Higher Hardness Values Research Articles

Transforming olive-processed waste and almond shells into high-quality Biofuels: a comprehensive development and evaluation approach

ABSTRACT Amidst the energy crisis, biomass energy has emerged as a pivotal solution, given its abundant distribution, impressive storage capabilities, and carbon-neutral nature. The study aims to develop biofuels of good quality using various agroalimentary waste products, Examining the pelletization process of including wet olive pomace (wet olive pomace (2 phases)(OP)), de-oiled olive pomace (DOP), olive stones (OS), and almond shells (AS), this research assesses its effectiveness in enhancing both bulk and energy densities, highlighting it as the optimal method for such enhancement. The preparation of these biofuels without binder has yielded promising results in terms of bulk density, hardness, calorific value, and ash content. Tests comparing biofuels to commercial olive pomace pellets (COP) showed the following: Using biomass with moisture content below 15%, granulometry of 1 mm or smaller, and no binder produces high-quality pellets. These pellets had high density (889, 675, 643, and 621 kg/m3), high hardness (99.18%, 99.80%, 98.92%, and 99.14%), and high heating values (18.93, 20.29, 22.51, and 20.38 MJ/kg) at average temperatures and pressures. These results are comparable to those of commercial products. In general, biomass and solid biofuels offer credible alternatives to produce energy in the form of electricity, heat, or both, using various processes, such as combustion, pyrolysis, and gasification. The knowledge gained from this research is very helpful in developing and improving bioenergy systems and promoting sustainable methods of producing energy from agricultural wastes.

The Effect of Boriding Temperature and Time on the Structural and Mechanical Properties of M42 Steel

In this study, the effect of boriding temperature and time on the structural and mechanical properties of M42 high speed steel were investigated. Samples placed in Ekabor II powder were exposed to pack boriding treatment at 900°C and 1000°C for 4 hour and at 950°C for 2, 4 and 6 hours. Scanning electron microscope (SEM) images indicate that boron diffuses into the samples and a sawtooth-like cross-sectional morphology is formed. The presence of boron has also been proven by Energy Dispersive X-ray spectrometry (EDX). In addition, it was determined that boron layer thickness increased with increasing boriding temperature. When the microhardness values were examined, it was observed that the sample borided at the highest temperature had the highest hardness value and the hardness values decrease with the decreasing of boriding temperature. Similar results were also obtained regarding the boriding time. The highest microhardness and layer thickness values were obtained after 6 hours of boriding. Additionally, it was observed that the hardness values of borided samples decreased as they moved from the surface to the inner parts.

STRENGTHENING OF THE SURFACE BY FRICTION

The study is devoted to the application of the method of surface hardening by friction Object of study - the process of surface hardening by friction.Subject of study - samples of 65G steel the method allows achieving high values of hardness, strength and wear resistance of materials in a short time and at much lower cost compared to other processing methods. The aim and objectives of the study are to investigate the nature of surface hardening of steel samples by friction. To achieve this goal, the following tasks are envisaged: manufacturing samples from 65G steel in the form of plates, preliminary heat treatment of samples for their maximum thermal hardening, hardening of the surface of samples by friction, analysis of the microstructure and microhardness of each sample, comparison of the microstructure, microhardness and depth of hardening of these samples, conclusions on the influence of processing factors on the hardening result. Based on the experimental data obtained, we constructed graphs of microhardness changes in the cross-section of the samples and studied the microstructures. It can be seen that after friction treatment, a layer with a modified structure is formed in the surface of the samples. The microhardness of the surface is significantly higher (approximately 2 times) than the microhardness of the main part in the samples. Metallographic analysis has shown that the layer formed in the samples has a martensitic structure characterized by a higher degree of dispersion and microhardness compared to the martensitic structure obtained during the previous heat treatment. Changes in the microstructure and microhardness of the samples that were surface hardened using different processing modes were compared. Certain differences in the characteristics of their hardened «white» layers were found. It is also shown that the hardened «white» layer is located along the entire length of the surface in the samples and is continuous and homogeneous.

