Higher Hardness Values Research Articles

Investigation on the Interrelationship between the Chemical Composition, Heat Treatment Parameters and the Phase Transformation Process, Microstructure Evolution and the Mechanical Properties of Austempered Steel

The interrelationship between chemical composition, heat treatment parameters, and phase transformation, microstructural evolution and the mechanical properties of austempered steel was studied. Two samples of steel with different percentage composition of carbon of 0.56 and 0.76 were used for the study. They were austentized at the respective temperatures of 8000C, 8400C, 9000C and 9600C for 30 minutes. They were thereafter quenched using bitumen-palm kernel oil, and subjected to austempering isothermal heat treatment at 4200Cfor different time durations of 5, 15, 30, 45 and 60 minutes. The samples were tested for tensile strength, elongation, hardness and impact strength. They were also subjected to microstructural characterization to determine the phases in the microstructures and their effects on the properties of the developed materials. Results obtained revealed that the dominant phases in the microstructure were bainite, matensite and traces of retained austenite. It was found that decreasing austenitizing temperature yields finer grain structures with increase in tensile strength and elongation with decrease in hardness and relatively little effect on the impact strength. At any given austenitizing temperature, shorter austempering holding time yielded optimum properties in tensile strength and elongation while higher hardness values were associated with shorter holding time. These results proved that the process conditions have strong correlation with both the microstructures and the mechanical properties. It was concluded that the most promising microstructures with respect to excellent strength-ductility property are those obtained at the ausenitizing temperature range of 800 -8400C for the austempering time range of 5 – 30 minutes. These materials have potential for load bearing application while those austenitized within the range of 900 - 9600C using austempering time range of 5 – 15 minutes are candidate material for wear resistant application.

Prospects for Improving Physical and Mechanical Properties of Corundum Ceramics

The prospects for improving microhardness and strength characteristics of corundum ceramics (Al2O3) modified by zirconium dioxide (3YSZ) are investigated. Ceramic samples are molded by semi-dry pressing followed by sintering. It is experimentally established that an increase in 3YSZ content in Al2O3/3YSZ composite ceramics fired at temperatures above 1450 oC increases strength and decreases microhardness. Ceramics of optimal composition (100–x) Al2O3–x 3YSZ, x = 5–10 wt. % 3YSZ has high strength and hardness values, and the average value is 700MPa and 22.3±1.8 GPa.

Effect of plasma nitriding on tribological properties of nickel‑boron-nanodiamond electroless coatings

This study is an effort to investigate the synergic effect of nano-diamond (ND) addition and plasma nitriding (PN) treatment on tribological and structural properties of nickel‑boron (NiB) coatings. NiB/ND nanocomposites containing different amounts of NDs (0.0, 0.1, 0.5, and 1.0 g/L) were produced in an electroless bath. Then, plasma nitriding was conducted on the samples for 1 h at 400 °C in an N2-H2 environment. To study phase analysis and examine the surface morphology of the samples, X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were utilized. The wear behavior and friction were determined under the normal load of 10 N using the pin-on-disk method. The surface roughness, microstructure, and microhardness were also assessed. The results showed that, as the ND concentration increased, the amorphous structure of as-plated (AP) Ni-B transformed to a semi-crystalline one. Moreover, the amorphous structure of the as-deposited NiB/ND coatings changed to a crystalline one after plasma nitriding, which resulted in a higher hardness value. NiB/0.5ND coating showed the highest hardness value (1523 HV0.1) and the highest wear resistance (0.8×10−10 Kg/N.m). The smoothest wear trace with no visible cracks is related to the worn surface of PN NiB/0.5ND sample, suggesting that the NiB/ND nanocomposite can be a promising candidate for surface engineering processes.

