Surface modification by in-situ grown TiC in the bainitic matrix using TIG arcing

A novel approach to synthesize surface composite by in-situ grown VC reinforcement in steel matrix via TIG arcing

In previous work, the low-power laser/arc hybrid welding technique was used to weld a magnesium alloy, and high-quality weld joints were obtained. For the pulsed laser and alternating current (ac) tungsten inert gas (TIG) arc, there are two typical phase matching modes between the laser pulse and the ac TIG arc: laser pulse acting on the positive wave, during which the tungsten electrode is the cathode, and laser pulse acting on the negative wave of ac TIG arc, during which the tungsten electrode is the anode. The welding plasma behaviors, welding penetrations, and weld bead appearances of the two phase matching modes are studied. The result shows that both the welding penetration and the weld appearance with laser pulse acting on the negative wave of TIG arc are better than those with laser pulse acting on the positive wave. The differences of the welding quality induced by the two phase matching modes are analyzed from the aspects of power input and spot force. Following this, the pulsed triggering and controlling system of pulsed laser and ac TIG arc was designed to control the phase matching mode in order to improve the welding quality in pulsed laser/ac TIG arc hybrid welding process.

Surface modification via in situ formation of titanium carbide in ferrous matrix through TIG arcing

Surface modification of AISI 8620 steel by in-situ grown TiC particle using TIG arcing

In the present paper, Tungsten Inert Gas (TIG) arc with Constant Voltage (CV) power source is modelled if arc length changes. And TIG arc with Constant Current (CC) power source is also modelled if arc length changes. The TIG arc is assumed on base material of water-cooled copper. For the CV power source, maximum temperature of arc plasma and arc current increase with decrease of arc length. For the CC power source, arc voltage changes but maximum temperature of arc plasma is almost constant in spite of change of arc length. Arc power increases with decrease of arc length for the CV power source. On the other hand, arc power decreases with decrease of arc length for the CC power source. For the CV power source, arc power changes largely if arc length changes. However, for the CC power source, arc power changes little if arc length changes. Heat input from welding power source is more stable using a CC power source than a CV power source at TIG welding with a change of arc length.

Eliminating hole defects and improving microstructure and mechanical properties of friction stir welded joint of 2519 aluminum alloy via TIG arc

The discrete microstructural characterization and the formation of stainless steel layer on mild steel where produced in cladding deposits, and fusion boundary region were investigated using tungsten inert gas (TIG) arc, high current pulsed arc and constricted plasma arc. The experimental procedure involved making bead-on-plate method for controlled travel speed, employing filler metal by using tungsten inert gas arc, pulsed current gas tungsten arc and transferred plasma arc, with subsequent sectioning and examination of the reaction interface. For TIG arc cladding, using filler metal of small diameter the deposit does not become stainless steel, but on using 3.2 mm diameter filler metal it becomes stainless steel with less than 50% dilution. For pulsed arc cladding, the complete stainless steel is not obtained on account of the existence of an incomplete mixture, particularly at the fusion boundary region. However, on using a large diameter filler metal at a pulse frequency of 500 Hz, the complete stainless steel microstructure has been accomplished. The plasma arc cladding can be achieved in such a way that the conversion into stainless steel on the mild steel surface — which is the microstructures of cellular austenite in cladding deposit and cellular dendritic austenite containing δ or σ-phase in fusion boundary region — is possible irrespective of the melt penetration and the dilution. The following conditions were found to be beneficial for the formation of stainless steel microstructure layer on the mild steel: using large diameter filler metal, below 50% dilution, and further rendering arc localized and constricted.