Comparative investigation of various protein or protein-based powders addition on texture properties of egg white and yolk gels

ABSTRACT The objective of this research was to investigate and compare the effects of various protein or protein-based powders (WPC, SPI, BSA and hemoglobin) addition on transform of texture properties in egg white (EW)/egg yolk (EY) gels. Results showed that the highest hardness value (38.5 N) was detected in BSA-treated EW gels, while the lowest values (46.6 N) were obtained in hemoglobin-treated EY gels. Additionally, significantly increased value of free –SH groups was obtained in SPI/BSA/hemoglobin-treated EW/EY solutions, and increased value of protein solubility was obtained in EY solutions treated by WPC/SPI/BSA/hemoglobin relative to those of the control. The EW solutions treated by BSA/hemoglobin reached significantly higher H 0 values than those of other groups. SDS-PAGE analysis showed that the hemoglobin-treated EW solution had slightly intense bands of ovoinhibitor, ovotransferrin and ovalbumin, and the EY solutions treated by WPC/SPI/BSA had higher level of covalent crosslinking. The EW gels treated by WPC/hemoglobin exhibited relatively more ordered protein secondary structures (α-helix and β-sheet) than those of the SPI group. SEM results suggested that WPC/BSA-treated EW gels developed uniform, porous and fiber-like structure, while SPI/BSA-treated EY gels developed rougher structure.

Investigation of the Bonding Mechanism of Al Powder Particles through Pulse Current Sintering Technology

Compared with traditional powder metallurgy, pulse current sintering is an advanced powder-forming technology, but its bonding mechanism is still an open topic for debate. In this paper, pulse current sintering is used as the connection technology and millimeter-sized Al particles are used as the research object. In the whole sintering process, no pressure was loaded; the function of the pulse current was the only source of heat with which to achieve the bonding of Al particles. The bonding mechanism of pulse current sintering was investigated from the perspective of material connection behavior. The results show that the pulse current density of the particle surface reaches 3.48 × 105 A/m2 instantly, while the current density of the particle center is only 8187 A/m2 at the initial stage, which is the main difference between pulse current sintering and traditional powder metallurgy sintering. With the densification process, the current density and temperature distribution in the contact region as well as the center of Al particles contact region tend to be more consistent. Finally, dense interfacial bonding was obtained, and the contact region of Al particles also demonstrated a high hardness value of 0.6385 GPa and yield strength value of 212.83 MPa. The whole process can be considered as a comprehensive action of melting (evaporation), diffusion, and plastic deformation. Based on the above results, a new technology, named high-frequency pulse current sintering, was proposed.

Candelilla Wax and Glycerol Monostearate-Based Oleogels as Animal Fat Substitutes in Bologna Sausages.

The aim of this study was to produce Bologna sausages rich in unsaturated fatty acids and to evaluate this replacement on the structural characteristics. For the purpose of a comparative analysis, three different types of sausages were produced, distinct only in the type of fat used: I. sausages obtained with pork backfat (PBF), II. sausages produced with oleogel formed from refined sunflower oil and glycerol monostearate (GM_OG), and III. with candelilla wax oleogel (CW_OG). The meat composition was also analyzed to better understand the process in the dynamics and the finished products were analyzed both uncooked and cooked. The enhanced oil-binding capacity of oleogels suggests their potential value as substitutes for saturated fats (>99%). In terms of meat composition textural analysis, the highest hardness value was registered for PBF_C of 25.23 N, followed by a CW_OG_C of 13.08 N and a GM_OG_C of 12.27 N. However, adhesiveness, cohesiveness, springiness index, and gumminess showed similar values between samples. Reformulation of products with oleogels as a fat source abundant in mono- and polyunsaturated fatty acids resulted in uncooked products exhibiting reduced hardness values of 49.01 N (CW_OG_US) and 40.51 N (GM_OG_US), compared to 65.03 N (PBF_US). Color results of the cross-section color can indicate the potential for consumer acceptance due to the reduced color differences between the conventional and oleogel samples.