Pengaruh Metode Pengelasan TIG dan SMAW Terhadap Sifat Mekanik Baja Karbon SS400

Welding methods that greatly affect welding, heat input in a process that can affect the cooling rate, an increase in the amount of heat input used, the cooling rate will be slower, and vice versa increasing the heat input used, the cooling rate will be faster, the cooling rate is faster. will quickly increase the hardness value of the welding results. This research was conducted on 6 pieces of SS400 carbon steel plate with dimensions of 250x100x10mm. The welding method used is the TIG and SMAW method, with a welding position of 1G and the type of connection is single v butt joint, the electrode used is E6010 with a diameter of 2.6 mm. There are 3 welding samples, where sample 1 was welded by the TIG method, sample 2 by the SMAW method. and sample 3 using the combined TIG&SMAW method. Rockwell hardness testing uses the ASTM E-18 standard with area testing on weld metal, HAZ and Base metal. Tensile testing using the AWS D1.1 standard and the microstructure standard used ASTM E3. The highest average tensile strength value is found in the combined combined sample (sample 3) of 467.5 MPa. From the test results, it was found that the sample that had the highest hardness value was a combined sample of TIG and SMAW in the weld metal area of ​​34.5 HRC. The distribution of the perlitee phase in sample 1 was 15.39%. In sample 2 as much as 15.80%, and in sample 3 as much as 15.52%. The teaching method greatly affects the mechanical properties of the welding results.

The effects of boriding process on tribological properties and corrosive behavior of a novel high manganese steel

• Borided HMS unexpectedly exhibited saw-tooth morphology. • Borided HMS has superior adhesion properties. • Boriding increases service life, wear and corrosion resistance of HMS. In this study, wear and corrosion behavior of a novel borided high manganese steel (HMS) produced by the researchers was investigated. After the sheets were cold-rolled, they were annealed. HMS was borided at 850, 900, and 950 °C for 2, 4, and 6 h through the pack-boriding process. Borided HMS uncommonly exhibited a saw-tooth morphology like low alloy steels due to similar crystal structures of MnB and FeB. XRD analysis showed the existence of SiC, FeB, MnB and Fe 2 B phases. The present study indicated a silicon-rich zone by EDX mapping. The formation mechanism of silicon-rich zones was explained and expressed with the term “compact transfer of silicones”. The boriding time and temperature increased the thickness of the boride layer from 26.13 μm to 109.04 μm. The highest hardness value was observed in sample 5 (1757 HV 0.05 ). The activation energy of borided HMS was quite low compared to several high alloy steels in the literature. Daimler-Benz Rockwell-C adhesion test showed that adhesions of borided HMS surfaces were sufficient. The "egg-shell effect" that emerge due to the high silicon rate did not occur. In the wear tests applied under 5, 10, and 15 N loads, the borided HMSs exhibited a better wear resistance compared to the base metal (BM). However, the wear test was applied under 5 N load and BM had a better performance than several borided HMSs because of the phase transformations. In general, the borided samples had lower corrosion rates compared to the unborided ones.

Nanomechanical characterization of Ti-base nanostructure-dendrite composite

Abstract The present work represents the first localized nanomechanical analysis of the single phases present in an alloy, providing a better understanding of the macroscopic behaviour of the material. The Ti60Cu14Ni12Sn4Nb10 and Ti60Cu14 Ni12Sn4Ta10 alloys under investigation show a very similar elastic response of the nanostructured matrix in spite of a slightly higher hardness in the latter. Nevertheless, the dendritic phase exhibits substantially higher values of hardness for both alloys, with an increase of about 32% in both cases. The elastic modulus increases by up to 36% in the Ta-containing alloy and by up to 23% in the Nb-containing alloy, compared to the matrix. The different nanomechanical response explains, together with the effect of the dendrites restricting crack propagation, the increased ductility of the Nb-containing alloy compared with the Ta-containing alloy.

Attractive tribological properties of Al2O3 coating prepared by SPS in comparison with APS in different environment

Al 2 O 3 coatings were prepared by atmospheric plasma spraying (APS) and suspension plasma spraying (SPS). The microstructure, phase composition and nano-hardness of the two coatings were tested. Meanwhile, the friction and wear performance of SPS and APS in different environments were systematically studied. The results showed that both coatings exhibited a stable friction state and low wear rate under different environments. The special fine structure and high hardness value of SPS coating made its wear resistance much higher than that of APS coating. Additionally, the wear mechanisms of the two coatings in dry sliding friction were mainly abrasive wear, fatigue wear and adhesive wear. The APS coating had slight abrasion, while the SPS coating exhibited a negative abrasion state, in the seawater environment.

