Kamel Touileb, Abousoufiane Ouis, Rachid Djoudjou, Abdeljlil Chihaoui Hedhibi, Hussain Alrobei, Ibrahim Albaijan, Bandar Alzahrani, El-Sayed M. Sherif and Hany S. Abdo.
Flux activated tungsten inert gas (ATIG) welding is a variant of tungsten inert gas (TIG) welding process with high production eciency, high quality, low energy consumption, and low cost. The study of activating flux mechanism by increasing weld penetration has direct significance in developing flux and welding process. This study has been conducted on 430 ferritic stainless steel alloy. Design of experiment is used to get the best formulation of flux. Based on Minitab17 software, nineteen compositions of flux were prepared using the mixing method. Fluxes are combinations of three oxides (MoO3-TiO2-SiO2). Using the optimizer module available in Minitab 17 software, the best formulation was obtained to achieve the best weld depth. Hence, the obtained depth is twice greater than that achieved by conventional TIG welding. Moreover, mechanical properties and corrosion resistance have been investigated for TIG and ATIG welds respectively in tensile, impact, and hardness tests, and in potentiodynamic polarization measurement test.
Keywords: ATIG; ferritic stainless steel; weld shape; mechanical properties; corrosion resistance
published in: 2020-06-04 22:56:34
K. Touileb, A. Hdhibi, R. Djoudjou, A. Ouis and M. L. Bouazizi
This work is a study of the effects of oxides combination on the morphology of 316L stainless steel welds. A series of thirteen weld lines were carried out using thirteen different oxides. Based on the depth and ratio D/W results, three candidate oxides were selected: Ti2O, Mn2O3, and SiO2. Mixing method available in Minitab 17 software is the most appropriate method to find the optimal combinations to get the best depth and D/W ratio. According to simplex lattice degree four, nineteen combinations of these oxides were prepared. The results show that the optimal composition of flux was: 66%SiO2-34% Mn2O3. The depth and D/W ratio increased to 8.85mm and 0.98 respectively for optimal ATIG, whereas for the conventional TIG welding, the depth and the ratio D/W didn't exceed 1.65mm and 0.17 respectively. For TIG weld joint the hardness is about 47 HRA and it increases to 77 HRA for the optimal ATIG weld joint. The absorbed energies in Charpy impact test are 146 and 138kJ in the weld zone and in the heat affected zone respectively for the TIG welding and they dropped to 111 and 74kJ for the optimal ATIG welding. The fracture surface examined by scanning electron microscope (SEM) shows a ductile fracture for TIG weld with small dimples but ductile-brittle fracture for ATIG weld. Energy dispersive spectroscopy (EDS/SEM) analysis shows the formation of FeS2 and SiO2 in the weld zone causing low absorbed energy for ATIG weld.
Keywords-ATIG; 316L austenitic stainless steel; ATIG welding mixing method; ternary flux
published in: 2020-06-04 15:08:45
Abdeljlil Hdhibi, Kamel Touileb, Rachid Djoudjou, Abousoufiane Ouis, Mohamed Lamjed Bouazizi and Jamel Chakhari.
Tungsten inert gas (TIG) is a wide common process used in fabrication due to its low cost equipment, high quality and accuracy welds but has low productivity related to the low penetration depth in single pass. A new perspective, the Activated Tungsten Inert Gas (ATIG), in which the same equipment as TIG is used, except that a thin layer of activated flux is deposited on a workpiece surface. In this work, eight kinds of oxides were tested on 316L austenitic stainless steel. Three levels of welding current were used to study the effect of different activating fluxes on weld bead geometry and mechanical properties. X-ray Photoelectron Spectroscopy (XPS) was used for the first and the second level energy for different ATIG welds to analyze the relationship between the weld shape and oxygen content in welds. The experimental results showed that the weld profile is related to the thermodynamic stability of selected oxides and in relation to the energy provided. ATIG with TiO2, SiO2, MnO2 oxides presented the deepest welds followed by Cr2O3, Fe2O3, and ZnO. Finally ZrO2, CaO oxides had no effect on the weld depth. The ATIG welded joint showed better tensile strength than TIG. The ATIG hardness measurements carried out showed also better if not the same as TIG weld except for the Silicon oxide weld. Results of the impact test showed that, except for the titanium dioxide TiO2 which has a good benefit, the weldment using the other oxide fluxes exhibits worse withstanding to sudden shock than TIG welding.