Thermal, Microstructural, and Mechanical Analysis of Complex Lattice Structures Produced by Direct Energy Deposition.

Lattice structures have gained attention in engineering due to their lightweight properties. However, the complex geometry of lattice structures and the high melting temperature of metals present significant manufacturing challenges for the large-scale fabrication of these structures. Direct Energy Deposition (DED) methods, such as the Wire Arc Additive Manufacturing (WAAM) technique, appear to be an interesting solution for overcoming these limitations. This study provides a detailed analysis of the manufacturing process of carbon steel lattice structures with auxetic geometry. The study includes thermal analysis using infrared thermography, microstructural characterization through metallography, and mechanical evaluation via hardness and mechanical testing. The findings reveal the significant impact of heat input, thermal cycles, and deposition sequence on the morphology and mechanical properties of the lattice structures. Fast thermal cycles are related to areas with higher hardness values, smaller strut diameters, and porous formations, which shows that controlling heat input and heat dissipation is crucial for optimizing the properties of lattice structures produced using WAAM.

Impact of melon seed oil cake with different particle sizes on bread quality

Melon seed oil cake (MSOC), as the secondary by-product from melon seed oil pressing process, has high potential nutritional value. The aim of this study was to assess the effect of incorporating MSOC as wheat flour substitute and its particle size on bread quality; three particle size fractions of MSOC (coarse, medium, and fine) and two substitution levels (3 and 6%, w/w) were employed. Functional properties and colour of different particle sizes of MSOC were assessed, and the physical properties of bread made with MSOC were explored and compared to control bread (100% wheat flour). Results showed that bread made with 3% MSOC had relatively satisfactory quality in terms of specific volume (2.64–2.86 mL/g), hardness (14.31–15.04 N) compared to the control bread (specific volume 2.79 mL/g and hardness 13.87 N). Bread made with fine particle size of MSOC (2.64 mL/g and 15.04 N at 3% substitution level; 2.44 mL/g and 16.03 N at 6% substitution level) had lower specific volume and higher hardness values than the bread made with medium (2.80 mL/g and 14.31 N at 3% substitution level; 2.50 mL/g and 15.50 N at 6% substitution level) and coarse (2.86 mL/g and 14.72 N at 3% substitution level; 2.52 mL/g and 15.12 N at 6% substitution level) particle sizes of MSOC. These results indicate that using 3% MSOC with larger particle size could be more suitable for making bread with relatively satisfactory quality. Overall, MSOC could be re-introduced into food chain as ingredient for bread production, which offers possibilities to develop novel sustainable foods. Future work will be conducted on sensory quality and consumer acceptance to provide a desirable quality of bread.Graphical

Harnessing the Role of Three Lactic Acid Bacteria (LAB) Strains for Type II Sourdough Production and Influence of Sourdoughs on Bread Quality and Maillard Reaction Products.

This study tested the effect of Companilactobacillus paralimentarius E-106, Lactiplantibacillus paraplantarum N-15 and Lactiplantibacillus plantarum SC-9 on the amount of Maillard reaction and aroma profile in bread making with main bread quality parameters. The specific volumes of sourdough and control breads were in the range of 2.97-3.04 cm3/g, and the control II bread had the highest hardness values on all days. The FAST index value was determined to be between 40.48% and 81.22% in all breads. The FAST index value was found to be higher in the control breads than in the sourdough breads. In the volatile compounds analysis, 72 volatile compounds were detected. The variety of volatile compounds in the breads with sourdough addition was higher than the control breads. Among the tested strains, Companilactobacillus paralimentarius E-106 demonstrated superior properties for bread characteristics in comparison to other strains as a type II sourdough starter. In summary, improved aroma profile and decreased Maillard reaction products can be provided by sourdough addition without changing the bread quality, along with meeting consumer demand for less additive use.

