What Does Sintering Mean?
May 26, 2025| Sintering in powder metallurgy is a critical process that involves heating to induce mutual bonding and diffusion between powder particles, resulting in the formation of dense bodies or products with certain shapes and properties. During the sintering process, diffusion between powder particles, neck formation, and compaction between particles are key steps in achieving powder particle bonding.
The principle of sintering
The principle of sintering mainly includes the following aspects:
1. Diffusion between powder particles: At high temperatures, diffusion occurs between powder particles, where atoms diffuse from high concentration areas to low concentration areas. This diffusion effect is the key to achieving powder particle bonding during the sintering process.
2. Neck formation between particles: During the sintering process, the surface of the powder particles begins to melt, forming a thin layer of liquid phase. When the liquid phase flows between adjacent particles through diffusion, a small neck is formed between the two particles, making the bonding between the particles more firm.
3. Compaction between particles: During the sintering process, after a period of sintering, the neck between powder particles gradually increases, making the overall body or product denser.
Sintering process flow
The process of sintering technology includes pre-treatment, raw material preparation, molding, sintering, and post-treatment:
1. Pre processing: mainly involves screening, cleaning, and impurity removal of raw materials to improve their uniformity and purity.
2. Raw material preparation: Mix high-purity metal or non-metal powders in a certain proportion, and then use equipment such as ball mills to mix and refine them to obtain a uniform mixed powder.
3. Molding: The mixed powder is pressed into a green body with a certain shape through a mold. Common molding methods include compression molding, injection molding, and extrusion molding.
4. Sintering: The process of heating and sintering the formed body in a sintering furnace. During the sintering process, by controlling conditions such as temperature, time, and pressure, the powder particles are combined to form a dense body or product.
5. Post treatment: mainly involves cleaning, annealing, and surface treatment of sintered bodies or products to improve their performance and quality.
Factors affecting sintering
The sintering process is influenced by many factors, which can be divided into three categories:
1. Factors related to the temperature characteristics of materials, including free surface energy, interfacial energy, and volumetric free energy, as well as lattice, grain boundary, surface diffusion coefficient, etc.
2. Powder characteristics: including effective contact area, surface activity, volume activity, contact surface orientation, etc.
3. External factors: including sintering atmosphere, sintering temperature, sintering insulation time, heating and cooling rates, particle surface layer adhesion state, etc.
The importance of sintering atmosphere
The sintering atmosphere is one of the important factors affecting the performance of sintered products. The sintering atmosphere of metal powder metallurgy can be divided into three types: protective atmosphere, controllable atmosphere, and air atmosphere. Different sintering atmospheres play different roles in the sintering process, such as protective atmospheres that can prevent oxidation of sintered parts, reduce oxides on the surface of powder particles, and remove gases and moisture adsorbed on the surface of powder particles; Controllable atmosphere can control the carbon content in powder metallurgy sintered products; The air atmosphere mainly passes through a certain amount of air gas in the sintering furnace, which is suitable for the application of small and complex metal parts and MIM ceramic materials in sintered products.
In summary, sintering in powder metallurgy is a complex process that combines powder particles into dense materials or products with specific shapes and properties by controlling conditions such as temperature, pressure, and atmosphere. This process has a wide range of applications in fields such as automotive components, mechanical parts, electronic components, and energy materials.