Keywords-ATIG; austenitic stainless steel; weld shape; mechanical properties
published in: 2018-10-20 11:14:57
Abousoufiane Ouis, Kamal Touileb, Rachid Djoudjou and Abdulhakim Okleh
The present study has been conducted in order to determine the influence of negative bias voltage applied to substrate on adhesion of copper films deposited on carbon steel substrates. The adhesion strength has been evaluated by the scratch test. Coatings were deposited by a DC magnetron sputtering system. The substrates were firstly mechanically polished and then ion-etched by argon ions prior to deposition. Adhesion was found to increase with the bias voltage. The critical load had a value of 9.5 g for an unbiased substrate and reached 18.5 g for a bias voltage of -600 V. Equally important, the interface width, measured using Auger electron spectroscopy, increased as a function of the bias voltage. The width of the interface is related to the time of ion milling in the Auger spectrometer. The size of this width is obtained from the Auger elemental depth profiles through measuring the depth of the interface coating/substrate. The width had a value of 335 min with a bias of -600 V whereas it didn't exceed 180 min when the substrate was unbiased. Therefore, the effect of the bias voltage was to expand the interface because of the diffusion phenomenon and physical mixing of materials at the interface. Moreover, the critical load increased with the increase of the interface width.
Keywords:DC sputtering, Ar ion bombardment, Bias voltage, Adhesion, Auger electron spectroscopy....
published in: 2017-03-12 22:03:06
Kamel Touileb, Rachid Djoujou and Abousoufiane Ouis
The aim of this paper is to study the effect of the
viscous dissipation on the surface tension and its role on the
shape of weld pool. Experiments were conducted on four
different casts of ferritic stainless steel with different content in
the sulfur and titanium. The results show in particular that the
presence of titanium solid compounds affects the role of sulfur as
surfactant element. Titanium in the presence of carbon and
oxygen, titanium forms solid compounds which affect the
Marangoni convection due to the sulfur element in the weld pool.
The viscous dissipation due to these compounds alters the flow
rate of the molten metal. We expect that the viscosity of metal
liquid was altered by these solid compounds. The viscous
dissipation due to these compounds contributes to heat the
molten metal leading to larger weld bead.
Keywords-GTA welding; Marangoni; viscosity; ferritic stainless
steel; solid compounds; hardness
published in: 2017-03-12 21:59:08
In order to improve the adhesion of copper films deposited by DC magnetron
sputtering on carbon steel substrates, a negative bias voltage was applied to the
substrate during the film deposition process. The scratch test was used to evaluate the
adhesion strength of the films on the substrates. Chemical elements identification and
interface width measurement were carried out by Auger electron spectroscopy (AES).
The experimental results show that a variation of the bias voltage causes a change in
the behavior of the interface width in similarity to that of the critical load. The size of the
interface width is obtained from the Auger elemental depth profiles through measuring
the depth of the interface between the coating and the substrate. It had a value of 45
min for an unbiased substrate and increased to 310 min at a bias of 450 V. In this
case, the interface is relatively wide and the effects of diffusion and physical mixing of
materials at the interface become preponderant. Then, the interface width decreases to
130 min at 600 V in which case it gets narrower and the phenomenon of film
densification becomes more involved. In all cases, the substrate temperature
generated by the bias voltage has also an effect. Moreover, it was observed in this
study that the critical load increases with the size of the interface width. As a result, the
application of a bias voltage contributes positively to the enlargement of the interface
and consequently enhances the adhesion strength.
published in: 2017-03-12 21:53:01
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