sinter neck formation

Sintering Neck

Sintering neck is a phenomenon that is usually the result of incorrect temperatures, timeframes, and / or powder properties when powder metallurgy is used. It typically has two sources associated with it: (1) high green compacted compact hardness or high shear strength of a given material; and (2) unbalanced or improperly sized particles within a given particle population. Sintering neck can appear as misaligned holes, burrs, or other types of defects at the base of the part or at the location of the sintering furnace.

High Green Compacted Compact Hardness or High Shear Strength

High green compacted compact hardness or high shear strength occurs when the intense pressure of vibration that is imparted during a compaction cycle is greater than the compressibility of the material. This results in a blunting of the real corners, resulting in a higher than normal green hardness in the compacts. As a result, in the subsequent sintering and debinding cycle, the high green hardness may cause non-uniform shrinkage, leaving hard edges that can protrude into the geometry of the part.

Particle Size Mismatch

Particle size mismatch is another factor that can cause sintering necks. This occurs when the powder is not within a specified particle size range, or when there is an uneven distribution of particle sizes. As such, this can lead to a surface topography with varying levels of embedding depth and can lead to areas where there is a low melting temperature due to a low solids content. This can result in a localized fusion area, known as a sintering neck, near the cooling surface of the part.

Countermeasures for Sintering Neck

There are numerous countermeasures available to address the root cause of sintering neck, including:

• Adjustment of compaction parameters

• Adjustment of sintering time/temperature

• Adjustment of powder properties

• Addition of debinding materials

• Use of additives to improve shelf life or binding strength

• Use of solvents to control necking

• Use of an advanced sintering furnace

By implementing one or more of these countermeasures, manufacturers can ensure that sintering necks are avoided and that the desired quality of the part is achieved.

Conclusion

Sintering neck is a common issue that can occur during powder metallurgy if the parts are not properly prepared and processed. If left unaddressed, sintering neck can lead to poor part quality and even product failure. However, by understanding the root causes and implementing the proper countermeasures, this issue can be avoided. By doing so, manufacturers can ensure that their parts are of the highest quality and reliability.

Sintering neck is a certain shape which forms during sintering process. It is a neck-shaped almost dome-like configuration at the end of a sintered product, which indicates the state of complete and uniform sintering of the product. Sintering neck is generally cylindrical or elliptic in shape and the diameter and length of the neck are related to the sintering temperature, sintering time and the properties of the sintered material.

Sintering neck is formed during the sintering process due to the combination of material compaction, self-organization and diffusion. An area of sintered material at the top of the product is subjected to higher temperatures and faster cooling rates than the other parts, which causes it to sinter more rapidly. This results in the formation of a neck-like area, where the particles rearrange themselves due to inter-particle forces and form a three-dimensional network structure.

The formation of the sintering neck is an important physical property, as it indicates the completion of sintering process and whether the material has been sintered properly. The sintering neck can be used for analysis of various mechanical properties of the product, such as strength and toughness. It can also be used to infer the degree of porosity of the material.

The advantages of sintering neck check includes the possibility of understanding the sintering process at a microscopic level, better quality control and failure analysis capabilities. Sintering neck is a reliable indicator of the completion of sintering and the overall quality of the sintered product. It can help to reduce cost and improve overall quality of the product.