On Dynamic Recrystallization during the Friction Stir Processing of Commercially Pure Ti and Its Influence on the Microstructure and Mechanical Properties

Friction stir processing (FSP), a severe plastic deformation process, was applied on commercially pure Ti to obtain an improved microstructure. The process yielded a refined microstructure and higher mechanical properties at room temperature (RT). Yet the microstructure was found to contain bright bands demonstrating high hardness values of about 500 HV. High-resolution scanning electron microscopy (HRSEM) as well as electron backscattering diffraction (EBSD) analysis indicated that these bands were composed of extra-fine equiaxed α-Ti grains with an average radius of 1–2 microns. In addition, a retained β phase was detected at the boundaries of these α-Ti grains, together with a small quantity of separate β grains. The results of a fractography study conducted on broken tensile specimens showed that the material that underwent FSP was free of defects and that the fracture started at these bands. It is proposed that these bright bands are due to excessive deformation occurring during the processing stage, leading to an accelerated dynamic recrystallization (DRX) process. In turn, these heavy deformation regions act as a strengthening constituent, making the material superior to the parent material as far as its mechanical RT properties are concerned. Consequently, this means that the FSP of CP-Ti has the potential to serve as an industrial means of improving the mechanical properties of the material.

Nanostructuring of an additively manufactured CoCrFeNi multi-principal element alloy using severe plastic deformation: Comparison of two materials processed by different laser scan speeds

Experiments were conducted to reveal the refinement of the microstructure and the evolution of the hardness of an additively manufactured (AM) CoCrFeNi multi-principal element alloy (MPEA) processed by severe plastic deformation (SPD) using high pressure torsion (HPT) technique. AM was carried out by laser powder bed fusion (L-PBF) technique at two different laser scan speeds. The as-built alloys for both laser scan speeds have a single-phase face-centered cubic (fcc) structure with <110> fiber texture parallel to the building direction. X-ray line profile analysis (XLPA) revealed that the dislocation density was considerably high even in the AM-processed state before HPT (3 × 1014 m−2) which increased by two orders of magnitude during HPT. The saturation of the lattice defects (dislocation density and twin fault probability) as well as the crystallite size occurred at a shear strain of about 10 during HPT. In both AM-processed alloys, <111> fiber texture developed parallel to the normal of the HPT-processed disks. For both laser scan speeds, the initial grain size in the AM-processed samples was refined from 70 to 90 μm to the nanocrystalline regime after 10 turns of HPT. Additionally, nanotwins formed with a probability of about 3 %. The initial hardness of the AM-processed MPEA samples for both laser scan speeds was 2700–2800 MPa, which is superior to that of CoCrFeNi produced by casting (about 1380 MPa). This can be explained by the high dislocation density in the AM-processed specimens. The formation of nanostructure with high lattice defect density during HPT resulted in a very high hardness value of about 5500 MPa in the AM-processed CoCrFeNi MPEA samples for both laser scan speeds.

Compositional Design and Thermal Processing of a Novel Lead-Free Cu–Zn–Al–Sn Medium Entropy Brass Alloy

In the current work, a novel medium entropy copper alloy was designed with the aim of avoiding the use of expensive, hazardous or scarce alloying elements and instead employing widely available and cost-effective alternatives. In order to investigate this unknown region of multicomponent alloy compositions, the thermo-physical parameters were calculated and the CALPHAD method was utilized. This led to the design of the Cu50Zn25Al20Sn5 at. % (Cu53.45Zn27.49Al9.08Sn9.98 wt. %) alloy with a relatively low density of 6.86 g/cm3 compared with conventional brasses. The designed alloy was manufactured through vacuum induction melting, producing two ingots weighing 1.2 kg each, which were subjected to a series of heat treatments. The microstructural evolution of the alloy in the as-cast and heat-treated conditions was assessed through optical and scanning electron microscopy. The hardness of the as-cast and heat-treated alloy at room temperature was also studied. The alloy was characterized by a multiphase microstructure containing a major Cu-rich (Cu–Zn–Al) matrix reinforced with a secondary Zn-rich (Zn–Cu) phase and pure Sn. In terms of mechanical properties, the developed alloy exhibited high hardness values of roughly 378 HV0.2 and 499 HV0.2 in the as-cast and heat-treated conditions, respectively.

