Copper in the molten state infiltrated in pores of tungsten skeleton by capillary forces, thereby connected to each other and form a dense material integrally. The advantage of using this method is that tungsten wire can distribute uniformly and copper wire can effectively induce. Since the most difficult to achieve tungsten copper contact with fiber-structure is how to make the fibers uniformly distribute in the matrix, whose distribution will affect the final properties directly. The weaving process can control tungsten wire to adjust the spacing between fibers. In addition, the distribution of copper wire at a high temperature infiltration, which presents the liquid copper supplement, under the action of surface tension, integration can reduce the surface area, prompting tungsten copper contact materials densification.

Tungsten wire diameter, infiltrated temperature and time all have an effect on the process. It uses tungsten fiber to take place of tungsten powder of conventional PM. Too large granularity of tungsten powder will have segregation and appear large area Cu-rich region, the binding force between the tungsten particles is also poor; too small granularity will prone to accumulate, leading to difficult to form a passage between the capillary and even hinder the formation of closed-cell infiltration were, so that the anti-arc erosion capacity decreases dramatically.

Fiber-structure has straight route so its density is higher after infiltration. But with the decreasing fiber diameter, it easily to form when copper was infiltrated pointed or wedge-shaped space, and solidification resistance is also large so that the defect forms. In addition, infiltration temperature has an optimum range, below the temperature which the sintered skeleton strength decreases, and the extension of sintering time, decrease the efficiency and increase energy consumption; the high temperature which the copper was in favor of lowering the viscosity of infiltration, but on the other hand the surface tension of liquid copper is reduced, and has an adverse effect on infiltration.

Tungsten copper is a psudoalloy, which is composed of two kinds of immiscible and has a great difference in physical and chemical properties metals. Since it has both advantages of W and Cu (high hardness, high strength, excellent corrosion resistance of W, excellent electrical and thermal conductivity of Cu) so that it has a broad application prospect in high-pressure, high-load vacuum circuit breaker and microelectronics fields. Due to the special nature of tungsten copper material itself, it is basically prepared by PM (Powder Metallurgy) process, but also for this reason that makes the structure and properties of tungsten copper alloy products subject to certain restrictions.

In order to make the organizational structure of tungsten copper contact more reasonable, the relevant researchers made many attempts in recent years, such as PIM (Powder Injection Molding), functionally graded materials, nano-structure and W-Cu tungsten fiber reinforced composite structure. Here we focused on the preparation of the fibrous structure of tungsten copper contacts and analyze the factors that affect performance and ablative infiltrated. The use of vacuum infiltration process, and select netting lamination to tungsten as weft, warp knit copper-dimensional net. Under vacuum condition, liquid copper has better liquidity and there is no air in the pores, which is more conducive to liquid copper fill-in. Tungsten braided copper mesh (copper as the infiltration time of induction of copper) and copper billets, and then the two stacked together in a vacuum sintering furnace infiltration, and sintered copper above the melting point (about 1300 ℃).

In China, the main material of EB (electron beam) tungsten filament is Double spiral wire. Double spiral wire can heating the cathode evenly. What’s more, the Double spiral wire can eliminate the influence of the magnetic field which is cause by the cathode electron beam. However, the process to make the Double spiral wire is more complex, if the users cannot operate dissolution of molybdenum correctly, it will cause a lot of substandard products. Against to the unqualified phenomenon of the cold resistance of EB tungsten filament, people should try to improve the process of molybdenum core wire dissolution.

Molybdenum core wire dissolution is a pure chemical reaction process. Molybdenum has a strong chemical stability, so that people used a mixture of concentrated sulfuric acid, concentrated nitric acid and water as an etching solution. During the reaction, the temperature and time of the reaction should be to control by a strict operation. In addition, people should also pay attention to the phenomenon of the reaction, the reaction speed would change for the different temperature and the seasons. Due to the low temperatures in winter, the reaction is difficult to control the, it is more likely to cause the cold resistance of EB tungsten filament unqualified.

There exist the remaining acid in the surface of EB tungsten filament without washing cleanly. Oxidation would make the tails of EB tungsten filament become black. Molybdenum wire of cold resistance of EB tungsten filament is mainly caused by the incomplete reaction.

The cold resistance of EB tungsten filament unqualified will produce a lot of waste, causing serious environmental pollution. Therefore, people need to understand the reason to reduce pollution and improve the ecological environment.

SEM (scanning electron microscope) of the electron microscope has a lower degree of vacuum, and a large beam current. Therefore, the life time of tungsten filament of SEM is limited. Generally speaking, it can last for only a few dozen hours. The life time of tungsten filament of SEM has a direct impact on the cost of the instruments operation and the effective time of operation. Consequently, it would cause more pollution and other adverse consequences. Therefore, the tungsten filament of SEM needs a regular maintenance or repair. Users can take the following measures to maintain tungsten filament and extend the life time of instruments.

Firstly, check the condition of tungsten filament, if possible, users should put the component of tungsten filament on the dissecting microscope to check again. The rate of evaporation of the filament surface is related to the temperature of the filament, users can adjust a higher height to decrease the temperature of the filament. The material can choose a thick filament gasket. And then users should adjust the current of tungsten filament. During the maintenance of tungsten filament of SEM, users should check the saturation of the filament timely. Under an unsaturated condition, current of tungsten filament should be adjusted to the saturated condition. Finally, keep the vacuum degree of Scanning electron microscope lens.

Other measures to maintain tungsten filament of SEM are: 1. Before exchange the filament, users should remove dampness and air of the new filament. 2. Do not switch filament frequently in the daily work.