Defect and Diffusion Forum Vol. 406

Abstract: The present study, aims to investigate, under welding parameters of current, voltage and gas flow, the effects of welding parameters on tensile strength of AISI 304L ASS welds using response surface methodology (RSM). The RSM and variance analysis (ANOVA) were used to check the validity of quadratic regression model and to determine the significant parameter affecting tensile strength of welds. Hence, ANOVA clearly revealed that the contribution of each factor is 71.40% of voltage, 19.2% of current and 8.30% of gas flow. It was found that combined contributions of welding parameters contributes significantly to the metallurgical changes by varying fractions, morphology and grain size of metallic compounds. Furthermore, the optimum automatic welding conditions lead to produce the best possible weld quality in the range of our experiment using desirability function approach for single response of RSM optimization factors, in which it concluded that tensile strength components are influenced principally by voltage. Finally, the ranges for best welding conditions are proposed for serial industrial production.

Abstract: Various facilities are used in mineral processing to prepare raw material. Practically, two types of balls are used, cast balls and forged balls. They are respectively made from high chromium cast iron and forged steel and are supplied in different sizes and chemical compositions. The cast and forged balls have different microstructures and consequently display dissimilar wear behavior. The target aimed in this work is to achieve a comparative study taking into account the type of microstructure, mechanical properties, and wear behavior of these two kinds of materials. Specimens have undergone chemical, metallographic and XRD characterizations. Subsequently, these samples were subjected to hardness measurements, abrasion and friction tests in order to evaluate their wear behaviour. Tribological tests, under unlubricated environment, are carried out on both types of grinding balls in order to study the wear system. Corrosion tests are also performed on forged steel and high chromium cast iron ball samples. The obtained results reveal a large difference in terms of chemical composition and microstructural components. Chromium cast iron balls are more resistant to friction, whereas forged balls are more resistant to abrasion. Additionally, the corrosion tests reveal a narrow discrepancy in corrosion behaviour between the studied materials.

Abstract: In this study, a local mineral clay was used as an adsorbent for the elimination of a cationic dye: methylene blue (MB), in an aqueous solution by adsorption technique. Early on, we performed mineralogical and textural analyses of a clay sample using various techniques, namely X-ray diffraction, Brunauer-Emmett-Teller analysis and Fourier-transform infrared spectroscopy. The experimental results showed that this adsorbent is a mesoporous and non-swelling clay with illite and kaolinite as the major components with a specific area of about 110m²/g. The study of MB adsorption on the clay was carried out by optimizing the conditions of adsorption, notably the initial concentration of pollutant C₀, the mass of clay m, the contact time t, the potential of hydrogen of the solution pH and the temperature T. Experimental results have shown that the equilibrium data are well adjusted by a Langmuir isotherm equation. Thermodynamic parameters such as the changes in Gibbs free energy, enthalpy, and entropy were determined from batch experiments. Results revealed that the adsorption of MB onto illitic clay was endothermic and spontaneous process. Kinetic modeling was also carried out. Experimental data adjusted the kinetic model of pseudo-second order with two stages of intraparticle diffusion.

Abstract: In the present work we have reported the realization and characterization of CH₃NH₃PbI₃/c-Si heterojunction. It was achieved by deposing CH₃NH₃PbI₃ perovskite film on (P) doped single crystalline Silicon (c-Si) substrate by spin coating. The structural, optical and electrical properties of perovskite film were investigated. The electric characterization of the realized device was achieved through I-V and G-f measurements. The recorded I-V characteristic exhibits a rectifier behavior. This curve was used also to determine diode parameters; the ideality factor, the saturation current, the series resistance and the potential barrier. However, the conductance method was used to assess the interface state N_ss via (G/ω) versus angular frequency ω curve. The results were used to justify the large values of the ideality factor and the series resistance.

Abstract: It is well known that the mechanical resistance of austenitic stainless steels can be increased considerably by cold rolling process.¶ The cold rolling effect on corrosion resistance of AISI 304L stainless steel in 3% Sodium Chloride solution was investigated by potentiodynamic polarisation and by Scanning Electronic Microscopy (SEM). The pitting corrosion in this environment is related to the rate of cold deformation. The cold rolling induces important changes in the microstructure and involves phase transformation (γ→a'). The AISI 304L developes martensitic structure after 16% cold working. The potentiodynamic results show a moderate variation of the passivity zone, a remarkable decrease in the pitting potential and a free potential. The results also show an increase in the current density. However, it seems that the critical deformation rate appears to start at approximately 50% of the rolling deformation where the passivation current is minimal. After the polarisation tests, metastable pits are observed using SEM and the most probable initiation causes are discussed