Plasma protective ceramic coating of the Al2O3–Ni system from cladded powder mixture

To solve the problem of increasing the adhesive-cohesive strength of multifunctional plasma coatings used to protect parts of power and machine building equipment from wear and corrosion, a ceramic coating of the Al2O3–Ni system, obtained from a powder mixture based on corundum clad nickel. The coating was applied by the method of high-energy plasma powder spraying (on the “Thermoplasma” installation) on the intermetallic sublayer of the Ni–Co–Cr–Al–Y system. The aim of this work was to study the microstructure, phase composition, mechanical, tribological and adhesion properties of a plasma ceramic coating formed from a powder material based on aluminum oxide clad with a refractory metal component (nickel). According to the research results, it was found that the initial powder material has a multi-phase composition (Ni + α-Al2O3 + γAl2O3) and a spherical morphology of particles. From it, during high-energy plasma spraying, a coating is formed with a phase composition (Ni + γ-Al2O3 + γ'-Ni3Аl), a layered microstructure with nickel interlayers and a columnar structure of oxide grains. The coating has high values of hardness and adhesive-cohesive strength, low coefficient of friction and is recommended for wear protection of parts of power engineering and mechanical engineering.

The Mechanical Integrity of Self-Healing Coating Embedded with Microencapsulated Vegetable Oil

The challenge of self-healing coating is the mechanical integrity of the coating system embedded with microcapsules. This paper emphasis the mechanical integrity of self-healing coating embedded with microencapsulated vegetable oil (waste sunflower oil). The mechanical integrity of the coating system was determined by the bending and Vickers test. The microencapsulation of waste sunflower oil was successfully produced microcapsules with a mean diameter of 1 μm and a rough shell structure that matchable to embedded in coating matrix. The embedment of microcapsules into the coating matrix has generated self-healing performance with ability to self-heal after 5 days. The mechanical integrity of coating system was increased and demonstrated higher maximum stress (654.25 N/mm2) and higher hardness value (4.40 HV) as compared to the reference sample. It can be concluded that, the microencapsulated waste sunflower oil as an alternative natural vegetable oil to be embedded in the coating system to generate self-healing performance and induce higher mechanical integrity. This finding was able to contribute to the advancement of the future of metal coating industries.

Effect of Sintering Temperature on Hardness of Bioactive Glass/Cordierite

In this study, a composite of bioactive glass and cordierite (BG/cordierite) was proposed to increase the strength of bioactive glass (BG). Both BG and cordierite were separately synthesized with the method of glass melting and used to fabricate BG/cordierite with sintering temperature in the range from 600 to 1000 °C. The BG/cordierite were characterized using X-ray diffraction (XRD), density, bulk density, porosity and hardness test. The XRD pattern shows amorphous phase and crystalline phase such as combeite, wollastonite and larnite appeared after sintering. The highest hardness value show by BG/cordierite with sintering temperature 950 °C (BG/C950) with 251 Hv.

Study of wear performance of wheel and rail steels under dry sliding conditions

The demand for efficient railway services has significantly increased in the past years due to an increased demand for the high-speed transportation of goods with high loads. The increase in loads and velocities has resulted in increased problems associated with rolling contact fatigue (RCF), rolling and sliding wear on the wheel and rail materials causing a reduction of service life of wheel/rail systems. Rail operating companies spend significant funds in maintenance and replacing damaged rails and wheels caused by wear. In addition, unscheduled maintenance due to wear and RCF often lead to poor availability of railway networks. For this study, dry sliding wear was investigated on wheel and rail steels using RTEC Multi-Function Tribometer. The results demonstrated that the rig was successful in simulating sliding wear, and that the fractions of the wear components could be varied, and it also provided instrumentation. Information on coefficient of friction against sliding distance and applied force were obtained which were used to compare sliding wear performance of both wheel and rail steels. The wheel was found to perform better than the rail under the same conditions due to its high initial hardness values and smaller interlamellar spacing.

Mechanical properties of room-temperature injection molded, pressurelessly sintered boron carbide

Boron carbide (B4C) is of interest in the armor community due to its combination of extreme hardness and low density. However, it is difficult to utilize these properties in many applications due to the challenges associated with forming near-net shapes of B4C, combined with its low inherent sinterability without the application of external pressure. In this study, highly loaded (51 vol. %) aqueous B4C suspensions were developed and injection molded at room temperature followed by pressureless sintering up to 2075 °C. Three different sintering aids (Y2O3, Al, and Al2O3) were used to aid the densification process. B4C parts were sintered to high density (up to 97.7% relative density) and high hardness values (up to 3200 Vickers). The flexural strength of the samples was limited by grain pullout during polishing of the tensile surface; the strength was correlated to the maximum grain pullout flaw measured at the intersection of the tensile surface and the fracture surface (R2 > 0.98). The robust performance of the B4C suspensions and their resulting densities and hardness demonstrate the room-temperature injection molding process as a viable alternative for low-cost near-net shaping of B4C components.

