What is vacuum sintering?

Vacuum sintering is a technique that uses molds or other tools to shape metal or ceramic powder into a desired form, and then heats it to a temperature below its melting point to harden it. Unlike casting or pressing, vacuum sintering does not require contact with the mold, and therefore can be used for high-melting-point or reactive materials.

1. What is Vacuum Sintering?

Vacuum sintering refers to the phenomenon where raw material particles bond together during heating, thereby reducing the gaps between particles and shrinking the overall size. Vacuum sintering is widely used in ceramic manufacturing and powder metallurgy, and the production process is stable. A typical vacuum sintering process includes six steps: mixing/crushing, forming, debinding, vacuum sintering, machining/polishing, and inspection.

2. What are the advantages and disadvantages of vacuum sintering?

Advantages of Vacuum Sintering: Vacuum sintering eliminates the need for molds during heating and vacuum sintering, allowing the production of parts of specific shapes, even from high-melting-point or reactive materials that cannot be produced by casting. Furthermore, since it does not require extrusion molds to deform the material like forging, vacuum sintering can be used even if the material does not undergo plastic deformation. Therefore, vacuum sintering is widely used for forming ceramics and high-melting-point metals. Additionally, even ceramic and metal composites that separate due to density differences during casting can be manufactured by mixing powders together and vacuum sintering. Porous materials can be created by stopping vacuum sintering when the powder particles slightly bind together.

Disadvantages of vacuum sintering: Vacuum sintering requires pulverizing the material, which can increase manufacturing costs (depending on the material). Another disadvantage is that the powder shrinks during vacuum sintering, resulting in lower dimensional accuracy. Furthermore, if the gaps between powder particles are large, porosity remains within the material, making it difficult to manufacture dense parts. Depending on the application, porosity can lead to stress concentration, thereby reducing mechanical strength and fatigue strength.

3. Applications of Vacuum Sintering
Vacuum sintering technology is used to manufacture mechanical parts because even high-melting-point materials are easily shaped. Small steel gears and similar components are also manufactured using vacuum sintering. Because mass production reduces production costs, this process is widely used to manufacture complex-shaped mechanical parts. Vacuum sintering is also highly efficient for mechanical parts made of high-melting-point metals such as tungsten and molybdenum.

Products using vacuum sintering technology include grinding wheels, cutting tools, refractory materials, ceramic blades, and ferrite magnets. Powdered high-speed steel blades are renowned for their long-lasting sharpness. Most ceramic parts are made through vacuum sintering. Mechanical structural components and functional ceramics used in ceramic heaters and sensors are produced by vacuum sintering raw material powders. Hard alloys (made by vacuum sintering tungsten carbide (WC) with cobalt (Co)) and cermets (a ceramic-metal composite material) are also made through vacuum sintering. Vacuum sintering can also produce porous materials with complex shapes, which is why they are used in filters and air diffusers. Vacuum-sintered oil-impregnated bearings are self-lubricating bearings made of porous metal impregnated with lubricant.