In this paper, the fabrication of submicron α-Al2O3/Al composites from Al-SiO2 system by tungsten inert gas (TIG) arc processing technology was investigated and the submicron α-Al2O3/AlSi9Cu3 composite was prepared by dilution and ultrasonic electromagnetic coupling treatment. The microstructures, phase analysis and mechanical properties of the composites were characterized by optical microscope (OM), scanning electronic microscopy (SEM), energy dispersive spectrometer (EDS), x-ray diffraction (XRD), tensile and microhardness testing, respectively. The results revealed that the morphologies and distribution of α-Al2O3 and silicon was significantly affected by the TIG arc current. With the optimum current (120 A), the in situ reaction was complete, the substituted Si phase was presented in rod-shape or needle-shape and agglomerated at the α-Al grain boundary to form Al-Si eutectic phase, and the grain refinement of α-Al phase was the most obvious. The average size of generated α-Al2O3 particles was about 500 nm, while these particles mainly distributed uniformly along the α-Al grain boundary. Ultrasonic and electromagnetic treatments could promote the uniform distribution of α-Al2O3 particles in the AlSi9Cu3 matrix, while these particles could affect the formation of α-Al dendrites and decrease the secondary dendrite arm spacing from 19.8μm to 10.4 μm. The tensile strength, elongation, and microhardness of the α-Al2O3/AlSi9Cu3 composite with 5vol % particles yielded 282 MPa, 5.8%, and 127HV, respectively. Compared with those of the matrix alloy, they increased 17.9%, 23.4%, and 45%, respectively.

Numerical investigation of transport phenomena of arc plasma in argon-oxygen gas mixture

Arc plasma diagnostics by spectroscopy have been often used to measure the arc properties, such as the temperature. Measurements of an axially asymmetrical arc plasma require the optical computed tomography technique. This study constructed the simultaneous and multidirectional measurement system by six sets of CCD camera and interference filter with monochromatic imaging method. The deviation of the central wavelength of the filters was calibrated by tilting operation, and the sensitivity of detectors was calibrated by referencing the stationary and axially symmetric tungsten inert gas (TIG) arc plasma. We could perform the temperature measurement of the transient and asymmetrical TIG arc plasma such as in the transition period between the peak 150 A and base 10 A current of a 50 Hz pulsed TIG arc with 30° tilted torch. It was revealed that the high-temperature area of 30° tilted arc is larger than that of perpendicular arc. The comparison of pulsed and continuous arcs shows that the arc shape and the temperature variation reasonably followed the current change as long as the changing rate was about −113 A/ms.

Effect of high power CO2 and Yb:YAG laser radiation on the characteristics of TIG arc in atmospherical pressure argon and helium

Tungsten inert gas (TIG) arc welding–brazing has been recently developed and is being increasingly implemented in various industrial applications. Nowadays, this process gains much attention in joining of dissimilar metal combinations. This review paper explains the principles underlying TIG arc welding – brazing of dissimilar metal combinations and highlights the above benefits in a number of practical applications. The process mechanism of TIG brazing is different from the conventional welding processes and it will bridge the gap between the two substrates by the addition of fillers under the concentrated heat source of TIG electrode. TIG brazing technique is one of the best alternative process among the other joining process for effective joining of dissimilar metals, which have various melting temperatures and physical properties. It is very important to understand the process mechanism and its compatibility with the various dissimilar materials joining. The present study focuses on the addressing of progress of TIG brazing process in modern days and its applications in the various industries, and to bring the awareness to the manufacturers about the importance of this process from this review report. Keywords: Tungsten inert gas (TIG) arc welding–brazing, Dissimilar metals, Microstructures, Mechanical properties.

TIG arc-induced non-contact MIG arc ignition

Tungsten Inert Gas (TIG) arcing is a widely accepted process used in several industrial applications of welding and surface modification. The selection of optimized TIG arcing parameters plays a critical role in obtaining the desired properties of the weld joints and the modified surface. The current investigation proposes a finite element simulation model for the TIG arcing process intending to predict the thermal characteristics and residual stresses for AISI 4340 structural steel. An independent model was developed for the prediction for a profile of the weld bead, independent from any empirical parameter. The TIG arcing process introduces concentrated heat input to the material which may cause the temperature to rise more than the melting point in the fusion zone and cause microstructural phase transformation in the material and considered in the Finite Element (FE) model. The model has been validated on AISI 4340 steel plates. However, the model can be applied to other materials because it is dependent only on material properties. The residual stress analysis has also been done through the model and validated with the experimental method.KeywordsFinite element modeling (FEM)Tungsten inert gas (TIG) weldingResidual stresses

Measurements of population densities and temperature distributions have been performed in a double-flux tungsten inert gas (TIG) arc plasma column using high-resolution spectroscopy. The experimental conditions have been chosen to mimic typical welding conditions with argon gas. The results show that the plasma is dominated by metallic vapour species in the vicinity of the molten anode, while a nearly pure argon plasma is observed in the cathodic region.