Due to the excellent properties of Ti (C,N)-based ceramics, such as high hardness, excellent wear resistance, exceptional thermal deformation resistance, and sound chemical stability, they have been ...widely used in cutting tools or molds. Thus, revealing their tribological behavior against hard materials is of great significance. Some studies have reported the tribological behavior of Ti(C,N)-based cermets and hard cermets, but so far, the effects of Mosub.2C additions on the frictional properties of Ti(C,N)-based cermets are still unclear. In this study, Ti(C,N)-10WC-1Crsub.3Csub.2-5Co-10Ni-x Mosub.2C cermets (x = 4, 6, 8, 10 and 12 wt.%) were sintered using a vacuum hot-pressing furnace. Furthermore, the core–rim morphologies of the sintered samples were observed in SEM images. Then, the wear resistance of the cermets was studied against a Sisub.3Nsub.4 ball at a 50 N load using the fretting wear test. Finally, the wear mechanism was characterized using a combination of SEM, EDS and XPS. The experimental results indicated that the wear mechanisms of the cermets were mainly abrasive wear, adhesive wear, and the formation of an oxide film. As the content of Mosub.2C increased from 4 wt.% to 12 wt.%, the friction coefficient and wear volume had a variation law of first decreasing and then decreasing, and reached minimum values at 6 wt.% and 12 wt.%, and the lowest friction coefficient and wear rate were 0.49 and 0.9 × 10sup.−6 mmsup.3/Nm, respectively. The 6 wt.% Mosub.2C greatly improved the hardness and fracture toughness of the cermet, while the 12 wt.% Mosub.2C promoted the formation of an oxide film and protected the friction surface. The cermet with 6 wt.% Mosub.2C is recommended because it has comprehensive advantages in terms of its mechanical properties, tribological properties, and cost.
In this study, the mechanical properties in a Zr-Nb alloy plate with bimodal basal texture microstructure have been evaluated by tensile, Vickers hardness and nano-indentation tests. Based on the ...results, the strength-hardness relationship is discussed with special attention paid to its textured microstructure. It is found that the correlation between strength and hardness varied greatly depending on whether the loading direction is parallel or perpendicular to the normal direction of the plate, demonstrating that the strength-hardness relationship is texture-dependent. In addition, the relation between strength and nano-hardness is obtained by subjecting specimens to cold rolling at various reduction rates. This allows for the evaluation of the strengthening effect using convenient and non-destructive nano-indentation tests instead of elaborate tensile tests, which may have particularly useful applications for nuclear engineering components when considering the irradiation strengthening occurred in these materials.
This study focuses on the synthesis of TiC-TiBsub.2/Fe coatings with varying amounts of aluminum (Al) using tungsten inert gas (TIG) cladding and investigates the impact of Al addition on ...microstructure refinement and performance enhancement of the coatings. The coatings were prepared on a mild steel substrate using TIG cladding. X-ray diffraction (XRD) analysis revealed the presence of TiC, TiBsub.2, Alsub.xTi, and Alsub.xFe phases in the coatings. Scanning electron microscopy (SEM) images showed that the addition of Al improved the microstructure, reducing defects and enhancing the distribution of reinforcing phases within the coatings. The particle size of the reinforcing phases was significantly refined by the addition of Al. The micro-hardness of the coatings was significantly higher than that of the substrate, with the maximum micro-hardness of the coating reaching 955.5 ± 50.7 HV0.1, approximately six times that of the substrates. However, excessive Al addition led to a reduction in hardness due to a decrease in the quantity of hard phases. The wear tests showed that all the coatings had lower wear loss compared to the substrate material, with the wear loss initially decreasing and then increasing with the increasing Al content. Samples with a 28.57 wt.% Al addition exhibited the best wear resistance, with approximately 16.8% of the wear volume loss compared to mild steel under the same testing conditions, attributed to the optimal combination of reinforcement phase quantity and matrix properties.
