and maintaining a high moisture content of the bread crumb after 1 day of storage, compared to bread without added β-glucans.

Effect of pH-shifting and ultrasound on soy/potato protein structure and gelation

The substitution of meat proteins with plant-based proteins from various sources is often motivated by nutritional considerations. However, the inherent limited solubility of plant proteins, which results in suboptimal techno-functional properties, remains a persistent challenge in food formulation. The purpose of this study was to investigate the impact of pH-shifting (P), high-intensity ultrasound (U), and ultrasound-assisted pH-shifting on the structure and solubility of soy protein isolate (SPI), potato protein isolate (PPI), and the soy/potato protein complex (SPI/PPI complex). Additionally, a detailed examination of the gel properties of SPI, PPI, and the SPI/PPI complex was conducted to assess the changes that occurred before and after modification. The results of particle size, zeta potential, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), free sulfhydryl (R-SH), surface hydrophobicity (H0), Fourier transform infrared spectrum (FTIR) and fluorescence intensity showed that P and U treatment promoted the unfolding of proteins structures and decreased particle size, and augmented protein-water interactions, leading to enhanced solubility. The pH-shift and ultrasound (PU) treatment further amplified these structural alterations in proteins. Consequently, the gelling characteristics of the modified proteins were substantially improved, with notable increases in hardness, elasticity, and water-holding capacity (WHC). The findings facilitate developing more targeted plant protein-based gel products that specific techno-functional attributes, concurrently allowing for modifications to their nutritional profiles.

Influence of Graphene Nanoplatelets and Post-Curing Conditions on the Mechanical and Viscoelastic Properties of Stereolithography 3D-Printed Nanocomposites.

This study presents an innovative approach to improving the mechanical and viscoelastic properties of 3D-printed stereolithography (SLA) nanocomposites by incorporating graphene nanoplatelets (xGNP) into photopolymer matrices. Utilizing an SLA 3D printer, photopolymer formulations with xGNP concentrations of up to 0.25 wt% were successfully produced. Post-print curing was carried out using two different methods: ultraviolet (UV) curing and high-temperature curing at 160 °C. Mechanical characterization using nanoindentation showed a significant increase in elastic modulus by 104% and an increase in hardness by 85% for nanocomposites containing 0.25 wt% xGNP. Furthermore, dynamic mechanical analysis (DMA) revealed a 39% improvement in storage modulus for samples without post-curing and an improvement of approximately 30% for samples subjected to high-temperature curing. These significant improvements highlight xGNP's potential to not only increase the performance of SLA 3D-printed components but also streamline the manufacturing process by reducing or eliminating energy-intensive post-curing steps. This innovative integration of graphene nanoplatelets paves the way for the production of high-performance, functional 3D-printed products and offers significant advances for various industries with a high impact. The results highlight the transformative role of nanomaterials in additive manufacturing and position this work at the forefront of materials science and 3D printing technology.

Effects of Efficient Ethylene Remover on the Lignification of Fresh Faba Bean (Vicia faba L.) during Storage.

Postharvest ethylene accumulation and lignification are significant issues affecting the storage quality of fresh faba beans, resulting in rapid quality decline. However, there is still a lack of effective preservation methods to preserve the quality of faba beans during storage. This study aimed to investigate the regulation of lignification in faba beans during storage using a high-efficiency ethylene remover (HEER), examining physiological responses, key enzyme activities, and transcriptomic changes. Results showed that the HEER treatment inhibited the lignification, reducing it by 45% and lowering the respiratory rate of fresh pods by 32.8% during storage. Additionally, the HEER treatment suppressed respiration rates and the activities of lignin synthesis-related enzymes, including phenylalanine ammonia-lyase (from 353.73 to 246.60 U/g), cinnamic acid-4-hydroxylase (from 635.86 to 125.00 U/g), 4-coumarate: coenzyme A ligase (from 1008.57 to 516.52 U/g), and cinnamyl-alcohol dehydrogenase (from 129.42 to 37.12 U/g), thus slowing lignin accumulation. During storage, the hardness of fresh faba bean increased by 9.79% from the initial period, being 1.44 times higher than that of HEER. On days 8 and 16 of storage, the respiratory rate of the treated beans decreased by 24.38% and 4.12%, respectively. Physiological and enzyme activity analyses indicated that HEER treatment-induced increase in hardness was associated with the phenylpropanoid metabolic pathway. Moreover, the HEER significantly down-regulated the expression of several key genes, namely FaPAL, FaC4H, and FaCAD. This study helps to deepen the understanding of the inhibition of lignification by HEER and provide new insights for the development of preservation technology of faba bean.

