Introduction:
In powder metallurgy process, pre-sintering is an important step that is carried out before the final sintering process. Pre-sintering involves heating the compacted powder at a temperature below the melting point of the metal, allowing it to undergo partial bonding. This intermediate step has several benefits and plays a crucial role in the overall production of parts using powder metallurgy.

Increased toughness of the component:
One of the main reasons for performing pre-sintering is to increase the toughness of the component. During pre-sintering, the compacted powder undergoes a certain amount of solid-state diffusion, resulting in the formation of metallurgical bonds between the powder particles. These bonds help to strengthen the structure of the part and enhance its toughness. The partial bonding that occurs during pre-sintering creates a network of interconnected particles, which can resist the propagation of cracks and improve the overall mechanical properties of the component.

Increased density of the component:
Another advantage of pre-sintering is that it helps to increase the density of the component. Powder metallurgy involves the compaction of metal powders into a desired shape before sintering. However, the compaction process alone may not achieve the desired density. Pre-sintering helps in further densification of the component by promoting particle rearrangement and particle metallurgical bonding. This densification leads to improved mechanical properties and dimensional accuracy of the final part.

Facilitate bonding of non-metallic particles:
In some powder metallurgy applications, non-metallic particles or additives are included in the powder mixture to enhance certain properties. Pre-sintering provides an opportunity for these non-metallic particles to bond with the metal matrix. The heat and pressure during pre-sintering allow for diffusion and interdiffusion between the metal and non-metallic particles, resulting in the formation of strong interfaces. This bonding of non-metallic particles can improve the overall performance and functionality of the component.

Facilitate machining of the part:
Pre-sintering can also help in facilitating the machining of the part. The pre-sintered component has improved mechanical strength and dimensional stability compared to the green compact. This enables easier machining operations such as drilling, milling, and grinding. By pre-sintering the component, its hardness and strength can be increased, making it more suitable for subsequent machining processes.

Conclusion:
Pre-sintering plays a crucial role in the powder metallurgy process by increasing the toughness and density of the component. It also facilitates the bonding of non-metallic particles and improves the machinability of the part. Overall, pre-sintering is a critical step in the production of high-quality powder metallurgy components.