Many metal parts, tools, and equipment used in the automotive, aerospace, and agriculture industries are made using powder metallurgy. Powder metallurgy is a more sustainable process that provides manufacturers advantages of accuracy, lower costs, reduced waste, and higher production speeds than other metal part forming processes like liquid metal molding.
Powder Metallurgy and the Significance of Additives
During the process of powder metallurgy, elemental metal or metal alloy powders are combined with additives such as binders and lubricants to be consolidated into molds or dies. This is followed by a formation process to create compacts, also known as green bodies, which have the intended shape of the part but low mechanical strength. A sintering step finishes the process and metallurgically bonds the metal particles just below their melting point. The sintered particles produce a final part that increases strength and density when cooled. A simplified overview of the powder metallurgy process flow is depicted below.
While lubricant and binder additives may make up a small portion of the powder metallurgy process by weight, they play a significant role in its success. The lubricant additives are critical during compaction to ensure that metal particles easily slide into place. Lubricants also help to provide clean separation from the molds or dies after pressing. The binder additive is necessary such that the compacts have sufficient mechanical strength (referred to as green strength at this stage) to hold their shape until the subsequent sintering step.
Some parts made from powder metallurgy can be intricately shaped or thin walled. Thus, it is especially important to use high-quality lubricant and binder additives to ensure that these compacts do not deform prior to sintering. The best-performing additives will allow many types of parts to be reliably and accurately formed using powder metallurgy with excellent quality and efficiency.
POLYOX™ Additives for Powder Metallurgy
POLYOX™ are thermoplastic polyethylene oxide polymers with a high molecular weight that serve as ideal binders and lubricant additives for powder metallurgy processes. There are several key properties of POLYOX™ that make it perfect for the powder metallurgy manufacturing process:
Several grades of POLYOX™ may be considered for powder metallurgy processes. They are listed below in addition to the recommended use rates per application. In general, molecular weight coincides with the melting temperature of POLYOX™. Therefore, if a lower burnout temperature is needed, a grade with a lower molecular weight should be chosen.
| Grade | Molecular Weight (g/mol) | Use Rate (wt%) |
| WSR N10 | 100,000 |
Injection molding binder: 10–20 Thermoplastic extrusion binder: 10 Lubricant: Less than 3 |
| WSR N80 | 200,000 | |
| WSR N750 | 300,000 | |
| WSR 301 | 4,000,000 |
Summary
Binder and lubricant additives are essential to the accuracy and efficiency of powder metallurgy processes, where they directly impact the integrity and quality of finished parts. POLYOX™ provides the necessary binding, lubricating, and rheology modifying properties to powdered metal compacts to enable highly efficient production of parts of various shapes, thicknesses, and complexity. In addition, since POLYOX™ may be burned off cleanly and at low temperatures or washed out using water or alcohol, it affords powder metallurgy manufacturers flexibility and ease for removal prior to sintering.
Click below to request a sample of POLYOX™ to use in your powder metallurgy process.
