Exploring Different Types of Vacuum Sintering Techniques

In recent years, improving densification has been a research direction that has attracted much attention in the field of special ceramics. The degree of densification often plays a crucial role in its properties, especially its mechanical properties.
The first method is to adjust the composition and structure of the green body, such as optimizing the particle size of the raw materials, improving the molding process, etc., that is, compacting it as much as possible. Generally speaking, the density of the green body has a great influence on the density of the product. influence, but not all factors.
Another factor that has a great impact on the density of ceramics is the vacuum sintering method. Today we will take a look at which vacuum sintering methods can help improve the density of special ceramics.

New process of traditional sintering method
The traditional solid-phase sintering process uses a high-temperature electric furnace to heat the ceramic body to sinter it. It has the advantages of simple equipment and easy control of the process flow. However, traditional pressureless sintering is difficult to achieve high densification. Therefore, vacuum pressureless sintering, atmosphere sintering and two-step sintering methods have been developed in recent years to promote sintering densification by improving sintering conditions and routes.
1
Vacuum pressureless sintering
Vacuum pressureless sintering evacuates the furnace to sinter the sample under low pressure. Compared with ordinary solid-state sintering, vacuum pressureless sintering can inhibit the growth of grain size and effectively discharge the gas in the green body under a longer holding time, and the resulting grain size is more uniform.
2
Atmosphere sintering method
Atmosphere sintering usually uses an inert gas atmosphere. When sintering non-oxide ceramics, the lower oxygen partial pressure in the atmosphere helps to remove oxides from the body and accelerates the shrinkage of the body. When sintering oxide ceramics, a higher oxygen defect concentration will be formed inside the green body, thereby promoting the diffusion of atoms, increasing the density of the sintered body, and lowering the sintering temperature.
3
Two-step sintering method
Sintering densification is achieved by controlling the temperature regime during the sintering process. This method first raises the furnace temperature to a higher temperature T1 at a certain heating rate, and then quickly lowers the temperature in the furnace to a lower temperature T2 and keeps it warm for a certain period of time. T1 is generally the same as or slightly higher than the sintering temperature of traditional processes, thus providing sufficient thermodynamic driving force for the system to enable grain boundary diffusion; T2 is usually 100°C lower than T1, which can ensure the sustainability of grain boundary diffusion and It can inhibit the speed of grain growth. Therefore, the two-step sintering method can obtain relatively dense ceramic materials at lower temperatures while controlling the abnormal growth of grains.
Vacuum pressureless sintering, atmosphere sintering and two-step sintering methods are more conducive to sintering densification than traditional pressureless sintering. However, these sintering methods have the disadvantages of high sintering temperature and long sintering time. Therefore, new sintering methods need to be developed.

Learn More:

What Is Aluminum Vacuum Brazing

Titanium alloy vacuum brazing process

Why Switch To Brazing In A Vacuum Furnace