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The aim of this study is to investigate the microstructural, mechanical, and electrochemical characteristics of as cast Ti 7Mo 8Nb alloy, compared with the as sintered Ti 7Mo 8Nb alloy. The microstructural examination of as-cast specimen revealed an occurrence of fine and coarse acicular needles; however, the as-sintered alloy exhibited a Widmanstätten alpha structure within equiaxed beta grains and acicular alpha phase. In terms of mechanical characteristics, the as-sintered alloy showed superior yield strength and hardness measuring 1260 MPa and 380 ± 20 HV, respectively compared to the as cast alloy of 1200 MPa yield strength and 340 ± 25 HV hardness. The elastic modulus of as cast alloy was (49.2 GPa) which was higher than that of the as sintered alloy (44.9 GPa). Experiments involving wear tests have demonstrated a decrease in wear rate for the as-sintered alloy. The corrosion investigations revealed that as-sintered alloy showed better corrosion resistance compared with the as-cast alloy. The aforementioned assertion finds substantiation in empirical data indicating decreased corrosion and passivation current densities, an elevated negative phase angle reaching approximately 80°, an augmented impedance modulus, and an expanded Nyquist semicircle diameter for the alloy in its as-sintered state. These enhanced corrosion properties indicate that the as-sintered alloy possesses a surface with more stable passive film. The results of EIS analysis, using an equivalent circuit, suggest that the dual oxide layer comprises a dense base passive film and an outer porous layer. The optimum combination of high strength, unique corrosion resistance, and low elastic modulus make the as-sintered alloy a highly promising material for use in orthopedic biomedical applications. [ABSTRACT FROM AUTHOR]

Membrane technologies have developed as one of the main contributors to the resolution of water-related problems. This study seeks to examine the impact of active carbon nanoparticles (ACNPs) on the characterization and mechanical properties of polyethersulfone (PES) ultrafiltration membranes. The PES-AC composites were prepared using the phase inversion technique with a doctor blade by including ACNPs at varied weight percentages (0.01, 0.02, 0.03, 0.04 wt%). Produced membranes were characterized using FTIR, TGA, SEM, and XRD techniques, and the mechanical properties were evaluated using a tensile test, following the guidelines of the ASTM 638M-3 standard, utilizing a uniaxial universal testing machine. SEM images reveal that PES pure membranes consist of a porous bulk layer and dense skin layer. The addition of ACNPs decreased the pore size of the membranes with total thickness varying from 140 to 150 μm. Fourier-transform infrared spectroscopy (FTIR) indicated that with increasing ACNPs concentration, the peak intensities are related to C–C stretching bonds and acidic C–O groups. The XRD analysis showed that with higher ACNPs loading, there are a decrease in the amorphous phase of mixed matrix membranes (MMMs) and the highest intensity (2θ = 12.99°) at 2% ACNPs concentration. The tensile strength of the MMMs increased and reached an ideal value of 3.386 MPa when loaded with 2% ACNPs. Also, the optimum rate of tensile strain with 40% enhancement was achieved with 2% ACNPs compared with the pristine PES membrane. [ABSTRACT FROM AUTHOR]

• Calculated stresses in Demag CC2000 track plate exceeds the permissible stresses. • Chemical composition of Demag CC2000 track plate do not meet specifications. • Microstructure of G22NiMoCr5-6 is tempered-martensitic structure. • High carbon content in G22NiMoCr5-6 affects impact energy. A repetitive failure of crawler track plate made of G22NiMoCr5-6 of heavy-duty crane is observed to be occurring with an average rate of one track plate fractured every 100 working hours, presenting a great problem that may impose hazard on personnel and raising direct and indirect costs required for maintenance, spare parts, and downtime costs. The objective of this research is to investigate the cause of track plate failure. An experimental investigation is carried out including chemical composition, tensile test, impact toughness, hardness test, and metallographic observation along with fractography analysis. Also, working stresses are defined by applying the finite element method. Based on the results of the experimental and computational analysis, the fracture of track plate made of G22NiMoCr5-6 predominantly resulted from deficiency in the track plate geometry design which increases stress concentration within the fracture region, in addition, slight deviation of material properties compared to those prescribed by the standard may have played a role in exacerbating the problem. [ABSTRACT FROM AUTHOR]

