Powder metal technology is actually quite interesting... If you can wade through all the industry lingo and terminology. For a newbie, the intro to powder metallurgy and the powder metal industry can definitely be confusing and intimidating.
Let’s demystify it. Here are some quick facts to ease your entry into the world of powder metallurgy, including some of the many advantages of powder metallurgy.
Powder Metal 101: 5 Things to Know About Powder Metallurgy and Sintering
1. Sintering Doesn't Melt the Powder Metal
Sintering in powder metallurgy is a form of heat treatment. The sinter process heats up the material to just below its melting point. This sintering temperature allows the metals to keep their beneficial properties while fusing them tightly together.
Think of sintering like a glass of ice water. While the ice cubes do melt eventually, they first fuse together at each point of contact.
2. Powder Metallurgy Is a Green Manufacturing Process
97% of the material that enters the powder metallurgy process exits as part of the final product. Good luck finding similar net shape capabilities in any other manufacturing processes. This means very little waste and scrap. PM is a win-win for your wallet and the environment.
Other metal forming processes, specifically casting, leave waste behind at multiple stages of manufacturing. Foundries are infamous for creating:
- Air pollution
- Liquid pollution
- Solid waste
3. Compaction Creates a Compact
Powder compaction is an early step in the powder metallurgy process.
It all starts with an alloy of iron powder, a related alloy, or a totally different metal powder. Intense pressure is applied to the powder so it retains the shape of its mold. The resulting component is called a compact.
Properties that influence powder metal compaction include particle size, shape, composition, and size distribution. The type of powder and how you manufacture it also influences its behavior under pressure.
While it may look like your final product, the compact still needs to undergo sintering to fully fuse the particles together.
4. Density Matters
The denser your component, the better physical properties it has. Density is directly correlated to yield strength, tensile strength, and overall component durability. We also use porosity to indicate component density.
Final product density depends on a few factors:
- Friction between particles
- Compaction force
- Sintering setup
- Particle size
To achieve the highest performing components, powder metal manufacturers use their expertise to minimize friction between particles and optimize their sintering setup for your materials.
Compaction force depends on the manufacturer’s machinery, and you can control particle size in your specifications.
5. Necking: Not Just for Teenagers
Necking is a type of deformation where relatively large amounts of strain localize disproportionately in a specific spot on our material. The resulting decrease in the local cross-sectional area becomes the "neck."
When particles fuse like the ice in your glass, the contact points are called necks. As necking between particles grows, the space between the particles (porosity) decreases. As porosity decreases, density increases.
Powder metal manufacturers aim to keep the metal particles in the necking state for as long as possible to minimize porosity in the final product.
Want More Fun Facts About Powder Metallurgy?
These are only five interesting facts about powder metals. If we tried to collect them all, we’d have to write an entire book.
If you have questions about this article, sintering, or anything else powder metallurgy-related, we’re happy to be a learning resource. (We're PM Review-approved.)
If you want to dig into more specific powder metal materials, we suggest you start with our favorite branch of materials -- soft magnetic composites. Click here for powder metallurgy 101 on soft magnetic composites, or, if you're feeling brave, click the button below for resources for intermediate and advanced articles.
(Editor's note: This article was originally published in January 2018 and was recently updated.)