Microstructure and tribological properties of aluminum matrix composites reinforced with ZnO–hBN nanocomposite particles

Abstract In this study, pure and hBN-doped ZnO nanoparticles were synthesized by sol–gel method. ZnO–hBN nanoparticles were mixed with pure aluminum powders and samples were prepared using powder metallurgy processing parameters. It was observed that Al, ZnO, and hBN nanocomposite particles formed homogeneously. With the addition of ZnO–hBN, significant changes occurred in hardness, wear, and friction coefficient values compared to pure Al samples. The highest hardness value in the samples is mesh. It was obtained as 105 HB in 10 wt.% hBN added sample. In the wear tests, it is seen that the wear resistance is seven times higher in the 1 wt.% hBN added sample compared to the pure Al sample, while the friction coefficient decreases with the increase of the hBN additive.

Microstructural Characterization of AlCrCuFeMnNi Complex Concentrated Alloy Prepared by Pressureless Sintering.

A significant and increasing number of studies have been dedicated to complex concentrated alloys (CCAs) due to the improved properties that these metallic materials can exhibit. However, while most of these studies employ melting techniques, only a few explore powder metallurgy and pressureless sintering as production methods. In this work, a microstructural characterization of AlCrCuFeMnNi CCA samples obtained by powder metallurgy and pressureless sintering using mixtures of powders with different compositions was carried out. One batch of samples (B1) was prepared using commercial powders of Al, Cr, Cu, Fe, Mn, and Ni. Another batch (B2) used mixtures of CrFeMn, AlNi, and Cu powders. A third set of samples (B3) was obtained by adding 1% at. of Mg to the B2 powder. The samples were characterized by X-ray diffraction, scanning and transmission electron microscopy, energy dispersive spectroscopy, density measurements, and hardness tests. Thermodynamic calculations were also used to complement the microstructural characterization. All the obtained samples exhibited high relative density and hardness values. However, B3 samples showed a higher hardness, attributed to the finer distribution of oxide particles, which was promoted by the presence of Mg during sintering. These last samples presented a hardness/density ratio of 62 HV/(g cm-3), surpassing that of some martensitic stainless steels and nickel-titanium alloys.

Investigation on electrochemical corrosion behavior and mechanical properties of Fe-nano particles produced by high-energy ball milling technique

Abstract This study focuses on converting iron particles from grinding sludge, after removing impurities, into Fe-nanoparticles using high-energy ball billing. The goal is to examine the corrosion behaviors and mechanical properties of these Fe-nanoparticles. Nanostructured Fe-powder was synthesized through a process involving 10 h of high-energy ball milling, followed by conventional hot pressing and sintering. Structural and microstructural properties were thoroughly examined using techniques such as X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and elemental diffraction spectroscopy. Upon sintering, SEM and TEM analyses unveiled the formation of a nanostructured alloy within the samples. Notably, the milled sample exhibited high hardness value, measuring at 155 HV. However, it is noteworthy that the un-milled sample demonstrated superior compression strength compared to its milled counterpart. Furthermore, the corrosion behavior of the samples was evaluated through electrochemical corrosion studies. Interestingly, the sample subjected to 10 h of milling (coin number 5) displayed a significantly lower corrosion rate, measuring at 1.3921 mm/year, suggesting enhanced corrosion resistance attributed to the nano structuring process.