Abstract: In the field of mechanics and biomaterials, particular attention is directed to the finishing step of pieces because it conditions several properties of materials, namely surface quality and microhardness. The mechanical surface treatment (TMS) by burnishing is one among the most competent finishing operations aimed toward improving the characteristics of surface and also the lifetime of components. Although this treatment is extremely effective, but it is very necessary to choose the appropriate combination of process parameters to realize better results. This work aims to improve, by ball burnishing, the microhardness of 316L stainless steel used for the manufacture of biomedical hip prostheses. This property is vital because it directly influences other final properties such as tensile strength, wear resistance and fatigue life. The response surface method based on Box-Behnken model is followed for experiments and an empirical model expressing the relationship between microhardness and process parameters (burnishing force, feed rate, and ball diameter ) is developed. The optimal regime for maximum hardening is also established. The results show that burnishing treatment, carried out on a flat surface, makes it possible to significantly hardening the surface of 316L stainless steel by obtaining a greater value by up to 67% compared to the untreated surface. Scanning electron micrographs show a very thin surface layer containing grains deformed plastically in the burnishing direction.

Abstract: In cutting process, the wear of the tool remains posed, it describes their progressive failure in regular operation. The tool wear phenomena is mainly caused by abrasion of hard particles, shearing of micro welds between tool and work-material and the exchange of particles between the tool and work material leading to a several forms of tool wear, however, we focused in this study on the frontal wear, also called wear on clearance surface or flank wear. For efficient use of cutting tool according to the technical requirement, the comprehension and the knowledge of the cutting tool wear evolution is necessary. In order to meet this indispensable need, the present paper proposes a two-step tool flank wear monitoring technique based on vibratory signals analysis during the turning operation using a P30 grade metal carbide tool and C45 (XC48) steel. Firstly, discrete wavelet transforms (DWT), has been used to decompose the signal and extract the information, then the scalar indicator Root Mean Square (RMS) value has been used to evaluate the cutting tool stability level. The proposed method offers the possibility to accurately predict break-in tool wear phase, accelerated tool wear phase and the stability period, in which a high quality machining process is guaranteed.

Abstract: In this employ, we deliberate the effectuality of corroding inhibition of carbon steel API 5 L Gr – B in HCl 1M solution using the n-butanolic extract taken of Inula Viscosa plant. The repressive strength was observed by the electrochemical methods, Videlicet potentiodynamic condition and impedance measurements. The results indicated that the forbiddance efficiency increases with exploding choose attention. A maximum inhibition rate of 92.37 % was recorded at 600 ppm of inhibitor denseness according to the potentiodynamic measurements. The extract seems to be a goodness corroding inhibitor of electrode writing based on the obtained results. The adsorption on the element articulator was instituted to obey to Langmuir isotherm. In expansion, the HOMO and LUMO analyzing were carried out utilizing the useful thickness hypothesis strategy (DFT / B3LYP). Since HOMO and LUMO are the foremost critical orbitals in atoms, they are exceptionally valuable for understanding certain atomic properties. In expansion, from the outcome of the DFT calculations, we obtained as follows: the total dipole moment of the molecule (μ), the absolute hardness (η), the absolute electronic negativity (χ).

Abstract: The present work is a contribution in investigating the effect of heat treatment on microstructure, hardness and friction wear of A105N steel. Samples of 25x25 mm2 cross-section and 15mm thickness have been prepared from the as-received material and then heat-treated. The samples were austenitized at 1050°C for 60 minutes followed by water quenching, then tempered at 500 and 700°C for 120 minutes. Microstructural changes and their effect on the wear resistance and hardness were investigated according to the applied heat treatments. The main results show that after quenching the structure is mostly composed of quenched martensite, which confers high hardness and friction resistance to the steel. While the tempered structure is composed of tempered martensite and ferrite. As the temperature rises to 700°C, the tempered martensite decreases and is fully transformed to ferrite and cementite. A good wear resistance expressed by a low friction coefficient and a low wear rate is achieved by tempering at 500°C.

Abstract: Concrete is a complex porous material. This porosity comes from the air trapped during mixing and also from the free water that did not react with the cement. In this work, we varied the porosity rate in concrete specimens, in order to evaluate its effect on the acoustic and mechanical properties of the material during its maturation age. These test pieces were made according to EN 196-1: 2016 of different dimensions and with three mass ratios Water/Cement (W/C=0.45, W/C=0.50 and W/C=0.65). The ultrasonic measurements were done in the direct transmission mode, using 54 kHz nominal frequency transducers, transmitting in the longitudinal mode. The results showed an increase in the propagation velocity with the age of maturation for all W/C ratios and an overall decrease in its value with this ratio. On the other hand, the attenuation coefficient increased slightly with the frequency in a quasi-linear manner, while its overall value decreased with the age of maturity of the concrete. For comparison, a destructive method was used. This consisted of crushing tests to determine the compressive strength. This latter increased with the age of maturation of the concrete for all W/C ratios, but decreased when these ratios increased. These results showed the same trend as those obtained for the ultrasonic group velocity. This allowed us to deduce a correlation law between the acoustical and mechanical parameters for all ratios with a high determination coefficient. These investigations confirm the effectiveness of ultrasonic methods in evaluating the quality of concrete.