During the welding process, arc performance not only connects with power supply unit and the environmental conditions, it also depends largely on the tungsten electrode’s arc performance. Good arc performance directly determines the use and application range of tungsten electrodes. The organizational structure of the tungsten electrode has a certain impact on tungsten electrode’s arc performance. In general, the integrity and uniformity of the tungsten electrode structure will directly affect the arc performance. If tungsten electrodes inside has splitting, delamination, micro-cracks, voids, mezzanine or severe non-uniform grain structure, the arc process is instability. So it will occur arc breaking, arc blasting, drift, and the worst case will cause thermal and electric, conductivity decreased, so that electrode’s local will overheating, melting, deformation, reducing the arc performance. In addition, at high temperatures, the electrode structure is closely related to the chemical composition. At High temperature, the doped rare earth oxides is easily migration, evaporation, dilution resulting in recrystallization coarsening to cause cracks.

Organizational structure and chemical composition of the tungsten electrode can affect their physical and mechanical properties, thus affecting its arc performance. Tungsten electrode as an important part in welding tool should have good physical and mechanical properties, such as, high melting point, high boiling point, low vapor pressure, good thermal conductivity and electrical conductivity, high temperature strength and high recrystallization temperature and creep and other good properties. If the physical property and mechanical properties of the tungsten electrode is defective, then it can result in electrode deformation and melting during the welding, leading arc performance deterioration. Different type rare earth tungsten electrodes have different deformation resistance and high temperature resistance. In general, tungsten electrode doped with two rare earth oxides is better than pure tungsten electrode and tungsten electrode doped with three rare earth oxides is better than tungsten electrode doped with two rare earth oxides.

With the increase of the added amount of TiC, its grain refinement, solid solution strengthening effect began to appear, which is beneficial for improving the bending strength of tungsten carbide buttons. And thereafter continue to add TiC, sintered body appeared in the ring structure with non-normal tissue, which is thus the core parts containing lower amounts of solid solution WC and an outer layer containing a high amount of WC solid solution consisting of the ring with will make the structure appear flexural strength decreased more obviously. The variation of fracture toughness is similar to the bending strength.

From the point of view fracture surface, tungsten carbide button after fracture section added TiC is smoother and the distribution is more uniform. And by observing the hard phase of WC and Co binder phase section can be found in WC grains tend to diversify, it also shows that the fracture of the alloy phase is broken along the border and the bonded phase WC grains and binder phase, rarely WC grains through the break, and it is related to the dispersion of fine-grained solid solution with TiC phase of strengthening.

Furthermore, there are some pores in the section, especially the surface of alloy without adding TiC. In the process of solid phase sintering, because of rigid WC skeleton hinder shrinkage during cooling of briquettes contraction and solidification Co generated carbide makes it impossible to completely fill the screen, resulting in the formation of pores shrink tube; on the other hand, uneven distribution and the gas generated during sintering forming agent is one of the reasons. In addition, TiC also has an influence on the routes of cracks expanding. It will have containing and pinning effect on the movements of WC grain boundaries. And owing to a great difference of elastic modulus and coefficient of thermal expansion, the residual stress of TiC and the matrix in the process of sinter cooling, which resulting in cracks in the offset process of moving forward, extending the cracks propagation path.

Tungsten electrode arc performance is affected by physical and chemical property, mechanical properties, chemical composition and organizational structure. The following will analyzes the influence of tungsten electrode chemical composition on arc performance in welding process.

Pure tungsten electrode has high electron work function and it is not conducive to high electron stream emission, so the service life and arc performance is poor, which directly affect the welding performance. In order to improve the disadvantages of pure tungsten electrode, with further research, manufacturers developed rare earth tungsten electrode and multiple rare earth tungsten electrodes. According to the current density formula of physics emission mechanism Je = AT₂exp (-eφ / kT) shows that, in order to reduce eφ (electronic charge), we can add rare earth oxides or other elements in tungsten electrodes to low eφ’s value. Different types of rare earth tungsten electrodes having a particular Je value, so they arc performance are relatively stable.

Tungsten electrodes chemical composition’s type, content, distribution and high temperature characteristics determine the ignition and stability of the arc. In terms of content, taking single rare earth doped tungsten electrode as example, rare earth oxide content is higher, the better the arc performance of the electrodes. In addition, the uniformity distribution and high temperature evaporation and diffusion behavior of rare earth oxides also affected arc performance to some extent. The main reason for arc performance deterioration is caused by doped rare earth’s evaporation and decomposition. Different type rare earth tungsten electrode under different conditions has difference arc performance, tungsten electrode doped with two rare earth oxides is better than pure tungsten electrode and tungsten electrode doped with three rare earth oxides is better than tungsten electrode doped with two rare earth oxides.

Tungsten electrode during operation, the ends of the electrodes will produce ring mushroom nodules, called "Rim" phenomenon. This is because tungsten electrode surface has more added rare earth oxide content than the central portion, in favor of arc in a short time. When the protective gas is mixed with a small amount of O₂ or welding parameters transferred to short-term overload state, it will occurs "Rim" phenomenon. This phenomenon is still under study, some scholars believe that this is due to the tungsten oxide and rare earth oxides evaporation, decomposition, precipitation and segregation at the high temperature to occur dephlegmation and segregation precipitation. In fact, it is the chemical composition of the tungsten electrode changed at high temperatures. "Rim" phenomenon is good for arc in short time, but for a long time will lead to surface additives concentration reduction affected arc electrode performance and increased consumption.

TiC has higher melting point, boiling point, hardness and excellent chemical stability so that it can be widely used in tungsten carbide materials. In order to analyze the effect of TiC on tungsten carbide button, we study from the hardness, the density, the bending strength, fracture toughness and other mechanical properties. The experiment shows that with the increase of the addition amount of TiC, relative density of tungsten carbide button is rising. This is due to tungsten carbide button without TiC has some internal pores or defects by the raw material and the problems in the overall process, its relative density is lower; on one hand, TiC added refine the micro-structure of tungsten carbide button, on the other hand, ne-grained TiC particles uniformly distributed in the gap between the WC particles were packed efficiently so that the distribution of the alloy grain structure more uniform and reasonable, and thus increased densification of tungsten carbide buttons.

Viewed from the hardness, TiC has better hardness than WC, so with fine grains having a dispersion strengthening effect of TiC added, the hardness of the material also increased. However, when TiC is increased to a certain amount, the hardness of the tooth carbide ball longer because TiC added increasing amounts of rises, inside the material has been basically compact at this time. For the bending strength, with the increase of TiC addition amount of the bending strength of tooth carbide ball was dropped after the first rise and then fall. This is due to the TiC added after sintering temperature is lower than the carbonization temperature, dissolved in WC TiC slow imbalance occurs alloy, WC in solid solution reduced the amount of binder phase of Co carbide wettability deteriorated.