Corrosion and wear performance of La2O3 doped plasma electrolytic oxidation coating on pure Mg

With the aim of improving the corrosion and wear resistance of pure magnesium, La2O3 nano-particles are added into the PEO electrolyte. The influence of the particles on coating formation, morphology and performance is investigated. Results indicate that the porosity and thickness decrease remarkably after the particle incorporation which influences the corrosion and wear resistance in return. The coating with 1 g particle addition shows lowest porosity and highest hardness value, resulting in superior corrosion and wear performance, which implies the feasibility of the proposed strategy in fabricating functionalized PEO coatings on Mg-based materials.

Ultralow Lattice Thermal Conductivity and Enhanced Mechanical Properties of Cu and Sb Co-Doped SnTe Thermoelectric Material with a Complex Microstructure Evolution

SnTe is an exceptionally promising eco-friendly thermoelectric material that continues to draw immense interest as a source of alternative energy recovered from waste heat energy. Here, we investigate the effect of introducing Cu as a single doping element rather than phase separated in SnTe followed by Sb co-doping to tune the lattice thermal conductivity. A microstructure evolution was observed which influences the thermoelectric performance of these SnTe-based materials. An overall power factor of ∼22 μW/cmK2 and an ultralow lattice thermal conductivity of 0.39 W/mK are reported. A maximum ZT of 0.86 is also reported with an all-time record high hardness value of 165 Hv among SnTe-based thermoelectric materials. Through DFT calculations, we show that Cu opens the band gap of SnTe, whereas Sb in the presence of Cu introduces resonance levels and causes band convergence. This kind of enhanced thermoelectric performance is paramount for the application of SnTe in recovery of heat into useful electrical energy.

Effect of treatment temperature on the initial performance of layers of water-based paints in heat-treated pine and beech wood

Hardness, surface roughness, and adhesion strength were determined for water-based opaque paints applied to heat-treated wood material surfaces. For this purpose, Scotch pine (Pinus sylvestris L.) and beech (Fagus orientalis Lipsky) woods were used as experimental material. Specimens were subjected to heat treatment at 3 different temperatures (150, 180, and 210 °C) and 2 different periods (2 and 4 h) under laboratory conditions. Two-component water-based paints with commercial codes D17 and D45 were applied to the surfaces. The hardness, surface roughness, and adhesion strength values of painted samples were determined according to the applicable standards. The results showed that there were higher values of hardness and surface roughness of water-based paints in short-term heat treatment compared with long-term heat treatment. A general decrease in pine with D17 and D45 paints applied to the surfaces and in beech with D45 in adhesion strength was detected depending on the increasing heat treatment temperature and duration. An increase was observed in beech samples with D17 paint applied.

Microstructural, mechanical, oxidation resistance and tribological properties of TaMgN films

ABSTRACT A series of composite TaMgN films with various Mg content were deposited using reactive magnetron sputtering. The microstructural, mechanical, oxidation resistance and tribological properties of the films were measured. The results showed that when the Mg content is between 0 and 11.9 at.-%, the films are composed of fcc-(Ta,Mg)N and hcp-(Ta,Mg)N phases. While the further increase of Mg content induced the appearance of hcp-Mg phase and the films consisted of fcc-(Ta, Mg)N, hcp-(Ta, Mg)N and hcp-Mg, the hardness of the thin films was first increased and then decreased with the increase of Mg content due to the combined action of solution strengthening, internal stress and phase composition. The highest hardness value is 33 GPa, (Mg content is 11.9 at.-%). With a further increase of Mg content, the average friction coefficient further increased gradually, while the wear rate first decreased and then increased.