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The industry has always strived to design “hard” and “crack-resistant” glass. However, simultaneously realizing these properties in oxide glasses has been rare. Although Al2O3-rich ...hard and crack-resistant oxide glasses have been reported in the last decade, they exhibit two significant technological challenges that hinder their translation from laboratory to industry: (1) high processing temperatures (>2000 °C) and (2) small glass-forming regions (near eutectic). The present study reports the structural design of a hard and high modulus glass with high crack initiation resistance designed in the peraluminous region of rare-earth containing MgO–Al2O3–B2O3–SiO2 system. The glass can be processed at a temperature ≤1650 °C and exhibits Vickers hardness (Hv) of 7.84 GPa (at 1.96 N load) and indentation crack resistance (ICR) of 26.5 N. These Hv and ICR values are significantly higher than most commercial or non-commercial glasses (prior to thermal tempering, densification near Tg, or chemical strengthening). The glass has been scaled up to successfully produce slabs of dimensions 100 mm × 100 mm × 8 mm at laboratory scale with optical transmission of 90 ± 2 %. The results presented here are scientifically intriguing and have considerable tangible implications, as they pave the path for the design and development of stronger glasses for functional applications.
This paper investigates the joint effect of high current pulsed electron beam (HCPEB) and denaturant CeOsub.2 on improving the microstructure and properties of Al-20SiC composites prepared by powder ...metallurgy. Grazing Incidence X-ray Diffraction (GIXRD) results indicate the selective orientation of aluminum grains, with Al(111) crystal faces showing selective orientation after HCPEB treatment. Casting defects of powder metallurgy were eliminated by the addition of CeOsub.2. Scanning electron microscopy (SEM) results reveal a more uniform distribution of hard points on the surface of HCPEB-treated Al-20SiC-0.3CeOsub.2 composites. Microhardness and wear resistance of the Al-20SiC-0.3CeOsub.2 composites were better than those of the Al matrix without CeOsub.2 addition at the same number of pulses. Sliding friction tests indicate that the improvement of wear resistance is attributed to the uniform dispersion of hard points and the improvement of microstructure on the surface of the matrix after HCPEB irradiation. Overall, this study demonstrates the potential of HCPEB and CeOsub.2 to enhance the performance of Al-20SiC composites.
Among the various ceramic substrate materials, Sisub.3Nsub.4 ceramics have demonstrated high thermal conductivity, good thermal shock resistance, and excellent corrosion resistance. As a result, they ...are well-suited for semiconductor substrates in high-power and harsh conditions encountered in automobiles, high-speed rail, aerospace, and wind power. In this work, Sisub.3Nsub.4 ceramics with various ratios of α-Sisub.3Nsub.4 and β-Sisub.3Nsub.4 in raw powder form were prepared by spark plasma sintering (SPS) at 1650 °C for 30 min under 30 MPa. When the content of β-Sisub.3Nsub.4 was lower than 20%, with the increase in β-Sisub.3Nsub.4 content, the ceramic grain size changed gradually from 1.5 μm to 1 μm and finally resulted in 2 μm mixed grains. However, As the content of β-Sisub.3Nsub.4 seed crystal increased from 20% to 50%, with the increase in β-Sisub.3Nsub.4 content, the ceramic grain size changed gradually from 1 μm and 2 μm to 1.5 μm. Therefore, when the content of β-Sisub.3Nsub.4 in the raw powder is 20%, the sintered ceramics exhibited a double-peak structure distribution and the best overall performance with a density of 97.5%, fracture toughness of 12.1 MPa·msup.1/2, and a Vickers hardness of 14.5 GPa. The results of this study are expected to provide a new way of studying the fracture toughness of silicon nitride ceramic substrates.
