Rassim Younes

This study investigates the effect of heat treatment on the microstructure and mechanical performance of high-manganese steel intended for mining crusher applications. The applied heat treatment consists of austenitization at 1050°C followed by ice quenching (AQ), and subsequent tempering at 200°C (QT200), 400°C (QT400), and 600°C (QT600). Microstructural characterization was performed using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). In addition, microhardness measurements, impact toughness tests, tribological analysis using a tribometer, and surface roughness evaluations were conducted to assess the mechanical and surface properties of the material. The results show that heat treatment significantly modifies the microstructure by promoting phase transformations and the precipitation of secondary carbides. Among the investigated conditions, QT400 leads to a refined martensitic structure with M₃C-type carbide precipitation at grain boundaries. This condition provides the best balance between wear resistance and impact toughness. The minimum wear rate recorded is 0.072 mg/s for the QT400 sample.

In this study, AISI 301 and AISI 420 stainless steels were deposited on an AISI 4135 substrate using the wire arc spray process (WASP). X-ray spectrum analysis revealed the presence of a body centred cubic (bcc) structure in both coatings. In particular, the AISI 301 coating showed the additional identification of chromium carbide Cr ₇ C ₃ . Conversely, the AISI 420 coating manifested the presence of a body centred cubic (Fe, Cr) structure, which is indicative of the formation of solid solutions and the development of carbides, due to significant statistical variations in the composition. Vickers HV _0.3 microhardness measurements were carried out and showed that the AISI 420 coating had a higher hardness (549 ± 17 HV _0.3 ) compared to the AISI 301 coating (383± 18.75 HV _0.3 ). The formation of oxides, a phenomenon not present in the AISI 301 coating, is attributed to this difference in hardness. The wear resistance of the AISI 301 and AISI 420 stainless steel coatings was evaluated at different sliding speeds (0.5 and 1 m/s) and under different applied loads, its expose the AISI 420 had less wear rate (2,64E ⁻⁰⁸ mg/m ± 1,66667E ⁻⁷ ) than AISI 301 (1,13E ⁻⁰⁵ mg/m ± 5,63E ⁻⁰⁷ ) . Moreover, the corrosion behaviour of specimens was determined. It is noteworthy that AISI 420 coating provides 93.5% effective protection higher than that of AISI 301 coatings.

This study focuses on producing alumina using a modified citrate method. The process involves thermally activating a chelate through biphasic drops between

Coating efficiency and quality can be significantly improved by carefully optimizing the coating parameters. Particularly in the flame spray method, the oxygen/fuel ratio, which is classified as oxidizing flame stoichiometry (excess oxygen) and reduces flame stoichiometry (excess acetylene), and spray distance are the most critical factors, as they correlate significantly with coating porosity and corrosion performance. Hence, understanding the effects of these parameters is essential to further minimize the porosity, improving the corrosion performance of thermally sprayed coatings. In this work, a NiWCrBSi alloy coating was deposited via the oxyacetylene flame spray/Flexicord-wire (FS/FC) method. The effect of the flame oxygen/fuel ratio and spray distance on the microstructure properties and corrosion behavior of the coatings was investigated. Afterwards, the microstructure, phases’ compositions, spray distance, and corrosion performance were studied. The equivalent circuit model was proposed, and the corrosion mechanism was discussed. The obtained results highlight that the oxygen-to-fuel ratio is a promising solution for the further application of flame spray/Flexicord-wire (FS/FC) cermet coatings in hostile environments. Depending on the flame’s oxygen/fuel ratio, careful selection of the flame stoichiometry provides low porosity and high corrosion performance.

Different techniques are usually employed to evaluate the mechanical properties of arc-sprayed coatings. In many situations, comparing properties is complex, and values extracted from tensile tests are required for structural projects. X6CrNi18-8 stainless steel and molybdenum were sprayed onto a mild steel substrate using the electric arc thermal spray technique to discuss this issue. After a detailed microstructure characterization, tensile tests were performed on both coatings to determine the yield strength and total elongation. Easy techniques were also applied: Vickers hardness and Charpy impact test. Tensile tests have shown that applying coatings increased the steel substrate’s total elongation. Molybdenum coating presented a higher impact resistance than the X6CrNi18-8 one, resulting in no correlation between elongation and Charpy values. On the other hand, correlations between hardness and yield strength were identified, opening a discussion on the effects of the microstructure and type of test used.