Influence of β Grain Orientation on the Stress‐Induced Martensite Formation in Cold‐Rolled Metastable β Ti–5Mo–5V–5Al–3Cr Alloy

Solution‐treated metastable β Ti–5Mo–5V–5Al–3Cr (Ti 5553) alloy processed through cold rolling at strain levels of 5–45% results in stress‐induced martensitic transformations (SIMT). Further, the cold‐deformed sample is annealed at 860 °C for 5 min to achieve recrystallization and relieve internal stresses. The influence of recrystallized β grain orientations on Ti‐5553 deformation behavior is characterized using nanoindentation tests. As β grain orientation changes from near <111> to <001> direction, the alloy exhibits an increase in hardness (from ≈6.3 to ≈6.6 GPa) and a decrease in elastic modulus (from ≈127 to ≈120 GPa). It can be inferred that a threshold stress is necessary to activate SIMT in each orientation due to the stress gradient from the top surface to the indent tip at a certain penetration depth in the sample. Additionally, the influence of alloying elements (e.g., Mo, V, Al, and Cr) on β phase stability as a function of grain orientations is confirmed using the electron probe microanalyzer. Observations indicate that <111> grain orientation is most preferred, followed by <101> for promoting stress‐induced martensite, while <001> is least preferred.

Comparison of tribological performance of hard chrome and heat-treated electroless Ni–P platings

The search for alternatives to hard chrome platings, which have been used in the aviation sector for an extended time but have begun to be abandoned due to their negative effects on human and environmental health, has continued in recent years. Hard chrome plating's primary application in the aviation sector is for wear performance. Electroless Ni–P platings lack the necessary hardness and wear resistance compared to hard chrome platings. The purpose of this study was to determine whether these coatings might be used in place of hard chrome plating and to determine how heat treatment affected the tribological performance of electroless Ni–P platings applied to steel substrates. Hard chrome and electroless Ni–P platings were applied to five different steel substrates. The coatings’ microstructure, bending, corrosion resistance, hardness, and dry sliding wear tests were conducted. It has been shown that heat treating the Ni–P platings can result in appreciable increases in hardness and tribological performance. In the heat-treated coatings, hardness values were higher than those of the hard chrome platings. It was concluded that although hard chrome plating showed better wear resistance, heat-treated electroless Ni–P platings have the potential to compete with hard chrome platings in terms of tribological performance.

Powder Metallurgical Processing of Al–5 wt% Cu Matrix Composites Reinforced with MoSi2 and WSi2 Particulates

Herein, investigations on the microstructural, physical, and mechanical properties of molybdenum disilicide (MoSi2)‐ and tungsten disilicide (WSi2)‐reinforced aluminum (Al)–copper (Cu) matrix composites are reported. Powder metallurgy methods such as mechanochemical synthesis (MCS), mechanical alloying (MA), cold pressing, and pressureless sintering are combined to produce composites. First of all, MoSi2 and WSi2 nanoparticles are synthesized by MCS and selective acid leaching, yielding reinforcement materials for Al–Cu matrix. Powder blends consisting of 95 wt% Al and 5 wt% Cu are mixed with metal disilicides at different weight percentages (1, 2, and 5 wt%). MA for 4 h is conducted on these overall blends using a high‐energy ball mill. Microstructural and thermal properties of the as‐blended and mechanically alloyed powders are determined, and then they are compacted under 450 MPa and sintered at 550 °C for 2 h. Mechanical characterization of the composites reveals an increase in hardness and wear resistance with an increasing amount of reinforcement content. Among bulk samples, 5 wt% WSi2‐reinforced composites have the highest microhardness (165 ± 15 HV) and lowest wear rate (1.69 × 106 μm3 Nm−1) values. However, under the compression forces, the highest toughness and strength are obtained from 2 wt%‐reinforced composites.

