From microwave sintering temperature and holding time point of view, the sintering temperature rises to a certain temperature, density tungsten copper contact materials increases, the relative density of up to 99.8%, close to fully densification. This is due to the temperature rise reduces the wetting angle, improved copper solution on a solid phase wettability of tungsten, reducing the resistance of the particle rearrangement process, the particles rearrangement sufficiently improve the densification rate. Meanwhile, temperature increases can also reduce the viscosity of liquid copper and increase in liquid copper capillary force mobility, which will be conducive to densification. But thereafter the temperature increased, lower relative density decreased, which is due to the reduced coefficient of viscosity, the effect of gravity copper deposited on the bottom of the fluid will gradually lead to the formation of a new gas into the pores, thereby reducing the density.

The sintering additive also has a great impact on the tungsten copper contacts sintering densification. The experiments show that adding a small amount of Co, Ni can significantly improve the solubility of W, and help to improve the ability of densification. In the liquid phase sintering process, W in solid solution reacted with sintering aid or intermediate phase. And the product will form a continuous layer of wrapping on W grains surface, which can significantly reduce the surface tension between the liquid and the copper particles W and improve wettability of the two phases.

In addition, copper liquid under the action of capillary force, the gap between the W particle flow and cause a rearrangement of W particles, thereby significantly promoting compact shrink compact. However, copper liquid flow too often will lead to the emergence of copper accumulation pool, even reduce the uniformity of the sample. Overall, by analyzing the experimental data, in the manufacture of tungsten copper alloy contact process, the microwave sintering technology compared to conventional sintering has a significant advantage in heating rate and sintering cycle; sintering additive selection can promote the densification of tungsten copper contacts；samples of microwave sintering has more uniform microstructure and better mechanical properties.

Except conventional sintering process, microwave sintering as a new sintering process is also gradually began to apply in the tungsten copper material. It uses special microwave band has the fine structure coupled with a basic material to generate heat, and material dielectric loss in the electromagnetic field of the material as a whole it is heated to the sintering temperature to achieve densification. Microwave sintering has many advantages, such as volumetric heating, heat conduction from the inside out and stepwise temperature distribution within the high outside low, which are beneficial for heating rate, sintering time and energy efficiency. For powder metallurgy industry, it is essential that lower cost of production and lower energy consumption, so microwave sintering has a broad prospect in tungsten copper contact.

Tungsten copper (W-Cu) contact is a kind of psudoalloy that consist of W and Cu immiscible and with a great difference in the melting point, which means it is difficult to achieve higher density by conventional sintering method and it has a bad influence on the electrical and thermal conductivity, hermeticity and other mechanical properties. Compared with conventional sintering process, microwave sintering can effectively improve the density of tungsten copper contact materials to improve the microstructure and increase other comprehensive performance.

The full name of EB tungsten filament is electron beam tungsten filament.

The properties of EB tungsten filament (electron beam tungsten filament) include its small size, non-sagging, good breaking resistance. On the one hand, it has a nice corrosion resistance. On the other hand, the EB tungsten filament has a long life for plating as well as the high thermal conductivity.

Applications of EB tungsten filament:

1. EB tungsten filament can be applied in vacuum coating with e-gun.

A vacuum coating is a kind of technology, which can produce the thin film material by physical method. The electron beam heating has a higher flux density than that of the electric heating. What’s more, the electron beam can evaporate the high melting point materials. The kinetic energy of evaporating particles of the electron beam tungsten filament is large, and it benefits to obtain the membranous layer with a good bonding densification.

2. EB Tungsten filament can be used for emitting tubes filament cathode.

Actually, EB tungsten filament has extensive application in many fields. But people should know the correct way to use it, or its properties would be decreased.