There is a need to investigate a novel non-traditional surface hardening procedure for heat-resistant steel micro-alloyed with boron. In this research, boron powder pack processing was employed. Steel samples were boronized and mechanically investigated using hardness, three-point bending, and wear tests. Scanning electron microscopes and EDX were used to examine the microstructure before and after boronization. Boron was added in the form of a 50/50 combination of borax and boric acid in a crucible inside an induction furnace at 1050 °C for 30 min. The application of borax and boric acid 50/50 increased flexural strength from 614 to 1526 MPa and a further increase to 1700 MPa is achieved when ammonia bicarbonate (25%) with borax and boric acid 50/50 (75%) were used. The combination of ultra-fast boronizing and ammonia causes both surface and bulk hardening, which increases flexural strength. The produced steels are suitable for thermal and neutron shielding. [ABSTRACT FROM AUTHOR]

Oils and grease have beneficial effects on moving parts such as connecting rod, gears, shafts, and engine to reduce wear and friction. The properties of lubricants such as tribological and rheological properties are an important role in oils and grease characterization. Nano additives on lubricant oils play an important role in anti-wear; reduce the coefficient of friction and enhance the rheological properties. The Tribological and rheological behavior of base oil 15W50 which have different concentrations of multi-wall Carbon Nanotubes (MWCNTs) (0.5, 1, 1.5, and 2 wt%), and constant amount of graphene nanosheets (GNSs) (0.5 wt%) were investigated. This research is the first one in studying the effect of hybrid nano additives of (MWCNTs) and (GNs) on the tribological and rheological properties of lubricant oils. Tribological characterization was carried out on four ball testing model under different loads (200, 400, 600, and 800 N). The kinematic viscosity, flash point, pour point, and thermal conductivity of nanofluid added 15W50 lubricant are estimated and compared with base oil. The results showed that nano additives improve the wear scar and coefficient of friction by 78% and 48%, respectively. The flash point, thermal conductivity, kinematic viscosity, and pour point, were improved by 15%, 77%, 76.8%, and 20%, respectively compared with the base oil. The hybrid addition of CNTs/GNs nanoparticles enhanced the properties of 15W50 engine oil. [ABSTRACT FROM AUTHOR]

Carbon nanotubes have a lot of applications in mechanical fields. This is because nanomaterials have many superior mechanical properties such as very high strength-to-weight ratio, high modulus-to-weight ratio, high corrosion resistance, and super intelligence properties, which make them as smart materials. One of these attractive applications is the use of carbon nanotubes in vehicle brake friction material. Therefore, the fabrication and testing processes of these nanomaterials should be performed carefully to evaluate their mechanical, tribological, and noise properties. In this paper, friction material mixed with carbon nanotubes have been fabricated with different carbon nanotube contents and the same fabrication parameters. The carbon nanotubes have been produced using the conventional submerged arc discharge technique. The produced friction materials have been cut into pieces with standard sizes and then tested mechanically and tribologically. The results of tests have illustrated that the addition of carbon nanotubes into the friction materials could improve their mechanical properties (hardness, strength, and modulus) and also could enhance their tribological properties (wear rate and friction coefficient). Moreover, the tests showed that the presence of carbon nanotubes in friction materials could reduce the noise, vibration of the friction materials, and reduce the temperature rise due to the effect of friction, which means that the carbon nanotubes could raise the thermal conductivity of friction material, while the friction coefficient has stayed within the allowable standard limits (0.35–0.45). Surface morphology shows that the presence of carbon nanotubes in the friction materials could help to avoid surface friction cracks or fins within the normal operating conditions. The good combination of mechanical and tribological properties was obtained at 0.5% carbon nanotubes. [ABSTRACT FROM AUTHOR]

The aim of this research is to investigate the effect of various coke sizes on the properties of carburized mild steels; therefore, five sets of samples were prepared and carburized at different temperatures and times. Three sets were carburized at 850, 900 and 950 °C for 120 min, while two other sets are carburized at 1000 and 1050 °C for 120 min. All sets were carburized using three different sizes of coke, namely A (<0.4 mm), B (1:1.6 mm) and C (4:5 mm). After carburization, all sets were quenched in water and then tempered at 200 °C for 15 min. After tempering, different mild steel samples were subjected to microstructure observation, hardness test, Charpy impact test, tensile testing and adhesive wear test. The experimental results were analyzed and show that mild steels carburized at 1050 °C with intermediate coke grain size B (1-1.6 mm) give the optimum results for the mechanical and wear properties which may be due to the microstructure obtained at this temperature (martensitic case and bainitic core). This indicates that coke size B gives the optimum combination of surface area and porosity needed for the reaction kinetics, as well as the highest wear resistance after different carburizing temperatures. [ABSTRACT FROM AUTHOR]