Tungsten copper electrode densification problems

Under normal infiltration, sintering conditions between tungsten and copper are two metals are immiscible and invasive low, which also makes the two powder densification process by certain obstacles, making it difficult to achieve high densification and the desired structure. But only by increasing the pressure and sintering temperature, although to some extent, can increase the density of the final product, but brought a lot of problems in the process conditions and comprehensive performance assurance, the following aspects in general:

1. Densification degree and rate

Actually, the densification problems can be specifically divided into densification degree, rate and the conditions. In the practical applications, related density is the measuring index of densification, which should be higher than 98%. In addition, reasonable densification condition is also a direction of research. Viewed from the mechanism of metal powder sintering, the basic conditions for achieving higher densification as follow: First of all, the solid phase can be partially dissolved in the liquid phase. Then the contact angle of solid and liquid phase should be zero. Finally, rearrangement of liquid particles independent should not exceed 35% of the volume of sintering.

For tungsten copper electrode in W-Cu system at regular infiltration and sintering conditions, the two-phase mutual infiltration is poor, tungsten copper in the liquid is almost insoluble (10^-5atm%, at 1200 ℃ under), the precipitate was dissolved and particulate substances such rounding migration mechanism can not occur in the liquid phase sintering densification process, relying only under particle rearrangement also want action undertaken. Thus, the densification rate is relatively slow, a relatively low degree of densification. Conventional infiltration sintering and liquid phase sintering simply can not meet the 98% relative density.

By increasing the molding pressure to increase the green density can be achieved to improve the final density of purposes, but only within a certain pressure range and a limited role, unduly increasing the pressure has caused loss compacts stratification and molding tool wastage. Another method is to increase the sintering temperature until the 1400-1500 ℃, density can be significantly improved, but apparently sintering conditions require too harsh and severe size distortion at high temperatures, liquid copper excessive overflows components shifted. Therefore, improving the sintering activation of system by shortening the distance of powder particles is the most effective method of densification improving and rate and simplifying the requirements.

• < Prev
• Next >