What is MIM process vacuum sintering furnace?

The MIM vacuum sintering furnace operates by heating under vacuum conditions to induce atomic migration at the interface between powder particles, thereby transforming a powder into a dense structure. This technology is applicable not only to metals but also to the preparation of ceramics and composite materials. In the MIM process, vacuum sintering furnaces are typically used for high-temperature sintering after debinding to remove residual organic binders and tightly bind the metal powder particles.

In addition, vacuum heat treatment equipment such as vacuum sintering furnaces and vacuum brazing furnaces also play a key role in the MIM process. These equipment can sinter and heat treat materials under vacuum or a protective atmosphere, thereby improving material properties and quality. For example, using a vacuum furnace for debinding and sintering can effectively reduce oxidation reactions, prevent the formation of impurities and oxide layers, and provide a uniform temperature distribution, ensuring uniform and consistent part quality during the sintering process.

MIM Vacuum Sintering Process

1. Mixed Feed
A homogeneous feed is prepared by mixing approximately 90% metal powder and 10% binder by weight. The particle size of the metal powder used in the MIM process is generally between 0.5 and 20 μm. Binders have two main functions: first, maintaining the shape of the injected product; second, bonding the metal powder particles. This allows the feedstock to develop rheological and lubricating properties when heated in the injection molding machine barrel, acting as a carrier to guide the metal powder into the mold.
2. Injection Molding
Specialized feedstock is loaded into the injection molding machine barrel and heated to a specified temperature (generally the binder’s melting point, between 170-195°C). It is then injected into a customized mold under appropriate pressure to form a green body. Continuous optimization of the injection molding process is required through simulation, mold design and fabrication, and parameter adjustment to improve injection performance and ensure uniform injection.
3. Debinding
Binder is removed from the green body using physical or chemical methods. The part is transformed from a mixture of metal powder and binder into a pure debinded blank, maintaining its shape and structure. The debinding process must ensure that the binder is gradually expelled from different parts of the blank along the microchannels between the particles while maintaining the product’s shape, without compromising the blank’s strength. The key to this process is controlling the amount of residual binder in the blank. If debinding is not performed properly, excess binder will remain. During high-temperature sintering, the decomposition and vaporization of a large amount of binder can easily cause product cracking. Excessive debinding can lead to adverse consequences such as metal oxidation and structural deformation. Therefore, the selection of the debinding process and control of process parameters are particularly important.
4. Vacuum Sintering
The debinded blank is placed in a high-temperature, negative-pressure controlled chamber. Under the protection of a gas atmosphere, it is slowly heated to remove any residual binder. Porosity between the binders causes shrinkage during sintering. Different materials experience varying shrinkage rates during sintering, generally ranging from 15% to 18%. Controlling shrinkage by controlling parameters such as sintering time and temperature is crucial.
5. Post-Processing
The precision of sintered parts produced using the MIM process is generally within ±0.3%. To eliminate shrinkage differences during the sintering process and homogenize product quality, necessary post-processing is required based on different precision requirements, size specifications, applications, or surface treatments. This includes processes such as shaping, CNC machining, tapping, sandblasting, laser engraving, polishing, grinding, cleaning, and PVD.