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134 results on '"Basha, Beriham"'

36. Hydrogen embrittlement resistance in advanced high strength : vanadium bearing and TRIP-assisted steels

Author

Basha, Beriham and Rivera-Díaz-del-Castillo, Pedro Eduardo Jose

Subjects
hydrogen embrittlement, bearing, TRIP, vanadium, RCF, rolling contact fatigue, inclusions, tensile, 100Cr6, modelling, thermal desorption analysis, austenite, bainite, steel
Abstract

Advanced high strength steels undergo a series of microstructural transitions associated with damage, these lead to failure especially when hydrogen enters the lattice and gets trapped in defects. It is desired to design advanced steels highly resistant to hydrogen embrittlement (HE), while preserving a balance between their superior strength and ductility. For this purpose, a new 100Cr6 bearing steel is proposed with 0.3 wt.% vanadium, compared to a previous grade containing 0.5 wt.% vanadium, for which a new heat treatment is proposed. Mechanical testing was carried out on hydrogen-free and hydrogen-charged specimens to evaluate the potency of V4C3 traps to reduce the HE susceptibility in such steels. The nature of crack propagation and HE mechanisms in 100Cr6, 100Cr6+0.3V and 100Cr6+0.5V were assessed using hydro-hardness technique, which provides direct observation of hydrogen diffusion to cracks. The results showed that pre-charged 100Cr6+0.5V are anomalously weaker compared to 100Cr6+0.3V. Slow strain rate tests (SSRT) on notched round bar specimens have been carried out at a constant tensile crosshead speed of 0.005 mm min−1. Failure was more pronounced in vanadium-free specimens as V4C3 limited the transition from ductile to brittle fracture mode in 100Cr6+0.5V steel. Rolling contact fatigue (RCF) test was also carried out to study the propagation of cracks under rolling contact fatigue conditions. It was concluded that 100Cr6+0.5V steel has longer bearing life and higher resistance to hydrogen embrittlement than 100Cr6. However, microstructural analysis confirmed the presence of non-metallic inclusions (NMIs) in 100Cr6+0.5V steel and the disadvantageous effects on its mechanical properties were recorded. A crucial consequence of plastic deformation during RCF is the transformation-induced hydrogen desorption which occurs when retained austenite transforms into martensite. This mechanism can be investigated through studying the HE susceptibility of transformation induced plasticity (TRIP) steels. An intensive study was carried out to optimise the TRIP steel heat treatment aiming to achieve an ultimate tensile strength (UTC) of 1303 MPa. The microstructure showed lower bainite structure consisting of ferrite plates, film-like and blocky retained austenite. The most promising microstructure with respect to the expected UTC was obtained after bainitic isothermal tempering at 302 °C for 24 to 30 minutes. Thermal desorption analysis was used to study desorption of hydrogen from TRIP steel. The high activation energy of diffusion indicates that the hydrogen is trapped in retained austenite which is considered as irreversible trap. However, there was no evidence demonstrating the advantage of retained austenite on preventing embrittlement after saturation with hydrogen. As a result, it can be inferred that a finer and lower fraction of retained austenite can reduce the mass of trapped hydrogen minimising the susceptibility to HE in TRIP-assisted steels.

Published
2020
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41. WO3–NiO/rGO Based Photocatalyst for Effectively Degradation of Colored and Colorless Pollutants Using Solar Light Irradiation.

Author

Basha, Beriham, Shakir, Imran, Alrowaili, Z. A., Al-Buriahi, M. S., Anwar, Mamoona, Yousaf, Sheraz, and Warsi, Muhammad Farooq

Subjects
*FOURIER transform infrared spectroscopy, *METHYLENE blue, *PRECIPITATION (Chemistry), *PHOTODEGRADATION, *X-ray diffraction, *IRRADIATION
Abstract

In this study, the precipitation and sonication methods were used to fabricate WO3–NiO/rGO nanohybrid. The structural, spectral and optical characteristics of the as-synthesized samples were confirmed using X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), and UV–Visible spectroscopy. In comparison to pure WO3, NiO and WO3–NiO, WO3–NiO/rGO nanohybrid demonstrated increased photocatalytic degradation activity for rhodamine B and methylene blue under solar light irradiation. The percent degradation values for WO3, NiO, WO3–NiO and WO3–NiO/rGO nanohybrid for methylene blue were 64%, 81%, 86% and 95%, and for rhodamine B were 58%, 80%, 92% and 96%. The lower recombination of photo-generated holes and electrons as a result of the creation of a heterojunction between WO3 and NiO and the improved optical bandgap energy of WO3-NiO nanocomposite and its hybrid with rGO are the potential causes of this enhanced photocatalytic degradation. WO3–NiO/rGO nanohybrid demonstrated outstanding photocatalytic performance and positioned itself as a viable candidate in the catalysis industry. [ABSTRACT FROM AUTHOR]

Published
2024
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42. Synthesis, Structural and Radiation-shielding Properties of Li2O-Al2O3-SiO2 Glass–ceramic System.

Author

Basha, Beriham, ÇALIŞKAN, Fatih, Öztürk, Bünyamin, Olarinoye, I. O., Arslan, Halil, Alrowaili, Z. A., and Al-Buriahi, M. S.

Abstract

The Li2O-Al2O3-SiO2 (LAS) glass system has high commercial values due to its very low thermal expansion coefficients and its very high chemical resistance among other properties. In this study, the preparation of LAS-based glass–ceramics (G-Cs) is reported, and the influence of P2O5 as a nucleating agent for crystallizing the amorphous glass structure at different rates into this glass composition, on the physical, structural, and mechanical properties is presented. The influece of different crytalization temperature on the crystal size and micreostructure as well as the radiation absorption abilities of the G-Cs were also investigated. The G-Cs were prepared using the melt and quench method and subjected to different temperature regimes to crystallise. The crystallinity of the prepared samples was examined with the aid of X-ray Diffraction analysis, while their chemical composition was probed using energy dispersive spectroscopy (EDS). The mass attenuation coefficients (MACs) of the samples were estimated for 15 keV–15 MeV photons using the well-known WinXCom software. Lithium silicate with the main phase formulation Li0.75Al0.75Si2.25O6 was identified as the main crystalline phase within the residual glass phase. The increase in P2O5 content slightly diminishes the photon absorption abilities of the G-Cs. However, the G-Cs showed better photon absorption prowess compared to some notable shielding materials. The G-Cs are thus important shielding materials useful for radiation control purposes. [ABSTRACT FROM AUTHOR]

Published
2024
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