Introduction to the molding process of zirconia ceramics

1. Zirconia ceramic dry press molding

Dry pressing molding uses pressure to press ceramic powder into a certain shape, its essence is under the action of external force, the powder particles are close to each other in the mold, and firmly combined by internal friction to maintain a certain shape.

The main defect in dry-pressed green is lamination, which is due to the internal friction between the powder and the friction between the powder and the mold wall, resulting in the pressure loss inside the green body.

The advantages of dry press molding are that the green body size is accurate, the operation is simple, it is convenient to realize mechanized operation, the moisture and binder content in the dry press green green is less, and the drying and firing shrinkage is small.

It is mainly used to form simple shape products, and the length-diameter ratio is small, and the increase in production cost caused by mold wear is the deficiency of dry press molding.

2. Zirconia ceramic hot die-casting molding

Hot die casting molding is to mix ceramic powder with binder (paraffin) at a higher temperature (60~100 °C) to obtain slurry for hot die casting, and the slurry is injected into the metal mold under the action of compressed air, cooled under pressure, and demolded to obtain wax blank.

The wax blank is dewaxed under the protection of inert powder to obtain a blank blank, and the blank is then sintered into porcelain at high temperature, and the green billet formed by hot die-casting is accurate in size, uniform internal structure, small mold wear, high production efficiency, suitable for various raw materials.

The temperature of wax paste and mold needs to be strictly controlled, otherwise it will cause underinjection or deformation, so it is not suitable for manufacturing large parts, and the two-step firing process is more complex and has high energy consumption.

Sintering of zirconia ceramics

The sintering methods that can be used for zirconia ceramics usually include: (1) pressureless sintering (2) hot pressing sintering and reaction hot pressing sintering, (3) hot isostatic sintering (HIP), (4) microwave sintering, (5) ultra-high pressure sintering (6) discharge plasma sintering (SPS), (7) in-situ pressure molding sintering, etc.