Microstructural analysis of a HP 40Nb alloy aged

In this paper, the change in the microstructure of the centrifugally cast heat-resistant alloys of HP40 Nb after exposure to 0.5h and 2h of ageing times at 1123K and 1323K were investigated. The microstructures of the as-received alloy and aged conditions were examined using light microscopy (LM) and scanning electron microscopy (SEM) equipped with an energy dispersive spectroscopy (EDS). The chemical composition of various phases and precipitates observed in the aged sample microstructure was characterized by the means of scanning electron microscopy SEM via backscattered electron (BSE). The present results indicate that ageing enhanced the occurrence of different phenomena such as the transformation of primary M7C3 to M23C6 carbides and precipitation of secondary M23C6 carbides. It can be summarized that the present phases and the morphology of secondary carbides in the microstructure of aging results in higher values of hardness.

First-principles investigations of tricarbon: From the isolated C3 molecule to a novel ultra-hard anisotropic solid

Based on crystal chemistry considerations and quantum density functional theory ground state calculations, rhombohedral rh-C3 and hexagonal h-C6 carbon allotropes are proposed and energetically calculated as new stable ultra-hard phases likewise lonsdaleite. Along the two kinds of carbon in linear C2-C1-C2 lattice, distorted tetrahedra C2(sp3) with an angle of 106.17{\deg} (smaller than ideal 109.4{\deg}) and C1(sp)-like hybridizations are inferred from charge density projections. The calculated elastic constants point to a strong anisotropy of mechanical properties of rh-C3 and h-C6 with an exceptionally large C33 values (1636 GPa and 1610 GPa, respectively), exceeding that of lonsdaleite (1380 GPa), due to the presence of aligned tricarbon units along the hexagonal c-axis. Both phases are characterized by large bulk moduli and high hardness values that are slightly less than those of lonsdaleite and diamond. Weak metallic behavior of both new phases is identified from electronic band structure calculations.

Effect of Grade 5 titanium interlayer on microstructure and pitting corrosion behaviour of AA1100/A36 explosion welds

Explosion welding is a solid-state welding process that is used for the metallurgical joining of similar and dissimilar combinations of metals and alloys with varying physical and mechanical properties. In this process the metal surfaces are brought into sufficiently close contact, the valence electrons overcome the repulsive forces and result in sharing of their orbits. In recent years ocean acidification is the main problem due to a variety of pollutants. In naval applications A36 steel is used for making ship hulls that are very poor in corrosion. The present study is aimed to improve the corrosion resistance of the A36 steel by cladding aluminium alloy (AA110) using the explosion welding technique. Grade 5 titanium alloy has been used as an inter-layer between AA110 and A36 plates. The presence of Ti-6Al-4V inter-layer facilitated good bonding between aluminium and steel dissimilar weld joint with smooth bond line. The microhardness values were measured at various points start from the weld interface and towards both base metal regions. Higher hardness values were observed in the bond region and the Inter-layer regions, owing to the inherent higher hardness of Titanium and the formation of Martensitic structure near the bond region, as a result of higher and sudden impact energies. Potentiodynamic polarization tests were made in 3.5% NaCl solution. Corrosion resistance in AA1100 is higher than A36. All the observed results were correlated with microstructural features as evidenced by SEM studies.

Vacuum drying as a natural preservation method of post-harvest lemon might accelerate drying duration and produce the high-quality of dried lemon slices

Lemon (Citrus limon B.) is one of the local fruits abundant in Indonesia. The dried lemon fruit was required for storage, extended shelf-life, minimizing decay, and simple distribution. This research applied vacuum drying to lemon slice dehydration in order to achieve quick times and preserve product quality. Vacuum drying with combinations of temperature (40, 50, 60 oC) and vacuum pressure (-38 and -69 cmHg) was applied to drying lemon slices until the final moisture content (9-11% w.b) was reached. The color, hardness value, and vitamin C content were analyzed on dried lemon slices. As a result, 60 °C with -38 cmHg indicates the fastest time to achieve a dry lemon slice and the highest hardness value. The 40 °C with -69 cmHg indicated the best vitamin C content of 76.40 (mg/100 g dw) and color value of L* (64.35 ± 0.57), H (77.0 ± 0.78), a*(6.43 ± 0.55), b*(27.92 ± 1.87), and c* (28.65 ± 1.91). The higher vacuum pressure accelerated the drying time and preserved the quality of the dried lemon slice. The higher temperatures led to the quality deterioration though also accelerate drying time. Experiment with more enhanced vacuum pressure and decreased temperature on lemon drying was required.