Plasma Spraying NiCoCrAlY-Cr2O3-AgMo Coatings: Fabrication and Tribological Mechanisms

The increasing demand for high-performance aircraft engines has led to a greater emphasis being placed on advanced sealing coating technologies. Developing long-life, self-lubricating, and wear-resistant coatings is of significant research value. This study focuses on the fabrication of a novel self-lubricating and wear-resistant NiCoCrAlY-Cr2O3-AgMo composite coating. This coating was deposited onto a GH4169 substrate utilizing plasma spraying. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD) methods were employed to characterize the elemental composition and microstructure of the fabricated NiCoCrAlY-Cr2O3-AgMo composite coating. Microhardness measurements across the coating cross-section indicated a gradual increase in hardness from the GH4169 substrate to the NiCoCrAlY-Cr2O3-AgMo coating. The average hardness of the GH4169 substrate was 413.92 HV0.2, while the CoNiCrAlY bonding layer region exhibited an average hardness of 467.60 HV0.2. The NiCoCrAlY-Cr2O3-AgMo coating itself demonstrated an average microhardness of 643.22 HV0.2. Room temperature friction tests indicated that the average coefficient of friction (COF) of the GH4169 substrate was 0.665. In contrast, the NiCoCrAlY-Cr2O3-AgMo coating exhibited a significantly lower average COF of 0.16, representing a 75.94% reduction compared to the uncoated GH4169 substrate. High-temperature friction tests were conducted at 400 °C, 500 °C, and 600 °C, indicating average COF values of 0.438, 0.410, and 0.268, respectively, for the NiCoCrAlY-Cr2O3-AgMo coating. Specifically, at 600 °C, the formation of a lubricious NiMoO4 tribofilm on the coating surface was observed. This tribofilm effectively reduced the wear rate of the GH605 pin to 2.78 × 10−6 mm3/N·m, highlighting the potential of the NiCoCrAlY-Cr2O3-AgMo coating to reduce wear in high-temperature sliding contact applications.

Microstructure and high temperature tribological behavior of nickel-based superalloy with addition of revert

The recycling of revert plays a crucial role in cost-efficiency and green manufacturing of superalloy. In this study, optical microscopy, scanning electron microscopy coupled with energy dispersive spectroscopy, tensile test, and tribological analysis were employed to investigate the microstructure, mechanical properties, and tribological behaviors of vacuum induction melted superalloys of 100% original material (Sample 1) and 40% original material + 60% revert (Sample 2). Dry sliding tests were conducted at 300 and 730 °C. The addition of revert promotes microstructure refinement, hardness increase, and carbide formation, at the cost of 18.5% ductility loss. During the high-temperature dry sliding process, abrasive, adhesive, and oxidative wear mechanisms were observed on the contact surfaces. Sample 2 exhibited a lower wear rate and coefficient of friction at both 300 and 730 °C. Additionally, a more continuous and wear-resistant tribolayer was formed on the wear track of Sample 2, effectively mitigating matrix oxidation compared to Sample 1. At 730 °C, a thick tribolayer developed on the wear surface of Sample 2, characterized by a hard and wear-resistant glaze layer on the outermost surface. The continuous sliding induced matrix heating, which facilitates recrystallization in the subsurface of Sample 2, induced by increased inclusions and carbides from the revert. The analysis of wear debris further illustrated the variations of wear mechanism at different temperatures. These findings are meaningful for understanding the high-temperature behavior of superalloys and optimizing alloy recycling process.

Optimizing Surface Hardness and Corrosion Resistance in 316L Stainless Steel via SMRT and Plasma Nitriding.

Increasing the mechanical strength of stainless steel is fundamental to expanding its applications and extending its useful life, especially due to its impressive corrosion resistance. However, many processes that make possible increasing the hardness and wear resistance of these steels also compromise their performance when they are subjected to corrosive environments. Because of the need to increase surface hardness without jeopardizing corrosion resistance, this study explores the impact of a surface mechanical rolling treatment (SMRT) with volumetric reductions of 50% and 70%, together with high-temperature plasma nitriding (PN) (450, 500, and 550 °C), on 316L steel. X-ray diffraction analysis analyzed the composition and structure of the resulting coatings. Mechanical strength was assessed using Vickers microhardness, while corrosion resistance was tested in a 3.5%-by-weight NaCl solution. The results indicate a substantial increase in surface hardness in all of the nitrided samples. Notably, the samples were subjected to rolling with 50% and 70% volumetric reduction, and subsequent nitriding at 550 °C showed a reduced impairment of corrosion resistance. This shows that the methodology adopted in this study, consisting of SMRT and PN, can increase the useful life and expand the applicability of stainless steels commonly used in various industry sectors.

Use of carbon black powder for surface treatment of stainless steel substrates via a low-cost CO2 laser

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.