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
تم النشر في: 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....
تم النشر في: 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
تم النشر في: 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.
تم النشر في: 2017-03-12 21:53:01
Abousoufiane Ouis & Michel Cailler
The adhesion strength of copper thin films on E24 carbon steel substrates was studied
using the scratch test via the critical load. Coatings were deposited by a DC magnetron
sputtering system. All substrates were mechanically polished; some of them were directly
coated and others were ion-etched by argon ions prior to deposition process. The effects of
substrate negative bias voltage during the film growth were investigated. Experimental
results showed that the critical load depended on the bias voltage and that the higher bias
voltage, the better adhesion. It was also observed that the deposition rate of deposited films
gradually decreased with the increase of the substrate bias voltage. Furthermore, the working
pressure during the substrate ion bombardment etching greatly affected the critical load.
Scanning electron microscopy was used to observe the scratch tracks to accurately evaluate
the critical load. Substrate surface profiles obtained by a mechanical profilometer showed
that the critical load increased with the increase of the surface roughness. The analysis by
Auger electron spectroscopy revealed that the interface, in case of an unbiased substrate,
was relatively narrow and abrupt. However, in case of a bias voltage application, the interface
was wider and more diffuse. These results suggest that the mechanisms involved in
critical load enhancement are due firstly to the substrate surface roughness and the substrate
temperature generated by the ion bombardment, secondly to the physical mixing in the
interfacial domain and the densification of the deposited material created by the bias
Keywords: sputtered films; argon ion bombardment; bias voltage; adhesion scratch test;
mechanical profilometer; scanning electron microscopy; Auger electron spectroscopy
تم النشر في: 2017-03-12 21:48:43
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