As semiconductor chips have been integrated to enhance their performance, a low-dielectric-constant material, SiCOH, with a relative dielectric constant k ≤ 3.5 has been widely used as an intermetal ...dielectric (IMD) material in multilevel interconnects to reduce the resistance-capacitance delay. Plasma-polymerized tetrakis(trimethylsilyoxy)silane (ppTTMSS) films were created using capacitively coupled plasma-enhanced chemical vapor deposition with deposition plasma powers ranging from 20 to 60 W and then etched in CFsub.4/Osub.2 plasma using reactive ion etching. No significant changes were observed in the Fourier-transform infrared spectroscopy (FTIR) spectra of the ppTTMSS films after etching. The refractive index and dielectric constant were also maintained. As the deposition plasma power increased, the hardness and elastic modulus increased with increasing ppTTMSS film density. The X-ray photoelectron spectroscopy (XPS) spectra analysis showed that the oxygen concentration increased but the carbon concentration decreased after etching owing to the reaction between the plasma and film surface. With an increase in the deposition plasma power, the hardness and elastic modulus increased from 1.06 to 8.56 GPa and from 6.16 to 52.45 GPa. This result satisfies the hardness and elastic modulus exceeding 0.7 and 5.0 GPa, which are required for the chemical–mechanical polishing process in semiconductor multilevel interconnects. Furthermore, all leakage-current densities of the as-deposited and etched ppTTMSS films were measured below 10sup.−6 A/cmsup.2 at 1 MV/cm, which is generally acceptable for IMD materials.
•Three models of ISE (Martens, Oliver-Pharr and Gong-Miao-Peng) are compared.•The hardness for each model were studied in function of the samples stiffness.•It is possible obtain hardness values ...independent of the indentation load.•Without tip correction, the hardness is strongly depends on the load applied.
Instrumented Hardness Tests (IHT), also known as nanoindentation, establishes itself throughout the years as a standard method to characterize superficial elasto – plastic properties of materials, with a greater capability to evaluate thin films. The main advantage of this test lies on the application of dynamical load – unload cycles, generally with values of few mN and displacements below 200 nm, granting more information about the material beyond hardness, as elastic modulus, creep, fracture resistance, among others. However, the difficulty to achieve an adequate contact between sample and penetrator complicate the interpretation of its results. Several theoretical models were developed in order to diminish this effect achieving relative success. Each theory takes in consideration different aspects of the phenomenon and its application produces diverse mechanical properties values, which makes difficult the comparison among them. The aim of this work is to measure materials mechanical properties in accordance with ISO 14577 Martens model, the Oliver – Pharr (OP) method and the approximation developed by Gong, Miao and Peng (GMP) which are typically used on IHT, in order to find a possible relation among them. Aluminum, silicon (1 0 0) and soda-lime glass bulk materials were measured using a Fischerscope HV100 equipment with a Berkovich indenter. Dynamical load – unload cycles were applied to the samples with its maximum value ranging between 3 mN and 25 mN, during a total time of 120 s each cycle. The hardness calculation was performed according to the ISO 14577 Martens hardness model with indenter tip correction and considering the indentation size effect (ISE). The Oliver – Pharr method was calculated contemplating the non-linearity of the unload curve, adjusted by a power law. The Gong – Miao – Peng approximation was very similar to the OP technique, differing by the use of a virtual contact load and an indenter response based on a conical geometry instead the revolution paraboloid one, which is typically used. The results obtained confirm the hardness values variations among the models, which differ mostly at low load cycles. The comparison between the hardness calculations made by each model and the indenter response are presented as final result.
Prolonged computer work and smartphone use can cause stiffness of the neck and shoulder muscles, including the trapezius muscle. Hence, muscle hardness quantification is clinically beneficial. The ...present study aimed to examine the reliability of trapezius muscle hardness measurement using a portable muscle hardness meter and ultrasound strain elastography. Overall, 20 healthy young men participated in this study. Prior to measurement, the participant's subjective symptoms, particularly shoulder muscle stiffness, were rated using an 11-point verbal scale. Furthermore, hardness of the right and left upper trapezius muscles was assessed. In the strain elastography assessment, muscle hardness was evaluated using strain ratio. Results showed that, in quantifying upper trapezius muscle hardness, both portable muscle hardness meter and strain elastography had an excellent intra-tester reliability (>0.9). However, the correlation coefficients between muscle hardness values assessed using a muscle hardness meter and those evaluated with strain elastography did not significantly differ, and the scores for subjective shoulder stiffness did not correspond to muscle hardness values. Therefore, the hardness of the trapezius muscle does not directly reflect the subjective shoulder stiffness. Future studies should thoroughly examine the location of the shoulder stiffness, and check whether it is accompanied by local pain or tenderness.
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