A comparative analysis of compressive and wear failure of laser-powder bed fused Stainless Steel 316L produced with different hatch spacing in stripe and contour patterns

The selection of hatch spacing is crucial in additive manufacturing processes to produce a defect free Stainless Steel 316L (SS) components, especially in laser powder bed fusion (LPBF) process. Improper selection of hatch spacing could lead to various failure regimes (like vertical cracking, porosity, and un-melted particles) in Stainless Steel 316L (SS) component produced through laser powder bed fusion (LPBF). Further, the failure regimes have a direct impact on the hardness, compression strength, friction, and wear properties of LPBF SS components. The present study has taken substantial efforts to analyse the impact of various hatch spacing (0.08 mm, 0.10 mm. and 0.12 mm) in stripe and contour patterns, in terms of morphology, mechanical, and tribological properties of LPBF SS components. Also, the present study elucidates how variations in hatch spacing influences the features like particle fusion, crack formation, density, hardness, surface roughness, compression, and wear properties. The stripe pattern with low hatch spacing of 0.08 mm showed better particle fusion and high surface roughness; whereas the high hatch spacing has produced voids, un-melted powder particles, and cracks in the stripe and contour pattern. High densities and hardness values were attributed to the stripe patterns with more effective melting and fusing of powder particles. XRD analysis revealed the stable phase compositions across various hatch spacing with a predominant FCC crystal structure. Residual stress distribution was significantly influenced by the hatch spacing for both stripe and contour patterns. Importantly, the low hatch space leads has promoted the tensile residual stress formation and vice versa for the higher hatch spacing. Stripe patterns showed higher compression strengths with buckling and shear mode as a compression failure. The stripe pattern demonstrated a low specific wear rate (SWR) and coefficient of friction (COF) compared to the contour pattern, with respect to the various hatch spacing. Furthermore, the simulated body fluid (SBF) lubrication regime played a significant role in reducing the COF. Patches, groves, furrows, and craters demonstrated the abrasive and adhesive failure for both stripe and contour pattern, which is further detailed in the article.

SC-XRD structural characterization, insights of key electronic, and nonlinear optical properties of dimethoxybenzenesulfonate crystals: A combine experimental and DFT approach

Currently, dimethoxybenzene sulfonyl-based crystals (MDBS, EDBS and DBSC) were synthesized by in situ nucleophilic substitution reactions and their structures were confirmed via SC-XRD analysis. The key-electronic and NLO properties of afore-said crystals were investigated through quantum chemical study. For this purpose, M06/6-311G(d,p) functional of DFT/TDDFT approaches was utilized. A comparative study between DFT and XRD values of gemeterical parameters shwed harmony.Frontier molecular orbital findings revealed that among synthesized crystals, DBSC showed lesser energy (4.18 eV) with more red shift (322.758 nm) than MDBS (5.306 eV) and EDBS (5.320 eV). Global reactivity parameters (GRPs) were also examined from the energies of HOMO/LUMO. Among all crystals EDBS had higher value of hardness (η = 2.660 eV) while DBSC showed higher global softness (σ=0.240 eV) that indicated greater polariziability and interamolecular charge transfer in DBSC. The decreasing order of dipole moments of synthesized crystals was found as: DBSC (7.934 D) > MDBS (7.420 D) > EDBS (7.380 D). Further, from GRP it is revealed that MDBS-DBSC crystals having greater hardness values were less reactive and more stable as suggested by NBO and SC-XRD investigations. Owing to the unique properties of DBSC, significant NLO properties: hyperpolarizability (βtot=1.30 × 10−30esu) and second-order hyperpolarizability (γtot=22.1 × 10−36esu) were investigated in this crystal. The efficient NLO properties observed in DBSC underscore its potential use for advanced NLO applications.