Except reduction temperature, the thickness of the material layer will affect tungsten powder granularity and distribution. Theoretically, increasing thickness of the material reduction of tungsten powder tungsten powder particles loaded boat will thicken; and in turn reduce the material thickness of tungsten powder particle size means the boat will be relatively finer. However, in actual production, thick boat loading volume will cause the powder particle size distribution is widened, especially caused bimodal, multimodal and tail peak. In addition, WC powder of different particle size distribution produced by the hardness of tungsten carbide button as the particle size distribution will be broadened and significantly reduced. The reason is that the particle size distribution wider tungsten powder there will be large differences in the thickness of the particles, the difference in the process of carbonation will cause uneven WC grain growth, which make the same batch of powder in both the coarse particles have a single crystal by the fine-grained particles composed of polycrystalline. When the carbonization temperature is low, the fine particles carbonization completely, while the coarse particles are non-complete; when the high temperature carbonization, coarse grains are also complete carbonized, but the fine particles becomes single crystal and grows up.

In the production of tungsten carbide buttons, use single crystal and polycrystalline particles coexisted WC powder, mixed alloy material crushing prolonged, single crystal grains not crushed easily or crushed consistency is poor. Thus, by optimizing the production process of tungsten powder, such as reduction temperature control, carbonization temperature, the amount of loading the boat, etc., to fabricate homogeneous single crystal or polycrystalline WC powder, which is beneficial for improving the performance of tungsten carbide buttons.

Tungsten carbide button mainly consist of tungsten carbide (WC) and cobalt (Co), which has high hardness, high strength, high melting point, excellent wear resistance and chemical stability. So it has a broad application prospect in oil exploitation and other geological drilling industries. Tungsten carbide button inlayed on drill bit to impact, rotate, crush and shear the rock. Since most of the drilling depth deeper, dig a longer length, and some may reach thousands of meters. Tungsten carbide button if other reasons due to wear, breakage or failure occurs repeatedly replace the drill bit will seriously affect the overall drilling efficiency.

Therefore, it put higher requirements tor the hardness and wear resistance of tungsten carbide buttons. And both of mechanical and physical properties depend on its content and structure. The original properties of WC powder, especially physical properties directly determine the structure of tungsten carbide buttons. The quality of WC powder is inseparable from tungsten powder reduction, in order to achieve WC powder with high quality, we need to combine tungsten powder reduction parameters and optimize, which can remarkably improve tungsten carbide button properties.

From the preparation process of WC powder, its basic process is APT (Ammonium Paratungstate) → Hydrogen (H2) pre-reducing → Blue tungsten → Hydrogen (H2) reducing → Tungsten (W) powder → Carbonizing → Tungsten carbide (WC) block → Crushing → Sieved and granulation → WC powder. Through experimental analysis, WC powder during the preparation of the whole of the main factors including temperature, material thickness and grain size distribution. Temperature control is one of the important conditions for the reduction of the impact of tungsten powder, good temperature control and promoting the reduction rate, conducive to the completion of the crystalline tungsten powder and tungsten can effectively eliminate the defects of structure inside. If the reduction temperature is too high, tungsten powder will agglomerate, tungsten powder granularity distribution widened, which will also widen the distribution of WC powder granularity.

Before HIP process, tungsten powder mixed with a certain amount of copper, cold isostatic pressing, low temperature pre-sintered to give semi-finished copper by infiltration. It uses argon (Ar) as pressure transmission medium, temperature control (tungsten-rhenium thermocouple measurement), pressure, dwell time and other relevant parameters, before and after the HIP process copper tungsten contact material hardness, density, bending strength and conductivity of comparative measurements. The density uses conventional Archimedes drainage method; the hardness uses Rockwell hardness HRB and refers to Brinell hardness HB; flexural strength is measured by GB electrical contact material basic performance; electrical conductivity is measured by eddy current conductivity tester.

The experimental result shows that HIP densification mechanism of tungsten copper contacts is similar to the cast alloy, which removes internal defects by deformation - closed - diffusion under high temperature and high pressure and achieves completely densification. Therefore, it requires after-infiltrated material should have good closure, all internal defects, osteoporosis and so can not in communication with the outer surface. If all the defects can not be guaranteed enclosed inside the blank in the process of infiltration, the density after HIP process changes little, even no change. In addition, HIP treatment effect is also related to the content of copper. When the HIP temperature reaches a temperature close to the melting point of copper, its surface will be leaking copper beads phenomenon. Overall, HIP process can promote tungsten copper contact completely densification, which remarkably improves the mechanical and physical properties, and effectively solves dispersion and reliability.