Powder metallurgy has a long history dating back millennia but has remained relevant in the modern age by continuing to progress and evolve. Current powder metallurgy processes are used in applications in the automotive, aerospace, green energy and power tool industries. The advent of metal injection molding has allowed for more sophisticated production, while the development of soft magnet composite metal powder has allowed powder metallurgy to be on the cutting edge when it comes to the electric motor revolution.
History
Powder metallurgy involves compacting metal powder and then sintering to bond the powder together. Sintering is heating below the melting point. The earliest evidence of sintering dates back to 3,000 BC in ancient Egypt. This process usually involved shaping raw iron ore and then sintering this shape to strengthen it. Later, around 1,200 BC, metal powders were introduced to the metal forming process and powder metallurgy was born. At this time, the ability to heat metal to melting point had not yet been achieved; so sintering metal was the way to create metal components.
During the industrial revolution, technological advancements allowed for heating metal to melting point. Thus began a phaseout of the powder metallurgy process. However, powder metallurgy would return each time a new metal (first platinum and later tungsten) with a higher melting point was introduced. To form metal products using these materials, powder metallurgy became the go-to process.
In modern times, powder metallurgy has found its niche in the mass production of metal products with intricate features. The variety and different mixtures of metal powders allows for completely customized material properties and the sintering heating process is a big energy saver when compared against competing processes that require enough energy to heat to melting point.
Standard Process
The standard powder metallurgy process consists of three processes followed by a variety of optional post-processing methods. These processes are as follows:
- Powder Mixing
- Compacting (Forming)
- Sintering
- Post-Processing
I. Powder Mixing
The process begins by mixing the raw material. Metal powder of many types is available – iron, copper, platinum, etc. In addition to metal powder, there is generally some lubricating agents added to the powder mix to increase formability in the next step and to add lubricating attributes to the final product. These mixes are customizable and can be mixed in different combinations.
II. Compacting (Forming)
Next, the powder mix is placed into a mold (or die) and is then compressed from both the top and bottom. After compacting, the newly formed piece is ejected from the press. The resulting piece is formed close to the required final dimensions but is very brittle.
III. Sintering
A sintering furnace heats the metal hot enough to allow the metal particles to bond together, but not up to melting point. Because the temperature does not reach the melting point, the metal retains its shape from the compacting process. The metal particles first bond on the surface, but as the metal is subjected to higher temperatures for longer periods, the internal particles will also bond.
IV. Post-Processing
In many cases, production is complete after sintering. However, most manufacturers will incorporate some post-processing operations depending on the specific requirements of the final product. Some examples include sizing (re-inserting the final piece into the compacting mold), machining (to achieve more detailed cuts), heat or steam treatment (to increase hardness and provide some surface protections), and/or oil-impregnation (to create a self-lubricating part).
Wrap Up
In summary, powder metallurgy is a versatile manufacturing process that allows for unique customization options. As powder metallurgy manufacturer with a rich 70+ year history, Porite is well-positioned to bring your powder metallurgy project to life. Contact us today to speak with our team of experts about your project.
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