An integrated experimental and analytical approach on mechanical characterization of advanced powder metallurgy aluminium metal matrix composites reinforced with different particulates

Over the last few decades, ‘Discontinuously Reinforced Particulate Composites (DRPCs)’ are a popular class of composite materials with considerable challenge in processing, characterization and machinability because of their increased strength-weight ratio, stiffness, specific strength and oxidization when compared to various metals and their alloys. This paper discusses experimental and numerical investigation on mechanical characteristics of aluminum metal matrix reinforced with various reinforcement particulates such as silicon carbide, aluminium oxide, and zirconium oxide, compaction pressure (kN) and hold time (s) based on Design of Experiments (DOE) and Finite Element Analysis. Initially this paper discusses the process optimization of Aluminum Matrix reinforced with different particulates experimentally to identify the favourable processing conditions by varying reinforcement materials, compaction pressure (kN) and hold time (s) based on TDOE (Taguchi’s Design of Experiments). Further, this paper concentrates to determine ‘maximum principal stress, equivalent elastic strain and equivalent (von-mises) stress’ based on Finite Element Analysis (ANSYS Workbench-2023R1). The results of the experimentation showed that the highest hardness values were achieved with ZrO2 reinforcement material. Increasing the compaction pressure from 8 to 12 kN resulted in a slight decrease in surface roughness and porosity. Higher compaction pressures have assumed to facilitate better particle distribution and improved interfacial bonding, leading to smoother surfaces and lower void content. The simulation results showed that the maximum principal stress achieved were (2235.8 MPa) SiC, (3444.4 MPa) Al2O3, and (3582.5 MPa) ZrO2. The equivalent elastic strain achieved was (0.2488) SiC, (0.2421) Al2O3 and (0.262) ZrO2. The equivalent (Von Mises) stress achieved was (28751 MPa) for SiC, (24880 MPa) for ZrO2 and (26972 MPa) for Al2O3. This experimentation and simulation demonstrated that the PM process can be used to fabricate DRAMMC with different reinforcement particulates. The understanding gained experimentally and analytically from this research can be applied for future processing of Aluminum Matrix Reinforced with different particulates.

The effect of plasma electrolytic oxidation of aluminum alloys on the structure and properties of protective oxide-ceramic coatings

The results of the studies of electrical modes of the high-frequency high-voltage plasma electrolytic oxidation (PEO) on the properties of the formed protective coatings on the B95 T1 and D16ч T aluminum alloys are presented. The control of the PEO process was carried out by changing the amplitude values of anode and cathode voltage pulses. The local mechanical characteristics and the structure of the PEO coatings were studied using instrumentedindentation and scanning electron microscopy. As a result of the studies, optimal modes of the PEO process were determined: potentiodynamic modes with a smooth decrease in the amplitude of anode voltage pulses at a speed of 5 V/min and a smooth increase in the amplitude of cathode voltage pulses at a speed of 1 V/min. The coatings formed in the optimal modes of the PEO were characterized by a reduced number of defects (microcracks, craters, pores) and high values of hardness of 27.5–27.8 GPa and elastic modulus of 286–309 GPa averaged over their thickness. These characteristics turned out to be higher by 33–45% and 15–30%, respectively, compared with a hardness and elastic modulus of the coatings, formed in other studied PEO modes.

Quenching Process Optimization of Leaf Springs as Tengkuit Material using the Taguchi Method Approach

Tengkuit is a traditional tool used by farmers to care for katuk, chilies, lumai, and others. The problem that farmers complain about is frequent wear and tear and chipping, which according to farmers and craftsmen must maximize quality and this must increase production costs and farmers' expenses. As time goes by, innovations have been made by humans to increase the durability of an object or material by increasing its hardness to save or reduce production costs. This research used qualitative approach with the taguchi method. The Taguchi method is a new engineering technique that aims to improve product and process quality while minimizing costs and resources. Taguchi's experimental design is more efficient because it allows searches involving many factors and numbers, and has good large-scale violent response. The maximum check value is the optimal parameter value for the tengkuit making process. Temperature and cooling media are very influential factors in testing hardness for making tengkuit. The results of the hardness research were shown as the lowest hardness value at a temperature of 600°C, with well water cooling media with a value of 24.3 HRC, and the highest hardness value at a temperature of 800°C. with bromus oil cooling media at a temperature of 700 ° C and a hardness value of 42.9HRC.